Operating mechanism for high tension electric switch gear

Abstract

Operating mechanism for high tension electric switch gear comprising hydraulic cylinder means for reciprocating a rack, a pinion engaged with the rack for rotation thereby, and a three bar toggle linkage connected between said pinion and the rotary stack of the switch for operating the switch; said mechanism being characterized by its economy, compactness, foolproof operation, safety features and power.

Claims

1. Operating mechanism for a high tension electric switch having a rotatable input shaft, comprising hydraulic pump means, a double-acting hydraulic cylinder having a piston and a piston rod reciprocated thereby, valve means for supplying fluid under pressure from said pump means selectively to the opposite ends of said cylinder for venting the end of the cylinder opposite the end to which fluid under pressure is supplied, a rack connected to said piston rod for reciprocation thereby, a pinion meshed with said rack for rotation in opposite directions upon reciprocation of said rack, a bearing assembly for said rack and and pinion comprising slide bearing means for guiding the reciprocal movements of said rack, a pair of annular bearings to opposite sides of said slide bearing means, a shaft journalled in said annular bearings, said pinion being secured to said shaft in meshed engagement with said rack, and means for connecting said pinion to the switch input shaft, Said cylinder and said rack and pinion multiplying the fluid power output of said pump and providing high operating forces for opening and closing the switch. 2. Operating mechanism for a high tension electric switch having a rotatable input shaft, comprising a power drive shaft rotatable in opposite directions, a first crank connected with said drive shaft for oscillation thereby, a second crank connected with the switch input shaft, a link extending between and pivotally connected at its ends to said cranks, said link comprising a pair of end members pivotally connected respectively to said cranks, a a clamp on each of said end members, and a straight link piece extending between said members and secured thereto by said clamps, said first crank being oscillated by said drive shaft through an arc of movement slightly greater than 180* wherein the arcuate movement is principally to one side of its axis of rotation between first and second end positions in both of which the pivotal connection between first crank and said link is beyond said one side of a line drawn between said axis and the pivotal connection of said link and said second crank, and stop means to the side of said first crank opposite said one side engageable by said first crank in its said end positions, whereby the linkage comprised of said cranks and said link is over toggle and abutted against a stop means in each of its end positions to prohibit reversal of movement of said second crank except by operation of said first crank. 3. Operating mechanism for a high tension electric switch having a rotatable input shaft, comprising a rack, power means for reciprocating said rack, a pinion meshed with said rack for rotation in opposite directions upon reciprocation of said rack, a first crank secured to said pinion for oscillation thereby, a second crank secured to said input shaft, a link extending between and pivotally connected at its ends to said cranks, said first crank being movable through an arc in excess of 180* between first and second end positions and having an overtoggle relationship with said link in both of said end positions, and stop means engaged by said first crank means in both said first and second overtoggle end positions, whereby movement of said second crank means in either direction is prevented without actuation of said power means. 4. The operating mechanism of claim 3 wherein the path of movement of said first crank adjacent said first and second end positions is substantially perpendicular to the direction of movement of said second crank, whereby upon each rotation of said first crank said second crank is slowly accelerated with a high force to movement ratio, moved rapidly and then slowly decelerated with a high force to movement ratio. 5. Operating mechanism for a high tension electric switch having a rotatable input shaft, comprising a drive shaft mounted in spaced parallel relation to said input shaft, a first crank secured to said drive shaft, a second crank secured to said input shaft, a link extending between and pivotally connected at its ends to said cranks, means for oscillating said drive shaft and said first crank through an arc of movement slightly greater than 180* between first and second end positions, said first crank in each of its said end positions extending generally in the direction of movement of said second crank so that said first crank when in the vicinity of its end positions moves generally perpendicular to the direction of movement of said second crank, the pivotal connection between said first crank and said link in each of said end positions being located beyond a line drawn between the axis of rotation of said first crank and the pivotal connection of said link and said second crank so that the linkage comprised of the two cranks and said link is overtoggle in each end position, and stop means engaged by said first crank in each of its said end positions for retaining the same against further overtoggle moveMent and thereby locking the linkage in both end positions.
United States Patent Weston et a1. 1 Dec. 25, 1973 OPERATING MECHANISM FOR HIGH TENSION ELECTRIC SWITCH GEAR Inventors: Donald E. Weston, East Sebago, Maine; Julius W. Timmerman, Brookfield, Wis. 11. K. Porter Company, Inc., Chicago, 111. Filed: Mar. 1, 1971 Appl; No.: 119,549 Assignee: 1.1.5. Cl 91/418, 74/89.l7, 92/136, 200/48 Int. Cl. Fl5b 11/08 Field of Search 74/89.l7, 520, 422, 74/29; 60/52 R; 200/48; 91/418; 92/136 References Cited UNITED STATES PATENTS 8/1937 Milliken 200/48 3,165,291 1/1965 Osen 74/520 3,338,140 8/1967 Sheesley 74/89.l7 1,616,841 2/1927 Beebe 60/52 R 3,172,182 3/1965 Assmann 74/520 3,459,056 8/1969 Lea 74/29 Primary Examiner-Charles J. Myhre Assistant Examiner-Wesley S. Ratliff, Jr. Att0rneyGary, Juettner, Pigott & Cullinan [5 7] ABSTRACT Operating mechanism for high tension electric switch gear comprising hydraulic cylinder means for reciprocating a rack, a pinion engaged with the rack for rotation thereby, and a three bar togglelinkage connected between said pinion and the rotary stack of the switch for operating the switch; said mechanism being characterized by its economy, compactness, foolproof operation, safety features and power. 5 Claims, 3 Drawing Figures PAIENIEBHEBM 3,780,625 SHEET 2 [1F 2 OPERATING MECHANISM FOR HIGH TENSION ELECTRIC SWITCH GEAR BACKGROUND OF THE INVENTION High tension electric switch gear, especially outdoor disconnect switches, become quite mammoth and are subject to severe weather conditions, such for example as heavy icing. Consequently, they require extremely powerful operating mechanisms. Usually, the switch is operated upon rotation of a shaft or an insulator stack which aids in supporting the switch in insulated position above ground and from grounded supporting structures; the shaft or stack being rotated by means of a crank arm connected thereto and a reciprocable link pivotally connected to the crank arm for oscillating the same through a predetermined arc. Heretofore, such mechanisms have been expensive, frequently of questionable reliability and serviceability, and often underpowered. SUMMARY OF THE INVENTION The present invention provides a highly improved switch operating mechanism characterized by the combination of a hydraulic cylinder power input, a rack and pinion drive, and a three bar toggle linkage interconnecting said drive and the aforesaid rotary shaft or stack; the mechanism providing significant advantages in terms of each of economy, reliability, serviceability, power output and safety. Other objects and advantages of the invention will become apparent from the following detailed description, as taken in conjunction with the accompanying drawings: THE DRAWINGS FIG. 1 is a front view of an electrical switch embodying the operating mechanism of the invention; FIG. 2 is an enlarged top plan view of the switch showing the relative positions of the switch blade and the three bar toggle linkage in the opened and closed positions of the switch; and FIG. 3 is a further enlarged elevational view of the remainder of the operating mechanism. DETAILED DESCRIPTION In order to acquaint those skilled in the art with the manner of making and using my improved switch operating mechanism, I have shown and will now describe what I presently regard to be the best mode of carrying out the invention. For purposes of illustration, the operating mechanism of this invention has been shown in FIGS. 1 and 2 as associated with a relatively simple side break disconnect switch adapted for outdoor service. The switch comprises a base 10, a stationary insulator stack 12 extending upwardly from adjacent one end of the base and carrying a stationary contact 14 at its upper end (which contact is preferably of the type shown and described in the co-pending application of Donald E. Weston, Ser. No. 47,429, filed June 18, 1970), a rotatable insulator stack 16 journaled on the base adjacent the opposite end thereof and extending upwardly therefrom, and a movable switch blade 18 carried on the upper end of the stack 16 and adapted to be swung thereby through an arc of approximately 90 in the horizontal plane between a switch closed position wherein the blade is engaged in the contact 14 (as illustrated in tension electric lines. As is conventional in the art, the insulators l2 and 16 may be several feet tall and the blade 18 may be several feet long to insure an adequate air gap between the conductive elements in switch open position to prevent striking of an arc therebetween at the potential of the electrical system. Consequently, the rotary stack 16 is journaled in a very heavy bearing secured to the base 10, and even so the stack and blade impose substantial thrust load on the bearmg. The switch shown is of course only illustrative of the switches to which this invention is applicable, other examples being shown in US. Pat. Nos. 3,240,887, 3,488,752 and 3,566,055. According to the present invention, the stack 16 is rotated by means of a double acting hydraulic cylinder 20 including a reciprocable piston rod 22 which is secured to and adapted to reciprocate a rack 24 having gear teeth thereon. The rack 24 meshes with a pinion 26 having complementary gear teeth thereon, the length of the rack in relation to the size, number and spacing of the gear teeth being such as to rotate the pinion in the order of about upon each stroke of movement of the rack. Extending between the rotary insulator l6 and the pinion 26 (or the shaft on which the pinion is mounted) is what is herein termed a three bar toggle linkage comprising a crank arm or bar 30 rigidly connected with the pinion, a crank arm or bar 32 rigidly connected with the rotary insulator adjacent its base, and an intervening bar or link 34 pivotally connected at its opposite ends to the two crank arms. Preferably, the link 34 is comprised of end castings 36 pivotally connected to the respective cranks and each including a pipe clamp 38, and an intervening piece of pipe 40 secured to the castings by the clamps. By virtue of this structure, the spacing between the pinion and the rotary insulator need not be precisely measured or precisely maintained when the switch is being installed, since a piece of pipe of whatever length is necessary can be clamped to the castings 36 and then cut to proper length, which is accomplished very easily in the field at great economy. As shown in FIG. 2, the crank arm 32 extends at an angle of about 45 to the vertical plane of the axis of the switch blade. In the switch closed position, as shown in solid lines in FIG. 2, the crank arm 30 extends substantially parallel to said plane, but is pointed slightly toward said plane so that the pivot axes of the link 34 and the axis of the crank 30 are not in a straight line. Any attempt at this time to move the rotary stack 16 and crank arm 32 in switch opening direction, i.e., clockwise, would result in turning the crank 30 counterclockwise, which is not its direction of opening movement. Thus, the linkage is over center or over toggle and the blade is locked in closed position by virtue of its engagement in the contact 14, which prevents counterclockwise movement of the blade, and engagement of the crank 30 with a fixed stop 42, which prevents further counterclockwise movement of the crank 30 and thus clockwise movement of the crank 32 and the blade 18. Consequently, the blade is fixedly locked in closed position against both physical and electrical stresses that might be imposed thereon. When the crank arm 30 is rotated in the clockwise direction by the pinion 26 however, the crank arm 30 moves back on and then out of toggle whereupon the crank 30 andthe link 34 pull the crank 32 clockwise to swing the switch blade to open position. As the blade approaches full open position, the crank 30 again moves onto and then over toggle relative to the link 34 and thereafter abuts against a stop 44. Now, any attempt to move the blade 18 and crank 32 toward closed position, i.e., counterclockwise, would result in an effort to pull the crank 30 further clockwise, which is prevented by the stop 44-, whereby the blade 18 is locked in full open position and cannot be swung toward the closed position, except upon actuation of the cylinder and rotation of the pinion 26. Thus, the three bar linkage 30, 32, 34, while providing a very compact and economical structure facilitating field erection of the switch, additionally provides the safety features of having the switch blade fully locked in both its switch open and its switch closed positions. Turning now to H6. 3, the preferred embodiment of the hydraulic cylinder 20 and its operating mechanism are shown compactly mounted in an enclosure or housing 50. The mechanism preferably comprises an electric motor 52 driving a hydraulic pump 54 for supplying hydraulic fluid under pressure selectively to the opposite ends of the cylinder 20. A reservoir 56 for hydraulic fluid is provided, and a manually operated pump 58 is also interconnected with the pump 54 to accommodate manual operation of the mechanism in the event of an electric power failure. Pressure fluid from the pump, either the motor operated pump 54 or the hand operated pump 58 is supplied to a selected end of the cylinder 20 under the control of a four-way valve 60 which operates to vent one end of the cylinder 20 to the pump inlet while connecting the other end of the cylinder 20 to the pump outlet. The valve 60 is under the selective control of a pair of solenoids 62 for automatic operation, or in the event of a power failure, under the selective manual control provided by a pair of push buttons 64. Preferably, the pumps are capable of supplying hydraulic fluid to the cylinder at pressures up to 2,500 psi., although the normal operating range may be about 200 to 500 psi., depending upon the existing resistance to movement of the blade 18, for example the comparative resistance factors of clear summer weather and sever winter conditions wherein several inches of ice may build up on the blade 18 and its contact 14. Preferably, the motor 52, pumps 54 and 58, reservoir 56 and valve 60 are secured to a common mounting plate 66 for assembly as a unit into the housing 50. The cylinder 20 is preferably pivotally mounted on a wishbone extension 68 of a bearing assembly 70 so as to accommodate minor degrees of component misalignment, the assembly 70 being fixedly secured to the housing 50. The rack 24 is secured to the outer end of the piston rod 22 and is preferably guided for reciprocal movement in slide bearing surfaces 72 formed in or on the assembly 70. For example, the slide bearings may comprise a grooved raceway for the rack, or may consist of a rotatable bearing mounted on a vertical axis parallel to and behind the axis of rotation of the pinion 26 for holding the rack in mesh with the pinion. The assembly '70 further provides a pair of vertically spaced annular bearings 74 to opposite sides of the rack 24 for reception therein of a rotatable shaft 76 to which the pinion 26 is secured in the space between the bearings 74. The assembly thus serves to mount and guide both the pinion 26 and the rack 24 whereby the same are mounted and retained in meshed engagement with one another. The shaft 76 extends upwardly through a sealed opening in the housing 50 and carries at its upper end the pinion crank 30 for effecting the switch actuating movements previously described. The housing 50 thus serves as a sealed enclosure for all mechanism components bearing reference numerals 52 and higher, whereby these components are completly shielded and protected from the adverse weather conditions to which the switch per se is exposed. Adjacent the lower end thereof, the shaft 76 carries a pair of actuating arms 78 for engagement respectively with a pair of adjustably mounted limit switches 80 or the like which serve to discontinue operation of the motor 52 when the shaft 76 and crank 30 reach the respective ends of their arcuate path of movement, i.e., with the crank 30 abutting respectively against the stops 42 and 44. For the sake of convenience, the stops 42 and 44 have been illustrated and described herein as being associated with the crank 30, whereby to clarify their cooperative relationship and functions. However, in a commercial embodiment of the switch mechanism, it would be preferable not to have the stops exposed to the weather, but rather to mount the same within the housing 50; for example, to cooperate with an additional crank arm on the shaft 76, or in the alternative to build the stops directly on the rack 24. At its lower end, the shaft 76 may carry a further crank arm or cam 82 for performing additional control functions as may be desired, such for example as closing the circuits of remote indicator lights or the like. In a preferred embodiment of the above-described apparatus, the pumps 54 and 58 produce a normal operating pressure of 200 to 500 psi., have a normal full load pressure of 1,500 psi., and are preferably capable of producing up to 2,500 psi. fluid pressure. The cylinder 20 may for example have a 2 /2 inch bore and a piston stroke of 8 inches. With the power amplifying charac'teristics of the rack and pinion, this arrangement results in a power output at the shaft 76 of 15,000 inch lbs. at 1,500 psi. fluid pressure. The three bar linkage 30, 32, 34 then further amplifies the power output to provide in the 1,500 psi. example approximately 40,000 lbs. of force at the blade end as it enters or leaves the contact 14. Thus, extremely great force is provided for forcing the blade into and out of the stationary contact. Experimental tests have been conducted with this apparatus under laboratory conditions of extreme icing, and the switch has never failed to open or to reach fully closed position in normal operation of the mechanism of this invention. Because of the force produced, the switch blade 18 may be swung directly into extremely high pressure limited area contact with the contact structure 14 without necessity for rotating the blade about its own axis as has been necessary in switches such as those illustrated and described in Pat. 3,240,887 and 3,488,752. By virtue of this capability, a side break switch such as shown herein, or a circuit breaker such as shown in US. Pat. No. 3,566,055, can now be closed against very heavy forces, both physical and electrical, and specifically can be used to close even a high current faulted circuit since the direct contact provided by elements M and 18 mitigates the arcing that inherently would occur under these conditions with the switches of U.S. Pat. Nos. 3,240,887 and 3,488,752. The three bar linkage 30, 32, 34 provides the particular advantage of imparting a cyclic movement to the rotary stack 16 and the blade 18 wherein the blade upon each movement thereof, either opening or closing, is first moved slowly to provide relatively gentle blade acceleration under conditions of ahigh force to movement ratio, is then swung rapidly through the major part of its arc of movement, and finally is gently deccelerated to a smooth shockless stop, again with a high force to movement ratio. This is accomplished by virtue of the relative dispositions of the cranks 30 and 32 and the fact that the crank 30, adjacent the opposite ends of its 180 or more path of movement, is moving substantially perpendicular to the direction of movement of the crank 32 whereby very little movement is imparted to the crank 32 for each degree of movement of the crank 30. On the other hand, in that part of the movement of crank 30 which generally parallels the path of movement of the crank 32, there is essentially a one-to-one relationship, whereby the crank 32 is moved essentially at the same rate as the crank 30, and thus much faster than at the ends of the path of movement of the crank 30. Manifestly, due to the fact that the crank 30 is moving arcuately, there is a smooth transition between the two extreme conditions above defined. Thus, the blade i8 is in sequence gently accelerated, swung rapidly and then gently deccelerated, which is of very substantial advantage in switch operation especially in operation of switches such as disclosed in U.S. Pat. No. 3,566,055. Also, as earlier described, the three bar linkage provides a positive blade lock in both of its end positions. A particular feature of the hydraulic mechanism of the invention is that the opposite ends of the cylinder 20 are directly connected to the inlet and the outlet of the pumps 54 and 58 (through the four-way valve 60) and are never dumped to the reservoir 56. The reservoir 545 is simply in a stand-by condition to accommodate replenishment of lost fluid and expansion space should there be a surge of fluid. Basically, there is a closed hydraulic circuit between the pump and the cylinder, whereby the physical link provided by the hydraulic fluid is a solid link, not a resilient link. Thus, piston operation is always positive and always the same, even at widely disparate temperature ranges. Also, because there is a solid hydraulic link, hydraulic stops may be provided at one or both ends of mechanism operation (for example where the hydraulic system is used independently of the three bar linkage, or the latter is not made to over-toggle at one end of blade movement, or as a further safety factor) by the provision of poppet valves in the hydraulic lines to the cylinder, whereby to lock the fluid in the cylinder thereby to prevent movement of the rack and pinion. The presence of the manually operated pump 58 in parallel with the pump 54, affords the particular advantage that full force for either opening or closing the switch can be provided even, and perhaps most importantly, in the event of a power failure. Mechanical switch operating mechanisms cannot provide this advantage, since they are inherently limited to the amount of force personnel can apply to the mechanism. Here, the same operating force can be applied, at the same speed and with the same characteristics of switch movement, even in the event of power failure. Thus, the objects and advantages of this invention have been shown to be attained in a convenient, economical and practical manner. While l have shown and described what I regard to be the preferred embodiment of our invention, it is to be appreciated that various changes, rearrangements and modifications may be made therein without departing from the scope of the invention as defined by the appended claims. What is claimed is: 1. Operating mechanism for a high tension electric switch having a rotatable input shaft, comprising hydraulic pump means, a double-acting hydraulic cylinder having a piston and a piston rod reciprocated thereby, valve means for supplying fluid under pressure from said pump means selectively to the opposite ends of said cylinder for venting the end of the cylinder opposite the end to which fluid under pressure is supplied, a rack connected to said piston rod for reciprocation thereby, a pinion meshed with said rack for rotation in opposite directions upon reciprocation of said rack, a bearing assembly for said rack and and pinion comprising slide bearing means for guiding the reciprocal movements of said rack, a pair of annular bearings to opposite sides of said slide bearing means, a shaft journalled in said annular bearings, said pinion being secured to said shaft in meshed engagement with said rack, and means for connecting said pinion to the switch input shaft, said cylinder and said rack and pinion multiplying the fluid power output of said pump and providing high operating forces for opening and closing the switch. 2. Operating mechanism for a high tension electric switch having a rotatable input shaft, comprising a power drive shaft rotatable in opposite directions, a first crank connected with said drive shaft for oscillation thereby, a second crank connected with the switch input shaft, a link extending between and pivotally connected at its ends to said cranks, said link comprising a pair of end members pivotally connected respectively to said cranks, a a clamp on each of said end members, and a straight link piece extending between said members and secured thereto by said clamps, said first crank being oscillated by said drive shaft through an arc of movement slightly greater than wherein the arcuate movement is principally to one side of its axis of rotation between first and second end positions in both of which the pivotal connection between first crank and said link is beyond said one side of a line drawn between said axis and the pivotal connection of said link and said second crank, and stop means to the side of said first crank opposite said one side engageable by said first crank in its said end positions, whereby the linkage comprised of said cranks and said link is over toggle and abutted against a stop means in each of its end positions to prohibit reversal of movement of said second crank except by operation of said first crank. 3. Operating mechanism for a high tension electric switch having a rotatable input shaft, comprising a rack, power means for reciprocating said rack, a pinion meshed with said rack for rotation in opposite directions upon reciprocation of said rack, a first crank secured to said pinion for oscillation thereby, a second crank secured to said input shaft, a link extending between and pivotally connected at its ends to said cranks, said first crank being movable through an arc in excess of 180 between first and second end positions and having an overtoggle relationship with said link in both of said end positions, and stop means engaged by said first crank means in both said first and second overtoggle end positions, whereby movement of said second crank means in either direction is prevented without actuation of said power means. 4. The operating mechanism of claim 3 wherein the path of movement of said first crank adjacent said first and second end positions is substantially perpendicular to the direction of movement of said second crank, whereby upon each rotation of said first crank said second crank is slowly accelerated with a high force to movement ratio, moved rapidly and then slowly decelerated with a high force to movement ratio. 5. Operating mechanism for a high tension electric switch having a rotatable input shaft, comprising a drive shaft mounted in spaced parallel relation to said input shaft, a first crank secured to said drive shaft, a second crank secured to said input shaft, a link extending between and pivotally connected at its ends to said cranks, means for oscillating said drive shaft and said first crank through an arc of movement slightly greater than between first and second end positions, said first crank in each of its said end positions extending generally in the direction of movement of said second crank so that said first crank when in the vicinity of its end positions moves generally perpendicular to the direction of movement of said second crank, the pivotal connection between said first crank and said link in each of said end positions being located beyond a line drawn between the axis of rotation of said first crank and the pivotal connection of said link and said second crank so that the linkage comprised of the two cranks and said link is overtoggle in each end position, and stop means engaged by said first crank in each of its said end positions for retaining the same against further overtoggle movement and thereby locking the linkage in both end positions.

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