US2079027A - Apparatus for dispensing liquid hydrocarbons - Google Patents

Description

Ma 4,19 37. D MYON 2,079,027

APPARATUS FOR DISPENSING LIQUID HYDROCARBONS Filed July 26, 1955 5 Sheets-Sheet l May 4, 1937.

D. MYON 2,079,027

APPARATUS FOR DISPENSING LIQUID HYDROCARBONS Filed July 26, 1955 5 Sheets-Sheet 2- May 4, 1937. MYQN 2,079,027

APPARATUS FOR DISPENSING LIQUID HYDROCARBONS Filed July 26. 1955 5 Sheets-She t a ay ,'1937. I D MYON 2,079,027

APPARATUS FOR DISPENSING LIQUID HYDROCAR BONS Filed July 26, 1955 5 SheetsSheet 4 j e nfov Nv May 4, 1937. D. MYON 2,079,027

APPARA'i'US FOR DISPENSING LIQUID HYDROCARBONS Filed July 26, 1935 5 Sheets-Sheet 5 Ihuen/nr o h Patented May 4, 1937 TENT OFFICE APPARATUS FOR DISPENSING LIQUID HYDROOARBONS Daniel Myon, Paris, France, assignor to Societe dEtude de Distributeurs Automatiques S. E.

D. A., Paris, France Application July 26, 1935, Serial No. 33,373 In France July 26, 1934 Claims.

This invention relates to improvements in the principle of operation and in the construction of apparatus for-dispensing liquid hydrocarbons, and more particularly in those of these apparatus comprising two measuring vessels of the same capacity, alternately being filled up and emptied, in which the inversion of the function respectively fulfilled by said vessels is obtained by utilizing the pressure of the liquid on the down side of the pump feeding the apparatus.

The invention more particularly refers, among apparatus of this type, to those in which the distribution of the liquid, for filling up and emptying the measuring vessels, is ensured by coupled J slide valves alternately putting each of said ves' sels in communication either with the piping supplying the liquid under pressure, or with the dispensing piping, these slide valves constituting a unit moving as a block and rigid, in its displacements, with two driving pistons which, according as the thrust of the liquid is exerted on one or the other of them, cause the displacement of the entire system in one direction or in the opposite direction.

, Finally, theinvention also consists in the use, in combination with new devices producing new effects, of a known device by means of which the admission of the liquid under pressure, on either of the drivingpistons of the system mentioned in the foregoing paragraph, is itself controlled by an auxiliary slide valve, or by a series'of auxiliary slide valves, on the driving piston or pistons of which the thrust of the liquid under pressure is alternately exerted in one direction or the other.

The invention is essentially characterized by the following points, which can be taken either separately, or in combination together or with other known devices:

1. The main and the auxiliary sets of slide valves operate in the same manner, that is to say they each comprise, distinct or combined, two three-way slide valves and two driving pistons operating in opposite directions, these two sets of slide valves being hydraulically and reciprocally associated together, in such a manner that the displacement from end to end of one of the sets of slide valves causes, by reversal of the admission of fluid under pressure on the driving pistons of the other set, said other set to pass from the I 1 position it occupied to the extreme opposed position. Both measuring vessels can be considered as being respectively connected to the two pipe lines connecting each of the coupled slide valves of the main set to one of the driving pistons of the auxiliary set.

2. The two systems of unbalancing springs (unsetting springs), respectively associated with each of the sets of double slide valves, according to a known arrangement such that alone the extreme positions of the latter are positions of stable equilibrium, are adjusted relatively to each other in such a manner that the minimum pressure necessary for setting in action the auxiliary set of slide valves is markedly greater than the maximum pressure necessary for setting in action the main set of associated slide valves.

7 3. The locking devices adapted, according to a known principle, to prevent premature inversions, or, more generally, untimely inversions of thedispensing system, do not act directly on the main set of slide valves, but temporarily prevent the displacements of the auxiliary set of slide valves. k

, In the accompanying drawings:

Fig. 1 diagrammatically illustrates, by way of example, a form of carrying the invention into practice.

Fig. 2 shows the main system in an intermediate position.

Fig. 3 illustrates a modification of the system of slide valves applied to the main system.

Fig. 4 shows another modification applied to the auxiliary system.

Figs. 5, 6, 7 and 8 illustrate other forms of carrying the invention into practice.

The liquid to be dispensed, delivered bya feed pump (not shown), enters the main set I of as sociated slide valves, through pipes 2 2 This main set is, on the other hand, in communication, through pipes 3 3 with measuring vessels, Ili [6 and, simultaneously, as indicated later on, with the auxiliary set 2| of associated slide valves. Finally, the main set also communicates, through a pipe 4, with the dispensing piping.

Ports are provided in the cylindrical body I opposite pipes 2, 2 these ports respectively causing this body to communicate with two upwardly extending chambers 11*, Il in which a certain quantity of air always remains trapped, these chambers acting, as indicated later on, as power accumulators during certain phases of the cycle of operation.

Two piston valves 5*, 5 and two driving pistons 6 6 move as a unit in the cylindrical body. These four pistons are rigidly connected by an axial rod 1. The intermediate portion of this rod is provided with a cam member 8, on which bears a roller 9. The roller 9 is supported in a fork or bracket H the stem of which ends in a flange I2 reciprocable in a housing IE on the cylindrical body A spring I confined in the housing presses against the flange and thus forces the roller 9 against the cam 8.

The two driving pistons 6 6 respectively limit, at the ends of the cylindrical body two chambers l3", l3 into which open pipes M M extending from the auxiliary system 2|.

The auxiliary system is similar to the main system and comprises a cylindrical body 2| in which move two piston valves 25, 25 and two driving pistons 26*, 26 rigidly connected by an axial rod 21. Into the cylindrical chamber 2| open two pipes 22 22 in direct communication, similarly to pipes 2 2 of the main system with the delivery side of the feed pump. The pipe 24 serves to return the liquid either to the storage tank (not shown) of the plant, or to the suction side of the feed pump (not shown). Finally, pipes 23 23 are respectively in communication with the pipes I4 Hi of the cylindrical body of the main system, whilst pipes 34 34', leading to chambers 33 38 which chambers are delimited, at both ends of cylindrical body 2|, by the driving pistons 26, 26 Pipes 34 34 communicate at the other end with the pipes 3 3 of the main system and, consequently, with the measuring vessels Ili I6".

Finally, a chamber [8 is provided into which the pipe 4 opens and from which the hose l9 dispenses the measured liquid to the consumer. In this chamber |8 moves a float secured to one of the arms 36 of a bell crank rocking about a pivot pin 31, and the other arm 38 of which moves to the right for a purpose hereinafter set forth when the float is lifted. The rod 21 is provided midway of its length with a cam portion 28. A housing is formed on the cylinder 2|, opposite the cam 28 and within this housing is a piston 32 on a rod 3| to the end of which adjacent the cam is attached a roller 29 bearing on the piston and urging the same toward the cam. The rod 3| extends into the chamber I8, passing through a packing gland in the wall of said chamber. The rod 3| and the arm 38 of the bell crank are so located that when the float is lifted, arm 38 moves beneath the free end of rod 3| and prevents movement thereof, thus preventing movement of the pistons in the cylinder 2|.

The whole is furthermore characterized by the fact that the respective adjustment of the springs Ill and 30 is such that the pressure necessary for compelling the roller 29 to ride up the incline of the cam 28 thus allowing movement of pistons Mi --26 is materially greater than that which suflices for holding the roller 9 in engagement with cam 8.

The operation of this apparatus is as follows:

Both systems of slide valves being initially in the position shown in Fig. l, the liquid delivered by the feed pump, through pipe 2 passes through the main system between the pistons 5 and 6 then it flows, through pipe 3*, into the measuring vessel lfi which it progressively fills up, this vessel being provided, according to a known principle, with a device allowing the air it contains to escape in the atmosphere, whilst preventing the issue of the liquid. As long as the vessel |6 is not full, the pressure cannot increase therein, and cannot increase either in chamber 33 which is in permanent communication with this vessel I6 As soon as the vessel 6 is full, the pressure of the liquid, which continues to be delivered by the feed pump, increases, until the thrust exerted by this liquid on piston 26 overcomes the thrust in reverse direction exerted by spring 30, through the medium of roller 29 and cam 28, on the stem 21. The block of four associated pistons of the auxiliary system then begins to move towards the left and the liquid contained in chamber 33 that flows towards a portion of the main system, delimited by pistons 5 and 5 which portion, being in communication with the outlet pipe 4, cannot be under pressure at this moment.

The shape of the incline 28 being such that the thrust exerted towards the right by roller 29 first regularly diminishes when the set of pistons of the auxiliary system slides towards the left, then becomes nil, then reverses, the stroke of said set of pistons, once initiated, takes place from end to end, so that it occupies the position indicated in dotted lines in Fig. 1. In this position, the pistons and 26 delimit, in the cylindrical body 2|, an isolated chamber which puts pipe 22 in communication with pipe 23''. The liquid under pressure delivered by the pump then flows, according to this path, towards chamber l3 in which the pressure increases until it is suflicient for overcoming the antagonistic thrust exerted by the spring |8, through the medium of roller 9, on the incline 8. The set of four pistons 6 5 5 6 then moves as one block towards the right, and occupies the position indicated in dotted lines in Fig. 1, whilst the liquid contained in chamber l3 flows, without back pressure through pipe M through the space delimited, in the cylindrical body 2 I, by the pistons 25* and 25 towards the return pipe 24 stem 21 being at this time in the dotted line position of Fig. 1.

In the new position of the set of pistons of the main system, the measuring vessel l6 previously filled up as above stated, is in communication, through the space delimited, in the cylindrical body I, by the pistons 5 5 with the pipe 4 dispensing the liquid to the consumer, and through which it is emptied, whilst the measuring vessel I6 is in communication, through the space delimited, in the cylindrical body by pistons 6 and 5 with pipe 2 through which it is supplied with the liquid delivered by the pump.

The parts are therefore at this moment, relatively to the vertical axis XX, in a position exactly symmetrical to that which has been considered as the initial position, and the sequence of operations which has just been described is therefore repeated in an identical manner, but with inversion of the indicia a. and b appropriate to the various parts mentioned in this description.

Finally, it is to be noted that, during this second phase of the operation, the liquid filling the measuring vessel 5 by flowing through pipe 4, accumulates in chamber l8, before flowing to the exterior through the hose l9, and lifts the float 29. During this movement, the upper end of the arm 38 of the bell crank comes opposite the lower end of the rod 3| of roller 29, preventing the latter from moving away for allowing the incline 28 to pass. Any sliding movement towards the right of the set of pistons of the auxiliary system 2| is therefore prevented as long as the float remains lifted. The sections, lengths and levels of the hydraulic paths extending, on the one hand, from the measuring vessels to chamber l3 and, on the other hand, from this chamber to the end of the hose l9 dispensing the liquid to the consumer, are so computed that it is impossible for the float to move down again as long as the measuring vessel I6 is not completely emptied. It results therefrom that, if the measuring vessel |6 should be completely filled up before the measuring vessel I6 is, entirely emptied, the thrust exerted by the liquid underpressure on piston 26 Whatever value it may reach, could not cause the set of pistons of the auxiliary system to move towards the right as long as float 20 by lowering has not allowed roller 29 to move away for permitting the incline 28 to pass.

The advantages of the device are the following:

1. The adjustment of the springs of the rollers i the hydraulic circuit on the down side of the pump, where air under pressure can be retained,

are always sufficient forensuring, not only the complete stroke of the set of pistons of the auxiliary system, but also that of the set of pistons of the main system which succeeds to it without interval, even if pumping was interrupted from the beginning of thestroke of the set of pistons of the auxiliary system, or if the unsetting springs of both systems were not sufficient in themselves for ensuring the completion of said strokes.

2. In any device where the pressure of the liquid delivered by thepump is exerted, without relay, on the driving pistons of the main system, there occurs, as soon as the displacement of the system begins to uncover theports putting the delivery side of the pump in communication with an empty measuring vessel, a very sudden drop of pressure owing to the fact that theliquid under pressure flows towards this chamber. This suddenness of the drop of the driving pressure can be uid, and towards which the liquid delivered by the pump can flow only by compressing theunsetting spring of the main system. It results therefrom that between the moment, where, in its stroke, the

block of pistons of the auxiliary system begins to uncover theports between which new communications will be established, and the moment where, these new communications having determined the setting inaction of the block of pistons of the main system, these latter pistons will begin to uncover in their turn the ports which will be put in communication by the displacement of said pistons, a certain interval of time elapses during which the drop of pressure at the delivery side of the feed pump is insignificant, and during this time the pressure which continues to be exerted on the driving piston of the auxiliary system, and which is added to the action of the unsetting spring of the system, determines the covering the ports but partially (Fig. 2), no perturbance results therefrom in the operation of the dispensing apparatus.

In fact, as soon as pumping is resumed for continuing the delivery of liquid, or for effecting a new delivery, as the chamber W has remained in communication with the delivery side of the pump, the liquid under pressure will again exert its action on the driving piston which, owing to the offset relation between both unsetting springs, will enter in action under the influence ofthis pressure before the auxiliary system has been itself influenced by the latter, so that the block of slide valves of the main system must entirely complete the stroke begun, before an inversion is possible.

Moreover, if the partial uncovering of the port of pipe 3 has allowed the measuring vessel l6 to be emptied sufficiently slowly in order that the float 20 should not be lifted, no perturbance of the operation can result therefrom, as the function of this float being only to prevent the movements of inversion of the auxiliary system, and the movements of the latter being possible only when there is at the delivery side of the pump a pressure sufficient for overcoming the resistance of the unsetting spring of said auxiliary system, it is obvious that before this minimum pressure has been reached, by putting the pump again in action, a materially lower pressure will be attained which will determine the completion of the stroke device acting, not on the displacements of the.

main system, but on those of the secondary system, on which are exerted, owing to its much more reduced dimensions, resulting thrusts relatively small, mechanical actions proportionally much more efiicient are available, for given volume of the float, resulting inreduced risks of wedging, shearing and various perturbances in the operation of the locking device. I

Thus, in particular, instantaneous unlocking can be obtained when, the level of the liquid lowering in the intermediate chamber wherein moves the float, the latter begins to move and to act by its weight on the mechanism it controls. On the contrary, when the locking device acts, in the known devices, directly on the main system of slide valves, the considerable thrusts to which this system is subjected cause seizing between both members, the coming in contact of which stops the operation of the mechanism, so that the driving action of the weight of the float is insuflicient for disengaging these members: it is therefore necessary, for unlocking to take place, to wait a certain period of time in order that, under the influence of the slight leakage always occurring in the delivery members, the driving hydraulic pressure is sufliciently reduced on the driving piston for the wedged members to disengage from each other.

Many other forms of construction, in which the same eflect are obtained by slightly different means, can be resorted to without departing from the scope of the invention, the main features above set forth being preserved.

Thus, each of the two systems (the main and auxiliary systems), or one of them only, can be divided into two groups each composed of a three-way piston valve and of a driving piston, both groups being mechanically associated together so that they always move with each other.

The groups thus mechanically associated can be arranged either in alignment with each other (Fig. 3), or parallel to each other (Fig. 4), or according to any other relative setting.

In the form of construction illustrated in Fig. 3, the tipping device of the main system is slightly different from that described above; the rigid rod 40 connecting both groups constituting the main system, is provided with a slide 4| in which is fitted the end 42 of a link 43 capable of pivoting about its other fixed end 44. To this link is attached, at 45, the tipping spring iii.

In the modification illustrated in Fig. 4 applied to the auxiliary system, another form of construction of the tipping and locking device is shown. Both groups of pistons are connected by a lever 46 capable of rocking about the pivot 41 and on the arm 48 of which is attached, at 49, the tipping spring 30 which always tends to restore it towards either of its extreme positions.

A float 55, contained in chamber l8, carries a small bar 5! having, on each of its branches 52 and 53, a notch, indicated at 54 and 55, respectively. When the float 50 is lifted by the presence of liquid in chamber I8, the notched bar 5| ensures the locking of the groups of pistons of the auxiliary system. In either of the main and auxiliary systems, or in both simultaneously, a group constituted by a piston valve and two driving pistons can be substituted for the group composed of two piston valves and two driving pistons. The connection of both systems necessitates certain inversions of the hydraulic paths and gives rise to four different combinations of the'whole, one of which is in accordance with the form of construction illustrated in Fig. l, and the others The tipping and locking device of the auxiliary system is that shown in Fig. 4; the tipping device of the main system is that illustrated in Fig. 3.

On the other hand, in each system of slide valves, the relative positions of the pipes supplying and delivering liquid under pressure can be inverted, the inlet pipe being at the center of the device, and the delivery pipes being arranged near the ends.

Finally, the tipping spring can be constituted by any other means than that shown in Fig. l, as well as the locking device of the auxiliary system of slide valves. for both these devices, forms of construction departing from that illustrated in Fig. 1.

What I claim as my invention and desire to secure by Letters Patent is:

1. Apparatus for dispensing liquids, more particularly liquid hydrocarbons, comprising two measuring vessels, a'liquid inlet pipe under pressure, a delivery pipe, a first system or main system of slide valves comprising two coupled piston slide valves adapted, according to their position, to put the liquid inlet pipe under pressure in communication with one or the other of the two measuring vessels and to put the measuring vessel, which is not in communication with the said pipe, in communication with the delivery pipe, two driving pistons displaceable in two driving chambers for varying the position of the piston slide valves, a second system or auxiliary system of slide valves comprising two coupled piston slide valves adapted according to their position Thus, in Fig. 4 are shown,

communication with one or the other of the I driving chambers of the main system.

2. Apparatus for dispensing liquids, more particularly liquid hydrocarbons, comprising two measuring vessels, a liquid inlet pipe under pressure, a delivery pipe, a first system or main system of slide valves comprising two piston slide valves mounted on a piston rod and adapted, according to their position, to put a liquid inlet pipe under pressure in communication with one or the other of the two measuring vessels and to put the measuring vessel, which is not in communication with the said pipe, in communication with the delivery pipe, two driving pistons mounted on the said rod and displaceable in two driving chambers for varying the position of the piston slide valves, a second system or auxiliary system of slide valves comprising two piston slide valves mounted on a piston rod and adapted according to their position, to put the said liquid inlet pipe in communication with one or the other of the driving chambers of the main system, two driving pistons mounted on said rod and displaceable in two driving chambers for varying the position of the piston slide valves, two pipes connecting the measuring vessels to the said driving chambers of the auxiliary system, a liquid tank, a return pipe leading to said tank adapted, according to the position of the piston slide valves of the auxiliary system, to be put in communication with one or the other of the driving chambers of the main system, an incline integral with the piston rod of the main system, a roller pressed against said incline by the action of a spring, a second incline integral with the piston rod of the auxiliary system, a roller pressed against said incline by the action of a spring which is stronger than the corresponding spring of the main system.

3. Apparatus for dispensing liquids, more particularly liquid hydrocarbons, comprising two measuring vessels, a liquid inlet pipe under pressure, a delivery pipe, a first or main system of slide valves comprising two coupled piston slide valves adapted, according to their position, to put the liquid inlet pipe under pressure in communication with one or the other of the two measuring vessels and to put the measuring vessel, which is not in communication with the said pipe, in communication with the delivery pipe, two driving pistons displaceable in two driving chambers for varying the position of the piston slide valves, a second or auxiliary system of slide valves comprising two coupled piston slide valves adapted, according to their position, to put the said liquid inlet pipe in communication with one or the other of the driving chambers of the main system, two driving pistons for the auxiliary system displaceable in two driving chambers for varying the position of the piston slide valves, two pipes connecting the measuring vessels to the said driving chambers of the auxiliary system, a return pipe leading to the tank adapted, according to the position of the piston slide valves of the auxiliary system, to be put in communica- 2,079,027 'tion with one or the other of the driving chambers of the main system, means for resisting the displacement of the main system, means for resisting the displacement of the auxiliary system, so

constructed and arranged that the displacement ticularly liquid hydrocarbons, comprising two measuring vessels,a liquid inlet pipe under pressure, a delivery pipe, a first system or main system of slide valves comprising two piston slide valves mounted on a piston rod and adapted, according to their position, to put the liquid inlet pipe under pressure in communication with one or the other of the two measuring vessels and to put the measuring vessel, which is not in communication with the said pipe in communication with the delivery pipe, two driving pistons mounted on the said rod and displaceable in two driving chambers for varying the position of the piston slide valves, a second system or auxiliary system of slide-valvescomprising two piston slide valves mounted on a piston rod and adapted, according to their position, to put the said liquid inlet pipe in communication with one or the other of the driving chambers of the main system, two driving pistons, mounted on said rod and displaceable in two driving chambers for varying the position of the piston slide valves, two pipes connecting the measuring vessels to the said driving chambers of the auxiliary system, a liquid tank, a return pipe leading to said tank adapted, according to the position of the piston slide valves ofthe'auxiliary system, to be put in communication with one or theother of the driving 'chambers of the main system, an incline integral with the piston rod of the main system, a roller pressed against said incline by the action of a spring, a second incline integral with the piston rod of the auxiliary system, a roller pressed against said incline by the action of a spring which is stronger than the corresponding spring of the main system, a chamber interposed in the liquid delivery pipe, a float in said chamber, means for preventing the displacement of the roller of the auxiliary system by the corresponding incline when the said fioat is lifted.

5. Apparatus for dispensingliquids, more particularly liquid hydrocarbons, comprising two measuring vessels, a liquid inlet pipe under pressure, a delivery pipe, a first system or main system of slide valves, comprising two piston slide valves mounted on a piston rod and adapted, according to their position, to put the liquid inlet pipe under pressure in communication with one or the other of the measuring vessels, and to put the measuring vessel, which is not in communication with the said pipe, in communication with the delivery pipe, two driving pistons mounted on the said rod and displaceable in two driving chambers for varying the position of the piston slide valves, a, second system or auxiliary system 01' slide valves comprising two coupled piston slide valves adapted, according to their position, to put the said liquid inlet valve in communication with one or the other of the driving chambers of the main system, two driving pistons displaceable in two driving chambers for varying the position of said piston slide valves, two pipes connecting the measuring vessels to the said driving chambers of the auxiliary system, a return pipe leading to the tank adapted, according to the position of the piston slide valve of the auxiliary system, to be put in communication with one or the other of the driving chambers of the main system, means for resisting the displacement of the main system comprising an oblong eye formed in the piston rod, a crank the end 'of which engages in said eye, a spring connected on they one hand to said crank and on the other hand to a fixed point perpendicular to the axis of rotation of the crank, means for resisting the displacement of the auxiliary system soconstructed and arranged that the displacement of the auxiliary system could only be effected for a, pressure of the inlet liquid higher than that which caused the displacement of the main system, an air accumulator connected to the hydraulic circuit.

6. Apparatus for dispensing liquids, more partic'ularly liquid hydrocarbons, comprising two measuring vessels, a tank, a liquid inlet pipe under pressure, a delivery pipe, a first system or main system of slide valves comprising two coupled piston slide valves adapted, according to their position, to put the liquid inlet pipe under pressure in communication with one or the other of the two measuring vessels and to put the meas uring vessel, which is not in communication with the said pipe, in communication with the delivery pipe, two driving pistons displaceable in two driving chambers for varying the position of the piston slide valves, a second system or auxiliary system of slide valves comprising a first group formed by a piston slide valve and a driving piston for the displacement of said piston slide valve mounted on the same piston rod, a second group formed by a piston slide valve and a driving piston for the displacement of said piston slide valve mounted on another piston rod parallel to the first one, a beam oscillating about a fixed axis in its center and pivoted to the ends of the two piston rods, a pipe connected to the liquid inlet pipe and adapted, according to the position of the auxiliary system, to be put in communication with one or the other of the driving chambers of the main system, two pipes connecting the measuring vessels to the driving chambers of the auxiliary system, a return pipe leading to the tank adapted, according to the position of the piston slide valves of the auxiliary system to be put in communication with one or the other of the driving chambers of the main system.

7. Apparatus for dispensing liquids, more particularly liquid hydrocarbons, comprising two measuring vessels, a tank, a liquid inlet pipe under pressure, a delivery pipe, a first system or main system of slide valves comprising two coupled piston slide valves adapted, according to their position, to put the liquid inlet pipe under pressure in communication with one or the other of the two measuring vessels and to put the mealuring vessel, which is not'in communication with the said pipe, in communication with the delivery pipe, two driving pistons displaceable in two driving chambers for varying the position of the piston slide valves, a second system or auxiliary system of slide valves comprising on a common piston rod a piston slide valve and two driving pistons displaceable in two driving chambers, a pipe connected to the liquid inlet pipe and put in communication, according to the position of the piston slide valve of the auxiliary system, with one or the other of the driving chambers of the main system, two pipes connecting the measuring vessels to the driving chambers of the auxiliary system, two return pipes leading to the tank adapted, according to the position of the piston slide valve of the auxiliary system, to be put in communication with the driving chamber of the main system separated by the piston. slide valve of the auxiliary system from the liquid inlet pipe.

8. Apparatus for dispensing liquids, more particularly liquid hydrocarbons, comprising two measuring vessels, a tank, a liquid inlet pipe under pressure, a delivery pipe, a first system or main system of slide valves comprising, carried by one and the same piston rod, a piston slide valve and two driving pistons displaceable in two driving chambers, the said piston slide valve adapted, according to the position of the main system, to put the liquid inlet pipe in communication with one or the other of the measuring vessels and to put the measuringvessel, which is not in communication with the said pipe, in communication with the delivery pipe, a second system or auxiliary system of slide valves comprising two coupled piston slide valves adapted, according to their position, to put the liquid inlet pipe in communication with one or the other of the driving chambers of the main system, two driving pistons displaceable in two driving chambers for varying the position of the piston slide valves, two pipes connecting the measuring vessels to the said driving chambers of the auxiliary system, a return pipe leading to the tank adapted, according to the position of the piston slide valves of the auxiliary system, to be put in communication with one or the other of the driving chambers of the main system.

9. Apparatus for dispensing liquids, more particularly liquid hydrocarbons, comprising two measuring vessels, a liquid inlet pipe under pressure, a delivery pipe, a tank, a first system or main system of slide valves comprising, carried by one and the same piston rod, a piston slide valve and two driving pistons displaceable in two driving chambers, the said piston slide valve adapted, according to the position of the main system, to put the liquid inlet pipe in communication with one or the other of the measuring vessels and to put the measuring vessel, which is not in communication with the said pipe, in communication with the delivery pipe, a second system or auxiliary system of slide valves comprising, mounted on a common piston rod, a piston slide valve and two driving pistons displaceable in two driving chambers for varying the position of the said piston slide valve, a pipe connected to the liquid inlet pipe and adapted, according to the position of the piston slide valve of the auxiliary system, to be put in communi cation with one or the other of the driving chambers of the main system, two pipes connecting the measuring vessels to the driving chambers of the auxiliary system, two return pipes leading to the tank adapted, according to the position of the piston slide valve of the auxiliary system, to be put in communication with the driving chamber of the main system separated by the piston slide valve of the auxiliary system from the liquid inlet pipe.

10. Apparatus for dispensing liquids, more particularly liquid hydrocarbons, comprising two measuring vessels, a tank, a liquid inlet pipe under pressure, a delivery pipe, a first system or main system of slide valves comprising two slide valves mounted on a piston rod and adapted, according to their position, to put the liquid inlet pipe in communication with one or the other of the measuring vessels and to put the measuring vessel, which is not in communication with the pipe, in communication with the delivery pipe, two driving pistons mounted on the said rod and displaceable in two driving chambers for varying the position of the piston slide valves, a second system or auxiliary system of slide valves, comprising a first system formed by a piston slide valve and a driving piston mounted on the same piston rod, a second group formed by a piston slide valve and a driving piston for the displacement of said piston slide valve mounted on another piston rod parallel to the first one, a lever pivoted to the ended the two piston rods, a pipe connected to the liquid inlet pipe and adapted, according to the position of the auxiliary system, to be put in communication with one or the other of the driving chambers of the main system, two pipes connecting the measuring vessels to the driving chambers of the auxiliary system, a return pipe leading to the tank and adapted, ac-

cording to the position of the piston slide valve of the auxiliary system, to be put in'communication with one or the other of the driving chambers of the main system, a chamber interposed in the liquid delivery pipe, a float in said chamber, means for resisting the displacement of the main system comprising an oblong eye formed in the piston rod of this system, a crank the end of which engages in the said eye, a spring connected on the one hand to said crank and on the other hand to a fixed point perpendicular to the axis of rotation of the crank, means for reslsting the displacement of the auxiliary system comprising an arm integral with the lever pivoted to the ends of the piston rods of said system, a small bar carried by the float, two notches in said small bar adapted, when the float is lifted, to form stops or abutments for the end of said arm, a spring connected to said arm, the fixed connecting point of which is arranged symmetrically with respect to the said notches, so that the displacement of the auxiliary system could only be effected for a pressure of the inlet liquid higher than that which caused the displacement of the main system, and an air accumulator connected to the hydraulic circuit.

DANIEL MYON.

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