GB1602568A

GB1602568A - Body having fluid passages

Info

Publication number: GB1602568A
Application number: GB2310978A
Authority: GB
Original assignee: Buckell R A
Current assignee: Buckell R A
Priority date: 1978-05-26
Filing date: 1978-05-26
Publication date: 1981-11-11

Description

(54) BODY HAVING FLUID PASSAGES (71) I, RAYMOND ALBERT BUCK ELL, a British Subject, of 41, Belmont Crescent, Maidenhead, Berkshire, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the follo,wing statement: This invention relates to machines for example, fluid pumps and internal combustion engines or other machines using a working fluid.

At present such machines use metal castings for defining the various fluid passages and such castings are expensive especially in respect of the considerable machining that is required.

Moreover castings very often have blow holes or other irregularities which create difficulties in manufacture and it is an object of the present invention to provide a construction of such a machine which avoids some of these difficulties.

According to the present invention, a machine body has passages for fluid, the passages being defined by one or more metal components, externally reinforced by a plastics moulding which is thick in comparison with the metal components, with an elastomeric layer between the components and the moulding.

The metal components may be of stainless steel or other expensive corrosion resistant metal, but because they are so thin, perhaps less than 1/8th inch in wall thickness, they will not make the body very expensive. Sufficient strength to withstand substantially internal fluid pressures can be established by the external plastics moulding which is relatively cheap, and which might be at least five times as thick as the metal components.

The thin components might be liable to deform under substantial internal pressure, and such deformation could crack the plastics moulding and so the elastomeric layer of perhaps 1/8th inch or less in thickness is included between the metal components and the plastics moulding.

In order to prevent a corrosive fluid from attacking the plastics material, the metal components where they join, may include '0' ring or other fluid seals, but it would also be poss- ible to have a single metal component of complicated form made as a lost-wax casting because the thin walls will make such a casting economical to use, and lost-wax casting is accurate enough for there to be little machining required of the finished casting.

It is to be noted that the external plastics moulding may be one which can be cast at a temperature of say 1500-2000C which is noit high enough to establish dangerous distorting stresses in the corrosion resistant metals, so that even after the plastics body has been moulded around the metal components, little or no further machining will be required, and an accurate fluid body can be provided at a reasonable cost.

The wall thickness of the resin body may be several times as thick -- perhaps five times as the metal lining components.

The invention may be carried into practice in various ways and certain embodiments will now be described by way of example, with reference to the accompanying drawings in which: FIGURE 1 shows a sectional elevation of a fluid pump embodying the invention; FIGURE 2 is a section on the line II--II in FIGURE 1; FIGURE 3 is a view similar to FIGURE 1 of another embodiment; and FIGURE 4 is a sketch of a manifold for the embodiment of FIGURE 3, and also embodying the invention.

The pump of FIGURES 1 and 2 comprises three cylinders 11 on parallel axes 12 each of which has a piston 13 arranged to be recipro cated radially in relation to the cylinder 11 by a driving shaft 14. The pistons 13 are driven with a 1200 phase shift between them so that the cylinders provide pressure fluid reasonably continuously to a fluid outlet passage 115.

Fluid is drawn into each cylinder 11 on the suction stroke of its piston 13 from an inlet passage 116 which is common to all three cylinders 11.

FIGURE 1 shows that each cylinder 11 con sists of a stainless steel cylindrical sleeve 17 having a radial bore 18 for the piston 13. At each end of the sleeve 17 is an automatic spring loaded one-way valve arranged as an outlet valve 19 at the connection to the passage 115 and arranged as an inlet valve 21 at the con- nection to the passage 116. The piston 13 slides in a sleeve 25 which fits into the bore 18 in each sleeve 17 and contains a conventional seal 26.

The sleeve 25 is machined from standard stainless steel tube and so are the components 15, 16 and 22 defining the inlet and outlet passages 115 and 116.

The pump casing is made in three separate parts 27, 28 and 29, which are eventually bolted together to hold the pump in assembly by bolts passing through bolt holes 31.

Each part-casing is made in a similar manner in that the components each contains, for example, the component 15 and end sleeve 22 in the part-casing 27, are positioned in a mould and are coated with a layer 30 perhaps 1/32 inch thick of a polyurethane or other rubbery or elastomeric material which can allow for some distortion of the components 15 and 22 without correspondingly deforming the resin body 27. The space in the mould around the layer 30 is then filled with a glass-ball filled with epoxy resin, which when cured forms the body 27 in which the components are embedded.

The expensive metal of the components 15 and 22 may be so thin that it tends to deform under the fluid pressures within it, and that might cause cracking of the resin part-casing were it not for the layer 30.

In a similar manner the sleeves 17 and 25 are assembled together, coated with an elastomeric layer, and embedded in the part-casing 28, and the components 22 and 16 are assembled together, coated, and embedded in the moulded part-casing body 29. The valves 19 and 21 are fitted at the ends of the sleeve 17 together with seals 32, if required, after which the three part-casings are bolted togetehr to complete the assembly.

The plastics material described is strong and provides reinforcement against bursting loads in the passages so that the metal sleeves can be thinner than if they had to carry full pressure themselves.

Thus expensive metals can be used most economically and since they are all of simple cylindrical tubular form there is a minimum of machining.

It has been found that a pump of this kind can be made at substantially lower cost than the equivalent pump made by machining a one piece casting, and there is an additional advantage that the fluid passages are all defined by components made from stainless steel or some other corrosion resistant material, which is thin enough not to be expensive.

A component such as 25 may be machined from solid tube to have the form shown in FIGURE 1, and to have an internal screw thread at its end for a cap to the seal 26, but it could equally be a fairly simple casting. It could be an easy fit in the bore 18 in the wall of the tube 17 but is preferably a force fit, so that the components are conveniently located together when inserted in the mould prior to filling the mould space with the resin material.

The hole in a tube such as 16 can have a bevelled side as shown in FIGURE 1 formed by the bevel on the end of the drill for making the hole to correspond with a similar bevel on the end of the component 22.

It is to be noted that the material of the part-casings 27, 28 and 29, which has been generally described above as being a resin can be of a wide range of materials, including for example glass fibre. The requirements are that it should be cheaper than the stainless steel or other metal for the components such as 25, 17 and 15 for defining the fluid passages so that sufficient cf it can be used to give the body adequate strength to withstand the pressures involved. Also it should be possible to cast it at a temperature not much above 200or.

For some working fluids it does not matter if there is accidental contact of the fluid with the resin material of the part-casings, but for some corrosive fluids this cannot be permitted, so that it may be necessary to have '0' rings or other seals at the junctions between the various metal components.

In another embodiment as shown in FIG URE 3, that problem is avoided by forming the components 17 and 25 not as two separately made tubes fitted together, but as a single lost-wax casting of, for example, stainless steel.

Lost wax castings enables castings of quite complicated shapes to be made with a tolerance or perhaps plus or minus .002 or .005 inches, which may only require grinding after casting, and no other machining operation, but lost-wax casting methods are only economical for making fairly light castings perhaps up to about 8OZ in weight.

They would not be contemplated for a pump body of the kind known in the prior art in the form of fairly massive metal castings which require subsequent machining.

However if the components of the pump body defining the fluid passages are made quite thin, for example less than 1/8 or 1/16 of an inch in wall thickness, a lost-wax casting method is suitable so that the pump lining for the central part casting can be as shown in FIGURE 3, and then there is no need to provide a seal between the pumping cylinder and the radial casing defining the bearings for the piston.

In the embodiment of FIGURE 3, the principle of operation is the same as in the embodiment of FIGURES 1 and 2, but there is a single stainless steel lost-wax casting 41 externally lined with a rubbery coating 30 as described above, and then surrounded by a cast resin 43.

Inlet and outlet valves can be fitted at 44, and 45 in recesses in the casting, and the body 43 can be finally closed at each end by castings 46 and 47 for example of aluminium, bolted to the casing 43, and including '0' rings at 48 to establish god fluid seals.

If the pump was not a single cylinder pump, but was a three cylinder pump as described with reference to FIGURE 2, the components 46 and 47 could be elongate members extending over the end of the three cylinders side by side, and each consisting of three standard stainless steel tubes, the central one being a 'T piece, and the outside ones angle pieces joined together with short straight tubes all the junctions being sealed together by '0' ring seals. The complete assembly could be made as the other components of the pump by fitting the stainless steel components together with their seals, painting a rubber coating on their outer surfaces and then casting them into a resin loody in an appropriate mould to produce an end manifold as shown diagrammatically in FIGURE 4.

The particular pump described is for pumping water to be desalinated in reverse osmosis equipment and can operate at a flow rate of 5 gallons per minute delivering fluid at a pressure of 1250 lbs per square inch.

The invention is equally applicable to other machines, for example, internal combustion engines, where the cylinders and valve passages and interconnections would be defined by similar simply machined hollow cylindrical components.

A sealing compound can be disposed at the joints between the components, and it will be seen that the fluid can flow through passages defined entirely by the component material, so that there can be no contamination.

In one example, the various components of one pump sub-assembly were grit blasted on the external surfaces, care being taken to protect their internal surfaces by masking tapes.

They were then assembled in correct alignment in a demountable mould. 200 grammes of a commercial eposcide resin (Araldite F) were mixed with 64 grammes of a liquid hardener which is essentially 4.4 diamino diphenyl methane. The mixture was heated to 60 C and outgassed using appropriate vacuum techniques.

900 grammes of solid glass microspheres in the size range 400-500 microns were combined with 200 grammes of glass microspheres in the size range 30-60 microns to achieve bimodal packing and the mixture heated to 80"C.

The resin hardener mixture at 60"C was then added to the warm glass heads, the mixture outgassed by vacuum and poured round the pump assembly mounted in the mould. The mould was then placed in an oven and cured at 1200C for one hour.

The mould was removed from the oven, cooled, and disassembled to remove the moulded pump sub-assembly and the subassembly was post cured for 4 hours at 1800C.

If desired, the moulding material could in dude carbon, glass, or other fibre reinforcement, particularly around the holes 31. Also the moulded casing could be externally protected by sheet metal or metal angle at vulnerable points.

In the example described, the wall thickness of the moulded casing is at least about five times the wall thickness of the stainless steel tubes or lost-wax castings.

The invention is related to the invention, the subject of British Patent No. 1,463,981 in the name of Birchill Engineering Ltd.

WHAT I CLAIM IS: 1. A machine body having passages for fluid, the passages being defined by one or more metal components, externally reinforced by a plastics moulding which is thick in comparison with the metal components, with an elastomeric layer between the components and the moulding.

2. A body as claimed in Claim 1 in which the, or one of the, metal components comprises a lost-wax casting.

3. A body as claimed in Claim 1 or Claim 2 in which there are two or more metal components in the form of tubes sealed together.

4. A body as claimed in any of the preceding claims in which the metal components are of stainless steel or other corrosion resistant metal.

5. A body as claimed in any of the preceding claims in which the metal components have walls no more than 1/8th inch thick.

6. A body as claimed in any of the preceding claims in which the plastics moulding has a wall thickness at least five times that of the metal components.

7. A fluid pump or motor, the fluid passages in which are in a body as claimed in any of the preceding claims.

8. A pump or motor as claimed in Claim 7 including inlet and outlet valves assembled with the body.

9. A body having passages for fluid arranged substantially as herein specifically described with reference to FIGURE 1, FIGURE 3 or FIGURE 4 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

and 45 in recesses in the casting, and the body 43 can be finally closed at each end by castings 46 and 47 for example of aluminium, bolted to the casing 43, and including '0' rings at 48 to establish god fluid seals.

If the pump was not a single cylinder pump, but was a three cylinder pump as described with reference to FIGURE 2, the components 46 and 47 could be elongate members extending over the end of the three cylinders side by side, and each consisting of three standard stainless steel tubes, the central one being a 'T piece, and the outside ones angle pieces joined together with short straight tubes all the junctions being sealed together by '0' ring seals. The complete assembly could be made as the other components of the pump by fitting the stainless steel components together with their seals, painting a rubber coating on their outer surfaces and then casting them into a resin loody in an appropriate mould to produce an end manifold as shown diagrammatically in FIGURE 4.

The particular pump described is for pumping water to be desalinated in reverse osmosis equipment and can operate at a flow rate of 5 gallons per minute delivering fluid at a pressure of 1250 lbs per square inch.

The invention is equally applicable to other machines, for example, internal combustion engines, where the cylinders and valve passages and interconnections would be defined by similar simply machined hollow cylindrical components.

A sealing compound can be disposed at the joints between the components, and it will be seen that the fluid can flow through passages defined entirely by the component material, so that there can be no contamination.

In one example, the various components of one pump sub-assembly were grit blasted on the external surfaces, care being taken to protect their internal surfaces by masking tapes.

They were then assembled in correct alignment in a demountable mould. 200 grammes of a commercial eposcide resin (Araldite F) were mixed with 64 grammes of a liquid hardener which is essentially 4.4 diamino diphenyl methane. The mixture was heated to 60 C and outgassed using appropriate vacuum techniques.

900 grammes of solid glass microspheres in the size range 400-500 microns were combined with 200 grammes of glass microspheres in the size range 30-60 microns to achieve bimodal packing and the mixture heated to 80"C.

The resin hardener mixture at 60"C was then added to the warm glass heads, the mixture outgassed by vacuum and poured round the pump assembly mounted in the mould. The mould was then placed in an oven and cured at 1200C for one hour.

The mould was removed from the oven, cooled, and disassembled to remove the moulded pump sub-assembly and the subassembly was post cured for 4 hours at 1800C.

If desired, the moulding material could in dude carbon, glass, or other fibre reinforcement, particularly around the holes 31. Also the moulded casing could be externally protected by sheet metal or metal angle at vulnerable points.

In the example described, the wall thickness of the moulded casing is at least about five times the wall thickness of the stainless steel tubes or lost-wax castings.

The invention is related to the invention, the subject of British Patent No. 1,463,981 in the name of Birchill Engineering Ltd.

WHAT I CLAIM IS: 1. A machine body having passages for fluid, the passages being defined by one or more metal components, externally reinforced by a plastics moulding which is thick in comparison with the metal components, with an elastomeric layer between the components and the moulding.
2. A body as claimed in Claim 1 in which the, or one of the, metal components comprises a lost-wax casting.
3. A body as claimed in Claim 1 or Claim 2 in which there are two or more metal components in the form of tubes sealed together.
4. A body as claimed in any of the preceding claims in which the metal components are of stainless steel or other corrosion resistant metal.
5. A body as claimed in any of the preceding claims in which the metal components have walls no more than 1/8th inch thick.
6. A body as claimed in any of the preceding claims in which the plastics moulding has a wall thickness at least five times that of the metal components.
7. A fluid pump or motor, the fluid passages in which are in a body as claimed in any of the preceding claims.
8. A pump or motor as claimed in Claim 7 including inlet and outlet valves assembled with the body.
9. A body having passages for fluid arranged substantially as herein specifically described with reference to FIGURE 1, FIGURE 3 or FIGURE 4 of the accompanying drawings.