US2990110A - Fluid compressors - Google Patents

Description

June 27, 1961 w. MccoMBlE 2,990,110

FLUID COMPRESSORS Filed Dec. 10, 1957 2 Sheets-Sheet 1 FIG. 1.

g c T d/S 14 16 4 12 2 1o A 9 Inventor FA EZJEWMK M/WCb/WF/E At ney June 1961 F. w. MCCOMBIE ,990,110

FLUID COMPRESSORS Filed Dec. 10, 1957 2 Sheets-Sheet 2 FIG.3.

Inventor Attorney 2,990,110 FLUID COMPRESSORS Frederick Walter McCornbie, London, England, assignor to Megator Pumps and Compressors Limited, London, England Filed Dec. 10, 1957, Ser. No. 701,770 Claims priority, application Great Britain Dec. 13, 1956 8 Claims. (Cl. 230-179) This invention relates to compressors for gaseous fluids, or exhausters hereinafter referred to for convenience of description as compressors, the invention being concerned with a compressor which includes displacement chambers or cylinders which are slidably associated with port plates, or their equivalents, formed with suction and delivery ports which are opened and closed as a result of the recriprocal movement of the displacement chambers or cylinders over the surface of the port plates. The displacement chambers may each comprise a shoe containing an eccentric disc as disclosed by British Patents Nos. 592,432, 616,618, 617,750, 622,792 and 639,017, or a plurality of cylinders each containing an associated piston, the cylinders in this case being reciprocated over their associated port plates by means of suitably arranged eccentrics or crank-pins carried by a driven shaft.

In such compressors the body or casing of the compressor is either filled with liquid, or alternatively, the casing is mounted within a reservoir or accumulator, the casing being formed with openings in its walls whereby liquid placed in the reservoir or accumulator can pass into engagement with the working parts of the compressor and act as a sealing and lubricating medium.

With existing designs of such compressors wherein the displacement chamber or cylinder as a result of its movement opens and closes suction and delivery ports in the port plate, opening and closing of these ports is necessarily symmetrical about the dead centre or end of travel of the displacement chamber or cylinder so that, for example, if the delivery port is to open at the exact beginning of the stroke, it must close at the exact termination of the stroke.

For the most efficient working, the delivery port should remain closed during the delivery stroke until the air or gas in the displacement chamber or cylinder has been compressed to the delivery pressure, and the delivery valve should then open quickly and close quickly at the end of the stroke. The chief object of the invention is to achieve such a desirable operation.

A compressor having three displacement chambers or three cylinders and having eccentrics or crank-pins arranged at 120 relative to one another, is generally most adaptable to this invention, but it can be applied to compressors having any number of chambers or cylinders greater than one.

Hitherto, it has been the practice for the delivery port in the port plate, with which the port in the displacement chamber or cylinder registers during the delivery stroke, to lead directly into the body of the compressor from which the delivery branch is taken.

According to the present invention, in a compressor of the kind set forth including a plurality of displacement chambers or cylinders operating in sequence, the effective delivery valve opening of any one displacement chamber or cylinder is under the control of another displacement chamber or cylinder so arranged in the cycle of operations as to give a retarded timing. In this way the effective valve opening can be delayed until the air or gas in the chamber has been compressed to the delivery pressure, and a quick opening movement can be obtained if required.

Referring to the drawings:

FIGURE 1 is a transverse section of one form of compressor constructed in accordance with the present invention, the section being taken on the line A--B in FIGURE 2;

FIGURE 2 is a section on the line CD in FIGURE 1;

FIGURE 3 is a vertical section through an alternative form of compressor; and

FIGURE 4 is a section on the line E-F in FIG URE 3.

Referring in the first case to the construction shown in FIGURES 1 and 2, a compressor is illustrated of the kind including a driven shaft 1 and three compressor assemblies each comprising fluid passage means including a port plate 7 and compressor means including an expansible chamber 3 and a pistonlike element 2 therein, the compressor means of said assemblies being cyclically operable by the shaft 1 which carries in this case three eccentric discs 2 arranged at an angle of to each other in the plane of rotation, each disc revolving within the expansion chamber or encircling shoe 3 defining a displacement chamber 5 and composed of rubber, synthetic rubber, plastic or other suitable material, the shoe fitting closely around the opposite faces of the disc and contacting its periphery at two diametrally positioned points. The shoe, as will be seen clearly in FIG- URE l is cut away as at 4 for the passage of the shaft 1, the shoe engaging the shaft whilst pressure is being built up, the pressure of liquid within the casing 6 serving normally to maintain the shoe in rubbing contact with a port plate 7 which is carried by a cover 8 closing an opening in one side of the casing 6. The port plate is formed with inlet means including a suction port 9 leading from a suction passage 10 which is common to the three suction ports of the compressor indicated in FIGURE 2 by reference numerals 9, 9a and 9b, the suction passage 10 having an inlet connection at one end as at 11.

The shoe is formed with a common suction and delivery port 12 and is cut away at its upper end as at 13 for a purpose hereinafter described.

In addition to suction ports 9, 9a and 9b the port plate 7 is provided with delivery means including three delivery ports 14, 14a and 14b and with outlet means including three outlet ports 15, 15a and 15b.

It will be appreciated, therefore, that reciprocal movement of each shoe over the port plate will first of all connect port 12 with suction port 9 in the port plate, which will have the effect of drawing in gaseous fluid to the interior of the shoe. As a result of rotational movement of the eccentric within the shoe this fluid will be compressed therein and as the combined suction and delivery port 12 moves into register with delivery port 14, the compressed fluid within the shoe will be forced through delivery port 14 and into its associated delivery passage 16. If reference is now made to FIGURE 2 it will be seen that passage 16 connects delivery port 14 with outlet port 15a associated with the adjacent displacement chamber 5 and consequently although the fluid can pass from shoe 3 through delivery port 14 into passage 16, it cannot enter the interior of the casing through outlet port 15a until the latter is uncovered by the adjacent shoe, thus providing a retarded delivery of fluid.

As the shoe controlling the opening of outlet port 15a is arranged at 120 relative to the preceding adjacent shoe, it will be travelling at approximately its maximum speed at the point of opening outlet port 15a thus giving the desired quick opening movement. The effective closing movement occurs at the end of the stroke when the displacement chamber 5 itself covers the delivery port 14.

It will be appreciated that the passage 16 connecting delivery port 14 with outlet port 15a will be connected to the interior of the displacement chamber 5 at the beginning o'f'the discharge stroke and any compressed fluid in the ports and passage 16 could then re-expand into the displacement chamber and impair the efficiency of the compressor. It is, therefore, desirable that passage 16 should be filled with liquid after the fluid has been discharged through port 1511 and before it is again connected to the displacement chamber. For this purpose the shoe is cut away at 13 and consequently after the compressed fluid has been discharged into the interior of the compressor casing, liquid can enter passage 16 by way of delivery port 14 and fill this passage. The slowing down and reversal of movement of the displacement chamber during the suction stroke tends to create an increase in the pressure in the liquid at its trailing end where the port 14 has been uncovered, and this pressure together with the momentum of the fluid and liquid previously discharged through the port tends to fill the passage with liquid. This effect is enhanced by shaping its upper part as at 13 so that the liquid is virtually scooped into the delivery port 14 and into its associated passage 16.

Referring now to FIGURES 3 and 4, an alternative construction is illustrated wherein the displacement chambers are defined by a number of cylinders 17, each containing an associated piston .18 which in turn is carried by a connecting rod or link 19 mounted upon an eccentric 20 carried by a driven shaft 21. To prevent angular movement of the connecting rods or links 19, a second shaft 22 is provided carrying further eccentrics 23, the connecting rods 19 thereby coupling the shafts 21 and 22 together.

In this case the cylinders 17 will reciprocate vertically over the faces of covers 8' containing suction, delivery and outlet ports which for convenience of description are given the same reference numerals as in FIGURES 1 and 2 with a prime added.

The operation of the compressor is, therefore, similar to that previously described, the only other constructional differences being that in this case the compressor is intended to be mounted in position within a reservoir or accumulator, the casing 6' being therefore provided with comparatively large openings 24 in its walls through which liquid can pass into its interior and provide adequate sealing and lubrication for the moving parts.

The operation of the cylinders and pistons is comparable with the shoes and associated eccentric discs previously described and it is proposed, therefore, not to describe the operation of this particular type of compressor in detail.

. As will be seen from FIGURE 4, the arrangement of the various ports is similar to the arrangement shown in FIGURE 2, three pairs of opposed cylinders being provided, adjacent eccentric discs being arranged at an angle of 120 relative to each other in the plane of rotation. The cylinders may be composed of metal, but it is preferred to construct them from a thermoplastic or thermohardening synthetic resin composition, or alternatively to form them from natural rubber or synthetic rubber, the cylinders being if necessary provided with internally positioned metal liners.

The connecting rods 19 are fitted with laterally projecting pins 25 for entry into slots or openings 26 in the cylinders for preventing rotational movement of the cylinders about their axes, whilst the pistons are formed with extensions 27 which can engage the shaft 21 whilst pres sure is being built up within casing 6', the pressure within the casing normally holding cylinders 17 in operative engagement with their associated port plates.

I claim:

1. A compressor comprising a casing for receiving a compressible fluid and having a discharge opening, port plate means in said casing and having a plurality of sets of inlet, delivery and outlet ports with said outlet port in communication with said casing, a plurality of hollow shoes each defining an expansion chamber and mounted forsliding movement against said port plate means with an aperture formed through the wall thereof facing said plate means, said shoes being respectively cooperative with one set of ports and movable for alternate communication between the chamber of each shoe through its aperture with the inlet and delivery ports of its set and alternate closure of the outlet port of said set, drive means in said casing and connected with said shoes for reciprocating the shoes in out of phase relation and operating their expansion chambers for conveying the compressible fluid into and out of said chambers via said shoe apertures and inlet and delivery ports, and outlet means respectively connecting the delivery port of each set with the outlet port of another set, said drive means being constructed and arranged to reciprocate said shoes in such out of phase relation that each outlet port is closed by its respective shoe to retard expelling of the fluid from the respective outlet means to the casing until the fluid in said outlet means is compressed to outlet pressure by another of said shoes.

2. A compressor according to claim 1 wherein said drive means include a plurality of circular eccentrics in out-ofphase relation and enclosed by said shoes respectively, each eccentric engaging the interior walls of its associated shoe and forming said expansion chamber therebetween.

3. A compressor according to claim 1 wherein said shoes comprise cylinders, and said drive means include a piston reciprocally mounted in each cylinder, and a plurality of out-of-phase crank elements respectively connected to said pistons.

4. A compressor according to claim 1 wherein said discharge opening is in the upper part of said casing to retain a head of liquid therein, both said delivery and outlet ports of each set being in communication with said casing, said inlet port of each set being disposed between the delivery and outlet ports, the strokes of said shoes and the spacing of the delivery and outlet ports for each shoe being such that said delivery and outlet ports are opened to said casing at opposite ends of the shoe strokes respectively to admit liquid from said casing through said delivery port to fill said outlet means prior to the discharge of fluid from the shoe chamber through said delivery port.

5. A compressor according to claim 4 wherein said drive means include a plurality of circular eccentrics in out-of-phase relation and enclosed by said shoes respectively, each eccentric engaging the interior walls of its associated shoe and forming said expansion chamber therebetween.

6. A compressor according to claim 4 wherein said shoes comprise cylinders, and said drive means include a piston reciprocally mounted in each cylinder, and a pltu'ality of out-of-phase crank elements respectively connected to said pistons.

7. A compressor according to claim 4 wherein said shoes are each provided with a scoop portion on the end cooperative with the respective delivery port for forcing liquid through said port into said outlet means as it moves toward its compression stroke.

8. A compressor comprising a casing for receiving a compressible fluid and having a discharge opening, and a plurality of compressor assemblies in said casing and cyclically operable between intake and outlet positions; each of said assemblies including inlet means for connection with a source of fluid, delivery means, outlet means incommunication with said casing, and compressor means including an expansible chamber and means for expanding and contracting said chamber, said expanding and contracting means being cyclically operable to cause said compressor means to charge said chamber from said inlet means and discharge from said chamber to said delivery means while also intermittently interrupting communication of said outlet means with said casing; said outlet means of each one of said assemblies being in communication with the delivery means of another of said assemblies; and driving means in said cas ing and operatively connected with said compressor means to operate said assemblies in such out of phase relation that delivery of the fluid through each outlet means to the casing is retarded by the compressor means of one of said assemblies until the fluid in said outlet means is compressed to outlet pressure by the compression means of another assembly.

References Cited in the file of this patent UNITED STATES PATENTS Rockwell Nov. 9, 1948 McCombie d- July 24, 1951 MoCombie July 24, 1951 McCombie Nov. 26, 1957 FOREIGN PATENTS Great Britain Sept. 17, 1947

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