US3509721A - Multiple motor hydraulic drive system - Google Patents

Description

- ay 5, 1970 J. M. CRAWFORD 3,509,721

MULTIPLE MOTOR HYDRAULIC DRIVE SYSTEM Filed March 28, 1969 2 Sheets-Sheet 1 ENG/NE INVENTOR. (/OHA/ A//Z 6X24 WFOE/J y 1970 J. M. CRAWFORD 3,509,721

MULTIPLE MOTOR HYDRAULIC DRIVE SYSTEM Filed March 28, 1969 2 Sheets-Sheet a ILEZ 45 44 35 MJA 25 24 /5 MM LEM-57E I?) I2 ENG/NE- ENG/NE- 2 ave/[v5- 5 I 22 22 22 AUX/L/AEY a AUX/U42) E AUX/L/AEY EQU/PME/W' EOU/PMEA/T EOU/PMEA/T 2a 2a 26 I 34 c. 1 c. u g PUMP PUMP lli 42 I 42 a lib I111 IN @a Ill 65 slams INVENTOR. (/OH/V A/f. CeAm F-o/e/a f 1 E4 g h United States Patent O 3,509,721 MULTIPLE MOTOR HYDRAULIC DRIVE SYSTEM John M. Crawford, 121 Whitworth, Ponca City, Okla. 74601 Continuation-impart of application Ser. No. 748,139,

May 27, 1968, which is a continuation-in-part of application Ser. No. 540,766, Apr. 6, 1966. This application Mar. 28, 1969, Ser. No. 819,509

Int. Cl. F16d 31/06 US. Cl. 60-53 Claims ABSTRACT OF THE DISCLOSURE A system for driving a plurality of hydraulic motors particularly useful on a vehicle or ship having equipment thereon required to be driven by hydraulic pressure. A prime mover drives a primary pump which may supply fluid to both the drive system and the auxiliary equipment. In the drive system, the output of the primary pump is directed in parallel to a plurality of constant volume pumps having their rotors mounted on a common shaft. Each constant volume pump has its discharge connected to a hydraulic motor to be driven, and a four-way, opencenter valve controls the flow of fluid from each constant volume pump to its respective motor, such that all motors may be operated in synchronism or each motor may be individually operated at any desired speed and in either direction. Braking of the hydraulic motors is obtained by directing the discharge from all the motors through a single control valve which may be used to maintain a back pressure on the motors.

CROSS REFERENCES TO RELATED APPLICATION This is a continuation-in-part of applicants co-pending application entitled, Hydraulic Drive System, No. 748,139, filed May 27, 1968, which in turn is a continuation-in-part of applicants application of the same title, Ser. No. 540,766, filed Apr. 6, 1966, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to improvements in hydraulic drive systems employing a plurality of drive motors.

Description of the prior art Many vehicles and ships employ hydraulically driven auxiliary equipment requiring operation at various times, both when the drive system of the vehicle or ship is in operation and when such drive system is not in operation. For example, many vehicles and ships are employed in seismic exploration utilizing a hydraulically driven vibrator. Further, such hydraulically driven vibrators require a prime mover and pump being operated at a relatively constant speed for proper operation of the vibrator. Prior to my inventions, separate prime movers were required for the vibrators and the drive systems of the vehicles or ships, resulting in excessive first and operating costs. Further, the mechanical type drive system employed on vehicles used in seismic exploration place severe limitations on the use of the vehicles on rough terrain, and the use of a mechanical drive system in a ship requires the propeller shaft to be extended through the hull of the ship, resulting in serious sealing and vibrational problems.

SUMMARY OF THE INVENTION The present drive system is particularly useful for driving the wheels of a vehicle having hydraulically operated equipment, such as a seismic vibrator, thereon, and

3,509,721 Patented May 5, 1970 for driving the propellers of a ship having hydraulically operated auxiliary equipment thereon, but may be used in any system wherein two or more hydraulic drive motors may be desirably utilized.

In one aspect, the present invention contemplates a system for driving a plurality of hydraulic motors comprising a primary pump having a relatively constant pressure output and being driven by a prime mover. A plurality of constant volume pumps equal to the number of hydraulic motors to be driven have their rotors connected to a common shaft and have their inlets connected in parallel to the output of the primary pump. A four-way, open-center valve is provided for each constant volume pump and associated hydraulic motor, having one port connected to the outlet of the associated constant volume pump, a second port connected to the forward port of the associated motor, a third port connected to the reverse port of the associated motor, and a fourth port connected to the supply of fluid for the primary pump. A control or operating lever is connected to each of the fourway, open-center valves to selectively direct (a) all of the fluid discharged from the associated constant volume pump to either port of the hydraulic motor; (b) a variable portion of the fluid discharged from the associated constant volume pump to either port of the associated motor while directing the remaining portion of the fluid back to the fluid supply, and alternately, (c) all of the fluid discharged from the associated constant volume pump back to the fluid supply, and all of the fluid in the hydraulic motor circulates so that the motor may free wheel, such that both the speed and direction of rotation of each motor may be individually controlled.

An object of the invention is to provide a hydraulic drive system for driving a plurality of hydraulic motors wherein the hydraulic motors may be individually controlled as to speed and direction.

Another object of the invention is to provide a hydraulic drive system for driving a plurality of motors wherein the motive fluid pressure will be automatically directed to the motor requiring the most power.

A further object of this invention is to provide a hydraulic drive system for a plurality of hydraulic motors wherein cavitation of the motors will be prevented when it is desired to slow down the system being driven by the hydraulic motors.

Another object of this invention is to provide a hydraulic drive system for a vehicle having hydraulically driven auxiliary equipment thereon, wherein the same prime mover may be used for both the drive system and the auxiliary equipment.

Another object of the invention is to provide a drive system for a vehicle wherein the vehicle will have a maximum of maneuverability and may be operated on a great variety of different terrains.

A still further object of the invention is to provide a hydraulic drive system for a ship wherein the propellers of the ship may be driven by the same prime mover as is employed for driving hydraulically operated auxiliary equipment associated with the ship.

Another object of the invention is to provide a propulsion ystem for a ship in which the propeller rotation may be quickly changed or reversed without changing speed of the prime mover.

Another object of the invention is to economize the construction and operation of vehicles and ships having hydraulically operated auxiliary equipment thereon.

Another object of the invention is to provide a 'hydraulic drive system which is highly adaptable, simple in construction, and which will have a long service life.

Other objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawing which illustrates the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic illustration of a hydraulic drive system constructed in accordance with this invention.

FIG. 2 is a schematic illustration of a typical four-way, open-center valve employed in the system of this invention.

FIG. 3 is a schematic illustration of a modification of the basic drive system with respect to the arrangement and plumbing of the four-way, open-center valves.

FIG. 4 is a schematic illustration of another modification which may be employed in the basic system of this invention.

FIG. 5 is a schematic illustration of the drive system of this invention as may be employed in ships.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in detail, and particularly FIG. 1, reference character generally designates a drive system constructed in accordance with this invention. The system 10 employs a prime mover 12 of any desired type, such as a diesel engine, driving a primary pump 14. The pump 14 is a relatively constant pressure pump, such as a multiple piston, variable stroke pump. The fluid supply for the pump 14 is indicated on the drawing by the word sump and will normally be simply a storage tank.

The discharge port 16 of the pump 14 is connected by a conduit 18 to the inlet port 20 of a first control valve 22 designated V in the drawing. The control valve 22 is preferably a four-way valve, and may be electrically, hydraulically or manually controlled. One of the ports 24 of the valve 22 is connected to the sump for bypassing or circulation of the output of the pump 14, and another port 26 of the valve 22 is connected to hydraulically operated auxiliary equipment (not shown), such as a seismic vibrator, in the event the system 10 is employed inconjunction with such auxiliary equipment. The remaining port 28 of the control valve 22 is connected in parallel to the inlet ports 30 of a plurality of constant volume pumps 32.

The pumps 32 may be of any suitable type of construction, such as a vane type pump, where the pumps will operate as motors in response to a pressure differential applied across the rotors thereof, as well as functioning as pumps when the rotors are turned. The rotors of all of the pumps 32 are mounted on a common shaft 34 for the automatic transfer of power between the various rotors, as will be referred to in detail below. It should also be noted that although the pumps 32 are illustrated in the drawing as being separate pumps, it will be understood by those skilled in the art that the pumps 32 could all be combined in a common housing, as is found in a multiple pump chamber, vane type pump.

A throttle valve 36 is interposed in the common connection of the control valve 22 to the inlet ports 30 of the pumps 32 to control the total amount of fluid being directed to the pumps 32 from the primary pump 14. The throttle valve 36 will thus control the speed of rotation of the rotors of the pumps 32 to control the overall speed of operation of the drive system 10, as will be further described. The throttle valve 36 is designated V, in the drawing and may be of any suitable construction, but is preferably manually operated.

The discharge port 38 of each constant volume pump 32 is connected to a first port 40 of what is known as a four-way, open-center valve 42. The valve member (not shown) of each valve 42 is ported in such a manner that all of the fluid directed into the port 40 of the valve may be directed through any one of the remaining three ports 44, 46 or 48; when fluid is directed from port 40 to port 46, ports 44 and 48 are in communication; a portion of the fluid entering the port 40 may be directed through 4 either of the ports 44 or 48 while the balance of the fluid is directed out of the port 46; and while fluid is being directed from the port 40 through either of the ports 44 or 48, fluid may be also directed to the port 46 from the port 44 or 48 not connected with the port 40.

The rotor of each valve 42 is controlled by an operating lever 51, as schematically illustrated in FIG. 2, to control the flow of fluid between the various ports of the valve. In the full line position of the lever 51 marked F, the rotor of the valve is in such a position that all of the fluid directed into the port 40 (FIG. 1) is directed out of the port 44, while the fluid at the port 48 is directed out of the port 46. In the dashed line position marked N in FIG. 2, all of the fluid present at port 40 of the valve is discharged through the port 46, while the ports 44 and 48 are in communication with one another. In the dashed line position marked R in FIG. 2, all of the fluid present at port 40 is discharged through port 48 and the fluid present at 44 is directed out port 46. The intermediate positions of the lever 51 between the positions F and N, as well as between the positions R and N, control the variable flows of fluid between the port 40 and the ports 44 or 48 while fluid is also being directed from the other port 44 or 48 to the port 46.

The port 44 of each valve 42 is connected to the A or forward port of a hydraulic motor 50, and the port 48 of each valve 42 is connected to the B of reverse port of the respective hydraulic motor 50. As illustrated in FIG. 1, four of the motors 50, designated M M M and M, are employed which may be, for example, for the purpose of driving the four wheels 52 of a motor vehicle. It should also be noted that in this basic construction of the system, there are corresponding numbers of pumps 32, valves 42 and motors 50. Finally, it may be noted that the motors 50 may be of the same construction as the pumps 32 to minimize inventory requirements and provide an economical construction and operation.

The system 10 is particularly useful when the spacing between the wheels 52 on opposite sides of the vehicle are substantially equal to the iength of the wheel base, that is, the spacing between a center line through the front wheels 52 (say those associated with motors M and M and a center line through the rear wheels 52.

The ports 46 of all the valves 42 are connected in parallel to a common control valve 54, and the output of the valve 54 is in turn connected to the sump. The valve 54 is designated V in the drawing to indicate its function as a brake for the motors 50 as will be referred to more in detail below. The valve 54 may be of any suitable construction which may provide a throttling action.

OPERATION OF EMBODIMENT OF FIGS. lAND 2 In operation of the system 10, the engine 12 will be operated at a constant speed at all times it is desired to either drive the vehicle containing the system 10, or to operate auxiliary hydraulic equipment, such as a seismic vibrator, which may be mounted on the vehicle. The primary pump 14 is therefor also operated at a constant speed and directs a flow of fluid at a relatively constant pressure and variable volume to the inlet port 20 of the first control valve 22. When the auxiliary equipment is being operated, the control valve 22 is shifted to a position such that the fluid discharge from the pump 14 is directed out the port 26, and the port 28 is closed. On the other hand, when it is desired to move the vehicle, the control valve 22 is operated to direct the discharge from the primary pump 14 out the port 28 and the port 26 is closed. When the auxiliary equipment is not being operated and the vehicle is not desired to be moved, the control valve 22 can be positioned to direct the discharge from the primary pump 14 out through the port 24 back to the sump, in the event it is desired to keep the engine 12 and pump 14 in operation. However; the primary pump 14 may be so constructed as to have no output (have a zero stroke) when the output pressure of the pump reaches a predetermined maximum value. In this latter event, the throttle valve 36 may be closed and control valve 22 may be retained in a position to keep the ports 20 and 28 thereof in communication when the vehicle is stationary and the auxiliary equipment is not being operated.

Let it be assume that it is desired to move the vehicle forward from a stopped position. The control valve 22 will therefore be set in a position to direct the discharge from the primary pump 14 to the throttle valve 36. The throttle valve 36 is gradually opened to provide a gradually increasing flow of fluid to the constant volume pumps 32 to gradually accelerate the rotors of the pumps and the common shaft 34. In view of the fact that the pressure at the inlet ports 30 of all of the constant volume pumps 32 will be essentially the same, and in view of the fact that all of the rotors of the pumps are connected by the common shaft 34, the pumps 32 will be operated at the same speed. It should be further noted that the operating lever 51 of each of the control valves 42 is turned to its forward or F position shown in FIG. 2. As a result, the fluid being discharged from each constant volume pump 32 will be directed through its respective valve 42 and out through the respective port 44 to the forward port A of its respective motor 50. Thus the motors 50 will be gradually accelerated to drive the wheels 52 and move the vehicle forward in a smoothly accelerating manner. The fluid being discharged from each motor 50 through its respective port B will be directed into the port 48 of the respective valve 42 and out through the respective port 46 to the braking valve 54. Assuming the braking valve 54 is in a fully opened position, this fluid will be simply returned to the sump for reuse by the drive system 10.

Now assume it is desired to stop the vehicle and then reverse the direction of the vehicle. The levers 51 are gradually moved from their full line F positions illustrated in FIG. 2 into the N or neutral positions, at which time the fluid being discharged from each constant volume pump 32 will be directed through the port 46 of the respective valve 42 and through the braking valve 54 to the sump, such that all of the motors 50 will simply be recirculating fluid through the valves 42. As previously noted, when a valve 42 is set to provide communication between the ports 40 and 46 thereof, communication is also established between the ports 44 and 48 thereof. Thus the vehicle will coast to a stop. It may also be noted that as the operating levers 51 are moved from the F to the N positions, the supply of fluid to the forward ports A of the motors 50 will be gradually reduced to prevent a sudden change in the operation of the motors.

To then reverse the direction of movement of the vehicle the operating levers 51 of all of the valves 42 are gradually moved from the N positions to the R positions. During this movement of the operating levers, fluid from each constant volume pump 32 is directed into its respective port 48 at a gradually increasing rate to gradually accelerate the motors 50 in the reverse direction. When the operating levers 51 reach the R positions, the vehicle will be moving in a reverse direction at a maximum speed, with the fluid flowing through each motor 50 being discharged from the A port thereof and through the ports 44 and 46 of its respective valve 42 to the braking valve 54.

When the throttle valve 36 is fully open, the vehicle associated with the system will be driven at full speed, either forward or reverse, depending upon the settings of the operating levers 51. In either event, the motors 50 will all be operated at uniform speeds, even though one of the wheels 52 may lose traction. In the event one of the wheels 52 does lose traction, the fluid flowing through the respective motor 50 will have a minimum resistence to flow through the motor and the resulting reduced pressure on the forward port A or reverse B thereof (depending upon whether the vehicle is moving forward or reverse) is reflected back to the discharge port 38 of the respective associated constant volume pump 32. The increased pressure differential across that pump will convert that pump into a motor to apply torque on the common shaft 34 and thereby increase the pressure output of each of the remaining constant volume pumps. As a result, the power not being utilized in operating a wheel which has lost traction will be automatically transferred to the other Wheel of the vehicle which is being driven by the system 10, to assure that adequate power will be available for moving the vehicle. Conversely, should one of the wheels 52 tend to become stuck and the rotation thereof retarded, an increased pressure differential will build up between the ports A and B thereof and increase the back pressure on the associated constant volume pump 32, tending to retard the speed of rotation of all the constant volume pumps 32. However, the power being supplied by the remaining constant volume pumps 32 on the common shaft 34 will tend to continue rotation of the affected constant volume pump 32, such that an additional force or torque will be exerted on the rotor of the affected constant volume pump to overcome the back pressure resulting from the affected Wheel 52.

When the vehicle employing the drive system 10 is in full forward or full reverse, the vehicle may be quickly stopped by closing the braking valve 54. To this end, the braking valve 54 is preferably treadle operated by the driver of the vehicle. As the valve 54 is closing, the flow from each of the. motors 50 is progressively decreased to retard the speed of rotation of the motors 50. And, when the valve 54 is fully closed, fluid will be prevented from flowing through any of the motors 50; and the motors 50, along with their associated wheels 52, will be held in a stopped position. The throttle valve 36 is preferably closed at the same time as the braking valve '54 to minimize back pressure on the constant volume pumps 32. It should be noted that the back pressure on all of the motors 50 imposed by closing the braking valve 54 will prevent the motors from cavitating, as would be the case if the vehicle were stopped by closing the throttle valve 36 while applying a mechanical bra-king action on the wheels 52 and the wheels were not stopped before the supply of fluid was stopped.

Let it now be assumed that the vehicle is being moved full forward and the wheels associated with the motors M and M are the front wheels of the vehicle. Let it be further assumed that the vehicle is to be turned to the right. In this event, the operating lever 51 associated with the valve 42 connected to the motor M will be moved from the F toward the -N position to bypass a portion of the fluid from the respective constant volume pump 32 to the sump via the port 46 of the respective valve to retard the speed of rotation of the respective wheel 52. At the same time, the lever 51 associated with the valve 42 connected to the motor M will also be moved toward a neutral position, but to a lesser extent, to retard the speed of rotation of the associated motor 50 and accommodate the turning of the vehicle. The speed of operation of the motor M may be varied in a like manner and to an extent depending upon the shortness of the turn being made by the vehicle. When turning to the left, motors M and M and perhaps motor M would be slowed in a similar manner. The vehicle may also be turned by placing the operating levers 51 of the valves 42 associated with the wheels on one side of the vehicle in their neutral positions while retaining the levers 51 of the valves associated with the wheels on the opposite side of the vehicle in their F or R positions. Since the motors 50 associated with the valves 42 having their ope-rating levers 51 in neutral position will simply free wheel, the vehicle will turn gradually toward that side.

EMBODIMENT OF FIG. 3

A vehicle employing the present drive system may also be steered by driving the wheels on one side of the vehicle at one speed and driving the wheels on the other side of the vehicle at a different speed, similar to the method of steering tractors and other large vehicles having a single track on each side thereof. To utilize such a steering method, the valves 42 controlling the operation of the motors M and M have their operating levers 51 connected to a common linkage 56 as schematically illustrated in FIG. 3. Operating levers 51 of the valves 42 controlling the motors M and M are similarly connected by a linkage 58. With this arrangement it will be seen that the motors M and M, will be operated at the same speeds and in the same direction by manipulation of a linkage S6, and the motors M and M will be operated at the same speeds and in the same direction by manipulation of the linkage 58. Thus, the motors M and M may be decreased in speed, or stopped, while the motors M and M are operated at a higher speed to turn the vehicle to the left. The reverse operation of the motors would cause the vehicle to turn to the right.

In some environments it is desirable to utilize tracks rather than wheels for supporting the vehicle. Under these circumstances, the wheels 52 on one side of the vehicle may receive a single, continuous track therearound, while the wheels 52 on the opposite side of the vehicle receive a similar track. It would then be necessary to drive only a single motor on each side of the vehicle. With this arrangement, the ports 48 of the valves 42 associated with the Wheels and motors on one side of the vehicle may be interconnected by a conduit 60 and 3-way valve 61, and the ports 44 of the same two valves 42 may be interconnected by a conduit 62 and 3-Way valve 64. The same arrangement would apply for the remaining two valves 42 associated with the wheels and motors on the opposite side of the vehicle.

With a system as illustrated in FIG. 3 and as just described, all of the fluid discharged from the two constant volume pumps 32 associated with the motors M and M may, by proper positioning of the associated valves 61 and 64, be directed either to the forward port A of the motor M or to the reverse port B of the motor M to provide a maximum application of pressure to such motor. Similarly, all of the fluid discharged from the two constant volume pumps 32 associated with the motors M and M may, by proper positioning of the associated valves 61 and 64, be directed either to the forward port A of the motor M or to the reverse port B of the motor M It will also be understood either the motor M or the motor M could be placed in either a free wheeling condition for a gradual turn or a reverse condition for a sharp turn of the vehicle to the left or the right, as the case may be. On the other hand, if the tracks extending around the wheels on each side of the vehicle were later removed for use of the vehicle in a different environment, the valves 61 and 64 may be positioned to close off the conduits 60 and 62. In this latter event, both motors on each side of the vehicle would be su-pplied with equal amounts of fluid in the same manner as previously described in connection with FIG. 1.

EMBODIMENT OF FIG. 4

In the event the motors 50 do not utilize equal amounts of fluid for equal speeds of operation, such as when a motor becomes worn and more fluid must be passed through the motor to obtain a speed of operation equal to the speed of operation of a new motor, the modification shown in FIG. 4 may be utilized. In this modification, a valve 66 may be connected across the ports A and B of each motor 50 to bypass a selected amount of fluid around one or more of the motors. For example, if one of the motors 50 is worn more than another motor 50, a portion of the fluid delivered to the unworn motor could be bypassed by means of the associated valve 66 to equalize the speeds of operation of the motors when the motors were being supplied with equal amounts of fluid from their associated constant volume pumps 32. The valves 66 will be required to bypass a very moderate amount of fluid and will therefore normally be needle type valves, or equivalent.

EMBODIMENT OF FIG. 5

For shipboard use, it is preferable to employ a plurality of prime movers 12, such as three diesel engines as shown in FIG. 5, as a safety measure. With this arrangement, each engine 12 is drivingly connected to a primary pump 14, and each primary pump 14 is in turn connected to a control valve 22 in the same manner as previously described. One port of each control valve 22 may be connected to hydraulically driven auxiliary equipment and the ports 28 of all of the control valves 22 are connected in parallel to a pair of constant volume pumps 32. The rotors of the constant volume pumps 32 are mounted on a common shaft 34, as before, and the output of each constant volume pump 32 is directed to a hydraulic motor 50 through a four-way, open-center valve 42 in the same manner as in the system previously described in connection with FIG. 1. Each hydraulic motor 50 is drivingly connected to a propeller 68 employed in propelling the ship. With this arrangement, two propellers 68 are normally required and the motors 50 may be mounted on the outside of the hull of the ship to prevent the necessity of extending the drive shafts of the propellers through the hull. Auxiliary propellers giving side thrust at the bow or stern, or both, may also be utilized in the system and such auxiliary propellers may be driven by motors connected to the control valves 22 if desired.

In operation of the shipboard version of the present drive system as shown in FIG. 5, either two or all three of the engines 12 are operated at the same time, particularly when the auxiliary equipment is being operated at the same time the ship is underway. With this arrangement, one or two of the control valves 22 may be turned to direct the output of the associated pump 14 to the auxiliary equipment, while the remaining control valve or valves 22 is turned to direct the output of the associated pump 14 to the inlets of the constant volume pumps 32. The constant volume pumps 32, valves 42 and motors 5t) operate in the same manner as previously described in connection with FIG. 1 to drive the propellers 68 at the desired speeds and in the desired directions with the exception that, in this system, the valves 42 are preferably employed as the sole means for accelerating and decelerating the propellers 68.

In the event the auxiliary equiment is not required to be in operation while the ship is underway, all of the control valves 22 may be turned to direct the outputs of the pumps 14 to the constant volume pumps 32. Further, in the event of a malfunction of one or two of the .engines 12, the remaining engine or engines may be employed to operate the constant volume pumps 32 at a reduced power with full steering and maneuverability of two (or more) propellers available from only one operating engine until the malfunction can be controlled.

From the foregoing it will be apparent that the present invention provides a hydraulic drive system for a plurality of hydraulic motors wherein the system is highly adaptable and may be employed in various environments. When used on a vehicle containing hydraulically operated auxiliary equipment, such as seismic vibrators, the same prime mover is employed for operating the auxiliary equipment and the drive system and the power supplied by the prime mover may be quickly and easily directed to either the auxiliary equipment or the drive system for moving the vehicle. When the present drive system is employed on vehicles, the vehicles can be used on a great variety of terrains, using four wheel drives, two wheel 9 drives, or track drives. When used aboard ship, the presen drive system is highly adaptable and will reduce both the first and maintenance costs of the ship.

Changes may be made in the arrangement and combination of parts or elements as herefore set forth in the specification and shown in the drawing without departing from the spirit and scope of the invention.

What is claimed is:

1. A system for driving a plurality of hydraulic motors, each of which has a forward and a reverse port, comprising:

a prime mover;

a primary pump drivingly connected to the prime mover and having an inlet and an outlet;

a supply of hydraulic fluid connected to the inlet of the primary pump;

a rotary, constant volume pump for each of the hydraulic motors to be driven and being capable of functioning as a motor as well as a pump, each of said constant volume pumps having an inlet and an outlet with the inlet thereof connected to the outlet of the primary pump;

a common shaft connected to the rotors of all of said constant volume pumps for transfering power between said constant volume pumps; and

a four-way, open-center valve for each constant volume pump having a first port connected to the outlet of the associated constant volume pump, a second port connected to the forward port of the associated motor, a third port connected to the reverse port of the associated motor, and a fourth port connected to the fluid supply;

each of said valves having an operating lever adapted to be positioned to direct (a) all of the fluid discharged from the associated constant volume pump to either port of the associated motor; (b) a variable portion of the fluid discharged from the associated constant volume pump to either port of the associated motor while directing the remaining portion of said discharge to the fluid supply; and alternately, (c) all of the fluid discharged from the associated constant volume pump to the fluid supply while providing communication between the second and third ports of the respective valve, whereby both the speed and direction of rotation of each motor may be individually controlled,

2. A system as defined in claim 1 characterized further to include a control valve having an inlet and an outlet;

means connecting the outlet of the control valve to the fluid supply; and

means connecting the inlet of the control valve to the fourth ports of all of the four-way, open-center valves,

whereby a back pressure may be selectively imposed on the outlets of the motors and form a braking action on the motors while preventing cavitation in the motors.

3. A system as defined in claim 1 characterized further to include a throttle valve interposed in the connection of the primary pump to the constant volume pumps, whereby the speeds of the motors may be controlled as a group.

4. A system as defined in claim 1 characterized further to include a bypass control valve interconnecting the forward and reverse ports of each motor to selectively bypass fluid around any of the motors in the event all of the motors do not require the same amount of fluid for the same speed of operation.

5. A system as defined in claim 1 characterized further to include a second prime mover, a second primary pump drivingly connected to the second prime mover having an inlet connected to the fluid supply and its outlet connected to the inlets of all the constant volume pumps.

6. A drive system for a vehicle having a pair of wheels 10 on each side thereof with the wheels on each side adapted to selectively receive a crawler track extending around both wheels, comprising:

a prime mover;

a primary pump drivingly connected to the prime mover, and having an inlet and an outlet;

a supply of hydraulic fluid connected to the inlet of the primary pump;

a rotary, constant volume pump for each of the wheels capable of functioning as a motor as well as a pump, each of said constant volume pumps having an inlet and an outlet with the inlet thereof connected to the outlet of the primary pump;

a common shaft connected to the rotors of said constant volume pumps for transferring power between said constant volume pumps;

a rotary, fluid motor drivingly connected to each of the wheels of the vehicle, each of said motors having a forward and a reverse port;

a four-way, open-center valve for each constant volume pump and associated motor having a first port connected to the outlet of the associated constant volume pump, a second port connected to the forward port of the associated motor, a third port connected to the reverse port of the associated motor, and a fourth port connected to the fluid supply;

an operating lever on each of said valves adapted to be positioned to direct (a) all of the fluid discharged from the associated constant volume pump to either port of the associated motor; (b) a variable portion of the fluid discharged from the associated constant volume pump to either port of the associated motor while directing the remaining portion of said discharge to the fluid supply; and, alternately, (c) all of the fluid discharged from the associated constant volume pump to the fluid supply while providing communication between the second and third ports of the respective valve;

a conduit and 3-way valve interconnecting the second ports of the valves associated with the motors on each side of the vehicle for selectively directing the fluid discharged from the associated constant volume pumps to the forward port of only one of the associated motors; and

a conduit and 3-way valve interconnecting the third ports of the valves associated with the motors on each side of the vehicle for selectively directing the fluid discharged from the associated constant volume pumps to the reverse port of only one of the associated motors.

7. A drive system for a vehicle having a pair of wheels on each side comprising:

a prime mover;

a primary pump drivingly connected to the prime mover, and having an inlet and an outlet;

a supply of hydraulic fluid connected to the inlet of the primary pump;

a rotary, constant volume pump for each of the wheels capable of functioning as a motor as well as a pump, each of said constant volume pumps having an inlet and an outlet with the inlet thereof connected to the outlet of the primary pump;

a common shaft connected to the rotors of said constant volume pumps for transferring power between said constant volume pumps;

a rotary, fluid motor drivingly connected to each of the wheels of the vehicle, each of said motors having a forward and a reverse port;

a four-way, open-center valve for each constant volume pump and associated motor having a first port connected to the. outlet of the associated constant volume pump, a second port connected to the forward port of the associated motor, a third port connected to the reverse port of the associated motor, and a fourth port connected to the fluid supply;

an operating lever on each of said valves adapted to be means providing substantially equal volumes of fluid positioned to direct (a) all of the fluid discharged for the motors; from the associated constant volume pump to either a supply of hydraulic fluid connected to said means; and port of the associated motor; (b) a variable portion a four-way, open-center valve for each motor having of the fluid discharged from the associated constant a first port connected to one of said means, a second volume pump to either port of the associated motor port connected to the forward port of the associated while directing the remaining portion of said dismotor, a third port connected to the reverse port of charge to the fluid supply; and, alternately, (c) all the associated motor, and a fourth port connected of the fluid discharged from the associated constant to th fluid supply; volume pump to the fluid supply while providing each of said valves having an operating lever adapted communication between the second and third ports to be positioned to direct (a) all of the fluid disot' the respective valve; charged from the respective means to either port of a first linkage connected to the operating levers of the the associated motor; (b) a variable portion of the four-way valves associated with the. motors on one fluid discharged from the respective means to either side of the vehicle for corresponding movements of 15 port of th a o iated motor whil directing the resaid levers; and maining portion of said discharge to the fluid supply; a second linkage connected to t Operating levers Di and alternately, (c) all of the fluid discharged from the four-way valves associated With the motors On the respective means to the fluid supply while providthe opposite side of the vehicle fOI. corresponding ing communication between the second and third movements of said levers. ports of the respective valve, whereby both the speed '8. A system for driving a plurality of propellers and auxiliary equipment of a ship, comprising:

a plurality of prime movers; a. primary pump for each prime mover drivingly connected to the respective prime mover and having an comprising; inlet and an outlet; means providing substantially equal volumes of fluid for a supply of hydraulic fluid connected to the inlets of th m t the primary pumps; a supply of hydraulic fluid connected to said means; a P r of rot ry, Constant Volume P p Capable of a four-way, open-center valve for each motor having functioning as motors as Well as P p each of Said a first port connected to one of said means, a second and direction of rotation of each motor may be individually controlled. 10. A system for driving a plurality of hydraulic moconstant volume pumps having an inlet and an outlet tors, each of which has a forward and a reverse port,

with the inlet thereof connected to the outlets of all the primary pumps; common shaft connected to the rotors of said conport connected to the forward port of the associated motor, a third port connected to the reverse port of the associated motor, and a fourth port connected to the fluid supply;

stant volume pumps for transferring power between said constant volume pumps;

a four-way valve interposed in the connection of each primary pump and the constant volume pumps having a third port connected to the auxiliary equipment and a fourth port connected to the fluid supply; 4

a rotary, fluid motor for each propeller drivingly connected to the respective propeller;

a four-way, open-center valve for each constant volume pump and associated motor having a first port connected to the outlet of the associated constant volume pump, a second port connected to the forward port of the associated motor, a third port connected to the reverse port of the associated motor, and a fourth port connected to the fluid supply; 7

an operating lever on each of said four-Way, open-center valves adapted to be positioned to direct (a) all of the fluid discharged from the associated constant volume pump to either port of the associated motor; '(b) a variable portion of the fluid discharged from the associated constant volume pump to either port of the associated motor While directing the remaining each of said valves having an operating lever adapted to be positioned to direct (a) all of the fluid discharged from the respective means to either port of the associated motor; (b) a variable portion of the fluid discharged from the respective means to either port of the associated motor while directing the remaining portion of said discharge to the fluid supply; and alternately (c) all of the fluid discharged from the respective means to the fluid supply while providing communication between the second and third ports of the respective valve, whereby both the speed and direction of rotation of each motor may be individually controlled; and

a valve interposed in the connection between all of the fourth ports of the four-way, open-center valves and the fluid supply adapted to restrict the discharge of fluid from the motors and the four-way, open-center valves to provide a braking action on the motors.

References Cited UNITED STATES PATENTS portion of said discharge to the fluid supply; and, 2,291,578 7/ 1942 1011118011- alternately, (c) all of the fluid discharged from the 2,301,098 11/ 1942 TWymaI! -53 XR associated constant volume pump to the fluid supply 2,316,926 9 3 WiHett.

While providing communication between the e 60 2,431,719 12/1947 Wilkin 60 53 0nd and third ports of the respective four-way, open- ,437,139 3/ 1948 Tucker 6 0-53 XR center valve, whereby both the speed and direction of rotation of the propellers may be individually controlled. 9. A system for driving a plurality of hydraulic motors, each of which has a forward and a reverse port, comprismg:

EDGAR W. GEOGHEGAN, Primary Examiner

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