US2965942A - Buckle construction for safety belts - Google Patents

Description

Dec. 27, 1960 A. G. CARTER BUCKLE CONSTRUCTION FOR SAFETY BELTS 4 Sheets-Sheet 1 Filed Jan. 18. 1956 [NVEN TOR Andrew G. Coffer Dec. 27, 1960 A. G. CARTER BUCKLE CONSTRUCTION FOR SAFETY BELTS 4 Sheets-Sheet 2 Filed Jan. 18 1956 IN V EN TOR. An drew G. Car fer Dec. 27, 1960 CARTER I 2,965,942

- BUCKLE. CONSTRUCTION FOR SAFETY BELTS Filed Jan. 18. 1956 4 Sheets-Sheet 5 fig- 63 20 Andrew G. Carfer Q am??? K Dec.27,1960 A. G. CIZAIR'II'ERI f 2,965,942

BUCKLE CONSTRUCTION FOR SAFETY BELTS Filed Jay. 18. 1956 I v '4 Sheets-Sheet 4 fig. /2.

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. r f flgi Afforne Andrew affer United States Patent BUCKLE CONSTRUCTION FOR SAFETY BELTS Andrew G. Carter, 2930 Lake Drive S.E., Grand Rapids, Mich.

Filed Jan. 18, 1956, Ser. No. 560,020

8 Claims. (Cl. 24-170) This invention relates to the construction of buckles for safety belts, and provides an improvement over the invention described and claimed in my application Serial Number 511,388, filed in the United States Patent Office on May 26, 1955, which issued as Patent No. 2,904,866 on September 22, 1959.

Further research and experiment in the performance of these units has established the existence of a rather dangerous situation in practically all safety-belts that are controlled through the action of a release lever. It appears to be well within the range of possibility that the inertia of the lever itself, during crash conditions, may be sufi'icient to swing the lever to the release position. Conventional lever design provides for the pivoting of the lever adjacent one end, and at a position considerably removed from the center of gravity of the lever. The usual position of the buckle in the front of the wearer positions the buckle so that the sudden deceleration accompanying the crash will cause the inertia of the lever to exert a considerable opening moment about its pivot point, which may become sufiicient in magnitude to operate the release mechanism.

This invention provides a buckle mechanism which is relatively free from the possibility of accidental or inertiaoperated unlocking. The relative freedom of this buckle mechanism from the effects of inertia is accomplished by making the release lever itself as light as possible, and by freeing that member from the direct responsibility of maintaining the two buckle components in an engagement. The cam member which actually holds the two buckle components together is formed of relatively heavier material, but the center of gravity of this member is close enough to the axis of rotation so that the inertia effect becomes negligible. A relatively light spring can be used to bias the cam member into the locking position, with a somewhat heavier spring being used on the release lever. With the use of a light release lever, a spring can be used which will hold the lever against the effects of inertia without unduly amplifying the opening force required to manually disengage the buckle. The use of a much lighter spring on the cam, and the independent movement of the cam with respect to the opening lever, permits the buckle components to be shoved together into engagement with a minimum of force.

A mechanism embodying this invention also provides for the insertion and engagement of the two buckle components without movement of the release lever, this arrangement permitting the user to grasp both buckle components firmly as they are shoved into engagement. The grip of the hand on the buckle component equipped with the lever does not need to allow for movement of the lever during the coupling operation.

This invention also provides a very effective arrangement for adjusting the length of the belt. The function of the releasing lever becomes two-fold according to this invention. It not only functions as a controlling member for the release mechanism, but also controls the 2 engagement of the buckle unit with the belt itself. When the release lever is in the extended or release position, it becomes possible to adjust the belt length, or tension. With the release lever in the normal position, the tension adjustment is secure against displacement.

- The several features of this invention will be analyze in detail through the discussion of the particular embodi- In the tion corresponding to a partially-completed engagement.

Figure 6 is a perspective view showing the details of the collar used for positioning the spring ends.

Figure 7 is a perspective view showing the details of the cam member responsible for holding the buckle components in engaged position.

Figure 8 shows a bottom view of the engaged buckle components, and illustrating the normal position of the belt-tension adjustment. v Figure 9 is a partial section in elevation shownon an enlarged scale from that of Figure 8, showing the belttension adjustment in the normal position.

Figure '10 illustrates the unit shownin Figure 9,with the release lever in the open position, and the tension, adjustment free to accommodate relative movement of the belt and the buckle component.

Figure 11 is a section taken on the plane 11-11 of Figure 10.

Figure 12 is a bottom view of a modified form of the invention.

Figure 13 is a side view of the modification illustrated in Figure 12.

Figure 14 is a section taken on the plane 1414 of Figure 13. v 7 Referring to the drawings, the buckle component 20 is an essentially flat plate provided with the slot 21 for receiving a loop of the belt 22. The openings 23 and 24 are formed to engage parts of the opposite buckle component generally indicated at 25 for the transfer of belt tension. 7

Referring particularly to Figures 2 and 3, the buckle component 25 has a frame which includes the relatively fiat base 26 and the parallel side flanges 27 and 28. The base 26 is provided with the preferably integrally formed portions 29 and 30 for co-operation with the openings 23 and 24, respectively, of the buckle component 20. The positioning of the openings 23 and 24 on the component 20, and the formed portions 29 and 30 on the component 25, may be reversed if desired.

In particular, the surfaces 31 of the projections 29 and 30 are responsible for the transfer of belt-tension from one buckle component to the other. These surfaces are preferably slanted with respect to a normal to the base; 26 at an angle of 20 to 25 degrees, if the members are to be left in their original condition established by the forming dies. This angle can be regarded as having critical limits-of between fifteen and thirty degrees from the normal, with the greater angles causing an increased tendency for the buckle component 20 to slip out of the engagement with the projections 29 and 30. As this tendency increases, the loading on the locking mechanism correspondingly increases to the point where distortion becomes objectionable. If a finish coating of chrome plate is used, accompanied by a high degree of polish, 15 to 20 degrees becomes a critical range. Below fifteen degrees, any roughness resulting from manufacture orfrom subsequent abrasion will interfere with release under load, as when removing an injured passenger from a wreck. Over twenty degrees applies excessive loading to the frame, shaft, and to the mating buckle component. These critical angle ranges seem to reflect particular rela tionships between the coefficients of friction involved and the deflection characteristics of the illustrated structure. Excessive thicknesses of material of the buckle components would make possible greater angles of deviation of the active surfaces from the perpendicular, but observance of the critical ranges makes possible greater economy and minimizes weight. It should be noted that the openings 23 and 24 in the buckle component 20 are beveled from both sides along the edges 32 and 33 so that these surfaces will conform to the surfaces 31 regardless of the orientation in which .the component 20 is shoved into engagement with the component 25.

The flanges 27 and 28 provide for the mounting of the shaft 34, the hexagonal head 35 of the shaft being received in the similarly-shaped opening in the flange 27 to assure non-rotative positioning of the shaft with respect to the frame of the buckle. A cam member 36 (refer to Figure 7) is rotatably mounted on the shaft 34, and consists of the opposite cam portions 37 and 38 connected by the cross bar 39. The formation of the cam portions 37 and 38 is selected so that a small amount of clearance is provided for the belt buckle component 20 when it is inserted in the fully engaged positions shown in Figure 2. The purpose of the cam portions 37 and 38 is to maintain the projections 29 and 30 in engagement with the openings 23 and 24. Referring to Figure 3, it is important that the flanges 27 and 28 of the frame, the cam portions 37 and 38, and the projections '29 and 30 are grouped in such a manner that (a) the earns 37 and 38 areas close as possible, respectively, to the flanges 27 and 28 and (b) the abutments 29 and 30 are as close as practical to. the cam portions 37 and 38, respectively. If the projections 29 and 30 are positioned closer to the center of the device,a strong tendency takes place for the coupling member 20 to bow upward (and the frame downward) in the center in response to the forces generated atthe surfaces 31'. The distance from the cam portions 37 and 38 to the flanges 27 and 28, respectively, determines the magnitude of the bending moment imposed on the shaft 34. If the engagement of the cam portions 37 and 38 is displaced toward the center of the unit, the same generation of forces will create an increase in bending moment which will cause the shaft to bow upward, and thereby tend to permit the release of the component 20 from the projections 29 and 30. In summary, minimizing the bending moment on the shaft 34 dictates the placement of the cam portions 37 and 38 close to the flanges 27 and 28, and the minimizing of the distorting moment in the frame and in the component 20 requires that the engagement of the openings 23 and 24 with the projections 29 and 30 be as close as possible to the earns 37 and 38, respectively. The arrangement shown in Figure 3 appears to be the most effective manner of satisfying these two requirements.

The cam portions 37 and 38 are formed with small ledges, as shown at 40 and 41 in Figure 7, which are disposed to abut the edge 42 of the release lever 43. A torsion spring 44 has one of its ends 45in engagement with the cross-bar 39 of the cam member 36, the opposite end 46 of the spring 44 being positioned by the lug 47'of the collar 48. The collar 48 is rotatably mounted on the shaft 34, and has a second lug 49 which is engaged by the spring- 50.; The opposite end of the spring 50 from the collar 48 is turned radially inward accuses with respect to the shaft 34 at 51, where it engages the groove 52 in the shaft. The net result of this arrangement is that the spring 50 is held at its end 51 in a relationship which is fixed with respect to the frame of the buckle, as a result of the non-rotative mounting of the shaft 34. The collar 48 is biased in such a direction that the lug 49 engages the edge 42 of the release lever 43 to urge it toward closed position. The spring 50 is stronger than the spring 44, and the inter-action of the spring 50 and the release lever 43 in positioning the collar 48 results in the positioning of the end 46 of the spring 44 in a relationship which is fixed with respect to the lever 43. The cam member 36 is therefore biased with respect to the lever.

In the assembly of the device, the shaft 34 is inserted progressively from the left, as shown in Figure 3, so that the lever and cam portions are traversed in sequence. After the end of the shaft has engaged the lever and the cam member at one side, the spring 44 is preferably inserted and placed in the position in which it deviates sufficiently from the axis of the assembled position that the collar 48 may be rotated to properly tension the spring 44. When the shaft is then swung into its proper alignment, the collar 48 will have its angular position about the shaft 34 determined by the edge of the release lever 43. The spring 50 may then be assembled in position, and the shaft 34 may be rotated while in a position sufiiciently withdrawn to the left, as shown in Figure 3, for the hexagonal head 35 to be free of the similarlyshaped recess in the flange 27. Such rotation creates the necessary tension in the spring 50, after which the shaft may be shoved into the position shown in Figure 3, followed bythe insertion of the snap ring 53. Due to the relatively thin material of the flanges 55 and 56 of the release lever 43, bushings 57 and 58 are forced into position in these flanges in order to give a greater bearing area in engagement with the shaft 34. it is preferable that the bushings 57 and 58 be hardened.

Referring to Figure 4, the release of the buckle involves the movement of the lever .3 in a clockwise direction to the point that the cam member 36 is driven (at the ledges 4i and 41) in a similar direction a sufiicient amount to permit the coupling member 20 to rise over the projections 29 and 30, and thereby be free to be withdrawn. The re-engagement of the coupling members takes place as shown in Figure 5. As the coupling member 20 is pushed to the left, the cam portions 37 and 38 are rotated by the force applied by the end 59 of the coupling member 24 The movement of the cam members a sufiicient amount to permit the insertion of the coupling member 28 takes place without any corresponding movemeut of the lever 43, and the engagement is opposed only by the spring 44. During the engagement of the coupling members, the ledges 4t) arid 41 swing away from the edge 42 of the locking lever.

Referring particularly to Figures 8 through 11, inclusive, the invention also provides a very effective length adjustment arrangement. The base 26 of the frame is cut out as shown at 60, and receives a knurled pin 61 having parallel slots in the opposite ends, respectively, which engage the sheet material forming the base portion 26. An enlarged portion is provided in the cutout at 62 to permit the insertion of the pin 6f, after which the pin is slid to the portion 63' of the cutout. After the insertion of the pin in the position illustrated in Figure 8, a pair of drive pins 64 and 65 are forced through suitable openings in the flanges 27 and 28, and which project on the inside of the flanges a sufficient amount to bar the movement of the pin 61 into the area of the enlarged cutout 62. This arrangement is best shown in Figure 11. The slots 66 in the opposite ends of the pin 61 permit a sliding movement of the pin within the confines of the portion 63 of the cutout 60.

The belt section 67 is looped around the pin 61; and when the release lever 43 is in the position shown. in

Figmre 10, the belt may be moved with respect to the pin 61. After the correct tension adjustment has been made, and the release lever 43 returned to the closed position shown in Figure 9, tension applied to the upper portion of the belt section 67 will tend to cause the pin 61 to move to the left and grip the belt portion 68 between the pin 61 and the edge of the cutout 60. The degree of gripping at this particular point is relatively slight, but is sufiicient to maintain a firm engagement of the belt with the knurled periphery of the pin 61 to create the effect of a jamming action which prevents slippage of the belt as long as the release lever 43 holds the belt in the position shown in Figure 9. It may be noted that the belt may be shortened while the lever is in the down position by pulling on the lower portion 69 of the belt, and that the jamming action referred to above does not take place in response to such pulling movement. When the upper section 70 of the belt 67 is pulled, however, no movement takes place unless the direction of pull is at such an angle that the lever 43 must be elevated to provide for it. In fact, the lever must be held free of the upper section 70 of the belt in order to loosen belt tension, since the pressure of the lever alone against the belt will ordinarily suffice to create enough action against the periphery of the pin 61 to prevent movement of the belt. When the lever is held completely free of the belt, as shown in Figure 10, the upper portion 70 may be pulled out to increase the efiective length of the belt. Referring to Figures 12, 13, and 14, a modified form of the invention is shown which has the primary purpose of permitting the tension adjustment of the belt with one hand. In this modification, a frame 71 is provided with an opening 72 in the base similar to the opening 60 in Figure 8. A loop of belt material consisting of the upper strand 73 and the lower strand '74 surrounds the knurled pin 75. Figure 14 most effectively illustrates the engagement between the pin 75 and the frame 71 at the edge of the opening 72. The pin 75 is slotted on a generally diametral plane, as indicated at 76, and this slot communicates with the cylindrical periphery of the pin through the slot 77. The width of the slot 77 is such that the pin 75 may be inserted into engagement with the frame at the wide portion of the opening 72, after which movement into this area is prevented by the presence of the drive pins 78 which are similar in function to the pins 64 and 65 shown in Figure 8.

Since the jamming action which effectively prevents slippage of the belt around the knurled pins 75 and 61 must be accompanied by the confinement of the lower belt sections between the edge of the opening 72 and the pin, it follows that movement of the pin in a direction to release such confinement would permit the belt to be adjusted to increase the effective length. To make such adjustment possible without disengaging the buckle, a positioning member 79 is pivotally mounted on the frame 71 with the rivets 80 and 81. The positioning member 79 consists of a pair of opposite cam portions 82 and 83 connected by a crossbar 84. Figure 13 illustrates the nor mal position of the unit when the belt is under tension, and it will be noted that a small amount of clearance exists between the cam portions 82 and 83 and the pin 75. As the positioning member 79 is rotated in a counterclockwise direction'as shown in Figure 13, however, the increase in radius of the cam portions 82 at the point indicated at 85 in Figure .13 comes to bear against the pin 75, and displaces it to the right. Such displacement effectively removes the jamming action previously existing between'the pin, the belt, and the edge of the opening 72. Manipulation of the positioning member is most effectively accomplished through the insertion of the thumb under the crossbar 84, a maneuver which can be accomplished easily with one hand without disengagement of the buckle components. 1

The extension of the ends of pin 75 beyond the sides of he m a o m v it c i s oz's pthepip d e t y 6 with the fingers and move it with respect to the frame to release the jamming action. This maneuver requires somewhat greater strength and also greater dexterity than does the operation of the positioning member 79.

The particular embodiments of the present invention which have been illustrated and discussed herein are for illustrative purposes only and are not to be considered as a limitation upon the scope of the appended claims. In these claims, it is my intent to claim the entire invention disclosed herein, except as I am limited by the prior art.

I claim:

1. A safety-belt buckle, comprising: a first coupling member, said first coupling member being in the form of a substantially flat plate and having belt-engaging means and a pair of apertures disposed opposite each other in a direction parallel to the width of a belt normally engaged by said first coupling member; and a second coupling member, said second coupling member including a frame having a substantially flat base portion and lugs projecting from said base portion and adapted to engage said apertures, said frame also including opposite parallel flanges disposed on the same side of said base portion as said lugs and with said lugs therebetween, a shaft extending between said flanges and non-rotatively mounted therein, a cam member rotatably mounted on said shaft between said flanges, said cam member having opposite similar cam portions at the ends thereof and a bar portion extending between said vcam portions, a lever member rotatably mounted on said shaft and having spaced flanges received between said frame flanges and cam member respectively and also having a driving portion disposed to engage and induce rotation of said cam, member on rotation of said lever member from a position adjacent said base portion toward a position perpendicular thereto, first biasing means, said first biasing means urging said lever toward a position against said base portion and including a first torsion spring surrounding said shaft and having one end thereof fixed with respect to said shaft, said first biasing means also including a collar rotatably mounted on said shaft and having a portion in driving engagement with said lever, said first torsion spring having one end thereof connected to said collar, second biasing means, said second biasing means urging said cam portion against said lever member driving portion and including a second torsion spring surrounding said shaft and, having one end thereof bearing against said cam member and the opposite end thereof positioned by said collar member, said first torsion spring being of greater strength than said second torsion spring, said cam member being formed to maintain the engagement of said first coupling member with said lugs with said lever adjacent said base portion, and provide clearance for the escape of said first coupling member from said lugs on rotation of said' lever to a position approaching perpendicularity to said base portion, said second coupling member also having a belt-receiving portion.

2. A safety-belt buckle, comprising: a first coupling member, said first coupling member being in the form of asubstantially fiat plate and having belt-engaging means and a pair of apertures; and a second coupling member, saidsecond coupling member including a frame having a sub stantially flat base portion andlugs projecting from said base portion and adapted to engage said apertures, said frame also including opposite parallel flanges disposed on the same side of said base portion as said lugs and withsaid lugs therebetween, a shaft extending between saidflanges and non-rotatively mounted therein, a-cam memberrotatably mounted on said shaft between said flanges, said: cam member having opposite similar cam portions at the ends thereof and a bar portion extending between said cam portions, a lever member rotatably mounted on saidshaft and having spaced flanges received between said frame flanges and cam member respectively and also having a drivingportion disposed-to engage and induce-rotationof said-cam member on rotation of said lever mew 7 her from a position adjacent said base portion toward a position perpendicular thereto, first biasing means, said first biasing means urging said lever toward a "position against said base portion and including a first torsion spring surrounding said shaft and having one end thereof fixed with respect to said shaft, said first biasing means also including a collar rotatably mounted on said shaft and having a portion in driving engagement with said lever, said first torsion spring having one end thereof connected to said collar, second biasing means, said 's'eco'nd biasing means urging said cam portion against said lever memberv driving portion and including a second torsion spring surrounding said shaft and having one end thereof bearing against said cam member and the opposite end thereof positioned by said collar member, said cam member being formed to maintain the engagement of said "first coupling member with said logs with said "lever adjacent said base portion, and provide clearance for the escape of said first coupling member from said lugs on rotation of said lever to a. position approaching perpendicularity to said base portion, said second coupling member also having a beltreceiving portion.

3. A safety-belt buckle, comprising: a first coupling member, said first coupling member being in the form of a substantially flat plate and having belt-engaging means and a pair of apertures; and a second coupling member, said second coupling member including a frame having a substantially flat base portion and lugs projecting from said base portion and adapted to enaage'said apertures. said frame also including opposite parallel flanges disposed on the same side of said base portion as said lugs and with said lugs therebetween, a shaft extending between said fianges and non-rotatively mounted therein, a cam member rotatably mounted on said shaft between said flanges, a lever member rotatably mounted on said shaft and having a driving portion disposed to engage and induce rotation of said cam member on rotation of said lever member from a position adjacent said base portion toward a position perpendicular thereto, first biasing means, said first biasing means urging said lever toward a position against said base portion and including a first torsion spring surrounding said shaft and having one end thereof fixed with respect to said shaft, second biasing means, said second biasing means urging said cam portion against said lever member driving portion and including a second torsion spring surrounding said shaft and having one end thereof bearing against said cam member and the opposite end thereof positioned by said lever member, said cam member being formed to maintain the engagement of said first coupling member with said lugs with said lever adjacent said base portion, and provide clearance for the escape of said first coupling member from said lugs on rotation of said lever to a position approaching perpendicularity to said base portion, said second coupling member also having a belt-receiving portion. g

4. A safety-belt buckle, comprising: a first coupling member, said first coupling member having belt-engaging means and at least one aperture; and a second coupling member, said second coupling member including a frame having a base portion and a lug projecting from said base portion and adapted to engage said aperture, said frame also including opposite parallel flanges disposed on the same side of said base portion as said lug and with said lug therebetween, a shaft extending between said flanges, a cam member rotatably mounted on said shaft between said flanges, a lever member rotatably mounted on said shaft and having a driving portion disposed to engage and induce rotation of said cam member on rotation of said lever member from a position adjacent said base portion toward a position perpendicular thereto, first biasing means, said first biasing means urging'said'lever toward a position against said base portion, second biasing means, said second biasing means urging said cam member to locking position to maintain the engagement of said lug and aperture, said cam member being formed tomaint-ain the engagement of said first coupling member with said lug with said lever adjacent said base portion, and provide clearance for the escape of said first coupling member from said lug on rotation of said lever to a position approaching perpendicularity to said base portion, said second coupling member also having a belt-receiving portion.

5. A safety-belt buckle, comprising! a first coupling member, said first coupling member having belt-engaging means; and a second coupling member, said first and second coupling members having at least one interengageable lug and lug-receiving portion respectively, and said second coupling member including a frame having opposite parallel flanges, a shaft extending between said flanges, a cam member rotatably mounted on said shaft between said flanges, a lever member rotatably mounted on said shaft and having a driving portion disposed to engage and induce rotation of said cam member on rotation of said lever member from a position adjacent said frame to ward a position perpendicular thereto, first biasing means, said first biasing means urging said lever toward a position against said frame, second biasing means, said second biasing means urging said cam member against said lever member to maintain engagement of said lug and lug-receiving portion, said cam member being formed to maintain the engagement of said lug and lug-receiving portion with said lever adjacent said frame, and provide clearance for the escape of said lug from said lug-receiving portion on rotation or said lever to a position approaching perpendicularity to said frame, said second coupling member also having a belt-receiving portion.

6. A safety-belt buckle, comprising: a first coupling member, said first coupling member having belt-engaging means; and a second member, said first and second coupling members having at least one interengageable lug and lug-receiving portion respectively, and said second coupling member including a frame having opposite parallel flanges, a shaft extending between said flanges, a cam member rotatably mounted on said shaft between said flanges, a lever member rotatably mounted on said shaft and having a driving portion disposed to engage and induce rotation of said cam member on rotation of said lever member from a position adjacent said frame toward a position perpendicular thereto, first biasing means, said first biasing means urging said lever toward a position against said frame, second biasing means, said second bias-. ing means urging said cam member toward locking position to maintain engagement of said lug andlug-receiving portion, said cam member being formed to maintain the engagement of said lug and lug-receiving portion with said lever adjacent said frame, and provide clearance for the escape of said lug from said lug-receiving portion on rotation of said lever to a position approaching perpendicularity to said frame, said second coupling member also having a belt-receiving portion.

7. A safety-belt buckle, comprising: a first coupling member, said first coupling member having belt-engaging means; and a second coupling member, said first and second coupling members having at least one interengageable lug and lug-receiving portion respectively, and said second coupling member including a frame having opposite parallel flanges, a shaft extending between said flanges, a cam member rotatably mounted on said shaft between said flanges, a lever member rotatably mounted on said frame and having a driving portion disposed to engage and induce rotation of said cam member on rotation of said lever member from a position adjacent said frame toward a position perpendicular thereto, first biasing means, said first biasing means urging said lever toward a position against said frame, second biasing means, said second biasing means urging said cam member toward locking position to maintain engagement of said lug and lug-receiving portion, said cam member being formed to maintain the engagement of said lug and lug-receiving portion with said lever adjacent said frame, and provide clearance for the escape of said lug from striding-receiving portion on rotation of said lever to a position approaching perpendicularity to said frame, said second coupling member also having a belt-receiving portion.

8. A safety-belt buckle, comprising: a first coupling member, said first coupling member having belt-engaging means and a pair of apertures disposed opposite each other in a direction parallel to the width of a belt normally engaged by said first coupling member; and a second coupling member, said second coupling member including a frame having a base portion and lugs projecting from said base portion and adapted to engage said apertures, the interengaged surfaces on said lugs and said first coupling member being disposed at an angle to a normal to the axis of belt tension of between fifteen and twenty degrees for the control of releasing tendencies, said frame also including opposite parallel flanges disposed on the same side of said base portion as said lugs and with said lugs therebetween, a shaft extending between said flanges, a cam member rotatably mounted on said shaft between said flanges, said cam member having opposite similar cam portions at the ends thereof and a bar portion extending between said cam portions, a lever member rotatably mounted on said shaft and having a driving portion disposed-to engage and induce rotation of said cam member jacent said base portion toward a position perpendicular thereto, first biasing means, said first biasing means urging said lever toward a position against said base portion, second biasing means, said second biasing means urging said cam portion against said lever member driving portion, said carn member being formed to maintain the engagement of said first coupling member with said lugs with said lever adjacent said base portion, and provide clearance for the escape of said first coupling member from said lugs on rotation of said lever to a position approaching perpendicularity to said base portion, said second coupling member also having a belt-receiving portion.

References Cited in the file of this patent UNITED STATES PATENTS 805,573 Messenger Nov. 28, 1905 866,535 Sudell Sept. 17, 1907 1,775,174 Roy Sept. 9, 1930 2,538,641 Eisner Jan. 16, 1951 2,622,293 Wermlinger Dec. 23, 1952 2,904,866 Carter Sept. 22, 1959

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