ZA201101567B - A reciprocating pump - Google Patents

Description

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A RECIPROCATING PUMP

FIELD OF THE INVENTION

This invention relates to pumps and, in particular, to pumps of the reciprocating type.

BACKGROUND TO THE INVENTION

A reciprocating type pump is a positive displacement pump that causes a fluid to move by trapping a fixed amount of the fluid before forcing or displacing the trapped fluid into a discharge conduit or desired region. Movement of the fluid is achieved by means of a reciprocating device such as a piston or diaphragm that is received within a pump body and is operable to perform reciprocating motion within the body to displace the fluid. In pumps of the piston type, a piston is received within a cylindrical cavity and is operable to reciprocate within the cavity, the cavity and the piston together defining an operating chamber into, and from which, the fluid to be pumped is received and expelled by means, respectively, of inlet and outlet valves associated with an inlet and outlet of the chamber.

The piston may be driven in a number of ways, but in one common embodiment of a reciprocating pump, the piston is driven by a driving fluid. In this instance, the pump has a drive chamber and an operating or pump chamber, each of the chambers having a reciprocating device, such a piston, the pistons of the two chambers being operatively coupled. The driving piston in the drive chamber is caused to reciprocate under the action of the driving fluid. This causes the operating piston in the operating chamber to reciprocate, thereby pumping the fluid desired to be pumped. Generally, the two chambers are not in fluid communication with each other.

Generally, inlet and outlet valves of varying types and in varying combinations are mounted, respectively, in an inlet and outlet of the drive chamber. During a suction stroke the drive piston retracts and the inlet valve opens allowing fluid into the drive chamber. During a drive stroke the piston urges fluid through the outlet valve into an outlet conduit. Both the inlet and outlet valves are generally one way check valves.

Similarly, the fluid to be pumped is drawn into and expelled from the pump chamber via an inlet and an outlet controlled by check valves. It will be appreciated that a single port may provide both an inlet and outlet to a pump chambers, provided that a suitable valve system is mounted at the port to control the fluid flow to and from the relevant chamber.

In one embodiment of such a reciprocating pump, the drive and operating cylinder chambers are arranged end to end and co-axially. In some instances, for example where the diameter of the operating chamber cylinder is smaller than that of the drive chamber cylinder, it is not convenient that the two cylinders comprise an integral one piece unit, and they comprise separate cylinder bodies that are assembled prior to use. In any event, the pump generally includes end plates or flanges at the free ends of the cylinders and the assembly, comprising the cylinder body or bodies and the end plates are secured by means of external nuts, bolts, and/or tie-rods or by threaded connection of the cylinders to end covers, so as to hold the pump, as a unit, together. This connection thus provides axial stability to the pump.

If external nuts, bolts, and tie-rods are used to connect the drive and pump cylinders, the diameter of the pump is increased, since end flanges must have greater diameters than their associated chamber cylinders. On the other hand, if the end flanges are threadedly

EA Fe A _+20117 01364 connected to the ends of the chamber cylinders, then the orientation of the inlet and/or outlet ports on the end flanges is difficult to define.

If the pressure ratio of a pumped medium is high relative to a drive medium, such as, for example, where compressed air is used to pump liquids at high pressure, then the pump cylinder, which is anchored to an end flange of the drive cylinder, causes significant bending loads in the drive cylinder flanges, tending to cause them to bow, as the load is applied to an unsupported area, which is commonly of greater diameter than the diameter of the bore of the drive cylinder.

OBJECT OF THE INVENTION

It is thus an objective of this invention to provide a reciprocating pump that addresses the stress and size constraints of present pumps of this type.

SUMMARY OF THE INVENTION

According to the invention there is provided a reciprocating pump including a hollow pump body defining a cylindrical bore and being closed at opposed ends by first and end plates, at least one of which is removable, the pump body and the end plates defining a chamber into which is received a piston operable for reciprocating motion; and fastening means extending axially within the cylindrical bore between the end plates and operable to releasably secure the at least one removable end plate to the pump body.

In this specification, the phrase “end plate” is to be given a wide interpretation and includes a formation of any shape that closes off an open end of a cylinder.

In one embodiment of the invention, the pump is a two-chambered pump, the pump body being a first pump body and the chamber being a drive chamber; the pump includes a second hollow pump body defining a cylindrical bore and :

_ extending co-axially from the second, intermediate end plate of the first pump body and being closed at an opposed end thereof by a third end plate, the second pump body and : the second and third end plates defining an operating chamber into which is received an operating piston operable for reciprocating motion, the operating piston being operably connected with the piston the drive chamber; and the fastening means extend axially from the third end plate to the first end plate to releasably secure the assembled end plates and pump bodies.

Then the drive piston and the operating piston may be connected by way of a drive shaft which is sealingly received through an aperture in the second end plate.

The two pump bodies and the intermediate end plate may be integrally formed. Instead, they may comprise separate components.

A discharge outlet may be defined in the third end cover. It will be appreciated that further inlets and outlets may be provided in the remaining end plates and/or in the body walls of the pump.

In one embodiment of the invention, the second body has a diameter smaller than that of the first body and the bore of the second body is smaller than that of the first body.

The fastening means may comprise a plurality of tie rods extending between the first and third end plates externally of the second pump body and internally of the first pump body. Then, each of the plurality of tie rods may be sealingly received through a respective aperture defined in the drive piston. Further, opposed ends of each of the plurality of tie rods may be sealing received through a respective aperture defined the first and third end plates.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example, with reference to the accompanying non-limiting diagrammatic drawings. In the drawings:

Figure 1 shows a sectional side view of a prior art reciprocating pump;

Figure 2 shows a sectional side view of a reciprocating pump in accordance with the invention;

Figure 3 shows an exploded view of the reciprocating pump of Figure 2; and

Figure 4 shows a perspective view of the reciprocating pump of Figure 2.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings, like numerals generally indicate like components, unless otherwise indicated.

In Figure 1 a typical reciprocating positive displacement two chamber pump (1) is shown. The operation of such a pump is well known and will be described only briefly herein.

The pump (1) has a pair of cylinders (2) and (3), respectively referred to as the drive and operating cylinders, which are closed at their ends by first and third end flanges (4) and (5), respectively, located on opposing sides of an intermediate second end flange (6) to define a drive chamber (7) and an operating or pump chamber (8). A piston (9) is operable to reciprocate within the drive chamber (7). A second piston (10) is operatively housed within the operating chamber (8) and is adapted to reciprocate therein. The piston (10) is connected by means of a connecting rod (11) to the piston (9) so that two pistons move in unison. The connecting rod (11) is received through an aperture (12) defined in the intermediate end flange (6) and a fluid-tight seal is maintained between the connecting rod by means of an o-ring (13). Similarly, the pistons (9, 10) are provided with o-rings (13) on their walls for sealing against the cylinder walls of their respective chamber cylinders (2,3). As depicted, the operating chamber (8) has a diameter smaller than the diameter of the drive chamber (7).

The cylinder (2) has a pair of inlet/outlet ports (14), each of which has a two-way valve (not shown) operatively connected thereto, the valves being operable to selectively draw a driving fluid (say, air under pressure) into, or expel the driving fluid from, the upper and lower parts (15,16) of the drive chamber (7) to selectively urge the piston (9) to reciprocate within the chamber (7).

The operating chamber (8) has an outlet check valve (not shown) associated with an outlet port (17), which only allows fluid under pressure to exit the chamber (8). An inlet check valve (not shown) is mounted at an inlet (18) in the wall of the cylinder (3) on an opposed side of the piston (10). A passageway (19) controlled by a check valve (20) permits the selective flow of the fluid to be pumped from the inlet (18), via the passageway (19) to the outlet (17), as the piston (10) reciprocates.

The drive and operating cylinders (2) and (3) are connected to each other by means of external tie-rods (21,22). Tie-rods (21) connect and secure the first end flange (4) to the intermediate end flange (6), while tie-rods (22) connect and secure the third end flange (5) to the intermediate end flange (6).

In the embodiment of the invention illustrated in Figures 2 to 4 of the drawings, a reciprocating pump (100) is similar to that of Figure 1, but has a different arrangement for securing the components of the pump in an assembled unit.

In particular, tie rods (23) that secure the pump body components together extend through the intermediate end flange (6) while spanning between the first and third end flanges (4,5). Moreover, each tie rod (23) is sealingly received through an axial aperture defined through the piston (9) and opposed ends (25) of each tie rod (23) are received through apertures (26) defined in the first, third and intermediate end flanges (4,5 and 6), the respective apertures (24,26) sealing against the tie rods (23) by means of rubber o- rings (13).

Threaded nuts (27) are provided to fasten the threaded ends (25) of each tie rod (23) and to tension the tie rods (23).

Although the pumping cylinder (3) and the drive cylinder (2) are shown as separate components in Figure 2 - 4, it will be appreciated that they may comprise a single integrally formed stepped cylinder. The stepped cylinder may, for example, be a stainless steel component of unitary construction.

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The applicant believes that the invention overcomes the stress and size constraints of prior art reciprocating pumps. Unlike known pumps, tie rods of this invention are housed within at least one of the chambers of the pump and the piston of that chamber runs on the tie rods. This distributes the load on the end plates more evenly and enables the end plates to withstand the forces exerted by the pump more readily. It has the additional advantage of reducing the outer dimensions of the pump.

Claims (10)

: cL Lo i t— 9 CLAIMS

1. Areciprocating pump including a hollow pump body defining a cylindrical bore and being closed at opposed ends by first and end plates, at least one of which is removable, the pump body and the end plates defining a chamber into which is received a piston operable for reciprocating motion; and fastening means extending axially within the cylindrical bore between the end plates and operable to releasably secure the at least one removable end plate to the pump body.

2. The reciprocating pump as claimed in claim 1, wherein the pump is a two-chambered pump, the pump body being a first pump body and the chamber being a drive chamber; the pump includes a second hollow pump body defining a cylindrical bore and extending co-axially from the second, intermediate end plate of the first pump body and being closed at an opposed end thereof by a third end plate, the second pump body and the second and third end plates defining an operating chamber into which is received an operating piston operable for reciprocating motion, the operating piston being operably connected with the piston the drive chamber; and the fastening means extend axially from the third end plate to the first end plate to releasably secure the assembled end plates and pump bodies.

3. The reciprocating pump as claimed in claim 2, wherein the drive piston and the operating piston are connected by way of a connecting rod, which is sealingly received through an aperture in the second end plate.

4. The reciprocating pump as claimed in claim 2 or claim 3, wherein the two pump bodies and the intermediate end plate are integrally formed. :

5. The reciprocating pump as claimed in any one of claims 2 to 4, wherein a discharge outlet is defined in the third end cover.

6. The reciprocating pump as claimed in any one of claims 2 to 5, wherein the second body has a diameter smaller than that of the first body. :

7. The reciprocating pump as claimed in claim 6, wherein the fastening means comprises a plurality of tie rods extending between the first and third end plates externally of the second pump body and internally of the first pump body.

8. The reciprocating pump as claimed in claim 7, wherein each of the plurality of tie rods is sealingly received through a respective aperture defined in the drive piston.

9. The reciprocating pump as claimed in claim 7 or claim 8, wherein opposed ends of each of the plurality of tie rods are sealing received through a respective aperture defined the first and third end plates.

10. A reciprocating pump substantially as herein described with reference to Figures 2 — 4 of the accompanying diagrammatic drawings. DATED THIS 28THDAY OF FEBRUARY 2011 BOWMAN SN) INC. FOR THE APPLICANT