US2452916A - Rotary tap switch - Google Patents

Description

N V. 2, 1948- R. A. K. FLEISCHMANN 2,452,915

ROTARY TAP SWITCH 3 Sheets-Sheet 1 Filed Oct. '7, 1947 INVENTOR. Rude-Z JZ-Jif .7 Zezsc7rmanrr,

Nov. 2, 1948. R. A. K. FLEISCHMANN 6 ROTARY TAP SWITCH Filed Oct. 7, 1947 3 Sheets-Sheet 2 INVENTOR. Rude Zf .JZJKFZez'schmann 1948- R. A. K.-FLEISCHMANN 2,452,916

ROTARY TAP SWITCH 3 Sheets-Sheet 3 Filed Oct. 7, 1947 Patented Nov 2, 1948 ROTARY TAP SWITCH' Rudolf A. K. Flelschmann, Philadelphia, Pa., as-

signor to The Eastern Specialty Company, Philadelphia, Pa., a corporation of Pennsylvania Application October 7, 1947, Serial No. 778,340

7 Claims.

The object of this invention is to provide a rotary tap switch comprising the necessary elements by which a plurality of electric circuits may be controlled by the movement of a single manually operable member, such as a rotary knob, and wherein the parts are assembled and housed in such manner as to yield a sturdy and compact 'assembly of parts, protected against the elements and the accumulation of dirt or other foreign matter.

A further object of the invention is to provide a structure of the character indicated, including in its make up sliding contacts of heavy metal adapted to stand up under heavy electrical loads and precision, snap action switch assemblies adapted to make or break the circuit in such relation to the sliding contacts as to prevent arcing and burning of the latter.

A further object of the invention is to provide a structure of the character recited wherein the elements utilized for the actuation of the precision, snap action switch or switches are of such nature as to impose very little resistance to the movement of the operating member and wherein the sliding contacts are under uniform resistance to their movement; whereby jumpy operation of the switch is avoided and a smooth and even movement of the parts is assured. These and other advantages of the invention will be best understood in conjunction with a consideration of the accompanying drawings wherein:

Fig. 1 is a side elevation of a rotary tap switch constructed in accordance with the invention.

Fig. 2 is a longitudinal sectional view, but differing from Fig. 1 in that Fig. 2 provides for two ,sets of contacts instead of one set as in Fig. 1.

Fig. 3 is an exploded, perspective view illustrating the relationship of certain of the parts of the switch.

Fig. 4 is a front elevation of one of the switch section assemblies, hereinafter described.

Fig. 5 is a sectional view on line 5-5 of Fig. 4 with the tie rods added.

Fig. 6 is a horizontal sectional view on line 5-4 of Fig. 4.

Figs. 7 and 8 are, respectively, front and edge elevations of the common contact element.

Figs. 9 and 10 are face and edge elevations, respectively, of the slider or wiping contact element.

Figs. 11 and 12 are face and sectional views, respectively, of one of the cup cams showing the stop pins adjusted for a five position tap switch.

Figs. 13 and 14 are face and sectional views, respectively, of a cup cam having its stop pins adjusted for a three position tap switch.

Like numerals designate corresponding parts in all of the figures of the drawings.

In the drawings 5 designates a panel upon which the switch assembly may be mounted by 2 means of screws, one of which is indicated at B. These screws enter the front bearing plate 7 of the switch assembly. The parts of the switch are tied together by tie rods 8, the forward ends of which are secured in the plate I. These tie rods pass through the several elements of the switch and at the rear end of the structure they pass through a rear assembly plate 9. Outside of said plate said tie rods carry nuts l0. Tightening of these nuts binds all of the elements of the switch assembly together.

An operating knob ll located outside of the panel and made of any suitable insulating material, is securedupon the operating shaft l2. A pointer 13 upon the knob serves to indicate the position to which the knob has been turned and the front face of the panel may be provided with suitable indexing marks with which this pointer may cooperate.

The forward end of the shaft I2 is journaled in the plate 'i and the rear end of said shaft is journaled in a suitable bearing insert 14, that is carried by a cup-like detent assembly casing IS. A plurality (in this case two) switch section assembly units l6 and I! are held by the tie rods 8 in alignment with and in position between the elements i and [5, there being a spacer disk l8 of insulating material between the forward switch assembly l1 and the plate 1.

Each of the switch section assemblies comprises a ring or annulus I9 of insulating material into which are molded a plurality of individual contact members 20. Externally threaded ends 2| of these contact members 20 are adapted to have secured thereto the conducting wires of the several circuits that are to be controlled by this switch.

The individual contact members 20 are relatively thick and rugged in construction being preferably formed of blocks of copper or other suitable metal of high electrical conductivity, and at their inner ends they are provided with flattened portions 22 which are exposed and all of which lie in a plane to be wiped over and contacted by a sliding or wiping element hereinafter described. In addition to carrying the individual contacts 20 the annular members I9 also carry a' common contact 23. The outer end of this contact is externally threaded at 24 for attachment to a conductor not shown, constituting a continuation of the circuit. The inner end of the common contact 23 is fixed to a collector ring 24a. The outer edge of this ring, about its entire circumference, lies in the plane occupied by the faces of the portions 22 of. the individual contacts. The shaft I2 is provided in its length with a portion that is polygonal (preferably square) in cross-section, such portion being indicated at 25. A correspondingly shaped portion 26 is mounted upon the shaft 25 and turns thereaeeaem with. This portion 26 may be merely a sleeve or" fiber or like insulating material or it may be made by winding insulating material upon the shaft 25. In either case this angular portion serves as an insulating mounting for, and a means for imparting rotation to the disks 21 of sliding or wiping contact members which make continuous contact with the exposed edge 28 of the associated collector ring 24a and which make contact with the individual contacts according to the po-- sition to which the knob ii is turned. To this and these disks 2! are provided with the portions 25 which are disposed in position to contact the edge of the collector ring 28. These portions 29 may be of elongated arcuate form of such length as to provide a bearing on the edges of .the collector ring of such extent as to prevent any tendency of disks 2'! to wabble. However the same efiect may be secured by providing a sufficient number of pins upon the disks 2'! and in the position indicated by the part 29 to give the desired elongated hearing. The reason that it is desirable to provide an elongated hearing at this point is that while the disks 2] are forced to rotate with the insulating portion 26 (because of the angular formation of the latter), these disks are free to have limited endwise movement upon said angular portions and they are thrust toward the collector ring by stout spring washers to or the equivalent thereof. In all switches of this type with which I am familiar the desired pressure of contact has usually been secured by making the equivalent of the disks 2i of yieldable or spring material. This has made it necessary to make these members relatively light. It will be observed that in the present construction these members have been made heavy and rugged and capable of carrying considerable electrical loads and that the desired pressure of contact between them and the members with which they make contact is secured by rendering these members bodily movable and then actuating them by sepa= rate spring members such as the washers 30 which may be made as heavy and powerful as is required by the conditions under which the device is to be used. Further, by this procedure I am able to use relatively heavy copper for the disks 21. This material while highly desirable from the standpoint of electrical conductivity does not have the resiliency to adapt it to function both as a part of the collector and as a spring tensioning element. The pressure exerted by the washers is not only imposed upon the members 29 but also upon the individual wiping shoes 30 mounted upon the outer portions of the disks, and having their contacting faces disposed to wipe over the surfaces of the individual contacts 2d.

To preserve the clarity of the drawings 1 have indicated those surfaces which are in elevation and are of insulating material by the capital letter I enclosed in a circle.

A conventional thrust bearing 32 is disposed,

between switch section assembly i6 and the rear face 33 of cam cup 34. The outturned edge of this cam cup is provided with a plurality of notches constituting cams 35. These cams engage steel balls 36. These balls are thrust outwardly and into engagement with the cams by springs 31, disposed in cup-like sleeves 38, the springs bearing between the outer ends of these sleeves and the balls.

When the cam cup is rotated by the turning movement of the angular portion of the shaft 25 the cams act to thrust the balls 38 inwardly against the tension of their springs to cause these balls to thrust outwardly upon the plungers 40 of light, snap action switches 4|. Two of these switches have been illustrated as being secured to the plate 9 by bracket 42. It is common practice to employ such switches in conjunction with rotary tap switches of this character, to interrupt the circuit during the time that the heavier contacts of the tap switch are being adjusted to new positions. Such an arrangement is shown, for example, in the patent to Chamberlain 447,230. These precision, snap action switches have now attained a distinct status in the art and may be purchased upon the open market. It is therefore deemed to be unnecessary to show their internal construction. It is sufticient to say that they comprise relatively light contacts which spring or snap quickly from closed to open position, and viceversa, and in that respect they dififer from the much heavier sliding contacts such as those indicated at 20, 28 and 3! and which contacts are adapted to carry much heavier current than could be carried by a light, snap action switch. However it will be noted that this invention contemplates the use of two of the snap action switches. This is because the rotary tap switch is adapted for use in three wire circuits and in order to interrupt the current in a three wire circuit, during the adjustment of the sliding contacts, two of the legs of the three wire circuit, would have to be interrupted. It should be noted therefore that in making provision for this necessary use of two snapaction switches, I have so positioned and mounted them that one balances the other in imposing resistance to the action of the cams 35. This in conjunction with the fact that the sliding contacts are under uniform pressure throughout their path of rotation, gives a very smoothly acting switch. stop pins 63 upon the cup cam 33 coast with the stop pin 44 on the member B5 to limit the throw of the cam. to suit the number of tapoiIs that are provided for. It will be observed, by reference to Figs. 11, 12, 13 and 14 that there are eight cam notches on each cam cup and that there are eight holes 43a in the back wall of the cam cup to receive the shanks 43b of the stop pins 53. These stop pins may be shifted in accordance with the number of tapoff circuits to be accommodated. In Fig. 11, for example, these pins are shown positioned for a five position switch while in Fig. 13 they have been positioned for a three position switch.

I preferably form upon one switch assembly annulus a projection ila adapted to enter a socket ifia in the associated annulus l6. This assures that the parts can be brought together in only one way and that the right one.

It will be seen that the proposed assembly of parts provides a tap switch in which the parts are of rugged construction, closely compacted in assembly, occupying little space and in which the shifting from one circuit to another is efiected by a single turning movement of the knob. The mechanical advantage yielded by the cams and rolling balls makes the turning oi! the knob an easy task while the uniform" pressure of the sliders in all positions of circumferential adjustment renders the movement smooth and steady. The cams and balls not only eiiect the shifting of the plungers of the snap action switches but they act as detents to hold shaft l2 and the sliders in the positions to which they are indexed.

The wiping heads 3| are preferably of such width in the direction of the circumference of the disks 2'! as to be of the shorting type, that acsae'ie is they make contact with the next individual contact before leaving the preceding one. Thus in an intermediate position of the knob ll these heads span two adjacent fixed contacts. This is desirable in certain circuit applications where the circuit should be make-before-break. In other applications,'such as a transfer switch controlling a plurality of thermocouples, the circuit E. M. F. is so low that a destructively high short circuit cannot occur, and the shorting type of construction is therefore not an objection.

Where the sliding shoe always rides on a fixed contact surface in all positions, its friction is constant and uniform, without any sticking action. It does not require any extra force to move the sliding shoe into full engagement with a fixed contact.

This is further assured by the manner in which the contacts are mounted. They are molded into the annular members as inserts, and are immovably held-into position. A final machining cut is taken over all the radial contacts and the center contacting ring, so that all contacting surfaces are in one plane.

Where the circuit requires a non-shorting type of switch, the snap switch at the end of the assembly controls the power supply as previously explained. In all case, whether the switch is shorting or non-shorting," the ball and spring detent is used to position the sliding shoe correctiy. It will be observed that the assembly shown and described, comprises what may be considered a main switch assembly consisting of the relatively heavy and rugged sliding contacts 2|, II and 3| and an auxiliary switch assembly consisting of the much lighter, snap action switches II and that all necessary elements have been brought into the compact and rugged assembly shown in Fig. 1. A single hand operated main shaft traverses and actuates the moving parts and the two snap switches, necessary in a three wire circuit, are so spaced upon opposite sides of this shaft as to balance each other in the action of the device. This prevents any tendency of the shaft to bind by reason of off side strain and renders the device smooth and easy in operation.

It is to be understood that the invention is not limited to the precise construction set forth but that it includes within its purview whatever changes come within either the terms or the spirit of the appended claims.

I claim:

1. A rotary tap switch comprising a manually operable rotative shaft, an operating handle carried thereby, a plurality of radial contacts disposed around said shaft, a wiper actuated by said shaft to move over said contacts, a precision, snap action switch including an operating plunger movable endwise and in substantial parallelism with said shaft, a cam element carried by said shaft comprising a cup-like body rotated by said shaft in a plane transverse to the shaft and having upon its free edge a plurality of cam forming notches, a cup in which said plunger is disposed, a spring in said cup about said plunger, and a ball in said cup against which the spring bears, said ball being positioned and dimensioned to be engaged by said cam forming notches and to thrust against said plunger against the action of said spring to thereby actuate the switch in synchronism with the movement of the wiper over said radial contacts.

2. A rotary tap switch comprising a manually operable rotative shaft, a plurality of radial con- 6 tacts disposed around said shaft, a wiper actuated 1 by said shaft to move over said contacts, a pair of precision, snap action switches disposed in balanced relation upon opposite sides of said shaft, said switches comprising operating plungers. disposed and movable in substantial parallelism with each other and with said shaft, cam members operated by said shaft, and connections between said cam members and said plungers for simultaneously moving said plungers endwise upon rotation of said shaft.

3. A structure as recited in claim 2 wherein said connections comprise free balls disposed between the cam members and the plungers and springs surrounding said plungers and engaging said balls to thrust them toward said cams and away from said plungers.

4. A rotary tap switchcomprising a shaft, a handle upon the shaft for manually operating the same, a rigid metallic slider mounted for operation by said shaft, means for insulating the slider from the shaft, said slider being mounted for bodily endwise movement with respect to the shaft, spring means tending to move said slider endwise of the shaft, a metallic collector ring surrounding the shaft, a member carried by the slider making continuous contact with the collector ring in all positions of the operating handle, a plurality of individual contacts disposed radially around the shaft, said slider comprising a contact member which makes contact with the individual contact members in the rotative movement of said shaft, the action of said spring being such as to move the slider with its contacting parts into engagement with the individual contact members and a common contact member carried by the collector ring, a cam carried by said shaft having a plurality of cam forming portions, a pair of precision, snap action switches, plungers for operating said switches and connections against which said cam forming portions of the cam acts to simultaneously move said plungers to open the snap action switches.

5. A rotary tap switch comprising a shaft, a handle upon the shaft for manually operating the same, a rigid metallic slider mounted for operation by said shaft, means for insulating the slider from the shaft, said slider being mounted for bodily endwise movement with respect to the shaft, spring means tending to move said slider endwise of the shaft, a metallic collector ring surrounding the shaft, a member carried by the slider making continuous contact with the collector ring in all positions of the operating handie, a plurality of individual contacts disposed radially around the shaft, said slider comprising a contact member which makes contact with the individual contact members in the rotative movement of said shaft, the action of said spring being such as to move the slider with its contacting parts into engagement with the individual contact members, a common contact member carried by the collector ring, a cam carried b said shaft having a plurality of cam forming portions, a pair of precision, snap action switches, plungers for operating said switches and connections against which said cam forming portions of the cam act to simultaneously move said plungers to open the said switches said connections in cluding free balls which lie between the ends of the plungers and said cam forming members and springs which act to thrust the balls away from the plungers and into engagement with said cam prising a longitudinally extending shaft, a knob upon said shaft for rotating the same, a plurality of annular members of insulating material surrounding the shaft, a plurality of radially disposed individual contact members carried by said annular members of insulating material and having portions exposed at a flat side face thereof, a common contact member carried by each of the said annular members, a collector ring carried by each of the said common contact members each of said collector rings havingv an edge portion that is disposed in the plane in which the exposed faces of the individual contact members lie, an insulating sleeve upon the shaft, a plurality of rigid slider contact members engaged with said sleeve to be turned thereby, each of the slider contact members comprising parts engaging the collector ring and the individual contact members respectively, a cup-like body of insulating material having its open side abutting one of the said annular members to thereby form a chamber, a cam member of cup formation within said chamber and upon the shaft, stops carried by the cam and by the cup-like body respectively for limiting the turning movement of the cam under the influence of the shaft, a plurality of cam forming notches in the free edge of the cup-like cam, sleeves carried by the cup-like body of insulating material, balls movable in said sleeves and engageable with the cam forming notches, springs in said sleeve tending to thrust the balls into engagement with said notches and a pair of precision, snap action switches disposed in balanced position upon opposite sides of the shaft and comprising plungers against which the balls are thrust by the said cam and against the tension of said spring.

'7. A rotary tap switch comprising a rotative essences manually operable shaft, a plurality of radial, relatively heavy, fixed contacts disposed around said shaft and insulating portions by which said contacts are supported in insulated relation, a relatively heavy wiper contact supported upon said shaft for making contact with said fixed contacts, a pair of relatively light snap action switches disposed in balanced relation upon opposite sides of said shaft, a cam mounted upon said shaft and comprising a cam body rotated in a plane transverse to the axis of the shaft. a plurality of cam forming projections and 'depres sions upon said body. plungers comprising the actuating members of the snap action switches and rolling members disposed between the ends of said plungers and said cam, springs tendin to thrust the plungers toward the cam, said cam serving when moved to actuate said plungers and said springs serving to snap said plungers into the depressions of the cam to thereby hold the shaft against accidental movement from the position to which it has been manually indexed.

RUDOLF A. K. FLEISCHMANN.

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

UNITED STATES PATENTS Bentley June 10, 1947

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