US2568465A - Electrical contact device - Google Patents

Description

Sept. 18, 1951 sco-rr 2,568,465

ELECTRICAL CONTACT DEVICE Filed Jan. 5, 1949 Inventor:

H i s Att orh ey.

Patented Sept. 18, 1951 snsc'rarcar. CONTACT mavrcs Benjamin B. Scott, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application January 3, 1949, Serial No. 68,818

3 Claims. (Cl. 201--63) My invention relates to electrical contact devices more particularly to electrical contact devices for resistance winding machines and has for its purpose the provision of a simple and reliable device to secure a continuous electrical contact to moving enamel insulated electrical resistance wire.

The manufacture of linear and non-linear precision resistances entails the placement of wire turns at exact positions on card brushing edges corresponding to the formula to which the card is being wound. Placement accuracy of turn positions is basically dependent upon the accuracy of resistance measurement which is diiiicult of attainment at high winding speeds in excess of 150 R. P. M. and for smaller than 0.0015" diameter. The present invention permits continuous contact of wire sizes as small as 0.001" at ordinary speeds and winding speeds in excess of 300 R. P. M. where wire is of suflicient diameter to provide the required tensile strength.

My invention eliminates these diiliculties by the use of an insulated wheel having sharply ground peripheral serrations around which the wire loops as it is fed to the winding head. A roller of tough resilient non-conducting material spring biased towards the toothed wheel causes the teeth to penetrate the enamel insulation coating of the wire to make continuous contact with the metal.

Previously, a stripping device attached to the winding head removed a portion of the insulation to lay a section. of the wire circumference bare along the whole length of the wire. This bare portion was positioned outward on the finished resistance and contact with the brushing edge of each turn was made by a flexible contact finger after each turn was wound; If the cumulative resistance to any turn did not conform to the cumulative resistance to the corresponding point on the master resistance the succeeding turn was so positioned as to compensate for the error.

In carrying out my invention, the sliding brush of the master resistance means is placed at the point on the master linear resistance having the same cumulative master resistance as the cumulative resistance of the wire being wound from the start to the contacting device. As the winding head and the cam device are moved by the same lead screw, the wire is wound on the card in a position corresponding to the position of equal resistance on the master resistance. Thus, my invention places each turn of wire in its true position rather than adjusting the position of each turn of wire to compensate for the previous turn that has been inaccurately positioned on the card.

For a more complete understanding of my invention, reference is directed to the accompanying drawing of one embodiment of my invention. Fig. l is a view of the contacting device mounted on the winding carriage of a winding machine and its position in relation to the resistance being wound. Fig. 2 is a detailed perspective view of the contacting device. Fig. 3 is the wiring diagram of the machine.

Referring to the drawing, my preesnt invention may be embodied in a contacting device I which may be combined with a winding machine such as that described in my copending application, S. N. 58,669 dated November 6, 1948. Wire 2 from a reel, not shown, threads over guide pulley 8 pivoted upon the non-conducting base 4 which is mounted upon the winding carriage 5 of the winding machine 6. The wire is looped once around the peripherally serrated wheel 1 of electrically conducting material and having sharp teeth I pivotally mounted upon the member 8 which is mounted upon the base 4 upon a pivot at 9 and oscillates between stops l0 and II. Components corresponding to serrated wheel I, member 8, base 4, pivot 9, and stops l0 and II comprise an apparatus which forms a portion of the subject matter of my copending application, Serial No. 82,113 filed March 18, 1949, on a "Contact Device for Moving Wires. A wheel I4 having a tough tire l5 of Vinylite, or other appropriate resilient material, is pivotally mounted on the arm I! pivoted upon the member 8 at l3. A spring H with adjustment I8 is connected between arm l2 and member 8 biasing the wheel l4 towards the serrated wheel I with sufiicient force to cause the serrations to pierce the varnish or enamel insulating coating of the wire 2 'to make continuous contact with the metal {of the wire.

The motor l9 operates the .drive shaft through the worm 2| and worm wheel 22. The shaft 20 operates the divided winding shaft 23 through the gears 24, 25 and 26, 21 to wind the wire on the card 28. Gears 29, 29', differential 30, gears 3i and 32 operate the lead screw 33 which provides simultaneous motion to the lead carriage 5 and the cam carriage 34. The cam 35 and the follower 36 cause the contact 31 to move over the master resistance 38 to vary the master resistance between the wires 39 and 40.

The beginning 4| of the resistance being wound is electrically connected through the commutator 42 insulated from the shaft 23 and the spring contact 43 to the wire 44. A terminal 45 attached to the member 8 is provided with a spring ontact bearing upon the serrated wheel I to connect the serrated wheel to the wire 49, thus allowing a continuous reading of the resistance being wound between wires 44 and 46.

The subtended portion of the master resistance and the resistance being wound, are series connected in a Wheatstone bridge circuit with the ratio resistors 48 and 49. A D. C. supply is connected from a point between the ratio resistors to a pivot between the master resistance and the resistance being wound. A galvanometer 50 connected across the ratio resistors indicates direction of unbalance of the bridge circuit.

A hand wheel 50 operating through the worm 52, the worm wheel 53 and the shaft 54 projecting through the hollow gear 3| operates the spider of the differential 30 to change the position of the lead screw 33 with relation to the winding shaft 23 increasing or decreasing the lead of winding upon the card 28. At the same time the slider 31 is moved on the master restistance 38 so that when the galvanometer reaches zero, the wire is wound on the card at the point corresponding to the point of contact of brush 3'! on the master resistance.

By the use of the method outlined in my invention, continuous positive contact is maintained regardless of the speed of travel of the moving wire. The wire insulation is so slightly damaged by the entry of the sharp edges of the contacting wheel that the nicks caused by the teeth on a small wire having a thin insulation coating can be seen only under a microscope. Preferably as shown the serrated wheel is on the same side of the wire as the card so that the wire is wound on the card with the nicks facing or against the card. The side of the wire provided with the nicks is, therefore, always on the compression side of the wire surface whereby fracture of the wire is prevented, as would be possible if the wire were wound with the nicked sides on the outside of the finished card where the wire surface is in tension.

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

1. A contacting device for making continuous electrical contact with a moving wire coated with an insulation comprising a rotatable serrated conducting wheel of electrically conducting material for penetrating said insulation and maintaining electric contact with a loop of said wire,

a smooth wheel provided with a resilient tire, a

spring biasing said smooth wheel toward tangential contact with said serrated conducting wheel so as to press the wire against the teeth oi said serrated wheel to cause the teeth to penetrate the insulation on the wire and make a continuous electrical contact between the metal of the moving wire and said serrated wheel 2. In a winding machine for winding turns of resistance wire coated with insulation upon a turn supporting card, a contacting device for making continuous electrical contact with said wire during winding comprising a serrated conducting wheel for penetrating said insulation and maintaining electric contact with a loop of said wire, a smooth circumferenced wheel in rolling contact with said wire loop, an adjustable spring biasing said smooth wheel towards said serrated conducting wheel so that the serrations of said serrated wheel pierce said insulation to contact the metal of said wire, a terminal provided with a spring contact engaging said serrated wheel so that continuous electrical contact is maintained between said wire and said terminal.

3. An electrical contacting device for making continuous electrical contact with a moving wire coated with an insulation, comprising two coacting wheels, one of said wheels being provided with a resilient, circumferential surface, the other of said wheels provided with circumferential serrations, means for passing a wire between said wheels, a spring for biasing one of said wheels toward the other so that said serrations pierce the insulation on the wire and provide a continuous electrical contact between the metal of the moving wire and said serrated wheel.

BENJAMIN B SCOTT.

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

UNITED STATES PATENTS Number Name Date 1,992,859 Cooper Feb. 26, 1935 2,069,623 Pickhaver Feb. 2, 1937 FOREIGN PATENTS Number Country Date 661,959 Germany Sept. 17, 1932

Images