GB2389630A

GB2389630A - A pump having a plastic valve plate

Info

Publication number: GB2389630A
Application number: GB0311903A
Authority: GB
Inventors: Keith Larke
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-24
Filing date: 2003-05-23
Publication date: 2003-12-17
Also published as: WO2003100253A1; AU2003232342A1; GB0311903D0

Abstract

A fluid pump (10) which can operate at pressures from 0 to approximately 100 psi is disclosed. The pump (10) has a rotational drive shaft (13), driven by a motor (12) with a lower valve plate (14) being seated on the motor (12). A drive mechanism, connected to the drive shaft (13) is mounted on the lower valve plate (14) and is adapted to drive valve elements (17). A fluid input means (16) so operably connected to the valve elements (17) which draw fluid from the fluid input means (16) and expel the fluid through an output (19). The lower valve plate (14) is formed of a plastics material. The plastics material is a poly (phenylenesulphide) which includes p-phenylene rings within its chain. An inert filler is included within the plastics material, which filler is glass, a mineral or mixture thereof.

Description

l' _t_ 2389630 -1 AN IMPROVED FLUID PUMP

Field of the Invention

Ihe present invention relates to an improved fluid pump and in particular to a pump which is capable of running at higher pressures up to approximately 100psi S Background to the Invention

The ability and need to pump a fluid from one location to another and also to alter the pressure of that fluid is widely recognised and utilised Pumps find uses in such diverse places as chemical plants, vehicles such as cars, buses or boats and toilets Pumps operate on a number of different principals, the particular type 10 used being dependent on the function to which the pump is to be put One particular type of pump, a diaphragm pump operates by means of a number of one-way valves through which the fluid can be drawn in one direction, but through which the fluid cannot flow in the reverse direction Diaphragm pumps have the advantage over certain other types of pump in that, in 15 common with peristaltic pumps, the fluid behalf pumped does not come into contact with the motor This means that a wide range ol' types of fluid can be pumped without risk of damage to the motor components Diaphragm pumps can moreover deliver a wide range of pressures at a high rate (unlike peristaltic pumps) and so are quite versatile 20 Prior art diaphragm pumps suffer from a disadvantage in that they are expensive

One of the primary reasons for the high cost is that one of the components, a lower valve plate, is formed from metal It is a shibboleth in the industry that

-2 metal must be used as the lower valve plate should not be able to flex Should it flex, then the pump will perform poorly, if at all - Metal components are however expensive to manufacture both in terms of the material itself but also in terms of the moulds required 'I'he costs of the moulds 5 can be an order of magnitude greater than for moulds used to form plastic materials It is an object of the present invention to seek to address the above problems and to provide an improved diaphragm pump Sum nary of the Invention 10 According to a first aspect of the present invention there is provided a fluid pump capable of operating at pressures from () to approximately I OOpsi, the fluid pump comprising a motor driving a rotational drive shaft, the pump including a lower valve plate seated on the motor, the valve plate having 15 mounted thereon a drive mechanism connected to the drive shaft, the drive mechanism being adapted to drive valve elements, the pump further including a fluid input means operably connected to the valve elements, operation of the valve elements drawing fluid l'rom the fluid input means and expelling the fluid via a fluid output means, and characterized in that 20 the lower valve plate is formed of a plastics material The use of a plastics material means that the pumps can be made lighter and substantially cheaper than has previously been the case Advantageously, the plastics material is a poly(phenylenesulphide) The poly(phenylenesulphide) gives a lightweight and durable component Preferably 25 the poly(phenylenesulphide) comprises p-phenylene rings to increase the crystalline character of the material and increase its strength, durability and

resistance to solvents I'ret'erably, the poly(phenylenesulphide) includes an inert filler The filler is advantageously a glass, mineral or mixture thereof The tensile properties of the poly(phenylenesulphide) are thereby improved 5 According, to a further aspect ot' the invention, there is provided a lower valve plate for use in a diaphragm pump, the valve plate being formed from a plastics material having a high tensile strength Brief Description of the Drawings

I'he invention will now be described with reference to the accompanying 10 drawings which show by way of example one embodiment of a water pump In the drawings Figure I is a perspective exploded view of a pump illustrating the component parts, and Figure 2 is a perspective view of a lower valve plate 15 Detailed Description of the Invention

The pump 10 illustrated in Figure 1 is mounted to a support stand I I The pump 10 comprises a motor 12 to drive a rotating shall 13 The motor 12 is seated within a lower valve plate 14, the plate 14 being shown more clearly in Figure 2 In order to provide etTicient pumping a number of' diaphragm valves are included, 20 the valves being mounted on a housing 15 Fluid enters the pump 10 by means of the input tubes 16 The action of the diaphragm valves 17 causes the fluid to be drawn into the volume between the housing, 15 and a wobble board 18 'I'he directional character of the valves 17 enable fluid to pass into the volume, but prevent the fluid Tom exiting A further valve 19 however acts in the opposition 25 direction so that fluid drawn in is effectively pushed out through the further valve 19 By varying the diameter of the tubing 20 leading from the further valve 19,

! -4 the pressure of the fluid in said tubing, 19 can be made to suit the particular application The means to open and close each diaphragm valve 17 is provided by a drive mechanism 21 mounted on the wobble board 18 'I'hc mechanism 21 is itself 5 powered by the cave shad 130fthe motor 12 Duc to the nature of the mounting for the valves and the wobble board IX, the timid being pumped is isolated from the motor This t'eature means that a wide range of fluids including those which are nammable or corrosive can be pumped As examples, water and diesel have so t'ar been successfully pumped.

10 Furthermore, due to the materials used pressure in a range ot'0 to approximately lOOpsi can be safely accommodated The self-priming pumps disclosed herein tind application in a wide number ot' positions They can for example, can be used on caravans, boats or buses as well as in an industrial plant environment It is important when designing a pump to run at the pressures contemplated in the 15 present invention that the lower valve plate does not flex Should this happen then the performance of the pump is severely impaired The primary reason tor this impairment is that the wobble board 18 is unable to drive the diaphragm valves ctTectively Unlike prior art water pumps, the primary component parts of the pump are

20 formed from a plastic material In particular, the lower valve plate is tonged of a plastics material Plastics have been used t'or this particular component in prior art pumps These have however been of low mechanical strength, formed for example from polypropylene, and as such the pumps have only been capable of running at relatively low pressures However, in order for a pump to perform at 25 higher pressures, a lower valve part formed of metal have until now been used I'he metal components are known not to flex under the conditions used.

The chief drawback of metal components are that they are expensive both in terms of materials and the costs of manut'acture The cost of conventional pumps is therel'ore often prohibitive It is however a well entrenched belief in the industry

( -S -

that plastics cannot be used for the component parts for the pumps as they will give poor performance and so metal ones have remained in use It has been found however that when using a certain type of plastic material, the problems of flexing are overcome Furthermore, plastic materials have an 5 advantage over metals during any processing step in that they can be easily moulded into any appropriate form and articles Once a mould is formed, articles can be quickly and cheaply made It has been found that if the lower valve plate is made from a poly(phenylenesulphide) (PPS) then the pumps can easily perform at higher 10 pressures with little wear and tear on the parts Cheaper and durable high pressure pumps can therefore be produced Poly(phenylenesulphide) can be formed Irom a number of units of phenylensulphide When the pare- grouping is used as a monomer however' the chains of the polymer tend to be linear and so materials formed therefrom tend to 15 have a highly crystalline structure and possess the properties normally associated therewith (for example high melting point) Furthermore, due to the stability of the crystalline structure, the polymers also have low solubility and are virtually insoluble below 200C Moreover, PPS is also well known as a fire-retardant due to its tendency to char rather than burn 20 It has been furthermore found that the addition of a glass or a mineral to the Pl'S gives component parts a still greater performance 'I'he resulting polymer has the following selected characteristics

( - 6-

TABLE I

PROPERTY I VALUES

_ _ I'cnsile strength, Ksi. 18 0 -- 19 5 Plexural strength, Ksi 27 5 - 29 0 I;lexural Modulus, Msi 2 6 _..... _. .. __

Compressive strength, Ksi 35 Water absorption, % 0 02 .. . . Mold shrinkage, in/in 0 002 -- 0 006 _ It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the 5 invention

Claims

( -7 Claims

1. A fluid pump capable of operating at pressures from O to approximately 100psi, the fluid pump comprising: a motor driving a rotational drive shaft, 5 the pump including a lower valve plate seated on the motor, the valve plate having mounted thereon a drive mechanism connected to the drive shaft, the drive mechanism being adapted to drive valve elewcats; the pump further including a fluid input means operably connected to the valve elements. operation of the valve elements drawing fluid from the 10 fluid input means and expciling the fluid via a fluid output means, and characterized in that the lower valve plate is formed of a plastics material.

2. A pump according to Claim 1, wherein the plastics material is a poly(phenylenesulphide).

3. A pump according to Claim 2, wherein the poly(phenylenesulphide) 15 comprises p-phenylene rings.

4. A pump according to Claim 2 or Claim 3, wherein the poly(phenylenesulphde) includes an inert filler.

5. A pump according to Claim 4, wherein the filler is a glass, mineral or mixture thereof.

20

6. A lower valve plate for use in a diaphragm pump, the valve plate being formed from a plastics material having a high tensile strength.

7. A pump substantially as herein described with reference to and as illustrated by the accompanying drawings.