Патент USA US2407651код для вставки
Sept 17, 19461» J. T. BUTTERFIELD ETAL, 2,407,550 WIPER CONTACT FOR ELECTRICAL DEVICES Filed 001;. 21 , 1945 2 Sheets-Sheet 1 FIG] J. 7'. BUTTERF/ELD MM, K/VAPP B. F. RU/VYON INVENTORS (9 2pm % W(@@( 19V ' A TTORA/EK 2,407,650 Patented Sept. 17, 1946 UNITED STATES PATENT OFFICE 2,407,650 WIPER CONTACT FOR ELECTRICAL DEVICES Joseph 'I‘. Butter?eld, Summit, N. J., Harry M. Knapp, Flushing, N. Y., and Benjamin F. Run yon, Basking Ridge, N. J., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 21, 1943, Serial No. 507,140 3 Claims. (Cl. 201-56) 2 1 This invention relates to wiper contacts and more particularly to wiper contacts suitable for ance element is clamped in place at therequired spaced points, parts of the resistance element be use in rheostats or potentiometers. tween the points of clamping are often more or The object of the invention is to provide in a rheostat or potentiometer, having a plurality of turns of wire on a support, a wiper contact that will successively engage the turns of wire with out skipping any of the traversed turns when the contact making parts of the rheostat or less bulged away from the drum-type support, and the edge of the resistance element presented for engagement by the wiper contact is in wave like form. In such cases, if the contact end of the wiper contact were of pin-point form the Wiper contact might run off the resistance ele ment at the bulged points during its traverse of the resistance element. The edge of the resist ance element presented for engagement by the ‘ potentiometer are relatively moved. A feature of the invention resides in the con ducting means provided in the Wiper contact. Another feature resides in means provided for supporting the conducting means of the wiper contact. wiper contact may also in some cases have some of its parts in slightly higher or lower planes than 15 In the drawings: other parts due to slight inaccuracies in clamp ing the resistance element in place with respect with part of a casing broken away to obtain a to a desired line of travel of the wiper contact or slight differences in the distance the Various turns of wire extend beyond an edge of the sup View of the wiper contact and its supporting porting card. Fig. 1 is an under-surface plan view of a potentiometer in Which the invention is used and Fig. 2 is an enlarged view of the wiper contact and its supporting means; Fig. 3 is a side view, partly in section, of the wiper contact and its supporting means and taken on the line 3—3 in Fig. 2; Fig. 4 is an enlarged view, partly in section, of parts of the wiper contact and means pro vided for supporting the wiper contact; _ In the present invention we provide a wiper means; contact which will faithfully perform its function 25 of successively engaging the turns of wire on the resistance element. The wiper contact will not run off the resistance element during its traverse thereof and will not skip or bounce over any of the turns of wire the wiper contact is required to engage during its operation along the resistance element. For the purpose of simpli?cation in explaining the invention, and not in the sense of limiting it in application, the device in which it is used will be considered to be and hereinafter referred to Fig. 5 corresponds to Fig. 4 but shows one of 3.0 the parts adjusted to a different position; Fig. 6 is an enlarged View, in perspective and partly in section, of a contact element; and as a potentiometer. Fig. '7 is a side view, partly in section, of the As shown in Fig. 1 the potentiometer 8 com wiper contact and its supporting means and 3.5 prises a casing 9 in which is suitably supported shows in full and dot-dash lines parts of the in an annular support 10 around the outer curved vention adjusted to different positions. surface of which is supported a resistance ele In some potentiometers now required and in ment ll comprising a card-like support [2 on volving a winding of resistance wire on a card like support and a wiper contact to selectively 40 which is wound a resistance wire, the turns of which extending over one, edge of the card-like engage the turns of wire, it is found quite im_ support 12 are indicated at 43 in Fig, 1. Con portant to insure that the wiper contact will not centric with the support In and the resistance skip or bounce over some of the turns of wire and element II is a hoop 14 in which screws I5 are a precise predetermined pressure will be main tained by the wiper contact against the turns of 45 supported at spaced points, the hoop l4 being drilled and tapped to receive the screws [5 and resistance wire it engages. In some of the the inner ends of the screws [5 having bearing potentiometers, above mentioned, the resistance engagement with blocks l6 so that when the element involving the wire-wound card is screws i5 are tightened the blocks I6 will clamp clamped at predetermined spaced points to a drum-type support in order that certain prede 50 the resistance element H to the support I0 at required spaced points, the spaced points being termined electrical potentials will be obtained predetermined and indicated by the marks I‘! on when the potentiometer is operated in an electri the support I0. It will be seen that between cal system and the wiper contact engages the points in line with the marks I‘! where the re resistance element at points in direct radial line with the points of clamping. When the resist 55 sistance element l l is clamped the resistance ele 5 2,407,65G 6 of the free end of the arm 29'. A convenient way of bending the bracket 30 is to insert a screw driver in the aperture 591and use the screw metal fork IQ of the wiper contactv I8 is so mounted relative to the resistance element that an initial spring pressure is developed in the sheet metal fork l9. As shown in Fig. 3 the sheet metal fork l9 extends diagonally from its point driver as a lever to bend the bracket 3!) to a required form; one of the forms of the bracket 33 may be made to take that shown in Fig. 7 in which the bracket 30 has been bent to pro of support on the insulating plate 48 to a point considerably below the 4 level of the arm 29. vide an off-set form as indicated at 80. It will be seen as shown in Fig. 1 that the arm When the arm 29 is mounted in the potentiometer 8 shown in Fig. 1, the arm 29 is in a plane only 29 extends from the shaft 21 in the central por tion of the potentiometer 8 and toward the loca tion of the resistance element H, the bracket 38 extends angularly of the free end portion of the arm 29 and the tines 2| and 22 of the sheet metal fork l9 extend in spaced relation with the bracket 15 slightly above the plane of the edge of the resist ance element H, the contact piece 23 is resting on the edge of the resistance element II and wire on the resistance element H are wound on the sheet metal fork i9 is slightly bowed to ob the tines 2| and 22 of the wiper contact are ?exed so that a required initial spring pressure is de veloped in the tines. In some of the potenti 30 and so that the contact piece 23 crosses and ometers, for instance, we have stressed the tines is in engagement with the resistance element I I. 2| and 22 so that the contact piece 23 bears By turning the shaft 27 thecontact piece 23 may against the resistance element It with a pres be caused to sweep over and frictionally engage sure of the order of 65 grams. The pressure may the turns of resistance wire extending over the 20 be increased or reduced as desired simply by edge of the card-like support l2. . bending the free portion of the bracket 33 as In potentiometers in which the present inven shown in Fig. '7 in which two of the many pos tion is found of particular value, the potenti sible forms to which the bracket 39 may be shaped ometers are sometimes operated at a substantially are shown. In the full-line position shown in constant and relatively high speed, the turns of 25 this ?gure the bracket 36 has been bent so that the card-like support at a constant pitch and the wiper contact must therefore traverse a predeter tain a certain desired spring pressure and in the dot-dash line position the bracket 3i! has been mined number of turns of the resistance wire on further bent so that the sheet metal fork i9 is the engaged edge portion of the resistance ele 30 bowed still more to obtain a greater spring pres ment and arrive on a predetermined turn of the sure. The bracket 36 may be bent to the forms resistance wire at the end of a predetermined shown simply by placing the blade of a screw period of time. The potentiometer must be so driver in the elongated aperture 59 and using the constructed and arranged that certain-predeter screw-driver as a lever to bend the bracket. By mined voltages will be obtained when the wiper 35 increasing or decreasing the spring tension of contact reaches points in line with the marks I‘! the sheet metal fork Hi the amplitude of vibra on the support l0 and in line with which are tion of the wiper contact may be changed to meet clamped predetermined points of the resistance a required condition and if the amplitude of element II. To insure that the contact piece 23 vibration is ‘found not suincient to make the of the wiper contact 18 will engage a ‘predeter 40 contact piece 23 come into engagement with cer mined turn of the resistance wire on the resist tain turns of the resistance wire extending in a ance element | I when in line with a predeter slightly lower plane than other turns the spring mined mark |‘| and will not skip or bounce over pressure may be increased to make the wiper the turn of resistance wire at that point, the contact have a, su?icient overthrow in its move sheet metal fork I9 is made to have a natural 45 ment to reach the lower turns of resistance frequency of vibration such that the contact piece wlre. will engage the required turns of resistance wire. The particular structure and arrangement Theoretically, and as an example, in the case shown for mounting the bracket 39 on the arm when the pitch of winding the wire on the card 29 permit adjustment of the bracket 3i! in regard like support is 160 turns per inch and the maxi 50 to its extension from the arm 29. As already mum speed of movement of the wiper contact is pointed out in the speci?cation, the screws 3| 6 inches per second, the natural frequency of the wiper contact is made so that its tracking frequency of vibration is a minimum of 960 cycles per second. In this case and assuming 55 that there are 160 turns of wire per inch of travel of the wiper contact, the contact piece on the wiper contact will engage each turn of Wire in succession and will arrive on a predetermined and 32 are securely mounted on the arm 29 and the plate 33 is secured against movement since the holes therein for the screws 3| and 32 snugly . ‘accommodate the screws. The holes 4| and 42 in the bracket 30 are considerably larger in diam eter than the enlarged portion 3% of the screws 3| and 32 and by loosening the screws 3| and 32 the bracket 33 may be released for movement 60 on the arm 29 within limits permitted by the enlarged portions 38 of the screws 3| and 32 and turn of wire at the end of the predetermined period of time. In this example it is also as sumed that the turns of wire traversed are in a the relatively large apertures 4| and 42 in the common plane. In cases where the number of bracket 38. The angle of extension of the bracket turns of wire per inch of travel of the wiper con 30 relative to the arm 29 may be changed by tact and the maximum speed of travel of the 65 loosening the screws 3| and 32 and by manually wiper contact are greater than the above ex turning the bracket 30 on its point of support ample, the wiper contact would be made to have on the arm 29 and within the limits permitted a natural frequency of vibration greater than the by the screws 3| and 32 and the apertures 4| frequency above mentioned. and 42. By turning the bracket 38 in this manner In order to obtain a required pressure of the the angle of extension of the contact piece 23 contact piece of the wiper contact against the relative to the direction the resistance wire in turns of resistance wire and to obtain a suf?cient the resistance element || extends over an edge amplitude of vibration to make the wiper con of the card-like support l2 may be changed. tact reach a turn of wire located in a slightly The wiper contact l8 may, therefore, be adjusted lower plane than an adjacent turn the sheet 75 so that the contact piece 23 extends either angu 2,407,650 8 larly or in parallel relation with turns of the resistance wire on an edge of the card-like sup port [2. The bracket 39 may be also adjusted longitu dinally to extend a shorter or longer distance from the arm 29 so that when the arm 29 is in a given position and the contact piece 23 is found tions relative to turns of wire on the resistance element. What is claimed is: 1. A wiper contact to frictionally traverse an electrical element, said wiper contact comprising an arm, a bendable bracket supported at one end on said arm, a reed-type conducting member secured at one end on the unsecured end of said to be either forward or backward of a predeter ‘bracket and having an unsecured end portion mined turn of resistance wire it is desired to select for the given position of the arm 29, the 10 extending into contact with the electrical ele ment, and said bracket having an aperture formed bracket 30 may be, in effect, shortened or length therein between the secured end of said ‘bracket ened to bring the contact piece 23 to the desired and said conducting member to provide a hold turn of resistance wire. for means to be applied to said bracket to bend The pitch of winding the resistance wire on the said bracket to change the pressure of said reeds card-like support 12 is usually so short that it type conducting member on the electrical ele would be difficult to adjust the wiper contact l8 to engage a desired turn of the wire simply by ment. shifting the bracket 36 longitudinally by hand. 2. A wiper contact comprising an arm, an aper In order that very precise longitudinal adjust tured bracket supported at one end on said arm and extending angularly of said arm, spaced ment of the bracket 30 may be made, the slots 43 and 45 are provided in the bracket 35 and the screws mounted on said arm and extending plate 33, respectively, the slot 43 being enlarged and beveled at 44. For a normal setting of the bracket 30 the slots 43 and 45 will be in registry as shown in Fig. 3. To move the bracket 38 longitudinally from the position shown in Fig. 3, through the apertures in said bracket, the aper tures in said bracket being larger than the diam eter of said screws, an apertured plate disposed between the heads of said screws and said bracket, the apertures in said plate being of sub stantially the same diameter as said screws, said and after the screws 3! and 32 are loosened, the plate and said screws cooperating to clamp said blade of a screw-driver may be inserted in the slots 45 and 43 and the screw-driver operated as bracket to said arm, a reed-type contact sup a lever to move the bracket 39, the wall of the 30 ported at one end on the free end of said bracket, slot 45 being used as a fulcrum point in the oper and said bracket and said plate, each, having a ation of the screw-driver. slot formed therein and into which the blade of In Fig. 4 the bracket 30 has been moved longi a screw-driver may be inserted to longitudinally tudinally to the left from the position shown in move said bracket when said screws are loosened. Fig. 3 to make the bracket 3i) extend a greater 35 3. In a variable electrical resistance device, in distance from the arm 29. To move the bracket which the resistance element is a resistance wire 30 slightly back from this position very precise wound in a plurality of turns, a wiper contact, movement may be accomplished by simply plac means to cause relative movement of said resist ing the screw-driver blade in the slot 45 and ance element and said wiper contact, said wiper driving the blade end down against one side of 40 contact being operable to selectively engage the the beveled portion 44. In Fig. 5 the bracket 30 turns of said resistance wire and comprising, in has been moved longitudinally to the right of the combination, an arm having a free end extending positions shown in Figs. 3 and 4 and presumably in the vicinity of said resistance element, screws mounted in spaced relation on the free end of by means of a screw-driver. This movement is, in effect, the same as shortening the bracket 33. 45 said arm, a bracket mounted at one end on and After the required longitudinal adjustment of the extending angularly of the free end of said arm, said bracket having apertures formed therein to bracket 39 has been made to bring the contact piece 23 to a required position on a predeter receive said screws and of larger diameter than mined turn of the resistance wire on the card said screws, a plate apertured to accommodate like support l2, the screws 3| and 32 are tight 50 said screws and cooperating with said screws to ened to press the plate 33 against the bracket 30 clamp said bracket to said arm, a slot formed and thus clamp the bracket 39 in the required in said plate, a second slot formed in said bracket, said slots being normally in registry with each position on the arm 29. other and providing apertures through which a It will be seen from the foregoing description and the drawings that we have provided a wiper 55 tool may be inserted to longitudinally move said bracket to change the distance said bracket ex contact suitable for use in a precision potenti tends from said arm, a fork of conducting mate ometer, the wiper contact may be made to have rial having its closed end mounted on said a predetermined natural frequency of vibration bracket, means to mount said fork on said to meet certain requirements, the wiper contact will not skip or bounce over turns of a Wire 60 bracket, tines on said fork extending backwardly along and in spaced relation with said bracket wound resistance element when the potentiom and a bar of contact material bridged across and eter is operated, and the structure and arrange~ secured to said tines and arranged to friction ment of the parts permit increasing or decreas ally engage the turns of resistance wire on said ing the contact pressure, adjustment of the am- 65 resistance element. plitude of vibration of the wiper contact and JOSEPH T. BUT'I'ERFIELD. adjustment of the position of a contact piece HARRY M. KNAPP. embodied in the wiper contact to required posi BENJAMIN F. RUNYON.