GB1600944A

GB1600944A - Percusiive hand tool

Info

Publication number: GB1600944A
Application number: GB1676378A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1977-06-29
Filing date: 1978-04-27
Publication date: 1981-10-21
Also published as: ES471261A1; DE2738057A1; CH634250A5; NL7806873A

Abstract

A drilling or percussion hammer with a percussion mechanism driven by electric motor is proposed in which a striker (23), connected via an air cushion to a drive member (24) performing an axial reciprocating movement, releases its energy to a tool guided in the drilling or percussion hammer. Via a ring (20) provided with a driving pin (21), the drive member (24) is supported on a rotating curved track (118) closed upon itself. Rolling-contact bodies (100, 100') are inserted between the curved track and the ring. A device of maximum effectiveness for converting the rotary movement of the drive motor into an axial movement of the air-cushion percussion mechanism is thereby created. <IMAGE>

Description

(54) A PERCUSSIVE HAND TOOL (71) We, ROBERT BOSCH GMBH, a German company of Postfach 50, 7000 Stuttgart 1, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a percussive hand tool, and is an improvement in, or a modification of, the invention described and claimed in the specification of our Patent No. 1 484 659.

The specification of Patent No. 1 484 659 describes and claims a percussive hand tool comprising a motor, a tool holder, a striker arranged to strike the tool holder, a driving member arranged to be so driven by the motor as to perform axial to-and-fro movements which are imparted to the striker through the agency of an air cushion, and a cam follower engaging a continuous cam track arranged for rotation by the motor. for producing the to-and-fro movements of the driving member.

Such a percussive hand tool has the following advantages: a) The conversion of rotary motion into the axial to-and-fro movements imparted to the striker, can be achieved with three shafts arranged parallel to the axis of the hand tool.

b) An expensive bell crank drive which is required with a motor arranged co-axially with respect to the driving member, is no longer needed.

c) Complete control is provided over the manner in which the entire impact mechanism moves.

d) The tool runs quietly and does not stress the operator excessively.

The present invention is concerned with the form of continuous cam track and cam follower arrangement shown in Figure 3 of the parent patent specification.

In the percussive hand tool in accordance with the present invention, the cam follower comprises a ring mounted on the continuous cam track by means of antifriction bearings.

There are a number of alternative ways in accordance with the invention, in which the ring may be mounted on the continuous cam track. For example, it may be mounted between two axial roller bearings, preferably also on a radial plain bearing bush, on a radial roller bearing, preferably also between two axial roller bearings or between an axial roller bearing and an angular contact bearing.

The roller bearings are preferably needle bearings.

In all those arrangements, the cam track preferably has substantially the same crosssectional shape as the ring.

In a preferred form of hand tool, the cam track forms part of a planar wobble plate.

In an alternative arrangement, the ring is mounted on two angular contact bearings.

In that case, it is preferable for the cam track to be in the form of a shallow groove which does not enclose the ring.

As in the arrangement of Figure 3 of the parent patent, the cam follower may also comprise a pivot pin rotatably guided in one end of the driving member which may be a piston sealingly and slidingly guided in a guide tube.

In order that the invention may be clearly understood and readily carried into effect, a number of continuous cam track and cam follower arrangements in accordance with the invention and which are more specifically applicable to the hand tool illustrated in Figure 3 of the parent patent specification, will now be described with reference to the accompanying drawings, in which: Figure I is a reproduction of Figure 3 of the parent patent specification, Figure 2a is an end view, partly in section, showing how the pivot pin is rotatably guided in the driving member, Figure 2b is a sectional view showing the cam follower ring mounted on one arrangement of antifriction bearings, and Figures 3 to 5 are further sectional views each showing the cam follower ring mounted on another arrangement of antifriction bearings.

The percussive hand tool illustrated in Figure 1 has a housing 1 in which is arranged an electric, preferably universal, driving motor 2, a drive 3 and an impact mechanism 4. At its rear end, the housing 1 changes into a hand grip 5. A switch provided with a push button 6 through which the electric motor 2 can be set in operation, is incorporated in the hand grip 5. A current supply cable is led in at the lower end of the hand grip 5. A tool holder 8 is arranged on the housing 1 at the forward end remote from the hand grip 5, which serves for the reception of tools such as drills or chisels - not shown in detail.

The end of the motor shaft carries a motor pinion 12 which drives an intermediate shaft 44 through a gearwheel 43. The intermediate shaft 44 carries a drum made up of mating parts 47, 47' and which is provided with a groove forming a continuous cam track arranged on the periphery of the drum between the mating parts 47, 47'. The flank of the groove nearest to the motor 2, which also forms the plane of division of the parts 47, 47' of the drum, is inclined with respect to the axis of the drum or the axis of the intermediate shaft 44, that is to say, it assists in providing a cam track forming part of a planar wobble plate. A cam follower comprising a ring 20 and a pivot pin 21 extending radially therefrom, is rotatably guided in the cam track. The radial pin 21 drives the impact mechanism 4.

The impact mechanism 4 of the drill hammer is arranged in the interior of a fixed guide tube 22. It consists of a striker 23 sealingly and slidingly guided in the guide tube 22 and a driving member formed as a piston 24 likewise sealingly and slidingly guided in the guide tube 22. A number of air ducts are arranged in the wall of the guide tube 22, which can be opened and closed by the striker 23. The inner end of the tool holder 8 formed as a dolly extends into the forward end region of the inner space of the guide tube 22 remote from the piston 24.

The rear end 25 of the piston 24 remote from the tool holder 8, is forked and carries a pivot pin 26. A transverse bore 27 in which the radial pin 21 engages with clearance, is arranged centrally in the pivot pin 26. Thus the radial pin 21 can easily move axially in the transverse bore 27.

Furthermore, the forward end of the intermediate shaft 44 facing the motor 2 is formed as a pinion 45 which engages with a gear ring 29 which is arranged on a rotary sleeve 30. The rotary sleeve 30 is rotatably mounted on the forward portion of the fixed guide tube 22 and at its forward end it has a flange 31 which, through an internal spline arranged at its drilling end, engages for rotation in a corresponding external spline on the tool holder 8. A spring 32 is arranged on the outside owt the rotary sleeve 30, which on the one hand, is supported against the housing flange of the sleeve 30 carrying the gear ring 29 and on the other hand is supported on a flange arranged on the tool holder 8.

By means of a sliding and locking mechanism (not shown) arranged at the forward end of the housing 1, the tool holder 8 may be moved between a position in which it is driven percussively during a drilling operation and another position in which a purely drilling operation is possible.

In this position, the rear end of the tool holder 8 is pulled out of the interior of the guide tube 22 far enough for the impact mechanism 4 to be taken out of operation so that no air cushion can any longer be built up between the striker 23 and the piston 24.

As can easily be seen, a rotary motion of the drum 17 produces a to-and-fro movement of the piston 24. Through the air cushion formed between the piston 24 and the striker 23, which acts as an energy store, the striker 23 is likewise displaced in an axial to-and-fro movement. During striking of the inner end of the tool holder 8, the striker 23 gives up its energy which is finally effective as an axial impact on the tool held in the tool holder 8. The tool holder 8 is set in rotary motion by the pinion 45, the gear ring 29 and the spline arranged on the flange 31.

The conversion of the rotary movement into a to-and-fro movement through a wobble plate drive according to the invention, is essentially cheaper than a crank drive used in known machines and at the same time does away with the expense of the otherwise necessary bell crank drive. Furthermore, the reciprocating masses are smaller and the tool is of an extremely short construction due to the impact mechanism driven by the wobble plate lying directly above the intermediate shaft 44.

For percussive operation of the tool, the intermediate shaft 44 and drum 47, 47' can be connected through a cone clutch 48 to the gear wheel 43 which meshes with the motor pinion 12.

The cone clutch 48 is retained in its uncoupled condition through a spring 49 which is supported in a bore arranged concentrically in the intermediate shaft 44, on the one hand by the base of the bore and on the other hand by a ball 50 engaging the housing of the tool.

When the operator presses the tool against rock, the tool holder 8 is displaced rearwards into the tool until a flange 51 on the tool holder 8 serving as an abutment surface for the spring 32 comes into engage ment with the flange 31 on the rotary sleeve 30 whereby the rotary sleeve 30 is displaced inwards. The flange on the rotary sleeve 30 carrying the gear ring 29 urges the interme diate shaft 44 in an axial direction through the flange 46, the cone clutch 48 engages so that the drum 47, 47' is driven and the tool begins to "hammer". If the operator moves away from the rock then the spring 49 disengages the clutch 48 and the impact mechanism stops.

As well as a friction clutch the clutch 48 can also be made as a dog clutch.

The specific arrangements in accordance with the invention, for mounting the cam follower on the cam track of the drum by means of antifriction bearings, are illustrated in Figures 2 to 5.

Figure 2a shows how the radial pin 21 of the cam follower is inserted in the transverse bore 27 in the pivot pin 26.

In Figure 2b, the ring 20 of the cam follower is mounted between two axial roller bearings 100 and 100'. The ring 20 is also mounted on a radial plain bearing bush 101. In this embodiment, the cam track 118 is formed between two parts 117' and 177" of a drum 117 arranged on an intermediate shaft 14 mounted for rotation in bearings 102 and 102'. Friction losses are considerably reduced by the use of the bearings 100 and 100' and the plain bearing bush 101.

In the embodiment illustrated in Figure 3, the plain bearing bush 101 of Figure 2b is replaced by a roller bearing 101a which reduces the friction losses still further.

In Figure 4 a ring 120 is mounted on the cam track by means of an axial roller bearing 105 and a ball cage 106 acting as an angular contact ball bearing, for absorbing axial and radial forces.

In Figure 9, a drum 217, consisting of juxtaposed parts 217' and 217" provides a cam track in the form of a shallow groove on which a ring 220 is mounted by means of two ball cages 107 and 107', each acting as an angular contact ball bearing and which absorb axial and radial forces. In this arrangement, the shallow groove is not deep enough to enclose the ring 220.

The roller bearings used in the embodiments of Figures 2 to 4 are preferably needle bearings as shown in the drawings.

The percussive hand tools in accordance with the invention may be produced very cheaply, very simply and are also easy to repair. They need only three axially parallel shafts mounted in six axially parallel bearings, without any loss in functional safety.

WHAT WE CLAIM IS: 1. A percussive hand tool comprising a motor, a tool holder, a striker arranged to strike the tool holder, a driving member arranged to be so driven by the motor as to perform axial to-and-fro movements which are imparted to the striker through the agency of an air cushion, and a cam follower engaging a continuous cam track arranged for rotation by the motor, for producing the to-and-fro movements of the driving member, the cam follower comprising a ring mounted on the continuous cam track by means of antifriction bearings.

2. A percussive hand tool according to claim 1, in which the ring is mounted between two axial roller bearings.

3. A percussive hand tool according to claim 2, in which the ring is also mounted on a radial plain bearing bush.

4. A percussive hand tool according to claim 2, in which the ring is also mounted on a radial roller bearing.

5. A percussive hand tool according to claim 1, in which the ring is mounted between an axial roller bearing and an angular contact bearing.

6. A percussive hand tool according to any one of claims 2 to 5, in which the cam track has substantially the same crosssectional shape as the ring.

7. A percussive hand tool according to any one of claims 2 to 6, in which the cam track forms part of a planar wobble plate.

8. A percussive hand tool according to any one of claims 2 to 7, in which each roller bearing is a needle bearing.

9. A percussive hand tool according to claim 1, in which the ring is mounted on two angular contact bearings.

10. A percussive hand tool according to claim 9, in which the cam track is a shallow groove which does not enclose the ring.

11. A percussive hand tool according to any preceding claim, in which the cam follower also comprises a pivot pin rotatably guided in one end of the driving member.

12. A percussive hand tool according to any preceding claim, in which the driving member is a piston which is sealingly and slidingly guided in a guide tube.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

pinion 12.

The cone clutch 48 is retained in its uncoupled condition through a spring 49 which is supported in a bore arranged concentrically in the intermediate shaft 44, on the one hand by the base of the bore and on the other hand by a ball 50 engaging the housing of the tool.

When the operator presses the tool against rock, the tool holder 8 is displaced rearwards into the tool until a flange 51 on the tool holder 8 serving as an abutment surface for the spring 32 comes into engage ment with the flange 31 on the rotary sleeve

30 whereby the rotary sleeve 30 is displaced inwards. The flange on the rotary sleeve 30 carrying the gear ring 29 urges the interme diate shaft 44 in an axial direction through the flange 46, the cone clutch 48 engages so that the drum 47, 47' is driven and the tool begins to "hammer". If the operator moves away from the rock then the spring 49 disengages the clutch 48 and the impact mechanism stops.

As well as a friction clutch the clutch 48 can also be made as a dog clutch.

The specific arrangements in accordance with the invention, for mounting the cam follower on the cam track of the drum by means of antifriction bearings, are illustrated in Figures 2 to 5.

Figure 2a shows how the radial pin 21 of the cam follower is inserted in the transverse bore 27 in the pivot pin 26.

In Figure 2b, the ring 20 of the cam follower is mounted between two axial roller bearings 100 and 100'. The ring 20 is also mounted on a radial plain bearing bush 101. In this embodiment, the cam track 118 is formed between two parts 117' and 177" of a drum 117 arranged on an intermediate shaft 14 mounted for rotation in bearings

102 and 102'. Friction losses are considerably reduced by the use of the bearings 100 and 100' and the plain bearing bush 101.

In the embodiment illustrated in Figure 3, the plain bearing bush 101 of Figure 2b is replaced by a roller bearing 101a which reduces the friction losses still further.

In Figure 4 a ring 120 is mounted on the cam track by means of an axial roller bearing 105 and a ball cage 106 acting as an angular contact ball bearing, for absorbing axial and radial forces.

In Figure 9, a drum 217, consisting of juxtaposed parts 217' and 217" provides a cam track in the form of a shallow groove on which a ring 220 is mounted by means of two ball cages 107 and 107', each acting as an angular contact ball bearing and which absorb axial and radial forces. In this arrangement, the shallow groove is not deep enough to enclose the ring 220.

The roller bearings used in the embodiments of Figures 2 to 4 are preferably needle bearings as shown in the drawings.

The percussive hand tools in accordance with the invention may be produced very cheaply, very simply and are also easy to repair. They need only three axially parallel shafts mounted in six axially parallel bearings, without any loss in functional safety.

WHAT WE CLAIM IS: 1. A percussive hand tool comprising a motor, a tool holder, a striker arranged to strike the tool holder, a driving member arranged to be so driven by the motor as to perform axial to-and-fro movements which are imparted to the striker through the agency of an air cushion, and a cam follower engaging a continuous cam track arranged for rotation by the motor, for producing the to-and-fro movements of the driving member, the cam follower comprising a ring mounted on the continuous cam track by means of antifriction bearings.
2. A percussive hand tool according to claim 1, in which the ring is mounted between two axial roller bearings.
3. A percussive hand tool according to claim 2, in which the ring is also mounted on a radial plain bearing bush.
4. A percussive hand tool according to claim 2, in which the ring is also mounted on a radial roller bearing.
5. A percussive hand tool according to claim 1, in which the ring is mounted between an axial roller bearing and an angular contact bearing.
6. A percussive hand tool according to any one of claims 2 to 5, in which the cam track has substantially the same crosssectional shape as the ring.
7. A percussive hand tool according to any one of claims 2 to 6, in which the cam track forms part of a planar wobble plate.
8. A percussive hand tool according to any one of claims 2 to 7, in which each roller bearing is a needle bearing.
9. A percussive hand tool according to claim 1, in which the ring is mounted on two angular contact bearings.
10. A percussive hand tool according to claim 9, in which the cam track is a shallow groove which does not enclose the ring.
11. A percussive hand tool according to any preceding claim, in which the cam follower also comprises a pivot pin rotatably guided in one end of the driving member.
12. A percussive hand tool according to any preceding claim, in which the driving member is a piston which is sealingly and slidingly guided in a guide tube.
13. A percussive hand tool with a cam

follower mounted on a continuous cam track by means of antifriction bearings, substantially as herein described with refer ence to Figure 1 modified in accordance with Figure 2, Figure 3, Figure 4 or Figure 5 of the accompanying drawings.