US2796491A - Electric circuit contacts - Google Patents

Description

June 18, 1957 T. R. STUELPNAGEL ETAT. 2,796,491

ELECTRIC CIRCUIT CONTACTS Filed March l, 1954 United States Patent ff) ELECTRHC CRCUIT CONTACTS Thomas R. Stuelpnagel, Inglewood, and Pol R. Verbeke,

Los Angeles, Calif., assignors to Hughes Tool Company/,Houtem Tex., a corporation of Delaware Application March 1, 1.954, Serial No. 413,302

Claims. (Cl. 20G-.405)

of contact failure which must be overcome is the formation of spires which attends the transfer of metal to the positive contact when the contacts are separated.

'H-In many prior art circuit contact devices, protective circuits are connected between the contacts to suppress arcing .and sparking when the contacts are separated. This provision is elective to reduce the volume of metal transfer, but it does not prevent the formation of yslender spires, which lengthen progressively with the number of make-and-break operations. These spires may ultimately form a link zbetween the contacts `which cannot be broken with the force available, and this possibility necessitates frequent inspection and maintenance to keep the contacts inoperation. It is for these reasons that, in many instances, bulky and 'costly electronic amplifying systems must be relied on to develop the power required to control electric circuit operations.

`,The present invention overcomes the rabove-mentioned disadvantages and provides means whereby sensitive contacts may be employed where great reliability of operation is required 'and where .available space for necessary electrical components is at `a premium. fIn accordance with this invention, a cylindrical contact surface is continuously or intermittently rotated. A movable contact is spaced from the periphery of the rotating contact, against which it may be brought into engagement. Bearing against the periphery of the rotating contact is an element for keeping the surface of the rotating contact smooth .and clean, which element causes a continuous shearing action against the cylindrical contact surface when the Ilatter is rotating, to thereby substantially reduce build-up of metal transfer 'and prevent spire formation.

It is, therefore, an object of this invention to provide rotatable circuit contact means capable of reliable operation over a long operating life by continuously removing spires formed by contact actions, and which contact means is suitable to be controlled with a minimum amount of power.

lt is another object of this invention to provide electric circuit contact means comprising .a minimum number of -component parts of simple design, capable of providing reliable operation without attention, and with which sensitive contact operation over a long cont-act 'life is realized.

`The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompany- 2,796,491 Patented June 18, 1957 2 ing drawings, in which preferred embodiments of the invention are illustrated by way of example. 'The scope of the i-nvention is pointed out in the appended claims: In the drawings:

Fig. 1 is a perspective view of electric circuit control apparatus employing contact means in accordance with this invention; and

Fig. 2 is a modification of the arrangement .shown in Fig. 1.

Referring tothe drawing, in which like reference characters indicate like parts throughout, and referring more particularly to =Fig. 1, a control circuit 10 is connected to the terminals 12 of an electromagnet 14. The electromagnet 14 is provided with a movable armature 16. An electric -circuit contact arm 18 having a contact portion 21 is aflixed to or integral with armature 16 for vmovement therewith when electromagnet 14 is energized.

Contact arm 18 is positioned such that contact portion 21 is adjacent the 'cylindrical contact surface 20 of a rotary contact element 19. A spring 17 is attached to the armature y16 and the frame of electromagnet 14 to normally bias the member 18 out of contact with the surface 20. When armature 16 is attracted by electromagnet 14, contact 271 is -brought into engagement with surface 2 0. Element 19 is preferably a slip-ring -type of contact and is `supported on and insulated from the shaft 22 of a motor 24.

vBearing against surface 2.0 is a Contact 26 which is aV spring metal element arranged to maintain constant .shearing engagement against surface 20. When a circuit is connected between contact 2,6 and contact 18, and when electromagnet 14 is energized to bring contact 21 to bear upon surface 2l), rotation of element 19fby motor 24 causes a shearing action by contact 26 which action prevents the aforementioned spire build-up by `scraping off any minute metal particles that are deposited on surface 2.0 from contact 18.

A load circuit 2,8 and a |power source, indicated as ,a batt-ery 30, are serially connected between contact 26 and 'cont-act arm 18. Motor `24 may vbe supplied with energy either from battery 30 or from 'a :separate power source `32, as indicated schematically in the drawing by the provision of a switch 34 for Selecting the source of energy for driving motor 24.

A conventional contact protection circuit 35 is connected between the contact 26 land contact arm 18. `Circuit 35 is `designed to give maximum protection against arcing and sparking which the particular load circuit 28 tends to cause.

Fig. 2 illustrates a modification of the arrangement above described, including power relays controlled yby a sensitive relay for alternatively energizing two control circuits and for performing the function of the motor 24 of tFig. 1. 'Referring to Fig. 2, a second rotary contact element `19 is supported on shaft 22 and spaced from element `19. A movable contact arm 18 having a contact portion I21 xed to armature 16, is .positioned such that contact 21 is adjacent the peripheral surface 20 'of element 19. Armature 16 is arranged for actuation in opposite directions Iby a polarized electromagnet 14. When armature 16 is moved in one direction, contact 21 engages surface 20, and movement of the armature in the opposite direction causes contact 21' to engage the surface 20'. A contact 26 bears against the peripheral surface 20 of element 19 to perform the same function 'as above described for contact 26 in Fig. 1.

Contacts 21 and 21', rotary elements 19, 19 are connected between the respective windings of a pair of power electromagnets 48, 48', and a source such as a battery 30. The power electromagnetsV 48, 48' are provided with The surface of contact 21 is .020l in diameter.

3 respective armatures arranged to actuate relatively large power contact assemblies 50.

A pair of ratchet wheels 42, 42 are secured to the shaft 22. Pawls 44, 44 are supported on armatures `tact 26 and surface 20 for removing any microscopic spires resulting from the engagement of contact 21 with surface 20. Reversal ofrcurrent through coil 14 causes armature 16 to move in the opposite direction, whereupon contact 21 disengages surface 20 and contact 21' engages surface Electromagnet 4S is thus energized to attract armature 46 and pawl 44' to rotate ratchet wheel 42 and cause a shearing action between contacts 26 and surface 20.

The power contacts 50 are connected to control the energization of an appropriate utilization device such as a power load 52. By this arrangement, the sensitive relay 14 energizes the power relays 48, 48 to control substantially any desired amount of power.

In one practical arrangement of the above-described Vcontact structure, the separation of contact 21 from surface 20 is .002 when the electromagnet 14 is deenergized. The spring 17 was adjusted to provide approximately three grams of force to separate contact 21 from surface 20. This embodiment with member 19 rotated at approximately three revolutions per minute, performed more kthan 20,000,000 cycles of make-and-break operations withoutl substantial change in the physical condition of the contact surfaces and without the necessity of cleaning or other attention.

From the foregoing description, it will be apparent thatV the present invention provides an improved type of electrical contact device particularly suitable for sensitive contact operation, presenting substantially no maintenance problems, and capable of a degree of reliable operation drical contact having a peripheral surface; a movable contact constructed and arranged such as to make and 50 break contact with said peripheral surface; first means energizable by the low power circuit for actuating said movable Contact; second means responsive to actuation of the movable contact for rotating the cylindrical contact; land a resilient element having an end portion in shearing engagement with the peripheral surface of said cylindrical contact such that said shearing engagement is effective, when the cylindrical contact is rotated, for scraping olf metal deposited on the peripheral surface as a result of the movable contact making and breaking contact with the cylindrical contact.

2. A sensitive contact system for energizing an electrical circuit from a low power control circuit, said con- -tact system comprising: a rotatably supported cylindrical contact having a peripheral surface; a movable Contact vconstructed and arranged such as to make and break -contact with said peripheral surface; a resilient element having an'end portion in electrically conductive but shearing engagement with said peripheral surface such that rotation of the cylindrical contact is eective for scraping off metal deposited on said surface as a result for rotating said cylindrical contact, said means including an electromagnetic element, a source of electrical energy, and an actuating circuit embracing the cylindrical contact, the movable contact, the resilient element, said electromagnetic element, and said source of energy.

3. A sensitive contact'system for energizing an electrical circuit from a low power control circuit, said contact system comprising: a rotatably supported cylindrical contact having a peripheral surface; a movable contact constructed and arranged such as to make and break 0 contact with said peripheral surface; a resilient element having an end portion in electrically conductive but shearing engagement with said peripheral surface such that rotation of the cylindrical contact is effective for scraping olf metal deposited on said surface as a result of the 5 movable contact making and breaking contact with the cylindrical contact; a control circuit embracing electromagnetic means for actuating the movable contact; first means responsive to actuation of the movable contact for rotating said cylindrical contact, said first means includ- 0 ing an electromagnetic element adapted to rotate the cylindrical contact, a first source of electrical energy, and an actuating circuit embracing the resilient element, the movable contact, the cylindrical contact, said electromagnetic element, and said source of energy; and second means for rotating said cylindrical contact independently of the first means, said second means including v a second source of electrical energy and a selectively operable switch adapted for disconnecting the electromagnetic element of the rst means from thefirst source l of electrical energy and for connecting said magnetic element to said second electrical energy source. 4. A sensitive contact system for energizing an electrical circuit from a low power control circuit7 said conltact system comprising: a cylindrical contact having a peripheral surface; a movable contact arranged such as to make and break contact with said peripheral surface; first means energizable by the lower power control circuit for actuating said movable contact; a ratchet wheel; a shaft supporting the ratchet wheel and the cylindrical contact such that rotation of said wheel effects rotation of said cylindrical Contact; a pawl constructed and arranged for rotating the ratchet wheel; secondV means responsive to the actuation of said movable contact for actuating said ratchet wheel; and a resilient element having an end portion in shearing engagement with the peripheral surface of said cylindrical contact such that said end yportion is effective, when the cylindrical contact is rotated, for scraping oif metal deposited on the peripheral surface by the contact making and breaking action of the movable contact with said peripheral surface.

5. A sensitive contact system for energizing an electrical circuit from a low power control circuit; said contact system comprising: a rotatably supported cylindrical contact having a peripheral surface; a movable contact constructed and arranged such as to make and break contact with said peripheral surface; a resilient element having an end portion in electrically conductive but shearing engagement with said peripheral surface such that rotation of the cylindrical contact is effective for means responsive to actuation of the movable contact for rotating the cylindrical contact, said means including a ratchet wheel, a shaft supporting the ratchet wheel and the cylindrical contact such that rotation of said wheel effects rotation of the cylindrical Contact, a pawl 0. constructed and arranged for rotating the ratchet wheel, an electromagnetic element adapted for actuating sa1d pawl, a source of electrical energy, and an actuating circuit embracing the resilient clement, the rotating contact, the movable contact, the electromagnetic element,

and the source of electrical energy.

(References on following page) References Cited in the le of this patent 1,610,555 2,422,842 UNITED STATES PATENTS 2,572,105 232,806 Davis Oct. 5, 1880 988,442 Burnham Apr. 4, 1911 1,062,380 Apple May 20, 1913 992,597

6 Kindl Dec. 14, 1926 Molyneux et a1. June 24, 1947 Bronstein Oct. 23, 1951 FOREIGN PATENTS France July 11, 1951

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