US2591491A - Variable delivery positive displacement pump - Google Patents

Description

April 1, 1952 R. AMSLER 2,591,491

VARIABLE DELIVERY POSITIVE DISPLACEMENT PUMP Filed Jan. 23,. 1948 Patented Apr. 1, 1952 VARIABLE DELIVERY POSITIVE DISPLACE- MENT PUMP Rudolf Amsler, Neuhausen on Itheinfall, Switzerland, assignor to Schweizerische Industrie- Gesellschaft, Neuhausen on Rheinfall, Switzerland Application January 28, 1943, Serial No. 4,016 In Switzerland March 5, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires March 5, 1965 14 Claims.

The invention relates to a pump for delivering liquid media, and particularly to a pump in which the quantity of liquid delivered is variable at will between no delivery and maximum pump output.

Pumps are required for many installations in which the pump discharge must be variable within, wide limits with the pump running at a constant driven speed and maintaining a constant discharge pressure.

For this purpose only positive displacement pumps can be used, since the above-mentioned conditions cannot be fulfilled with centrifugal pumps. Where the regulating ranges are large, such as are often demanded, the known positive displacement pumps are not economical, since their efficiency diminishes greatly with diminishing delivery.

In the present invention the pump discharge may be varied, step by step within the desired range, without any change in the delivery pressure or driving speed. In addition, the pump provided by the present invention has the essential advantage that its efficiency remains substantially constant over nearly the entire regulating range. Any drop in efiiciency occurs only when the pump is delivering exceedingly small quantities.

According to the invention the pump consists of a series of positive displacement pumps having a common drie and being connected in parallel for delivering liquid into a common delivery chamber, a control member being provided for establishing communication between the common delivery chamber and the number of pumps required for supplying the momentarily desired quantity of liquid, while simultaneously establishing communication between the delivery and suction sides of the remaining pumps.

The invention is illustrated in the accompanying drawings, in which:

Fig. l is a longitudinal section through one embodiment of the invention,

Fig. 2 a section on the line A-A of 1 through the delivery chamber,

Fig. 3 an end view in the direction of the arrow Fig. d a section on the line B-B of 1 through the suction chamber,

Figs. 5 and 6 developments of the surfaces of the control piston in two different positions.

Fig. 7 a longitudinal section through a second embodiment of the pump,

Fig. 8 a section on the line C-C of 7 through the delivery chamber, and

Fig. 9 a development of the surfaces of the control piston for the pump illustrated in Fig. 7

The casing l consists, of a cylindrical hollow body 2, a flange 3 and a projecting delivery duct 4. The hollow cylinder 2 is closed at both ends, at one end by a cover 5 and at the other by a closing plate 6. The duct 4 communicates with the hollow cylinder 2 through a number of ports I. In the casing I live screw pumps 3 of known type are arranged parallel to. the axis of the casing. The casings of the separate pumps 8 are inserted at one end in bores Spf the flange 3 and at the other end in bores H) in the cover 5. Cover 5 and flange 3 are secured in spaced rela tion to one another after insertion of the pumps 8. Each casing of the pumps 8 communicates with a cylindrical hollow space H in the flange 3 at its delivery end and with a corresponding hollow space I 2 in the cover 5 at its suction end. In the hollow cylinder 2 of the casing I a piston i3 is movably arranged, which divides the interior of the casing I into two hollow spaces, the delivery chamber l4 and the suction chamber E5. The control piston I3 is rigidly connected to a rod l6 which projects through the bore ll in the closing plate 6. The rod 16 carries also, rigidly connected to it, a balancing piston [8, which with the closing plate 6 defines a further space, the balancing space [9, in the interior of the casing I. The control piston I3 is so shaped that its cylindrical surfaces in development (Figs. 5 and .6) appear as a narrow step-shaped strip .or edge 20, which, contacts the inner wall of the casing l, to render the delivery chamber l4 water-tight against the suction chamber l5. Suitable means (not shown) are provided exteriorly of the casing l for moving the rod l6 so as to vary the position of the control piston 13 and the balancing piston IS with respect to the casing l and for adjustably fixing the pistons in the desired position. The rod It has a transverse bore 2| and a longitudinal bore 22 which establish communi'- cation between suction chamber [5 and balanc ing space IS. In the wall of the casing l are passages 23 which connect the common delivery chamber [4 to the delivery chambers 'II of the separate pumps 8. The suction chambers I! of the pumps 8 are connected in a similar manner with the common suction chamber I5 through passages 24, which are provided in the wall of the cover 5. The cover 5 is provided with an in let or suction duct 39 which terminates in the suction space l5. The driving shafts 25 for the separate pumps 8 are rotatably positioned in bores 25 in the cover 5. A toothed pinion 21 is secured to the outer end of each shaft and engages with a spur gear 28 rigidly connected to the main driving shaft 29, which rotatably positioned in an axial extension of the casing and in a bore 30 in the cover 5. The shaft 29 is driven by any desired means at a constant speed. Delivery chamber I I and suction chamber I2 of each of the separate pumps 8 are connected to each other by a passage 3! provided in the casing of each pump. A spring-loaded adjustable safety valve 32 of usual construction is positioned within the passage 3I and normally blocks the passage.

The rotating movement of the shaft 29 is transmitted through the spur gear 28 and the pinions illustrates, in development, the conditions which occur after shutting down two pumps. The passages 23a and 23b communicate with the suction chamber I5, while the other passages communicate with the delivery chamber I4. Here, the quantity delivered is three-fifths of the maxi 1 mum quantity. The control piston I3 may be so 21 to the driving shafts 25 of the separate pumps 8. The pumps draw liquid from the suction chamber I5 through the passages 24 and the hollow spaces I2 and deliver it into the corresponding delivery chambers II. The liquid then flows through the passages 23 in the casing'l into the common delivery chamber I4. From the delivery chamber I I the fluid flows through the ports 1 and the delivery duct 5 to a point of use. In Fig. 1 the control piston is set for maximum delivery. All connecting passages 23 from the delivery chambers II of the separate pumps 8 open into the central delivery chamber I4. In Fig. 5, .above the development of the surfaces of the control piston I3,'the development of the cylinder 2 is correspondingly indicated (by the passages 23 shown in dotted lines) All passages 23 lie below the boundary between delivery and suction chambers. If the demand for liquid diminishes, the rod I6 is manipulated and the control piston I3 is moved towards the left in the cylinder 2, for example, until it is in the position I3. The displacement of the rod I6 and the piston I3 is accomplished without effort, since the entire system (rod, control piston, balancing piston) is relieved of pressure due to the connection between the suction chamber I5 and balancing space I9. piston I3, the passage 23a is first of all gradually covered by the ,lowest control edge of the strip 28 of the control piston. The quantity of liquid flowing from the delivery chamber II of the respective pump 8 into the common delivery chamber I5 is correspondingly diminished. The remaining amount of the constant delivery of this pump then flows through passage 3I back into the suction chamber I2, after the safety valve has been opened due to an increase in pressure caused by the throttling. When the sealing strip 28 has covered the passage 23a entirely, the entire output of the respective pump 8 is delivered through passage 3I into the suction chamber- I2. From this position onwards, the lowest pump 8 is completely cut out and the quantity of delivery of the series of pumps is reduced, in'the embodiment shown, by one-.fifth of its maximum value. By further moving the control piston I3 the inner control edge of the sealing strip 20 gradually frees the passage 23a so as to establish communication with the suction chamber I5. The corresponding pump 8 from that moment delivers directly into the suction chamber I5. The power required for driving this pump, which has to overcome only avery slight resistance to flow, falls to approximately zero. The drop in efiiciency of the series or pumps is consequently insignificant in consequence of the regulation effected. By further displacement of the control piston I3, other pumps 8 may be successively cut out and connected to the suction chamber I5. Fig. 6

displaced that all pumps 8 will deliver into the suction space I5, and the quantity delivered by the series of pumps consequently reaches the zero value. The successive cutting-out of the separate pumps 8 and the connecting of them to the suction chamber i5 could be carried out in any desired manner. With a suitable arrangement of the passages and suitable shaping of the piston I3, it would for instance be possible to effect regulation by rotation of the piston.

In the positions of the control piston I3, wherein one of the passages 23 is partly or wholely covered by the sealing strip 28 of the surfaces of the piston, there will be an appreciable drop in the overall efficiency, since on. the one hand the total quantity delivered is reduced, but the power required for the series of pumps increases, since one of the pumps has then to deliver its full delivery quantity, or the main part of it, against a pressure determined by the setting of the safety valve, and this pressure is greater than the pressure of the pump. The efficiency will therefore only remain at the desired value if none of the passages 23 is fully covered by the control surface of the piston I3. The actuating 7 equipment for the rod I6 must be designed in Upon movement of the control 7 such a way that the piston can only be moved to positions where the separate pumps deliver entirely into the delivery chamber or entirely into the suction chamber. of the number of steps, to which the number of separate pumps 8 built into the pump corresponds, it will be possible to comply with most of the conditions occurring in practice.

Nevertheless there are cases where it is necessary to provide a continuous regulation with'good efiiciency, of the quantity of liquid delivered. The pump according to the invention may be made to comply with these requirements by a suitable design of the control edge or surfaces of the control piston.

In Figs. '7, 8 and 9 a second embodiment of the pump is illustrated diagrammatically.

The characteristic of this embodiment is the design of the control piston 33, the sealing strip 34 of which has control edges that are smoothly curved as shown in Fig. 9. The control piston is positively displaced by rotation as well as by axial movement. The passages 35 connecting the delivery chamber II of the separate pumps 8 to the common delivery chamber I4, are arranged in echelon in the direction of the piston axis. Generally the construction of the remainder of the pump is in principle identical with that of the first-described embodiment of the invention. In the pump illustrated in Figs. 7, 8 and 9, three separate pumps 8 have been provided.

The rod 36 projecting from the casing I is tubular and receives and is connected to the driving shaft 31, for rotation therewith, by a, key 38. The rod 36 is formed integrally with the control piston 33 so that rotary movement of the shaft is transmitted to the control piston 33. The keyed connection of the shaft and rod permits relative axial displacement of the rod 35 and the piston 33. In Fig. 9 the development of the surfaces of the control piston 33 is illustrated. The passages in the cylinder jacket are By a corresponding choice shown in dotted lines. With the piston positioned as illustrated in Fig. 7, the, outlet passages 35 of all pumps 8 open with their full cross-section into the common delivery chamber I4 for maximum delivery. If the control piston 35 is displaced axially, the passage 35a situated nearest the control piston is passed over by the control edge. During rotation of the control piston the corresponding passage will, for a time (see passage 35a. in Fig. 9), communicate with the delivery chamber, and for a time with the suction chamber. The passage will never be entirely uncovered. Consequently there will be no undesirable drop in efilciency. The quantity delivered by the. respective pump 8 to the common delivery chamber M will fluctuate in the course of rotation of the piston 33. Inconsequence of the rapidity with which the control piston 33 is. rotated, however, this fluctuation is not perceptible at the point of use. If the piston is dis.- placed further, the pump whose discharge passage lies in the path of the sealing strip 34, will, during each rotation of the, piston, communicate with the suction chamber for an increased portion of the revolution and consequently the quantity of liquid delivered will be decreased. The total quantity delivered continually diminishes with increasing axial displacement of the piston 33, until the piston is in the dotted line position 33, at which position all pumps communicate continuously with the suction chamber and the quantity delivered has therefore reached the zero value. The, position of the passages 35"" relative, to the control edge of the control piston, is indicated in Fig. 9.

It is obvious that other mechanical arrangements. can be made to. utilize the effect of my invention. I' do not, therefore, desire to be limited to the constructions described, but to the constructions falling within the scope of the following claims.

Having now described my invention, what I claim as new and desire to protect by Letters Patent is as follows:

1. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel and mounted on said casing in a circle about the casing axis, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps. in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump. inlet, a control piston in said casing adjacent said opening separating said delivery chamber and said suction chamber, means for axially displacing said piston in said casing, said piston having a control. surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication between the outlets of the remaining pumps and said suction chamber, and drive means for rotating said control piston.

2. A pump having a wide regulating range for delivering a variable. quantity of liquid, comprising, a casing, a. plurality of positive displacement pumps connected in parallel and mounted on said casing in a circle: about the casing axis,v a

in development common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings separating said delivery chamber and said suction chamber, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish, communication between the outlets of the remaining pumps and said suction chamber. and a drive shaft rotating at a constant speed for actuating said pumps, said control piston being fixedly mounted on said shaft for rotation thereby.

3. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel and mounted on said casing in a circle about the casing axis, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings separating said delivery chamber and said suction chamber, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication between the outlets of the remaining pumps and said suction chamber, a balancing piston in said casing at one end of said delivery chamber forming a balancing chamber, and a rod extending axially into said casing, said control piston and said balancing piston being fixedly secured to said rod at spaced points.

4. A, pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel and mounted on said casing in a circle about the casing axis, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings separating said delivery chamber and said suction chamber, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of, said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to. establish communication between the. outlets of the remaining pumps and said suction chamber, a balancing piston in said casing at one end of said delivery chamber forming a balancing chamber, and a rod extending axially into said casing, said control piston and said balancing piston being fixedly secured to said rod at spaced points, means being provided for establishing communication between said balancing chamber and said suction chamber.

5. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, acasing, a plurality of positive displacement pumps connected in parallel and mounted on said casing in a circle about the casing axis, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings separating said delivery chamber and said suction chamber, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication between the outlets of' the remaining pumps and said suction chamber.

6. A pump having a wide regulating range for delivering a variable quantity of liquid, com'- prising a casing, a plurality of positive displacement pumps connected in parallel and mounted on said casing in a circle about the casing axis, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a' plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means'establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said'delivery chamber, said control surface being adapted to establish communication between the outlets of the remaining pumps and said suction chamber.

'7. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings, means for axially displacing said piston in saidccasing, said piston having a'control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication-be- 8' tween the. outlets of the remaining pumps and said suction chamber. I

8. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising a plurality of equal displacement positive displacement pumps, means for driving =said pumps at a constant speed, a suction chamber, a delivery chamber, means establishing communication between each pump inlet and said suction chamber, means establishing communication between each pump outlet and said delivery chamber, and a'control device for rendering said means establishing communication between each pump outlet and said delivery chamber ineffective individually as to each pump and simultaneously establishing communication between the outlet and the inlet of the individual pump.

9. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings, means for axially displacing said piston in said casing, said piston having'a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such Of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication between the outlets of theremaining pumps and said suction chamber, said openings being formed in said casing in a plane at right angle to the axisthereof.

10. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a, plurality of positive displacement pumps connected in parallel, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing,ca plurality of openings in said casing in said delivery chamber establishing com-' munication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casingadjacent said openings, means for axially displacing said piston in said casing, said piston having a'control surface on its peripheryat one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication between the outlets of theremaining pumps and said suction chamber, said control surface being formed in a step shape, the number of steps corresponding to the number of pumps.

11. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel, a common suction chamber for said pumps in said casing, a common delivery chamber for said umps in said casing, a plurality of openings in said casing in said delivery chamber establishing communicationbetween eachpump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication between the outlets of the remaining pumps and said suction chamber, said openings being arranged in echelon in the direction of the casing axis.

12. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of v said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication between the outlets of the remaining pumps and said suction chamber, said control surface being in the form of a smooth curve having at least one peak.

13. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel and mounted on said casing in a circle about the casing axis,

a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings separating said delivery chamber and said suction chamber, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demandand said delivery chamber, said control surface being adapted to establish communication between the outlets of the remaining pumps and said suction chamber, said openings being formed in said casing in a plane at right angles to the axisof the casing, said control surface being formed in a step shape, the number of steps corresponding to the number of pumps and openings.

14. A pump having a wide regulating range for delivering a variable quantity of liquid, comprising, a casing, a plurality of positive displacement pumps connected in parallel and mounted on said casing in a circle about the casing axis, a common suction chamber for said pumps in said casing, a common delivery chamber for said pumps in said casing, a plurality of openings in said casing in said delivery chamber establishing communication between each pump outlet and said delivery chamber, means establishing communication between said suction chamber and each pump inlet, a control piston in said casing adjacent said openings separating said delivery chamber and said suction chamber, means for axially displacing said piston in said casing, said piston having a control surface on its periphery at one edge thereof for controlling said openings to establish communication between the outlets of such of said pumps as will satisfy the delivery demand and said delivery chamber, said control surface being adapted to establish communication between the outlets of the remaining pumps and said suctionchamber, said openings being arranged in echelon in the direction of the casing axis, said control surface being in the form of a smooth curve having at least one peak, and drive means for rotating said control piston.

RUDOLF AMSLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,990,263 Benedek Feb. 5, 1935 2,114,076 Golz Apr. 12, 1938 2,272,771 Hawley Feb. 10, 1942 2,276,895 Vosseler et al Mar. 17, 1942 2,370,526 Doran Feb. 27, 1945 2,382,701 Egersdorfer Aug. 14, 1945

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