US1821787A - Retarding device - Google Patents

Description

Sept; 1, 1931. c. H. BLACK RETARDING DEVICE Filed m 19, 1929 Ihve'ntor': Code! Ie H. Black, b9

His Attorneg.

' tacts at high speed.

are often set up in Patented Sept. 1 193i CADELLE H. BLACK, OF BROOKLINE, PENNSYLVANIA, ASSIGNOR '10 GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK nmmme nnvrcr.

Application filed August 19, 1929. Serial No. 887,086.

My. invention relates to retarding devices, and more particularly to retarding devices of the dash-pot type which are particularly adapted for checking the motion of structure without shock within a small part of theentire range of movement, as in the operation of fluid-break switches.

In fluid-break switches, as oil switches for example, wherein high openingX speed of the movable contact is required, t e kinetic energy of the contact structure acquired during its opening movement is generally such that an appreciable rebound thereof towards the stationary contact results unless this energy is gradually and substantially completely absorbed or dissipated in some manner within a comparatively small degree of travel by the time the movable contact has reached its full open position; In other words, the mova le contact structure should engage its movement limiting means near the endof the opening stroke without appreciable impact, while-being permitted to initially move away from the stationary con- I Rebound of the movable contact is particularly objectionable in that abnormal stresses the apparatus due to the concussive force of the rebound, and moreover if the rebound is an'appreciable part of the entire stroke, arcing between the contacts may be reestablished.

A principal object of my invention is the provision of retarding means for gradually and substantially completely dissipating the kinetic energy of moving structure within a comparatively small part of its entire travel.

Another obj ect-of my invention is the pro vision of a dash-pot structure for dissipating'within a comparatively brief interval the kinetic energy of movable switch contact structure adapted to open at varymg speeds, whereby rebound if said contact structures towards the stationary contact structure of the switch is substantially precluded.

Another obj ect'is the provision of a retarding device which is comparatively inexpensive, rugged and simple in construction.

Other objects and advantages of my invention will become apparent from the fol-1 descend rapidly, the magnitude of the magnetic forces of the lowing description taken in connection with the accompanying drawings wherein: Fig. 1 is an elevational view, partly in section, of

dashpot structure embodylng my invention;

' Fig. 2 is an elevational view, partly in section, of circuit breaker apparatus.

Referring first to Fig. 2, there is illustrated an oil circuit breaker of a well known type comprising a tank or oil-containing 'rece taclel within which the switch contacts not shown) are immersed in the oil body 2. The operating rod 3 of the movable switch con-- tact extends upwardly into a superstructure 4 withinwhich is mounted an operating mechanism comprising well known arrangements of linkages, connected to the main operating rod 5. Vertical mpvement of the rod 5 in a downward direction is effective to raise the switch rod 3 ahd thereby cause closure of the switch contacts Tripping of the rod 5 ii the usual manner by a relay orby a manual operation, causes the rod 3 to its speed being dependent on current'tending to separate the switch contacts, with the result that the movable conlimit of opening movetact approaches its A pivoted llIlk memment with great force. ber 6 operativel which is adapte 'to rotate in a counter-clockwise direction upon collapse of the linkage structure holding the movable contact in its closed position, is provided with a striking edge 7 adapted to engage the movable plunger 8 of the dash-pot structure 10 during final opening movement of the switch.

A circuit breaker and an associated dashpot structure as described above have been previously. used .and known, and broadly form no part of my resent invention.

Referring now to ig. 1, there is illustrated a retarding device 9 structure of a type particularly adapted use in connection with a circuit breaker as illustrated in Fig. 2. The structure comprises an outer housing'lO and a cover member 10a hermeticall'y'sealed with respect to the housing, as by a weld or equivalent seal 11. The housing 10 may be cylindrical, or of increasing cross-sectional area with respect toits connected to the rod 3 and comprising a dash-pot height, as of frustro-conical shape as shown, for the purpose of saving s ace and providing a compact structure. ousing 10 may also be provided with mounting lugs 12 for securing the device in any suitable manner to its associated circuit breaker structure.

Mounted within and disposed centrally of housing 10 is a cylindrical-chamber 13 extending above the upper portion of housing 10 and closed at its upper end, as by a plug member 14. Member 14 is provided wit an a erture centrally thereof for receiving the p unger rod 8 secured at its lower end to a piston member 16 mounted for reciprocal movement within cylinder 13. Piston 16 is normally and resiliently biased, as by a spring 17 towards the upper part of cylinder 13, as illustrated in Fig. 1. The cylinder 13 is provided With a restricted vent 18 adjacent the top of housing 10, the internal diameter of the cylinder adjacent the vent being somewhat increased so that piston 16 leaves the vent uncovered at all times. Vents or apertures 19 are likewise disposed in the wall-of cylinder 13 below piston 16, and as illustrated, are graduated in size, the graduations being longitudinally of the movement of the piston whereby the more restricted apertures are near the lower end of the cylinder. However, it will be apparent that the apertures maybe formed in any suitable manner-to provide a graded vent area. A preferably viscous fluid 20 as oil partially fills housing 10 and likewise cylinder 13, the apertures 19 providing communication between the inner chamber formed by the cylinder 13 and the outer chamber formed by the walls of cylinder 13 and housing 10. The outer chamber, which is annular in shape, has an air confining space 21 of predetermined size above the level of the oil body which may be in communication with the upper part of the inner cylinder through the restricted vent 18.

Assuming now that the device illustrated in Fig. 1 is mounted in the usual manner with respect to a circuit breaker structure of the type illustrated in Fig. 2, and that the circuit breaker is being tripped open, plunger 8 will be engaged by the striking edge 7 of the collapsing linkage structure as the movable contact nears the limit of its opening movement. Due to the fact that the magnetic forces tending to force apart the switch contacts are not constant, but depend upon the current which the switch is interrupting, the kinetic energy and speed of the moving switch structure will vary, thereby necessitating dissipation of varying amounts of energy by the energy absorption device for substantially a constant length of stroke. In other words, in order to function properly the energy absorption or retarding device should so restrain the opening movement of the switch that it reaches the limit of its movement without setting up severe stresses in the apparatus. Moreover, if the kinetic energy of the movable switch structure has not been absorbed or dissipated by the time it reaches its fully open position, the resulting impact tends to cause rebounding of the structure from the dash-pot plunger towards the closed position of the switch, thereby creating an undesirable situation in that arcing between the switch contacts might be reestablished. On the other hand, if the retarding device oflers too sudden a resistance to movement of the circuit breaker mechanism, there will also be rebound from the aforesaid plunger. In order to provide for the above conditions of operation, my retarding device is so designed that the initial retarding movement ofi'ers comparatively little resistance to the moving structure, bound due to high initial resistance, the latter part of the retarding movement gradually dissipatin the kinetic energy of the moving structure y the time it has reached its limit of movement. I

When a sudden force acts on plunger 8 tending to depress the piston 16, the oil within cylinder 13 is forced into-the outerchamber through apertures 19 at a high initial rate. As piston 16 descends, the larger apertures 19 are progressively closed, thereby increasing the resistance to fluid fiow as the piston nears the comparatively restricted apertures or vent area near the bottom of the cylinder. Concurrent with flow of the oil through apertures 19, the oil level in the outer chamber rises rapidly at first to compress the air, or equivalent gaseous fluid within the space 21. As the level of the oil in the outer chamber continues to rise in response to continued descent of piston 16 the work done in compressing the air increases. In order that the device may absorb varying amounts of energy, depending upon the weight of the movable circuit breaker mechanism and the opening speed of the breaker, or may absorb equal amounts of kinetic energy where difierent speeds and weights of mechanism are involved, the size of the restricted vent 18 bears such relation to the size of the lower apertures 19 and to the volume of the air-confining space 21, that the rate of flow of oil through the lowest apertures 19 during the last stage of movement of the piston is substantially the same as the rate of air flow through the upper vent 18. That is, when the piston in its downward movement has reached the apertures 19 immediately above the lower most apertures, there will be no back pressure built up against the piston due to the fact that the air in space 21 is'being released through vent 18 at the same rate as the oil is being forced from cylinder 13. Accordingly the energy of the compressed air which would otherwise cause reverse movement of the piston from its final position, is not effective to exert back pressure on the piston when thereby preventing reithas reachedthe downward limit of its stroke. It must follow therefore, that the work done in compressing the air in space 21 at the maximum rate which must be proin a less rapid rate of compression of theair and an accordingly less amount of work done. Therefore the device will work as smoothly and as effectively to dissipate the kineticenergy of the movable contact structure over substantially the entire range of work u to and including the maximum for which it is designed.

I have found that a retarding device constructed in accordance with my invention when used for absorbing and dissipating the kinetic energy of movable circuit breaker mechanism serves to check the moving structure near its limit of movement without ap preciable rebound or impact. The problem of eificiently retarding the movement of oil switch contact structure has been troublesome ever since circuitbreakers of large interrupting capacities have come into use. Prior designs have not been altogether successful due to the fact that the amount of energy which can be dissipated for a givenstroke of the retarding device is not variable over a wide range, as must be the case where the circuit breaker is called upon to interrupt currents of widely varying magnitude and also where the retarding device must adapt itself to circuit breakers of different sizes.

My retardingdevice may be interchangeable with different types of circuit breakers having different opening speeds since in such case the work done in compressing the air is dependent on the rate at which the piston is depressed. If acomparatively light weight contact structure is operated at highspeed the energy dissipated may be the same as in the case of a heavier contact structure operated at a lower 5 eed. In each case the i as escape of air throug vent 18 permits the amount of work done in compressing the air to correspond to the kineticenergy which must be dissipated by the time the piston has reached the lowermost apertures 19.

When piston 16 has been depressed to its lowermost position during the energy dissipating operation, it is gradually restored to its original positionby spring 17 the air which was previously forced into the upper part of cylinder 13 being returned by way of vent 18 to maintain the volume of air within the outer chamber substantially constant. Return of the piston to its upper position also results in equalization of the oil levels within the inner and outer chambers so that the device is in readiness for another retarding operation.

What I by Letters Patent of the United States, is:

1. In a system for dissipating the kinetic energy of a moving structure during its movement to a limiting position, retarding means comprising a substantially cylindrical chamber, a second chamber disposed exteriorly of said cylindrical chamber, said cylindrical-chamber provided with apertures communicating with said second chamber, a

liquid contained within and partly filling said chambers, said chambers communicating through a restricted vent above the level of said liquid, and a member movable within said cylindrical chamber for transmitting the impact of said moving structure to the liquid within said first-named chamber whereby liquidis forcedinto the outer chamber to compress the gas above said liquid.

2. In a system for dissipating the kinetic energy of a moving structure during its movement to a limiting position, retarding means comprising a cylidrical chamber, a second chamber disposed exteriorly and concentrically of said cylindrical chamber, said cylidrical chamber provided with vent areas graduated with respect to the longitudinal axis ofthe chamber, said vent areas communicating with the aforesaid outer chamber at different levels thereof, a comparative- 2i viscous fluid contained within and partly ling said chamber-s, said chambers .communicating through a restricted vent above the -level of said fluid for regulating the work done in compressing the gas in said second chamber, and a piston member movable within the cylindrical chamber for transmitting the impact of said moving structure to said viscous fluid.

3. In a system for dissipating the kinetic claim as new and desire to secure energy of a moving structure, retarding means comprising a fluid chamber, a piston mounted for movement within said chamber, a second chamber communicating through vents with said first-named chamber, and a liquid partly filling said chambers, the space above the liquidlevel in said second chamber comprising an air cushion, said second chamber being provided with a restricted vent above the level of said liquid so that thework done in forcing liquid into said outer cham-,

ber is regulated in accordance with the degree of impact transmitted to said piston.

4. Retarding means for preventing rebound of a switch contact structure during opening movement thereof, comprising an inner chamber having apertures in the walls thereof, said apertures being graduated in size and more restricted in opening at the lower part of said chamber, an outer chamber disposed substantially concentrically of said inner chamber and in communication therewith at its lower portion through said apertures, a viscous liquid partially filling said chambers, said chambers communicating through a restricted vent above the level of said liquid, and a piston movable within said inner chamber adapted to progressively close said apertures during its energy abscrbin stroke, whereby said llquid is forced by sai 7 piston from said inner chamber through apertures gradually decreasing in size and number into said outer'chamber to com res's air in the upper ortion thereof, sai re.- stricted vent regu ating the work done in compressing said air.

5. A dash-pot structure for preventing rebound of a movable contact structure in oil circuit breakers, comprising a housing, a c linder and associated piston disposed centrally of and within said housing, said cylinder comin sai housing and chamber w municating with the interior of said housing through apertures disposed in the wall of said cylinder adapted to be progressively closed by movement of said piston, resilient means normally biasing said piston towards the upper part of said cylinder, an oil body partially filling said housing and cylinder} thereby forming an air-confining space 0 predetermined size in the upper part of the housing, said air-confining space communicating with said cylinder through a restricted vent for regulating the work done in compressing the air, at different rates, and means associated with said contact structure for en= gaging and depressing said'piston to force oil rom said cylinder into the outer housing during the switch opening movement where- .by the kinetic energy of said moving structure is substantially dissipated by work done in compressing the air in said space by the time the pistonhas reached its limiting position.

' 6. In an oil circuit breaker system, a dashpot structure for retarding the opening moye- 'ment of the switch mechanism without appreciable rebound, comprising 'a sealed housing, a cylindrical chamber mounted centrally of and within said housing, the wall of said chamber being perforated along the lower part thereof to providecommumcation with the interior of said housing, the perforations being gradually more restricted. near the lower art of said cylinder, a piston mounted d cylindrical chamber adapted to pro gresaiveiy close said perforations during its downward stroke, a spring normally biasing said iston towards the upper part of sai cham r, an oil body partially fillingsaid ereby there is an n per air-confining space formed by the we is of said housing and chamber, said air-confining space provided with a restricted vent for regulating the work done in compressing the air at different rates, and means associated with the aforesaid switch mechanism for engaging and depressing said piston during opening movement of the switch to force oil from said chamber into said housing and thereby perform work upon the partially con-

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