GB2032999A - Packingless reciprocating pumps - Google Patents

Abstract

A reciprocating pump has a reciprocating assembly formed of a piston rod (12) and a tubular piston (32) which is free to move with respect to the piston rod to open and close an inlet valve (39) defined between cooperating surfaces on the piston and the piston rod as a result of reciprocation of the assembly. The piston (32) may be movably located between plates (29, 38) fixed to the piston rod and a spring may act between one of the plates and the piston. Alternatively, a spring may act between an independent piston and the cylinder wall to urge the inlet valve closed. A plurality of the pumps may be usefully grouped into a radial pump assembly driven from a common shaft. <IMAGE>

Description

SPECIFICATION Packingless reciprocating pumps This invention relates to reciprocating pumps of the kind used to deliver a fluid under pressure, for instance water, to an outlet.

According to this invention, the reciprocating member includes a piston rod and a piston which is axially movable with respect to the piston rod and is provided with an axial bore for transferring fluid from the inlet to the outlet, the piston co-operating with means on the piston rod to seal the inlet from the outlet on the discharge stroke of the reciprocating member. The cylinder wall may be provided with a labyrinth seal which co-operates with the piston to provide the necessary seal.

The invention may usefully be incorporated in a radial type pump in which there are a plurality of pump units disposed around a common drive member, such as a cam, for the respective reciprocating members.

In order that the invention may be fully appreciated, preferred embodiments of it in the form of reciprocating pumps for water under high pressure are shown in the accompanying drawings, in which: Figure 1 is a longitudinal cross-section through a single pump unit; Figure 2 is an end view, partly broken away, of a radial pump, Figure 3 is a longitudinal, mostly in section, view of the pump of Fig. 2, and Figure 4 is a view of a modification of the radial pump shown in Figs. 2 and 3.

As shown in Fig. 4, the fluid which is to be discharged communicates with a pump inlet 10 in the form of a chamber within a body part 11 mounted on a crank case. This houses a piston rod 1 2 which undergoes reciprocatory motion, when the pump is in use, under the control of a crank (not shown). The piston rod 12 slides in a fixed sleeve 12a sealed with respect to the body part 11 by a low pressure seal 1 3 and, in the bottom dead centre position the rod 1 2 is sealed against the sleeve 12a by '0' rings 12b.

The outlet 14 from the pump is located laterally in a pump body part 1 5 remote from the body part 11. The two body parts 11 and 1 5 are joined to the respective ends of a main pump body 16. This consists of a cylinder member 1 7 having a cylinder bore 1 8 terminating in a passageway 1 9 of reduced diameter with respect to the cylinder bore 1 8 and discharging into the outlet 14 of the pump body part 15 through a non-return valve 1 9a.

The necessary seal between a spigot portion 20 containing the outlet passageway 1 9 and fitting into a socket 21 on the body part 15, is provided by an O-ring of similar seal 22.

The inlet end of the cylinder member 1 7 carries externally a cylinder body 24 which is a close fit on the external surface 25 of the cylinder member adjacent its inlet end.

Another O-ring or similar seal 26 is provided between the cylinder part 24 and the extremity of the cylinder surface 25. At this point the cylinder part 24 includes a stepped shoulder formation 27 and between this and its inlet end, where it is a tight fit into a socket formed on the pump body part 11 the cylinder part 24 tapers from a maximum internal diameter at the socket 28 to its minimum internal diameter adjacent the end of the cylinder member 1 7.

A long hollow piston 32 having a bore 37 is slidingly accommodated in the bore 1 8 of the cylinder member 1 7. The piston is externally cylindrical and forms a close fit within the cylinder bore 18, the wall of the bore 1 8 is machined to form a labyrinth seal (not shown) and a polymeric seal and bearing ring 34 is located in a peripheral groove 35 located in the wall of the bore 1 8 adjacent the inlet end of the cylinder member 1 7. The piston undergoes reciprocal action by virtue of its connection to the piston rod 1 2. This is provided by means of a spacer tube 36 longer than the piston 32 and located coaxially within the bore 37 of the piston.The tube 36 is located about the piston rod 1 2 and spaces a solid inlet valve plate 29, sealed to piston rod 1 2 by an O-ring, from a perforated end plate held on the piston rod 1 2 by a nut and washer screwed to the end of the piston rod.

The piston 32 has a length slightly less than the distance between the facing surfaces of the inlet valve plate 29 and the perforated plate 38 at opposite ends of the tube 36.

In one end position of the shaft 12, that illustrated in the drawing, there is continuous fluid communication from the inlet 10 via the port between the valve plate 29 and the tapered chamber 31 to the space 39 left between the inlet valve plate 29 and the associated end of the piston 32. This space 39 is in fluid communication with the piston bore-37 and through the perforated plate 38 with the cylinder bore 1 8 or discharge member. On movement of the piston rod 1 2 from the bottom dead centre position the piston 32 remains stationary momentarily until the adjacent end of the piston is contacted by the end face of the inlet valve plate 29. This seals the inlet 10 from the outlet 1 4 and the fluid in the discharge chamber becomes pressurised and discharged through the non-return valve 19a to the outlet 14.On movement of the piston rod 1 2 from the top dead centre position the piston 32 again remains momentarily stationary until it contacts the perforated plate 38 so opening up the space 39 once again and establishing communication between this inlet and the cylinder bore 18.

Figs. 2 and 3 illustrate another embodiment of this invention which is a radial-type pump which incorporates six reciprocating piston and cylinder units which are equally spaced around a central drive shaft 1 00. The drive shaft 100 isjournalled in bearings 101 and 102 and carries a drive cam 103. A multi-part housing 104 carrying the bearings 101 and 102 is provided with passageways constituting fluid inlet passageways connected to a principle fluid inlet opening 1 05. Each pump unit 106 is of the same construction and only one will now be described.

A multi-part piston 110 is arranged to reciprocate in suitable bores extending consecutively radially through associated parts of the housing 104. Guide piston part 111 is connected to a cam follower 11 2 by a pivot connection and is secured to a radially outwardly located piston part 11 3 which forms an inlet valve element and a flexible seal 114 is provided between the housing and the connection between the piston parts 111 and 11 3 in order to seal the crank case from an inlet chamber 11 5 located above the seals 114 and connected to the inlet opening 105.

A piston rod element 116 is fixedly secured to and extends radially outwardly from the piston parts 111 and 113. The piston rod 116 is surrounded by a hollow pumping piston part 11 7 which is formed as a cylindrical element with a flange 11 8 on its lower inner surface.

The radially inwardly located end surface of the piston part 11 7 is held normally in contact with the piston part 11 3 by a spring 11 9 which extends between the flange 11 8 and a washer 1 20 which is secured to the radially outward end of the piston rod 11 6. The bore of the cylinder in which the pumping piston part 11 7 reciprocates is formed with a spiral groove formation 121 which constitutes a labyrinth type seal between the inlet chamber 11 5 and a compression chamber 122 of the pump located radially outwardly of the pump unit.A non-return valve 1 23 is located between the compression chamber and an outlet chamber 1 24 connected to an outlet (not illustrated).

In operation of the pump described the drive shaft 100 is rotated, after the inlet and outlet connections have been made, and this causes the cam 103 to rotate and so to cause the cam followers 11 2 to reciprocate radially with respect to the axis of the shaft 100. The cam followers transmit the motion derived from the cam to the piston parts 110, 11 3 and 11 6 so that these reciprocate with the cam follower 11 2. On the radially inward movement of the pumping piston, the inertia of the pumping piston part 11 7 together with the negative pressure created in the compression chamber 1 23 results in the compression force of the spring 11 9 being overcome and the pumping piston part 11 7 moving relative to the piston rod 11 6 to open an inlet valve between the piston parts 11 7 and 11 3 so that inlet, low pressure, fluid, for example water, is drawn from the inlet chamber 11 5 into the space in the interior of the hollow piston pumping part 11 7 and past the washer 1 20 into the compression chamber 1 22. The non-return valve 1 23 prevents the return of fluid from the outlet chamber 1 24. Upon passing the bottom dead centre position the piston parts commence a radially outward movement and the inlet valve between the piston parts 11 3 and 11 7 becomes securely closed as the pressure increases in the chamber 1 22 and after a certain pressure, determined by the non-return valve 123, is reached fluid is ejected into the outlet chamber 124.

Fig. 4 illustrates one pump unit only of the radial pump of Figs. 2 and 3 and shows a modification in which the piston rod element 116 is omitted and a spring 11 9a acts between a flange 11 8a on a pumping piston part 11 7a and a crown portion 150 of the cylinder chamber 122a. The piston part 11 7a does not therefore have any direct connection with the parts 111 a and 1 a which are controlled by the drive cam and function as a piston rod. Nevertheless, the pump unit functions substantially as described above in relation to the pump unit of Figs. 2 and 3.

Claims (16)

1. A reciprocating pump including a cylinder and a reciprocating assembly, the reciprocating assembly including a piston rod and an associated piston axially movable with respect to the piston rod and reciprocable in the cylinder, the piston being provided with a through bore for transferring fluid from a fluid inlet to a fluid outlet disposed on either side of the piston, the piston and piston rod having cooperating means for engagement for sealing the inlet from the outlet on the discharge stroke of the reciprocating assembly.

2. A pump according to claim 1 wherein the cooperating means are surfaces of the piston and the piston rod.

3. A pump according to claim 1 or claim 2 further including resilient means for urging the cooperating means towards the said sealing engagement.

4. A pump according to any preceding claim wherein said piston rod extends axially in said cylinder and through said bore and said piston is axially movable with respect to the piston rod between axially spaced-apart plates fixed to the piston rod.

5. A pump according to claim 4 wherein one of said plates and said piston define said cooperating means.

6. A pump according to claim 5 wherein the other of said plates is perforated to provide communication between the through bore and the cylinder space.

7. A pump according to any one of claims 4 to 6 wherein a spring acts between one of said plates and said piston to urge said cooperating means into said sealing engagement.

8. A pump according to any one of claims 1 to 3 wherein a spring acts between a surface of the cylinder and the piston for urging said cooperating means into sealing engagement.

9. A pump according to claim 8 wherein said bore is an axial bore and said cooperating means are respectively a face perpendicular to said bore or said piston surrounding said bore and face perpendicular to said bore on said piston rod.

10. A pump according to any preceding claim wherein a labyrinth seal is provided between said cylinder and said piston.

11. A pump according to any preceding claim wherein a non-return valve is provided in said fluid outlet.

1 2. A pump according to any preceding claim wherein said cooperating means are located adjacent to said fluid inlet.

1 3. A pump according to claim 1 and substantially as hereinbefore described with reference to Fig. 1 or to Fig. 4 of the accompanying drawings.

14. A radial pump assembly comprising a central drive shaft carrying at least one pump operating cam and a plurality of pumps according to anyone of claims 1 to 1 3 arranged radially about the drive shaft with their piston rods operatively connected to followers of said cam.

1 5. A radial pump assembly according to claim 1 wherein said fluid inlets are arranged adjacent the radially inner ends of said pistons.

16. A radial pump assembly substantially as hereinbefore described with reference to Figs. 2 and 3 of the accompanying drawings.