GB2300757A

GB2300757A - Rotary stepping switch

Info

Publication number: GB2300757A
Application number: GB9509327A
Authority: GB
Inventors: Bun Wong
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-05-09
Filing date: 1995-05-09
Publication date: 1996-11-13
Anticipated expiration: 2015-05-09
Also published as: CN1044531C; CN1144968A; GB2300757B; HK1011116A1; GB9509327D0

Abstract

A rotary stepping switch comprises a body (11-13, Fig 3), a rotor (34,44), a plurality of stationary switch contacts (31A,31B,41A,41B) located within the body around the rotor, a movable switch contact (33,43) carried on the rotor, and a driving disc (20) supported for angular movement within the body for rotating the rotor in a driving direction to move the movable switch contact into or out of contact with one or more of the stationary switch contacts. The switch includes a one-way clutch (23,39) provided between the driving disc and the rotor for enabling the driving disc to impart a stepwise drive to the rotor, and a one-way stop to stop the rotor against rotation upon return rotation of the driving disc in a non driving direction. At least one stationary switch contact 70A is provided by a one piece strip 71 which has first and second portions 73,75 folded or bent about respective substantially parallel axes to form opposite sides of a clip 78 for clipping an end 81 of a cable/wire 80 upon insertion of the end 81 into the clip 78.

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 body, a rotor supported within the body for rotation about an axis, a plurality of stationary switch contacts located within the body around the rotor, a movable switch contact carried on the rotor, an angularly reciprocatable driving member supported for angular movement within the body about the axis for rotating the rotor in a driving direction to move the movable switch contact into or out of 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 body to stop the rotor against rotation upon return rotation of the driving member in a non-driving direction, at least one of said stationary switch contacts being provided by a one-piece strip which has first and second portions folded or bent about respective substantially coparallel axes to form opposite sides of a clip for clipping an end of a cable/wire upon insertion of the cable/wire end into the clip.

Preferably, the second portion of trip is folded or bent out of the first portion.

More preferably, the second portion of strip is provided by a part cut out from the first portion, thereby leaving behind a hole through which the cable/wire end is to be inserted into the clip.

It is preferred that the hole is a complete hole.

More preferably, the part providing the second portion of strip is substantially a central part with respect to the width of the first portion.

In a preferred embodiment, the first portion of strip has first and second sections adjoining along a fold line, and the part providing the second portion is cut out from the first section of the first portion, with the second portion and the second section providing the sides of the clip.

Preferably, the sides of the clip extend with respect to each other at an angle of substantially between 450 and 750, through the open side of which angle the cable/wire end is to be inserted into the clip.

More preferably, the opposite sides of the clip extend with respect to each other at an angle of substantially 600.

It is an advantage that the second portion of strip has a substantially V-shaped free end for providing a two-point contact with the cable/wire end.

In a specific preferred construction, the strip has a series of four sections formed through folding about substantially co-parallel axes, with the first section providing contact with the movable switch contact on the rotor and the third and fourth sections providing the clip.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a top perspective view of a first embodiment of a rotary stepping switch in accordance with the invention; Figure 2 is a partially exploded top perspective view of the rotary stepping switch of Figure 1, showing three separate layers thereof; Figure 3 is a fully exploded side perspective view of the rotary stepping switch of Figure 1, showing parts thereof; Figure 4 is a plan view of the principal parts of the rotary stepping switch of Figure 3; Figure 5 is a cross-sectional side view of the rotary stepping switch of Figure 3, showing assembly of the parts; Figure 6 is a see-through top perspective view of the rotary stepping switch of Figure 3, showing axial connection of the central parts;; Figure 7 is a bottom perspective view of a second embodiment of a rotary stepping switch in accordance with the invention; Figure 8 is a partially exploded bottom perspective view of the rotary stepping switch of Figure 7, showing four separate layers thereof; Figure 9 is a plan view of a layer of the rotary stepping switch of Figure 2 or 8, showing the approach of a cable/wire to a self-gripping switch contact; Figure 10 is a simplified perspective view corresponding to Figure 9; Figure 11 is a plan view corresponding to Figure 9, showing the final connection of the cable/wire to the self-gripping switch contact; and Figure 12 is a simplified perspective view corresponding to Figure 11.

Referring firstly to Figures 1 to 6 of the drawings, there is shown a first rotary stepping switch 9 embodying the invention, which switch 9 comprises a plastics body 10 formed by a base (drive) layer 11, a middle (switch) layer 12 and a top (switch) layer 13 engaged co-axially together through snap-fitting action. The base layer 11 has an open-top casing having an internal integral upstanding central shaft 14 and an integral screw-threaded side tube 15. The tube 15 serves to support, in co-operation with a screw-threaded brass nut 16 in a manner as generally known in the art, the assembled switch 9 on a wall of an electrical appliance (not shown). The base layer is closed by a top lid 17 which has a central hole 18.

The switch 9 incorporates a stepping drive mechanism 19 inside the casing of the base layer 11, which is provided by an angularly reciprocating driving disc 20 having a central hole 21 for rotatably disposing on the shaft 14.

The disc 20 has a central upstanding collar 22 around the hole 21. The collar 22 is divided into four identical quadrants which have corresponding sloping arcuate top surfaces to form a ring of four consecutive asymmetrical teeth 23. The teeth 23 are exposed extending just through the hole 18 of the lid 17. The disc 20 includes a radially expanded rim portion 24 extending angularly for about 900, to which a pull-chain 25 is secured. The pull-chain 25 exits through the tube 15 for pulling by a user to rotate the disc 20. A coil spring 26 is disposed on the shaft 14 for urging the disc 20 upwards against the lid 17 and for biassing the disc 20 against rotation by the pull-chain 25 so as to subsequently return the disc 20 to an initial rest angular position.Such rotation of the disc 20 is limited to an angle of about 900 in either direction by opposite ends of the rim portion 24 hitting a pair of corresponding side hook-like lugs (projections) 60 provided integrally on opposite sides of the base layer 11, said lugs 60 extending upwards beyond the lid 17. Under this arrangement, the drive mechanism 19 provides a 900 angular stepping action each time when the pull-chain 25 is pulled.

The switch 9 includes a first switching mechanism 30 inside the casing of the middle layer 12, which is provided by a pair of diametrically-opposite stationary switch contacts 31A and 31B located within respective correspondingly shaped recesses 32 of the middle layer 12 and by a movable switch contact 33 carried on a tubular vertical rotor 34.

The stationary switch contacts 31A and 31B are formed by respective bent copper strips which have corresponding upper and lower contact fingers 35A and 35B with respect to the rotor 34. Each recess 32 has, on its outer side, a cutout 36 to provide access for a cable/wire to be connected to the respective stationary switch contact 31A/31B.

The rotor 34 has, at about mid-length thereof, an integral flange 37 extending angularly for about 1350. The movable switch contact 33 is provided by a generally cylindrical copper ring which has an upper circular portion 33A and a part-circular lower portion 33B extending for about 2250.

The movable switch contact 33 is fitted co-axially on the rotor 34 such that its lower portion 33B is in an angular position supplementary to that of the rotor flange 37. The rotor 34, together with the movable switch contact 33, is placed co-axially just within a central recess 38 of the middle layer 12, with the upper contact finger 35A of one stationary switch contact 31A and the lower contact finger 35B of the other stationary switch contact 31B bearing against the upper and lower halves of the rotor 34, respectively, where the respective upper and lower portions 33A and 33B of the movable switch contact 33 lie against.

The upper end of the rotor 34 has a non-circular hole 50 (see Figure 6). The lower end of the rotor 34 is divided into four identical quadrants which have corresponding sloping arcuate bottom surfaces to form a ring of four consecutive asymmetrical teeth 39. These teeth 39 are complementary to the teeth 23 of the disc 20 such that when the rotor 34 and the disc 20 are co-axially engaged together, the teeth 39 and 23 inter-engage to form a oneway clutch (ratchet) which permits the disc 20 to engage and thus rotate the rotor 34 in one (driving) direction upon pulling of the pull-chain 25 but not in the opposite (non-driving) direction.In the said opposite direction, when the rotor 34 is held against return rotation (as hereinafter described), the disc 20 rotates back under the torsional action of the spring 26 to return to the initial rest angular position with its teeth 23 disengaging from and sliding past over the then stationary teeth 39 (slipping of the one-way clutch) upon receding of the axial urging action of the spring 26. In this arrangement, the rotor 34 is rotated stepwise through 900 by the disc 20 upon each angular stepping action of the drive mechanism 19 every time when the pull-chain 25 is pulled. Thus, the rotor 34 has four stable angular positions and, in turn, the first switching mechanism 30 has four corresponding switching conditions.

In all the four angular positions of the rotor 34, the upper contact finger 35A of the stationary switch contact 31A is always in contact with the upper portion 33A of the movable switch contact 33 because the upper portion 33A is circular (3600). On the other (lower) end of the rotor 34, the lower contact finger 35B of the other stationary switch contact 31B is in contact with the lower portion 33B, that being part-circular (225 ), of the movable switch contact 33 only when the rotor 34 is in three out of the four angular positions but not in the remaining angular position.

Accordingly, the first switching mechanism 30 has three switched-on conditions with the rotor 34 in the said three angular positions, and only one switched-off condition with the rotor 34 in the remaining angular position.

In the switched-off condition, a potential difference equal to the mains supply voltage may appear between the stationary switch contacts 31A and 31B and hence across the gap between the associated upper portion 33A and contact finger 35B. The rotor flange 37 is provided, extending between the upper portion 33A and the contact finger 35B, to considerably reduce the risk of any accidental flashover or arcing striking across such a gap by physically extending the creep path concerned.

The switch 9 further includes a second switching mechanism 40 inside the casing of the top layer 13, which is provided by four equi-angularly-spaced stationary switch contacts 41A (X1) and 41B (X3) located within respective correspondingly shaped recesses 42 of the top layer 13 and by a movable switch contact 43 carried on a generally cylindrical vertical rotor 44. Each stationary switch contact 41A/41B is formed by a bent copper strip. The stationary switch contact 41A has an upper contact finger 45A with respect to the rotor 44, whereas each stationary switch contact 41B has a lower contact finger 45B. Each recess 42 has, on its outer side, a cutout 46 to provide access for a cable/wire to be connected to the respective stationary switch contact 41A/41B.

The rotor 44 has, at about mid-length thereof, an integral substantially 3600 annular flange 47. The movable switch contact 43 is provided by a copper washer having four equiangularly spaced depending side limbs 43A (X3! and 43B (xl). The limb 43B is about twice as long as the other three limbs 43A. The movable switch contact 43 is disposed co-axially over the upper end of the rotor 44, with the shorter limbs 43A reaching just short of the flange 47 and the longer limb 43B reaching the lower end of the rotor 44 through a gap in the flange 47.The rotor 44, together with the movable switch contact 43, is placed co-axially just within a central recess 48 of the top layer 13, with the upper contact finger 45A in contact with any one of the four limbs 43A and 43B and the lower contact fingers 45B selectively in contact with the longer limb 43B.

The lower end of the rotor 44 has a bottom projection 51 which has a non-circular cross-section corresponding to that of and for fitting from above into the hole 50 of the first-mentioned rotor 34, thereby engaging the two rotors 34 and 44 co-axially together through a plug-in connection such that the upper rotor 44 is rotatable by the lower rotor 34. The lower rotor 34 has four stable angular positions, as described above. Accordingly, the upper rotor 44 also has four corresponding stable angular positions which define respective switching conditions of the second switching mechanism 40.

In all the four switching conditions, the upper contact finger 45A of the stationary switch contact 41A is always in contact with the movable switch contact 43 via an adjacent one of the four limbs 43A and 43B. On the other (lower) end of the rotor 44, the longer limb 43B is in contact with an adjacent lower contact finger 45B of the three stationary switch contacts 41B only in three out of the four switching conditions, which three switching conditions are therefore switched-on conditions. In the remaining switching condition, that being a switched-off condition, the longer limb 43B is not in contact with any of the lower contact fingers 45B.

In the switched-off condition, a potential difference equal to the mains supply voltage may appear between the stationary switch contact 41A and the other three switch contacts 41B and hence across the gap between the associated shorter limbs 43A and contact fingers 45B. The rotor flange 47 is provided, extending between the shorter limbs 43A and the contact finger 45B, to considerably reduce the risk of any accidental flash-over or arcing striking across such a gap by physically extending the creep path concerned.

The first and second switching mechanisms 30 and 40 demonstrate two examples of many possible switching mechanism designs which are to be determined by the switching requirements of the external electrical appliance to be controlled by the switch 9.

As best shown in Figure 4, each of two adjacent quadrants 44A of the rotor 44 radially expands gradually in the same angular direction to form a pair of asymmetrical side teeth. The teeth 44A are engageable with the contact fingers 45B of the stationary switch contacts 41B to form a one-way stopping arrangement (ratchet) which acts in the opposite angular direction to the one-way clutch between the disc 20 and the other rotor 34. The one-way stopping arrangement serves to hold the two rotors 34 and 44 against return rotation (as hereinbefore mentioned) when the oneway clutch slips, thereby maintaining the latest switching conditions of both of the switching mechanisms 30 and 40.

The three layers 11 to 13 are snap-fitted tight co-axially together to form the switch body 10. The base layer 11 has a pair of vertical side lugs 60, as described above. The middle layer 12 has two vertical apertures 61 through a pair of opposite sides and two vertical hook-like lugs (projections) 62 on the other pair of opposite sides, said lugs 62 extending upwards beyond the top side of the middle layer 12. The top layer 13 has a pair of vertical apertures 63 through a pair of opposite sides. The base layer 11 is secured to the middle layer 12 by means of the lugs 60 of the former engaging through the corresponding apertures 61 of the latter and snap-fitted therewith. The middle layer 12 is secured to the top layer 13 by means of the lugs 62 of the former engaging through the respective apertures 63 of the latter and snap-fitted therewith, as clearly shown in Figure 5.

For reinforcement of the snap-fit engagement, each aperture 61/63 is provided with, on the immediate outer side thereof, a depending flat lug (protrusion) 64 which is to engage snugly into an aligned recess/channel 65 provided on the immediate outer side of the associated hook-like lug 60/62. Broadly speaking, the co-operation between the lug 60/62 and the associated aperture 61/63 and between the lug 64 and the associated recess 65 serve to provide a double engagement. Looking in a different perspective, the subsidiary lug 64 protects the root of the associated principal lug 60/62 where the lug 60/62 would be most vulnerable to breakage.

Insofar as the core of the switch 9 is concerned, the engagement between the disc 20 and the lower rotor 34 enables transmission of rotational drive from the former to the latter. The engagement between the lower and upper rotors 34 and 44 enables onward transmission of the rotational drive from the former to the latter.

Referring now to Figures 7 and 8 of the drawings, there is shown a second rotary stepping switch 109 embodying the invention, which switch 109 comprises a plastics body 110 formed by a base (drive) layer 111, a first middle (switch) layer 112, a second middle (switch) layer 212 and a top (switch) layer 113, all engaged co-axially together through snap-fitting, in the same manner as described in relation to the first switch 9. Comparing the second switch 109 with the first switch 9, it is noted that the base, middle and top layers 111, 112 and 113 of the former are almost the same as the corresponding layers 11, 12 and 13 of the latter, except that the layer 112 has four instead of two stationary switch contacts.

The second middle layer 212 has a design practically the same as or at least not much different to that of the other middle layer 112 (or 12), in that the only difference resides in the bottom end of its rotor 234. The rotor 234 has a non-circular bottom projection 251 which is the same as the rotor bottom projection 51 of the top layer 13 (or 113) instead of the ring of teeth 39 of the middle layer 12 (or 112). The bottom projection 251 is needed for onward transmission of the rotational drive from the rotor of the first middle layer 112 to the rotor 234 of the second middle layer 212, in the same manner as described in relation to the projection 51.The rotor inter-engagement between the first and second middle layers 112 and 212 and between the second middle layer 212 and the top layer 113 of the second switch 109 is substantially the same as that between the middle layer 12 and the top layer 13 of the first switch 9.

It is important to note that the first switch 9 is convertible into the second switch 109 by mere insertion of the additional middle layer 212. The three-layer construction of the switch 9 provides a basis for expansion into a more-than-three multi-layer construction for such rotary stepping switches, through the addition of one or more of the middle layer 212, in order to achieve a greater number of or more complicate switching combinations as may be required. Such expansion does not necessitate the use of any new parts and is therefore readily achievable.

It is envisaged that the drive layer 11/111 and the first switch layer 12/112 may be constructed as a one-piece basic unit, as opposed to having separate layers, because they are always in co-operation. In a different embodiment, the switch layer 12/112 may be provided on each side of the drive layer 11/111 for expansion of the switch 9/109 in both axial directions. For this purpose, the drive layer 11/111 may incorporate a pair of driving discs 20 on opposite sides to co-act with the rotors 34 of the respective switch layers 12/112.

Reference is finally made to Figures 9 to 12 of the drawings. All the stationary switch contacts 31A, 31B, 41A and 41B described above have the same general construction, which fall into two specific types, namely the first type covering the switch contacts 31A and 41A now collectively designated by reference numeral 70A and the second type covering the switch contacts 31B and 41B now collectively designated by reference numeral 70B.

The switch contact 70A (31A/41A) is provided by an integral one-piece copper strip 71 which is bent or folded about coparallel (vertical) axes into a series of four sections as shown in Figures 10 and 12 and is located in position as shown in Figures 9 and 11. Inner end section 72 of the strip 71 is cut to about half width and suitably bent for use, in an up-side-down position contrary to the position shown, as the upper contact finger 35A/45A described above.

Outer end section 73 of the strip 71 is intact, whilst the adjoining section 74 is cut to form a rectangular tongue 75 which is folded slightly inwards from the section 74 to leave a rectangular hole 76 behind. The tongue 75 is a central part with respect to the width of the section 74, by reason of which the hole 76 is a complete hole.

The tongue 75 is inclined at an acute angle of between 450 to 750, and preferably about 600, with the outer end section 73, whereby a clip 78 is formed which has the section 73 and the tongue 75 as its opposite sides. The free end of the tongue 75 is configured to form a prismatic V-shaped tip 77 facing the outer end section 73.

In use, a cable/wire 80 having a bare end 81 is to be inserted into the switch contact 70A through the hole 76 of the strip 71. The cable/wire end 81 enters from behind into the clip 78 (through the open side of the acute angle of the clip 78) to reach between the clip's opposite sides 73 and 75, thereby pushing the tongue 75 to bend away from the end section 73. The tongue 75 urges the cable/wire end 81 tightly against the end section 73 on the opposite side, resulting in a self-clamping action upon opposite sides of the cable/wire end 81. Such a clamping action provides improved electrical conduction as well as mechanical strength. The V-shape of the tip 77 not only locates the cable/wire end 81 but also provides a two-point contact with the cable/wire end 81.The V-shaped tip 77 bites into the cable/wire end 81 upon withdrawal of the cable wire 80 so as to avoid any accidental withdrawal.

The switch contact 70A is used for wire connection to the mains power supply, whilst the switch contact 70B is used for wire connection to an electrical appliance.

Although this is not quite as shown in the drawings (for simplicity), the switch contact 70B (31B/41B) has a configuration more or less the same as that of the switch contact 70A, for use in the same manner. The only difference is that the strip making the switch contact 70B has only about half the width of the switch contact 70A and an un-cut inner end section for use as the lower contact finger 35B/45B described above. Returning to the drawings, the switch contact 70B does not have the tongue 75 and the hole 76. The outer end section of the switch contact 70B (equivalent to the outer end section 73) is used, in similar manner to the tongue 75, to urge the cable/wire end 81 tightly against one side of the associated recess 36.

The invention has been given by way of example only, and various other modifications of and/or alterations to the described embodiments 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 body, a rotor supported within the body for rotation about an axis, a plurality of stationary switch contacts located within the body around the rotor, a movable switch contact carried on the rotor, an angularly reciprocatable driving member supported for angular movement within the body about the axis for rotating the rotor in a driving direction to move the movable switch contact into or out of 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 body to stop the rotor against rotation upon return rotation of the driving member in a non-driving direction, at least one of said stationary switch contacts being provided by a one-piece strip which has first and second portions folded or bent about respective substantially coparallel axes to form opposite sides of a clip for clipping an end of a cable/wire upon insertion of the cable/wire end into the clip.

2. A rotary stepping switch as claimed in claim 1, wherein the second portion of strip is folded or bent out of the first portion.

3. A rotary stepping switch as claimed in claim 2, wherein the second portion of strip is provided by a part cut out from the first portion, thereby leaving behind a hole through which the cable/wire end is to be inserted into the clip.

4. A rotary stepping switch as claimed in claim 3, wherein the hole is a complete hole.

5. A rotary stepping switch as claimed in claim 4, wherein the part providing the second portion of strip is substantially a central part with respect to the width of the first portion.

6. A rotary stepping switch as claimed in any one of claims 3 to 5, wherein the first portion of strip has first and second sections adjoining along a fold line, and the part providing the second portion is cut out from the first section of the first portion, with the second portion and the second section providing the sides of the clip.

7. A rotary stepping switch as claimed in any one of the preceding claims, wherein the sides of the clip extend with respect to each other at an angle of substantially between 450 and 750, through the open side of which angle the cable/wire end is to be inserted into the clip.

8. A rotary stepping switch as claimed in claim 7, wherein the opposite sides of the clip extend with respect to each other at an angle of substantially 600.

9. A rotary stepping switch as claimed in any one of the preceding claims, wherein the second portion of strip has a substantially V-shaped free end for providing a two-point contact with the cable/wire end.

10. A rotary stepping switch as claimed in any one of the preceding claims, wherein the strip has a series of four sections formed through folding about substantially coparallel axes, with the first section providing contact with the movable switch contact on the rotor and the third and fourth sections providing the clip.

11. A rotary stepping switch substantially as hereinbefore described with reference to any one or more of Figures 1 to 12 of the accompanying drawings.