US1974225A - Rotary pump - Google Patents

Description

Sept. 18, 1934. Y c. H. vARLEY 1,974,225

ROTARY PUMP Filed Nov. 8, 1933 2 sheets-sneer 1 (3 7/- Var/6 /Nve Tall Sept. 18, 1934. A c. H. VARLEY i 21,974,225

l ROTARY PUMP Filed Nv. 8, 1933 2 Sheets-Sheet 2 37"A if??? Patented Sept. 18, 1934 PATENT OFFEC ROTARY PUllIP Cromwell Hanford Varley,

Acton, London,

England, assignor to Varley Pumps and Engineering Limited, London, England Application November 8, 1933, Serial No. 697,207

In Great Britain July 27, 1932 7 Claims.

This invention relates to pumps of the class wherein the iiuid to be operated upon is admitted into a conduit extending between an inlet and an outlet and therein subjected to displacement, in volumes which are comparatively suddenlyreleased to the discharge, by relatively moving members having co-operating parts, for instance, intermittently forming contacts or sealing regions, which determine the various events of the cycle mi irrespective of pressure. It is concerned thus with pumps of a class embracing those set forth for instance in my United States patent specification No. 1,550,624 and British patent speciiications Nos. 154,261 and 217,615 and has for its 'object improvements with a view to the more satisfactory and efcient, e. g. smoother and quieter working of pumps of such class.

It has been found that in the operation of the aforesaid class of pump with substantially incompressible fluids as distinct from air or other gaseous or elastic fluids, a knocking occurs, more especially when the pump is Worked at high speeds and high rates of delivery; and investigation into this has shown that the knocking is due to dii'erences between. the fluid pressure at the discharge end of the conduit and the pressure of the said displaced volumes at the instants when they are released to the discharge; the latter pressure being less than the former, with a more or less violent counter-flow action as a result. For

instance, in the patented construction of pumps referred to above the trouble arises due to the crescent or like chamber (there may be more than one) enclosed between the moving contacts of the displacer and the casing not being fully filled with liquid at the point` of the cycle when it is opened to the discharge side of the pump and by an inward rush of liquid into the rareed liquid` inI said chamber from the discharge side in a direction counter to the direction of paracyclic movement of the displacer; paracyclic as dened in the earlier patent specications above referred to. v

According to this invention uid is introduced' into a volume of fluid being operated upon prior to releaseof the latter to the discharge. "Ihus, in a pump of the class referred to means are provided for introducing fluid into a volume of fluid entrained in the operating conduit (or in process of being entrained e. g. before it is quite isolated from the suction) at a point in the cyclel sufliciently in advance y of `the instant at which the entrained Volume is released to discharge pressure to ensure that at such instant the said volume will be completely filled wtih fluid. Consuch movement being (Cl. 10S-131) veniently such means comprises a chamber of a capacity Variable against resilient resistance and adapted so to be placed in communication with and isolated from a volume of iiuid being operated upon as to receive iiuid from the operating conduit at the pressure of the pump discharge and to re-introduce such iiuid at the said point of the cycle.

' Other features of the invention and its preferred mode of application to pumps operating in accordance with the aforementioned prior patentswill be set-forth in the description and claims which followz- Referring to the accompanying drawings:-

Figures 1 and 2 are diagrammatic sections of a 7d known construction of pump, the displacer element occupying top dead-centre and bottom dead-centre positions respectively;

Figure 3 is an inside elevation of a cover for a pump of the kind shown in Figures 1 and 2 hav- 75 ing superimposed thereon in correct relationship a displacer and its co-operating casing interior;l

Figure 4 is an outside elevation of the cover shown in Figure 3;

Figure 5 is a section on the line X--X of Figure 4; and

Figure 6 is a section on the line Y-Y of Figure 4. A

In the construction of pump shown in Figures 1 and 2 of the drawings, the displacer a executes "l5 a paracyclic motion, as indicated by the arrows x, :c and by the circle y which is traced by a point z centrally of the displacer, within the C-shaped interior of a stator or casing b; the fluid being entrained in the outer crescent-like chamber c (see Figure 1) and, as the displacer moves in a cycle through the position shown in Figure 2, being displaced from the pump inlet at z' to the discharge or outlet at d. A similar operation takes place in the inner crescent chamber ci (see Figure 2) and efficient sealing between the displacer and the stator is provided by cooperation of the resilient contact pieces e1, e2, es, e4, e5, e6 with complementary arcuate surfaces f1, f2, f3, f4, f5, fs; all as already well known. iO Considering the action of the above device upon water or other uid in the outer crescent c it will be seen that in Figure l the seal between e1 and f1 is about to be broken and the fluid in the outer crescent c about to be thus released to the discharge side; while a seal has just been eiiected between e2 and f2 behind the volume of fluid in the said crescent. y

Referring now to Figure 3, and introducing one convenient mode of applying the invention to Sil:

such a construction of pump, the displacer a when in the full line position, a few degrees before top dead-centre and before the contacts e1, f1 separate, will be seen to have just uncovered the radially outermost side of the port p formed in the side cover g of the pump; when it is in the chain-dotted position ai, at an earlier stage of the cycle it completely covers the said part, and at a still earlier stage just before contact is first established between the said contacts, it has just closed or covered said port at the same side thereof. The outer edge of the port is of complementary shape to the outer edge of the displacer, so as to ensure sharp uncovering or opening of the port. Y

It will be understood also that so far as the outer crescent c is concerned the port will thus be opened from some few degrees before topv centre position while the displacer performs the greater part of the cycle which restores it to the position just before contact at e1, f1 is reestablished.

The side cover, as shown in Figures 4, 5 and 6, has cast integrally on its exterior opposite the port p a housing h comprising a portion having a cylindrical bore :i into which the port p opens. Freely slidable within the bore j is provided a hollow cylindrical piston lc, called the compensator piston, which is resiliently loaded by a helical compression spring l of suitable strength, the outer end of which spring is conveniently restrained by the cover h1 suitably applied to the housing. An annular enlargement 71 of the housing interior at the inside end of the bore 9 facilitates manufacture, more particularly machining of the bore 9'. The outer side of the piston is in communication with the pump suction via the passages m, m1, m2, ma and opening m4 which form part of a suitable by-pass valve device,

preferably one so constructed and operating that on a predetermined uid pressure being reached the fluid escapes past co-operating valve faces and acts upon an increased area of the valve proper. Preferably such Valve comprises means for ensuring a leak-away of fluid inhibitive to premature opening of the valve proper at low pressures and to such end may have a seating region of smaller area than the valve proper and connected with a restricted annular space surrounding the latter, or may have means permitting partial escape of fluid through the valve proper, such as holes in the latter opposite an annular space in the vicinity of the valve seat. The form of valve shown in the drawings Figs. 5 and 6 comprises co-operating surfaces of the valve proper and seating thereof, the latter having a skirt or its equivalent embracing the end region of the former and defining a narrow annular clearance divergent or stepped to a larger diameter in the direction of lift of the valve proper. The latter is of cylindrical form, having spring or like loading means therefor, and uid passage means placing the back of the valve proper in communication with a chamber which surrounds the co-operating seating parts and contains said annular space, and as shown there may also be incorporated dashpot or like damping means operative upon the valve proper. In operation of the compensator above described, the piston will occupy an intermediate position in the bore 7 dependent upon the pressures acting upon it.

Describing now the operation of the pump with reference to the port p and compensator device and their action in respect of the outer crescent ,chamber c; while the displacer a moves through the upper part of its cycle and the elements e1, f1 are disengaged the fluid in said chamber c is open to the discharge, and the port p being uncovered, a pressure of fluid equal to the discharge pressure acts upon the end of the piston 7c forcing the sameback against the spring l to an extent depending upon the strength of the latter and the head against which the pump is operating. When the displacer reaches the corn- `plete cut-off position with respect to the port p,

just prior to its reaching the chain-dotted position in Figure 3, the fluid under said pressure acting upon the piston in the space i is isolated from both crescents c and c1 and it remains so Vuntil just-before `the displacer reaches the fullline position, uncovering the port to the outer crescent c. Pressure reduction or rarefaction of the fluid in the said crescent c, occurring in the ordinary way with such a pump from the said full-line position of the displacer until the latter reaches the position in which it is shown in Figure 1, is prevented or compensated by the timely and controlled opening of the port p with admission therethrough into the crescent c of fluid substantially at the discharge pressure from the piston k. By this means pressure difference on opposite sides of the sealing elements e1, fi as these are severed is eliminated and backward rush of fluid from the region of the discharge or outlet d in counterow to the movement of the displacer no longer takes place. During continuation of the cycle fluid is again charged into the chamber of the compensator piston as above; it is then isolated at discharge pressure and released again into the crescent c, these events taking place with each complete cycle of the displacer.

The same series of events occurs during every cycle with respect to the inner cresment ci, the port p having its radially innermost edge suitably positioned and shaped to conform with the inner edge of the displacer for co-operation of these parts in an appropriate manner.

It will be understood that for correct operation cf a compensator device such as that described above the shape and disposition of the port pi is of primary importance in order that the introduction of uid therethrough may be suitably controlled, and will be related not only to the shape of the displacer but also to the area of the piston lc, to the resistance of the spring Z and to the working pressure differences between discharge and suction sides of the pump. It has been found by experiments in connection with a pump as shown, and operating against about fifteen pounds pressure per square inch in which the port p was arranged to be opened to the outer crescent c with the displacer a at positions ranging from top dead-centre (as in Figure 1) to 35 before top dead-centre, that some 15 to 20 gave satisfactory results. In Figures 3, 4 and 5 a port has been shown so arranged as to have opened sharply some few degrees before 22 Maj in advance of top dead-centre. In practice it is best arranged to open at the 22%,;o position to allow for tolerance in casting where the port is not to be machined. Premature uncovering of the port produces excessive displacement of the compensator piston owing to the port opening substantially before the contacting elements e2, f2 come into operation, and the fluid at the pressure of the compensator being discharged or short circuited back to the suction. Also, as will be obvious, in suchva case a reduction of pumping capacity is experienced,

and further the substantial movement of the piston, necessarily accompanied by considerable iiow of fluid back into the compensator each cycle produces pulsation of the pump discharge. Whereas a pump unprovided with a compensator device operating as above described may require means for elimination or reduction of pulsations as for instance air chambers or vessels connected with suction and discharge sides, or alternatively a balance valve comprising spring loaded piston connected at opposite sides directly with the discharge and suction sides, the compensator device when fitted (and subject to the foregoing considerations) serves also in this capacity, notwithstanding that the piston thereof corresponding to the piston in the balance valve is isolated from the pressure of the discharge side for some 30 while the port p is completely covered by the displacer.

By operating according to the invention the action of a pump can be considerably smoothed and whereas considerable hammer or knocking took place in one construction of pump delivering about fteen gallons per minute, the fitting of a. compensator not only eliminated such defect but enabled the pump to be speeded up to twenty gallons per minute without recurrence of the trouble.

It is to be understood that modifications and additions may be introduced within the scope of the invention as herein defined, the specific description having been given by way of example only.

I claim:

l. In a pump having a casing dening a pumping chamber extending between inlet means and outlet means and a displacer cyclically movable therein and co-operating therewith across the pumping chamber when in movement to perform at determinate positions of the displacer the events of entraining fluid from the inlet region of the pumping chamber, displacing it towards and releasing it to the outlet region, a Huid chamber of a capacity governed by a resiliently movable partition and adapted to receve fluid at discharge pressure, and means for introducing such fluid at said pressure into said pumping charnber at a point of the pumping cycle closely in advance of the release event.

2. In a pump having a casing defining a pumping chamber extending between an inlet and an outlet, a displacer cyclically movable therein and fluid sealing devices co-operating in succession across the pumping chamber with said casing and said displacer when the latter is in movement to determine the events of entraining fluid from the inlet of the pumping chamber, displacing 1't towards and releasing it to the outlet, a fluid chamber cf a capacity governed by a resiliently movable partition and adapted to receive fluid at discharge pressure, port means connecting said chamber with said pumping chamber and adapted to be covered by said displacer during a portion of the pumping cycle between an entraining event and a successive release event, and to be uncovered by said displacer closely in advance of such release event.

3. In a pump having a casing defining a pumping chamber extending between an inlet and an outlet and a displacer cyclically movable therein and co-operating therewith across the pumping chamber in movement to determine the events of entraining fluid from the inlet displacing it towards and releasing it to the outlet, a fluid chamber adapted to receive fluid at discharge pressure of a capacity governed by resilient means yieldable against such pressure, port means connecting said chamber with said pumping chamber at a region thereof disposed nearer to the outlet than to the inlet and adapted to be covered and uncovered by said displacer during a porton of the pumping cycle between associated entraining and release events, said port means having an edge conforming in shape to a marginal region of said displacer and located to coincide with such region when the displacer occupies a position slightly in advance of the release event.

4. In a pumping combination according to claim l, passage means separated from said variable capacity fluid chamber by said resiliently movable partition and leading to the inlet region i' of said pumping chamber.

5. In a pumping combination according to claim 1, passage means separated from said fluid chamber by said resiliently movable partition and leading to the inlet side of the pump, passage ll means leading from the discharge side of the pump to the inlet side of the pump and relief valve means operative in said second-mentioned passage means.

6. In a pumping combination according to claim l, passage means separated from said fluid chamber by said resiliently movable partition and leading to the pump inlet side of the pump, passage means leading from the discharge side of the pump to the inlet side of the pump, including a resiliently loaded valve co-operating with a port leading from said second passage means to the discharge side of the pump and having a body portion in part occupying said first passage means leading from said resiliently movable partiif tion.

'7. For pumps operating upon substantially incompressible fluids and comprising a casing defining a pumping chamber within which a displacer executes a cyclic movement to displace uid from an inlet at one end to an outlet at the other, a side cover for said casing comprising an external housing containing a compensator chamber and passage means connecting the same r to the inlet side of the pump and to the outlet side of the pump, a port penetrating said cover from said compensator chamber to the pumping chamber in a position such as to be in the path of said displacer, a partition reciprocatable in I CROMWELL HANFORD VARLEY.

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