GB2287830A

GB2287830A - Rotary stepping switch

Info

Publication number: GB2287830A
Application number: GB9405079A
Authority: GB
Inventors: Bun Wong
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-03-16
Filing date: 1994-03-16
Publication date: 1995-09-27
Anticipated expiration: 2014-03-16
Also published as: HK1000946A1; GB2287830B; GB9405079D0; CN2243713Y

Abstract

A rotary stepping switch (10) comprises a casing (11), a rotor (23) supported within the casing (11) for rotation about an axis, a plurality of stationary switch contacts (20) located within the casing (11) around the rotor (23), a movable switch contact (22) carried on the rotor (23), a driving member (30) supported for angular movement within the casing (11) about the axis for rotating in a driving direction (Y) the rotor (23) to move the movable switch contact (22) into or out of electrical contact with one or more of the stationary switch contacts (20) and a one way clutch (28, 32) between the driving member (30) and the rotor (23) for imparting a stepwise drive from the driving member (30) to the rotor (23). The casing (11) is formed by first and second parts (12 and 13) which are secured together through a snap-fitting action between A hooked lug (9) and aperture (8). <IMAGE>

Description

ROTARY STEPPING SWITCH The present invention relates to a rotary stepping switch.

According to the invention, there is provided a rotary stepping switch which comprises a casing, a rotor supported within the casing for rotation about an axis, a plurality of stationary switch contacts located within the casing around the rotor, a movable switch contact carried on the rotor, an angularly reciprocatable driving member supported for angular movement 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 for enabling the driving member to impart a stepwise drive to the rotor, and one-way stopping means provided within the casing and comprising first and second parts for inter-engagement to stop the rotor against rotation upon return rotation of the driving member in a non-driving direction opposite to the driving direction, said casing being formed by first and second parts which are secured together through a snap-fitting action between co-operable first and second snap-fitting means provided on the first and second casing parts, respectively.

Preferably, the first snap-fitting means is provided by a projection extending from the first casing part substantially in the direction of the axis.

More preferably, the second snap-fitting means is provided by an aperture formed on the second casing part, through which aperture the projection is arranged to pass and snapfit therewith.

It is preferred that the projection has a lateral protrusion for effecting the snap-fitting action.

In a preferred arrangement, the co-operable first and second snap-fitting means are provided on each of opposite sides of the switch casing.

Advantageously, the casing parts further include cooperable first and second inter-engaging means provided adjacent the corresponding first and second snap-fitting means for reinforcing the holding together of the casing parts.

It is preferred that the inter-engaging means are provided by a projection and a recess or aperture into which the projection can engage fitly.

In a specific construction, the projection is provided on the second casing part and the recess or aperture is provided on the first casing part.

Preferably, the inter-engaging means is provided in alignment with the snap-fitting means.

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 an exploded perspective view of a casing of the rotary stepping switch of Figure 1; Figure 3 is a perspective view of the switch casing of Figure 2, in an assembled condition; Figure 4 is a cross-sectional side view of the switch casing of Figure 2, likewise in a dissembled condition; Figure 5 is a cross-sectional side view of the switch casing of Figure 4, in an assembled condition; Figure 6 is an exploded perspective view of the casing of a conventional rotary stepping switch; Figure 7 is a perspective view of an upper casing part of the rotary stepping switch of Figure 1, containing therein a rotor and movable and stationary switch contacts; Figure 8 is a perspective view of the movable and stationary switch contacts of Figure 7; and Figures 9A to 9D are schematic perspective views of the movable and stationary switch contacts of Figure 8, with the movable switch contact rotated to respective different angular switching positions relative to the stationary switch contacts.

Referring firstly to Figure 1 of the drawings, there is shown a rotary stepping switch 10 embodying the invention, which switch 10 comprises a plastics casing 11 formed by an upper casing part 12 and a lower 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 integral central tubular shaft 15 upstanding therefrom.

The shaft 15 passes through a central hole 16 formed in the partition 14 and points with its free end 15A coaxially at an integral central tubular post 17 depending from a top wall 12A of the upper casing part 12.

Referring now to Figures 2 to 5, the casing parts 12 and 13 are secured together, on opposite sides 11A and 11B thereof, in order to form the assembled switch casing 11.

On each casing side llA or 11B, the upper casing part 12 has a central vertical aperture 8 and the lower casing part 13 has a central upstanding integral lug 9 for insertion through the corresponding aperture 8. The apertures 8 and the lugs 9 have substantially the same width. Each lug 9 has an outwardly stepped free end 9A, forming a lateral hooking protrusion thereon, arranged to engage the outer side of rim 8A of the upper end of the aperture 8, thereby securing the casing parts 12 and 13 together through a tight snap-fitting action.

Immediately on the outer side of the aperture 8 on each casing side 11A or 11B, there is provided a depending integral lug 6 which has substantially the same width as the aperture 8 and is aligned therewith. Immediately on the outer side of the lug 9 on each casing side 11A or 11B, there is formed a vertical recess 7 (or aperture if closed on the open side) which has substantially the same width as the lug 9 and is aligned therewith. With the upstanding lugs 9 snap-fitted through the corresponding apertures 8, the depending lugs 6 pass fitly into the upper ends of the respective recesses 7, thereby reinforcing the holding together of the casing parts 12 and 13 against the action of any unintended external force, such as twisting or pulling, during installation or use.

As mentioned above, each upstanding lug 9 has substantially the same width as the associated aperture 8, whereby they are bodily engaged together sideways. Also, each depending lug 6 is substantially as wide as the associated recess 7, whereby they are bodily engaged together sideways. With the use of two opposite lugs 9 and 6 on each casing side llA or 11B, the (vertical) length of such sideways interengagement is therefore extended, that being the sum of the length of the lugs 9 and 6.

It is to be appreciated that the roots of the upstanding lugs 9 are most vulnerable to breakage when the switch casing 11 is subject to an unintended external force during manufacture or use. The risk of such breakage is reduced when the roots of the upstanding lugs 9 are protected by the engagement between the depending lugs 6 and the corresponding recesses 7.

Figure 6 shows a conventional rotary stepping switch in which the upper and lower casing parts are secured together by two rivets on opposite sides of the switch casing. The rivets used are invariably of a metal material and the use thereof is consequently not cost effective. Fitting of the rivets, when their smaller ends are flattened, frequently causes damage to the plastics switch casing. It is also understood that the use of rivets will necessarily increase the size of the switch.

Reference is also made to Figures 7 and 8 of the drawings.

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. The rotor 23 forms part of the switch mechanism 18 and is preferably a onepiece rotor.

The stationary switch contacts 20 are each formed by a bent copper strip, and are divided into two groups 20A and 20B, the former group 20A of one being located in a relatively deeper recess 21A (lower contact 20A) and the latter group 20B of three being located in respective relatively shallower recesses 21B (upper contacts 20B). Four cutouts 24 are formed in corresponding corners of the upper casing part 12, each of which provides access for a wire to be connected to the respective stationary switch contacts 20.

The rotor 23 has a central axial bore 23A through which the shaft 15 extends in order to support the rotor 23 for rotation thereon. The rotor 23 further includes an annular protruding integral peripheral rib 23 positioned at about half-length of the rotor 23. The movable switch contact 22 is provided by a copper plate which has a washer-like central part 22A and four equi-angularly spaced radial limbs 22B and 22C. The limb 22C is about twice as long as the other three limbs 22B. All the limbs 22B and 22C are folded up to extend perpendicularly to the central part 22A, thereby forming a can-like configuration. The switch contact 22 is then disposed co-a:ially from below closely on the bottom half of the rotor 23, with the shorter limbs 22B reaching right behind the rotor rib 23B and the taller limb 22C reaching the top end of the rotor 23. The rotor rib 23B is discontinued at where the taller limb 22C crosses it. The rotor 23 has four vertical recesses 23C at equal intervals around its periphery for accommodating the corresponding contact limbs 22B and 22C such that the contact limbs 22B and 22C are fitted just wholly within the respective recesses 23C and lie in flush with the rotor peripheral surface.

As illustrated in Figures 9A to 9D, the construction and arrangement of the switch contacts 20 and 22 are designed to provide a number of different switching combinations using the movable switch contact 22 proper to provide electrical connection bridging across the stationary switch contact 20A (live-L) and any one of the other stationary switch contacts 20B (load-l, -2 & -3). The movable switch contact 22 is arranged to have four stable angular switching positions (defined by the stationary switch contacts 22B as hereinafter described), with the taller contact limb 22C in alignment with the corresponding stationary switch contacts 20A and 20B.

In each of the four switching positions, the lower stationary switch contact 20A is in electrical contact with the appropriate limb 22B or 22C of the movable switch contact 22. In the switching positions as shown in Figures 9A to 9C, the taller limb 22C of the movable switch contact 22 is also in electrical contact with the appropriate one of the upper stationary switch contacts 20B, thereby resulting in electrical connection of the lower stationary switch contact 20A selectively with the upper stationary switch contacts 20B. In the switching position as shown in Figure 9D, the taller limb 22C of the movable switch contact 22 is aligned with the lower stationary switch contact 20A but not with any one of the upper stationary switch contacts 20B, thereby resulting in a switched-off condition of the rotary stepping switch 10.

As shown in Figures 1 and 7, the lower end of the rotor 23 is divided into four quadrants 26 which are enlarged in both radially outward and axially downward directions. In an angular direction as shown by arrow X in Figure 1, 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 periphery of the rotor 23 and a second ring of four consecutive asymmetrical teeth 28 extending axially downwardly from the lower end of the rotor 23. The shorter side of each asymmetrical tooth 27 and 28 lies in an imaginary plane passing through the axis of the rotor 23.

The drive mechanism 19 includes an angularly reciprocating driving disc 30 having a ventral 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 Figure 1, whereby a ring of four consecutive asymmetrical teeth 32 extending axially upwards is formed around the top of the collar 31.

The shorter side of each asymmetrical tooth 32 lies in an imaginary plane passing through the axis of the collar 31.

The teeth 28 and the teeth 32 have the same asymmetrical triangular profile, and are pointing in respective opposite directions X and Y such that they are complementary to each other and can engage with each other firmly when the teeth 32 is rotated in the Y direction relative to the teeth 28 but otherwise not or at the most very loosely when the teeth 32 is rotated in the X direction.

The driving disc 30 is urged 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 thereof 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 collar teeth 32 and rotor teeth 28 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 supporting tube 34 which serves to support, in co-operation with a screw-threaded brass nut (not shown) in a manner as generally known in the art, the assembled rotary stepping switch 10 on a wall of an electrical appliance (not shown).

The driving disc 30 has a radially expanded sector 36 over an angle of about 90 , , said sector 36 having opposite circumferential ends 36A and 36B. A beaded string or chain 37 runs into the switch casing 11 through the supporting tube 34 and has its inner end secured to the near end 36B of the sector 36 by engaging within an integral tubular seat 38 depending from the sector end 36B.

The coil spring 33 has upper and lower radial legs 33A and 33B, with the upper leg 33A pointing radially outwards to engage the seat 38 (not shown) and the lower leg 33B pointing radially inwards to engage within a vertical slot 15B formed in the shaft 15. The coil spring 33 is prestressed so as to bias the driving disc 30, in the direction of arrow X as shown in Figure 1, towards an angular rest position in which the sector end 36A abuts with an integral post 40 upstanding from the bottom wall 13A of the lower casing part 13.

In operation, the chain 37 is pulled in order to rotate the driving disc 30 in the driving direction Y against the torsional biassing 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 supporting tube 34. At this time the driving disc 30 will have been rotated for slightly more than 900, and so will the rotor 23, which is in driven engagement with the driving disc 30 in the driving direction Y through the inter-engagement between the teeth 28 and 32.

The rotation of the rotor 23 in the direction Y is not hindered by the three upper stationary switch contacts 20B which are simply slid past by the corresponding teeth 27.

At the end of the pulling stroke of the chain 37, the rotor 23 and hence the movable switch contact 22 will have been rotated for about 900 to the next switching position.

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 back in the direction X by the driving disc 30 through a relatively loose engagement between the corresponding teeth 28 and 32, but will soon be stopped when the upper stationary switch contacts 20B come into firm engagement with the shorter sides of the corresponding forthcoming teeth 27 on the periphery of the rotor 23, thereby defining a stable angular switching position for the movable switch contact 22. This results in a one-way ratchet or stopping action between the upper stationary switch contacts 20B and the rotor teeth 27.

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 back for about 900 with its teeth 32 coming back into engagement with the teeth 28 of the rotor 23 but at one tooth (900) behind. The rotary stepping switch 10 is then ready for the next switching operation.

Referring back to Figure 8, which shows the switching condition where the taller limb 22C of the movable switch contact 22 is in electrical contact with the upper stationary switch contact 20B &num;2. Under this condition, both the tips of the upper stationary switch contacts 20B &num;1 and &num;3 on opposite sides are right above the respective shorter limbs 22B of the movable switch contact 22 and at close proximity thereto. While the lower stationary switch contact 20A is at live voltage and in turn the movable switch contact 22 and hence the said shorter contact limbs 22B on opposite sides, accidental sparking, arcing or flashover may occur across the gap(s) from the said shorter contact limbs 22B to the tips of the respective aligned upper stationary switch contacts 20B #1 and #3. The annular rib 23B serves to extend the vertical path along the surface of the rotor 23 in the said gap(s), thereby avoiding or at least reducing the likelihood of such undesirable sparking, arcing or flashover between adjacent switch contacts 20 and 22 which are not intended to be in electrical contact.

Such surface extension may be achieved in any other manners, such as by the use of an annular groove formed in and around the periphery of the rotor 23, in replace of the annular rib 23B.

The invention has been given by way of example only, and various other 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, a rotor supported within the casing for rotation about an axis, a plurality of stationary switch contacts located within the casing around the rotor, a movable switch contact carried on the rotor, an angularly reciprocatable driving member supported for angular movement 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 for enabling the driving member to impart a stepwise drive to the rotor, and one-way stopping means provided within the casing and comprising first and second parts for inter-engagement to stop the rotor against rotation upon return rotation of the driving member in a non-driving direction opposite to the driving direction, said casing being formed by first and second parts which are secured together through a snap-fitting action between co-operable first and second snap-fitting means provided on the first and second casing parts, respectively.

2. A rotary stepping switch as claimed in claim 1, wherein the first snap-fitting means is provided by a projection extending from the first casing part substantially in the direction of the axis.

3. A rotary stepping switch as claimed in claim 2, wherein the second snap-fItting means is provided by an aperture formed on the second casing part, through which aperture the projection is arranged to pass and snap-fit therewith.

4. A rotary stepping switch as claimed in claim 2 or claim 3, wherein the projection has a lateral protrusion for effecting the snap-fitting action.

5. A rotary stepping switch as claimed in any one of the preceding claims, wherein the co-operable first and second snap-fitting means are provided on each of opposite sides of the switch casing.

6. A rotary stepping switch as claimed in any one of the preceding claims1 wherein the casing parts further include co-operable first and second inter-engaging means provided adjacent the corresponding first and second snap-fitting means for reinforcing the holding together of the casing parts.

7. A rotary stepping switch as claimed in claim 6, wherein the inter-engaging means are provided by a projection and a recess or aperture into which the projection can engage fitly.

8. A rotary stepping switch substantially as hereinbefore descried with reference to Figures 1 t 5 and Figures 7 to 9D of the accompanying drawings.

8. A rotary stepping switch as claimed in claim 7, wherein the projection is provided on the second casing part and the recess or aperture is provided on the first casing part.

9. A rotary stepping switch as claimed in any one of claims 6 to 8, wherein the inter-engaging means is provided in alignment with the snap-fitting means.

10. A rotary stepping switch substantially as hereinbefore described with reference to Figures 1 to 5 and Figures 7 to 9D of the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A rotary stepping switch comprising a casing, a rotor supported within the casing for rotation about an axis, a plurality of stationary switch contacts located within the casing around the rotor, a movable switch contact carried on the rotor, an angularly reciprocatable driving member supported for angular movement 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 for enabling the driving member to impart a stepwise drive to the rotor, and one-way stopping means provided within the casing and comprising first and second parts for inter-engagement to stop the rotor against rotation upon return rotation of the driving member in a non-driving direction opposite to the driving direction, said casing being formed by first and second separate parts which are secured together through a snapfitting action between co-operable first snap-fitting means in the form of a projection extending from the first casing part substantially in the direction of the axis and second snap-fitting means in the form of an aperture provided on the second casing part, through which aperture the projection is arranged to pass and snap-fit therewith.

2. A rotary stepping switch as claimed in claim 1, wherein the projection has a lateral protrusion for effecting the snap-fitting action.

3. A rotary stepping switch as claimed in claim 1 or claim 2, wherein the co-operable first and second snapfitting means are provided on each of opposite sides of the switch casing.

4. A rotary stepping switch as claimed in any one of claims 1 to 3, wherein the casing parts further include cooperable first and second inter-engaging means provided adjacent the corresponding first and second snap-fitting means for reinforcing the holding together of the casing parts.

3. A rotary stepping switch as claimed in claim 4, wherein the inter-engaging means are provided by a projection and a recess or aperture into which the projection can engage fitly.

6. A rotary stepping switch as claimed in claim D, wherein the projection is provided on the second casing part and the recess or aperture is provided on the first casing part.

7. A rotary stepping switch as claimed in any one of claims 4 to 6, wherein the inter-engaging means is provided in alignment with the snap-fitting means.