US 3267224 A
Description (OCR text may contain errors)
Ill m 1' M ill I P. E. VEGA ELECTRICAL SWITCH WITH FLOATING BRIDGE CONTACT STRUCTURE 2 Sheets-Sheet 1 a I o O 0 Z 25 o O 0 9 OO HTTORNEY5 INVENTOR. P601. E. VEGH Aug. 16, 1966 P. E. VEGA 3,267,224
ELECTRICAL SWITCH WITH FLOATING BRIDGE CONTACT STRUCTURE Filed Oct. 17, 1962 2 Sheets-Sheet 2 INVENTOR PfiUl. E. V581? flT TORNE Y6 United States Patent 3,267,224 ELECTRICAL SWITCH WITH FLOATING BRIDGE CONTACT STRUCTURE Paul E. Vega, North Hollywood, Calif., assignor to Aerovox Corporation, New Bedford, Mass., a corporation of Massachusetts Filed Oct. 17, 1962, Ser. No. 231,135
2 Claims. (Cl. 20011) This invention relates to the art of electrical switches, more particularly to an improved instrument switch permitting selective completion of any one or more of a plurality of desired circuits by manipulation of the switch.
As conducive to an understanding of the invention, it is noted that a variety of so-called instrument switches have been evolved in which an electrical circuit is completed between a commutator ring and one or more of a plurality of spaced contacts whereby the circuits coupled to said spaced contacts may be selectively energized or de-energized by moving -a brush member over the commutator into electrical connection with the desired contacts. In order to obtain an effective and efficient switching function permitting utilization with delicate instruments, it is desirable to insure positive metal to metal contact between the brushes and the commutator ring and contacts thereby preventing a high resistance connection. It is further desirable to reduce friction between moving components so as to minimize wear and increase the service life of the switch.
It is accordingly among the objects of this invention to provide an electrical switch permitting eificient selective making or breaking of one or more of a plurality of electrical circuits with positive metal to metal contact and with a minimum number of elements that are not likely to become deranged even with long use.
According to one illustrative embodiment of the invention, the instrument switch comprises a contact plate of insulating material upon which one or more commutator rings are supported along with a plurality of spaced contacts. Terminal connectors extend through the contact plate from each of the contacts, and from the commutator ring, to facilitate their electrical connection in a circuit to be controlled by the switch. A brush block assembly including a brush supporting plate of insulating material is rotatably mounted with respect to said contact plate. A plurality of pairs of openings are formed in the brush supporting plate and a U-shaped brush member is arranged loosely on the supporting plate with the legs of the brush member extending through said openings. One leg of the brush member extends into wiping cont-act with a commutator member and the other leg extends into wiping contact with a contact. A cantilever spring having one end anchored to the brush supporting plate has a foot at its free end, biased against the brush member to force the legs through the openings against the contact and commutator. The foot contacts the brush member with substantial point contact providing a fulcrum on which the brush member may rock. A mounting plate is arranged at a spaced distance from the contact plate, and a shaft extends rotatably through said mounting plate into engagement with said brush supporting plate so that by manipulation of a knob on the free end of the shaft the brushes may bemoved to a desired contact. A star wheel is desirably secured to the shaft for rotation therewith and a spring pressed rollerdetent engages between the teeth of the star wheelto provide stepping movement of the brush block assembly with respect to the contact plate.
In the accompanying drawings in which are shown one or more of various possible embodiments of the several features of the invention;
' of like radius of curvature.
FIG. 1 is a side elevational view of the novel instrument switch,
FIG. 2 is a bottom plan view of the switch showing the terminals of the commutator rings and contacts,
FIG. 3 is an enlarged cross-sectional view on line 3-3 of FIG. 2 illustrating the desired relationship between switch components,
FIG. 4 is a cross sectional view on line 44 of FIG. 3 illustrating the top of the brush block assembly, and,
FIG. 5 is an enlarged detailed view of the star wheel and spring pressed roller detent controlling the stepping action of the brushes between contacts.
As shown in the drawings, the instrument switch 10 comprises a contact plate 11, here shown of a square configuration formed of a suitable electrical insulating material such as linen base phenolic or glass-epoxy, having a plurality of commutator members here shown as ring segments 12, 12, 13, 13' arranged thereon. In the illustrated embodiment the commutator rings are of the segmented type, each ring segment extending through an arc of slightly less than so as to provide separation between rings Four commutator ring segments are shown, but it will be appreciated by those skilled in the art that a greater or lesser member may be employed. Arranged on arcs having radii of curvature larger than the radii of curvature of the commutator ring segments are a plurality of contacts 14, 14, and 15, 15'. The angles sub-tended by the arcs along which the contacts are arranged are preferably substantially equal to the arcs sub-tended by the commutator ring segments with which the contacts are to be electrically connected. As shown in FIG. 4, groups of contacts 14, 14' and 15, 15 are associated respectively with commutator ring segments 12, 12' and 13, 13'.
Hollow bored contact stems, as shown in FIG. 3, extending through the contact plate 11 provide contact terminals 20 for coupling of the contacts to an electrical circuit to be controlled by the switch 10. commutator terminal strips 22 are electrically coupled to the commutator ring segments through the contact plate 11. A flanged bearing sleeve 25 is centrally arranged, extending through contact plate 11 at the center of the arcs of the commutators and contacts.
Brush block assembly 30, as shown in FIGS. 3 and 4, comprises a brush supporting plate 31 of a circular configuration having a diameter substantially equivalent to the outer diameter of that of the outer arc of contacts 15, 15'. Plate 31 is fabricated of an electrically insulating material similar to that of the contact plate 11 and is formed with spaced pairs of openings 32, 33, 34 and 35, extending through plate 31. Four such pairs of openings are here provided corresponding to the number of commutator ring segments and contact groups respectively.
U-shaped brush members 37, each having an inner commutator engaging leg 38, and an outer contact engaging leg 39 are arranged with legs 38 and 39 extending respectively through the inner and outer of the pairs of openings 32, 33, 34 and 35 as best seen in FIGS. 3 and 4.
A cantilever or leaf spring 45 of a configuration as shown in FIGS. 1, 3 and 4 is riveted or otherwise secured at 46 to brush supporting plate 31. Pressure foot 48 having an arcuate free edge extends from the end of spring 45 into fulcruming contact with brush member 37. The arcuate configuration of the free edge of foot 48 provides a fulcrum for brush member 37 due to the point contact between spring 45 and brush member 37 thereby permitting rocking of the brush member with respect to plate 31 about the contact point and also concentrating the spring forces at the point of contact, and insuring dependable contact at such point.
'pin 57 is secured to plate 55 for a purpose to be made hereafter apparent. Headed detent supporting pivot pin 60 is similarly secured to plate 55 along with spring stop pin 61.
Shaft 65 extends rotatably through bushing 56 and is upset or otherwise shaped to form flare 57 as shown in FIG. 3. Beyond thefiare 57 the shaft extends through collar 50 which is secured to the shaft 65 by means of set screws 51. The free end of shaft 65 extends rotatably through bearing sleeve 25. Knob 67 is secured to the end of shaft 65 adjacent mounting plate 55 by knob set screw 68.
Star wheel 70, as shown in FIGS. 3 and 5, is fixed to shaft 65 for rotation therewith. Spaced stops 71 and 72 are formed in the surface of star wheel 70 positioned to contact stop pin 57 on mounting plate 55. The angle between stops 71 and 72 between which pin 57 engage is equal to the angle sub-tended by the commutator segments and the contact groups. The number of teeth on star wheel 70 is such as to provide an intertooth valley 75 for each desired switch step.
Detent 80 is pivoted on detent pivot pin 60 and is formed with detent roll 81 on its free end. Roll '81 rides over the teeth of star wheel 70 into intertoo'th valleys 75. Hairpin spring 83 is wound about detent pin 60 with one spring leg bearing against spring stop pin 61 and the other spring leg bearing against detent spring pin 84 to bias roll 81 against the star wheel.
The aforedescribed mounting plate 55, and contact plate 11 are maintained in desired assembled relationship with respect to the other components by means of machine screws 85 extending through plates 55 and 11, and through spacers 86 arranged between the plates. Nuts 87 engage screws 85 to maintain the switch components in assembled relationship.
In use of the instrument switch above described, the commutator terminals and contact terminals are electrically connected in conventional fashion to the circuits to be controlled by the switch. It is preferred that alternate contacts of each group be inactive dummies providing land for the brushes to wipe over thereby insuring a break before make mode of operation and insuring a smooth wiping action of the brushes over the contact surfaces.
After desired circuit connections are made, manual manipulation of knob 67 to rotate shaft 65 effects rotation of star wheel 70 and brush block assembly 30. The detent 80 is cammed away from the center of star wheel 70 over the tooth of the star wheel into the star wheels next intertooth valley 75. Where alternate contacts are dummies, the rotation of shaft 65 permitted by the star wheel 70 and detent 80 will provide for stepping of the brush assembly 30 through an are having an angle equal to the angle of the are between active contacts. Thus, at each stepping of the brush block assembly, the brushes will move from one active contact in any contact group to another.
' In order to insure that the brush members only move to make a connection between a given commutator ring segment and its associated contact group, stops 71 and 72 in engaging limit pin 57 limit the movement of the brush plate assembly 30 through this desired range.
It will be observed that the legs 38 and 39 of brushes 37, as best shown in FIG. 1, are chamfered at their edges thereby increasing the facility with which the brushes ride onto the contact surface. Any irregularities in the path of travel of the brushes over the commutator rings and contacts is accommodated by the free floating mount of the brush 37 on brush supporting plate 31. The brush rocks on fulcrum provided by the point of contact be tween the foot 48 of cantilever spring 45, with the spring forces exerted on the spring remaining constant. c
The instrument switch above described provides means for insuring desired positive metal to metal wiping contact between the brush members and the contacts and commutation rings, thus reducing electrical resistance and distributing frictional wear to extend the service life of' the switch.
As many changes could be made in the above construction, and many apparently widely different embodiments ,1
of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:
1. An electrical switch comprising a contact plate, a plurality of spaced contacts arranged in a ring on said contact plate, an arcuate commutator member spaced from said contacts, a rotatable brush supporting plate, a free floating brush member of U-shaped configuration carried by said support plate and movable over said commutator member and said contacts, a cantilever spring of relatively thin sheet spring stock carried by said support plate and biasing said brush member against said contacts and commutator member to engage the same, and a foot on said cantilever spring having an arcuate edge providing a fulcrum on which said brush member may rock, and providing substantial point contact between the cantilever spring and the brush.
' 2. An electrical switch comprising a contact plate, a. plurality of concentric arcuately arranged groups of contacts on said contact plate, a plurality of commutator ring segments corresponding in number to said groups of contacts on said contact plate, a brush supporting plate rotatably mounted adjacent said contact plate, said brush supporting plate being formed with a plurality of pairs of spaced openings, one of the openings of said pair being aligned with one of said corn-mutator rings and the other of the openings of one of said pairs being aligned with one of said contact groups, a plurality of brush members corresponding in number to said groups of contacts loosely carried by said brush supporting plate, each of said brush members being U-sha'ped in configuration with one of the legs of said brush member extending through one of said openings and another of the legs of said brush member extending through the other of said openings, thereby bridging the gap between said commutator segment and said group of contacts, a cantilever spring on said brush supporting plate, and 'a foot on said cantilever spring having an arcuate free end engaging said brush member to provide a fulcrum on which said brush member may rock.
References Cited by the Examiner UNITED STATES PATENTS 7 698,200 4/1902 Hinds 2001l.23
969,055 8/1910 Hammond 20011 2,090,505 8/1937 Uhle ZOO-11.22 2,186,638 1/1940 Hall 20011.24 2,402,736 6/1946 Davis 200ll.22 2,430,215 11/1947 Doucette 200164 2,489,626 11/1949 Doucette 200-11.22 2,504,027 4/ 1950 Kuh'lman 20011 2,771,520 11/1956 Stevens ZOO-15 ROBERT K. SCHAEFER, Primary Examiner.
BERNARD A. GILHEANY, KATHLEEN H. CLAFFY,
E. JAMES SAX, Examiners.
I. R. SCOTT, Assistant Examiner.