US838459A - Air-compressor. - Google Patents

Description

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PATENTBD DBG. 11., 1906.

L. H. ROGERS.

AIR COMPRESSOR.

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L. H. ROGERS.

AIR COMPRESSOR.

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PATENTED DBO. 11, 1906.

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APPLIUATON FILED NOV. 7, 1904.

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PATENTED DEC'. ll

L. H. ROGERS.

AIR COMPRESSOR.

APPLIGATION FILED Nov. 7, 1904.

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AIR-COMPRESSOR.

Specification of Letters Patent.

Patented Dec. 11, 1906.

Application filed November 7,1904. Serial. No. 231.800.

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Be it known that l, LEBBEUS H. Roenns, of New York, N. Y., have invented a new and useful Improvementin Air- Compressors, which invention is fully set forth in the following` specification.

This invention relates to air-compressors, and more particularly to the kind of air-compressors known as rotary compressors.

lVhile the invention is specially adapted to compression of air, it may be used for the compression of any other gas or as a simple pump,

It has heretofore been proposed, as in the construction shown in the application of Bror F. Bergh, Serial No. 157,661, filed May 18, 1903, and application made by myself on September 9, 1904, Serial No. 223,913, to construct a rotary pump or compressor in which a rotary drum provided with longitudinal channels opening on the periphery of the drum revolves in a suitable casing provided with inlet and outlet ports, suitable pistons in the lshape of closely-fitting bars working in the channels in the drum and actuated by suitable cam-faces carried by the casing. The compressors of the character indicated require great nicety of fit of the parts, and particularly of the drum within the casing, and there is necessarily incident to such close fitting of parts a large amount of friction.

One of the particular objects of the present invention is to eliminate the large amount of friet-ion incident to the previous constructions and at the same time to improve the efficien cy of the structure as a whole.

Nith this object in view the invention consists in a suitable casing, within which a drum is mounted to revolve, the exterior diameter of the drum, however, being somewhat less than that of the interior of the casing, to the end that there shall be no frictional contact between the two. Said drum is provided with a plurality (preferably four) of longitudinal channels, which are closed at their ends and also closed on the periphery of the drum, suitable inlet and outlet ports being provided for the admission of the fluid and the emission thereof under the action of piston-bars moving in said channels and actuated by suitable cam-faces carried by the casing. There are provided in the heads of the casing or in suitable parts carried thereby a plurality of grooves or channels, either two or four, as may be desired, with which channels the ports leading into the piston-channels of the drum register, half of said channels in the casing being in constant communication with the atmosphere if the device is an air-compressor and the other half leading to the reservoir for the compressed fluid. During each revolution of the drum the piston-channels of the drum are in communication first with the channels leading from the atmosphere to the interior of the drum, and then communication being severed between the atmosphere-channels the pistonchan# nels are in communication with the channels leading to the reservoir. The first of these communications occurs during the time when the piston-bars in the piston-channels are on the back stroke, and the second of these communications occurs when the pistons are upon their outward or compressing stroke.

During the operation of the com ressors as heretofore constructed there was a ways a tendency to force the driving-shaft of the drum against that side of its bearings which lies opposite to the compressing side of the drum, with resultant friction an vconsequent wear of the parts, and according to the present invention means are provided for opposing to this side thrust of the shaft of the drum a pressure substantially equal to that in the reservoir where the compressed fiuid is stored, to the end that the two pressures on the shaft may substantially counterbalance each other, thereby avoiding the undue friction and wear heretofore experienced.

According to the improvements set forth in my previous application above referred to the undue clatter from noise incident to the operation of said compressor is avoided by subjecting the rear of the compressor-pistons in the channels of the drum to a pressure substantially equal to that of the iiuid in the compressed-air reservoir, thereby preventiner the shift of the bearings or trunnions of sai piston-bars from one side to the other of the cam-groove which is employed for actuating the same, and in the present invention this same idea is retained.

Various mechanical expressions may be given to the inventive idea involved, since the invention itself is not limited to a single specific structure of the machine. In order,

however, to describe the invention properly, I have illustrated in the accompanying drawings the best embodiment of the inventive idea with which l am familiar.

In said drawings, Figure l is a central lon- IOO ating-shaft and the channels and the conduit the conduit for permitting atmospheric air ted lines.

" ably having one of its heads 2, Fig. 1, formed gitudinal section of the compressor, taken on the line 1 1 of Fig. 2 and Fig. 2 is a cross-sectional View of the compressor. Fig. 3 is also a sectional view of the compressor, taken on the line 3 3 of Fig. 1 looking toward the integral head of the compressor, for the purpose of showing the various channels in said head and the ports formed therein as well as the cam-groove for operating the piston-bars in the drum. Fig. 4 is a sectional view taken on the broken line 4 4, Fig. 2, showing the means of conducting pressure to the side of the operby which pressure is led to the rear of the piston-bars within the drums. Fig. 5 is a sectional detail on the line 5 5 of Fig. 2, showing to enter the piston-channels in the drum. Figf 6 shows in section, on the line 6 6 of Fig. 2, the ends of the casing and drum and various conduits leading from one to the other. Fig. 7 is a sectional plan taken on the line 7 7 of Fig. 2; and Fig. 8 is a side elevation of a cam-plate which may be employed in the ends of the cylinder. Fig. 9 is a like elevation of a ring employed to close the ends of the piston-channels in the drum and Fig. 10 is a sectional detail showinU a means of constructing the air-ports leading from the atmospherechamber to the interior of the drum. Fig. 11 is a perspective view of the compressor with a part broken away to show the means for providing pressure on one side of the operating-shaft; and Fig. 12 is a like view of the drum with the rings for closing the ends of the piston-channels removed, one of said rings, however, being indicated in dot- F ig. 13 is a transverse sectional view through one of the chambered bearings.

Referring to the drawings, 1 is a casing substantially cylindrical in form and preferintegral therewith. Connected to said casing are two chambers. One of these chambers 3 is in open communication with the atmosphere and will hereinafter be designated as the atmosphere-chamber, and the other chamber 4 is in open communication with the reservoir and is partially filled with some liquid, as oil, and will hereinafter be designated the oil-chamber. As here shown, the atmosphere-chamber 3 and the oil-chamber 4 are formed integral with the casing 1, though it will be readily understood that, if desired, they may be formed separately therefrom and connected thereto by ksuitable conduits, hereinafter to be mentioned. The atmosphere-chamber 8 is in communication with the atmosphere through any suitable valve 5, Fig. 11, provided with a strainer 6 to prevent the entrance of extraneous matter, and the oil-chamber 4 is in communication with a third chamber l7, which will hereinafter be designated as the condensing-chamber. This chamber is in l ervoir through conduit 8. (See Fig. 2.) A

suitable conduit '(or conduits) 9, Figs. 2, 3,

and 11, leads from the interior of the casing 1 to the upper portion of the oil-chamber 4, and other conduits 10 lead from the bottom of the oil-chamber to the interior of said casing, said conduits 10 being preferably formed in the body of the heads of the casing 1.

Mounted in suitable bearings in the casingheads is a shaft 12, carrying a drum 13, to which it is keyed, so that the revolutions of the shaft impart like revolutions to the drum within the casing. The exterior diameter of this drum 18 is slightly less than the interior diameter of the casing, as will clearly appear from an inspection of Figs. land 2, so that the drum revolves within the casing without any peripheral frictional contact therein. Formed ,the particular number thereof is not essential,

any suitable or desired number being employed. These piston-channels 14, 15, 16, and 17 are closed on their sides and bottoms, as shown, and. co not open to the periphery of the drum. For the purpose of facilitating the formation of the channels within the drum and for machining them so as to enable the pistons to move therein with substantially an air-tight fit, they are originally formed open at the outer or peripheral portion of the drums and also open at the ends. After having been duly machined the peripheral sides of the channels are closed. air-tight-as, for example, by plates 18, whose exterior sides are form ed on an arc conforming to the curve of the drum, and therefore form a part of the periphery of the drum. The plates are secured in 'position by*V any suitable means, as by screws 19. (See Fig. 12.) Mounted within the piston-channels and so as to fit snugly therein are pistons in the form of bars 20, 21, 22, and 23. These bars reciprocate within the channels toward and from the periphery of the drum, the same being actuated by trunnions orwrist-pins 24, provided. with suitable antifrictional bearings 25, which engage a suitable cam, here shown in the form of an eccentric groove 26, formed either directly in the heads of the casing 1 or in a suitable plate fixed ly secured to said head on the interior of the casing. As shown in Fig. 10, this eccentric or cam groove 26 is formed d irectly in the integral cylinder-head. 2 of the casing, while in Fig. 1 said groove 26 is shown as formed on the interior face of a plate 27, hereinafter designated the cam-plate. While, as above indicated, the cam-groove 26 may be formed in the casing-heads, as shown in Fig. 10, preferably the cam-plate 27 is employed, and this construction will be hereinafter referred to in describing the invention. Said cam-plate is iixedly secured to the cylin- ITO eea/tee der-head in any suitable way, as by dowelpins 28 28, Figs. 1 and 4.

The piston-channels 14, 15, 16, and 17 have their ends closed by a ring 29, (see Fig. 9,) secured to the ends of the drum in any suitable manner, as by screws or bolts. The said rings 29, while closing the peripheral portions of the piston-channels leave that portion of said channels which is nearer to the axis of the drum open at the ends, the closed portion of the channels, however, being such that no matter what may be the position of the pistons themselves that portion of the channels which is between the front face of the pistons and the periphery of the drum is always entirely closed, while that portion which is to the rear of said pistons is always open at the ends only. Each of the rings 29 is or may be provided with ports 30, formed at intervals around its extent, leading Jfrom the confined space of the several channels in front of the pistons to the exterior` of the rings.

Formed in the face of the cani-plate 27 or in the head of the casing, if such cam-plates are not employed, are two grooves 31 32, nearly semi-annular in extent and so positioned that the ports 3() in the ring 29 open into or lie immediately opposite said grooves during the revolution of the drum. 'lhe ends of these grooves are separated by a portion of the cam-plate or cylinder-head, as the case may be, which is not cut away. One of these grooves, as groove 31, Fig. 8, is in open communication with the atmosphere by way of the atmosphere-chamber 3, and the other of said grooves 32 communicates by way of the conduits 9 9 with the compressed-air reservoir via the oil-chamber 4 and the condensing-chamber 7. For the purpose of connecting the groove 31 with the air-chamber 3 by way of an air-tight conduit l preferably proceed in the manner indicated in Fig. 5. ln that figure is shown a hole drilled through the cylinder-head immediately opposite the groove 31, the same passing not only through the cylinderehead, but, if the cam-plate 27 is employed, passing also through said plate. /Vithin the hole thus drilled there is inserted a closely-fitting pipe 33, whose inner end registers with the groove 31 and whose outer end is closed, as by a screw-plug 34. There is next drilled an opening through the outer wall of the atmosphere-chamber 3 and from thence down through the inner wall and into the pipe 33, after which a pipe 35 is passed into said opening with an air-tight fit, one end of said pipe just reaching the pipe 33 and the other end opening into the atmospherechamber 3, after which the opening in the exterior wall of the atmosphere-chamber is closed, as by a plug 36. It will thus be seen that the air may pass from the chamber 3 via the conduits or pipes 35 and 33 into the groove 31 in the cam-plate 27, the two pipes 34 and 35 serving as air-tight linings to thus reach the conduit or pipe 33 by passing through the walls of the casing only, this construction being regarded as the equivalent of the one shown in F 5.

lhile as above described there is a groove 31 and a groove 32 at each end of the casing formed either in the cam-plate or the casinghcad, it will be readily understood that the i said grooves might be omitted from one of said cam-plates or cylinder-heads and be formed only in the other, or, if desired, a groove 31 mightbe formed atene end of the casing and a groove 32 at the other end. /Vhere both grooves are formed at each end, the air will be both taken into the pistonchannels from the atmosphere and forced out at both ends via grooves 31 and 32, respectively, whereas if groove 31 is formed at one end and groove 32 at the other end the air at atmospheric pressure will be taken in at one end and compressed air be forced out at the other end. Any of the constructions indicated would fall within the spirit of the in, vention.

As thus far described the operation of the compressor is as follows: The drum 13 being revolved by power applied to the shaft 12, the pistons are reciprocatod in the piston channels by the engagement of their trun nions with the eccentric or cam groove 26 in the opposite ends of the casing. Referring to Fig. 2, it will be seen that as the drum revolves in the direction indicated by the arrow each piston after it passes the entrance to the conduit 9, leading to the oil-chamber, will be forced by the cam-groove 26 toward the bottom of its channel. Immediately after the piston passes the mouth of the channel 9 the port 30 in the rino' 29, opening into the pistonchannel, will register with the groove 31, (shown in dotted lines in Fig. 2 and in full lines in Fig. 8,) and air at atmospheric pressure will thereby be admitted via atmosphere-chamber 3, conduits or pipes35 and 33, groove 31, and port 30 to the piston channel in front of the piston therein. The piston continues to recede toward the bottom of the channel under the influence of the cam-groove v26 until it reaches a point diametrically opposite the mouth of the conduit 9, at which point the groove 31 terminates, and for a small portion of the revolution the port 3() is thereafter closed by reason of its end passing over the nfn-grooved portion of the cam-plate or the casing-head intervening between the grooves 31 and 32. At this point, as well as at the point diametrically opposite, there is liable to be some wear of the parts, and for the purpose of rendering it easy to repair this wear wear-blocks 37 38 the port 30 into the groove 32, (shOWIl in dotted lines in Fig. 2,) from which it passes, via the conduit 9, into the upper portion of the oil-chamber 4, and thus through port 39 into the condenser 7 and on through the conduit 8 t0 a Suitable reservoir.

An inspection' of Fig. 2 will show that when the port 30 reaches the upper end of the com- A pressing-groove 32 the piston is at its eX- treme outer stroke, but that, nevertheless, it does not impinge upon the plate 18, constituting the peripheral wall of the channel, a slight space 40 being left between the outer face of the piston and the inner face of the plate 18, thus providing a buffer of compressed air to prevent hammering of the piston against the outer wall of the channel within which it plays. The drum having revolved so as to carry its port 30 beyond or o ut of register with its groove 32, it crosses the intervening space between the lastnamed groove and the atmosphere-groove' 31, passing over the wear-plate 38 in so doing. It will be observed that in the revolutions of the drum 13 the only friction occurring be- 'p tween the drum and the casing within which it revolves is that occurring at the point where the rings 29 contact with the camplates 27 or with the heads of the casing when said cam-plates are omitted, as shown in Fig. 10. There being no peripheral contact of the drum with its casing, all frictional contact with the drum at that part is entirely eliminated.

It will be observed that the oil in the oilchamber 4 is constantly subjected to the pressure of the compressed-air reservoir, and this pressure is employed, preferably in conjunction with gravity, to force the oil to the interior of the drum and also to the interior of the casing surrounding the drum. The conduits for transmitting the oil to these parts are as follows: By reference to Figs. 1 and 6 it will be observed that when thecamplates 27 are employed they rest upon annular ledges 41, formed by counterboring the casing-heads, thereby leaving circular spaces 42 to the rear of said cam-plates. These spaces 42 are in open communication with the oil-reservoir 4 by way of a conduit 43, preferably formed in the metal of the casinghead. Communication is established between the spaces 42 and the interior of the rings 29 on the drum through suitable ports 44, formed through the cam-plate 27. It Will thus be seen that oil readily passes from the oil-chamber 4 via the conduit 43, space 42, ports 44, through the ring 29, and thence into the piston-channels at the rear of the pistons, such channels being open at the ends to the rear of the istons, as before stated, For the purpose ofp cleaning the conduit 43 the same is continued downward and outward for a short distance below the point of its entrance to annular space 42 and its open mouth closed by a removable plug 45, as clearly shown in Figs. l and 6.

Referring now to Figs, l and 4, it will be observed that the circular space 42 in the casing-head has opening thereinto a conduit 47, formed in a prolonged portion of the casing-head, which conduit 47 communicates by suitable ports 48 with chambers 4 9, opening out directly against the shaft 12 Since the space 42 is in open communication with the oil-chamber 4 via the conduit 43, it will be seen that the chambers 49 49 will be filled with oil, which oil is under pressure equal to the pressure in the compressed-air reservoir.

During half the revolution of the drum the pistons in the piston-channels are moving outward and acting to compress the air in said channels, and the reaction is sustained by that side of the shaft on which the pistons are acting to compress the air, thereby tending to crowd the shaft against its bearings on the side of the working pistons more firmly or with greater friction than on the side opposite to said working pistons.

ose of counteracting this pressure against the shaft the chambers 49 49 in the shaftbearings are located on that side of the shaft diametrically opposite the working pistons in the drum, and since the oil in the chambers 49 49 is subjected to the same pressure that exists in the compressed-air reservoir and since the pistons in moving outward `meet a resistance substantially identical with that in the compressed-air reservoir it follows that the same force which tends to produce the uneven friction on the shaft is also eX- erted to prevent such friction, the shaft being balanced, as it were, between two pressures,

For the pur- IIO In addition to the communication which is purpose of illustrating the invention the communication is from the lower or oil portionof the chamber 4 to the casing through a port 50, Fig. 2, formed in the metal between the oil-chamber and the interior of the casing. By thus surrounding the drum on all sides with a iiuid under pressure equal to that in the compressed-air reservoir and preferably by surrounding it with oil under suoli pressure it will be seen that the drum is suspended, as it were, in space sustained by an equal pressure upon all sides and that all frictional contact of the drinn with any of the parts of its inclosing casing with the single exception of the rings 29, which are secured to and revolve with the end of said drum, there is no frictional contact of any part of the drum with the casing.

It will of course be understood that the grooves 31 and 32 may be formed in the face of the ring or rings 29 adjoining the end walls of the casing instead of in said end walls, whether said end walls are composed of the cam-plate or of the integral portion of the wall itself. Moreover, it will be readily appreciated by those skilled in the art that the total areas of the chambers 49, formed in the shaft-bearings, should be equal to the total area of the piston-surfaces and which at any one time is actively engaged in compressing the air into the reservoir. Though this is not absolutely essential, it will be apparent that the friction will be reduced to a minimum by thus proportioning the areas of the parts.

IVhat is claimed is- 1. In a pump, a cylindrical casing, a drum closed on its periphery and having inlet and outlet ports in its ends and revoluble in said casing, a piston in said drum, and means for operating said piston.

2. In a pump, a cylindrical casing having inlets and outlets in its ends, a closed cylindrical drum having end ports registering with said inlets and outlets when the drum is revolved, a piston carried by said drum, and means for revolving the drum and operating the piston.

3. In a pump, a cylindrical casing, a reservoir, a conduit leading from the interior of said casing to said reservoir, a drum is said casing having a closed cylindrical periphery, a piston in said drum, a port in the end ofthe drum forward of the piston and registering with said conduit leading from the interior of said casing to said reservoir, and a second conduit leading from a source of fluid-supply to the space in the drum forward of the piston.

4. In a compressor-pump, a piston-carrying drum having openings only at its ends, a casing within which said drum is revolved, and inlet and outlet conduits in said casing communicating with the end openings in the drum.

f 5. In a compressor, a piston-carrying drum having openings only at its ends, an oilchamber, a casing within which said drum is revolved, a conduit leading from the front of the piston in the drum to a suitable reservoir in communication with said oil-chamber, and a conduit leading from said oil-chamber to the rear of said piston.

G. In a compressor, a piston-carrying drum having openings only at its ends, an airchamber, an oil-chamber, a casing within which said drum is revolved, a conduit leading from said air-chamber to the interior of said drum, and a second conduit leading from the interior of the drum to said oil-chamberj 7 In a compressor, a casing, a revolving cylindrical drum closed on its periphery therein, a compression-piston playing in a channel in said drum, and inlet and outlet ports to said channel through the ends of the drum.

8. In a compressor, a casing, a cylindrical piston carrying compression drum having inlet and outlet ports revolving concentrically in said casing without peripheral contact therewith, and means revolving said drum.

9. In a compressor, a casing, a cylindrical drum revolving concentrically therein without peripheral contact therewith, a piston working in a channel in said drum, and inlet and outlet ports for' said channel leading through conduits in the walls of said casing.

10. In a compressor, a casing, a drum having a closed periphery and revolving in said casing without peripheral contact therewith, a piston working in a channel in said drum, and inlet and outlet ports for said channel leading through conduits in the end walls of the drum and casing.

11. In a compressor, a casing, a drum having a closed periphery and revolving in said casing without peripheral contact therewith, piston-channels in said drum, pistons working therein, end closures for that part of the channels forward of the working faces of the pistons, and inlet and outlet ports leading through said end closures.

12. In a compressor, a casing, a compression-drum having a closed periphery and provided with inlet and outlet ports and revolving in said casing without peripheral contact therewith, and means for revolving said drum. l

13. In a compressor, a casing, a compression-drum having a closed periphery and revolving in said casing without peripheral contact therewith, a source of compressed fluid, a conduit leading from said source to the space in the casing surrounding the drum, and means revolving the drum.

14. In a compressor, a revolving drum closed on its periphery and having a plurality of longitudinal piston-channels, pistons therein, end closures for that portion of said channels in advance of the working faces of the pistons, outlet and inlet ports through said IIO closures,.means conducting fluid under pressure to the rear of said pistons, and' means for operating'said pist ons.

15. In a compressor, a reservoir, a revolving'drum closed on its periphery and having a plurality of longitudinal piston-channels, pistons therein having trunnions engaging cams eXterior't-o said drum, end closures for that portion of said channels in advance of the working faces of said pistons, inlet-ports leading `from the atmosphere through said closures to said channels, eXit-portsleading through said closures from said channels through conduits to said reservoir, and means for revolving said drum.

16. In a compressor, a reservoir, a revolving drum closed on its periphery and having a plurality of interior longitudinal pistonchannels, pistons therein, means subjecting the periphery of the drum and the rear faces of the ypistons to reservoir-pressure, and a conduit leading 'from the front or working faces of said pistons to said reservoir.

v17. In a compressor, a reservoir, a casing, a piston-carrying drum with closed periphery revolving in said casing and provided with inlet and outlet ports, and means subjecting the periphery of said drumto reservoir-.pressure.

18. In a'compresson a reservoir, a casing, a'drum with closed periphery revolving in said casing without peripheral contact therewith, compression-pistons Working Vin said drum, and means constantly subjecting the periphery of said drum and the rearfaces of said pistons to reservoir-pressure.

19. In a compressor, a reservoir, a casing, a drum with closed periphery revolving in said casing without peripheral contact therewith, compression piston-channels in said drum, pistons in said channels, annular closures for thatpart ofthe ends of said channels forward ofthe working faces of said pistons,

an oil-chamber, a conduit from said oilchamber'to said channels at the rear of the pistons, an exit-conduit from said channels in front of thepistons to the oil-chamber, and a conduit from said reservoir to the oil-chamber.

20. In a compressor, a shaft, bearings for the same, a drum-on said shaft carrying pistons each of said pistons exerting a side thrust ofthe shaft onfits bearings during one ypart of `its stroke, and means for applying `fluid-.pressure to said shaft to balance said thrust.

21. 'In a compressor, a casing, a shaft, chambered bearingsfor said shaft, a drum on said shaftcarrying pistons, each of said pis- `tons exerting a side thrust'of the shaft onits lbearings during one part of its complete stroke, a reservoir communicating with said drum, and a fluid-pressure conduit from said vreservoir to said chambered bearings.

22. In a rotary compressor, a casing, a

shaft, a drum thereon and driven thereby, compression-pistons carried vby said drum, each of said pistons exerting a sidethrust of the shaft during one part of its complete stroke, a reservoir, and means opposing-reservoir-pressure on the shaft to the compression thrust of the pistons.

23. In a rotary compressor, a shaft, a drum thereon and driven thereby, pistons in said drum and having trunnions engaging stationary grooves exterior to and eccentric to the drum, each of said pistons exerting a side thrust of the shaft during one part ofits complete stroke, and meanssubjecting the shaft to fluid-pressure in opposition to said thrust.

24. In a compressor, a'reservoir, a casing, a shaft having chambered bearings in the end walls of said casing, said chambers opening on said shaft and communicating with said reservoir, a drum on said shaft within the casing, compression-pistons carried by said drum each of said pistonsexerting a side thrust of the shaft on its bearings during/its compression-stroke,and a conduit leading from the working faces of said pistons to the reservoir.

25. In a compressor, a reservoir, a compression-piston for forcing fluid into saidreservoir, a shaft against which'the thrust of said piston reacts, and means subjecting said shaft 'to reservoir-pressure in opposition to said thrust, whereby the unequalfictionof the shaft on its bearings is avoided.

26. In a compressor, a reservoir, an oilcharnber in communication therewith, a compression-piston for forcing air or gas into said reservoir, a shaft against whichthe thrust of said piston reactsvduring-a part of its complete stroke, and a conduit conducting the oil from said chamber to the side of said shaft to oppose said'thrust.

27 In a rotary compressor, a reservoir, a casing having inlet and outlet conduits and cam-grooves in its end walls,the inlet leading from the atmosphere yand the outlet tothe reservoir, a rotary drum having a closed periphery and compression-channels with-pistons therein, means on said pistons engaging said cam-grooves, and ports in the vends-of said compression-channels alternately -communicating with said inlet and outlet conduits.

28. In a rotary compressor, the combination of a reservoir, a casing, removable plates constituting the end walls of-said casing, inlet and outlet conduits forrned insaidiplates, the one leading from the atmosphere and the other to the reservoir, cam-grooves also formed in said plates, a rotary drum having a closed pe- IOO IIO

29. In a compressor, a reservoir, Aa casing, a shaft having bearings 1n said casing, a drum with closed periphery mounted on said shaft,

compression-pistons playing in channels in.

said drum, and means subjecting said shaft, the periphery of said drum and the rear faces of said pistons to reservoir-pressure.

30. In a compressor, a reservoir, an oilchamber communicating therewith, a casing, a shaft having bearings in said casing, a drum with closed peripher r mounted on said shaft, channels in said drum, and a conduit leading from said oil-chamber to the shaft-bearings, to the rear faces of said pistons, and to the interior of said casing surrounding said drum.

31. In a compressor, a compression-piston, a surface against which compression is effected, and means stopping the compression-stroke of the piston just short of said surface, whereby a film of compressed fluid intervenes between said piston and surface at the end of the stroke.

32. In a compressor7 a compression-drum having a closed periphery, piston-channels in said drum, pistons in said channels acting to compress the fluid between said pistons and the walls of said drum, and means istopping the compression-stroke of the pistons before contacting with the walls of the drum,where by a film of compressed Huid is left between said pistons and said wall.

In a compressor, a chamber containing a fluid, a casing, a removable plate in the end of said casing, a drum in said casing, and an air-tight conduit passing through the wall of the casing and the said plate, said conduit extending between said chamber and thedinterior of said casing.

34. In a compressor, a casing, a removable plate in the end of said casing, an air-chamber, a passage extending between said chamber and the interior of the casing and passing .through the walls of the casing and said plate nd an air-tight lining to said passage spanning the crack or line of demarcation between tlie casing and plate.

35. In a rotary compressor, a casing, a compression piston therein, an operatingshaft for said piston having bearings, a reservoir, and means for applying the fluid-pressure in said reservoir to the bearing side of said shaft.

36. In a rotary compressor, the combination of a casing having an inlet and outlet, a revoluble shaft having bearings in said casing, said bearings being provided on one side with fluid-pressure chambers opening on said shaft, a drum on said shaft, a piston in said drum, and means for applying the fluid-pressure of the compression-stroke of said piston to the back of the piston and to said shaft during the entire revolution of said drum.

In testimony whereof I have signed this specification in the presence of two subscribing witnesses.

LEBBEUSH. ROGERS.

I/Vitnesses:

II. I). ROGERS, Jr., STELLA ROGERS.

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