US3177307A - Tap changer rotary switch with radially spaced movable contact members and motion limiting means - Google Patents

Description

April 6, 1965 H. .WEB ETAL 3,177,307

TAP CHANGER ROTARY W TCH WI RADIALLY SPACED MOVABLE CONTACT MEMBERS AND MOTION LIMITING MEANS Filed Sept. 6. 1961 E I H1 United States Patent M 3,177,307 TAP CHANGER RUTARY SWITCH WITH RADI- ALLY SPAQED MOVABLE CGNTACT MEMBERS AND MUTIUN LIP /HTTNG MEANS Hans J. Weber and Charles E. Glatz, Pittsburgh, Pa, assignors to Allis=Chahners Manufacturing Company, Milwaukee, Wis.

Filed Sept. 6, 1961, Ser. No. 136,264 1 Claim. (Cl. 20011) This invention relates to a switch for electrical apparatus and in particular to a rotary type switch designed for handling heavy currents and high voltages found in such apparatus as line transmission transformers.

Where it is desired to make a variety of circuit connections involving several stationary contacts a general practice has been to provide a rotary type switch. The stationary contacts are arranged in a circular pattern with a movable contact pivotably mounted at the center of the stationary contacts. Some of the many requirements for this type of switch is that the movable contact and the stationary contacts, in addition to having long life, exert high pressure against each other. The movable contact should also be self-aligning on the stationary contacts and apply a strong wiping action against them. Mechanical stresses should also be absorbed by the switching mechanism in order that the mechanism has a high life expectancy. In power circuits the contact areas should be substantial and adequate clearances should be provided between the stationary contacts to avoid flashovers.

The switch of this invention embodies all of the above mentioned features with only a minimum number of parts. Briefly, it comprises a plurality of contact posts mounted in an arcuate pattern on an insulating panel. A pair of movable contacts, mounted in a contact holder which is pivotably fixed to the center of the insulating panel, straddle the contact posts. A biasing means disposed between the two movable contacts assures their making good connection with the contact posts.

It is therefore one object of this invention to provide a new and improved electrical switch.

Another object of the invention is to provide a new and improved rotary switch for making a number of circuit connections.

Another object of this invention is to provide a new and improved switch suitable for high voltage applications.

Objects and advantages other than those mentioned above will be apparent from the description when read in connection with the drawing in which:

FIG. 1 is a front view in elevation of the switch of this invention;

FIG. 2 is a cross section taken along the lines IIII of FIG. 1;

FIG. 3 is a schematic showing of the switch of this invention applied to the tapped windings of a transformer, and

FIG. 4 is an isometric view of the switch.

As shown in FIGS. 1 and 2, an insulating panel 11 supports six stationary contact posts 14 arranged in a circular pattern. If preferred, the posts 14 may be arranged in an arcuate pattern other than circular. The panel 11 may be of any standard insulating material such as a phenolic or polyester substance and if desired may be stamped or molded into the illustrated design. For improved dielectric properties, elongated apertures 21 may be formed between each of the stationary contact posts, taking care that these apertures are not of such a size as to materially reduce the strength of the panel. At the base of the panel are two spaced mounting members 23 with juxtaposed right angle shoulders 24. With the provision of the shoulders the panel may be snugly mounted on a rectangular insulating support 26 of sufli- 3,177,307 Patented Apr. 6, 1965 cient structural strength and secured thereto by a bolt 28 extending through the base mounting members 23 and the support 26.

While the illustrated embodiment of this invention shows six stationary contact posts 14, it is to be understood that a greater or lesser number may be used if arranged in an arcuate pattern. These posts may be formed from one of the numerous electrical conductive materials available and may either be molded in with the insulating panel 11 or fixed separately to it as illustrated. Each contact post 14 contains a shoulder element 30 which abuts the rear side 31 of the panel. The posts extend through the panel 11, and at a point approximately flush to the front 34 of the panel have an indentation (not visible) for seating a lock washer 33. Permanent electrical connections between each post and its corresponding lead 35 may be accomplished through crirnps 36 or conventional fastening hardware.

Extending through the center point of the circular arranged posts is an operating shaft 39. The shaft 39 is journaled for rotation in the panel 11. Fixed to the rectangular end 51 of the shaft is a contact holder 43. In the particular instance this is accomplished by providing a rectangular hole 44 through the fixed end 46 of the contact holder 4-3 so that it is complementary with a rectangular portion of the shaft end 41. A roll pin 47 may be inserted through the fixed end 46 of the contact holder and the shaft end 41 to prevent displacement of the contact holder 43.

The contact holder has a pair of spaced parallel tines 49 radially extending from the center of the contact posts 14. Slidably mounted between the two tines 49 along their longitudinal axis are a pair of juxtaposed inner and outer contacts 51 and 52. The sliding action of the two contacts is radial and is accomplished with pins 54 extending through sides 55 of the contacts at an intermediate point and into elongated apertures 57 in the two tines Q9. The two inner ends 58 of the two contacts 51 and 52 straddle a pair of the contact posts 14. Each inner end 58 has a projected face 66 for making contact with two of the contact posts. Outer end 62 of each contact 51 and 52 has a shoulder 63. Positioned between the juxtaposed shoulders 63 is a compressed spiral spring 64. T o avoid current flow through the spring which may prematurely age it, insulation 65 may be provided at one end. One of a number of ways for aligning the spring 64 and limiting the amount of movement between the two contacts may comprise an insulating cylinder 67 contained within the spiral spring 64 and seats 65. The compressed spring 64 exerts force against each of the outer ends 62 of the contacts 5i and 52 and in turn the inner ends 58 of the contacts are forced solidly against a pair of the contact posts 14.

It is to be noted that each of the contacts 51 and 52 is curved and is concentric to the circle defined by the stationary contact posts 14-. The outer contact 52 is longer than the curved inner contact 51 due to the perimeter differences. Because the current flows in the same direction in each of the parallel contacts Si and 52., a magnetic force is present which tends to pull the two contacts more solidly against a pair of contact posts 1- in order to obtain an equal division of current in the two contacts 51 and 52 and therefore maximum attraction between them, the longer outer contact 52 is provided with a greater cross sectional area. The ratio of the cross sectional areas of the two contacts 51 and 52 is approximately the same as the inverse ratio of their current carrying lengths in order to get maximum attraction. Thus, with the combination of the forces of the spring 64 and the compression and the magnetic forces acting on the contacts 51 and 52, positive pressure is exerted on the contact posts 14.

In FIG. 3 a transformer 69 is schematically illustrated with a primary winding 70 and a tapped two section secondary winding 71. Leads 35 from the tapped sections of the secondary winding are fixed to the stationary contact posts 14. By operating the movable contacts 51 and 52 about the posts 14 varying amounts of the secondary winding 71 are added and subtracted and a variety of voltages may be obtained. A conventional lever or handle, not illustrated, may be secured to rectangular projection 73 of contact holder 43 for movement of contacts 51 and 52 about the posts 14.

While only one embodiment of the present invention has been illustrated and described, it Will be apparent to those skilled in the art that modifications other than those mentioned above may be made without departing from the spirit of the invention or from the scope of the appended claim.

Having now particularly described and ascertained the nature of our said invention and the manner in which it is to be performed, we declare that what we claim is:

An electric switch comprising: an insulating panel; a plurality of generally parallel contact posts mounted in an arcuate pattern on said panel; a radially extending contact holder mounted at the center of said contact posts to rotate on an axisgenerally parallel to said posts, said holder having a fork member with a pair of spaced parallel tines; a pair of radially spaced juxtaposed contacts positioned between said tines for rotation from post to post, each said juxtaposed contact having a pin laterally extending through an intermediate section, each said pin being supported in an elongated aperture longitudinally aligned in each of said tines, one axially displaced end of each of said juxtaposed contacts comprising an arcuate length straddled across a pair of adjacent contact posts, the opposite axially displaced end of each of said juxtaposed contacts having a biased compression spring disposed therebetween and urging said juxtaposed contacts against said adjacent posts; and means positioned between said juxtaposed contacts and having a length slightly less than the space between said juxtaposed contacts for limiting their relative motion;

References Cited by the Examiner UNITED STATES PATENTS 593,286 11/97 Waite ZOO-11 1,752,213 3/30 Treanor. 2,078,331 4/37 Leidy. 2,604,556 7/52 Daly et al y 200-15 X 2,686,236 8/54 Hodtum 20011 2,760,017 '8/ 5 6 Stenersen 200-11 2,918,541 12/59 Waite 200-11 2,921,996 1/60 Dulude ZOO-11 BERNARD A. GILHEANY, Primary Examiner.

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