US3231694A - High voltage switch with cam operated high pressure contacts - Google Patents

Description

J. N. HUGHES Jan. 25, 1966 HIGH VOLTAGE SWITCH WITH CAM OPERATED HIGH PRESSURE CONTACTS 2 Sheets-Sheet 1 Filed March 30, 1964 1|||||||m iinm FIG. 3

INVENTOR. JAMES N. HUGHES FIG. 2

ATTORNEY J. N. HUGHES Jan. 25, 1966 HIGH VOLTAGE SWITCH WITH CAM OPERATED HIGH PRESSURE CONTACTS 2 Sheets-Sheet 2 Filed March 30, 1964 INVENTOR. JAMES N. HUGHES BY ATTORNEY United States Patent Ofi ice 3,231,694 Patented Jan. 25, 1966 3,231,694 HIGH VOLTAGE SWITCH WITH CAM OPERATED HIGH PRESSURE CONTACTS James N. Hughes, Griflin, Ga., assignor to Southern States, line, a corporation of Georgia Filed Mar. 30, 1964, Ser. No. 355,559 1 Claim. (Cl. 200-48) This invention relates to electric switches and more particularly to contact pressure applying and relieving means for use primarily on high current heavy duty disconnect type switches.

It is well known that the current carrying capacity of heavy duty switch contacts is materially improved by substantially increasing the contact pressure. In the socalled air-break type of high voltage switch, contact pressure is increased when the switch is closed by swinging the blade of the switch between the spaced elements of a jaw contact and thereafter the switch blade is rotated about its longitudinal axis to engage the spaced jaws of the jaw contact and to establish a high pressure contact. Of course the movable contact in this type of switch is shaped in such a way that its narrow dimension allows easy entry of the switch blade between the jaws which are thereafter contacted when the longer dimension of the contact is rotated into contact therewith. Such air-break type switches are satisfactory although the frictional effect of the high pressure engagement of the contacts due to rotation of the switch blade affords substantial resistance and requires a substantial operating force particularly near the end of a contact closing operation. Occasionally rotation of the blade and the resultant sliding action of the blade contact on the jaw contact elements results in deleterious effects on the contact surfaces.

A principal object of this invention is to provide an improved pressure applying and pressure relieving means for a high current heavy duty type electric switch wherein a minimum of operating force is needed to achieve the high pressure contact relationship and wherein deleterious effects on the contacts are completely eliminated insofar as such effects may be attributed to high pressure sliding contact of the relatively movable contacts.

Another object of the invention is the provision of an improved high current high capacity switch which is characterized by easy operation and wherein the contact pressure is controlled with a minimum of operating parts.

Still another object of the invention is to provide an improved high capacity electric switch which is unusually durable and which requires a minimum of maintenance and which is relatively free of contact damage due to operation of the switch.

The invention in one form as applied to an electric switch of the so-called knife blade or disconnect type comprises a fixed post type contact having oppositely disposed contact surfaces, a movable switch blade having a pair of parallel spaced conductors arranged to straddle the fixed contact when the switch is closed with each conductor in engagement with one of the contact surfaces on the fixed contact, an operating arm pivotally mounted on the switch bladejand arranged to operate a cam for causing the blade conductors to engage the contact surfaces of the fixed contact under spring pressure after the switch is closed. According to a feature of the invention a latch is provided for engaging a part of the movable mechanism controlled by the operating arm whereby the pressure applying mechanism is held in the pressure relieving switch open position except when the switch is closed. If desired, a contact locking element may be mounted on the operating arm and arranged to engage a cooperating contact on the fixed switch contact whereby the switch is held closed against inadvertent opening. I

For a better understanding of the invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawings in which FIG. 1 is a side view of a disconnect type switch to which the invention has been applied; FIG. 2 is an enlarged view of the upper right hand portion of FIG. 1 and showing the switch closed; FIG. 3 is a side view of FIG. 2; FIG. 4 is a view similar to FIG. 2.but showing the pressure applying mechanism in the pressure relieving position, the switch parts being depicted after the blade has been moved a slight distance from the closed position toward the open position; FIG. 5 is a side view of FIG. 4; and in which FIG. 6 is an enlarged perspective view of both the fixed and movable contacts shown in the switch closed position with the contacts under pressure.

With reference to FIG. 1, the numeral 1 depicts a switch base which preferably is constructed of a metal channel in conventional fashion. Aflixed to base 1 are switch pedestals 2 and 3. Mounted on switch pedestal 2 is a conventional insulator stack 4 while a similar conventional insulator stack 5 is mounted on switch pedestal 3. Secured to insulator stack 4 is a terminal pad 6 while a similar terminal pad 7 is secured to insulator stack 5. A switch blade generally designated by the numeral 8 is pivoted at 9 in conventional fashion to switch terminal 10 which is integrally formed with terminal pad 7. As is best seen in FIGS. 2 and 6 a fixed contact post 11 is formed integrally with terminal pad 6 and constitutes the fixed terminal of the switch.

For operating the switch blade to the open and .closed positions an operating arm 12 is provided. As can best be understood from FIG. 2, a locking element 13 on arm 12 is arranged to engage a complementary locking element 14 formed on the fixed contact 11. Locking element 13 forms an integral part of operating arm 12 which is pivotallymounted on bolt 15 on the conductors 16 and 17 which make up the main body of the switch blade 8. The conductors 16 and 17 are mounted in conventional fashion on the pivot pin 9. The opposite ends of conductors 16 and 17 are arranged to support the pressure applying and pressure relieving mechanism constructed according to this invention. For example as is best shown in FIGS. Sand 6 a cam' plate 18 is afiixed to the outer surface of conductor 16 and is secured thereto by a pair of bolts 19 and 20. As is shown in the drawing, the heads of the bolts fit snugly against the outer surface of the cam plate 18 while suitable locking nuts threadedly engage the bolts and are secured flat against the inner surface of conductor 16. Of course lock Washers may be used, if desired. These nuts are indicated by the numerals 21 and 22. The right hand ends of the bolts 19 and extend through oversized openings formed in the conductor 17 so that conductor 17 may move sidewise from left to right as viewed in FIGS. 3 and 5. Secured to the right hand ends of bolts 19 and 20 are nuts 23 and 24 and their associated locking nuts 25 and 26.

For the purpose of applying and relieving contact pressure, i.e., for causing the conductors 16 and 17 to move toward and away from each other thereby to securely grip the post contact 11 or to release the contact 11, suitable cams 27 and 28 are arranged to cooperate respectively with cam surfaces 29 and 30 formed on cam plate 18. Cam 27 is mounted on bolt 15 and is securely aflixed thereto so that when operating arm 12 is operated, the cam 27 rotates relative to cam surface 29. For example, as viewed in FIG. 2 when operating arm 12 is moved in a counterclockwise direction about the bolt 15 cam 27 is rotated in such a fashion as to increase the contact, pressure, i.e., to draw the conductors 16 and 17 closer together thereby to grip the post contact 11. These cams and cam surfaces are simply inclined steps on a disc-like structure as shown so that rotation of the operating arm 12 in the counterclockwise direction draws the conductors 16 and 17 toward each other. A helical compression spring 31 is housed in a cup-like cover 32. When the bolt 15 is drawn toward the left due to the pressure applying force of operating arm 12, spring 31 exerts against the outside surface of conductor 17 a force which tends to urge conductor 17 toward the left as viewed in FIG. 3, for example. In this manner contact pressure is increased.

In order to provide a balanced pressure applying and relieving mechanism, the two cams such as 27 and 28 are employed which cooperate with cooperating cam surfaces 29 and 30. Cam 28 is provided with a crank arm 33 to which av link 34 is pivoted at 35. The link 34 is pivoted at 36 to crank 37 formed integrally with cam 27. Cam 28 is mounted on a bolt 38 having a cup-shaped housing 39 in which a compression spring (not shown) is disposed. Bolt 38 and associated structure operates in a manner identical to bolt 15 and associated structure so that a detailed description thereof is not deemed necessary.

For the purpose of determining the limit of travel of bolt 15 toward the right, a pair of lock nuts 40, 41 are mounted on bolt 15 while similar nuts 42 and 43 are affixed in position on bolt 38.

The operating movement of operating arm 12 swings the cams 27 and 28 in a counterclockwise direction as viewed in FIG. 2 and causes tension to be applied to the bolts 15 and 38 which in turn causes their associated compression springs housed within the cup- shaped housing 32 and 39 to urge the conductor 17 into engagement With post contact 11. Thus the conductors 16 and 17 securely grip the contact 11 therebetween.

Contact 11 as is best shown in FIG. 3 is provided with four contact surfaces 44, 45, 46 and 47. In this way a balanced application of force is achieved as will be understood by those skilled in the art. j

For the purpose of holding the operating arm 12 and associated parts in the pressure relieving position when the switch is open, a suitable latch mechanism is employed so that when the switch is operated to the closed position the conductors 16 and 17 will be spaced apart sufliciently to allow the conductors 16 and 17 to stradle the fixed contact 11 with ease. Such latch mechanism is designated in the drawing by the numeral 48 and is pivotally mounted on the pin 49 formed integral with the cam plate 18. A torsional spring 50 is provided with a hooked end portion 51 which engages the latch 48 and with another end portion 52 which engages a post 53 formed integral with the cam plate 18. Thus a counterclockwise bias is imparted to the latch 48 as viewed in FIG. 6. Latch 48 is provided with a latching surface 54 which is arranged to engage a latching surface 55 formed on latch element 56 which in turn is integrally formed with the cam 27. Thus with the latching surface 54 in engagement with latching surface 55 counterclockwise rotation of cam 27, bolt 15 and operating arm 12, as viewed in FIG. 6 for example, is impossible. In this manner the operating arm 12 is prevented from causing a premature For the purpose of relieving the latch 48 from its holding action relative to operating arm 12 near the end of a closing operation, a latch operating lever 59 is formed integral with latch 48 and is arranged to engage a latch operating stud 57 formed integral'with terminal pad 6 as best shown for example in FIG. 4. Thus when latch relieving arm 59 engages the stud 57 the entire latch is rotated clockwise and thereafter with the conductors 16 and 17 disposed astride the fixed contact 11, it is possible to rotate the operating arm 12 in a counterclockwise direction and to impart suitable contact pressure to the contacts as will be understood.

For the purpose of determining the extreme clockwise limit of travel of arm 12 a stop 58 is formed integral with the cam plate 18 and is arranged to be engaged by the crank 37.

While I have shown and described a particular embodiment of the invention, I do not Wish to be limited thereto in the appended claim to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is: I

An electric switch comprising a fixed contact having a pair of contact surfaces, a pivotally mounted blade having a pair of parallel spaced conductors arranged to straddle said fixed contact when the switch is closed with said conductors in engagement with said contact surfaces respectively, an operating arm pivotally mounted on said blade, a first cam connected with said arm, a first cam surface on the outer side of one of said conductors and in engagement with said first cam, a helical compression spring on the pivotal mounting of said arm and in engagement with the outer side of the other of said conductors so that movement of said arm imparts a force to said spring and in turn causes transverse movement of said conductors relative to the pivotal mounting for said operating arm thereby to vary the space therebetween and in turn to vary the pressure between said conductors and said contact surfaces in a manner dependent solely on the force of said spring, a first crank mounted on said first cam, a second crank mounted on a second cam, a link interconnecting said cranks, a second cam surface on said one conductor and arranged to cooperate with said second cam, said second cam and cam surface being disposed on the opposite side of said fixed contact from said first cam and cam surface in switch closed position,

and latch means for preventing movement of said arm relative to said blade when said switch is open and operable to release said arm for movement relative to said blade in coordination with closing movement of said blade.

References Cited by the Examiner v UNITED STATES PATENTS 2,085,792 7/ 1937 Cornell et a1 20048 2,261,843 1 1/ 1941 Cornell 20048 2,272,506 2/1942 Bowie 20048 X 2,879,348 3/ 1959 Ortwig 20048 X ROBERT S. MACON, Acting Primary Examiner.

KATHLEEN H. CLAFFY, Examiner. WILLIAM C. GARVERT, Assistant Examiner.

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