FR2613122A1 - DIFFERENTIAL HYDRAULIC CYLINDER FOR CONTROLLING ELECTRIC CIRCUIT BREAKERS - Google Patents

Abstract

Jack in which the annular chamber 14 of the cylinder 4 is always subjected to the high pressure of an accumulator 18. The piston 6 of the jack is free of any sealing lining in regard to the inner surface 38 of the cylinder and this piston mechanically actuates a valve 42 which sealingly closes off a seat 44 surrounding the feed/purge orifice 28 of the cylinder, at the bottom end of travel of the piston 6. The invention allows the cylinder 4 to be made in the form of a casting whose inner cylindrical surface 38 requires no accurate machining such as grinding or honing.

Description

Differential hydraulic cylinder for the control of circuit breakers

  electric. The present invention relates to a differential hydraulic cylinder for the control of electric circuit breakers, of the type in which the annular chamber of the jack, defined by the inner surface of the cylinder of the jack and by the outer surface of the outgoing rod of the piston, is connected in

  permanence to a high-pressure hydraulic source.

  The outgoing rod of the cylinder is coupled to the moving contact of the circuit breaker and a supply / purge port, formed in the bottom of the main chamber of the jack, can be selectively connected to said high pressure source ("Supply" position) to push the piston , or to a low pressure tank ("Purge" position) to let the piston return to its initial position under the effect of the high pressure P

prevailing in the annular chamber.

  The first maneuver brings out the piston rod and brings the circuit breaker into the engaged or closed position, while the second maneuver tilts the rod into the cylinder and

  brings the circuit breaker to the tripped or open position.

  Such hydraulic circuit breaker controls, and differential cylinder, are well known and have been described for example in French Patent No. 2,317,532 (or U.S.

NR 4.026.523).

  2 zo2613122 The realization of the differential cylinders, for this application, presents constructive difficulties, in particular because they must guarantee a permanent and absolute seal, during very long durations, despite the very high hydraulic service pressures P, of the order of 300 to 400 bar and high speeds of the order of 10 to 15 meters / second.These cylinders must therefore comprise at least, as shown in the aforementioned prior patent, a first seal at the passage of the outgoing rod through the bottom of the cylinder and a second seal on the piston. The first of these gaskets is relatively easy to achieve to obtain an absolute seal. Indeed, this seal is fixed and it is easy to obtain a rectified and polished piston rod that does not wear the seal. On the other hand, the piston rod, which is solid, does not vary in diameter under the effect of the pressure and the liner is practically not subjected to pressure variations since the annular chamber is always subjected to pressure permanent P supplied by an oleo-pneumatic accumulator constituting the source of fluid

hydraulic pressure.

  The second of these seals, that is to say that ensuring the seal between the piston and the cylinder, must withstand much more operating conditions

difficult.

  Indeed this seal, mounted on the piston, is movable and is subject to high acceleration and shock because the maneuvers are performed in very short times, less than a few hundredths of a second; it is subject to high pressure variations between the engaged and the triggered positions; the cylinder expands under the influence of pressure <of the order of 300 to 400 bar); the inner surface of the cylinder must be perfectly ground and polished to preserve the integrity of the liner; finally, at the end of trigger stroke, the seal can be subjected to considerable overpressures (several thousand bar) which are prejudicial to the behavior of the seal if we do not take certain precautions, which lead to structural complications. Heretofore, the piston linings have only been satisfactorily completed in relatively complicated forms (about which many patents have been filed) and costly. Preferably, so-called "spring" gaskets are used which are formed of one or more rings of elastic material held compressed by a spring. An example of such a spring pad is shown in Figure 2 of the aforementioned prior art. In any case, such piston seals can only cooperate with a cylinder surface

perfectly polished.

  Apart from the disadvantage of the difficulty of producing the piston liners and the surface condition of the cylinder, the differential cylinders also have the drawback that a large cross-section duct or passage must be provided for rapid transfer. at high speed, between the master bedroom and

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  the annular chamber of the cylinder. Indeed, the engagement or tripping maneuvers of the circuit breaker (that is to say, the outward stroke or the return stroke of the cylinder piston) must be performed in a very short time, of the order of a few hundredths. second, which requires avoiding any braking by

slowed circulation of oil.

  Hitherto, this transfer passage of large section has usually been made by means of a jacket surrounding the cylinder of the cylinder, the annular gap between the jack and the jacket itself constituting this passage. An example of such an embodiment, which further complicates the construction of the differential cylinder, is shown in Figure 3 of the aforementioned prior patent. The present invention aims to overcome the disadvantages of differential hydraulic cylinders known to date and allow a much simpler and more economical construction while ensuring reliability

  better thanks to the reduction of the number of constituents.

  In the text that follows, the term "engagement stroke" will be used to denote the displacement of the piston from the bottom of the main chamber towards the bottom of the annular chamber and the term "trigger stroke" to designate the

  reverse movement of the piston in the opposite direction.

  The invention relates to a. differential hydraulic cylinder of the type defined in the foregoing in which the piston is devoid of a seal cooperating with the inner surface of the cylinder of the cylinder, and wherein the piston

2613122

  is mechanically associated with a valve ensuring the permanent sealing of the supply / purge port of the main chamber of the cylinder when the piston is in the end position of

trigger stroke.

  According to this arrangement, the outer cylindrical surface of the piston is in substantially sliding contact

  direct, metal on metal, with the inner surface of the cylinder.

  In the absence of any seal, there is of course an oil leak between the piston and the cylinder, but the inventor discovered that this leak was negligible during the movements of the piston, in one direction or in the other, who

  last only a few hundredths of a second.

  In the "engaged" position, the pressures (P) are identical on both sides of the piston, so it does not occur

  no leak on both sides of the piston.

  In the "triggered" position, the pressure P prevailing on the annular face of the piston reaches the opposite face of the piston, because of the leakage existing between the piston and the cylinder, but it is then stopped by the tight closure of the valve which has been actuated by the piston at the end of its trip stroke. This avoids any permanent oil flow in the tripped position, which would be unacceptable on a circuit breaker control. According to a simple solution, the valve is integral with the opposite opposite face of the piston and the valve seat is formed at the periphery of the supply / purge port of the piston.

master bedroom.

  As will be seen in what follows this arrangement of the piston without lining provides other important advantages, including the possibility of making the cylinder in the form of a casting requiring only simple machining, which would be incompatible with a piston seal. Furthermore, it is possible to directly bring the transfer channel of strong section between the main chamber and the annular chamber of the jack, which reduces

  considerably the number of parts constituting the cylinder.

  The invention will be better understood on reading the

  following description and examination of the accompanying drawings on

  which: Figure 1 is a schematic representation of a differential cylinder according to the prior art and a hydraulic control circuit breaker known in which is incorporated the cylinder. FIG. 2 is a sectional view of a differential jack

according to the present invention.

  FIGS. 3 and 4 are partial views showing two other embodiments of the closure valve actuated by

the piston.

  Figure 5 is an axial sectional view of a differential cylinder according to the invention with cylinder block come from foundry. FIG. 6 is a sectional view along line 6-6 of FIG.

Figure 5.

  FIG. 1 shows, for locating the prior art, the known hydraulic diagram of a control of

  circuit breaker with differential jack.

  This control comprises a differential cylinder 2 comprising a cylinder 4 (a piston 6, an outgoing piston rod 8 which is coupled to the mobile contact 10 of a circuit breaker to establish or cut the circuit between the fixed contacts 12-12 'of the circuit breaker The position shown in FIG. 1 is the tripped position of the circuit-breaker (open contacts), in which the piston 6 is close to its lower position in the cylinder, The annular chamber 14 of the jack situated above the piston 6 and surrounding the piston rod 8 is permanently connected, via a pipe 15, to a high-pressure oleopneumatic accumulator 18 (for example 300 to 400 bar), the pressure in this chamber 14 tending to bring the

  circuit breaker in the tripped position.

  In the main chamber 20 of the cylinder is provided a passage or orifice 28 which can be connected selectively, by a supply / purge line 22, on which is interposed a three-way valve 24, or, via a pipe 22 'and a transfer line 16, to the accumulator 18 or, via a pipe, to a low-pressure bleed tank 26 (position

shown in Figure 1).

  The operation is sufficiently known to suffice to indicate that the setting in the supply position of the valve 24 establishes the HP in the chamber 20 on the large surface of the piston 6. The latter is pushed back up to against the reduced force exerted by the same HP on its surface

  annular, which brings the circuit breaker into the engaged position.

  The triggering is obtained by setting bleed position of the valve 24 (position of Figure 1). The HP permanently prevailing in the annular chamber 13, pushes the piston 6 downwards, the oil contained in the main chamber 20 of the cylinder being purged rapidly at high speed, thanks to the fact that the supply / purge port 28 and the associated hydraulic units 24-25 have strong sections, which allows the triggering maneuver to be carried out in a very short time,

a few hundredths of a second.

  A hydraulic control with differential jack, for circuit breaker, of the above type has been described for example in French Patent 2,317,532 (or US Pat. No. 4,026,523) and shown

in Figure 3 of these documents.

  The known differential cylinders, like that shown in FIG. 1, comprise a seal 30 at the passage of the outgoing rod 8 through the bottom 32 of the jack and, also, a seal 34 on the piston 6 to ensure the seal between the piston and the inner surface of the cylinder 4. This seal has been represented in the form

  known from a spring pad of the kind shown in FIG.

  re 2 of the aforementioned prior patent and it must ensure the permanent sealing of the chamber 14, under pressure

  from about 300 to 400 bar, in the triggered position shown.

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  The appended FIG. 2 is a sectional view of a differential jack according to the invention, all the elements already described.

  bearing the same reference number.

  As can be seen a seal 30 is provided at the passage of the piston rod 8 through the bottom vitreous 32 of the cylinder 4, but the piston 6 of the cylinder is devoid of any seal ensuring the seal between the piston 6, metal, and cylinder 4, metal. It follows that the outer cylindrical surface 36 of the piston 6 slides substantially directly, metal on metal, on the inner surface 38 of the cylinder 4, but without sealing between these two surfaces and without the surface 38 has a machining

particularly accurate.

  The piston 6 carries, under its lower face 40, a projecting part forming a truncated-conical valve 42 adapted to close, at the end of the triggering stroke (position shown in FIG. 2), the supply / purge orifice 28, which is at the low pressure in the end position of the

  trigger shown in solid lines in FIG.

  The valve 42 may fit sealingly on a frustoconical valve seat 44 formed on the edge of the orifice 28, in the screwed bottom 46 of the cylinder. Of course, the valve seat 44 may be constituted by an insert, made of

  hardness appropriate to that of the valve, in the bottom of the cylinder 46.

  In the engaged position of the circuit breaker, the passage al. imentation / purge 28 of the cylinder is connected to the accumulator 18 by the pipes 22-22'-16 and the valve 24 in the supply position. The piston 6 is pushed upwards in the cylinder and occupies the position shown in dashed lines in Figure 2 o the piston is designated by the reference 6 'and the valve that carries it by the reference 42'. The same pressure P prevailing on both sides of the piston F1 force exerted upward on the cylinder to maintain the closed circuit breaker is: F1 = P.Si-P (Si-s) = Ps (E, being the surface of the piston and s the surface or section

  of the rod 8) as is usual on a differential cylinder.

  In this position, which is the normal service position of the circuit breaker and which can last for weeks, the absence

  of seal on the piston is without

  deny since the same pressure P reigns below the piston (in the main chamber 20) and above the piston (in the chamber

ring 14).

  To trigger the circuit breaker, the supply / purge / purge passage is set by means of the valve 24 and the piston is pushed down by the force F2 = P (S1-s), the purge pressure P. under the piston being substantially atmospheric pressure, at least during the beginning of the acceleration of the piston. At the end of the trigger stroke,

  the solid line position shown in FIG.

  pet 42 applies to its seat 44 and sealingly closes the passage 48, which determines at the same time a limit stop piston stroke. The pressure P permanently prevailing in the annular chamber 14 can not escape through the purge passage and there is therefore no permanent circulation of oil which should be compensated by a pump (not shown)

recharging the accumulator 18.

  The pressure P prevailing in the annular chamber 14 can at most gain, by the leak existing between the piston 6 and the cylinder, the lower face of the piston 6, that is to say the volume, at this reduced moment, of the main chamber 20. The piston 6 is therefore subjected to pressure P both on its upper annular surface "Si-s" and on its annular surface

  lower "S-S2", S2 being the section of the valve 42.

  To obtain an application force sufficient to ensure a good seal of the valve 42 on its seat, the section S2 of the valve must be significantly greater than the section s of the rod, for example of the order of 50%. Good results have been

  obtained with values between 25% and 100%.

  During piston engagement or trip trips, which last only a few hundredths of a second, oil leaks that occur between the piston and cylinder represent a negligible volume that does not slow down the

maneuvers of the cylinder.

  It can thus be seen that the combination consisting of a piston without gasket and a valve, actuated mechanically by the piston, to close the supply / bleed orifice at the end of the triggering stroke, makes it possible to

12 2613122

  fulfill all operating and safety conditions

  hydraulic circuit breaker control.

  Ion only eliminates a piston seal, delicate realization, but still; as indicated with respect to the cylinder 4 in FIG. 2 and as will be seen in more detail with reference to FIGS. 5 and 6, all

  precise machining (lapping) of the inner surface 38 of the cylinder.

  FIG. 2 shows a frustoconical valve 42 connected to the piston, but it is possible to choose any other type of valve, for example a valve of the ball valve type in which the shutter member is a sphere or a portion of a sphere 48 ( FIG. 3) or a plane valve (FIG. 4) consisting of the upper face 50 of the bottom 46 of the cylinder against which a circular lip 52 machined in the lower surface 54 of the piston 6 is applied. Of course, the reverse arrangement, in which the sealing lip would be carried by the face

  upper 50 of the bottom of the cylinder could also be used.

  It can be provided, to cooperate with the lip 52, a pad

  annular 56 of suitable material.

  It should be noted that, even with a plane valve, the tightness at closing of the valve is easy to achieve thanks to the fact that, in the low position of the piston 6, the guiding of this piston is ensured at two distant points ( on the one hand, the lining 30 of the rod 8 and, on the other hand, the contact between the piston and the cylinder). Thus, the parallelism of the bearing face

  The valve is reproduced faithfully at each maneuver.

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  The valve may be integral, or integral, of the piston 6, as shown in Figures 2 and 4, or it may have a certain degree of freedom, as shown in Figure 3 o the hemispherical valve 48 is engaged in a housing 58, formed in the piston 6, where it is retained by an elastic ring 60. Finally, it is possible, as in FIG. 3, to provide a spring 62 interposed between the valve 48 and the piston 6 so that the valve closes on its seat 44 a little before the end of stroke of the piston to limit the end shock

running on the flapper.

  Finally, according to another variant, not shown, the valve (42 or 48), instead of being directly carried by the piston, can be actuated by the latter, at its end of stroke, by a member, for example a rod order, carried by the

piston.

  It should be recalled here that, in the diagram of FIG. 2, the pipe 16, which is connected to the orifice 64 opening into the annular chamber 14 of the cylinder 4, must be a pipe with a large cross-section to allow rapid transfer.

  oil between the two chambers 14 and 20.

  FIG. 5 is a sectional view of a preferred embodiment of the invention in which the cylinder 4 of the jack is

  a piece coming from a foundry and not a steel tube.

  In this figure there is shown, in the left part, the piston 6 in the upper position (engaged position) and, in the right part, the piston 6 in the low position (released position). The piston 6 carries on its underside, a frustoconical valve 42 which cooperates with a frustoconical seat 44 cut on the edge of the supply / purge port 28 in the plug 46

forming the bottom of the cylinder.

  In the piece of cast iron forming the cylinder 8, the transfer channel 16 ', of large section, is cast-in, which therefore no longer needs to be connected to the orifice 64 of the annular chamber 14 as separate constituent. Figure 6

  shows in cross-section along the line 6-6 of the

  re 5; the transfer channel 16 'inside the core block

4.

  The inner cylindrical surface 38 of the cylinder block needs to undergo simple and economical machining, without lapping or polishing, since no lining on the piston 6 does not risk

  to be damaged by imperfect machining of the cylinder.

  We thus arrive at a constructive solution much less expensive than that of the differential cylinders known until now, while maintaining the qualities of safety and reliability

  required for the control of electric circuit breakers.

1d5 2613122

REPVIDICATIOIS

  1. Differential hydraulic cylinder, for control oleo

  pneumatic circuit breaker circuit which comprises a cylinder (4), a piston (6) and an outgoing piston rod (8) defining, in the cylinder, an annular chamber (14) on one side of the piston and a main chamber (20). ) on the other side of the piston, said outgoing rod (8) being coupled to the moving contact (10) of the circuit breaker, said annular chamber (14) being permanently connected to a source (18) of high pressure hydraulic fluid and said chamber main cylinder (20) comprising, in the bottom (46) of the cylinder, a supply / purge port (28) of said chamber (20), said differential cylinder being characterized in that the outer cylindrical surface (36) of the piston ( 6) is substantially in non-sealed, metal-on-metal, direct sliding contact with the inner surface (38) of the cylinder (4), said piston being free from gasket with the cylinder, in that the piston is mechanically associated & a valve (42) ensuring the sealing said orifice (28) at the end of the return stroke of the piston (6) towards said bottom (46) of the cylinder; and in that the surface (S2) of the valve (42) is of the order of 50%

  upper section (s) of the rod (8) of the piston (6).

  2. Cylinder according to claim 1, characterized in that the valve (42 48- 52) is carried by the piston (6) and projects below the main surface of the piston turned

to the master bedroom (20).

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  3. Jack according to one of claims 1 or 2,

  characterized in that the valve (42-53) is integral with the piston (6).

  4. Jack according to one of claims 1 to 3,

  characterized in that the valve (42-48-52) cooperates with a seat provided in the bottom (46) of the cylinder around the edge of the orifice (28) supply / purge, said seat constituting a stop of

limit switch for the piston (6).

  5. Jack according to one of claims 1 to 4,

  characterized in that the valve (42) is a frustoconical valve

  which cooperates with a frustoconical seat (44).

  Jack according to one of claims 1, 2, 4 or 5,

  characterized in that the valve (48) is a separate part of the

  piston and is retained in a housing (58) formed in the piston.

  7. Jack according to claim 6, characterized in that elastic means (62) are interposed between the valve

(48) and the piston (6).

  8. Cylinder according to one of the preceding claims,

  characterized in that the cylinder body (4) is a piece of

foundry.

  9. Cylinder according to claim 8, characterized in that the casting part constituting the body of the cylinder also comprises, foundry, a transfer pipe (16 ') of large section, opening into the chamber

annular (14) of the cylinder.