US2791966A

US2791966A - Rotary pump with output pressure limiter

Info

Publication number: US2791966A
Application number: US363084A
Authority: US
Inventors: Moulton Lloyd Jackson
Original assignee: Curtiss Wright Corp
Current assignee: Curtiss Wright Corp
Priority date: 1953-06-22
Filing date: 1953-06-22
Publication date: 1957-05-14
Anticipated expiration: 1974-05-14

Description

' May 14, 1957 J. MoULToN ROTARY PUMP WITH OUTPUT PRESSURE LIMITER Filed June 22, 1955 /fs e ROTARY PUD/E WHTH OUTPUT PRESSURE LllVII'IER Lloyd llaclrson Moulton, Mentor, Ohio, assigner, by mesne assignments, to Curtiss-Wright Corporation, Marquette Metal Products Division, Cleveland, @hie Application .lune 22, 1953, Serial No. 363,084

4 Claims. (Cl. 10S-42) The drawing partially shows one known type of rtary pump which is reversible in operation in the sense that the main inlet and outlet passages of the pump become reversed (inlet becoming outlet and vice versa) whenever the direction of rotation of the impeller means of the pump is reversed. Gne object is to provide an improved pump output fluid pressure limiting bypass valve mechanism for a reversible pump such as outlined above, which mechanism, particularly, is capable of reversible action, in situ, to limit the pump output or discharge pressure by short-circuiting of uid from whichever side of the pump may be serving as outlet or discharge side to the suction or intake side. A further object is to provide a double or reversibly acting, spring loaded, pump pressure relief valve mechanism which limits the output or discharge liuid pressure of the pump through a single bypass port and enables independent adjustment of spring loading or valve closing force. Another Objectis to provide an improved pump discharge pressure limiting, twoway-acting, spring loaded, pressure relief bypass valve mechanism for liquid pumps, which mechanism has a simple and readily applicable means for damping oscillations or iluttering actions of the valve in event such tend to occur.

Other objects and features will become apparent from the following description of the illustrative form, as shown more or less schematically in the accompanying drawing, wherein:

Fig. l is a sectional View through a known type of rotary fluid pump incorporating the present invention in the form of a built-in valve mechanism assembly, nearly all parts of which are shown in longitudinal central cross section.

Fig. 2 is a similar fragmentary assembly sectional View of the valve mechanism whose principal parts are in fluid bypassing position relative to the pump.

Pump housing 5 of illustrative pump P has a main inlet (or outlet) 6, main outlet (or inlet) 7, a correspondingly connected supply or suction passage 8 and a delivery or pump output passage 9. A pump-chamberforming sleeve lll contains a circular rotor or impeller 12 having radially movable vanes 14 which, during operation of the pump, are suitably maintained in wiping or fluid-impelling contact with the interior peripheral surface lll of the sleeve lil and with axial end walls of the chamber (not shown). When the rotor is turned in the counterclockwise direction, as indicated by the arrow thereon, fluid to be pumped is received into the crescent shaped pump chamber portions l5 and i6 through radial ports i7 and i8 in the wall of the sleeve itl and is propelled, by conventional action of the rotor 12 and its vanes 14, through radial discharge ports i9 and 20 in the wall of the sleeve which ports are connected to pump discharge passage 9.

Passages

8 and 9 are separated from each other, in part, by a partition wall portion 22 of housing 5, at respective sides of which wall portion 22

portions

8 and 9 of the passages form inlet and discharge chambers for the bypass valve mechanism hereof L aired States Patent 'O n n 2,791,966 ,A Patented Mayld, 1957 generally indicated at 25. Mechanism 25, as shown, is arranged as follows.

Identical

pump base portions

26 and 27 of the housing 5 are provided with cylindrical aligned bores 28 intersecting the chambers 8' and 9 respectively. The bores Z8 are snugly occupied by cup-shaped, cylinder-forming

members

30 and 31 whose mutually adjacent ends are open into the valve chambers 8 and 9' and whose outer ends are closed by

wall portions

32 and 33.

Flange portions

32 and 33 at the closed ends provide for conventional `'attachment of the

members

30 and 31 to the pump housing, as yby screws, not shown.4 For enabling intercommunication of the relatively high and

low pressure passages

8 and 9 of the pump through the partition wall 22 a relatively smooth bore 35 through said wall, aligned with bores 28, constitutes a bypass valve port, shown in Fig. l as closed by a disc-like valve plug 36 slidably and sealingly iitting the bore 35.

The valve plug 36 is aA central portion of a double headed shuttle member or unit. 37 (shown as one piece), having piston or

head portions

38 and 39 slidably and sealingly occupying respective cylinder bores di) and il of the cup-shaped members 3d and 31. The

piston portions

33 and 39 are joined together and'to the plug by a tubular stem 42 which is open from end to end (bore 42a), so that fluid can move from one cylinder/piston chamber (e. g. 44) into the other (e. g. 45) through the hollow stem.

T he valve plug 36 is normally maintained generally centered in sealing relationship to the bypass port '35 (see Fig.

. l) by spring and abutment assemblies 50 and Si. (hereinafter usually called centering spring assemblies) within the respective cup-shaped cylinder forming members 30 and 3l. Each centering spring assembly Sil and 5l resists movement of the plug 36 theretoward, but enables port opening and closing movement of the valve plug and piston unit 37 in either of two directions under the influence of Huid pressure in passage portions S or Si' (whichever contains fluid at pump output or discharge pressure as determined by the direction of operation of the pump). The springs (described later) are capable of being independently preloaded to resist movement of the valve plug 36 out of its centered position, which among other advantages, allows the plug to be madel with only suilicient length to providel .adequate sealing surface in contact with the wall which defines the enacting port.

The elective cross sectional area of the plug 36, exposed to liuid pressure in the acting pump discharge passage portion (8 or W), is greater than the effective cross sectional area of the

pistons

38 and 39 exposed in the dis-- charge passage, so that, when, for example, the tiuid pressure in -right hand space -8 (which is simultaneously exposed to both the plug 36 and piston 38) reaches a predetermined, desired maximum, value, the shuttle unit 37 will be moved toward the left (see Fig. 2) against the restraint ot the centering spring assembly 51, opening the port 35 for spill or bypassing of pumped fluid to the intake side of the pump. The pressure relief or limiting action is exactly the same as just described if space 9', at the left of wall 22, contains pump discharge or output pressure, except that the shuttle unit 37 moves to the right from bypass-port-sealing position against the resisting force of centering spring assembly 50.

The centering spring assemblies 5t) and 5l are identical in construction and only one (5d, right, Fig. l) will therefore be described in detail. Coil spring 51 surrounds a stili supporting pin or rod 55 mounted in a bore 56 in cylinder wall 32, the pin having a reduced diameter partly threaded portion 57 exposed beyond said Wall 32 which renders the pin accessible for rotary adjustment (purpose given later) by a suitable tool. Pin

55 is lnormally secured "in axially fixed position on the cup-shaped cylinder-forming member lSt) `by a "suitable externally exposed nut 58 on the outer end of the pin, which nut forces a conical sealing shoulder 59 of the pin against a mating shoulder-'on thewall '32 `of member 30. The coil spring 54 is maintained under predetermined axial strain, properly lto resist port-opening movement of valve plug 36 thereto\vard,'by supporting discs 60 and 6i carried by the pin 55. Disc 60 is slidably mounted on its supporting pin, and, in the centered position of the valve plug 36 inthe valve port 35, a head 62 of the pin abuts the disc Y69. Disc 61 is threaded 'on pin 55 and is slidingly keyed, as at 464, to the cylinder member 30, so that turning of the pin y55 by the operator (assuming nut 58 is temporarily loosened), will 'adjust the disc 6i axially on the pin 55 and thereby set the spring force at proper value. The head 62 on the `inner end ofthe -pin 55 -is smaller than the inner diameterof the hollow Vstem 42 so that `the head lcan freely enter the hollow stem when the unit 37 moves toward the right to allow pressure relier" valve action (not illustrated) as to

passage

9, 9.

The return or valve-centering spring assembly 51, at the left of wall 22, is, as already mentioned, the same as the assembly 50 just above described and the same characters (primed) are applied thereto. Fig. 2 shows the valve plug and piston unit 37 in pressure relieving or iiuid bypassing position in respect to pump output or

discharge passage portions

8, 8.

As is well known, a spring loaded valvc mechanism of the general type herein shown is apt to be subject to fluttering action or chatter under somewhat unpredictable circumstances. Flutter can be damped or eliminated by flow rate control commonly known as dash-pot action. In the present mechanism, assuming thc various spaces within shuttle unit 37 and

cylinders

30 and 31 are filled with the liquid being pumped (or other liquid) the liquid has to move from one piston cylinder space (e. g. 44) into the other (e. g. 45) in order to permit opening and closing movement -of the valve plug 36. The rate of movement can be governed by provision of an oriticed member 64 shown as occupying the bore 42a of the hollow stem 42 of unit 37. The orifice 65 (diameter and length selected by trial) forms with the rest of the assembly a double acting, flutter damping, dashpot.

I claim:

l. In and for a rotary pump of the type having inlet and outlet passages which, respectively, become 'outlet and inlet passages upon reversal of direction of input rotation to the pump; a two way acting pump pressure relief valve having wall means forming two valve chambers respectively connected to said passages .and agenerally cylindrical port through a portion of 'said wall means for intercommunication of said chambers, a generally cylindrical plug slidably occupying the port and having a normal position sealing the port, pistons connected to the plug at each side thereof alongits axis and .4 having effective piston areas smaller than the effective areas of the-plu'gwhich "can be exposed *to Ypump output fluid pressure in the respective chambers, so that the net fluid pressure acting on the plug and one piston tends to move the plug out of the port, cylinders slidably mating the pistons, springs in each of the cylinders each capable of exerting force axially 'on its associated piston Whenever the vplug is moved out of its normal port-sealing position in a direction to return the plug to sealing position, and tlid-passage-forming means connected to enable iluid communication between the cylinders at all times.

2. The arrangement according to claim l wherein the pistons are connected to the plug by a hollow stem membcr which is always open from end to-end for iiuid communication between respective cylinders.

3. The arrangement according to claim 2 wherein lluid ilow restricting orifice means in the interior of the hollow stem is provided for damping valve oscillation or flutter.

4. In vcombination with a luid pump having a hollow casing, an impeller therein, Aand chambers which serve as relatively vhigh and low pressure spaces, rigid wall means defining portions of both said chambers and having a generally cylindrical by-pass port therethrough, the casing having generally cylindrical openings on opposite sides of said wall means along the axis of the port, cup shaped sleeves closing respective said openings and adapted to constitute cylinders with open ends adjacent respective chambers, a relief valve member having a plug portion slidable in said port and capable of scaling it, the valve member having piston portions respectively occupying the open ends of the sleeve cylinders and slidable therein, spring means connected to act axially in opposite directions upon the valve member and capable of normally holding its plug poltion in sealing relationship to lthe port, the plug portion having relatively oppositely facing eiective transverse areas exposed to pressures in respective chambers for movement of the plug portion to unsealing positions in opposition to the spring means, and the piston portions having effective transf verse areas smaller than those of the plug portion and exposed to pressures in the chambers in a manner to assist the spring means, whereby the lplug portion will be moved to port unsealing positions by predetermined uid presssure difference in the chambers, and venting means for the cylinder-constituting spaces ofthe two sleeves.

References Cited'in the ile of this patent UNITED STATES PATENTS 2,122,045 Rose June 28, '19'3-8 A2,309,683 Wahlmark IFeb. 2, 1943 2,696,787 Iaworowski et :al Dec. 14, 1954 FOREIGN PATENTS 435,729 Italy May 21, 1948 563,631 Great Britain Aug. 23, 1944