US3410307A

US3410307A - Installations comprising several free piston autogenerators supplying a receiver with driving gases

Info

Publication number: US3410307A
Authority: US
Inventors: Szereszewski Pinchas Paul
Original assignee: Participations Eau Soc Et
Current assignee: Societe dEtudes et de Participations Eau Gaz Electricite Energie SA
Priority date: 1964-06-10
Filing date: 1965-06-09
Publication date: 1968-11-12
Anticipated expiration: 1985-11-12
Also published as: GB1088478A; FR1417141A

Description

Nov. 12, 1968 P. P. SZERESZEWSKI 3,410,307

INSTALLATIONS COMPRISING SEVERAL FREE PISTON AUTOGENERATORS SUPPLYING A RECEIVER WITH DRIVING GASES Filed June 9, 1965 3 Sheets-Sheet l lNVE/V TOR P/MCHAS 'PAu/ \sze-rzeszsws i z, and W ATTORNEYS N 1968 P. P. SZERESZEWSKI 3,410,307

INSTALLATIONS COMPRISING SEVERAL FREE PISTON AUTOGENERATORS SUPPLYING A RECEIVER WITH DRIVING GASES Filed June 9, 1965 3 Sheets-Sheet 2 \at f a /NVE/\/TUR TD/IVQHAS 7 00/ Szsrees 2.5a) sm' ATTORNEYS Nov. 12, 1968 3,410,307

INSTALLATIONS COMPRISING SEVERAL FREE PISTON AUTOGENERATORS P. P. SZERESZEWSKI SUPPLYING A RECEIVER WITH DRIVING GASES 3 Sheets-Sheet 5 Filed June 9, 1965 ATTORNEYS United States Patent 3,410,307 INSTALLATIONS COMPRISING SEVERAL FREE PISTON AUTOGENERATORS SUPPLYING A RECEIVER WITH DRIVING GASES Pinchas Paul Szereszewski, Asnieres, France, assignor to Societe dEtudes et de Participations Eau, Gaz, Electricite, Energie, S.A., Geneva, Switzerland Filed June 9, 1965, Ser. No. 462,664 Claims priority, application France, June 10, 1964, 977,819 7 Claims. (Cl. 137--610) ABSTRACT OF THE DISCLOSURE The invention relates to means for automatically controlling the motion speeds of the valve members of three way valve systems between positions where they respectively connect the free piston autogenerators of an installation constituted of several of said autogenerators with either a receiver engine, such as a turbine, which is to be supplied with the driving gases produced by said autogenerators or the atmosphere, said autogenerators being connected with both for intermediate positions of said valve members. These means are adapted to restrain the speed of the motion of each of said valve members when it is desired to connect the corresponding autogenerator with the receiver engine as well as, preferably, on the last portion of the travel of said valve member in the opposite direction.

The invention relates to installations comprising several free piston autogenerators which supply a receiver, in particular a turbine, with driving gases.

It is known to connect the exhaust outlets for driving gases generated by several autogenerators of a common installation to a common collector located upstream from the receiver engine and to provide between each autogenerator respectively and the common collector a three way valve system comprising a valve which, dependant upon its positions in said system, controls either the connection between the corresponding autogenerator and the collector, or the connection between said autogenerator and a space under low pressure such as the atmosphere, .or further the connection between said autogenerator and both the collector and the atmosphere.

The control of the known three way valve systems requires from the supervisor of the installation a great attention and the performance of a certain number of successive operations in the case, for instance, where one of the autogenerators is to be started and connected to the common collector at a time where the other autogenerators of the same installation are already working.

The object of the invention is to simplify the operations to be performed by said supervisor and to automatize the motions of the valve as soon as they are started in one direction or in the other either by the supervisor or by a governor.

The invention is more particularly concerned with the control of a three way valve system provided, between each autogenerator and the collector, upstream from the receiver and which is likely, in its extreme positions, to connect the autogenerator either with the receiver or with a space under low pressure for instance the atmosphere, whereas, in its intermediate positions, it permits more or less throttled connections between the autogenerator and, on the one hand, the collector and, on the other hand, the space under low pressure.

According to the invention, the control means for the operation of the valve member of said three way valve system are arranged in such manner that they automatiice cally cause, when it is desired to connect the autogenerator with the collector, a slow motion of the valve with a progressive increase of the section of the throttled communication between the autogenerator and the collector and a concomitant progressive decrease of the section of the throttled communication between the autogenerator and said space under low pressure whereas, when it is desired to disconnect the autogenerator from the collector, they cause a rapid motion of said valve member, at least in the first portion of the stroke thereof, toward the position in which said valve member closes the communication between the autognerator and the collector and opens completely the communication between the autogenerator and the space under low pressure.

According to a preferred embodiment of the invention, said valve is contrived in a manner such that it comprises, on either side of the part of its body which carries the surfaces coming into contact with valve seats provided in the chamber of said three way valve system for closing completely the communication between the autogenerator and either the collector in one of its extreme positions or the space under low pressure in its other extreme position, protruding extensions the respective diameters of which decrease toward their extremities so that they cooperate with the one or the other of said valve seats for producing said throttled connections between the autogenerator and, on the one hand, the collector and, on the other hand, the space under low pressure, the sections of said throttled connection varying progressively when said valve member moves progressively from one of said seats to the other.

Other objects of the invention will appear as this description proceeds in connection with preferred but nonlimitative embodiments of said invention and with reference to the appended drawings in which:

FIG. 1 shows diagrammatically a part of the installation in accordance with the invention, said part comprising in particular one of the autogenerators supplying the collector of the installation with driving gases and means controlling the communication of this autogenerator either with the collector or with the atmosphere:

FIGS. 2, 3 and 4 show the said control means in several operating positions;

FIG. 5 is a diagram showing the respective evolutions of the delivery pressure when one of the autogenerators is connected with the common collector for two different working conditions of said installation.

FIGS. 6 to 8 show other exemplary embodiments, according to the invention, of the means controlling the operation of said three way valve system.

Referring first to FIGURES 1 to 4, they show an installation comprising for instance three piston autogenerators and a turbine fed with driving gases supplied by said autogenerators.

The installation comprises a collector 1 and three gas supply pipes 2 2 2 leading thereto, each of said pip s connecting one autogenerator to said collector. Only one of said autogenerators shown at 3 is represented in FIG. 1, this autogenerator being connected to the pipe 2,. The collector 1 is further connected through a pipe 4 to a turbine 5 which is driven :by the driving gases supplied by the working autogenerators to the collector 1.

Each of said free piston autogenerators comprises, as well known, a driving or motor part working preferably according to a two stroke diesel cycle and a compressor part compressing and delivering air to the motor part. The driving gases delivered by the autogenerator are constituted by the mixture of uncompletely expanded combustion gases formed therein and of the excess of scavenging air supplied by the compressor part to the motor part. After its exhaust from said motor part, this mixture arrives first to an exhaust pot 6 and afterwards to a three way valve system 7 within which a valve member 8 is provided. This three way valve system is connected, on the one hand, to said exhaust pot 6, on the other hand to the pipe 2,, communicating with the collector 1 and finally to a conduit 9 which opens to the atmosphere. In the position shown in FIG. 1, the valve member 8 closes the communication between the exhaust pot 6 and the pipe 2,, by its application on the valve seat 8 and it permits the large opening of the communication between said exhaust pot and the conduit 9.

In the positions shown in FIGS. 2 and 4, said valve member provides throttled communications between the exhaust pot 6 and simultaneously the collector 1 on the one hand, and the conduit 9 on the other hand.

Finally, in the position shown in FIG. 3, the valve member opens fully the communication between the exhaust pot 6 and the collector 1 and closes the communication between the exhaust pot 6 and the conduit 9 by its application against the valve seat 8 Concerning the control means of said valve member, for opening for example the connection between one autogenerator 3 and the collector 1 supplied under a given pressure with the driving gases from other autogenerators of the same installation, they are arranged, according to the invention, in a manner such that they cause a slow motion of the valve member in the direction of the opening of the communication between the newly started autogenerator 3 and the pipe 2 which leads to the collector 1 and the concomitant closing of the communication between the same autogenerator 3 and the conduit 9, so that the pressure of the gases supplied by the autogenerator 3 may increase progressively and that consequently an equalization occurs between the pressures existing in the exhaust pot 6 and the collector 1.

During the slow motion permitting the connection of the autogenerator 3 with the collector 1, the valve 8, starting from the position shown in FIG. 1, passes through the intermediate position such as shown in FIG. 2 and finally stops at the end of the connection period in the position shown in FIG. 3 in which it opens a large communication between the exhaust pot 6 and the collector and closes completely the conduit 9.

FIG. 5 shows the changes in the pressures within the exhaust pot 6 during the performance of this connection operation in the case, on the one hand, where the pressure in the collector 1 is relatively high, for instance equals 3 atmospheres and, on the other hand, where the pressure in the same collector is low, for instance equals or nears 0 atmosphere. The abscissae in said diagram correspond to the stroke of the valve member 8 or to the time of duration of said stroke, whereas the ordinates correspond to the pressures in the exhaust pot 6.

In the two cases it can be seen that the pressure within the exhaust pot 6 first increases up to an intermediate position of the valve member. In the first case, the pressure further increases beyond this intermediate position to approximately equal said pressure of 3 atmospheres within the collector. However, in the second case, the pressure within the exhaust pot 6 decreases after this intermediate position of the valve member to become approximately equal to the one existing in the collector 1, thus practically to the atmospheric pressure.

Still according to the invention the control means of the valve member 8 are arranged such that they control a rapid return stroke of said valve member-namely in the direction where it opens the communication between the exhaust pot 6 of the autogenerator 3 and the conduit 9 and closes at least partially the communication between said exhaust pot 6 and the collector 1at least in the first part of said stroke. This last motion of the valve member permits the decrease and the suppression of the feeding of the turbine by the concerned autogenerator when the load of the same suddenly decreases, for

instance on the case of the cut out of an alternator driven by said turbine.

According to a preferred embodiment of the invention, one provides that this rapid motion which produces a rapid decrease of the delivery of driving gases from the concerned autogenerator to the collector is stopped before the complete closing of the pipe 2 by said valve member, in an intermediate position, for instance in the one shown in FIG. 4, the further motion of said valve in the same direction being again slowed down. In such a manner, the supply of gases to the collector 1 is sufliciently reduced and one avoids a too rapid decrease of the pressure within the exhaust pot 6, such a too rapid decrease in pressure being likely to stop the autogenerator 3. Another reason which justifies the slow operation of the end portion of the return-stroke of the valve member 8 in the direction of closure of the pipe 2,, lies in the fact that the sudden decrease in load of the turbine lasts only a short time, for instance during only a few seconds, and that afterwards the valve member 8 must permit the passage of sufficient quantities of gas toward the turbine in order to maintain the turbine in idling operation or, if the case should be, to enable the same to deliver a reduced power.

The valve member 8 is advantageously provided, on either side of its median portion which carries the surfaces resting against the

valve seats

8 or 8 for the extreme positions of the valve member, with

protruding extensions

10 and 11 the diameters of which decrease toward their extremities and the side surfaces of which cooperate with the

seats

8,, and 8,, respectively, for con trolling the increase or decrease of the sections of the throttled passage for the gases between the exhaust pot 6 and the pipe 2,, as well as between the exhaust pot 6 and the conduit 9, according to predetermined laws, during the motions in either direction of said valve member. The generating lines of the side walls of said protruding extensions are chosen such as to correspond to the desired laws of variation of the sections of said throttled passages in function of the intermediate positions of said valve member.

The control means of the valve 8 such as defined here above may be of different nature, for instance of pneumatic, hydraulic or electric nature.

A preferred hydraulic embodiment of the control means according to the invention which appears to be particularly advantageous is shown in FIGS. 1 to 4.

According to this embodiment, the valve member 8 is mounted on a rod 12 carrying a piston 13 which divides one cylinder 14 in two compartments a and b. The cylinder 14, which is closed on the side directed toward the valve 8, is provided with an inlet 15 for a liquid under pressure and opens by its other side into a second cylinder 16 having a larger diameter. A piston 17, which is slidably fitted on an extension 12 of the rod 12, works in said cylinder 16 (FIG. 1), the extension 12,, extending beyond the piston 13 on the opposite side thereof with respect to the valve member 8. The compartment b is thus limited on one side by the piston 13 and on the other side by the piston 17. The compartment 0 of cylinder 16 which is located on the opposite side of the piston 17 communicates with an accumulator 20 of fluid under pressure through an opening 18 controlled by a valve 19.

The compartments b and c are interconnected by a conduit 21 provided with a throttle 22. In addition, another conduit 23, equally comprising a throttle 24, is connected with the conduit 21.

The valve 19, as shown in FIGS. 1 to 4, is shaped as a stepped piston, the part thereof having the smaller diameter closing the opening 18 when said part is applied against the border of said opening. Said part of smaller diameter works in a space d having a larger diameter which is connected with the accumulator 20 through a conduit 25.

The portion of the valve 19 having the largest diameter operates in a cylinder 26, a spring 27 being lodged therein, said spring tending to move the valve 19 toward the opening 18 in order to ensure the closing thereof. In addition, the bottom of said cylinder 26 is connected through a conduit 28 and an electrovalve 29, either with the accumulator 20 through a further conduit 31 or with the atmosphere through an outlet 31. The pressure generated in the accumulator 20 is far superior to the pressure which is fed by the inlet into the compartment (1. For instance the pressure in compartment a is equal to 3 atmospheres whereas the pressure which is permanently generated in the accumulator is for instance equal to 12 atmospheres. This pressure is maintained in the accumulator 20 by a pump not represented.

The operation of the control means which have been described here above is as follows.

In is assumed first that the valve member 8 is in the position shown in FIG. 1, that is to say in the position for which it closes the communication between the exhaust pot 6 of the autogenerator 3 and the collector 1 and enables the communication of said exhaust pot with the conduit 9.

In order to maintain the valve member 8 in this position, the electrovalve 29 is in the position shown equally in FIG. 1. In such a position, it closes the communication between the accumulator 20 and the interior space of the valve 19 within the cylinder 26. Consequently, the pressure which reigns in the accumulator 20, and which is supplied in the space a by its action upon the shoulder 19 formed by the portion having the largest diameter of the valve 19, maintains the same against the spring 27 in the position for which the opening 18 is open.

Thus the pressure in the accumulator 20 is transferred to the space c within which it acts on piston 17 to apply the same against an abutment shoulder 32. In addition, the pressure of the accumulator is fed through the conduit 21 and the throttle 22 in the compartment b of the cylinder 14 and thus acts on the piston 13 which maintains the valve member 8 in the position shown in FIG. 1 since the pressure fed by the accumulator 20 is higher than the pressure fed to the compartment a through the inlet .15. When it is desired to connect the autogenerator 3, after its starting, with the collector 1, the electrovalve 29 is brought into the position shown in FIG. 2. In this position, it opens the communication of the accumulator 20 with the cylinder 26. The pressure of said accumulator, reinforced by the action of the spring 27, causes the valve 19 to move to the position for which its closes the opening 18 (see FIG. 2). Hence the spaces 0 and b are cut off from the accumulator 20. The pressure still existing in the compartment a thus causes the motion first of the piston 13 slowly toward the right side against the resistance of the liquid contained in the compartment b and which escapes through

conduits

21 and 23 and the

throttles

22 and 24. After the piston 13 has moved along a first part of its range of motion in the right direction with respect to the valve member 8, it abuts an extension 17, of the piston 17 so that the latter starts, under the driving effect of the pressure in the compartment 0, to move also to the right, this last motion being also slowed down owing to the fact that the piston 17 must drive out the liquid contained in the compartment 0 through the conduit 23 and throttle 24. The motion of the valve member 8 and of the

pistons

13 and 17 to the right is stopped when the median part of said valve member comes into contact with the valve seat 8 that is to say in the position where said valve member opens the communication between the exhaust pot 6 of the autogener-ator 3 and the collector 1 and concomitantly closes the communication between said exhaust pot 6 and conduit 9. The slow motion of the valve memher from left to right has been obtained through the resistance opposed by the liquid in the compartments b and c to the action of the

pistons

13 and 17. Thus the pressure in the exhaust pot 6 has had the time to adapt itself to the pressure in the collector 1.

In the positions shown in FIG. 3, the valve member 8 and its control elements connect completely the autogenerator 3 with the collector 1. If it is desired to dis connect the autogenerator 3 from the collector 1, the electrovalve 29 is again brought into the position shown in FIG. 1 and equally in FIG. 4. As a consequence, the valve 19 opens, following the setting in communication of the cylinder 26 With the atmosphere whereas the shoulder 19,, of the valve 19 is still subjected to the pressure of the accumulator 20. The consequence of the opening of the valve 19 is the immediate action of the pressure reigning in the accumulator 20 on the piston 17. Owing to the importance of this pressure, both

pistons

17 and 13, together with the: valve member 8, are moved rapidly to the left from the position shown in FIG. 3 to the intermediate position shown in FIG. 4 in which the piston 17 is stopped by its application against the abutment shoulder 32. For this intermediate position of the valve member 8, the flow of the driving gases generated in the autogenerator 3 toward the collector 1 is strongly reduced. If the electrovalve 29 remains in the last position, the valve 8 is caused to proceed further to the left under the action of the pressure in the accumulator 20 which is supplied to the piston 13 through the throttle 22 against the pressure existing in the compartment a. Thus the further motion of the valve member 8 toward the left, starting from the intermediate position shown in FIG. 4, is strongly slowed down.

It can be noted that a flap 33 has been shown in the conduit 9 in FIGS. 1 to 4. This flap is only used to cause the variation of pressure in the exhaust pot 6 in the case where the autogenerator 3, which has been started, is not immediately connected with the collector 1. Consequently the flap 33 is of no use in the normal situation where it is desired to connect the autogenerator 3, after its starting, with the collector. In this last instance, all the operations are performed by the motions of the valve member 8.

Of course many alternatives of the control means of the valve member 8 in the chamber of said three Way valve system 7 can be contrived without departing from the scope of the invention. Such alternatives are represented in FIGURES 6 to 8.

In FIG. 6 the embodiment represented in FIGS. 1 to 4 is slightly modified to have the same pressure accumulator delivering fluid under pressure either to the compartment c of cylinder 16 or in the compartment a of cylinder 14. This may be achieved for instance by connecting conduit 23 to inlet 15 by a line 35 and by further connecting the electrovalve 29 to said line 35 through a line 36 (FIGURE 6).

It will be appreciated that when the electrovalve 29 is in the position shown in FIG. 6 it enables the accumulator to supply fluid under pressure in the compartment c of cylinder 16 while the compartment a is open to the atmosphere, thereby ensuring the closure of the connection between the collector 1 and the exhaust means 6 in the aforesaid conditions.

On the contrary when the electrovalve is in the position shown in FIGURES 2 and 3 it enables the supply of the compartment (1 of cylinder 14 with fluid under pressure while it operates valve 19 to close the opening 18 of the compartment c of cylinder 16. The fluid pressure acting on piston 13 thus move the same slowly in the direction where said valve member opens the connection between said exhaust means 6 and said collector 1 against the resistance of the fluid compartment b and 0.

Still another embodiment is shown in FIGURES 7 and 8 in which the same elements than in the former figures are referred to by the same reference numbers. An accumulator 40 of fluid under pressure is controlled by an electrovalve 41 to supply said fluid under pressure either through a line 42, to the exterior compartment a defined by the piston 13 in the cylinder 43 of the control means for the displacements of said valve member 8 or, through a line 44, to the exterior compartment 0 defined in said cylinder 42 by the piston 17.

FIG. 7 shows the electrovalve 41 in the position in which it allows the fluid under pressure to be fed in said compartment c while compartment a is connected with the atmosphere through line 42 and outlet 45. As described above piston 17 is then able to push rapidly piston 13 together with the valve member 8 in the direction where the latter closes partially the connection between said collector and said exhaust means until said piston 17 is stopped by abutment 46. The piston 13 is then allowed to move further but slowly in the same direction until complete closure of the last lmcntioned connection owing to the supply under reduced flow of fluid under pressure in the central compartment b through line 21 throttled in 22.

On the contrary when electrovalve 41 is in the position shown in FIG. 8 it is the compartment a which is connected with the source of fluid under pressure 'while the supply to compartment 0 is cut off. The pressure in cornpartment a is thus able to move piston 13 toward piston 17, the former driving the latter away from its abutment 46 in the last portion of its stroke, the motions of said pistons in the last mentioned direction being slowed down owing to the reduced flow of the fluid driven out from compartments b and c In a general manner, while the above description discloses what are deemed to be practical and eflicient embodi ments of the present invention, said invention is not limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the invention as comprehended within the scope of the appended claims.

What is claimed is:

1. An installation comprising free piston autogenerators, each of which is provided with exhaust means, a collector, communication means between each of said exhaust means and said collector, a three way valve system within said communication means, said three way valve system comprising a chamber connected to the concerned exhaust means, the collector and a space under low pressure, a valve member in said chamber which in a first extreme position connects said exhaust means to said collector only, in a second extreme position connects said exhaust means to said space only, and, in intermediate positions between said extreme positions, provides throttled communications of said exhaust means with both said collector and said space, said valve member being shaped such that the sections of the respective throttled communications vary regularly in function of the respective distances between any intermediate position considered and the extreme positions respectively of said valve member, means operative to move said valve member in either direction between said first and second respective extreme positions and means for restraining the speed of the motion of said valve from said second extreme position, where it connects said exhaust means to said space only, toward said first extreme position where it connects said exhaust means to said collector only.

2. An installation according to claim 1 further comprising means for restraining the speed of the motion of said valve from an intermediate position thereof toward said second extreme position where it connects said exhaust means to said space only.

3. An installation according to claim 1 wherein the communications between said chamber and respectively said collector and said space under low pressure are provided with seats for said valve member, the latter comprising two protruding portions extending from either side of the surfaces of said valve member coming respectively in contact with said seats in either one of said first and second extreme positions, said protruding portions cooperating with said seats for ensuring said regular variations of the sections of said throttled communications in function of the respective distances of said intermediate positions of said valve member to said extreme positions.

4. An installation comprising free piston autogenerators, each of which is provided with exhaust means, a collector, communication means between each of said exhaust means and said collectors, a three way valve system within said communication means, said three Way valve system comprising a chamber connected to the concerned exhaust means, the collector and a space under low pressure, a valve member in said chamber which in a first extreme position connects said exhaust means to said collector only, in a second extreme position connects said exhaust means to said space only, and, in intermediate positions between said extreme positions, provides throttled communications of said exhaust means with both said collector and said space, a system comprising a cylinder and a piston working in said cylinder, said piston being rigid with said valve member for controlling the displacements thereof, sources for supplying in said cylinder fluid under different pressures in said cylinder on the opposite sides of said piston, the higher pressure being fed on the side of said piston where it causes the same to move said valve member in the direction where it closes the connection between said collector and said exhaust means, a throttled outlet in said cylinder on the side of the piston subjected to the highest fluid pressure, means operative to cut off the connection between the source supplying the highest pressure and said cylinder, thereby enabling the lower pressure fluid to move the piston in the direction where it opens the connection between said exhaust means and said collector, said piston being slowed down during this motion by the limited flow of the fluid driven out from said cylinder through said throttled outlet.

5. An installation comprising free piston autogenerators, each of which is provided with exhaust means, a collector, communication means between each of said exhaust means and said collectors, a three way valve system within said communication means, said three way valve system comprising a chamber connected to the concerned exhaust means, the collector and a space under low pressure, a valve member in said chamber which in a first extreme position connects said exhaust means to said collector only, in a second extreme position connects said exhaust means to said space only, and, in intermediate positions between said extreme positions, provides throttled communications of said exhaust means with both said collector and said space, a system comprising cylinder means, a first piston rigidly connected to said valve member and a second piston slidable in said cylinder means, an abutment in the central compartment defined in said cylinder between said first and second pistons for limiting the displacements of said second piston toward said first piston, means for supplying fluid under a lower pressure and a higher pressure to respectively the first and second exterior compartments defined in said cylinder by said first and second pistons, control means operative to cut off the highest pressure supplied to said second compartment, a throttled connection between said central compartment and said second compartment, a throttled outlet from said second compartment, said first piston being so positioned in said cylinder means with respect to said second piston that, when said control means are operated to cut off the highest pressure supply of fluid to said second compartment, said first piston moves said valve member in the direction where it opens the connection between said collector and said exhaust means and, during its stroke, abuts said second piston and drives it away from said abutment, said first piston being slowed down during said stroke by the limited flow of the fluid driven out through said throttled outlet whereas, when said control means are operated to permit the supply of the highest pressure on said second piston it is rapidly pushed back until said abutment together with said first piston, the latter being then caused to end slowly the second portion of its return stroke under the fluid supplied to it through said throttled connection.

6. An installation according to claim wherein the diameter of said second piston is greater than the diameter of said first piston.

7. An installation comprising free piston autogenerators, each of which is provided with exhaust means, a collector, communication means between each of said exhaust means and said collectors, a three way valve system within said communication means, said three way valve system comprising a chamber connected to the concerned exhaust means, the collector and a space under low pres sure, a valve member in said chamber which in a first extreme position connects said exhaust means to said collector only, in a second extreme position connects said exhaust means to said space only, and, in intermediate positions between said extreme positions, provides throttled communications of said exhaust means with both said collector and said space, a system comprising a cylinder, a first piston rigidly connected to said valve member and a second piston slidably fit in said cylinder, an abutment in the central compartment defined in said cylinder between said first and second pistons for limiting the displacements of said second piston toward said first piston, means for supplying a fluid under pressure, control means in said last mentioned means operable to permit the supply of either one of the first and second exterior compartments defined in said cylinder by said first and second pistons respectively, a throttled connection between said second compartment and said central compartment, a throttled outlet from said second compartment, said first piston being so positioned in said cylinder with respect to said second piston that, when said control means are operated to supply said fluid under pressure to said first compartment, said first piston moves said valve member in the direction where it opens the connection between said collector and said exhaust means and, during its stroke, abuts said second piston and drives it away from said abutment, said first piston being slowed down during said stroke by the limited flow of the fluid driven out from said second compartment through said throttled outlet whereas, when said control means are operated to permit the supply of said second compartment with fluid under pressure, said second piston is rapidly pushed back until said abutment together with said first piston, the latter being then caused to end slowly the second portion of its return stroke under the fluid supplied to it through said throttled connection.

References Cited UNITED STATES PATENTS 1,718,673 6/1929 Wettstein 25126 X 2,148,616 2/1939 Gruber 91-189 X 2,206,957 7/1940 Hose 25126 2,327,942 8/1943 Thoresen 137609 X 2,517,061 8/1950 Stackelberg 137-625. 11 2,981,290 4/1961 Meyer 251-122 X 2,991,631 7/1961 Ray 137-62511 X 3,199,536 8/1965 Thompson 137609 FOREIGN PATENTS 451,779 10/1948 Canada.

WILLIAM F. ODEA, Primary Examiner. D. H. LAMBERT, Assistant Examiner.