US 3073123 A
Description (OCR text may contain errors)
United States Patent 9 3,073,123 HYDRAULIC SYSTEM Robert F. Hodgson and Charles A. L. Ruhl, Kalamazoo, Mich., assignors to The New York Air Brake Company, a corporation of New Jersey Filed Sept. 27, 1961, Ser. No. 141,139 2 Claims. (Cl. 6053) This invention relates to the control of multiple motor hydraulic systems.
In multiple motor systems of the type in which a plurality of motors are supplied with fluid from a single pump, there are two basically diflerent ways in which the motors may be connected with the pump. In one arrangement, hereinafter called the series arrangement, the pump supplies fluid to a first motor, from which the fluid passes to a second motor and so on throughout the series. The fluid flows from the last motor in the series to the sump from which the pump draws fluid. In the other arrangement, hereinafter called the parallel arrangement, the pump draws fluid from a sump and supplies it to a manifold to which the inlet connections of all the motors of the system are connected. The motor exhaust connections all comunicate with a manifold which is connected to the sump. The circuit preferably, but not necessarily includes a directional control or reversing valve which in the series arrangement will reverse the order and direction of flow through the plurality of motors and which in the parallel arrangement will serve to reverse the connections between the manifolds and the pump and sump respectively.
Each arrangement has some characteristics which are advantageous and some which are not. A series arrangement is characteristically a high-speed system, but the available torque is limited. The parallel arrangement is characteristically a low-speed high torque system. Frequently, a single multiple motor system must have the attributes of both systems. It is the object of this invention to provide a system in which the system may be shifted from the series arrangement to the parallel arrangement and vice-versa by the automatic actuation of a selector valve mechanism. The selector valve is a pressure-operated valve, the actuating fluid being taken from the system between the pump and the motors. The valve is controlled in such a way that with low back pressure on the pump, the series arrangement is provided and with high back pressure the parallel arrangement is provided.
The preferred embodiment of the invention will be described having reference to the accompanying drawing in which:
FIG. 1 is schematic diagram, partly in axial section showing the essential elements of the system.
FIG. 2 is a diagram of a system embodying a modification of the invention.
Refer first to FIG. 1. Reference numerals 11 and 12 indicate respectively a pump and a sump from which the pump draws fluid. A reversing valve of conventional form is shown at 13. The reversing valve 13 has a supply connection 14 from pump 11, an exhaust connection 15 to the sump 12 and two motor connections 16 and 17.
Connected with the motor ports is a selector valve 18. The selector valve 18 comprises a body having a valve bore 19 formed therein. A sump connection 21 extends from one end of the bore 19 and a supply and exhaust valve housing 22 closes the other end. The bore is encircled by four axially spaced motor grooves 23, 24, 25, and 26. Grooves 23 and 26 are connected to the motor connections 16 and 17.
Reference numerals 27 and 28 indicate reversible motors of conventional form. A first connection 29 extends from groove 23 to motor 27 and a second connection 31 extends from groove 25 to the other side of motor 27. Similar connections 32 and 33 extend from grooves 26 and 24 respectively to the opposite sides of motor 28.
A valve plunger 34 is shiftable in valve bore 19. Three lands 35, 36, and 37 are formed on valve plunger 34 and are axially separated from one another by encircling grooves 38 and 39. A spring 41 biases valve plunger 34 toward the illustrated position.
The supply and exhaust valve housing 22 encloses a motor chamber 42, a spring chamber 43 and valve guide 44. A groove 45 encircles the valve guide 44 between its ends and is connected by a conduit 46 to the sump 12. A VZ-lltfi 47 is reciprocable in the guide 44 and is biased to the position shown by spring 40. A restricted axial counterbore 48 is formed in valve 47. A cross-drilled diametral port 49 extends through valve 47 and intersects counterbore 48 at its inner end. A pair of flat surfaces 51 are formed on opposite sides of the valve 47 and lie parallel with the cross-drilled port 49. A connection 52 extends from the end of valve guide 44 to the supply connection 14.
The reversing valve 13 is preferably a conventional three-position directional control valve-of the type having a neutral position in which it blocks the motor ports 16 and 17 and interconnects the supply and exhaust connection 14 and 15, a first actuating position in which port 16 and sump connection 15, and port 17 and supply connection 14 are interconnected, and a second actuating position in which port 17 and sump connection 15, and supply connection 14 and port 16 are interconnected.
When reversing valve 13 is in either of its actuating positions, a back pressure develops in the connection 14 which is a function of the load on the motors 27 and 28. So long as this pressure remains below a predetermined amount, determined by the characteristics of spring 40, the parts of the selector valve and the supply and exhaust valve 47 assume their illustrated positions. In this illustrated position a flow path extends from connection 16 through groove 23, connection 29, motor 27, connection 31, grooves 25, 38, and 24, connection 33, motor 28, connection 32 and groove 26 to connection 17. Fluid passes through the parts of the path in the order stated in one actuating position of reversing valve 13 and in the reverse order in the other actuating position.
When pressure reaches the predetermined amount referred to, supply and exhaust valve 47 will be moved to the left, first interrupting communication from motor chamber 42 past the flats 51 to groove 45 and then uncovering the ends of port 49 to admit fluid under pressure from the connection 52 to the motor chamber 42. This fluid will shift valve 34 to the left against the bias of spring 41 to a second position. The supply and exhaust valve will then assume a lap position in which cross port 49 and flats '51 are blocked. In this second position, of valve 34, groove 26 is connected with groove 25 by valve groove 39, and groove 23 is interconnected with groove 24 by valve groove 38. Land 36 prevents flow from groove 24 to 25 in this position of the selector valve. Thus connections 29 and 33 communicate with the port 16 and connections 31 and 32 communicate with port 17. Fluid may flow from 16 to 17 through the motors 27 and 28 or in the reverse direction depending upon the position of the reversing valve 13. This is the parallel arrangement of the motor system.
Selector valve plunger 34 will return to illustrated position when pressure in connection 14 drops sufliciently to permit spring 40 to shift supply and exhaust valve 47 from lap position to its illustrated position in which motor chamber 42 is vented, so that spring 41 may return valve plunger 34 to its illustrated position. The pressure required to open the supply is greater than that which will permit opening of the exhaust, and the supply and exhaust valve is lapped when an intermediate pressure exists in the conduit 52.
It will, be apparent that in the illustrated position of selector valve plunger 34, the motors are connected in the series arrangement defined in the opening part of the specification. Thus under light motor loads that highspeed low torque operation characteristic of the series arrangement is achieved. In its left hand position, selector valve plunger 34 establishes the parallel arrangement and the low-speed high torque operation of the parallel arrangement is made available. The changeover is automatic and requires no action by the operator.. Changeover is achieved without regard to the direction of flow established by the reversing valve.
As shown in FIG. 2 the supply and exhaust valve can equally well be operated by pressure fluid tapped from ports 16 and 17. The connections comprise conduits 53 and 54, each connected at one end with connection 52 from the supply and exhaust valve. A check valve 55 in each of lines 53 and 54 prevents reverse flow from the connection 52. The operation of this modification will be apparent from that of the modification shown in FIG. 1 and need not be described; a
The inventive concept isnot limited to use with the preferred embodiment illustrated and described herein,
and no limitation to this embodiment is implied except to said exhaust connection and in the second of which the flow paths established between the motor ports and the supply and exhaust connections, in the first position, are reversed; a selector valve means shiftable between first and second positions, in which respectively it connects said motors in series flow relation between said motor ports or in parallel flow relation between said motor ports; a singe-acting expansible chamber motor connected to shift said selector valve means from said first toward second position; yielding means biasing the motor and the selector valve means toward first position; a fiow passage connecting the expansible motor chamber with said supply connection; and a supply and exhaust valve means in said flow passage yieldingly biased toward its exhaust position and shiftable, against said bias and in response to pressure in said flow passage, to supply position in which flow communication to said motor chamber is established, when said pressure exceeds a first predetermined amount, or to exhaust position in which the passage is blocked and the motor chamber is vented, when pressure in said passage is below a second lower predetermined amount, or to a lap position when pressure in said passage is intermediate said predetermined amounts.
2. The combination defined in claim 1 and branching connections in said flow passage connected to said motor ports, and providing the connection between the supply connection and the flow passage and a check valve in each branch connection preventing reverse flow from the flow passage to the motor port associated therewith.
References Cited in the file of this patent UNITED STATES PATENTS 2,541,290 Robinson Feb. 13, 1951 2,541,291 Robinson Feb. 13, 1951 2,541,292 Robinson Feb. 13, 1951 2,953,903 Skoog et al Sept. 27, 1960 2,959,923 Shook Nov. 15, 1960