US2034159A

US2034159A - Compressor

Info

Publication number: US2034159A
Application number: US641987A
Authority: US
Inventors: Everett W Swartwout
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-11-10
Filing date: 1932-11-10
Publication date: 1936-03-17
Anticipated expiration: 1953-03-17

Description

March 17, 1936. E W` SWARTWOUT l 2,034,159

COMPRESSOR Filed Nov. 10, 1932 3 Sheets-Sheet 2 March. 17,1936- E. w. sWARTwoUT 2,034,159

COMPRESSOR Filed Nov. l0, 1932 3 Sheets-Sheet 3 INVENTOR. Ever UW u/ arf uf TTORNEY Patented Mar. 17, 1936 TJNiTs sTaTgs PATENT orrics 29 Claims.

This invention relates to compressors.

More particularly, this invention relates to iluid compressors which compress air or gas from any given pressure to a relatively higher pressure.

v The compressors may be of any type including those of the double acting, single and multiple stage types, and those of the multiple cylinder single stage type, operated to produce either a vacuum or to increase pressures above atmospheric pressure, and may be driven by any type of prime mover.

An object of my invention is to provide a new means for compressing a fluid, a new compression cycle characterizing the operation, and a new compressor embodying the principles of my invention.

According to my invention, I provide a compressor, which when compared to the conventional or prior art type of compressor, greatly decreases the usual losses due to the expansion of the uneXpelled compressed fluid remaining in the clearance volumes after delivery has ended, suddenly reduces the pressure in the clearance spaces after delivery has ended, spontaneously super-charges the new charges to be compressed, greatly increases the volumetricA eficiency, and increases the isothermal compression eiiciency.

A further object according to my invention, is to provide compressors which when operated at constant speed, with means to vary the quantities delivered exactly in proportion to the demand for air or gas in quantities varying in increments from of full capacity down to zero capacity, and at the same time, consuming power approximately in proportion to the quantities delivered.

The accompanying drawings show one representative embodiment of my invention. Its principles may be applied in various ways without departing from the invention, as comprehended by the scope of the appended claims.

Fig. l is a side elevation of one form of my invention, partially in vertical central section terminating at the inlet and discharge openings.

Fig. 2 is a detail cross-sectional view, taken on line 2 2 of Fig. 1, and on a radial plane approximately at right angles to the plane of the section shown in Fig. 1. Fig. 2 shows the piston advanced toward the left as compared with its position in Fig, l.

Fig. 3 is a side elevation partially in vertical central section, showing a complete assembly of a vertical, two cylinder, single acting belt driven compressor embodying my invention, independent of my variable capacity control and regulating equipment.

Fig. 3a is a sectional plan view through the cylinder head block of Fig. 3 above the valves.

Fig. 4 is a diagram of the compression cycle 5 typiiying the operation of the conventional or prior art type of compressor.

Fig. 5 is a diagram of the compression cycle embodying my invention, independent of the variable capacity features.

10 Fig. 6 is a diagram showing two compression 20 Fig. 8 is a side elevation of the compressor shown in Fig. 1, and shows one form of a complete assembly including the variable capacity regulating and control equipment embodying my invention.

Fig. 9 is a transverse partial horizontal sectional detail of a by-pass interconnecting the two respective opposite ends of the compressor cylinder, and includes the control valve shown in Fig. 8 of this complete arrangement embodying my invention.

Fig. 10 is a partial vertical sectional detail of the pressure regulating control of Fig. 8, laid horizontally.

Referring to Figs. 1 and 2a single cylinder, single stage, double acting, direct connected, motor driven compressor is shown in Which, the cylinder l, the head end head plate 2, and the crank end head plate 3 are bolted together and to the frame 4. In the description which follows, reference to bolts obviously needed to bolt stated parts together Will not be made. The crank shaft 5 is supported at one end by bearings mounted in the frame and at its opposite end by an outboard bearing in accordance with the usual practise. The rotor of the motor 6 is mounted directly on the crank shaft 5 and transmits the power for operating the compressor by way of rotating the counterweighted crank 'l which is secured to the crank shaft 5 by the key 8. The crank pin Q is also rmly attached to the counterweighted crank 'l and is rotated by the crank shaft 5. The connecting rod I0 transmits motion from the crank pin 9 to the crosshead Il which reciprocates the piston rod I2 and the attached piston I3. The piston I3 is provided with the usual piston rings I4, I5, to reduce the leakage past the piston I3 to a minimum as it is reciprocated in the cylinder I.

The inlet pipe opening I6 connects with the chamber II from which the inlet stream of uid to be compressed is divided to alternately pass through the respective inlet passages I8, I9 leading to the inlet valve chambers 20, 2| respectively. The inlet valve 22 is positioned in the head plate 2 and held in place by the bonnet 24 and the stud 26. The inlet valve 23 is positioned in the head plate 3 and held in place by the bonnet 25 and the Stud 2'I. Preferably, I employ automatic inlet valves 22, and 23 of the standard plate type of construction which depend for their opening and closing entirely upon pressure differences so as to admit air or gas to the cylinder I through the

heads

2, 3 and prevent its return from the cylinder I when being compressed.

'I'he discharge valves 28, 29 are also preferably of the standard construction plate type of automatic valves positioned respectively in the

heads

2, 3 and retained in position by the

bonnets

30, 3| and the

studs

32, 33 respectively. The discharge valve 28 associated with the valve chamber 34 and the passage 36, and the discharge valve 29 associated with the valve chamber 35 and the passage 37, which valve chambers join in the compartment 38 to which the discharge pipe 39 is attached. The discharge valves 28, 29 are provided to automatically permit the discharge of compressed air or gas from the cylinder I under the condition that its pressure exceeds that of the discharge line 39, and to prevent the return of fluid to the cylinder on the suction strokes of the piston I3. The discharge valve 28 is provided with the seat section 49 and the guide section 4I so as to control its limits of movements when opening and closing. The control parts of the discharge valve 29 are similar in construction to those of the discharge valve 28. The inlet valves 22, 23 are preferably similar in-construction to the discharge Valve 28, but positioned so as to operate in the reverse direction of travel of fluid to that of the discharge valves 28, 29.

For cooling the parts, I provide the water jacket 42 in the head plate 2, the water jacket 43 in the cylinder I, and the water jacket 44 in the head plate 3.

Referring to Fig. 2, the piston I3 is shown at or near`its extreme position of travel toward the head plate 2 thus leaving the space indicated adjacent the port 45 between the cylinder I, the head plate 2, the inlet valve 22 and the discharge Valve 28 which is called the clearance space, or clearance volume, or compression compartment, at the head end of the cylinder I. Likewise, there will be a clearance space, or clearance volume or compression compartment indicated adjacent the port 46 between the piston I3 and the head plate 3 operative when the piston I3 has travelled to its extreme position at the crank end of the cylinder I. In each of these clearance spaces, and in all prior types of compressors, an unexpelled charge of compressed fluid remains in the clearance volume after the normal expulsion or delivery of the compressed fluid has been completed at or near the end of each stroke of the piston. The trapping of some of the compressed fluid in the clearance space, when re-expanded to intake pressure, is equivalent to a certain amount of free air at inlet conditions which is not delivered by the compressor.

This re-expansion of the unexpelled compressed fluid which remained in the clearance space ensues for and consumes a considerable portion of the return stroke of the piston before the pressure in the cylinder has become reduced to permit the opening of the inlet valves which depend for their opening and closing entirely upon pressure diierences. This clearance volume expansion causes a late opening of the inlet valves which greatly reduces the quantities sucked into the cylinder to be compressed, and also greatly reduces the net delivered capacity of compressors operating according to these principles, and is a primary reason why the average industrial compressor of the prior type delivers only from 40% to 80% of its piston displacements, depending upon its size, and the pressure differences to which the fluid has been compressed. The ratio between net delivery and piston displacement determines the volumetric efliciency of the compresser.

According to vmy invention, I provide the passage-4I having the ports 45 and 49 at the head end of the cylinder I to form a by-.pass about the piston E3 and interconnect the clearance Space with the interior of the cylinder I on the opposite side of the piston I3 when the piston I3 has most nearly approached the head 2 at or near this end of its stroke. Likewise, I provide the passage 48 having the ports 46 and 56 at the crank end of the cylinder ,I to form a by-pass about the Vpiston I3 and interconnect the clearance space with the interior of the cylinder I on the opposite side of the piston I3 when the piston I3 has most nearly approached the head 3 at or near the other end of its stroke. The piston I3 covers .and uncovers the

ports

49 and 59 as it travels and reverses .its direction of travel at or near the respective ends of its strokes. The

ports

49, 59 are positioned in the interior walls of the cylinder I at locations immediately adjoining the piston I3 on its sides opposite the clearance space when the said piston I3 is at or near the respective ends of its strokes. The ports 49, 56 may be rectangular in shape of opening into the cylinder I, and positioned with the longer sides of the respective rectangles in planes parallel to the faces of the said piston I3. The number of passages 4l, 48 and the respective ports is such as to provide any desired capacity to become fully effective in aggregate area of openings at each of the respective ends of the cylinder I with a minimum travel of the piston I3. Expulsion of compressed iluid is terminated just prio-r to the end of each stroke of the piston I3 due to the opening of the ports 49, 5I] by the travel of the piston I3, The uncovering of the port 49 by the piston I3 in its travel toward the head 2 at or near the end of its stroke by-passes the fluid about the piston I3 and elects a ashing over of the unexpelled compressed uid from the clearance space 45 through the passage 41 and the port 49 into the interior of the cylinder I which at this stage is being lled with a new charge of huid at inlet pressure. Likewise, the uncovering of the port 56 at the opposite end of the cylinder I by reverse travel of the piston I3 in the direction of the head 3, by-passes the fluid abo-ut the piston I3 and effects a flashing over of the unexpelled compressed huid from the clearance space 46 through Ythe passage 48 and the port 50 into the interior of the cylinder I which at this stage is being filled with a new charge of fluid at inlet pressure. These alternating Hash-overs from the clearance spaces at or near the respective opposite ends of the strokes of the piston I3 eifect a sudden and partial compression of the respective new charges which have been sucked into the cylinder I3, and as these initiatory compressions are effected prior to the beginning of the respective compression strokes of the piston I3, and entirely independently of extra valves, extra cylinders, and do not require auxiliary co-mpression chambers, the phenomena is herein defined as spontaneous super-charging. The flashing over of the compressed uid from the clearance space into the cylinder I reduces the pressure in such clearance space and equalizes the pressures on the opposite sides of the piston I3 at the pressure to which the new charge in the cylinder I has been raised as a result of the spontaneous supercharging of the said new charge.

Travel of the piston I3 toward the crank end head plate 3 covers the port i9 and closesthe passage l thus preventing further communication at this time between the clearance space within the cylinder I between the piston I3 and the crank end head plate 3. Simultaneously, compression from the previously resultant partial or initiatory compression begins in the cylinder I between the piston I3 and the crank end head plate 3, and also, re-eXpansion of the reduced pressure volume begins on the opposite side of the piston I3 in the crank end clearance space. The pressures on the opposite sides of the piston I3 are equalized up to the point of the closing of the port 49 by the piston I3. The closing of the port 49 and the re-expansion of the reduced pressure volume in the head end clearance space, which now includes the volume of the passage 131, requires much less travel of the piston i3 in proportion to the whole stroke of the piston I3 than similar travel of the piston in a prior art conventional type of compressor in which the clearance volume is re-expanded from the relatively higher discharge pressure. Therefore, according to my invention, the opening of the inlet valves 22 and the consequent beginning of the suction portion of the stroke occurs markedly earlier than in the prior type, which feature of my invention results in improved volumetric eiciency.

As the piston I3 approaches the crank end of the cylinder I, compression is completed and expulsion takes place while the piston I3 covers the port 59 of the passage 4S. Further travel of the piston toward the head plate 3 now uncovers the port 50, discontinues expulsion, establishes communication between the crank end clearance space through the passage 4B to the interior of the cylinder between the piston I3 and the head end head 2, resulting in the flashing over of compressed fluid from the crank end clearance space to spontaneously super-charge the new charge sucked in behind the piston I3, reduction of the pressure of the crank end clearance space, including the passage 48, and equalization of the pressures on the two sides of the piston I3. Reverse, and return travel of the piston i3 continues the equalization of pressures on the two sides of the piston I3 until the port 50 of the passage 48 is closed by the face of the piston nearest the head 2. Further travel of the piston in its stroke effects re-eXpansio-n of the reduced pressure volume in the crank end clearance space down to the inlet pressure, the opening of the inlet valve 23, and the sucking in of a new charge through the inlet valve 23,

while on the opposite side of the piston I 3, compression of the partially compressed fluid is taking place between the cylinder I, the head 2 and the piston I3, followed by expulsion through the discharge valve 28, the opening of the port 459 and the passage 4'! and a repetition of the cycle. Thus, by automatically by-passing the piston I3 effective upon its own travel, at or near the respective ends of its strokes, liberally sized inlet and discharge valves and passages may be employed to thereby reduce the losses through the valves, whereby earlier opening of the inlet valves occurs in each suction stroke, the volumetric efiiciency is greatly increased, and the overall efficiency is higher than heretofore obtained.

Referring to Fig. 3, I provide a vertical compressor of the two cylinder, single acting, single stage type with the crank 5| to operate the elongated trunk piston 52, and at 180 degrees from the crank 5I, the crank 53 is provided to operate the o-pposite elongated trunk piston 5G. lThe cranks 5I, 53 may be integrally forged with the crank shaft 55 and mounted in the bearings 5E, 5l, 53 supported by the crank case 59. The cylinder block t5, having the water `iacket 5I may contain the two parallel cylinders 62, 63 and may be mounted directly upon the crank case 55. The piston 52 is shown connected by the crank 5I of the crank shaft 55 with the connecting rod 64, and the opposite piston 5t is shown connected by the crank 53 of the crank shaft 55 with the connecting rod 65. The cylinder head block 56, having the water jackets 6l, houses the

inlet valves

68, 69, their bonnets ie, i, their studs. l2, 13, the inlet opening 'ifi and the passages l5, 76, the block 53 is bolted to and supported by the cylinder block 65. The cylinder head block 55 also houses the discharge valves Ili, IGI, their studs M2, and such discharge valves communicate with the

cylinders

52, 53 respectively and with the outlet opening ILlli, through the outlet passages M5, Hit respectively. The bonnets of the discharge Valves Mii, Ifi, are not shown, being similar to the bonnets le, 'il of the inlet valves 63, 55. The

inlet valves

68, 59 and the discharge valves Mii, Mii are preferably of similar construction to corresponding valves of Fig. l.

The cylinder 62 is connected with the cylinder 53 by the passage TI. The port 'I8 of the passage 'il is opened to communication with the passage 'il and the cylinder 63 above the piston 55 when the piston 52 is in its lowest position as shown. Upward travel of the piston 52 closes off communication between the cylinder 62 and the cylinder 63 following which compression and eX- pulsion is effected within and from the cylinder 62. A simultaneous downward travel of the piston 513 effects the re-expanding of its clearance volume, the sucking in of a new charge, and then the opening of the port 82 and the passage 85, thus establishing communication through the port Si and the cylinder 52 to effect the flashover of the uneXpelled compressed fluid remaining above the piston 52 after expulsion has ended, thus super-charging the new charge in the cylinder 53, thus reducing the pressure in the clearance space above the piston 52 and eifecting a reduction in the loss of capacity due to the re-expansion of the clearance volume above the piston 52 as it travels downwardly, after which the cycle is repeated. A complete cycle of the piston 55 is harmonized at 180 degrees with the piston 52 and the phenomena which takes place in the cylinder 53 is similar to that which takes place in the cylinder 62. The cycle in cylinder 63 is traced to include suction of the new charge upon downward travel of the piston 54, opening of the port 82 and spontaneous supercharging of the new charge above the piston 54, upward travel of the piston 54 effecting compression followed by expulsion or delivery, opening of the port I8 by the piston 52, the flash-over to the cylinder 62 of the clearance volume to reduce the pressure in the clearance volume above the piston 54, then, downward travel of the piston 54, upward travel of the piston 52, closing of the port 'I8 and the passage I'I by the piston 52, re-expansion of the reduced pressure clearance volume above the piston 54, the resultant earlier opening of the inlet valves above the piston 54, the consequent greater volumetric efficiency, and then alternating repetitions of the cycle in the opposite cylinders G2 and 63. rIThus, the eiect is in substance the same as that obtained in the double acting compressor of Figs. l and 2. The pulley 83 is mounted directly on the crank shaft 55 for driving the compressor with a belt from a suitable motor.

Referring to Fig. 4, the diagram illustrates and bounds by lines the compression cycle of the typical conventional prior art type of fluid compressor. The 4diagram is a pressure volume diagram, usually called an indicator diagram, with absolute pressures plotted as ordinates, and with volurnes plotted as abscissas. In the diagram, A B C D A represents an ideal indicator card taken from a standard conventional type of an air compressor with clearance. In this case A G represents the stroke of the piston of the machine and C E represents the volume of the clearance, that is the volume between the face the piston at the end of its stroke and the discharge valves, and consists of the actual volurne between the piston and the cylinder head plus the volume of the ports and passages connecting the cylinder with the inlet and discharge valves. Air is discharged at the absolute pressure P2 along B C and at point C the piston reverses in direction and the discharge valve closes. As the piston travels backward the volume of air represented by C E expands along C D until the absolute inlet pressure P1 is reached at D when the inlet valve opens. It is evident that the actual volume drawn into the cylinder is now A D instead of the piston displacement A G and the ratio of A D to A G is called the volumetric eniciency of the compressor.

Referring to Fig. 5, similar points are shown on the diagram for comparison with the diagram shown in Fig. 4 and these similar points are denoted by the same lettera, and also, additional points are shown by additional letters to diierentiate between the diagrams according to Figs. 4 and 5, and, when these points are connected with lines, the boundary of the diagram, Fig. is obtained. The diagram, Fig. 5 represents my new method of compressing a fluid and my new compression cycle characterizing my new method of compressing according to my invention in its most fundamental form. Tracing the pressure volume indicator card as shown on the diagram, Fig. 5, AIBCI-IJ HDA represents an ideal indicator card according to my invention. In this case A G represents the stroke of the piston I3, Figs. 1 and 2, and C E represents the Volume of the clearance 45, that is the volume between the face of the piston I3 at the end of its stroke and the discharge valve 28 and consists of the actual volume between the piston I3 and the -cylinder head 2 plus the volume of the ports and passages connecting the cylinder I with the inlet valve 22 and lthe discharge valve 28, plus the Volume of the -passage 41. Air is compressed adiabatically along the line I B and discharged or expelled at the discharge absolute pressure P2 along B C and at the point C the piston I3 uncovers the port 59, delivery or expulsion ceases, the discharge valve 28 closes, the pressure in the clearance i5 drops vertically on this diagram spontaneously supercharging the new charge of free air on the opposite side of the piston I3. This vertical pressure drop is represented by the line C H, the pressure on both sides of the piston I3 are equalized on the constant pressure line H J at the super-charge absolute pressure Pa after which the piston I3 reverses its direction of travel, line J I-I, and closes the port 49. As the piston I3 travels toward the head plate 3, the volume of air in the clearance 135 represented by the volume C E expands from the .spontaneoussuper-charged absolute pressure P3 along the line H D until the absolute inlet pressure P1 is reached at D when the inlet valve 22 opens. It is evident that the actual volume drawn into the .cylinder I is A D and that the ratio of A D to the piston displacement A G is much greater than that of the diagram represented by Fig. 4. After suction has taken place along D A, the port 50, Fig. 2, is opened by the piston I3, the passage i3 by-passes the piston i3, and spontaneous super-charging from the vertical downward expansion of the clearance i5 on the opposite side of the piston suddenly and vertically increases the pressure between the piston I3, the head 2, and the cylinder I from the absolute inlet pressure P1 along the line A I to the spontaneously super-charged absolute pressure P3 from which the cycle is repeated. The operations of a double acting compressor as shown in Figs. l and 2, and also of a two cylinder single acting compressor as shown in Fig. 3 are harmonized and synchronized in the juxtaposed diagrams shown in Fig. 6.

Referring to Fig. 6, the pressure volume diagram 34 represents the phenomena which occur in the cylinder I between the piston i3 and the head plate 2, Figs. l and 2, and also in the cylinder 62 above the piston 52, Fig. 3. Simultane ously, the phenomena occurring in the cylinder I between the piston i3 and the head plate 3, `Figs. 1 and 2, and in the cylinder 63 above the piston 54 of Fig. 3, are shown by the pressure volume diagram 85, Fig. 6. The two diagrams are placed in juxtaposed position with respect to each other, andthe points are projected upon the circle 86 to simultaneously show now the phenomena as they occur on the opposite sides of the piston i3 are harmonized and synchronized, and to show the interdependence of the phenomena which occur o-n the opposite sides of the piston I3. The arrows in the diagrams 84, $5 show the direction of travel of the piston I3 in the cylinder I. The simultaneous phenomena as they occur in the cycles on the opposite sides of the piston I3 are as followsz-Diagram 85, vertical downward expansion of clearance Volume and flash-over to opposite side of piston, line kl', diagram Sii, vertical rise in pressure from spontaneous super-charging along line Iam- Diagram Bd, compression, line cd and expulsion, line de, diagram 85, re-expansion of clearance volume, line Zg and suction, line glu-Diagram 84, vertical downward expansion of -clearance and flash-over to opposite side of the piston, line ej', diagram 85, vertical rise in pressure from the inlet pressure, or spo-ntaneous super-charging, line hi;-Diagram 34, re-eXpansion ci clearance volume, line fa., suctionQline ab, diagram 85, compression, line and expulsion or delivery, line ik, which completes the cycle. The details of the phenomenaJ of each of the diagrams 38, and 85 are the same as those more fully outlined in Fig. with the accompanying description.

Thus, I have shown means for by-passing about the piston of a double acting compresso-r at or near the respective ends of its strokes, for periodically interconnecting the respective ends of the cylinder and similar means for interconnecting the two opposite compression ends of the respective pairs of cylinders of a single acting compressor at or near the respective ends of the strokes of the piston operating therein, to spontaneously super-charge the new charges sucked in to be compressed, to periodically equalize the pressures in opposite compression compartments. to cause earlier opening of the inlet valves and the sucking in of a larger charge to be compressed, all when operating at full capacity, and at the same time producing higher overall eiliciency.

Referring to Fig. '7, I show the phenomena as they occur in the operation oi' compressors according to my invention, in which the beginning of a suction stroke on one side of the piston I3, and the beginning of a compression and expulsion stroke on the other side of the piston IS are both delayed and varied in length to vary the capacity continuously in increments in exact proportion to the demand for compressed iuid to maintain a relatively constant pressure in the discharge pipe. Similar to the showings in Fig. 6, the two pressure volume indicator diagrams 81, 88 are placed in juxtaposed position with respect to each other, and the points are projected upon the circle B9 to simultaneously showthe phenomena synchronized as they occur on the opposite sides of a double acting piston, and to show how these diagrams are bounded by lines in sequence and which are traced as followsz-Diagram 81, vertical downward expansion of the clearance volume and flash over to the opposite side of piston, line en', diagram 88, vertical rise in pressure from the inlet pressure due to the spontaneous supercharging of the new charge along line hz'-Diagram Si', by-pass interconnecting the opposite ends oi the cylinder is kept open to equalize the pressures on the opposite sides of the piston in a double acting compressor shown by the constant pressure line nf, and by the constant pressure line io in diagram 88, following which the by-pass interconnecting the opposite ends of the cylinder is closed in response to the action oi a pressure responsive re gulator;-Diagram 81, by-pass closed and consequent beginning of the delayed re-expansion of the clearance volume, line a, and suction along the relatively short line ab, diagram SS, by-pass closed, and consequent delayed beginning o adiabatic compression represented by the line oi which is followed by the relatively short delivery along the line jk;- The by-pass interconnecting the opposite ends of the cylinder is again opened, the pressures on the respective opposite sides of the piston in a doubie acting compressor are again equalized, and as shown on diagram 83, vertical downward expansion oi the clearance occurs along the line kp', and the ilash ovei` to the opposite side oi the piston spontaneously super-charges the newly sucked in charge along the line bc of diagram 81;-The valve in the by-pass interconnecting the respective ends of the cylinder is periodically kept open to produce equal pressures on the respective sides of the piston along the lines cm of diagram 81, and pl, diagram 88. The by-pass interconnecting the opposite ends of the cylinder is again closed following which adiabatic compression takes place along the line 1nd, and delivery along the relatively short line de of diagram 81, while in diagram 88, re-expansion of the clearance from the spontaneously super-charged pressure down to the inlet pressure occurs along the line Zg, the delayed opening of the inlet valve having taken pla-ce at the point g, after Which suction of the partial capacity new charge occurs along the relatively shortened line gli, after which the cycle is repeated. It will be understood that if the by-pass valve interconnecting the opposite ends of the cylinder is held open throughout the entire stro-ke of the piston, the capacity of the compressor will be zero and no compression will take place, also if the by-pass interconnecting the ends of the cylinder is kept closed continuously, the capacity of the compressor will be 100%, and that varying capacities as required are effected by closing the said bypass valve at different points in the stroke of the piston corresponding to the variable requirements.

Figs. 8 and 9 show the compressor disclosed in Figs. 1 and 2 of my invention with the added features of my invention which embody the means of Varying the capacity exactly in proportion to the demand for compressed fluid according to the controlled cycle for compression of a iiuid as particularly disclosed in Fig. '7 herein. Like numerals denote the same parts as shown in Figs. 1 and 2, and their description will not be repeated. In

addition to the disclosure according to Figs. 1'

and 2 of my invention, I provide according to Figs. 8 and 9, means for periodically interconnecting the respective opposite ends of the cylinder I, and means for periodically disconnecting the said respective ends oi the cylinder I, and pressure responsive means for controlling the timing of the interconnecting and disconnecting of the said opposite ends of the cylinder I, and the duration of time during each stroke of the piston I3 for which the said opposite ends oi the cylinder I are interconnected and disconnected to delay the beginning of, and make unefective, a portion of each of the suction and compression strokes of the piston i3 to vary the quantity of compressed iiuid sucked in through the inlet pipe I6 and delivered into the discharge pipe 3S in exact proportion to the-demand. It will be understood that when the demand for compressed fluid decreases, the pressure in the 'discharge pipe increases until the eiiective capacity of the compressor is reduced. Also, when the demand increases, the pressure in the discharge line decreases until the effective capacity of the compressor is increased. Therefore, I also provide pressure responsive control means eiective in operation in accordance with the required variations in capacity.

The cylinder I is provided with the by-pass passages 4'! and 48 as disclosed in Figs. and 2, and also with the by-pass passage Sil connecting with the cylinder I and the head plate 2 by the passage 9i, and connecting aiso with the opposite end of the cylinder I, and the head plate 3 by the passage 92. The valve 93 is provided to periodically open and close the by-pass passage 90 in response to variations of pressure in variation with the demands upon the compressor, for variations in delivery. The valve 93 and the valve gear which operates it may be oi the semirotative or Corliss type Valve and valve gear, or, they may be of any other of the well known types of non-releasing valve gears and valve mechanisms which would be suitable for the requirements. When the valve 93 is opened and held open, the pressures on the two respective sides of the piston i3 are equalized to delay the beginning of adiabatic compression on the one side of the said piston I3 and to simultaneously delay the beginning of re-expansion of the clearance volume on the opposite side of the piston I3, both of which begin when the valve S3 is closed, all as shown in Fig. 7.

Referring to Fig. 8, the valve closing arm 94 is Xed onto the stem 95 of the valve 93 and connected by a rod S0 with the piston of a dash pot 91. The valve opening arm 9S is loosely mounted on the stem of the valve 93 and traveis independently of the arm 04. The trip cam 99 is pivoted to the arm 93, and the trip arm |00 is also pivoted to the arm 98 and has a pin |0| engaging with the cam 05. The latch block |02 is attached to the closing arm 94, and the latch block |03 is attached to the trip arm |00. The wrist lever |04, mounted on the bracket |05 is connected by the rod |06 with the opening arm 90. The wrist lever |04 is also connected by the rod |01 with the rocker |03, and by the rod |09 with the eccentric strap H0 and the eccentric III, mounted on the auxiliary shaft ||2 and which is operated at twice the speed of the crank shaft 5 by the gears |I3 and ||4 to operate in harmony with the successive strokes of the piston I3.

eferring to Fig. 10, an automatic regulator is provided which operates in response to changes in the pressure in the discharge pipe as shown, or it may be varied in application to operate in response to changes in the pressure in the inlet pipe for compressors used as vacuum pumps. The automatic regulator determines the points of tripping and closing the by-pass valve S3 if and after it has been opened. The regulator comprises a vertical cylinder I |5, mounted on the bracket H5, a plunger III tted in the lower end of the cylinder H5, a weighted sleeve IIS tted and movable vertically on the cylinder H5, a spring ||9 interposed between the plunger lll and the upper end of the sleeve I I8. A checking or retarding device may consist of the dash pot |20 xed to the upper end of the sleeve H8, and a plunger |2|, xed to the stand |22 which is mounted on the bracket H6. The sleeve Il may be adjustably weighted by the divided rings |23 to determine the pressure which the compressor is to maintain. The cylinder IE5 is connected below the plunger I II with the discharge pipe 3S by the pipe |24. The sleeve H3 is connected by crank arms |25 engaging a groove |25 see Fig. 8, and with a rocker shaft |21 supported by the stand |22. One arm of the L- lever |28, suspended by a bar |29 from the shaft |21, is connected by a rod I 30 with a corresponding arm |3| on the shaft |21. The other arm 32 of the lever |28 is connected by the rod |33 with the trip cam 99. The bar |29 is connected by the rod |34 with the eccentric strap |35 of the eccentric |36 which is mounted upon the shaft ||2 and driven by the shaft 5 through the gears H3, H4. The eccentric through the rocker |08 and wrist lever |04, vibrates the valve opening arm 98 through a constant arc, and

opens the by-pass valve 93 at or near the end of each stroke of the piston I3 immediately following the end of expulsion of compressed fluid from the cylinder i if the cam 99 is in position to permit the engagement of the trip blocks |02, |03. The times or points of tripping the blocks |02, |03 and the consequent closing of the by-pass valve 93 after being opened, is determined by the pressure regulator according to Fig. 10 which moves the cam 99 into position to disengage the trip blocks |02, |03 sooner or later according to the pressure exerted on the plunger Ill. An increase in pressure in the discharge pipe 39 causes the trip blocks |02, |03 to be engaged longer and the by-pass valve 93 to be closed later to effect reduced delivered capacity. A decrease in pressure in the discharge pipe causes the trip blocks |02, |03 to become disengaged earlier thus causing the relatively earlier closing of the by-pass valve 53 to increase the delivered capacity, The limit of operation is reached when the trip blocks |02, |03 remain disengaged all of the time thus keeping the by-pass valve 93 closed continuously to effect full capacity, that is delivery from the compressor all as otherwise disclosed in the compression cycle according to Figs. 6 and 7 of my invention. In variable capacity compressors according to my invention, the compression line leading up to expulsion, and the expulsion which follows, and the pressure of spontaneous super-charging caused by the ashover past the piston I3 is determined from the normal volume of the clearances 45, and 46 and the other usual factors. The re-expansion of the clearances from the pressure of the said spontaneous super-charging down to the inlet pressure is based upon a Variable clearance dependent upon the normal volume of the clearance space 45 or space 46, Figs. 1 and 2, plus the volume swept through by the piston I3 up to the time of the closing of the by-pass valve 93, Figs. 7, 8 and 9.

The displacement of a fluid compressor is the Volume displaced by the net area of the piston in cubic feet per minute. compressor is the actual amount of fluid in cubic feet per minute at inlet conditions which is compressed and delivered. Volumetric eiciency is the ratio of capacity to the displacement of a compressor. umetric eiciency depends upon cylinder clearance and the absolute ratio oi compression. The absolute ratio of compression is the ratio of the discharge pressure P2 pounds absolute pressure divided by the inlet pressure P1 pounds absolute pressure and is expressed as R. The mean eiTective pressure is obtained from the indicator diagram, and when substituted in the well known formula, and also when considering volumetric eiciency, the indicated horse power per 10G cubic feet of free fluid per minute actually delivered by the compressor is obtained for the adiabatic compression of the fluid. The actual indicated horse power of any compressor is greatly modified by the amount of iiuid it actually delivers in proportion to its piston displacement and, or volumetric efficiency. The method of calculating the horse power theoretically required to compress a fluid isothermally is also well known. The ratio of the theoretical isothermal horse power to the actual horse power per 100 cubic feet of fluid actually compressed and delivered per minute is the basis for a real comparison between any two compressors. The relations between absolute pressures, absolute temperatures and vol- The capacity of a Other things being equal, the vol- 'y urnes in adiabatic compression and expansion may be found in the well known exponential equations.

No compressor ever delivers an amount of fluid equal to its piston displacement because of various effects of operating conditions, but primarily, because of the clearance loss. For the purpose of better showing the advantages of co-mpressors according to my invention, and also to compare the power consumption and eiciencies of the same with the conventional prior type of compressor, similar structural features such as inlet and discharge valves and the like, are considered duplicated, and also operating conditions such as speed, inlet and discharge pressures, and inlet temperatures are considered the same for each type.

Whereas I have described my invention by reference to specific embodiments thereof, it will be understood that many modifications and changes may be made without departing from the spirit of the invention.

I claim:

1. In a compressor, the combination with a cylinder having clearance spaces, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, and means associated with the said cylinder and the said piston for eiiecting reductions in the pressure of the fluid in the clearance spaces prior to the re-expansion of the fluid in the clearance spaces upon reverse travel of the said piston.

2. In a compressor, the combination with a cylinder having clearance spaces, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, dis- 'charge valve means, inlet and discharge openings, said inlet openings communicating with Said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, and passage means respectively communicating with said clearance spaces and provided with openings located in the 'cylinder within the limit of travel of the piston and covered and uncovered by the piston at respective stages of its travel.

3. In a compressor, the combination with a cylinder having compression compartments, of a p-iston reciprocating therein, po-wer operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, and means associated with the compression compartments of said cylinder and the said piston for eiiecting spontaneous supercharging of the new charges to be compressed without the use of auxiliary compression compartments or auxiliary compressors.

4. In a compressor, the combination with a cylinder having clearance spaces, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, and means for periodically equalizing the pressures in the clearance spaces and the cylinder at or near the respective ends of the strokes of the said piston, and for continuing said equalization of pressures during portions of the return strokes of the said piston.

5. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openingscommunicating with said 'clearance spaces on opposite sides of the piston for all stages of position of the piston and passage means respectively communicating with the compression compartments and respectively having ports communicating respectively with the inlet and discharge openings for automatically by-passing the said piston at or near the respective ends of the strokes of the said piston.

6. In a compressor, the combination with a cylinder having compression compartments, of a piston means reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston and passage means respectively communicating with the compression compartments and respectively having ports communicating respectively with the inlet and discharge openings, said ports being controlled by the operation of the said piston at or near the respective ends of the strokes of the said piston.

7. In a compressor, the combination with a cylinder means having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, and passage means and port means for said passage means controlled by the operation of the said piston at or near the respe'ctive ends of the strokes of the said piston for periodically effecting equal pressures in the respective compression compartments and the cylinder means.

8. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, and means associated with the said cylinder and the said piston for effecting reductions in the pressures in the compression compartments prior to the reversals of direction of travel of the said piston, re-expansion of the compression volumes from relatively low pressures to the inlet pressures, and relatively earlier opening of the said inlet valve means.

9. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet Valve means, discharge valve means, inlet and discharge openings, and means associated with the said cylinder and the said piston for eiiecting reductions in the pressures in the compression compartments to a pressure greatly lower than the discharge pressure, re-expansion of the compression volumes from the relatively low pressure to the inlet pressure, relatively earlier opening of the inlet valves, the sucking in of relatively larger charges to be compressed, and higher volumetric eiliciency.

10. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, and means for by-passing the said piston at or near the respective ends of its strokes to eiect flash-overs to the opposite compression compartments and simultaneous supercharging therein, reductions in the pressures in the compression compartments prior to the reversals of direction of travel of the said piston, re-eXpansion of the compression volumes from relatively low pressures, relatively earlier opening of the inlet valves, the sucking in of relatively larger charges to be compressed, and higher volumetric eiiiciency.

1l. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, and ash-over means controlled by the operation of the said piston for effecting equal pressures on both sides o-f the said piston at or near the respective ends of the strokes of the said piston, the pressure on the one side being the pressure to which the new charges of. fluid have been initially increased in pressure by supercharging, the pressure on the other side of the said piston means being the reduced pressure from which re-expansion of the clearance volumes begin, to effect improved volumetric efficiency and improved isothermal compression eiciency.

12. In a compressor, the combination With a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, and iiash-over means communicating respectively with the compression compartments and having ports communicating respectively with the inlet and discharge openings, said ports being controlled by the operation of the said piston for effecting equal pressures in the compression compartments at or near the respective ends of the strokes of the said piston, the pressure in the compression compartments being substantially the pressure to which the new charges of fluid to be compressed have been initially increased in pressure by super-charging, the pressure in the compression compartments being the reduced pressure from which re-expansion of the clearance volumes begin, to effect improved volumetric efliciency and improved isothermal compression eiciency.

13. In a compressor, the combination with a cylinder having compression compartments, of

a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, passage means communicating respectively with said compression compartments and having ports communicating respectively with said inlet and said discharge openings controlled by the operation of the said piston means to periodically interconnect and disconnect the respective ends of the cylinder to effect flash-overs from the compression compartments to simultaneously super-charge the new charges of fluid to be compressed on the opposite side of the said piston means and to reduce and equalize the pressure on the compression side of the said piston at the relatively small resultant pressure prior to the closing of the said port and passage means and the beginning of re-eXpansion of. the compression volumes by reverse travel of the said piston.

14. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, passage means respectively communicating with the compression compartments and respectively having ports communicating with said inlet and discharge openings, said ports being controlled by the operation of the said piston to periodically interconnect and disconnect the compression compartments to eiiect ash-overs from the compression compartments after delivery has ended to simultaneously supercharge the new charges of fluid to be compressed in the compression compartments and to reduce and equalize the pressures in the compression compartments at the relatively small resultant pressures prior to the closing of the said port and passage means and the beginning of re-expansion of the compression Volumes by reverse travel of` the said piston.

15. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, passage means communicating with one of the compression compartments and having ports communicating with an inlet valve and passage means communicating with another of the compression compartments and having ports communicating with a discharge opening, said ports being respectively controlled by the operation of the said piston means to periodically interconnect and disconnect the ends of the said cylinder to effect flash-overs from the compression compartments respectively on the one sideof the piston to equalize the pressures on the two respective sides of the said piston at the relatively low resultant pressure prior to the closing of one port of its passage means and the beginning of reexpansion of the clearance volumes to effect reexpansion of the compression volumes in relatively small portions of the return strokes of the said piston means, relatively earlier opening of the inlet valves, the sucking in of relatively large charges in proportion to the piston displacements, and relatively high volumetric efficiency.

16. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, passage means communicating with one of the compression compartments and having ports communicating with an inlet opening and a second passage means communicating with another of the compression compartments and having ports communicating with a discharge opening, each of said ports being respectively controlled by the operation of the said piston to periodically interconnect and disconnect the compression compartments to effect flash-overs from the compression compartments and equalize the pressures in the compression compartments respectively and to effect re-expansion of the compression compartments in relatively small portions of the return strokes of the said piston, relatively earlier opening of the inlet valves, the sucking in of relatively large charges to be compressed in proportion to the piston displacement. and relatively high volumetric and isothermal compression eciencies.

17. In a compressor, the combination of a pair of cylinders, pistons respectively reciprocated therein, power operated means, means for operating and synchronizing the operation of the said pistons, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages. of position of the piston and passage means in each cylinder, means respectively communicating with the inlet and discharge openings and with the clearances of the cylinders respectively effective upon the operation of said pistons toperiodically interconnect and disconnect the two respective cylinders at or near the ends of the strokes of their said piston.

18. In a compressor, the combination of a pair of cylinders, pistons respectively reciprocated therein, power operated means, means for operating and synchronizing the operation of the said pistons, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston and passage means in said cylinders respectively communicating with the inlet and discharge openings and having ports controlled by the operation of the said pistons respectively to periodically interco-nnect and disconnect the two respective cylinders at or near the ends of the strokes of the said pistons.

19. In a double acting compressor, the combination of a pair of cylinders, each having compression compartments, pistons respectively reciprocated therein, power operated means for operating said pistons, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on o-pposite sides of the piston for all stages of position of the piston means for periodically equalizing the pressures in the compression compartments on the respective sides of each piston at or near the respective ends of its strokes, means for continuing the equalization of pressure in the compression compartments during portions of the strokes of said pistons, and pressure responsive means for controlling said continuing means to vary the delivered capacity of the compressor.

20. In a variable capacity compressor, the combination of a plurality of cylinders, each having compression compartments, pistons respectively reciprocated therein, power operated means for operating said pistons, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston and passage means for each cylinder respectively communicating with the inlet and discharge openings and having ports controlled by the operation of said pistons to by-pass the pistons, said passage means the piston passage means for each cylinder communicating respectively with the inlet and discharge openings and further including passages respectively interconnecting and disconnecting the opposite ends of the said cylinders, and means for predetermining the effective period of operation of said passage means.

'22. In a variable capacity compressor, the combination of a plurality of cylinders, each having compression compartments, pistons respectively reciprocated therein, power operated means for operating said pistons, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston passage means for each cylinder communicating respectively with the inlet and discharge openings and further including passages respectively interconnecting and disconnecting the opposite ends of the said cylinders, and pressure responsive means for predetermining the eiective period of operation of said passage means.

23. In a variable capacity compressor, the combination of a plurality of cylinders, each having compression compartments, pistons respectively reciprocated therein, power operated means for operating said pistons, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston passage means for interconnecting and disconnecting the opposite ends of the said cylinders, valve means for said passage means, valve gearing for opening said valve means, and for closing said valve means during any portion of the return strokes of the said pistons, and pressure responsive means for controlling said valve gearing.

24. In a variable capacity compressor, the combination of a cylinder, having compression compartments, a piston reciprocated therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston and passage means communicating with the inlet and discharge openings and with the compression compartments respectively for decreasing the eiective length of the respective strokes of the said piston and for increasing the effective volumes of the compression compartments.

25. In a variable capacity compressor, the combination of a cylinder, having compression compartments, a piston reciprocated therein,

s power operated means for operating said piston,

inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings 'communicating with Vsaid clearance spaces on opposite 'sides of the piston for all stages of position of the piston passage means communieating with the inlet and discharge openings and with the compression compartments respectively for decreasing the effective length of the respective strokes of the said piston and for increasing the eiective volumes of the compression compartments, and pressure responsive means for controlling the effective period of operation of said passage means.

26. In a compressor, the' combination of a cylinder having compression compartments, a piston reciprocated therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, said inlet vopenings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston means for periodically equalizing the pressures 'in the compression compartments respectively at or near the respective ends of the strokes of the said piston means, and means for continuing the's'aid equalization of pressures in the compression compartments respectively during a portion of the return stroke of 'said piston.

2'7. In a compressor, the combination with a cylinder 'having compression compartments, of aY piston 'reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with clearance spaces between the ends of the cylinders and the ends of the piston. on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on oppoanni@ site sides of the piston for'all stages of position of the piston, and means associated with the compression compartments of said cylinder and the piston for periodically interconnecting and disconnecting the respective compression compartments with the interior of the cylinder when the said piston is at or near the respective ends of its stroke.

28. In a compressor, the combination with a cylinder having compression compartments, of a, piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge valve means, inlet and discharge openings, said inlet openings communicating with said clearance spaces on opposite sides of the piston, for all stages of position of the piston, said discharge openings communieating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, and means controlled by the operation of the said piston for effecting equal pressures on both sides of the said piston means at or near the respective ends of the strokes of the piston, said pressure equalizing means including a chamber arranged to Communicate with an inlet opening and having ports communicating with the compression compartments, said ports being closed and opened by the piston.

29. In a compressor, the combination with a cylinder having compression compartments, of a piston reciprocating therein, power operated means for operating said piston, inlet valve means, discharge Valve means, inlet and discharge openings, said inlet openings communicating with the clearance spaces on opposite sides of the piston for all stages of position of the piston, said discharge openings communicating with said clearance spaces on opposite sides of the piston for all stages of position of the piston, and means controlled by the -opera- Vtion of the said piston for periodically eiecting equal pressures in the compression compartments of the cylinder, said pressure equalizing means including a chamber arranged to communicate with an inlet opening, said chamber having ports communicating respectively with the compression compartments, said pressure equalizing means further including a chamber arranged to communicate with a discharge opening and having ports arranged to communicate respectively with the compression compartments. Y

EVERETT W. SWARTWOUT.