US3807910A

US3807910A - Compressor

Info

Publication number: US3807910A
Application number: US00249914A
Authority: US
Inventors: W Paget
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-05-03
Filing date: 1972-05-03
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30

Abstract

A small multistage nonlubricated compressor for air and other gases has annular concentric low-lift inlet and discharge reed valves. At least the discharge valve is backed by a backing member that has the curvature of the open discharge valve. Each cylinder has a set of interchangeable liners each of which has inlet openings through the side walls thereof, and the inlet openings of each liner of a set are spaced different distances along the axis of the liner from the openings of the other liners of the set. Selection of an appropriate liner thus predetermines the cylinder capacity without upsetting the dynamic balance of the compressor.

Description

United States Patent [191 Paget 1 COMPRESSOR [76] Inventor: Win W. Paget, 2044 Lancaster Rd,

Homewood, Ala. 35209 [22] Filed: May 3, 1972 [21] Appl. No.: 249,914

[451 Apr. 30, 1974 Primary Examiner-William L. Freeh Attorney, Agent, or Firm-Young & Thompson 5 7 ABSTRACT A small multistage nonlubricated compressor for air and other gases has annular concentric low-lift inlet and discharge reed valves. At least the discharge valve is backed by a backing member that has the curvature of the open discharge valve. Each cylinder has a set of interchangeable liners each of which has inlet openings through the side walls thereof, and the inlet openings of each liner of a set are spaced different distances along the axis of the liner from the openings of the other liners of the set. Selection of an appropriate liner thus predetermines the cylinder capacity without upsetting the dynamic'balance of the compressor.

14 Claims, 17 Drawing Figures [52] US. Cl 417/564, 137/525.3 [51] t. F04b 21/02 [58] Field of Search a; 417/534, 454, 564

[56] References Cited UNITED STATES PATENTS 3,403,847 10/1968 Parker .1 417/454 2,935,248 5/1960 Gerteis 417/564 3,070,122 12/1962 Weatherhead et a1... 417/564 3,066,856 12/1962 Frank 417/564 2,213,256 9/1940 Paget 417/562 1,996,763 4/1935 Halleck 417/564 m I 1 I i 26 2B I5 PATENTEDAPR 30 m4 SHEET 1 OF 3 COMPRESSOR The present invention relates to compressors, more particularly of the small multistage nonlubricated type for compressing air and other gases.

It is known to provide concentric valving in compressors, in which annular flat valves require only a relatively low lift and a low clearance volume while providing comparatively large valve areas. However, the guidance of such valves is difficult because of friction problems and resulting wear on the valves and/or their guides.

Accordingly, it is an object of the present invention to provide compressors with substantially annular inlet and discharge valves, which operate substantially frictionlessly and with very little wear.

Another object of the present invention is the provision of compressors with annular valves that can operate at very high speed with relatively low inertia.

It is also known to provide compressors with means for varying the capacity of the cylinder. In single-stage compressors, a common means for doing this is to use eccentrics of various throws, in combination with means for adjusting the cylinder assemblies axially for the purpose of maintaining minimum end clearance. However, it is particularly advantageous to provide some means for varying cylinder capacity in the case of two-stage compressors, as small nonlubricated compressors are required at a wide range of capacities and discharge pressures. When it is attempted to change the capacity of a cylinder of a multicylinder compressor by changing the throw, the dynamic balance is disturbed; and this is particularly disadvantageous in the case of high-speed compressors.

Accordingly, it is an object of the present invention to provide means for changing the capacity of a compressor cylinder without upsetting the dynamic balance thereof.

Still another object of the present invention is the provision of means for increasing the capacity of a compressor cylinder without enlarging the same.

Finally, it is an object of the present invention to provide compressors which will be relatively simple and inexpensive to manufacture, easy to assemble, adjust, operate, maintain and repair, and rugged and durable in use.

Other objects, features and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinalsectional view ofa compressor according to the invention;

FIG. 2 is an' elevational view of the inner side of a compressor head;

FIG. 3 is a cross-sectional view taken on the line 33 of FIG. 2;

FIG. 4 is an elevational view of the discharge valve seat;

FIG. 5 is an axial view of the inlet valve stop plate, as seen from the left of FIG. 1;

FIG. 6 is an elevational view of the inlet valve seat;

FIG. 7 is an elevational view of a first embodiment of inlet valve;

FIG. 8 is an edge view of the inlet valve of FIG. 7;

FIG. 9 is an elevational view ofa second embodiment of inlet valve;

FIG. 10 is an elevational view of the discharge valve;

FIG. 11 is an edge view of the discharge valve;

FIG. 12 is an elevational view of the discharge valve backing member;

FIG. 13 is a cross-sectional edge view of the discharge valve backing member;

FIG. 14 is a fragmentary view of the left end of FIG. 1, showing a modification in which the inlet and outlet valve seats are made integral with each other;

FIG. 15 is a view similar to the left end of FIG. 1, but showing another modified construction;

FIG. 16 is an elevational view of an inlet valve for use with the FIG. 15 embodiment; and

FIG. 17 is an elevational view of a discharge valve for use with the FIG. 15 embodiment.

Referring now to the drawings in greater detail, and first to FIG. 1, there is shown a two-stage compressor according to the present invention comprising an open crankcase 1 which supports a drive shaft 2 in bearings 3. Conventional drive means (not shown) are provided for rotating shaft 2. Diametrically opposed eccentrics 4 and 5 are keyed to shaft 2 to be driven thereby and are connected by bearings to the inner ends of connecting rods 6 and 7 which in turn drive pistons 8 and 9 of the two compressor stages.

Low pressure cylinder 10 has an inlet 11 and a discharge 12 and a generally cylindrical cylinder liner 13. High pressure cylinder 14 has an inlet 15 and a discharge 16 and a generally cylindrical liner 17. Discharge 12 is connected to inlet 15 by finned tubing (not shown).

In addition to the annular inlet and discharge valves to be described hereinafter, each cylinder liner 13 or 17 has an annular series of openings 18 or 19 through the side wall thereof, the openings 18 communicating with inlet 11 and the openings 19 communicating with inlet 15. All ofthe openings of a given liner are at the same location along the axis of the liner. However, for each cylinder, there is a set consisting of a plurality of liners that are identical to each other except for the location of the openings, the openings of each liner of the set being at a different axial location from the openings of the other liners of the set.

As the liners 13 or 17 of each set would differ from each other in appearance only by the axial location of the openings 18 or 19, it is not believed to be necessary to show in the drawing more than one liner of each set.

The liners 13 and 17 need not function both in the same way. To illustrate this point, the liner 13 has been shown as a liner which increases the capacity of its associated cylinder without enlarging the same; while the liner 17 decreases the capacity of its cylinder. Specifically, when the piston 9 is at the bottom of its stroke, the lip 20 of piston 9 will only partially expose the openings 18. The intake movement creates an underpressure in cylinder 10, due to the resistance to air flow of the inlet valves and passages; but when the openings 18 are exposed, this underpressure is quickly relieved by a flow of air in through the openings 18. Upon the return or compression stroke, however, the lip 20 of piston 9 will seal the openings 18 before the pressure can rise to expel through openings 18 the same amount of air that entered through openings 18. In other words, the amount of air compressed in cylinder 10 per stroke will be greater because of openings 18 than if no openings 18 were provided; and the capacity of cylinder -is thus increased for a given stroke or throw of piston 9, without an actual enlargement of the cylinder.

The liner 17 is shown as an example of an arrange ment in which the cylinder capacity is selectively decreased. At the bottom ofits stroke, the lip 21 of piston 8 is a substantial distance below the openings 19, so that the capacity of cylinder 14 is correspondingly reduced by the outflow of air through openings 19 during the first portion of the compression stroke, without the need for changing the length of that stroke. It is to be noted, in connection with high-pressure cylinder 14' and the openings 19 of its liner 17, that, in addition to the conventional piston ring 22 at the lip 21 of piston 8, a rearwardly spaced ring 23 is also provided to prevent leakage back along the piston after ring 22 has passed the openings 19 during the compression stroke. A corresponding second piston ring is not needed in the low-pressure stage.

The liners l3 and 17 may be made of any suitable self-lubricating material such as graphite, polyimide, polytetrafluoroethylene, etc. The outer surfaces of the pistons in sliding contact therewith may be hardchrome plated in the case of graphite liners or may be of aluminum with a hard anodized peripheral surface if the liners are of polyimide or polytetrafluoroethylene.

Air to be compressed in each stage is drawn in through an annular inlet valve and discharged through an annular discharge valve, the inlet and discharge valves being concentric and of the flexible or reed type. The valves of the high-pressure stage will be described hereinafter, it being understood that those of the lowpressure stage'can have the same general configuration if not the same dimensions. v

The left end of the compressor as shown in FIG. 1 is closed by a cylinder head 24 which is best seen in FIGS. 2 and 3 as comprising a peripheral flange 25 that borders inlet and

discharge passageways

26 and 27, respectively, and that clamps the outlet valve seat 28 (FIG. 4) between itself and the casing 1 when head 24 is secured to casing l by conventional bolts (notshown). Head 24 has a central hollow boss 29 in which is received the screw-threaded shank 30 of the inlet valve stop plate 31 (FIG. 5 A nut 32 retains stop plate 31 in the FIG. 1 position, with inlet valve seat 33 (FIG. 6) clamped between plate 31 and boss 29. Inlet valve seat 33 has an annular series of inlet openings 34 therethrough and disposed thereabout.

In FIGS. 7 and 8 is shown an inlet valve 35 for use in the compressor of FIG. 1, comprising a very thin annular wafer of stainless steel or the like, having a pair of diametrically opposed tabs 36 integral therewith on its inner periphery, and a similar pair' of diametrically opposed tabs 37 on its inner periphery at 90 to the tabs 36.

Inlet valve stop plate 31 has a pair of diametrically opposed relatively shallow recesses 38 therein which receive tabs 36 of valve 35 with minimum clearance. Thus plate 31 in effect pinions valve 35 to the under side of inlet valve seat 33 on a line passing through tabs 36.

Plate 31 has relatively deeper recesses 39 therein, that are diametrically opposed to each other and at 90 to recesses 38; and the tabs 37 are free to ride in recesses 39.-The depth of recesses 39 thus limits the lift of valve 35 when valve 35 opens by bending about the imaginary line passing through tabs 36. Thus tabs 36 are retainer tabs for securing valve 35 to its seat, while tabs 37 limit the lift of valve 35 when they strike the bottoms of recesses 39. Upon the intake stroke of the piston, air to be compressed is drawn on through inlet passageway 26 through openings 34 and past the flexed valve 35 into the cylinder chamber; while upon the compression stroke of the piston, valve 35 is forced against seat 33 and the openings 34 are thus all closed.

An alternative form of inlet valve 40 is shown in FIG. 9, which is a thin flat wafer of stainless steel or the like. as in the embodiment of FIGS. 7 and 8, but which is not centrally open. Instead, valve 40 has lift-limiting tabs 41 which perform the same function as the tabs 37 in FIG. 7; but the internal portion of valve 40 is delimited by two W-shaped slots 42 which are connected to the outer periphery of valve 40 by bridges 43 that serve to fasten the peripheral or flexing portion of valve 40 to the central or secured portion of valve 40. Needless to say, when the valve of FIG. 9 is used, it is not necessary to provide plate 31 with recesses 38.

An outlet valve 45 suitable for use with the compressor of FIG. 1 is shown in FIGS. 10 and 1], which may also be a thin flat annular wafer of stainless steel or the like. Valve 45 has retention tabs 46 diametrically opposed on its inner periphery, which are secured with minimum clearance in recesses 47 on an annular boss 48 of cylinder head 24. Boss 48 backs up inlet valve seat 33 radially outwardly of openings 34; and by receiving tabs 46 in recesses 47, boss 48 secures discharge valve 45 against seat 33 along an imaginary line passing through tabs 46 with the outer periphery of outlet valve 45 overlying the inner periphery 49 of discharge valve seat 28. The discharge outlet of the cylinder is thus the annular space between the outer periphery of inlet valve seat 33 and the inner periphery 49 of v discharge valve seat 28.

A discharge valve backing member 50 is provided, as shown in FIGS. 12 and-13, which is of spring steel and is generally annular in shape and is substantially thicker than valve 45. Backing member 50 has a natural curvature in its unstressed condition as shown in FIG. 13 and has diametrically opposed tabs 51 on its inner periphery. Tabs'5l, like the tabs 46 on valve 45, are also received in the recesses 47 on boss 48 of cylinder head 24, so that boss 48 holds discharge valve 45 and its.

backing member 50 in sandwich relationship with the backing member 50 normally curving away from valve 45 about a bend line that passes through tabs 51. Boss 48 has lugs 52 thereon, as seen in FIGS. 2 and 3, lugs 52 pressing on those portions of backing member 50 which are shown at the extreme left and right of FIG. 13, thereby to flatten backing member 50 only somewhat from its unstressed condition as shown in FIG. 13 and to urge member 50 against valve 45 at least along the imaginary line passing through tabs 51. Backing member 50 is of course on the side of valve 45 which is opposite the piston.

Upon the intake stroke of the piston, valve 45 will be drawn flat against the adjacent portions of

seats

28 and 33 and will close the annular discharge opening. But upon the compression stroke of the piston, the air leaving the cylinder will flex valve 45 about the bend line passing through tabs 46, and valve 45 will progressively spread out against backing member 50. Valve 45, like valve 35, thus operates frictionlessly and without substantial wear. Indeed, the cushion of air trapped between valve 45 and backing member 50 ensures that even at the highest speeds, valve 45 will not be subjected to damage.

One might wonder why valve 45 needs a backing member 50 but inlet valve 35 does not. The answer is that the inlet valve opens slightly after the piston passes top dead center and closes slightly after bottom dead center. In both of these positions, the piston is traveling slowly and the pressure differential across the valve is relatively small.

By contrast, the discharge valve 45 opens when the piston is at about midstroke, at about the fastest point in the travel of the piston. The rate of pressure change in the cylinder at this point is almost unbelievably rapid. In certain high-speed high-pressure compressors of the general type of the invention, the rate of pressure change at this point can be over 2 million pounds per square inch per second. Even a very light discharge valve with very low lift will still have enough inertia to cause the instantaneous pressure in the cylinder to exceed the discharge pressure by at least percent. This overpressure literally tires the discharge valve off its seat, and the kinetic energy of the opening discharge valve is accordingly quite great. The backing plate absorbs or withstands this kinetic energy, and it is for this reason that the shape of the backing member is such as to conform to the natural shape to which the discharge valve deflects upon opening, so as to avoid what would otherwise be high local stresses in the discharge valve as it comes to a stop. The importance of the air cushion between the discharge valve and the backing member will thus be apparent.

In FIG. 14, a modified form of the invention is' disclosed, in which the

separate valve seats

28 and 33 of FIGS. 1, 4 and 6 are replaced by a single integral seat 53 having inlet openings 34' therethrough. However, instead of an annular discharge passageway, seat 53 has an annular series of discharge openings 54 therethrough which are alternately covered and exposed by valve 45. Naturally, the lip 21 of piston 8 is omitted in this embodiment.

FIG. 15 shows a fragmentary cross section similar to the left end of FIG. 1, but of a modified form of the invention in which the valves and their backing plates are reversed as to their radial order .and are of a modified construction. In FIG. 15, the inlet valve 55 is the radially outer of the inlet and discharge valves, and is backed up by a backing member 56 suitably curved as was backing member 50 in the embodiment of FIG. 1, for the purpose not only of minimizing wear on inlet valve 55 but also of urging valve 55 against its seat. As best seen in FIG. 16, valve 55 is provided with three equally peripherally spaced notches 57. A dowel 58 is disposed in each notch 57, and backing member 56 has a curvature such as to press inlet valve 55 against its seat at the location of each of the three dowels 58. Inlet valve 55 thus flexes upon opening, into contact with backing member 56 between the dowels 58 but is held against movement relative to the dowels 58 by backing member 56 at the location of the dowels 58 and hence does not rub against'dowels 58 or undergo any other appreciable form of wear. Of course backing member 56 also has correspondingly spaced notches (not shown).

Discharge valve 59 (FIG. 17) is similarly backed by a backing member 60 by which it is held against its seat at the locations of three dowels 61 disposed in three notches 62in the inner periphery of valve 59.

An advantage of the construction of FIGS. 15-17 is the simplicity of producing a notch rather than a tab.

It will be evident from a comparison of FIGS. 7l3, on the one hand, and FIGS. 16 and 17 on the other hand, that the number of tabs or notches, and in general the number of points at which the inlet and discharge valves are secured to their seats against flexure, is variable. In general, the thinner the material of the valve, the greater will be the number of, points of securement; and the higher the operating speed of the compressor, the greater will be the inertia of the moving portions of the valve and the thinner will be the valve material so as to reduce that inertia to a minimum.

From a consideration of the foregoing disclosure, therefore, it will be evident that all of the initially recited objects of the present invention have been achieved.

Although the present invention has been described and illustrated in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Thus, for. example, although each valve and each backing member in the illustrated embodiments has been shown as being unitary, it is of course possible to subdivide these radially into a plurality of concentric valves and backing members between one common valve seat and one common valve retainer. These and other modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

valve seat at a plurality of regions spaced about the periphery of said valve and restraining the-valve from any motion relative to said valve seat at said regions, said valve being free to flex to an open position between said regions, and means limiting the lift of said valve between said regions.

2. A compressor as claimed in claim I, said one opening comprising a continuous annular slot.

3. A compressor as claimed in claim 1, said opening comprising an annular series of spaced openings.

4. A compressor as claimed in claim 1, said valve comprising a flat annular wafer of thin sheet material.

5. A compressor as claimed in claim 1, said valve comprising a circular wafer of thin sheet material having a pair of arcuate slots that define between them a central securing region of said valve which is interconnected with a peripheral region of the valve by a plurality of peripherally spaced bridges of the material of the valve.

6. A compressor as claimed in claim 1, said valve having equally spaced projections on a periphery thereof by which said regions are secured to a said valve seat.

7. A compressor as claimed in claim 1, said valve having projections on a periphery thereof by which said lift is limited.

8. A compressor as claimed in claim 1, there being two said regions diametrically opposed about the periphery of said valve, said valve flexing to an open position spins about an imaginary line interconnecting said regions.

9. A compressor as claimed in claim 1, which is a nonlubricated compressor.

10. A compressor as claimed in claim 1, said limiting means comprising a backing member having the curvature that is assumed by the opening valve.

11. A compressor as claimed in claim 10, said backing member being an annular spring substantially more rigid than said valve.

12. A compressor as claimed in claim 1, said valve having equispaced notches in a periphery thereof, and dowels in said notches at said regions of said valve.

13. A compressor as claimed in claim 12, said periphery being the outer periphery thereof.

14. A compressor as claimed in claim 12, said periphery being the inner periphery thereof.

Claims

1. A compressor comprising a cylinder, a piston reciprocable in the cylinder, means for reciprocating the piston, the cylindEr having inlet and discharge openings communicating with the interior of the cylinder, annular valve seats concentric with said cylinder and bordering said inlet and discharge openings, and valves for opening and closing said openings, each of said valves comprising an annular flexible valve concentric with said cylinder and overlying one of said openings, means maintaining said annular valve against the adjacent valve seat at a plurality of regions spaced about the periphery of said valve and restraining the valve from any motion relative to said valve seat at said regions, said valve being free to flex to an open position between said regions, and means limiting the lift of said valve between said regions.

2. A compressor as claimed in claim 1, said one opening comprising a continuous annular slot.

9. A compressor as claimed in claim 1, which is a nonlubricated compressor.