JP2000326263A - Rotary hammer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the intrusion of dust from an area of a bit into a cylinder by providing a striking member capable of being driven corresponding to the reciprocation of a piston slidable in the cylinder by the air cushion between the piston and the striking member, with a member capable of striking an end of a bit held in a hammer. SOLUTION: A rotary hammer comprises a cylinder 2 mounted in a housing 1 and a tool holder 4 mounted at the front and back of the housing 1. The cylinder 2 includes a piston 6 connected to a spindle of an electric motor directing in the vertical direction through a trunion 8 accmodated in the cylinder 2 and a crank arm 10. The cylinder 2 has a function of the combined ram 12 and bead piece, is connected with the piston 6 by the air cushion formed therebetween, and accomodates the ram 12 or the striking member slidable along a shaft of the cylinder 2 under the operation of the piston. A web 22 provides a seal substantially not intercepting the axial sliding of the ram 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotary hammer, and more particularly, to a hammer incorporating an air cushion hammer mechanism.

[0002]

2. Description of the Related Art Such a hammer is slidably installed in a cylinder and a tool holder capable of holding a hammer bit or a chisel bit to act on a work object. And an air cushion hammer mechanism including a ram and a piston for reciprocating the ram within the cylinder by an air cushion between the ram and the ram. The ram strikes the beatpiece, which strikes the rear or adjacent end of the chisel bit or hammer inserted into the tool holder, thereby transmitting the strike from the ram to the bit. Beatpieces generally have a much smaller stroke in a cylinder than a piston or ram does, and typically only move a few millimeters when the hammer is used in its working mode. .

[0003] Beatpieces have many purposes. One of the reasons for the existence of the beat piece is that it forms a barrier against the inflow of dust from the work object via the tool holder to the air cushion mechanism. This is a particularly important feature, as significant amounts of dust are generated from the work piece by the action of the hammer, otherwise the seal between the reciprocating component and the cylinder will be of poor quality, It is important to keep dust out of the air cushion mechanism as friction between the cylinder and the cylinder increases. However, the presence of the beatpiece has the disadvantage that it causes a reduction in the impact energy transmitted to the tool. For example, it is estimated that about 20-30% of the impact energy is lost due to the presence of the beat piece.

[0004]

It has been proposed to provide a hammer without any beat pieces, in which, for example, Hilti A
G. FIG. The ram strikes the end of a bit that is inserted into the tool holder, as described in CA-950288 of U.S. Pat. However, such a hammer has the disadvantage that it is necessary to provide a sufficient seal between the ram and the cylinder to prevent dust from entering the air cushion, Inevitably causes frictional deceleration of the ram, thereby reducing the strength of the impact on the bit held in the tool holder. The effect of the seal on reducing the impact strength is greater than the effect of the seal placed between the beatpiece and the cylinder, because the stroke of the ram is much greater than that of the beatpiece.

[0005]

According to one aspect, the present invention is directed to a cylinder, a piston capable of reciprocating within the cylinder, and a slidably mounted piston within the cylinder between the piston and the striking member. And a striking member capable of striking the end of the bit held in the hammer because the striking member can be driven in response to the reciprocating motion of the piston by the air cushion. Provide a hammer having the feature of having a web of a soft, impermeable material extending from a striking member to prevent ingress of dust from the area of the bit into the cylinder.

[0006] More advantageously, given that the web acts as a barrier against the backflow of dust from the tool holder to the cylinder, the web may be a part of the housing in front of the cylinder or behind the tool holder. The web of flexible material preferably extends radially from the striking member to the cylinder, even though it can extend to the end. In addition, the material of the web should have sufficient slack, i.e. extra length, so that the striking member allows axial sliding in its entire range within the cylinder. Such axial movement generally corresponds to the stroke of the ram in a conventional hammer, rather than the stroke of a beatpiece.
In this regard, the striking member may hereinafter be referred to as a ram. Such extra length is most conveniently formed, for example, by folding the web in a concertina (a type of accordion).

[0007] The hammer according to the present invention has a striking force, since the striking energy applied to the bit is not reduced by the presence of the beat piece, nor by the presence of a sliding sealing element placed between the ram and the cylinder. It has the advantage that energy can be maximized.
This form of seal avoids having to provide all other seals, such as a sliding seal between the striking member and the cylinder, which would reduce the strength of the impact on the bit, so that the web is It is preferable to form only a seal against the inflow of dust into the air. Such an arrangement is particularly advantageous in the case of a hammer that is powered by a battery rather than the main power, in terms of more efficient use of power, and thus increasing the operating time of the hammer during charging of the battery.

Another problem associated with hammers that use an air cushion hammer mechanism is that the striking member remains in a position in front of the hammer when the hammer is separated from the work piece. Generally, the hammer mechanism is required to continue running while the hammer bit is being applied to the work piece, but if the bit is disengaged from the work piece, the piston will The hammer mechanism must stop, despite continuing to reciprocate in the cylinder. To move the beatpiece and / or bit to the forward position, the striking member strikes the beatpiece if a beatpiece is present, or strikes the bit if no beatpiece is present, and It is necessary to fasten itself and it is also preferred that it be held in that position. In that position,
Since the vent holes in the cylinder are normally exposed so as not to activate the air cushion, the operation of the hammer is continued only when the tool bit re-engages the work piece.

This is achieved according to another aspect of the present invention which provides a hammer capable of receiving a tool bit for acting on a work object, the hammer reciprocating within the cylinder. An air cushion hammer mechanism comprising a piston capable of being moved and a striking member slidably mounted within the cylinder and driven by the piston using an air cushion between the piston and the striking member, The hammer is characterized in that it comprises an arrangement for fastening the striking member in a position in front of it, the hammer comprising a resilient ring mounted in the cylinder and extending around the striking member. , Since the striking member has an intermediate portion of varying diameter, at a given position of the striking member within the cylinder, The inter contacts the ring with a resilient,
A substantially closed chamber is formed in a cylinder extending around the resilient ring, and further forward movement of the striking member reduces the volume of the chamber;
The striking member is tightened by the elastic ring.

The middle portion of the striking member preferably increases in diameter in the rearward direction, so that forward movement of the striking member radially expands the elastic ring. This radial expansion, which opposes the resilience of the ring, makes the ring counteract the forward movement of the striking member and increases the radius due to the elevated air pressure acting on the radially outer surface of the ring. The force inward in the direction facilitates the action of the ring clamping the striking member. The striking member preferably has, for example, a waist in the shape of a groove extending in the circumferential direction, and when the striking member is at the front position and the elastic ring can hold the striking member at that position, the hammer is used. Until re-engagement with the work object, the waist can receive an elastic ring.

When the striking member is detained, its forward movement is preferably dampened, and it is preferred that the striking member does not return to fly rearward due to the pressure of the air in the chamber, for the reason that This causes a reactivation of the hammer mechanism. Therefore, the bleed hole
It is formed in a cylinder and discharges air from the chamber when the striking member is in a forward position.

[0012] The need to detain and hold the striking member depends on whether the striking member acts on a beatpiece that transfers striking energy from the striking member to the bit, or whether the striking member has no intermediate beatpiece. And whether the bit is hit directly or not, this form of the invention is compatible with both forms of hammer.

Another problem which arises, in particular, with hammers that do not have individual beat pieces is the problem of shock or impact being reflected back along the tool bit by the work piece. As it is highly desirable to mitigate such hits, they are dampened to prevent discomfort and injury to the driver of the hammer and reduce the risk of damage to the hammer. Thus, in accordance with yet another aspect of the present invention, there is provided a hammer having a tool holder and a housing capable of receiving a tool bit for acting on a work object, wherein the hammer comprises one bit. Retained in the tool holder by the above fixing elements, the hammer comprises one or more cushion elements placed between the tool holder and the housing, so that it is reflected back along the bit by the work object. The impact is transmitted to the housing via the tool holder and the cushion element. The reverse impact is preferably transmitted from the bit to the tool holder by a fixing element. One form of a rotary hammer is described below by way of example with reference to the accompanying drawings, which are schematic cross-sectional views through a section of the hammer along the cylinder axis of the hammer.

[0014]

Referring to the drawings, the rotary hammer comprises a housing 1, a cylinder 2 installed in the housing, and a tool holder 4 mounted on the front of the housing. Many elements of the housing,
The tool holder and other parts of the hammer are known per se and have not been reprinted for clarity.
The cylinder includes a piston 6 which is connected via a trunnion 8 contained therein and a spindle of a vertically oriented electric motor (not shown) via a crank arm 10. Cylinder 2 also provides the function of a combined ram and beatpiece, connected to piston 6 by an air cushion formed between them, and along the axis of cylinder 2 under actuation of the piston. The ram 12 or the striking member slidable in this way is housed. An annular seal 14 made of polytetrafluoroethylene is installed in the annular storage at the rear end of the ram 12. The seal has a generally "L" shaped cross section in its radial plane and is described as an "L seal".

The ram 12 has a relatively small diameter front portion 16, a relatively large diameter rear portion 18 which is slidably fitted within the cylinder 2 and a middle portion 20 having a diameter between the two. . A tapered web 22 of a soft, impervious material, e.g., a plastic elastomeric polymer material, extends from the front end of the front portion 16 of the ram 12 to the front end of the cylinder, and includes a pair of clips 24. And 26 are retained at each end by the ram 12 and the cylinder 2 respectively, so that the arrangement is substantially impermeable to air and dust. The web 22 has a rearward position where the front ends of the cylinder and ram are relatively close to each other and a foremost portion where they are shown to be axially separated from each other by the length of the front 16 of the ram. Between the ram 12 and the ram 12 in the cylinder. The web is schematically illustrated by two different shapes above and below the cylinder axis, where the web 22a is folded in a fold substantially parallel to the axis (as shown above the cylinder axis). On the other hand, as shown below the cylinder axis, the web 22b is a concertina having a substantially normal fold on the cylinder axis. With either configuration, the web provides a seal that does not substantially hinder the axial sliding of the ram 12.

A tool holder 4 (only part of which is shown) is installed in front of the housing 1 and is sandwiched between chambers in the housing, and has a front end fixed to the housing by bolts 26. It is closed by a plate 27. The tool holder comprises a cylinder 28 having an opening capable of receiving the shank (shaft) of the bit 30, which has an increasing radius at its rear end 32 and is formed in the housing 1. And the front end 1 of the ram 12
6 and the web 22 are stored. The rear end 32 of the cylinder forming the tool holder is seated in the chamber by a pair of elastic cushion rings 34 and 36, one of which is connected to the front plate 27 of the housing and the rear side. It is located between the ends 32, the other of which is located between the rest of the housing and its rear, so that the tool holder can move axially to a small extent. The bits shown are
The bit has the standard shape of a bit having a pair of grooves 40 and a pair of holding storage portions 38 for receiving a spline that enables the bit to rotate.
-25 51 125 and sold under the name "SDS Plus". The bit is held in the opening of the tool holder 4 by one or more fixing elements 42, which move radially outward through an opening 44 in the tool holder to insert and remove the bit. Allowed and movable radially inward to the position shown, to keep the bit in the tool holder, but shown to allow it to move axially to a limited extent Can be fixed in that position by a method that has not

The cylinder 2 has a vent hole 4 on its side wall.
It has two rows 6 and 48 and another hole 50 at its front end. In addition, the cylinder 2 is formed from a resilient polymeric material which is held in place relative to the inner shoulder 54 of the cylinder by a retaining ring 56 which itself is held in place by a snap ring 58. An elastic ring 52 is provided. The retaining ring 56
For example, the shape as formed by a large number of cut-out portions allows free passage of air in the axial direction. Since the intermediate portion 20 of the ram 12 is a truncated body, it has a front end 100 whose diameter gradually increases to the diameter of the intermediate portion, and the outer shape of the front portion 100 corresponds to the inner shape of the elastic ring 52. Generally has a waist 101 to be refilled. The diameter of the elastic ring 52 and the waist 101 of the ram 12 is such that the elastic ring needs to expand radially in order to pass over the truncated portion 100 of the ram and into the waist 101. is there.

In operation, the electric motor is:
The piston 6 is reciprocated in the cylinder 2. While the ram 6 and bit 30 are at their forefront, as shown, the reciprocating motion of the piston 6 is such that the air in the cylinder 2 is discharged or replenished through the vent hole 48. Do not move the ram 12. When the bit 30 is engaged with the work object, the bit moves rearward (to the right as shown) and engages the front end of the ram 12 and the vent hole 48 is closed by the rear of the ram. Until the ram is pushed back, separating the ram from the resilient ring 52. Since the ram 12 and the piston are then connected by an air cushion between them, the reciprocation of the piston
The rear end of the bit 30 is hit by the ram, and the work object is hit by the bit. In this operation, dust formed by the work object enters the cylinder 2 by means of a flexible web 22 which seals the front end of the air cushion mechanism while allowing movement of the ram over its entire length of its stroke. Is prevented. If necessary, to reduce the amount of dust in the chamber, the motor causes air to flow forward and into the chamber via opening 60 and from the chamber via opening 62. Can be drained.

As the bit strikes the work object, the reflection of the strike back along the bit causes the front end of the securing element 42 to strike at the front end 64 of the retaining groove. The fixing element 42 transmits this impact to the tool holder 4 and thus to the hammer body 1, but the impact is mitigated by cushion rings 36 and 34 which act to counteract any impact.

As the ram 12 reciprocates within the cylinder 2, air is forced through the vent holes 46 on the side of the cylinder and through the holes 50 at the front of the cylinder, thus allowing air to pass through the web 22. Since the air pressure before the ram is kept relatively constant (at least compared to the air pressure between the piston and the ram), the movement of the ram 12 is not hindered and the flexible web 22 is not damaged.

When the bit 30 has been removed from the work piece and it is necessary to stop the movement of the hammer, the ram 12 strikes the bit 30 and moves it to the foremost position as shown. As the rear portion 18 of the ram passes through the front vent hole 46, the ram prevents further inhalation or discharge of air through the vent hole. At about the same time, the front end of the truncated body portion 100 contacts the rear side of the resilient ring 52, so that the mid-ram portion 20, the front-facing surface of the ram rear portion 18, the region of the mid-ram portion. A closed annular chamber 70 formed by the opening of the cylinder 2 and the radially outwardly facing surface 72 of the resilient ring. As the ram 12 continues to move forward, the resilient ring 52 rides over the truncated body portion, thereby expanding radially against its resilient resilience. This radial expansion thus creates a resistance to further forward movement of the ram 12. in addition,
The forward movement of the ram 12 reduces the volume of the annular chamber 70 and increases the pressure in the annular chamber. The pressure in the center of the elastic ring 52 is maintained in the area in front of it, however generally unchanged, since air can pass through the hole 50 and escape into the area in front of the cylinder surrounded by the web 22. You. Elastic ring 5
The differential pressure between the central area of the two and the annular chamber 70 thus exerts an additional radially inward force on the ram by the ring 52 which increases the force caused by the elasticity of the ring. And assists the resilient ring in stopping the ram. As the ram 12 continues to move forward, the elastic ring 52
It climbs up on an annular ridge 102 that separates the frustum portion 100 from 1 and then sits on the waist 101 as shown, which holds the ram in place. Once the ram 12 is secured, a small bleed (blown) hole 7
The ram 4 is formed so as to allow air to be blown out of the chamber 70 and thus acts as a damping mechanism, so that the ram is not driven backward by leaving the predetermined position due to the air pressure in the chamber 70.

[Brief description of the drawings]

FIG. 1 is a schematic side cross-sectional view through a section of a hammer along a cylinder axis of the hammer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Housing 2 ... Cylinder 4 ... Tool holder 6 ... Piston 12 ... Ram 14 ... Annular seal 20 ... Middle part 22 ... Web 30 ... Bit 34, 36 ... Cushion ring 46, 48 ... Vent hole 52 ... Elastic ring

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Michael Stilm, Germany, 61440 Oberursel, Grunbeisenberg 9A

Claims (13)

[Claims] 1. A hammer capable of receiving a tool bit (30) for acting on a work object, comprising a cylinder (2) and a piston (6) which can be reciprocated in the cylinder. A bit that is slidably mounted in the cylinder and can be driven in response to the reciprocation of the piston by an air cushion between the piston and the striking member, so that the striking member is held in the hammer (30)
And a striking member (12) capable of striking the end of the air cushion hammer mechanism.
A hammer comprising a web of flexible, impervious material extending from the striking member to prevent dust from entering the cylinder from the area of the bit. 2. A web (22) comprising a striking member (12).
2. The hammer according to claim 1, wherein the hammer extends between the cylinder and the housing of the hammer. 3. A web (22) is provided for accommodating axial movement of the striking member in the cylinder (2).
The hammer according to claim 1 or 2, wherein the hammer is folded or in the form of a concertina. 4. The web (22) comprises a cylinder (2).
A hammer according to any of the preceding claims, comprising only a seal against dust ingress into the hammer. 5. The hammer according to claim 1, wherein the hammer comprises means for generating a flow of air in a forward direction around the web from the area of the cylinder. Hammer. 6. A hammer capable of receiving a tool bit (30) for acting on an object to be worked, said hammer comprising a cylinder (2) and a piston (6) which can be reciprocated in the cylinder. A hammer mechanism comprising a striking member (12) slidably mounted in the cylinder and driven by the piston using an air cushion between the piston and the striking member, the hammer comprising: An arrangement for retaining the striking member in a forward position thereof, wherein the hammer comprises a resilient ring (52) mounted within the cylinder and extending around the striking member; (12) is the intermediate part (10
0), so that at a given position of the striking member in the cylinder, the middle part (100) of the striking member is in contact with the resilient ring (52) and the substantially closed chamber is Formed in a cylinder (2) extending around the ring (52) with a further forward movement of the striking member reduces the volume of the chamber (70) and reduces the volume of the resilient ring (52). A hammer that tightens the striking member. 7. The middle portion (100) of the striking member increases in diameter in the rearward direction so that forward movement of the striking member (12) causes the resilient ring (52) to expand radially. The hammer according to claim 6. 8. When the striking member (12) is in a position in front of it and allows the elastic ring (52) to hold the striking member, the striking member may move the elastic ring (52). 7. An acceptable waist (101).
Or the hammer according to 7; 9. The cylinder according to claim 6, wherein the cylinder has a bleed hole to release air in the chamber when the striking member is in the forward position.
The hammer according to any one of the above. 10. A retaining ring (56) formed by a cut-away portion to allow air to flow axially past the retaining ring (56), such that the elastic ring (52) 7. A holding device in a predetermined position.
10. The hammer according to any one of claims 1 to 9. 11. A hammer comprising a tool holder (4) and a housing (1) capable of receiving a tool bit (30) for acting on a work object.
0) is held in the tool holder by one or more fixing elements (42) and a hammer is provided between the tool holder (4) and the housing (1) by one or more cushioning elements (34, 36). The impact reflected back by the work object along the bit (30) is reduced by the tool holder (4) and the cushion element (34, 3).
A hammer transmitted to the housing via 6). 12. The hammer according to claim 11, wherein a reverse hit from the bit is transmitted from the bit to the tool holder by a fixing element. 13. The first cushion ring (34)
Installed between the front of the tool holder (4) and the housing (1), a second cushion ring (36)
A hammer according to claim 11 or 12, arranged between the rear of the tool holder and the housing (1).