Hydraulic Lifting Apparatus With Constant Pull Regulation

Abstract

In order to exert a constant pull on a rope attached to a load and wound up on a winch by the motor of a hydrostatic transmission mounted on a floating boat moving up and down, a pressure responsive valve is actuated by a predetermined high pressure in the hydrostatic transmission when the boat and winch are raised, and relieves the pressure in a cylinder chamber of an hydraulic adjusting motor so that the volume of fluid displaced by the pump of the transmission is reduced, whereby the lifting movement is slowed down, and the pull on the rope maintained constant when the boat with the winch is raised by waves to a higher level.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a hydrostatic drive transmission, particularly for winches on a boat, for example, winches for winding up fishing nets. The hydrostatic drive transmission includes a main pump, whose displaced volume of fluid is adjustable, and a hydraulic main motor driven by the main pump. The adjusting means of the main pump regulates the pump between reversed conditions, and in idling condition.

The regulation of such a drive for obtaining a constant pull of a rope wound up on a winch driven by the hydraulic motor, is of great importance for winches operated on boats for winding up and letting off fishing nets. The required constant pull regulation is sometimes referred to as mooring regulation.

When such a regulation is provided, the pull on the rope is maintained constant during the lifting of a fishing net, independent of the up and down motion of the boat due to high waves. If the pull on the rope rises above a predetermined force, it is necessary that the hydrostatic drive transmission yield, and the motor runs in reversed direction of rotation, permitting a paying-out of the rope, irrespective of the rising of the winch, but avoiding slackening of the rope. If the load and pull on the rope is reduced, for example when the boat moves from a wave crest to a valley, it is necessary that the hydrostatic transmission is automatically adjusted to a lifting operation so that continuous pulling of the ropes in the opposite direction takes place at a constant pull of the ropes.

This type of "constant pull" or "mooring" regulation requires due to the frequent change of the direction of rotation of the hydraulic drive motor, a pump adjustable through a zero or idling condition. A hydraulic piston and cylinder motor is used for operating the adjusting means of the transmission pump.

In a known apparatus with "constant pull" regulation, the pull on the ropes during the lifting operation is determined in accordance with the pressure in the high pressure conduit of the hydrostatic transmission, and this pressure is measured by a manometer and transformed by the same into an electric signal controlling an electromagnet operating a valve which is associated with a hydraulic cylinder and piston motor forming the adjusting means of the pump. The electric part of this constant pull regulation is very expensive if a comparatively reliable regulation is to be obtained.

SUMMARY OF THE INVENTION

It is one object of the invention to provide the hydrostatic drive with a "constant pull" regulation which is independent of electric parts, and permits a simple construction.

Another object of the invention is to provide a hydraulic circuit controlled by the pressure in the hydrostatic transmission to adjust the hydrostatic transmission in such a manner that the pull of the rope wound up by the hydraulic motor remains constant.

Another object of the invention is to provide apparatus mounted on a floating boat for lifting a load with a constant force, irrespective of the up and down movement of the boat caused by waves.

An embodiment of the lifting apparatus of the invention comprises a hydrostatic drive transmission including a driven main pump having adjusting means for regulating the displaced volume, a hydraulic drive motor, and high pressure, and low pressure conduits; a hydraulic adjusting motor with adjusting means and including a cylinder, and a piston forming first and second chambers in the cylinder; pump conduit means connecting a control pump with the first chamber; control conduit means between the control pump and the second chamber; control valve means in the control conduit means having a first control position for connecting the control pump with the second chamber, and the second control position connecting the second chamber with a low pressure discharge area.

As a result, the adjusting motor is operated in the first and second control positions, respectively, to adjust the adjusting means of the main pump to cause increase or reduction, respectively, of the volume displaced by the main pump, and rotation of the drive motor for lifting and lowering a load.

In accordance with the invention, pressure responsive valve means in the control conduit means have a normal position permitting flow through the control conduit means, and an actuated position connecting the second chamber with a low pressure discharge area.

The high pressure conduit of the hydrostatic transmission is connected with the pressure responsive valve means and shifts the same to the actuated position when a predetermined pressure is reached in the high pressure conduit.

When the pressure in the second chamber is reduced in this manner, the pressure in the first chamber operates the adjusting motor to adjust the adjusting means to reduce the volume displaced by the main pump and thereby the speed of the hydraulic drive motor. When the predetermined pressure is exceeded while the main pump is adjusted by the adjusting motor to idle, the direction of rotation of the drive motor is reversed by the adjusting motor and adjusting means.

The first chamber in the cylinder of the adjusting motor is traversed by the piston rod, and consequently the piston on this side has a smaller effective pressure surface than on the side of the second chamber.

When the pressure responsive valve means is placed in the actuated position by high pressure in the conduit of the hydrostatic transmission, the flow in the control conduit means from the control pump to the second chamber is interrupted.

In the preferred embodiment of the invention, the pressure responsive valve means include first and second pressure responsive valves which have a normal position connected in series. The pressure responsive valves are responsive to different predetermined high pressures in the high pressure conduit of the hydrostatic transmission to move to actuated positions connecting the second chamber of the adjusting motor with the low pressure discharge area.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE of the drawing is a schematic, partially sectional view illustrating a hydraulic lifting apparatus in connection with a winch mounted on a floating boat.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A main pump 1 and a hydraulic drive motor 2 are connected by low pressure and high pressure conduits 5 and 6 to form a hydrostatic transmission. The main pump 1 is adjustable so that the volume displaced by main pump 1 can be varied by adjusting means, schematically represented by arrow 9, resulting in different speeds of the drive motor 2 which drives a winch 3 on which a rope 4 is wound up or paid out. The rope may be connected with a fishing net, and it is desired that the pull on rope 4 is maintained constant irrespective of the raising and lowering of a floating boat carrying the winch 3. It will be understood that the pull on rope 4 will increase when the level of the boat and winch 3 rises, and that the pull on rope 4 is decreased when the level of the boat and winch 3 goes down due to the movement of waves.

Adjusting means 9 of main pump 1 are operated by a hydraulic adjusting motor 7 which includes a piston 35 forming in the cylinder a first pressure chamber 10 through which the piston rod 8 passes out of the cylinder, and a second chamber 15. Due to piston 8, the effective surface 35a is greater than the annular effective surface 35b of piston 35.

The outer end of piston rod 8 is articulated to the schematically shown adjusting means 9, and a lever 36, pivotally mounted on a stationary point 36a, is articulated at 36b to piston rod 8. An auxiliary control pump 13 pumps pressure fluid through a pump conduit 13a, 12 and 11 into the first chamber 10, urging piston 35 to the right to reduce the volume of the second chamber 15. A pressure limiting valve 14 is provided in the pump conduit 13a to limit the pressure in the pump conduit and chamber 10.

The second chamber 15 in the cylinder of the adjusting motor 7, is connected by a control conduit 16, 26, in which two pressure responsive valves 17 and 18 are located, with a port in a control valve means 19 which, in the illustrated position b of the respective valve slide piston 19a, is separated from the pump conduit 20, 12, 13a. However, if valve slide piston 19a is shifted to the position a, control conduit portion 26 is connected with the pump conduit portion 20 and with the control pump 13. When control valve slide piston 19a is shifted to the left as viewed in the drawing to the control position c, the control conduit portion 26 is connected with a discharge conduit 50 for discharging into a low pressure discharge area, schematically indicated by an open container T.

The high pressure conduit 6 of the hydrostatic transmission 1, 2, 5, 6 is connected by a high pressure conduit 25 with two selector valves 23 and 24 each of which can be operated by operator actuated electromagnetic means 23a and 24a to move from the illustrated closed position b to an open position a in which pressure fluid is supplied from conduit 6, 25 to selector conduits 21, 22 which supply pressure to the pressure responsive valves 17, 18 which are adjusted to different predetermined pressures to open when the pressure supplied through conduits 21, 22 exceeds the predetermined pressure to which the respective pressure responsive valves 17 or 18 was adjusted by adjustment of springs 17a and 18a. When either of the two pressure responsive valves 17 and 18 responds to an excessively high pressure in conduits 6, 25, 21, 22, the control conduit portion 16 is connected with discharge conduits 51 or 52 which discharge through a discharge conduit 53 into a low pressure container T. When normal high pressure prevails in the conduit 6 of the hydrostatic transmission 1, 2, the conduit portions in pressure responsive valves 17 and 18 connect the control conduit portions 26 and 16 with each other. Excess pressure in conduit 6 can only become effective when one of the selector valves is shifted to the position a, and pressure fluid is supplied to the respective pressure responsive valve 17 or 18. Also, to obtain discharge into the low pressure discharge conduit 53 from the second chamber 15 through control conduit 16, it is necessary that the pressure in conduits 6, 25 and 21 or 22 exceeds the predetermined pressures to which the pressure responsive valves 17 and 18 were adjusted.

As noted above, the control valve means 19 includes a shiftable valve slide piston 19a which has a normal position of rest b, and two control positions a and c.

Two end chambers are formed in the cylinder of the control valve 19 at opposite ends of the valve slide piston 19a, and are connected with conduits 27 and 28, respectively, which end in pressure regulating valves 29 and 30 which are schematically shown, and indicate by arrows that the conduits 27 and 28 are connected in the position of the valves 29 and 30 as shown in the drawing with a discharge conduit 54 opening into a low pressure discharge container T. Consequently, no axial pressure is exerted on the valve slide piston 19a which remains in the illustrated position of rest b in which the connection between the control pump 13 and the control conduit means 26, 16 with pressure responsive valves 17 and 18 is interrupted. The pressure regulating valves 29 and 30 cooperate with springs 29a and 30a whose force can be varied by operation of a manual lever 31 which is fixedly connected to plate 31a on which 29a and 30a abut.

The input pressure of the pressure regulating valves 29 and 30 corresponds to the pressure in the pump conduit 12, 32. In the illustrated neutral position of control lever 31 shown in the drawing, the conduits 27 and 28 are connected by the pressure regulating valves 29 and 30 with a low pressure region, for instance a low pressure discharge container T, while pump conduit 32 is closed so that there is no pressure in the end chambers of control valve 19 which could displace the control valve slide piston 19a out of the position of rest b.

If the control lever 31 is moved to the position 33 shown in broken lines, the spring 29a is tensioned to a certain degree, while the pressure regulating valve 29 is shifted upwardly to a position in which conduit 27 is no longer connected with the discharge conduit 54, but is connected with the pump conduit 12, 32 so that the pressure at the left end of control valve 19 increases, and control valve slide 19a is shifted to the control position a in which the pump conduit 12, 20 is connected with the control conduit portion 26.

Due to the shifting of control valve slide piston 19a, the connecting rod 29 moves to the right and compresses the spring 38 in the cylinder 37 of a resetting device which is pivotally connected with lever 36.

The distance of movement of control valve slide piston 19a depends on the pressure adjusted at the pressure regulating valve 29 and on the characteristics of the spring 38. Spring 38 is selected to have a substantially constant spring characteristic, and to offer the same resistance irrespective of the lengths of deformation. Due to the constant characteristics of spring 38, the distance which the control valve slide piston 19a moves, is directly influenced by the magnitude of the control pressure preselected by the operation of lever 31 in the position 33. In the control position "a" of control valve slide 19a, the pump conduit 12, 20 is connected with the control conduits 26, 16 and pressure responsive valves 17, 18 as explained above. Consequently, the second chamber 15 of the cylinder of the adjusting motor 7 is supplied with pressure fluid having the same pressure as the pressure fluid in chamber 10 supplied through pump conduit 13a, 12, 11.

Since the second chamber 15, the effective pressure surface 35a is greater than the effective pressure surface 35b in chamber 10, due to the presence of piston rod 8 in chamber 10, the equal pressure on opposite sides of the piston 35 results in a force acting on piston 35 to move the same to the left together with piston rod 8 so that the schematically shown adjusting means 9 are turned for adjusting the main pump 1 out of the idling condition to a condition in which main pump 1 displaces a greater volume of fluid so that hydraulic motor 2 is driven, and drives winch 3.

The rope 4 is wound up on winch 3, and a certain pull is exerted on rope 4. At the same time, the pivoted lever 36, which is connected by member 37, spring 38, and linking rod 39 with control valve slide piston 19a, is also displaced by the action of piston rod 8, and moves control valve slide piston 19a back to the position of rest b.

As soon as the resetting means 37, 38, 39 have placed control valve means 19 in the position of rest b, the control conduit 26, 16 is separated from the pump conduit 20 so that the communication between the chamber 15 and the pump conduit 13a, 12, 20 is interrupted, and no pressure fluid is supplied to chamber 15, ending the movement of piston 35 and piston rod 8 to the left so that the adjusting means 9 is no longer operated. Piston 35 has moved a distance which corresponds to the distance of movement of control slide valve piston 19a determined by the control pressure.

The displacement of piston 35 of the adjusting motor 7 is at the same time a measure of the adjustment of main pump 1 by the adjusting means 9, and consequently also a measure of the number of revolutions of the hydraulic drive motor 2. The greater the pressure in conduit 27 acting on the control valve slide piston 19a selected by the operation of lever 31 toward the position 33 and consequent compression of spring 29a, the farther piston 35 moves to operate adjusting means 9 to adjust main pump 1 to displace a greater volume.

When control lever 31 is turned from the position 33 to the position 40 shown in broken lines, the pressure regulating valve 29 returns to a position for causing idling of the main pump when lever 31 is in the position shown in full lines whereupon the pressure regulating valve 30 is placed in a position corresponding to the position 40 of the control lever, i.e., shifted upwardly so that conduit 28 is connected with the pump conduit portion 32, and control valve slide piston 19a is shifted to the control position c. The distance which control valve slide piston 19a moves depends again on the magnitude of the control pressure acting through conduit 28 on the right end of the control valve slide 19a, and determined by position 40 of lever 31, and the compression of spring 30a.

In this control position, the chamber 15 is connected by control conduit portion 16, the control conduit portions in pressure responsive valves 17 and 18, and by control conduit portion 26 with the discharge conduit 50 discharging into a low pressure container T. Since chamber 10 is still under pressure from pump conduit 13a, 12, 11, and piston 35 encounters no resistance in chamber 15, piston 35 moves with piston rod 8 to the right as viewed in the drawing, and operates the adjusting means 9 in the opposite direction than before so that main pump 1 is regulated to pump fluid in a reversed flow so that drive motor 2 is driven in the reversed direction of rotation, and winch 3 pays out the rope 4. In this manner, the pull on rope 4 is maintained constant, even if the winch 3 together with the boat on which it is supported is rapidly moved upward by a wave.

If the pressure in the high pressure conduit 6 drops below the predetermined pressure to which pressure responsive control valve 17, or 18, respectively, was set, the respective pressure responsive valve returns to its normal position opening the control conduit means 16, 26 and connecting through control valve 19, the pump conduit 20 with control conduit means 26, 16. Due to the increased pressure in chamber 15, piston 35 is again displaced to set the adjusting means 9 to a position in which drive motor 2 rotates winch 3 to wind rope 4 so that the pull on rope 4 again increases. Since the pressure in the pressure conduit 6 is a measure of the torque occurring at the winch 3, the pull or tensile force, acting on rope 4 remains constant if the pressure in the high pressure conduit 6 remains constant.

The pressure responsive valves 17 and 18 are preset to different predetermined pressures by adjustment of the respective springs 17a and 18a. By selective operation of the selector valves 23 and 24, one or the other pressure responsive valve is connected with conduit 25 and high pressure conduit 6, and controls the regulation of the main pump 1 in accordance with the pressure preset of the respective pressure responsive valve 17 or 18. In accordance with the predetermined pressures to which the valves 17 and 18 are set, different pulling forces are maintained constant at the rope 4.

From the above description of the preferred embodiment of the invention, it will become apparent that an apparatus according to the invention, which is advantageously used on a boat for lifting fishing nets by means of ropes, mainly comprises the following elements:

A hydrostatic drive transmission 1, 2, including a driven main pump 1 having adjusting means 9 regulating the displaced volume, a hydraulic motor 2, and low pressure and high pressure conduits 5, 6; a hydraulic adjusting motor 7 connected with the adjusting means 9, and including a cylinder and a piston 35 in the cylinder forming first and second chambers 10, 15; a source of pressure fluid, such as control pump 13; pump conduit means 13a, 12, 11 connecting the control pump 13 and the first chamber 10; control valve means 19 in the control conduit means 20, 26, 16 having a first position a for connecting the control pump 13 with the second chamber 15, and a second position c connecting the second chamber 15 with a low pressure discharge container T.

The adjusting motor 7 is operated in the first and second control positions a, c of control valve means 19, respectively, to adjust the adjusting means 9 to cause increase and reduction, respectively, of the volume displaced by the main pump 1 and the rotation of the drive motor 2 for lifting and lowering the load.

Pressure responsive valve means 17, 18 are provided in the control conduit means 26, 16 and have a normal position permitting flow through the conduit means 26, 16 and an actuated position connecting the second chamber 15 with the low pressure discharge container T, while interrupting in the actuated position the flow in the control conduit 26, 16 from the control pump 13 to the second chamber 15.

The high pressure conduit 6 of the transmission 1, 2, 5, 6 is connected with the pressure responsive valve means 17, 18 through selector valves 23 and 24 for shifting the same to an actuated position when a predetermined pressure is reached in the high pressure conduit 6.

As a result, the pressure in the second chamber 15 is reduced and the pressure in the first chamber 10 operates the adjusting motor 7 to adjust the adjusting means 9 to reduce the volume displaced by the main pump 1, and thereby the speed of the hydraulic drive motor 2.

When the predetermined pressure is exceeded while the main pump 1 is adjusted by the adjusting motor 7 to idle, the direction of rotation of the drive motor is reversed.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of hydraulic lifting apparatus differeing from the types described above.

While the invention has been illustrated and described as embodied in a hydraulic lifting apparatus for maintaining a constant pull on a rope wound up on a winch located on a boat, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can be applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

Claims

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. Hydraulic lifting apparatus with constant pull regulation, comprising a hydrostatic drive transmission including a driven main pump having adjusting means for regulating the displaced volume, a hydraulic drive motor, and low pressure and high pressure conduits; a hydraulic adjusting motor connected with said adjusting means, and including a cylinder, and a piston in said cylinder forming first and second chambers; a source of pressure fluid; pump conduit means connecting said source with said first chamber; control conduit means between said source and said second chamber; control valve means in said control conduit means having a first control position for connecting said source with said second chamber, and a second control position connecting said second chamber with a low pressure discharge region so that said adjusting motor is operated in said first and second control positions, respectively, to adjust said adjusting means to cause increase and reduction, respectively, of the volume displaced by said main pump, and rotation of said drive motor for lifting and lowering a load; and pressure responsive valve means in said control conduit means having a normal position permitting flow through said control conduit means, and an actuated position connecting said second chamber with said low pressure discharge region, said high pressure conduit of said transmission being connected with said pressure responsive valve means for shifting the same to said actuated position when a predetermined pressure is reached in said high pressure conduit so that the pressure in said second chamber is reduced and the pressure in said first chamber operates said adjusting motor to adjust said adjusting means to reduce the volume displaced by said main pump and thereby the speed of said hydraulic drive motor, and so that when said predetermined pressure is exceeded while said main pump is adjusted by said adjusting motor to idle, the direction of rotation of said drive motor is reversed.

2. Apparatus as claimed in claim 1 wherein said first chamber has a smaller effective pressure surface than said second chamber.

3. Apparatus as claimed in claim 1 wherein said pressure responsive valve means interrupts in said actuated position the flow in said control conduit means from said source to said second chamber.

4. Apparatus as claimed in claim 1 wherein said control valve means has a position of rest interrupting the flow in said control conduit means.

5. Apparatus as claimed in claim 1 wherein said control valve means includes a control valve slide piston, and hydraulic shifting means for shifting said control valve slide between said control positions.

6. Apparatus as claimed in claim 5 comprising resetting means connecting said adjusting means with said control valve slide piston.

7. Apparatus as claimed in claim 1 wherein said piston of said adjusting motor includes a piston rod projecting through said first chamber out of said cylinder and being connected with said adjusting means so that the effective pressure surface of said piston is smaller in said first chamber than in said second chamber.

8. Apparatus as claimed in claim 7 comprising resetting means including a pivotally mounted lever connected with said piston rod and with said adjusting means, and resilient means having constant resiliency characteristics and connecting said control valve means with said lever; and wherein said control valve means includes a valve slide piston movable between said control positions, and a link connecting said valve slide piston with said resilient means.

9. Apparatus as claimed in claim 1 wherein said pressure responsive valve means include first and second pressure responsive valves forming conduit portions in said control conduit means connected in series in said normal position; comprising selector valve means for individually connecting said pressure responsive valves with said high pressure conduit; and wherein said pressure responsive valves are responsive to different predetermined high pressures in said high pressure conduit of said transmission to move to actuated positions connecting said second chamber with said low pressure discharge region.

10. Apparatus as claimed in claim 9 wherein each of said selector valve means includes a selector valve having an open position and a closed position, and an electromagnetic means for shifting the respective selector valve between said positions thereof.