US2807215A - Variable displacement pump - Google Patents

Description

p 7 s. HAWXHURST 2,807,215

VARIABLE DISPLACEMENT PUMP Filed July 28, 1955 2 Sheets-Sheet 1 Inventor stgphen Hawxhm'st E: d-1 m QQWM 2,807,215 Patented Sept. 24, 1957 United States Patent OfiFice The present invention relates to variable displacement pumps which are employed for feeding or delivering fluids in predetermined quantities. More particularly, the invention is concerned with a variable displacement pump of this character in which the pumping action is obtained by the transmission of applied pumping force through a confined or partially confined liquid mass interposed between a solid piston and a floating member, the latter,

displacing the fluid and thereby subjecting it to the pumping action.

In carrying out the principles of the present invention, briefly, the invention contemplates the provision of a liquid filled cylinder in which there is disposed a reciprocable driving piston or plunger the stroke of which remains substantially constant, which is to say that the frequency and amplitude of its reciprocation does not vary. Also disposed within the cylinder and reciprocable therein is a freely floating piston and interposed between the two pistons is a column of an incompressible fluid, i. e. a liquid, the column being bodily displaceable in either direction within the cylinder under the influence of the movements of the first piston and the liquid column acting directly upon the floating piston to reciprocate the latter in timed relation to the reciprocation of the driving piston. The displacements of the floating piston may be employed for effecting displacements of the fluid undergoing pumping, either directly by forcing portions of the fluid out of the cylinder and replacing the same with each complete stroke of the floating piston, or the displacements of the floating piston may be transmitted to a displaceable flexible barrier which may be in the form of a movable diaphragm through a second liquid column'interposed between the floating piston and diaphragm, the flexible barrier serving to seal the fluid undergoing pumping from entry into the cylinder. In the former instance the floating piston constitutes the actual pumping element of the system while in the latter instance the flexible barrier constitutes the pumping element.

Variation in the displacements of the fluid undergoing pumping, in either instance outlined above, is effected by regulably bleeding a portion of the liquid column existing between the driving piston and the floating piston so that upon each pressure stroke of the driving piston against the liquid column a predetermined portion of the column may escape from the cylinder while that portion Which remains within the cylinder will become effective to displace the floating piston. Thus the actual displacement of the floating piston during each pressure stroke of the driving piston will be a function of the rate of bleeding of the liquid from the column thereof, maximum displacement taking place when no bleeding is permitted and minimum displacement taking place when maximum bleeding is effected.

Fluid pumps constructed in accordance with the principles of the present invention have a wide variety of applications, one important application being in connection with the pumping of corrosive fluids or fluids which are diflicult to seal in that they attack the usual pump packing or sealing elements ordinarily associated with conventional pumping apparatus. Another and similar application of the present pumping apparatus is in connection with the pumping of fluids which are potentially hazardous in that they react explosively in the presence of bituminous or other lubricating oils ordinarily em- 2 ployed with conventional pumping devices. Numerous other uses for the present pumping apparatus are contemplated and, in general, the same will be found useful for the pumping of fluids, whatever be their nature, in installations where it is desired that the fluid shall remain uncontaminated by contact with other fluids and, toward I this end, the invention provides for complete or absolute isolation of the fluid undergoing pumping from lubricating oils, pressure liquids such as may be employed in the liquid motivating column of thepumping system as outlined above, condensation liquids or the like, or from foreign liquids or abrasive particles and other foreign matter whatever may be'its source. p

The provision of a variable displacement pump of the character briefly outlined'above being among the principal objects of the present invention, a further object is to provide such a pump in which the liquid bled from the motivating column of pressure liquid is automatically replaced during each stroke of the driving piston so that the volume of the liquid column will not become permanently diminished and will at the commencement of each stroke of the driving piston remain constant.

Astill further object of the invention is to provide a pumping apparatus of this character in which the pumping and sealing diaphragm employed for the displacement of the fluid undergoing pumping is of an extremely flexible nature and is therefore capable of a large degree of distortion, thus enabling large displacements of fluid during each stroke of the driving piston, particularly when the apparatus is adjusted for maximum pumping effect.

Yet another object is to provide a variable displacement pump utilizing a driving piston and a diaphragm pumping element in conjunction with a body' of hydraulic fluid between the piston and diaphragm, in which the diaphragm is so constructed that it is not subject to as much strain as the usual diaphragm employed in diaphragm pump constructions and which therefore will not require frequent, if any, repair or replacement during the life of the pump; i i

Another object of the invention is to provide a variable displacement pump of the character briefly outlined above which will handle corrosive or valuable fluids without loss of such fluids by leakage through any part of the pump system.

The provision of a variable displacement pump which is extremely simple in its construction; one which is comprised of a minimum number of moving working parts and which therefore is unlikely to get out of order; one which is capable of ease of assembly and disassembly for purposes'of inspection of parts, replacement or repair; one which is rugged and durable and which therefore is possessed of a comparatively long life, one which is capable of asmooth and silent operation; one which is capable of being regulated for difierent fluid displacements without necessitating shutting down of the pump by a simple and single manual adjustment, and one which otherwise is well adapted to perform the services required of it are further desirable features that have been borne in mind in the production and development of the present invention.

Numerous other objects and advantages of the invention, not at this time enumerated, will become'more readily apparent as the nature of theinvention is better understood.

In the accompanying two sheets of drawings forming a part of this specification one illustrative embodiment of the invention has been shown by way of example.

In these drawings:

Fig.- 1 is a fragmentary sectional view, somewhat schematic in its representation, taken substantially longitudinally and centrally through a pump assembly embodying the principles of the present invention.

Fig. 2 is a sectional view similar to Fig. 1 showing the pump parts in positions which are displaced from the positions in which they are shown in Fig. 1, and

Figs. 3, 4 and 5 are diagrammatic views illustrating the manner in which variations in linear displacement of the effective pump parts serve to effect variations in the volumetric displacement of the fluid undergoing pumping.

Referring now to the drawings in detail and in par ticular to Figs. 1 and 2, the pump construction of the present invention involves in its general organization a cylindrical pump casing in which there is slidably disposed a piston 12 capable of being driven in its reciprocating movements by any prime mover, as for example through the medium of a crank pin 14 and connecting rod 16 such as has been diagrammatically shown in Figs. 3, 4 and 5 A second stemless or floating piston 18 is also slidably disposed within the casing 10 in spaced relation with respect to the piston 12 and a column 20 of an incompressible liquid is interposed between the pistons 12 and 18 so that the reciprocating movements of the piston 12 may be imparted to the floating piston 18 through the column 20, alternate compression and suction strokes of the piston 12 serving to move the piston 18 to the right and left respectively as viewed in The pistons 12 and 18 are grooved circumferentially to receive suitable packing material 22 which may be in the form of conventional 0 rings which are sufliciently tight as to prevent egress of the liquid from the column around the respective cylinders. prising the column 20 may be composed of any suitable fluid as for example a hydrocarbon oil or the like.

The path of movement of the floating piston 18 within the casing 10 is limited by a pair of spaced abutments 24 and 26 which may be in the form of split rings receivable in internal annular grooves 28 formed in the cylinder wall. The piston 18 is movable between the two abutments 24 and 26 from a fully retracted position wherein it engages the abutment 24 to a fully advanced position wherein it engages the abutment 26. The abutments are spaced apart longitudinally of the cylinder 10 a distance which is substantially equal to the amplitude of the stroke of the piston 12 plus the longitudinal thickness of the piston 18 so that when the column 20 is effectively sealed from escape from the casing 10 the full stroke of the piston 12 will be effective to move the piston 18 and the reciprocal movements of the two pistons will be equal in amplitude.

The liquid mass which comprises the column 20 is supplcd to the casing 10 between the two pistons 12 and I 18 through an inlet 30 communicating with a conduit 32 leading from a suitable sump, reservoir or constant head pump (not shown) and in which conduit there is interposed a one-way valve 34 of conventional design. The valve 32 is so designed that the inlet 30 is at all times effectively closed during the entire compression stroke of the piston 12, and is also closed during that portion of the suction stroke of the piston 12 wherein the piston 18 is capable of free travel between the abutments 24 and 26. Thus, with the liquid column 20 sealed oif from escape from the casing 10, the valve 34 will remain closed and no fluid will be drawn into the column 20 from the sump except possibly a negligible amount of replacement liquid that may be pulled through the valve 34 after a long period of operation with an attendant slight loss of the liquid.

The valve 34 is in the form of a casing 36 having a valve seat 38 associated therewith and normally closed by a valve element in the form of a ball 40 which is spring pressed as at 42 against the seat in the usual manner of operation of such one-way devices. The spring 42 is so designed that it will maintain the ball 40 seated at pressures within the column 20 which are somewhat below the pressure maintained within the sump which usually is atmospheric pressure. By such an ar- The liquid mass com- 9 Cir rangement the suction stroke of the piston 10 will be effective through the column 20 to move the piston 18 to its retracted position despite any reduction of internal pressure developed within the column 20 due to the frictional drag of the floating piston 18.

As will be described subsequently, means are provided for varying the amplitude of the effective stroke of the floating piston 18 to consequently vary the volumetric displacement of the fluid undergoing pumping. It is deemed suflicient at present to state that this means is in the form of a bleeder conduit 44 which communicates through the casing 10 with the liquid column 2% and in which there is interposed a variable orifice bleeder valve designated in its entirety at 46.

The above description has been based upon the more or less diagrammatic illustration of the invention shown in Figs. 1 and 2 wherein the driving piston or plunger 12. and the stemless or floating piston 13 are illustrated as being reciprocable in a common cylindrical casing 10. The abutment 24, in effect, divides the cylindrical casing 19 into two operating cylinders designated at 41 and 43 respectively, the piston 12. operating in the cylinder 41 and the piston 18 operating in the cylinder 43. The incompressible liquid column 21 which is interposed between the two cylinders 12 and 18 is bodily shiftable with the pressure and suction strokes of the piston 12 so that portions thereof are transferred from one cylinder to the other to translate the movements of the piston 12 into corresponding movements of the piston 18. It should also be noted at this point that when the floating piston 18 is drawn rearwardly against the abutment 24 during the suction stroke of the piston 12, the cylinder 43 is sealed from the cylinder 41 during the remainder of any suction stroke which the piston 12 may make after such engagement between the floating piston 18 and the abutment 24 so that a lost motion between the two pistons will exist during which time the valve 34 will admit replacement fluid to the liquid column 20. It will be understood of course that when the variable orifice or bleeder valve 46 is closed, no liquid from the column 2% may escape and therefore the valve 34 will remain inactive in the absence of replacement fluid requirements.

Still referring to Figs. 1 and 2, the end of the cylinder 10 remote from the driving piston 12 communicates with a pump chamber 58, the casing 52 of which is provided with an end wall 53 having a fluid inlet port 54 and a fluid outlet port 56 formed therein. The inlet port 54 communicates through a conduit 58 with the body of fluid undergoing pumping while the outlet port 56 is connected to the discharge conduit 6%). Suitable oneway valves 62 and 64 are interposed in the conduits 62 and s4 respectively.

interposed between the otherwise communicating cylinder 1t? and casing 52 is a deformable flexible barrier 66 which may take the form of a diaphragm, preferably one of deep cup-shape bellows-like configuration having one end closed as at 68 and the other end open as at 7t? and provided with a series of bellows folds 71 and a laterally extending annular flange 72. The flange 72 is interposed between cooperating flanges 74 and 76 provided on the cylinder 11) and casing 52 respectively and is sealingly clamped therebetween by means of a series of clamping bolt assemblies 73. Disposed partly within the cylinder 10 and partly within the pump chamber casing 52 is a second column 79 of an incompressible liquid, this latter column being interposed between the floating piston 18 and the diaphragm 56. The cylinder 10 may have formed therein an injection opening or port 80 normally closed by a threaded filler plug 82 and by means of which the space existing between the piston 18 and diaphragm 66 may be filled with the liquid of the column 79.

The particular liquid which cooperates to make up the incompressible column 79 will be chosen according to engineering exigencies to accommodate the particular installation with which the pump is associated. Where ordinary non-corrosive and chemically stable fluids are undergoing pumping, the column 79 may be composed of a suitable hydrocarbon oil. However, where the fluid being pumped is of a corrosive nature, or is such that it will react explosively or otherwise with such oil, then it is desirable to select for the column 79 an inert liquid which will present no hazard in the event of rupture of the diaphragm and consequent passage of the pumpage therethrough. For example, where the liquid undergoing pumping is liquid fiourine which reacts explosively inthe presence of ordinary hydrocarbon oils, the column 79 may becomprised of an inert fluid such as a liquid 'flourinated hydrocarbon.

The material employed in the construction of the diaphragm 66 as well as the specific shape thereof Will be chosen appropriately for the service required of it. For ordinary installations the diaphragm 66 may be constructed of an elastomeric material such as rubber or a rubber substitute having a high degree of resilience and. a high coeflicient of elasticity, in which case the diaphragm need not be of deep cup-shape configuration.

and the bellows folds'71 may be dispensed with. Under certain conditions the diaphragm 66 may be in the form of a deformable disk-like membrane the peripheral edges of which are clamped between the flanges 74 and 76 of the casing 52 and cylinder respectively. For corrosive chemical installations the diaphragm 66 is preferably made of a polytetrafluoroethylene polymer which is manufactured as described in Industrial and Engineering Chemistry, volume 318, page 870 of the September, 1946 issue, and is sold by E. I. du Pont de Nemours & Co. under the trade name Teflon. This material is characterized by its chemical inertness which is characteristic from extremely low temperatures up to 572 F. Through thi wide temperature range it resists the attack of corrosive reagents and dissolution by solvents. The diaphragm may be machined from molded Teflon to have a closed end and may assume any of the forms shown and described in the patent to Frank E. Payne et al., Number 2,758,856. Molded Teflon is a tough waxy solid, White to grey in color and it may be held at elevated temperatures over long periods of time.

From the above description it will be seen that Teflon is ideally suited as the diaphragm material for installations involving the pumping of either hot or cold corrosive fluids. Although Teflon has satisfactory tensile strength it lacks the resilience ordinarily required in the usual disk-shape or shallow cup diaphragms so that when it is employed for the diaphragm in the present pump construction it is desirable to resort to a deep cup construction with the cup sides having the series of bellows folds 71 to permit the required linear elongation of the diaphragm with a consequent large displacement of fluid from the pump chamber 50 at each pressure stroke of the driving piston 12. As shown in Figs. 1 and 2, the diaphragm is movable under the impelling influence of the liquid column 79 from a retracted or collapsed position wherein the end wall 68 thereof is remote from the end wall 53 of the pump casing 52 to an extended or expanded position wherein said end wall 68 is in close proximity to the end wall of the casing. It is obvious that the elongation of the diaphragm 66 will serve to expel a quantity of the liquid undergoing pumping from the pump chamber 50 through the one-way valve 64 and that contraction of the diaphragm will draw a replacement for it through the pump chamber 50 through the one-way valve 62 so that upon repeated successive expansional and contractional movements of the diaphragm an intermittent passage of the pumpage from the source of the fluid to a point of discharge will take place in the normal manner of reciprocal type pumps.

As previously stated, the volumetric displacement of fluid undergoing pumping may be varied by regulably wa t p controlling the bleeding of liquid in the column 2.0 through the conduit 44 and bleeder valve 46. 'The valve 46 is of conventional design and includes the usual valve casing 100 which is interposed in the conduit and which is provided with a liquid inlet port 102 and a liquid outlet port 104 both of which ports communicate with a valve chamber'106. The valve chamber 106 is provided with a conical valve seat 108 designed for cooperation with a conical valve element 110 formed at the free end of a valve stem 112. The valve stem 112 is formed with an enlarged threaded portion 114 threadedly received in the central bore 116 of a tubular guide cylinder 118 through which the valve stem 112 projects. The guide cylinder 118 is formed with the usual valve packing assembly 120 and a hand wheel 122 carried at the outer end of the valve stem 112 facilitates manipulation of the latter.

From the above description it will be seen that when the bleeder valve'116 is fully closed so that flowof the liquid of the column 20 through the bleeder conduit 44 is prevented, the full stroke of the driving piston 12 will be effective through the liquid column 20 to effect a full stroke of the floating piston 18 so that this latter piston will move from its retracted position in contact with the abutment 24 to its fully advanced position in contact with the abutment 26. Such full stroke of the floating piston 18 will similarly be effective through the liquid column 79 upon the diaphragm 66 and the latter will become expanded to the fullest extent of which it is capable and, under such conditions, maximum displacement of fluid from the pump chamber 50 will take place. This maximum displacement by the pump construction with the valve 46 fully closed its diagrammatically illustrated in Fig. 3. It is to be noted in connection with this diagrammatic illustration that a disk-type resilient diaphragm capable of linear expansion has been shown in lieu of the bellows type diaphragm of Figs. 1 and 2. It will be appreciated however that irrespective of the particular form of diaphragm employed, the essential features of the invention are at all times preserved. In the illustration of Fig. 3 the position of maximum displacement of the pistons 12 and 18 and of the diaphragm 66 have been illustrated in full lines and the comparatively large illustrated displacement of the diaphragm 66 represents a maximum displacement of fluid from the pump chamber 50.

In Fig. 4 the bleeder valve 46 is shown in a partially open position wherein a predetermined rate of escape of the fluid of the column 20 through the bleeder conduit 44 to the sump (not shown) is permitted. Under such conditions the constant head of the fluid undergoing pumping in the pump chamber 50 will reactthrough the floating piston '18 to build up a back pressure in the liquid column 20 so that a portion of the fluid in this column will be forceably expelled through the bleeder conduit 44 and valve 46, while the liquid of the column 20 which is not expelled due to the restriction of the size of the valve opening leading from the chamber 106 will become effective on the floating piston 18 to move the same forwardly in the cylinder 10 toward its fully advanced position. However, in this instance, the quantity of liquid in'the column 20 being diminished by the escape of a portion of the fluid through the valve 46, will drive the floating piston only a portion of its normal full stroke so that when the driving piston 12 has moved through its full stroke, the floating piston 18 will have moved to some point represented by its dotted line position in Fig. 4. Such partial stroke of the floating piston 18 will cause a correspondingly smaller displacement of the liquid contained in the column 79 so that only partial expansion of the diaphragm '66 will take place. This partial expansion of the diaphragm 66 will result in the displacement of a correspondingly smaller quantity of the fluid or pumpage contained within the pump chamber 50.. It is obvious that the degree of-opening of the valve 46 will control the rate of displacement of the fluid from the pump chamber 50, the greater the valve opening, the lesser the displacement of such fluid and vice versa.

'In Fig.5 anextreme condition has been illustrated wherein the bleeder valve 46 is moved to its fully open position so that the fluid contained within the column 20 may pass more or less freely through the conduit 44 and valve 46 to the sump during the advance stroke of the driving piston 12. With the liquid in the pump chamber 50 maintained at its constant head, the forward stroke of the piston 12 will serve to drive all of the liquid contained within the column 21 except for a small residual amount thereof into the bleeder conduit 44 while the floating piston 18 will not move from its position in engagement with the abutment 24. Thus, as shown in Fig. 3, there will be no displacement of the diaphragm 66 and as a consequence no pumping action will take place in the pump chamber 50.

Inasmuch as the disclosure of the drawings is schematic in its representation, the invention is obviously not to be limited to this representation which is only illustrative of the principles involved. For example, while the pistons 12 and 18 are shown as being reciprocable in a common cylinder, these pistons may be operatively disposed in separate and independent but communicating cylinders and for purposes of claiming herein the separate parts of the cylindrical casing 10 in which the two pistons reciprocate may be regarded as being independent cylinders which are in communication with each other. Likewise, while the diaphragm 66 has been interposed between the fluid in the pump chamber 50 and the inert liquid of the liquid column 7 9, this arrangement being advisable where corrosive or otherwise hazardous pumpage is concerned, the diaphragm 66 may, if desired, be omitted altogether and the floating piston 18 permitted to operate directly upon the pumpage. Additionally, while the displacea'ble member 66 for purposes of illustration has been shown in the form of a bellows-type diaphragm in Figs. 1 and 2 and has been shown as a disk-type diaphragm in Figs. 3, 4 and 5, this displaceable member may, if desired, assume the form of a second floating piston similar to the piston 13 and operable in a cylinder the walls of which define the pump chamber 50. The invention therefore is not to be limited to the disclosure herein as these and other changes may be resorted to without departing from the spirit of the invention. Only insofar as the invention has particularly been pointed out in the accompanying claims is the same so limited.

What I claim is:

1. In a device for pumping fluids, a pump housing defining a chamber provided with valved inlet and outlet conduits, a cylinder connected to said housing adjacent said chamber, a driving plunger mounted for reciprocation said cylinder, a free piston in said cylinder between the chamber and plunger, 21 displaceable barrier interposed between said piston and pump chamber and operable upon displacement in one direction to force fluid from the pump chamber through said outlet conduit and upon displacement in the opposite direction to draw fluid into said pump chamber through said inlet conduit, an incompressible column of actuating liquid effectively interposed between said piston and barrier for translating the movements of said piston in opposite directions into displacements of said barrier, a second column of liquid interposed between the piston and plunger, an inlet port in communication with said second liquid column, a one-way valve in communication with said port and operative to admit liquid to said port when a predetermined minimum degree of pressure exists within said second column, a bleeder port in communication with said second liquid column, and a variable orifice valve in communication with said bleeder port.

2. In a device for pumping fluids, a pump chamber having a wall provided with valved inlet and outlet conduits, a first cylinder in communication with said chamber, a floating piston slidably disposed in said floating piston and diaphragm, a second cylinder in fluid communication with the first cylinder, a driving plunger ,mounted for reciprocation in said second cylinder, means connected to the plunger for reciprocating said plunger, a second incompressible column of actuating liquid interposed between said driving plunger and said floating piston, an abutment in said first cylinder and extending intothe path of movement of the floating piston for limiting the movement thereof in said cylinder during the suction stroke of said plunger, said abutment in combination with the floating piston serving to seal said first cylinder from the second cylinder when the floating piston is in contact with said abutment, an inlet port in communication with said second liquid column, a one-Way valve in communication with said inlet port and operable to admit liquid to said port when a predetermined minimum degree of internal pressure exists within said second column, a bleeder port in communication with said second liquid column and a variable orifice valve in communication with said bleeder port.

3. In a device for pumping corrosive fluids, the combination set forth in claim 2 wherein said first liquid column is comprised of liquid which is chemically .inert with respect to the corrosive fluid undergoing pumping and in which said flexible diaphragm is comprised of a polytetrafluoroethylene polymer.

4. In a device for pumping fluids, a pump casing having one open end, a fluid inlet and a fluid outlet for said casing, an inlet valve and an outlet valve in communication with said fluid inlet and fluid outlet respectively, an elongated cylinder casing having a cylindrical bore extending therethrough in communication at one end with the interior of said pump casing, a flexible diaphragm extending across one end of said cylindrical bore and serving to seal the interior of said pump casing from the interior of said cylindrical bore, a floating piston reciprocable in said bore, a first incompressible column of liquid interposed between said floating piston and said diaphragm, a driving piston mounted for reciprocation in said bore on the side of said floating piston remote from said pump casing, a second incompressible column of liquid interposed between said driving piston and said floating piston, an abutment disposed within said cylindrical casing on the side of said floating piston remote from said pump chamber and against which said floating piston is adapted to bear to limit the movement of the latter in one direction during the suction stroke of said driving piston, an inlet port in communication with said second liquid column,

a one-way valve in communication with said second port and operable to admit liquid to said port when a predetermined minimum degree of internal pressure exists within said second column, a bleeder port in communication with said second liquid column and a variable orifice valve in communication with said bleeder port.

References Cited in the file of this patent UNITED STATES PATENTS 1,301,485 Mueller Apr. 22, 1919 1,650,377 Nixon Nov. 22, 1927 1,696,825 White Dec. 25, 1928 2,041,468 Grubbs May 19, 1936 2,424,595 Warren July 29, 1947 2,496,711 Goddard Feb. 7, 1950 FOREIGN PATENTS 350,817 Great Britain June 18, 1931 637,589 Great Britain May 24, 1950 t 673,850 France Oct. 14, 1929

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