US3622251A

US3622251A - Sealed piston compressor or pump

Info

Publication number: US3622251A
Application number: US875802A
Authority: US
Inventors: Charles Malcolm Allen
Original assignee: Battelle Development Corp
Current assignee: Battelle Development Corp
Priority date: 1969-11-12
Filing date: 1969-11-12
Publication date: 1971-11-23
Anticipated expiration: 1988-11-23

Abstract

A reciprocating piston compressor or pump in which the pistons are spaced from their housing walls and supported for reciprocation by elastomeric guides or supports that will allow the pistons to reciprocate. A preferred elastomeric support or guide consists of a telescoping metal-elastic belt wound around the piston and bonded to the housing and piston walls. Either the elastomeric guides or separate resilient seals seal the space between the piston walls and the housing so that upon reciprocation fluid may be pumped or compressed from an inlet valve to an outlet valve on one side of the seal and the reciprocating mechanism may be independently lubricated on the other side of the seal.

Description

United States Patent 3,200,757 8/1965 Steffes 92/97 X FOREIGN PATENTS 650,797 3/1928 France 92/97 Primary Examiner-Robert M. Walker Attorney-Gray, Mase and Dunson ABSTRACT: A reciprocating piston compressor or pump in which the pistons are spaced from their housing walls and supported for reciprocation by elastomeric guides or supports that will allow the pistons to reciprocate. A preferred elastomeric support or guide consists of a telescoping metalelastic belt wound around the piston and bonded to the housing and piston walls. Either the elastomeric guides or separate resilient seals seal the space between the piston walls and the housing so that upon reciprocation fluid may be pumped or compressed from an inlet valve to an outlet valve on one side of the seal and the reciprocating mechanism may be independently lubricated on the other side ofthe seal.

1 SEALED PISTON comrasssoa R PUMP BACKGROUND In the lubricating system of prior known compressors and pumps constructed on the reciprocating piston principle, lubricants commonly find their way into contact with the fluid being compressed or pumped. The mechanism (i.e., eccentric cam, crankshafi, etc.) utilized to effect piston reciprocation must, of course, be provided with a lubricant to prevent frictional wear. In spite of piston rings and other devices for confining the lubricant to the reciprocation efl'ecting mechanism there is at least some lubricant penetration to the areas of the intake and outlet valves. I

For example, it is common practice in refrigeration systems to have hermetically sealed motors and compressor units in which the lubricating oil and the refrigerant are intermixed. In open systems which are fitted with dynamic rotary shaft seals, such as automobile air conditioners, the lubricant and refrigerant are also intermixed and both may be lost when the dynamic rotary shaft seal fails.

Ofien there are problems of contamination in the manufacture and transfer of pure gases and air by the lubricant of the compressor mechanism. To avoid such contamination in this industry compressors have been constructed utilizing dry" lubricants such as Teflon coatings. Such dry lubricants suffer from leakage and wear rapidly providing a relatively short life for the compressor or pump. Also, the lubricating system may be adversely affected by the corrosive effect of the gases being pumped to measurably reduce the life of the mechanism.

Where the fluid material is or contains an abrasive, for example, water-coal slurries, concrete, etc., the pumps suffer from excessive wear due to the fact the abrasive material is in direct contact with the close fitting lubricated reciprocating or transfer mechanisms.

The food industry must also pump varieties of liquids and semiliquids intended for human consumption and obviously contamination by lubricants cannot be tolerated. In this industry the cleanliness and sterility of the apparatus handling the food is essential.

THE INVENTION I have now devised a compressor or pump wherein the piston is suspended in its housing for reciprocation by resilient members that are disposed to stretch or expand and contract. The circumferential space between the piston and the cylinder housing wall is sealed either by the resilient members or a separate flexible sealing member. By this means the reciprocating mechanism and the pumping chamber are sealed from one another and the lubricant and fluid being pumped are effectively isolated from one another.

By efiecting such a seal and preventing penetration of the fluid being pumped or compressed by the lubricant of the reciprocating mechanism (and or vice versa) the disadvantages of the prior known compressors and pumps described above are obviated.

The pump or compressor of the present invention is best described in conjunction with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a three-cylinder pump or compressor constructed in accordance with the present invention; and

FIG. 2 is a cross-sectional view of a preferred elastomeric guide or support as seen along the line 2-2 of FIG. 1.

In the pump or compressor of FIG. 1, three pistons are shown to be mounted within radially positioned cylindrical housings 11. Each piston 10 is spaced from the inner walls of its housing 11 and is supported therein by two linear motion piston guides 12. The pistons 10 are caused to reciprocate within their respective housing by a reciprocating mechanism shown in the present embodiment as an eccentric cam 13 which is caused to rotate on a drive shaft 14 by an appropriate power source (not shown). Springs 15 surrounding each piston 10 bear on lugs 16 attached to the pistons and cylindrical housing walls respectively to maintain each piston in constant contact with cam 13 so that rotation of the cam will cause each piston to appropriately reciprocate within their respective cylindrical housings.

Appropriate cover plates or manifolds 17 cover the ends of each cylindrical housing and are provided with inlet ports 18 and outlet ports 19. Ports l8 and 19 are provided with appropriately positioned intake and

exhaust reed valves

20 and 21, respectively. Each reed valve 20 is appropriately mounted to the inside surface of a manifold 17 and is disposed to resiliently flex to open and permit fluid from an external source (not shown) to enter the compression chamber 22 when pressure within the chamber 22 is less than that of the external source as when the piston 10 is being forced inwardly by spring 15. During the compression stroke of each piston or when the cam 13 is forcing the piston 10 outwardly to constrict chamber 22 the pressure within chamber 22 rises to cause the appropriate reed valve 20 to close. Reed valves 21, of course, operate oppositely closing when reed valves 20 are open and opening when reed valves 20 are closed.

It will be immediately appreciated that if the linear motion piston guide and seal 12 seals the space between the circumferential walls of piston 10 and the inner walls of cylindrical housing 11, lubricants essential for lubricating the reciprocating mechanism (which in their present embodiment consists of eccentric cam 13, shaft 14, and the bottom surfaces of pistons 10) cannot penetrate to chambers 22. Thus, fluids flowing through chambers 22 cannot be contaminated by the lubricants from chamber 24.

The preferred linear motion piston guide and seals 12 each consist essentially of an elongated metal tape 25 (see FIG. 2) that is bonded to an elastomer strip 26 which is, in turn, welded, bonded, or fused at one end to the inner surface of the walls of cylindrical housing I], wound about the piston 10, and bonded or fused to the circumferential surface of piston 10. In this manner the seal 12 will telescope in either direction to permit pistons 10 to reciprocate in the manner shown. If the winding is tight enough, such a guide may in itself constitute an adequate seal between

chambers

24 and 22.

Should the pressures employed in chamber 22 be too great, a penetration of seal 12 by the fluid being pumped or compressed may occur. In this event a resilient diaphragm such as that shown at 29 may be employed. Diaphragm 29, constructed of a resilient material and mounted between manifold 17 and cylindrical housing 11 to seal a chamber 22 from chamber 24 is preferably constructed of a strong elastomer which in conjunction with the piston guide and seal 12 will effectively prevent any penetration of lubricants into chamber 22 or penetration of the fluids being pumped or compressed into chamber 24.

It will, of course, be appreciated that inlet ports 18 and outlet or exhaust ports 19 of the device of FIG. 1 will generally communicate with conduits (not shown) disposed to convey fluid to and from the pump via inlet and

outlet chambers

23 and 25.

It will also be appreciated that seals, etc., that will effectively seal cumferential surface of pistons 10 and the inner surface of housing 11 and which will permit pistons 10 to reciprocate may be used in place of piston guide and seals 12 through the latter construction has been found to be preferable. For apparatus such as refrigerant compressors, the elastomer of the elastomer-metal laminates will preferably be constructed of materials such as Neoprene W since this material exhibits superior resistance to deterioration in the presence of refrigerant liquids and gases such as Freon.

The body structure, piston, and cylinder will generally be rron or aluminum and in some cases of any resilient diaphragm, the area between the cirsuitable plastics.

The present compressor concept renders it preferable that the piston amplitude be relatively low as compared to conventional piston type compressors. In the order of one-half inch or so (i.e., one-fourth inch to three-fourth inch).

Because of the internal friction and heating of elastomers, the metal laminate constituent of guides 12 may project beyond the elastomer to within the spacing between pistons W and the inner surface of cylindrical housing walls llll (see dotted outline 30 in MG. 1 so as to provide for cooling heat transfer surfaces. The metal laminate oi the lower seal nearest the lubricated cam actuator, may be projected into the lubricant for the purpose of cooling. in other cases tins from both upper and lower seals may project toward each other within the space between pistons 10 and housings Ill and coolant may be circulated between the piston and housing walls. For modest cooling requirements, ports may be open in the walls of cylinder housing lll to expose the region between the seals to a cooling fluid. Further, the motion of the piston may be used as a source of forced convection cooling.

The elastomer-metal laminates may be made by the present state of the art methods of coating a strip of metal with an equivalent thickness of uncured elastomer (0.010 inch or so). The laminated metal-elastomer strip is then wound on a ring mandrel cured and bonded to form a laminate. (Whose overall thickness may range from about one-fourth to three-eighths inch or more). The laminated spool is then inserted into an external ring and cured so that in the finished unit the elastomer is under substantial compressive stress. The compressive stress is sufficient that axial motion will not cause the elastomer to become tensioned. The assembly is then bonded, either by the elastomer or other suitable cohesive, to the piston and cylinders, thereby effecting a set of dual hermetic seals and nonsliding contact and nonlubn'cated piston guide bearings. Elastomer-metal composite bearings, made by the methods described, have high radial stifi'ness and will provide the needed stiffness to resist undesired radial displacement caused by the friction at the piston-eccentric lubricated contact.

In some applications, it may be desirable to replace the piston return spring 15, cam 13, and drive shaft 14 with a conventionally designed connecting rod and crankshaft piston reciprocating mechanism. The wrist pin bearing could be made of an elastomer-metal laminate bearing such as to provide angular oscillatory motion.

In some applications where gases are to be pumped and light weight is desirable, molded plastic components may be used for the piston, cylinder, and crankshaft housing. If specially corrosive gases or fluids are to be pumped, it may be desirable to place a barrier diaphragm over the type of the piston and seal to prevent the working fluid from contacting the piston seal assembly (such as diaphragm 29 described in conjunction with FIG. 1).

Valve means for inlet and outlet ports can be accomplished with conventional reed-type valves or other known and appropriate valving devices.

For use in the food industry, plastic or metallic construction may be employed and a sterile replaceable diaphragm 29 may be placed over the piston and elastomer seals. For many food applications, however, this would not be necessary as the pump is easy to disassemble and clean.

The pump may be driven by any external source including fluid pressure.

In certain applications, such as an automotive air-condition refrigerant compressor, the flexibility of the piston-guide seal provides a performance advantage. At very high speeds conventional compressors tend to produce excessive peak cylinder pressures due to the flow restriction of the discharge valves. In addition, the volumetric flow capacity of the compressor usually is higher than necessary. Deflection of the piston guide seal under these high-cylinder pressures would tend to increase the reexpansion volume at the top of the piston stroke and thereby cause a desirable reduction in the discharge flow from the compressor.

Refrigeration compressors at times experience damage due to slugging," that is, operation with large amounts of liquid in the cylindersv Because of the ability of the piston guide seal to deflect, this compressor would have exceptional ability to resist this kind of damage.

Although the preferred resilient guides or supports of the apparatus of the present invention consists of the wound, metal-elastomer tape of FlG. 2 that is disposed to telescope inwardly and outwardly with the reciprocation of pistons 10, it will be appreciated that in many instances other guides or supports may be employed. For example, diaphragms such as diaphragms l6 constructed of an elastomer such as rubber may be bonded to the pistons to act as a guide and support. The metal-elastomer tape of HG. 2 may be constructed entirely of an elastomer or entirely of a metal or may be constructed of a material not meeting either of the definitions of metal or plastomer. Such members may be any members capable of supporting the pistons Ml within the housings 11 while permitting them to reciprocate.

Iclaim:

1. A pump comprising:

a. a housing with at least one chamber;

b. a piston positioned within said chamber, the side surface of said piston being spaced from the walls of the chamber;

c. resilient guides or supports attached to the side surface of said piston and the walls of said chamber and positioned to span the gap therebetween, said guides or supports providing lateral support for said piston at each end in addition to allowing said piston to reciprocate within said chamber upon the application of an intermittent force to an end surface of said piston;

d. at least one inlet and at least one outlet port positioned in the housing walls of said chamber, said inlet port being provided with valve means disposed to open when the pressure outside said chamber is greater than the pressure inside said chamber and said outlet port being provided with valve means disposed to open when the pressure inside said chamber is greater than the pressure outside said chamber and closed when the pressure outside said chamber is greater than the pressure inside said chamber;

e. resilient sealing means sealing the space between said piston and said chamber walls positioned between said end surface and said ports so as to expand and contract to allow said piston to reciprocate; and

f. means for applying intermittent force to said end surface so that said piston will reciprocate and pump fluid from said inlet through said outlet ports.

2. The pump of claim I, wherein said resilient sealing means consists of the resilient guides or supports being continuous in the space between said piston and the chamber walls.

3. The pump of claim 1, wherein said resilient sealing means consist of at least one separate resilient diaphragm extending over said piston.

4. The pump of claim 1, wherein said resilient guides or supports are constructed of an elastomer.

5. A pump comprising:

a. a housing with at least one chamber;

c. resilient guides or supports attached to the side surface of said piston and the walls of said chamber and positioned to span the gap therebetween, said guides or supports providing lateral support for said piston in addition to allowing said piston to reciprocate within said chamber upon the application of an intermittent force to an end surface of said piston;

d. at least one inlet and at least one outlet port positioned in the housing walls of said chamber, said inlet port being provided with valve means disposed to open when the pressure outside said chamber is greater than the pressure inside said chamber and said outlet port being provided with valve means disposed to open when the pressure inside chamber is greater than the pressure outside said chamber and closed when the pressure outside said chamber is greater than the pressure inside said chamber;

f. means for applying intermittent force to said end surface so that said piston will reciprocate and pump fluid from said inlet through said outlet ports;

g. wherein one or more of said resilient guides or supports comprise elongated tapes attached at one end to the side surface of said piston wound about itself as well as said piston and attached to the inner surface of said chamber at the other end of said tape; said tape is bonded to said piston, previous layers of said tape, and to the walls of said chamber to provide a guide and support that will deflect with total elasticity a limited distance to permit said piston to reciprocate.

6. The pump of claim 5, wherein said tape consists of a metal-elastomer laminate.

7. The pump of claim 5, wherein said resilient sealing means consists of the guides or supports.

8. The pump of claim 5, wherein said resilient sealing means consists of a separate elastomeric diaphragm extending across said chamber to further seal between said one surface and said ports.

i i l l i

Claims

1. A pump comprising: a. a housing with at least one chamber; b. a piston positioned within said chamber, the side surface of said piston being spaced from the walls of the chamber; c. resilient guides or supports attached to the side surface of said piston and the walls of said chamber and positioned to span the gap therebetween, said guides or supports providing lateral support for said piston at each end in addition to allowing said piston to reciprocate within said chamber upon the application of an intermittent force to an end surface of said piston; d. at least one inlet and at least one outlet port positioned in the housing walls of said chamber, said inlet port being provided with valve means disposed to open when the pressure outside said chamber is greater than the pressure inside said chamber and said outlet port being provided with valve means disposed to open when the pressure inside said chamber is greater than the pressure outside said chamber and closed when the pressure outside said chamber is greater than the pressure inside said chamber; e. resilient sealing means sealing the space between said piston and said chamber walls positioned between said end surface and said ports so as to expand and contract to allow said piston to reciprocate; and f. means for applying intermittent force to said end surface so that said piston will reciprocate and pump fluid from said inlet through said outlet ports.

2. The pump of claim 1, wherein said resilient sealing means consists of the resilient guides or supports being continuous in the space between said piston and the chamber walls.

5. A pump comprising: a. a housing with at least one chamber; b. a piston positioned within said chamber, the side surface of said piston being spaced from the walls of the chamber; c. resilient guides or supports attached to the side surface of said piston and the walls of said chamber and positioned to span the gap therebetween, said guides or supports providing lateral support for said piston in addition to allowing said piston to reciprocate within said chamber upon the application of an intermittent force to an end surface of said piston; d. at least one inlet and at least one outlet port positioned in the housing walls of said chamber, said inlet port being provided with valve means disposed to open when the pressure outside said chamber is greater than the pressure inside said chamber and said outlet port being provided with valve means disposed to open when the pressure inside chamber is greater than the pressure outside said chamber and closed when the pressure outside said chamber is greater than the pressure inside said chamber; e. resilient sealing means sealing the space between said piston and said chamber walls positioned between said end surface and said ports so as to expand and contract to allow said piston to reciprocate; and f. means for applying intermittent force to said end surface so that said piston will reciprocate and pump fluid from said inlet through said outlet ports; g. wherein one or more of said resilient guides or supports comprise elongated tapes attached at one end to the side surface of said piston wound about itself as well as said piston and attached to the inner surface of said chamber at the other end of said tape; said tape is bonded to said piston, previous layers of said tape, and to the walls of said chamber to provide a guide and support that will deflect with total elasticity a limited distance to permit said piston to reciprocate.