US2453761A - Hot line jumper clamp - Google Patents

Description

Nv. 16, 194s.

R. B. sci-flooNMAKERA 2,453,761

Ho'r LINE JUMPER CLAMP Filed Jun 2l', 1947 IENTOR. .fr/wm Patented Nov. 16, 1948 UNITED STATES PATENT OFFICE HOT LINE JUMPER CLAMP Raymond B. Schoonmaken', Poughkeepsie, N. Y. Application June 21, 1947, Serial No.- 756,134

11 Claims. 1

This invention rela/tes to an improved snapaction clamping device for temporarily connecting tap wires or jumpers to live electrical circuits.

lIt is' sometimes necessary to provide a temporary b-y-pass around switches or other power distribution controlfapp'aratus to maintain service during the replacement or repair of such apparatus. connection to live or hot conductors and itis, therefore, of the utmostlmportanceto provide connection means that will 'reduce a'rcing or sparking to a minimum. The lineman may have to reach outwardly' from a pole or tower to place the jumper clamp Aon the lhot wire and it is also of importance to provide a hot line clamp which may be operated with a minimum of manipulation or adjustment.

In my presently cci-pending application Serial No, 575,178', entitled Electrical'jumper-S, filed January 29, 1945, of which the instant application is a continuation in part, IY-have disclosedf a snap action jumper clamp hav-ing a `hook-like jaw engageable over the hot wire and `a spring driven pressure plunger which snaps upwardly into engagement with the hot wire to clamp it firmly against thejaw. VI'l'iave found it desirable to provide a second, stronger, clamping spring effective after the plunger has' engaged the het wire to more tightly urge the plunger against the hot wire and; tlflerefore,` increase the clamping pressure thereon. Such a secondary spring is made effective after the first spring has oper'- ated to make the initial closure, andthe lineman.

brings said second spring intov play by simple twisting of the handle of the unit.

It is, therefore, an object of the* invention to provide a snap action rhot wire clamp which may be operated by one hand and which when in clamping position exerts sufficient pressure against thel hot wire to hold the clamp constantly tight regardless of vibrations ofthe wire.

It isv another object of the invention to provide aA hot wire jumper clamp which' includes a spring driven plunger effective to make im'- mediate;contact` against the hot wire and having a secondary stronger spring to` increasev the clamping pressure to perfect the` connection'.

It is still another object of the inventionto provide aY hot line jumper clamp so constructed that the linemans movements in fastening or removing theclamp on the hotr wire are away from the wire, thus minimizing the possibilityV wire during/such` of the* lineman'l striking the-hot attachment or removal'.

The* lineman makes his temporary It is another object of the invention to pro:- vide a jumper clamp having internal resistances so low that the IR drop when the clamp is in use isnegligible.

Other features and advantages` of the invention will be apparent from the following detailed description.`

Fig. 1 is a cross-section in elevation of a hot line jumper clamp embodying the present invention.

Fig. 2 is a View similar toliig. 1, but rotated through and showing the conductor or hot line imposition therein.

Fig. 3 is a plan section taken on lines of Fig. 2; and

Fig. 4 is la partial vertical section of the clamp operating elements when open position.

Referring to the drawings my improved hot wire jumper clamp I0 includes 'a metallic head or jaw portion II; which is preferably of age hardenable aluminum alloy or bronze. Said jaw portion is' advantageously cylindrical, and is formed with a relatively large diameter vchamber l2 extending concentrically from which is a smaller diameter cylindrical chamber I4. A side wall of chamber I4 is cut away intermediate its ends to permit the head to be placed over an electricity conductor. Preferably, the wall of said` chamber is formed with a V notch I5 adjacent its end so that the conductor or hot wire I6 is engaged `by the sides of said notch. Under most conditions of installation, the conductor will extend completely through the housing, as shown in Fig. 3.

An insulating cover, preferablyof natural or synthetic' rubber of equivalent, is molded about the head portion to completely envelop the same. The cover is shaped to afford the relatively wide entrance passage I8. I prefer to drill a plurality of holes 2D axially through the wall of the jaw member so that the molded cover will key with or enter said holes for bond therewith'.

Fitting tightly within the chamber I2 and in surface contact with the inner wall thereof thereis a cylindrical or sleeve-like cam 2l, a lower shoulder 22' of which abuts against the lower edge of the head portion I-I. Set screws 23 or equivalent prevent relative movement of the head portion and cam sleeve.

A sidewall opening of the cam sleeve provides a cam track 24 which drops downwardly from a short rise to forma detent 2B, and then climbs helic'aily to an upper detent notch 21. The upper wall28 provides a stop;

It will be seenirom Fig. 1 that shortly after 3 the commencement of climb of the cam track, the cam sleeve opening is bounded by a Vertical Wall 29, for a purpose later explained.

The handle of the jumper clamp has a rigid conductor core 38 having provision at its lower end for the attachment of a tap wire 3|, said tap wire being secured by compression means or equivalent (not shown) to insure proper electrical connection.

A handle cover 32 also preferably of neoprene or equivalent insulation material, is molded about the conductive core 30, and I prefer to form said core member with an enlarged body 33 about which the cover 32 is molded, and which serves to key the cover against movement. The cover is molded with corrugations 34 which prevent the cover from slipping in the hand when it is grasped during the aflixing or removal of the jumper to the conductor. The upper end of the handle cover has a skirt 35 which slidably and rotatably overlies the lower outer wall of cover I1. A suitable cable insulating sleeve 36 is aflixed to the end of the handle cover 32 to seal the lower end thereof about the tap wire 3|, and to restrain the bending of said tap wire at the connection with the conductive core 30.

Handle conductor 3U has a rigid cylindrical extension 31 on which is telescopically mounted a tubular pressure plunger 38. Said plunger is preferably of silicon bronze or equivalent and l provides an internal spring chamber 40. A relatively thick end wall forms a heavy head 4|. Immediately above the lower edge of said plunger, the side walls thereof are provided with mutually aligned diametrically opposed slots 42. For cooperation with said slots the cylindrical extension 31, is diametrically drilled to tightly receive a heavy cross-pin 43 which extends through the said slots substantially to the wall of the chamber I2. The pin is electrically conductive and is preferably of stainless steel.

A helical spring 45 is disposed about the member 31 and is confined between the lower edge of pressure plunger 38 and a shoulder `46 at the base of the cam sleeve 2|, said spring always urging the pressure plunger upwardly to the extent permitted by the slots `42. With no conductor I6 in position, the head 4I of the pressure plunger is above the apex of notch I5, as shown in Fig. 1.

Confined within the plunger 33 between its head 4| and the cylindrical member 3| there is a spring 48 which is substantially heavier than spring 45. For example, spring 45 may have a 35 lb. compression when its free length is reduced three-quarters of an inch, whereas the spring 48 has a 50 lb. load at free length.

Fig. 4 shows the position of the operating parts of the device in open position. The entire handle has been pulled downwardly until the pin 43 is within the detent 26. Spring 45 is under compression, whereas spring 48 is at free length. When the lineman wishes to make contact with the hot conductor |6 he hooks the clamp I0 over said conductor. The insulating surfaces 50, 5| prevent sparking until the conductor is within the chamber I4. The lineman pulls back, or down, on the handle to hook the conductor within the diametically opposed V-notches I5, which are so spaced as to hold the device against twisting on the conductor I6. He then gives handle 34 approximately a quarter turn to bring pin 43 out of the detent 26, whereupon spring 45 releases, driving the handle, and its associated member 31 and thereon mounted plunger 38 upwardly, the pin 43 following the vertical wall 29. The plunger strikes smartly against the underside of conductor I6. In this position, pin 43 is not at the upper limit of the cam track and the spring 48 is but slightly compressed, if at al1.

The lineman may thereupon increase the pressure of the plunger against the conductor by giving the handle an additional three-quarter turn so that the pin 43 is moved upwardly by the slope of the cam track, said slope being quite gradual, to obtain a relatively large mechanical advantage. The spring 48 is, therefore, placed under compression. At the completion of the rotation of the handle the pin 43 rests in the upper detent.

21 of the cam slot. The clamp is then in the Fig. 2 position.

It will be noted that spring 48 urges the member 31 downwardly and cross pin 43 is maintained in firm contact with the cam sleeve 2|. The main current path is through the wall of the head I| to the cam sleeve, thence to the pin 43 and handle conductor 3U to the line tap 3|. There are secondary paths which follow the coil spring 48 to the end of the member 31, as well as others which will be apparent from inspection of the figures. The respective current paths reduce the internal resistance to such extent that the IR drop when the jumper clamp is in use is negligible.

Sharp-edged ridges 3 I a, which may be arranged as a concentric series on the head 4| of the pressure plunger, penetrate the poorly-conductive oxide lm on exposed conductors, and improve the frictional grip of the clamp. Obviously, the surfaces of the V-notches I5 might be provided with such sharp-edged ridges, if desired.

To disengage the clamp from the hot wire the lineman grasps the handle 32 and rotates it to the left until pin 43 strikes the vertical guide wall 29. He then pulls the handle toward himself, that is, away from the hot wire, until at last an additional short turn will bring the pin 43 into engagement with the lower detent 26. The device is then locked in full open position. During the initial stages of the downward pull the spring 48 expands, maintaining contact of the plunger head with the conductor I6 and minimizing arcing during the commencement of the disengagement operation. The spring 45 being relatively light does not oifer any substantial resistance to the pull of the lineman. It will thus be seen that the double spring construction, that is the combination of the light spring 45 and the heavy spring 48, provides for very securely gripping the conductor I6 against the respective notches I5, while minimizing the amount of downward pull which the lineman must exert to release the jumper clamp.

It will be noted that the skirt 35 on the end of the handle sheathing 32 never disengages from the lower portion of the head covering l1, thus providing a continuous insulation during all stages of attachment and detachment.

After the rst step of hooking the clamp over the conductor |6 all of the movements of the lineman in engaging or releasing the conductor are downward or toward himself. Therefore, he is required to make no movements under strain which are in the direction of the hot wire |6 and if his grasp on the handle should slip his hand will move away from rather than toward the hot wire.

Thus, among others, the several objects of the invention as afore noted are achieved. Obviously numerous changes in construction and rearrangement of the parts might be resorted to Without entamer departing fromV the :spirit ci theinvention as dened by the claims.

` I claim:

1. A jumper clamp, comprising fahflxe`d,electri cally conductivejaw adapted to-be placed over a conductor in electrical connection therewith; an openeended, electricallycoriductive cylindrical structure extending-i" rom said jaw; a handle member Lmounted forVV axial androtatable movement with respect to said cylindrical structure, said handle member having an electrically conductive core extending within said cylindrical structure and axially movable therein; a pressure plunger slidably mounted on said core and extending toward said xed jaw to provide a movable jaw member ior clamping said conductor against said xed jaw; a spring for propelling said handle member and therewith associated pressure plunger toward said fixed jaw; a second spring disposed internally of said pressure plunger for exerting a thrust thereon; a sleeve i-lxed within said cylindrical structure in electrically conductive relation therewith, a wall of said sleeve being formed with a detent notch communicating with an upwardly extending wall opening; and a pin extending radially from said handle core and engageable with said detent to hold the handle in retracted position, with the first-named spring under compression and to disengage from said notch and enter said wall opening upon rotation of said handle to release said handle for propulsion toward said xed jaw by action of said iirstnamed spring, the extent of travel of said handle being such that the end of said pressure plunger will clamp said conductor against said fixed jaw; a cam track provided at the upper end of said sleeve in communication with said wall opening for engagement by said pin, said cam track and pin being effective, upon further rotation oi said handle to move said handle additionally in the direction oi said fixed jaw to place the secondnamed spring under compression to increase the said clamping pressure; and means for electrically connecting a lead wire to said jumper clamp in conductive relationship with said fixed jaw member.

2. A jumper clamp according to claim l, in which the side walls of said pressure plunger are slotted to engage with said pin to limit the relative movement of said plunger with respect to said handle core.

3. A jumper clamp according to claim 1, in which the rst-named spring is disposed about said handle core and abuts against the end of said pressure plunger.

4. A jumper clamp according to claim 1, in which the first-named spring is of less compressive strength than the second-named spring.

5. A jumper clamp according to claim 1, in which said jaw member has intermediate its ends an entrance for said conductor, the surfaces of said entrance being covered with insulation material.

6. A jumper clamp, comprising a fixed, electrically conductive jaw adapted to engage a conductor in electrical connection therewith; a rotatable handle portion extending from said jaw and movable toward or away from said jaw, said handle portion including an electrically conductive core and having an axially movable, electrically conductive, pressure plunger engageable with said conductor to clamp the same against said jaw; spring means for moving said handle member and therewith associated pressure plunger to bring the latter into said clamping lll engagement; deteritt means fors :releasablyf holdiing said" handle member 'retractedlfrom Asaidljaw with *saidr-spring `under compression; vafseconrl springy interposed `*between said' handle :core and thesaid pressurerplunger to `iincreaslethe clamp'- ing pressure thereof; cama means effective upon rotation.: of' said.1 handle i to compress. said `second springpand` means for; electrically connecting said handle core to a leadlwire;

755A- jumper clamppcomprisingfa xed, electrically conductive jaw adapted to engage a conductor in electrical connection therewith; a rotatable handle portion extending from said jaw and movable toward or away from said jaw, said handle portion including an electrically conductive core and having an axially movable, electrically conductive, pressure plunger engageable with said conductor to clamp the same against said jaw; spring means for moving said handle member and therewith associated pressure plunger to bring the latter into said clamping engagement; a second spring means operating on said pressure plunger to increase the clamping pressure thereof; and cam means operable on rotation of said handle member for compressing said second spring.

8. A jumper clamp, comprising a xed, electrically conductive jaw adapted to engage a conductor in electrical connection therewith; a handle portion movable toward or away from said jaw, said handle portion including an electrically conductive core and having an axially movable pressure plunger engageable with said conductor to clamp the same against said jaw, spring means for moving said handle member and therewith associated pressure plunger to bring the latter into said clamping engagement; a second spring means operating on said pressure plunger to increase the clamping pressure thereof; and cam means for compressing said second spring.

9. A jumper clamp, comprising a xed, electrically conductive jaw adapted to be placed over a conductor in electrical connection therewith; a handle portion movable toward or away from said jaw, and having an end structure engageable with said conductor for clamping said conductor against said jaw; spring means for urging said handle portion toward said jaw for clamping en.. gagement with said conductor; and a second spring means for increasing the clamping pressure after the initial engagement of said jaw and structure with said conductor.

10. A jumper clamp, comprising a xed, electrically conductive jaw adapted to be placed over a conductor in electrical connection therewith; a lead wire electrically connected to said jaw; a handle portion movable toward or away from said jaw; a pressure plunger slidably carried by said handle portion and movable toward said jaw, said plunger being engageable with said conductor to clamp the same against said jaw; spring means for urging said handle portion and associated pressure plunger in the direction of said jaw to cause said plunger to exert an initial clamping action against said conductor, a second spring acting on said plunger to increase the clamping pressure thereof; and means for compressing said last named spring for increasing the pressure exerted by said plunger against said conductor.

11. A jumper clamp, comprising a xed, electrically conductive jaw adapted to be placed over a conductor in conductive relationship therewith; a co-operating movable jaw member for clamping said conductor against said xed jaw,

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,250,175 Dossert Dec. 18, 1917 2,237,588 De Barbieri Apr. 8, 1941

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