US2231904A - Compressor - Google Patents

Description

Feb. 18, 1941. GUSTAFSQN 2,231,904

COMPRESSOR Original Filed Feb. 20', 1936 2 Sheets-Sheet l Kiwi:

Feb.'-18, 1941; A. N. GUSTAFSON coMPREssofi 2, Sheets-Shet 2 Original Filed Feb. 20, 1936 mmm? Gas/a 1%eyans.

Patented ob. 1 8,- 1941 PATENT OFFICE I 2.231.904 P corrrnssson Alfred N. Gustafson, West Chester, Pa, assignor to Schramm, Inc West Chester-J1, a corporation of Pennsylvania Original application February 20, 1936, Serial No.

64,808. Divided and this application Septemher 1, 1938, Serial No. 227,915

4 Claims. (Cl. 230-22) This invention relates to a compressor and I more particularly to a valve'arrangement which is particularly efiective in increasing the. efficiency of a compressor and reducing its size for a given capacity.

This application is a division of my application Serial No. 64,898, filed February 20, 1936',

While certain aspects of the present invention are of general applicability to compressors of a reciprocating piston type. the invention is particularly directed to the type of compressor which may be regarded as constructed by a conversion of an internal combustion engine. The-transfor- "mation of internal combustion engines into compressors constitutes a very economical method of producing high speed compressors. The engines are quite inexpensive because of quantity production and their running parts are so made as to be capable of operation at very high speeds. When'large size compressors are produced by such-transformation, all the cylinders of a multicylinder engine may be turned into-compressor cylinders. On the other hand, where small compressor units are to be provided only some of the cylinders may be transformed, the remaining ones being left to function as engine cylinders so that a combination engine and compressor is provided. A- satisfactory arrangement of this latter sort is illustrated in 'Schramm Patent No.-

1,738,12l, dated December 3, 1929. As shown in this patent, the two end cylinders of a fourcylinder engine have been transformed into compressor cylinders, while the two intermediate cylinders continue to function as engine cylinders. In cases where all of the cylinders are transformed, there is, of course, used a separate motor or-engine for driving purposes.

In accordance with the practice heretofore used, there has been substituted a modified cylinder head in order that'a greater compression ratio may be attained in the compression cylinders than would be permissible in engine cylinders, this substitution of head being also accomplished by elimination of the mechanically operated engine valves associated with the compressor cylinders and substitution of manifolds, etc., to produce the proper and necessary passages.. Automatic valves responsive to air pressure have been provided in the substitute cylinder heads, all as shown in the Schramm patent referred to above.

One of the requirements, in addition to the transformations indicated above, is the provision of suitable unloading mechanism which will stop the compressor action when the pressure in the inders by means such as illustrated in my. prior Patent N0. 2,023,418, dated December 10, 1 935,

so that as the compressor piston continues to reciprocate air is alternately drawn into and forced outwardl through the permanently held valve. Unloading of this nature is quite simply accomplished where the valves are of automatic' vne- Automatic intake valves, however, are not particularly satisfactory, inasmuchas, since they depend .for their operation upon air pressure, their operation variesquite considerably, depending upon the pressure in the receiver. Consider, for example, the diiferent conditions which exist when the receiver contains air at a low pressure and when it contains air at high pressure.- There is always residual clearance in the cylinder when the piston is. at its inner dead center. The pressure above the piston at thistime depends upon the pressure of the receiver and is substantially equal to it. As the piston then recedes from its inner dead center position, an automatic intake valve will not open until expansion of the gas in the cylinder, has taken place to such extent that the pressure is below atmospheric by-an amount such that the difference' in pressure will serve to open the intake valve against the relatively weak spring which acts upon it to normally hold it closed. It is obvious that the distance the piston must move before such opening takes place is very much affected by the pressure in the upper end of the cylinder when the piston is in its dead center position, which pressure is substantially equal to that of the receiver. The action of the intake valve accordingly varies very considerably with the receiver pressure and design can only be made to sheet proper working under one particular. condition. Desirably the intake valve should be open throughout substantially the entire intake stroke-of the piston.

The use of a mechanically operated intake valve will, of course, insure that the intake valve will operate the same for all pressure conditions. Difficulties in unloading then arise. Proposals have been made to produce unloading by throttling the intake of air. This procedure, however, is objectionable because the vacuum drawn above the Piston causes oil to pass into the upper portion. of the cylinder where, as successive compression and expansion of the residual, gas takes place, vaporization of the oil and consequent explosions may occur. There is also the grave danger of having so much oil accumulate that, because of the close clearances involved, the piston may eventually break the cylinder head.

It is the broad object of the present invention to provide a compressor combining the advantages of mechanically operated intake valves and automatic exhaust valves which, it may be remarked, have the great advantage of acting as automatic safety valves. In utilizing this .com-

bination, the automatic exhaust valves can be considerably enlarged so as to take up most, if not all, of the end of thecylinders. The'emciency is thereby increased, since a very small move- 8 ment of the exhaust valve is necessary to provide a sufiiciently large passage for the free flow of the compressed air to the receiver.

It is a further object of the invention to, provide improved unloading arrangements suit- 10 able for use in connection with mechanically operated intake valves.

The general'objects mentioned above, together with subsidiary objects relating particularly to details of construction, will be apparent from the 1 following description read in coniunction with the accompanying drawings, in which:

Figure 1 is an'enlarged transversesection of a compressor of L-head type embodying the features of the invention; and 2 Figure 2 is a diagram showing the associations of various elements with the compressor of Figure 1, a conventional unloader valve being shown therein in enlarged longitudinal section.

- Referring first to Figure 2, there is indicated 25 therein a four-cylinder engine the two end cylinders of which have been converted into compressor cylinders .by arrangement of parts as shown in Figure 1, intermediate cylinders being adapted to act as engine cylinders to furnish 30 the drive. It will be obviouswthat the invention is also applicable to cases in which there is an individual compressor and motor or separate engine. The substituted cylinder head in the case illustrated may, as usual, be so arranged as 85 to maintain conventional conditions at the ends of the cylinders; at the same time, however, providing close clearances in the compressor cylinders to secure maximum pressures and emciency of operation. In the present case. a sub- 40 stitute intake manifold 8 is illustrated communicating only with the intake passages of the engine cylinders, the manifold being connected to a conventional carburetor 8. The intake passages I0 of the .compressor cylinders may be 45 opened directly to the atmosphere or, if desired, may be connected to suitable air filters to avoid accumulation of dirt in the compressor mechanism. The exhaust manifold I2 may still be used. The exhaust valves of the compressor cyl- 50 inders are rendered inoperative by removing; for

example, the intermediate follower elements located between them and their operating cams. Preferably, however, particularly where there is a complete transformation to a compressor, a

85 substitute cylinder block is provided to eliminate the exhaust passages entirely.

Referring now to Figure 1, there is shown therein the unloading arrangement for the compressor. In this case the intake valve 82 is con- 60 tinuously operated through the pusher 80 by the cam 80,,on the cam shaft. The passage 00 from the automatic discharge valve 24 normally com-.

. municates through 88 with the receiver 88. A valve 82 is arranged to alternatively seat on an 65 upperseat carried by .the lower end of a'fittlng' 84 or upon a lower seat 81,- in which latter position it will cut of! communication between 00 and 88. A passage I00 furnishes communication between the atmosphere and the upper side 'of 70the valve 02.

into its upper seated position by a spring I02 iiffiarriesz at the upper end Oflts spindle, a piston I04 slidingin a cylinder I08 and arranged to be forced downwardly by air entering a tube 7 I08 arranged to receive airat recelverpressure.

The valve 82 is normally urged "I'he piston I04 is sufflciently large that upon communication of the upper end of the cylinder I08 with the receiver the'valve 02 will be snapped, downwardly against itslo'wer seat 81 with the result that communication is established between 5 the delivery side ofthe automatic delivery valve and the atmosphere. As the compressor continues to operate after this unloading takes place,

the piston I8- will draw air inwardly past the continuously operated intake valve 82 and will 10 force it outwardly throughthe delivery valve 24 to the atmosphere. Since the springs holding the delivery valve closed are very light, noappreciable amount of work is done in this action. At the same time there is no danger that oil will get above the piston. I

' Connection between the tank 30 and the tubes I08 occurs through a line 54 in which there is interposed a suitable snap valve of conventional type illustrated in detail in Figure 2. 2

The snap valve is of the type illustrated in -my prior Patent No. 2,023,418, dated December 10, 1935. This valve comprises a casing 82 surmounted by a bonnet 84 connected to the tank 80. A disc 88 having plane faces is located with- 25 in an upper cylindrical portion of the bore of casing 82 and is adapted for vertical movement between an annular plane seat 88 formed on bonnet 84 and an annular plane seat I4 formed on the upper end of a bushing 12. iThe disc and seats areflnely ground to insure air-tight contact between the disc faces and the respective seats. The disc flts the bore of the casing loosely whereby a slight clearance "is provided between its edge and the wall of the bore for leakage of air. 85

A spring I8 extending through-bushing 12 normally forces the disc against seat 88, its tension being adJustable by inward or outward movement of its abutment provided on a screw I8 threaded into the interior of the casing. A hole 80 ex- 40 tending axially through the screw furnishes communication between the interior of the casing below the disc and the atmosphere. A screen 8| prevents dirt particles from the tank 48 from entering the valve and causing faulty seating of thedisc. v

A fitting 82 communicates with the interior of the casing outside. of and below seat I4. The fitting is connected to the air line I08 which communicates with the various spaces above the V pistons I04. Within this fitting is a ball check valve resting on a seat '08 and retained in the fitting by cross pin 88.

In the operation of the device, so long as the pressure in-the supply tank is below the prede- 55 tel-mined maximum, the disc 88 will be held against its upper seat, and consequently the spaces above the pistons I04 will be open to the atmosphere through the ball check 84, which has a faulty fit upon its seat 00 so as to permit a slow 80 leakage of air. Under such conditions the spring I02 maintains the valve 82 in its upper position so that the cylinders may supply compressed air to the tank 20 through the exhaust valves 24. When the pressure in the tank 80 reaches a predetermined amount, the disc 88 is snapped to its lower seat on which it is held by reason of the effective increase of area acted upon by the-air at tank pressure. Air at the pressure of the tank then flows past the check valve 84 and depresses the pistons I04, moving the valves 82 to their lower seats so that air may be forced past the valves 24 directly to the atmosphere.

- When the pressure in the tank falls to a predetermined minimum, the disc 88 would be and held there by reason 01" the fact that the area on the upper side of the discis now substantially reduced. When this occurs, the spaces above the pistons I04 are open to the atmosphere and the compressed air may flow therefrom, preferably slowly, past the ill fitting check 84. This check is desirable inasmuchas the slow upward movement of the pistons Ill would insure that the engine shaft will make an appreciable number ofrevolutions before the load ls taken by the engine. In general an engine compressor unit of this character is furnished with a governor which is somewhat sluggish in operation and should be permitted to open the engine throttle before full load is imposed on the compressor. The delay provided by the slow movement of the valve 92 during compression strokes of the compressor pistons enables the governor to furnish sufiicient mixture to the engine as the load is gradually increased to avoid any sudden shock. of course, if the shock is immaterial, the check 84 may be eliminated, whereupon as soon as the valve 68 operatesdelivery of compressed air to the tank will take place.

It will be obvious that with the above arrangement the'pressure in the cylinder remains constantly approximately atmospheric during an unloaded period, the deviations from atmospheric pressure being only the minor ones due to friction in the passages and the light pressure of the exhaust valve springs.

It will be clear that numerous changes in the embodiment of the invention may be made without departing from its scope.

What I claim and desire to protect by Letters Patent is:

1. In combination, a receiver for compressed gas, a compressor connected to said receiver to deliver gas thereto including a cylinder and reciprocating piston therein, an intake valve for the cylinder, means for mechanically actuating the intake valve, and an exhaust valve operated automatically by the gas compressed in the cylinder when its pressure exceeds that in the receiver, and means for unloading the compressor when the pressure in the receiver exceeds a predetermined amount, said last named means comprising a valve arrangement to engage alternatively either of two seats and adapted when engaging one seat to provide for passage of gas from the exhaust valve to the receiver and when engaging the other seat to open the discharge side of the exhaust valve to the atmosphere and cut off communication between the exhaust valve and the receiver so that the pressures in the cylinder remain approximately atmospheric during unloading periods, and means for eiIecting complete movements of said valve arrangement between said two seats when such movements begin.

. 2. In combination, a receiver for compressed gas, a compressor connected to said receiver to deliver gas thereto including a cylinder and reciprocating piston therein, an intake valve for the cylinder, means for mechanically actuating the intakevalve,and an exhaust valve operated automatically by the gas compressed in the cylinder when its pressureexceeds that in the receiver, and means for unloading the compressor engaging one seat to provide for passage of gas from the exhaust valve to'the receiver and when engaging the other seat to open the discharge side of the exhaust valve to the atmosphereand.

cut oil communication between the exhaust valve and the receiver so that the pressures in the cylinder remain approximately atmospheric during unloading periods, means for effecting complete movements of said valve arrangement between said two seats when such movements begin, and means for slowing down movement of the valve arrangement to position to provide passages of gasfrom the exhaust valve to the receiver so that load is applied gradually to the compressor.

3. In combination, a receiver for compressed gas, a compressor connected to said receiver to deliver gas thereto including a cylinder and reciprocating piston therein, an intake valve for the cylinder, means for mechanically actuating the intake valve, and an exhaust valve operated automatically by the gas compressed in the cylinder when its pressure exceeds that in the receiver, and means for unloading the compressorwhen the pressure in the receiver exceeds a pre determined amount, said last named means comprising a valve arrangement to engage alternatively either of two'seats, the space within which the valve arrangement moves between the seats being continuously in communication with the discharge side of the exhaust valve, the side of one of the seats opposite the valve arrangement being continuously in communication with the atmosphere, and the side of the other of the seats opposite the valve arrangement being continuously in communication with the receiver, and means responsive to the receiver pressure for eflecting movements of thevalve arrangement from one seat to the other and pre venting floating of the valve arrangement'between the seats.

4. In combination, a receiver for compressed gas, a compressor connected to said receiver to deliver gas thereto including acylin-der and re- -ciprocating piston therein, an intake valve for the cylinder, means for mechanically actuating the intake valve, and an exhaust'valve operated automatically by the gas compressed in the cylinder when its pressure exceeds that in the receiver, and means for unloading the compressor when the pressure in the receiver exceeds a pre-- determined amount, said last named means comprising a valve arrangement to engage alternatively either of two seats, the space within which the valve arrangement moves between the seats being continuously in communication with the discharge side of the exhaust valve, the side of one of the seats opposite the valve arrangement being continuously in communication with the atmosphere, and the side of the ,other of the the valve arrangement to position to provide passage of gas from the exhaust valve to the receiver so. that load is applied gradually to the 'compressor.

' ALFRED N. GUS'IfAFSON.

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