EP0427647B1 - Pneumatic percussive apparatus with exchangeable worktool - Google Patents

Abstract

Percussive worktool. The device comprises a head (12) having a bore (20): - connecting with two chambers (14, 15), - containing a piston (30) which is free with respect to the bore and comprising a radial opening (33) capable of coinciding with one or the other of two recesses (25, 26) inside the bore (20) and respectively connecting with the chamber (15) and with the exhaust (7). Application to barker devices. <IMAGE>

Description

The present invention relates to percussion devices generally supplied by a pressurized fluid, such as compressed air responsible for generating the reciprocating rectilinear displacements of a piston or the like intended to strike the tail of a removable working tool.

Such devices, generally also known as impact hammers, are used in many fields of application for cutting, detaching and perforating various materials. As an example, it is possible to cite the application to jackhammers, debarking apparatuses or even strippers.

Such devices comprise a body containing a free counterweight, guided in movement by a sealing surface separating an exhaust cylinder and a working cylinder. The counterweight has, in the working cylinder, a piston head delimiting two chambers with variable volume which can be put in relation with a compressed air intake circuit and with the exhaust cylinder by means of a internal intercommunication bore in the counterweight. Each back and forth movement of the counterweight implies an active stroke at the end of which the counterweight is responsible for striking the tail of a working tool fitted or coupled at the end of the body by means of a locking coupling device. and quick unlocking.

It can be considered that such devices are generally satisfactory, but that on the basis of known embodiments, it appears necessary to be able to have, for given dimensions, devices having greater power efficiency, while being more balanced and less generators of vibrations imposed on operators.

The working efficiency of such percussion devices depends essentially on the weight of the counterweight, its speed of movement, the frequency of this movement and the useful stroke of the counterweight.

We could therefore consider increasing the weight of the counterweight to increase working efficiency. Such a proposal necessarily leads to an increase in the diameter of the body and does not appear to bring a particularly positive result on the strengthening of the percussion action, due to the reduction in the frequency of displacement which is its corollary. In addition, the increase in weight of the counterweight inevitably leads to an increase in the total weight of the tool, the dynamic balancing of which becomes more difficult to achieve in order to reduce, if not eliminate, the operating vibrations imposed on the operator.

One might think that it is possible to act on the speed of movement of the counterweight. To do this, it is absolutely necessary to modify the pressure of the animation fluid, that is to say to have a compressed air distribution network supplying an air pressure higher than that of current networks, generally limited to 7 or 8 bars. Such practical dependence is opposed to any possibility of action on the speed of movement.

One might think that it is possible to act on the frequency of movement of the counterweight in an alternative rectilinear stroke inside the body of the device. In reality, an action on this third parameter necessarily involves a modification of the weight of the counterweight and an increase in the pressure of the animation fluid. These two imperatives lead to the appearance of the drawbacks set out above.

The only apparent and practical possibility therefore appears to be the action on the travel of the flyweight in order to lengthen it. In structures of the type recalled above, this stroke is essentially defined by the length of the cylindrical seat ensuring the guiding of the counterweight and on either side of which the intercommunication orifice is in relation, either with the exhaust cylinder, either with the action and working cylinder. However, if this length is increased, all of the dimensional characteristics of the body of the apparatus must be reconsidered, which leads to an increase in diameter, an increase in length and a weighting of the whole.

The prior art knows another proposal for a structural embodiment of a pneumatic percussion device in which the working cylinder has two chambers with variable volume, delimited by the head of the counterweight and which can be put in relation of intake and exhaust respectively, not via an intercommunication orifice made in the counterweight, but by a valve box subjected to the action of the vacuum prevailing in the exhaust chamber.

For such a system to work, it is necessary to provide a permanent free exhaust which results in a very high consumption of animation fluid. As a general rule, consumption on the order of 40 to 60 m3 / hour should be used.

If, with such a structure, it is possible to act more easily on the increase in the travel of the counterweight, on the other hand, it becomes impossible to apply such a system for portable devices. Indeed, the supply of animation fluid to these devices is generally ensured from a relatively low power compressor, driven by a single-phase electric motor taking its energy from the electrical current distribution networks of the domestic type or still an autonomous generator. However, such compressors have a production capacity limited to 20 m3 / hour.

It is also known from patent application EP-A-181 468 , a pneumatic percussion device comprising a body of generally tubular shape provided at the end with a quick connector intended to receive the tail of a working tool. The body delimits, on both sides of a cylindrical bearing ensuring the guidance and the sliding of a free weight of percussion, an exhaust cylinder in which the tail protrudes and a working cylinder divided into two opposite chambers inversely variable volume. These two chambers are separated by a piston formed by the counterweight which extends axially in the two cylinders and which internally delimits a concentric bore communicating directly with the action chamber and containing a free valve. Alternatively, one of the chambers is connected to a compressed air emission circuit, while the other chamber communicates with the exhaust cylinder and vice versa.

Such an apparatus does not make it possible to remedy the problem of the increase in the useful length of the travel of the counterweight without generating an increase in weight or in length.

Patent application GB-A-2 010 714 has also proposed a hydraulic percussion device in which a movable piston is intended to strike a working tool. The piston internally delimits a bore in which a valve is slidably mounted, so as to be able to close off, under the action of the pressure supplied by a gas, intake orifices in relation to a transfer-reaction chamber.

This document also does not make it possible to remedy the problem posed.

The object of the invention is precisely to remedy the above drawbacks by proposing a new structure of a pneumatic percussion device, a new structure making it possible to increase the useful length of the travel of the counterweight without generating an increase in weight or length, with a view to providing portable type devices with increased working efficiency, although their power can be supplied from a compressor driven by a single-phase electric motor.

To achieve the above objective, the pneumatic percussion device is of the type comprising a body of generally tubular shape, which is provided at the end with a quick connector intended to receive the tail of a working tool and which delimits, on either side of a cylindrical bearing ensuring the guiding and the sealed sliding of a free percussion counterweight, an exhaust cylinder in which the tail projects and a working cylinder divided into two chambers opposite to inversely variable volume, respectively called action and transfer-reaction, by a piston formed by the counterweight which extends axially in the two cylinders and which delimits internally a concentric bore communicating directly with the action chamber and containing a free pilot piston, means being provided at the same time in the body and in the counterweight to alternately put one of the chambers in relation to a compressed air intake circuit and the other chamber in relation to the exhaust cylinder and vice versa.

According to the invention, the concentric bore of the counterweight is characterized in that it also communicates by a passage with the transfer-reaction chamber or with the exhaust cylinder, and in that the free pilot piston has , on the one hand, a blind well permanently opening into the bore and the action chamber and, on the other hand, at least one radial light of intercommunication between the well and one or the other of two internal recesses in the bore, respectively opening, for one, in at least one exhaust duct formed in the counterweight to always open in the exhaust cylinder and, for the other, in the transfer chamber reaction, the pilot piston being mounted free to slide in the bore of the counterweight between two extreme positions, respectively defined by the bottom of the bore and by a stop ring mounted in the latter and in which positions the radial light is placed in coincidence either with one or with the other of the recesses.

The object of the invention is also to provide such a device with means for coupling the tool capable of avoiding the risks of the tool shank being struck and likely to intervene, in particular in the event of animation at empty, due to the higher working power that an apparatus of the type of the invention can develop.

For this purpose, the apparatus according to the invention is also characterized in that the quick connector is associated with a shock absorber interposed between itself and the shank of the tool.

Various other characteristics will emerge from the description given below with reference to the appended drawings which show, by way of nonlimiting examples, embodiments of the subject of the invention.

Fig. 1 is a half-sectional elevation of the device according to the invention.

Fig. 2 is a cross section taken along line II - II of FIG. 1 .

Fig. 3 is a partial sectional elevation taken along the broken line III - III of FIG. 2 .

Figs. 4 to 7 are cross-sections showing different phases of operation of the device.

Fig. 8 is a partial sectional elevation showing different details of embodiment of one of the constituent assemblies of the device.

Fig. 9 is a cross section taken along line IX - IX of FIG. 1 .

Figs. 10 and 11 are two partial sectional elevations highlighting operating phases of the subassembly according to FIGS. 8 and 9 .

The pneumatic percussion device as illustrated in fig. 1 comprises a body 1 of generally tubular shape comprising an end piece 2 on which is adapted a connector 3 for quick coupling and uncoupling of the shank 4 of a working tool 5 whose shape of the active part is indifferent for this which relates to the invention.

The body 1 internally defines an axial cylindrical surface 6 on either side of which are formed, on the one hand, a cylinder 7 said exhaust communicating with the nozzle 2 and with vents 8 and, on the other hand , a working cylinder 9 , of larger diameter than the bearing 6 and extending inside of the body 1 opposite the end piece 2 . The cylinder 9 is closed by a connector 10 to which a handle or a handle 11 can be adapted, as well as means for connection to a network for supplying compressed animation fluid such as air.

The bearing surface 6 is intended to ensure the guiding and the sealed sliding of a percussion weight 12 the length of which is chosen so that it always extends partly in the cylinders 7 and 9 simultaneously. The percussion weight 12 comprises a head 13 forming a piston, guided inside the cylinder 9 in which it delimits two variable-volume chambers 14 and 15 respectively called action and transfer-reaction, as is apparent from the functional explanation described below. The transfer-reaction chamber 15 communicates via an annular groove 16 with at least one compressed air intake duct 17 leading to the connector 10 , in particular via a supply groove 18 . Such a groove can advantageously be provided when the supply circuit of the chamber 15 is provided by several conduits 17 which can be formed in the wall thickness of the body 1 .

The counterweight 12 is produced, as shown in FIGS. 2 and 3 , to delimit internally a concentric bore 20 opening in the plane of the transverse face of the piston 13 , so as to be in permanent relation with the action chamber 14 . The bore 20 communicates by its bottom with an axial hole 21 extended by a radial bore 22 opening at the periphery of the counterweight, preferably inside a flat 23 . The bore 22 is advantageously controlled by a calibrated nozzle 24 , preferably removable.

The bore 20 has internally two recesses 25 and 26 which are respectively in communication with radial holes 27 opening into the chamber 15 and with exhaust ducts 28 opening into the exhaust cylinder 7 .

The bore 20 internally contains a pilot piston 30 , of shorter axial length, capable of sliding freely between two stop positions, respectively defined by the bottom of the bore 20 and by a stop ring 31 mounted in the piston 13 so as to allow communication between the bore 20 and the chamber 14 to remain. The free pilot piston 30 has, internally, a blind well 32 opening in the bore 20 and communicating with one or more openings 33 made radially to open at the outer periphery of the free pilot piston 30 . The constructive characteristics of the free pilot piston 30 and of the counterweight 12 are such that in the stop position illustrated in FIG. 3 , in which the pilot piston is in abutment against the bottom of the bore 20 , the openings 33 open into the recess 26 , while in the opposite abutment position in abutment against the ring 31 , the openings 33 coincide with the chamber 25 .

The apparatus described above operates as follows.

From the position illustrated in fig. 1 , the connection of the apparatus to a compressed air supply circuit allows the admission of the pressurized fluid into the conduits 17 which convey it into the transfer-reaction chamber 15 . Due to the abutment position of the pilot piston 30 against the bottom of the bore 20 , the recess 25 is closed, so that the compressed air is developed only in the chamber 15 . The counterweight 12 is urged to move back in the direction of the arrow f₁ , as shown in FIG. 4 . This return stroke results in a reduction in the volume of the chamber 14 which is connected, by the bore 20 , the well 32 , the ports 33 and the recess 26 , with the exhaust ducts 28 allowing the evacuation of the air or the fluid contained in the chamber 14 towards the cylinder 7 and its exhaust through the vents 8 .

This race continues until the retraction of the counterweight 12 brings the bore 22 into the chamber 15 , as illustrated in FIG. 4 . The compressed air contained in this chamber 15 then acts through the hole 21 on the pilot piston 30 which is moved in the direction of the arrow f₂ into its position of rear stop in which the lights 33 then coincide with the recess 25 , while the pilot piston 30 closes the recess 26 . In this state illustrated by FIG. 5 , an exhaust from the chamber 14 is no longer possible, so that the air which remains stored constitutes a mattress progressively pressurized to form a pneumatic damper avoiding the counterweight, receding in the direction of the arrow f₁ , to strike the connection 10 .

In this position, the compressed air from the chamber 15 is also transferred, by the recess 25 , the well 32 and the bore 20 , in the direction of the chamber 14 , with a view to establishing a rise in pressure capable of generating the inversion of the rectilinear displacement travel of the counterweight, then biased in the direction of the arrow f₃ , as illustrated in FIG. 6 . This stroke in the direction of the arrow f₃ corresponds to the active stroke and takes place without immediate impact on the position of the free pilot piston 30 , since from the position according to FIG. 5 , the bore 22 is also in relation to the transfer chamber 15 , so that balanced pressures are exerted on either side of the pilot piston 30 .

When the stroke in the direction of the arrow f₃ brings the bore 22 into the exhaust cylinder 7 , as illustrated in FIG. 6 , the preponderant pressure prevailing in the chamber 14 , in the bore 20 and inside the well 32 , pushes the pilot piston 30 in the direction of the arrow f₄ as far as the stop position illustrated in FIG. 6 . Simultaneously, the lights 33 are placed in communication with the recess 26 , while the recess 25 is closed. Although the chamber 14 is then put into contact with the exhaust conduits 28 , the energy communicated to the counterweight continues to impart a displacement in the direction of the arrow f₃ to cause it to strike the tail 4 of the tool 5 , while simultaneously the compressed air is only supplied in the transfer chamber 15 . The compressed air then acts as a shock absorbing mattress preventing the head 13 of the counterweight 12 from striking the bottom of the chamber 15 in percussion limit switch on the tool, as illustrated in fig. 7 .

The compression imposed on the air mattress contained in the chamber 15 is responsible at the end of percussion for driving the counterweight 12 in the direction of the arrow f ₁ to execute a new operating cycle, as described above.

As is apparent from the above, the free pilot piston 30 and the existence of the two recesses make it possible to increase the useful stroke of the counterweight to the measurement comprised axially between the transverse planes passing through the bore 22 and the recess 25 which constitutes the means of intercommunication between the transfer chamber 15 and the chamber 14 . Thus, by such means, it becomes possible to increase the useful stroke of the counterweight 12 without increasing the diameter of the body 1 or, significantly and appreciably, the length of the latter.

The bore 22 is advantageously controlled by the nozzle 24 in order to laminate the exhaust air during the stroke of the pilot piston 30 in the direction of the arrow f₄ to avoid sudden contact between this piston and the bottom of the bore 20 . In this way, as with the presence of damping air mattresses at the end of the alternative travel of the counterweight 12 , it becomes possible to produce an apparatus of increased power which does not generate significant vibrations imposed on the operator.

According to a development of the invention, the device is provided with a connector 3 for quick coupling and uncoupling capable of preserving the shank 4 of the tool 5 against impacts likely to be applied when empty, it that is to say when such a tool is not in abutment against a work surface.

The quick connector 3 comprises a sliding ring 40 , threaded concentrically on the end piece 2 and urged in the locking position against a rod 41 by the action of an elastic return member 42 . The ring 40 envelops thrust balls 43 , for example three in number, which are mounted, as appears in FIGS. 8 and 9 , in through holes 44 shown by end piece 2 . The through holes 44 are associated with clearance cups 45 which are formed from the outer peripheral surface of the end piece 2 . The ring 40 , pushed by the spring 42 , holds the stop balls 43 in the holes 44 .

The ring 40 has, internally and near its edge of cooperation with the rod 41 , an annular groove 47 called a clearance, the hollow cross section of which is complementary to that of the cups 45 to define together a useful housing section corresponding to the diameter balls 43 . An elastic lock 48 is carried by the body 1 to immobilize the ring 40 in the axial position of abutment against the rod 41 .

The connector 3 comprises a shock absorber 49 interposed between the stop balls 43 and the shank 4 of the tool 5 , inside the end piece 2 . The shock absorber 49 comprises a drawer 50 of tubular shape having, in its outer periphery, axial grooves 51 in which are engaged the balls 43 passing through the holes 44 and whose diameter is greater than the thickness of the drawer 50 which has internally a regular polygonal conformation 52 ( fig. 9 ) complementary to that 53 of the shank 4 of the tool 5 . The drawer 50 has in the same number as the balls 43 and in coincidence of spacing and angular equidistance, through holes 54 in which are housed stop balls 55 projecting on either side of the drawer 50 . The balls 55 are engaged in axial grooves 56 formed in the internal surface of the endpiece and thus ensure the angular immobilization of the drawer 50 in cooperation with the balls 43 . The balls 55 are brought into abutment against the balls 43 by the movement of the drawer 50 under the action of an elastic return member 57 interposed between the latter and an annular plug 58 closing the end piece 2 while freeing a passage section able to be crossed by the conformation 53 and the shank 4 of the tool 5 .

As is usual, the tail 4 comprises, from the conformation 53 , a turning 59 in which penetrate the stop balls 55 in the position illustrated in FIG. 1 .

As appears from the examination of FIG. 1 and from the foregoing, in the illustrated position, the polygonal conformation 53 is angularly immobilized inside the drawer 50 , itself angularly immobilized inside the end piece 2 . The shank 4 can slide axially over the length of the turning 59 defining the relative sliding range relative to the stop balls 55 . In addition, the tool can thus be maintained by the cooperation between the regular polygonal conformations 52 and 53 in an angular orientation chosen by the operator to correspond to the adequate working position. The connector 3 therefore ensures an angular and axial connection of the tool 5 .

During each percussion, the counterweight 12 comes into contact with the end of the tail 4 , so that the polygonal conformation 53 comes to bear on the balls 55 which retransmit to the drawer 50 the axial thrust received. The slide 50 moves axially against the action of the elastic member 57 , which makes it possible to dampen the operating vibrations.

When he wishes to disconnect the tool 5 , the operator acts on the latch 48 to allow the ring 40 to slide in the direction of the arrow f₅ from the position according to FIG. 10 . The groove 47 is gradually brought into line with the clearance bowls 45 to delimit with the latter as many housings as abutment balls 43 which can thus be erased inside such housings. The thrust exerted by the spring 57 biases the slide in the direction of the arrow f₆ ( fig. 11 ), so that the stop balls 55 are brought into the holes 44 left free by the erasure of the balls 43 . The retraction of the stop balls 55 frees the internal passage section of the drawer 50 and allows the axial sliding of the conformation 53 of the shank 4 of the tool 5 . This position is illustrated in fig. 11 which makes it possible to understand that a coupling with another tool is effected by acting vice versa and then voluntarily bringing the ring 40 in the direction of the arrow f₇ to force the balls 43 to reintegrate the through holes 44 by pushing the balls 55 inside the holes 54 . In this position, the new tool 5 is immobilized angularly and axially on the body 1 by means of the connector 3 .

Claims (11)

1. Pneumatic power hammer, of the type comprising a body (1) of general tubular shape, which is provided on the end with an instant connector (3) adapted to receive the tail end (4) of a working tool (5) and which defines, on either side, a cylindrical bearing surface (6) for guiding and sliding an impact-free sink head (12), an exhaust cylinder (7) into which projects the tail end and a working cylinder (9) divided into two opposite chambers of inversely variable volume (14, 15), respectively called action chamber and transfer-reaction chamber, via a piston (13) formed by the sink head which extends axially in the two cylinders and defines on the inside a concentric bore (20) communicating directly with the action chamber (14) and containing a free pilot-piston (30), means being provided both in the body and in the sink head in order to alternately connect one of the chambers with a circuit (17) for letting in compressed air and the other chamber with the exhaust cylinder (7) and vice-versa, characterized in that the concentric bore (20) of the sink head (12) also communicates, via a passage (21, 22) with the transfer-reaction chamber (15) or with exhaust cylinder (7), and in that the free pilot-piston (30) has, on the one hand, a blind shaft (32) permanently issuing in the bore (20) and the action chamber (14) and, on the other hand, at least one radial slot (33) for intercommunication between the shaft and either one of two recesses (25, 26) internal to the bore, issuing, respectively, for one in at least one exhaust pipe (28) provided in the sink head, in order to always open out into the exhaust cylinder (7) and for the other, in the transfer-reaction chamber, the pilot-piston being mounted for free sliding in the bore (20) of the sink head (12) between two outermost positions defined respectively by the bottom of the bore and by a stop-ring (31) mounted in the latter and between which positions the radial slot (33) is placed in register either with one, or with the other of the recesses (25, 26).
2. Apparatus according to claim 1, characterized in that the passage (21, 22) of the sink head is controlled by a calibrated nozzle (24).
3. Apparatus according to claim 1 or 2, characterized in that the passage is formed by an axial hole (21) formed from the bottom of the bore (20) and by a radial hole (22) issuing on the periphery of the sink head.
4. Apparatus according to one of claims 1 to 3, characterized in that the passage opens out on the periphery of the sink head by a flat portion (23).
5. Apparatus according to claim 1, characterized in that the instant connector (3) is combined with a shock-absorber (49) interposed between said connector and the tail-end of the tool.
6. Apparatus according to claim 5, characterized in that the instant connector (3) comprises abutments (43) which are retractable by the controlled sliding of a ring (40) with elastic return movement, which ring is threaded on the end piece and in that the shock-absorber (49) comprises an annular slide valve (50) disposed on the inside of the end piece and carrying lock pins (55) urged against the retractable abutments by an elastic member (57) acting on the slide valve.
7. Apparatus according to claim 5 or 6, characterized in that the shock-absorber (49) comprises a slide valve immobilized at an angle in the end piece and having an inner cross-section of polygonal shape (52) which is complementary to that (53) of the tail end (4) of the tool.
8. Apparatus according to claim 6 or 7, characterized in that the shock-absorber comprises a slide valve immobilized at an angle inside the end piece by the retractable abutments (43).
9. Apparatus according to one of claims 6 to 8, characterized in that the retractable abutments are constituted by balls placed in through holes (44) provided in the end piece in combination with exhaust tanks (45), said balls being held in position by a slidable outer ring (40) having a peripheral releasing groove (47) capable of being placed in transversal alignment with the tanks to define housings complementary to the retractable balls and in that the lock pins (55) are constituted of balls housed in through holes (54) provided in an annular slide valve (50) of smaller thickness than the balls which are held such as to project on the inside of the slide valve by resting against the retractable balls, under the action of an elastic member (57) acting on the slide valve.
10. Apparatus according to claim 7, 8 or 9, characterized in that the slide valve (50) is immobilized at an angle inside the end piece at least by axial grooves (51) which it forms on the outside and in which are engaged the abutment balls (43) in non-retracted position.
11. Apparatus according to one of claims 5 to 10, characterized in that the shock-absorber comprises a slide valve (50) immobilized at an angle with respect to the end piece of the apparatus and defining a regular polygonal internal configuration complementary to that of the tail end of the tool which is thus able to be held in an angular orientation suitable for the working position selected by the operator.

Images