US3895779A

US3895779A - Hoisting winch, in particular for a boring machine

Info

Publication number: US3895779A
Application number: US403004A
Authority: US
Inventors: Pierre Cassez; Claude Pelisson
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-10-03
Filing date: 1973-10-03
Publication date: 1975-07-22
Anticipated expiration: 1992-07-22
Also published as: FR2201241B1; CH578482A5; FR2201241A1; BE805542A; NL7313610A; DE2349661A1; IT999604B; JPS49132750A; GB1439624A

Abstract

For hoisting a load and allowing the load to fall freely. The device comprises a rotatable drum around which a cable for attaching to the load is wound. A hydraulic drive motor is permanently coupled with the drum and comprises a stator and a rotor rotated by application of a main fluid pressure and capable of being rendered freely rotative relative to the stator by application of an auxiliary control fluid pressure. A fluid supply device is adapted to supply in an alternating manner the main fluid pressure for raising the load and the auxiliary control pressure for allowing the load to fall freely.

Description

United States Patent [191 Cassez et al. v

[451 July 22, 1975 3,283,668 ll/l966 HOISTING WINCH, IN PARTICULAR FOR A BORING MACHINE Inventors: Pierre Cassez, Bethune; Claude Pelisson, Seclin, both of France Assignee: Benoto-Sam, Paris, France Filed: Oct. 3, 1973 Appl. No.: 403,004

Foreign Application Priority Data Oct. 3, 1972 France 72.3495] [1.8. CI 254/150 FR; 91/44 Int. Cl. 866d 1/30 Field of Search 254/150 FH; 91/44 UP References Cited UNITED STATES PATENTS Louhio 91/44 3.776513 l2/l973 Mosley 254/150 FH Primary ExaminerRobert B. Reeves Assistant E.\'aminerHadd Lane Attorney. Agent. or Firm- Holman & Stern [57] ABSTRACT For hoisting a load and allowing the load to fall freely. The device comprises a rotatable drum around which a cable for attaching to the load is wound. A hydraulic drive motor is permanently coupled with the drum and comprises a stator and a rotor rotated by application of a main fluid pressure and capable of being rendered freely rotative relative to the stator by application of an auxiliary control fluid pressure. A fluid supply device is adapted to supply in an alternating manner the main fluid pressure for raising the load and the auxiliary control pressure for allowing the load to fall freely.

16 Claims, 5 Drawing Figures PATENTED JUL 2 2 1975 SI iEET PATENTEDJUL 22 I975 SHEET HOISTING WINCH, IN PARTICULAR FOR A BORING MACHINE The present invention relates to hoisting winches and more particularly to hoisting winches whereby it is possible to hoist a load and allow the load to fall freely. Such winches are employed in boring machines which comprise a grab bucket of the percussion or hammer type which produces a bored hole by successive impacts on the bottom of the hole and by successive discharges of material which is broken up by the impacts of the bucket. The bucket thereafter brings the material to the surface of the ground.

The fact that the load of such a winch must be capable of falling freely which produces a considerable acceleration of the winch implies that the winch cannot be directly coupled to the drive motor. Up to the present time this problem has been solved by providing between the winch and the drive motor a clutch device which allows the shaft of the winch to rotate freely as the load falls freely. However, this solution has the drawback of the use of a clutch device which is difficult to regulate and subject to wear.

Moreover, often in the use of such a winch it is desirable to arrange that the load does not fall completely freely and that the operator of the winch be capable of controlling the speed of the load in the course of its descent. This has been rendered possible in the past by providing a brake device coupled with the winch shaft. However, this brake device creates an additional difficulty in the construction of the winch in that it is necessary to co-ordinate with precision the operation of the brake device and the operation of the clutch device which presents numerous problems.

An object of the invention is to provide a hoisting winch of the type indicated hereinbefore which avoids use of a mechanical clutch device between the drive motor and the winch shaft and which consequently facilitates the co-ordination of the various operations to be carried out.

The invention provides a winch for hoisting a load and allowing the load to fall freely and comprising a rotatably mounted drum around which drum a traction cable is wound, the cable being attached to the load, and a drive motor for driving the winch, wherein said motor is permanently coupled to the drum and comprises a hydraulic motor whose rotor is capable of rotating freely with respect to the stator, that is to say, is capable of free-wheeling with respect to the stator, upon application of an auxiliary control pressure, said winch further comprising a supply device adapted to supply in an alternating manner a main pressure for operating the motor for raising the load and the auxiliary control pressure for the free fall of this load.

Further features and advantages of the invention will be apparent from the ensuing description with reference to the accompanying drawings.

In the drawings:

FIG. I is a diagrammatic side elevational view of a boring machine comprising a percussion grab-bucket in which there is employed a hoisting winch according to the invention;

FIG. 2 is a partial elevational view, partly in section, of a winch according to the invention;

FIG. 3 is a side elevational view, with parts cut away, of the winch shown in FIG. 2;

FIG. 4 is a hydraulic diagram of the winch according to the invention, and

FIG. 5 shows a perspective diagrammatic view of a hydraulic motor used for the winch of FIG. 2-4.

The winch according to the invention permits raising a load and allowing the load to fall freely with possibility of a regulation of its speed of descent. Such winches are employed in particular in boring machines employing a bucket or boring bit, in dredging machines for driving the bucket, in machines for cutting trenches by means of a bucket or boring bit, or like machines.

The ensuing description will apply to a boring machine employing a bucket of the percussion or hammer type, but it must be understood that the invention is not intended to be limited to this particular application.

With reference to FIG. 1, it can be seen that the boring machine comprises a vertical boring column A retained by guys B to a chassis C which may be mobile or stationary. Mounted on the chassis C is an internal combustion engine D and a hoisting winch E according to the invention which drives, through a cable F, the bucket in its up and down movement between the top G of the column A and the bottom of the bored hole. Note that in FIG. 1 the bucket is not visible and that the boring machine is only represented diagrammatically since it does not form part of the invention.

With reference now more particularly to FIGS. 2 and 3, the mechanical parts of the winch will first be described.

This winch is mounted on a base I from which vertically extend two

supports

2 and 3. Mounted in these supports is a drum 4 which is adapted to receive a cable F shown in FIG. I and is rotatable about an axis XX. The drum 4 comprises a cylinder 5 having at one end an attached end flange 6 secured to a housing 7 of a hydraulic motor 8. The stator 9 of the motor 8 is located inside the rotor and secured to the support 2 so as to be prevented from rotating.

The cylinder 5 has at the end thereof opposed to the flange 6 an end wall 10 to which a wheel 11 is connected to rotate with the wall 10, the wheel having on its periphery a cylindrical braking surface 12 with which co-operates a brake band 13. The wall 10 is integral with a journal 14 supported in a bearing 15 which is mounted in the support 3. A protection disc 16 is provided and defines one end of the surface on which the cable F may be wound around the drum 4.

The brake band 13 is secured at one end to a tensioning device 17 (FIG. 3) which is pivoted at 18 to the base 1 of the winch. The other end of the brake band 13 is pivoted to an arm 19 which is integral with a lever 20, the assembly comprising the arm 19 and the lever 20 being rotatable about a pivot 21 which is integral with the base 1 of the winch. The free end of the lever 20 is connected to a rod 22 of a cylinder device 23 whose cylinder is pivoted at 24 to the base 1. Inter-v posed between the piston 25 of the cylinder device 23 and the end cap 26 of the latter is a spring 27 which acts on the lever 20in such manner that when the cylinder device 23 is not connected to a source of pressure, the brake band 16 is applied against the peripheral surface 12 of the wheel 11 and the brake device is in its applied position.

The hydraulic motor 8 is of the reversible type, its rotor and its stator being rotatable with respect to each other by application of the main hydraulic pressure so as to produce a driving torque. Moreover, the rotor and the stator are rotatable with respect to each other substantially without friction and at very high speed upon cessation of the main hydraulic pressure and application of a command pressure which produces of course no torque. A motor of this type which is particularly appropriate for the winch according to the invention is that manufactured and sold by the Swedish firm Hagglunds under reference N 4150 and whose main hydraulic output is 4.71 litres/revolution. Such a motor comprises (FIG. 5) a stator H in which are movable radial pistons l subjected to the main pressure. Rotatable about this stator is a rotor K which is provided with a ring L having cams M. Rollers N integral with the pistons I undergo a radial to-and-fro movement while being in contact with the cam ring L. In the course of operation of the motor, the main pressure applied to the pistons l urges the rollers N to remain constantly in contact with the cam ring L of the rotor K so as to impart thereto a movement of rotation.

This motor also has a control port 80, which, when it is subjected to a second given auxiliary control pressure, causes the radial pistons I to move toward the axis Y Y of the motor and separates the rollers N from the cam ring L. Under these conditions, the rotor K of the motor free-wheels with respect to the stator H, the frictional forces being extremely low and resulting exclusively from the bearings of the motor.

Although this motor may be particularly appropriate for association with the winch according to the invention it is possible to employ other reversible hydraulic motors. For example, there may be employed the motor CH 800 sold by the firm Tractel. This motor comprises axial pistonswhich act on a moving plate, the pistons being capable of being separated from the plate so as to render the rotor freely rotatable with respect to the stator.

The winch is associated with a control device whose preferred construction is shown in FIG. 4. The latter shows diagrammatically the hydraulic motor 8 shown in FIG. 2 and the flow ports 8a and 8b to which the main pressure is applied and the control or command port 8c which receives the control or command pressure for rendering the rotor K freely rotatable with respect to the stator H. In FIG. 4, there is also shown diagrammatically the cylinder device 23 and the brake band 13 acting on the wheel 11.

The reversible hydraulic motor 8 is supplied by a pump unit 28 comprising two

pumps

29 and 30 having respectively a high output flow and a low output flow. These

pumps

29 and 30 draw in the hydraulic fluid from a tank 31 through the filter-32.

The presence of the two

pumps

29 and 30 enables the motor 8 to be driven at different speeds. The pump 30 is connected to a pipe 33 which is connected through a back-pressure valve 34 to a control directional valve 35 having five ports a to e. This valve can occupy three positions the intermediate position of which is the stable position shown in FIG. 4. In this position, the backpressure valve 34 is connected to a pipe 36 which is connected to a pipe 37 constituting the main return circuit of the hydraulic fluid. This pipe opens into the tank 31 through a back-pressure valve 38. The valve 35 may be put into the other positions manually. Thus the port a of the valve 35 may be put in communication with a pipe 39 which is directly connected to the port 8a of the motor 8. The port a is also connected to the safety valve 34 connected to the port I) of the valve 35. The pipe 39 is connected to the port c and the pipe 36 is connected to the port d. Moreover, the valve 35 has a port e which is connected to a pipe 40 leading directly to the tank 31.

The motor 8 can be supplied with fluid by the pump 30 when the valve 35 is placed in the position in which the ports a and c are connected to each other.

Connected to the circuit just described is a supply circuit to which the pump 29 delivers fluid at a high rate of flow. The pump 29 is connected to a pipe 41 which leads to a second directional valve 42 having four ports a, b, c and d. It is by means of this valve 42 that the pipe 41 may be put in communication with the back-pressure valve 34 when the port a and the port c are manually connected to each other. However, the valve 42 normally occupies the position shown in FIG. 4 in which the ports 12 and d are in communication with each other so that in its position of rest the valve 42 allows the pump 29 to deliver fluid directly to the return pipe 37 through a pipe 43. On the other hand, putting the ports a and c of this valve in communication with each other connects the two supply circuits of the motor 8 in series relation. Consequently, the motor 8 can be connected first to the low-flow pump 30 so as to obtain a low speed of the motor and thereafter to the pump 29 whose flow is added to that of the pump 30 which results in a high speed rotation of the winch.

The

pumps

29 and 30 are shown connected to the return pipe 37 through

safety valves

44 and 45 which are calibrated or set at pressures which have been calculated in accordance with the pressures furnished by the pumps so as to put them in short-circuit when the set pressures are reached.

The port 8b of the motor 8 is normally connected through a pipe 46 to a back-pressure valve 47 which is also connected to the pipe 37. The pipe 46 is connected to a three-way valve 48 to which a pipe 49 subjected to the output pressure of the pump 29 is connected. One way of the valve 48 is connected to a check valve 50 connected to the pipe 39.

The cylinder device 23 can receive a control pressure from a cylinder device-pilot valve 51 for releasing the brake controlled by a lever 52 accessible to the operator. This connection is established through a selector 53 having three ports a, b and c, the port 0 being connected to the pipe 39. The cylinder device-pilot valve 51 is connected directly to the control port of the hydraulic motor 8 through a pipe 54 to which the outlet of an accumulator 55 is also connected. The pipe 54 is connected to the tank through a return pipe 56 in which is inserted a valve 57 set or calibrated to open at a predetermined pressure.

The selector 53 is connected through a pipe 58 to a control port a of a piloted check valve 59 connected to the tank 31 and to the

safety valves

44 and 45. The latter are each provided with control ports a through which a control or command pressure may be applied so as to suppress the pressure setting of the valve. Note that a check valve 60 is inserted between thecheck valve 59 and the control port a of the safety valve 44.

The

pipes

37 and 36 are connected to each other through a restriction 61 and a check valve 62 connected in series.

The hoisting winch just described operates in the following manner:

It will be first recalled that when the winch is employed in a boring machine such as that shown diagrammatically in FIG. 1, the reversible hydraulic motor 8 must effect three distinct operations:

I. Raise the filled bucket.

2. Allow the bucket to fall freely or with a controlled braking thereof.

3. Unwind the cable F from the drum 4 when the bucket is not hooked to the cable F.

When the boring machine is at rest, the brake band 13 is applied against the braking surface of the wheel 11 so as to prevent the winch from rotating, the braking force applied to the band 13 being determined solely by the tension of the spring 27 placed in the cylinder device 23. By means of this arrangement, the machine is completely safe in operation. If the hydraulic pressure applied to the cylinder device 23 disappears, for example owing to a broken pipe, rotation of the winch is immediately stopped.

The valve 335 permits a progressive control of the rate of flow of hydraulic fluid therethrough and therefore controls the speed of the motor 8, that is to say the speed of the load.

Owing to the presence of the

valves

35 and 42 and the

pumps

30 and 29 associated therewith, the motor 8 can rotate at two speeds. The higher speed serves to furnish a normal hoisting force for hoisting the bucket and the lower speed permits applying to the traction cable F a higher hoisting force which may be necessary for extracting a bucket subjected to the suction effect in the bored hole, or for de-blocking a boring tool, or for carrying out auxiliary operations. The two hoisting forces are determined by the different calibrations or settings of the

safety valves

44 and 45.

In order to facilitate the description of the operation of this winch, there will now be examined in turn:

1. The hoisting of the load.

2. The automatic free-wheeling of the hydraulic motor 8.

3. The automatic or manual release of the brake 13.

4. The safety device precluding an accidental hoisting command during the free-wheeling of the motor 8.

5. The unwinding of the cable F from the drum in the absence of a load.

The operation of this winch will be described with the use of certain pressure values which are imposed by the utilization of the aforementioned Hagglunds hydraulic motor. It will be understood that these values are given merely by way of example and that the invention is not intended to be limited to the indicated values of pressure or to a hydraulic motor of a given type provided that it is possible to make the stator free-wheel with respect to the motor, as explained hereinbefore.

l. The hoisting of a load This operation is controlled manually by the operator who acts on the

valves

35 and 42, the valve 35 being actuated first so that the valve 42 can become opera tive.

When the valve 35 is actuated so as to interconnect its ports a and c, the output flow from the pump 30 is applied to the pipe 39 and consequently to the inlet port 80 of the motor, the return being through the valve 47, the pipe 37 and the valve 38.

When the valve 42 is actuated, the output flow from the pump 29 is added to that from the pump 30 in passing through the pipe 41 and the ports a and c of the valve 35. Otherwise, the flow from the pump 29 is returned directly to the tank through the pipe 37. In the course of the rising of the load, the brake 13 is automatically released since the selector 53 interconnects its ports b and c and therefore applies the main pressure of the motor to the cylinder device 23.

When the command from the

valve

35 and 42 ceases, the circuit is immediately in the condition for the free fall of the load which is however prevented by the action of the brake 13. Under these conditions, the motor 8 is free-wheeling.

2. The automatic freewheeling of the motor 8 As already mentioned, this free-wheeling is achieved by applying to the motor 8 an auxiliary control or command pressure through its port 80. In the presently described embodiment, the minimum pressure for freewheeling (the release of the rollers N of the stator H from the cam ring L of the rotor K) is about 0.6 kilogram/sq.cm whereas the maximum pressure allowed by the strength of the housing of the motor 8 is l kg/sq.cm. The oil required for this free-wheeling is supplied simultaneously by:

a. the accumulator 55 under a pressure of 0.5 kg/sq.cm which immediately returns its volume of oil stored in accordance with the pressure of the circuit which is' preferably 0.750 kg/sq.cm;

b. the pressurizing circuit supplied by way of the restriction 61 for a small part. This motor housing pressurizing circuit comprises:

the valve 57 set at about 0.750 kg/sq.cm and em ployed as pressure limiter;

the check valve 62 which maintains the pressure in the circuit upon stoppage of the machine and the pump unit 28;

a supply of the cylinder device-pilot valve 51 for permanently pressurizing the manual brake release circuit for the brake 13.

This pressurizing circuit, which is constantly under pressure, maintains the motor constantly in a freewheeling condition in the absence of other commands given by the operator. Thus the motor is always ready to permit a free fall of the load.

Note also that in the main return pipe 37 the backpressure valve 38 ensures an additional pressure drop by its calibration or setting so as to obtain a pressure of l kg/sq.cm at the inlet of the restriction 61.

Moreover, in order that the free wheeling of the motor 8 be achieved as described hereinbefore, it is essential that the supply ports 8a and 8b of the motor be connected to the tank 31 or at a very low pressure. This condition is achieved by:

l. The valve 35 which connects the port 8a of the motor to the tank 31 is in position of rest shown in FIG. 4.

2. The check valve 50 which connects the port 8b of the motor to the pipe 40. As the setting of the valve 50 is 0.050 kg/sq.cm there remains only a very low pressure at the port 8b. Without this valve, the port 8b would be under a retained pressure (2 kg/sq.cm) produced by the valve 47 and the free-wheeling of the motor could not be suitably achieved.

In the hydraulic motor of the present embodiment, this means that one half of the pistons I of the stator H remains extended at the end of the hoisting or at the start of the free fall of the load, as soon as the brake is released.

Now, the fact of entirely withdrawing the pistons I at the start of the free fall by application of the auxiliary pressure to the port 8c on one hand and by the suppression of the main pressure at the ports 8a and 8b of the motor on the other, precludes tapping of the rollers N against the cam ring L of the rotor K. Note that the fact of having fully withdrawn the pistons l at the start of the free fall precludes tapping of the rollers N against the cam ring L'of the housing.

When the winch has been stopped at the end of the hoisting, a very brief unwinding of the cable F occurs which is produced by the response time of the brake 1 band 13 which has for effect to move the pistons l away from thecam ring L.

The accumulator 55 performs a second function.

When the hoisting is commanded through the valve 35, the pistons l of the motor extend and bear against the cam ring L at the speed corresponding to the flow of the oil supply. The accumulator then absorbs the volume of oil delivered from the housing of the motor which is equal to the output volume of the pistons l with a variation in pressure which does not exceed the maximum allowed pressure of l kg/sq.cm. Simultaneously, the valve 57 discharges to the tank 31 so as to re-establish the normal pressure of the circuit (0.750 kg/sq.cm).

Itsaction alone, without the accumulator 55, would produce an instantaneous pressure rise upon extension of the pistons.

3. Release of the brake band 13 The brake band is released either manually or automatically. The latter case has already been examined.

The double control or command is effected by the selector 53. Depending on the force applied to the control lever 52 of the cylinder device 51, a pressure is established in the cylinder device 23 which reduces or completely cancels out the force of the spring 27. This variable hydraulic action brought about by the operator permits achieving a variable hydraulic pull on the brake band and affords a very sensitive progressivity in the braking. For the free fall, the operator acts in the manner described hereinbefore by utilizing the complete travel of the cylinder device 51 so as to transmit the pressure and volume of the oil to the cylinder device 23 and compress the spring 27. The compression of the spring completely releases the brake band 13 and causes the free fall of the load.

The automatic release when hoisting the load is achieved upon actuation of the valve 35 which puts the brake releasing circuit under pressure through the port of ,the selector 53 and supplies fluid to the cylinder device which compresses the spring 27 and releases the brake band 13.

In both cases, the spring 27 immediately resumes its braking action as soon as the hydraulic pressure in the cylinder device 23 is released. The selector 53 indeed permits the decompression and return of the oil from the port b to the port a in the first case and from the port b to the port 0 in the second case.

This brake device has two main advantages, namely the progressivity and the sensitivity in the manual release of the braking with possibility of allowing the free fall of the load and the safety of operation by brake action in the case of breakage of a hydraulic pipe.

4. Safety device precluding an accidental actuation for hoisting during the free-wheeling of the motor 8 It is clear that during the free fall of the load it is absolutely necessary to avoid a coupling between the rotor K and the stator H. indeed, bearing in mind the relatively high speed of rotation between the rotor and the stator, which may be of the order of 10 times higher than the normal speed of operation, the motor would be immediately destroyed.

In the presently-described case of the Hagglands motor, the speed in the free falling of the load may reach 500600 rpm whereas the normal speed is 70 rpm.

Moreover, in the case of the free fall of the load, the motor would act as a hydraulic pump and the high speed would produce the continuous percussion of the rollers N against the cam ring L without possibility of a coupling of the rotor K and stator l-l since the supply of oil would be very distinctly insufficient and the inertia of the moving parts would be excessive.

Consequently, the safety device comprises the pipe 58 which connects the outlet of the cylinder devicepilot valve 51 to the control port a of the piloted valve 59, the check valve 60 and the back-pressure valve 34.

Putting the brake release circuit under pressure by actuation of the cylinder device-pilot valve 51 opens the valve 59 and this puts the ports a which suppress the set pressure of the

safety valves

44 and 45 in communication with the tank 31. Consequently, these valves become discharge valves for the

pumps

29 and 30 which then deliver fluid directly to the tank through the respective discharge ports.

However, there is a residual pressure upstream of the

safety valves

44 and 45 due to the internal pressure drops (in the present case 3.5 kg/sq.cm), which may supply the valve 35. The back-pressure valve 34, which is set at 5 kg/sq.cm, precludes this supply and the valve 35 may be actuated without incident, even in the course of the free fall of the load.

When there is no brake release order, the piloted valve 59 is normally closed and permits the operation of the safety valves at the desired pressure settings. For this operation, the valve 60 isolates the internal piloting circuits of the

safety valves

44 and 45 by avoiding the discharge from the valve 45 to the valve 44.

5. Unwinding of the cable F from the drum in the absence of load The unwinding of the drum by a reversal of the direction of rotation of the hydraulic motor 8 avoids manually pulling on the cable to achieve a reverse rotation.

Actuation of the three-way valve 48 interconnects through its ports b and c the delivery side of the pump 29 and the outlet 8b of the hydraulic motor 8. By manually releasing the brake band 13 by means of the cylinder device 51 and actuating the valve 42, the residual pressure at the

safety valves

44 and 45, employed at this moment as discharge valves, produces the reverse rotation of the motor by way of the port 8b. The pressure ensuring the reverse rotation is maintained and limited by the back-pressure valve 47.

According to a modification of the invention, the pipe 49 may be connected to the port 0 of the valve 42 instead of putting it in communication with the safety valve 44. This connection is shown in dotted lines by the pipe 49A in FIG. 4.

Under these conditions. actuation of the three-way valve 48 interconnects through its ports b and c the delivery circuit of the pump 30 and the outlet 8b of the hydraulic motor 8. By manually releasing the brake band 13 by means of the cylinder device 51, the residual pressure at the safety valve 45, employed at this moment as a discharge valve, produces the reverse rotation of the motor by way of the port 8b. The pressure ensuring the reverse rotation is maintained andlimited by the back-pressure valve 47.

In order to once more effect the boring with the load falling freely, the three-way valve 48 must be returned to its initial position (intercommunication of the ports a and b).

Having now described our invention what we claim as new and desired to secure by Letters Patent is:

l. A winch for hoisting a load and allowing the load to fall freely, comprising a support, a drum which is rotatably mounted relative to the support, a traction cable wound round the drum for attaching to the load, a hydraulic drive motor permanently coupled to said drum for rotating the drum and comprising first and second main fluid pressure ports, a control fluid pressure port, a stator and a rotor, said winch further comprising a fluid supply device having pump means, a tank and a control device for selectively connecting said main fluid pressure ports to said pump means and said tank, said control device comprising first pipe means connecting said second main fluid pressure port to said tank and second pipe means connecting said first pipe means to said control fluid pressure inlet port for continuously applying thereto a control fluid pressure, whereby upon actuation of said control device, said rotor is drivable by application of main fluid pressure to said first inlet port and capable of rotating freely with respect to said stator from the moment of release of said control device by virtue of control fluid pressure remaining in said second pipe means.

2. A winch as claimed in claim 1, wherein said control device comprises an accumulator connected to said second pipe means for providing the volume of fluid required by said motor when said rotor passes from its driven state to its freely rotating state.

3. A winch as claimed in claim 2, wherein said control device further comprises a restriction and a check valve connected between said first and second pipe means.

4. A winch as claimed in claim 1, comprising a calibrated valve connected between said second pipe means and said tank for determining the maximum value of the control fluid pressure prevailing in said second pipe means.

5. A winch as claimed in claim 1, further comprising a brake device for exerting a force for selectively braking and stopping rotation of the drum, said brake device comprising a first hydraulic cylinder device for progressively de-activating said brake device, said first hydraulic cylinder device being connected to said second pipe means so as to be continuously supplied with hydraulic fluid from said second pipe means.

6. A winch as claimed in claim 5, wherein said brake device comprises a brake member combined with said drum so as to be capable of braking and stopping the latter, resiliently yieldable means for biasing the brake member against the drum, a second hydraulic cylinder device for releasing the brake member and a selector connected to said first and second hydraulic cylinder devices and to said first main fluid pressure port of said motor and being so arranged as to selectively apply fluid pressure to said second hydraulic cylinder device or to said first main fluid pressure port depending respectively upon'whether said first hydraulic cylinder device or said control device is actuated.

7. A winch as claimed inclaim 3, wherein said: control device comprises an accumulator connected to said second pipe'means for providing the volume of fluid required by said motor when said rotor passes from its'driven state to its freely rotating state.

8. A winch as claimed in claim 7, wherein said control device further comprises a restriction and a check valve connected between said first and second pipe means.

9. A winch as claimed in claim 5, wherein said control device comprises safety valve means connected to said pump means and to said tank for selectively shortcircuiting said pump means, said safety valve means being connected to said first hydraulic cylinder device so as to be actuated upon actuation of said first hydraulic cylinder device.

10. A winch as claimed in claim 1, comprising third pipe means connecting said main fluid pressure ports of said motor to each other, and a check valve connected in said third pipe means for isolating said ports when said motor is in the hoisting mode of operation by actuation of said control device.

1 1. A winch as claimed in claim 1, wherein said pump means comprises a high-flow pump and a low'flow pump, said control device comprising two control directional valves respectively connecting the high-flow pump and the low-flow pump to said motor.

12. A winch as claimed in claim 11, further comprising a brake device for exerting a force for selectively braking and stopping rotation of the drum, said brake device comprising a first hydraulic cylinder device for progressively de-activating said brake device, said first hydraulic cylinder device being connected to said second pipe means so as to be continuously supplied with hydraulic fluid from said second pipe means, said control means further comprising two safety valves connected respectively to each of said pumps and to said first pipe means for selectively short-circuiting said pumps, a piloted check valve and an auxiliary check valve, said safety valves being connected to said first hydraulic cylinder device through said piloted check valve which is directly connected to the safety valve associated with said low-flow pump and connected to the other safety valve associated with said high-flow pump through said auxiliary check valve, whereby said safety valves are actuated upon actuation of said first hydraulic cylinder device.

13. A winch as claimed in claim 12, wherein the connection between said high-flow pump and its associated safety valve comprises a branch pipe means connected to a three-way valve so arranged as to be selectively capable to apply residual pressure generated at said safety valve by virtue of shortcircuiting of said high-flow pump, to said second main fluid pressure port of said motor for ensuring inverse rotation of the latter.

14. A winch as claimed in claim 12, comprising a pipe for series connecting said two control directional valves and a branch connection on said pipe, said branch connection being connected to a three-way valve so arranged as to be selectively capable to apply a slight fluid pressure to said second main fluid pressure port of said motor for ensuring inverse rotation of the latter.

15. A winch as claimed in claim 11, wherein said two control directional valves are connected in series.

16. A winch for hoisting a load and allowing the load to fall freely, comprising a support, a drum which is rotatably mounted relative to the support, a traction 'cable wound round the drum for attaching to the load,

a hydraulic drive motor permanently coupled to said drum for rotating the drum and comprising first and second main fluid pressure ports, a control fluid pressure port, a stator and a rotor, said winch further comprising a supply device having a high-flow pump, a lowflow pump, a tank and control device, said control device comprising series connected control directional valves respectively connecting the high-flow pump and the low-flow pump to said motor, first pipe means connecting said second main fluid pressure port to said tank and second pipe means connecting said first pipe means to said control fluid pressure inlet port, an accumulator connected to said second pipe means, safety valves connected respectively to each of said pumps and to said first pipe means for selectively shortcircuiting said pumps, said winch further comprising a brake member resiliently biased against said drum, a brake release cylinder for releasing said brake member from said drum and a pilot cylinder selectively connected to said brake release cylinder for progressively actuating the latter and permanently connected to said

Claims

1. A winch for hoisting a load and allowing the load to fall freely, comprising a support, a drum which is rotatably mounted relative to the support, a traction cable wound round the drum for attaching to the load, a hydraulic drive motor permanently coupled to said drum for rotating the drum and comprising first and second main fluid pressure ports, a control fluid pressure port, a stator and a rotor, said winch further comprising a fluid supply device having pump means, a tank and a control device for selectively connecting said main fluid pressure ports to said pump means and said tank, said control device comprising first pipe means connecting said second main fluid pressure port to said tank and second pipe means connecting said first pipe means to said control fluid pressure inlet port for continuously applying thereto a control fluid pressure, whereby upon actuation of said control device, said rotor is drivable by application of main fluid pressure to said first inlet port and capable of rotating freely with respect to said stator from the moment of release of said control device by virtue of control fluid pressure remaining in said second pipe means.

6. A winch as claimed in claim 5, wherein said brake device comprises a brake member combined with said drum so as to be capable of braking and stopping the latter, resiliently yieldable means for biasing the brake member against the drum, a second hydraulic cylinder device for releasing the brake member and a selector connected to said first and second hydraulic cylinder devices and to said first main fluid pressure port of said motor and being so arranged as to selectively apply fluid pressure to said second hydraulic cylinder device or to saId first main fluid pressure port depending respectively upon whether said first hydraulic cylinder device or said control device is actuated.

7. A winch as claimed in claim 3, wherein said control device comprises an accumulator connected to said second pipe means for providing the volume of fluid required by said motor when said rotor passes from its driven state to its freely rotating state.

9. A winch as claimed in claim 5, wherein said control device comprises safety valve means connected to said pump means and to said tank for selectively short-circuiting said pump means, said safety valve means being connected to said first hydraulic cylinder device so as to be actuated upon actuation of said first hydraulic cylinder device.

11. A winch as claimed in claim 1, wherein said pump means comprises a high-flow pump and a low-flow pump, said control device comprising two control directional valves respectively connecting the high-flow pump and the low-flow pump to said motor.

13. A winch as claimed in claim 12, wherein the connection between said high-flow pump and its associated safety valve comprises a branch pipe means connected to a three-way valve so arranged as to be selectively capable to apply residual pressure generated at said safety valve by virtue of short-circuiting of said high-flow pump, to said second main fluid pressure port of said motor for ensuring inverse rotation of the latter.

16. A winch for hoisting a load and allowing the load to fall freely, comprising a support, a drum which is rotatably mounted relative to the support, a traction cable wound round the drum for attaching to the load, a hydraulic drive motor permanently coupled to said drum for rotating the drum and comprising first and second main fluid pressure ports, a control fluid pressure port, a stator and a rotor, said winch further comprising a supply device having a high-flow pump, a low-flow pump, a tank and control device, said control device comprising series connected control direCtional valves respectively connecting the high-flow pump and the low-flow pump to said motor, first pipe means connecting said second main fluid pressure port to said tank and second pipe means connecting said first pipe means to said control fluid pressure inlet port, an accumulator connected to said second pipe means, safety valves connected respectively to each of said pumps and to said first pipe means for selectively short-circuiting said pumps, said winch further comprising a brake member resiliently biased against said drum, a brake release cylinder for releasing said brake member from said drum and a pilot cylinder selectively connected to said brake release cylinder for progressively actuating the latter and permanently connected to said second pipe means and to each of said safety valves.