GB2266185A

GB2266185A - Rotary stepping switch.

Info

Publication number: GB2266185A
Application number: GB9208157A
Authority: GB
Inventors: Bun Wong
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-04-14
Filing date: 1992-04-14
Publication date: 1993-10-20
Anticipated expiration: 2012-04-14
Also published as: HK163596A; GB2266187B; GB2266187A; CN1033411C; GB9208157D0; HK163496A; GB9215713D0; CN1078825A; GB2266185B

Abstract

A rotary stepping switch comprises a casing formed by at least two parts (12 and 13) held together by a shaft (15), a rotor (23) supported within the casing by the shaft (15) for rotation about an axis, a movable switch contact (22) carried on the rotor (23), a driving member (30) supported for rotation within the casing about the axis for rotating in a driving direction (Y) the rotor (23) in order to move the movable switch contact (22) into or out of electrical contact with one or more stationary switch contacts (20A, 20B), one-way clutch means (32, 28) provided between the driving member (30) and the rotor (23) in order for the driving member (30) to impart a stepwise drive to the rotor (23), and one-way stopping means provided within the casing, eg direct engagement between the rotor (23) and a stationary contact, for stopping the rotor (23) against rotation upon return rotation of the driving member (30) in a non-driving direction (X). <IMAGE>

Description

ROTARY STEPPING SWITCH The present invention relates to a rotary stepping switch which is suitable for use in domestic electrical appliances.

According to the invention, there is provided a rotary stepping switch which comprises a casing formed by at least two parts, a shaft holding the casing parts together, a rotor supported within the casing by the shaft for rotation about an axis, a plurality of stationary switch contacts located within the casing, a movable switch contact carried on the rotor, an angularly reciprocatable driving member supported for rotation within the casing about the axis for rotating in a driving direction the rotor in order to move the movable switch contact into or out of electrical contact with one or more of the stationary switch contacts, one-way clutch means provided between the driving member and the rotor in order for the driving member to impart a stepwise drive to the rotor, and one-way stopping means provided within the casing for stopping the rotor against rotation upon return rotation of the driving member in a non-driving direction.

Preferably, the shaft is fixed at one end to the first one of said at least two casing parts and passes at the opposite end substantially through the second one of said at least two casing parts for engagement therewith.

Advantageously, the shaft is formed integrally with said first casing part.

In a preferred embodiment, the said opposite end of the shaft is expanded or deformed thereby engaging with said second casing part.

It is preferred that the driving member is rotatably supported on the shaft and is resiliently biassed by a spring to rotate in the non-driving direction.

In a specific construction, the driving member and the rotor are in direct axial engagement with each other and have on their respective engaging surface co-operable formations which provide said one-way clutching means.

Preferably, each formation is in the form of a ring of consecutive asymmetrical teeth, and the corresponding formations of the driving member and the rotor are complementary to each other.

In a particular arrangement, the one-way stopping means is provided by direct engagement between the rotor and at least one of the stationary switch contacts.

Preferably, the rotor has around its periphery a ring of consecutive asymmetrical teeth extending radially outwardly, and said at least one stationary switch contact is resiliently deformable so that it will engage with the forthcoming one of the said teeth only when the rotor is under the action of the driving member in the non-driving direction.

In a preferred embodiment, the end of the rotor engaging with the driving member are divided into sectors, each of which in the non-driven direction expands gradually from one end to the other end in both radially and axially outward directions in order to form the two rings of teeth.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of an embodiment of a rotary stepping switch in accordance with the invention; Figure 2 is a top perspective view of the rotary stepping switch of Figure 1; Figure 3 is a bottom perspective view of the rotary stepping switch of Figure 1; Figure 4 is a sectional side view of the rotary stepping switch of Figure 1; Figure 5 is a plan view of a lower casing part of the rotary stepping switch of Figure 1; and Figure 6 is an underneath plan view of an upper casing part of the rotary stepping switch of Figure 1.

Referring to the drawings, there is shown a rotary stepping switch 10 embodying the invention, which switch 10 comprises a casing 11 formed by an upper plastics casing part 12 and a lower plastics casing part 13, and a partition 14 sandwiched between the casing parts 12 and 13.

The lower casing part 13 has a bottom wall 13A and an integrally moulded central shaft 15 upstanding therefrom.

The shaft 15 passes through a relatively large central aperture 16 formed in the partition 14 and a relatively small central hole 17 formed in a top wall 12A of the upper casing part 12.

As shown in Figures 2 and 4, free end 15A of the shaft 15 reaches a position substantially level with the external surface of the upper casing part top wall 12A. In order to hold the casing parts 12 and 13 permanently together with the partition 14 therebetween, the free end 15A of the shaft 15 is to be deformed or expanded thermally, for example by means of plunging with the tip of a heated tool (not shown), such that the deformed or expanded free end 15A will engage rigidly with the hole 17.

The rotary stepping switch 10 further comprises a switch mechanism 18 located within the upper casing part 12 and a drive mechanism 19 located within the lower casing part 13.

The switch mechanism 18 is provided by four equi-angularly spaced stationary switch contacts 20 located within respective correspondingly shaped recesses 21 in the upper casing part 12 and by a movable switch contact 22 supported on a generally cylindrical rotor 23 which forms part of the switch mechanism 18.

The stationary switch contacts 20 are each formed by a corresponding S-shaped copper strip and are divided into two groups 20A and 20B, the former group 20A being located in relatively deeper recesses 21A and the latter group 20B being located in relatively shallower recesses 21B. Four cutouts 24 are formed in corresponding corners of the upper casing part 12, each of which provides access for wire connection to the respective stationary switch contacts 20.

Insofar as the deeper switch contacts 20A are concerned, a fill-in piece 25 is located in each recess 21A for holding the corresponding switch contact 20A in place as well as for blocking the unattended part of the corresponding cutout 24, i.e. the open end, as best shown in Figure 6.

The rotor 23 has a central axial hole 23A through which the shaft 15 extends in order to support the rotor 23 for rotation thereon. The movable switch contact 22 is formed by an inverted L-shaped copper plate, having its horizontal limb 22A disposed for about 240 around the upper end of the rotor 23 and its vertical limb 22B extending along generally the overall length of the rotor 23. Both ends of the copper plate horizontal limb 22A have corresponding inturned lugs 22C which engage in respective radial slots (not shown) in the rotor 23 in order to hold the switch contact 22 in place. The copper plate vertical limb 22B is sufficiently long to extend wholly across the stationary switch contacts 20A and 20B at different levels.

The construction and arrangement of the switch contacts 20 and 22 are designed to provide a number of different switching conditions using the movable switch contact 22 proper to provide electrical connection among the stationary switch contacts 20, as generally known in the art.

The lower end of the rotor 23 is divided into four sectors or quadrants 26 which are enlarged in both radially outward and axially downward directions. In an angular direction as shown by arrow X in Figures 1 and 6, each quadrant 26 expands gradually from one end to the other end in both radially outward and axially downward directions. Such a surface formation or profiling creates a first ring of four consecutive asymmetrical teeth 27 extending radially outwardly around the rotor 23 and a second ring of four consecutive asymmetrical teeth 28 extending axially downwardly from the lower end of the rotor 23. A recess 29 is formed in one of the teeth 27 for accommodating the thickness of the lower end of the vertical limb 22B of the movable switch contact 22.

The drive mechanism 19 includes an angularly reciprocating or reciprocatable driving disc 30 having a central hole 30A through which the shaft 15 passes in order to support the driving disc 30 for rotation thereon. The driving disc 30 has a central upstanding collar 31 around the hole 30A.

The collar 31 is divided into four identical quadrants, each of which slopes gradually upwards from one end to the other end in an angular direction as shown by arrow Y in Figures 1 and 5, whereby a ring of four consecutive asymmetrical teeth 32 extending axially upwards is formed around the top of the collar 31.

The tooth 28 and the tooth 32 have the same asymmetrical triangular profile, namely having a relatively shorter axially extending side and a relatively longer slightly inclined side, but are pointing in opposite directions X and Y such that they are complementary to each other and can mesh with each other fitly.

The driving disc 30 is urged co-axially from below towards the partition 14 by a coil spring 33 which is disposed on the shaft 15 and co-acts at opposite ends between the driving disc 30 and the bottom wall 13A of the lower casing part 13. The collar 31 of the driving disc 30 passes through the aperture 16 of the partition 14 and engages with the rotor 23, with the corresponding rings of teeth 28 and 32 in mesh to provide a one-way clutching action between the rotor 23 and the driving disc 30. The arrangement is such that the collar 30 is always resiliently urged by the coil spring 33 against the rotor 23.

The lower casing part 13 has on its side wall 13B an opening in the form of an integral laterally extending screw-threaded tube 34 which serves to hold the rotary stepping switch 10 on a wall of an electrical appliance (not shown) in co-operation with a screw-threaded brass nut 35, in a manner as generally known in the art.

The driving disc 30 has a radially expanded sector 36 over an angle of about 900, which sector 36 having opposite circumferential ends 36A and 36B. A beaded string or chain 37 runs into the switch casing 11 through the tubular opening 34 and has its inner end secured to the far end 36A of the sector 36 by engaging within a tubular seat 38 depending from the sector end 36A.

The coil spring 33 has upper and lower radial legs 33A and 33B, with the upper leg 33A engaging from behind the seat 38 and the lower leg 33B trapped between a pair of radial ribs 39 (Figure 5) formed on the bottom wall 13A of the lower casing part 13. The coil spring 33 is pre-stressed so as to bias the driving disc 30, in the direction of arrow X as shown in Figure 5, towards an angular rest position in which the sector end 36A abuts with an integral rod 40 (Figure 1) depending from the partition 14.

In use, the chain 37 is pulled in order to rotate the driving disc 30 in the driving direction Y against the torsional action of the coil spring 33. The driving disc 30 will eventually be stopped when the sector end 36B hits the lower casing part side wall 13B immediately behind the tubular opening 34. At this time the driving disc 30 has been rotated for slightly more than 900, and so has the rotor 23 which is in driven engagement with the driving disc 30 in the driving direction Y through the interengagement between the teethes 28 and 32.

The rotation of the rotor 23 in the direction Y is not hindered by the two stationary switch contacts 20B which are simply slid past by the corresponding teeth 27, as can best be understood from Figure 6. At the end of the pulling stroke on the chain 37, the rotor 23 and hence the movable switch contact 22 will have been rotated for about 900 to a different switching condition.

Upon release of the chain 37, the driving disc 30 will return in the direction X to its rest position under the action of the coil spring 33. The rotor 23 will initially be rotated slightly in the direction X by the driving disc 30 through a relatively weak engagement between the corresponding teeth 28 and 32, but will soon be stopped when the stationary switch contacts 20B come into engagement with the corresponding forthcoming teeth 27 on the periphery of the rotor 23. Such a one-way ratchet or stopping action between the stationary switch contacts 20B and the rotor teeth 27 can best be understood from Figure 6.

As the return driving force of the coil spring 33 is relatively much stronger than the engagement between the teethes 28 and 32, the driving disc 30 will continue to be returned to the rest position with its teeth 32 disengaged from and rotating past the corresponding teeth 28 on the rotor 23. Upon returning to its rest position, the driving disc 30 will have rotated backwards for about 900 with its teeth 32 coming back into engagement with the teeth 28 of the rotor 23 but at one tooth behind. The rotary stepping switch 10 is then ready for the next switching operation.

The invention has been given by way of example only, and various modifications of and/or alterations to the described embodiment may be made by persons skilled in the art without departing from the scope of the invention as specified in the appended claims.

Claims

1. A rotary stepping switch comprising a casing formed by at least two parts, a shaft holding the casing parts together, a rotor supported within the casing by the shaft for rotation about an axis, a plurality of stationary switch contacts located within the casing, a movable switch contact carried on the rotor, an angularly reciprocatable driving member supported for rotation within the casing about the axis for rotating in a driving direction the rotor in order to move the movable switch contact into or out of electrical contact with one or more of the stationary switch contacts, one-way clutch means provided between the driving member and the rotor in order for the driving member to impart a stepwise drive to the rotor, and one-way stopping means provided within the casing for stopping the rotor against rotation upon return rotation of the driving member in a non-driving direction.

2. A rotary stepping switch as claimed in claim 1, wherein the shaft is fixed at one end to the first one of said at least two casing parts and passes at the opposite end substantially through the second one of said at least two casing parts for engagement therewith.

3. A rotary stepping switch as claimed in claim 1 or claim 2, wherein the shaft is formed integrally with said first casing part.

4. A rotary stepping switch as claimed in claim 2 or claim 3, wherein the said opposite end of the shaft is expanded or deformed thereby engaging with said second casing part.

5 A rotary stepping switch as claimed in any one of the preceding claims, wherein the driving member is rotatably supported on the shaft and is resiliently biassed by a spring to rotate in the non-driving direction.

6. A rotary stepping switch as claimed in any one of the preceding claims, wherein the driving member and the rotor are in direct axial engagement with each other and have on their respective engaging surface co-operable formations which provide said one-way clutching means.

7. A rotary stepping switch as claimed in claim 6, wherein each formation is in the form of a ring of consecutive asymmetrical teeth, and the corresponding formations of the driving member and the rotor are complementary to each other.

8. A rotary stepping switch as claimed in any one of the preceding claims, wherein the one-way stopping means is provided by direct engagement between the rotor and at least one of the stationary switch contacts.

9. A rotary stepping switch as claimed in claim 8, wherein the rotor has around its periphery a ring of consecutive asymmetrical teeth extending radially outwardly, and said at least one stationary switch contact is resiliently deformable so that it will engage with the forthcoming one of the said teeth only when the rotor is under the action of the driving member in the non-driving direction.

10. A rotary stepping switch as claimed in claim 9 when dependent upon claim 7, wherein the end of the rotor engaging with the driving member are divided into sectors, each of which in the non-driven direction expands gradually from one end to the other end in both radially and axially outward directions in order to form the two rings of teeth.

11. A rotary stepping switch substantially as hereinbefore described with reference to Figures 1 to 6 of the accompanying drawings.