US2792687A - Variable displacement pump - Google Patents

Description

' JNVNTOR.

F. A. SNELL VARIABLE DISPLACEMENT PUMP Filed NOV. 6, 1955 May 21, 1957 4. 4 l. f f A 7 S m.\ AKW@ m ,m Alf N A 7 nited States Patent l i i 2,792,687 VARIABLE DEPLACEMENT PUMP Francis A. Snell, Proctorsville, Vt., assigner to tlre United States of America as represented by the Secretary of the Air Force Application Novemberu, 1953, Serial No. 390,768

3 Claims. (Cl". dll-$4.15)

This invention is directed to a novel variable displacement pulsator type of pump of an improved nature. The practical embodiment of the invention described herein is particularly applicable, for example, for driving an hydraulically operated shake table for testing seismological instruments. While single acting as shown, it may be either single or double acting as the application may require. Its construction is such that the single unit affords a wide range of amplitude of impulse transmission without any lost motion presenting simplicity, economy and eiciency in its operation.

The improved pump comprises a housing having an hydraulic chamber with a multiplicity of pistons of varying diameter mounted for reciprocation therein selectively whereby on reciprocation of a piston of particular diameter a predetermined amount of fluid is displaced from the housing to afford a predetermined control signal of a desired amplitude.

An object of the invention is to provide an improved variable displacement pulsator type pump.

A further object of the invention is to provide a novel variable displacement pulsator type pump employing a multiplicity of selectively operable pistons having a range of varying diameters whereby a selective displacement may be accomplished by the pump to afford a desired control.

Other objects and advantages o' the invention will be readily apparent to those versed in the art from the following specification taken in conjunction with the accompanying drawings wherein:

Fig. 1 shows the improved variable displacement pump in partial section in conjunction with a control unit;

Fig. 2 is a section along line 2 2 of Fig. 1 and shows the detent arrangement for locating the actuator relative to the piston housing for positive control of the pump displacement;

Fig. 3 shows a section indicated by line 3--3 in Fig. 1;

Fig. 4 shows a section on line 4 4 in Fig. 1.

As shown in Figure 1 of the drawings the improved pump comprises a piston housing 1 incorporating an oil chamber 2 at one end thereof. The other end of the piston housing is bolted to an actuator unit 3. A conduit connects the oil chamber 2 with a control unit 4.

The piston housing assembly in the practical embodiment of the invention shown has three bore holes 5 equidistantly spaced therein each having the bore red-ced by a bearing member 6, each bearing member having an aperture of a different diameter extending through to the oil chamber Z. Respectively arranged in the bores 5 are three pistons 7, 8 and 9 whose reduced portions 7', 8 and 9', each having a different diameter, bear in and extend through the corresponding bearing elements 6 threadedly engaging the housing. The stem extension on each piston has a collar lil adjacent one end thereof to bear in the respective bore hole S and guide the movement of the piston. A coil spring 11 surrounding each piston abuts the collar and the housing and the bearing element 6, biasing the pistons by a force against 2,792,687 Patented May 21, 1.957

thecollar members. Thel pistons are normally arranged so that their` extensions are ilush with the actuator end of the piston housing as shown in Figure 1 of the drawings. At the actuator end of the piston housing assembly isa flange and equidistantly arranged` about and adjacent the periphery are threaded holes 12.

The actuator assembly is` composed of a sleeve unit 13 having a ange 14 by which the actuator unit is bolted to the piston housing through matching holes 12. With* inthe sleeve unit 13 and rotatable relative thereto is an inner sleeve 15` having a iiange 16 in threaded engagement therewithV to seat on the stepped portion of the outer sleeve unit 13as shown in Figure 1. A plate 17 integral with the sleevelS has a singlehole `17 therethrough arranged to align selectively with the three piston stems 7, 8 and 9 in the piston housing. The inner sleeve at its outer end has a flange 18 bearing on the llange 14 on outer sleeve end. Connected to the flange 18 in a recess therein is a spring pressed detent 19. Spaced notches 19 in the outer sleeve member ilange 14', arranged to conform to the spacing of the pistons, cooperate with the spring detent to hold the rotatable sleeve 15 in predetermined positions relative to the pistons to align the hole 17 with a selected piston. A plunger unit 2t) within the inner sleeve has a pin 21 threadedly related thereto and extending therefrom guided in the hole in the plate 17. A yoke 22 is connected to the outer end of the plunger which is rotatable relative thereto on a stem 22 from the yoke connected to the plunger and the yoke has bearing plates 23 of a hardened material thereon. The yoke is operated by an eccentric 24 having an outer ball bearing fitting closely between the bearing plates 23.

When the actuator assembly and the piston housing assembly are assembled, the ends of the pistons 7, 8 and 9 adjacent the actuator unit are flush with the bolted together faces of the piston housing and the flange 14 of the sleeve of the actuator housing. This permits the pin 21 with its connected sleeve and plunger to be rotated freely relative to the pistons being limited only by the detent 19 engaging a notch 19 whereby the pin Z1 is -aligned with a piston 7, 8 or 9 of the desired diameter.

The operation of the pump unit is effected by rotating the sleeve and plunger unit of the actuator assembly to align the pin 21 with the selected piston 7, S or 9 of a particular diameter. The pistons not selected will not atleet the motion imparted in the hydraulic system since they are held against movement by their springs 11 against the plate 17 integral with the inner sleeve 15.

The eccentric element 24 imparts a simple harmonic motion to the plunger 20 to actuate the selected piston to displace a predetermined amount of fluid in the hydraulic system to provide the required amplitude of motion to the control unit 4 of the hydraulically operated shake table as evidenced by the master cylinder in Figure 1 of the drawings shown connected by a iiow line to the hydraulic cylinder 2 in which the pistons 7', 8 and 9 are operative to selectively displace a predetermined amount of uid dependent on their diameters.

While only three pistons of ditferent diameters have been employed in the practical embodiment of the invention shown herein the number may be varied to conform to the desired application. Many other modifications and applications of the invention will be readily apparent to those versed in the art and such lie within the scope of the following claims.

What is claimed is:

l. A variable displacement pump comprising a piston housing providing a hydraulic chamber at one end thereof, pistons of dilerent diameters mounted in said housing for reciprocation therein, an actuator housing, a plunger assembly within the actuator housing having an actuating ice pin at one end thereof adapted for selective alignment with the pistons, and means associated with the plunger assembly for selective alignment of the plunger pin with the desired piston whereby on actuation of said plunger a predetermined uid impulse maybe selectively'produced. v

2. A variable displacement pump comprising a piston housing, ahydraulic chamber at one end thereof having an opening for connecting the luid in the chamber with a control means, pistons of different diameters arranged equidistantly about and reciprocable within the housing, a sleeve connected to said piston housing and arranged coaxial therewith, a plunger assembly within the sleeve and rotatable with respect thereto, the plunger being reciprocable therein, motion transmitting means on said plunger adapted for selective alignment with the pistons of different diameters, and means for imparting motion to said plunger means upon selective alignment of the motion transmitting means.

3. A variable displacement pump comprising a housing, hydraulic fluid in one end thereof, pistons of different diameters arranged in equally spaced fashion from the central axis of the housing and reciprocable therein, an actuator unit connected with the housing including plunger means reciprocable to selectively actuate the pistons, means to selectively align the plunger means with a piston of a desired diameter whereby on actuation of the plunger means a selected iluid displacement may be obtained,

References Cited in the le of this patent UNITED STATES PATENTS Giuliano Sept. 18, 1951

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