Abstract:
A fluid power system for actuating three separately controllable double acting fluid motors each selectively providing a separate function in which the number of hydraulic lines to the motors is minimized. A first function valve supplies power to the first motor and a second function valve provides power to a selector valve which selectively connects the power to the second and third motors. The selector valve is pilot actuated from one of the lines to the first motor and a control valve supplies power to the one line for actuating the selector valve. The system is particularly useful for a lift truck for minimizing the number of hydraulic lines connected to the motors on the carriage of the truck.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to an improved fluid power system for actuating three separately controllable double acting fluid motors which selectively provide separate functions. In particular, the present invention is directed to a conventional lift truck in which the motors are provided on the movable carriage and the controls are mounted on the truck body. Because of the movement of the carriage relative to the body, it is important to reduce the number of hydraulic fluid lines extending from the body to the carriage. Various power systems such as shown in U.S. Pat. Nos. 3,692,198 and 4,161,256 have been disclosed for solving this problem. 
     The present invention is directed to an improved fluid power system which reduces the number of hydraulic fluid lines between the control and the actuated motors to four and provides a more simple and easily operable system. 
     SUMMARY 
     The present invention is directed to a fluid power system having a fluid power source for activating three separately controllable double acting fluid motors each of which selectively provides a separate function and each of which has a pair of actuating fluid lines. A first function valve is connected between the power source and the pair of lines connected to the first motor for actuating the first motor. A second function valve is connected between the fluid source and a pair of power lines. A selector valve is connected to at least one of the power lines for receiving fluid therefrom and is connected to the second and third motors for selectively connecting one of the second and third motors to the power lines. A pilot control line is connected between one of the pair of lines to the first motor and to the selector valve for actuating the selector valve and a control valve is connected between the fluid source and said one of the pair of lines to the first motor for supplying fluid to and actuating a selector valve. 
     A still further object of the present invention is the present invention is the provision of a selector valve which is a six-way, two positioned hydraulically controlled pilot valve. 
     A still further object of the present invention is wherein the first motor is a clamping motor and the pilot control line to the selector valve is connected to the closing line of the first motor. 
     A still further object of the present invention is the provision of a power system for a lift truck in which three double acting fluid motors are connected to the movable carriage of the lift truck and the fluid power system has only four hydraulic lines connected between the body and the carriage. The first and second function valves and control valve are mounted on the body and the selector valve is mounted on the carriage. All of the actuating valves are mounted on the truck body and only four hydraulic lines extend to the motors and the selector valve. 
     Other and further objects, features and advantages will be apparent from the following description of a presently preferred embodiment of the invention given for the purpose of disclosure and taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic hydraulic circuit of the preferred embodiment of the present invention as used on a lift truck, and 
     FIG. 2 is a schematic hydraulic circuit of another embodiment of the present invention as used on a lift truck. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     While the present invention may be useful in other applications, it is particularly useful and advantageous in connection with a lift truck and for purposes of illustration will be described in that connection. 
     Referring now to FIG. 1, a first motor generally indicated by the reference numeral 12 consists of a first hydraulic piston and cylinder assembly 14 and a second hydraulic piston and cylinder assembly 16 which actuate clamps 18 and 20 of a fork lift clamp. A pair of lines 22 and 24 are connected to the first motor 12 for actuating the double acting motor 12. 
     A second motor 26 may include a hydraulic piston and cylinder assemby and be connected to the conventional pivot or side shift mechanism of a lift truck. Of course, the lines 27 and 28 may be connected, as is conventional, to the motor 12 to form an internal side shift whereby the motor 12 acts both as a clamping motor and as a side shift motor. A pair of lines 27 and 28 are connected to the second motor 26 for communicating fluid to and from the motor 26 for actuation. A third motor 30 which may be a reversible hydraulic motor, rotates in either direction depending upon the direction of flow in its connected pair of lines 32 and 34. The motor 30 may be used as the rotation motor in a lift truck. 
     Generally, the above description of motors on the carriage of a lift truck is conventional. However, the carriage moves relative to the truck and the fluid power source and controls are positioned on the truck. This requires that hydraulic lines extend through conventional hose reels between the truck and the carriage and it is therefore important to keep the number of hydraulic lines to a minimum. 
     The power system 10 of the present invention provides a simple, but effective way of selectively and individually actuating each of the motors 12, 26 and 30 from a fluid power source 40 such as a pump with only four lines. 
     The present power system 10 includes a first function valve 42 which may be any suitable valve such as a manually operated three position four-way valve which is connected between the fluid power source 40 and sump 44. Preferably the valve 42 is spring-loaded to a neutral position 46 and is manually actuated to connect position 48 or 50 to the fluid source 40 and sump 44. The valve 42 has its output connected to a pair of hydraulic power lines 52 and 54 which are connected to the fluid lines 22 and 24 of the first motor 12, preferably through conventional pilot operated check valves 56 and 58. Thus, actuation of the first function valve 22 will actuate the first motor 12. For example, assuming the valve 42 is actuated to place position 48 between the inlets and outlets of the valve fluid will flow through line 52 into motor line 22 to cause the clamps 18 and 20 to move together and expel fluid through motor line 24 to power line 54 and to the sump 44. Conversely, the valve 42 is actuated in the reverse direction to bring position 50 between the inlets and outlets, and fluid will be supplied to power line 54 and motor line 24 to cause the clamps 18 and 20 to move apart while venting hydraulic fluid through motor line 22 and power line 52 to the sump 44. Power lines 52 and 54 extend from the truck to the carriage. 
     A second function valve 60 is provided having its input connected to the power source 40 and sump 44 and having its output connected to fluid power lines 62 and 64 leading to the carriage for supplying the power for actuating either the second motor 26 or the third motor 30. The valve 60 may be any suitable valve and may be similar to valve 42 and includes positions 66, 68 and 70. In order to selectively connect the power lines 62 and 64 to one of the motors 26 and 30, a selector valve 70 is provided which may be any suitable valve such as a six-way, two positioned spring return and hydraulically piloted valve. The input to the valve 70 is connected to the power lines 62 and 64 and the outputs are connected to fluid motor lines 27 and 28 leading to motor 26 and to fluid motor lines 32 and 34 connected to motor 30. The valve 70 has positions 72 and 74. The valve position 72 when positioned between the valve input and output motor 30 is connected to the power lines 62 and 64 and thus motor 30 can be controlled in either a forward or reverse direction by actuation of the second function valve 60. When position 74 of the selector valve 70 is placed between the input and output of valve 70, the fluid motor lines 27 and 28 of the motor 26 are connected to the fluid power lines 62 and 64 and can be controlled in either a forward or reverse direction by actuation of the second function valve 60. The pilot control line 80, which is connected to the selector valve 70, is connected to one of the power lines 52 and 54 and is preferably connected to the closing or holding line 52. The pilot control line is entirely on the carriage of the lift truck and thus only the fluid power lines 52, 54, 62 and 64 need extend between the truck and the carriage. 
     In order to actuate the selector valve 70 through the pilot control line 80, a control valve 90 is provided on the truck connected between the fluid power source 40 and the power line to which the pilot control line 80 is connected, such as 52, through a control line 92. The valve 90 may be any suitable valve such as a three-way, two position valve which may be actuated by any suitable means such as manually, electrically, or hydraulically, here shown as manually actuated. The valve 90 has positions 94 and 96 in which 94 shuts off communication between the power source 40 and the line 52 and provides a return to a suitable sump 98 or 44. When position 96 is moved to between the input and the output of the valve 90, fluid power from the power source 40 is transmitted to the line 52 and to pilot control line 80 for actuating the selector switch 70. A restrictor 100 is provided in the control line 92 for limiting the venting of fluid from line 52 to the sump 98. 
     In operation, the first function valve 42 may be selectively actuated to control the first motor 12 for moving the clamps 18 and 20 to pick up or release a load. While the application of power fluid to the line 52 will cause the actuation of the selector switch 70, the second motor 26 and the third motor 30 are not actuated so long as the second function valve 60 is in the neutral position 66. When it is desired to actuate the third motor 30, the second function valve 60 is actuated at a time while the first function valve 42 and the control valve 90 are in the deactuated position. When it is desired to actuate the second motor 26, the control valve 90 is actuated to supply fluid from the power source 40 through the power line 52 and the pilot control line 80 to shift the selector valve 70 and then valve 60 is actuated to control the direction of movement of the second motor 26. It is to be noted that the application of power through the control valve 90 to the power line 52 will not adversely affect any load engaged by the first motor 12 as it merely applies a holding force to the first motor 12 similar to the holding force already applied to the load. 
     The present invention, therefore, allows selective actuation of the motors 12, 26 and 30 but only requires four hydraulic lines 52, 54, 62 and 64 to extend between the truck and the movable carriage. 
     A further embodiment of the present invention is best seen in FIG. 2 wherein like parts are numbered similarly to those in FIG. 1 with the addition of the suffix &#34;a&#34;. The embodiment of FIG. 2 is identical to the embodiment of FIG. 4 with the exception that one of the power lines from the second function valve 60a, such as line 64a, is connected directly to the second motor 26a and the third motor 30a such as to lines 28a and 34a, respectively. In addition, a two-position, three-way valve 172 is substituted for the six-way valve 72 and is connected between the second power line, such as 62a, and selectively controls the actuation of the second motor 26a and the third motor 30a by being selectively connected to lines 27a and 32a, respectively. 
     In operation, the first motor 12a is again controlled in either the full forward or reverse direction by actuation of the first function valve 42a. The third motor 30a is actuated in the forward or reverse direction by the second function valve 60a when position 170 of valve 172 is positioned, as shown in FIG. 2, between the power line 62a and the line 32a. When the selector valve 172 is shifted by actuation of the control valve 90a to bring position 174 of the selector valve 172 into position between the line 62a  and the line 27a, the second motor 26a is actuated in the forward or reverse direction by actuation of the second function valve 60a. Again, in this embodiment in FIG. 2, only four hydraulic lines 52a, 54a, 62a, and 64a extend between the truck and the carriage. 
     The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While a presently preferred embodiment of the invention is given for the purpose of disclosure, numerous changes in the details of construction and arrangement of parts, will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention and the scope of the appended claims.