US2344058A

US2344058A - Free piston machine

Info

Publication number: US2344058A
Application number: US433803A
Authority: US
Inventors: Pescara Raul Pateras
Original assignee: PARTICIPATIONS SOC ET
Current assignee: D'ETUDES ET DE PARTICIPATIONS Ste; PARTICIPATIONS SOC ET
Priority date: 1939-08-04
Filing date: 1942-03-07
Publication date: 1944-03-14
Anticipated expiration: 1961-03-14

Description

March 14; 1944- P. PATERAS PESCARA FREE PsToN MACHINE Filed March '7, 1942 2 Sheets-Sheet 1 ,EN WN 5% 0,. o a u o M kN Nh wn ww hh M WN M f w NN N n E m NNN mw hh MN i NN J NQN ww BNQ h im. N m. Nm

lr'nven'iWfRmM Paems Pescara.,

March 14 1944- P. PATERAs PESCARA 2,344,058

2 Sheets-Sheet 2 hvenor: czu/ Paeras Pescara.

FREE PI STON MACHINE Filed March 7. 1942 Patented Mar. 14, 1944 FREE rls'roN MACHINE Raul Pateras Pescara, Estoril, Portugal, assignor of one-tenth to Societe'dEtudes et de Participations, Eau, Gaz, Electricite, Energie S. A., Geneva, Switzerland,l a society of Switzerland Application March "l, 1942, Serial No. 433,803 In Luxemburg August 4, 1939 18 Claims.

The present invention relates to free piston machines, that is to say machines including at least one reciprocating element the stroke or amplitude of movement of which can vary freely within certain limits. contrary to what takes place in the case. of machines including connecting rods and crankshafts.

Among these machines, the invention is more especially, although not exclusively, concerned with the auto-generators of this kind, that is to say machines of the free piston type which deliver compressed air utilized, either wholly or partly, for the scavenging and the feed of the motor part of the machine, the mixture of the combustion gases and of the excess of scavenging air being fed to a receiver apparatus in which it expands, for instance a turbine.

The chief object of the present invention is to provide a machine of the type above mentioned which is better adapted to meet the requirements of practice than those used for the same purpose up to the present time.

According to an important feature of the invention, the machine of the type above y', set forth is devised in such manner that at least a portion of the compression work takes place during the return strokes of the reciprocating elements, and the pneumatic accumulators of energy to be included in the machine are made in such manner that they are capable of absorbing the whole of the work produced during an exceptional motive stroke of an amplitude higher than the maximum stroke corresponding with the normal running of the machine.

In a preferred embodiment of the invention, means are provided so as to be brought into play when such an exceptional stroke occurs for reducing the power developed in the motive part of the machine during the next active stroke.

According to another feature of the invention, the machine of `the type above set forth being still of the kind in which at least a portion of the compression work is produced during the return stroke (taking place under the action of the pneumatic energy accumulators) of the reciprocating elements, said accumulators are made in such manner that, at least for the exceptional strokes, any increase of amplitude of the strokes of the reciprocating elements corresponds, in the compressor part of the machine, to such an increase of the amount of air that is sucked in that the compression work produced during the return stroke increases at the rate of at least one third of the increase of energy stored up in the pneumatic accumulators during the preceding outward stroke.

According to still another feature of the invention. the starting position of the reciprocating elements is chosen at a point of their stroke which is nearer the inner end of said stroke than the outer end thereof that corresponds to the maximum amplitude admissible under normal running conditions, the pressure of the compressed air used for starting the machine being chosen in accordance with the position thus chosen for the starting of the parts.

Other features of the present invention will result from the following detailed description of some specific embodiments thereof.

Preferred embodiments of the present invention will be hereinafter described with reference to the accompanying drawings given merely by way of example, and in which:

Fig. 1 is a diagrammatical view, partly in section of an auto-generator made according to a first embodiment of the inventori;

Fig. 2 is a similar view of an auto-generator made according to another embodiment of the invention.

The following description relates, for the description of a machine of the free piston type according to the invention, to the specific case of an auto-generator of this type in which at least a portion of the compression work isproduced during the return stroke of the reciprocating elements of the machine, such a case being chosen by way of example.

Concerning first the general construction of the machine, with the exception of the pneumatic energy accumulators to be included in said machine, itis of any suitable conventional or other kind, for instance such as that illustrated by Fig. l.

In this embodiment of my invention, I provide, in a motor cylinder I, two motor pistons 21 and 22, adapted to cooperate respectively, close to the outer ends of their strokes, with inlet ports 3 and outlet ports I, respectively, the outlet prts 4 communicating with a discharge pipe 5.

Two compressor pistons 61 and 62 are rigidly associated with said motor pistons, respectively.

The inward faces of tnese compressor pistons cooperate with cylinders 11 and 12, fitted with inlet valves 8 and outlet valves 9. The outward faces of these compressor pistons cooperate with chambers or cylinders |01 and Ill2 which constitute the pneumatic energy accumulators. 'Ihe pressure in these energy accumulators depends upon the feed pressure to be obtained from the auto-generator machine.

I provide kinematic means for synchronizing the movements of pistons 21 and 2', these means consisting for instance of racks ||1 and I |I rigid with said pistons, respectively, and both in mesh with a pinion I2.

The fuel is fed to the motor cylinder through any suitable means. for instance, as illustrated by the drawings, by means of a fuel injector I3 fed by a pump Il actuated by a cam Il carried by the spindle of the synchronizing piston I2.

Cylinder I is surrounded by a iiuidtight casing It, fed with air under pressure for the scavenging and the feed of the engine through the discharge valves of the compressor part of the machine.

In machines of this type, up to the present time. the pneumatic energy accumulators llil and |02 were so dimensioned as to act only as stabilizing means, and in order to avoid any risk of the ends of said accumulators being deteriorated by pistons il and 6 moving beyond the normal ends of their outward strokes, safety means were provided for limiting the strokes of said pistons, said mea'ns being constituted by the synchronizing system above described.

Now, according to the present invention, the synchronizing means do not so limit the amplitude of the outward displacements of the pistons, but the energy accumulators are made capable of absorbing the whole of the motive Work developed during an outward stroke of exceptional amplitude (for instance a stroke for which the whole of the scavenging air contained in cylinder I has combined with a great excess of fuel exceptionally injected into said cylinder).

Consequently, with such a construction, in the case of such an exceptional stroke, the pistons do not come to strike against the ends of pneumatic accumulators I01 and |02, whereby perfect safety is ensured, and this safety is obtained without imposing any particular stress upon 'the synchronizing means, which can then be built much lighter than in the machines of this kind made up to this time.

It sumces, for this purpose, to give suitable dimensions to accumulatcrs I01 and Iii2 and to position their ends in such manner that pistons $1 and 62 cannot touch them even at the ends of the y exceptionally long strokes.

But if several exceptionally long strokes took place consecutively, the work absorbed by the compressor element might be insufficient for absorbing the excess of energy stored up in the pneumatic accumulators. In this case, the amplitudes of the successive strokes would go increasing, finally exceeding the limit value for exceptional strokes that has been reckoned upon when dimensioning the pneumatic energy accumulators.

In order to obviate this drawback, according to the present invention, I provide correcting means, adapted to be brought into play when there is an outward stroke of exceptional amplitude of the pistons, for reducing the power produced in the motor element of the machine during the next motive stroke of the pistons.

In particular, in a preferred embodiment of my invention, these correcting means act on the means for injecting fuel into cylinder I.

Such an arrangement is shown, by way of example, by Fig. 1.

In this construction, one of the reciprocating elements of the machine, for instance piston l1,

is provided with a push-piece I'l adapted, when the outward strokes of the pistons exceed the maximum amplitude corresponding to normal running conditions. to come into contact with a rocking lever Il. This lever Il is adapted to open (when so pivoted) nrst a valve i0 and then a valve 20, these valves controlling two distinct compressed air circuits.

' The first of these circuits ibrollght into play as soon as the reciprocating elements move beyond the limit position corresponding to normal running conditions and it' acts; upon the quantitative adjustment member 2| of the injection pump Il. For instance, as shown by the drawing (Fig. 1), valve Il, when opening, causes a iluid under pressure to act upon a piston 2l movable in a cylinder 22. this piston 2l being operatively connected, through an eccentric 24, with a link 2l adapted to control member 2 I. The whole is devised in such manner that the linflow of compressed air into cylinder 22 (resulting from the opening of valve I9) corresponds to a reduction of the rate of feed of fuel pump i4.

'I'he second of the circuits above mentioned is arranged in such manner that the opening of valve 20 ensures the blocking of the piston of pump i4, for instance through the action of a piston 26 sliding in a cylinder 2l, to which compressed air is fed as soon as said valve 20 is opened.

Finally, I provide cocks or the like 28 and 29 for vreleasing the pressures in cylinders 22 and 2l after each correcting operation.

A second example of such a correcting device I is illustrated by Fig. 2.

In this example, the pivoting of rocking lever I8 produces'the opening of a discharge valve I0 mounted on the delivery circuit of pump I4.

For instance, as shown by the drawings, valve 30 is subjected to the action of a push-piece 3| one of the faces of which receives the thrust of a spring 32 which tends to keep valve 30 in the closed position thereof.

The other face of said piston 3| is subjected.

' when lever I8 is pivoted by push-piece I1, to the action of compressed air, for instance by bringing a chamber 50 into communicationl with accumulator Il)1 through a conduit 5|, the inflow of compressed air to piston 3| being controiled`by a valve 33 subjected to the action of rocking lever Il, and the movements of said lever producing the opening of said valve 33 and, therefore, the discharge of pump I4.

It will be readily understood that, in both of the examples above described, the correction eiect is obtained as desired since the amount of fuel that is injected into the motor cylinder I (and consequently the power that is produced in this cylinder) is the smaller as the preceding stroke has exceeded to a greater degree the extreme position that can be admitted when working under normal conditions.

Furthermore, I have found that it is advantageous, according to the invention, to obtain that these correcting means are brought into action for an amplitude of the stroke of the pistons which depends upon one of the working characteristics of the machine, for instance the discharge pressure in casing I8.

This result can be obtained, for instance, as follows (Figs. 1 and 2):

Said casing I8 is connected, through a conduit 34, to a cylinder 35 with which coacts a piston 38 subiectedto the action of a suitable return spring such as 3l.

asume This piston 30 is connected te the axis 3l about which the rocking lever Il is pivoted, whereby a displacement of piston 30 resulting from an increase of the pressure in casing Il produces a displacement of rocking lever I8 away from push-piece |1, which delays the action of the correcting means.

With an auto-generator made as above described, every time an outward stroke of the pistons exceeds the maximum amplitude, that is to say over reaches the limit position, admissible under normal working conditions, two consequences occur:

(a) On the one hand, an excess of energy is stored up in the pneumatic accumulators; and

(b) On the other hand, a supplementary amount of air is sucked in into the compressor elements. which supplementary amount of air produces, during the next return stroke, an excess of compression work.

It will be readily understood that, according as the working of the pneumatic accumulators is characterized by a more or less rapid rise of pressure as a function of the displacement of the pistons, the same amount of energy stored up by said acoumulators may correspond to dlerent strokes of the pistons. Therefore, the supplementary amount of air sucked in by the compressor elements when a given excess of energy is stored up by the accumulators may vary in accordance with the construction factors of said energy accumulators.

According to a feature of the present invention said energy accumulators are made in such man ner that the compression work produced during the return stroke is increased at such a rate that its increase is always at least one third of the increase of works stored up in the pneumatic accumulators during the preceding outward stroke, this result being obtained by suitably choosing the ratio of the extreme pressures brought into play in said pneumatic accumulators.

Finally, the auto-generator above described is advantageously f completed by providing it with starting means.

An example of such starting means is illustrated by Fig. 2.

I provide, on the end of one of the pneumatic energy accumulators, |01 in this case, means forming a chamber 39 communicating with said accumulator through an orifice adapted to be closed by a valve 40 coupled with a piston 4|. This piston 4| is slidable in a cylinder 42 and it is fitted with a check valve 43 adapted to permit the flow of air under pressure only from cylinder 42 toward chamber 39.

Cylinder 42 is connected through a conduit 44 with a source of compressed air.

'I'his starting device will operate in the following manner:

The pistons are first brought into a starting position which will be hereinafter defined in a more explicit manner. Then compressed air is sent into cylinder 42. 43, into chamber 39, which is separated from accumulator I01 by valve 40. If, now, conduit 44 is opened to the atmosphere, there is produced a drop of pressure on the right hand side of piston 4I, which, under the effect of the pressure existing in chamber 39, moves toward the right, and thus lifts valve 40 from its seat. vThe compressed air contained in chamber 39 then escapedinto accumulator l01 and produces the This air flows past valve starting of the reciprocating elements ofthe machine. Concerning now the starting position that the reciprocating elements must occupy, it is advan- 5 taaemis to determine it in advance.

This position is preferably chosen nearer to the inner end of the stroke than -to the outer end corresponding to the maximum stroke admissible when the machine is running normally in continuous manner. In this way, I avoid Vthe obtainment of too important a motive work during the first outward stroke after the starting, for which stroke there is generally an excess of fuel in the feed air, and for which, furthermore, the compression work to be absorbed on the next stroke is relatively small, al1 these circumstances tending to give rise to motive strokes of exceptional amplitudes.

The pressure of the compressed air used for startingthe machine is chosen of a value sumcient for ensuring the necessary compression in cylinder and this starting pressure is then higher to what would have been necessary had the starting positions of the pistons been chosen 25 nearer to the ends of the outward strokes.

s When the machine is provided with correcting means such as those jlust above described, it is advantageous to provide means whereby said correcting means are caused to act for strokes of relatively small amplitude as long as the starting period is lasting, that is to say during a certain number of reciprocations after the starting of the machine and until the latter has reached its normal themiic state. This result may be obtained in the manner illustrated by Fig. 2.

In this embodiment, the source of compressed air used for starting the machine is connected, with the interposition of a check valve 45 or the like, to a cylinder 46 provided with a discharge cock 41. This cylinder 4 8 contains a plunger piston 48 rigid with the piston 38 which carries the rocking lever 33. The whole is arranged in such manner that the compressed air acting on plunger piston 48 causes rocking lever I8 to move toward push piece I1.

With such a device it will suilice, once the machine is well started, to open cock 41 for allow-` tion corresponding to the working pressure existing at this time in the machine.

In order suitably to position the parts for the starting of the machine, it would be sufficient to provide a mark, for instance on push piece |1, indicating the position thereof with respect to the end of accumulator |01. But it is preferable to provide, on the compressed air circuit serving to start the machine, safety means s uch that chamber 39 can be fed with compressed air only when the `reciprocating parts are in the correct position for starting the machine. These'safety l means may be constituted, for instance, by making use of push-piece I1 as a distribution slidevalve. In the example shown by the drawing (Fig. 2) anannulargroove 49 is provided in said push-piece in a portion thereof which registers with conduit 44 when the reciprocating elements have reached the correct strating position.

Anyway whatever be the particular embodiment that is chosen, the opera-tion thereof results suiliciently 'clearly from the preceding explanations for making it unnecessary to enterf into further explanations.

ing rocking lever il freely to assume the posi- The advantages of the machines according to the invention also result from the above description ofsome preferred embodiments.

Of course, the whole or a part of the arrangements above described might be applied tofree piston machines other than auto-generators, and, in particular, to vmotor compressors in which at least ay part of the compression -work is eifected from the principle of the present invention, as

comprehended lwithin the scope of the appended claims.

What I claim is:

l. A free piston machine which comprises, in combination, a stationary frame, at least one reciprocating element movable with respect to said frame with an amplitude of movement variable. within given limits, in accordance with the motive action exerted on 'said element, means for exerting successive actions on said element in one direction, and a pneumatic energy accumulator cooperating with said reciprocating element for returning it in the other direction, said accumulator |being adapted to absorb thewhole of the work produced during a motive stroke of said reciprocating element of an amplitude higher than the maximum amplitude admissible under normal running conditions of the machine.

2. A free piston machine which comprises, in combination. a stationary frame, at least one reciprocating element movable with respect to said frame with an amplitude of movement variable, within certain limits, in accordance with the motive action exerted on said element, means for exerting successive motive actions on said element, in one direction, a pneumatic energy accumulator adapted to cooperate with said reciprocating element for returning it in the opposite direction, said accumulator being capable of absorbing the Whole of the Work produced during a motive stroke of said reciprocating element of an amplitude higher than the maximum amplitude admissible under normal running conditions of the machine, and means, operative by such an exceptional stroke of said element, for reducing the action exerted .by said motive means during the next stroke, in the rst mentioned direction, of said motive means.

3. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in accordance 'with the motive action,V exerted on said piston, means for feeding, at intervals -of time, a motive fluid to said cylinder for driving said piston in one direction, a compressor device associated with said piston adapted to perform at least a portion of the compression work during the return strokes of said piston, and a pneumatic energy accumulator associated with said piston for producing the return strokes thereof, said accumulator being capable of absorbing the whole of the work produced during a motive stroke of said piston of an amplitude higher than the maximum amplitude admissible under normal running conditions of the machine.

4. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in accordance with the motive action exerted on said piston, means for feeding. at intervals of' time, a motive -iiuid to said cylinder for driving said piston in one direction, a compressor device associated with said piston 'and cylinder adapted to perform at least a portion of the compression work during thereturn strokes of said piston, a pneumatic energyaccumulator associated with said piston for producing the return strokes thereof, said accumulator being capable of absorbing the whole of the work produced during a motive stroke of said piston of an amplitude higher than the maximum ampitude admissible under normal running conditions of the machine, and means operative by said piston on auch an exceptionally long stroke thereof for reducing the feed of motive fluid to said cylinder on the next motive stroke of said piston.

5. A free piston machine which comprises, in combination, a motor cylinder'and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in accordance with` the motive 4action exerted on said piston, means for feeding, at intervals of time, air and fuel to said cylinder, whereby the combustion of said fuel in said air produces the successive motive strokes of said-piston.' a compressor device.associated with said piston and cylinder adapted 'to produce atleast a portion of its compression work duringthe return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor cylinder and a piston rigid with said motorpiston and adapted to cooperate with-said accumulator cylinder so that the fluid compressed in said accumulator cylinder during the motive strokes of the motor piston produces the return strokes of said motor piston, said accumulator cylinder being so dimensioned and havingv its end so positioned that it is capable of absorbing the whole ofthe work produced during a motive stroke of the motor piston of an amplitude higher than the maximum amplitude admissible under normal working conditions of the machines, without `said ,accumulator piston touching saidend of said accumulator cylinder.

6. A free piston .machine which comprises, in combination, a motor cylinder, and at least one motor piston movable therein withl an amplitude of movement variable, within certain limlits in accordance with the motive action exerted on said piston, means for feeding, at intervals of time, air and fuel to said cylinder, whereby the combustion of said fuel in said air produces the successive motive strokes of said piston, a compressor device associated with said piston and cylinder adapted to produce at least a portion of its compression work during the return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor cylinder and an accumulator piston rigid with said motor piston and adapted to cooperatewith said accumulator cylinder so that the uid compressed in said accumulator cylinder during the motive strokes of the motor piston produces the return strokes of said motor piston, said accumulator cylinder being so dimensioned and having its end so posif tioned that even for motive strokes of the motor piston of an amplitude higher than the maxiymum amplitude admissible under normal working conditions of the machine, said accumulator piston ds not come. `into ycontact 'with said end of said accumulatorvcylinder, vand means operative by said accumulatorpl'stnn at the ends of such exceptionally long strokes thereof, for reducing the feed of fuel to be supplied by said feeding means to said motor cylinder for the next motive stroke of said motor piston.

7. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable within certain limits in accordance with the motive action exerted on said piston, said cylinder being provided with at least one inlet port for theinflow of air to said cylinder, a fuel pump, driven by said piston for feeding fuel to said cylinder, a compressor device associated with said piston and cylinder adapted to produce at least a portion of its compression work during the return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor cylinder and an accumulator piston rigid with said motor piston and adapted to cooperate with said accumulator cylinder so that the i'luid compressed in said accumulator cylinder during the motive strokes of said motor piston produces the return strokes of said motor piston, said accumulator cylinderbeing so dimensioned and having its end so positioned that, even for exceptionally long motive strokes of the motor piston, i. e., strokes of an amplitude higher than the maximum amplitude admissible under normal working conditionsof the machine, said accumulator piston does not come into contact with said end of the accumulator cylinder, means for regulating said fuel feed pump, and means operative by said accumulator piston, at the end of such an exceptionally long stroke thereof, for acting on said pump regulating means so as to reduce the rate of delivery of said pump for the next motive stroke of said motor piston. l

8. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable within certain limits in accordance with the motive action exerted on said piston, said cylinder being provided with at least one inlet port for the iniiow of air to said cylinder, a fue1 pump, driven by said piston, for feeding fuel to said cylinder, a compressor device associated with said piston and cylinder adapted to produce at least a portion of its compression work during the return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor cylinder and an accumulator pistony rigid with said motor piston and adapted to cooperate with said accumulator cylinder so that the uid compressed in said accumulator cylinder during the motive strokes of said motor piston produces the return strokes of said motor piston, said accumulator cylinder being so dimensioned and having its end so positioned that, even for exceptionally long motive strokes of the motor piston, i. e., strokes of an amplitude higher than the maximum amplitude admissible under normal working conditions of the machine, said accumulator piston does not come into contact with said end of the accumulator cylinder, a delivery conduit for said pump adapted to convey the fuel therefrom to said motor cylinder, regulable discharge means on said conduit adapted to permit the discharge of fuel on its way to said cylinder, and means operative of fuel on its way to said cylinder, and means operative by said accumulator piston, at the end of such an exceptionally long stroke thereof, for opening more or less said discharge means so as to reduce the rate of feed of fuel to said motor cyslitxder for the next motive stroke of said motor p n. v

9. A free piston machine which comprises, in combination, a motor cylinder and at least `one motor piston movable therein with an amplitude of movement variable within certain limits in accordance with the motive action exerted on said piston, said cylinder being provided with at least one lmet port for the inflow of air to said cylinder, a fuel pump, driven by said piston, for feeding fuel -to said cylinder, a compressor device associated with said piston and cylinder and adapted to produce at least a portion of its compression work during the return strokes of-said piston, a pneumatic energy accumulator cylinder rigid with-said motor cylinder and an accumulator piston rigid with said motor piston and.

adapted to cooperate with said accumulator cyl index. so that the fluid compressed in said accumulator cylinder during the motive strokes'of said motor piston produces the -return strokes of said motor piston, said accumulator cylinder being so dimensioned and having its end so positioned that, even for exceptionally long motive strokes of the motor piston, i. e., strokes of an amplitude higher than the maximum amplitude admissible under normal working conditions of the machine, said accumulator pistondoes not come into contact with said en'd of the accumulator cylinder, means operative by said accumulator' piston whenever its stroke exceeds the maximum admissible amplitude above mentioned for reducing the feed of fuel from said pump to said cylinder, and means operative by 'said accumulatbr piston, for strokes thereof of an amplitude exceeding a still greater value, for blocking said pump.

10. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in accordance with the motive action exerted on said piston, said cylinder being provided with -.inlet means for the inflow of air to said cylinder, fuel feed means for supplying fuel to said cylinder, a compressor device associated with said piston and cylinder and adapted to produce at least a portion of its compression work during the return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor cylinder and an accumulator piston rigid with said motor piston and adapted to cooperate with said accumulator cylinder for producing the return strokes of said motor piston. said accumulator cylinder being so dimensioned and having its end so positioned that, even for exceptionally by said lever when so pivoted for acting on said fuel feed means so as to reduce the amount of fuel fed to said motor cylinder for the n ext motive stroke of said motor piston.

11. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in

accordance with the motive action exerted thereon, said cylinder being provided with inlet port means for the inflow of air to said cylinder, fuel feed means for supplying fuel to said cylinder, a compressor device associated with said piston and cylinder and adapted to produce at least a portion of lits compression work during the return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor piston and adapted to cooperate with said accumulator cylinder for producing the return strokes of said motor piston, said accumulator cylinder a compressor device associated with said piston l and adapted to perform at least a portion of its being so dimensioned and having its end so positioned that, even for exceptionally long motive strokes of the piston, i. e., strokes of an amplitude higher than the maximum amplitude admissible under normal working conditions of the machine, said accumulator piston does not come into contact with said end of said accumulator cylinder, correcting means operated by said accumulator piston at the end of such an exceptionally long stroke thereof for acting on said fuel feed means so as to reduce the amount of fuel fed to said motor cylinder for the next motive stroke of said motor piston, and means responsive to variations of the delivery pressure of said compressor device for adjusting said correcting means in accordancewith the value of said delivery pressure.

12. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude i of movement variable, within certain limits, in accordance with the motive action exerted thereon, said cylinder being provided with inlet port means for the inflow of air to said cylinder, fuel feed means for supplying fuel to said cylinder, a compressor device associated with said piston and cylinder and adapted to produce at least a portion of its compression work during the return strokes of said piston, a casing adapted to receive the compressed fluid from said compressor device, a pneumatic energy accumulator cylinder rigid with said motor cylinder and an accumulator piston rigid with said motor piston and adapted to cooperate with said accumulator cylinder for producing the return strokes of said motor piston, said accumulator cylinder being so dimensioned and having its end so positioned that, even for exceptionally long motive strokes of the motor piston, exceeding the maximum admissible amplitude for normal working conditions, said accumulator piston does not come into contact with said end of said accumulator cylinder, a push piece carried by said accumulator piston and extending through said end of the accumulator cylinder, a rocking lever adapted to be pivoted by said push piece only at the end of such exceptionally long strokes of said motor piston, a movable support for the pivot axis of said lever, a cylinder rigid with above mentioned cylinders, a piston in said last mentioned cylinder rigid with said movable support, means for connecting the inside of the casing of said compressor device with said last mentioned cylinder, and means operative by said rocking lever for controlling said fuel feed means.

13. A free piston machine which comprises,

'in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in accordance with the motive action exerted on said piston, means for feeding, at intervals of time, a motive fluid to said cylinder so as to obtain the motive strokes of said piston,

compression Work during the return strokes of said piston, and a' pneumatic energy accumulator associated with said piston for obtaining the return strokes thereof, said accumulator being capable of absorbing the whole of the work produced by a motive stroke of said piston of an amplitude higher than the maximum ampliture admissible under normal running conditions of the machine; said accumulator being further so proportioned that the increase in the compression work of the compressor device produced during a return stroke after a motive stroke of such exceptional amplitude is at least one third of the increase of energy accumulated in said pneumatic accumulator during said exceptional motive stroke.

14. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in accordance with the motive action exerted thereon, said cylinder beingprovided with inlet means for the inow of air to said cylinder, fuel feed means for supplying fuel to said cylinder, a compressor device associated with said piston and'cylinder and adapted to produce at .least a portion of its compression work during the return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor cylinder and accumulator piston rigid with said motor piston and adapted to cooperate with said accumulator cylinder for producing the return strokes of said motor piston, said accumulator piston being so dimensioned and having its end so positioned that, even for exceptionally long motive strokes Aof said motor piston, exceeding the maximum admissible amplitude for normal Working conditions, said accumulator piston does not come into contact with said end of the accumulator cylinder, and means for starting the reciprocating motion of said motor piston, the starting position thereof being nearer the inner end of its stroke than the outer end thereof corresponding to the maximum amplitude admissible under normal working conditions.

15. A free piston machine which comprises, in combination, a motor cylinder and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in accordance with the motive action exerted thereon, said cylinder being provided with inlet means for inflow of air thereinto, fuel feed means for supplying fuel to said cylinder, a compressor device associated with said piston and cylinder and adapted to produce at least a portion of its compression work during the return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor cylinder and an accumulator piston rigid with said motor piston and adapted to cooperate with said accumulator cylinder for producing the return strokes of said motor piston, said accumulator cylinder being so positioned and dimensioned that, even for exceptionally long motive strokes of said motor piston, exceeding the maximum admissible amplitude for normal working conditions, said accumulator piston does not come into contact with the end of said accumulator cylinder, means forming a chamber adjacent said accumulator cylinder, means for filling said chamber with fluid under pressure, and means for causing said fluid under pressure to pass from said chamber into said accumulator cylinder for starting the machine, the starting position of said motor piston being nearer the inner end of its stroke than the outer end thereof corresponding to the maximum amplitude admissible under normal working conditions,

16. A free piston machine which comprises in combinatioma motor cylinder and at least one motor piston movable therein with an amplitude of movement variable, within certain limits, in accordance with the motive action exerted thereon, said cylinder being provided with inlet means for the inflow of air thereinto, fuel feed means for supplying fuel to said cylinder, a compressor device associated with said piston and cylinder and adapted to produce at least a portion of its compression work during the return strokes of said piston, a pneumatic energy accumulator cylinder rigid with said motor cylinder and an accumulator piston rigid with said motor piston and adapted to cooperate with said accumulator cylinder for producing the return strokes of said motor piston, said accumulator cylinder being so positioned and dimensioned that, even for exceptionally long motive strokes of said motor piston, exceeding the maximum admissible amplitude for normal working conditions, said accumulator piston does not come into contact with the end of said accumulator cylinder, means forming a closed chamber, adapted to contain a uid under pressure, means for causing fluid under pressure to pass from said chamber into said accumulator cylinder for starting the machine, and means operative only when said motor piston is in a predetermined position with respect to said motor cylinder, for permitting the last mentioned preceding means to work only for this relative position of the motor piston and cylinder, this starting position of the motor piston being nearer the inner end of its stroke than the outer end thereof corresponding to the maximum amplitude inadmissible under normal working conditions of the machine.

1'7. A machine according to claim 15 further including correcting means operated by the accumulator piston at the end of exceptionally long strokes thereof for acting on said fuel feed means so as to reduce the amount of fuel fed to the motor cylinder for the next stroke of the motor piston, and means for adjusting said correcting means so as to cause them to act for a smaller value of said exceptionally long strokes during the starting period of the machine.

18. A machine according to claim 15 further including a push piece carried by said accumulator piston and extending through the end of the accumulator cylinder, a rocking lever adapted to be pivoted by said push piece at the end of strokes of amplitudes exceeding a predetermined value, a movable support for the pivot axis of said lever, means operative by said rocking lever for controlling said fuel feed means so as to reduce the feed when the lever is pivoted by the push piece, and means operative by the means for filling the starting chamber with fluid under pressure for displacing said movable support toward said push piece when said chamber is illled with fluid under pressure.

RAUL PATERAS PESCARA.