Radial Piston Pump

The present invention relates to pumps in general, and more particularly to improvements in hydraulic pumps wherein one or more pistons are movable in discrete cylinders of the pump housing to thereby effect the flow of fluid from an inlet port to an outlet port with simultaneous pressurization of the fluid.

It is known to provide the housing of a radial piston pump with several cylinders for discrete pistons which are reciprocable by a rotary member to thereby draw fluid from the inlet port and to pressurize the fluid on its way to the outlet port. As a rule, the pump comprises check valves which are interposed between the cylinders and the outlet port to prevent return flow of pressurized fluid into the cylinders. It is also known to install in such pumps a plurality of valves each of which acts not unlike a flow restrictor and automatically seals the inlet port from the respective cylinder when the pressure of fluid at the outlet port rises to a predetermined value. A drawback of such pumps is that they must be equipped with several flow restrictors which contribute to the initial and maintenance cost of the machine. Moreover, the body of the pump must be formed with an intricate network of channels, bores and similar passages for pressurized fluid in order to enable the valves to react in response to increasing fluid pressure at the outlet port. Still further, such pumps are often associateed or provided with discrete pressure relief valves which prevent excessive rise of fluid pressure at the outlet port. Such pressure relief valves also contribute to the initial and maintenance cost of the pumps.

An object of the invention is to provide a novel and improved pump wherein a single valve suffices to insure the termination of fluid inflow from the inlet port to the cylinder or cylinders when the pressure of fluid at the outlet port reaches a preselected value and wherein such valve also prevents the fluid pressure at the outlet port from reaching or exceeding a value which would be hazardous to the pump, to attendants and/or to the machines which receive pressurized fluid from the pump.

Another object of the invention is to provide a multiple-piston pump with a simple housing which need not be formed with a complex system of passages for the flow of fluid and which can insure uniform distribution of fluid to all of the cylinders.

A further object of the invention is to provide a radial pump wherein a single valve suffices to act as a safety valve as well as a means for automatically sealing the cylinders from the fluid-admitting port when the pressure of fluid at the outlet port rises to a preselected value.

The invention is embodied in a hydraulic pump, particularly in a radial piston pump, which comprises a housing having at least one cylinder, a fluid-admitting first port or suction port, a first passage (e.g., including a system of bores machined into the housing) connecting the cylinder with the first port and a second port which serves to discharge pressurized fluid and is communicatively connected with the cylinder (preferably through the medium of a check valve which does not permit pressurized fluid to flow from the second port into the cylinder), a piston which is reciprocable or otherwise movable in the cylinder to thereby draw fluid from the first port by way of the first passage and to force pressurized fluid into the second port, a rotary shaft or analogous means for moving the piston in the cylinder, and valve means movably installed in the first passage for movement between first, second and third positions. The housing is further formed with a second passage (e.g., a single channel) which connects and second port with a portion of the first passage so that the pressurized fluid in the second port and second passage can act upon the valve means to move the latter from the first position in which the valve means permits fluid to flow from the first port into the cylinder by way of the first passage but not from the second passage into the first passage while the pressure of fluid in the second port is within a relatively low first range. The thus displaced valve means then moves to a second position in which the valve means seals the first port from the cylinder while the pressure of fluid in the second port is within a higher second range. If the pressure of fluid in the second port exceeds the second range, the valve means is moved to the third position in which the second port can communicate with the first port by way of the second and first passage so that highly pressurized fluid can flow into tank or an analogous source of fluid which is connected with the first port. The valve means preferably comprises a reciprocable valve member one end of which is acted upon by a resilient element tending to maintain the valve member in the first portion and the other end of which is acted upon by pressurized fluid in the second passage.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved pump itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

FIG. 1 is an axial sectional view of a radial piston pump which embodies one form of the invention;

FIG. 2 is a sectional view as seen in the direction of arrows from the line II--II of FIG. 1; and

FIG. 3 is a fragmentary axial sectional view of a slightly modified radial piston pump.

Referring to FIGS. 1 and 2, there is shown a radial piston pump having a housing or body including main housing section 10 and a removable second section or cover 11 sealingly secured to one end of the main section 10 by bolts 9 or analogous fasteners. The housing 10, 11 has a centrally located bore 12 for an antifriction ball bearing 13 and an antifriction roller bearing 14. These bearings surround a drive shaft 15 having an eccentric portion 16 disposed between the bearings in line with four radially extending cylinders in the main housing section 10. FIG. 1 shows two of these cylinders at 18 and 19. The eccentric portion 16 of the shaft 15 is surrounded by a cylindrical sleeve 17 which is rotatable on the portion 16 and is contacted by the inner end faces of four pistons which are reciprocable in the respective cylinders in response to rotation of the shaft 15. The pistons in the bores 18, 19 of FIG. 1 are numbered 20 and 21. The four pistons are equally spaced from each other, as considered in the circumferential direction of the shaft 15. The outer ends of the cylinders are sealed by threaded plugs including those shown at 22 and 23.

The bore 12 communicates with a coaxial bore 24 which is machined into the section 10 and constitutes an extension of the bore 12. The bore 24 receives the antifriction roller bearing 14 and its outer end is sealed by a cupped metallic sealing element 25 which extends inwardly close to the eccentric shaft portion 16 so that it confines the bearing 14.

The main housing section 10 is further formed with an annular recess or space 27 which surrounds a median portion of the sealing element 25, i.e., the latter seals the radially innermost portion of the recess 27 from the bore 24 and hence from the bearing 14. The recess 27 communicates with radially outwardly extending blind bores 28, 29, 30 and 31 each of which is parallel with but spaced from one of the cylinders in the main housing section 10. The outer end portions of the blind bores 28-31 communicate wth transverse bores which are parallel to the axis of the shaft 15 and each of which further communicates with one of the cylinders in the main housing section 10. The transverse bores which connect the blind bores 28, 29 of FIG. 1 with the respective cylinders 18, 19 are shown at 32 and 33. The other two transverse bores are shown in FIG. 2, as at 34 and 35. The outer ends of the transverse bores 32-35 terminate in the right-hand end face of the main housing section 10, as viewed in FIG. 1, and are sealed by spherical sealing elements 8. These spherical elements are a press-fit in the housing section 10.

The blind bore 28 which is associated with the cylinder 18 is traversed by a cylindrical bore 36 for a reciprocable valve member 37. As shown in FIG. 2, the bore 36 for the valve member 37 is parallel to the blind bores 30, 31 and its diameter equals or closely approximates the diameters of certain portions of the valve member 37 so that the latter is slidable therein with a minimum of clearance. The bore 36 communicates with a low-pressure inlet or suction port 38 of the main housing section 10. The port 38 extends at right angles to the bore 36 and is connected with a tank or another suitable source of hydraulic fluid by a conduit, not shown. That portion of the bore 36 which connects the inner end portion of the suction port 38 with the blind bore 28 is shown at 40.

The valve member 37 comprises a plunger-like end portion or land 41 which engages a retainer 7 for a helical valve spring 42. This spring is mounted in a bore 43 of the main housing section 10 and reacts against a sealing plug 44 having threads mating with internal threads machined into the section 10 at the outer end of the bore 43. The spring 42 tends to maintain the valve member 37 in a first or right-hand end position, as viewed in FIG. 2, in which a smaller-diameter portion 45 of the valve member 37 allows fluid to flow between the suction port 38 and blind bore 28 (by way of the portion 40 of the bore 36). The smaller-diameter portion 45 of the valve member 37 is located between the land 41 and a similar land or plunger 46. The diameters of the lands 41, 46 are preferably identical. The land 46 is disposed between the smaller-diameter portion 45 and a relatively short second smaller-diameter portion 47 of the valve member 37, and the portion 47 is followed by a plunger or land 48 having two flats 49 extending in parallelism with the axis of the valve member 37. The land 48 is followed by a third smaller-diameter portion 48' which constitutes the right-hand end portion of the valve member 37, as viewed in FIG. 2, and extends into a channel or passage 50 of the main housing section 10. The land 46 has two annular shoulders 52 and 53 which respectively face the portion 40 of the bore 36 and the passage 50.

The passage 50 communicates with a second port 54 which serves to supply pressurized fluid to a conduit (not shown) connected to a consumer, e.g., to a cylinder and piston unit or to another hydraulic motor. The port 54 further communicates with a transverse bore 55 which, in turn, communicates with an annular space 56 machined into that end face of the cover 11 which abuts against the main housing section 10. The annular space 56 communicates with the outer portions of cylinders in the main housing section 10 by way of bores including a bore 57 for the cylinder 18 and a bore 58 for the cylinder 19. The space 56 communicates with each of the four cylinders. The left-hand ends of the bores 57, 58 (and of the other two bores), as viewed in FIG. 1, contain tongue-like one-way check valves (shown at 59, 60) which prevent the flow of pressurized fluid from the port 54 back into the cylinders. The check valves do not appreciably interfere with the flow of pressurized fluid from the cylinders into the annular space 56 and thence into the port 54. If desired, the tongue-like check valves may be replaced by other types of check valves, and each thereof may further include a resilient element 6 which yieldably opposes the movement of the respective tongue in a direction to allow fluid to flow from the cylinders into the space 56.

The space 56 is disposed between two sealing rings 61, 62 which are recessed into the inner end face of the cover 11. These sealing rings prevent leakage of pressurized fluid outwardly and/or inwardly between the abutting faces of the main housing section 10 and cover 11.

When the piston 20 assumes its inner end position (nearest to the axis of the shaft 15), its outer end face 20' allows fluid to flow from the transverse bore 32 into the cylinder 18. Analogously, when the piston 21 assumes its inner end portion, the outer end face 21' of this piston allows fluid to enter the cylinder 19 via transverse bore 33. The outer end portions of the cylinders contain suitable springs which urge the inner end faces of the respective pistons against the peripheral surface of the eccentric portion 16 on drive shaft 15. A helical spring which reacts against the plug 22 and biases the piston 20 radially inwardly is shown at 5.

When the shaft 15 is driven by an electric motor or another suitable prime mover, and the piston 20 reaches its inner end position (shown in FIG. 1), the transverse bore 32 admits fluid into the outer portion of the cylinder 18. The transverse bore 32 receives fluid from the suction port 38 via bore 36 for the valve member 37 and blind bore 28. The bores 36, 28, 32 constitute a passage which connects the port 38 with the cylinder 18, and this passage contains the valve member 37. As mentioned above, the outer end face 20' of the piston 20 allows fluid to flow from the bore 32 into the cylinder 18 when the piston 20 reaches or is close to its inner end position. As long as the pressure of fluid at the outlet port 54 (and hence also in the passage 50) is relatively low, the spring 42 maintains the valve member 37 in the first end position of FIG. 2 in which the smaller-diameter portion 45 of the valve member 37 allows fluid to flow from the port 38, via bore portion 40 and into the blind bore 28. The shoulder 52 of the land 46 is then remote from the bore portion 40. The eccentric portion 16 of the shaft 15 thereupon moves the piston 20 radially outwardly (i.e., toward the outer end position corresponding to that of the piston 21 in FIG. 1) whereby the end face 20' moves outwardly and beyond the transverse bore 32 so that the cylinder 18 is temporarily sealed from the suction port 38. As the piston 20 continues to move radially outwardly, it pressurizes the fluid in the outer portion of the cylinder 18 and causes such fluid to flow into the port 54 via bore 57, check valve 59 in the annular space 58 and transverse bore 56 in the cover 11.

The piston 20 thereupon begins to move radially inwardly under the action of the helical spring 5. The check valve 59 closes to prevent return flow of pressurized fluid from the port 54 into the cylinder 18. The pressure in the outer portion of the cylinder 18 drops so that the piston 20 sucks fluid from the port 38 as soon as the outer end face 20' of the piston 20 allows fluid to flow from the transverse bore 32 into the cylinder 18. The cross-sectional areas of bores constituting the passage which supplied fluid to the cylinder 18 can be selected in such a way that the outer portion of the cylinder 18 is only partially filled with fluid during inward movement of the piston 20 when the shaft 15 is rotated at a high speed.

When the pressure of fluid in the port 54 (and hence also in the passage 50) rises beyond a first range of pressures, the pressurized fluid acts upon the end face of the end portion 48' and upon the adjacent shoulder of the land 48 of the valve member 37 whereby the latter moves in a direction to the left, as viewed in FIG. 2, the stresses the spring 42. The shoulder 52 reaches the bore portion 40 and seals the suction port 38 from the blind bore 28 when the fluid pressure in the port 54 and channel 50 rises to the lower limit of a second range of pressures. This terminates the admission of non-pressurized fluid to all four cylinders in the main housing action 10 (note that the blind bore 28 communicates wtih a third passage including the annular recess 27 and the blind bores 29-31). Consequently, the pressure of fluid in the port 54 normally cannot rise beyond that pressure which is necessary to effect a movement of the valve member 37 against the opposition of the spring 42 to that (second) position in which the shoulder 52 prevents the flow of fluid from the port 38 into the blind bore 28 and hence into the other three blind bores 29-31. However, it can happen that the pressure of fluid at the outlet port 54 rises beyond that range of pressures which are needed to effect the sealing of blind bore 28 from the suction port 38. This can happen if the fluid is permitted to leak from the port 38 into the bore 28 after the shoulder 52 reaches the respective end of the bore portion 40 or when the consumer (which is connected to the port 54) receives pressurized fluid from another pump or form an accumulator. The pressure of fluid in the port 54 and passage 50 then continues to rise and ultimately reaches a value at which the spring 42 undergoes additional deformation because the valve member 37 is pushed further in a direction to the left, as viewed in FIG. 2 (third position of the valve member). The shoulder 53 of the land 46 then moves into the inner portion of the port 38 and allows this port to communicate with the passage 50 and port 54 along the path including the space surrounding the smaller-diameter portion 47 of the valve member 37 and the spaces adjacent to the flats 49 on the land 48. Thus, the valve including the valve member 37 then performs the function of a pressure relief valve or safety valve by allowing fluid to flow directly from the high-pressure port 54 to the low-pressure port 38. Such versatility of the valve is desirable because the pump can operate properly at excessive pressures in the outlet port even though it does not embody a discrete safety valve.

The annular recess 27 constitutes a manifold or distributor space which supplies fluid to the blind bores 29-31. As mentioned above, the recess 27 receives fluid from the suction port 38 via bore 28 and bore portion 40 when the latter is not sealed by the shoulder 52 on the land 46 of the valve member 37. The recess 27 actually constitutes a radially outwardly extending portion of the bore 24 in the main housing section 10, and the bore 24 can be said to constitute an extension of the bore 12 for the drive shaft 15.

FIG. 3 illustrates a slight modification of the main housing section. This section, denoted by the reference character 110, has a blind bore 112 corresponding to the bore 12 of FIG. 1 and including an innermost portion 24' which constitutes an equivalent of the bore 24 as well as of the annular recess 27 of FIG. 1. The blind bores 128, 129 (and the other two blind bores) communicate directly with the innermost portion 24' of the bore 112. FIG. 3 further shows the transverse bores 132, 133, the bore 136, the valve member 137, spherical sealing elements 108, the cupped sealing element 125, a portion of the drive shaft 115 and the antifriction roller bearing 114.

Without further analysis, 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 which fairly constitute essential characteristics of the generic and specific aspects of the above described contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.