US2933069A

US2933069A - Control system for fluid operated mechanism

Info

Publication number: US2933069A
Application number: US620075A
Authority: US
Inventors: Jean Louis Gratzmuller
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-11-04
Filing date: 1956-11-02
Publication date: 1960-04-19
Anticipated expiration: 1977-04-19
Also published as: GB840977A; FR1135122A; DE1152469B; CH355199A

Description

5 Sheets-Sheet J.

April 19, 1960 J. L. GRATZMULLER CONTROL SYSTEM FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 II V I vVHUU n um llllll I I ham/An??? l w r v Aprll 19, 1960 J. L. GRATZMULLER 2,933,069

CONTROL SYSTEM FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 5 Sheets-Sheet 2 April 19, 1960 J. L. GRATZMULLER 2,933,069

CONTROL SYSTEM. FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 5 Sheets-Sheet 3 April 9, 1960 .1. L. GRATZMULLER 2,933,069

CONTROL SYSTEM FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 5 Sheets-Sheet 4 April 19, 1960 J. L. GRATZMULLER 2,933,069

CONTROL SYSTEM FOR FLUID OPERATED MECHANISM Filed Nov. 2, 1956 5 Sheets-Sheet 5 Izwezvmp 7. .Grwzzmu 6661 2,933,069 Patented Apr. 19, 1960 ice 2,933,069 CONTROL SYSTEM FOR FLUID OPERATED MECHANISM Jean Louis Gratzmuller, Paris, France Application November 2, 1956, Serial No. 620,075 Claims priority, application France November 4, 1955 4 Claims. (Cl. 121-38) This invention relates broadly to the art of electric control apparatus.

More particularly, the invention relates to circuit-breaking and making apparatus hereafter called circuit-breakers whatever their specific nature. Still more particularly, the invention is concerned with control means for actuating the movable contact means of a circuit-breaker.

A circuit-breaker has to fulfill two main functions:

1) a permanent function, namely causing high strength currents to pass through its contacts without excessive heating.

(2) a transient function, namely switching-off or -on currents having different characteristics (for example, short-circuit currents, capacity currents, etc.) and doing so without mishap, either in the apparatus or in the mams.

Now, all known circuit-breakers offer deficiencies preventing them from ensuring satisfactorily either their permanent or their transient function, or even both.

Accordingly, it is an object of this invention to provide an improved circuit-breaker capable of assuming both the above mentioned functions in a satisfactory manner.

In particular, the transient function of a circuit-breaker implies stabilizing of the speed of its movable contact means at each point of its stroke, at a value comprised between two predetermined limit values which correspond to imperative electrical and mechanical conditions.

On the other hand, as regards the circuit-breaking stroke of the movable contact means, the same should be subjected to an initial acceleration as strong as possible so as to reduce to a minimum the total duration of the current cut-ofi? operation between the separation of the contacts and the complete extinguishment of the are.

It is therefore a further object of the invention to provide, in and for a circuit-breaker, a control device including a source of power capable of imparting to the movable contact means of the circuit-breaker a very high initial acceleration as well as maintaining its speed during its whole stroke at a value at least equal to a predetermined minimum value, the said device furthermore comprising means to brake the movable contact means as a function of its own speed, so as to maintain the said speed at each point of the stroke under a predetermined maximum value. The above mentioned minimum and maximum values are defined by the electrical and mechanical conditions to be fulfilled by the circuit-breaker.

Still another object of the invention is to design the hereabove mentioned braking means in such a manner that their action varies as a function of the speed of the movable contact means according to such a law that the said action becomes effective but only at a substantial speed so that it does not practically impair the said in itial acceleration.

Now, in practice, only the accumulation of power by resiliency (elastic deformation of solids and gases) permits designing, in a practical and not exceedingly expensive shape, a superabundant and rapidly available source of power.

Accordingly, it is a more particular object of the invention to use, as a source of power for each stroke of the movable contact means, a resilient power accumulator such as a spring, a compressed gas, etc.

It has been found that the use of the elasticity of gases, for at least one of the two opposed operations to be effected, is particularly cheap.

Now, the best known device using the elasticity of gases as a source of power, is the oil-and-air accumulator.

In particular, the applicant has described in the US. Patents No. 2,724,412, No. 2,746,486 and U. S. Patent application No. 307,863 filed September 4, 1952, now Patent No. 2,804,094, an oil-and-air accumulator particularly well adapted to be used for controlling circuit breakers in the hereabove enumerated conditions.

Consequently, another object of the invention is to use, as a source of power for controlling a circuit-breaker in the manner described, an oil-and-air accumulator, preferably of the type described in the above cited prior application.

A further object of the invention is to provide a circuit breaker control device of the type described, wherein a displacement of the movable contact means causes a corresponding displacement of a hydraulic liquid. This latter displacement being obtained, for example, by providing a permanent kinematic interconnection between the said movable contact means and one or more hydraulic jacks.

It is one of the main objects of the invention to obtain the required regulation of control of the speed of the movable contact means by controlling the said liquid displacement.

In this connection, when liquid flows through a conduit, it follows a law which is comprised between two limits, the law governing laminar flow, and the law governing turbulent flow. if the flow is purely laminar, that is, with very low speed, the difference in pressure between the upstream side and downstream side of any defined zone in the conduit, that is the loss of pressure is proportional to the speed. It is also proportional to the viscosity. The other limit is in instances of a purely tubulent flow, turbulent flow corresponding to high speed, great pressure differences, and low viscosity. In such a case, the law is that the loss of pressure is proportional to the square of the speed. This loss no longer is dependent upon viscosity, and is proportional to the density.

Accordingly, it is an object of this invention to ensure that the control of the circuit breaker, namely, the braking means therefor is a calibrated permanently open restriction means formed by a sharp-edged orifice, so as to obtain a law of How in the conduit(s) approaching as nearly as possible the law of the square of the speed. in connection with this sharp-edged orifice, it may be defined as a circular orifice cut in a thin plate, which results in that the flow in the conduit(s) follows a law much nearly approaching the law of the square of the speed than to the law of the laminar flow.

With this arrangement, at low speeds, the rate of flow of the liquid is practically not restricted so that a maximum acceleration is imparted to the movable contact means while at high speeds, the intensity of the braking efiect at each point of the stroke is substantially proportional to the square of the movable contact speed, so that it easily maintains the said speed between the suitable limits. This method of controlling the speed of the movable contact means moreover offers the essential advantage of being practically independent of temperature variations, since the rate of flow of a fluid through a sharp-edged orifice is but slightly responsive to variations of viscosity of the said fluid.

In a particular embodiment of the invention, at least for one stroke of the movable contact means, the resilientr 3 V ly accumulated power provided to ensure the said stroke is transmitted to the said movable contact means through a liquid and a jack fed with the same under the control of a hydraulic valve. V

A Well-knowndifficulty'of circuit'breaker control is to lock them in their circuit making position.

It is accordingly a further object of the invention to control both strokes of the circuit breaker of the movable contact means by means of hydraulic valves, all usual mechanical locking means being excluded.

For this purpose, a specific object of the invention is to design the circuit breaker control device in the manner described in the US. patent application Ser. No. 479,620, filed January 3, 1955 in the name of the applicant.

In this arrangement, the circuit-making stroke, as Well as the locking in circuit-making position of the movable contact means are effected. by means of a single-acting hydraulic jack fed with oil from an oil-and-air accumulator of the type described, while the circuit-breaking stroke is ensured by a spring armed during the circuitmaking stroke and released asthe oil contained in the said jack is evacuated at a' sufficiently high rate.

The said arrangement furthermore permits controlling the. speed of the movable contact means during both strokes of the sameby incorporating one or more calibrated permanently open restriction means formed by a sharp-edged orifice in the feeding and evacuation ducts.

of. the jack.

Another advantage of the c'"cuit control device with hydraulic transmission, according to the invention, is that of offering but a very small natural inertia. Therefore a control device of this type, capable of generating a superabundant force controlled by calibrated orifices determining a well defined stabilized speed with a high initial acceleration, may be easily designed at low cost. Such a control is capable, in turn, of determining a well defined stabilized speed of the movable contact means, whichever may be the nature of the electrical or mechanical phenomena resisting itsdisplacement.

In particular, it has been mentioned at the beginning of this preamble, thatthe permanent function of a circuit-breaker consists in causing high strength currents to pass through its contacts without excessive heating. The hydraulic control according to the invention, which is described above, is capable of generating superabundant driving forces and hence overcoming considerable resisting stresses, precisely permits establishing electrical contacts of a heretofore unknown quality, capable of fulfilling satisfactorily the said permanent function by subjecting the metal contact members to ahigh contact pressure. I

Since the control device according to the invention permits establishing electric contacts under a pressure which may be given a heretofore never used order ofmagnitude and sinceit also permits both imparting to the movable contact means a very high initial acceleration and stabilizing its speed during its whole stroke, the said device offers a possibility of designing circuit breakers capable of fulfilling in an'entirely satisfactory manner the above defined permanent and transient function.

Accordingly, still another object of the invention is to provide a circuit breaker equipped with'a control device of the type described and includingcontacts established under a pressure which maybe chosen if desired at a value having the same order of magnitude as the force available in the said device.

Finally, the two main types of contacts adapted to be used in a circuit breaker are the abutment contacts and thesliding contacts; the first ones offer many drawbacks and tend to be more and more abandoned in favor of the second ones;

It is therefore a more specific object of the invention to provide a circuit breaker equipped with a control de vice of the type described operatively connected with a movable contact means, slidably mounted in a connecting inafter described with reference to the accompanying.

drawings, given merely by way of example and 'in which:

Figure 1 is a diagrammatic view in longitudinal section,

of a circuit-breaker according to the invention.

Figure 2 illustrates in a diagrammatic manner a first' embodiment of the hydraulic control device according to the invention, comprising a single-acting jack with circuit-breaking spring.

Figures 3 and 4 are detail views showing two different constructions of a calibrated sharp-edged orificeaccording to the invention.

Figure 5 is a modification of Figure 2 showing a modified arrangement of'the calibrated sharp-edged orifices.

Figure 6 is a longitudinal axial sectional view of an oiland-air accumulator of the type described in the above cited references, which may be used as a source of re silient power in the control device according to the invention.

Figure 7 is an axial sectional view of a spring hydraulic accumulator also adapted to be used as a source of resilient power. 1

Figure 8 is an elevational partly sectional view of the contact mechanism of a circuit-breaker according'to the invention. e

Figure 9 is a part sectional view along line 99 of Fig. 8. a

Figure 10 shows a double-acting jack during a circuitbreaking stroke.

Figure 11 shows the same device during a circuitmaking stroke.

Figures 12, 13 and 14 illustrate. modified forms of con struction of the device in Figures 10 and 11.

Figure 15 shows anon-differential double-acting jack, supplied by two different sources of pressure.

Figure 16 hows a differential double-acting jack, one compartment of which is constantly in communication with a source of pressure.

Figure 17 is a modification of the form shown in Figure 2 in which only the circuit-making stroke of the circuitbreakeris controlled.

Figure 18 is a modification of the form shown in Figure 13 in which only the circuit-breakingstroke of the circuitbreaker is controlled.

Figure 1 shows by way. of example, which is,,of course,

non-limiting, a single-pole circuit-breaker which can be controlled by a device according to the invention. This circuit-breaker comprises essentially, a movable contact 1- sliding in a contact sleeveZ connected to one of the conductors 3 of the circuit to be broken. In the circuitmaking position illustrated, the movable contact 1 isengaged in a tulip-shaped fixed contact 4, electrically connected to the other conductor 5 of the. said circuit. In the example illustrated, the movable contact Iris rigidly connected to a control rod 6 by means of an insulating member 97. In the usual manner, the. movable contact 1 and the insulating member 97 are immersed in oil as indicated at 98 and 99 respectively.

In all the embodiments illustrated-in Figures 2, 5 and 10 to 18 and described below, it is assumed, by way of simplification, that the rod 6. is connectedrdirectly to the piston of a control jack and consequentlythis rod is indicated on the various figures by the same reference numeral (6) as in'Figure 1. It is obvious that the-invention isin no way limited to this mode of connection and that any kinematical device, which may or may not be a step-up device, could be interposed between the controljack and the rod 6, the gear ratio being variable in the course of the stroke of the movable contact. Moreover, it would also be possible to provide 'a plurality of jacks, for example single-acting jacks, connected to the rod 6 by a kinematical device.

Moreover, in order to simplify the description, it is assumed that the upward stroke of each of the jacks illustrated in Figures 2, 5 and 10 to 18, effects the circuitmaking stroke of the circuit-breaker in Figure 1 and that the downward stroke of each of said jacks efiects the circuit-breaking. It is obvious that this arrangement could be reversed without in any way changing the hydraulic circuits illustrated.

In the embodiment illustrated in Figure 2, the control of the rod 6 is effected by a single-acting jack, the cylinder of which is seen at '7 and the piston at 8, connected to the rod 6 by its rod 9. At 10 is seen a spring adapted, to effect the circuit-breaking stroke as oil is evacuated from the jack 7, while the subjection to pressure of said jack etiects the circuit-making operation. The hydraulic circuit in Figure 2 comprises a resilient accumulator of hydraulic power 11 fed by a pump 12 from a reservoir, with liquid such as the oil 13. The accumulator l1 feeds the jack 7 by means of pipes M, 15 and 16, under the control of a valve 17 of a set of valves 18. The evacuation of the oil from jack 7, takes place through the

pipes

16, 19 and 20 under the control of the valve 21 in the set of valves 18. Still for the sake of simplification, it is assumed that the valves 17 and 21 are controlled by simple push-

buttons

22 and 23 respectively.

According to the invention, in this example, a calibrated permanently open restriction means formed by a sharp-edged orifice 24 is interposed in the path of the liquid under pressure feeding the jack '7 and a second calibrated permanently open restriction means formed by another sharp-edged orifice 25 is interposed in the evacuation path of the liquid coming from the jack 7. The orifices 24 and 25 are illustrated diagrammatically in Figure 2 in the form of simple apertures pierced in diaphragms inserted, in the example illustrated, in the

pipes

15 and 19. In Figures 2, 5 and 10 to 18 the calibrated sharp-edged orifices have been shown in the shape of a gap in a single solid line. In practice each of the orifices may consist of a passage such as 26 (Figure 3) drilled in a member 27 interposed in the path of the liquid to be controlled.

The power of the speed of the movable contact means, in function of which the intensity of the braking action exerted by the calibrated sharp-edged orifice varies, increases as the ratio between the length and the cross section of the passage decreases; the said power tends to become equal to 2 as the said ratio tends towards 0.

According to another preferred embodiment, each orifice such as 28 (see Figure 4) may be drilled in a detachable diaphragm 29 which may, for example, be held by means of screw-bolts 32, between

flanges

30 and 31 of two lengths of pipe joined together by the said flanges. This last arrangement is particularly advantageous and permits designing a sharp-edged orifice ensuring a braking intensity practically proportional to the square of the speed of the movable contact.

Actually, if x is the distance covered by the movable contact at the start of its stroke, and u the volume of oil displaced by the jack since the start of its stroke, for a given value of x, an elemental volume du will correspond to an elemental displacement dx. There will be a ratio k between a'x and sin and this ratio will be constant if the reduction in movement between the rnovable contact and the movable member of the jack is constant; said ratio will be variable as a function of x if the said reduction is not constant; this ratio provides the Formula 1:

dx=k du (1) It v is the speed of the movable contact, e the delivery of the jack, there is obtained a relationship expressed by the Formula 2:

tit being the elemental time.

If the flow of liquid were controlled by passing it through a conduit having its length tending towards inf. co) the loss of p would tend towards the following limit:

0 being a constant coefificient and m a coefiicient depending on the viscosity of the liquid. For a conduit of a great length the actual value of the loss of pressure would be but slightly difierent from this theoretical value. In the case of calibrated permanently open restriction means formed by sharp-edged orifices the loss of pressure p is given by the Formula 4:

0 being a coefiicient independent of viscosity. Since the viscosity of a liquid depends on its temperature, it is thus possible to provide a loss of pressure practically independent of the temperature, experience proving that under these conditions the rate of flow obtained for a given loss of pressure obeys almost strictly the law of dynamic flow of a liquid through a theoretic sharp-edged orifice.

By combining the Formulae 3 and 4 on the one hand and 2, on the other hand, Formulae 5 and 6 are obtained:

p= imv (5) giving in both cases the loss of pressure as a function of the speed of the movable contact means of the circuit breaker.

The sharp-edged orifice corresponding to Formula 6 is particularly advantageous since it permits a greater initial acceleration than when the speed is controlled by means of a long passage. Actually, if pc is the loss or" pressure corresponding to the stabilized speed, when the instantaneous speed is equal to /s of the said stabilized speed, the Formula 5 will give a loss of pressure equal to /3 of 20, according to Formula 7:

while Formula 6 (case of sharp-edged orifice) will give a loss of pressure equal to ,6 of po according to Formula 8:

As a specific illustrative example I have given hereafter the characteristics or a 70,000 volt high voltage line circuit-breaker which is equipped with a control device according to the invention, of the type described above with reference to Figure 2, the said device including a hydraulic jack directly acting upon the movable contact rod and which has been found utterly satisfactory for both permanent and transient functions defined at the beginning of this specification (rating current 1200 amperes, cut-oil? ctu'rent 20,000 amperes).

The control device is equipped with an air-and-oil accumulator of the type described in the above cited references, having a maximum pressure of about 4,300 p.s.i. and a minimum pressure of about 2,800 p.s.i. The strength of the circuit-breaking spring when fully com pressed is about 1,100 lbs.

The single connecting jack has a cross section of about .9 sq. in. and a stroke (equal to that of the movable con- 7 feeding of the jack and, hence, the circuit-making speed has a diameter of about The calibrated orifice controlling the delivery of the jack and hence the circuitbreaking speed has a diameterof about The length of both calibrated orifices is about The movable contact rod has a diameter of about 1 and its weight is about 7 kgs. Themoving parts of the jack weigh about 10 lbs. and the spring has an equivalent mass of about 5 lbs., which gives an overall weight of the moving assembly of about 22 lbs.

With the specific control device hereabove described, at the beginning of the circuitbreaking stroke, the whole initial strength of the spring, viz. 1,100 lbs. is available. If the frictions after starting are estimated to about 110 lbs, the movablecontact will be actuated by a resultant force of:

1,l00ll0==990 lbs.

so that the said movable contact is subjected to an initial acceleration of:

and after the first /s of its circuit-breaking that corresponds substantially to the above-mentioned period of initial acceleration, to an average velocity of about -.t3' per second.

In the embodiment shown in Figure 5, the structure of the control jack is identical with that in Figure 2, but a slightly diflerent arrangementis adopted for the hydraulic circuit enabling the calibrated orifices to be interposed in the immediate vicinity of the jack 7. For this purpose and inorder to effect the supply and drainage of the liquid through a single pipe 33, two non-return valves 3d, are provided, interposed in two branches from the said single pipe 33, namely 36 and 37, in which branch pipes the constriction means are likewise interposed, being designated respectively by the reference numerals 3% and 39. In the example illustrated, the jack 7 is connected to the two

branch pipes

36 and 37, likewise by means of a single pipe 33a. As a resultof the presence of the non-return valves 34 and 35, the calibrated aperture 38 exclusively controls the drainage delivery, while the calibrated aperture 39 exclusively controls the supply delivery.

The air-and-oil accumulator shown in Figure 6 is provided with three special packing devices, as follows:

(a) as described in the first reference hereabove cited, the piston of the accumulator comprises a packing ring 103 made of plastic material and mounted in an annular groove 104 of the lower face 105 of the piston. This packing ring is continuously subjected through a pressing member 101 to'the action of a spring 102 bearing on the upper face 106 of the piston and that compresses it axially.

, (b) the air compartment, as described in the second reference hereabove cited, is kept tight by means of a cylinder head 107 freely fitted at the air side extremity of the cylinder 108 and which is prevented from escaping by means of a nut 109, a packing ring 110 made of plastic material being interposed between the nut 10% and the cylinder head 107. Under these conditions, the head 107 is pressed against the packing ring 110 with a pressure that increases as the air pressure in the accumulator increases.

wardly by means of-a threaded cylinder head 112. The

, 8 V pipe conducting oil from and to the accumulator, is shown at 113. A

This" oil-and-air accumulator maybe used as a source of resilient power for actuating the movable contact Another example of a source of resilient power,

adapted to be used under the same conditions, is the spring hydraulic accumulator shown in Figure 7. The said spring accumulator essentially comprises a cylindrical casing 114 provided with a long axial hollow embossment 115, which acts as a cylinder for a plunger 116 having a packing terminal pad 117. A compression spring 118 compresses the oil contained in the compartment 119 of the cylinder through a flanged sleeve 120 and the piston 116 on which the said sleeve bears. The spring 118 bears at one end on the flange 120a of the sleeve 120 and at its other end on the head 121 of the cylindrical casing :114. g

In Figures 8 and 9 is shown a circuit-breaker according to the invention of the general type of Figure l.

The circuit-breaker shown in Figures 8 and 9 differs from all known circuit-breakers by the quality of its electrical contacts obtainable only by the use of the control device with hydraulic transmission according to the invention.

In the example shown the tulip-shaped stationary contact generally designated by 4 and the connecting sleeve generally shown at 2, in which the movable contact rod 1 is slidably mounted, are both constituted by a plurality of members 122 having the general shape of shoes hearing against the cylindrical wall periphery of the said rod around which they are suitably distributed. Each member 122 is urged towards the axis of the rod 1 by a strong compression spring 123 having a high elasticity.

Owing to this arrangement, each member 122 is pressed on the rod 1 with a predetermined force; now, when'two metal surfaces are pressed against each other with a predetermined force, the deformation of both contact surfaces produces a metal-to-metal contact area that depends only on the nature of the metals and the contact pressure. If the latter is sufficient there will be obtained a metal-to-metal contact area suflicient to ensure without excessive heat the passage of the strong electrical current flowing through the line.

70,000 volt high voltage line circuit-breaker previously described, the permanent function of which is to ensure" the passage through its contacts of a rating current of 1200 amperes, the sum of the forces pressing the 'members 122 of each

contact

2 and 4, has been chosen equal to about 550 lbs. device hereabove described in which at the beginning of the circuit-breaking stroke a motive power of 1,100 lbs. is available, would permit overcoming a static friction resistance of 550 lbs. for each contact, so that it permits using an overall force of contact pressure having the same value.

Figures 10 and 11 illustrate another embodimentin which the hydraulic control device comprises a doubleacting jack 40, the piston 41 of which is connected directly to the rod 6, which is rigidly connected to the movable contact to be controlled. In this embodiment, each of the

compartments

42 and 43 of the jack 40 may either be brought into communication with a source of liquid under pressure, not illustrated in this figure, or set to exhaust, the supply to and the drainage from each of the said compartments being effected through a single pipe, namely 44a, 44b, for the

compartment

43, and 45a, 45b for the compartment 42, under the control of a set of valves 46 selectively eitecting either the bringing of one pipe 47, connected to the source, into communication nectcd to exhaust, into communication with the pipe 45a Precisely, the specific control (Figure 10), or, on the other hand, the simultaneous establishment of communication between the pipes 47 and 45a on the one hand, and 48 and 44a on the other hand (Figure 11).

The control of the set of valves 46 is illustrated, still by way of simplification, in the form of two push-buttons, respectively 49 and 50, the depression of the push-button 49 effecting the establishment of the communication described above, illustrated in Figure 10, and determining the circuit-breaking stroke of the circuit-breaker, while the depression of the bush-button 50 determines the establishment of the communications described above, illustrated in Figure 11 and determining the circuit-making stroke of the circuit-breaker.

In the embodiment shown in Figures 10 and 11, the calibrated

orifices

51 and 52 are respectively provided in the

non-return valves

53 and 54, the direction of action of said non-return valves being selected in such a manner that the calibrated

apertures

51 and 52 only control the drainage from the

compartments

43 and 42 respectively.

Figure 12 illustrates a modified form of construction of the device which has just been described with reference to Figures 10 and 11, and only differs therefrom in the direction of action of the

non-return valves

53 and 54, this direction being chosen in such a manner that the calibrated

orifices

51 and 52 only control the supply delivery to the

compartments

43 and 42 respectively.

Figure 13 illustrates another modification of the device in Figures 10 to 12, in which only the compartment 42 of the double-acting jack is controlled. In the example illustrated, this control affects both the supply delivery to said compartment by means of a calibrated orifice 55, and the drainage delivery from the said compartment by means of a calibrated orifice 56. Non-return valves, 57 and 58 respectively, are provided to prevent the supply delivery from passing through the orifice 56 and the drainage delivery from passing through the orifice 55.

Figure 14 illustrates an inverted arrangement of Fig ure 13, that is to say in which only the compartment 43 of the jack is controlled, the control applying, in this example again, both to the supply and to the drainage.

In Figure 15, the device comprises a doubleacting jack 59, which is non-difierential, that is to say in which the piston 60 is provided with two opposed rods 61, 62 which are of the same cylindrical section, the rod 61 being assumed to be connected to the rod 6 of the circuit-breaker in Figure 1, for example. One of the compartments, 63, of the said jack is permanently connected to a first source of liquid under pressure, consisting, in the example illustrated, of an hydraulic accumulator 64. The other compartment, 65 of the jack 59 is controlled, in the same manner as in Figure 13, by two calibrated

orifices

55 and 56, the action of which is selected by

nonreturn valves

57 and 58 respectively. The supply to or the drainage from the jack 65 are eifected under the control of a set of valves'66 supplied from a second source of liquid under pressure consisting, for example, of a hydraulic accumulator 67 fed by a pump 68 from a reservoir 69. In Figure 16, the control jack 70 is differential, that is to say it comprises a cylindrical compartment 71 and an annular compartment 72, the latter being permanently in communication, through

pipes

73, 74 and 75, with a source of liquid under pressure consisting of a hydraulic accumulator 76 fed by a pump 77 from a reservoir 73. The cylindrical compartment 71 of the jack 79 may be brought into communication either with the accumulator 76, or with the reservoir 78, under the control of a set of valves 79. In this embodiment, two calibrated orifices 8t) and 81 control respectively and exclusively, as a result of the presence of non-return valves, 82 and 83 respectively, the former the drainage of the compartment 71 and the latter the supply to the said compartment.

Figure 17 illustrates a control device identical with that in Figure 2 except that it only comprises one calibrated orifice 24 controlling the. supply to the compart ment 87 of the jack 7.

In a similar manner, Figure 18 illustrates a device identical with that in Figure 13, except that only the drainage from the compartment 42 is controlled by an orifice 56, a non-return valve 58 forcing the drainage delivery to pass through the calibrated orifice 56 while it allows the supply delivery to pass freely through a pipe 84 bypassing the calibrated orifice 56.

The invention is in no way limited to the examples described and illustrated; it may be modified in many ways available to one skilled in the art, according to the applications envisaged and without going outside the scope of the invention.

In particular, although, as already indicated, the control may be applied indiscriminately either to the supply to or to the discharge from a jack, for either stroke of the movable contact of a circuit-breaker, nevertheless, in certain cases, it is a greater advantage to control the circuit-breaking stroke by inserting the calibrated orifices according to the invention in the evacuation system of the jack to enable the said orifices to play their stabilizing part even in the presence of parasitic forces acting in the direction of the circuit-breaking stroke.

Furthermore, in Figures 15 and 16, the control of the supply and of the evacuation could be effected equally well in respect of the compartments 63 (Figure 15) and 72 (Figure 16) as in respect to the compartments 65 (Figure 15) and 71 (Figure 16) as illustrated.

What is claimed is:

1. In combination, with a movable member adapted to be moved in two directions, a liquid pressure motor operably coupled with said member for moving the same in at least one of said two directions, a source of liquid under pressure, conduit means in communication between said source and motor for conducting liquid under pressure thereto, control valve means in said conduit means operable when open to permit liquid under pressure to flow from source to said motor to initiate movement of said member in said at least one direction, said source being under a constantly available pressure far in excess of that required to move said member at a speed higher than the optimum speed desired, and a calibrated permanently open restriction means formed by a sharp-edged orifice constituting a speed limiting orifice disposed in said conduit means between said control valve and said motor and operable to establish flow characteristics in the conduit means to apply a braking effect on said member that increases at a rate which is higher than the rate of increase of the speed of movement of the liquid in the conduit means without adversely limiting the initial acceleration of the member.

2. In combination with a movable member adapted to be moved in opposite directions relative to a desired position, a piston and cylinder means, one of said means being permanently kinematically connected to said member, a source of liquid under a constantly available pressure, force applying means for normally urging said memher to move in one of said two directions at a speed higher than the optimum speed desired, a tank, valve controlled conduit means operable when open to respectively provide communication between said source and said cylinder, or between said cylinder and said tank, whereby flow of liquid under pressure from said source to said cylinder etfects movement of said member in the other of said two directions, said source being under such pres sure as to be capable of moving said member at a speed higher than the optimum speed desired, and when said tank is in communication with said cylinder said force applying means effecting movement of said member in said one direction, said member being normally retained in said desired position by pressure of liquid in said cylinder, and in each of said conduit means a calibrated permanently open restriction means formed by a sharpedged orifice constituting a speed limiting orifice opera- 11 ble to establish flow characteristics in the conduit means to apply a braking effect on said memberthat increases at a rate which is higher. than the rate of increase of the speed of movement of the liquid in the conduit means, without adversely limiting th'e initial acceleration of the member.

3. In combination with a movable member adapted to be moved inopposite directions relative to a desired position, a piston and cylinder means, one or" said means being permanently kinematically connected to said member, a source of liquid under a constantly available pressure, force applying means for normally urging said member to move in one of said two'directions at a speed higher than the optimumspeed desired, a tank, conduit means including portions operable when open to respectively provide communication between said source and at least one end of said cylinder, or between said end of said cylinder and said tank, whereby flow of liquid under pressure from said source to said one end of the cylinder eifects movement of said member in the other of said two directions, valve means controlling said conduit means, said source being under such pressure as to be capable of moving said member at a speed higher than the optimum speed desired, and when said tank is in communication with said cylinder said force applying means eitecting movement of said member in said one direction, said member being normally retained in said desired position by pressure of liquid in said cylinder, and in at least one portion of said conduit means a calibrated permanently open restriction means formed by a sharp-edged orifice constituting a speed limiting orifice operable to establish flow characteristics in the conduit means to apply a braking eifect on said member that increases at a rate which is higher than the rate of increase of the speed of movement of the liquid in the conduit means, without adversely limiting the initial acceleration of the member.

4. In combination with a movable member adapted to be moved in opposite directions relative to a desired position, a piston and cylinder means, one of said means being permanently kinematically connected to said mem ber, a source of liquid under a constantly available pressure, force applying means for normally urging said member to move in one of said two directions at a speed higher than the optimum speed desired, a tank, conduit 12 a means including portions operable when open to respectively provide communication between said source and at least one end of said cylinder, or between said end ofsaid cylinder andsaid tank, whereby flow of liquid under pressure from said source to said one end of the cylinder effects movement of said member in the other of said two directions, manually operable valve means controlling said conduit means, said source being under such pressure as to be capable of moving said member at a speed higher than the optimum speed desired, and when said tank is in communication with said cylinder said force applying means efiecting movement of said memher in said one direction, said member being normally retained in said desired position by pressure of liquid in said cylinder, and in each portion of said conduit means between said manually operable valve means and said one end of the cylinder, a calibrated permanently open restriction means formed by a sharp-edged orifice constituting a speed limiting orifice operable to establish flow characteristics in the conduit means to apply a braking effect on said member that increases at a rate which is higher than the rate of increase of the speed of movement of the liquid in the conduit means, without adversely limiting the initial acceleration of the member.

7 References Cited in the file of this patent UNITED STATES PATENTS 674,858 Trier May 28, 1901 353,785 Henry May 14, 1907 1,037,039 Murphy Aug. 27, 1912 1,993,195 Temple Mar. 5, 1935 2,127,501 Dall Aug. 23, 1938 2,275,872 Trencham et al. Mar. 10, 1942 2,523,572 ians son Sept. 26, 1950 2,533,559 Chipman Dec. 12, 1.950 2,548,221 Kelle Apr. 10, 1951 2,669,628 I Van Sickle Feb. 16, 1954 2,736,295 Peek Feb. 28, 1956 FOREIGN PATENTS 726,789 Germany Oct. 26, 1942 1,056,143 France Oct. 21, 1953 1,098,565 France Mar. 9, 1955