|Publication number||US2770702 A|
|Publication date||Nov 13, 1956|
|Filing date||Apr 7, 1954|
|Priority date||Apr 7, 1954|
|Publication number||US 2770702 A, US 2770702A, US-A-2770702, US2770702 A, US2770702A|
|Inventors||Fjellstedt Thorsten A|
|Original Assignee||Mcgraw Electric Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (3), Referenced by (1), Classifications (7)|
|External Links: USPTO, USPTO Assignment, Espacenet|
mm M, 1956 Filed April 7, 1954 mmm Jr1 m |m 1tm rrn;r1 .l x 4m M T. A. FJELLSTEDT EJWJU LATCH FOR SINGLE AND DOUBLE THROW HOOK OPERATED DISCONNECT SWITCH 2 Sheets-Sheet 1 IN VEN TOR.
Thorst a4. Eiel edt B 3244 v ttorny WOW. M, M56 T. A. IFJELLSTEDT W J LATCH FOR SINGLE AND DOUBLE THROW HOOK OPERATED DISCONNECT SWITCH Filed April '7, 1954 2 Sheets-Sheet 2 fly 5 1 Q 30 '5 e7 20 g 44 INVENTOR. 'T/zar 1: v4. Fm, tedt United States Patent LATCH FOR SllNGLE AND DOUBLE THROW HOOK OPERATED DISCONNECT SWITCH Thorsten A. Fjellstedt, Ingleside, Ill., assignor to McGraw Electric Company, Milwaukee, Wis., a corporation of Delaware Application April 7, 1954, Serial No. 421,531
Claims. (Cl. 200-469) This invention relates to electric switches, and more particularly to a latch usable in combination with a hook stick operated air-break disconnect switch.
A principal object of this invention is to provide a simplified latching mechanism which positively secures a movable switch blade in closed circuit position relative to a fixed terminal but, nevertheless, permits facile release thereof by a mechanically advantageous camming action even under adverse conditions, such as where the switch is covered with ice.
Another object is to arrange the elements of the latch operating mechanism so that during opening of the switch most of the initial applied force is expended in prying the blade free of the latch prior to appreciable movement of the switch blade relative to the fixed terminal.
A further object is to provide a latch which is equally adaptable for use on single or double throw switches and whose performance is largely unaffected by either lateral or longitudinal misalignment between the movable switch blade and the stationary elements.
These and other objects will become apparent by referring to the specification and the following drawings in which: r
Fig. 1 is an elevation view of a double throw switch embodying the invention;
Fig. 2 is a bottom view of the switch shown in Fig. 1;
Fig. 3 is an enlarged elevation view of the invention, partly in section, showing the latch in engaged position; Fig. 4 shows the latch in released position; i t
Fig. 5 is an end elevation view of the invention, partly in section, with parts removed.
Refer now to Fig. 1 where the novel latch assembly is shown adapted to cooperate with a hook operated double throw air-break disconnect switch mounted upon insulators l and in spaced longitudinally relative to the axis of the switch blade. The center insulator 1a carries a U-shaped hinge member 2 having spaced upstanding legs 3 spanned by a pin 4 upon which the swingable tubular blade 5 may be pivoted. Electrical connection to the hinge member 2 and its integral legs 3 is made through an adapter 6 which supports the hinge member 2.
On the end insulators 1 are mounted laterally spaced contact fingers or clips 10 for receiving therebetween the free end of blade 5 in very high pressure electrical con tact engagement. To enhance pressure engagement between clips 10 and blade 5, flat contact springs 11 are juxtaposed to the clips 10. One end 12 of each contact "spring 11 bears against a clip 10 and the other end 13 of each spring bears against an adapter base 14 to which clips ltl are rigidly fastened by riveting or other well known means. Contact springs 11 are activated by retaining pins 16 carried by a tie bar 15 disposed laterally through clips 10 and springs 11. Obviously, when the switch blade 5 is inserted between clips 10, the pins 16 will react against springs 11 in such manner as to develop contact pressure and prevent excessive divergence of the clips 10.
The novel latching assembly for retaining switch blade 5 in contact engagement with clips 10 and for prying the blade to open circuit position is shown in Fig. 1 displaced from the contact clips 10 in a direction along the longitudinal axis of blade 5 as indicated generally by the reference numeral 20.
Latch assembly 20 comprises a support member having two laterally spaced legs 21 integral with a bottom portion 22 which is fastened to adapter base 14 by means of bolts 23. A pivot pin 24 bridges the legs 21 and has its ends peened to prevent lateral removal therefrom. A latch 25 is journaled on pin 24 between the legs 21 for pivotal movement.
Note in Fig. 3 that latch 25 is provided with a transverse web 26 perforated by a hole 27 for receiving the hooked end of a helical tension spring 28. The other end of spring 28 is hooked in a hole 29 in the bar 15 which spans the contact clips 10 transversely. Hence, spring 28 urges latch 25 to pivot at all times in the direction of the longitudinal axis of blade 5 toward the contact clips 10. To limit the pivotal movement of latch 25 toward contact clips 10, the latch is provided with a stop in the form of a lateral projection 30 which abuts a margin of leg 21 in opposition to the force created by spring 28. Movement of latch. 25 against the tensile force of spring 28 is likewise limited by a projection 31 as is evident from an inspection of Fig. 4.
Blade 5 is provided through its diameter with a latching pin 40 which projects from either side of the the blade periphery for positively engaging latch 25 when the blade is swung to closed circuit position between contact clips 10. Latching pin 40 may be rigidly affixed in blade 5, as shown, or it may be journaled for rotation in the blade. In the latter construction it is necessary to retain the pin 40, against transverse movement with re spect to blade 5, by snap rings or other means (not shown) engaging pin 40 where it emerges from each side of blade 5 immediately adjacent the periphery thereof. A bifurcated hook-ring lever member 41 straddles the free end of blade 5 and is pivotally carried on the latching pin 40.
One end of the bifurcated lever member 41 is provided with an annular ring 42 at its mid-section for receiving a hook stick (not shown) when it is desired to actuate the latch 25 for the purpose of operating the switch. The distance from latching pin 40 to the center of annular ring 42 constitutes a lever arm which is long in comparison with its corresponding resistance or prying arm, thereby enabling :an appreciable mechanical advantage to be developed when initially prying switch blade 5 and actuating latch 25.
, At the other end of the bifurcated lever member 41 beyond latching pin 4th will be seen two comparatively short arms 43 projecting away from the center of latching pin 40 at an angle relative to each other. Arms 43 terminate in cam followers in the form of wing-like portions 44 extending laterally therefrom, there being a total of four arms and four corresponding wing-like portions. When the switch blade 5 is swung to fully closed position, such as in Fig. 1, the wing portions 44 strike against short cam surfaces 32, thereby acting as positive means for limiting inward movement of the blade.
Cam surface 32 on latch 25 is a segment of a curve having radii emanating from a point such as point 35 offset from the center of the latch pivot pin 24 in a direction toward contact fingers ll). Hence, any force exerted normal to the cam surface 32 will have a component tending to rotate the latch 25 about pin 24- in a clockwise direction, according to the law of moments, when viewed advantage and ice breaking ability.
in Fig. 3. This is an especially important feature because it assures that catch 33 will be urged into engagement with latching pin 40 even if spring 28, which normally biases catch 33; in a clockwise direction, is weakened or entirely removed. Oby iously, if the radii of short cam surface 32 emanated from the center of pin 24, any force applied to surface 32 would be transmitted radially to the pin affe'cting a thrust thereon instead of a rotational force thereabout.
Rocking movement of the bifurcated lever member 41 on pivot pin 48 is limited by a fixed cylindrical stop pin 45 which penetrates the diameter of blade parallel to pin '40 and is adapted for abutment with an arcuate recess 46 defined by short arms 43.
In closing a switch of the type described herein the operator willfusually swing the blade 5 into latched position rapidly, but firmly, by means of a hook stick engaged with ring 42. Then, in accordance with the customary carefulness of such operators, the blade 5 is tested for positive latching by attempting to open it through exerting a pull directly on the blade adjacent its free end at aiplace other than in ring 42. By reason of a small clearance existing between pin 40 and catch 33 when the blade 5 is swung to its full closed position the operator, when testing, will effect a slight rotation of blade 5 on its main pivot pin 4 which will take up this free play between the pin and catch. Conversely, the operator may, after testing the blade for positive latching, push on it directly through the medium of a hook stick to restore the aforementioned clearance, and urge blade 5 as deeply as possible into contact fingers It When it is desired to fully release blade 5 from latch 25 prior to swinging the blade to open circuit position or to take advantage ofthe double throw feature, it is merely necessary to engage ring 42 with a hook stick (not shown) and pull thereon. As seen in the preceding para-graph either one of two conditions may exist at this time; first, where there is clearance between pin 40 and catch 33 such as occurs when the switch blade 5 has been tested and; second, where there is no clearance such as occurs when the blade by pulling directly on it has been tested but the clearance between pin 40 and catch 33 has not been restored.
Under the first condition, pivoting the lever member 41 will cause wings 44 to bear reactively on cam surface 32 and pry the locking pin 4% into contact with catch 33 without tending to swing the catch clear of the pin because latching pin 49 is in substantially the same vertical plane as pivot pin 24. Consequently, the entireforce transmitted through the hook stick is expended in breaking static seizure between fingers 19 and blade 5 and in fracturing ice which -may be present about the latch assembly. V p I Under the second condition, when there is no clearance between latching pin hi and catch 33, pivoting the lever memberdfl will cause earn followers in the form of wings 44 to pry the latch 25 and catch 33 clear-of pin 40 without any swinging movement of blade 5 occurring. However, under either condition, continued actuation of lever memher '41 will ultimately cause the short prying arms 43 to swing about latching pin 4 in the manner shown in Fig.
.4, permitting wings 44 to exert a latch releasing force on cam surfaces 32:: until catch 33 is cleared. Fig. 5 clearly shows that the sides on latch 25 is such as to permit ongagement with pin 4t) but to allow free passage therebetween of wings id when the switch is swung through the latch into full open or closed circuit position.
It should be noted here that the ratio of the lever arms, extending from the center of pin 40 to ring 42, to the comparatively short prying arm 43, extending from the same pin to-wings d4, results in obtaining optimum mechanical in addition, it is to be especiaily noted that all reactive forces tending to pry the switch open are exerted between the bifurcated =rnem'ber 41 and latch 25, in contradistinction to the action in prior art switches where a 'pivota'ble prying member frequently reacts against a fixed element, thus making the double action described herein impossible in prior art switches.
Closing the switch blade 5 into electrical connection with the contact clips 10 simply involves swinging latch pin 40 into sliding contact relation with beveled margin 3311 on latch until catches 33 thereof engage pin 40. Spring 28 will stretch and recoil to hold the latch 25 firmly against latch pin 40, thereby preventing switch opening by vibratory forces incidental to heavy short .circuit currents and other forces to which the switch may be subjected.
Note that beveled margin 33a constitutes a long inclined plane which maybe struck anywhere by latching pin when blade 5 is being pressed into the latch. This feature enables the blade and latch to cooperate effectively though there may be consideraable discrepancy in the spacing between insulators 1 and 1a. Furthermore, lateral misalignment of the blade 5 relative to latch 25 may also be appreciable because the outwardly flared clips 10 act as a guide channel to properly position the blade within latch 25. Moreover, even if blade 5 were not guided by clips 10, the latch 25 would operate properly because it can tolerate misalignment to the extent that only apart of pin 40 projecting from one side of blade 5 need engage with a catch 33 on the latch 25.
Although this specification and its accompanying drawings disclose an embodiment of the invention which facilitates convenient explanation of its structure and mode of operation, other modifications of theinvention are intended to be within the purview of the disclosure and claims.
For example, it has been found advantageous in practice to make the free end of blade 5, which carries the assembly constituting the stop pin and bifurcated lever member 41, an entirely separable part from blade 5. Such modification facilitates adapting the same size latch 20 and same size lever member 41 to a switch blade 5 having greater or lesser diameter than the one illustrated in the drawings. This is accomplished by attaching the aforementioned assembly to the free end of blade 5 by any suitable coupling means such as a reducer or a cap which does not interfere with the electrical engagement of blade 7 5 by fingers 10.
evident from the drawings that all parts are symmetrical inthemselves and symmetrically arranged to facilitate double throw operation as well. Likewise, thelatch is shown embodied in a switch mountedhorizontally overhead, but those skilled in the art will immediately recognize that the latch will retain the switch blade in a selected position if the switch were mounted vertically or in any intermediate position.
It is claimed:
1. In an electric switch, the combination of a hinge member, a contact member and a switch blade mounted on said hinge member for swinging movement relative to said contact member, a latch juxtaposed to said contact member, said latch having a cutaway portion defining intersecting catch and cam surfaces, said cam surface being intermediate said catch and the pivot axis of said latch,'-a spring interposed between said contact member .on each furcation and extending adjacent said cam surfaces on said latch when said switch is in latched position,
a stop pin transversely through said switch blade intermediate said arms, and a hook stick ring integral with 'said bifurcated member, whereby rocking of said bifurcated member by means of said hook ring will urge said latch clear of said latch pin and pry against said cam surfaces to urge said blade toward open circuit position.
2. In a double throw electric switch, the combination of a hinge member, contact members displaced from said hinge member and a switch blade mounted on said hinge member for swinging movement relative to said contact members, a pivotable spring biased latch juxtaposed to each contact member respectively, each latch having a cutaway portion defining intersecting catch and cam surfaces, said cam surface being intermediate said catch and the pivot axis of said latch, a fixed latch pin transversely through said blade selectively engageable with one of said catches in substantially the same plane as the latch pivot, a bifurcated member straddling said blade at its free end and pivotally mounted on said latch pin, prying arms disposed on opposite sides of said latch pin on each furcation thereof, a stop pin transversely through said switch blade intermediate said prying arms, a wing-like portion integral with each arm and projecting laterally therefrom adjacent said cam surfaces when said switch is in latched position, and a hook stick ring integral with said bifurcated member, whereby rocking of said bifurcated member by means of said hook ring will urge said latch clear of said latch pin and pry against said cam surfaces to urge said blade to open circuit position for selective engagement with either of said contact members.
3. In an electrical switch, the combination of, a base, a stationary contact on said base, a hinge member spaced from said base, a switch blade pivotally mounted on said hinge member for engagement with said stationary contact, a latch pin extending transversely through the free end of said blade, a latch having a cutaway portion defining a catch and being pivotally mounted on said base about an axis parallel to the axis of said latch pin and resiliently urged from a first position wherein said latch pin is free of said catch portion to a second position wherein said catch portion intereferes with said latch pin to prevent opening of said switch blade, and a hook stick lever pivotally mounted intermediate its ends on said latch pin, one end of said lever constituting an eye portion adapted to receive a hook stick and the other end thereof having a cam follower, said latch having a cam surface intersecting with said catch portion in the path of rotation of said cam follower and at an angle to the plane defined by the axis of the latch pin and the pivot axis of said latch, whereby rotation of said lever will cause said cam follower to strike said cam surface with a force which will tend to rotate said latch from said second to said first position and the reaction force on said camming surface will have a component along said axes tending to rotate said blade toward open position.
4. A latch assembly for selectively engaging and re leasing the free end of a radially swingable switch blade, comprising, a latch pivotally mounted adjacent the circumferential path of said blade, said latch having a cutaway portion defining a catch projecting toward the pivot axis of said blade and also defining dissimilar arcuate cam surfaces intermediate said catch and said latch pivot, one of said cam surfaces being generated by an arc having a center of curvature displaced from the pivot axis of said latch in a direction toward the pivot axis of said blade, and said one cam surface being wholly displaced toward the pivot axis of said switch blade from a plane through the latch pivot and catch, a transverse latch pin carried by said switch blade for engagement with said catch, a lever member pivotally mounted intermediate its ends on said latch pin, a hook stick ring integral with said lever at an end remote from the pivot axis of said blade, a cam follower integral with said lever at its other end, whereby swinging said cam follower into contact with said one cam surface will stop the swinging movement of said blade and rock said latch toward engagement with the latch pin carried by said blade.
5. A latch assembly for selectively engaging and releasing the free end of a radially swingable switch blade, comprising, a latch pivotally mounted adjacent the path of circumferential movement of said blade, said latch having a cutaway portion defining a catch projecting toward the pivot axis of said blade and also defining dissimilar arcuate cam surfaces intermediate said catch and said latch pivot, one of said cam surfaces being generated by an are having a center of curvature displaced from the pivot axis of said latch in a direction toward the pivot axis of said blade and the other cam surface extending from said catch into intersection with said one cam surface, a transverse latch pin carried by said switch blade for engagement with said catch, a lever member pivotally mounted intermediate its ends on said latch pin, a hook stick ring integral with said lever member at an end remote from the pivot axis of said blade, a cam follower integral with said lever member at its: other end and projecting adjacent the intersection of said cam surfaces, whereby pivoting said lever member by means of said hook stick ring will cause said cam follower to rock said latch free of latch pin and pry against said one cam surface to initiate swinging of said blade.
References Cited in the file of this patent UNITED STATES PATENTS 2,063,954 Ramsey Dec. 15, 1936 2,214,180 Reynolds Sept. 10, 1940 2,224,380 Crabbs et a1. Dec. 10, 1940
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2063954 *||Apr 19, 1930||Dec 15, 1936||Schweitzer & Conrad Inc||Switch|
|US2214180 *||Feb 5, 1938||Sep 10, 1940||Albert & J M Anderson Mfg Comp||Electrical switch|
|US2224380 *||May 17, 1939||Dec 10, 1940||Westinghouse Electric & Mfg Co||Disconnecting switch|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US4233481 *||Mar 29, 1979||Nov 11, 1980||Kruger Jack L||Mechanical transfer switch|
|U.S. Classification||200/320, 200/555, 200/325|
|International Classification||H01H31/00, H01H31/28|