WO2005122203A1

WO2005122203A1 - Appliance function switch

Info

Publication number: WO2005122203A1
Application number: PCT/NZ2005/000123
Authority: WO
Inventors: Andrew Palmer; James Richardson; John Carroll
Original assignee: Robertshaw Controls Company
Priority date: 2004-06-09
Filing date: 2005-06-09
Publication date: 2005-12-22

Abstract

An appliance function switch has a housing (108) and a shaft (110) mounted in the housing for rotation about a shaft axis. At least one switching cam (116) on the shaft has a varying radial extent around the circumference of the shaft in a plane tranverse to the shaft axis. An indexing profile (124) on the shaft axially independent from the switching cams interacts with an indexer mounted in the housing. The indexer engages the indexing profile to align the shaft at each of a plurality of predefined rotational positions. A switch is located in the housing to be activated according to the radial extent of a respective cam.

Description

"APPLIANCE FUNCTION SWITCH"

FIELD OF THE INVENTION The present invention relates to function selector switches for appliance control.

BACKGROUND In the control of ovens and other appliances it is necessary to provide different functions or modes of operation. An oven for example may have different desirable modes of cooking such as bake, grill, defrost, or any combination in conjunction with the use of a fan or thermostat. Known in the art is provision for various switching configurations in order to achieve selection of a function. Interlocked push buttons for example are used where a range of exclusive options are to be selected. A digital control system dependant on microprocessors is also becoming common which allows the user to select a function or mode of operation using a digital display and push buttons. In United States Patent No. 4,727,227 a microswitch unit for a measuring instrument where a number of cams on a shaft are frictionally retained to adjustably actuate a series of microswitches. Other patents disclosing switches with rotating controls, not all suitable as an appliance function switch, include US 4,059,738, US 5,772,011, US 4,743,820, US 4,370,566 and US 5,668,359.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an appliance function switch that at least goes some way toward overcoming the above disadvantages or which will at least provide the industry with a useful choice. Accordingly in a first aspect the present invention may be broadly said to consist in an appliance function switch comprising: a housing, a shaft mounted in said housing for rotation about a shaft axis, at least one switching cam on said shaft, having a varying radial extent around the circumference of said shaft, in a plane transverse to said shaft axis, an indexing profile on said shaft axially independent from said switching cam(s), an indexer mounted in said housing that engages said indexing profile to align said shaft at each of a plurality of predefined rotational positions relative to said housing, and for at least one said switching cam, at least one switch mounted in said housing to be actuated by said radial extent of said switching cam. This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred forms of the present invention will now be described with reference to the accompanying drawings: Figure 1 is an exploded view showing the components of an appliance function switch according to the present invention. Figure 2 is a perspective view of the switch of Figure 1. Figure 3 is a cross section illustrating the shaft and indexing mechanism of the switch of Figure 1. Figure 4 is an exploded view showing the mounting plates and an optional thermostat according to the switch of Figure 1. Figure 5 is an exploded view of an alternative embodiment arrangement of the present invention. Figure 6 is a perspective view of the assembled switch of Figure 5. Figure 7 is a cross section of the switch of Figure 5 illustrating the indexing mechanism. Figure 8 is an exploded view of the switch of Figure 5 including a mounting plate. Figure 9 is an exploded view of a switch according to a second alternative arrangement of the present invention. Figure 10 is a perspective view of the switch of Figure 9. Figure 11 is a cross section of the switch of Figure 9 illustrating the shaft, indexing mechanism and rotational limiter inside the housing. Figure 12 is an exploded view of the switch of Figure 9 arrangement including a thermostat and mounting plate. DETAILED DESCRIPTION Three preferred embodiments of the invention are illustrated in the drawings and described herein. The first embodiment is illustrated in Figures 1 to 4. Features of the first embodiment are indicated by reference numerals beginning at 100. The second embodiment is illustrated in Figures 5 to 8. Features of the second embodiment are indicated by reference numerals beginning at 200. The third embodiment is illustrated in Figures 9 to 12. Features of the third embodiment are indicated by reference numerals beginning at 300. For the three embodiments equivalent features are indicated by equivalent reference numerals in with the indicated preface. For example the indexing profile is referenced as 124 in the first embodiment, 224 in the second embodiment and 324 in the third embodiment. The switching apparatus of the present invention includes a housing 108, a shaft mounted inside the housing 102, a number of switching cams on the shaft 116, an indexing profile on the shaft 124 with an accompanying indexing mechanism 120, 122 and one or more microswitches 114 mounted inside the housing which are actuated by the rotation of the cams on the shaft. The apparatus is controlled by an external control knob that is connected to the shaft

110 and is rotated by the user of the appliance. The rotational position of the shaft is discretely aligned by an indexing mechanism inside the housing. As the shaft rotates, each cam also rotates and actuates a lever depending on the height of the cam surface 118. If the cam surface is raised it will either directly or indirectly actuate a switch or switches. Each angular position of the shaft corresponds to a different function or modes of operation depending on which switches have been activated. For example, when used to control an oven, each angular position corresponds to a function such as light function, bake, grill, defrost, or any combination including the use of a fan.

The Outer Control Knob The switching apparatus is controlled by an outer control knob (not shown) which is manually manipulated by a user. The outer control knob has a cavity for receiving a front end of a modular shaft. The control knob may be connected to the shaft by spring mechanisms, fasteners or friction clamping arrangements and the optional threaded bush 186. An indicator mark or the shape of the outer control knob is used to identify the shaft position. The indicator or shape of the knob is chosen or designed depending on the application of the switching apparatus. The Control Shaft The shaft 110 is contained and supported inside the housing 108, described below. One embodiment of the shaft as shown in Figures 1-4 includes two sections. A first section of the shaft shows one end that protrudes from the housing through a mounting plate 136. These Figures show the side of the shaft machined flat 112 to ensure correct orientation between the control knob and the shaft. Other methods which ensure correct orientation, for example a spline, may also be used. A spigot 186 as shown in the figures acts as a bush to the shaft, and also has a thread on the outside for fastening the switching apparatus to a mounting plate 136 via a nut 148. The threaded spigot extends from the wall of the housing a sufficient distance as to overcome the thickness of any mounting plate such that the nut can still be secured. The mounting plate may be further secured by fasteners such as screws 147 which secure in nuts 146 captured in the housing. The second section of the shaft 111 has a number on cams along its length. The number of cams is not fixed, instead the quantity is chosen by the designer of the appliance depending on the quantity of functions that need to be controlled. The back of the first shaft has a machined flat 112 and the front second shaft has a keyed hole extending axially through the centre of the shaft axis, this allows them to engage and rotationally lock together. An alternative embodiment of a switching apparatus 346 containing a shaft is shown in Figures 9-12 where an optional thermostatic switch 334 having a shaft extendable through the length of the housing is shown. The shaft also has a machined flat suitable for engaging with an external control knob. Indexing Mechanism The indexing mechanism controls the shaft to predetermined rotational positions and is provided by a detent cam and indexer contained in the housing. The indexer incorporates a ball or nose cone 120 and a spring 122 which is held in the housing 108. The spring biases the ball or nose cone towards the shaft. The shaft is provided with an integral cam 124 with a detent profile which corresponds to the profile of the ball or nose cone. The number and spacing of the detents are variable depending on the number of indexed positions required in the particular switching configuration. The spring and ball or nose cone is housed in an aperture in the housing. The spring is entirely within the aperture with the surface of the ball or nose cone protruding from the aperture. A grub screw is also inside the aperture above the spring. The purpose of the grub screw is to provide a variable force to directly adjust the compression of the spring. The change in compression causes a change in the feel of the control knob to the customer. Winding the grub screw out releases the spring and allows the control knob to move with less force. Winding the grub screw in compresses the spring requiring more force to turn the control knob. The indexing cam is typically mounted on the first shaft section 110. An alternative embodiment of an indexing mechanism is shown in Figures 9-12. Here, the indexing mechanism is made up by a spring loaded wire bar 322 and displaceable member 342. The displaceable member is a cylinder with an indent running around the outside of its entire circumference. The width of the indent is comparable to the thickness of the spring loaded wire bar. This alternative indexing mechanism is lodged within an open faced chamber or recess in the housing 380. An aperture or neck with width slightly larger than the diameter of the displaceable member exists at the bottom of the recess and houses the displaceable member. An indexing cam as described above has its top surface 324 adjacent the neck. The displaceable member is biased by the spring loaded wire bar through the neck to engage with the detents on the cam providing discrete rotational positions of the indexing cam. In each embodiment the rotation of the control knob by the user corresponds to a predetermined switching function. As the user rotates the shaft via the outer control knob, the detent mechanism ensures that the shaft moves between predetermined positions corresponding to the predetermined switching functions. This arrangement allows the customer to adjust the feel of the device under normal operating conditions i.e. from detent to indent or between where there is no detent. Individual Cams Each cam has a cam profile 116 to activate a switch, as described below. The cams consist of annular ridges around a predetermined part of the shaft circumference. Rotation of the shaft causes each cam to activate a corresponding lever of follower that in turn activates a corresponding switch 114. Any given angular position can result in any of the given switches being active or inactive according to whether the profile of the cam at that point is high or low. Thus the annular profile of each cam is designed depending on the switching requirements of the particular configuration. The cam profiles are integral with the shaft 111 by either being pre-machined or machined during assembly to the shaft. Shown in Figures 9-12 is an optional rotation limiting cam 302. This cam engages with the walls of the housing 351 to restrict the rotation of the shaft within predefined limits. The rotational limiting extrusion can be an additional part of the indexing cam described above, or part of the shaft. Cam Combinations A plurality of cams 118 is permanently connected on the shaft at predetermined axial positions. Figure 1 shows six cams mounted along the shaft. However, it will be appreciated that more or less cams may be mounted along the modular shaft as required, for example four or eight. Additional cams, levers and corresponding switches allows the device to activate more than one multi-functional or multiplexed type actuators at one time. The number and combination of the cams is chosen depending on the number of switches and the switching sequence required in each particular configuration. In one example the shaft sections and desired cam combination are integrally moulded from plastic. Housing The housing of this switching apparatus is made from two identical components 108, with one of the components a mirror image of the other. In one example the components of the housing are molded from a plastic material. Each half is provided with clips 106 which engage with corresponding protrusions 126 in the other half of the housing as the switching apparatus is assembled. The two components clip together to form the assembled housing. The clip consists of two different portions each located on opposite sides of the housing components such that when the housing is assembled each portion interacts to lock the components together. In an application such as heated appliance control it would be desirable to make the housing and enclosed apparatus from a flame retardant material. This could, for example, be achieved by using fibre glass content in the plastic. One skilled in the art will contemplate using different materials depending on the application of the switch. The housing may be additionally secured by fasteners such as screws 145, or 252. The housing contains the modular shaft sections 110, associated cams and the switches. The housing is provided with apertures 151 to directly mount the housing to an appliance using screws 147 or other fasteners. The housing can encapsulate any number of multi functional or multiplexed actuators

147, which are held together in the housing without any fasteners or mounting hardware. The housing provides support for the shaft described above by having at least two walls where bearing components can be mounted. Semicircular recesses 130, 132 in the walls of each housing section enclose the shaft completely when assembled. Each semicircle has a centre of curvature aligned along the axis of the shaft 110, and orientated perpendicular to the shaft. A number of partition walls or journals are formed between the inner and outer walls of the housing when the housing is assembled. In Figures 1-4 that illustrate the first embodiment there are three journals where the indexing cam 124 is mounted between the first and third portions and the switching cams are mounted between the first and second portions. The journals in this embodiment enclose around only the shaft. In Figures 5-8 which illustrate the second switching apparatus embodiment there are two journals formed in the outer walls of the housing. The journal formed in the front wall of the housing encloses the indexing cam 271. Figures 9-12 which illustrate the third switching apparatus embodiment the journals exist in the wall of the housing. Here the indexing cam 302 is located inside the recess of the preformed journal. Individual Switches The switches 114 used in the configurations shown in the drawings are microswitches. Alternatively, other multiple outlet switches could be used such as multi-functional or multiplexed type actuators. If a multiplexer type actuator is used, the action of the switch depends on the level to which the switch is depressed. Accordingly, different cam profiles will be required. Typically a gang of switches is aligned side by side along the axial extent of the shaft. Figures 1-4 and 9-12 illustrate a switch arrangement where two switches 114, 314 are aligned on opposite sides of the shaft 111, 312, and actuated by a single cam. Accordingly any number of switches could be aligned around a single cam on the shaft if necessary. The switches are preferably held in place by clipping into the housing or by one or more fasteners, such as rivets 143. In the second embodiment the master switch is also held in place by rivet 249. Where switches are desired to have common terminals, such as a common earth, clips such as 144 in Figure 1, may electrically connect the respective terminals. Each switch is mounted in the housing at positions corresponding to the longitudinal positions of each cam on the shaft. Each switch is mounted with the plunger side facing the shaft, and the connections side facing the outside of the housing. Each switch is also orientated perpendicular to the shaft and cams. The switches in Figures 1 and 2 are divided into two groups of three axially aligned microswitches. One group is located in one half of the housing and the other group is located in the other half of the housing. This arrangement of switches reduces the overall size of the switching apparatus. Each microswitch is provided with a plunger 128 that is operated by a corresponding lever arm or follower 141 via the corresponding cam as the shaft rotates. The follower is ideally pivotally interposed between a cam profile 118 and switch plunger 128 in an axis parallel to the shaft. The configuration of the follower is such that a first surface placed against a cam can be actuated such that the opposite or second surface will be actuated in the opposite direction. In another embodiment as shown in Figures 5-8 the first surface of the follower or lever is a freely rotating roller 219, placed against the profile of the cam in a parallel axis of rotation thereto. The second corresponding surface 218 is placed against the switch plunger such that the plunger will be actuated when the profile of the cam is raised. Alternatively the switch plunger may be actuated directly by the profile of the cam as illustrated in Figures 9-12. It will be appreciated that more or less switches may be required than is shown in the drawings depending on the switching sequences required for any particular configuration. Accordingly there also may be a master switch on a master cam. Connection to Other Components Although this device is shown as a single unit, other devices such as a thermostat, sensor(s) or other actuator devices may also be connected. An exploded view of the invention including a thermostat 334 is shown in Figures 4 and 12. In one configuration, the additional actuator device or thermostat will be attached using a mounting clip or screws. The shaft of the thermostatic switch shown in these figures is axially aligned with the cam shaft inside the housing of the switching apparatus. The shaft of the thermostatic switch has a machined flat 335 and the shaft of the switching cam has a keyed aperture 272. This allows the two shafts to engage and rotationally lock together. The shaft of the thermostatic switch further extends from the front of the housing allowing a control knob to be attached. The casing of the thermostat may be secured to the housing by clips or by fasteners such as screws 140. This modular embodiment of the cam shaft easily allows other similar devices to be fastened to the back of the switching apparatus. The output of the switches detailed above can be connected to a printed circuit board (PCB) 253. The PCB may contain other electronic circuitry for activating appliance functions after a switch actuation has been made. Potential Applications Such a switching arrangement could find application in appliance control, as already mentioned, for example a multifunction oven and grill. Further possible applications include automotive equipment, lights, fans or industrial control devices.

Claims

CLAIMS:

1. An appliance function switch comprising: a housing, a shaft mounted in said housing for rotation about a shaft axis, at least one switching cam on said shaft, having a varying radial extent around the circumference of said shaft, in a plane transverse to said shaft axis, an indexing profile on said shaft axially independent from said switching cam(s), an indexer mounted in said housing that engages said indexing profile to align said shaft at each of a plurality of predefined rotational positions relative to said housing, and for at least one said switching cam, at least one switch mounted in said housing to be actuated by said radial extent of said switching cam.

2. An appliance function switch as claimed in claim 1 wherein said shaft is modular and includes a first shaft portion and a second shaft portion engaged to said first shaft portion.

3. An appliance function switch as claimed in claim 2 wherein said first shaft portion includes at least one said switching cam and said second shaft portion includes said indexing profile.

4. An appliance function switch as claimed in any one of claims 1 to 3 wherein said shaft has a keyed hole at at least one end extending coaxially with said shaft axis and an actuator shaft is engaged in and extends from said hole.

5. An appliance function switch as claimed in any one of claims 1 to 4 wherein said indexer includes a displaceable member housed in an aperture and projecting from the aperture, and a spring biasing said indexer against said indexing profile.

6. An appliance function switch as claimed in claim 5 wherein said member is a ball or nose and said indexing profile includes a plurality of detents spaced around the circumference thereof.

7. An appliance function switch as claimed in either claim 5 or claim 6 wherein said aperture comprises a hole and a grub screw closes an end of said hole and rotating said grub screw in said aperture in one direction moves said grub screw toward said indexer and compresses said spring and moving said grub screw in the other direction releases said spring.

8. An appliance function switch as claimed in claim 5 wherein said spring comprises a spring bar located in a seat in said housing, a surface of said spring bar pressing against said displaceable member in said aperture.

9. An appliance function switch as claimed in claim 8 wherein said seat in said housing comprises an open faced chamber, and said aperture comprises a neck portion of said open faced chamber, said spring bar being lodged in said open faced chamber with an intermediate portion of said spring bar spanning across said neck portion, with said displaceable member retained in said neck portion.

10. An appliance function switch as claimed in ay one of claims 1 to 9 wherein at least one said switch includes a follower arrangement interposed between a cam profile and a plunger on said switch.

11. An appliance function switch as claimed in claim 10 wherein at least one said follower comprises a lever having a pivot on said housing, a first surface bearing against a said switching cam profile and a second surface positioned to act on the plunger of said switch as said switching cam acts on said first surface.

12. An appliance function switch as claimed in claim 11 wherein said first surface is at one end of said lever and said second surface is at the other end of said lever. - i l ¬

ls. An appliance function switch as claimed in claim either claim 11 or claim 12 wherein said first surface comprises the surface of a roller connected for free rotation on an axis of rotation substantially parallel to said axis of said shaft.

14. An appliance function switch as claimed in any one of claims 11 to 13 wherein the pivot axis of said lever is substantially parallel with the pivot axis of said shaft

15. An appliance function switch as claimed in any one of claims 1 to 14 wherein the switching cams are integral with said shaft.

16. An appliance function switch as claimed in claim 15 wherein the switching cams comprise annular ridges around a predetermined part or parts of the circumference of said shaft.

17. An appliance function switch as claimed in any one of claims 1 to 16 wherein the housing has at least two spaced apart walls, and said walls include locale for bearing components that said shaft can rotate in.

18. An appliance function switch as claimed in claim 17 wherein said shaft has a first bearing portion having a circular transverse cross section centred on said shaft axis, said first end located in a first journal of said housing, and a second bearing portion having a transverse cross section centred on said shaft axis located in a second journal of said housing.

19. An appliance function switch as claimed in claim 18 wherein said switching cams are between said first and second journals, and said indexing cam is located axially outside said journals.

20. An appliance function switch as claimed in either claim 18 or claim 19 wherein said shaft includes a third bearing portion spaced from said first and second portions and said indexing cam is located between first and third bearing portions, and said housing includes a third journal located to support said third portion, and said indexer is located between said first and third portions

21. An appliance function switch as claimed in any one of claims 18 to 20 wherein said housing includes two identical components and each said journal comprises two semicircular recesses, said recesses of each component having centres of curvature aligned along shaft axis, and orientated perpendicular to the axis.

22. An appliance function switch as claimed in any one of claims 1 to 21 wherein said housing allows for and includes an arrangement of switches to be mounted about said shaft at an axial position corresponding to the positions of said cams.

23. An appliance function switch as claimed in any one of claims 1 to 22 wherein said housing comprises two identical housing components that slot together to enclose said shaft, switches and indexing mechanism, with one housing component reversed in at least one plane.

24. An appliance function switch as claimed in claim 23 wherein each said housing component is adapted to house a gang of switches at predetermined axial positions, said positions, and the connection arrangement for said housings being such than the axial positions are interleaved with one said housing reversed and fitted to the other said housing.

25. An appliance function switch as claimed in either claim 23 or claim 24 wherein said housing includes clips which hold said housing components together, each said clip comprising a first portion and a second portion where said portions are located on opposite components, each said component having second portions to match first portions of the other component and an equal number of first said portions to match second portions of the other component.

26. An appliance function switch as claimed in any one of claims 1 to 25 wherein said indexing profile may include a rotational limiting element cooperating with said housing to limit rotational movement of said shaft to a predetermined angular range.

27. An appliance function switch as claimed in claim 1 wherein said shaft includes a single switching cam.

28. An appliance function switch as claimed in claim 27 said switching cam and/or indexing cam is less than a complete circumference of said shaft, and said shaft and said housing include complementary angular rotation limiting features.

29. An appliance function switch as claimed in any one of claims 1 to 26 wherein said housing includes an open frame along at least one side, said open frame adapted to accommodate at least one switch where the plunger of said switch faces said shaft and the connections of said switch face outside said housing.

30. An appliance function switch as claimed in claim 29 wherein said open frame is shaped to accommodate a gang of switches, side by side, and said cams are spaced along said shaft at the same spacing as the plungers of said switches.

31. An appliance function switch as claimed in either claim 29 or claim 30 wherein said housing includes a said open frame on at least two locations spaced around said shaft.

32. An appliance function switch as claimed in claim 31 wherein said housing includes at least two housing components and each said housing component includes a said open frame, said open frame being on opposite sides of said shaft with said components engaged to form said housing.

33. An appliance function switch as claimed in any one of claims 7 to 21 wherein said housing locates a bush having a threaded spigot, said bush having a cylindrical bore supporting a portion of said shaft and said spigot extending from an end of said housing, said shaft projecting from said spigot.

34. An appliance function switch as claimed in any one of claims 7 to 21 wherein said housing includes a spigot projecting from one end, said spigot having an external thread, said shaft projecting through said spigot.

35. An appliance function switch as claimed in claim 33 including a cover plate or mounting plate having an aperture sized to accommodate said spigot, said spigot projecting through said aperture, with a nut threaded onto said spigot to retain said plate to said housing.

36. An appliance function switch as claimed in any one of claims 1 to 35 including a thermostat having a casing and a projecting shaft having a keying feature, said casing being fixed to said housing and said thermostat shaft being axially aligned with and engaging within said switch shaft.

37. An appliance function switch as claimed in claim 36 wherein said thermostat shaft projects through said switch shaft and said housing.

38. An appliance function switch as claimed in any one of claims 1 to 37 wherein at least one of said switches is a multiple pole switch.

39. An appliance function switch as claimed in claim 38 wherein one said switch comprises a master switch and the other said switches each comprise a multiple pole switch.

40. An appliance function switch as claimed in claim 9 wherein at least said portion of said spring bar spanning said neck portion is shallow compared to the depth of said open faced chamber, and said displaceable member is round in at least one plane and includes a circumferential groove with said spanning portion of said spring bar acting in said groove.