GB2547629A

GB2547629A - Revised push-pull switch

Info

Publication number: GB2547629A
Application number: GB1522834.9A
Authority: GB
Inventors: Aston Mark; Smith Frank; Beverley Les
Original assignee: TEW Engineering Ltd
Current assignee: TEW Engineering Ltd
Priority date: 2015-12-23
Filing date: 2015-12-23
Publication date: 2017-08-30
Anticipated expiration: 2035-12-23
Also published as: GB2547629B; GB201522834D0

Abstract

An electronic sub-assembly 40 for a switch 10 comprises at least one switching element 80 connected to control electronics 85 by a flexible strip 90, which deforms to permit insertion of the sub-assembly into a switch housing 20. A mechanical sub-assembly 30 for a switch comprises an elongate bushing 50 having a mounting portion 55 and a neck portion, an elongate actuation shaft 60 mounted in the bushing, and a light pipe located within and co-axial to the actuation shaft. The housing comprises a plurality of recesses 25 to accommodate the mechanical and electronic sub-assemblies. The electronic sub-assembly may comprise an LED indicator 100 adapted to indicate multiple switch states by variation in colour and/or intensity, and may be driven by a constant current source. The mechanical sub-assembly may comprise at least one bearing located between the shaft and the bushing to allow longitudinal movement of the shaft along its axis within the bushing but limit shaft motion in a lateral direction. A spring may bias the shaft to a default position within the bushing whether the switch is pushed or pulled. Either or both of the mechanical and electronic sub-assemblies may be inserted into the housing fully assembled.

Description

Revised push-pull switch

This invention relates to a switch for push-pull actuation, in particular to a high-reliability dual pole changeover switch with built-in indication. Specifically, the invention relates to improvements to the switch described in UK Patent GB2503298, entitled “Push-pull actuated switch”, of which the applicant is the proprietor (and which contents are hereby incorporated by reference in their entirety), although these improvements are also applicable more widely.

As for the earlier patent, the switch described herein is intended for use with a tile for a mosaic mimic system. These systems are used to provide information regarding, and control of, complex systems such as rail networks. They are built from tiles which are capable of receiving components such as meters, switches and lamps, typically mounted on a grid so as to provide a fascia. They may also be combined with a mounting plate or struts for mounting of components. The switches described herein are suitable for mounting on such tiles.

It was found that the previous generation of switch exhibited several disadvantages such as: • The various electronic and electromechanical components were hand assembled into a mechanical body of the switch. This required a skilled operator to assemble two switches, an LED, a resistor, a diode and various lengths and thicknesses of wire into the body. • All the connections were formed by solder joints some of which had to be made in confined spaces and the connections into the crimps on the connector were compromised by the cable size requirements imposed by the internal structure. • The contacts on the back of the switches had to be protected by a layer of Epoxy to ensure they did not short to the switch body. • The resistor and diode had to be protected by sleeving to isolate them from the body and ensure they did not get broken. • The cables had to be routed with care to ensure they were not trapped or chaffed. In particular the cable to the LED was very fine and followed a route that was tedious and difficult. • The LED itself was mounted in a custom connector inside the end of the actuator assembly. Many of the switch failures were due to the problems with the connections to the LED, wire fractures, solder joint failures and connector failures were among the more common problems. • Because the LED was so close to the operator great care had to be taken to ensure electrostatic discharge would not damage the LED. This further increased the complexity of the wiring and the assembly as it required a specific earth connection wire. • Use of a resistor to regulate the current meant that different assemblies were necessary for each combination of supply voltage and supply type to ensure the LED light output (which is proportional to the current) was consistent (despite the power dissipation being proportional to the square of the voltage). For example, six assemblies would be required to cover each of 12V, 24V and 48V in both DC and AC. The lack of flexibility and storage costs were a commercial disadvantage.

There is therefore a need for a new switch design which is both easier to assemble and more robust. At least some of the problems outlined above may be addressed by the invention described below.

According to one aspect of the invention, there is provided an electronic sub-assembly for a switch, comprising: at least one switching element; control electronics; and a flexible strip, connecting the switching element to the control electronics; wherein the strip is deformable to permit insertion of the sub-assembly into the switch housing.

Preferably, at least one of the switching element and the control electronics is adapted to be inserted into and held securely by a recess of the switch assembly.

Preferably, the switching element is adapted to fit the recess such that it is operable by an actuating element of the switch.

Preferably, the electronic sub-assembly further comprises an indicator, preferably an LED. The LED may be driven by a constant current source. The LED may be adapted to indicate multiple switch states by variation in colour and/or intensity.

According to another aspect of the invention there is provided a mechanical sub-assembly for a switch, comprising: an elongate bushing having a mounting portion and a neck portion; an elongate actuation shaft mounted in the bushing; and a light pipe located within and coaxial to the actuation shaft.

Preferably, the mechanical sub-assembly further comprises at least one bearing located between the shaft and the bushing to allow longitudinal movement of the shaft along its axis within the bushing but limit motion of the shaft in the lateral direction.

Preferably, the at least one bearing comprises first and second bearings provided between the actuation shaft and the bushing, preferably each bearing being an annular sleeve; wherein the first bearing is provided in the mounting portion of the bushing and the second bearing is provided in the neck portion of the bushing

Preferably, the mechanical sub-assembly further comprises a spring adapted to bias the shaft to a default position within the bushing whether the switch is pulled or pushed.

Preferably, the mechanical sub-assembly further comprises a grounding connector adapted to provide grounding of the actuation shaft.

According to another aspect of the invention there is provided a housing for a switch having a plurality of recesses, wherein a first recess is adapted to accommodate an electronic sub-assembly and a second recess is adapted to accommodate a mechanical sub-assembly (as described above).

Preferably, at least one of the mechanical sub-assembly and the electronic sub-assembly is insertable into the housing fully assembled. More preferably, the mechanical sub-assembly and the electronic sub-assembly are separately insertable into the housing fully assembled.

Preferably, the respective recesses accommodating the sub-assemblies are arranged so as to align the indicator with the light pipe such that light output by the indicator is visible at the distal end of the shaft to a user of the switch.

According to another aspect of the invention there is provided a switch comprising: a housing, an electronic sub-assembly and an mechanical sub-assembly (as described above).

According to another aspect of the invention there is provided a tile for a mosaic mimic system, incorporating a switch as described above.

According to another aspect of the invention there is provided a system for controlling a transport network, incorporating a switch and/or a tile as described above.

According to another aspect of the invention there is provided a transport network incorporating a system as described above.

According to another aspect of the invention there is provided a method of fabrication of a switch comprising inserting an electronic sub-assembly and a mechanical sub-assembly into a housing, preferably wherein the electronic sub-assembly, the mechanical sub-assembly and the housing are as described above.

There is also provided a push-pull switch comprising: a housing having a plurality of recesses; a mechanical sub-assembly, adapted to be accommodated by a first recess in the housing, comprising an elongate bushing having a mounting portion received in the recess and a neck portion protruding from the housing; and an elongate actuation shaft mounted in the bushing; and an electronic sub-assembly, adapted to be accommodated by a second recess in the housing, comprising at least one switching element; wherein the relative arrangement of first and second recesses in the housing maintains the actuating element and the switching element in proximate alignment to allow the switching element to be activated by operation of the actuating element.

Further features of the invention are characterised by the dependent claims.

The switch described may allow for its constituent parts and sub-assemblies to be made and tested separately and the switch to be assembled in a clean and simple way. It may also simplify the process of removal and replacement of the parts and sub-assemblies.

Aspects of the invention may provide one, some or all of the following, in any appropriate combination.

The invention extends to methods and/or apparatus substantially as herein described with reference to the accompanying drawings.

Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied apparatus aspects, and vice versa.

Equally, the invention may comprise any feature as described, whether singly or in any appropriate combination.

The invention will now be described, purely by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a cut-away of a push-pull switch with sub-assemblies in situ;

Figures 2 and 3 show the electronics sub-assembly in more detail; and Figure 4 shows example circuit diagrams of the electronics sub-assembly.

Overview

Figure 1 shows a cut-away of a push-pull switch 10 comprising a housing 20 comprising a plurality of recesses 25 accommodating two sub-assemblies, mechanical sub-assembly 30 and electronic sub-assembly 40. Generally, recesses 25 comprise a plurality of interconnecting recesses or sub-recesses 25-n to accommodate the various parts of the sub-assemblies, at least some of which are designed to hold parts of the sub-assemblies 30, 40 firmly in place.

Mechanical sub-assembly 30 comprises: • an elongate or cylindrical sleeve or bushing 50 comprising a mounting plate 55 located in the housing 20 and a neck portion 50 protruding from the housing 20 (the neck portion 50 held secure by the mounting plate 55 being accommodated in recess 25-1 in the housing 20) • an actuation shaft 60 mounted within the bushing 50 • an actuation knob or cap 65 at the distal end of the shaft 60 • at least one bearing, preferably in the form of an annular sleeve, located between the shaft and the bushing to allow longitudinal movement of the shaft along its axis within the bushing but limit motion of the shaft in the lateral direction • a grounding connector 67 (accommodated in recess 25-2) providing a high quality connection between the actuating shaft 60 and the switch body to provide grounding of the actuating shaft 60. In some embodiments a sliding spring contact and copper slip are provided. • an actuating element in the form of a paddle block 70 at the proximate end of the shaft 60, the paddle block 70 being located in a reciprocating recess 25-3 allowing movement of the block 70 in the axial direction of the shaft 60 between first and second positions to allow actuation of switching elements of the electronic sub-assembly • a connecting wire 75 for interfacing to the switch body

Not shown is a light pipe located within and extending co-axially along the shaft 60.

Bushing 50 contains a spring (not shown) that biases the shaft 60 to a default or neutral resting position within the bushing 50 whether the switch is pulied or pushed. This is achieved by compressing the spring from one end or the other depending upon the direction of operation.

Electronic sub-assembly 40 comprises: • at least one, preferably a pair of switching element(s) 80 • a printed circuit board (PCB), comprising a rigid backboard 85 on which are mounted control electronics and a flexible (data/power) connecting strip 90 linking via connectors 92 to two interface modules 95 for interfacing to the switching element(s) 80 • a light-emitting diode (LED) indicator 100 mounted on the PCB backboard 85

• a plurality of connecting wires 105 for interfacing to the PCB

The switching elements 80 are typically push-button switch modules or micro-switches.

The connecting wires pass from the circuit board through a connector block 110 located at the end of the housing 20 remote from the shaft 60 and on to external electronics.

Assembling the push-pull switch involves inserting the mechanical sub-assembly 30 connector block 110 and the electronic sub-assembly 40 (with push-button switching elements 80 and interface modules 95 attached) into the appropriate recesses 25 in housing 20, routing the flexible connecting strip 90 such that the push-buttons 80 are aligned either side of the paddle block 70. Recesses 25-5 provide anchoring for the interface modules 95 and/or switching element(s) 80 to allow accurate positioning of the switching element(s) 80 in the in the longitudinal (in this embodiment, parallel with the main axis of the shaft 80) and preferably also transverse directions. The recess 25-4 accommodating the rigid backboard 85 and recess 25-1 accommodating the mounting plate 55 of the bushing 50 are arranged so as to align the LED 100 with the light pipe in the shaft 60.

The two sub-assemblies 30, 40 which form the switch when combined within the housing 20 produce a high reliability dual pole changeover switch with built-in indication. All the unique features of the mechanical assembly are retained but improved and modified to remove the need for adjustment of the assembly.

Actuation of the switch 100 is achieved by pushing or pulling the knob 65, causing the shaft 60 to move in the direction of its main axis within the bushing 50. Paddle 70 is thereby likewise caused to move in the same axial direction, actuating one or other of the switching elements 80. The spring retracts the shaft 60 back to a neutral (resting) position with neither switching element 80 is actuated.

Figures 2 and 3 show the electronics sub-assembly in more detail.

The electronic sub-assembly 40 uses a combination of a flexi-rigid PCB integrating all the electronics and switching onto one easy to manufacture and install sub-assembly. LED 100 is positioned so as to produce a cone of light that is captured by the light pipe which runs up the centre of the switch shaft 60 to the actuation knob 65 to provide status indication to a user of the switch. This removes the need for the diode to be fitted in the end of the shaft and improves overall reliability and life by eliminating the need for long, fine, fragile cables and the connector. This also eliminates the need for a special earth connection. Further, because LED 100 is no longer close to the operator the risk of electrostatic discharge causing damage has been effectively eliminated. LED 100 is driven by a constant current source meaning that one design can cover a range of requirements eg. 12 to 48 volts AC and DC supplies, with consistent LED light output. This means it is not necessary to maintain the voltage and series cabling within tight tolerances to ensure the LED indicator 100 shows consistent brightness across switches.

In some embodiments, an alternative LED indicator 100 is used which changes colour and/or has variable intensity to indicate multiple switch states.

All the components can be assembled and tested in the full circuit before the assembly is paired with the mechanics. Only the two switches 80 and the external connector 110 require any manual assembly and these could potentially be automated or eliminated if manufacturing volumes were large.

The majority of the solder joints are made automatically in a factory controlled process. This includes the previously problematic connections to the LED 100.

In some embodiments the switches 80 are soldered directly onto the flexible connecting strip 90 of the electronics sub-assembly 40 and there is no longer a need to protect these joints to eliminate shorts.

Interfacing with the push-pull switch 10 is by way of a plurality of connecting wires 75, 105. In this embodiment, nine short wires 75, 105 are used to connect to the push-pull switch 10 via connector block 110. Eight of these wires 105 are identical and used to connect to the PCB 85 and the ninth wire 75 is used to connect to the switch body to provide an earth connection. All wires are sized correctly for the current carried and the crimp connection.

The final assembly will now operate on systems with AC and DC supplies over a voltage range from 12 to 48 Volts. Thus only one assembly is required to cover the previously described range.

Figure 4 shows example circuit diagrams of the electronics sub-assembly.

It will be understood that the invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Reference numerals appearing in any claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

Claims

1. An electronic sub-assembly for a switch, comprising: at least one switching element; control electronics; and a flexible strip, connecting the switching element to the control electronics; wherein the strip is deformable to permit insertion of the sub-assembly into the switch housing.

2. An electronic sub-assembly according to claim 1, wherein at least one of the switching element and the control electronics is adapted to be inserted into and held securely by a recess of the switch assembly.

3. An electronic sub-assembly according to claim 2, wherein the switching element is adapted to fit the recess such that it is operable by an actuating element of the switch.

4. An electronic sub-assembly according to any preceding claim, further comprising an indicator, preferably an LED.

5. An electronic sub-assembly according to claim 4, wherein the LED is driven by a constant current source.

6. An electronic sub-assembly according to claim 4 or 5, wherein the LED is adapted to indicate multiple switch states by variation in colour and/or intensity.

7. A mechanical sub-assembly for a switch, comprising: an elongate bushing having a mounting portion and a neck portion; an elongate actuation shaft mounted in the bushing; and a light pipe located within and co-axial to the actuation shaft.

8. A mechanical sub-assembly according to claim 7, further comprising at least one bearing located between the shaft and the bushing to allow longitudinal movement of the shaft along its axis within the bushing but limit motion of the shaft in the lateral direction.

9. A mechanical sub-assembly according to claim 8, wherein the at least one bearing comprises first and second bearings provided between the actuation shaft and the bushing, preferably each bearing being an annular sleeve; wherein the first bearing is provided in the mounting portion of the bushing and the second bearing is provided in the neck portion of the bushing

10. A mechanical sub-assembly according to any of claims 7 to 9, further comprising a spring adapted to bias the shaft to a default position within the bushing whether the switch is pulled or pushed.

11. A mechanical sub-assembly according to any of claims 7 to 10, further comprising a grounding connector adapted to provide grounding of the actuation shaft.

12. A housing for a switch having a plurality of recesses, wherein a first recess is adapted to accommodate an electronic sub-assembly according to any of claims 1 to 6; and a second recess is adapted to accommodate a mechanical sub-assembly according to any of claims 7 to 11.

13. A housing according to claim 12, wherein at least one of the mechanical sub-assembly and the electronic sub-assembly is insertable into the housing fully assembled.

14. A housing according to claim 13, wherein the mechanical sub-assembly and the electronic sub-assembly are separately insertable into the housing fully assembled.

15. A housing according to any of claims 12 to 14 when dependent on any of claims 4 to 6, wherein the respective recesses accommodating the sub-assemblies are arranged so as to align the indicator with the light pipe such that light output by the indicator is visible at the distal end of the shaft to a user of the switch.

16. A switch comprising: a housing according to any of claims 12 to 15; an electronic sub-assembly according to any of claims 1 to 6; and an mechanical sub-assembly according to any of claims 7 to 11.

17. A switch substantially as herein described with reference to the accompanying figures.

18. A tile for a mosaic mimic system, incorporating a switch according to Claim 15 or 16.

19. A system for controlling a transport network, incorporating a switch according to claim 15 or 16 and/or a tile according to Claim 17.

20. A transport network incorporating a system according to Claim 18.

21. A method of fabrication of a switch comprising inserting an electronic sub-assembly and a mechanical sub-assembly into a housing.

22. A method according to claim 21, wherein the electronic sub-assembly is according to any of claims 1 to 6, the mechanical sub-assembly is according to any of claims 7 to 11 and the housing of any of claims 12 to 15.