EP0715932A1 - 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 process for automatic regulation of the stroke of the striking piston of a percussion device driven by an incompressible fluid under pressure and a device for implementing this process.

Percussion devices driven by an incompressible fluid under pressure are supplied with fluid, so that the result of the hydraulic forces applied successively on the striking piston, displaces the latter 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 formed, above the piston, a chamber which, delimited in part by the latter, is called so conventional: upper room. When this chamber is supplied with pressurized fluid, the hydraulic force which is created there allows the piston to describe its stroke. At the other end of the bore, in which the piston moves, is provided a second chamber, also partially delimited by the piston, conventionally called: lower chamber. The resulting force of the fluid pressure in the lower chamber ensures the displacement of the piston for its return stroke.

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

It is known that, for a given overall power, it is preferable to privilege the energy per blow compared to the strike frequency, when the tool of the apparatus meets a hard ground, while it is preferable to privilege the strike frequency with respect to the energy per blow when the tool encounters soft ground.

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

To adjust the striking frequency and the energy per stroke 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 an automatic adaptation 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 upper chamber or the 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, these are high-performance systems well suited to high-power devices, but which are very expensive and require a large number of circuits, which makes them not very compatible for small and medium-power devices. , such as 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 of the energy by stroke of the piston of a percussion apparatus, which is simple, reliable and compact. , to be able to equip in particular small and medium power devices.

To this end, the invention relates to a method of regulating the striking stroke of a percussion device, driven by an incompressible fluid under pressure, comprising a piston moving inside a cylinder and delimiting therewith. ci an upper chamber and a lower chamber supplied sequentially with fluid under high pressure by the action of a distributor connected to a control device making it possible to vary the stroke of the striking piston, and comprising a drawer mounted in a cylinder on the '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 position axial of the drawer, to one of several channels opening into the cylinder and capable of being placed in communication with the lower chamber at the end of the movement of movement of the striking piston upwards, characterized in that it co nsist, during the piston rebound phase following impact, to determine the possible existence of an instantaneous flow of fluid flowing from the upper chamber to the high pressure fluid supply circuit, determined to starting from the differential pressure between these two circuits then, if such a flow is detected, supplying pressurized fluid to the pilot to move the drawer thereof in a direction of elongation of the stroke of the impact piston.

It is, in fact, acting on the steering device according to the direction and the measurement of the instantaneous flow flowing from the upper chamber at the moment when the position of the distributor corresponds to the rebound phase of the piston. hit. If, in soft soil, the rebound is small, the differential pressure resulting from the instantaneous flow flowing from the upper chamber will be small, and the control device will not be actuated, keeping the strike piston a short stroke. On the contrary, 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 a differential pressure controlling l 'supply of pressurized fluid to the control device in order to lengthen the stroke of the impact piston.

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

It is important to perfectly control the moment at which the piloting 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 implementing this method comprises a control slide subjected to the opposing pressures of fluid prevailing, respectively, in the upper chamber and in the supply circuit of the upper fluid chamber under high pressure, this drawer opening a circuit for supplying the device for controlling the fluid under pressure, 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 chambers connected, respectively, to the upper chamber and to the channel for supplying fluid under high pressure, and into which open two channels connected, respectively, to a source of pressurized fluid and to the piloting, these two channels being capable of being brought into communication by a groove which the control slide comprises, in a certain axial position thereof.

The source of pressurized fluid supplying the piloting device through the cylinder of the control slide, can be constituted by the high pressure supply circuit itself or, by the upper chamber. The cylinder of the control slide 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 piloting device, taking into account the operating cycle of the device, the supply pipe of the piloting device with pressurized fluid passes through a drawer device, the movement of which is mechanically linked to the movement of the distributor, and which comprises a groove which, depending on the position of the drawer, allows or does not allow the passage of pressurized fluid in the direction of the selector slide stroke of the striking piston, belonging to the steering system.

Preferably, the groove of the drawer, associated with the distributor, is positioned in such a way that it allows the passage of pressurized fluid only during the start of the stroke of the distributor drawer, at a time when the distributor still allows the supply of high pressure fluid to the upper chamber.

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

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

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

The choice of small or large strike stroke is established from a control device which, depending on the position of the stroke selector piston 13, can connect channels 11 and 12 or channels 10 and 12 respectively. 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.

In accordance with the invention, the device comprises a drawer 15 comprising two opaque piloting chambers: on the one hand the chamber 20 connected by a channel 22 to the channel for supplying fluid 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 comprises 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 stroke selector drawer 13.

The circuit for controlling the travel selector 13 comprises a channel 14 connected to the conduit 5 for fluid under high pressure, the drawer 15, the channel 16, the drawer 23, and the channel 18 opening onto a section of the travel selector drawer 13.

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

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

FIG. 3 represents 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 the tool 3 and repels the fluid in the channel 17, while the main distributor 4 is still in the position of figure 1 and begins to pass from the position of figure 1 towards the position of figure 2.

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

Beyond a certain flow rate, this differential pressure is sufficient to raise the drawer 15. At this time, the drawer 15 puts the channel 14 and the channel 16 in communication via a groove 15a. During this communication, the distributor 4 changes position, and the slide 23, linked to this distributor, briefly connects the channel 16 to the channel 18. The fluid passing successively from the channel 14 to the channel 16, then to the channel 18, supplies the piloting section of the travel selector 13, and allows this selector to be pushed back against the action of the spring 19. This selector 13 then puts the pilot channel 12 into communication of the main distributor 4 with the channel 10 corresponding to the large striking stroke of the piston 1.

The slide 15 is set in motion only when the instantaneous flow goes from the upper chamber 8 to the channel 5, via the channel 17. When the flow in the channel 17 is in the direction of filling of the upper chamber 8, the drawer 15 remains stationary.

According to another variant of the invention, the channel 22 can be connected to the channel 17, instead of the channel 5. In fact, the movement of the slide 15 is only sensitive to the pressure drop due to the instantaneous flow coming out of the upper room 8.

FIG. 3 shows the position of the moving parts when, during the rebound of the piston, the slide 23, the movement of which is linked to that of the distributor 4, lets the fluid pass from channel 16 to channel 18 and the selector 13, a selected moment, as a function of the relative position 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 an annular groove, making it possible to connect both the channel 16, the channel 18 and, through a calibrated orifice, the low pressure circuit 6. During the operation of the apparatus, the movements of the striking piston 1 and of the distributor 4 remain constantly linked to each other. Thus, at a precise position of the 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 the drawer 23, it is possible to predict precisely the time period of the operating cycle during which the passage of fluid between the channels 16 and 18 will be authorized.

The right choice is to establish communication between channels 16 and 18, a few moments after the shock. In fact, when the piston hits the tool, the drawer 15 tends to rise under the effect of water hammer due to the sudden stop of the striking piston, then goes back down immediately, if the ground is soft , but stays raised a little longer if the ground is hard. The drawer 23 eliminates the influence of pressure variations in the upper chamber 8, by letting the fluid flow towards the selector 13 only a little later, when the lifting of the drawer 15 corresponds effectively to the presence of a flow installed from the upper chamber 8 to the channel 5, and therefore, to a rebound of the piston on 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 towards the low pressure circuit 6, all the fluid coming from the spool 15 and the channel 16 Thus, the channel 18 no longer receives fluid, but on the contrary discharges through the channel 28 the fluid contained in the control chamber of the drawer 13, allowing the striking piston to be kept in small stroke.

FIG. 4 represents a variant of the invention according to which the distributor 4 and the drawer 23 form only one piece. In this variant, the channel 28 is eliminated and replaced by a channel 29 or a channel 30 comprising a calibrated orifice and connecting the channel 18 with the low pressure circuit 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 quantity of fluid discharged through the channel 29 or 30, then the drawer 13 is pushed upwards, so as to select the large stroke of the striking piston.

FIG. 5 represents another embodiment of the invention, in which the drawer 15 is constituted by a valve, or valve, allowing energy recovery. During the rebound phase of the piston, this valve, specially fitted out according to the invention, comprises a groove 15a making it possible to connect the channel 14, supplied with high pressure, with the channel 16, at the time of its lifting.

On hard ground, during its rebound phase, the piston 1 delivers the fluid contained in the upper chamber 8, directly through the passage 25, then the channel 26 towards the high pressure circuit 5, by lifting the valve 15. The valve 15 remains raised as long as the pressure drop due to the flow between the channels 25 and 26 is greater than the value of the supply pressure 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 flow rate intended for evacuation of the upper chamber 8.

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

FIG. 6 represents 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 rate in the channel 27 is able to be established , the upper house is obviously under pressure. The fluid supply can therefore be taken in the upper chamber 8 instead of being taken as previously by the inlet channel 5.

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

It goes without saying that the invention is not limited to the sole embodiments of this device, described above by way of examples; on the contrary, it embraces all of its variant embodiments. Thus in particular that the number of positions of the selector drawer 13 could be greater than two, without departing from the scope of the invention.

Claims (11)

Method for regulating the striking stroke of a percussion device, driven by an incompressible fluid under pressure, comprising a piston (1) moving inside a cylinder and delimiting with it an upper chamber (8 ) and a lower chamber (9) supplied sequentially with 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 drawer (13) mounted in a cylinder one of the faces of which can be subjected to fluid pressure and comprising a return device (19), this drawer comprising a groove connected, on the one hand, to the distributor (4) and, on the other part, and depending on the axial position of the drawer, to one of several channels (10, 11) opening into the cylinder and capable of being placed in communication with the lower chamber (9) at the end of the movement of movement of the upward striking piston, characterized in that it c Onsiste, during the rebound phase of the piston after impact, to determine the possible existence of an instantaneous flow of fluid flowing from the upper chamber (8) to the fluid supply circuit (5) under high pressure, determined from the differential pressure between these two circuits then, if such a flow is detected, supplying pressurized fluid to the control device to move the slide (13) thereof in a direction of lengthening of the stroke of the impact piston. Method according to claim 1, characterized in that it consists in carrying out the possible supply of pressurized fluid, of the piloting device (13), only during the rebound phase of the piston, at the start of the movement of the distributor and while the distributor still supplies the upper chamber with fluid under high pressure. Apparatus for implementing the method according to any one of claims 1 and 2, characterized in that it comprises a control slide (15) subjected to the opposing pressures of fluid prevailing, respectively, in the upper chamber and in the high pressure fluid supply circuit of the upper chamber, this slide (15) opening a supply circuit (14, 16, 18) of the pilot device (13) in pressurized fluid, when the difference between the pressure in the upper chamber (8) and the pressure in the supply circuit exceeds a predetermined value. Apparatus according to claim 2, characterized in that the control slide (15) is mounted in a cylinder delimiting with the slide two opposite chambers connected, respectively, to the upper chamber (8) and to the supply channel (5) in fluid under high pressure, and into which open two channels (14, 16) 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 in communication by a groove (15a) that comprises the control slide (15), in a certain axial position thereof. Device according to claim 4, characterized in that one (14) of the channels opening into the cylinder of the control slide communicates with the supply pipe (5) of the device with high pressure fluid. Apparatus according to claim 4, characterized in that one (14) of the channels opening into the cylinder of the control slide communicates with the upper chamber (8). Apparatus according to any one of claims 3 to 6, characterized in that the conduit (16) for supplying the piloting device with pressurized fluid passes through a slide device (23), the movement of which is mechanically linked to the movement of the distributor (4) and which comprises a groove (24) which, depending on the position of the drawer, allows or not the passage of pressurized fluid towards the drawer (13) stroke selector of the striking piston, belonging to the device steering. Apparatus according to claim 7, characterized in that the groove (24) of the drawer (23), associated with the distributor (4), is positioned in such a way that it does not allow the passage of pressurized fluid until the start of the stroke of the distributor drawer (4), at a period when the distributor still allows the supply of the upper chamber (8) with fluid under high pressure. Apparatus according to any one of claims 7 and 8, characterized in that the drawer (23), associated with the distributor (4), is independent of the distributor drawer and mechanically linked to the latter. Apparatus according to any one of claims 7 and 8, characterized in that the drawer (23) associated with the distributor, and the drawer (4) of the distributor form a single piece. Apparatus according to any one of claims 3 to 10, characterized in that it comprises a leakage channel (28), (29), (30), in permanent or momentary communication with the supply circuit (18) of the piloting device (13) in pressurized fluid, intended to evacuate, at each cycle a defined quantity of fluid, in order to bring the drawer of the piloting device (13) in the direction of reduction of the stroke of the impact piston, when this control device is no longer sufficiently supplied with pressurized fluid.

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