US2205288A - Control rheostat - Google Patents

Description

June 18, 1940. o. H. HASSELBAUM CONTROL RHEOSTAT Filed Sept. 7, 1938 2 Sheets-Sheet 1 June 13, 1940- o. H. HASSELBAUM 2,205,288

CONTROL RHEOSTAT 2 Sheets-Sheet 2 Filed Sept. 7, 1938 OFF ACCESSORY H/ //0 HI lb? HEATER rune: M SPEEDS A00. #1 Mn l/EATEI? All 0 figasselauwv full Patented June 18, 1940 "UNITED STATES 2,205,288 PATENT OFFICE CONTROL RHEOSTAT Application September 7, 1938, Serial No. 228,785

8 Claims.

This invention relates to a control rheostat structure, and more particularly to such a rheostat structure which is utilized for controlling electrically-operated accessory elements in an automobile.

An object of this invention is to provide a novel rheostat structure of this type which will control a plurality of operating elements, together with an indicating lamp therefor.

Another object is to provide an arrangement in which the indicating lamp is illuminated at its maximum brilliancy for all positions of control.

A further object is to provide an arrangement in which the controlled elements are electric motors and in which the speed of one motor is varied independently.

A still further object is to devise a novel arrangement of parts for accomplishing the above objects in which a maximum facility of control and manipulation with a minimum complexity of construction is secured.

The foregoing and other objects of my invention will be best understood from the following description of exempliflcations thereof, reference being had to the accompanying drawings, wherein:

Fig. 1 is a top view of the control unit of one embodiment of my invention with the switch and lamp assembly removed therefrom, wherein there is also shown diagrammatically a circuit with which the control unit may be used;

Fig. 2 is a back view of the control unit shown in Fig. 1;

Fig. 3 is an end view of the control unit viewed from the bottom of Fig. 2;

Fig. 4 is an end view of the control unit together with the switch arm and indicating lamp assembly in place thereon, as viewed from the top of Fig- Fig. 5 is an enlarged cross-section taken along line 5-5 of Fig. '7, showing the internal construction of the switch arm and indicating lamp assembly;

Fig. 6 is a view looking at the top of the construction shown in Fig. 5;

Fig. 7 is a top view of the assembled device showing the various positions of control;

Fig. 8 is a view similar to Fig. l of another embodiment of my invention;

Fig. 9 is a back view of the control unit shown in Fi 8;

Fig. 10 is an end view of the control unit viewed from the bottom of Fig. 8;

Fig. 11 is an end view of the control unit together with the switch arm and indicating lamp assembly in place thereon as viewed from the top of F18. 8;

Fig. 12 is an enlarged cross-section taken along line l2-l2 of Fig. 14, showing the internal construction of the switch arm and lamp assembly;

Fig. 13 is a view looking at the top of the structure of Fig. 12; and

Fig. 14 is a top view of the assembled modification of Fig. 8 showing the various positions of control.

In the drawings, l represents an insulating body made of ceramic material or other suitable refractory insulation. The body I is provided at one end thereof with two square holes 2 extending through said body. In each of the holes 2 is mounted a coil 3 of resistance wire. Due to the fact that the holes 2 are square and the coils 3 are round, sufficient space is left between the walls of the holes 2 and the sides of the coils 3 through which air may freely circulate, thus providing cooling of the coils 3. The two coils 3 are connected in series by means of a loop 4 on the back of the body I. The loop is secured in place and electrically connected to a conducting pin extending through the insulating body i to the front thereof where it is provided with a contact head 5'. The two outer ends 8-8 of the two coils 3 are connected respectively to the two pins 1 and 8 likewise extending through the insulating body I. The coil ends 8-6 thus are securely retained in place on the body I. The ends of the pins I and 8 at the front of the insulating body are provided with contact heads 1' and 8', respectively. The pin 1 supports a binding terminal 9 on the back face of the insulating body I, whereby an external electrical connection may be made thereto. Adjacent the above-mentioned contacts there is supported on the front face of the insulating body I a conducting switch plate Hi which is secured in place by means of a pin ll extending through the body I to therear face thereof, where it engages and supports another binding terminal I2. An elongated contact strip I3 is also secured to the front face of the insulating body I by means of a pin l4 extending through said body to the rear face thereof, where said pin ll supports a still further binding terminal l5. The switch plate In is cut away centrally at Hi from which a radial cut I! is made so as to provide an insulating gap in the continuity of said switch plate l0. As indicated by the dotted lines in Fig. 1, the three-legged switch arm I8 is adapted to cooperate with the various contacts on the front face of the insulating body I. In order that this three-legged switch unit shall always be in proper engagement with the contacts, it is desirable that all of the bearing surfaces upon which the three legs of said switch unit ride shall lie in a single plane. Thus an elongated contact strip l 9 is connected to the contact head I, and lies in the same plane as said contact head. Likewise the head of the pin ll lies in the same plane and the switch plate III is provided with a raised section so as to keep the surface of said switch plate adjacent the pin ll likewise in the same plane. The elongated contact strip l3 and the contact heads 5 and 8 likewise lie in the plane referred to. It will be noted that all of these co-planar contact surfaces are concentrically disposed around the center point, forming the axis of rotation of the switch arm [8. At one point in this concentric circle there is an insulating gap, and in order to provide a coplanar bearing surface at said insulating gap, the body l is provided with a raised insulating bearing portion 2 l. The circular portion of the switch plate in immediately surrounding the central cutaway portion l5 likewise lies uniformly in the same plane as the other contacts. The insulating gap E7 in said switch plate (0 is provided with a raised insulating bearing surface likewise lying in the same plane so as to insure a continuity of bearing surface for another leg of the switch unit, as will be described below.

The typical circuit shown in Fig. 1 may consist of a battery 22, one terminal thereof being connected by means of a conductor 23 to the binding terminal :12, and thus to the switch plate ID. The other terminal of the battery is grounded at 24. A heater motor 25 may have one terminal thereof connected by means of a conductor 26 to the binding terminal 9, and thus to the contact 1' and contact strip 59. The other terminal of the heater motor may be grounded at 21. An accessory which may consist of a defroster motor 28 may have one terminal thereof connected by means of a conductor 2 to the binding terminal 95, and thus to the elongated contact strip l3. Ihe other terminal of the accessory motor 23 may be grounded at 30. An indicating lamp 3! has one terminal thereof connected through the electrical connection 32 to the switch arm assembly i8, the other terminal of said lamp being grounded at 33.

The switch arm unit 18, as previously indicated, comprises three legs or arms, two long arms 34 and 35 and a shorter arm 36. The two long arms 34 and 35 are provided respectively with bearing surfaces 3'! and38 which are adapted to engage the outer circle of contacts previously referred to, while the shorter arm 36 is provided with a bearing surface 39 which is adapted to contact the more centrally-located circular portion of the switch plate ID. The switch arm assembly 18 is carried by a conducting sleeve 40. For this purpose the assembly 18 has provided centrally therein a relatively elongated slot 42 which slides over the outer end of the sleeve 49. The elongation of the slot 42 permits the switch assembly unit 18 to rock relatively with respect to the sleeve 40, but its shape does not permit a relative rotation therebetween in the plane of actuation. In order to keep the switch assembly i8 on the sleeve 40, an outer stop member 43 is provided on said sleeve. A spring 44 biases the switch assembly I8 to the outer end of the sleeve 40. The sleeve carrying said switch assembly is mounted on and supported by an insulating plate 45 on one side thereof. The opposite side of the insulating plate 45 has supported thereon a conducting lamp socket sleeve 48 insulated from the sleeve 40. At the center of the insulating plate 45 within the sleeve 46 is located a central contact rod electrically connected to the sleeve 40 and adapted to contact the center base contact of a lamp 3|, which is adapted to be received within the sleeve 46. In order to retain the lamp-3| in place within said sleeve, it is provided with a plurality of indented tongues, affording bayonetreceiving recesses 48 for receiving the bayonet pins in the base of the lamp 3i, and thus retaining said lamp in place within the socket sleeve 46. A translucent operating head 46' is mounted non-rotatably on the outer end of the sleeve 46. The construction of the lamp socket and translucent head is more fully described and claimed in my co-pending application entitled Control rheostat unit, filed simultaneously herewith.

In order to yieldably hold the switch in predetermined definite operating positions, the structure is provided with a detent plate 49. lhis plate is carried by the insulating plate 45 and is retained thereon bp means of a plurality of tongues 50 passing through and engaging corresponding recesses in the insulating plate 45. The detent plate 49 is provided with a center opening 5| through which the sleeve 40 extends so as to insulate said sleeve from said detent plate. An additional insulating plate 52 overlies the opening 5| in the detent plate 49 so as to form a bearing surface for the lower end of the spring 44. In this way the switch arm assembly I8 and its associated conducting structure is insulated from the detent plate 49 which constitutes a grounded portion of the switch structure. The detent plate is provided with an annular portion 53 which is cut away along a limited portion thereof to provide shoulders 54-54. In the annular portion 53 there is formed a detent projection 55. Cooperating with said detent plate 49 is a casing 56 which is carried by an outer sleeve 51 in which the socket sleeve 48 freely rotates. The casing 56 is provided with a number of circularly-disposed detent indentations 58 which cooperate with the detent projection so as to yieldably retain the switch arm as sembly in predetermined positions of operation. The casing 58 is also provided with an upstanding stop 59 which engages the shoulders 54 at the opposite limits of operation of the switch arm assembly, and prevents further rotation. The switch arm assembly and indicating lamp unit is secured as a whole to the insulating body l by means of a plurality of tongues 60 formed on the lower edge of the casing 55. These tongues 60 are adapted to fit into corresponding grooves 6i. When the ends of the tongue 60 are bent over on the rear face of the insulating body I, the entire structure is maintained in its assembled relationship. For the purposes of mounting the assembled structure in position in an automobile, the sleeve 51 is provided with external threads and a plurality of clamping nuts 53.

When the structure described above is connected in the circuit, as shown in Fig. 1, and the head 46 is rotated to the off position, the switch arm unit l8 will occupy the position indicated by the dotted lines in Fig. 1. In this position, none of the three switch arms engages the switch plate Hi to which the battery 22 is connected, and thus all of the operating elements, including the lamp 3|, are deenergized. As the switch assembly is rotated in a counter-clockwise direction, the bearing surface 38 of the long arm 35 rides off the insulating portion 2| onto the pin H which is electrically connected to the switch plate 10. The bearing surface 31 of the other long switch arm 34 remains in engagement with the elongated contact strip l3. Since the battery 22 is connected to the switch plate 10 and the accessory 28 is connected to the contact strip Hi, the above operation of the switch, which interconnects the switch plate I and the strip l3, energizes the accessory motor 28. At the same time,

since the lamp 3| is electrically connected to the switch assembly l8, which engages the battery-energized switch plate M, the lamp would likewise be energized to its full brilliancy. Therefore, in said position of actuation, the accessory motor 28 will be energized and the lamp 3| will be illuminated to full brilliancy.

If, however, the switch assembly is rotated from the off position in a clockwise direction, the bearing surface 38 of the long switch arm 35 will ride onto the elongated contact strip IS. The bearing surface 31 of the other long contact arm 34 will remain in engagement with the elongated contact strip l3. At the same time the bearing surface 38 of the short contact arm 36 will come into contact with the switch plate III, which being connected to the battery 22 will thus energize both contact strips l3 and l8. Since the accessory 28 is connected to the contact strip I3 and the heater motor 25 is connected to the contact strip l9, this position of actuation will energize both accessory and heater motor. In this case likewise the lamp 3| being connected to the switch arm assembly I8, which is in contact with the battery-energized switch plate I, will be energized to its maximum brilliancy.

In this position of the switch it will be noted that none of the resistance of the coils 3 is connected in series with the heater motor 28, and thus said motor will be operated at its maximum high speed.

If the switch assembly is now rotated clockwise to the next position, the bearing surface 31 of the long switch arm 84 will leave the elongated contact l3 and come into contact with the portion 20 of the switch plate ID. This will deenergize the accessory motor 28 since said accessory motor can only be energized through the contact strip l3. However, due to the provision of the elongated strip l8 and the continuouslyconductive centrally-circular portion of the switch plate "I, the other circuit connections will be unchanged and the heater motor 25 will continue to operate at this high speed while the lamp 3| will likewise be energized to full brilliancy,

When the switch assembly is rotated clockwise to thenext position, the bearing surface 38 of the long arm 35 will travel from the contact I to the contact 5. The bearing surface 31 of the other long arm 34 will ride up onto the end of the pin The bearing surface 39 of the short arm 36 will remain in electrical contact with the switch plate I. This connection interposes the resistance of the right-hand coil 3 in series with the heater motor 25, which is thereby slowed down to its medium speed. However, the lamp 3| is still d rectly connected through the switch assembly I8 directly to the switch plate I8, and thus directly to the battery 22. Under these conditions, the lamp 3| remains energized to its maximum brilliancy.

When the switch assembly is rotated clockwise to the next position, the bearing surface 38 of the long arm 35 will leave the contact 5' and engage the contact 8'. The bearing surface 31 of the other long arm 34 will leave the pin II and engage the insulating section 2|. This, however, does not deenergize the switch arm inasmuch as the bearing surface 39 of the short arm 36 easily remains in engagement with the switch plate l0. Under these cond tions the resistance of both coils 3 is connected in series with the heater motor 25, which therefore operates as its lowest speed. As explained above, the

lamp 3| still is maintained at its maximum brilliancy.

It will be noted that in'each position of actuation of the switch, the bearing surfaces of the three arms of the switch assembly l8 are in engagement with the bearing surfaces of the underlying contact structure which all lie in the same plane. Thus the switch arm assembly |8 is maintained uniformly in an elevated position, insuring an adequate and substantially equallydisposed pressure on all of the three switch arms. In each position of actuation of the switch, the projection snaps into a corresponding depression 58 in the casing 56. In this way the switch is yieldably but firmly retained in its predetermined positions of actuation. The operator can easily feel this snapping action, and in this way is enabled to actuate the switch accurately without visually observing the same.

As pointed out and claimed in my co-opending application, the relative position of the heating coils 3 to the switch structure, in which said switch structure is out of substantial heat transfer relation with respect to said coils, prevents the heat generated from said coils from reaching and injuring the switch structure.

Another embodiment of my invention which is illustrated in Figs. 8 and 14, inclusive, permits the system to be controlled so that the speed of the heater motor may be varied whether or not the accessory motor is energized. In this embodiment 64 represents an insulating body similar to the body in Fig. 1. The body 64 is provided at one end thereof with two square holes 65 extending through said body. In each of the holes 65 is mounted a coil 66 of resistance wire. In this case likewise there is provided spaces around the coils wherein cooling air may circulate. The two coils '66 are connected in series by means of a loop 61 at the back of the body 64. This loop is secured in, place and electrically connected to a conducting pin 68 extending through the insulating body 64 to the front thereof where it is provided with a contact head 68'. The two ends 6868 of the two coils 66 are connected respectively to two pins I0 and H likewise extending through the insulating body 64. The pins 10 and 1| are provided respectively at the front of said body with contact heads 10' and H, respectively. Two additional pins 14 and I5 symmetrically disposed with respect to the pins 68 and 10 are mounted in the insulating body 64 on the opposite side of the pins 1|. Conducting strips 12 and 13 connect the pins 68 and 18 to the pins 14 and 15, respectively. The pins 14 and I5 extend through the body 64, and are provided at the front face thereof with contact heads 14' and 15. The pin 15 supports a binding terminal 16 on the back face of the insulating body 64. Adjacent the above-mentioned contacts there is supported on the front face of the insulating body 64 a conducting switch plate 11 which is secured to the body 64 by a conducting pin 18 extending through the body 64 to the rear face thereof where it supports another binding terminal 18. concentrically disposed with the partial circle of contacts described below but located at a greater radius than said contacts, there is provided an arcuate contact strip 80 secured to the face of the insulating body 64 by means of a conducting pin 8| extending through said body to the rear face thereof where it supports another binding terminal 82. The pin 8| is located atone end of said contact strip 80, the other end of said strip being maintained I tinuity of the plane bearing surfaces.

in place by a lug 83 fitting into a recess in the face of the insulating body 04. As in the case of the previous embodiment, a three-legged contact arm is adapted to overlie and make various connections with the contact surfaces described above. With a three-legged switch arm of this kind as previously indicated, it is desirable to provide a continuity of bearing surface in one plane in order that said switch arm is supported uniformly in each position of actuation thereof. For this reason the top surfaces of the various contacts, the switch plate I1, and the contact strip 80 are all disposed substantially in a single plane. The switch plate 11 is cut away at the upper side thereof in order to provide an insulating gap. In order to maintain the continuity of the plane bearing surface, the insulation of the body H is raised at within this cut-away portion. The switch plate TI is likewise cut away at the central portion thereof, and provided with a radial cut therefrom in a manner similar to that described in connection with Fig. 1. In the radial cut, the insulation of the body 64 is likewise raised in order to maintain the con- Also at the point 54', the insulation of the body 64 is raised to the plane of the contact surfaces.

The typical circuit shown in Fig. 8 may consist of a battery 86, one terminal thereof being connected by a conductor 01 to the binding terminal l9 and thus to the switch plate II. The other terminal of the battery 86 may be grounded at 88. A heater motor 89 may have one terminal thereof connected by means of a conductor 90 to the binding terminal I6, and thus to the contact I5. It will be noted that the contact is likewise connected to the contact I0 through the intermediary of the conducting strip 13. The other terminal of the heater motor 80 may be grounded at SI. An accessory 92, which may consist of a defroster motor, has one terminal thereof connected by means of a conductor 93 to the binding terminal 82, and thus to the arcuate contact strip 80. The other terminal of the accessory 92 is grounded at 94. An indicating lamp 95 has one side thereof directly electrically connected by means of a connection 96 to the switch arm 84. The other side of the indicating lamp is grounded at 91. V

The three-legged switch arm assembly 04 is provided with one long leg 98, a shorter leg 90, and a still shorter leg I00. The longest leg 98 is provided at its outer end with a bearing surface IOI. which is adapted to ride upon the arcuate contact strip 80. Said leg 90 is also provided with a relatively elongated bearing surface I02 which is adapted to engage the various contacts of the partial circle of contacts only. It will be noted that the bearing surface IOI when in contact with the strip 80 lifts the leg 90 so that the bearing surface I02 is raised and does not contact the switch plate 11. Thus each arm makes contact at but one point thereon, insuring a positive engagement in each switch position. The leg 95 is provided with a bearing surface Ill. The front face of the shortest leg I 00 constitutes its own bearing surface. The switch arm assembly 04 is mounted on a sleeve I04 in a manner similar to that described in connection with the sleeve 40 of Fig. 5. The switch arm 04 may be rocked relative to the sleeve I04 but cannot rotate with respect thereto. A spring I05 biases the switch arm 84 to the outer end of said sleeve I04. The sleeve I04 carrying the switch arm assembly 04 is mounted on the insulating plate I06 which likewise carries on Its opposite side the lamp socket sleeve I01. The insulating plate I06 carries within the sleeve IN the center contact rod I00 which is electrically connected to the sleeve I04 and the switch arm assembly 04. The lamp socket sleeve I0! is likewise provided with a plurality of bayonet-recessed tongues I09. Sald lamp socket sleeve is adapted to receive the lamp 90, which thereby is placed In the circuit shown diagrammatically in Fig. 8. The lamp socket sleeve I01 likewise has securely connected thereto the translucent head I I0 through which the illumination afforded by the lamp 9! may be observed.

A mounting sleeve III surrounds the socket sleeve I 01 and is rotatable freely thereon. The sleeve I II likewise carries the casing II2 which may be fastened to the insulating body 04 by a plurality of tongues II I which are adapted to fit into grooves II4 formed in the outer edge of the insulating body 64. By having the outer ends of the tongues I03 turned over onto the rear face of the insulating body 64, the entire structure is maintained in assembled position.

The insulating plate I06 is cut away along a considerable portion of its circumference in order to provide a pair of shoulders I I5I I 5. These shoulders are adapted to cooperate with a stop II6 formed in the casing III. In this way the rotation of the switch element is kept within the correct limits of rotation. The sleeve III which serves to mount the assembly in the automobile structure may be provided with a pair of locking nuts II! which are threaded onto the external surface of the sleeve III.

When the structure described above is connected in the circuit shown in Fig. 8 and the head H0 is rotated to the off position, the switch arm assembly 84 will occupy the position indicated by the dotted lines in Fig. 1. In this position, none of the contact arms of said switch assembly is in electrical connection with the switch plate 11 which is the only element directly connected to the battery 00. Therefore, the heater motor 88, the accessory 92, and the lamp 0! are deenergized. As the switch assembly is rotated in a counter-clockwise position, the bearing surface I03 of the arm 80 leaves the insulating sec tion 05 and comes into contact with the switch plate I1, thus energizing the switch arm assembly 84 and likewise the indicating lamp 05 directly electrically connected thereto. At the same time the bearing surface IOI of the leg 90 rides up onto the arcuate contact strip 00, which being directly connected to the accessory motor 92 energizes said accessory motor which thereupon operates at its maximum speed. In this position of the switch, however, the heater motor 0! is deenergized, and is therefore not set in operation.

As the switch assembly is rotated counterclockwise to the next position, the bearing surface I00 leaves the switch plate 11 and engages the contact I5. However, the switch arm assembly 04 is not thereby deenergized because the contact leg I00 has come into engagement with the switch-plate 11. In this position of the switch, the circuit arrangement of the accessory motor 92 and the lamp 95 is unchanged. However, the heater motor 00 is directly connected from the contact I5 through the switch arm assembly 04 to the battery 06, and therefore said heater motor operates at its maximum speed.

If the switch is then moved counter-clockwise to its next position, the circuit arrangements are unchanged except for the fact that the bearing surface I03 leaves the contactli and engages the contact 14'. This interposes the resistance-of the right-hand coil 00, as viewed in Fig. 8, into the circuit of the heater motor 33 which is thereupon slowed down to its medium speed. The next counter-clockwise operation of the switch brings the bearing surface I03 into engagement with the contact II, and thus interposes the entire resistance of both coils 63 into the circuit of the heater motor 03, in this way slowing the speed of said motor toits minimum value. Throughout the operation of the heater motor 09, it will be noted that none of the resistance is included in the circuit of the accessory motor 90, and therefore said motor operates at its full speed.

If in starting from the off position the head H0 is rotated in the clockwise position, both the leg I00 and the bearing surface I03 of the leg 93 will electrically engage the switch plate 11, thus energizing the switch arm 04. The bearing surface I02 of the arm 98 will at the same time engage the contact 10. Since the motor 09 is directly connected to the contact 10 through the strip I3, said heater motor is likewise directly connected to the battery 86, and thus will be operated at its maximum speed. It will be noted, however, that the arcuate strip 00 which energizes the accessory motor 32 is of limited length so that it no longer engages the bearing surface IN, and therefore is deenergized in this and in successive positions,

As the switch H0 is rotated further in the clockwise position, the bearing surface I02 will successively engage the contact 88' and II. successively interposing the resistances of each of the coils 66 into the circuit'of the heater motor 89, and thus causing said heater motor to operate at its medium and low speeds, successively. It will be noted, furthermore, that in each of these various positions of actuation in which the switch arm assembly 84 is energized, the lamp 33 will be directly connected to the battery 00, and therefore will be operated at its maximum brilliancy.

Of course it is to be understood that this invention is not limited to the particular details of construction as described above as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. A switch structure comprising a body of insulation having a flat face, a resistance mounted on said body, a plurality of contacts electrically connected to spaced points on said resistance and mounted on said face and arcuately disposed thereon, a plurality of arcuate contacts concentrically disposed with respect to said contacts also mounted on said face, three terminals connected respectively to said resistance and to each of said arcuate contacts for establishing an external electrical connection to said resistance and to each of said arcuate contacts, a multiple-legged switch arm overlying said contacts and rotatable in a plane parallel to said face around the center of said contacts as an axis, the legs of said switch arm being displaced from each other inthe plane of actuation to such a degree with respect to said contacts that simultaneous connections are made to one of said first-named contacts and to each of said arcuate contacts in each position of the switch except for the foil" position.

2. A switch structure comprising a body of insulation having a flat face, a resistance mounted on said body, a plurality of contacts electrically connected to spaced points on said resistance and mounted on said face and arcuately disposed thereon, a plurality of arcuate contacts concentrically disposed with respect to said contacts also mounted on said face, means for establishing an,

external electrical connection to said resistance and to each of said arcuate contacts, a rigid three-legged switch arm overlying said contacts and rotatable in a plane parallel to said face aroundthe center of said contacts as an axis, the

three legs of said switch arm being displaced from each other in the plane of actuation to such a degree with respect to said contacts that three simultaneous connections are made to three of said contacts, said contacts being disposed in substantially a single plane, the face of said insulating body being provided with a raised portion in the spaces between conducting portions of said contacts, said portion having its surface in said single plane, whereby in each position of actuation or motion of said switch arm, the three legs thereof are provided with co-planar supporting surfaces.

3. A switch structure comprising a body of insulation having a flat face, a resistance mounted on said body, a plurality of contacts electrically connected to spaced points on said resistance and mounted on said face and arcuately disposed thereon, a plurality of arcuate contacts concentrically disposed with respect to said contacts also mounted on said face, three terminals connected respectively to said resistance and to each of said arcuate contacts for establishing an external electrical connection to said resistance and to each of said arcuate contacts, a multiplelegged switch arm overlying said contacts and rotatable in a plane parallel to said face around the center of said contacts as an axis, the legs of said switch arm being displaced from each other in the plane of actuation to such a degree with respect to said contacts that simultaneous connections are made to one of said first-named contacts and to each of said arcuate contacts in each position of the switch except, for the "off position, one of said arcuate contacts having a continuously conducting surface except for an insulating gap in the of! position of the switch, said conducting surface being in contact with one of said switch arm legs in each position of said switch except the "off position, an indicating lamp having one terminal in constant electrical connection with said switch arm, and having its other terminal grounded.

4. A switch structure comprising a body of insulation having a flat face, aresistance mounted on said body, a plurality of contacts electrically connected to spaced points on said resistance and mounted on said face and arcuately disposed thereon, each of said contacts except the end contact thereof being connected to another contact and rotatable in a plane parallel to said face around the center of said contacts as an axis, the three legs of said switch arm being displaced from each other in the plane of actuation, one of said arcuate contacts having a continuously conducting surface except for an insulating gap in the off position of the switch, said conducting surface being in contact with one of said switch arm legs in each position of said switch except for the "off position, another of said arcuate contacts being of limited length and located adjacent said first-named arcuate contact, another of said legs contacting said latter arcuate contact in the position of actuation on one side of the off position and successively contacting the first set of resistance contacts in successive positions of actuation onthe other side of the "oi.f position, the third leg contacting said first-mentioned arcuate contact in said latter positions of actuation and contacting the second set of resistance contacts in the former position of actuation.

5. A switch structure comprising a body of insulation having a fiat face, 'a resistance mounted on said body, a plurality of contacts electrically connected to spaced points on said resistance and mounted on said face and arcuately disposed thereon, each of said contacts except the end contact thereof being connected to another contact of a second set of contacts, said second set of contacts being symmetrically disposed with respect to said first-named contacts on the other side of said end contact and likewise arcuately supported on said face, an arcuate contact concentrically disposed with respect to said contacts also mounted on said face, three terminals connected respectively to said resistance and to each of said arcuate contacts for establishing an external electrical connection to said resistance and to said arcuate contact, a three-legged switch arm overlying said contacts and rotatable in a plane parallel to said face around the center of said contacts as an axis, the three legs of said switch arm being displaced from each other in the plane of actuation, said arcuate contact having a continuously conducting surface except for an insulating gap in the off position of the switch, said conducting surface being in contact with one of said switch arm legs in each position of said switch except the oil? position, one of said legs engaging successive contacts of the first set of resistance contacts in successive positions of actuation on one side of the off position, another of said legs engaging successive contacts of the second set of resistance contacts in successive positions of actuation on the other side of the off position, whereby said single resistance is utilized as a controlling factor in two different circuit arrangements.

6. A switch structure comprising a body of insulation having a substantially fiat face, a resistance mounted on said body, a first set of con tacts electrically connected to spaced points on said resistance, mounted on said face and arcuately disposed thereon, each of a plurality of said first set of contacts being connected to another contact of a second set of contacts, said second set of contacts being likewise arcuately mounted on said face concentrically with the first set of contacts, two arcuate contacts concentrically disposed with respect to said sets of contacts and also mounted on said face, three terminals connected respectively to said resistance and said arcuate contacts for establishing external electrical connections thereto, a switch arm overlying said contacts and rotatable in a plane parallel to said face around the center of said contacts as an axis, said switch arm having contact portions interconnecting successive contacts of said first set of contacts and one of said arcuate contacts in a position of actuation on one side of the off position and interconnecting successive contacts of said second set of contacts and both of said arcuate contacts in successive positions of actuation on the other side of the off" position, whereby said single resistance is utilized as a controlling factor in two difierent circuit arrangements.

'7. A switch structure comprising a body of insulation having a substantially fiat face, a resistance mounted on said body, a first set of contacts electrically connected to spaced points on said resistance, mounted on said face and arcuately disposed thereon along part of a circle, each of a plurality of said first set of contacts being connected to another contact of a second set of contacts, said second set of contacts being likewise arcuately mounted on said face along an other part of said circle, an arcuate contact disposed in another circle concentric with said first circle and also mounted on said face, a second arcuate contact mounted on said face and having an arcuate contact surface disposed along another part of said first-named circle adjacent said first arcuate contact and having a second arcuate contact surface disposed in a third concentric circle, three terminals connected respectively to said resistance and said arcuate contacts for establishing external electrical connections thereto, a three-legged switch arm overlying said contacts and rotatable in a plane parallel to said face around the center of said contacts as an axis, the three legs of said switch arm being of different lengths to engage contacts respectively in said three concentric circles.

8. A switch structure comprising a body of insulation having a substantially flat face, a resistance mounted on said body, a first set of contacts electrically connected to spaced points on said resistance, mounted on said face and arcuately disposed thereon along part of a circle, each of a plurality of said first set of contacts being connected to another contact of a second set of contacts, said second set of contacts being likewise arcuately mounted on said face along another part of said circle, an arcuate contact disposed in another circle concentric with said first circle and also mounted on said face, a second arcuate contact mounted on said face and having an arcuate contact surface disposed along another part of said first-named circle adjacent said first arcuate contact and having a second arcuate contact surface disposed in a third concentric circle, three terminals connected respectively to said resistance and said arcuate contacts for establishing external electrical connections thereto, a three-legged switch arm overlying said contacts and rotatable in a plane parallelto said face around the center of said contacts as an axis, the three legs of said switch arm being of different lengths to engage contacts respectively in said three concentric circles, one of said switch arms having an elongated contact surface engaging said first-named arcuate contact and the first-named arcuate contact surface of said second arcuate contact in the position of actuation on one side of the oil position and contacting only one of said sets of contacts in the position of actuation on the other side of the "ofi position.

- OSCAR H. HASSELBAUM.

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