CA1081925A - Method of producing split bearing rings - Google Patents
Method of producing split bearing ringsInfo
- Publication number
- CA1081925A CA1081925A CA342,256A CA342256A CA1081925A CA 1081925 A CA1081925 A CA 1081925A CA 342256 A CA342256 A CA 342256A CA 1081925 A CA1081925 A CA 1081925A
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- Canada
- Prior art keywords
- notch
- ring
- wedge
- bearing ring
- stress
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
- 238000000034 method Methods 0.000 title claims abstract description 17
- 230000002093 peripheral effect Effects 0.000 abstract description 11
- 238000005096 rolling process Methods 0.000 description 9
- 239000000463 material Substances 0.000 description 7
- 230000007423 decrease Effects 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- 238000003825 pressing Methods 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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- Rolling Contact Bearings (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE, A method of splitting bearing rings in a direction obliquely crossing their axes. This method comprises forming a notch of substantially V-shaped cross-section in the inner or outer peripheral surface of a bearing ring obliquely or in a V-direction or forming a notch of substantially V-shaped cross-section in an end surface of a bearing ring at a predetermined angle with respect to the surface, heat-treating the bearing ring, and exerting wedge stress along the notch by a wedge type press-breaking tool.
Description
~08~9'~5 The present invention relates to a me-thod of producing s~li-t bearing rings, and more particularl~ i-t relates to a method of splitting bearing rings in a direction obliquely crossing their axes by exerting wedge stress in a notch of substantially V-shaped cross-section formed in a peripheral or end surface o~ a bearing ring.
Generally, in a split bearing ring, splitting is effected by forming a notch in an end surface or inner peripheral surface of a bearing ring to be split and then applying a ring press-breaking method using a press. According to this conventional method, since it is difficult to split a ring obliquely or in a V-form at a predetermined angle with respect to the axis of the ring (oblique splitting), in the case of a thin-walled article it is usual practice to form a notch in the inner peripheral surface or an end surface and split the ring axially (parallel splitting) by pressing it in a direction crossing the notch at right angles. However, in the case of a thick-walled article, splitting is effected usually by turning.
With this method by turning, ho~ever, although oblique split-ting is possible by separately producing two rings each havingan end surface inclined with respect to the axis by turning, the yield of material is low. Thus, the method is disadvan-tageous from the standpoint of productivity.
In addition, in splitting bearing rings, oblique splitting may be said to be the most desirable splitting method in the light of the following conditions.
- The split line resulting from oblique splitting crosses the major axis of the contact ellipse at an angle on the bearing rolling surface and the contact surface contacts only a portion of the split line with respect to line contact or similar rolling contact, so that stress concentration at the split region can be greatly reduced, resulting in remarkable improvement of the life of the bearing.
9'~5 Accordingly, the presen-t invention has been developed in view of the above problems encountered in producing split bearing rings and has for its object the provision of a method of producing split bearing rings which is capable of splitting rings in any desired direction and provides a high yield of ma-terial and high productivity.
According to a feature oE the present invention, the inner or outer peripheral surface of a bearing ring is formed with a notch which extends obliquely or in a V-form, and after the ring is heat-treated or further ground, wedge stress is exerted along the notch by wedge type press-breaking means, thereby splitting the rlng in a direction obliquely crossing the axis thereof.
According to a second feature of the invention, an end surface of a bearing ring is formed with a notch of substan-tially V-shaped cross-section at a predetermined angle with respect to the end surface, and after the ring is heat-treatad or further ground, wedge stress is exerted in the notch by wedge type pressure-breaking means with an edge having a greater angle than the notch angle, thereby splitting the ring obliquely of the axis thereof.
These and other features of the invention will become more apparent as the description proceeds, when considered with the accompanying drawings illustrating embodiments of the invention.
Figures 1 through 11 show a first embodiment of the invention, wherein a peripheral surface of a bearing ring is formed with a notch.
~ Figure 1 is a perspective view of a bearing ring formed with an obliquely extending notch.
Figure 2 shows how to split the bearing ring shown in Figure 1.
Figure 3 is a perspective view of a bearing ring formed with a notch extending in a V-form.
Figure ~ is an enlarged plan view of the principal portion of the bearing ring shown in Figure 3.
Figure 5 is a schematic view showing how compressive stress acts in a flat plate according to a wedge type pressure-breaking method.
Figure 6 isa graph showing variations of F(a/b)/~
relative to a no-tch depth a.
Figure 7 is a graph showing variations of Kl relative to a notch angle ~.
Figure 8 is a schematic view showing the relation between a crack and a hole formed in a bearing ring.
Figure 9 is a schematic view showing an instant when the crack reaches the hole.
Figure 10 is a graph showing a region for a notch bottom curvature p where no hard^~ling crack occurs with respect to a notch depth a.
Figure 11 is a schematic view showing the relation of a wedge angle 2~ relative to a notch angle 2y.
Figures 12 through 25 show a second embodiment of the invention wherein an end surface of a bearing ring is formed with a notch.
Figures 12 and 14 are perspective views of bearing rings to be split.
Figures 13 and 15 show how to split the bearing rings shown in Figures 12 and 14, respectively.
Figures 16 and 20 are perspective views of bearing rings to be split in a V-direction.
Figure 17 is an enlarged front view of the principal portion of the bearing ring shown in Figure 16.
Figures 18 and 19 are schematic views showing how to split the bearing ring shown in Figure 16.
Figure 21 is an enlarged front view of the principal 8:1L9'~5 portion of the bearin~ rings shown in Figure 20.
Figure 22 is a schematic view showing stress acting in a flat plate accor~ing to a wedge type pressure-breaking method.
Figure 23 is a graph showing the relation between a notch depth a and breaking stress.
Figure 24 is a gr~ph showing the relation between a notch dep-th a and notch bottom curvature.
Figure 25 is a schematic view showing the relation between a wedge shape and a wedge angle.
First of all, an embodiment of the invention wherein a peripheral surface of a bearing ring is formed with a notch will be described.
Referring to Figure 1 showing a first embodiment of the invention, a bearing ring to be split is designated at 1 and the outer peripheral surface thereof is formed with a notch 2 of substantially V-shaped cross-section. As shown in Figure
Generally, in a split bearing ring, splitting is effected by forming a notch in an end surface or inner peripheral surface of a bearing ring to be split and then applying a ring press-breaking method using a press. According to this conventional method, since it is difficult to split a ring obliquely or in a V-form at a predetermined angle with respect to the axis of the ring (oblique splitting), in the case of a thin-walled article it is usual practice to form a notch in the inner peripheral surface or an end surface and split the ring axially (parallel splitting) by pressing it in a direction crossing the notch at right angles. However, in the case of a thick-walled article, splitting is effected usually by turning.
With this method by turning, ho~ever, although oblique split-ting is possible by separately producing two rings each havingan end surface inclined with respect to the axis by turning, the yield of material is low. Thus, the method is disadvan-tageous from the standpoint of productivity.
In addition, in splitting bearing rings, oblique splitting may be said to be the most desirable splitting method in the light of the following conditions.
- The split line resulting from oblique splitting crosses the major axis of the contact ellipse at an angle on the bearing rolling surface and the contact surface contacts only a portion of the split line with respect to line contact or similar rolling contact, so that stress concentration at the split region can be greatly reduced, resulting in remarkable improvement of the life of the bearing.
9'~5 Accordingly, the presen-t invention has been developed in view of the above problems encountered in producing split bearing rings and has for its object the provision of a method of producing split bearing rings which is capable of splitting rings in any desired direction and provides a high yield of ma-terial and high productivity.
According to a feature oE the present invention, the inner or outer peripheral surface of a bearing ring is formed with a notch which extends obliquely or in a V-form, and after the ring is heat-treated or further ground, wedge stress is exerted along the notch by wedge type press-breaking means, thereby splitting the rlng in a direction obliquely crossing the axis thereof.
According to a second feature of the invention, an end surface of a bearing ring is formed with a notch of substan-tially V-shaped cross-section at a predetermined angle with respect to the end surface, and after the ring is heat-treatad or further ground, wedge stress is exerted in the notch by wedge type pressure-breaking means with an edge having a greater angle than the notch angle, thereby splitting the ring obliquely of the axis thereof.
These and other features of the invention will become more apparent as the description proceeds, when considered with the accompanying drawings illustrating embodiments of the invention.
Figures 1 through 11 show a first embodiment of the invention, wherein a peripheral surface of a bearing ring is formed with a notch.
~ Figure 1 is a perspective view of a bearing ring formed with an obliquely extending notch.
Figure 2 shows how to split the bearing ring shown in Figure 1.
Figure 3 is a perspective view of a bearing ring formed with a notch extending in a V-form.
Figure ~ is an enlarged plan view of the principal portion of the bearing ring shown in Figure 3.
Figure 5 is a schematic view showing how compressive stress acts in a flat plate according to a wedge type pressure-breaking method.
Figure 6 isa graph showing variations of F(a/b)/~
relative to a no-tch depth a.
Figure 7 is a graph showing variations of Kl relative to a notch angle ~.
Figure 8 is a schematic view showing the relation between a crack and a hole formed in a bearing ring.
Figure 9 is a schematic view showing an instant when the crack reaches the hole.
Figure 10 is a graph showing a region for a notch bottom curvature p where no hard^~ling crack occurs with respect to a notch depth a.
Figure 11 is a schematic view showing the relation of a wedge angle 2~ relative to a notch angle 2y.
Figures 12 through 25 show a second embodiment of the invention wherein an end surface of a bearing ring is formed with a notch.
Figures 12 and 14 are perspective views of bearing rings to be split.
Figures 13 and 15 show how to split the bearing rings shown in Figures 12 and 14, respectively.
Figures 16 and 20 are perspective views of bearing rings to be split in a V-direction.
Figure 17 is an enlarged front view of the principal portion of the bearing ring shown in Figure 16.
Figures 18 and 19 are schematic views showing how to split the bearing ring shown in Figure 16.
Figure 21 is an enlarged front view of the principal 8:1L9'~5 portion of the bearin~ rings shown in Figure 20.
Figure 22 is a schematic view showing stress acting in a flat plate accor~ing to a wedge type pressure-breaking method.
Figure 23 is a graph showing the relation between a notch depth a and breaking stress.
Figure 24 is a gr~ph showing the relation between a notch dep-th a and notch bottom curvature.
Figure 25 is a schematic view showing the relation between a wedge shape and a wedge angle.
First of all, an embodiment of the invention wherein a peripheral surface of a bearing ring is formed with a notch will be described.
Referring to Figure 1 showing a first embodiment of the invention, a bearing ring to be split is designated at 1 and the outer peripheral surface thereof is formed with a notch 2 of substantially V-shaped cross-section. As shown in Figure
2, the bearing ring 1 is split by wedge type pressure-breaking means 3 along the notch, i.e., in a direction obliquely cross-ing the axis. In this connection, it is to be noted that the compressive load necessary for splitting an outer diameter 108.5 x inner diameter 85~ x width 41 mm ring was about 6 tons.
In the case of splitting in a V-direction, as shown in Figures 3 and 4, a small hole 14 is centrally formed in the outer peripheral surface of a bearing ring 11 and notches 12a and 12b are formed in a V-form with said small hole 14 located at the crossing point of the V. The material, after being heat-treated and ground, is broken along one notch 12a and then along the other notch 12b by wedge type pressure-breaking means, whereby it is split along the split line obliquely crossing its axis.
The conditions of the stress exerted by the wedge type pressure breaking means 3 in the notch 2 or notches 12_ and 12b are as follows.
~1)8~Z5 If an appro~ima~ion ~o -the stress condi-tions of such bearing ring is made by taking a flat plate sl shown in Figure 5 as an example, with the wedge stress represented by P the stress ~max in the bottom of a notch Nl is given by the following equa-tions.
6max = 2K ... (1) X = ~ .F(a/b) . (2) 6max. = ~,~r F(a/b) ... (3) F(a/b) = (l-ajb)3/2 ~ a/b) + 2-13(1 - a/b)~ (4) ~: The curvature of the front end of the notch K: Stress magnification factor F(a/b): Compensation factor a: Notch depth b: Plate thickness F(a/b)/J~~ varies according to the notch depth a, as shown in Figure 6. In the equation (3), with ~ taken as being constant if 6max as breaking stress is uniquely determined by the material, then as F(ajb)/~ increases, P decreases. That is, breaking stress decreases. Therefore, the smaller the notch 20 ~depth a, the greater the advantage. Further, the relation between compressive stress W and wedge stress P depends on wedge angle 20 and is expressed by the following equation.
P = W2 cot ~.
Therefore, the smaller the wedge angle, the greater the advantage.
However, the wedge angle should be greater than the notch angle~
If the breaking stress at the bearing end is 180 Kg/mm , the stress magnification factor Kc of the front end of the crack at _5_ . ... ~, ~
the time of crack occurrence is given as follows.
From the equ~tion (1), Kc = 1802J~ . (5) From the equa-tion (2), Kc = ~fi~r Fc(a/b) ...(6) On the other hand, the K for the Eront end of the crack when the crack propagates is given as follows. From the equations (1) - (6), k = 90 ~ ~~ Fc(a/b) In a practical range (b = 10-60, a = 1-3), as seen from Figure 6, ~ F(a/b) > o 5 Therefore, K ~ 90 ~ x 0.5. . (7) If the Kic of bearing steel is 50 Kg ~ /mm , then from K> Kic =
50, for e, 0-4 mm it is seen that breakage occurs at once after a crack occurs in the notch. In addition, if the product hardness decreases, the Kic value increases, making breakage more difficult.
Therefore, the product hardness HRC should suitably be not less than 50. Practicalranges for (I) crack stopping hole diameter 2r, (II) notch bottom curvature Q, (III) wedge angle 28, (IV) notch shape 2~ and (V) notch angle ~ are-as follows.
(I) Crack stopping hole diameter 2r:
When breakage occurs in a V-form, the essential condition is that the crack should stop at the central hole 14 shown in Figures 3 and 4. Therefore, if the radius of the hole 14 is r, with an assumption made as shown in Figure 8 the magnification factor K of the front end of the crack when the latter propagates is given as follows.
K = v7~ F(a/b). ..(2) ~LOB1925 When the crack reaches the hole 1~, -the stress ~max in the inner periphery of the hole is as follows.
6max = ~r~~ . ... (1) If the initial notch curvature is ~, then K = 90 /~ Fc .. (8) In a practical range (b = 10-60, ac = 1-3), Fc = 1.4-0.7, When the crack reaches the hole 14, if the hole position is at the middle of the ring and b =0 5~ then from the equation (4) F(a/b) = 4.87.
K = 0 ~ x 4vr~ ~ 90 ~ x O.7 x ~
When considered under the condition that it should not break at once after the crack occurs (PCO.4)~
.
K > 90 v7~ x 0.7 x 4 ~ = ~ , ...(9) At the instance when the crack reaches the hole 14, the condition shown in Figure 9 is established and the magnification factor of the hole approximately doubles~ (The equation (2') changes to the equation (2)).
Therefore, K ~ 2 x 3~b- ' From the equation (1), ~81g~
2x2x3~ 3~
6maX ~ 180 ~--. r > 18.6 Thus, when the ring width is 18.6 x 4, the essential condition for the crack to s-top at the hole is tha-t the radius r of the hole is r ~ 1. When breakage occurs at once, ~ _ 0.4. It is seen that r increases with p. Since it is desirable that the hole diameter 2r be small from the standpoint of the rolling life, it is desirable tha-t the notch bottom curvature Q be small.
Suitably, the notch bottom curvature ~ should be not more than 0.4. However, if the notch bottom curvature ~ is too small, there is a possibility that a hardening crack will occur during heat treatment. Therefore, it is necessary to set a lower limit to the notch bottom curvature ~ and this will now be described.
(II) Notch bottom curvature p:
Assuming that the stress acting on a bearing material upon occurrence of a hardening crack is not less than 30 Kg/mm and that the heat treatment stress is not more than +5 Kg/mm2, the shape factor Kt is within the range Kt < 6 and no hardening crack will occur. This is taken as the notch bottom curvature region for prevention of hardening crack relative to the notch depth a and is shown in Figure 10. If the notch bottom curvature ~ is 0.4 mm, it follows that the notch depth a is allowed to have a value of up to 6 mm.
(III) Wedge angle 20:
Reduction of the wedge angle 2a is desirable since this reduces breaking load, but 20 < 20 <60 is suitable from the standpoint of the strength of the wedge. In addition, the hardness of the wedge is, of course, higher than that of the product.
(IV) Notch shape 2~:
As shown in Figure 11, 2~<28. Since the bearin~ and wedge .
:
8~L9~5 will be deforme~ whe~ subjected to wedge s-tress, i-t is necessary that there be a subs-tantial difference between the angles ~
and ~. The condition 2H - 2~ > 20 is suEficient for ordinary bearing rings though no-t necessarily definite since the size of wedge s-tress is influenced by the hardness of ma-terial.
Therefore, 2~ - 2~ is suitably 0 - 20~. The notch dep~h a varies with the wall thickness, etc., and the greater the notch depth, the more a~vantageous to splitting, bu-t when splitting operation is considered, 3~ a c 10 is suitable.
(V) Notch angle ~:
When splitting is effected simply with an angle ~ with respect to the axis, the stress magnification factor K of the front end of a crack varies with respect to ~ as shown in Figure 7. The smaller ~, the better since the breaking load is reduced. However, if the angle ~ is large, the stress concentra-tion caused by rolling contact is high~ Therefore, the angle - should be determined with consideration given to these two conditions. The stress concentration caused by rolling contact is also influenced by the curvature of the race and rolling bodies, and ~ should be determined with this point taken into account. That the breaking load at the time of splitting is high is not so serious a problem to the production of bear1ngs, after all, ~ is suitably 10 - 30.
As has been described so far, the first feature of the present invention lies in forming a notch in the inner or outer diameter of a bearing ring obliquely or in a V-form, heat-treating and grinding the ring, and exerting wedge stress along the notch by wedge type pressure-breaking means having an edge of larger angle than the notch, thereby obliquely splitting the bearing ring. Therefore, bearing rings can be easily split in any desired direction and the yield and productivity are high. More particularly since the breaking load re~uired when a wedge is used is little influenced by the wall thickness, though influenced _g_ by the notch bot-tom curvature, this method is very ef~ective even in the case o~ thick-walled articles. Further, even in -the case of a bearing ring which does not need to be split at an angle with respect to its axis, the use of wedge stress for breaking with a notch formed in an end surface for receiving a wedge is advantageous over the conventional ring breaking procedure.
Moreover, the arrangement is simple and very advantageous.
II. Next, another embodiment of the invention in which an end surface of a bearing ring is formed with a notch will now be described.
A bearing ring 21 shown in Figure 12 is formed with a notch 22 of substantially V-shaped cross-section for splitting purposes.
As shown in Figure 13, it is placed on a support 26 at a prç-determined angle and wedge stress is exerted along the notch 22 by wedge type pressure-breaking means 23, whereby the bearing ring is split in a direction obliquely crossing its axis. In this connection, the compressive load required for splitting an outer diameter 200~ x inner diameter 160~ x 100 mm width 100mm ring was about 13 tons.
A bearing ring 31 shown in Figure 14 has annular flanges 31a and 31b around its outer periphery. One end surface of the bearing ring 31 is formed with a notch of suhstantially V-shaped cross-section for splitting purposes while the other end surface ;~
is formed with a support surface 35 at right angles with the load line so that the ring 31 may be supported with the notch 32 vertically positioned. Therefore, the bearing ring 31, supported at its support surface 35 on the support 36 as shown in Figure 15, will be split by the wedge type pressure-breaking means 35 in a direction obliquely crossing the axis.
In this way, when oblique splitting is to be effected along the notch formed in the end surEace, not only the bearing ring 21 whose inner and outer diameters are straight but also the bearing ring 31 having flanges on its outer periphery can be --10- , simply split and that with hiyh precision.
In the case of splitting in a V-direction, as shown in igures 16 and 17, a bearing ring ~1 to be split is formed with a small hole 44 centrally of -the width of its peripheral surface and the opposite end surfaces o~ the ring 41 are formed with notches ~2a and 42b of V-shaped cross-section with their bottoms directed -toward the small hole 44. In other words, the small hole 44 is located at the intersection of the directions of propagation of the two notches. Further, the end surfaces are.
formed with support surfaces 45a and 45b so that the ring 41 may be supported against a load applied in the direction of the notch 45a or 45b. In splitting operation, as shown in Figures 18 and 19, the beari.ng 41, after being heat-treated and ground, is positioned at its one suppor-t surface 45a on the support 46 and subjected to wedge stress, causing the notch 42a to propagate to the small hole 44, whereupon the ring is turned upside down and positioned at its other support surface 45b on the support 46 and similarly the notch 42b is caused to propagate to the small . hole 44. As a result, the bearing ring 41 is split in a direction obliquely crossing its axis along the V-form split line. In : addition, in splitting operation, if a pin for pr~vention of deformation of the small hole during loading is inserted in the small hole 44,. splitting can be facilitated..
Figures 20 and 21 show the arrangement of notches 52a and : 52b and a small hole 54 formed in a bearing ring 51 which is to be split in a V-direction and which has annular flanges 51a and 51b, it being understood that if the small hole were located on the rolling surface, troubles would be caused. Thus, the small hole 5~ is located to avoid the rolling surface, and the notches 52a and 52b of V-shaped cross-section are formed in the end surfaces of the ring 51 in such a manner that the notch bottoms are directed toward the small hole 54. The opposite end surfaces are further formed with support surfaces 55a and 55b 33L9'~5 verticall~ with respect to the load lines so that the ring 51 may be effectively supported against a load applied in a direction of the notch 52a or 52b. The splitting operation for the bearing ring 51 i5 the same as for the previous ring 41.
The stress conditions established by wedge type pressure-breaking means 23, 33 and ~3 in the notches 22, 32, 42a and 42b, and 52a and 52b in the bearing rinys 21, 31, 41 and 51, respect-ively, are as follows.
First of all, the stress conditions in a flat plate S2 shown in Figure 22 will be taken as an example and used to make an approximation to the stress conditions in a bearing ring. With wedge stress represented by P, as in the case of the previous notch N1 formed in the peripheral surface, the stress 6max in the notch bottom is given by the following equations.
6max = 2K
K = ~__ x F(a/b) -4P F (a/b) 6 max = x ~r~
F(a/b) = a/ )3/2 - (1 a/b) 1/2 + 2.13 (1 - a/b) ; ~ ,, where ~: curvature of front end of notch K: stress magnification factor F(a/b): compensation factor F(a/b)/~ varies with the notch depth a, as shown in Figure 23. ;~
If ~in the equation (3) is constant and 6 max as the breaking stress is uniquely determined by the material, then as F/~
increases, P decreases. Therefore, the smaller the notch depth a, the greater the breaking load 6max and the more advantageous.
. . , ' '' ' ~
L08~9Z~
The relation between compressive load W and wedye stress P
depends upon wedge angle 20 and expressed by the follo~ing equation:
P = W2 co-t ~. Therefore~ the smaller the wedge angle 20, the more advantageous. However, the wedge angle should always be greater than the notch angle.
If the breaking s-tress is 180 Kg/mm2, then the stress magnification factor Kc for the front end of a crack when the latter occurs is as follows.
From the equation (1), Kc = 180 2 = 90 ~ (5) .. .. .
From the equation (2), Kc = - aCc Fc(a/b) ...(6~
On the other hand, the K for the front end of a crack when the latter propagates is as follows.
From the equations (1)-(6), 90~ F (a/b) For the range b = 50-600 and a = 2-12, as seen from Figure 12, ~ F(a/b) > o 4 Therefore, K ~ 90 ~ x 0.4.
If the Kic of bearing steel is 50 Kg ~ /mm2, from K ~ Kic = 50 in the equation (7) it is seen that for Q ~ 0.6 mm the bearing steel will be broken at once after a crack occurs in the notch.
In addition,practical ranges for (I) small-hole diameter - 2r, (II) notch bottom curvature Q, (III) wedge angle 20, and (IV) notch shape 2~ are as follows.
(I) Small hole diameter 2r:
When a bearing ring is to be split in a V-form, the essential condition is that the crack from one of the notches should stop at the small hole. Therefore, with the radius of the small hole represented by r, when the crack reaches the small hole, the stress 6max in the inner periphery of the small hole is as follows.
~L~81~25 Gmax = 2K . (1l) When -the initial notch bottom curvature is represented by ~, K = 90 ~ ~ FF ...(8j For practical range (b = 50-600 and a = 2-12), `= O.95-0.4 Fc When the crack reaches the small hole, if a/b = 0.5 with the small hole located at the middle of the ring end surface, then from the equation (4), F(a/b) = 4.87.
Substituting this in the equation (8) gives K = 90 ~ c~ x ~_7 > 90 ~ x 0.4 x ,~ '.
When considered under the condition that breakage should not occur at once after a crack occurs (Q < 0.6), then K ~ 90 ~ x 0 ~ 6 x 0.4 x ~ . - ... (9') ~;
. .
From the equations (1') and (g'), -~
2 x Jçr 2 7 ~;
- ~. . . -.
..r ~2.28/a Thus, when a is 228, the essential condition for the crack to stop at the small hole is that the radius r of the small hole is not less than 1 mm. In order for breakage to occur at once, ~ >0. 6r It is seen that r increases with ~. Since it is desirable that the hole diameter 2r be small from the standpoint of the rolling life, it is desirable that the notch bottom curvature ~ be small. Therefore, suitably, the notch bottom curvature Q should be not more than 0.6. ~lowever, if the notch bottom curvat~1re ~ is -too small, there is a possibility that a hardening crack will occur during heat treatment. Therefore, it is necessary to set a lower limit to the notch bo-ttom curvature ~.
(II) Notch bottom curvature Q:
Assuming that the stress acting on a bearing material upon occurrence of a hardening crack is not less than 30 Kg/mm2 and that the heat trea-tmen-t stress is not more than -~5 Kg/mm2, the notch shape factor Kt is within -the range Kt < 6 and no hardening crack will occur. This is taken as the notch bottom curvature ~ region for prevention of hardening crack relative to the notch depth a and is shown in a graph in Figure 13.
According to this graph, if the notch bottom curvature ~ is 0.4, it is seen that the notch depth a is allowed to have a value of up to 6 mm.
(III) Wedge angle 2a:
Reduction of the wedge angle 2~ is desirable since this reduces breaking load, but 20 _2~ C60 is considered suitable from the standpoint of the strength of the wedge.
(IV) Notch shape 2y~
As shown in Figure 14, the relation between wedge angle 2 and notch shape 2Y is always such that 2~ ~ 20. Since the bearing and the wedge will deform when subjected to wedge stress,.
it is necessary that there be a substantial difference between the angles ~ and ~. The condition 20 - 2~ > 20 is sufficient for ordinary bearing rings though not necessarily definite since the size of the wedge stress is influenced by the hardness of material.
The formation of notches 2, 12, 23, 24 and 33, 34 in bear-ing rings 1, 11, 21 and 31 to satisfy khe above conditions and the application of wedge type pressure-breaking means will facilitate splitting.
~ 319'~
As has been described so far, the second feature of the present invention lies in Eorming a substantially V~shaped notch in an end surface of a bearing ring at a predetermined angle with respect to the surface, heat-treating and grinding the ring and exer-ting wedge stress by wedge type pressure-breaking means having an edge of larger angle than the no-tch, thereby splitting the bearing ring in an oblique direction or V-direction.
According to this method, bearing rings can be easily split in ~ -any desired direction wlthout being influenced by the shapes of the inner and outer diameters. The yield and productlvity are high. Furthçr, loading a bearing ring at its end surface allows the use of a small-sized pressing device regardless of the size of the outer diameter of the bearing ring. The merits in practical use are very great.
While there have been described herein what are at present considered preferred embodiments of the several featur~s of the invention, it will ~e obvious to those skilled in the art that modilications and changes may be made without departing from the essence of the invention.
It is therefore to be understood that the exemplary embodi-ments thereof are illustrative and not restrictive of the ~^
invention, the scope of which i5 defined in the appended claims and that all modifications tha~ come within the meanlng and range of equivalency of the claims are intended to be included therein.
.~ . ' ' ' .
`; ' ' , . '
In the case of splitting in a V-direction, as shown in Figures 3 and 4, a small hole 14 is centrally formed in the outer peripheral surface of a bearing ring 11 and notches 12a and 12b are formed in a V-form with said small hole 14 located at the crossing point of the V. The material, after being heat-treated and ground, is broken along one notch 12a and then along the other notch 12b by wedge type pressure-breaking means, whereby it is split along the split line obliquely crossing its axis.
The conditions of the stress exerted by the wedge type pressure breaking means 3 in the notch 2 or notches 12_ and 12b are as follows.
~1)8~Z5 If an appro~ima~ion ~o -the stress condi-tions of such bearing ring is made by taking a flat plate sl shown in Figure 5 as an example, with the wedge stress represented by P the stress ~max in the bottom of a notch Nl is given by the following equa-tions.
6max = 2K ... (1) X = ~ .F(a/b) . (2) 6max. = ~,~r F(a/b) ... (3) F(a/b) = (l-ajb)3/2 ~ a/b) + 2-13(1 - a/b)~ (4) ~: The curvature of the front end of the notch K: Stress magnification factor F(a/b): Compensation factor a: Notch depth b: Plate thickness F(a/b)/J~~ varies according to the notch depth a, as shown in Figure 6. In the equation (3), with ~ taken as being constant if 6max as breaking stress is uniquely determined by the material, then as F(ajb)/~ increases, P decreases. That is, breaking stress decreases. Therefore, the smaller the notch 20 ~depth a, the greater the advantage. Further, the relation between compressive stress W and wedge stress P depends on wedge angle 20 and is expressed by the following equation.
P = W2 cot ~.
Therefore, the smaller the wedge angle, the greater the advantage.
However, the wedge angle should be greater than the notch angle~
If the breaking stress at the bearing end is 180 Kg/mm , the stress magnification factor Kc of the front end of the crack at _5_ . ... ~, ~
the time of crack occurrence is given as follows.
From the equ~tion (1), Kc = 1802J~ . (5) From the equa-tion (2), Kc = ~fi~r Fc(a/b) ...(6) On the other hand, the K for the Eront end of the crack when the crack propagates is given as follows. From the equations (1) - (6), k = 90 ~ ~~ Fc(a/b) In a practical range (b = 10-60, a = 1-3), as seen from Figure 6, ~ F(a/b) > o 5 Therefore, K ~ 90 ~ x 0.5. . (7) If the Kic of bearing steel is 50 Kg ~ /mm , then from K> Kic =
50, for e, 0-4 mm it is seen that breakage occurs at once after a crack occurs in the notch. In addition, if the product hardness decreases, the Kic value increases, making breakage more difficult.
Therefore, the product hardness HRC should suitably be not less than 50. Practicalranges for (I) crack stopping hole diameter 2r, (II) notch bottom curvature Q, (III) wedge angle 28, (IV) notch shape 2~ and (V) notch angle ~ are-as follows.
(I) Crack stopping hole diameter 2r:
When breakage occurs in a V-form, the essential condition is that the crack should stop at the central hole 14 shown in Figures 3 and 4. Therefore, if the radius of the hole 14 is r, with an assumption made as shown in Figure 8 the magnification factor K of the front end of the crack when the latter propagates is given as follows.
K = v7~ F(a/b). ..(2) ~LOB1925 When the crack reaches the hole 1~, -the stress ~max in the inner periphery of the hole is as follows.
6max = ~r~~ . ... (1) If the initial notch curvature is ~, then K = 90 /~ Fc .. (8) In a practical range (b = 10-60, ac = 1-3), Fc = 1.4-0.7, When the crack reaches the hole 14, if the hole position is at the middle of the ring and b =0 5~ then from the equation (4) F(a/b) = 4.87.
K = 0 ~ x 4vr~ ~ 90 ~ x O.7 x ~
When considered under the condition that it should not break at once after the crack occurs (PCO.4)~
.
K > 90 v7~ x 0.7 x 4 ~ = ~ , ...(9) At the instance when the crack reaches the hole 14, the condition shown in Figure 9 is established and the magnification factor of the hole approximately doubles~ (The equation (2') changes to the equation (2)).
Therefore, K ~ 2 x 3~b- ' From the equation (1), ~81g~
2x2x3~ 3~
6maX ~ 180 ~--. r > 18.6 Thus, when the ring width is 18.6 x 4, the essential condition for the crack to s-top at the hole is tha-t the radius r of the hole is r ~ 1. When breakage occurs at once, ~ _ 0.4. It is seen that r increases with p. Since it is desirable that the hole diameter 2r be small from the standpoint of the rolling life, it is desirable tha-t the notch bottom curvature Q be small.
Suitably, the notch bottom curvature ~ should be not more than 0.4. However, if the notch bottom curvature ~ is too small, there is a possibility that a hardening crack will occur during heat treatment. Therefore, it is necessary to set a lower limit to the notch bottom curvature ~ and this will now be described.
(II) Notch bottom curvature p:
Assuming that the stress acting on a bearing material upon occurrence of a hardening crack is not less than 30 Kg/mm and that the heat treatment stress is not more than +5 Kg/mm2, the shape factor Kt is within the range Kt < 6 and no hardening crack will occur. This is taken as the notch bottom curvature region for prevention of hardening crack relative to the notch depth a and is shown in Figure 10. If the notch bottom curvature ~ is 0.4 mm, it follows that the notch depth a is allowed to have a value of up to 6 mm.
(III) Wedge angle 20:
Reduction of the wedge angle 2a is desirable since this reduces breaking load, but 20 < 20 <60 is suitable from the standpoint of the strength of the wedge. In addition, the hardness of the wedge is, of course, higher than that of the product.
(IV) Notch shape 2~:
As shown in Figure 11, 2~<28. Since the bearin~ and wedge .
:
8~L9~5 will be deforme~ whe~ subjected to wedge s-tress, i-t is necessary that there be a subs-tantial difference between the angles ~
and ~. The condition 2H - 2~ > 20 is suEficient for ordinary bearing rings though no-t necessarily definite since the size of wedge s-tress is influenced by the hardness of ma-terial.
Therefore, 2~ - 2~ is suitably 0 - 20~. The notch dep~h a varies with the wall thickness, etc., and the greater the notch depth, the more a~vantageous to splitting, bu-t when splitting operation is considered, 3~ a c 10 is suitable.
(V) Notch angle ~:
When splitting is effected simply with an angle ~ with respect to the axis, the stress magnification factor K of the front end of a crack varies with respect to ~ as shown in Figure 7. The smaller ~, the better since the breaking load is reduced. However, if the angle ~ is large, the stress concentra-tion caused by rolling contact is high~ Therefore, the angle - should be determined with consideration given to these two conditions. The stress concentration caused by rolling contact is also influenced by the curvature of the race and rolling bodies, and ~ should be determined with this point taken into account. That the breaking load at the time of splitting is high is not so serious a problem to the production of bear1ngs, after all, ~ is suitably 10 - 30.
As has been described so far, the first feature of the present invention lies in forming a notch in the inner or outer diameter of a bearing ring obliquely or in a V-form, heat-treating and grinding the ring, and exerting wedge stress along the notch by wedge type pressure-breaking means having an edge of larger angle than the notch, thereby obliquely splitting the bearing ring. Therefore, bearing rings can be easily split in any desired direction and the yield and productivity are high. More particularly since the breaking load re~uired when a wedge is used is little influenced by the wall thickness, though influenced _g_ by the notch bot-tom curvature, this method is very ef~ective even in the case o~ thick-walled articles. Further, even in -the case of a bearing ring which does not need to be split at an angle with respect to its axis, the use of wedge stress for breaking with a notch formed in an end surface for receiving a wedge is advantageous over the conventional ring breaking procedure.
Moreover, the arrangement is simple and very advantageous.
II. Next, another embodiment of the invention in which an end surface of a bearing ring is formed with a notch will now be described.
A bearing ring 21 shown in Figure 12 is formed with a notch 22 of substantially V-shaped cross-section for splitting purposes.
As shown in Figure 13, it is placed on a support 26 at a prç-determined angle and wedge stress is exerted along the notch 22 by wedge type pressure-breaking means 23, whereby the bearing ring is split in a direction obliquely crossing its axis. In this connection, the compressive load required for splitting an outer diameter 200~ x inner diameter 160~ x 100 mm width 100mm ring was about 13 tons.
A bearing ring 31 shown in Figure 14 has annular flanges 31a and 31b around its outer periphery. One end surface of the bearing ring 31 is formed with a notch of suhstantially V-shaped cross-section for splitting purposes while the other end surface ;~
is formed with a support surface 35 at right angles with the load line so that the ring 31 may be supported with the notch 32 vertically positioned. Therefore, the bearing ring 31, supported at its support surface 35 on the support 36 as shown in Figure 15, will be split by the wedge type pressure-breaking means 35 in a direction obliquely crossing the axis.
In this way, when oblique splitting is to be effected along the notch formed in the end surEace, not only the bearing ring 21 whose inner and outer diameters are straight but also the bearing ring 31 having flanges on its outer periphery can be --10- , simply split and that with hiyh precision.
In the case of splitting in a V-direction, as shown in igures 16 and 17, a bearing ring ~1 to be split is formed with a small hole 44 centrally of -the width of its peripheral surface and the opposite end surfaces o~ the ring 41 are formed with notches ~2a and 42b of V-shaped cross-section with their bottoms directed -toward the small hole 44. In other words, the small hole 44 is located at the intersection of the directions of propagation of the two notches. Further, the end surfaces are.
formed with support surfaces 45a and 45b so that the ring 41 may be supported against a load applied in the direction of the notch 45a or 45b. In splitting operation, as shown in Figures 18 and 19, the beari.ng 41, after being heat-treated and ground, is positioned at its one suppor-t surface 45a on the support 46 and subjected to wedge stress, causing the notch 42a to propagate to the small hole 44, whereupon the ring is turned upside down and positioned at its other support surface 45b on the support 46 and similarly the notch 42b is caused to propagate to the small . hole 44. As a result, the bearing ring 41 is split in a direction obliquely crossing its axis along the V-form split line. In : addition, in splitting operation, if a pin for pr~vention of deformation of the small hole during loading is inserted in the small hole 44,. splitting can be facilitated..
Figures 20 and 21 show the arrangement of notches 52a and : 52b and a small hole 54 formed in a bearing ring 51 which is to be split in a V-direction and which has annular flanges 51a and 51b, it being understood that if the small hole were located on the rolling surface, troubles would be caused. Thus, the small hole 5~ is located to avoid the rolling surface, and the notches 52a and 52b of V-shaped cross-section are formed in the end surfaces of the ring 51 in such a manner that the notch bottoms are directed toward the small hole 54. The opposite end surfaces are further formed with support surfaces 55a and 55b 33L9'~5 verticall~ with respect to the load lines so that the ring 51 may be effectively supported against a load applied in a direction of the notch 52a or 52b. The splitting operation for the bearing ring 51 i5 the same as for the previous ring 41.
The stress conditions established by wedge type pressure-breaking means 23, 33 and ~3 in the notches 22, 32, 42a and 42b, and 52a and 52b in the bearing rinys 21, 31, 41 and 51, respect-ively, are as follows.
First of all, the stress conditions in a flat plate S2 shown in Figure 22 will be taken as an example and used to make an approximation to the stress conditions in a bearing ring. With wedge stress represented by P, as in the case of the previous notch N1 formed in the peripheral surface, the stress 6max in the notch bottom is given by the following equations.
6max = 2K
K = ~__ x F(a/b) -4P F (a/b) 6 max = x ~r~
F(a/b) = a/ )3/2 - (1 a/b) 1/2 + 2.13 (1 - a/b) ; ~ ,, where ~: curvature of front end of notch K: stress magnification factor F(a/b): compensation factor F(a/b)/~ varies with the notch depth a, as shown in Figure 23. ;~
If ~in the equation (3) is constant and 6 max as the breaking stress is uniquely determined by the material, then as F/~
increases, P decreases. Therefore, the smaller the notch depth a, the greater the breaking load 6max and the more advantageous.
. . , ' '' ' ~
L08~9Z~
The relation between compressive load W and wedye stress P
depends upon wedge angle 20 and expressed by the follo~ing equation:
P = W2 co-t ~. Therefore~ the smaller the wedge angle 20, the more advantageous. However, the wedge angle should always be greater than the notch angle.
If the breaking s-tress is 180 Kg/mm2, then the stress magnification factor Kc for the front end of a crack when the latter occurs is as follows.
From the equation (1), Kc = 180 2 = 90 ~ (5) .. .. .
From the equation (2), Kc = - aCc Fc(a/b) ...(6~
On the other hand, the K for the front end of a crack when the latter propagates is as follows.
From the equations (1)-(6), 90~ F (a/b) For the range b = 50-600 and a = 2-12, as seen from Figure 12, ~ F(a/b) > o 4 Therefore, K ~ 90 ~ x 0.4.
If the Kic of bearing steel is 50 Kg ~ /mm2, from K ~ Kic = 50 in the equation (7) it is seen that for Q ~ 0.6 mm the bearing steel will be broken at once after a crack occurs in the notch.
In addition,practical ranges for (I) small-hole diameter - 2r, (II) notch bottom curvature Q, (III) wedge angle 20, and (IV) notch shape 2~ are as follows.
(I) Small hole diameter 2r:
When a bearing ring is to be split in a V-form, the essential condition is that the crack from one of the notches should stop at the small hole. Therefore, with the radius of the small hole represented by r, when the crack reaches the small hole, the stress 6max in the inner periphery of the small hole is as follows.
~L~81~25 Gmax = 2K . (1l) When -the initial notch bottom curvature is represented by ~, K = 90 ~ ~ FF ...(8j For practical range (b = 50-600 and a = 2-12), `= O.95-0.4 Fc When the crack reaches the small hole, if a/b = 0.5 with the small hole located at the middle of the ring end surface, then from the equation (4), F(a/b) = 4.87.
Substituting this in the equation (8) gives K = 90 ~ c~ x ~_7 > 90 ~ x 0.4 x ,~ '.
When considered under the condition that breakage should not occur at once after a crack occurs (Q < 0.6), then K ~ 90 ~ x 0 ~ 6 x 0.4 x ~ . - ... (9') ~;
. .
From the equations (1') and (g'), -~
2 x Jçr 2 7 ~;
- ~. . . -.
..r ~2.28/a Thus, when a is 228, the essential condition for the crack to stop at the small hole is that the radius r of the small hole is not less than 1 mm. In order for breakage to occur at once, ~ >0. 6r It is seen that r increases with ~. Since it is desirable that the hole diameter 2r be small from the standpoint of the rolling life, it is desirable that the notch bottom curvature ~ be small. Therefore, suitably, the notch bottom curvature Q should be not more than 0.6. ~lowever, if the notch bottom curvat~1re ~ is -too small, there is a possibility that a hardening crack will occur during heat treatment. Therefore, it is necessary to set a lower limit to the notch bo-ttom curvature ~.
(II) Notch bottom curvature Q:
Assuming that the stress acting on a bearing material upon occurrence of a hardening crack is not less than 30 Kg/mm2 and that the heat trea-tmen-t stress is not more than -~5 Kg/mm2, the notch shape factor Kt is within -the range Kt < 6 and no hardening crack will occur. This is taken as the notch bottom curvature ~ region for prevention of hardening crack relative to the notch depth a and is shown in a graph in Figure 13.
According to this graph, if the notch bottom curvature ~ is 0.4, it is seen that the notch depth a is allowed to have a value of up to 6 mm.
(III) Wedge angle 2a:
Reduction of the wedge angle 2~ is desirable since this reduces breaking load, but 20 _2~ C60 is considered suitable from the standpoint of the strength of the wedge.
(IV) Notch shape 2y~
As shown in Figure 14, the relation between wedge angle 2 and notch shape 2Y is always such that 2~ ~ 20. Since the bearing and the wedge will deform when subjected to wedge stress,.
it is necessary that there be a substantial difference between the angles ~ and ~. The condition 20 - 2~ > 20 is sufficient for ordinary bearing rings though not necessarily definite since the size of the wedge stress is influenced by the hardness of material.
The formation of notches 2, 12, 23, 24 and 33, 34 in bear-ing rings 1, 11, 21 and 31 to satisfy khe above conditions and the application of wedge type pressure-breaking means will facilitate splitting.
~ 319'~
As has been described so far, the second feature of the present invention lies in Eorming a substantially V~shaped notch in an end surface of a bearing ring at a predetermined angle with respect to the surface, heat-treating and grinding the ring and exer-ting wedge stress by wedge type pressure-breaking means having an edge of larger angle than the no-tch, thereby splitting the bearing ring in an oblique direction or V-direction.
According to this method, bearing rings can be easily split in ~ -any desired direction wlthout being influenced by the shapes of the inner and outer diameters. The yield and productlvity are high. Furthçr, loading a bearing ring at its end surface allows the use of a small-sized pressing device regardless of the size of the outer diameter of the bearing ring. The merits in practical use are very great.
While there have been described herein what are at present considered preferred embodiments of the several featur~s of the invention, it will ~e obvious to those skilled in the art that modilications and changes may be made without departing from the essence of the invention.
It is therefore to be understood that the exemplary embodi-ments thereof are illustrative and not restrictive of the ~^
invention, the scope of which i5 defined in the appended claims and that all modifications tha~ come within the meanlng and range of equivalency of the claims are intended to be included therein.
.~ . ' ' ' .
`; ' ' , . '
Claims (2)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of producing a split bearing ring said method comprising:
(a) forming a notch in one of the edge surfaces of said ring, said notch including at least a first portion having a V-shaped cross-section, wherein the axis bisecting the angle of the V is at an oblique angle with the axis of said ring;
(b) heat treating said ring;
(c) applying a wedge stress along said notch using a wedge type pressure breaking means, wherein the angle of the wedge of the breaking means is greater than the angle of the V-shaped cross-section of said notch, whereby said ring is split along said notch.
(a) forming a notch in one of the edge surfaces of said ring, said notch including at least a first portion having a V-shaped cross-section, wherein the axis bisecting the angle of the V is at an oblique angle with the axis of said ring;
(b) heat treating said ring;
(c) applying a wedge stress along said notch using a wedge type pressure breaking means, wherein the angle of the wedge of the breaking means is greater than the angle of the V-shaped cross-section of said notch, whereby said ring is split along said notch.
2. A method of producing a split bearing ring as set forth in claim 1 including forming said notch with a second portion in the edge surface of said ring, said second portion having a V-shaped cross-section, said first portion being formed in one of the legs of the V of the second portion.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA342,256A CA1081925A (en) | 1976-09-17 | 1979-12-19 | Method of producing split bearing rings |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP51-112047 | 1976-09-17 | ||
| JP11204776A JPS5337262A (en) | 1976-09-17 | 1976-09-17 | Manufacturing method of split bearing ring |
| CA278,596A CA1073645A (en) | 1976-09-17 | 1977-05-17 | Method of splitting bearing rings |
| CA342,256A CA1081925A (en) | 1976-09-17 | 1979-12-19 | Method of producing split bearing rings |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081925A true CA1081925A (en) | 1980-07-22 |
Family
ID=27165084
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA342,256A Expired CA1081925A (en) | 1976-09-17 | 1979-12-19 | Method of producing split bearing rings |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1081925A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113182629A (en) * | 2021-05-08 | 2021-07-30 | 洛阳轴承研究所有限公司 | Split bearing ring processing tool |
-
1979
- 1979-12-19 CA CA342,256A patent/CA1081925A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113182629A (en) * | 2021-05-08 | 2021-07-30 | 洛阳轴承研究所有限公司 | Split bearing ring processing tool |
| CN113182629B (en) * | 2021-05-08 | 2023-06-23 | 洛阳轴承研究所有限公司 | Split bearing ring processing tool |
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