GB2262467A

GB2262467A - Apparatus for reducing vibration transmission in hand-held tool

Info

Publication number: GB2262467A
Application number: GB9126979A
Authority: GB
Inventors: Anthony Best; Stephen John Neads
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1991-12-17
Filing date: 1991-12-17
Publication date: 1993-06-23
Also published as: TW224436B; GB9126979D0; EP0551719A1; ES2094884T3; EP0551719B1; DE69215494T2; DE69215494D1

Abstract

An air-operated percussive tool incorporates apparatus for reducing vibration transmission from a working end portion (1) to a hand grip (2), thereby to reduce vibration transmission to the user. The apparatus includes a male frustoconical portion (3) whose tip is located facing a female bed (4) with the base of portion 3 attached to grip (2) whilst bed (4) is attached to portion (1). Three rubber balls (5) are trapped between the portion (3) and bed (4) and the balls are located in their mean positions under compression. Oscillatory movement of bed 4 parallel to the longitudinal axis of frustocone 3 causes balls 5 to roll on the male and female surfaces and effectively provide a rising spring rate or stiffness. Apparatus is also disclosed for reducing vibration transmissions from the working portion to the casing 12 of the tool using floating resilient ball arrangement 13 in which a set of balls are linked together. <IMAGE>

Description

2262467 APPARATUS FOR REDUCING VIBRATION TRANSMISSION IN HAND-HELD TOOL is

This invention relates to an apparatus for reducing vibration transmission in a hand-held tool and more particularly relates to apparatus f or reducing vibration transmission from a working portion of a hand-held tool to the user of the tool.

Previous attempts to reduce hand/arm vibration in a percussive tool have generally centred around either the isolation of the operator's grip by means of sprung handles or by employing a means of cutting power to the tool as the operator force increases.

One limitation of the springs solution is that a damper is required as well as the spring in order to obtain the optimum effect. Also, the mass of the sprung handles is relatively small compared with the mass of the tool and, since a coil spring usually functions linearly, high deflections are experienced. As a result, the option to reduce the power to help achieve the desired effect has been investigated. Power regulation of the tool has obvious disadvantages to efficiency, in that it reduces the blow frequency and intensity.

According to one aspect of the present invention, there is provided an apparatus for reducing vibration transmission from a working portion of a hand-held tool to the user of the tool, the apparatus including a floating, resilient ball arrangement interposed between a handle portion and the working portion of the tool.

The tool may be a percussive tool, such as a chipper, digger, needle gun, scaler, hammer drill or a demolition tool.

The tool may be air operated. The tool could also be electrically operated.

Preferably, the resilient ball arrangement comprises balls, preferably three, which can be of rubber, located between a male part on one of the portions and a f emale part on the other of the portions.

The male part can be a frustoconical parf- joined to the handle portion and the f emale part can be a f emale bed joined to the working portion of the tool or _vice versa, the bed facing the frustoconical portion with the balls lying compressed on the bed and the external surface of the frustocone.

oscillatory movement of the female bed parallel to the longitudinal axis of the frustocone causes the balls to roll on the male and female surfaces.

The balls can be located by pins or the like.

In the case of an air-operated tool, at least one and preferably each ball is provided with a bore through which air under pressure can be transmitted from the frustoconical portion to the female bed and thence to the action of the working part of the tool.

According to another aspect of the present invention, there is provided an apparatus for reducing vibration transmission from a working portion of a hand-held tool to a casing of the tool, the apparatus including a floating, resilient ball arrangement interposed between the casing and the working portion of the tool.

This resilient ball arrangement can be in the form of a set of balls in a ring around the internal periphery of the casing and around the outer periphery of part of the working portion of the tool, thereby separating and isolating the two portions.

The set of balls can be linked together.

The balls can be located within shells which are curved to urge the balls towards their mean positions.

is For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a sectional view of part of a hand-held percussive tool showing apparatus for reducing vibration transmission from a working portion thereof to the user thereof, the tool being illustrated at mid- stroke, Figure 2 is a sectional view taken on the line II-II in Figure 1, Figure 3 is an exploded perspective view of part of the apparatus and showing a modification, Figure 4 is a sectional view of another part of the tool showing apparatus for reducing vibration transmission from the working portion to a casing of the tool, this view also being illustrated at mid-stroke, and Figure 5 is a section view taken on the line V-V in Figure 4.

Referring firstly to Figures 1 to 3, an air-operated percussive tool is illustrated which incorporates apparatus for reducing vibration transmission from a working end portion 1 to a hand grip 2, thereby to reduce vibration t ransmission to the hand/arm of the user. Such apparatus will be briefly referred to hereafter as the "vibration isolator".

The vibration isolator in the form illustrated comprises a male frustoconical portion 3 whose tip is located facing a f emale bed 4. The base of the frustoconical part is attached to the handle grip 2, whilst the bed 4 is attached to the working end portion 1 of the tool.

Three substantially spherical rubber balls 5 are trapped between the portion 3 and bed 4. The apparatus as depicted in Figure 1 is carrying a mean static load.

The balls are located in their mean positions under compression by means of nylon tubes 6A and 6B located in bores 7 of the balls 5, the tubes having portions protruding from the surfaces of the balls so that these protruding portions are located in corresponding bores 8A and 8B in the portion 3 and bed 4, respectively. The tubes 6A and 6B in each bore 7 are spaced apart to give sufficient clearance for compression and expansion movement of the ball 5 in which the bore is located. The tubes 6A, 6B may be nylon inserts which are glued, bonded or simply press fits.

As illustrated, the bores form an integral part of the compressed air supply to the working end portion of the is tool from an air supply bore 9 in the handle grip 2, the bore 9 passing down the centre of the tapered portion 3 and communicating with the bores 8A, 7 and 8B. The bores 8B lead on to a cycle valve illustrated generally at 10. Experiments have shown that for the operating range of the vibration isolator, the airways through the vibration isolator remain sufficiently consistent to allow the required air flow.

The portion 3 need not be pure frustoconical but can be given a gently curving taper and/or can incorporate an angular change in the direction of taper. The tubes 6A and 6B serve to locate the balls 5 on the taper, especially when the parts I and 2 are driven off-centre.

In the case where the tool is only electrically-operated, then the tubes 6A, 6B (or pins) simply serve as locating means.

The modification shown in Figure 3 takes the form of three radiallyextending wings 11 on the portion 3 which run in slots 12 parallel to the longitudinal axis of the tool. These wings also act as anti-rotation means if the rotational stiffness of the balls is overcome, thereby acting as a travel limiter. Also, they act as a rebound stop or travel limiter in the axial direction.

In use, the percussive tool will oscillate at around 4mn at 25 Hz/sec. The acceleration levels experienced with the balls is very high and so the resilient material of the balls must be of a suitable hardness. The apparatus provides a high radial stiffness and a low (soft) axial stiffness with rising rate. In comparison, a normal coil spring would have a constant rate. The balls effectively provide a rising spring rate or stiffness. The rising rate can be varied by varying the degree of slope on the rolling surfaces.

The other end of the tool is diagrammatically illustrated in Figures 4 and 5, where a casing 12 is shown leading up to the handle end of the tool and obviously since the casing 12 is attached to the handle grip 2, it must not be allowed to short out the effect of the vibration isolator. Accordingly, another floating resilient ball arrangement 13 is provided between the working end portion 1 and the casing 12 in the region where the actual tool 14 is located. This effectively forms another vibration isolator but in this case the balls are not provided with locating pins but are linked to the ring of balls and are located in outer and inner shells 15, 16, respectively. The balls may be moulded together or may be linked by other means.

In this case, the axial stiffness is intended to be lower, and with a constant rate, but the radial stiffness is intended to be higher than is the case with the vibrator isolator at the hand grip end of the tool. The shells 15 and 16 are curved to urge the bracelet of balls towards their mean positions. The balls are compressed and in this case, they have a shallow curve.

Such a construction at the end of the tool most adjacent the actual tool 14 reduces the required length in that location as compared with prior art bearings and it is resistant to ingress of foreign material. To assist in this, a circular floating seal 17 is provided between the tool 14 and the ball arrangement 13.

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Claims

CLAIMS:

1. An apparatus for reducing vibration transmission from a working portion of a hand-held tool to the user of the tool, the apparatus including a floating, resilient ball arrangement interposed between a handle portion and the working portion of the tool.

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2. An apparatus according to claim 1, wherein said resilient ball arrangement comprises three balls located between a male part on one of the portions and a female part on the other of the portions.

3. An apparatus according to claim-2, wherein the balls are of rubber.

4. An apparatus according to claim 2 or 3, wherein said male part is a frustoconical part joined to said handle portion and the female part is a female bed joined to the working portion of the tool.

5. An apparatus according to claim 2, 3 or 4, wherein the balls are located by pins or the like.

6. An apparatus according to claim 4, wherein at least one of said balls is provided with a bore through which air under pressure can be transmitted from the frustoconical portions to the female bed and thence to the action of the working part of the tool.

7. An apparatus according to any one of the preceding claims and further comprising a second apparatus for reducing vibration transmission from a working portion of the tool to a casing of the tool, the apparatus including a second floating, resilient ball arrangement interposed between the casing and the working portion of the tool.

8. An apparatus according to claim 7, wherein said second resilient ball arrangement is in the form of a set of balls in a ring around the internal periphery of the casing and around the outer periphery of part of the working portion of the tool, thereby separating and isolating the two portions.

9. An apparatus according to claim 8, wherein the balls in said set of balls are linked together.

10. An apparatus according to claim 8 or 9, wherein the balls of the set of balls are located within shells which are curved to urge those balls towards their mean positions.

11. An apparatus according to any one of claims 2 to 10 and further comprising means to limit relative rotation between said male and female parts.

12. An apparatus according to any one of claims 2 to 11, and further comprising means for acting as a rebound stop or travel limiter in an axial direction of relative movement of the male and female parts.

13. An apparatus for reducing vibration transmission from a working portion of a hand-held tool to the user of the tool, substantially as hereinbefore described with reference to the accompanying drawings.

14. An apparatus for reducing vibration transmission from a working portion of a hand-held tool to a casing of the tdo-1-, the apparatus including a floating, resilient ball a 9 arrangement interposed between the casing and the working portion of the tool.

15. An apparatus according to claim 14, wherein said resilient ball arrangement is in the form of a set of balls in a ring around the internal periphery of the casing and around the outer periphery of part of the working portion of the tool, thereby separating and isolating the two portions.

16. -An apparatus according to claim 15, wherein the balls of the set are linked to one another.

17. An apparatus according to claim 15 or 16 wherein the balls are located within shells which are curved to urge the balls towards their mean positions.

18. An apparatus for reducing vibration transmission from a working portion of a hand-held tool to a casing of the tool, substantially as hereinbefore described with reference to Figures 4 and 5 of the accompanying drawings.

19. A hand-held tool incorporating apparatus according to any one of the preceding claims.

20. A tool according to claim 19 and being air operated.

21. A tool according to claim, 19 and being electrically operated.

22. A tool according to claim 19 and being a percussive tool.

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23. A tool according to claim 22 and being in the form of a chipper, digger, needle gun, scaler, hammer drill or a demolition tool.

24. A tool according to any one of claims 19 to 23, substantially as hereinbefore described with reference to the accompanying drawings.

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