GB2278958A - Energy regulators - Google Patents

Abstract

An energy regulator having a set of switch contacts 14, 16 which in use control the flow of electric current to a load has a snap-acting switch contact arm 18 which is operated by a bimetallic actuator 9 and has an electric heater 60 which heats the bimetallic actuator 9 when current flows to the load. The bimetallic actuator is thereby caused to flex and in so doing opens the switch contacts. The cycle then recommences. The cycle-length is adjusted by means of a control knob attached to a plastics spindle 4 which is integral with a cam body 6 which in turn is used to adjust the operation of the bimetallic actuator 9. The cam body and spindle are partly hollow and the regulator has a housing with an upstanding pillar 10 over which the cam body 6 and spindle 4 engage. The housing is formed by two mouldings which are snap fitted together and which cooperate to locate components of the regulator. An actuator (314, Fig 7) may extend through the spindle 4 for actuating a further switch. The cam body 6 has upper and lower cam track surfaces associated with respective contact sets and an edge surface engaging a detent spring (218, Fig 4). A terminal of the regulator comprises a folded spade portion (402, Fig 9) and a spring tongue (404) for preventing withdrawal of the terminal from the housing. <IMAGE>

Description

Energy Requlators The present invention relates to energy regulators for controlling the supply of electrical energy to electrical loads such as cooker hot plates or grills.

Typically, energy regulators comprise a microswitch having a set'of switch contacts arrangeable in the eledtrical supply circuit to the electrical load, a snap-acting switch contact arm operatively associated with a bimetallic actuator, and electrically energisable heating means associated with the bimetallic actuator.

In such constructions, electrical power is initially supplied to the load and to the heating means which may be connected either in parallel or in series with the load. The heating means heats the bimetallic actuator, causing it to deform to the point where it causes snapaction of the contact arm to open the switch contacts and interrupt the power supply to both the load and the heating means. The bimetallic actuator then cools and deforms in the opposite direction to the point where the contact arm undergoes reverse snap-action to close the contacts once more, whereupon the cycle recommences.

Thus such regulators operate on the principle of supplying power to the load over a proportion of an operating cycle, the proportion being settable by control means coupled in use to a user actuated control member e.g. a knob via a spindle. The control means normally comprises a rotary control cam member having a cam body with one or more cam tracks, and against which a cam follower, for example provided on an ambient compensating bimetal coupled to the bimetallic actuator, abuts. These components are mounted within a housing.

Such constructions are hereinafter referred to as "energy regulators of the kind described".

Traditionally, the cam member is of a plastic or ceramic material which is mechanically fastened and keyed onto a metallic spindle, onto which is mounted, in use, a knob for operation by a user. This is a rather cumbersome form of construction. From a first aspect, the present invention provides an energy regulator of the kind described wherein the cam body and spindle are integrally moulded in a plastics material. Thus the cam member effectively includes the spindle. This considerably simplifies, and thus reduces the cost of, assembling the regulator, since there is no need to produce separate elements and join them together.

The use of a moulded cam body and spindle also gives scope for certain other changes to the traditional methods of construction of energy regulators. In particular it gives the possibility of changing the way in which the cam body is mounted in the regulator. Up to now, the mounting has been via the spindle which is journaled in an upper end face or support bracket of the regulator housing. This is a rather complicated form of mounting. In accordance with a second aspect of the invention, therefore, there is provided an energy regulator of the kind described wherein said cam body and/or spindle is/are at least partly hollow and the regulator housing is provided with an upstanding pillar over which the cam body and/or spindle matingly engages.

This is a particularly simple arrangement which considerably facilitates assembly of the regulator.

Preferably the internal surface of the cam/spindle and the external surface of pillar are frustoconical to facilitate manufacture when these components are moulded. The pillar may be integrally moulded in the housing and may be hollow to save weight, and to permit various other functions as described in more detail below.

The cam/spindle may have an internal bearing surface provided, for example by an internal shoulder, which engages with a cooperating bearing surface provided on the pillar, for example at its upper end.

Alternatively, or in addition, the cam/spindle may have a bearing surface formed at or adjacent its lower end for engagement with a lower bearing surface formed on or surrounding the pillar.

The cam body/spindle may be biased into contact with the pillar by the forces of the various cam followers acting on the cam. This avoids the need for additional means for fixedly locating the cam/spindle in the regulator.

Preferably, the housing is a two-part moulded plastics housing, the pillar being provided on a lower housing part, and the spindle extending through a hole in an upper housing part for connection to a knob.

Preferably the two housing parts fit together through one or more snap-fit connectors for ease of assembly.

Furthermore, the upper housing part may be provided with means for mounting the regulator to an appliance such as an electric cooker. This particular two-part construction and mounting arrangement is a considerable improvement over existing constructions since the component of the regulator may all be assembled in the lower moulding part, and the upper moulding part then snapped on to close the regulator and provide for a mounting to an appliance. From a third aspect, therefore, the invention provides an energy regulator of the kind described comprising a first housing moulding mounting components of the regulator, a second housing moulding for closing said regulator and preferably having means for mounting the regulator to an appliance, and means for preferably snap fitting the first and second housing mouldings together.

The snap fitting means may comprise, on one of the parts, a resilient tongue having an aperture engaging over a tooth provided on the other part. The tooth tapers outwardly in the direction of interconnection of the parts, so that the tongue is deflected outwardly as it moves over the tooth until the aperture snaps in behind the tooth.

The means for attaching the regulator to the appliance may comprise, for example, wells moulded into the top surface of the upper housing part into which self tapping screws may be threaded, or an upstanding threaded boss which can be inserted through a hole in the appliance and retained by a nut.

In a preferred arrangement, all of, or the majority of, the components of the regulator are mounted in the first housing moulding, and the second housing moulding acts to locate components of the regulator. This obviates the need for additional separate locating or fixing means, such as screws, rivets etc. for the components. This is a radical departure from established practice, and from a fourth aspect, therefore, the invention provides an energy regulator of the type described comprising a first housing moulding mounting a plurality of components, a second housing moulding mounted to said first housing moulding to close said regulator and acting to locate components of the regulator.

Thus a greatly reduced number of fixing components may be required in accordance with this aspect of the invention, saving not only material costs but also assembly costs. A particularly advantageous arrangement is provided when, as described above, the housing moulding snap fit together, since this avoids the need for screw fixing means, for example.

Returning to the provision of a hollow cam body and spindle, this has several other advantages. In a particularly preferred arrangement, an actuator member may extend through the core of the spindle for actuation of means arranged below the spindle. This provides a particularly compact arrangement, whereby further switch means, for example, may be mounted in the base of or below the base of the regulator and operated by an actuator extending out the other end of the regulator.

Such an arrangement in itself is a new departure in broad terms and from a fifth aspect therefore, the invention provides an energy regulator of the kind described wherein said spindle is hollow and an actuator member extends through said spindle for actuation of means arranged below said spindle.

The further means may comprise switch means. Such switch means may control, for example, the supply of electrical energy to an auxiliary load in a split-load appliance such as a split-ring heating element. The actuator may be either linear or rotary in action. In one embodiment, for example, the actuator may be a push rod having one end extending from the top of the spindle for operation by a user, with the other end cooperating with the switch means. The rod may be biased towards the user, for example by spring means acting on a button mounted on the actuator. The button may be mounted within a knob mounted on the spindle.

Returning to the arrangement of the cam body, this may carry a number of cam tracks for various purposes.

In a particularly preferred arrangements, the upper and lower surfaces and the edge surface of the cam body are profiled to perform a variety of functions. For example the upper surface may have cam tracks for co-operation with a main control cam follower and a cam follower associated with an auxiliary output of the regulator, while the lower surface may have tracks for controlling the opening and closing of sets of switch contacts in the neutral side of the circuit through the regulator and in a pilot light circuit.

Preferably the edge surface is profiled so as to give a desired 'feel' during rotation of the-spindle and cooperates with spring means mounted in the regulator housing.

Such an arrangement maximises utilisation of the cam surfaces, and from a sixth aspect therefore, the invention provides an energy regulator the kind described wherein said cam body comprises an upper surface having at least one cam track associated with a first set of switch contacts, a lower surface having at least one cam track associated with a second set of contacts, and an edge surface engaging spring means mounted in the regulator housing so as to give a desired feel as the spindle is rotated.

The edge of the cam body is preferably provided with one or more discrete detent portions for engagement with the spring means.

The depth or profile of the detents may be varied to vary the feel during rotation. For example in the 'off' position of the regulator, a fairly deep detent may be provided so that a certain degree of force is needed to move the spindle from that position. Nominal power settings, for example 1 to 9 may be indicated by say smaller detents which will retain the spindle in the desired rotation and position.

By simply modifying the cam moulding tool, for example by using a series of inserts, the feel may be modified to give the desired characteristics.

The spring is preferably a bow-type spring retained at both its ends in the housing and having a nose which engages with the edge surface of the cam body.

Preferably the shape of the nose and the detents are such that the nose will engage in the detent on its flanks rather than at its tip. This arrangement minimises the effect of backlash.

The invention also seeks to provide an improved electrical terminal for use in, for example, an energy regulator. Thus from a seventh aspect, the present invention provides an electrical terminal comprising a spade portion formed by folding over the end portion of length of metallic material to a double thickness, and a resilient retaining portion comprising a spring tongue released from said material, the tongue being arranged such that as the terminal is pushed into a receiving slot, it will deflect until it has passed fully through the slot whereinafter it will spring out to latch permanently in position.

The terminal may be made in a multi stage progression tool. This acts upon a strip of material in successive stages at a number of stations to form the shape of the terminal, fold over the edge portions of the strip (which will be the end portions of the terminal) to form the spade portions, from the spring tongue, and finally shear the formed terminal from the end of the strip. The forming, folding and releasing of the spring tongue can be done in any convenient order.

The tongue may be released from the end edge of the terminal, or from within the body of the terminal.

The invention also extends to an energy regulator comprising a terminal in accordance with the seventh aspect of the invention received in a slot formed therein.

Some preferred embodiments of the invention will now be described by way of example, with reference to the following drawings in which: Fig. 1 is a perspective view of an energy regulator in accordance with the invention; Fig. 2 is a vertical section through a cam/spindle in accordance with the invention; Fig. 3 is a horizontal section along the line X-X of Fig. 2; Fig. 4 is a top view of a cam/spindle in accordance with the invention mounted in a regulator housing; Fig. 5 is a vertical sectional view of the mounting of a cam/spindle in accordance with the invention in a regulator; Fiy. 6 is a view along the line VI-VI in Fig. 5 during assembly of the regulator; Fig. 7 shows schematically a further embodiment of the invention; Fig. 8 shows a terminal in accordance with the invention; and Fig. 9 is a view along line IX-IX of Fig. 8.

The energy regulator of Fig. 1 comprises a moulded housing comprising a lower moulding 2 and an upper moulding (not shown). A control spindle 4 is rotatably journaled in the housing and extends through an opening in the upper housing moulding, for operation by a user.

The spindle 4 is plastics and is integrally moulded with a cam body 6 having a number of cam surfaces, for purposes to be described below. In use, a knob (not shown) is fitted to the spindle 4.

The spindle/cam moulding 4 is hollow and is provided with a frusto-conical bearing surface 8, which engages a pillar 10 formed integrally with and upstanding from the base of the lower moulding 2.

Further details of the cam body 6 and its mounting will be given later.

The regulator is placed in the electrical supply circuit to the load being regulated, for example a cooker hot plate. The current supply to the load is controlled by a snap-action microswitch 7 operated by a bimetallic actuator 9 which is heated by a heater 60.

The microswitch 7 is arranged in the line side of the supply to the load. A generally U-shaped double line-in tab 12 mounts a fixed contact 14 which co-operates with a movable contact 16 mounted on one end of a switch contact arm 18.

The contact arm 18 is a generally rectangular member. A generally U-shaped cut-out in the contact arm 18 releases a central tongue 22 which is bowed and acts both as a compression member and an over-centre spring.

It is integral at one end with the portion of the contact arm 18 mounting the contact 16 and at the other end engages in a notch 24 formed in an upwardly extending support pillar 26. The pillar 26 is an upper portion of a line out tab 28.

The end 29 of the microswitch arm 18 remote from the contact 16 is coupled to a free end 30 of the bimetallic actuator 9, which itself forms one arm of a generally U-shaped bimetallic element 32. The other arm 34 of the element 32 acts as an ambient temperature compensator in a manner known in the art, and is connected to the actuator 10 by a connecting limb in the form of a flanged web 36. The arm 34 carries a cam follower 38 which is biased into engagement with a first cam track 40 provided on the upper surface of the cam body 6 of the spindle 4 by virtue of the moments generated by the C spring 22. Rotation of the spindle 4, causes the cam follower 38 to move up or down, which in turn causes the free end 30 of the bimetallic actuator 10 to move up or down thus varying the distance through which its free end 10 must move to cause operation of the switch due to heating during use and thus changes the nominal "setting" of the load.

The cross-web 29 of contact arm 10 is provided with laterally extending lugs 42 which engage with notches 44 formed in downturned end portions 46 of the actuator 10.

The lugs 42 are biased into the notches 44 by the spring tongue 22, which places the contact arm 18 in tension.

The bimetallic actuator 9 is generally rectangular and formed with a rectangular cut-out 48 which allows access to the tongue 22 during assembly, so that the tongue may be pushed into the notch 24 to 'cock' the switch.

The bimetallic element 32 is pivotally mounted in V notches 52,54 provided in the housing 2 by lugs 56. The lugs 56 are biased into the notches 52,54 by the spring tongue 22, which via the contact arm 18 places the bimetallic actuator 9 in compression.

As mentioned above, the bimetallic actuator 10 is heated at its root end by a ceramic substrate heater 60 mounted at the end of the actuator adjacent the pivotal mounting. The heater comprises a ceramic substrate 62, on which is printed a resist heating element 64. First and second electrical terminals 66,68 are provided at opposite ends of the element 64. The heater 60 rests on an arched fulcrum 70 formed across a root portion of the actuator 10. The second terminal 68 of the heater 60 engages under a substantially rigid tongue 72 released and folded back from the cut out 48 of the actuator 10.

The first terminal 66 of the heater is contacted and biased downwardly by an end portion of an electrically conductive spring arm 74 which is biased downwardly by the upper moulding of the housing when the latter is assembled. The other end of the arm 74 is formed integrally with a tab 80 extending through the housing 2 for connection into the heater supply circuit.

The electrical circuit to the heater 60 is completed through the tongue 72, the bimetallic actuator 10, the contact arm 18, the contacts 14,16 and the line in tab 12. This circuit is in parallel with the supply to the load being controlled, which passes through the line in tab 12, the contacts 14,16, the central tongue 22 of the actuator arm 18, the fulcrum 24 and the line out tab 28.

The regulator also comprises means for supplying energy to a two-part load such as a split-grill. A first, fixed, contact 80 is mounted on an extension 82 of the line-out terminal 28, and a second, movable contact 84 mounted on a resilient electrically conductive member 86 connected to a secondary line-out terminal 88. The resilient member 86 has a bent down cam follower 90 which engages an inner cam track 92 on the upper surface of the cam body 6. When the contacts 80,84 are closed, electrical energy is supplied to both parts of the load, through the respective line-out terminals 28 and 88. When power is to be supplied to one part of the load only, the control knob is twisted to such a position that the cam follower 86 rides up the inner cam track 92 to open the contacts 80,84, whereby power is supplied only through the main line-out terminal 28.

The lower surface 94 of the cam body 6 is provided with an inner 96 and an outer 98 cam tracks. The inner cam track 96 is engaged by a cam follower arranged on a resilient member connected to a neutral terminal member 100 to deflect the member and open a set of contacts (not shown) in the neutral side of the supply in 'off' position of the regulator. The outer track 98 is engaged by a follower attached to a resilient contact mounting or forming member in a neon indicator circuit through the regulator. The track profile is such that a set of contacts is opened when the cam body 6 in the 'off' position (and thus a neon indicator extinguished), but closed in the other angular positions of the cam body 6.

Figs. 2 and 3 show an integral cam and spindle moulding 200 for use in a regulator as generally described with reference to Fig. 1.

In addition to cam tracks 202, 204, 206, 208 provided on its upper and lower surfaces for the purposes described above, the outer edge surface 210 of the cam body portion 212 is provided with detent means 214, 216, which, as shown in Fig. 4, engage with a bow spring 218 which is retained in the lower housing moulding 220 by lugs 222, 224. The detents are positioned in the 'off' and 'maximum' positions of the cam/spindle 200 so that the cam/spindle will be selectively retained in those positions as it is rotated.

The profiles of the detents and the nose 226 are such that the nose 226 engages with the detent by its flank portions 228, 230, rather than its tip 232 to avoid backlash problems. Of course further detents may be provided in other angular positions around the edge, for example at position corresponding to nominal power settings of the regulator. Inserts in the moulding tool for the cam body allow a variety of indents and friction feels to be provided easily for different applications.

With reference to Figs. 5 and 6, the mounting of the cam/spindle moulding 200 in the housing is shown in more detail. The track detail has been omitted for clarity. It ill be seen that the housing comprises a lower moulding 220 and an upper moulding 238, the top of the spindle extending through an aperture 240 in the upper moulding. A hollow pillar 242 is moulded integrally with the lower moulding 220. The cam/spindle moulding 200 is hollow and has a frusto-conical internal surface 244 for engagement over the outer surface of the pillar 242.

A step 246 provided at the base of the pillar 242 acts as a thrust bearing against the lower edge 248 of the cam/spindle moulding 200. A further bearing is provided by the engagement of the upper end 247 of the pillar 242 and a shoulder 249 formed in the cam/spindle moulding 200. A slight clearance exists between the frusto conical surfaces of the moulding 200 and the pillar 242.

As mentioned above in relation to Fig. 1 the cam/spindle moulding 200 is biased downwardly by the cam followers engaging in the upper cam tracks 202, 204.

However upward axial movement of the moulding 200 is prevented by a shoulder 250 on the moulding 200 engaging the surface 252 around the aperture 240. This effectively locates the moulding 200 axially.

The upper housing moulding 238 is snap-fitted onto the lower housing moulding 202. A plurality of resilient tongues 254 having centrally arranged slots 256 are provided on an outer edge of the upper housing moulding, to engage with latches 258 provided on the lower housing moulding 202. As is apparent from Fig. 6, as the upper housing moulding 238 is moved down onto the lower housing moulding 220, the tongue 254 will deflect over the latch 258 until the latch 258 enters the slot 256.

The upper housing moulding 238 also has means for mounting the regulator to an overlying surface. These means comprise two circular wells 260, which can receive self tapping screws (not shown).

A further embodiment of the invention is shown schematically in Fig. 7.

An energy regulator 300 is mounted to a support plate 302 by self tapping screws 304, 306, as described above. The integral cam/spindle moulding 308, and the pillar (not shown) on which it is mounted in a manner as described above are hollow. The top of the cam/spindle moulding extends through an aperture 310 in a fascia panel 313 of an appliance, such as a cooker, and has mounted on it a control knob 312.

An linearly movable actuating member or push rod 314, has a button 316 which is biased upwardly against a shoulder 318 in the knob 312 by a coil spring 320. The push rod 314 extends through the cam/spindle moulding 308 into a push-button type switch unit 322 mounted under the regulator 300.

The switch unit may be used to control say the supply to an auxiliary output, as an alternative to the cam arrangement described above, for example, or for any other desired purpose. Of course the actuator need not be a push rod as shown and could be a rotary actuator for example.

Figs. 8 and 9 illustrate a terminal in accordance with the invention. The terminal 400 illustrated has a spade portion 402 which, as can be seen from Fig. 9 comprises a double thickness of folded strip material.

A spring tongue 404 is pressed out of the stock 406 to extend at an angle through a slot 408 formed in the free end of the folded over spade material 410.

As can be seen from Fig. 9, the terminal is pushed down through a slot 412 in say a housing moulding 414, and as it does, the spring tongue 404 will deflect into the plane of the spade portion 402 until the tongue passes completely through the slot 412 at which point it will spring out to latch with the under surface 416 of the moulding 414 to prevent withdrawal of the terminal.

The terminal 400 is produced from a strip of material which passes through a progression tool having a plurality of stations at which different operations are performed on the strip. The strip has a width equal to the extended length of the terminal. A typical sequence of operations would be as follows:1. Stamp out the tongue clearance slot 408.

2. Shear in the tongue 404.

3. Stamp out profile of terminal to shape shown in phantom line 420 (Fig. 8).

4. Fold leaf 422 (Fig. 8) over onto stock 406 and form spade portion 402.

5. Shear off completed terminal along edge 424.

The terminal 100 shown in Fig. 1 is formed in a similar manner, only the spring tongue 404 is formed on the folded part of the spade portion to avoid the need for a clearance slot 408.

Claims (17)

Claims

1. An energy regulator of the kind described wherein said cam body and/or spindle is/are at least partly hollow and the regulator housing is provided with an upstanding pillar over which the cam body and/or spindle matingly engages.

2. An energy regulator as claimed in claim 1, wherein internal surface of the cam/spindle and the external surface of the pillar are frustoconical to facilitate manufacture when these components are moulded.

3. An energy regulator as claimed in claim 1 or 2, wherein the pillar is integrally moulded in the housing.

4. An energy regulator as claimed in claim 1, 2 or 3, wherein the pillar is hollow.

5. An energy regulator as claimed in any preceding claim, wherein the cam/spindle is provided with an internal bearing surface which engages with a cooperating bearing surface provided on or surrounding the pillar.

6. An energy regulator as claimed in any preceding claim wherein the cam body/spindle is biased into contact with the pillar by the forces of cam followers acting on the cam.

7. An energy regulator as claimed in any preceding claim wherein the housing is a two-part moulded plastics housing, the pillar is provided on a lower housing part, and the spindle extends through a hole in an upper housing part for connection to a knob.

8. An energy regulator as claimed in claim 7 wherein the two housing parts fit together by means of one or more snap-fit connectors.

9. An energy regulator as claimed in claim 7 or 8, wherein the upper housing part is provided with means for mounting the regulator to an appliance such as an electric cooker.

10. An energy regulator as claimed in any preceding claim, wherein the cam body and spindle are integrally moulded in a plastics material.

11. An energy regulator of the kind described wherein the cam body and spindle are integrally moulded in a plastics material.

12. An energy regulator of the kind described comprising a first housing moulding mounting components of the regulator, a second housing moulding for closing said regulator and preferably having means for mounting the regulator to an appliance, and means for preferably snap fitting the first and second housing mouldings together.

13. An energy regulator of the type described comprising a first housing moulding mounting a plurality of components, a second housing moulding mounted to said first housing moulding to close said regulator and acting to locate components of the regulator.

14. An energy regulator of the kind described wherein said spindle is hollow and an actuator member extends through said spindle for actuation of means arranged below said spindle.

15. An energy regulator the kind described wherein said cam body comprises an upper surface having at least one cam track associated with a first set of switch contacts, a lower surface having at least one cam track associated with a second set of contacts, and an edge surface engaging spring means mounted in the regulator housing so as to give a desired feel as the spindle is rotated.

16. An electrical terminal comprising a spade portion formed by folding over the end portion of length of metallic material to a double thickness, and a resilient retaining portion comprising a spring tongue released from said material, the tongue being arranged such that as the terminal is pushed into a receiving slot, it will deflect until it has passed fully through the slot whereinafter it will spring out to latch permanently in position.

17. An energy regulator substantially as hereinbefore described with reference to the accompanying drawings.