US1724934A - Compound-reciprocating compressor - Google Patents

Description

Aug. 20, 1929.

H. HOPFLER COMPOUND RECIPROCATING COMPRESSOR Filed Nov. 25 1927 2 Sheets-Sheet 1 NVENTD {IL-MA,

Patented Aug. 20, 1929.

UNITED STATES PATENT OFFICE.

HANS HOPPLER. or WINTERTHUR, SWITZERLAND, ASSIGNOR TO THE FIRM or SULZER FBERES socIE'TE' ANONYME, or WINTERTHUR, SWITZERLAND.

COMPOUND-RECIPROCATING COMPRESSOR.

Application filed November 25, 1927, Serial No. 235,556, and in Germany December 1, 1926.

The present invention relates to compound reciprocating compressors and has for its object to provide an improved construction of such apparatuswhich will permit a reduction in weight and in space occupied as compared with compressors of equal output constructed in accordance with previous proposals.

It has already been proposed to arrange the cylinders of such compressors in tandem either horizontally or vertically but with this construction an excessive amount of space was occupied in the direction of length or of height of the apparatus. In addition several stuffing boxes were necessaryfrom which trouble might arise during operation. In other known forms of compressor the cylinders were arranged side by side but here again a considerable amount of space was 2 occupied and several sets of piston and connecting rods were necessary thus increasing the weight of the apparatus; also at least two stufling-boxes were necessary. Attempts have been made to reduce the weight and space occupied by providing a compressor of this type with a simple differential piston but it has been found that in such cases the working pressures set up unequal tresses in the frame work and mechanism of the compressor, and also caused a certain irregularity in running which could only be compensated by the provision of a large flywheel.

According to the present invention a compound reciprocating compressor is provided with a double-acting differential piston stepped on both sides and adapted to compress the working fluid in stages and to de liver it to a final delivery chamber through an intermediate receiver. Preferably the inlet and outlet pipes and valves are so positioned on the cylinder that changes of shape produced by stresses due to heating cancel one another and, in addition, safety valves are provided which constitute by-pass valves, each of which is adapted to connect the suction and delivery chambers of one stage, the number of valves being equal to the number of stages employed. Conveniently the arrangement of these safety valves is such that the vessel into which the working fluid is normally discharged, for example, the condenser of a refrigerating machine, may be emptied when required by opening the safety valves and thus establishlng communication between the delivery and suction chambers of the several stages.

The invention may be carried into practice in various ways but one construction according thereto is diagrammatically illustrated by way of example in the accompanying drawings, in which Figure 1 shows a longitudinal section through a two-stage compressor,

Figure 2 is a section on the line 12-?) of Figure 1,

Figure 3 is a section on the line (ll-a, of Figure 1,

Figure 4 is a view in section on the line cc of Figure 3, and

Figure 5 is a diagram illustrating the arrangement of pipes hitherto used for the purpose of emptying the vessel into which the compressor normally delivers the working fluid.

In the construction illustrated in the drawings the compressor comprises a central portion 1 and two cylinder heads 2 and 3 closed by covers 4 and 5 respectively. Within the cylinder is adapted to recipro- Cate a double-acting differential piston 6 operated by means ofa piston rod 7 passing through a stuffing box 8. The inlet pipe 9 of the compressor which may be connected for example to the evaporator of a refrigerating machine opens out into the central portion 1 and conveys working fluid to the inlet valves 10 and 11 of the first stage I. The working fluid is discharged from the cylinder of the first stage through outletvalves 12 and 13 whence it passes through a pipe 14; connected to a receiver which is not shown in the (drawing. This receiver is also connected to the inlet pipe 15 of the second stage II carried by the cylinder head 2.

The second stage of the compresser is constituted by the two outer ends or cylinder heads 2 and 3 and is provided with inlet valves 17 and 20 and outlet valves 18 and 21, the valve 20 being connected to the inlet pipe 15 by means of a conduit 19 while the outlet valve 21 is connected to the discharge pipe 16 of the second stage through a conduit 26 shown in chain lines in Figure 1.

The manner of operation of the compressor is as follows. Assuming the piston to be moving towards the left in Figure 1 then the working surface 22 of the first stage and the working surface 24 of the second stage will deliver compressed fluid through the valves 12 and 18 respectively, the fluid which passes through the valve 12 entering the receiver while that which passes through the valve 18 is discharged through the pipe 16 which may, for example, be connected to the condenser of a refrigerating machine. At the same time working fluid will be drawn in through the inlet 9 and inlet valve 11 of the first stage and also through the inlet 15, conduit 19 and inlet valve 20 of the second stage, the fluid which is drawn into the second stage coming from the receiver to which it has been delivered; under pressure by the first stage. On the return stroke of the piston towards the right in Figure 1 the fluid previously drawn into the first stage through the valve 11 will be discharged through the valve 13 and'pipe 14 into the receiver while that drawn into the second stage through the valve 20 will be discharged through the valve 21, conduit 26 and pipe 16 into the condenser. At the same time a further quantity of fluid will be drawn in to the first stage through the pipe 9 and valve 10 this fluid coming from the evaporator. Simultaneously fluid will be drawn into the second stage from the receiver through the pipe 15 and valve 17 so that at each stroke of the piston a quantity of fluid is drawn into the cylinder of each stage while at the same time a quantity of fluid compressed during the previous stroke is discharged from the cylinder of each stage.

The suction chamber 27 and delivery chamber I of the first stage are connected through a safetyvalve 28 constituting a bypassvalve shown Figure 2. Similarly the suction chamber 29 and the delivery chamber II of the second stage are connected by asafety valve 30 (Figure 3) also constituting a by-p'ass "alve. By turning these valves through 180 degrees communication may be established between the conduit 31 connected to thesuction chamber 29 and the conduit 32 connected to the delivery chamber II so that the contents of the condenser mav return directly to the evaporator.

With this construction the arrangement of the pipes shown in chain lines in Figure 5 which were hitherto necessary for the emptying of the condenser may be omitted. In Figure 5 the condenser is assumed to be at the lefthand side of the diagram and hitherto when it was necessary to empty the condenser the valves 33 and 34 had to be closed so that the fluid was conveyed, as shown by the dotted arrows, through the pipe 35 to the first stage of the compressor and then through the pipe 14.- into the second stage whence it was discharged through the pipe 36 into the evaporator assumed to be disposed on the righthand side of the diagram. lVith the construction according to the pres ent invention the by- pass valves 28 and 30 permit the suction and delivery valves to be interchanged when it is necessary to empty the condenser so that the pipes 35 and 36 can be dispensed with.

The inlet pipe 9 together with the inlet valves 10 and 11 through which the working fluid is drawn in at about "20 C. are positioned on the cylinder between the outlet valves 18 and 21 through which the fluid passes at a temperature of about C. after being compressed in the first stage. This arrangement provides room for expansion of the cylinder heads 2 and 3 due to the increase in temperature. The outlet valves 12 and 13 together with the outlet pipe 14 through which the compressed fluid passes from the first stage at a temperature of about60 G. are disposed between the inlet valves 17 and 20 through which the working fluid enters the second stage at a temperature of about 10 C. With this arrangement of the valves the expansion of the central portion 1 due to this higher temperature is balanced by the relative contraction of the cylinder heads so that changes of shape produced by stresses due to heating are avoided.

The cylinder heads may be attached to the central portion and the cylinder covers to the cylinder heads by any known method. Further, the central portion is designed to be symmetrical so that the suction side may be interchanged with the delivery side.

It will be appreciated that with a compressor according to the present invention only one stuffing box is necessary and the working pressure is used to the best advantage, while, in addition the compressor occupies less space and weighs less than compressors of equal output hitherto proposed.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. In a compound reciprocating compressor, the combination of a cylinder comprising a central portion constituting a low pressure chamber, a cylinder head connected to each end of said cylinder, said cylinder heads each having a portion therein constituting a high pressure chamber, and a double-acting differential piston stepped on both sides movably disposed in said chambers and adapted to compress the working fluid in stages therein and to deliver said fluid to a final delivery chamber through an intermediate receiver.

2. A compound reciprocating compressor as set'forth in claim 5, said cylinder having openings for inlet and outlet pipes so positioned that changes of shape produced by stresses in the cylinder structure due to heating cancel one another. 7

3. A compound reciprocating compressor as set forth in claim 5, including in the combination safety valves connecting the suction and delivery chambers of said low and high pressure stages.

4. A compound reciprocating compressor as set forth in claim 5, including in the combination a safety valve on said cylinder connecting the suction and delivery chambers of said low pressure stage and a safety valve on each of said cylinder heads connecting the suction and deliver chambers of said high pressure stage, said safety valves being adapted to be turned through 180 for emptying the vessel to be discharged by the working fluid.

5. In a two-stage compound reciprocating compressor, the combination of a cylinder having a central portion constituting a chamber of relatively large diameter, a cylinder head connected to each end of said cylinder, said cylinder heads each having a chamber therein of the same diameter, which diameter is less than that of said central chamber, and a double-acting differential piston having a central portion of relativel large diameter arranged in said central 0 amber and end portions of equal but smaller diameter arranged in said cylinder head chambers, said cylinder together with said cylinder heads having portions thereof constituting an intermediate receiver adapted to receive the Working fluid compressed in said chambers.

In testimony whereof I have aflixed my signature.

HANS HOPPLEB.

CERTIFICATE OF CORRECTION.

Patent No. 1,724,934. Granted August 20, 1929, to

HANS HOPPLER.

It is hereby Certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 3, strike out the words "to provide", and line 28, for the word "tresses" read stresses";

page 2, lines 124 and 130, claims 2 and 3, and page 3, line 5, claim 4, for

"claim 5" read "claim 1"; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1st day of October, A. D. 1929.

M. J. Moore, (Seal) Acting Commissioner of Patents.

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