US3499286A

US3499286A - Controllable hydraulic power unit

Info

Publication number: US3499286A
Application number: US767726A
Authority: US
Inventors: Karl E Reischl
Original assignee: Bucyrus Erie Co
Current assignee: NORTHWEST ENGINEERING Co A CORP OF
Priority date: 1968-10-15
Filing date: 1968-10-15
Publication date: 1970-03-10
Anticipated expiration: 1987-03-10

Description

2 Sheets-Sheet 1 K. E. REISCHL CONTROLLABLE HYDRAULIC POWER UNIT INVENTOR KARL E. REI SCHL ATTORNEY March 10, 1970 Filed Oct. 15, 1968 March 10, 1970 K. E. REISCHL CONTROLLABLE HYDRAULIC rowan mm Filed Oct. 15, 1968 2 Sheets-Sheet 2' INVE NTOR KARL E- REISCHL ATTORNEY United States Patent O U.S. C]. 60-53 8 Claims ABSTRACT OF THE DISCLOSURE The hydraulic power unit for driving the hoist cable drum on a crane on a ship has six pumps driven by an A-C motor to power four hydraulic motors on the hoist drum. Five of these pumps are connected through sequence valves to direct fiuid flow to, or around the motors, depending upon the fluid pressure reflecting the load on the hoist cable. A 4-way control valve and solenoid valves can reverse the fluid flow through the motors. Flow control valves and the 4-way valve can meter fluid flow through the motors. Spring-set brakes can lock the cable drum.

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of US. application Ser. No. 631,083, filed on Apr. 14, 1967, now abandoned of the same title and by the same inventor.

BACKGROUND OF THE INVENTION The present invention relates broadly to the field of hydraulic power units, and more specifically it relates to a hydraulic power unit for hydraulic motors of any sort that is both externally controllable and automatically responsive to the load on the motors so as to drive the motors at a higher speed when the load drops below its pre-set minimum. The invention was created to satisfy a need for a hydraulic power unit for the main cable drum of a ship mounted crane that hoists floating objects between the sea and the ship. Such a power unit must be able to control floatable loads with precision. Also such a power unit must respond automatically to the eifect of wave action on the ship and on the load, and to do that, it must be able to vary the speed of the hoist cable on the drum through a range from Zero to three hundred feet per minute.

Prior to the present invention, the only known approach to the problem was the use of variable displacement pumps and motors. (See US. Patents Nos. 1,804,- 945; 1,902,972; and Re. 20,051 and 2,440,961.) In such power units, fluid pressure from the main pressure line between the pump and the motor was used to actuate a plunger in a cylinder so as to control the output of the variable displacement pumps. A spring loaded, relief valve, bleed-off arrangement was employed to prevent an overload. However, variable displacement pumps are extremely expensive and the fluid capacity of single pump limits the size of the load that can be controlled through a sufficiently broad range. Finally, the accuracy of control achieved by that means leaves something to be desired.

Accordingly, the present invention responds to the need for a hydraulic power unit capable of handling any practical volume of fluid flow to provide broad range control of heavy loads. Employing sequence valves for automatic bleed-off control, the present invention achieves a hydraulic power unit capable of automatic speed control responsive to the load on hydraulic motors being driven. Employing, as well, both meter-in and meter-out valve controls on the hydraulic motors, the present invention also permits precise operator control of the load.

SUMMARY OF THE INVENTION The present invention relates to a controllable hy draulic power unit, and more specifically the invention resides in a hydraulic power unit wherein a hydraulic motor is driven by a plurality of pumps, at least one of which is connected to a hydraulic motor through a pressure responsive bleed-off means so that when a line pressure exceeds a pre-set maximum the output of at least that one pump will be shunted around said motor.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a schematic diagram of a first embodiment of the invention.

FIG. 2 is a schematic diagram of a second embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, six constant displacement

hydraulic pumps

1, 2, 3, 4, 5, and 6 are driven by a prime mover 7, which is an AC motor 7, through a common drive m ans 8, which though represented by a broken line in the drawing, is a conventional gear box in the actual working model embodiment. The six pumps 1-6 are in the form of three double pumps which have their

respective suction ports

9, 10, 11, 12, 13, and 14 connected in common to manifolds 15, 16, and 17. The manifolds 15, 16, and 17 are connected to a suction line 18, which terminates in a reservoir 19 containing hydraulic fluid 20, and which draws the hydraulic fluid 20 from the reservoir 19. The six pumps 1-6 serve to drive four rotary

hydraulic motors

21, 22, 23, and 24 which are represented near the top in the drawing. The hydraulic motors 21-24 have

pinions

25, 26, 27 and 28 fastened on their respective drive shafts, and the pinions 25-28 engage a gear 29 that is connected to drive a cable drum 30.

A pair of

brake pinions

31 and 32 also engage opposite sides of the gear 29 and are mechanically connected, respectively, to brake

drums

33 and 34.

Brake shoes

35 and 36, respectively, are normally set against the

brake drums

33 and 34 by a spring bias means represented as the

springs

37 and 38. The bias springs 37 and 38 bear against the respective pistons 39 and 40 in the hydraulic cylinders 41 and 42, and the

piston rods

43 and 44 are fastened to the

brake shoes

35 and 36. The entire brake apparatus just described is merely functionally representative of the actual structure of the brakes used, inasmuch as the brakes employed on this embodiment are commercially available items and, taken alone, are not the present invention.

A hoist cable 45 is wound on the cable drum 30 to be paid out or wound in as the operator desires. The hydraulic motors 2124 and the cable drum 30 with the associated brake apparatus and mechanical gearing are mounted on the jib of the crane as shown in the co-pending application of the same inventor, owned by the same assignee, entitled Crane Jib, filed on Apr. 6, 1967, and having a Ser. No. 628,934. The operation of this embodiment of the invention may also be more fully appreciated when considered in light of the following copending applications of this inventor and owned by the same assignee relating to the same crane: Rope Pay-out Apparatus, Ser. No. 627,552, filed on Mar. 31, 1967 now Patent No. 3,399,868, issued Sept. 3, 1968; Hoist Line Hook, Ser. No. 629,612, filed on Apr. 10, 1967, now Patent No. 3,445,133, issued May 20, 1969; and Load Snubber for a Crane, US. Patent No. 3,386,592 dated June 4, 1968. The crane described in the mentioned co- Patented Mar. 10, 1970 pending application is mounted on an oceanographic survey vessel, and the jib is pivotally suspended from the :rane boom to be used for hoisting floating vessels and objects of various sorts to and from the survey ship. It rnust be contemplated that the wave action will cause the floating survey ship and the vessel being hoisted to be moving relatively to one another at speeds up to 300' feet per minute. To achieve precise operator control over the object being hoisted, some automatic system is needed to :ompensate for the relative movement of the crane and :he object being hoisted. The embodiments shown here provide such an automatic control by means of the hyiraulic circuitry connecting the constant displacement pumps 1-6 and motors 21-24, and, at the same time by :he same circuitry, they give the crane operator precise :ontrol over the load at all times, whether hoisting or lowering.

Continuing the description of the first embodiment shown in FIG. 1, the first pump 1 has its pressure port 46 :onnected through a working line 47 to one port 48 of 1 manually controlled 4-way directional control valve 49, which is also a flow control valve capable of metering the volume of flow through it. A brake line 50 branches from the Working line 47 and feeds the

rod ends

51 and 52 of he bores of the respective hydraulic brake cylinders 41 and 42. The second pump 2 has its pressure port 53 connected to a manually operated flow control valve 54, and, :hrough the flow control valve 54, a sequence valve 55 and a check valve 56, which is in series with the sequence valve 55, to a common Working line 57. The third pump 5 has its pressure port 58 connected through series connected sequence valve 59 and check valve 60 to the comnon working line 57. Similarly, the 4th, 5th, and 6th pumps have their

pressure ports

61, 62, and 63 respeczively connected through

sequence valves

64, 65 and 66 and check valves 67, 68 and 69, respectively, to the common working line 57. Each of the

sequence valves

55, 59, 64, 65 and 66 has a

pilot line

70, 71, 72, 73 and 74 respectively, containing a

needle valve

75, 76, 77, 78, and 79 connected to detect the fluid pressure in the common Working line 57 and each of the

sequence valves

55, 59, 64, 65 and 66 has a bleed-off

line

80, 81, 82, 83, and 84 connecting it to a drain line 85. The drain line 85 empties Into a main return line 86 which terminates in the reservoir 19 and which contains a cooler 87 with a bypass cirzuit containing a spring loaded check valve 88, and a filter.

The

sequence valves

55, 59, and 64-66 along with the associated pilot lines 70-74, bleed-01f lines 80-84 and the drain line 85 combine to provide an automatic bleed-off :ontrol means that is responsive to the load on the hoist cable 45. The load on the hoist cable 45 is reflected back through the cable drum and the motors 21-24 so that the fluid pressure in the common working line 57, which is detected by the

sequence valves

55, 59, and 64-68 through :he respective pilot lines 70-74, is a function of the load on the hoist cable 45. The main purpose for this antomatic bleed-off control is to accelerate the wind-in of the hoist cable 45 when its load is light, reflecting wave action lifting the load, and to decelerate the wind-in of the hoist cable 45 when the load increases. This function maintains relatively constant tension in the hoist cable 45 and it provides mechanical advantage to the prime mover 7 to make its load more uniform.

The common working line 57 is connected through a normally open 2-way solenoid valve 89 to a hoist working line 90, and the 2-way solenoid valve 89 is energized through a push button 91, which, although it is illustrated in the center of the drawing, would probably be mounted an an operator handle 92 of the 4-way valve 49 for the :onvenience of the crane operator. The common working line 57 is also connected through a second 2-way solenoid valve 93, which is normally closed, to a lowering working tine 94. The second 2-way solenoid valve 93 that is connected to the lowering working line 94 is operated by another push button 95 that would also be mounted on the operator handle 92 of the 4-way valve 49 for the convenience of the operator. The push bottons 91 and 95 for both 2-

Way solenoid valves

89 and 93 are connected to appropriate electrical energizing sources for the solenoids which operate the

valves

89 and 93, but, since the appropriate circuitry is well known in the art, it is not detailed here.

The two

solenoid valves

89 and 93 combine with the 4-way control valve 49 to provide reversing and full range operation in either direction. By sacrificing the full range of speeds in one or the other direction of motors 21-24, operation of the

solenoid valve

89 or 93 for that direction can be eliminated.

The common working line 57 is connected at one end of a shock suppressor 96, draining to the drain line 85, and the other end of the common working line 57 is connected through a relief valve 97 to the main return line 86. The shock suppressor 96 is a commercially available component that operates on abrupt relative increases in line pressure to allow a small amount of fluid to bleed through the shock suppressor 96 from the common working line 57 back to the reservoir through the drain line 85. The relief valve 97, by contrast, responds to pressure levels, and spills over into the main return line 86 whenever the pressure in the common working line 57 exceeds a pre-set maximum.

The hoist working line 90 joins hoist

input ports

98, 99, 100, and 101 of each of the

motors

21, 22, 23, and 24, respectively to another port 104 of the 4-way control valve 49, through a manually operated flow control valve 102, which bypasses a check valve 103. Similarly the lowering working line 94 joins lowering

input ports

105, 106, 107, and 108 of the respective motors 21-24 to a third port 109 in the 4-way control valve 49, and through a relief valve 110, to the main return line 86. Each of the motors 21-24 also has a

drain line

111, 112, 113, and 114 that empties into the reservoir 19. A fourth port 115 of the 4-way control valve 49 opens into the drain line 85, which connects it through the main return line 86 to the reservoir 19, to provide the main return path for fluid driving the motors 21-24 in either direction. A relief valve 116 connects the working line 47 to the drain line to prevent an overload in the working line 47. The flow control valve 54 connected to the pressure port 53 of the pump 2 also has a drain line 117 connected through a drain line 85 and the main return line 86 to the reservoir 19.

When the operator handle 92 of the 4-way valve 49 is set in its hoist control range, fluid flows from the hoist Working line through the hoist input ports 98-191 of the motors 21-24, through the motors 21-24 and out of lower input ports -108. When the operator handle 92 of the 4-way valve 49 is set in its lowering control range, fluid flows from the lower working line 94 into the lower input ports 105-108 of the motor 21-24 and out of the hoist input ports 98-101. Due to the meter-in and meterout controls provided by this embodiment as well as other operations described below, it would be misleading to assume that the terminology hoist working and lower working, used here merely to distinguish two structures, were definitive of the functions of the two working

lines

90 and 94. However, that distinguishing terminology does describe the general direction of fluid flow vis-a-vis the motors 21-24 during those two phases of operation. This embodiment of the invention employs three. types of hydraulic controls for the cable drum 30, in addition to the mechanical braking that is efiected through the

brake shoes

35 and 36 acting on the

respective brake drums

33 and 34. The 4-way control valve 49 is, in addition to being a directional control valve, also a flow control valve, and it provides both meter-in and meter-out control of the motors 21-24. The flow control valve 102 in the hoist working line 90 provides meter-out control of the motors 21-24 during lowering of the cable 45. The flow control valve 54 connected to the pressure port 53 of the second pump 2 permits limited meter-in control to the motors 21-24 under some common operating conditions.

In discussing the operation of this embodiment of the present invention, assume, unless specifically indicated otherwise, that the A-C motor 7 is continuously driving all six pumps 1-6 simultaneously at a constant speed. The control of the speed and direction of rotation of the cable drum 30 by the motors 21-24 is thus effected by the valving described.

As initial postulates, let the hoist cable 45 be connected to a floating vessel of some sort that the operator desires to hoist from the sea onto the ship on which the crane including this power unit is mounted. Let it be further postulated that the operator has moved the handle 92 of the 4-way valve 49 into its full speed hoist position which commands the power unit to wind-in the cable 45 at a rate of about 40 feet per minute. Since the operator performs no further operations, the 2-Way solenoid valve 89 between the common working line 57 and the hoist working line 90 remains in its normally open position, and the 2-Way solenoid valve 93 between the common working line 57 and the lower working line 94 remains in its normally closed position.

Add to the foregoing postulates the condition that wave action is carrying the vessel to be hoisted upward at a rate of 300 feet per minute with respect to the crane on which the cable drum 30 is mounted. No load will appear on the hoist cable 45, and since fluid pressure in the power unit is a function of the load on the cable 45, the fluid pressure reflected from the motors 21-24 back through the hoist working line 90 and the 2-way solenoid valve 89 to the common working line 57 will be at a minimum. Fluid from the first pump 1 through the brake line 50 will overcome the pressure of the. springs 37 and 38 in the brake cylinders 41 and 42 to release the

brake shoes

35 and 36 from their

respective brake drums

33 and 34. The preponderance of the output of the first pump 1, however, will flow through its working line 47 to the 4-way valve 49 and through the 4-way control valve 49 and the check valve 103 and the hoist working line 90 to the several hoist input ports 98-101 of the respective motors 21-24. At the same time, the entire output from the

pressure ports

53, 58, and 61-63 of the second, third, fourth, fifth, and sixth pumps 2-6 will flow through the

respective sequence valve

55, 59, and 64-66 and check valve 56, 60, and 67-69 to the common working line 57, and from the common working line 57 through the normally open 2-way solenoid valve 89 and the. hoist Working line 90 and the hoist input ports 98-101 of the motors 21-24. The combined output of all six pumps 1-6 will drive the motors 21-24 at a speed suflicient to wind-in the hoist cable 45 onto the cable drum 30 at a rate of 300 feet per minute.

As the wave action crests so that the movement of the load with respect to the crane decelerates, an increasing load on the cable 45 is reflected back through the drum 30 and the gear 29 and pinions 25-28 to the motors 21-24, and through the hoist working line 90 and the normally open 2-Way solenoid valve 89 to the common working line 57. This embodiment of the invention, it is contemplated, will be called upon to hoist loads of about 40,000 pounds, and to accomplish the necessary functions with currently available hydraulic components, maximum operating line pressures in the neighborhood of 2,000 pounds per square inch are anticipated. The

sequence valves

66, 65, 64, 59 and 55 on the sixth, fifth, fourth, third, and second

hydraulic pumps

6, 5, 4, 3 and 2 are set at progressively increasing pressure levels from about approximately 350 pounds per square inch for the sequence valve 66 for the sixth pump 6 to about 1,200 pounds per square inch for the sequence valve 55 for the second pump 2. Thus, when the increasing fluid pressure in the common working line 57 exceeds approximately 350 pounds per square inch, or thereabout, this pressure,

detected by the pilot line 74 to the sequence valve 66 connected to the sixth pump 6, actuates that sequence valve 66 to spill the output of the sixth pump 6 into the bleedotf line 84 to the drain line 85 and back to the reservoir 19 through the main return line 86, which includes the cooler 88 and the filter.

Thus, the volume of fluid flow through the motors 21- 24 is reduced by the amount of the output of the sixth pump 6, which is being shunted directly from the pump 6 to reservoir 19 and back to pump 6. Assuming the pumps 1-6 have equal outputs, the fluid flow through the motors 21-24 is reduced by one-sixth, and the speed of the motors 21-24 is reduced commensurately. Accordingly, the load seen by the prime mover 7 is also reduced, giving the prime mover 7 a mechanical advantage against the load on the crane.

As the wave action continues to transfer more of the load to the hoist line 45, the fluid pressure in the common working line 57 increases as a function of that increase in the load on the hoist line 45. At preset, progressively increasing pressure levels, the

sequence valves

65, 64, 59, and 55 will successively divert the outputs of the fifth, fourth, third, and second pumps, 5, 4, 3, and 2 back to the reservoir 19 through the respective bleed-off

lines

83, 82, 81 and 80. As each

pump

6, 5, 4, 3, and 2 is successively shunted, so to speak, around the motors 21-24, the motors speeds decrease incrementally and the mechanical advantage seen by the prime mover 7 increases incrementally. The abruptness of the step-like changes in fluid flow is moderated by the action of the shock suppressor 96, which serves to modulate the steps. Thus, while the changes remain nevertheless incremental, they are graduated to avoid shock waves in the hydraulic fluid, as well as other undesirable effects.

Having hoisted the vessel, or load, from the sea, suppose that the operator desires to suspend the vessel on the cable 45 for a period of time. If the operator wishes to hold the vessel using the hydraulic system, he sets the operator handle 92 of the 4-way valve 49 at its lowest hoist speed position, and he will close the flow control valve 102 in the hoist Working line 90. Thus, only a minute flow of fluid will pass through the 4-way valve 49 from the first pump 1 to the motors 21-24, and that at 2,000 pounds per square inch pressure, which will also maintain the

brake shoes

35 and 36 released from the

respective drums

33 and 34. The line pressure will, of course, actuate all of the

sequence valves

55, 59, 64-65 to shunt the outputs of the remaining pumps 2-6 around the motors 21-24. Since only a min-ute amount of fluid will be metered-out of the motors 21-24 through 4-way valve 49 to the reservoir 19 through the lowering pressure line 94, impact loads may dump small amounts of flucildg to the reservoir 19 through the relief valves 116 an Should the operator prefer to hold the crane load using the brakes, he will set the operator handle 92 of the 4-Way valve 49 in its hold position. The 4-way valve 49 will then shunt the output of the first pump 1 from the port 48 connected to its working line 47 to the port 115 connected to the reservoir 19 through the drain line 85 and the return line 86. The other two ports 104 and 109 to the hoist working line and the lowering working line 94, respectively, will be closed, trapping the fluid in those lines. The back pressure thus imposed on the

sequence valves

55, 59, 64-66 actuates them to shunt the outputs of the pumps 2-6 to the reservoir. With the outputs of all of the pumps shunted to the reservoir 19, there is insuflicient fluid pressure in the system to overcome the

springs

37 and 38 in the cylinders 41 and 42. Hence, the

springs

37 and 38 force the

brake shoes

35 and 36 against the

respective brake drums

33 and 34 to prevent their rotation. Since the brake drurns 33 and 34 are linked to the cable drum 30 through the

respective pinions

31 and 32 and the gear 29, the cable drum 30 and cable 45 with its load will be locked in position.

Suppose now that the operator should want to lower the load, or vessel back into the sea. He will set the operator handle 92 of the 4-way valve 49 in its lowering position so that it will lower the vessel at the maximum normal lowering speed of to feet per minute, and will depress the push button 91, which is mounted on the operator handle 92, to energize the solenoid and to actuate the normally open solenoid valve 89 to its closed position thus disconnecting the common working line 57 from the hoist working line 90. This traps the fluid in the common working line 57 to exert a line pressure against the

sequence valves

55, 59, and 64-66 such that the ouptuts of the second, third, fourth, fifth, and sixth pumps 26 will be shunted to the reservoir 19, around the motors 21-24. The output from the first pump 1 will release the

brake shoes

35 and 36 from the

drums

33 and 34, and it will flow through the 4-way valve from the port 48, which is connected to the working line 47, to the port 109, which is connected to the lower working line 94, and from the lower working line 94, the fluid is pumped into the lowering input ports 105-108 of the respective motors 21-24. The fluid flowing out of the motors 21-24 through the hoist input ports 98-101 is metered out through the flow control valve 102 before passing through the 4-way valve 49 to the reservoir 19 through the drain line 85 and the main return line 86. Alternately, or simultaneously, the 4-way valve 49 can also meter-out the flow of fluid during lowering, to control the lowering speed of the load.

This embodiment shown also provides a high speed lowering feature. Should the operator wish to lower the hoist cable 45 with an empty hook very quickly, he need only actuate the push button 95, which may be mounted on the operator handle 92 of the 4-way valve 49, to energize the solenoid of the normally closed solenoid valve 93. In so doing, the operator would relax the pressure in the common working line 57 against the

sequence valves

55, 59, and 64-66, with the result that the output of the remaining five pumps 26 would be channeled into the common working line 57, and from there through the now opened 2-way solenoid valve 93 to the lower working line 94. Thus the entire output of all six pumps 1-6 could be applied to the lowering of the hoist cable 45.

Also, in the situation where a launch or other vessel m-ust be lowered into heavy seas, the operator could have the benefit of automatic, high speed take-up of the hoist cable 45 to compensate for wave action, and thus to maintain proper tension in the cable 45 at all times until it is released from the load. In such a situation the operator would have the handle 92 on the 4-way valve 49 set to a desired speed in its lowering control range and both

solenoid valves

89 and 93 closed. By releasing the push button 91 on the operator handle 92 when the load on the hoist cable 45 is seen to be floated by wave action, the operator would de-energize the solenoid valve 89 between the common working line 57 and the hoist working line 90 to restore the solenoid valve 89 to its normally open condition. Thus the output of the second, third, fourth, fifth, and sixth pumps 2-6 would be pumped into the hoist input ports 98-101 of the motors 21-24, reversing the direction of the motors 21-24 from relatively low speed lowering to high speed hoisting. The output of all six pumps 1-6 would complete the circuit to the reservoir 19 through the relief valve 110 in the lower working line 94. Since the first pump 1 would be opposed by the remaining five pumps 2-5 in this situation, the output of the first pump 1 would bypass the motors 21-24 through the lower working line 94 and return directly to the reservoir 19 through the relief valve 110 in the lower working line 94, whereas the output of the remaining five pumps 26 would pass through the motors 21-24 to the lower working line 94.

The circuitry of the second embodiment shown in FIG. 2 has much in common with that described above in the first embodiment, and insofar as the two are identical there is no need to repeat a detailed description of those portions of the second embodiment. Both embodiments have a prime mover 7 in the form of an electric motor 7 that is mechanically linked by a mechanism 8 to drive a plurality of pumps 1-6 simultaneously which draw the fluid 20 from the reservoir 19. Each embodiment employs a fluid motor means 21-24 in the form of the four rotary hydraulic motors 21-24 which drive a load, i.e., the cable drum 30 with its cable 45, through the mechanical linkages shown, which are identical. The motor means 21- 24 have first and second motor port means in the form of a hoist input port 98-101 and the lowering input port 108, respectively. The motor means 21-24 also have the same drain lines 111-114 which empty into the reservoir 19. The first and second motor port means 98-101 and 105-108, are respectively connected to the first motor conduit 90, which is the hoist working line 90, and the second motor conduit 94 which is the lowering working line 94. In each embodiment, the plurality of pumps 1-6 can be considered to include the first pump means 1 and the second pump means 2-6, the second pump means 26 being connected through pressure

sensitive valves

55, 59, 64-66, e.g., the

respective sequence Valves

55, 59, 64-66, either to the reservoir 19 or to the pumping conduit '57 which has been referred to as the common working line 57. The first pumping means 1 is connected through the other pumping conduit 47 to one of the pair of

ports

48 and 115 on one side of the four-way flow control valve 49, which is the flow control valve 49 for the power unit. The other side of the four-way flow control valve 49 has the pair of ports 104 and 109 which are connected to the first and

second motor conduits

90 and 94, respectively.

The second embodiment differs from the first primarily in the brake mechanism and associated circuitry, and in the use of a double two-way valve means in place of the two-way valve means 89 and 93 in the first embodiment. The double two-way valve 120 has a spool 121 with two annular lands 122 and 123 to guide or obstruct fluid flow and a piston 124 at its bottom end. The top land 122 is fitted with a spring seat 125 upon which a compression spring 126 bears to hold the spool 121 in its normal, closed position shown in FIG. 2. The spool 121 is reciprocally housed in a jacket 127 that has a drain port 128 connected to the drain line 86, a pressure port 129 connected to the common working line 57 and third and

fourth ports

130 and 131 connected to the two motor conduits 9'4 and 90, respectively. A drain line 132 empties along with the motor drain lines 111-114 into the reservoir 19. The double two-way valve 120 is pilot actuated and controlled by a solenoid operated pilot valve 133. The solenoid operated pilot valve 133 has a solenoid 134 connected to an electrical energizing source (not shown) through push-button 135 which, for the convenience of the operator, would preferably be mounted on the handle 92 of the four-way flow control valve 49. The solenoid operated pilot valve 133 has its valve portion 136 connected to receive fluid from the common working line 57 and drains along with the motors drains 111-114 to the reservoir 19. A pilot line 137 connects the pilot valve 136 to the piston 124 at the bottom of the spool 121 of the double two-way valve 120, so that when the solenoid operated pilot valve 133 is open, fluid pressure from the common working line 57 will drive the spool 121 up to open both normally closed

ports

130 and 131 of the double two-way valve 120. In place of the manually operated flow control valve 102 in the hoist motor line 90 of the first embodiment, the second embodiment employs a counter balance valve 138 that has its pilot line 139 connected to a brake line 140, which is also unique to the second embodiment. The check valve 103 could be either integral with the counter balance valve 138, or external to it.

The brake line 140 in the second embodiment of FIG. 2 takes off from the lowering motor conduit 94, as distinguished from the brake line 50 in the first embodiment of FIG. 1 which takes off directly from the first pump means 1, and this difierence reflects a diflerence in the brake mechanism. In the first embodiment, the brakes were normally set and would be released anytime the fourway control valve 49 was actuated to either raise or lower the cable 45. In the second embodiment, the

brake shoes

35 and 36 are respectively normally locked into the

brake drums

33 and 34 in the first embodiment, but the

brake drums

33 and 34 are connected through sprag clutches 141 and 142, respectively, to their brake pinions 31 and 32. The sprag clutches 141 and 142 also called overruning clutches allow the

pinions

31 and 32, respectively, to turn freely when the cable drum 30 is driven to hoist the cable 45, but they lock against any lowering pressure on the cable drum 30. Hence, the brake line 140 is connected into the lowering motor conduit 94 so that when the four-way flow control valve 49 is actuated to lower the cable 45, the fluid pressure in the lowering motor conduit 94 will release the brakes 41 and 42.

With the double two-way valve 120 in the normal position shown in the drawing, and with the four-way flow control valve 49 actuated for hoist, fluid from the second pump means 2-6 will be blocked by the double two-way valve 120 so that pressure in the common working line 57 immediately rises sufiiciently to cause the pressure

sensitive sequence valves

55, 59 and 64-66 to shunt the output of the second pump means 2-6 back to the reservoir 19 through the drain line 86. However, the output from the first pump means 1 passes through the flow control valve 49 and the hoisting motor conduit 90 to the motors 21- 24, and from the motors 21-24 back through the lowering motor conduit 94, the flow control valve 49 and the common drain line 85 to the reservoir 19. This will produce a low-speed hoisting.

If the operator desires high-speed hoisting, he will close the push-button 135 to energize the solenoid 134 on the solenoid operated pilot valve 133. This opens the valve portion 136 so that fluid under pressure from the common working line 57 will drive the spool 121 upward in the double two-way valve 120. When this occurs, both the third and

fourth ports

130 and 131 are open, and fluid can flow from the second pump means 2-6 into the pressure port 129, through the double two-way valve 120 and out the third port 130 to drive the motor means 21-24 at maximum speed, unless the load on the motor means is such as to reflect suflicient back pressure to actuate one or more of the

sequence valves

55, 59 and 64-66.

It the double two-way valve 120 is restored to its normal position by allowing the push-button 135 to open, and if the four-way flow control valve 49 is actuated to its lowering position, the operator can achieve a low speed lowering. With the operator handle 92 of the fourway flow control valve 49 in the reverse position and the push-button 135 released so as to deenergize the solenoid operated pilot valve 133, leaving the double two-way valve 120 in its normal positions as shown on the drawing, the output of the second pump means 2-6 will be shunted to the reservoir 19. Whenever the double two-way valve 120 is in its normal position, with the spool 121 at the lower end of its travel in the jacket 127 as it appears in the drawing, fluid flow from the second pump conduit 57 is blocked and immediately develops suflicient pressure to actuate the pressure

sensitive valve

55, 59, 64-66 so as to divert the output from the second pump means 2-6 back to the reservoir 19. When the four-way flow control valve 49 is in its lowering position, fluid flows from the first pump means 1 through the four-way flow control valve 49 into the second motoring conduit 94 and thus into the second motoring port means 105-108 of the motor means 21-24 and out of the first motor port means 98-101 to the first motoring conduit 90, and from there back through the four-way flow control valve 49 and the common drain line 86 to the reservoir 19. The fluid pressure in the second motoring conduit 10 94 is also transmitted to the brake line 140 to drive the pistons 39, 40 and the brake cylinder 41 and 42, respectively, toward the blind end so as to release the brakes permitting the cable drum 30 to pay out cable 45. The pressure in the brake line 140 is transmitted through thepilot line 139 of the counter balance valve 138 to open the counter balance valve 138 allowing fluid to flow around the check valve 102.

Suppose, hypothetically, that a load on the end of the cable 45 being lowered settles in the water in the trough of a wave and then begins to rise creating slack in the cable 45 during lowering. Retaining the four-way flow control valve 49 in its lowering position, the operator then closes the push-button 135 energizing the solenoid 134 of the solenoid operated pilot valve 133, which opens the valve portion 136 so that the pressure in the pilot line 1.37 can open the double two-way valve 120 by driving the spool 121 upward against the compression spring 126. Under those circumstances, the output of the first pump means 1 would continue to try to drive the motor means 21-24 in a lowering direction, but it is overcome by the output of the second pump means 2-6 which is now able to enter the first motoring line to drive the motor means 21-24 in the hoist direction. Simultaneously, the double two-way valve also opens the second motor line 94 to the common return line 85 so that the output of the first pump means 1 is shunted back to the reservoir 19 along with the return from the second pump means 2-6 after it leaves the motor means 21-24. This releases the pressure in the brake line so that the counter balance valve 138 which is operated by the pressure in the brake line 140 to the pilot line 139 also closes, blocking the return to the common drain line 86 through the four-way flow control valve 49. With the pressure in the brake line 140 released, the brakes return to their set position as illustrated in the drawing, and the slack is taken up in the cable 45 against the sprag clutches 141 and 142, respectively, on the

brake drums

33 and 34.

Under normal operating conditions with the double two-way valve 120 opened, the pressure sensitive valve means 55, 59, 64-66 will function in the usual manner to provide an automatic response to wave action, for example, so that the speed with which the motor means 21-24 are driven will depend upon the load imposed on the motor means 21-24 from the cable drum 30 from the cable 45. Inasmuch as this has already been described in connection with the first embodiment, it will not be repeated here.

The present invention, as exemplified in the embodiments described above, provides a power unit for a cable drum on a crane that makes possible the accurate and precise operator control of a load on the hoist cable 45 of the crane even under rapidly varying conditions. To achieve that goal an automatic response to some conditions is necessary and the invention provides this in the pressure

responsive valves

55, 59, 64-66 and associated circuitry. In addition it is essential that the operator be able to control the cable drum with a minimum number of control devices to actuate, for most operators are provided with but two hands and feet, and with these he must control not only the cable 45 but also the boom hoist, jib hoist, swing, and probably an auxiliary hoist cable. A power unit for the cable drum that requires too many controls could cause a dangerous state of operator confusion in a crisis, and might even demand more appendages than nature has provided whereupon an accident would inevitably occur with resulting damage, injury, and possible loss of lives. While achieving that result, the present invention also ensures that the power unit will be reliable, stable, durable and economical.

The subject matter that constitutes the present invention is set forth in the claims that follow.

What is claimed is:

1. A hydraulic power unit for driving and controlling a cable drum comprising the combination of a hydraulic motor means connected to drive a cable drum and having a first port means to receive fluid for driving it in one direction and a second port means for receiving fluid to drive it in an opposite direction;

a reservoir of hydraulic fluid;

a pump means including a plurality of pumps having suction ports connected to pump said fluid from said reservoir having pressure ports, and at least one of said plurality of pumps having a pressure sensitive valve connected to its pressure port to divert said fluid from at least said one pump back to said reservoir when fluid pressure exceeds a preset maximum substantially less than maximum normal operating pressure;

a directional control valve having an Operator handle, being adapted to alternately connect said first and second port means of said motor means to said reservoir responsive to a position of said operator handle and having flow control capability;

and a two-way valve means operator actuatable to connect said pump means to at least one of said port means of said motor means.

2. A hydraulic power unit as set forth in claim 1,

wherein said pump means includes a first pump means and a second pump means;

and said second pump means includes a plurality of pumps.

3. A hydraulic power unit as set forth in claim 2,

wherein each of said plurality of pumps in said second pump means has its pressure port connected to a pressure responsive valve means adapted to divert fluid flow to said reservoir when said fluid pressure exceeds a preset maximum.

4. A hydraulic power unit for driving and controlling a cable drum comprising the combination of a hydraulic motor means connected to drive a cable drum and having a first port means to receive fluid for driving it in one direction and a second port means for receiving fluid to drive it in an opposite direction;

a reservoir of hydraulic fluid;

a pump means including a plurality of pumps having suction ports connected to pump said fluid from said reservoir having pressure ports, said plurality of pumps having a first pump means and a second pump means with said second pump means being made up of more than one pump, and at least one of said plurality of pumps having a pressure sensitive valve connected to its pressure port to divert said fluid from at least said one pump back to said reservoir when fluid pressure exceeds a preset maximum;

a directional control valve having an operator handle,

being adapted to alternately connect said first and second port means of said motor means to said reservoir responsive to a position of said operator handle and having flow control capability;

and a two-way valve means operator actuatable to connect said pump means to at least one of said port means of said motor means, said two-way valve means including one two-way valve connected between said second pump means and said first port means of said motor means and another two-way valve connected between said second pump means and said second port means of said motor means.

5. A hydraulic power unit as set forth in claim 2, wherein said two-way valve means includes a double two-way valve connecting said first port means of said motor means to said second pump means and connecting said second port means of said motor means to said reservoir.

6. A hydraulic power unit as set forth in claim 2 wherein said directional control valve is a four-way valve adapted to alternately connect said first port means of said motor means to said first pump means and to said reservoir and to alternately-connect said second port means of said motor means to said reservoir and to said first pump means.

7. A hydraulic power unit for driving and controlling a cable drum comprising the combination of a hydraulic motor means connected to drive a cable drum and having a first port means to receive fluid for driving it in one direction and a second port means for receiving fluid to drive it in an opposite direction;

a reservoir of hydraulic fluid;

a pump means including a plurality of pumps having suction ports connected to pump said fluid from said reservoir having pressure ports, said plurality of pumps having a first pump means and a second pump means with said second pump means being made up of more than one pump, and at least one of said plurality of pumps having a pressure sensitive valve connected to its pressure port to divert said fluid from at least said one pump back to said reservoir when fluid pressure exceeds a preset maximum, each of said pumps in said second pump means having its pressure port connected to a pressure responsive valve means adapted to divert fluid flow to said reservoir when said fluid pressure exceeds a preset maximum and said second pump means [being connected to a shock suppressor and said shock suppressor drains to said reservoir;

8. A hydraulic power unit as set fotrh in claim 1 wherein said two-way valve means. is solenoid operated and controlled by a switch on said operator handle of said directional control valve.

References Cited UNITED STATES PATENTS 1,047,329 12/ 1912 Sundh.

2,042,247 5/ 1936 Blood 60-52 2,074,618 3/ 1937 Roeder.

2,160,920 6/ 1939 Strawn 60-52 XR 2,27 6,895- 3/1942. Vosseler et a1. 6053 XR 2,395,302 2/ 1946 Slomer 6053 XR 2,724,335 11/ 1955 Eames.

3,161,022 12/ 1964 Sandoy.

FOREIGN PATENTS 437,812. 11/1935 England.

EDGAR W. GEOGHEGAN, Primary Examiner US. Cl. X.R.