EP0715932B1 - Method and apparatus for adjusting the stroke of a non-compressible fluid-actuated percussion device - Google Patents

Abstract

The regulator consists of a piston (1) which moves inside a cylinder between upper (8) and lower (9) chambers which are fed in sequence with a high-pressure fluid by a distributor (4) linked to a control member allowing the piston stroke to be varied. The regulator incorporates a slide valve (13) with a return spring (9), located inside a cylinder with one of its faces capable of being subjected to a fluid pressure. The regulator is able, during the piston rebound phase following an impact, to establish the presence of an instantaneous flow of fluid from the upper chamber (8) to the feed circuit (5) at a pressure determined from the pressure differential between the two circuits. In the event of a flow being detected, fluid is fed under pressure to the slide valve so that the stroke of the piston is increased.

Description

The subject of the present invention is a method of regulation automatic stroke of the impact piston of a percussion device driven by an incompressible fluid under pressure and an apparatus for setting implementing this process.

Percussion devices driven by an incompressible fluid under pressure are supplied with fluid, so that the resultant hydraulic forces applied successively on the piston of strike, move it alternately in one direction then in the other.

In devices of this type, the piston moves alternately inside a bore or cylinder, in which is provided, above the piston, a chamber which, delimited in part by this one, is conventionally called: upper room. When this chamber is supplied with pressurized fluid, the hydraulic force, which is created there, allows the piston to describe its stroke. To the other end of the bore, in which the piston moves, is provided a second chamber, also partly delimited by the piston, called conventionally: lower house. The resulting force of fluid pressure in the lower chamber ensures displacement of the piston for his return run.

The overall power of a device is expressed by the product the value of the strike frequency and the value of the energy by stroke.

It is known that, for a given overall power, it is preferable to favor energy per shot over the frequency of strikes when the tool of the device encounters hard ground while it is preferable to favor the strike frequency over energy by blow when the tool meets soft ground.

The energy per blow is the kinetic energy given to the piston, which depends on the stroke and the supply pressure.

To adjust the hitting frequency and energy per hit suitable for the hardness of a given terrain, two known solutions are described by patents EP 0 214 064 and EP 0 256 955 in the name of the Applicant.

Patent EP 0 214 064 describes an apparatus which makes it possible to obtain automatic adjustment of the percussion parameters, thanks to the presence in the cylinder of the apparatus of a channel supplied with fluid according to the position of the piston after the impact and the possible rebound of the piston on the tool.

Patent EP 0 256 955 describes an apparatus which makes it possible to obtain the same result, depending on the pressure variations in the chamber upper or lower chamber, consecutive to the rebound effect of the piston on the tool, thanks to the presence of a hydraulic element sensitive to these variations.

In both cases, they are well performing systems suitable for high power devices, but which are very expensive and require a large number of circuits, which makes them few compatible for small and medium power devices such as than those used for perforation or demolition.

The object of the invention is to provide a method and an apparatus for its implementation, allowing an automatic adaptation of the frequency and energy per stroke of the piston of a percussion device, which is simple, reliable and compact, in order to be able to equip in particular small and medium power devices.

To this end, the invention relates to a method for regulating the impact stroke of a percussion device, driven by a fluid incompressible under pressure, comprising a piston moving at the interior of a cylinder and delimiting with it an upper chamber and a lower chamber supplied sequentially with high fluid pressure by action of a distributor connected to a control device allowing the stroke of the striking piston to be varied, and comprising a drawer mounted in a cylinder on one side of which acts a spring and the other side of which can be subjected to fluid pressure, this drawer comprising a groove connected, on the one hand, to the distributor and, on the other hand, and depending on the axial position of the drawer, to one of several channels opening into the cylinder and capable of being connected with the lower chamber at the end of the displacement movement of the piston strikes upwards, characterized in that it consists, during the phase of piston rebound following impact, to determine existence possible instantaneous flow of fluid flowing from the upper chamber to the high pressure fluid supply circuit, determined at from the differential pressure between these two circuits then, if such flow is detected, to supply pressurized fluid to the control to move the drawer thereof in a direction of elongation of the stroke of the impact piston.

It is, in fact, to act on the steering system in function the direction and measurement of the instantaneous flow flowing from the chamber high when the position of the distributor corresponds to the kickback piston rebound. If there is little rebound in soft soil important, the differential pressure resulting from the instantaneous flow flowing of the upper chamber will be unimportant, and the piloting device will not will not be actuated, keeping the strike piston a short stroke. At otherwise, if the device works in hard ground, the rebound energy will be significant, and the pressure drop created by the instantaneous flow of fluid flowing out of the upper chamber will be significant, creating pressure differential controlling the supply of pressurized fluid to the piloting device, in order to lengthen the stroke of the impact piston.

Advantageously, this process consists in carrying out the feeding possible in pressurized fluid, of the control device, only during the piston rebound phase, at the start of the movement of the distributor and while the distributor still supplies the upper chamber in high pressure fluid.

It is important to perfectly master the moment when the control device must be supplied with pressurized fluid, in order to neutralize the hydraulic information resulting from the sudden stop of the piston during its impact under the tool.

According to a characteristic of the invention, an apparatus for implementation of this process includes a subject control drawer at the opposing fluid pressures prevailing, respectively, in the upper chamber and in the upper chamber supply circuit in fluid under high pressure, this drawer opening a supply circuit for the pressure fluid control device, when the difference between the pressure in the upper chamber and the pressure in the supply circuit exceeds a predetermined value.

Advantageously, the control drawer is mounted in a cylinder delimiting with the drawer two opposite connected chambers, respectively, to the upper chamber and to the fluid supply channel under high pressure, and into which two connected channels open, respectively, to a source of pressurized fluid and to the piloting, these two channels being capable of being put in communication by a groove in the control drawer, in a certain axial position thereof.

The source of pressurized fluid supplying the control device through the cylinder of the control drawer, can be constituted by the high pressure supply circuit itself or, through the upper room. The cylinder of the control drawer can therefore be connected to one or the other of these two pressure sources.

Advantageously, and in order to control the moment at which the pressurized fluid can be supplied to the control device, taking account of the operating cycle of the device, the supply duct of the pressure fluid control device passes through a drawer device, the movement of which is mechanically linked to movement of the dispenser, and which includes a groove which, according to the drawer position, allows or not the passage of pressurized fluid in direction of the striking piston stroke selector, belonging to the steering system.

Preferably, the groove of the drawer, associated with the dispenser, is positioned so that it does not allow the passage of fluid under pressure that during the start of the dispenser drawer stroke, at a moment when the distributor still allows the supply of the upper chamber in high pressure fluid.

The drawer, associated with the dispenser, can be either independent of the dispenser drawer, or be an integral part thereof.

According to another characteristic of the invention, this device has a leak channel, in permanent communication or momentary with the supply circuit of the control device in pressurized fluid, intended to evacuate, at each cycle a quantity defined fluid, to bring the control device drawer back into the direction of reduction of the stroke of the impact piston, when this control device is no longer sufficiently supplied with fluid under pressure.

Figure 1 représente une vue en coupe longitudinale d'un premier appareil ;

Figure 2 représente une vue en coupe longitudinale du même appareil dans une autre position de fonctionnement ;

Figure 3 représente une vue en coupe longitudinale du même appareil dans une autre position de fonctionnement ;

Figure 4 représente une vue en coupe longitudinale d'une variante du même appareil ;

Figure 5 représente une vue partielle d'une variante de l'appareil de figure 1 ;

Figure 6 représente une vue en coupe longitudinale d'une variante de l'appareil 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 schematic drawing, representing by way of nonlimiting examples, several embodiments of this device:

Figure 1 shows a longitudinal sectional view of a first device;

Figure 2 shows a longitudinal sectional view of the same device in another operating position;

Figure 3 shows a longitudinal sectional view of the same device in another operating position;

Figure 4 shows a longitudinal sectional view of a variant of the same device;

Figure 5 shows a partial view of a variant of the device of Figure 1;

6 shows a view in longitudinal section of a variant of the device of FIG. 1.

The device, shown in Figure 1, is a percussion device comprising a piston 1 sliding in a body 2, and coming to strike at each cycle a tool 3. A main distributor, mounted in the body 2, including a drawer 4, allows to put the upper chamber 8 provided above of the piston, alternately in relation to the fluid supply high pressure 5, as shown in figure 1, or with the low circuit pressure 6, as shown in figure 2. In addition, the piston 1 forms with the body 2, a lower annular chamber 9, permanently supplied by channel 5, so that each position of the dispenser drawer, causes the strike stroke of piston 1, then the ascent stroke.

The choice of small or large strike stroke is established from a control device which, depending on the position of the selector piston 13, can connect channels 11 and 12 or the channels 10 and 12. Channel 12 is connected to a control section of the main distributor 4, while channels 10 and 11 open into the cylinder containing the piston 1.

According to the invention, the device comprises a drawer 15 comprising two opposite pilot chambers: on the one hand the chamber 20 connected by a channel 22 to the fluid supply channel 5 under high pressure and, on the other hand, the chamber 21 connected to the upper chamber 8. The apparatus also includes a second drawer 23 whose movement is mechanically linked to the movement of the drawer 4 of the main distributor and which includes a groove 24 making it possible to stop or let pass the fluid between a channel 16 coming from the first drawer 15 and a channel 18 ending in the control chamber of the travel selector drawer 13.

The control circuit of the race selector 13 comprises a channel 14 connected to the high pressure fluid conduit 5, the slide 15, the channel 16, the drawer 23, and the channel 18 opening onto a section of the drawer stroke selector 13.

When the ground, encountered by the tool, is soft, the piston 1 does not rebound on tool 3 after impact, drawer 15 is constantly kept in the low position by the supply pressure from the channel 5 and accumulator 7 via channel 22 and applying to the largest diameter of the drawer, while the section annular of this slide is connected to the low pressure circuit 6 by a channel 24.

Channel 14, connected to supply channel 5, does not communicate not with channel 16. The control section of the race selector 13 is not supplied and this selector, thanks to the spring 19, remains in position low, connecting the control channel 12 of the distributor 4 with the channel 11 corresponding to the small strike stroke of the piston 1.

Figure 3 shows the position of the moving parts when the ground, encountered by the tool, is hard. The striking piston 1 rebounds just after its impact on tool 3 and pushes the fluid back into the channel 17, while the main distributor 4 is still in the position in figure 1 and begins to move from the position of figure 1 to the position of figure 2.

The instantaneous flow of fluid in channel 17, at the time of rebound of the piston, creates a pressure drop, and therefore, establishes a pressure differential between the upper chamber 8 and the outlet of the channel 22 in the supply channel 5.

Beyond a certain flow, this differential pressure is sufficient to lift the drawer 15. At this time, the drawer 15 communication channel 14 and channel 16 via a groove 15a. During this connection, the distributor 4 changes position, and the drawer 23, linked to this distributor, briefly connects the channel 16 to channel 18. The fluid passing successively from channel 14 to channel 16, then on channel 18, feeds the control section of the selector stroke 13, and allows this selector to be pushed back against the action of the spring 19. This selector 13 then communicates the control channel 12 from main distributor 4 with channel 10 corresponding to the large piston stroke 1.

The drawer 15 starts to move only when the flow snapshot goes from upper room 8 to channel 5, through the channel 17. When the flow in channel 17 is in the direction of filling the upper chamber 8, the drawer 15 remains stationary.

According to another variant of the invention, the channel 22 can be connected to channel 17, instead of channel 5. Indeed, the movement of the drawer 15 is only sensitive to the pressure drop due to the instantaneous flow leaving the upper room 8.

Figure 3 shows the position of the moving parts when, during the rebound of the piston, the slide 23, whose movement is linked to that of the distributor 4, allows the fluid to pass from the channel 16 to the channel 18 and the selector 13, at a chosen time, depending on the position relative of the groove 24 of this drawer and the outlet of the channels 16 and 18. This drawer 23 has a central channel 28 opening into a groove annular, making it possible to connect both channel 16, channel 18 and, at through a calibrated orifice, the low pressure circuit 6. During the operation of the device, the movements of the striking piston 1 and the distributor 4 remain constantly linked to each other. So at a position precise stroke of the piston 1, the distributor drawer and the drawer 23 will therefore be in a precise position. By choosing the position of the groove 24 of drawer 23, it is possible to precisely predict the lapse of time of the operating cycle during which the fluid passage between channels 16 and 18 will be allowed.

The right choice is to establish communication between channels 16 and 18, a few moments after the shock. Indeed, at the time of the shock of the piston on the tool, the drawer 15 tends to lift under the effect of the blow of ram due to the sudden stop of the striking piston, then goes down immediately, if the ground is tender, but remains raised a little longer if the ground is hard. The drawer 23 eliminates the influence of pressure variations in the upper chamber 8, not letting the fluid flow, towards the selector 13, only a little later, when the lifting of the drawer 15 actually corresponds to the presence of an installed flow rate of the upper chamber 8 towards channel 5, and therefore, a rebound of the piston on a hard ground.

When the ground is not hard enough to justify the passage of the impact piston in large stroke, the calibrated orifice contained in the channel 28 evacuates to the low pressure circuit 6, all of the fluid from drawer 15 and channel 16. Thus, channel 18 does not receive more fluid, but on the contrary evacuates through the channel 28 the fluid contained in the pilot chamber of the drawer 13, allowing the maintenance in small stroke of the impact piston.

FIG. 4 represents a variant of the invention according to which the distributor 4 and the drawer 23 form a single piece. In this variant, channel 28 is deleted and replaced by channel 29 or a channel 30 comprising a calibrated orifice and connecting the channel 18 with the low circuit pressure 6. In this embodiment, if the amount of fluid injected through the channel 16 in the control chamber of the drawer 13 is greater than the amount of fluid discharged through channel 29 or 30, then the drawer 13 is pushed up, so as to select the long stroke of the piston hit.

Figure 5 shows another embodiment of the invention, in which the drawer 15 is constituted by a valve, allowing energy recovery. During the rebound phase of piston, this valve, specially fitted out according to the invention, comprises a groove 15a making it possible to connect the channel 14, supplied in high pressure, with channel 16, when it is lifted.

On hard ground, during its rebound phase, the piston 1 discharges the fluid contained in the upper chamber 8, directly through the passage 25, then channel 26 to the high pressure circuit 5, lifting the valve 15. The valve 15 remains raised as long as the pressure drop due to the flow between channels 25 and 26 is greater than the pressure value power multiplied by a constant depending on the sections of the valve. The supply pressure being kept constant moreover, the valve 15 therefore remains open from a planned discharge rate of the upper room 8.

Throughout the duration of the passage of fluid through this valve 15, the throat of the valve connects the channel 14 with the channel 16. This allows, by the passage of fluid through the slide 23, to supply the channel 18 and therefore to control the race selector 13 so as to obtain a large stroke of the piston for hard ground.

Figure 6 shows another embodiment of the invention, according to which the channel 14 is replaced by a channel 27 in communication with the upper chamber 8. When the flow in the channel 27 is able to establish itself, the upper chamber is obviously under pressure. The fluid supply can therefore be taken from the upper room 8 instead of being taken as previously by the canal of arrival 5.

As is apparent from the above, the invention provides a improvement and simplification of the current state of the art in the area of automatic selection of strike stroke of these devices.

It goes without saying that the invention is not limited only to embodiments of this apparatus, described above by way of examples; on the contrary, it embraces all of its variant embodiments. It is thus in particular that the number of positions of the selector drawer 13 could be greater than two, without leaving the framework of the invention.

Claims (11)

1. Method for regulating the striking stroke of a percussion apparatus, actuated by an incompressible fluid under pressure, comprising a piston (1) moving inside a cylinder and delimiting therewith an upper chamber (8) and a lower chamber (9) supplied in a sequential manner with a fluid under high pressure by the action of a distributor (4) connected to a control device making it possible to vary the stroke of the striking piston, and comprising a slide valve (13) mounted in a cylinder of which one of the faces may be subjected to a fluid pressure and comprising a return device (19), this slide valve including a throat connected, on the one hand, to the distributor (4) and, on the other hand, according to the axial position of the slide valve, to one of several channels (10,11) emerging in the cylinder and capable of being put into communication with the lower chamber (9) at the end of the upwards displacement movement of the striking piston, characterized in that it consists, during the rebound phase of the piston following impact, of determining the possible existence of an instantaneous flow of fluid passing from the upper chamber (8) to the circuit (5) supplying fluid under high pressure determined from the differential pressure between these two circuits and then, if such a flow is detected, of supplying the control device with fluid under pressure so as to displace the slide valve (13) thereof in the longitudinal direction of the stroke of the striking piston.
2. Method according to claim 1, characterized in that it consists of supplying, as required, fluid under pressure, from the control device (13), only during the rebound phase of the piston, at the start of the movement of the distributor and while the distributor once more supplies the upper chamber with fluid under high pressure.
3. Apparatus for implementing the method according to either of claims 1 or 2, characterized in that it includes a control slide valve (15) subjected to opposing fluid pressures existing respectively in the upper chamber and in the circuit supplying the upper chamber with fluid under high pressure, this slide valve (15) opening a circuit (14,16,18) supplying the control device (13) with fluid under pressure when the difference between the pressure in the upper chamber (8) and the pressure in the supply circuit exceeds a predetermined value.
4. Apparatus according to claim 2, characterized in that the control slide valve (15) is mounted in a cylinder delimiting with the slide valve two opposite chambers connected, respectively, to the upper chamber (8) and to the channel (5) supplying fluid under high pressure, and in which two channels (14,16) emerge connected, respectively, to a source of fluid (5,8) under pressure and to the control device (13), these two channels being capable of being put into communication via a throat (15a) which includes the control slide valve (15) in a certain axial position thereof.
5. Apparatus according to claim 4, characterized in that one (14) of the channels emerging in the cylinder of the control slide valve communicates with the conduit (5) supplying the apparatus with fluid under high pressure.
6. Apparatus according to claim 4, characterized in that one (14) of the channels emerging in the cylinder of the control slide valve communicates with the upper chamber (8) .
7. Apparatus according to any one of claims 3 to 6, characterized in that the conduit (16) supplying the control device with fluid under pressure passes through a device with a slide valve (23), of which the movement is linked mechanically to the movement of the distributor (4) and which includes a throat (24) which, according to the position of the slide valve, allows or does not allow fluid under pressure to pass in the direction of the slide valve (13) selecting the stroke of the striking piston, belonging to the control device.
8. Apparatus according to claim 7, characterized in that the throat (24) of the slide valve (23), associated with the distributor (4), is positioned so that it only allows fluid under pressure to pass during the start of the stroke of the slide valve (4) of the distributor, at a time when the distributor still enables the upper chamber (8) to be supplied with fluid under high pressure.
9. Apparatus according to either of claims 7 or 8, characterized in that the slide valve (23) associated with the distributor (4), is independent of the slide valve of the distributor and is linked mechanically to the latter.
10. Apparatus according to either of claims 7 or 8, characterized in that the slide valve (23) associated with the distributor, and the slide valve (4) of the distributor form a single piece.
11. Apparatus according to any one of claims 3 to 10, characterized in that it includes a leakage channel (28), (29), (30), in permanent or momentary communication with the circuit (18) supplying the control device (13) with fluid under pressure, designed to evacuate a definite quantity of fluid at each cycle, so as to bring the slide valve of the control device (13) into the direction of a reduction in the stroke of the striking piston, when this control device is no longer sufficiently supplied with fluid under pressure.

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