US2930402A

US2930402A - Hydraulic multi-valve power unit

Info

Publication number: US2930402A
Authority: US
Inventors: Louis J-M Gamet
Original assignee: LA PRECISION INDUSTRIELLE
Current assignee: LA PRECISION INDUSTRIELLE
Priority date: 1955-10-03
Filing date: 1956-09-17
Publication date: 1960-03-29
Anticipated expiration: 1977-03-29
Also published as: DE1066872B; GB843393A; FR1133606A

Description

March 29,1960 1...]. -M. GAMET 2,930,402

HYDRAULIC MULTI-VALVE POWER UNIT Filed Sept. 17. 1956 SSheets-Sheet 1 34 J n, mm

5 Sheets-Sheet 2 L. J. M. GAMET HYDRAULIC MULTI-VALVE POWER UNIT March 29, 1960 Filed Sept. 17, 1956 March 29, 1960 1.. J. -M. GAMET 2,930,402

HYDRAULIC MULTI-VALVE POWER UNIT Filed Sept. 17. 1956 5 Sheets-Sheet 3 March 29, 1960 J. M. GAMET 2,930,402

HYDRAULIC MULTI-VALVE POWER UNIT Filed Sept- 17, 1956 5 Sheets-Sheet 4 1 84- as I March 29, 1960 J. -M. GAMET HYDRAULIC MULTI-VALVE POWER UNIT 5 Sheets-Sheet 5 Filed Sept. 17. 1956 United States Patent 2,930,402 HYDRAULIC MULTLVALVE POWE R UNIT Louis J.'-M. Garnet, Bougival, France, assignor'to La Precision Industrielle (Socit Auonyme), Rueil-Malmai- Certain mechanisms, such as machine tools, are often operated automatically by hydraulic means.

In fact, such means are capable of transmitting considerable forces along flexible pipes, and apart from the source of hydraulic pressure the operation of these means requires only the functioning of distributing valves to direct the pressure to the mechanism to which pressure is to be applied. By actuating these valves by suitably disposed electric contacts, complete automation can be achieved.

However, the usual hydraulic circuits are complicated Paitented I Mar. 29, 1am

ensure the tightness of the joints between the bores of two contiguous blocks connected with each other and locked together, a plastic ring may be provided in a groove around the opening of a bore into one of the 5 sides.

because they require numerous pipes and corresponding are attempted, to manufacture lengths of rigid pipes of precise dimensions and shape. However, such precision is essential to ensure perfect mating of the individual connections. Systematic use of flexible ducts avoids the need for precision but increases the risks of rupture, and in all practical cases the complexity and the length of the circuits leads to ineflicient use of the hydraulic force and lengthens the time of response; moreover, .each joint is liable to leakage. it

It isan object of the present invention to provide a hydraulic multivalve power unit'which encompasses-arrangements of a plurality of hydraulic control circuits and reduces the risks and disadvantages mentioned above. Another object of the present invention is to reduce, the number of pipes required in the hydraulic circuit to those required to connect the unit, to the mechanisms being hydraulically operated.

A further object of the present invention is to provide a hydraulic multivalve power unit in which the operating members of said valves may be dismantled without breaking down or dismantling the hydraulic circuits or the components thereof.

Still, a further object of the present invention is to provide a hydraulic multivalve power unit in which the assembly of the various components of said unit simultaneously provides a liquid tight joining of the said components.

- The present invention includes substantially parallelepipedic blocks, each block being provided with intercommunicating bores and having a cavity extending into said block from its top face to which at least one of said bores leads; a control member, fitted in said cavity, being movable therein-to control therein the opening of said bore.

- providing adjusted pressure.

To ensure positive control of a mechanism in both di- "rect'ions', it is usual to employ double-acting servo motors. It can be demonstrated thattwo eIementS are i needed in the hydraulic circuits needed for such motors,

namely: double distributor valves and relief valverneans Moreover, when. these distributor valves are electrically actuated (electric valves), such actuation can beeither by limit switches or by pressure-controlled contacts. Finally, the speed of the servo motor can be regulated with the use of exit chokes.

The unit according to the invention can be adapted to provide (1') electric valves I (2) relief valve means providing adjusted pressure (3) pressure-controlled contacts, and

(4) exit chokes, as desired.

Moreover, the hydraulic pressure in the circuit is produced by a pump immersed in a liquid-filled tank and the :various ganged blocks are mounted on the underside of the lid of said tank; the lid is such that mobile member of each block is accessible through .the .lid.

This arrangement of the pump and unit-offers the advantage that any leakage occurring in these members, as well as the normal return of liquid to the tank, flows immediately into the tank itself. V

The control means of the moving components of the constituentse.g. the electromagnets where provided-- may be located outside the tank so that they are accessible without even requiring the tank lid to be lifted.

Moreover, the blocks used in a complicated hydraulic circuit may be arranged along one edge of the lid, that is to say adjacent to a lateral wall ofthe tank, so that the outlet openings leading to the servo motors can passinstallation for-hydraulic circuits; 7

.Fig. 2 is a plan view of the installation diagrammatically in Fig. 1; Y

Fig. 3 is an enlarged section on IIIIII of' Fig-1.21 Fig. 4 is a section on lV-IV of Fig. 3; 1 Fig. 5 is an enlarged section on VV of Fig. '2; Fig. 6 is asection on VI-VI of Fig. 5; Fig. 7 is 'a diagram of another hydraulic circuit; and Fig. 8 is a diagrammatic representation of the operation of the circuit shown in Fig. 7. a

In the. diagram shown in Fig. l the fluid, such as oil,

required for the operation of the circuit is containedin a tank 1. This fluid is placed under pressure by'a pump 2 which may be, for example, a gear pump immersed in said tank. In theembodiment ilustrated this pump comprises three gearsone driVing'gear-S and-two driven gears. 4 and 5 substantially opposite eachother, supplying pressurized fluid to pipes 6 and'7. The pipe Econtrols a machinehydraulically actuated tool chuck, shown diagrammatically and designated as a wholeby 8; The pipe 7 controls a feed mechanism, designated as a whole as 9, actuating a tool for machining the workpiece clamped in the chuck 8.

The chuck 8 comprises a double-acting jack, i.e. a jack having two opposing compartments 10a and 10b separated by a mobile piston 11. This jack turns as a whole in the bearings 12, together with the chuck.

to the accompanying The chuck comprises jaws 13 which grip the workpiece 14 and are actuated by movement of the rod 15 of the piston 11 via articulated links 16.

Such a chuck, which is well known, grips the workpiece 14 when the pressure fluid is forced into'the com partrnent 10b and opens up and releases the workpiece when the pressure fluid is injected into the compartment 10a and the compartment 10b is emptied.

The pressure fluid is supplied to the compartments- 10a and 10b through pipes 17a and ,17b fed by an elec* tric distributor valve 18 which forms part of the unit EV. The valve comprises a cylindrical slide 19 of the spool type whose constrictions define three distribution chambers, namely: two extreme chambers 20a and 20b and the center chamber 200. The pipes 17a and 17b, and the pipes 26a and 26b and the upper end of 6 align with the distribution chambers in a manner that will be apparent from the subsequent description. The pressure fluid is injected into the chamber 20c through pipe 6 in which the pressure is regulated by a relief valve means providing adjusted pressure BPI. This means comprises a valve 21 on which acts a spring 22 which controls the return of the fluid into the tank through the duct 23.

The way in which this relief valve means functions is well .known. When the pressure in pipe 6 exceeds the pressure of spring 22, the valve 21 is lifted and the fluid returns to the tank so that the pressure in pipe 6 cannot exceed that which is determined by the state or tension of the spring 22. This pressure is indicated by a pressure gauge M1.

A return pipe 24 to the tank is connected with the distributor valve 18; it is connected wtih the fluid return bores 25a and 25b drilled into the body of the distributor and communicating with each other. At the level of the outlet bores leading to pipes 17a and 17b there are provided other bores 26a and 26b communicating with the pressure-controlled contacts MCa and MCb. Each of these pressure-controlled contacts comprises a small piston 27 on which the fluid exerts pressure, a counter spring 28 and a contact member 29 which, as shown, may be closed by increasingthe pressure in MCa or opening in the same condition.

The slide 19 is actuated by an electromagnetically-operated plunger 30 associated with an electromagnet comprising a coil 31 and the stationary core 32. The upper extremity of the plunger is conical and is located in a frusto-conical opening of said core; consequently when the coil 31 is energized, the current forces the plunger 30 down, and depresses the slide 19, against the return spring 33. Actually the unit EV is an electric distributor valve.

The part of the hydraulic circuit just described functions as follows:

In the position shown in Fig. 1 the electromagnet 31 of EV is not excited and the fluid is, therefore, pressed through

pipes

6 and 17a into the compartment 10a, and as a consequence the chuck is kept open. Until the piston 11 reaches its extreme position, the pressure in compartment 10a remains relatively low; however, when the piston 11 reaches this position, the pressure in compartment 10a, and the pipes leading to it, rises until it is such that the pressure-controlled contact MCa is actuated. Actuation of this contact alters the state of the electric control circuit (which is not illustrated and will be such as to suit the ultimate purpose in hand). As a result the electromagnet of EV is excited.

When the electromagnet of EV is excited, the slide 19 moves into the depressed position and the pressure fluid will pass, via the centre chamber 200 through the pipe 17b into compartment 10b. The piston 11 then moves to the left, and as a consequence the chuck closes. As before, at the end of the stroke, the pressure prevailing in compartment 10b, and the system leading 10 it, actuates the pressure-controlled contact MCb.

In these two cases the displacement of the slide 19 empties the jack compartment opposite to that into which the fluid is forced through the bores 25a and 25b into the pipe 24 and thence into the tank 1.

The tool feed device 9 likewise comprises a double acting hydraulic jack having two compartments 34a and 34b separated by the piston 35. The piston rod 36 supports a tool 37 for machining the workpiece 14 and two control cams 38 and 39 which can he slid along the piston rod 36. With the cam 38 c'o-o'perates a contact device 40 and with cam 39 a contact device 41.

The adjustment of the position of the cams 38 and 39 is such that the cam 38 co-operates with contact 40 as soon as the tool approaches the workpiece 14, where as the cam 39 acts on the contact 41 when the tool has terminated its working stroke.

The compartments 34a and 34b are supplied by pipes 42a and 42b respectively via a distributor 43 forming part of the electric valve EVD which is similar to the electric valve EV. The essential differences between the electric valve EV and the electric valve EVD are the following:

The electric valve EVD comprises no pressure-controlled contact and, on the other hand, its fluid return bores 44a and 44b are connected via a duct 45 with the fiuid return bores 46a and 46b of another electric valve EVR associated with EVD. In the electric valve EVR (which is also similar to EV and EVD) a direct fluid return bore 47b communicates with the tank 1, the location of this bore in the block EVR being the same as the location of the bores feeding the pipes 17a and 42b in the electric valves EV and EVD respectively. A second fluid return duct 47a (similar in location to 26b of the valve EV) feeds the pressure fluid through a choke or regulating valve R into the return duct 48.

As before there is provided on the delivery side of the pipe 7, which is attached to the central inlet union of EVD, a pressure-regulating relief valve unit BP2 associated with a pressure gauge M2. This relief valve means functions in a manner analogous to that of relief valve means BPl.

This second part of the hydraulic circuit functions as ,follows:

In the position shown in Figure l, i.e. when the electromagnets of EVD and EVR are unenergized, cornpartment 34b is pressurised and the tool 37 is retracted from the workpiece 14. It will be realized that this arrangement ensures the security of the installation since, when the control circuits are currentless, the tool 37 is automatically retracted from the workpiece.

To cause the tool to approach the workpiece, the electromagnet of EVD is excited. The slide 49 will thereupon descend so that the pressure fluid flowing in from pipe 7 is injected into pipe 42b, and as a result the piston 35 is forced to the left. At this moment, through the pipe 42a and the fluid return pipe 44a and the pipe 45, the fluid from compartment 34b is forced through the bore 46b into the lower compartment 50b defined by the slide 51 in the electric valve EVR. The return passage for the fluid from the compartment 34 to the tank 1 is thus formed and free.

When the tool approaches the workpiece, the cam 38 closes the contact 40 which actuates the electromagnet of the electric valve EVR. The slide of the latter descends and thus interrupts the free discharge of fluid through 47b and, via

bores

46a and 47a, makes this discharge possible via the regulating valve R. According to the extent to which the cone 52 of this regulating valve is screwed into its seating by turning the milled button 53, thedischarge of fluid through 47a, 48 is more or less restricted whereby the rate of advance of the cutting tool is controlled.

On termination of the work cycle, the contact 41 is valves EVD and EVR is switched ofi and as a result thechydraulic installation is returned to the position represented by Fig. 1. The tool 37 is thus retracted at its maximum speed. A new cycle is started by intentionally exciting the electromagnet of EVD.

The electric circuits have not been illustrated but are easy to visualise. They may comprise in association with contacts 4% and 41 re-energising contact relays to ensure the continuity of the-transient effect achieved by actuating the

contacts

40 and 41.

Theinvention enables the circuit shown in Fig. 1 to be formed with only the ducts 17a, 17b 42a, 42b and partially 6 and 7 (represented by heavy lines), as separate pipes and all other pipes drawn in fine lines being bores machined in metal blocks belonging to the units EV, EVD, EVR, BPl, BP2, MCa, MCb and R; the ducts shown in dotted lines are suppressed and the fluid returns directly from the correspondingoutlets of the bores to the .tank 1 by gravity.

A plan view of the installation shown in Fig. lis shown in Fig. 2. I

On the'underside of the lid 54 (see Figs. 3 and 5) of the tank lthere are fixed ganged metal blocks of rectangular parallelepipedic shape bearing the reference numbers of the diit'erent units to which they belong. blocks arelocated close to one lateral wall 55 (Fig. 2) of the tank provided with apertures in which there are unions for the

pipes

17a, 17b, 42a, 42b. The side faces of all blocks are identical so that they can be assumbled in a gang and locked together by means of threaded assembly pins 56, which traverse them and nuts 57. The electric valve blocks and relief valve blocks are placed side by side, whereas the accessories (pressure-controlled contacts MCa, MCI) and-regulating valve R) are arranged on the backsof the units with which they are associated. In Fig. 2 the pipes are shown with the reference numbers used in Fig. 1; these pipes are in the form of bores. To make it easier to understand the arrange ment of these bores, the electric valve unit EVD and the relief valve unit BP2 areexplained below in greater detail, as an example, with reference to Figs. 3, 4 and 5 and 6 respectively.

As has been mentioned hereinbefore, the electric valve unit EVD comprises a parallelepipedic block 59 traversed from side to side by bores through which the assembly pins 56 can be pushed. Furthermore, a vertical bore 60 goes from the top to the bottom of this block, and in this vertical bore there is provided a bush 61 having a smooth and cylindrical centre bore and on the outside five

grooves

62a, 62b, 62c, 62d and 62e which thus form between the bush and the bore five compartments corresponding to the five ducts which are associated with an electric valve, as shown in Fig. 3. Each of said five compartments debouches into the interior of the bush via bores. These five ducts are: the bore 58 which (in Fig. 1) is an extension of the duct 7, Le. the supply pipe for pressurised fluid, and which debouches in the centre groove 62c; the two outlet bores 42:! and 42b, the former of which debouches tangentially into the groove 62d and the latter (bores 42% and 42%) debouches into groove 62b; finally the two fluid return ducts 44a and 44b which, in the case of an electric valve such as EV, debouch externally, downwards, via the opening which is closed by means of the screw plug 63 and which, in the case of the electric valve EVD illustrated in Fig. 3, communicates with the adjacent electric valve EVR by way of a bore 45 associated with the duct bearing the same reference number. This bore can be provided originally in the body of an electric valve block, being plugged up if not needed, or else it may be drilled in the body of an electric valve as and when required.

Consequently, if the bore 58 is supplied with oil under pressure, the center chamber 200 may feed either the pipes 42a or 42b via the

compartments

62c and 62d or .6211 respectively, while oil may escape from 42a, owing to the upperchamber 20b in the bore 44a,-.via the

compartments

62d and 62a and frorn42b in the borwflbwfii the compartments 62a and 62b.

Conversely, the oil under pressure may be admitted through the bore 45 and supplied to the ducts 42aor 42b, owing to the chambers 2012 or 20c, via the compart ments 62 e and 62d or 62a and 62b respectively. In this case, oil may escape through the bore 58, owing to the chamber 290, via the compartment 62c and the compartment 6211 or 62d. T

In the case of the electric valve EV which, as shown in Fig. 2, comprises the same bores (except forbore 45) as the electric valve EVD, there are provided two further bores 64a and 64]) which debouch into corresponding

bores

42 a and 42 1: respectively.

In the electric valve EVR the bore equivalent'to 42 a is either plugged up or not provided, whereas the bore corresponding to 42% (indicated by 65 in Fig. 2) is pres ent; it debouches externally (on the underside of EVR) through the bore 66 (which corresponds to the vertical bore 42% in the electric valve EVD shown in Figs. 3 and 4), but which, in the vaseof the electric valve EVR, is not closed at its bottom end.

In the electric valve EV the corresponding bore is likewise closed (the vertical bores closed at their base'are represented in Fig. 2 by concentric circles). Finally, the electric valve EVR comprises a bore 67 (Fig. 2) which is an extension of the bore 45 and which connects EVD with the bores 46a and 46b of EVR.

As will be realised from Fig. 3 the bush 61 in the dif- I ferentelectric valves is closed at its bottom end by'a cap 63 housing the spring 33, and the cap is held in position by pins 69. Through a washer 70 set at'the lower end of the slide 49, the extremity of the bush 61 serves asan abutment for said slide 49 when the latter is urged up wardly by the action of spring-33. At'its top end the bush 61 is provided with a collar 71 secured by the screw 72. The collar is fixed to the block by the screw 73-and in this way the bush 61 is fixed'also. The armature 32 of the electromagnet controlling the valve is attached'to the outside of the lid 54 by means of bolts 74, and each block is fixed to the lid by means of bolts 75. 'Theprovision of a bush, such as 61, ensures that the superposed orifices controlled by the slide 49 will be accurately spaced and not affected by any imperfections of fitting or-shape ghiclir might occur inthe bores drilled directly into the The collar 71 is accessible through a hole in the lid'54 so that, after the armature has been removed by removal of the bolt 74, the whole assembly of the bush 61, slide 49, spring 33 and cap 68 can be withdrawn through this hole by simply unscrewing the screw 73. While this'is being done, all circuits remain undisturbed. The servic ing of the electromagnet does not involve the removal of any piping. v

In the embodiment illustrated the lid 54 is attached to an internal ledge 76' within the tank 1. Short lengths of tubing 77 and the unions 78 are provided for connection of the ducts 42a and 42b (or 17a and 17b in the case of electric valve EV) to their associated servo motors.

The relief valve means represented by Figs. 4 and 5 likewise consists of a parallelepipedic block 79 traversed by threaded assembly pins 56. In the plane of symmetry of this block there are provided three bores forming a Ushaped channel. To the bottom'end of therighthand ascending vertical bore 80 there are. connectedthe are used as shown in Fig; 2, is clos'edby'a screw plug87.

Thevertical bore 88, which debouches into this horizontal bore 86, thus provides a possible communication between the groove 85 and the tank 1.

Asin the case of the electric valves, the relief valve block is attached to the lid 54 by means of bolts 75. The compression of the spring 22 can be adjusted by means of the nut 89, the upward travel of this nut being limited by an annular member 90 held by means of bolts 91. When the member 90 is removed, the nut 89, and then the spring and the clappet can be removed without having to dismantle any piping.

When the pressure applied through the duct 7, acting on the underside of the dome 21, exceeds the force of the spring 22, said dome rises so that the pressure fluid can escape through the holes 84 into the groove 85 and thence return to the tank when there is no screw plug at the bottom of bore 88; or said fluid may be utilised, as shown in Figs. 7 and 8, in another apparatus when a plug (similar to 63, Fig. 3) is screwed into the base of the bore 88 and the bore 87 is left open.

Moreover, the leakages, which may occur externally along the dome 21, return directly in the tank through the hole 100 (Fig. 5).

It will be realised that the connection between the electric valves and the relief valve units is substantially achieved by bringing the

bores

82 and 52 close together; in similar manner connection between two adjacent electric valves is achieved by bringing the

bores

45 and 67 close together. To ensure the tightness of the connection, the side faces of the blocks are machined so that they are adequately plane and, around the orifice of one of the bores to be put in communication, there is provided a groove 92 in which a ring 93 of plastic material is inserted. The locking together of the electric valves and relief valve units by means of nuts 57 screwed on to the extremities of the threaded assembly pins-56 compresses the plastic rings 93, and in this manner a perfect seal between the connected bores is ensured. Similar rings are used to ensure a tight connection between EVR and R by means of bores 95 and 96 and between MCa, MCb and EV (ducts 26a and 26b) by means of bores 97 and 98.

The members MCa, MCb and R are, as shown in Fig. 1, of similar design as the blocks of the electric valves and relief valve units, that is to say that their mobile component (piston or cone) is housed in a vertical bore in the block and accessible from the top face of said block through the lid 54 of the tank.

Figs. 7 and 8 illustrate the application of the invention to the arrangement in cascade form of several relief valve units PBl, PBZ, PB3 which, in turn, control the electric valves EV1, EV2 and EV3.

The

springs

221, 222, 223 of these relief valve units are adjusted for decreasing compression so that the pump 2 (which, again, has three gears, although the two outlet ones are coupled) supplies to EV1 to strong pres sure determined by the spring 221, a lower pressure determined by the spring 222 to EV2, and an even weaker pressure to EV3 determined by the spring 223. In Fig. 7 the diagrammatic representations of pressure gauges M1, M2 and M3 show this decrease in the pressure. In fact, since, so long as the servo motor controlled by EV1 has not yet reached the end of its course, the pressure in the circuit C1 remains less than the pressure determined by the spring 221, the circuit C2 is not excited until the first servo motor has reached the end of its course. In like manner, the circuit C3 is not excited until the servo motor controlled by EV2 likewise reaches the end of its course. By this arrangement in cascade form there is achieved not only a successive decrease in the values of the control pressures, but also a cascade function of the controlled members.

Fig. 8 shows a diagrammatic representation of the operation of the circuit shown in Fig. 7.

This layout comprises six electric values and relief valve blocks in juxta-position. The relief valve units BPl, BP2 and BP3 are such as are shown in Figs. 5 and 6 with the difference, however, that the relief valve. units BPl and BP2 have no screw plugs 87 and instead the bores 88 are closed at their bottom end. On the other hand, BPS has the screw plug 87 inserted, while the screw plug has been removed from the bottom portion of bore 88. The electric valves are of the type described with reference to Figs. 3 and 4, that is to say that the communication between an electric valve and its associated relief valve unit is achieved by means of

bores

58 and 82. However, the electric valves EV2 and EV3 comprise additional bores 99 which start from the flank of these electric valve blocks facing the bores 86 of the relief valve units and debouch into the compartment 62c of the electric valves EV2 and EV3. The level of the bore 86 provided in the relief valve units is essentially that of the compartments 620 so that the passage 99 can be formed by two bores at right angles to each other. In the interest of precision it is, in fact, advantageous to drill all bores perpendicularly to the block faces in which they terminate. Any unused portions of bores are plugged up in known manner.

In conclusion, it is possible to assembly any desired hydraulic circuit incorporating electro-valve blocks, relief valve blocks, and pressure-controlled contact blocks using as separate tubular ducts only those which serve the servo motors and the connecting pipe (which may be short and well protected) which connects the assembled blocks with the outlet of the pump 2.

The bores provided in the blocks and needed in all cases, can be originally drilled in these blocks, whereas the bores used only in some cases can be drilled on demand. If, however, they have been drilled originally, they may be closed by means of removable plugs. More especially, each electric valve originally comprises five superposed bores corresponding to the distributing slide, whereas the auxiliary bores connecting the pressure-controlled contacts or the electric valves among themselves are drilled only as required.

In the case of the relief valve units it is advantageous to drill all the bores shown in Figs. 5 and 6 as a standard feature of the unit.

In the pressure-controlled contact blocks and the regulating valve blocks all bores are always drilled from the start.

By virtue of the connection of the co-operating bores in two adjacent block faces, the positioning of said bores does not require extreme precision. Similarly, the use of the bush 61 affords a certain latitude in the positioning of the orifices of the staggered bores of the electric valves in the bore of the associated block.

What I claim is:

-1. A hydraulic multivalve power unit comprising an upwardly opened liquid containing tank having a flat lateral wall, said lateral wall having an upper part, provided with a horizontal row of at least two apertures; an apertured horizontal lid closing said tank; at least one substantially parallelepipedic valve distributor block secured to the under face of said lid and having a front face in parallel relationship with said wall of the tank and having a top face in parallel relationship with said lid; said block having lateral faces and having a vertical valve bore registering with one aperture of said lid, said block having a first horizontal bore substantially in the middle part thereof and disposed perpendicular to the lateral faces thereof and opening into said vertical valve bore; said front face of said block having two further horizontal bores registering with the apertures of said lateral wall of the tank; one of said horizontal bores opening into said vertical valve bore above said first horizontal bore and the second horizontal bore being downwardly prolongated to communicate with said vertical valve bore below said first horizontal bore; said block having intercommunicating bores communicating ing through said block; a spool type slide in said vertical valve bore controlling the communication of said first mentioned bores; a return spring urging said slide upwardly; an electromagnet carried by the upper face of said lid for urging said slide downwardly; means for energizing said'electromagnet; at least one substantially parallelepipedic relief valve block secured to the under face of said lid and having an upper face in parallel relationship with said lid and in abutment relationship with one lateral face of said valve distributor block; said relief valve block having a vertical valve bore and having a recessed vertical bore starting from the under face thereof, one lateral face of said block having a first horizontal bore perpendicular thereto and communicating with said two vertical bores in the upper part thereof, said last block having a further vertical bore, the axes of the vertical valve bore and of the further vertical bore defining a plane substantially parallel to the lateral faces of said abutting blocks, said valve vertical bore and said further vertical bore being intercommunicated by an intercommunicating bore, said blocks having a further horizontal bore perpendicular to said lateral faces and crossing said further vertical bore and in registering relationship with the first horizontal bore of said distributor valve block and a set of further bores perpendicular tothe said lateral faces and registering with the said set of further bores of said valve block; relief valve means intermediate the openings in saidvertical valve bore; assembling pins passing through said sets of further bores for tightly pressing said blocks against one another;.pum ping means in said tank for drawing liquid therefrom; connecting duct means between the outlet of said pump and the lower opening of said further vertical bore of said relief valve block and duct connections passing through the apertures of said lateral wall and leading to the openings of said two further horizontal bores of said valve block. v

2. A hydraulic multivalve power unit according to claim ,1, in which the upper end of said further vertical bore of said relief valve block is in registering relationship with an aperture of said lid and further comprising a pressure gauge passing through said aperture and connected to said bore.

3. A hydraulic multivalve power unit according to claim 1, in which said relief valve block has above the communication of said first horizontal bore with said vertical valve bore a hole issuing in the front face of said block, and in which the upper end'of said vertical valve bore of said relief valve block registers with an aperture of the lid and in which the relief valve means located in said vertical valve bore comprises a slidingly fitted dome shaped valve having apertures adapted to register with the communication of the first horizontal bore with said relief valve block in said valve bore by upward sliding of said dome shaped valve and a coil spring acting on the top of said valve for urging the same downwardly and means passing through the said 10 aperture of said lid for adjusting the compression of said spring. v a

4. A hydraulic multivalve power unit according to claim 1, in which at least one of the'two further horizontal bores ofthe distributor valve block communicates with the rear face of said block and further comprising a pressure-controlled contact block having an inlet open- I I ing in one plane face and means for tightly fastening said pressure-controlled contactblock against the said distributor valve block with the plane face of said contact block in contact with the rear face of said valve block and with the said inlet opening in register relationship with the entrance of one of said further horizontal bores into said rear face. p

5. A hydraulic multivalve power unit according to claim 1, wherein said valve distributor block has a further horizontal bore perpendicular to one lateral face thereof and communicating with said 'innerly intercommunicating bores and further comprising at least a further substantially parallelepipedic valve distributor block secured to the under face of said lid and in lateral abutting relationship with said lateral face of said first mentioned valve distributor block, said further valve distributor block having at least a vertical valve bore registering with one aperture of said lid, and intercommunicating I V bores, one end of which enters into the upper part of said valve bore and the other end into the lower part thereof, said further distributor valve block .having a horizontal bore perpendicular to the lateral face thereof, contacting said former distributor valve block, registering with said further horizontal bore thereof and communicating with said intercommunicating bores, the under face of said further block having a further vertical recessed bore prolongated for opening into said valve boreabove the lower part thereof, the rear face of said further block having a further bore opening into said valve bore below the upper part of said bore and a set of further bores perpendicular to the lateral faces of said further .block and registering with the said sets of said'distribw' tor valve block and said relief valve block; a spool type slide in said vertical valve bore for controlling the debouching of said first mentioned bores; a return spring .urging the base of said slide upwardly; an electromagnet;

carried by the upper face of said lid for urging said slide downwardly; means for energizing said electromagnet; and adjustable restricted passage means connected to the outlet of said further bore pierced in the rear face of said further block.

References Cited in the file of this patent UNITED STATES PATENTS Klopp Sept. 2, 1958.