US3793834A

US3793834A - Device driving a heavy body in reciprocating motion

Info

Publication number: US3793834A
Application number: US00208666A
Authority: US
Inventors: L Martin
Original assignee: Poclain SA
Current assignee: Poclain SA
Priority date: 1970-12-22
Filing date: 1971-12-16
Publication date: 1974-02-26
Anticipated expiration: 1991-02-26
Also published as: GB1354929A; BE776296A; IT943253B; DE2163303A1; ES398225A1

Abstract

The present invention relates to a device for driving a heavy body connected to a drive motor by a cable, whilst the forces transmitted to said body by the motor are alternately higher than and opposite the forces of gravity acting on this body, and lower than said forces of gravity, and a device antagonistic to said forces of gravity is permanently coupled to the drive motor. Said antagonistic device is constituted by a spring motor. The invention is applicable to the production of an installation for pumping petroleum oil products.

Description

United States Patent 1191 Martin I Feb. 26, 1974 DEVICE DRIVING A HEAVY BODY IN 2,597,050 5/1952 Audemar 60/54.5 R RECIPROCATING MOTION 2,554,381 5/1951 Patterson 60/53 L X 3,075,467 1/ 1963 Gallaway 417/405 X Inventor: Lows Martln, Senhs, France 3,213,763 10/1965 Pearson et al. 60/53 ww ux Assigneet Societe Anonyme Poclain, 3,237,406 3/1966 Spannhake et al. 60/51 X France Primary Examiner-Edgar W. Geoghegan [22] Flled: 1971 Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper 21 Appl. N0; 208,666 & Seinto [30] Foreign Application Priority Data [57] ABSTRACT Dec. 22, 1970 France 7046239 The present invention relates to a device for driving 3 Nov. 23, 1971 France 7141878 heavy body connected to a drive motor by a cable whilst the forces transmitted to said body by the motor [52] US. Cl (30/413,60/416, 60/905, are alternately higher than'and opposite the forces of 60/448 gravity acting on this body, and lower than said forces [5] llll. Cl. F151) l/(IZ of gravity, and a device antagonistic to said forces of [58] F'eld Search 60/52 P11 53 53 53 gravity is permanently coupled to the drive motor.

60/51, 371, 372, 413, 414, 416, 420; 417/405 Said antagonistic device is constituted by a spring motor. [56] References Cited The Invention is applicable to the production of an UNITED STATES PATENTS installation for pumping petroleum oil products. 2,564,285 8/1951 Smith 60/372 2,576,359 11/1951 Putnam 60/414 15 Claims, 6 Drawing Figures PATEMEDFEBZBJSM 3.793.834

' SHEET 1 UF 4 PATENTEDFEBZB I914 3.793.834

SHEET 3 OF 4 DEVICE DRIVING A I-IEAVY BODY IN RECIPROCATING MOTION The present invention relates to a device for driving a heavy body in reciprocating motion.

Certain piston pumps are known which are intended to be disposed at a great depth in the ground to drive back the material drawn up from the ground to ground level. Such is the case, for example, of pumps used by prospectors of petroleum oil products.

It is known that the above-mentioned pumps have their cylindrical body rendered integral with the conduit constituted by the hollow boring rods, whilst their piston is coupled, by bars coaxial to the said hollow rods, with a drive device of the type consisting of a motor coupled with a connecting rod-crank system. It must be specified that the bars and the piston constitute a generally very heavy assembly, connected to the drive device by a connecting cable. In order to avoid too great a variation of potential energy, during the reciprocating motion of the piston, the weight of said piston and the bars is often balanced, at least partially, by that of a counterweight mounted to rock in opposition to that of the piston and the rods.

However, it has been ascertained that this arrangement had a certain number of drawbacks, including in particular the necessity of accepting the clearance at the end of a lever of a heavy and cumbersome counterweight, which is dangerous. In addition, the alternate stresses due to the acceleration of the counterweight must be taken up by the drive device. This fact is of such nature as to lead to a limitation of the fluid flow of the pump, the maximum speed admissible being very quickly reached. The overall yield of the known pumping installations is therefore mediocre.

The invention intends to remedy this state of affairs and to this end proposes a novel device for driving in reciprocating motion, in which the energy is no longer accumulated in the form of displacement of very heavy masses, but on the contrary in elastic form, by choosing elements having a low inertia. It is applied to the driving in reciprocating motion of all heavy bodies.

The invention therefore has for its object a device for driving a heavy body in reciprocating motion, said heavy body being connected to a drive motor by a flexible traction connection, whilst the forces that may be transmitted to said body by said motor are alternately greater than and opposite to the forces of gravity and friction acting on this body, and smaller than said forces of gravity and friction, and a device which is antagonistic to Le, opposes, said forces of gravity is permanently coupled to the drive motor.

This latter device is constituted as a fluid motor; that is, a motor which resists but does not overcome the force of gravity acting on the body.

According to a first embodiment, the spring motor is constituted as a reversible fluid motor comprising two chambers permanently connected, one, to a first pressurised fluid accumulator, the other, to a second pressurised fluid accumulator.

In addition, the flexible traction connection is preferably wound on a winch, to which are connected the drive motor and the fluid motor.

The drive motor is advantageously constituted as a reversible fluid motor comprising two chambers connected. one, permanently to a third pressurised fluid accumulator, the other, selectively by means of a twoway distributor, either with a source of pressurised fluid, or with the third accumulator.

The source of pressurised fluid is preferably constituted as a volumetric hydraulic pump, on the delivery of which a fourth pressurised fluid accumulator is disposed in shunt. This source of pressurised fluid may however, as a variant, be constituted as a gas compressor, on whose delivery a fifth pressurised fluid accumulator is disposed in shunt.

Furthermore, the two position distributor comprises a movable element generally coupled with a control device capable of disposing it successively on each of its two positions; this control device is advantageously coupled to the fluid motor and is advantageously adjustable.

Finally, for reasons of simplicity of the installation, the second and third accumulators are often constituted as a single accumulator, the same applying for the first and fourth or first and fifth accumulators.

According to a second embodiment, the spring motor is constituted as the drive motor itself, which is a reversible fluid motor comprising two chambers permanently connected, one, by a first conduit, to a pressurised fluid accumulator, the other, by a second conduit, to a fluid tank, this reversible motor being in addition a motor with variable cubic capacity provided with a member for regulating said cubic capacity. The drive device comprises a source of pressurised fluid provided with a delivery conduit which is connected to the first conduit and to which a calibrated discharge valve is connected in shunt.

According to a first variant embodiment, the reversible motor has a rotor to which the member regulating the cubic capacity is coupled by a kinematic motion transmission chain.

According to a second variant embodiment, the reversible motor has a rotor to which the member regulating the cubic capacity is connected by means of a device detecting the speed of rotation of this rotor, and transmitting a stress that is a function of said speed.

The detector and transmitter device is preferably constituted by a reversible volumetric hydraulic pump whose drive shaft is coupled to the rotor of the reversible motor, whilst a volumetric double action receiver member is coupled with the member for regulating the cubic capacity. The volumetric pump'and the receiver member each have two chambers, one chamber of the pump being connected by a third conduit to a chamber of the receiver member, and the other chamber of the pump being connected by a fourth conduit to the other chamber of the receiver member. A diaphragm is interposed on a fifth conduit, which is connected in shunt on the third and on the fourth conduit, whilst, finally, the member regulating the cubic'capacity is coupled to a resilient return element, whose effect tends to hold said regulating member in a given position or to return it thereto.

The application of the invention to the drive of the movable member of a piston pump has been chosen by way of example.

In order that the invention be more readily understood, reference will now be made to the accompanying drawings, in which:

FIG. 1 is an elevational view of the complete pumping installation, which is provided with the drive device according to a first embodiment of the invention;

FIG. 2 is a schematic representation of a hydraulic drive device according to the invention;

FIG. 3 is an elevational view of a detail of a drive device according to the invention;

FIG. 4 is a schematic representation of a hydraulic drive device according to a second embodiment of the invention;

FIGS. 5 and 6 schematically show a first and second variant embodiment respectively of the control of the member regulating the cubic capacity of the drive motor of FIG. 4, said regulation being effected, respectively, either as a function of the position of the driven body, or as a function of the speed of drive of said body.

In FIG. 1, a train of hollow rods 1 has been driven into the ground 2 and has penetrated into a pocket of matter 3 in the form of more or less viscous fluid, but nevertheless capable of being drawn up by pumping. The body 4 of a piston pump, provided with valves 5, whose piston 6 is integral with the bars which connect it to the surface 8 of the ground 2 is, moreover disposed to be integral with the rods 1. At the upper end of the bars 7, a cable 9 is fixed and is in addition wound on the drum of a winch 10 supported by a structure 11 on the ground 8. The winch 10 is moreover coupled to a hydraulic motor 12 for effecting rotation thereof.

It will be specified that the movable equipment of the pump, constituted in the present case by the piston 6 and the bars 7, is very heavy. Furthermore, the movable member of the pump, in a variant embodiment, would have been able to be constituted by the cylinder 4, the piston 6 then being fixed.

FIG. 2 shows an embodiment of the device driving the winch l alternately in opposite directions. This FIG. shows that the motor 12 is coupled to the winch 10, but also that a hydraulic motor 13 is coupled to said winch, mechanically with the motor 12. The motors l2 and 13 are reversible motors that may operate either generator or as receiver.

The motor 13 comprises two chambers permanently connected, one by the conduit 14 to a first pressurised fluid accumulator 15, the other, by conduit 16, to a second pressurised fluid accumulator 17. It will be noted as from now that the dimensions of the accumulators l and 17 are such that, during rotation of the winch on either side of its average position, the pressures of the fluid remain substantially constant in the two accumulators, the pressure in accumulator being higher than that prevailing in accumulator 17.

As regards the motor 12,'it also comprises two chambers connected, one, permanently by the conduit 18 to the second accumulator 17, the other, by a conduit 19 to a two-position 20. Two other conduits terminate at the distributor 20: a conduit 21, connected in shunt on conduit 14 and a conduit 22 connecting the distributor 20 to the second pressure accumulator 17. In a first position of the movable element, the distributor -20 communicates the

conduits

19 and 21, conduit 22 being obturated at its connection to said distributor 20, whilst there corresponds to the second position of the movable element of the distributor 20 the communication of the conduits l9 and 22, and the obturation, at its connection with said distributor 20, of conduit 21.

Concerning the distributor 20, it will be specified that the movable element of this distributor is coupled by a connection 23 to the winch 10. In the present case, in the example shown, the distributor 20 is a slide valve distributor, whilst said slide is coupled by a connecting rod-crank system to the winch 10, the angular position of the shaft 10a of said winch consequently automatically controlling the position of the slide of the distributor 20.

It will further be noted that a conduit 24 connects

conduits

14 and 22. Two

non-return valves

25 and 26 are disposed in the conduit 24 so as to permit the circulation of the fluid from conduit 22 to conduit 14. A conduit 27, connected to conduit 24 between the two

valves

25 and 26 is moreover connected to conduit 19.

On the other hand, a conduit 33 connects the delivery of a pump 28 to conduit 14. In known manner, a conduit 29 connects the suction of the pump 28 to a fluid tank 30. Conduits 31, on which calibrated discharge valves 32 are interposed, connect

conduits

22 and 33 to which they are attached, to the fluid tank 30.

Of course, the invention comprises a number of possible variant embodiments. By way of indication, FIG. 3 shows the structure 11 which supports the winch. The latter is constituted by the main toothed wheel 10b to which the motor l2'is connected, whilst motor 13 is connected to a secondary toothed wheel 10c. A chain 9a is meshed on the two wheels.

In FIG. 4, it will be noted that a heavy body 38 is attached to the end of a cable 9 which is itself wound on the drum of a winch 10. This winch is coupled to a drive motor 39 by means of a movement transmission constituted, in the example shown, by a pulley 40, integral with the shaft 41 of the winch 10, by a pulley 42, integral with the driven shaft 43 of the rotor of the motor 39, and by a belt 44 which cooperates with the grooves of the pulleys and 42.

The motor 39 is of the hydraulic type, reversible and with variable cubic capacity. It is consequently provided with a lever 45 which constitutes the member for regulating the cubic capacity and which, in the present case, is mounted to pivot above an axis 39a between two

extreme positions

45a and 45b. The regulation is effected automatically as a function of the rotation of the winch 10 by means of a connection 46 connecting said winch 10 to said lever 45. Two embodiments of this connection 46 will be described hereinafter with reference to FIGS. 5 and 6, in which they are shown in detail.

As regards to circuit feeding the motor 39 with hydraulic fluid, it comprises a fluid tank 30, a pump 47 and a pressurised fluid accumulator 48. The motor 39 has two

chambers

49 and 50 which are either inlet chamber and delivery chamber, respectively, or vice versa. The chamber 49 is connected to the accumulator 48 by a first conduit 51, whilst the chamber 50 is itself connected to the tank 30 by a second conduit 52. The pump 47 is connected to the tank 30 by a conduit 53, and to a first conduit 51 by a conduit 54, in which is interposed a non-return valve 55. Finally, downstream of the valve 55 with respect to the pump 47, a conduit 56 is branched to the conduit 54 which it connects to conduit 52. A calibrated valve 57 is disposed in this conduit 56. It will further be noted that the non-return valve 55 permits the passage of the fluid from pump 47 towards the first conduit 51 and that the calibrated valve 57 permits the passage of the fluid from conduit 54 towards conduit 52.

The embodiment of the connection 46, shown in FIG. 5, corresponds to the obtaining of a regulation of the cubic capacity which is a function of the position of the heavy body 38 and thus a function of the angle of rotation of the winch 10. A pulley 58 is integral with the shaft 41 of the winch l0, and cooperates by means of a belt 60 with a pulley 59 which is mounted for rotation, the structure 11 supporting the winch 10. A cam 61 is integral in rotation with the axis 59a of the pulley 59.

Furthermore, the body 62 of a resilient double action return device is integral with the motor 39 by arms 63. A rod 64 is mounted to slide in the body 62 and comprises two

shoulders

65 and 66 between which are disposed two

discs

67 and 68, free to slide on rod 64. A spring 69 is disposed between the

discs

67 and 68 which it tends to maintain spaced apart, and in abutment on two internal shoulders of the body 62, respectively, shoulders 70 and 71. One of the ends of the rod 64 is provided with a shaft 72 extending into an eye 73 in the lever 45, whilst a fork 74 is integral with the other end of the rod 64, the cam 61 being introduced between the two branches of this fork and during its rotation being able to abut on one of these branches.

In the embodiment shown in FIG. 6, certain of the elements already described in FIGS. 4 and 5 are found again which bear the same reference numerals as in these two FIGS. It will simply be noted that the arm 63 has been replaced by an arm 63a which renders body 62 integral with body 75 of another device which will be described hereinbelow, this body 75 itself being integral with the motor 39 by arms 76. Furthermore, the rod 64 has itself been replaced by a rod 640 which is similar thereto except concerning the end fork 74 of the rod 64, which it does not have.

It will be noted that a reversible volumetric pump 77, comprising two chambers 78 and 79, has its drive shaft 80 coupled to the shaft 43 of the rotor of the motor 39. Furthermore, the body 75 is that of a double action ram or jack, having two

chambers

81 and 82, disposed on either side of the piston. A shaft 84 is integral with one end of the piston rod 83 and is introduced into an eye 85, in the lever 45. A conduit 86 connects the

chambers

78 and 82, whilst another conduit 87 connects the chambers 79 and 81. Finally, a conduit 88 connects conduits 86 and 87. A diaphragm 89 with calibrated aperture 90 is disposed in this conduit 88.

The devices which have just been described operate as follows:

The torques produced by the

motors

12 and 13 of FIGS. 1 to 3 are proportional to the respective products of the difference in pressures between the supply and delivery of each of said motors by the cubic capacity of the motor in question.

The motor 13 is in fact that which acts as a device antagonistic to or opposing the forces of gravity acting on the piston 6 and the'bars 7. The torque which it produces is substantially constant, since the difference in pressures of the fluids of accumulators l5 and 17 is itself substantially constant, and is lower, due to the choice of the characteristics of this motor, than the resistant static torque of the pump (4-5-6), i.e., the torque, when said latter is not actuated in pumping phase.

As regards motor 12, it constitutes the actual drive motor-of winch 10. When the distributor 20 is disposed in its first position, the chambers of the motor 12 are connected, by

conduits

19 and 14, on the one hand, and by conduit 18 on the other hand, to accumulators and 17. The torque produced by motor 12 is maximum, substantially constant and of the same direction as that of motor 13. The sum of the torques produced by the two motors is then greater and opposite the sum of the resistant static and useful torques in the course of pumping of the pump (4-56). When, on the contrary, the distributor 20 is in its second position, the two chambers of the motor 12 are both in communica tion with the sole accumulator 17, one by conduit 18, the other by conduits l9 and 22. The torque produced by the motor 12 is then substantially zero.

It will easily be understood that by choosing the first, then the second position of the distributor 20 alternately, the supply of motors l2 and 13 is regulated in order to obtain a drive torque greater than the resistant pumping torque, then lower than the static torque, alternately. The result of this arrangement is a reciprocating motion of the piston 6, upwardly for pumping, under the preponderant action of the two motors, then downwardly under the preponderant action of the weight of the piston 6 and the bars 7, against the action of the sole motor 13. The action of the latter enables, however, a tension to be maintained of the cable 9.

The reciprocating movement of the slide of the distributor 20 is easily obtained, by means of the connection 23, as a function of the rotation of the winch 10. It will be specified on this subject that it is simple, should the connecting rod-crank system given as example prove to be unsuitable, to provide a device which comprises end-of-stroke contacts of the rotation of the winch 10. Thus, FIG. 3 shows an embodiment which comprises a lever 34 mounted to tip about a shaft 35 fixed to the structure 11, said lever being provided with two cams 35a and 35b capable of cooperating with a, finger 36 integral with the toothed wheel 10b and being coupled, by a connecting rod 37, to the movable-element of the distributor 20. The cams 35a and 35b, whose positions on the lever 35 are adjustable, constitute the members adjusting the value of the stroke of the piston 6.

When the chambers of the motor 12 are placed in communication with the

accumulators

15 and 17, that is when the maximum drive torque of this motor is obtained, the fluid which has worked in the motor 12 escapes therefrom through conduit 18, then, through conduit 31 connected to conduit 22 and the calibrated valve 32, returns to tank 30. The lack of fluid in the circuit which results from this return to the tank is conpensated for by the fluid flow of the volumetric pump 28.

On the other hand, concerning the motor 13, only a transfer of a certain quantity of fluid is ascertained from the accumulator 15 to accumulator l7, and vice versa, according to whether the piston 6 is in its rising or falling stroke. Finally, the motor 13, combined with the two

accumulators

15 and 17, constitutes a spring motor of the hydraulic type. However, it could have as an equivalent a simple spring motor. In any case, energy is recovered during the descent of the piston 6, which is restored to the drive device at the moment the piston 6 rises again.

It will have been noted that the inertia of rotation of the motor 13 is much lower than the inertia which the conventional counterweights have. Furthermore, by adopting the motor 13, the dangerous clearance of such counterweights is also eliminated. Finally, as regards the overall size of the installation and facility of production, a gain is had, all the more so as the elements of a hydraulic circuit are very easily adaptable and installable, which, moreover, is known per se.

The operation of the embodiment which has been described in its two variants with reference to FIGS. 4 to 6 is given hereinafter.

Concerning firstly the variant embodiment shown in FIGS. 4 and 5, the succession of the operations is examined starting from the beginning of the rising phase of the heavy body 38. The winch 10 then possesses a certain angular orientation and its speed of rotation is zero. There corresponds to the angular orientation of the winch 10 an orientation of the cam 61, thus a position of the rod 64 which is displaced with respect to the median return position under the effect of the spring 69 and in cooperation with the

discs

67 and 68, and the

shoulders

65 and 66. The shaft 72 has therefore disposed the lever 45 in a position in which the cubic capacity is maximum, and therefore, in which the lifting drive torque of the motor 39 is maximum, with constant pressure of the supply fluid. The characteristic of constancy of the pressure will be gone into further hereinafter. Under these circumstances, the motor 39 drives the winch 10 in the direction of the rise of the body 38, the drive torque being higher than the resistant torque of the forces of gravity and friction.

The heavy body 38 rises and the cam 61 rotates, driving the rod 64 and the lever 45 in the sense of a reduction in the cubic capacity of the motor 39, thus of a reduction in the drive torque. A moment arrives when this drive torque becomes equal to, then lower than the resistant torque. The heavy body 38 continues to rise until its speed is annulled.

The body 38 then begins to descend, the torque, due to the forces of gravity, being greater than the drive torque whose action has not changed direction, but has simply reduced intensity. The cam 61 therefore rotates in opposite direction to that of the rise, and returns the lever 45 in the sense of an increase in the cubic capacity and the drive torque of the motor 39. The drive torque will therefore again become greater than the torque of the forces of gravity and friction. The heavy body 38 continues, however, to descend, but at reduced speed. When its speed is annulled, it is again driven upwardly, for a new cycle similar to the preceding one.

It is ascertained that with a single drive motor, the heavy body 38 can be driven in reciprocating motion, without having to use counterweights or the like.

It was indicated hereinbefore that the pressure of the supply fluid of the chamber 49 of the motor 39 was substantially constant during the rising motion of the body 38. This approximate constancy depends of course on the characteristics of the elements constituting the feed circuit of the motor 39 and in particular, as a function of the range of variation of the cubic capacity of the motor 39, on the cubic capacity of the accumulator 48 which must be sufficiently large, and on the fluid flow of the pump 47 which must also be sufficiently large to compensate for the delivery flow of the accumulator 48 in the motor 39.

The feed circuit operates as indicated hereinafter. The body 38 being stopped in low position, the rotor of the motor 39 is immobilised. The pump 47 draws from tank through conduit 53, and delivers to accumulator 48 through

conduits

54 and 51. If possibly the delivery pressure rose beyond a given value, the calibrated valve 57 would open and the pump 47 would deliver to the tank 30 through

conduits

56 and 52.

The pressure of the fluid contained in the accumulator 48 is such, and the cubic capacity of the motor 39 is regulated, so that the motor 39 drives the winch 10. The chamber 49 of the motor 39 is then fed with pressurised fluid by accumulator 48 and conduit 51, the fluid returning to tank 30, at low or zero pressure, through chamber 50 and conduit 52. The characteristics of the accumulator 48 are such that the supply pressure of the chamber 49 remains approximately constant, during the rise of the body 38, with, however, a slight pressure drop.

During the descent of the body 38, said latter drives the winch 10 and thus the motor 39 in the direction opposite that 'of the rise. The motor 39 operates as a pump, draws the fluid from the tank 30 through conduit 52 and chamber 50 and delivers the fluid into the accumulator 48. The pressure of the fluid in this latter thus increases both under the effect of the fluid delivered by motor 39 and under the effect of that which continues to be delivered by pump 47. It is therefore ascertained that the accumulation of the potential energy released by the descent of the heavy body 38 is effected, there again, in resilient form, by means of the combined effects of the motor 39 and the accumulator 48, these two elements constituting, in fact, a hydraulic spring motor.

It will further be noted that the total quantity of the fluid feeding the chamber 49, during the rise of the heavy body 38, is greater than the total quantity of fluid delivered by the motor 39 in the conduit 51 during the descent of said body 38. The actual operation as well as an examination of the operational diagram of the motor 39 confirm this point. This particularity explains the role of the pump 47, which is to supply the complement of fluid lacking at each cycle and the necessity of its presence.

Finally, the operation of the variant shown in FIGS. 4 and 6 will be examined. When the winch 10 rotates in the direction of lifting of the body 38, the volumetric pump 77 is driven by the shaft 43 of the motor 39. As an example, the case will be chosen of it delivering the pressurised fluid through its chamber 78 into the conduit 86. The flow of the delivered fluid is a function of, and generally proportional to, the speed of rotation of the shafts 43 and 80. This flow of fluid must be evacuated through the calibrated aperture of the diaphragm 89 in order to return to the other chamber 79 of pump 77. The effect of the diaphragm is to increase the pressure in conduit 86 in correspondence with the value of the flow of the fluid through the aperture 90. The fluid in the conduit 86 then acts on the piston of the jack, in the chamber 82 and repels the rod 83 to the left as viewed in FIG. 6, and the lever 45 in the sense of a reduction in the cubic capacity of the motor 39, thus in a reduction in the speed of rotation of the shaft 43. The speed of the motor 39 will then decrease until it is annulled. The lever 45 will be returned into median position by spring 69 and the winch 10 will then be driven in direction opposite the preceding one by the body 38 which will descend. The pump 77 will itself be driven in opposite direction and will deliver the fluid into conduit 87. As previously in the conduit 86, the pressure will rise in conduit 87, and the lever 45 will be repelled in the sense of an increase in the cubic capacity (and in the drive torque) of the motor 39 in a reverse direction. This operation is very similar to that of the variant embodiment shown in FIG. 5, but is no longer a function of the position of the heavy body, but of its drive speed.

Furthermore, it will be noted that the arrangements of FIGS. and 6 may be combined, in order to obtain a function which takes account both of the position and speed of the heavy body 38. 7

Finally, it will be recalled that the drive device described in FIGS. 1 to 3 comprises a drive motor which is fed periodically, firstly with pressurised fluid; in order to supply a positive drive torque during the active phase of the driven member, then in short-circuit, its inlet being connected to its delivery, in order to supply a zero torque during the passive phase.

The passage from one supply to the other, or from the obtaining of a given torque to a zero torque, is such as to produce shocks which may be harmful to the long life of the member driven, to which they are transmitted. The embodiment of FIGS. 4 to 6 functions, on the contrary in, such a way that the variation of the torque is continuous. In this way, no shock is produced during this functioning.

The invention is not limited to the embodiments that have just been described, but covers on the contrary all the variants that may be made thereof without departing from its scope. It may also be applied, inter alia, to the reciprocating drive of a ram for driving in piles and or piling.

I claim:

1. Drive device for driving a heavy body in reciprocating motion at continually variable speed, said body connected to a drive motor by a flexible traction connection, whilst the forces capable of being transmitted to said body by said motor are alternately greater than and opposite to the forces of gravity and friction acting on the body, and lower than said forces of gravity and friction, and a device antagonistic to said forces of gravity permanently connected to the drive motor, said antagonistic device being constituted as a fluid motor, said drive motor being constituted as a reversible fluid motor comprising two chambers connected, one, permanently to a pressurized fluid accumulator, the other, selectively by means of a two-position distributor, either with a source of pressurized fluid, or with said pressurized accumulator.

2. Drive device as claimed in claim 1, wherein the antagonistic device is constituted as a reversible fluid motor comprising two chambers permanently connected, one to a first pressurized fluid accumulator, the other to a second pressurised fluid accumulator.

3. Drive device as claimed in claim 2, wherein in addition the flexible traction connection is wound on a winch, to which the drive motor and the antagonistic device are connected.

4. Drive device as claimed in claim 1, wherein the source of pressurised fluid is constituted as a volumetric hydraulic pump, on whose delivery a pressurised fluid accumulator is disposed in shunt.

5. Drive device as claimed in claim 1, wherein the source of pressurised fluid is constituted as a gas compressor, in whose delivery a pressurised fluid accumulator is disposed in shunt.

6. Drive device as claimed in claim 1, wherein the two-way distributor comprises a movable element connected to a control device capable of disposing it successively in each of its two positions.

7. Drive device as claimed in claim 6, wherein the device controlling the movable element is coupled with the drive motor.

8. Drive device as claimed in claim 7, wherein the coupling of the movable element to the drive motor comprises a regulating device.

9. Drive device as claimed in claim 1, wherein the said antagnostic device is constituted as the drive motor itself which is a reversible fluid motor comprising two chambers connected permanently, one, by a first conduit, to a pressurised fluid accumulator, the other, by a second conduit, to a fluid tank, this reversible motor being in addition a motor with variable cubic capacity provided with a member for regulating said cubic capacity, whilst the drive device comprises a source of pressurised fluid provided with a delivery conduit which is connected to the first conduit and to which a calibrated valve is connected in shunt.

10. Drive device as claimed in claim 9, wherein the reversible motor has a rotor to which the member regulating the cubic capacity is connected by a kinematic motion transmission chain.

11. Drive device as claimed in claim 9, wherein the reversible motor has a rotor to which the member regulating the cubic capacity is connected by means of a device detecting the speed of rotation of this rotor and transmitting an effect which is a function of said speed.

12. Drive device as claimed in claim 11, wherein the detector and transmitter device is constituted as a reversible, volumetric hydraulic pump, whose drive shaft is coupled with the rotor of the reversible motor, whilst a double action volumetric receiver member is coupled with the member regulating the cubic capacity, the volumetric pump and the receiver member each have two chambers, one chamber of the pump is connected by a third conduit to a chamber of the receiver member, the other chamber of the pump is connected by a fourth conduit to the other chamber of the receiver member, a diaphragm is interposed on a fifth conduit which is connected in shunt to the third and to the fourth conduits and finally the member regulating the cubic capacity is coupled to a resilient return element whose effect tends to maintain said regulating member in a given position or to return it thereto.

13. Drive device as claimed in claim 2 wherein, additionally, the drive motor is constituted as a reversible fluid motor comprising two chambers connected, one, permanently to a third pressurized fluid accumulator, the other, selectively by means of a two-way distributor, either with a source of pressurized fluid or with the third accumulator, this third accumulator being constituted as said second accumulator.

14. Drive device as claimed in claim 2, wherein the source of pressurized fluid is a volumetric hydraulic pump and pressure accumulator means are disposed in shunt on the delivery of said pump, said accumulator means being constituted by said first accumulator.

15. Drive device according to claim 2, wherein the source of pressurized fluid is a gas compressor and pressure accumulator means are disposed in shunt on the delivery of said compressor, said accumulator means being constituted by said first accumulator.

Patent No. 3I793I834 Dated YT r 1974 Inventor (s) LOUIS TIN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Front page, at "[30]' line 3, change "7141878" to 7141874 Column 3, l'ine 53, after "two-position" insert distributor Signed and sealed this Both day of September 197 (SEAL) Attest:

McCOY M. GIBSON," JR. 0. MARSHALL DANN C Attesting Officer Commissioner of Patents FORM PC3-1050 (10-69) v Uscmawoc 87am :1 u.s. covuuunn "mime omc: ml o-su-au.