EP0019563A1 - Pneumatic percussive tool comprising a vibration damper - Google Patents

Abstract

A percussion tools such as a pneumatic hammer, drill, concrete braker and the like in which a ram is pneumatically reciprocated in a cylinder to drive a tool, has a head provided with the handles gripped by the user and forming a pneumatic cushion with the cylinder. According to the invention, this head carrying the handles is mounted with slight clearance slidably on the cylinder and the pneumatic cushion is formed between the upper end of the cylinder and the interior of the head. A sleeve attached to the head and surrounding the cylinder communicates with the cylinder through the usual reciprocation-producing valve and a portion of the air pressure is bled through the clearance into the cushion. A vent passage of the cylinder communicates with the cushion chamber and can register with a passage in the sleeve opening into the atmosphere.

Description

The present invention relates to a vibration damper for a pneumatic percussion device, that is to say a device intended to reduce the accelerations of variable direction, generating vibrations, to which the handles of pneumatic percussion devices are subjected.

A pneumatic percussion device such as a concrete breaker, a picker, etc., is essentially composed of a cylindrical body comprising a bore inside which a piston or striking mass is slidably mounted. The piston describes a reciprocating movement during which, at the end of its advance stroke, it strikes a tool, such as pick or chisel, engaged in a guide pin. A device of this kind also frequently includes parts ensuring the distribution of compressed air alternately in the chambers situated above and below the piston, and handles, one of which is generally equipped with a system. supply, often comprising a valve whose opening is controlled by a trigger.

In this type of percussion device, the reaction on the cylinder of the forces developed by the compressed air on the piston, on the one hand, and the return of the shock wave created by the impact of the piston on the peak , particularly important return when the peak is in contact with a hard and resistant material, rock for example, on the other hand, give the cylinder vibratory movements of variable frequency and acceleration, but whose high value frequently affects the articulations and users' blood circulation. Indeed, these vibrations are transmitted to the user's hands by the handles of the device, these being linked to the cylinder.

To reduce these vibratory movements which are detrimental to the health of the user, it has already been envisaged to separate the movements of the cylinder from those of the handles, by providing a mounted assembly sliding around the upper part of the body of the device, this assembly carrying the handles of the device and delimiting, between its internal wall and the top of the body of the device, a damping chamber supplied from a system of power supply provided on the assembly carrying the handles (see, for example, French patent No. 2,136,469).

Problems arise, however, for the supply of said damping chamber. If the channels ensuring this supply are of large cross section, the consumption of compressed air, therefore of energy of the damping device is high, and this energy is obviously lost for the main percussion function. Conversely, if the supply channels have a small cross section, they risk being quickly blocked by the dust and debris contained in the compressed air.

The invention aims to eliminate these drawbacks, by a technical solution which manages to reconcile the two contradictory requirements which have just been highlighted.

For this purpose, it relates to a vibration damper for pneumatic percussion device, composed of a cylindrical body having a bore inside which is slidably mounted a piston capable of striking a tool, and comprising a sliding mounted assembly around the upper part of the body of the device, this assembly carrying the handles of the device and delimiting, between its internal wall and the top of the body of the device, a damping chamber supplied from a supply system provided on the assembly carrying the handles, shock absorber in _. which, according to the invention, the above-mentioned sliding assembly, carrying the handles, is mounted with a set of determined value around the upper part of the body of the apparatus, the damping chamber being supplied through this set, and at least one channel is provided in the body of the device, between the aforementioned chamber and a point on the periphery of the body, this channel being extended outwards by another channel pierced in the sliding assembly carrying the handles.

Ainst is made of a pneumatic suspension device, powered by a clearance determined so as to limit the consumption of compressed air, which escapes through the channels of the sliding assembly and of the body, this device absorbing vibrations and dissociating the movements of the handles of those of the cylinder. In addition, the aforementioned clearance is delimited by two walls in relative movement which ensure a permanent "self-cleaning", avoiding its obstruction.

According to a preferred embodiment of this vibration damper, the above-mentioned assembly consists of a sleeve mounted to slide around the upper part of the body of the device, this sleeve comprising an annular chamber supplied with compressed air and communicating by lights with the clearance formed between said assembly and the body of the apparatus, and of a cylinder head surmounting said sleeve, this cylinder head being integral with the sleeve, comprising the handles and delimiting the aforementioned chamber by its internal wall.

Advantageously, the lumens of the sleeve are located opposite other lumens formed in the body of the device and connected to the compressed air distribution system for alternating movement of the piston. This arrangement combines the supply of the device for its fundamental function with the supply of the vibration damper, the latter supply being in the form of a "leak" through the clearance provided between the sliding assembly and the body of the device.

• Figure 1 est une vue d'ensemble, en coupe longitudinale,d'un appareil pneumatique à percussions du type brise-béton, équipé d'un amortisseur conforme à l'invention;
• Figure 2 est une vue en coupe transversale de cet appareil,suivant 2-2 de figure 1;
• Figure 3 en est une vue de détail, suivant la flèche F de figure 1.

In any case, the invention will be clearly understood with the aid of the description which follows, with reference to the appended diagrammatic drawing representing, by way of nonlimiting example, an embodiment of this amortization vibration generator:

• Figure 1 is an overall view, in longitudinal section, of a pneumatic percussion device of the concrete breaker type, equipped with a damper according to the invention;
• Figure 2 is a cross-sectional view of this apparatus, along 2-2 of Figure 1;
• Figure 3 is a detail view, along the arrow F of Figure 1.

The pneumatic percussion device, shown in FIG. 1, comprises in a known manner a cylinder 1 in the bore 2 of which a piston 3 is slidably mounted. The latter strikes a peak 4 guided by a socket 5, itself advantageously sliding mounted in the lower part of the bore 2 of the cylinder 1, so that it can follow the peak 4 in its movements. In the example considered of a concrete breaker, the peak 4 is held in angular position with respect to the cylinder 1 by means of grooves 6, provided between the bush 5 and the cylinder 1.

This cylinder 1 is closed, at its lower part, by a closing part 7 allowing the pick 4 to pass and, at its upper part, by two parts 8 and 9, fixed by means of bolts 10 (only one of which is indicated on the figure 1). These parts 8 and 9 contain the compressed air distribution system, with in particular air inlet channels 11 and an air distribution valve 12 indicated very schematically.

A sleeve 13 is slidably mounted around the upper part of the cylinder 1, the section of which has a circular contour, a clearance d being formed between the outer surface of the cylinder 1 and the bore of the sleeve 13. The latter comprises an annular chamber 14, completely surrounding the cylinder 1. Above the sleeve 13 is mounted, and fixed by means of screws 15, a cylinder head 16 which has two opposite lateral handles 17 and 18.

The annular chamber 14 has an opening air inlet 19, capable of being closed off by a valve 20, the supply of compressed air to the apparatus being effected by means of a connector 21. The opening of the valve 20 is controlled manually from 'a trigger 22, associated with the handle 17, this by means of a pusher 23 passing right through the cylinder head 16. The closing of the valve 20 is caused by a return spring 24 resting on an internal shoulder of fitting 21.

As shown more particularly in FIG. 2, the closure part 8 has, at its periphery, grooves 25 which cooperate with complementary grooves 26 formed inside the cylinder head 16. These grooves 25 and 26 allow axial sliding of the cylinder head 16 relative to the cylinder 1, and make it possible, from the handles 17 and 18 and also thanks to the grooves 6, to angularly actuate the peak 4.

Between the internal wall of the cylinder head 16, the closing pieces 8 and 9, and the part of the cylinder 1 projecting above the sleeve 13 inside the cylinder head 16, a chamber 27 is formed. The volume of this chamber 27 is variable, as a function of the relative position of the cylinder 1 and of the sleeve 13-cylinder head assembly 16, and in this regard it will also be noted that the stroke of the cylinder 1 is limited, on the one hand, by the support of the part 9 against the bottom of the chamber 27, and on the other hand, by the abutment of the grooves 25 of the part 8 against the upper face of the sleeve 13.

Lights 28 are formed between the annular chamber 14 of the sleeve 13 and the bore of the same sleeve.

These slots 28 are located opposite other slots 29 formed on the periphery of the cylinder 1 and connected to the channels 11 of the part 8, previously mentioned. As shown in Figure 3, the lights 28 have an oblong shape, while the lights 29 have an inverted "T" shape. These lights 28 and 29 are advantageously arranged symmetrically, for example in diametrically opposite pairs, to balance the forces generated by the air pressure.

Finally a channel 30 is drilled through the cylinder 1 and the closure parts 8 and 9, parallel to the axis of the cylinder, this channel opening on the one hand into the chamber 27, on the other hand at the periphery of the cylinder 1 , substantially opposite a last channel 31, drilled radially in the sleeve 13 and opening to the outside.

The compressed air, admitted into the annular chamber 14 through the opening of the valve 20, is directed by the lights 28 towards the cylinder 1. On crossing the set of value d, a small part of the air infiltrates between the cylinder 1 and the sleeve 13, and feeds the chamber 27. The other part of the air will, through the ports 29 and the distribution system 11-12, actuate the piston 3, in a known manner, putting into operation the device.

The air admitted into the chamber 27, through the value play d, lifts the assembly formed by the sleeve 13 and the cylinder head 16 with the handles 17 and 18, to a position in which the outlet of the channel 30, at the periphery of the cylinder 1, arrives opposite the channel 31, thus putting the chamber 27 in communication with the atmosphere. In this way, a balance is established, during operation, between the quantity of air admitted into the chamber 27 by the clearance between the cylinder 1 and the sleeve 13, on the one hand, and the quantity of exhaust air. outward through channels 30 and 31, on the other hand.

The movement of the assembly comprising the cylinder 1, the piston 3, the sleeve 5 and the closure parts 7, 8 and 9 results, at the level of the handles 17 and 18, by a slight variation in the air pressure in chamber 27. A judicious choice of the volume of this chamber 27, relative to the volume displaced by the movement of the cylinder 1, and facing the mass of the sleeve 13-cylinder head 16 assembly with the handles 17 and 18 , as well as the frequency of movements of the cylin dre 1 makes it possible to reduce the accelerations on the handles 17 and 18 to a value which is medically perfectly tolerable for continuous work. Furthermore, as a function of the force exerted by the user on the handles, the relative position of the lights 28 and 29, through which the percussion system is supplied, changes; it is thus understood that a studied shape given to these lights allows a dosage of the quantity of air admitted, therefore of the power of the device, according to the support exerted on the handles, so that the movement of the whole device

remains coordinated, until the support is completely removed, then until the device is removed, this latter operation then being carried out under very low power, therefore at very reduced power and, therefore, without excessive acceleration.

The device according to the invention prevents accelerations at the handles from reaching a value detrimental to the health of the user and, moreover, the design of the vibration damper leads to self-regulation of the supply of compressed air and of the power of the percussion device.

It goes without saying that the invention is not limited to the sole embodiment of this vibration damper which has been described above, by way of nonlimiting example; on the contrary, it embraces all of the variant embodiments and of applications comprising equivalent means. It is thus, in particular, that the field of application of the invention is in no way limited to concrete breakers or breakers, but can obviously extend to any pneumatic device with handles, driven by an alternating movement.

Claims (5)

1.- Vibration damper for pneumatic percussion device, composed of a cylindrical body having a bore inside which is slidably mounted a piston capable of striking a tool, and comprising a unit mounted to slide around the upper part of the body of the apparatus, this assembly carrying the handles of the apparatus and delimiting, between its internal wall and the top of the body of the apparatus, a damping chamber supplied from a supply system provided on the bearing assembly the handles, characterized in that the aforementioned sliding assembly (13,16), carrying them. handles (17,18), is mounted with a set of determined value (d) around the upper part of the body (1) of the device, the damping chamber (27) being supplied through this set (d) , and in that at least one channel (30) is provided in the body (1) of the device, - between the aforementioned chamber (27) and a point on the periphery of the body (1), this channel (30 ) being extended outwards by another channel (31) pierced in the sliding assembly (13,16) carrying the handles (17,18). 2.- vibration damper according to claim 1, characterized in that the aforementioned assembly consists of a sleeve (13) slidably mounted around the upper part of the body (1) of the device, this sleeve (13) comprising an annular chamber (14) supplied with compressed air and communicating by lights (28) with the clearance (d) formed between said assembly and the body of the apparatus, and a cylinder head (16) surmounting said sleeve (13 ), this cylinder head (16) being integral with the sleeve (13), comprising the handles (17,18) of the device and delimiting the aforementioned chamber (27) by its internal wall. 3.- vibration damper according to claim 2, characterized in that the lights (28) of the aforementioned sleeve (13) are located opposite other lights (29) formed in the body (l) of the device and connected to the compressed air distribution system (12) for the reciprocating movement of the piston (3). 4.- Vibration damper according to claim 3, characterized in that the first lights (28) have an oblong shape, while the second (29) have a shape of "T" reversed. 5.- Vibration damper according to claim 3 or 4, characterized in that the aforementioned lights (28,29) are arranged symmetrically, for example in diametrically opposite pairs.

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