US2189497A - Free piston machine - Google Patents

Description

5?@5 6 m@ R, PATERAS PESCARA 3899497 FREE PISTON MACHINE Filed Dec. 5l, 1937 2 Sheets-Sheet l i\1\ wx m\\ my @E lNVENTOR Raul Quieras escam @Y @QWQQM R. PATERAS PESCARA FREE PI'sToN MACHINE Filed Dec. 3l, 1937 Qbqaul Quieras @escara 2 Sheets-Sheet 2 INVENTOR Patented Feb. 6, 1940 UNITED STATES PATENT* oFI-ic-E Application December 31, 1937, Serial No. 182,866 In Luxemburg January 7, 1937 13 Claims.

The present invention relates to free piston machines and especially compressed free piston gas generators, that is to say machines in which the energy produced by the motor element serves to compress and to feed, at a pressure which can be varied, a mass of air utilized at least partly for the scavenging and the feed of said motor element, said energy being finally collected in the form of heat and pressure in the exhaust gases 10 which are caused to expand in a utilization machine such, for instance, as a turbine.

The invention is more especially, although not exclusively, concerned,y among these machines, with those including at least one double action compressor element, these machines being called,

in the following description, double action autogenerators.

'I'he object of the present inventionV is to provide a machine of the type above referred to which is better adapted to meet the requirements of practice, and, in particular, which has a better eiciency.

The essential feature of the present invention is the following:

First, in a double action auto-generator the compression works in the motor element and in the compressor elements which act during the non motive strokes of the movable motor parts, are ensured by the combined actions of pneu- 30 matic energy accumulators, based upon a known principle, of the expansion of compressed air in the clearance spaces of the other compressor elements, and, finally, of the essentially variable pressure exerted on the non-motive faces of the motive pistons.

Now, being given such a system, on the one hand I feed said energy accumulators at a constant initial pressure, and, on the other hand, I give the elements of said machines, especially o the energy accumulators, the motor and compressor elementsand the rods connecting 'said elements together relative dimensions such that the sum of the energies given back to said movable parts during each non motive stroke is sufficient, for the various values that the feed pressure of the motor element is to assume, for compressing the combustion supporting air .to a nal pressure ranging between the two limits which determine the zone of good thermic working of the machine.

In addition to this essential characteristic, the invention further includes certain other features (among which constructing features applicable in a general manner to all machinesy with free pistons) which are preferably used in combina- (Cl. 23o-56) tion with the essential characteristic above set forth.

Among these features, a second characteristic, relating also to .double action auto-generators, consists in providing the machines in question 5 with a double action compressor elemen-t disposed on one side of the motor element, and at least two pneumatic accumulators, advantageously of the constant initial pressure type, according to the chief feature of the invention, arranged, preferably in a symmetric manner, on either side of said motor element, in such manner as to reduce the efforts that are transmitted, from one movable system to the other, through the kinematic synchronizing parts of the machine.

According to another feature of the present invention, relating also to double action autogenerators, while feeding fluid under constant pressure, for normal values of the pressure, at which the motor element is fed, to the pneumatic accumulators with which the machine is to be provided, I vary, as a function of said feed pressure, and only for values of said pressure lower than said normal values, the energy' brought into play in said pneumatic accumulators, especially when starting said machines, and raising the pressure therein.

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 diagrammatic sectional view of a double action auto-generator made according to an embodiment of the invention;

Fig. 2 is a diagram intended to facilitate a good understanding of the invention;

Fig. 3 is an axial sectional view of a double action auto-generator made according to certain features of the invention.

Finally, Fig. 4 is a sectional view of the same auto-generator, on a line at right angles to the preceding one. 45

In the following description, it will be supposed that it is desired to obtain a double action compressor element included in an auto-generator.

The whole of the machine is made in any usual manner, and, in particular as shown by Fig. l.

In the same motor cylinder I, there are provided two coacting opposed pistons 2, connected respectively through rods 3 with the compressor pistons 4 coacting each, in a double action manner, with a cylinder 5 including distribution 55 members, such for instance as suction valves 6 and discharge valves l through whichvthe air compressed in cylinders 5 can pass into a casing I surrounding the motor cylinder I, and then penetrate into said cylinder through intake ports I uncovered by one of the pistons 2 when near to its external extreme position, the exhaust of the combustion gases and of the excess of scavenging air taking place through the exhaust ports Ill uncovered by the other piston 2 to an exhaust outlet I 0', which may lead to any suitable point of use.

The machine further includes, for each movable system, a pneumatic energy accumulator such, for instance, as a piston II', rigid with said system, sliding in a cylinder I I.

In such a machine, the total compression work performed when each movable system is returning to its initial position is the sum of the com-A pression work T1 performed by the face S1 of piston 2 in cylinder land of the compression work T2 performed by the face Sz of the compressor piston 4 in the cylinder 5.

Now the motive energies'which are called into play during the return stroke of said movable system are the following:

a. the energy T3 resulting from the action of the feed pressure upon the rear face S3 of said motive piston 2;

b. the energy T4 resulting from the pressure exerted upon the face S4'of said compressor piston 4 by the air present in the external clearance space of cylinder 5;

c. finally, the energy T5 supplied by the corresponding pneumatic accumulator, of a sec tion Ss.

According to the present invention, I proceed in the following manner:

I feed said pneumatic accumulators at a constant pressure, for instance, by means of orices II" uncovered by the pistons II' if the said pistons are in their inner dead point position; and,

I determine the elements of the machine, and especially the volumetric and manometric characteristics of its accumulators and also the dimensions of surfaces S2 to Ss with respect to surface Si, which is a data determined by the power which it is desired to obtain from the motor element, in such manner that the sum of the energies Ta, T4, Ts is suilicient, for the various values that the feed pressure of cylinder I is liable to take, for compressing the combustion supporting air up to a final pressure ranging between the two limits which limit the zone of good operation of the machine, from a thermic point of View, said machine being supposed, in the following description, to work on the Diesel principle.

In the diagram of Fig. 2, I have shown, as a function of the feed pressure of cylinder I, which 'la supposed to range from 1 to 4 kilogrammes per square centimeter, the following elements:

a. On the one hand, a set of curves numbered 3l, 4I, SII, 80 which represent the sum of the works Tr and T2 for flnal pressures in cylinder I equal respectively to 30, 40, 50 and 60 kilogs.

b. On the other hand, curves A, B, C, which represent respectively T3, the sum of T3 andT4 andthe sum of Ts, T4 and Ts.

In order to ensure, according to the essential feature of the present invention, a satisfactory working of the machine for all feed pressures ranging from 1 to 4 kgs., it suffices to arrange things in such manner that curve C, which reprecents the sum of .energies Ts, T4 and Ts remains constantly above that of the curves of the set of curves, corresponding to the sum of T1 and Tz, for instance curve 3l, below which the prelsures at the end of the compression would be insumcient for ensuring the ignition of the fuel.

And, furthermore, being given that the best possible efficiency of the machine is obtained between certain limit values of the final pressure ofv compression, care is preferably taken in such manner that, for usual feed pressures of cylinder I (for instance from 2 to 4 kgs. per sq. cm.) the nal pressure of compression varies only between said limit values.

For instance, supposing that the optimum eiliciency of said machine is obtained between certain limit values of the final pressure averaging 40 kgs. per sq. cm., care will be taken that the curve C, between 2 and 4 kilogs. has but small differences of ordinates with curve 40 of the set of curves corresponding to the sum of T1 and Tn.

For this purpose, the volumetric and manometric characteristics of the accumulators II, same as the sections Sz, S3, S4 (the values of which depend respectively upon the sections of rods 3 and pistons II) are advantageously chosen in such manner that the sums of Ta, T4 and T5, on the one hand and of T1 and T2, on the other hand, are substantially, for the average feed pressure (for instance 3 kgs. per sq. cm.) of the same value, corresponding to the final pressure4 of compression giving an optimum efficiency.

By way of example, for the machine, the working of which is illustrated by the diagram of Fig. 2, the final pressure complies with the following conditions:

It is equal to 39 kgs. per sq. cm. for a feed pressure of 3 kgs. per sq. cm.;

It varies only between 57 kgs. per sq. cm. for working with a feed pressure of 2 kgs. per sq. cm. and 38 kgs. per sq. cm. for a feed pressure of 4 kgs. per sq. cm.

It remains substantially constant between 3 and 4 kgs. which are the most common feed pres- It further appears from this diagram that,

for the lowest values of the feed pressure, for instance values ranging from l to 2 kgs. per sq. cm., the final pressure of compression would reach high values which would .risk deteriorating the machine, especially during periods corresponding to the starting and the rise of pressure.

In order to obviate this drawback, that is to say in order to obtain a satisfactory final compression pressure, for values of the feed pressure of cylinder I ranging between the limitathat are considered, it is advantageous to have recourse to one of the features of the invention according to which the feed pressure of the energy accumulators II is varied as a function of the feed pressure of cylinder I, and this only for the values,

of said pressure ranging between said limits. Furthermore, care is taken that the nal compression pressure is kept substantially constant when the feed pressure varies within the interval that is considered (from l to 2 kgs. per sq. cm.) for which the curve representing the sum of TaT4 and T5 then becomes the curve C".

For this purpose, I can, as already stated in application S. N. 707,595 connect, at each impulse, the pneumatic accumulators II with the discharge of the machine, for instance through a pressure relief device adjustable as a function of the feed pressure of cylinder I.

Fig. 1 shows such an arrangement. There is provided a receptacle a in which is maintained a pressure of a predetermined l amount, for example, fifteen atmospheres. A reducing valve b is interposed in the line i between the receptacle a and the opening in the wall of cylinder of the energy accumulator. The pressure reducing valve b is controlled by the pressure in the intermediate receptaclec to which the outlets of the compressor elements are connected. The pressure in this chamber c is transmitted through pipe h to cylinder g. and acts on one side of piston ein opposition to a spring f. .1A needle valve d which forms the controlling element of the pressure reducing valve b is connected to piston e.

'Thus as the pressure in the cylinder c varies, the

position of needle valve d will also vary and therefore the amount of pressure transmitted to opening II and energy accumulator II will be varied, being small when at the beginning of the operation because valve d' is almost closed and increasing as the pressure in receptacle c increases. When the pressure in c reaches the lowest normal kgs. per sq. cm. said energy accumulators the initial pressure of which must, according to the essential feature of the invention, be kept at a constant value, can be placed in communication, for each impulse, through suitable distribution elements, with a chamber in which the pressure is uniform.

In order to facilitate a good understanding of the present invention, I have considered, in what precedes, the variations of works T1 to T5 merely as a function of the feed pressure of cylinder I, excluding variations of length of stroke, which however produce, for each value of said feed pressure, variations of said works.

But it appears from the diagram of Fig. 2 that the chief element of the return energy is supplied by the energy accumulator Il, whereas most of the resisting work is absorbed by the compression of air by face Sz.' A reduction of the length of the stroke, that is to say a displacement of the end point of the stroke, in the inward direction, produces both a reduction of the motive work supplied by theenergy accumulator-and a reduction of the resisting work due to face Sz. These variations are of the same order of magnitude and it will be readily understood that it is always possible, by suitably choosing the dimensions of the variable elements that are considered and in particular of the energy accumulators II, to obtain that, within the practical limits that are considered for the feed pressure, the nal pressure of compression is but little influenced by variations of the length of stroke of the movable elements.

Of course, the characteristics of the invention, which have just been specified with reference to a double action auto-generator, including two symmetrical compressor elements, would similarly apply to other types of double action generators, and especially to machines of this type made according to another embodiment of the invention, and which will be more particularly referred to in what follows:

According to this embodiment, the machines of the type in question include a double action compressor element disposed on one side of the motor element and at least two pneumatic accumulators, of the constant initial pressure type,

disposed, preferably symmetrically, on either side ot said motor element.

It will be readuy'understood that, for a machine made in this manner, the eil'orts transmitted vfrom one movable element to the other through the synchronization members are still much lower than for machines of the saine kind in which most of the return energy of the movable elements would be ensured by a single pneumatic accumulator coactingwith one of the motor pistons and transmitted to the other piston through the intermediate of said synchronization elements.

For this purpose, it is advantageous to make `use of the embodiment shown by Figs. 3 and 4, by way of example, or any other equivalent arrangement, which is characterized in the following manner:

The whole of said machine is made in such manner as to include:

a. a motor cylinder I, provided with inlet ports 9 and outlet ports I0, in which motor cylinder are provided two motor pistons 21 and 22, connected together by synchronizing means, constituted, for instance, by connecting rods l2 pivoted to oscillating cranks I3;

b. a compressor piston I working on the double action principle in a cylinder 5 and connected with one of the motor pistons, for instance piston 21, through a rod I4;

c. pneumatic accumulators of the constant energy type, constituted, for instance, by cylinders |51 and |52, provided respectively in the body of each of the movable elements, which cylinders are caused to coact, as indicated in application S. N. 90,237, with stationary pistons |61 and |62, through the inside of which said cylinders are fed, in such manner that said pistons act as starting devices. As disclosed in such application, each pneumatic energy accumulator consists of two partial chambers |51, |51 and |52, |52' respectively. These two partial chambers are connected by a valve m. The stem of each valve connected with a piston n girovided with' a check valve o which opens inwardly. The pipes k serve to supply compressed air to the space behind piston n. In order to start the machine, compressed air is supplied through pipes k, and moves piston ln inwardly, thus closing valve. m. At the same time the compressed fluid passes through check valve o into the spaces |51', |51. Then when the supply of pressure to lines Ic is released and the pressure in these lines drops, piston n is moved outwardly and opens valve m, thus admitting the compressed fluid into the chambers |51 and |51'. The admission of air into these chambers acts to start the machine.

d. nally, a certain number of elements relating to distribution, to the guiding of the movable elements and the regulation of the injection. which elements are preferably made, according to features of the invention which will be hereinafter specified and some of which can be applied to free piston machines of another kind than double action auto-generators.

Concerning, then said distribution organs, they are arranged in such manner that air can penetrate into the compressor cylinder 5 through suction valves I1 and then pass into a casing 8 surrounding cylinder I, the air discharged by the face S2 of the compressor piston l penetrating directly into this casing through discharge valves through discharge valves i82 and a conduit I9 to which is connected a branch pipe 20 including a valve 2| through which it is possible to shortcircuit, in the exhaust conduit 22, at least a part of the air compressed by said face S4. said dis-l charge valves I 81 and Ilz being advantageously mounted on two discs Bland 5 which constitute respectivelythe opposed ends-of the compressor cylinder 5.

It should be noted that, for machines giving a large output, it is possible advantageously to substitute, for each suction or discharge valve, a plu.- rality of devices, such as valve boxes, kept in position by a tightening stirrup 23, which can eventually be devised in such manner as to cause it to exert equal pressures on these respective devices.

Concerning said exhaust conduit 22, which is subjected to the action of high temperatures, it is preferably fitted in such manner that it can expand freely. For instance, in order to obtain this result, said conduit is connected to cylinder I through the intermediate of annular flanges 24, with respect to which it can expand in a radial direction, these anges having, in any case a bearing surface against conduit 22 sumoient for ensuring a suitable fluid tightness thereof.

It will be readily understood that, with such an arrangement, said conduit can expand without creating tensions in cylinder I or in casing 8.

It is also possible, advantageously, to provide rod I4 with a packing disc I4' capable of engaging in cylinder I at a point close to the internal end of the stroke of the corresponding motor piston, thus avoiding losses of compressed air through ports I0.

Concerning now the guiding means for the movable elements of the machine, they are made in such manner that they prevent said elements from turning about their axis, and advantageously, for this purpose, for instance these means are constituted by providing each movable element with a single shoe, suchl as 26l and 26, these shoes being caused to coact with a slideway 21 fixed to casing 6, each shoe being itself preferably mounted in a swivel manner on the end of an arm 28 rigid with the corresponding movable part of the machine, in such manner that it is possible to detach it.

Advantageously, according to the present invention, I cause to coact with one of said shoes (for instance shoe 262), a system including a cylinder 29 and a piston 30 the movable element of which, for instance piston 30, is subjected to the action of a return spring 3| and can bear against the shoe 262 that is considered. Cylinder 29, which is advantageously made integral with the corresponding slideway, can be connected with a source of compressed air, in such manner that it is possible, by means of this device, of moving the movable elements of the machine and, in particular, of bringing them into their position that is most advantageous to obtain the starting of the machine, according to the method already set" forth in the application S. N. '107,595 and in the application Ser. No. 90,237 filed in the same name.

It will be readily understood that such a guiding system including a single shoe has, among other advantages, that oi' leaving the necessary freedom to the movable elements of the machine, the centeringoi which with respect to cylinder I can thus take place without interference.

Concerning finally the means for controlling the injection, they are made as follows:

Advantageously, they are constituted by a cam 32 connected through the intermediate of a leve 33 and a connecting rod Il with a lug 3l provided for this purpose on the piston 2. nid cam lcoacting with the push-piece II which determines the beginning of the injection.

I further provide means for regulating the position of the injection point as a function of the feed pressure of the engine (method already described in the Patent No. 2,015,133). In particular, such means may be constituted by interposingj between cam l2 and push-piece Il, an interm ate part of adjustable position, which may consist, for instance, of a roller I1 which is fitted at the end of a lever 3l controlled by an eccentric 36, itself driven by a piston Il, one of the faces of which is subjected to the action of the atmospheric pressure and of an antagonistic spring 4I, whereas its other face is subjected to the action of the feed pressure of the engine.

I Finally, whatever be the embodiment'that is chosen, I obtain a double action auto-generator the working and the advantages of which result sufficiently clearly from the above description for making it unnecessary to give any further description of said operation and said advantages.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and eiilcientl 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 of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What I claim is:

l. A free piston motor compressor comprising a motor element including a motor cylinder and a motoi piston freely movable in said cylinder, compressor means of the double acting type having substantially equal and variable delivery pressures on either side thereof, means enclosing a space adjacent the outer face of the motor piston, means connecting such space to the outlets of the two sides of said compressor means, intake means for said motor cylinder connected to said space, exhaust means for said motor cylinder for the escape of a mixture of the excess of compressed air and combustion gases therefrom, a connecting rod of less diameter than the motor piston connected thereto and to said compressor means, and a pneumatic energy accumulator operatively connected to said piston, said compressor means having a clearance space, the pressures in said ilrst space, said accumulator and said clearance space coacting to return said motor piston to compressing position.

2. A free piston motor compressor comprising a motor element including a motor cylinder and -motor pistons freely movable in said cylinder,

compressor means of the double acting type arranged on one side only of said motor cylinder and having substantially the same variable delivery pressures in both directions of movement, means enclosing a space adjacent the outer faces of the motor pistons, inlet means for the motor cylinder connected to said space, means connecting the outlet of said compressor means to said space, exhaust means for said motor cylinder for the escape of a mixture of the excess of compressed air and combustion gases, a connecting rod of less diameter than the motor iston connected thereto and to said compressor me ns, and energy accumulators arranged on either side of said motor element operatively connected to said pistons, said compressor means having a clearance space, the pressures' in said normal range of variation of the feed pressure of said motor element, and means adapted to work for values of the feed pressure of said motor element lower than the normal value thereof for giving the initial pressure in said energy accumulator a value depending upon that of the feed pressure of said motor element.

5. A free piston motor compressor according to claim 2 in which said energy accumulators are arranged in symmetrical relation to each other with respect to said motor element.

6. In a free piston motor compressor according to claim 1 in which said space enclosing means form a closed chamber surrounding said motor cylinder, said compressor means including two pressure chambers, means connecting said pressure chambers to said closed chamber. inlet means for said motor cylinder connected to said closed chamber, exhaust means connected to said motor element, means connecting one of said connecting means to said exhaust means, and valve means in said last connecting means, whereby at least a portion of the compressed air fed by one of said pressure chambers can be conducted to said exhaust means.

7. In a free piston motor compressor according to claim 1 having an exhaust pipe for said motor element, annular flanges for connecting said pipe to said motor cylinder, whereby said pipe may expand radially with respect to said cylinder.

8. In a device according to claim 1, in which said space enclosing means form a closed chamber around said motor cylinder, means connecting said chamber to said compressor means, a

disc carried by said connecting rod adapted and arranged to iit ln said motor cylinder at the end of the inward stroke of said motor piston.

9. Ina device according to claim 2, in which all of the sliding parts of said motor element, said compressor means and said energy accumulators are mounted coaxially, guiding means to prevent rotation of said sliding parts with re-A spect to their common axis.

l0. A free piston motor compressor according.l to claim 2, further including a casing for said machine, all the sliding parts of said motor element, said compressor means and said acfcumulators being mounted coaxially in said casing, and guiding means for lat least one of said parts including a slideway carried `by said casing, a radial arm carried by said part to be guided, and a shoe carried by said arm adapted to slide in said slideway.

11. A free piston motor compressor according to claim 2, further including a casing for said machine, all the sliding parts of said motor element, said compressor means and said accumulators being mounted coaxially in said casing, and guiding means for at least one of said sliding parts including a slideway carried by said casing, a single radial arm carried by said sliding part to be guided, and a shoe removably and turnably mounted at the outer end of said arm slidable in said slideway.

12. A free piston motor compressor according to claim 2, further including a casing for said machine, all the sliding parts of said motor element, said compressor means and said accumulators being mounted coaxially in said casing, guiding means for at least one of said sliding parts including a slideway carried by said casing, a single radial arm rigid withfthe sliding part to be guided, a shoe mounted on said arm slidable in said slideway, and compressed air operated means for displacing at will said shoe in said slideway.

13. A'free piston motor compressor according to claim 1, further including fuel injection means for said motor element, and means for automati.

cally controlling said fuel injection as a function of the feed pressure of the motor element. RAUL PA'I'ERAS PESCARA. n

Images