US2420409A - Multiple pressure pump - Google Patents

Description

* May 13, 1947.

E. L. BIVANS ET AL MULTIPLE PRESSURE PUMP Filed May 4, 1945 2 Sheets-Sheet 1 .ln van-bar's Paul K. Been 2B1" J .F'nuJ {4. Mantqum EFL] wwma Patented May 13, 1947 MULTIPLE PRES SURE PUMP Elbert Litton Bivans, Los Angeles, Paul K. Beemer, Inglewood, and Paul H. Montgomery, Los Angeles, Calif., assignors to Preco Incorporated, a corporation of California Application May 4, 1943, Serial No. 485,518

2 Claims. (01. 103-37) The present invention lies in the fleld of Pumps and compressors, and it is particularly concerned with the provision of a pump or compressor adapted to be selectively operated to produce multiple pressures or to pump diflering volumes of fluid. The particular embodiment which is hereinafter described in some detail has been designed with a view to specific use in connection with hydraulic presses, but it will be understood that the invention is not necessarily limited to such particular use, nor to operation upon liquids in distinction from other fluids. The specific illustrative embodiment will, however, be described as for use in connection with a hydraulic press, as typical but not limitative.

Hydraulic presses of various types and in various uses are commonly operated to move the plunger at relatively high velocity and with a low operating pressure until the plunger brings up against the work. After contacting the work, the plunger is then operated by a smaller volume of fluid at higher pressure. The present invention provides a simple form of pump mechanism which may be selectively and automatically operated to deliver either a large volume of fluid at relatively low pressure, or a small volume of fluid at relatively high pressure.

The general nature of the invention will be most readily understood after consideration of the typical embodiments described in the following specifications and illustrated in the accompanymg drawings in which Figs. 1 and 2 are vertical sections illustrating one form of pump embodying the invention, Fig. 1 illustrating operation for delivery of fluid at low pressure and Fig. 2 illustrating operation for delivery of fluid at high pressure. I

Fig. 3 is a section illustrating the essential parts of a modified form of pump mechanism, illustrating its operation for delivery of fluid at low pressure, 1

Fig. 4 is a similar view illustrating the operation of the pump of Fig. 3 for delivery of fluid at high pressure, and

Figs. 5 and 6 are diagrammatic sections 11-- lustrating further modifications.

One of the characteristics of our pump resides in its use of two or more movable fluid displace ment members of different eflective areas, both acting upon the same pressure fluid. These displacement members may, within the scope of our invention, be of any suitable number, and of any suitable types, such as for instance pistons, diaphragms or bellows. In the following described illustrative embodiment, the displacement members are shown as reciprocating plungers, and are shown as two in number.

The movable displacement members are opermechanism under contro1 of the back pressures which are exerted on the displacement members. In one form of the apparatus illustrated (Figs. 1 and 2) that selective operation is semi-automatic, while in other forms (Figs. 3 to 6) the selective operation is wholly automatic.

We have mentioned the fact that, within the scope of the invention, the fluid displacement members may be of any suitable known type. They may also have any suitable physical relation to each other so long as they both act upon, and are reacted upon by, the same pressure fluids. In our illustrative embodiments of the invention which utilize two displacement plungers, we prefer to adopt the simple arrangement of locating a diametrally smaller one of two displacement plungers within the larger one, in such a manner that the actuating mechanism, which is here connected to the smaller of the plungers, becomes the actuating mechanism for both the plungers when both are operating to produce a relatively low pressure, and becomes the actuating mechanism for the smaller plunger alone when it is operating to produce a relatively high pressure by reciprocation within a cylinder formed in the larger plunger.

Referring now more particularly to the form of pump shown in Figs. 1 and 2, the main pump cylinder II) has a large plunger II which may preferably be provided with a light spring l3 for urging it to its outermost position against a stop shoulder l2. Plunger II is the low pressure plunger of relatively large area. The smaller high pressure'plunger l4 operates in cylinder bore 15 in the larger low pressure plunger H.

In the form of apparatus shown in Figs. 1 and 2 an inwardl opening check valve It allows inflow of liquid through port l6 into cylinder l0 below the plungers; and an outwardly opening check valve I8 allows outward flow of the pressure fluid from port [1, through output tube l9 to the press or other apparatus where the pressure is used. Figs. 1 and 2 indicate that the pump mechanism may be mounted in a fluid reservoir 2|], from which fluid, such as oil,- is taken directly into inlet valve It. In such a design, the element shown at 2| may be the plunger cylinder of the hydraulic press to which the output tube i9 leads.'

II} the form of apparatus shown in Fig. 1, the

plunger l I.

outer end of high pressure plunger l4 isconnected by link 28 to an oscillatory arm 26 on an operat-.

'ing shaft 21, which shaft is here shown as being manually operated through an oscillatory handle 28. The smaller plunger is shown as having a shouldered head 28 at its upper end, this shouldered head seating on the upper end of larger plunger II when the two plungers are in the relation to each other which is shown in F As will be understood when the following described mode of operation is considered, the upper shouldered end 01' smaller plunger .may be considered as a part of the operating linkage or mechanism .ior the smaller plunger. .Consequently it may either be said that, in the relative positions 01' the plungers shown in Fig. 1, the operating mechanism of the smaller plunger has operating engagement with the larger plunger, or that the smaller plunger itself has such engagement with the larger plunger.

In operating at low pressure the two plungers maintain the relative positions shown in Fig. 1.

That flgure shows the whole mechanism with the the manner just described involves the application ot-a limited force to that plunger which is directly actuated; and the same operation may be obtained by mechanical application of a limited force, acting through the full stroke distance.

Such an arrangement is illustrated diagrammatically in Fig. 5, where an oscillating arm 280 may It will be understood that return spring i8 is merely a convenient means for moving larger plunger l I on its return stroke. When the pump is operating upon substantially non-expansive liquids there is no expansive pressure in the pump twoplungers at the upper or beginning end 01' the low pressure stroke. Downward movement of operating handle '28 from the position shown in full lines moves both plungers to the lower ends of their strokes. 1 The effective displacementarea is the aggregate area or thetwo plungers. A

. comparatively large volume or fluid, at relatively low pressure, is thus forced out of the pump cylinder ,to the hydraulic press, and continued reciprocation of handle 28 between the positions v shown in full and dotted lines in Fig. 1 will move the press plunger comparatively rapidly. 'As soon as the press plunger comes up againts its work; greater pressure per unit area is necessary to move it. The greater reaction pressure against the large aggr ate area of the two plungers is immediately felt by the operator, who then moves handle 28 up to a higher position, as shown in Fig. 2, lifting the small high pressure plunger l4 to the relative position shown in that flgure. The

' larger plunger ll being now supported by the higher fluid pressure which is necessary to move the press plunger, the operator now oscillates handle 28 and high pressure plunger ll between such an upper position as shown in Fig. 2 and a lower P ition where head 28 comes against larger Continued reciprocation of the smaller high pressure plunger causes the pumping of a relatively small amount of pressure fluid at relatively higher pressure. The relations of volumes and pressures in the two selective opera-.- tions oi the pump will of course be determined by the relative areas and strokes of the two displacement plungers, and they may be designed to provide any relative pressures and volumes which are desired.

In another mode of operation the stroke of smaller plunger l4 may always start from the uppermostposition shown in Fig.2. The first part of the downward stroke will bring plunger I4 to the position, shown in Fig. l, and a small volume of fluid will have been displaced against whatever pressure exists at the time. If the fluid pressure is low enough that the force applied to handle 28 can move larger plunger I I down, then the stroke may go on through the downward movement of the larger plunger. Whenever the pressure builds unto the point where the applied force will, not move the larger plunger down below the position of Fig. 1, then the stroke of the smaller plunger is automatically stopped inthe position of that figure. Manual operation in cylinder which can act return the larger plunger to the top of its stroke. If the pump be applied to expansive fluids, the return spring is not necessary; but when applied to non-expansive fluids the spring 'iorms a simple substitute for a positive mechanical means of moving the larger displacement plunger on its return stroke. Figs. 3 and 4 illustrate the essentials of anothertypical pump design which is adapted to be entirely automatic in its operation, controlled solely by the reaction pressures on the fluids which are being pumped. In these flgures the physical design is also somewhat dliierent from that shown in Figs. 1 and 2. The cylinder body 85, containing cylinder 88, is closed at its lower end by a plug 81 which contains the valve controlled inlet port 88 and outlet port 88, in which the check valves 48 and 4| are located.

The larger plunger 48 has shoulder 44 which brings up against a cylinder shoulder 48 to limit the upward or outward stroke of the plunger.

- The'smaller plunger 46, reciprocating in cylinder bore 41 in the larger plunger, is supported by a spring 48 with reference to the larger plunger. That spring 4'8 may be placed in any suitable physical position relative to the two plungers (for instance, in the design shown in Fig. 1 such a spring might be placed between head 28 on the smaller plunger and upper end of the larger plunger) But in Figs. 3 and 4 spring 48 is preferably shown as housed within larger plunger 48, with its lower end resting upon a suitable seat ring 48 in the larger plunger, and with the toot of 'the smaller plunger 48 resting upon the upper end of the spring. Such an arrangement will cause the larger-plunger to be pressed downwardly by a force equal to the strength of spring 48, whenever the smaller plunger is moved downwardly. And spring 48 is selected to be of such strength as to transmit to the larger plunger a downward force which is equal to the total low pressure on the larger plunger, plus such incidental pressures as that which is exerted by the return spring 50, and also plus the pressure necessary to overcome the inertia forces of the parts of the system moved by spring 48. At low operating speeds this last item may be negligible; at high speeds it is taken into account.

Return spring 58 is here shown as conveniently bearing at its upper end against the same seat ring 48 which roots the spring 48. In effect however spring 58 exerts itsupward pressure against larger plunger 43 to move that plunger upwardly on its return stroke, because spring 48 is considerably stronger than spring 50.

The design shown in Figs. 3 and 4 may be operated manually by such an operating mechanism as shown in Figs, 1 and 2. Figs. 3 and 4 show an operating mechanism which may either be manually driven or power driven. As shown in those figures an eccentric ring 55 is provided on an operating shaft 56. The operating shaft 56 may either be oscillated or continuously rotated, manually or by power. The eccentric ring 55 may bear directly upon the upper end of small plunger 48.

Fig, 3 shows the relative positions of the parts at the upper end of each stroke. If the fluid pressure in cylinder 36 is below that for which spring 48 is selected, the two plungers will move down as a, unit, to expel a full volume of fluid at relatively low pressure: and reciprocation of the two plungers will continue as long as the fluid pressure is below that which corresponds to the strength of spring 48. However, as soon as the fluid pressure for any reason rises above the specified pressure, then the fluid pressure will hold larger plunger 43 at the upper end of its stroke, while smaller plunger 46 moves downward to the relative position shown in Fig. 4, compressing spring 48. Continued operation will then reciprocate smaller plunger 46 between the relative positions shown in Figs, 4 and 3, with the effect of pumping out a relatively small volume of fluid at the desired relative high pressure. Operation in the high pressure range, continuously compressing and expanding spring 48 does not cause waste of power as the spring upon release returns substantially all its energy of compression to the system.

We have said that spring 50 may be inserted at any suitable place in the drive for the larger or secondary plunger; ior instance, between that plunger and the driving elements of the smaller or primary plunger. Fig. 6 shows such an arrangement diagrammatically, where the spring 50a is inserted between plunger II and head 29a of plunger Hi. This arrangement has been spoken of before as the equivalent of spring 48 of Figs. 3 and 4. In any of the arrangements which have been described, the secondarily driven displacement member (the larger plunger here) can be said to be driven from the drive of the primarily driven member (the smaller plunger here) although in some cases (e. g., Figs, 3 and 4) the drive is specifically through the primarily driven displacement member.

Some general remarks in final summary may be helpful to an understanding of the invention typified by the described embodiments. Broadly speaking, the two plungers may be regarded as two movable fluid displacement members, one primarily driven and the other secondarily driven from the primary displacement member or from its drive means. In the form of Figs. 1 and 2 the selective action which determines whether or not the secondary member is driven, or whether the primary member alone is driven, depends either upon volitional change of stroke of the primary driving means, or upon the fact that a limited force (for instance, manual) is applied to the primary drive and that the stroke of that drive and of the primary displacement member is automatically changed when the back pressure against the secondary member exceeds the applied force. In these forms of the pump the pressures per unit area which can be raised (assuming a limited force to be applied) depend entirely on the displacement areas oi' the displacement members.

In the form illustrated in Fig. 5 the selective action is also automatic .in the same manner as mentioned just above, the limitation of applied driving force in the primary drive being supplied by'spring 30. The same observations apply to this form as to the limited-force mode or operation mentioned Just above.

In the forms illustrated in Figs. 3, 4 and 6 the stroke of the primary drive and primary displacement member is not changed. The automatic selective action in these forms of the pump depends upon the fact that the drive of the secondary displacement member-from the primary unit-includes a limited force transmitting element ( spring 50 or 50a). In these forms. the unit pressure which can be raised by the secondary displacement member is determined by the total displacement area and the strength of the force transmitting element, regardless of how much power or force may be initially applied to the drive. But the unit pressure which can be raised by the primary displacement member is limited only by the amount or Iorce which is applied to it; the two pressures are not necessarily in a ratio determined by the areas of the displacement members.

The area ratios of the two displacement members need no be unequal, and the area of the primary member need not be smaller than that of the secondary; with any ratio the volumetric displacement of the two members together is of course greater than that of the primary alone, and only for volumetric ratios greater than two to one will the displacement area of the primary member be less than that of the secondary.

We use the terms primary and secondary, as applied to the displacement members, in the sense that the primary member is the one which is directly driven and the secondary is the one which is selectively driven with the primary.

We claim:

1. In pumps of the type which include primary and secondary reciprocable fluid displacement members each exposed to and acting upon the same pressure fluid between inlet and outlet valves and having inward fluid displacement strokes and outward fluid induction strokes, the primary member being reciprocable independently of the secondary; a selective operating system for the displacement members which includes, a fixed stop which forms a terminal limit to the outward stroke of the secondary member and defines a position from which that member starts its inward stroke, a spring acting on the secondary member tending to move it outward to a position against the limit stop, the secondary member being also held against the limit stop by the fluid pressure on that member, and driving mechanism for the two members including, means for reciprocating the primary member through either of two spatially separated reciprocative move-- ments. and a shoulder associated with the primary reciprocating means and adapted to drivingly engage the secondary member on inward movement only of the primary member to positively drive the secondary member inwardly, the primary member being otherwise free of connection with the secondary member and adapted to be reciprocated independently thereof, and the secondary member being at all times free to move inwardly from its outer stopped position excepting only for the spring pressure and the fluid pressure on it.

7 V 2. A selective operating system as specified claim 1, and in which the primary reciprocating means includes a yielding element adapted t 7 fmg under a predetermined pressure drivinz the 1862823 primary member inwardly. 5 zgjogo ELBERT m'rroN'BIvANs. 3222:: PAUL K. IBEEMER. 1829'451 PAUL H. MONTGOMERY. 10 5 REFERENCES CITED The following references are or record in the N m r tile 01" this patent:

8 UNITED sum mum's Name I Date Baker Mar. 3, 1031 Holveck June 14, 1982 Lindsay May 1, 1860 Stucky Oct. 15, 1878 McNab Nov. 11, 1930 I McNab Oct. 27. 19:41 Ten Eyck Mar. 1, 1901 FOREIGN PATENTS Country Date Great Britain 1885

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