Double-diaphragm pumps

Abstract

 A double diaphragm pump comprises a pair of axially spaced apart pumping chambers (1,2), each chamber has a pumping diaphragm (3,4) to divide each chamber into an inner (5,6) and an outer compartment (7,8). The outer end of each pumping chamber is closed by a cover (9,10) and the inner ends of both pumping chambers (1,2) are closed by a central element (11). Connection cylinder (12) extend between the diaphragms (3,4) and through the central element (11). The supply (13) of operating fluid to the outer compartments (7,8) causes the diaphragms (3,4) to oscillate and vary the capacities of the inner compartments (5,6). Each of the inner compartments (5,6) has an inlet (14) and outlet port (15) leading to unidirectional valves (16,17) to allow fluid to be drawn into one of the compartments (5,6) when the appropriate diaphragm (3,4) moves outwardly and expelled from that compartment when the diaphragm moves inwardly. The central element has a unitary partition wall (20) which extends between and closes the inner ends of the inner compartments (5,6), said wall being substantially solid over a major portion of its area apart from a sealed aperture (21) to allow the connection cylinder (12) to pass through it and being enlarged at its outer periphery (22) to carry the inlet and outlet ports (14,15) which are located respectively at the lower and upper portions of the element (11).

Description

[0001] This invention relates to double-diaphragm pumps and particularly to improved body design for such pumps.

[0002] Double-diaphragm pumps are known and described in EP-B 0 181 756 and EP 0 132 913. The pumps described in these documents have a central body which separates two inner chamber members that form, in conjunction with a pair of flexible diaphragms, the inner portions of two pumping chambers. The central body of the illustrated pumps contains a fluid operate valve system which controls the flow of pumped fluid to and from the inner portions of the pumping chambers.

[0003] Such pumps have the advantage over many other types of pumps that they can easily be installed "in line" into fluid transmission systems and the inlet and outlet manifolds are kept short. However, when draining such pumps for cleaning, changing fluid to be pumped, or other reasons, an appreciable residue of fluid remains within the pump body and must be removed by dismantling the pump or other means which results in the loss or contamination of the residual fluid. In the case of high value fluids such loss is unacceptable economically.

[0004] The present invention provides a double-diaphragm pump in which the fluid loss, when draining the pump, is greatly reduced, and the overall dimensions are less than those of known pumps having similar pumping capacity.

[0005] According to the present invention a double diaphragm pump comprises a pair of axially spaced apart pumping chambers, each chamber having a pumping diaphragm to divide each chamber into an inner and an outer compartment, the outer end of each pumping chamber being closed by an end cover and the inner ends of both pumping chambers being closed by a central element, connection means extending between the diaphragms and through the central element, means for supplying operating fluid to the outer compartments to cause the diaphragms to oscillate and vary the capacities of the inner compartments, and each of the inner compartments having an inlet and outlet port leading to unidirectional valves to allow fluid to be drawn into one of the compartments when the appropriate diaphragm moves outwardly and expelled from that compartment when the diaphragm moves inwardly and in which the central element has a unitary partition wall which extends between and closes the inner ends of the inner compartments, said wall being substantially solid over a major portion of its area apart from a sealing aperture to allow the connection means to pass through it and being enlarged at its outer periphery to carry the inlet and outlet ports which are located respectively at the lower and upper portions of the element.

[0006] Preferably the opposed surfaces of the substantially solid part of the unitary wall are substantially parallel.

[0007] In a convenient embodiment the opposed surfaces of the central element which form part of the inner chambers are of substantially overall concave shape.

[0008] The end covers can be of arcuate section and the edges of the diaphragms are held and located between the end covers and the central element.

[0009] Thus, the end covers may be substantially conical or, more preferably, of convexly curved form.

[0010] The connection means between the diaphragms can be provided as a hollow push rod for sealed reciprocating movement through said sealed aperture in the unitary partition wall to transmit axial displacement forces between the two diaphragms, the means for supplying operating fluid comprises a shaft extending axially in a sealing manner through the hollow push rod and through the end covers, and including passage means extending along the shaft for conveying operating fluid to and from at least one of the outer compartments, said push rod co-operating with the shaft to control communication between said passage means and said one or both of the outer compartments.

[0011] Preferably means are included which operated in conjunction with the shaft to clamp the end covers to the central element.

[0012] In one preferred embodiment the central element is made from a pair of dished plates rigidly secured together.

[0013] In another embodiment the central element is made from a single piece of material.

[0014] The unidirectional valves are preferably carried by readily detachable inlet and outlet manifolds connected respectively to the lower and upper parts of the central element and the valves can be ball valves.

[0015] Means for heating or cooling the fluid to be pumped can be included and which comprise a heating or cooling jacket formed in the enlarged outer periphery of the central element.

[0016] The invention can be performed in various ways and two embodiments will now be described by way of example and with reference to the accompanying drawings in which :

Figure 1 shows a schematic cross-sectional view of a pump in accordance with the invention;

Figure 2 is a cross-sectional along the line II-II of the manifolds of the pump shown in Figure 1;

Figure 3 shows an alternative embodiment of the manifolds of a pump in accordance with the invention;

Figure 4 shows the central element and manifolds of the pump shown in Figure 3; and,

Figure 5 shows an embodiment, partly in cross-section, of a pump according to the invention with facilities for heating or cooling the fluid being pumped.

[0017] In the construction shown in Figures 1 and 2 the double-diaphragm pump, according to the invention, comprises a pair of axially spaced apart pumping chambers 1 and 2. Each chamber has a pumping diaphragm indicated by reference numerals 3 and 4 which divide each pumping chamber 1 and 2 into an inner compartment, indicated by reference numerals 5 and 6, and an outer compartment 7 and 8 respectively. The outer end of each pumping chamber is closed by an end cover 9 or 10 and the inner ends of both pumping chambers 1 and 2 are closed by a central element 11.

[0018] Connection means 12 extend between the diaphragms 3 and 4 and through the central element 11. Means 13 for supplying operating fluid to the outer compartment 7 and 8 to cause the diaphragms 3 and 4 to oscillate and vary the capacities of the inner compartments 5 and 6, and each of these inner compartments 5 and 6 have an inlet port 14 and an outlet port 15 which lead respectively to unidirectional inlet and outlet valves 16 and 17 to allow fluid to be drawn into one of the compartments 5 or 6 when the appropriate diaphragm 3 or 4 moves outwardly and expelled from that compartment when the diaphragm 3 or 4 moves inwardly.

[0019] The central element 11 has a unitary partition wall 20 which extends between and closes the inner ends of the inner compartments 5 and 6 and this partition wall is substantially solid over a major portion of its area apart from a sealed aperture 21 to allow the connection means 12 to pass through it. The partition wall is enlarged at its outer periphery 22 to carry the inlet and outlet ports 14 and 15 which are located respectively at the lower and upper portions of the element 11.

[0020] As will be seen from Figure 1 the rims of the end covers 9 and 10 peripherally engage respectively the outer rims 23 of the outer periphery 22 of the central element 11. This central element 11 comprises two dish-like members 24, 25 which have a generally concave form with planar central portions 26, 27 which are held together by welding or other means to form the rigid unitary partition wall 20.

[0021] The central portions of the diaphragms 3 and 4 include embedded plates 28 and are connected to opposite ends of the connection means 12 which are in the form of a hollow push rod. This push rod is slidably mounted in the sealed aperture 21 which is centrally located in the rigid central zone of the unitary partition wall 20 formed by the planar portions 26 and 27. The end covers 9 and 10 are urged together and against the rims 23 of the members 24 and 25 by means of an axial shaft 30 which is held at one end by clamping means 31 and at the opposite end by a nut 32.

[0022] The clamping means carries a silencer 33.

[0023] The upper portion of the central element 10 formed by the members 24 and 25 is shaped to accommodate an exhaust manifold 34 in which is located a pair of balls 35 which provide the pair of outlet valves 17. The balls 35 are seated in circular valve seatings 36 which lead to the ports 15 (not shown in Figure 2) which are located as high as possible in the inner compartments 5 and 6.

[0024] The lower part of the members 24 and 25 is also shaped to accommodate an inlet manifold 37 which again contains a pair of balls 38 which provide the inlet valves 16 and which are located on valve seatings 39 which lead to the inlet ports 14 (not shown in Figure 2). The lower manifold 37 has an inlet pipe 40 and the upper manifold has an outlet pipe 41, as shown in Figure 2.

[0025] In Figure 2 two alternative configurations for the pipes 40 and 41 are shown. The balls 16 and 17 of the control valves act in the direction of gravity as non-return valves in well known fashion. The manifolds 34 and 37 are held securely in position at the uppermost and lowest portions of the members 24 and 25 by means of threaded studs 43.

[0026] The push-rod diaphragm assembly is reciprocated by air, gas or liquid under pressure supplied to the two outer compartments 7 and 8 alternatively to form a change-over spool or other means in known manner. Such a system is described in detail in EP-B-0 181 756 and the central passages for conveying the operating fluid are indicated by reference numeral 44. The reciprocating movement of the push-rod diaphragm assembly alternately increases and decreases the volume of the inner compartments 5 and 6. This leads to fluid being drawn into the compartment whose volume is being increased through one of the lower ports 14 from the manifold 37. Similarly fluid is expelled from the compartment whose volume is being reduced through one of the upper ports 15 into the manifold 34. Such operation is conventional for double diaphragm pumps.

[0027] Due to the design of the pump allows for the inlet and outlet manifolds 37 and 34 to be located at the outer periphery of the central element 11 so that a relatively thin unitary partition wall 20 can be used thus allowing a considerable reduction in the overall axial dimensions of the pump when compared with known constructions in which the manifolds are located within a central element. Moreover, because the inner compartments 5 and 6 are adjacent the central element 11 and the inlet and outlet valves 16, 17 are carried at the top of the inner compartments 5 and 6, the length of the manifolds is reduced to a minimum and minimum wastage of valuable fluids is achieved when draining down. The construction also provides for the easy removal of the inlet and exhaust valve manifolds due to their location adjacent the outer rim of the central element.

[0028] In an alternative construction, as shown in Figures 3 and 4, the same reference numerals are used to indicate similar parts to those in Figures 1 and 2. In this embodiment the construction of the ball valves has been simplified and the central element 11 is formed as a single body 50 by casting or machining from solid stock. The machine body 50 includes four lower inlet port openings 51 and two upper outlet port openings 52. The ports 51 enter directly into inner chambers 53 and the inlet manifold 54 is provided with circular ports 55 so that the balls 56 can bed directly into them and form the necessary seal. The ports 55 in the manifold set the lower limit of travel for the balls. The use of four manifolds in the lower portion of the machine body 50 ensures maximum filling for the pump chambers.

[0029] The upper outlet port openings 52 are also circular which also form seats 57 for the outlet balls 58. A manifold 59 encloses the exhaust valves formed by the balls 58 and sets the upper limit of travel. In the embodiment shown the inlet pipe 60 to the manifold 54 is horizontal and the outlet pipe 61 from manifold 59 is vertical. The choice of connection direction depends upon the construction of the relevant manifold and is independent of the main construction of the body of the pump.

[0030] The valve construction shown in Figures 3 and 4 could be incorporated in the construction shown in Figures 1 and 2 and similarly the valve arrangements shown in Figures 1 and 2 could be used in the construction shown in Figures 4 and 5 where the element 10 is made from a single body of material.

[0031] In an alternative construction (not shown) the ball valves can be replaced by flap valves of any convenient and known type.

[0032] In many cases the fluid to be pumped by a pump according to the invention must be heated or cooled to maintain its stability or fluidity. In prior art pumps it was necessary to construct an external jacket to contain the heat transfer medium. Because of the layout of the valves and the construction of the central element 11 the sides of the pump between the valves can be utilised to form a heating or cooling jacket. Figure 5 shows such a construction which can be used whether the element 11 is formed from two dish-like members 24, 25 or from a solid body of material as shown in Figures 3 and 4. Figure 5 shows a construction similar to that shown in Figures 3 and 4 but in which spaces 70 are provided in the enlarged outer periphery 22 of the unitary partition wall 20 which are closed by circumferential strips 71. The spaces 70 are interconnected by a channel 73 so that a heat transfer medium, such as water, can be pumped through the spaces by suitable connections (not shown). Thus, the spaces 70 can act as a heating or cooling jacket and the construction produced is more compact and less expensive than constructing a heating/cooling jacket to cover the complete pump.

Claims

1. A double diaphragm pump comprising a pair of axially spaced apart pumping chambers, each chamber having a pumping diaphragm to divide each chamber into an inner and an outer compartment, the outer end of each pumping chamber being closed by an end cover and the inner ends of both pumping chambers being closed by a central element, connection means extending between the diaphragms and through the central element, means for supplying operating fluid to the outer compartments to cause the diaphragms to oscillate and vary the capacities of the inner compartments, and each of the inner compartments having an inlet and outlet port leading to unidirectional valves to allow fluid to be drawn into one of the compartments when the appropriate diaphragm moves outwardly and expelled from that compartment when the diaphragm moves inwardly and in which the central element has a unitary partition wall which extends between and closes the inner ends of the inner compartments, said wall being substantially solid over a major portion of its area apart from a sealing aperture to allow the connection means to pass through it and being enlarged at its outer periphery to carry the inlet and outlet ports which are located respectively at the lower and upper portions of the element.

2. A double diaphragm pump as claimed in claim 1 in which the opposed surfaces of the substantially solid part of the unitary wall are substantially parallel.

3. A double diaphragm pump as claimed in claim 1 or claim 2 in which the opposed surfaces of the central element which form part of the inner chambers are of substantially overall concave shape.

4. A double diaphragm pump as claimed in claim 1, claim 2 or claim 3 in which the end covers are of arcuate section and the edges of the diaphragms are held and located between the end covers and the central element.

5. A double diaphragm pump as claimed in claim 4 in which the end covers are substantially conical or of convexly curved form.

6. A double diaphragm pump as claimed in any one of claims 1 to 5 in which the connection means between the diaphragms is provided as a hollow push rod for sealed reciprocating movement through said sealed aperture in the unitary partition wall to transmit axial displacement forces between the two diaphragms, the means for supplying operating fluid comprises a shaft extending axially in a sealing manner through the hollow push rod and through the end corners, and including passage means extending along the shaft for conveying operating fluid to and from at least one of the outer compartments, said push rod co-operating with the shaft to control communication between said passage means and said one or both of the outer compartments.

7. A double diaphragm pump as claimed in claim 6 including means operating in conjunction with the shaft to clamp the end covers to the central element.

8. A double diaphragm pump as claimed in any one of the preceding claims 1 to 7 in which the central element is made from a pair of dished plates rigidly secured together.

9. A double diaphragm pump as claimed in any one of the preceding claims 1 to 7 in which the central element is made from a single piece of material.

10. A double diaphragm pump as claimed in any one of claims 1 to 9 in which the unidirectional valves are carried by readily detachable inlet and outlet manifolds connected respectively to the lower and upper parts of the central element.

11. A double diaphragm pump as claimed in claim 10 in which the unidirectional valves are ball valves.

12. A double diaphragm pump as claimed in claim 10 in which the unidirectional valves are flap valves.

13. A double diaphragm pump as claimed in any one of the preceding claims including means for heating or cooling the fluid to be pumped, and which comprise a heating or cooling jacket formed in the enlarged outer periphery of the central element.

Drawing