US3676825A

US3676825A - Screw actuated linear motion potentiometer

Info

Publication number: US3676825A
Application number: US160619A
Authority: US
Inventors: David A Olson
Original assignee: Stackpole Carbon Co
Current assignee: Stackpole Carbon Co
Priority date: 1971-07-08
Filing date: 1971-07-08
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11

Abstract

The front wall of the oblong case of a linear motion potentiometer is provided with a longitudinal slot, in which a slide is disposed. The slide carries a bridging contact inside the case, where it engages spaced parallel resistor and collector elements. In front of the case and parallel to the slot is a lead screw rotatably supported from the case. Rigidly mounted on one end of the screw is a member for rotating it. An arm that is rigidly joined to the slide extends outwardly across the screw and is provided with a portion registering with the screw thread. When the screw is turned, it will move the arm and slide lengthwise of the case.

Description

United States Patent [151 3,676,825 Olson [45] July 11, 1972 54] SCREW ACTUATED LINEAR MO'HON 3,550,060 12/1970 Bang ..338/122 POTENTIOMETER Sachse ..338/181 Primary Examiner-Lewis l-l. Myers Assistant Examiner-Gerald P. Tolin Attorney-Brown, Murray, Flick & Peckham [57] ABSTRACT The front wall of the oblong case of a linear motion potentiometer is provided with a longitudinal slot, in which a slide is disposed. The slide carries a bridging contact inside the case, where it engages spaced parallel resistor and collector elements. In front of the case and parallel to the slot is a lead screw rotatably supported from the case. Rigidly mounted on one end of the screw is a member for rotating it. An arm that is rigidly joined to the slide extends outwardly across the screw and is provided with a portion registering with the screw thread. When the screw is turned, it will move the arm and slide lengthwise of the case.

7 Claim, 4 Drawing Figures Patented July 11, 1972 2 Sheets-Sheet l lA/VE/VTOR. By OAV/D 14. OLSON v ATTORNEYS.

Patented July 11, 1972 2 Sheets-Sheet 2 2a WIIIIIIIIIIIA E04 ATTORNEYS SCREW ACTUATED LINEAR MOTION POTENTIOMETER It is among the objects of this invention to provide a linear motion potentiometer, which is subject to both fine and coarse adjustments, which can be nearly entirely concealed from view behind a panel, which includes a case that can be used with or without means for making fine adjustments, which is compact, and which is not damaged if it is over-adjusted.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a side view, partly broken away;

FIG. 2 is a front view and section taken on the line [1-1] of FIG. 1;

FIG. 3 is an enlarged end view; and

FIG. 4 is a cross section taken on the line IV-IV of FIG. 2.

Referring to the drawings, the long rectangular case 1 of a linear motion potentiometer may be formed from any suitable material, such as a molded plastic or other rigid material. Preferably, the case is made from two molded half sections that meet along a central longitudinal plane extending through the front and back of the case. The two half sections may be held together by a central spring clip 2. The front wall of the case has a longitudinal slot 3 through it extending lengthwise of the case for most of its length. Preferably, the slot opens outwardly into a rectangular recess 4 in the outer surface of the front wall.

Slidably mounted in the case slot is a slide 6 that has laterally opening grooves 7 receiving the side walls of the slot so that the slide is locked in the slot and can move only lengthwise of it. Inside the case a metal collector strip 8 and an electric resistor strip 9 are mounted on opposite sides of the case. The collector strip is provided with a terminal 10 that extends out through the back of the case, and metal terminals 11 clamped onto the ends of the resistor strip likewise extend through the back. Between the two strips and in engagement with them there is a bridging contact that is carried by the slide. This contact may be a wire coil 12 encircling a central post 13 projecting rearwardly from the slide.

In accordance with this invention, a metal bracket is rigidly mounted on the case. This bracket has a flat body 15 engaging one side of the case and extending forward away from it. The bracket also has end portions 16 bent into parallel relation with each other and provided with openings that receive the ends of the case. The ends of the bracket therefore form frames around the ends of the case and are tightly connected to it by deformed portions 17 projecting into recesses 18 in the side of the case, as shown in FIG. 3. These same ends of the bracket may be provided with rearwardly extending tabs 19, by which the unit can be rigidly mounted in a supporting panel or circuit board.

In front of the case the bracket has another pair of parallel end portions 21, but these are for supporting a lead screw 22. The screw is located a short distance in front of the case and is parallel to the slot. The axis of the screw preferably lies in the central longitudinal plane of the case slot. The ends of the screw are rotatably mounted in the bracket ends 21 so that it can rotate. Rigidly mounted on the screw at one end is a manually rotatable member, such as a small drum or roller 23, which may be knurled to give better control over turning it. The roller is located between the bracket ends, so the adjusting mechanism is no longer than the case, thereby making the unit more compact so that it requires less space when installed.

In order for the screw to adjust the slide along the case when the screw is turned by the roller, the slide is provided with a forwardly projecting arm 25 that extends across one side of the screw. The arm may be integral with the slide, such as by molding both of them from a plastic. Extending lengthwise of the arm is a rib 26 that fits between adjacent convolutions of the screw thread. The rib is normally held in this position by the arm, which has some resiliency so that if the screw continues to be turned after the slide reaches the end of its path of travel, the convolutions of the screw thread can slide past the rib by bending the arm away from the screw slightly. This will avoid any damage to the slide-ad'usting mechanism.

It will be seen that as the ro ler is turned, the screw will cause the arm and slide to move lengthwise of the case. Since it is easy to turn the roller only a fraction of a turn if desired, it is possible to adjust the slide back and forth minute distances to obtain very fine adjustments. For quick coarse adjustments, the operator can use a finger or tweezers to bend the am away from the screw and then move the slide along the case without turning the screw. The slide can move the full length of the case slot, because it can move between the roller and the case. If desired, the outer end of the arm can be provided with a laterally projecting tapered pointer 27. When the potentiometer is mounted on a printed circuit board behind a panel 28, the panel is provided with an opening 29 no larger than the roller and through which a portion of the roller projects. The rest of the unit is concealed from view, except that the panel may be provided with a narrow slot 30, through which pointer 27 can be seen. The outer surface of the panel beside this slot is provided with a scale as shown in FIG. 2 to aid in positioning the pointer. With an open slot, access to the pointer is provided so that coarse adjustments can be made as previously explained. If that is not desired, the slot can be closed by a plastic window (not shown), on which the scale can be printed in place of on the panel.

The use of bracket 15 for supporting the lead screw and roller permits this adjusting mechanism to be quickly applied to the potentiometer case or left off. This allows the same case to be used, whether or not the adjusting mechanism is employed.

According to the provisions of the patent statutes, l have explained the principle of my invention and have illustrated and described what I now consider to represent it 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.

I claim:

1. A linear motion potentiometer comprising an oblong case having a front wall provided with a longitudinal slot therein, spaced parallel resistor and collector elements mounted in the case and extending lengthwise thereof, a slide disposed in said slot, a bridging contact in the case carried by the slide in engagement with both of said elements, a lead screw in front of the case parallel to the slot, means mounted on the case rotatably supporting the opposite ends of the screw, a manually rotatable member rigidly mounted on one end of the screw, and an arm rigidly joined to the slide and extending therefrom outwardly across the screw, said arm having a portion registering with the thread of the screw, whereby when said member is turned the screw will move said arm and slide lengthwise of the case.

2. A linear motion potentiometer according to claim 1, in which said arm is resilient and presses against the screw.

3. A linear motion potentiometer according to claim 1, in which the outer end of said arm is provided with a laterally projecting pointer.

4. A linear motion potentiometer according to claim 1, in which said arm is provided with a longitudinal rib fitting between adjacent convolutions of the screw tread.

5. A linear motion potentiometer according to claim 1, in which said screw-supporting means is a bracket having a side portion extending along one side of the case and parallel end portions surrounding the ends of the case and tightly engaging them, and the bracket also having end portions provided with openings rotatably receiving the ends of said screws.

6. A linear motion potentiometer according to claim 5, in which said rotatable member is disposed between said lastmentioned end portions of the bracket.

7. A linear motion potentiometer according to claim 6, and is spaced from the case far enough for said slide to be moved between the case and said member.

Claims

6. A linear motion potentiometer according to claim 5, in which said rotatable member is disposed between said last-mentioned end portions of the bracket.