GB1575518A

GB1575518A - Combined potentiometer and switch unit

Info

Publication number: GB1575518A
Application number: GB3001576A
Authority: GB
Original assignee: AB Electronic Components Ltd
Current assignee: AB Electronic Components Ltd
Priority date: 1976-07-19
Filing date: 1976-07-19
Publication date: 1980-09-24
Also published as: ES461466A1; FR2359492A1; DE2732462A1; NL7708035A; IT1084399B

Description

(54) COMBINED POTENTIOMETER AND SWITCH UNIT (71) We, A.B. ELECTRONIC COMPON- ENTS LIMITED, a British Company of, Abercynon, Mid-Glamorgan CF45 4SF, Wales, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to combined potentiometer and switch units There exists a requirement, specifically in the television field, for use in connection with certain types of cathode ray tubes (FRT), for high voltage capability variable resistor units, used in conjunction with simple change-over switches. The potentiometers are known specifically as "grey scale tracking controls", the switches as "gun switches".

The potentiometers are directly coupled to the anodes of the C.R.T. There are three individual colour guns in the type of C.R.T.

where the requirement exists, and the intensity of the electron beam from each gun is controlled by each individual control. In setting up the tube it is necessary on colour sets to adjust each of the colour guns individually, i.e. the red, green and blue guns. This setting up is carried out in the absence of colour on the grey scale signal card put out by the broadcasting authorities. The particular gun being set is isolated by switching off and earthing the other two guns. Having set the correct grey scale, all guns are switched into circuit and the colour reintroduced.

This facility is currently provided by a separate potentiometer and a separate changeover switch for each of the guns making a total fo six components requiring a total of eighteen terminals to be connected into the circuitry.

According to the present invention there is provided a rotary potentiometer and switch unit comprising at least one potentiometer comprising a resistive track connected between external terminals and a movable contact rotatable in contact with the resistive track and with a conductive collector ring, the or each potentiometer having associated therewith a changeover switch comprising an external terminal and a moving contact movable independently of the potentiometer movable contact and adapted to connect the said switch terminal selectively with the collector ring of the associated potentiometer or with a further contact.

By providing internal connections in the unit between the potentiometer and switch there is a saving of 2n terminals, where n is the number of potentiometers or switches, i.e. three in the case of a unit for setting up three colour guns.

Further reduction can be obtained by having the resistive tracks connected in parallel between common terminals (a saving of 2(n-1) terminals) and by providing a common external terminal for each of the said further contacts (a saving of n-l terminals).

In the specific instance given of three potentiometers and switches, the external terminals are reduced from the eighteen necessary for separate components to a total of six.

The invention will be further described by way of example with reference to Figures 1 to 11 of the drawings accompanying the provisional specification, which figures illustrate a preferred embodiment of the invention.

In the drawings: Figure 1 is a plan view of a preferred form of unit according to the invention; Figure 2 is a view of the unit of Figure 1 from the front, some parts of the switches being removed; Figure 3 is a view of the unit of Figure 1 from the rear, a resistor board being removed; Figure 4 is a view of the unit of Figure 1 from below; Figure 5 is a circuit diagram of the unit of Figure 1; Figure 6 is a view of the inner surface of the circuit board of the unit of Figure 1; Figure 7 is a rear view of the unit of Figure 1, similar to Figure 3, but with parts of the potentiometer removed; Figure 8 is a rear view of part of one of the potentiometers; Figure 9 is a section through the part of Figure 8; Figure 10 is a rear view of part of one of the switches; and Figure 11 is a section through the part of Figure 10.

As shown in Figure 5, a unit constituting a preferred embodiment of the invention consists of changeover switches to connect the potentiometer collectors or the OV terminal and BA, GA, RA terminals respectively, and potentiometers connected between the OV and +V terminals.

As shown in Figures 2, 10 and 11, each changeover switch is similar to the others and comprises a generally disc-shaped switch knob 1 of insulating material provided with a peripheral projection 2 to enable it to be rotated about a pivot 3. The pivots 3 are formed by raised projections on a housing 16, which projections enter apertures in the knobs 1 and are spun over at 3a to retain the knobs 1. The switch knobs are preferably coloured to indicate the gun to which they relate. The rear face of the switch knob is formed with a linear chordal ridge 4 adjacent the projection 2 and a raised central land 5 whose boundary is provided with two recesses 6. A switch spring 7 of conducting material is generally oval in shape with two inwardly directed projections 8 which fit resiliently into the recesses 6 of the land 5.The regions of the spring 7 in the vicinity of the most widely separated parts of the oval bend rearwardly and are formed with contact pips 9 and 10.

The contact pip 9 contacts resiliently either an upper conductive collector ring 11 or a lower conductive contact 12, depending on the position of the switch knob 1. The region of insulating material between the collector ring 11 and contact 12 is raised to make the action of the switch more positive. The remaining contact pip 10 is always in resilient contact with an arcuate terminal 13 of conducting material which is unitary with an external terminal portion BA, GA or RA respectively.

Projection 2 of the switch knob is provided with a stop 14 which abuts stops 15 provided on the insulating housing 16 to limit the movement of the switch knob.

The stop 14 may be included as part of a general thickening of the body of the knob 1 starting at the position of the ridge 4.

A rear view of the housing 16 is shown in Figure 7. It will be seen that collector rings 11 have annular rear portions 11' and lower contacts 12 are unitary with a rail 12' having an exterior terminal portion 12".

As shown in Figure 3, the rear side of the housing 16 is provided with peripherally toothed potentiometer knobs 17 (Figures 8 and 9) pivoted coaxially with, but independently of, switch knobs 1 by means of spigots 17a extending through the raised projections on the housing 16. Each potentiometer knob 17 is formed with a through hole 18 and raised locating portions 19, 20 and 21 to accommodate a potentiometer spring contact 22. Potentiometer spring contact 22 is generally heart shaped, with an inner arm 23 extending inwardly from a bridge portion 24 and an outer arm 25 extending outwardly from the region opposite the bridge portion 24. As shown in Figure 9, the arm 25 and connecting parts of the spring contact 22 extend as far as bridge portion 24 in a plane inclined rearwardly, and the inner arm 23 extends in a plane lying parallel to the plane of the housing 16.Thus, the configuration in cross-section is that of a "Y". The inner arm 23 rests on a correspondingly inclined part of the potentiometer knob 17 and the bridge portion clips under the portion 19, located by the further locating portions 20, 21. The inner arm and the outer arm having contact pips 26, 27 respectively.

The inner arm 23 of the potentiometer spring always bears through the hole 18, on the annular portion 11' of the collector ring 11.

The outer arm 22 bears on an arcuate resistive track 28 of a resistor board 29. The three resistive tracks are connected in parallel across terminals 30, 31 by means of a conductive coating 32. The resistor board 29 fits onto the back of the housing 16 to complete the unit.

Rotation of the potentiometer knob is limited by stops 33, 34.

WHAT WE CLAIM IS: 1. A rotary potentiometer and switch unit comprising at least one potentiometer comprising a resistive track connected between external terminals and a movable contact rotatable in contact with the resistive track and with a conductive collector ring, the or each potentiometer having associated therewith a changeover switch comprising an external terminal and a moving contact movable independently of the potentiometer movable contact and adapted to connect the said switch terminal selectively with the collector ring of the associated potentiometer or with a further contact.

2. A unit as claimed in claim 1, comprising a plurality of potentiometers and associated switches, in which all the potentiometers have their resistive tracks connected in parallel between common external terminals.

3. A unit as claimed in claim 2, in which the resistive tracks and connections between them and the terminals are printed on a single resistance board.

4. A unit as claimed in claim 1, 2 or 3, comprising a plurality of potentiometers and associated switches, in which all of the switches have the said further contacts connected to a common external terminal.

5. A unit as claimed in any of claims 1 to 4,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Figure 7 is a rear view of the unit of Figure 1, similar to Figure 3, but with parts of the potentiometer removed; Figure 8 is a rear view of part of one of the potentiometers; Figure 9 is a section through the part of Figure 8; Figure 10 is a rear view of part of one of the switches; and Figure 11 is a section through the part of Figure 10. As shown in Figure 5, a unit constituting a preferred embodiment of the invention consists of changeover switches to connect the potentiometer collectors or the OV terminal and BA, GA, RA terminals respectively, and potentiometers connected between the OV and +V terminals. As shown in Figures 2, 10 and 11, each changeover switch is similar to the others and comprises a generally disc-shaped switch knob 1 of insulating material provided with a peripheral projection 2 to enable it to be rotated about a pivot 3. The pivots 3 are formed by raised projections on a housing 16, which projections enter apertures in the knobs 1 and are spun over at 3a to retain the knobs 1. The switch knobs are preferably coloured to indicate the gun to which they relate. The rear face of the switch knob is formed with a linear chordal ridge 4 adjacent the projection 2 and a raised central land 5 whose boundary is provided with two recesses 6. A switch spring 7 of conducting material is generally oval in shape with two inwardly directed projections 8 which fit resiliently into the recesses 6 of the land 5.The regions of the spring 7 in the vicinity of the most widely separated parts of the oval bend rearwardly and are formed with contact pips 9 and 10. The contact pip 9 contacts resiliently either an upper conductive collector ring 11 or a lower conductive contact 12, depending on the position of the switch knob 1. The region of insulating material between the collector ring 11 and contact 12 is raised to make the action of the switch more positive. The remaining contact pip 10 is always in resilient contact with an arcuate terminal 13 of conducting material which is unitary with an external terminal portion BA, GA or RA respectively. Projection 2 of the switch knob is provided with a stop 14 which abuts stops 15 provided on the insulating housing 16 to limit the movement of the switch knob. The stop 14 may be included as part of a general thickening of the body of the knob 1 starting at the position of the ridge 4. A rear view of the housing 16 is shown in Figure 7. It will be seen that collector rings 11 have annular rear portions 11' and lower contacts 12 are unitary with a rail 12' having an exterior terminal portion 12". As shown in Figure 3, the rear side of the housing 16 is provided with peripherally toothed potentiometer knobs 17 (Figures 8 and 9) pivoted coaxially with, but independently of, switch knobs 1 by means of spigots 17a extending through the raised projections on the housing 16. Each potentiometer knob 17 is formed with a through hole 18 and raised locating portions 19, 20 and 21 to accommodate a potentiometer spring contact 22. Potentiometer spring contact 22 is generally heart shaped, with an inner arm 23 extending inwardly from a bridge portion 24 and an outer arm 25 extending outwardly from the region opposite the bridge portion 24. As shown in Figure 9, the arm 25 and connecting parts of the spring contact 22 extend as far as bridge portion 24 in a plane inclined rearwardly, and the inner arm 23 extends in a plane lying parallel to the plane of the housing 16.Thus, the configuration in cross-section is that of a "Y". The inner arm 23 rests on a correspondingly inclined part of the potentiometer knob 17 and the bridge portion clips under the portion 19, located by the further locating portions 20, 21. The inner arm and the outer arm having contact pips 26, 27 respectively. The inner arm 23 of the potentiometer spring always bears through the hole 18, on the annular portion 11' of the collector ring 11. The outer arm 22 bears on an arcuate resistive track 28 of a resistor board 29. The three resistive tracks are connected in parallel across terminals 30, 31 by means of a conductive coating 32. The resistor board 29 fits onto the back of the housing 16 to complete the unit. Rotation of the potentiometer knob is limited by stops 33, 34. WHAT WE CLAIM IS:

1. A rotary potentiometer and switch unit comprising at least one potentiometer comprising a resistive track connected between external terminals and a movable contact rotatable in contact with the resistive track and with a conductive collector ring, the or each potentiometer having associated therewith a changeover switch comprising an external terminal and a moving contact movable independently of the potentiometer movable contact and adapted to connect the said switch terminal selectively with the collector ring of the associated potentiometer or with a further contact.

5. A unit as claimed in any of claims 1 to 4,

in which the or each potentiometer collector ring extends through a housing plate so that on one side of the housing plate it is in contact with a potentiometer movable contact andon the other side it presents a portion engageable by the switch moving contact in one alternative position thereof.

6. A unit as claimed in claim 5, in which the said further contact of the switch is spaced from the collector ring portion on the said other side by an elevated part of the plate providing a snap action for the switch.

7. A unit as claimed in claim 5 or 6, comprising a plurality of potentiometers and associated switches, in which the collector rings are mounted on a common plate which also carries the external terminals of the switches and the said further contacts.

8. A unit as claimed in claim 7, in which the external terminals for the switches are connected to arcuate conductive cdntacts engaged with the switch moving contacts in and between both positions of the switch.

9. A unit as claimed in any of the preceding claims, in which the or each potentiometer movable contact is mounted on a rotary disc member having a through hole via which the movable contact has an arm extending to meet the collector ring.

10. A combined potentiometer and switch unit substantially as hereinbefore described with reference to Figures 1 to 11 of the drawings accompanying the provisional specification.