LINEAR MOTION VARIABLE RESISTOR WITH TRANSVERSE FINE ADJUSTMENT
United States Patent 3648215
An actuator is movable along the edges of parallel resistance and collector strips mounted in a case. The resistance strip is provided near each end with a transverse notch. Bridging contact means carried by the actuator engage both strips. Movably mounted in the actuator is an adjusting member that has an inner end connected with the contact means and that can be moved lengthwise to move the contact means forward and backward beside the strip notches to vary the distance from the point of engagement of the contact means with the resistance strip to the reduced areas of the resistance strip at the inner ends of the notches for fine adjustment of the resistor.
US Patent References:
SLIDE RESISTOR WITH FINE ADJUSTMENT
Eberwern - December 1970 - 3551871
Rheostat
Krauss - December 1927 - 1652017
SLIDE RESISTOR WITH FINE ADJUSTMENT
Eberwern - December 1970 - 3551871
Rheostat
Krauss - December 1927 - 1652017
Application Number:
05/121896
Publication Date:
03/07/1972
Filing Date:
03/08/1971
View Patent Images:
Export Citation:
Assignee:
Stackpole Carbon Company (St. Marys, PA)
Primary Class:
Other Classes:
338/181
International Classes:
H01C10/42; H01C10/00; H01C9/02
Field of Search:
338/118,122,160,176,180,181,183,195
Primary Examiner:
Myers, Lewis H.
Assistant Examiner:
Tolin, Gerald P.
Claims:
I claim
1. A linear motion variable resistor comprising an elongated case, parallel resistance and collector strips mounted therein at its opposite sides and extending lengthwise thereof, said strips having front and rear edges, the resistance strip being provided near each end with a transverse notch reducing the width of that strip at that location, an actuator movable lengthwise along the strips at their front edges, bridging contact means engaging the strips and carried by the actuator for movement thereby lengthwise of the strips, said contact means being movable forwardly and rearwardly in the case, and an adjusting member movably mounted in the actuator and projecting from its front and back, said member having an inner end connected with said contact means, and the adjusting member being adapted to be moved transversely of said strips in order to adjust the bridging contact means forward and backward beside said notches, whereby to vary the distance from the point of engagement of the contact means with the resistance strip to the reduced areas of the resistance strip at the inner ends of said notches for fine adjustment of the resistor.
2. A linear motion variable resistor according to claim 1, in which said notches extend more than halfway across the resistance strip.
3. A linear motion variable resistor according to claim 1, including an open frame projecting rearwardly from the actuator between the strips in a plane parallel thereto, said contact means being slidably mounted in said frame.
4. A linear motion variable resistor according to claim 1, in which said adjusting member is a screw threaded in the actuator and having its inner end rotatably connected with said contact means.
5. A linear motion variable resistor according to claim 4, including an open frame projecting rearwardly from the actuator between the strips in a plane parallel thereto, and said contact means including a block and a bridging contact member carried by the block, the block being slidably mounted in said frame, and the inner end of said screw being rotatably mounted in the block and secured thereto.
1. A linear motion variable resistor comprising an elongated case, parallel resistance and collector strips mounted therein at its opposite sides and extending lengthwise thereof, said strips having front and rear edges, the resistance strip being provided near each end with a transverse notch reducing the width of that strip at that location, an actuator movable lengthwise along the strips at their front edges, bridging contact means engaging the strips and carried by the actuator for movement thereby lengthwise of the strips, said contact means being movable forwardly and rearwardly in the case, and an adjusting member movably mounted in the actuator and projecting from its front and back, said member having an inner end connected with said contact means, and the adjusting member being adapted to be moved transversely of said strips in order to adjust the bridging contact means forward and backward beside said notches, whereby to vary the distance from the point of engagement of the contact means with the resistance strip to the reduced areas of the resistance strip at the inner ends of said notches for fine adjustment of the resistor.
2. A linear motion variable resistor according to claim 1, in which said notches extend more than halfway across the resistance strip.
3. A linear motion variable resistor according to claim 1, including an open frame projecting rearwardly from the actuator between the strips in a plane parallel thereto, said contact means being slidably mounted in said frame.
4. A linear motion variable resistor according to claim 1, in which said adjusting member is a screw threaded in the actuator and having its inner end rotatably connected with said contact means.
5. A linear motion variable resistor according to claim 4, including an open frame projecting rearwardly from the actuator between the strips in a plane parallel thereto, and said contact means including a block and a bridging contact member carried by the block, the block being slidably mounted in said frame, and the inner end of said screw being rotatably mounted in the block and secured thereto.
Description:
Linear motion variable resistors, such as potentiometers, are well known and are provided with actuators or slides that move contacts along resistance elements. In some cases it is desirable to be able to make finer adjustments than can be accomplished conveniently by normal movement of the actuators. It is therefore among the objects of this invention to provide a linear motion variable resistor in which both coarse and fine adjustments can be made by separate adjustments, and in which fine adjustments can be made quickly and easily after any coarse adjustment.
The preferred embodiment of the invention is illustrated in the accompanying drawings, in which
FIG. 1 is a side view of a potentiometer, with part of it broken away;
FIG. 2 is an enlarged fragmentary longitudinal section taken on the line II--II of FIG. 1; and
FIG. 3 is a cross section taken on the line III--III of FIG. 2.
Referring to the drawings, the long rectangular case 1 of a variable resistor, such as a rheostat or potentiometer, may be formed from a molded plastic or other suitable rigid material. The case preferably is made from two molded half-sections that have meeting edges extending from front to back across the end walls of the case and lengthwise along its back or base. The half-sections are joined tightly together in any suitable manner.
Inside the case a metal collector strip 2 and an electrical resistance strip 3 are mounted at the opposite sides and are parallel. The collector strip is provided with an integral terminal 4 that extends through the back of the case, while each end of the resistance strip is connected to a metal terminal 5 likewise extending through the back.
Between the two strips there is a bridging contact member that engages both of them. This contact member can be moved lengthwise of the strips by an actuator that is movable along the front edges of the strips. For example, the actuator may be a slide 7 that is slidably mounted in a central slot 8 extending lengthwise of the case in its front or top. The slide has laterally opening grooves 9 in its opposite sides receiving the side walls of the slot to hold and guide the slide. The ends of the outer sides of the slide may be provided with projections 10 for manually moving the slide lengthwise back and forth along the slot.
It is a feature of this invention that the bridging contact member is not secured in fixed position to the actuator or slide, but is adjustable forward and backward relative to it. Accordingly, the contact member is carried by a small block 12 movable in an open frame 13 projecting rearwardly from the slide and across the two strips in the space between them. The plane of the frame is parallel to the strips, and the frame is spaced from them. The block engages the parallel sides of the frame and, as shown in FIG. 3, is provided with a central passage 14 extending through it at right angles to the strips. Disposed in this passage is the bridging contact member, which may take the form of a pair of spaced contact slugs 15 urged apart by a coil spring 16 between them. The slugs project from the opposite sides of the block into engagement with the two strips.
The central portion of the slide is provided with an opening through it, in which an adjusting member is mounted for longitudinal movement. The inner end of this member is connected with block 12. Preferably, the adjusting member is a screw 18 threaded in the slide, with its inner end rotatably mounted in the front portion of the block and retained in it. The outer end of the screw is provided with means, such as a knob 19, for turning it so that the screw can be screwed inwardly or outwardly to adjust the block across the two strips. Such transverse adjustment of the bridging contact means would not, with the usual resistance strip, affect the adjustment of the resistor. However, since it is intended that turning the knob shall affect the electrical resistance of the unit, the resistance strip is provided near each end with a notch 21 that extends part way across it. The notches may extend from either edge of the strip. For best results, they extend more than halfway across the strip so that the areas of the resistance strip at the inner ends of the notches are less than half as wide as the rest of the strip.
When the bridging contact member is moved forward or backward beside the notches, the distance from the point of engagement of the contact member with the resistance strip to the reduced area of the resistance strip at the inner ends of the notches will be changed. Thus, regardless of the location of the contact member along the resistance strip when the contact member is at the back of the strip, it will engage the strip farther from the front or inner ends of the notches than if the contact were directly opposite those ends, so a longer resistance path will be provided. This is illustrated in FIG. 1 by the two broken lines A and B. Assuming that the contact member engages the resistance strip first at the right-hand end of line A and then at the right-hand end of line B, it will be seen that the distance from the first point to the left-hand end of lines A and B is less than from the second point, because line A is shorter than line B. There is a similar variation in distances between the contact member and the inner end of the other notch.
It will be realized that even though the contact member is moved all the way from its front position to its rear position after the slide has been moved along the case to a desired location, the change in distance (lines A and B for example) from contact to inner ends of notches 21 will be quite small. Consequently, the change in electrical resistance by such transverse movement of the contact member will be very small. Since the contact can be moved by the adjusting screw a very slight amount when desired, it will be understood that turning the screw permits extremely fine adjustments of the electrical resistance to be made quickly and easily after the slide has been moved along the case to an approximately correct position.
According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.
The preferred embodiment of the invention is illustrated in the accompanying drawings, in which
FIG. 1 is a side view of a potentiometer, with part of it broken away;
FIG. 2 is an enlarged fragmentary longitudinal section taken on the line II--II of FIG. 1; and
FIG. 3 is a cross section taken on the line III--III of FIG. 2.
Referring to the drawings, the long rectangular case 1 of a variable resistor, such as a rheostat or potentiometer, may be formed from a molded plastic or other suitable rigid material. The case preferably is made from two molded half-sections that have meeting edges extending from front to back across the end walls of the case and lengthwise along its back or base. The half-sections are joined tightly together in any suitable manner.
Inside the case a metal collector strip 2 and an electrical resistance strip 3 are mounted at the opposite sides and are parallel. The collector strip is provided with an integral terminal 4 that extends through the back of the case, while each end of the resistance strip is connected to a metal terminal 5 likewise extending through the back.
Between the two strips there is a bridging contact member that engages both of them. This contact member can be moved lengthwise of the strips by an actuator that is movable along the front edges of the strips. For example, the actuator may be a slide 7 that is slidably mounted in a central slot 8 extending lengthwise of the case in its front or top. The slide has laterally opening grooves 9 in its opposite sides receiving the side walls of the slot to hold and guide the slide. The ends of the outer sides of the slide may be provided with projections 10 for manually moving the slide lengthwise back and forth along the slot.
It is a feature of this invention that the bridging contact member is not secured in fixed position to the actuator or slide, but is adjustable forward and backward relative to it. Accordingly, the contact member is carried by a small block 12 movable in an open frame 13 projecting rearwardly from the slide and across the two strips in the space between them. The plane of the frame is parallel to the strips, and the frame is spaced from them. The block engages the parallel sides of the frame and, as shown in FIG. 3, is provided with a central passage 14 extending through it at right angles to the strips. Disposed in this passage is the bridging contact member, which may take the form of a pair of spaced contact slugs 15 urged apart by a coil spring 16 between them. The slugs project from the opposite sides of the block into engagement with the two strips.
The central portion of the slide is provided with an opening through it, in which an adjusting member is mounted for longitudinal movement. The inner end of this member is connected with block 12. Preferably, the adjusting member is a screw 18 threaded in the slide, with its inner end rotatably mounted in the front portion of the block and retained in it. The outer end of the screw is provided with means, such as a knob 19, for turning it so that the screw can be screwed inwardly or outwardly to adjust the block across the two strips. Such transverse adjustment of the bridging contact means would not, with the usual resistance strip, affect the adjustment of the resistor. However, since it is intended that turning the knob shall affect the electrical resistance of the unit, the resistance strip is provided near each end with a notch 21 that extends part way across it. The notches may extend from either edge of the strip. For best results, they extend more than halfway across the strip so that the areas of the resistance strip at the inner ends of the notches are less than half as wide as the rest of the strip.
When the bridging contact member is moved forward or backward beside the notches, the distance from the point of engagement of the contact member with the resistance strip to the reduced area of the resistance strip at the inner ends of the notches will be changed. Thus, regardless of the location of the contact member along the resistance strip when the contact member is at the back of the strip, it will engage the strip farther from the front or inner ends of the notches than if the contact were directly opposite those ends, so a longer resistance path will be provided. This is illustrated in FIG. 1 by the two broken lines A and B. Assuming that the contact member engages the resistance strip first at the right-hand end of line A and then at the right-hand end of line B, it will be seen that the distance from the first point to the left-hand end of lines A and B is less than from the second point, because line A is shorter than line B. There is a similar variation in distances between the contact member and the inner end of the other notch.
It will be realized that even though the contact member is moved all the way from its front position to its rear position after the slide has been moved along the case to a desired location, the change in distance (lines A and B for example) from contact to inner ends of notches 21 will be quite small. Consequently, the change in electrical resistance by such transverse movement of the contact member will be very small. Since the contact can be moved by the adjusting screw a very slight amount when desired, it will be understood that turning the screw permits extremely fine adjustments of the electrical resistance to be made quickly and easily after the slide has been moved along the case to an approximately correct position.
According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.