US3742821A - Arrangement for controlling regulatable pumps - Google Patents

Abstract

A cylinder housing is provided in its inner circumferential surface with a groove, and a control piston is slidable in the housing to opposite sides of a center position and is provided with a pair of axially saced grooves in its outer periphery which, when the piston is in center position, are located at opposite axial sides of the groove in the inner surface of the cylinder housing. A side member is guided in a stepped bore of the piston for axial sliding movement relative thereto and defines with the piston two pressure chambers each of which communicates with one of the outer grooves of the piston, and each of the chambers is provided with a relatively small port connecting it with a pressure fluid venting conduit.

Description

limited States Patent [1 1 Martin July 3, 1973 [54] ARRANGEMENT FOR CONTROLLING 3,677,138 7/1972 Goscenski 91/378 REGULATABLE PUMPS I Primary Examiner--William L. Freeh [75] lnvemor' ggfg z Harsewmkel Assistant Examiner-Gregory LaPointe y Attorney-Michael S. Striker [73] Assignee: Gebr. Claas, l-larsewinkel ub'er Gutersloh, Germany [57] ABSTRACT [22] Filed: Sept. 27, 1971 A cylinder housing is provided in its inner circumferen- Appl. No.: 184,095

tial surface with a groove, and a control piston is slidable in the housing to opposite sides of a center position and is provided with a pair of axially saced grooves in its outer periphery which, when the piston is in center position, are located at opposite axial sides of the groove in the inner surface of the cylinder housing. A side member is guided in a stepped bore of the piston for axial sliding movement relative thereto and defines with the piston two pressure chambers each of which communicates with one of the outer grooves of the piston, and each of the chambers is provided with a relatively small port connecting it with a pressure fluid venting conduit.

IMENIEUJUL3 m rs sum 2 or 2 1/ Eu r ARRANGEMENT FOR CONTROLLING REGULATABLE PUMPS BACKGROUND OF THE INVENTION The present invention relates generally to control arrangements, and more particularly to control arrangements for controlling regulatable pumps. Still more particularly the invention relates to an arrangement for controlling a regulatable hydraulic pump, particularly but not exclusively an axial piston pump.

It is already known to provide axial piston pumps in which the piston stroke is to be continuously regulatable in both directions of movement, that is of feed. This is accomplished, according to the prior art, via a control motor or arrangement having a control piston which precisely and immediately follows the movements of an associated manually adjustable control slider which is normally maintained in zero setting position by spring elements. The zero setting position can be temporarily controlled, independently of the manual control, by automatically operating devices in the region of the center position of the control piston, in order to obtain exact fixing of the center position of the control piston and thus of the zero setting position of the pump.

German Pat. No. 1,601 ,701 discloses an arrangement of this general character which affords precise centering of the control piston in automatic manner. The control piston operates as a differential piston with the piston rod being configurated as an additional control member. The actual slide member in this construction is connected with an actuating rod with a predeter mined axial play, which axial rod is provided with control surfaces and control bores in order to obtain fixing of the center position of the control piston. It has been found, however, that this prior-art construction is economically not well feasible because it is rather complicated in its construction and therefore expensive in its production. Also, such a construction is operable only when the control piston is configurated as a differential piston, and in order'to control the piston it is necessary to use oil from the main pressure oil circuit, requiring the provision of additional devices which act as force amplifiers when the control piston is to be moved out of its exact center position in which the pump is in zero setting position and no oil is passed through the main circuit. I

SUMMARY OF THE INVENTION It is, accordingly, a general object of the present invention to overcome the aforementioned disadvantages of the prior art.

More particularly it is an object of the invention to provide an arrangement of the general type here under discussion which is not possessed of the disadvantages attendant to the prior art.

A concomitant object of the invention is to provide such an arrangement which is very simple in its construction and therefore to produce, and which fulfills the requirements made of it in wholly satisfactory manner.

In pursuance of the above objects, and of others which will become apparent hereafter, one feature of the invention resides, briefly stated, in an arrangement for controlling regulatable pumps, especially axial piston pumps having continuous adjustment of the piston stroke in both directions, according to which a combination is provided of a cylinder housing having an inner circumferential surface, and a control piston slidable in the housing to opposite sides of a center position. The invention further provides an inner groove in the surface of the cylinder housing, being positioned to coincide with the center position and in communication with the source of pressure fluid. A pair of axially spaced outer grooves encircle the piston and are located at opposite axial sides of the inner groove when the piston is in its center position. A slide member is guided in the piston for axial sliding movement relative thereto and defines therewith two pressure chambers each communicating with one of the outer grooves. A pair of relatively small ports are provided, each connecting one of the chambers with a pressure fluid venting conduit.

In order to assure that despite exact center position of the control piston, and thus zero setting position of the pump which is being controlled, the function of the arrangement is fully effective, the arrangement is connected in the feed circuit of a pump which supplies or replenishes pressure fluid lost as a result of leakage.

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

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a somewhat diagrammatic longitudinal section through one embodiment of the invention;

FIG. 2 is a section similar to FIG. 1, taken in a plane at right angles to that of FIG. 1 and omitting details exteriorly of the device and which are the same as in FIG. 1; and

FIG. 3 is a view similar to FIG. 2 but illustrating a further embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail, and firstly the embodiment which is illustrated in FIGS. l and 2, it will be seen that reference numeral ll has been utilized to designate the regulatable pump which is to be controlled. Such pumps are already known per se and require no detailed discussion. The regulating device for the pump l is identified with reference numeral 2 and is moved or maintained against movement by the control piston 7, via a linkage 3, a connecting member 4, a pivot 5 and a member 6.

As the drawing clearly shows, the control piston 7 is slidably accommodated in a cylinder housing 8 and is provided with an axial stepped bore which in turn accommodates a slide member 9, a dished spring lit) and dish springs 11. A replenishing pump 12 supplies pressure fluid, for instance oil, via the conduits l3 and 14 to the one-way valves 15, via which leakage oil or oil which is used in the main fluid circuit, is replenished. In addition the pump 12 supplies oil via the conduit llfi, the bore 19, the longitudinal groove 20 and the bore 21 into the control chamber 22 which is defined between or by the members 7 and 9. Excess oil supplied by the pump 12 flows via conduits l3 and 14, and via the pressure-limiting valve 23 into the oil reservoir 36.

FIG. 1 also shows that the slide member 9 is provided with cylindrical control surfaces 24 and 25 which close the bores 26 and 27 in the center position, and that the member 9 is further provided with cylindrical recesses 28 and 29 which are connected via bores 30 and 31 of the center bore 32 in the member 9, free space 33 in the piston 7, bore 34 and conduit 35 with the reservoir 36.

It will be appreciated that if for instance a force acts on the member 9 in the left-hand direction in the drawing, and if this force is greater than the force exerted by the spring 11, the member 9 will shift towards the left in and with reference to the piston 7. As a result of this the control surface 24 opens the bore 27 so that oil under pressure can'flow through the bore 27 ahead of into the chamber 37. At the same time, oil can flow from the chamber 38 via bore 26 into the chamber 29, and from there through bore 31 and bore 32 into the free space 33, from where it exits via bore 34 and flows via conduit 35 into the reservoir 36. As a result of this, the piston 7 will move towards the left-at the same time activating the regulating device 2 of the pump luntil the left-hand force acting upon the member 9 terminates.

In accordance with the invention, and attention is now particularly directed to FIG. 2, the inner circumferential surface of the cylinder 8 is provided with an inner groove 39 and which is connected with the connection 19 of the pump 12 so that it is continuously under pressure. A control surface 40 provided on the piston 7 closes the groove 39 and is delimited at opposite lateral sides by the outer grooves 41 and 42 provided in the piston-7. The width of the groove 39 and of the grooves 41 and 42 is determinative of the length of the path required for the center position return.

When the piston 7 moves from the left-most position it assumes, back towards the center position, it can stop in any position and remain there without being arrested, until the right-hand edge bounding the groove 41 has moved beyond the left-hand edge bounding the groove 39. Thereupon, that is when this takes place, oil under pressure flows from the groove 39 into the groove 41, and from there through the channel 44 into the pressure chamber 45. It thus forces the member 9 in the piston 7 to move towards the right until the dished springs abut. As a result of this the piston 7 itself moves farther towards the right in the housing 8 until the control surface 40 closes the groove 39 and the supply of oil out of the groove 39 is terminated. The pretension springs 11 press the member 9 with the spring to its center orzero setting position, and oil in the chamber 45 escapes through the groove 49 into the space 28 and from there into the reservoir 36. The groove 49 could, of course, be omitted if the bead of the member 9 were to be accommodated in the bore of the piston 7 with greater play than illustrated.

The embodiment illustrated in FIG. 3 is largely the same as that in FIGS. 1 and 2, and any extraneous componentssuch as the pump 1, the device 2, etc.- which are shown in FIG. 1 have not been included in FIG. 3 because they should be understood as being the same as in FIG. 1. The embodiment in FIG. 3 in fact differs from that in FIGS. 1 and 2 only in that the pressure chambers 45a and 46a in this embodiment are not delimited by the actual bore accommodating the member 9, but instead by the walls oflarger bores which are provided at opposite ends of the bore for the member 9 and which accommodate pistons closing the chambers 45a and 46a. The bores from the grooves 410 and 42a to the chambers 45a and 46a are arranged analogously to those illustrated in FIG. 2, and the operation of the embodiment in FIG. 3 is the same as that in FIGS. 1 and 2.

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

While the invention has been illustrated and described as embodied in an arrangement for controlling regulatable pumps, it is not intended to be limited to the details shown, since various modifications and structural changes can be made without departing in any way from the spirit of the present invention.

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

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended 1. In an arrangement for controlling regulatable pumps, particularly axial piston pumps having continuous adjustment of the piston stroke in both directions, in combination, a cylinder housing having an inner circumferential surface; a control piston slidable in said housing to opposite sides of a center position, said piston defining at its opposite axial ends a first and a second fluid chamber; an inner groove in said surface, positioned to coincide with said center position and in communication with a source of pressure fluid; a pair of axially spaced outer grooves encircling said piston and located at opposite axial sides of said inner groove when said piston is in said center position; a slide member guided in said piston for axial sliding movement relative thereto and defining therewith two pressure chambers each communicating with one of said outer grooves; a pair of relatively small ports each connecting one of said chambers with a pressure-fluid venting conduit; and passage means communicating with the respective fluid chambers and controlled by said slide member so that, when said slide member moves towards said first chamber the pressure of fluid in the latter drops and the pressure of fluid in said second chamber increases, and vice versa.

2. In an arrangement as defined in claim 1; further comprising a pressure-fluid chamber in said piston, and a pressure-fluid conduit communicating with said pressure-fluid chamber; and wherein said inner groove is located in the region of said pressure-fluid chamber.

3. In an arrangement as defined in claim 1; and further comprising spring means biasing said slide member to a normal zero setting position.

4. In an arrangement as defined in claim 1; further comprising a replenishing pump for replenishing leaked pressure fluid, and a pump circuit through which pressure fluid supplied by said pump passes; and wherein said cylinder and piston are interposed in said pump circuit.

5. In an arrangement as defined in claim 1, said piston having a stepped axial passage, and said slide member being at least in part slidably received in said passage.

Claims (5)

1. In an arrangement for controlling regulatable pumps, particularly axial piston pumps having continuous adjustment of the piston stroke in both directions, in combination, a cylinder housing having an inner circumferential surface; a control piston slidable in said housing to opposite sides of a center position, said piston defining at its opposite axial ends a first and a second fluid chamber; an inner groove in said surface, positioned to coincide with said center position and in communication with a source of pressure fluid; a pair of axially spaced outer grooves encircling said piston and located at opposite axial sides of said inner groove when said piston is in said center position; a slide member guided in said piston for axial sliding movement relative thereto and defining therewith two pressure chambers each communicating with one of said outer grooves; a pair of relatively small ports each connecting one of said chambers with a pressure-fluid venting conduit; and passage means communicating with the respective fluid chambers and controlled by said slide member so that, when said slide member moves towards said first chamber the pressure of fluid in the latter drops and the pressure of fluid in said second chamber increases, and vice versa.

2. In an arrangement as defined in claim 1; further comprising a pressure-fluid chamber in said piston, and a pressure-fluid conduit communicating with said pressure-fluid chamber; and wherein said inner groove is located in the region of said pressure-fluid chamber.

3. In an arrangement as defined in claim 1; and further comprising spring means biasing said slide member to a normal zero setting position.

4. In an arrangement as defined in claim 1; further comprising a replenishing pump for replenishing leaked pressure fluid, and a pump circuit through which pressure fluid supplied by said pump passes; and wherein said cylinder and piston are interposed in said pump circuit.

5. In an arrangement as defined in claim 1, said piston having a stepped axial passage, and said slide member being at least in part slidably received in said passage.

Images