US1747948A - Air compressor - Google Patents

Description

Feb. 18, 1930. R. P. PESCARA AIR COMPRESSOR Filed Mach 24, 1927 s sheets-sheet l l l llllllllt/l Il." "nl Walzesscs Feb. 1s, 1930.

R. P. PESCARA AIR COMPRESSOR Filed March 24. 1927 3 Sheets-Sheet 2 Feb. 18, 1930. R. P. PESCARA I I 1,747,948

'AIR COMPRESSOR Filed March 24. 1927 3 sheets-s116121; 3

. @la 12? 14s 118 149 12a i L 1 L 1+ f 1 "I Y l f utilizes very little of the energy Patented. Feb. 1s, 1930 BAUL PATERAS PESCAIRA, 0F PARIS, FRANCE am conranssoa Application led llarch 24, 1927, Serial No. 177,988, and in France April 2, 1926.

My invention relates to air compressors of the type in which two pistons are utilized which act alternately as driving pistons and complressing pistons provided with means for sync ronizing the movement between Isaid istons, which vpistons move in separate cylingers in opposite directions and which means transmitted to said pistons for bringing a out the necessary kinematic transformation between said pistons.

The general obj ect of my invention is, principally to improve the disposition of the various parts of the apparatus, above mentioned, and render them much safer in operation than heretofore.

Briefly outlined, the invention consists in constructing the driving pistons and compressing pistons of a single piece, thus doing away with all the usual interconnecting parts, such as cranks or piston rods, as Well as the necessity of any synchronizing mechanism between the driving and compressing pistons. Said pistons are provided with cylinders having bores of di'erent diameters and are at least as long as their length of stroke. The synchronizing parts ofthe coupling mechanism of the two pistons are advantageously attached to the annular faces of the two pistons and at the same time, if desired may effect the compressing stroke oi one of the compressing p1stons. f

The compressing pistons may be disposed advantageously on the inside of the motor pistons at which time the bore of the driving pistons is made larger than that of the compressing pistons. In the latter case the syn- I f chronizing mechanism is coupled to the-pistons by means of arms attached thereto and extending through longitudinally extending openings in the heads of the driving piston cylinder conveniently dis osed. The coupling mechanism is establis ed in such a manner as to contribute to the safety of the compressor by opposing the tendency of the istons to blow out the cylinder heads, so t at in case one of said pistons receives an excessive amountof kinematic energy or that one of said pistons cannot transform said energy into work due to its corresponding valves not being properly seated, said coupling mechanism may act to transfer a part of the drivin energy to the other piston from that whic is unable to transform its energy into work in its corresponding compressing cylinder.

The invention consists further in providlng said coupling mechanism with a plurality of pinions or levers oscillating through an ang e of at least 360- by the-movement of said pistons and utilizing said pinions or levers for performing various functions in the compressor.

Another object of the invention is to provide a means for circulating water through said coupling mechanism and pistons which serves not only as a cooling medium for the compressor but also as a means for regulating the weight of said pistons.

Other objects of the invention will be obvious to those skilled in the art in the following specification taken inl connection with the accompanying drawing in which Fig. l is a. diagrammatic representation showing the coupling mechanism;

' Fig. 2 is a similar view showing a modified form of coupling mechanism;

Fig. 3 is a sectional elevation of a compressor constructed in accordance with the present invention, illustrating the disposition of the various parts and the water-cooling arrangement;

Fig. 4 is a piston detail.;

Fig. 5 is a detail of an orifice drawn to a large scale;

Fig. 6 is an elevational view with certain parts in section showing certain modifica'- tions;

Fig. 7 vis a viewof an ignition mechanism operated by the coupling mechanism' of the pistons;

Fig. 8 is a view of a modified compressor in elevation in which the drivin cylinder bore is made larger than that o the compressing cylinder; I F Fig. 9 is a sectional view'f'corresponding to i 8; A ,f

Fig. 10 is an elevation of a modification of the mechanism illustrated in Fig. 8; and

Fig. 11 is a sectional view corresponding to Fig. 10.

comprise a motor cylinder 15 and two larger cylinders 16 and 17 in which compression takes place. The bores of al1 three cylinders are arranged in axial alignment and `cylinder 15 opens into cylinders 16 and 17 respectively at each end. The pistons for said cylinders are cast in a single piece and comprise portions 20, 21 fitted in compressing cylinders 16 and 17 respectively and portions 18, 19 sliding in motor cylinder 15. The portions 18, 19 are made as long as the length of stroke of their respective pistons at least for obvious reasons. One of the `advantages derived from such a construction is the strengthening of the pistons and hence a smoother action of the pistons when working under load due to the increase in weight.

The mechanism for coupling the two pistons together is disclosed and claimed in my co-pending application Serial No. 177,938 filed March 24, 1927, in Figures 3 and 4 of said application. 'This mechanism comprisesv a double mechanical arrangement only half of which ishere visible in Fig. 1. Briefly said mechanism comprises rods 22, 23 disposed in parallel relation to cylinders 15, 16 :and 17 and which are attached respectively to pistons 18, 2O and 19, 21, by any convenient means at 24, 25 on the annular faces of said cylinders. Two guide bearings 26, 27 guide the extremities of rods 22, 23. 4 A lever 28 comprising two arms of equal length is pivoted on a stud d 29 fixed at the midpoint of cylinder 15 and extending in a direction normal to the surface thereof. Two links 30, 31 are attached at one end to rods 22,23 respectively and at their other ends tothe arms of lever 28.

The function of the mechanism thus far described will be obvious from a simple-inspection of Fig. 1. It will be suilicient to state that the coupling mechanism prevents the blowing out of the heads of cylinders 16 and 17 in case their corresponding valves fail to operate as pistons 20`and 21 cannot attain the extreme ends of their respective cylinders duc to the fact that at the end of their stroke cranks 30 and 31 align with lever 28 and prevent further movement of the pistons. Y

Referring to Fig. 2, the modified form of coupling mechanism is disclosed and claimed in my co-pending application in connection with Figs. 1 and 2, above mentioned. Here the cylinders 15, 16, 17 and pistons 18, 20 and 19, 21 are disposed in the manner described in connection with Fig. 1. Only half of the coupling mech-.mism is illustrated in this figure as previously. In this embodiment the rods 32, 33 are disposed parallel to the axis of cylinders 15,\16,.17 and are fixed to pistons 18, 20 and 19, 21 by anyconvenient means as shown at 34, l35,- on the annular faces of pistons 18, 2O and 19, 21 respectively. In this embodiment, the rods are placed in the same straight line. The extremities of rods 32, 33 slide in bearings 36, 37. A lever 38 havin two arms of equal length is pivoted on a stu 39 fixed atv the mid-point of cylinder 15 and extending in a direction normal tothe surface thereof as explained in connection with Fig. 1. Also two cranks or links 40, 41 connect the respective ends of the rods `32, 33 and lever 38.

In this embodiment also the coupling mechanism opposes the blowing out of the cylinder heads of 16, 17 by their respective pistons 18,

20 and 19,21 in much the same manner asprevously described. In this case, however,

when the piston reaches the end of its stroke, the cranks 40, 41 as well as lever 38 align with rods 32, 33 bringing all these elements on the dead center l point and preventing further movement of the piston toward its head.

v Referring to Figs. 3, 4 and 5, a motor cylin'- der 42 is provided at each end with compressthe pistons isA made hollow as shown in Fig. 4. and the interior of the pistons is divided into two compartments intercommunicating as shown at 49 by means of the partitions 47 and 48 which project into the portion ofthe piston having the smallest diameter.

Each piston carries a plurality of tubular Members 50r The tubular members of piston 46 are arranged in like manner.

Each tubular member of the pistons 45, 46 is provided with a hollow rod, two of which are shown at 53, 54. Since the other two tubular members are identical and similarly disposed, the description of one pair will suiiice.

The hollow rods 53, 54 are disposed parallel to the cylinders, 42, 43,44 of the machine. Each of said rods is provided with rack teeth 55 and 56 respectively which mesh with a pinion 57 mounted on a shaft 58 carried by the midpoint of cylinder 5 and extending in a direction normal to the surface thereof.

The rod 53 terminates in a piston 59 andv the longitudinally extending opening there-- in extends through said piston, the orifice formed thereby being closed by an automatic" f municates with the-interior of cylinder 61 by means of an opening 64 of' special form as clearly illustrated in Fig. 5.

The rod 54 likewise terminates in a piston 65 sliding in a pump cylinder 66 which' communi'cates with the exterior through pipe 67. The parts just described, however,fare not furnished with automatic valves or a special form of orifice as previously. The interior of rod 54 communicates freely with the outside through piston 65 pump cylinder 66 and pipe 67. Y p

Little need be saidvconcerning the dupllcate mechanism on the opposite side of the apparatus which is not visible in the drawing. The second rod of piston 45 is mounted thereon diametrically opposite to'ro'd 54 by means of a tubular member similar to 50. Said second rod carries a set of rack teeth similarA pump cylinder and a-pipe 69 (Fig. 3). The

orificeof pipe 69 is controlled by a valve in precisely the same manner as described in connection with rod 53. Similar to the visible parts, member '69 communicates to its respective pump cylinder through an opening similar to 64. VThe piston at the extremity of said rod is also lprovidedv with a valve asv already described in connection with the, visible parts.

The vrods just described are all provided with packing rings as illustrated at 70, 71

where said rods enter their` respective cylinders to provide a tightjoint and assure eiiicient compression within theicompression spaces 72, 73 of cylinders 43,144 thus permitting to utilize both sides of said pistons iin spite of stems 53, 54 entering saidv cyliners. Y The apparatus just described functions'in the following manner:

Suppose that piston 45 moves inwardly f from the outer end of the cylinder 43, then Vpiston 59 in combination with the valves 60 and 63 will act as a pumpand cause water to be drawn inY through pipe 68 through the hollow stem of the rod corresponding to 54 on the opposite side (not shown) to cir- ,culate along the. partition 47, pasa through orifice 49 and thence through the hollow stem of 53 out through opening 64, thiou h valve 63, which automatically opens by t 'e force of the water, and finally into the outlet pipe 62.

When piston 46 moves inwardly precisely the same circulation of water is set .up therein. A pump similar to that just described is situated opposite to rod 54 (not shown in the drawing) and draws in Water through the opening 67, through the piston 65, the hollow stem of rod 54, and finally leaves the device through the'outlet pipe 69.

In addition to cooling the mechanism this construction permits the mass of pistons 45 and 46 to be varied depending of course upon whether pipes 67 and 68 are connected or disconnected with a water supply.

vThe purpose of the special form of opening 64 is to produce a progressive reduction in cross-section between the outlet pipe and the pump cylinder and through which the water pushed back by piston 59 flows. If said pistons should move beyond the edge of orifice 64, a high resistance will be opposed to the movement thereof and hence to-the movement of the whole machine. This resistance progressively slows down the pistons 45 and 46 and prevents them from blowing out the heads of compressing cylinders 43, 44, if for any reason (such asa badlyseated valve for example) has allowed said pistons to pass beyond the limit of their normal stroke.

The rack teeth 55,r 56 on rods 53, 54 respectively, meshing with the pinion 57, as prerviously described, form a convenient means for synchronizing the reciprocating motions ofthe Qpistons without an appreciable expenditure of energy during normal operar Referring to' Fig. 6, the embodiment here- 1n represented comprises as before, a central motor cylinder 42 and two compressing cylinders 43, 44 arranged and disposed as previously described. Pistons 72, 73 are constructed and fitted to the bores of said cylinders in a manner already described. Said pistons are provided with rods 74, 75 having rack teeth 76,v 77 meshing. with a pinion 78, turning on a stud 79 which is mounted on cylinder 42 the arrangement being the same as heretofore described. A duplicate mechanism 'of that just described is arranged symmetrically on the reverse side of the'compressor'and is not seen in the drawing.

In orderto prevent accidental shocks between the compressing pistons and their respective cylinder heads, rods 7 5.and 76 carry collars 80 and 81. Between said collars and the frame of the compressor are disposed a series of Belleville washers 82, 83.

As previously described in connection with Fi .3, stuingboxes 84, 85 are providedfor rods 74, 75 permitting the spaces 87, 88 to be utilized for compressingpur ses.

The device just described unctions in precisely the same manner. as that described in connection with Fig. 3. The safety ofthe device, however, is greatly enhanced for should either compressing piston be driven beyond 'the length of its normal stroke, its

' will now be described. The pinion 78 is given the proper diameter and is adapted to make something less than a complete turn on its shaft 79 at each reciprocation of pistons 72, 73. The cani 86 of the ignition mechanism is adapted to be driven by pinion 78 in any convenient manner. The ignition device is of a well-known type in current use and comprises a contact pawl 89 normally held in contact with a platinum contact screw 90. A secondary contact pawl 92 is provided and both contact pawls are operated by cam 86. The breaking of contacts 89, 90 produces the spark for firing the motor cylinder. The ar- Y rangement is'such that each piston receives being ,fitted into a spark at the end of its stroke.. Thetype of ignition device illustrated iswell-known and` is used inv aviation and the secondary pawl 92 permits sparks to be given only when` cam 86 is turned in the direction of the arrow 91 so that the spark is given only when the pistons are in the 'proper end of their cylinders. A casing 93 houses the mechanism and the device is supported by a lever 94 which permits the positioning of cam 86 with respect to pawl 89 and hence allows advancing or retarding of the spark.

It is to be understood that the ignition device might' be equally used with the synchronizing mechanism ldisclosed in connection with Figs. 1 and 2. In this case the cam 86 would be adapted to be driven by oscillating levers 28 or 38. l

. Referring to Figs. 8 and 9 which shows the disposition of the piston synchronizing mechanism when the compressing cylinder bore is made smaller than that of the vmotor cylinder, a large centra-l motor cylinder 95 is provided at each end with smaller compressing cylinders 96, 97, said cylinders being arranged in axial alignment as before. Each piston is constructed as before and comprises a compressing portion l98, 99 and a large'vmotor portion 100, 101 said portions spectively.

On the annular faces of pistons '98, 100` and 99, 101 are attached the rods 102, 1.04 and 103,

, cylinders 96, 97 and 95 rename j 105 extending parallel to the common axis of the cylinders 95, 96, 97 and the rods 102, 103 and 104, 105 lying in the same straight. line res ivly. odsz102 and 104 on piston 98, 100 are attached to arms v106, 107 carried by a collar 108 slidably mounted on the outside of cylinder 96. Llkewise rods 103, 105 are attached to arms 109,' 110 carried by a collar 111 slidably mounted on the cylinder 97.

a At'the center of the apparatus are pivoted two levers 112, 113 each having two arms of equal length. Four connectingrods 114, 115,`

116, 117 are connected at one end to the extremities of said levers and at the other end to the arms 106, 107, 109, 110 of collars 108 and 111. c

The unctionof the mechanism just described is analogous to that'described in connection with Figs. 1 and 2 and need not be further discussed.

' Referring to Figs. 10 and 11 which show another formfofcthe'invention in which the bore of the compressing cylinders/is smaller than vrthat of the motor cylinder, a main cylinder 118 having a constant bore through its length is provided and is closed at its extremities by cover members 119, 120 which are provided with cylindrical portions 121, 122 extending into c linder 118 Abut `having a smaller diameter t an the bore thereof.

Two pistons 123, 124 are mounted to freelyslide in cylinder118. Each piston is prov-ided with an\-annular recess which forms the compressing portions 125, 126 of each piston. Said compressing portions are disposed concentrically with respect to, their pistons and are adapted to freely slide within'the cylindrical portions 121, 122 carried by members 119, 120. lfdesired, in order to utilize the space occupied by the annular piston, the pistons might carry the projecting cylindrlcal member and project into an annular recess in the cylinder, in which case, the exterior walls of the 'pistons would beprolonged. f

The cylinder 118 carries four longitudinally extending openings 127, 128, 129, 130 `the sides of which act as bearings for the rollers 131, 132, 133, 134 mounted respectively on me arms 135 and 136, 137 and 138 ixedrespectively in pairs to the pistons 123 and 124.

In the central part of the apparatus on one side of cylinder 118 are pivoted two levers 139, 140 and on the other side two levers 141, 142. Each lever has two arms of equal length whichare disposed in cross fashion with the arm of each lever on the same side.'v

Onthe arms 135, 136, 137, 138'of pistons 123, 124 are mounted four double armed levers 143, 144, 145, 146 the four extremities of which connect with four connecting rods, the bifurcated ends 147, v148, 149, 150, 151, 152, 153, 154 of which connect with the eight extremities of levers 139, 140, 141, 142.

The operation of the mechanism just described, a plurality of compressing cylinders, acommon motor lcylinder therefor, said cylinders being disposed in axial alignment, a plurality of hollow pistons mounted in said cylinders, a plurality of hollow rods on,each of said pistons and means for circulating cooling water throughsaid rods and said pistons during reciprocation of the latter.

2. In' an air compressor of the type described, a plurality of compressing cylinders,

a common motor cylinder therefor, said cylinders being disposed in axial alignmenta plurality of hollow pistons mounted in said cylinders, a plurality of hollow rods` on each of said pistons, means for circulating cooling water through said rods and said pistons during reciprocation of the latter and means interconnecting the rods on said vpistons for establishing a synchronous kinematic relation between the latter'.

3. In an 'air compressor of the type described a motor cylinder, coaxial compressing cylinders mounted'at each end thereof, a piston mounted in each ofsaid compressingcylinders having aportion extendin into said motor cylinder, a plurality of ro smounted on each of said pistons and extending through said compressing c linders, means 'interconnecting said rods 4 or 'producinga synchro.- nous relation betweeny said pistons andan airtight joint between said rods and said compresslng cylinders whereby said pistons may be utilized for compressing in both directions.

4. In an air compressor; of the type described, a plurality of compressing cylinders,

a common motor cylinder therefor, said c linders being in axial alignment, a plurality of hollow pistons mounted in said cylinders,

a plurality of hollow rods mounted on each of said pistons,.means for circulating cooling water through said rods and said pistons during reciprocation of the latter and an airtight joint between said rods and said compressing cylinders whereby. said vpistons may be utilized -for compressing in both direc-r tions. Y

5. In an air compressor of the type described, a plurality of compressing cylinders,

a common motor cyli-ndertherefor, said cylinders bein disposed in axial alignment, a plurality o hollow pistons mounted in said -tion between said compressing pistons.

cylinders, a baille plate dividing the interior of said pistons into two compartments, a plurality of couplings connected to each of said compartments, a plurality of hollow rods connected to said couplings, means connecting said rods for establishing a synchronous relation between said pistons and' means fo circulating cooling water through said rods and around said baiiie plate within said pistons.

6. In an air compressor of the type described, a plurality of compressing cylinders, a common motor cylinder therefor, said cylinders bein@ disposed in axial alignment, a pluralityfoiD hollow pistons mounted in said cylinders, a baiie plate dividing the interior of said pistons into two compartments, a plurality of couplings connected to each of said compartments, a plurality of hollow rods connected to said couplings and extending through said compressing cylinders, means connecting said rods for establishing a synchronous relation between said pistons, means for circulating cooling water through said rods and around said baiiie plate within said pistons and means providing an air-tight joint between said rods and said compressing "cylinders whereby said istons may be utilized for compressing in oth directions.

7. In an air compressor of the type described, a plurality of direct actuated compressing pistons mounted coaxially, compressing cylindersfor said compressing pistons, a plurality of hollow rods mounted on keach of said pistons, a piston mounted on each ofl said rods at the extremity thereof, a cylinder for each ofthe pistons of two of said rods havinga water inlet, a cylinder for each of the pistons of the remaining reds having a water outlet, lmeans on certain of said rods for -circulating cooling water through said rods and compressing pistons and means interconnccting the rods on said pistons for establishing a synchronous kinematic rela' y 8. In an air compressor of the type described, a plurality of direct actuated compressing pistons vmounted coaxially, compressingl cylinders lfor said pistons, a plurality of hollow rods mounted on each of said pistons, a piston mounted on each of said rods'at the extremity thereof, a cylinder for each of the pistons of two of said rods having a water inlet, a cylinder for each of the pistons of the remaining rods having a water outlet, means on certain ofl said rods for circulating cooling water through said rods and compressing pistons and air-tight joints between said rods and said compressing cylinders whereby said pistons may be utillzed for compressing in both directions.

9. In an air compressor of the ty e described, a plurality of direct actuated) compressing pistons mounted coaxially, compressing cylinders for said pistons, a plurallot ity ofV hollow rods mounted on each of said pistons, a piston mounted on each of said rods at the extremity thereof, a cylinder for each of the pistons of two ofA said rodshaving, a water inlet, a cylinder for each of the pistons of the remaining rods having a water outlet, means on certain of said rods for circulating cooling water through said rods and compressing pistons, means interconnectingl the rods on said pistons for establishing a synchronous kinematic relation between said compressing lpistons and means providing air-tight joints between said rods and said compressin cylinders whereby said pistons may be uti 'zed for compressing in both di, rections.

10. In an air compressor of the type described, a plurality of direct actuated coinpressing pistons mounted coaxially, compressin cylinders for said pistons, a plurality of ho low rods mounted on each of said pistons, a piston mounted on each of said rods at the extremeity thereof, a cylinder @or each of the pistons of two of said rods having a water inlet, a cylinder for each of theI pistons of the remaining rods having a water outlet, an automatic valve carried by each of the pistons of said last mentioned cylinders and a second automatic valve in said water outlet, said valves being so arranged and ldisposed that reciprocation of said compressing pistons will cause water to be circulated through the inv terior of said rods and said compressing pistons.

11. In an air compressor of the type described, a lurality of direct actuated compressing lpistons mounted coaxially, a plurality of hollow portions on the interior of vsaid pistons, compressing cylinders for said pistons, a plurality of hollow rods mounted on each of said pistons and connectin with the interior thereof, a bailie plate on t e interior of said pistons between said rods dividing the interior of said piston into two interconnecting chambers, a piston mounted on the extremity of each of said rods, a cylinder for each of the pistons of two of said rods having a water inlet, a cylinder for each piston of the remaining rods having a water outlet, anautomatic valve carried by each of the pistons ofsaid last mentioned cylinders and a second automatic valve in said water outlet, said valves being so arranged and disposed that reciprocation of said compressing pistons will cause water to be circulated around said baille plate and through the interior of said rods `and said compressin istons.

12. In an air compressor ofgtlie ty e described, a plurality of direct actuatedl compressing pistons mounted coaxially, compressing cylinders for said pistons, a plurality of hollow rods mounted on each of said pistons, a piston mounted on each of said rods at the extremity thereof,'a cylinder for each of the pistons of two of said rods having a water inimemes let, a cylinder for each of the pistons of the remaining rods having -a water outlet, an automatic valve carried by each of the pistons of said, last mentioned cylinders, a second automatic valve in said water outlet, said Valves being so arranged and disposed that reciprocation of said compressing pistons will cause water to be circulated through the interior of said rods and said compressing pistons and i pressing pistons mounted coaxially, compressin cylinders for said pistons, a plurality of ho low rods mounted on each of said pistons,

a piston mounted oneach of said rods at the i extremity thereof, a cylinder for each of the pistons of two of said rods havin a water inlet, a cylinder for each of the pistons of the remaining rods having a ywater outlet, an automatic valve carried by each of the pistons of said last mentioned cylinders, a second automatic valve in said water outlet, said valves being so arranged and disposed that reciprocation of said compressing pistons will cause water to be circulated through the interior of said rods and said compressing pistons and means interconnecting the rods on said pistons for establishing a synchronous kinematic relation between said compressin pistons.

14. In an air compressor of t e type described, a plurality of direct actuated compressing pistons mounted coaxially, compressing cylinders for said pistons, a plurality of hollow rods mounted on each of said pistons, a piston mounted on each of said rods at the extremity thereof, a cylinder for each of thev pistons of two of said-rods having a water inlet, a cylinder for each of the pistons of the remaining rods having a water outlet, an automatic valve carried by each of the pistons of said last mentioned cylinders, a second automatic valve in said water outlet, said valves being so arranged and disposed that reciprocation of said compressing pistons will cause water to be circulated through the interior of said rods and said compressing pistons, means providing an air-tight'joint between said rods and said compressing cylinders whereby said pistons may be utilized for compressing in oth directions and means interconnecting the rods on said pistons for establishing a synchronousV kinematic relation between said compressing pistons.

15. In an air compressor of the type described, a plurality of direct actuated compressing pistons mounted coaxially, com ressing cylinders for said pistons, a plurality of hollow rods mounted on each of said pistons,A

a piston mounted on each of said rods'at the extremity thereof, a cylinder for each of the pistons of two of said rods having a water intons of said last mentioned cylinders, a second automatic valve in said water outlet, said valves being so arranged and disposed that reciprocation of said compressing pistons will cause water to be circulated through the interior of said rods and said compressing pistons.

16. In an air compressor of the type depressing pistons mounted coaxially, compressing cylinders for said pistons, a plurality of hollow rods mountedV oneachof said pistons, a piston mounted on each of said rods at the extremity thereof, a cylinder for each of the pistons of two of said rods having a water inlet, a cylinder for each of the pistons of the remaining rods having a water outlet, an automatic valve carried by each of the pistons of said last mentioned cylinders, a second automatic valve in said water outlet said valves being so arranged and disposed that reciprocation of said compressing pistons will cause water to be circulated through the interior of said rods and said compressing pistons and a tapered orifice within said outlet between said last mentioned valves for progressively limiting the movement of said last mentioned pistons toward the end of their stroke.

17. In an air compressor of the type described, a main driving cylinder, compressying cylinders mpunted at the extremities thereof, compressing pistons mounted in said compressing cylinders having integral driving pistons extending into said main cylinder, a plurality of interconnected cavities in the interior of said pistons, a plurality of pumps disposed between said compressing cylinders there being one pump for each piston and means associated with said pumps and said pistons for circulating water through said pistons.

18. In an air compressor of the type described, a main driving cylinder, compressing cylinders mounted at the extremities thereof, compressing pistons mounted in said compressing cylinders having integral driving pistons extending into said main cyllnder, a plurality of interconnected cavities in the interior of said pistons, a plurality of pumps disposed between said compressing cylinders there being one pump for each piston, means for driving said pumps by said pistons and means associated with said pumps and said pistons for circulating water through said pistons.

19. In an air compressor of the type described, a. main driving cylinder, compressing cylinders mounted at the extremities thereof, compressing pistons mounted in said compressing cylinders having integral driving pistons extending into said main cylinder, a plurality of interconnected cavities on the interior of said pistons, a plurality of pumps disposed between said compressing cylinders there being one pump for each piston, means associated with said pumps and said pistons for circulating `water through said pistons and cushioning means associated with said pumps for retarding the motion of said compressing pistons when approaching one end of their stroke.

20. In an air compressor of the type described, a main driving cylinder,compress ing cylinders mounted at the extremities thereof, compressing pistons mounted in said compressing cylinders having integral driving pistons extending into said main cylinder, a plurality of interconnected cavities on the interior of said pistons, a plurality of pumps disposed between said compressing cylinders there being one pump for each piston, means associated with said pum s and said pistons for circulating water t rough said pistons, cushioning means associated with said pumps for retarding the motion of said compressing pistons when approaching one end of their stroke and means interconnecting said pumps for synchronizing said compressing pistons.

21. In an air compressor of the type described, a main driving cylinder, compressing cylinders mounted at the extremities thereof, compressing pistons mounted in said compressing cylinders having integral driving pistons extending into said main cylinder, a plurality of interconnected cavities on the Iinterior of said pistons, a plurality of pumps disposed between said compressing cylinders there being one pump for each piston, means associated with said pum s and said pistons for circulating water t rough said pistons, cushioning means associated with said pumps for retarding the motion of said compressing pistons when approaching one end of their stroke, a plurality of racks carried by said pumps and a pinion meshing with said racks whereby synchronous movement between said compressing pistons is assured.

.22. In an air compressor of the type described a plurality of direct actuated compressing pistons mounted coaxially, compressing cylinders for said pistons, a plurality of hollow rods mounted on each of said pistons, a piston mounted on each of said rods at the extremity thereof, a Cyllnder for each of the pistons of two of said rods having a water inlet, a cylinder for each of the pistons ot the remaining rods having a water outlet and means on certain of said rods for circulatinor cooling water through said rods and c D l l said compressing plstons. Y

RAUL PATERAs PSCARA.

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