US2680412A - Variable volume variable pressure pump - Google Patents

Description

June 1954 J. E. ENTWISTLE I 2,680,412

VARIABLE VOLUME VARIABLE PRESSURE PUMP Filed Aug. 8, 1950 3 Sheets-Sheet l ywu 2 INVEFAZZ. w A

June 8, 1954 J. E. ENTWISTLE 2,630,412

VARIABLE VOLUME VARIABLE PRESSURE PUMP Filed Aug. 8, 1950 3 Sheets-Sheet 5 INKENTOR.

Patented June 8, 1954 VARIABLE VOLUME VARIABLE PRESSURE PUMP J ohn E. Entwistle, Cleveland Heights, Ohio Application August 8, 1950, Serial No. 178,323

2 Claims. 1

This invention relates to fluid pumping devices and more particularly to, such devices ada ted to pump hydraulic fluid under pressure for various applications. In particular this invention relates to pumps of the radial piston type and to the kind of pump within that class wherein the radial pistons are carried in a rotating member or rotor, the pum likewise including means to vary the stroke of the pistons automatically in response to various requirements of an hydraulic system wherein the pump is availed of for use.

Heretofore, hydraulic pumps have in many cases been provided with manual means to vary the stroke of pistons associated therewith, and in cases where automatic means have been availed of in other types of pumps using pistons, the means for varying the stroke have been very complicated so as to require undesirably difficult manufacture.

It is therefore a primary object of this invention to provide a pump of the radial piston type wherein constant horsepower requirements are present and yet the pump provides variable pressure and/or variable volume of fluid, in response to the demands of an hydraulic system.

It is a further object of this inventionto provide a pump wherein means are provided for varying the volume and/or pressure in response to the requirements of the system.

It is a still further object of this invention to incorporate simple yet sensitive means for the above purposes which are automatic in operation in response to said requirements.

It is a further object of this invention to provide a novel arrangement of parts Within the pump itself to effect the required responses.

A still further object is to provide a pump delivering high volume at low pressure, as required for fast traverse motion, a pump also making available low volume-high pressure delivery, required for holding power which many modern machines and machine tools must have available, at the same time eliminating necessity for using two or more pumps and a complex arrangement of relief, by-pass, and control valves availed of at the present time.

Other and further objects of this invention will be apparent upon a consideration of the description of the invention as disclosed in the drawings in which:

Figure 1 is a longitudinal sectional view of one form of the pump of this invention, disclosing the various parts thereof in the minimum-volume maximum-pressure relationship.

Figure 2 is a transverse sectional view taken about on the line 22 of Figure 1.

3 Figure 3 is a longitudinal sectional view showing a somewhat different form of pump incorporating the principles of the invention therein.

Figure 4 is a fragmentary sectional view taken about on the line 4-4 of Figure 3 and illustrating certain of the operating parts of the modification of Figure 3.

Referring to Figure 1, it will be noted that the pump of my invention includes a drive-end housing generally denoted I, of substantially circular exterior configuration, a rotor housing 2 adjacent thereto, and a control end housing 3 adjacent said rotor housing. These three housings are suitably fastened together in any preferred manner, not further illustrated since the same will be obvious to those skilled in the art and comprise the main pump housing generally designated A. A rotor member 4 of circular form being a section of a cylinder and to be more particularly described hereinafter, is supported interiorly of the pump between the drive end housing 5 and. the control housing 3, within the rotor housing, and being of lessdiameter than the inner diameter thereof so as to be spaced slightly from the said rotor housing 2 (see Figure 2), an outlet chamber 5 and an inlet chamber 6 are formed, by the provision of lands or projections 1 and 8 formed integrally with the said rotor housing. The said lands or projections 1 and 8 are fitted with slide plates 9, adapted to engage the periphery of the rotor, the said slide plates being held in engagement with said periphery by means of the springs It. The slide plates are of substantially rectangular form and extend throughout the width of the rotor housing and rotor so as to provide a minimum of clearance between the end faces thereof, and the housings l and 3.

The rotor 4 as shown in Figure 1, is adapted to rotate within the pump between the housings l and 3, being fitted thereinto very closely, so as to provide a minimum amount of working clearance therebetween. The said rotor 4 includes a plurality of radially extending cylindrical chambers II, the said cylindrical chambers carrying closely fitted pistons 2, for reciprocation therein,

in a manner to be described.

The rotor i is supported for rotation interiorly of the pump, at one end, on the drive shaft 13,

by means of a hollow extension I 4, vsaid lattermember being hereinafter called a rotor drive member. The rotor drive member 14, is hollow interiorly and on its exterior is formed so as to provide clearance'between the drive end housing I, and the said drive member. The drive member 1 s is suitably fastened to the rotor member 4, by means of the cap screws 15. The drive shaft 13 .means of springs 21. seated in grooves formed adjacent the ends of is rotatably supported in the housing I, on a bearing l6, and a suitable seal i! is provided adjacent the said bearing and in the end of the housing I.

The rotor 4 is supported for rotation at the end opposite that just referred to, on a support ing member i8 fastened to the rotor 4, by means of cap screws I9 or in any other suitable manner as desired or requiredby the construction of the pump. The rotor supporting member is is in turn carried by a bearing 23, which bearing 26 is located in the annular opening 2 l, and pressed on a boss formed with thecontrolend housing 3 as seen in Figure 1. A cam member 22 is supported on the shaft member or portion 23, of a cam operating unit generally designated 24, in a manner to be hereinafter described, iinteriorly of the rotor member or rotor The cam member 22 is of circular configuration and is restrained from rotation relative the control end housing 3,

as .by the provision of key portions 25 formed integrally iYVith said .housing 3, as seen more clearly in Figure 2, extending vertically adjacent the center portion-of said housing. A 'comating vented. Suitablethrustplates 23d are provided :to receive the thrust of cam member 22 against =rotor-drive member [A (see Figure 1), when in accordance with conventional pump operation, "a thrust relationship is present. .are maintained inconstant contact with the pe- The istons i 2 riphery or the cam 22, at their inner ends by Suitable snap rings 25 the pistons :12, are provided, and the springs 2i surround the ends of the said pistons and are maintained thereon-by the'snap rings and contact-with-the inner periphery 28 of the rotor The'cam-ZZ may preferably be formed in two parts as seen in Figure '2, and includes a shaft opening therein, the-"axis of said shaft opening lying at an angle-to the'normal axis of said cam, bolts being provided to maintain the two parts atogether. Thecamoperating unit 25, previously referred to,.inc1udes a hollow shaft 29, the shaft portion 23 being connected thereto, preferably integrally. The axis of the shaft portion or member '23, .lies at an angle to the-axis of the shaft 25 and is adapted to be'received in the shaft opening in the cam 22 previously described. The control end housingfi is provided with a cylindrical opening 3i ,.in which the shaft 29 is adapt- .ed to reciprocate, this reciprocation in turn iinpartingmovement to the cam member 22 in a .verticaLdirection, by reason of the angular relationshipof .the axis-of the shaft portion .23 with the axisof the shaft 25.

Shaftportion 23 of the unit 24 is provided at one .end with a round bearing portion 3i adapted to Ieoeivethereona bearing 32, the said bearing being'held in place on the portion 3! by means of a snap ring .33. The bearing 32 is-mounted so as to fit closely in the hollow rotor drive member id, but at thesame time is permitted to reciprocate therein in a manner to be hereinafter set forth. It will be clear that during this reciprocation,.the drive member i l may be rotated with respect. to the shaft portion 23 but will not impart'any rotative motion to the said shaft portion 23.

carried thereby.

The hollow shaft 29 of the operating unit 2d includes a chamber 34 adapted to receive therein a piston member 35. The piston member 35 is connected to a shaft 36, the said shaft 36 in turn being secured to an end cap 3? on the housing 3, by means of a snap ring 38 adjacent the end of said shaft 33. The end cap 31 is sealingly engaged with the control end housing 3 in any suitable manner, the seals 3% 'being'provided therefor. A suitable threaded cap member 4!) is fitted into the end of hollow shaft 29 of the unit 24 so as to provide a chamber 4! surrounding the shaft 3%. Interiorly of the said shaft 29, a suitable compression spring 42 surrounds the shaft 3%, and is confined between cap 48 and a surface is of the piston member 35 previously referred to. It will be noted that the areas of the face 43, and an opposite face 44, of the piston member 35, are unequal by reason of the connection of the shaft 35 with the face 43 of the piston member, as

shown ,in'Figure l. A passage 31 extends axially through the shaft one end of the passage t? opening into the chamberl34 previously referred to, the other end of said passage being in alignment with a radial passage #38 formed in the end cap 3?. .A port 423 provided, whereby the passage 4? communicates with the chamber di. The

radial passage 48 in the end cap 3'! previously mentioned, is aligned so as to communicate with an angularly extending passage 50 formed in-the control end housing '3,the said passage 50 in turn communicating with a discharge outlet or port "hthe said port 5! opening into the outlet chamber ii previously referred to. ;An inlet port 52 is provided, the same being shown in Figure l as having alternative directions of opening whereby to communicate with the inlet chamber 8 previously mentioned.

As shown in the drawing Figures 1 and 2, the

pump and its related parts are in the position of -minimum stroke-maximum pressure operation, since the cam 22 is in axial alignment with the center of the rotor G, the pistons occupying what is known as a zero stroke position. It will be noted that movement of the cam operating unit 24 to the left will cause'the cam 22 to move downwardly from its position shown in Figure 1 whereby the cam will no longer be in the zero stroke position but will have been .moved down wardly by reason of the-offset shaft portion 23 .of the said unit .26 having been moved to the left, imparting movement to the cam as above described.

A description of the operation of the pump shown in Figures 1 and 2 will further clarify the construction thereof and its suitability for incorporation in hydraulic systems which require the same.

Initially, a rotating prime mover such as an electricmotor or the like, is suitably fastened to the drive shaft 13 to impart rotative movement thereto,.and thereby the rotor drive member 14 and the rotor'd, together with the pistons [2 Initially, it should be explained that this descriptionof operation will be based on the assumption that the rotor is moving in a clockwise direction as indicated by the arrow in Figure 2. Since the pump in the condition of operation shown in Figure 2, would be operating at maximum pressure (in pounds per square inch), the fluid pressure in the outlet chamber 5 would be the same maximum pressure as in vthe.chambersat the ends of the pistons l2. This pressure is in turn communicated to passages 50, R8, .4! and 49, to the chambers 4| and 34.

. piston 35.

Since the area of the face 44 of the piston 35 is greater than the area of the face 43 of said piston the total force on the face 44 will be greater than the total force on the face 43. This differential of forces will cause the shaft 29 to move to the right until the spring 42 has been compressed sufficiently so that the force exerted thereby equals the differential of forces on the faces 43 and 44, since the spring is of the usual construction, the actual force exerted by the spring is equal to the force exerted by the spring totally deflected, multiplied by the ratio of actual deflection, divided by the total deflection.

As was previously noted, the pump pressure,

(in the drawing of Figure 1) has caused the cam operating unit 24 to move to the right so that the spring force equals the differential of forces on the faces 43 and 44. In this position the cam 22 has moved so that the outer periphery thereof is centered axially of the rotor 4, and therefore no reciprocation of the pistons l2 will take place. pressure-minimum volume position of the pump,

, at which position no fluid is transmitted but the pressure is maintained. If the pressure demands of the system, to which the pump is connected begins to fall, the pressure in the chamber 34 will also drop. The total forces acting on the This is known as the maximum faces 43 and 44 will correspondingly drop, the difference of the forces on said faces, thereby being smaller. The spring 42 will therefore expand until the spring force is equal to the smaller "differential of forces. It will be obvious that the operating unit 24 will thereupon move to the left, thereby changing the position of the cam 22, and thus the stroke of the pistons l 2 is increased. The volume of fluid pumped by the pistons is therefore increased. The angle of the shaft portion 23 of the operating unit 24, is so proportioned that the stroke of the pistons, as imparted thereto by the cam 22, will vary directly inversely to the pressure. The function of pressure times flow volume remains constant, and since horsepower is a function of pressure times flow volume, the horsepower requirements of the pump will remain constant.

If the pressure demands of the system fall to zero pounds per square inch, there will be no differential of forces on the faces 43 and 44 of the This will permit the spring 42 to expand to its maximum length and thereby move the operating unit 24 to the left, in which position the right hand end of the chamber 34 will be substantially adjacent the face 44 of the piston 35. It is obvious that in this position the operating unit 24 will have been moved to its extreme left position and thereby the cam 22 will be at the bottom position of its movement. The periphery of the cam 22 will of course therefore, be in eccentric relation with respect to the rotor 4. Since rotor 4 is revolving, the pistons will reciprocate in the cylindrical chambers ll provided therefor, thus imparting a pumping motion to the said pistons. In order to further explain the cycle of action of this pump, a, particular chamber will be designated at the end of one of the pistons l2, namely, chamber 53 (Figure 2). As the piston associated with the chamber 53, begins to move outwardly with respect to the center of the rotor, during rotation of the latter, such motion will expel any fluid in the said chamber into the outlet chamber 5 previously mentioned and thus into the port 5| and passages 53, 48, 41 and 49 connected therewith, whereby the forces will be imparted to the respective faces of the 6. piston 35 as has been previously set forth. When the piston I2, associated with the chamber 53, has reached the extreme outward position of movement in contact with the cam 22, by reason of the eccentricity of the latter, substantially all of the fluid in the said chamber 53 will have been expelled therefrom into the outlet chamber 5|. At this point the piston above just referred to, will be passing the projection or land 8. As it passes land 8, the inward stroke of the piston will commence and will continue, to thereby create a vacuum within the chamber 53 into which fluid will rush until the end of the stroke of the piston 12, the same being then at the low point of the cam 22. At this point the chamber 53 will be passing the land or projection 1, and thereafter will commence its outward stroke to continue the cycle before noted. It will be clear that the fluid will enter the inlet port 52 under the vacuum created by the inward movement of the piston l2 previously described.

The cycle of action of a piston as just described, will of course be followed by each one of the pistons therein. During the last described condition of operation of the pump, wherein the cam 22 had moved to its lowermost position, thereby imparting the maximum stroke to the piston, the pump will be delivering the maximum volume of fluid at the minimum pressure of fluid.

In view of the above description, it will be apparent that any combination of pressure and volume may be automatically selected depending upon the demands of the system in which the pump of my invention is incorporated. It might also be noted that in accordance with best construction principles in the art in which this invention is found, the relative clearances between the respective parts will be held to a minimum so as to reduce to a minimum the leakage problems which are sometimes encountered.

It should also be noted that the pump above described may be rotated in a counterclockwise direction, the inlet and outlet ports 5! and 52 thereby being reversed, so that the pump will thus be a constant volume pump.

The modification of the pump of my invention, disclosed in Figures 3 and 4, includes similar parts therein and is adapted to operate in a similar manner to the pump of Figures 1 and 2. In this modification however, the cam adjusting means or cam operating unit, is the primary constructional difference.

As shown in Figure 3, the pump comprises a drive end housing 54 and a control end housing 55 adapted to support therebetween a rotor housing 56, the latter being of substantially the same configuration as that shown in Figure 2, including the lands or projections i and 8 of said figure, and the slide plates 9 backed by the springs it. The housing members above referred to are suitably fastened together in any desirable manner comprising a main housing 13 and enclose the rotor 51 therein, the latter being substantially the same type of rotor as in thepreviously described form of my invention. The pistons 58, supported in radial cylindrical chambers of the rotor 51, are adapted to reciprocate therein for the purposes of pumping fluid. The rotor is supported for rotation in the pump by a rotor supporting member 55. The member 59, bearing El and annular opening 52 are substantially identical to the corresponding parts disclosed in Figure 1. At the opposite side of the rotor and engaged therewith for support thereby, by means of cap screws 53 or the like, is a rotor drive member 64-.

EIhe-said: member L65 is l a plate like nrember' and is formed integrally with 'the'drive shaft ".65 0f .thelpump. The said drive shaft fiiincludes theresin,:alblind female drive section 86 and is rotatably supported in the drive housing upon a bearing BL A suitable seal may be incorporated adiacent the'lbearing 67 to prevent the escapeof the'hydraulic fluid in the pump :in accordance with known practice in this art.

Thepistons 53 are adapted-to coact with-a'cam or eccentric ss, the said cam being locatedgen- -erally substantially 'centrally of the rotorfi'i, "by meansof suitable springs '68 surrounding the inner ends of the said pistonmembers 58, abutting at their outward extremities the inner surface of the rotor 5'! and-at theirinner-extremi *ties, seated upon snap rings 7d fitted in grooves in the inner end of the piston whereby'the tens'ionof the said springs will maintain the pistons in constant engagement with the cam or eccentrio 68.

"The-said cam or eccentric 68 is provided with 'a'shaft =H preferably formed integrally therewith, the shaft ii in turn supporting the eccentric, said shaftbeing'fitted in a bearing '12. The'bearing -'|'2 is seated in a suitable opening provided in the control end housing 55 as seen in Figure 3. A suitable seal'may be provided adjacent thebearing 12 to prevent the escape of fluid in accordance with known practice. 'On the opposite end of shaftll, adjacent cam or eccentric $8, a bearing 12a is fitted into a suitable opening in the drive shaft 65. Adjacent the bearing "12 just mentioned, thecam operating-unit generally designated'lB (seeFigure 4) is shown as including a spur-gear' 'l l maintained in engagement with the end of the shaft'li by means of a snap ringi5 or in any other suitable manner, and held against rotation relative said cam H by'means of a key '18, said key being seated in a key-wayof the shaft 1% and a corresponding key way in the spur gear 14.

As shown in Figure 4, the spur gear T4 oi'the cam operating unit 13 is engaged with a rack member or piston rod H, the said member' i'l being preferably rectangular shaped in'crosssection and having teeth formed thereon, the said piston rod'llbein connected to pistonlfi. The piston 18 is provided with suitable passages 19 made by drilling or the like. The passages 19 in the pistonsls, are adapted to connect chambers 83 and 8! at opposite sides thereof-formed in the chamber in which the piston rec'iprocates. At the end opposite the piston, the rod'l-i is adapted to engage a spring 82, the said spring in turn being seated upon a suitable portion of thehousing provided therefore. The chamber '80 is connected to an outlet port 83, by means of a pas sage 84 formed in the housing 55. The last named outlet passage and connecting passage, correspond to the passages 5i and 56 of the pump shown in Figure l. A suitable inlet passage or port 85 is provided, which corresponds to the inlet port 52 of the previously disclosed form of my pump.

It will be clear from the foregoing that movement of the piston member 18, in response to an increase of outlet pressure will impart a rotative motion to the spur gear 18, whereby the shaft H connected to the cam 68, will likewise be rotated, to thereby impart rotation to the cam 58 as mentioned and thus increase or decrease the stroke of the pistons 58 previously reieerred to. This operation of course will correspond to the movement of the cam 22 of-Figure 1,-to increase'or-de- =crease'the stroke of the "pistons in response 'to :pressure changes in the hydraulic system towhich the pump or this disclosure is connected.

In theposition of-the parts of the modification disclosed in Figures 3 and 4, the cam eccentric '68 is shown in a maximum volume-minimum pressure position as-contrasted'with the-position of the cam'22 of Figures 1 and 2. As the pressure in *the system increases, the eccentric or =cam -68' will turn toward the minimum-volume maximum pressure position whereby the eccentric or cam-'68 will be in'a position wherein'its periphery will approach a concentric relationship withthe rotor 51 and cause the pistons 53-150 move toward their zero stroke position. At the zero strokeposition, nofiuid will-be delivered and'thus the pressure in the system'will be maintained. In view of the'foregoing, it will be clear that the last described form of my pump invention, discloses a device which operates in substantially the same manner as the unit of Figures 1 and 2, the difference residing in the form of cam and the mechanism or" the cam operating unit. Each pump is constructed so as to provide means renew is set'forth inthe following claims:

1. In a pump of the class described, in combination, a housing, fluid inlet and outlet chambers in said housing, a rotor in said housing,

cylinders and pistons in said rotor, the pistons being radially operable therein, means for rotating said rotor whereby fluid under pressure is delivered to said outlet chamber, a cam axially disposed with relation to said rotor for moving said pistons and varying the stroke thereof, 'a cam operating unit engaging said cam, and

means for translating pressure developed in said outlet chamber into movement of a part of the cam operating unit to 'vary the stroke-of saidpistons, said unit including a shaft member shiftable axially of the 'rotor, the cam being supported on said shaft member, a pressure chamber formed in saicl shaft, a fixed piston having opposite faces of different areas -confined in said pressure chamber, and conduit means to transfer fluid under pressure from the outlet chamber to the opposite faces in the pressure chamber, whereby the'pressure difierential effects movement of the shaft as specified.

2. In a pump of the .class described, in combination, a housing, 'fiuidinletand outlet chambers in said housing, a rotor in said housing, cylinders and pistons in said .rotor, the pistons being radially operable therein, means for rotating-said rotor whereby fluid under pressure is delivered .to said outlet chamber, a cam axially disposed with relation to said rotor for .moving said pistons and varying the stroke thereof, a cam operating unit engaging saidcam, and means for translating pressure developed in said outlet chamber into movement of apart of the cam operating unit to vary the stroke of said pistons, said unit including a shaft member shiftable with respect to the rotor, the cam being operable by said shaft,'a piston having opposite faces of'difierent areas being engaged with said shaft, apressurechamber-beingprovided for said pis- 9 ton, and conduit means being provided to transfer fluid under pressure from the outlet chamber to the pressure chamber for application to said opposite faces, whereby the pressure differential effects movement of the cam to vary the stroke as specified.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,149,728 Ciarlo Aug. 10, 1915 1,227,164 Manly May 22, 1917 1,283,249 Manly Oct. 29, 1918 Number 1 Number Name Date Schneggenburger Jan. 4, 1927 Phillips Apr. 26, 1938 Clark July 18, 1939 Ott Mar. 4, 1941 Tucker Aug. 4, 1942 McDonough Dec. 14, 1943 Budzien Oct. 18, 1949 FOREIGN PATENTS Country Date Italy 1938 Great Britain Aug. 23, 1938

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