US2178311A - Free piston engine - Google Patents

Description

Oct. 31, 4 R p E C FREE PISTON ENGINE Filed April 25, 1938 3 Sheets-Sheet 1 ///re/7/'ar: iay/ Pafexva Fe: care,

1939- R. P. PESCARA FREE PISTON ENGINE 3 Sheets-Sheet 2 Filed April 23, 1938 r Z MP w e W P FREE PISTON ENGINE Fiied April 23, 1958 s Sheets-Sheet 3 firremfor: iaa/ fife/as Pascara,

, Patented a. 31, 1939 PATENTQOFF-ICE FREE PIS'lON Enema Raul Patel-as Peacara, Paris, France Application April a, ma, Serial No. 203,921

In Luxemburg Aprll 29, 1937 19 Claims.

The present invention relates to free piston machines and it is more especially, although not exclusively concerned, among these machines with free piston auto-compressors, that is to say machins oi the free piston type adapted to supply compressed air.

The chief object of the present invention consists in providing a machine of this type which is better adapted to meet the requirements of i0 practice than the usual machines of the same type made up to the present time, and in particular in'imprc'ving the efllciency of said machines.

The esential feature of the present invention consists in the provision of means for injecting,

' .15 into the compressor part of said machines, an

invention, while injecting a certain amount of liquid into the compressor part of the machines of the type above mentioned, I causethe point of all injection to vary, preferably in an automatic a manner, as a function of one of the working characteristics of said machines, for instance as a function of the suction pressure thereof.

Other featureslof thepresent invention will.

35 resultfrom the following detailed description of some specific embodimentsthereof.v

Preferred embodiments of the present invention will be hereinafter described, with reference to the accompanying drawings, given merely by 40 way of example, and in which Fig; .1 shows in a diagrammatic manner, and

. in partial view, a free piston auto-compressor made according -to a first embodiment of the present invention; Y

45 Hg. 2 shows, on an tial view, another embodiment of the auto-compressor according to' the invention:-

Fig. 3 is a diagram of operation of the autocompressor shown by Fig. 1; Fig. 4 is a partial sectional view showing another embodiment of a compressor. made accordingto the invention; j

5 is a diagram of operation corresponding to the embodiment of Fig. 4. v

as l'lnally, rig-s s a-"partlal sectional view of enlarged scale, and in par- (Cl. zed-5t)- still another embodiment of an auto-compressor made according to the invention.

Although, in the following description with reference to the drawings, I have shown thespeciflc features of auto-compressors of the type 5 having free pistons, I wish it to be wellunderstood that the general principles of my invention illustrated by these examples also apply to '(Sther kinds of free piston machines.

Machines of the kind above referred to may be constructed, as fortheir general structure, in any conventional or other suitable manner, for instance they may be of the type in which the compression of air takes placein two distinct stages of compression.

. For -instance,as shown in a diagrammatical manner by Fig, 1, an auto-compressor may be made as follows: 1

I provide a motor cylinder llll, and in this cylinder two pistons I02 and I02 cooperate in such manner as respectively to uncover, near the ends of their outwa'rdstrokes, inlet ports I03,

and outlet ports I08. v These motor pistons I02 and I02 are associated, through piston rods 3 and 3', with c0n 1" pressor pistons 2 and 2'. The first of these last mentioned pistons, to wit 2, is mounted in a low pressure cylinder I, and the other is slidable in a high pressure cylinder l' fed with air from the low pressure portion of the machine.

' This low pressure portion of the machine is v provided, 'on the one hand, with a feed conduit -54, provided with an inlet check valve 55, and, on the other hand, with a discharge conduit 1, provided with an outlet check valve 5. I Likewise, the high pressure portion of the machine is provided with an 'inletcheck valve 55' and with a discharge check valve 5';

In a general manner, it is a known fact that it is advantageous, in'air compressors, in order 40 to reduce to a minimum the power necessary for ensuring compression and delivery of the compressed air, to carry outsthe compression so that \it is ,as isothermic as possible. It has already been endeavoured to obtain this result, in compressure of the typein which the pistons have aconstantstroke, by injecting into the compressed air a finely atomized liquid, either during the compression and delivery of said air or between the two stages of compression, the vaporization of this liquid having for its eilect to lower the teme perature of the. compressed air and thereforeto reduce the power necessary for ensuring the com- 'pression. a y

In order to obtain satisfactory results from '55 this operation of the machine, it is necessary to ensure that the amount of liquid injecting into it should not exceed the saturation limit for compressed air, as otherwise condensations would.

corresponding to variations of the mass of air compressed at each compression stroke, and consequently to variations of the amount of water necessary for saturating this mass of air.

According to the essential feature of the present invention, I inject, into the compressor part of said auto-compressor, an amountof liquid variable,'preferably in an automatic manner, as a function of one of the adjustment or operation characteristics of said machine.

It will be readily understood that, by proceeding in this manner, I can ensure that the amount of liquid which is injected (which liquid willbe supposed to consist of water in the following description) is always the optimum amount whatever he the variations of the mass of air compressedfor each compression stroke of the machine.

with this object in view, according to a first embodiment of the present invention (which. is to be preferred when the auto-compressor is to work with constant values of the suction and delivery pressures) I vary the amount of water that is injected into the compressor as a function only of the amount of air compressed for each stroke of the machine, that is to say as a function of the amplitude of the delivery strokes of the movable elements of the machine. The injection of water may be eifected into any suitable portion of the compressor part of said machine, for instance into cylinder l (as shown -by Fig. 2, or as shown by Fig. 4) into an intermediate reservoir, or again, as shown by Fig. 1, into the delivery pipe 4 of the low pressure stage of the machine, after the outlet valve 5 thereof.

I may then devise the elements of the system in such manner that the water injection takes place during the delivery period, or during the compression period, or even during the suction period.

I have shown in Fig. 3 the curves a--b-o-d representing the cycle of compression of an autocompressor for the maximum output of, compressed air. 1

If the injection of water is to take place during the delivery period a.b (case of Fig. 3), the system must be devised in. such manner that the amount of liquid that is injected varies according to a law which corresponds to an increase of said quantity when the variable delivery stroke increases. For instance the amount of liquid injected is proportional to the amplitude of said stroke, in which case, said amount is represented -by the ordinates of a straight line Inn, the amount of water that is injected being zero at m (where no compressed air is delivered) and maximum at n (where the amount of compressed air that is delivered is maximum).

There exist many embodiments of mechanisms for determining the amount of water injected tude of the delivery stroke. For instance, I may make use of the specific arrangement illustrated by Fig. 1 of the accompanying drawings.

In this embodiment, a prolonged portion, or extension of piston rod 3 constitutes a cam 6 adapted to coact with the piston i of a control device, such as a. pump 8 feeding water to an atomizing element 9 disposed, for instance, in the delivery conduit 4 of the compressor.

The length of this cam 6 is measured in such manner that it corresponds to the maximum length of the delivery stroke 0-11.

This cam is preferably arranged in such manner that it starts acting upon piston 1 as soon as the delivery stroke begins.

If now the injection of water is to take place during the compression period and if is also assumed that the working pressures are constant,

set forth and which consists in accumulating during one delivery stroke an amount of water which is a function of the amplitude of said stroke (being for instance proportional to this amplitude) and in injecting this amount of water but subsequently, for instance, in the present case, only during the next compression stroke.

Such an arrangemeht is preferably made as illustrated by Fig. 2.

In this embodiment, a cam surface 6, carried by an extension of rod 3, is caused to coact with the 'piston I of an accumulation pump 8' including chamber of variable volume, and an accumulator piston II subjected to the action of a spring ll.

The injection of water, which takes place for instance into cylinder i, is controlled by a valve 12, subjected to the return action of a spring It. This valve i2 coacts with an abutment l4 carried, preferably in an adjustable manner, on the piston rod 3, the whole being arranged in such manner that valve l2 ensures its own distribution, which means that it uncovers the feed passage for water under pressure once it is fully depressed (near the end of the suction stroke of the pistons).

This valve will then be kept in this depressed podtion by the pressure of the water that is injected, imtil the end of the injection, at which time the valve comes back onto its seat, where it remains until the end of the next suction stroke.

In the preceding description, it has been assumed that the delivery and suction pressures of the auto-compressor remained constant.

when at least one of these pressures varies, the mass of compressed air" delivered for each stroke of the machine varies also. I may therefore, advantageously, in this case, according to a second embodiment of my invention, vary the amount of water injected not only as a function of the delivery strokes, but also as a function of that or those of said pressure that is, or are, variable. y

In all cases, it will be advantageous to inject an amount'of water which is the moreimportant as the ratio of the delivery and inlet pressures is higher, that is to say as the compression work to be eflected is more considerable.

First, it will be assumed that only the delivery pressure variesand, further, that it is'desired, for instancaio produce the injection of shownby'the diagram ofFig. 5, the amount of liquid that is injected corresponds to a Straight line m-n 'or m'n according as the pressure of delivery is equal to p or p.

With this object in view, I may advantageously have recourse to the arrangement shown by way of example by Fig. 4.

The piston I of an injection pump 8 iscontrolled by a rod l5 bearing against an arm of an L-shaped piece IS, the other arm of which is connected, for instance through the intermediate of a lever I I, with the end of rod 3'; The point of contact of said rod IS with piece l6 can be moved to a variable distance from the pivoting axis l8 of said piece It so that the amplitudes of the strokes of said piston' I can be varied, which consequently varies the rate of delivery of said pump 8. I I I further provide, in order to control the displacements of rod It, a device subjected to theaction of the delivery pressure of the machine. This device may, for instance, consist of the system formed by a cylinder-J9 and a piston 20,

said piston being subjected, on' one of itsfaces,

to the action of spring- 2|, and on the opposite face, to the action of said delivery pressure, transmitted through a conduit 22. The whole is so devised that the point of contact of pieces l5 and I6 is more or less distant from the pivoting axis, l'8, this distance increasing when said delivery pressure increases,,or, in other words, the rate of delivery of the pump increasing when the delivery pressure increases.-

It will be readily understood that such a system permits of varying the amount of liquid injected in proportion with both the amplitude of the strokes ofihe-reciprocating parts'and the delivery pressure, therefore with the mass .Of air delivered by the machine at every delivery stroke. a.

; If, now, it is assumed that the feed pressure also varies, I may, in order to take account of these variations, cause said pressure to .act, through the intermediate of a conduit 23, upon the other face of piston 20,50 that the latter takes a position of equilibrium under the com-- ,bined actionof the delivery pressure and of the suction pressure, the contacting point of levers l6 and I! being the more distant from the pivoting axis l8 as,the ratio of compression is higher, that is to say as the compression work tobe supplied is more important. a

But I may also, according to another embodiment of my invention, provide a system for effecting a complementary regulationof the rate of feed of injected liquid as a function of at least one of the working temperatures of themachine. For instance; in the following description, I will consider the variations oi' the temperature of the air sucked in into cylinderl.

- Preferably, in this case, I arrange things in such manner that the rate'of feed of the liquid ofthe feed air becomes higher; k In this way, it will be possible to maintain the temperature of the air that is delivered at a.

substantially uniform value, at least within certhat is injected increases when the temperature.

tain limits of variation of the temperature of' the surrounding air.

' In this case also, in order to comply with these conditions, I may employ manydiiferent specific mechanisms. In particular, I may make use of the arrangement illustrated by Fig. 6 of the drawings. In this embodiment of my invention, the rate of feed of the water injected into the compressor is controlled not only by the amplitudes of the delivery strokes and by the temperature of the feed air, but also by one of the working pressures of the machine, for instance by the feed pressure of cylinder l.

Therefore, assuming, by way of example, that the delivery pressure remains substantially uniform and that the inlet pressure is variable, I must obtain a reduction of the amount ofwater injected into the compressor when said feed pressure increases, that is to say when the compression work to be eifected is beingreduced.

According to the embodiment shown by Fig. 6, the piston I of a pump 8 is controlled by a rod l5 one of the ends of which is pivoted to said of water injected into the compressor, independently of the variations of the strokes of the 'compressor piston 2. I

The displacements of rod l5 are controlled by a thermostatic device, such for instance as a deformable box 56, mounted along the path 'of' the feed air, advantageously in conduit 5|,

which deformable box is connected to the-other (intermediate) point of said rod l5 through suitable kinematic means. These means consist. for instance of rods 51 and 58 which coact revspectively with the ends of a bell crank lever'59,

arranged in such manner that, when deformable box 56 expands as a consequence of a rise of temperature of the feed air, rod [5 is moved away from axis l8, which causes the .rate of feed of injected water to increase. I

In order to permit a complementary regulation of the injection rate as a function of variations of the feed pressure of the machine, the pivoting by the end of the arm of a bent lever 5| which is pivotally mounted about a fixed axis 61 and the other armof which is connected,-through the intermediate of a rod 63, with a barometic or similar deformable box subjected to the action of said feed pressure, for instance conthe strokes of piston I, and therefore the amount Qaxis of thebell crank lever 59 is carried displacement of rod l5 such that the useful .l gth' 0f the lever arm extending from pivot It to the'point of contact of rod 15 and piece l5 decreases; that is to say that the rate'oi' injection also decreases.

- In all cases, whatever be the embodimentthat 'is, chosen, I obtain a free piston auto-compressor the compressor portion of which is cooled by a system of injection of water. the operation of which results sufliciently clearly fromnthe pre-' cedlng description for making it unnecessary to give any supplementary explanations.

In any case, such an auto-compressor has, among other advantages, that of working .with an optimum efliciency, at least within certain ture of the surrounding atmosphere.

limits of variation of the pressure and tempera- The system above described may be used either in this state, or in combination with certain other characteristic arrangements, such .as

will be hereinafter described, and which may eventually be employed separately.

According to a supplementary feature, which .will be supposed, in the following description,

to be applied to the auto compressor partly.

shown by Fig. 4, I provide means for automatically controlling the beginning of the injection of cooling liquid into the compressor as a function of at least one of the characteristics of operation of the machine, for instance as a function of the inlet pressure.

Vfith this object in view, I may advantageously, for instance as shown by Fig. 4, have the pivoting axis of piece it carried by the end 01 the rod of a piston 24 coacting with a cylinder 25 in which the pressure is equal to the inlet pressure of the air red to the machine. The

sor pistons, but they might be reciprocating parts of different structure and connection with the pistons, such for instance as oscillating connecting rods operative by the system which synchronizes the movements 01' the pistons.

On the other hand, as already above stated, the injection of water might be effected into the compressor portion of a free piston machine other than an auto-compressor, for instance an auto-generator, that is to say a machine having a single gaseous'circuit.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and eflicient embodiments of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition,- and form or the parts without departing from the principle of the present invention as comprehended within the scope of the appended claims.

a What I claim is: 4

l. A tree piston machine of the type described, w ich comprises, in combination, a compressor part,'adjustable means for injecting liquid into said compressor part, and means, responsive to variations in the inlet pressure of the compressor part. for controlling the time of operation of said liquid injecting means as a function of said inlet pressure.

piston for controlling the working of said liquid injecting means as a function of the amplitude of the strokes of said last mentioned piston.

3. A free piston machine of the type described,

which comprises, in combination, a compressor unit including at least one piston, a variable stroke pump for injecting liquidinto' said com-v pressor unit, and means operatively connected said pump so as to vary the with said last mentioned piston for operating delivery thereof as a iunotion of the amplitude of the strokes of said last mentioned piston;

4. A free piston machine of the type described, which comprises, in combination, a compressor unit including at least one piston, a variable stroke pump fed with a cooling liquid, means for connecting the delivery of said pump with said compressor unit, for injection of said liquid from said pump into said compressor unit, a reciprocating member for operating said pump, and a cam rigid with said last'mentioned piston for operating said reciprocating member in accordance with the amplitude of the strokes of said last mentioned piston.

A tree piston machine of the type described which comprises, in combination, a compressor unit including at least one reciprocating piston, an accumulation pump fed with a cooling liquid,

-a reciprocating member included in said pump and the amplitude of the movement of which determines the delivery of said pump, a rod carried by said compressor piston, cam means rigid with said rod adapted to cooperate with said reciprocating member for controlling the amplitude of the displacements thereof in accordance with the amplitude of the displacements of said compressor unit piston, a passage connecting the delivery of said pump with saidcompressor unit, a

valve for controlling said passage, and means operative by said compressor unit piston for controlling the opening of said valve.

A free piston machine of the type described, which comprises, in combination; a compressor unit, including'at least one reciprocating piston, a variable stroke pump adapted to be fed with a cooling liquid,, a reciprocating member included in said pump and the amplitude of the movement or which determines the delivery of said pump, means for connecting the delivery of said pump with .said compressor unit, an axis, a part pivoted about said axis, operatively connected with said compressor piston for oscillating in accordance with the displacements of said reciprocating piston, a lever pivoted to the outer end of said reciprocating member and adapted to cooperate with said oscillating part for transmitting the movements thereof to said reciprocating member of the pump, and means operative by variations of pressure or at least one element of saidcompressor unit for controlling the position of said lever, so that it cooperates with difl'erent points of said oscillating member according to the corresponding values 0! said pressure.

A-Iree piston machine of the type described, which comprises, in combination, a compressor unit, including at least one reciprocating piston, a variable stroke pump adapted to be fed with a cooling liquid, a reciprocating member included in said pump and the amplitude of movement of which determines the rate oi delivery of said pump, means for connecting the delivery of said pump with said compressor unit, an axis, an L- shaped piece pivoted about said axis, a rod for said compressor, plston,-a connecting rod interposed'between said rod and one branch of said L'-shaped piece, a lever pivoted to the outer end of said-reciprocating member or the pump and adapted to cooperate with the other branch of said L shaped piece for transmitting the oscillations thereof to said reciprocating member of the pump, a cylinder having at least one closed end connected to the delivery or said compres- I I 2,178,811 son a piston movable in saidcylinder, means for cording to the values of said temperature, re-- 'yieldingly opposing the action of the delivery pressure of said compressor on saidlast mentioned piston, and mechanical means for interconnecting said last mentioned piston with said lever, whereby the position of said lever is controlled by said delivery pressure of the compressor, so that said lever cooperates-with diflerent a variable stroke pump adapted to be fed with a cooling liquid,'a reciprocating memberincluded in said pump and the amplitude of movement of which determines the rate of delivery of said pump, means for connecting the delivery of said pump with said compressor unit, the last mentioned means including an atomizer for said liquid, whereby said liquid is introduced in the atomized state into said compressor unit, an axis, an L-shaped piece pivoted about said axis, a rod for'said compressor piston, a connecting rod interposed between said rod and one branch of said L-shaped piece, a lever pivoted to the outer end of saidreciprocating member of the pump and adapted to cooperate with the other branch of said L-shaped piece for transmitting the oscillations thereof to said reciprocating member of the pump, a cylinder havingone closed end connected to the delivery of said compressorunit, and the other closed end connected to the inlet of said compressor unit, a piston movable inside said cylinder, under the efiect of the opposed actions of said delivery and inlet pressures of the compressor unit, and mechanical means 'for interconnecting said last mentioned piston with said lever, whereby the position of said lever is controlled by .the. combined actions of said pressures, so'thatsaid lever cooperates with different points oi the second mentioned branch of said L-shaped piece according to the values of said pressures.

9. A free piston machine of the type described, which comprises, in combination, a compressor unit, including at least one reciprocating piston,

a variable stroke pump adapted to be fed with a cooling liquid, a reciprocating member included in said pump and the amplitude of the movement of which determines the rate of delivery of said pump, an atomizer, opening into said compressor unit, means for connecting the delivery of said pump with said atomizer, whereby atomized liquid is fed into said compressor unit, a fixed axis, a piece pivoted about said axis, mechanical means for connecting. said piston with said pivotin piece, whereby the reciprocating movement of said piston produces an oscillating movement of saidf pivoting piece, a lever pivoted to the outer end of. said reciprocating member of the pump and adapted to cooperate with said pivoting piece for transmitting the reciprocating movement thereof to the reciprocating member of the pump, a member movable in response to variations'of one of the characteristic temperatures of said compressor unit,-and mechanical means for interconnecting said last mentioned member with said lever associated with saidreciprocatwith different points of said pivoting piece ac.-

spectively. V

l0. Avfree piston machine of the type described, which comprises, in combination, a compressor unit, including'at least one reciprocating piston, a variable stroke pump adapted to be fed with a cooling liquid, a reciprocating member included in said pump and the amplitude of movement of which determines? the rate of delivery of said pump, an atomizer opening into said compressor unit, means for connecting the delivery of said pump with said atomizer, whereby atomized liquid is fed into said compressor unit, a

fixed axis, a piece pivoted about said axis,--said place being L-shaped, mechanical means for connecting one branch of said piece with said compressor unit piston, whereby the oscillating -movementof said' piston produces a rocking movement of said pivoting piece, a lever pivoted to the outer end of said reciprocating member of the pumpa'nd adapted to cooperate with the other branch of said L-shaped piece for transmitting the oscillating movement thereof to said reciprocating member of the pump, a thermometric deformable box subjected to the temperature of the air fed to said compressor unit, and mechanical means for interconnecting a movable part of said deformable box with said lever, whereby the position of said lever is controlled by the value of said temperature, so that said lever cooperates with different points of said pivoting piece according to the values of said temperature, respectively.

11. A free piston machine of the type described,

which comprises, in combination, a compressor unit, including at least one reciprocating piston,

a variable stroke pump adapted to be fed with a cooling liquid, a reciprocataingmember included in said pump and the amplitude of movement of which determines the rate of delivery of said pump, an "atomizer opening into said compressor unit, means for connecting the delivery of said pump with said'atomizer, whereby atomized liquid is fed into said compressor unit, a fixed,

axis, an L-shaped piece pivoted about said axis, mechanical means for connecting one branch of said L-shaped ,piece with the piston of said compressor unit, whereby the oscillating movement of said piston produces a rocking movement of said'pivoting piece, a lever pivoted to the outer end of said reciprocating member of the pump and adapted to cooperate with the other branch of said L-shaped piece for transmitting the.os-

ciliating movement thereof to said reciprocating member of the pump. a thermometric deformable box subjected to the temperature of the air fed to said compressor unit, 'mechanical' means, in-

cluding at least one lever and a pivoting axis for .said last mentioned lever, for interconnecting a is further influenced by said pressure.

12. A free piston machine of the type described, I

which'comprises, in combination, a compressor unit, including at least one reciprocable piston.

a variable stroke pump adapted to be fed with a cooling liquid, a reciprocable member included in said pump and the amplitude of movement of .which determines the rate of delivery 01' said said reciprocating member of the pump, whereby the movement of said piston is transmitted to said reciprocating member of the pump, a part movable vertically in response to variations of one of the functional factors of said compressor unit, and means for displacing said axis in connection with the vertical displacements of said last mentioned part, whereby the time at which the injection of cooling liquid by said pump into said compressor unit starts varies in accordance with variations of said "functional factor. I

' 13. A free piston machineof the type described, which'comprises, in combination, a compressor unit, including at least one reciprocating piston,

a variable stroke pump adapted to be red with a cooling liquid, a reciprocating member included in said pump and the amplitude of movement of which determines the rate of delivery or said pump, an atomizer opening into said compressor unit, means for connecting the delivery of said pump with said atomizer, whereby atomized liquid is fed into said compressor unit for each stroke of said pump, a movable axis, an L-shaped piece pivoted about said axis, mechanical means for connecting one branch of said L-shaped piece with the piston of said compressor unit, whereby the oscillating movement or said piston produces a rocking movement of said pivoting piece, a lever pivoted to the outer end of said reciprocating member of the pump and adapted to cooperate with the other branch of said L-shaped piece for V transmitting the oscillating movement thereof to respectively, a part movable vertically in respouse to variations of one of the functional factors of said compressor unit, and means for displacing said movable axis operative by the displacements of said last mentioned part, whereby the time at which injection of cooling liquid by said pump into said compressor unit starts varies in accordance with variations of said functional factor.

14. A tree piston motor compressor which comprises, in combination, a motor part and a compressor part, adjustable means for injecting noncombustible liquid in said motor compressor and means responsive to variations of length of the free piston stroke for controlling the working of said liquid injecting means so as to vary the rate of injection of said liquid into said motor compressor.

15. A tree piston motor compressor, according to claim 14, further comprising means responsive to variations of at least one 01' the pressures of operation of said motor compressor, said last mentioned means controlling together with said piston stroke responsive means said liquid in-.

jecting means so as to vary the rate of injection or said liquid into said motor compressor.

16. A free piston motor compressor, according to claim 14, further comprising means responsive to variations of the fluid inlet pressure to said motor compressor, said last mentioned means controlling together with said piston stroke responsive means said liquid injecting means so as to vary the rate of injection of said liquid into said motor compressor;

17. A free piston motor compressor, according to claim 14, further comprising means responsive to variations of the delivery pressuer of said motor compressor, saidlast mentioned means controlling together with said piston stroke responsive means said liquid injecting means so as to very the rate of injection of said liquid into said motor compressor.

18. A free piston motor compressor, according to claim 14, further comprising means responsive to variations of at least one of the temperatures of operation of said motor compressor, said last mentioned means controlling together with said piston stroke responsive means said liquid injecting means so as to vary the rate of injection of said liquid into said motor compressor.

19. A tree piston motor compressor, according to claim 14, further comprising means responsive to variations of the temperature of the air fed to said motor compressor, said last mentioned means controlling together with said piston stroke responsive means said liquid injecting means so as to vary the rate or injection of said liquid into said motor compressor.

RAUL PATERAS Pascaaa.

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