Contact terminal arrangement for electrical built-in switching unit

An electrical device (20), in particular an energy regulator or infinite switch, comprises a body portion (22) with one or more electrical elements (33, D, B, C, 47) mounted thereto. The body portion (22) and the electrical element(s) (33, D, B, C, 47) mounted thereto define an assembly having a minimum dimension which is termed the "thickness" of the assembly. At least one terminal (25, 57, 58, 59, 60, 61, 63) is also mounted to the body portion. The terminal has a mounting portion (27) and a contact portion (26) with the mounting portion (27) extending transversely to the thickness dimension to thereby result in a low-profile electrical device.

TECHNICAL FIELD
 The present invention relates to terminal arrangements provided in
 electrical devices. In particular, although not exclusively, the invention
 relates to low profile control devices for electrical appliances such as
 hot plates in electric stoves. However, it will be appreciated that the
 use of such a device is not restricted to domestic appliances.
 BACKGROUND ART
 Control devices, commonly known as energy regulators or infinite switches
 are used primarily in domestic appliances where it is required to control
 heating of an element in an oven or a hot plate. The control devices allow
 electricity through to the elements in pulses and it will be appreciated
 that longer pulses will lead to higher element temperatures. The length of
 these pulses can be lengthened or shortened by turning a knob on the
 control device so as to increase or decrease the element temperature. The
 knob is attached to an actuator shaft which is generally mounted
 perpendicular to a mounting plate which also supports a terminal housing.
 A number of electrical terminals are assembled into the terminal housing
 by sliding mounting portions of the terminals into slots in the housing
 extending in a direction perpendicular to the general plane of the
 mounting plate, i.e. parallel to the actuator shaft. (See FIG. 1) The
 terminals may be staked to retain them in position.
 There are a number of disadvantages inherent in this type of construction.
 Firstly, the construction requires the use of a separate mounting plate
 and housing. Secondly, the sliding of the terminals perpendicularly to the
 mounting plate to assemble the control device necessitates an overall
 depth of the device which is greater than the length of the terminals
 since the mounting portions of the terminals extend into slots aligned
 with the lengthwise direction of the terminals. The staking of the
 terminals is also an additional assembly step increasing the number of
 assembly operations.
 It is therefore an object of the present invention to overcome at least one
 of the abovementioned disadvantages or to provide the public with a useful
 choice.
 DISCLOSURE OF INVENTION
 In accordance with a first aspect of the present invention, there is
 provided an electrical device including: a body portion; one or more
 electrical elements mounted to the body portion, the body portion and the
 one or more electrical elements defining an assembly having a thickness
 dimension which is the minimum external (or principal) dimension of the
 assembly; and at least one electrical terminal mounted to the body
 portion, the electrical terminal having a mounting portion and a contact
 portion, the mounting portion extending transversely to the direction of
 the thickness dimension and being received in a recess extending from the
 side of the body portion, which side is substantially aligned with the
 thickness dimension, the mounting portion being adapted for sliding
 assembly into the recess.
 Preferably, the mounting portion extends substantially perpendicular to the
 direction of the thickness dimension. For example, the mounting portion
 may extend in either of the two orthogonal directions perpendicular to the
 thickness dimension, parallel to the general plane of the body portion so
 as not to contribute to the overall thickness of the electrical device.
 The mounting portion may be a planar member oriented such that the
 thickness dimension extends substantially perpendicular to the plane of
 the mounting portion. Further, it is preferred that the contact portion of
 the electrical terminal has a substantially planar contact surface which
 is substantially aligned with the thickness dimension. In a most preferred
 form of the invention the contact portion of the electrical terminals does
 not extend substantially beyond the thickness dimension. Thus, in the
 preferred form of the invention the terminal may be an L-shaped member
 whereby the mounting portion and the contact portion define respective leg
 portions of the L-shaped member.
 Suitably, the terminal is disposed at or adjacent a side of the body
 portion which is substantially aligned with the thickness dimension. A
 slot may be provided at the side of the body portion, the slot being
 complementary in shape to the mounting portion of the terminal and the
 mounting portion of the terminal being received in the slot.
 Advantageously, a frictional fit is provided between the mounting portion
 of the terminal and the body portion. Alternatively, a snap fit is
 provided between the mounting portion of the terminal and the body
 portion.
 Preferably, the body portion is substantially planar. In a preferred form
 of the invention, a plurality of terminals are provided and the electrical
 element(s) and the terminals are mounted to extend from the same face of
 the body portion. The device may further include a rotary control actuator
 mounted to extend from the other face of the body portion in a direction
 substantially aligned with the thickness dimension.
 In a commercial embodiment of the invention, the body portion is of a
 one-piece plastic moulded construction.
 In accordance with a second aspect of the present invention, there is
 provided a control device for an electrical appliance, including at least
 one electrical terminal and a substantially planar body portion, the
 electrical terminal being adapted for sliding assembly with the body
 portion in a direction substantially parallel to the plane of the body
 portion into a recess extending substantially parallel to the plane of the
 body portion.
 By "substantially planar", it is meant that the body portion extends
 largely within a single plane with an average thickness dimension
 transverse to the plane being substantially less than the extent of the
 body portion within the plane.
 Suitably, there are a plurality of electrical terminals assembled in this
 manner in the body portion. Each of the electrical terminals may include a
 mounting portion extending substantially parallel to the plane of the body
 portion and a contact portion extending substantially perpendicular
 thereto. The recesses may be in the form of slots, apertures or recesses
 and desirably a frictional fit is obtained between each electrical
 terminal and its respective receiving means.
 In a preferred form of the invention, a control actuator is also mounted to
 the body portion with the control actuator having a longitudinal axis
 extending substantially perpendicular to the plane of the body portion. In
 a most preferred form of the invention, the body portion is in the form of
 a one piece moulded mounting plate with the receiving slots integrally
 formed in the mounting plate.
 The control device may take the form of an energy regulator (infinite
 switch) incorporating a bimetallic switch and intended to be used in a
 domestic appliance. The body portion may be located behind a face plate
 provided on the electrical appliance.
 In accordance with a third aspect of the present invention, there is
 provided a control device for an electrical appliance including at least
 one electrical terminal and a control actuator having a longitudinal axis
 wherein the electrical terminal is adapted for sliding assembly in the
 control device in a direction substantially perpendicular to the axis of
 the control actuator into a recess substantially perpendicular to the axis
 of the control actuator.
 Preferably, a body portion is provided into which the electrical terminals
 may be slidably received during assembly. Suitably, the control actuator
 may take the form of an actuator shaft to which an actuator knob can be
 fitted, the longitudinal axis of the actuator shaft defining the
 longitudinal axis of the control actuator.
 In order that the invention may be more readily understood, one embodiment
 will now be described with reference to the drawings in which:

BEST MODE FOR CARRYING OUT THE INVENTION
 In FIG. 1, the prior art energy regulator 10 is shown to comprise a
 mounting plate 12 and a separate terminal housing 14. A control actuator,
 including a control shaft 15 is mounted to the mounting plate 12 and
 terminal housing 14. A number of electrical terminals 16 are shown which
 are staked or clipped in through slots in the housing 14, the slots
 extending perpendicularly to the plane of the mounting plate 12. It can be
 seen that the provision of slots in the terminal housing 14 which are
 aligned with the longitudinal direction of the electrical terminals 16
 leads to excess bulk of the regulator 10, particularly in the direction
 aligned with the axis of the control actuator 15. Typically, this
 dimension is 25 to 50 mm as shown in the figure.
 FIG. 2 illustrates an energy regulator 20 according to the preferred
 embodiment of the present invention. The mounting plate and the terminal
 housing are combined into a moulded plastic one piece body portion 22
 which is substantially planar apart from the boss for the mounting of the
 rotary control knob. The arrow indicates the general direction of the
 plane. With electrical elements mounted to one face of the body portion
 22, it will be appreciated that the thickness direction lies along any
 line perpendicular to this plane. A number of electrical terminals 25 are
 assembled with the one piece body portion 22 as shown in more detail in
 FIGS. 3 and 4.
 Each of FIGS. 3 and 4 shows a partial section through the body portion 22
 and a section through one of the electrical terminals 25. It can be seen
 that the electrical terminal 25 comprises a first contact portion 26 for
 making electrical contact with electrical components when the energy
 regulator 20 is installed into an electrical appliance (not shown). The
 electrical terminal 25 also comprises a second mounting portion 27
 extending transversely, in particular, at right angles to the first
 contact portion 26. The mounting portion 27 is received by a cooperating
 receiving means 30 provided in one side of the body portion 22. The
 receiving means 30 is in the form of an elongate slot substantially
 complimentary to the shape of the mounting portion 27. In the assembled
 configuration, it can be seen that the mounting portion 27 and the
 receiving slot 30 extend in a direction substantially parallel to the
 general plane of the body portion 22, which is substantially perpendicular
 to the central longitudinal axis of the control actuator 33 (See FIG. 2)
 and the thickness direction of the body portion. This configuration with
 all the terminals 25 having mounting portions 27 extending substantially
 parallel to the plane of the body portion 22 substantially reduces the
 bulk of the energy regulator in the direction perpendicular to the plane
 of the body portion 22.
 The mounting portion 27 is slidably receivable in the mounting slot 30 for
 easy assembly. A ramped projection 28 is provided on one face of the
 mounting portion 27 for retention within a further recess 34 provided in
 the body portion 22 to provide a snap fitting.
 The energy regulator 20 is intended primarily for use in domestic
 appliances. The energy regulator 20 controls the heating of elements in
 ovens or hot plates by allowing electricity to pass through to the
 elements in pulses. The energy regulator 20 also controls the length of
 the pulses so as to increase or decrease the element temperature.
 The energy regulator 20 incorporates a bimetallic switch 40 (FIGS. 5 and 6)
 to control the pulses of electricity between predetermined ones of
 electrical terminals 25. The bimetallic switch 40 is illustrated
 schematically in FIGS. 5 and 6.
 The bimetallic switch 40 includes a bimetallic strip C anchored at one end
 indicated by A. A ceramic heating element B is disposed on the top surface
 of the bimetallic strip C. The bimetallic switch 40 also includes a spring
 member D, the form of which is more clearly shown in FIGS. 10 to 12. As
 can be seen from FIG. 5, the spring member D is anchored at a first end F
 and a variable load is applied by the bimetallic strip at a second end 70
 opposite to the anchored end. The spring member D comprises a strip of
 spring metal with two spaced slots 72 both extending from a central
 portion 74 of the spring strip 77 towards the second end 70 but spaced
 from the second end. A transverse slot 75 connects the two parallel slots
 72 to define an elongate contact portion 77 having a free end centrally
 disposed relative to the spring strip D. A first contact 79 is attached to
 the free end of the elongate contact portion 77. The bimetallic switch 40
 also includes a second contact E engagable with the first contact when the
 switch 40 is in the closed position shown in FIG. 5.
 It can be seen that the first end F has a longitudinal groove 81 extending
 to the central portion 74 which it is believed, assists in establishing
 residual stresses within the spring strip D. An additional slot 83 is
 provided adjacent the first end F to stake the spring member D to the Load
 Terminal 63 as will be discussed later in connection with FIGS. 8 and 9.
 The bimetallic strip C can apply a varying load to the second end of the
 spring strip. The varying load will depend upon the heating of the
 bimetallic strip which determines the configuration of the bimetallic
 strip as well as an initial bias applied by the control actuator 33, a
 portion of which is shown in FIG. 7.
 The control actuator shaft 33 rotates a circular cam 45 which controls the
 location of a cam follower (calibration screw) 47 mounted to the
 bimetallic strip C.
 The operation of the bimetallic switch will now be explained.
 When the control actuator 33 is in the off position, the cam follower 47
 engages with the lowest point on the circular ramp 45 and little or no
 bias is applied to the bimetallic strip. The contacts to the heater B are
 also open and thus little or no load is applied to the second end of the
 spring member D so that the first and second contacts are open as shown in
 FIG. 6. When the control actuator shaft 33 is rotated to an operating
 position, the cam follower 47 is raised, thereby applying an upward bias
 to the bimetallic strip C, which in turn applies a load to the second end
 of the spring member D to close the contacts as shown in FIG. 5.
 Electricity then flows through these contacts to the appliance elements.
 Electricity also flows through these contacts to the ceramic heater B
 which heats the bimetallic strip C which is configured to bend downwardly
 upon heating. This causes the contacts to open as shown in FIG. 6,
 whereupon current flow to the ceramic heater B and to the appliance
 element will cease and the bimetallic strip C will gradually cool to
 resume the configuration shown in FIG. 5, forcing the contacts to again
 close. This cycle of repeated opening and closing sends electricity
 through to the appliance elements in pulses. By rotating the control
 actuator 33 and increasing the upward bias on the bimetallic strip C, it
 will be necessary to heat the ceramic heater B for a longer period of time
 to cause the necessary deflection in the bimetallic strip C. Thus, the
 length of the pulses through to the appliance elements will be increased
 and the appliance elements will therefore be heated to a higher
 temperature.
 When the control actuator shaft 33 is rotated to the "full on" position, a
 lobe on the circular ramp increases the bias to such an extent that the
 bimetallic strip applies a sufficient load to the spring member so that,
 irrespective of the deflection attained by the bimetallic strip, the
 contacts remain closed and the electricity flows continuously to the
 appliance elements.
 As shown in FIG. 7, the circular ramp 45 also includes a lateral lobe 50 to
 effect closing of an auxiliary switch to operate devices such as pilot
 lamps, extra elements, fans or safety circuits.
 The cam follower 47 is provided in the form of an adjustment screw which
 threadingly engages in a portion of the bimetallic strip C to enable fine
 tuning adjustment to the pulse rate.
 The bimetallic strip is configured into a U shape with one leg of the "U"
 forming the bimetal strip shown in FIGS. 5 and 6 and the other leg of the
 "U" defining a heat compensating portion which is the portion mounting the
 cam follower 47 shown in FIG. 7. The heat compensating portion acts as a
 compensator for when heat builds up within the energy regulator, ensuring
 that the pulses remain constant, irrespective of heat build up. The
 configuration of the bimetallic strip C can be most clearly seen in FIG.
 9.
 In connection with FIGS. 8 and 9, a detailed description of the components
 of the energy regulator 20 will now be provided.
 Up to this point, the numeral 25 has been used to collectively refer to the
 electrical terminals. Each of the terminals will now be individually
 identified in connection with FIGS. 8 and 9.
 Component Description
 Control Actuator (33)
 The control actuator 33 includes a moulded thermoplastic shaft which clips
 into and rotates in the body portion 22. Rotation of the shaft controls
 the switching mechanisms in the control device. It opens and closes the
 separate circuits within the control device. It also adjusts the output of
 the cycling mechanism by altering the attitude of the Bimetallic Strip C
 by means of the Cam Ramp 45 on one end. This component can have many forms
 to allow for many options of shaft size and switching operations. The
 shaft also provides part of the locking mechanism between it and the body
 portion 22, for a "Push-to-Turn" option of control operation.
 Body Portion (22)
 All terminals slide and clip in from sides. The control actuator shaft
 clips into it. The mounting mechanism of the control shaft is an integral
 part of the body portion 22. A protective terminal cover 55 also clips
 onto the body portion 22. This component also provides the second part of
 the locking mechanism with the control shaft for a "Push-to-Turn" option
 as described above.
 Terminal Cover (55)
 Moulded thermoplastic cover. This clips onto the body portion 22 to provide
 protection for the internal mechanisms of the control. It also
 incorporates a connecting strip from the neutral terminal to the ceramic
 heater.
 Phase Terminal (57)
 Pressed nickel plated steel terminal. This slides and clips into the body
 portion 22 and provides for two external electrical connection by means of
 standard 1/4" terminals. It provides the connection to the spring member D
 for the main cycling mechanism of the control. This component also
 provides for connection to the on-off terminal 59 for a phase break
 circuit (fill current, used with contacts), or a pilot light circuit (low
 current, no contacts used). The terminal with the phase/pilot connection
 can also be separated from the other terminal to provide an isolated
 circuit with the on-off terminals 59.
 Neutral Break Terminal (58)
 Pressed nickel plated steel terminal. This slides and clips into the body
 portion 22 and provides for external electrical connection by means of a
 standard 1/4" terminal. The blade part of this component is operated by
 the control shaft. It switches the neutral or second phase circuit
 depending on the application, between it and neutral terminal 61. This
 component also provides the force required on the control shaft for a
 "Push-to-Turn" option.
 On-Off Terminal (59)
 Pressed phosphor bronze terminal. This slides and clips into the body
 portion 22 and provides for external electrical connection by means of a
 standard 1/4" terminal. The blade part of this component is operated by
 the control shaft. It is used to switch a phase break circuit, pilot
 circuit or isolated circuit as described above in connection with the
 phase terminal 57. This component also provides the detenting (indexing)
 of the control by operating in depressions on the surface of the control
 shaft.
 Divided Terminal (60)
 Pressed phosphor bronze terminal. This slides and clips into the Mounting
 Plate and provides for external electrical connection by means of a
 standard 1/4" terminal. The blade part of this component is operated by
 the control shaft. It switches to a connection on the Load Terminal 63 to
 provide a circuit for a second load.
 Neutral Terminal (61)
 Pressed nickel plated steel terminal. This slides and clips into base 22
 and provides for two external electrical connections by means of standard
 1/4" terminals. It provides the connection to the neural break terminal 58
 for the neutral or second phase circuit. It also provides for contact to
 the neutral connector 64 to complete the neutral circuit with the Ceramic
 Heater B.
 Spring Member (D)
 Pressed titanium copper spring. This component is permanently staked to the
 load terminal 63 and completes the connection for the main cycling
 mechanism between the phase terminal 57 and the load terminal 63. The
 "tongue" of the trident has a contact on it which completes this circuit
 with the phase terminal 57. Self contained stresses put into this
 component when forming it provide the "snap action" for the switching of
 this circuit. The cycling of this circuit is controlled by the heating and
 cooling of the Bimetallic strip B which moves the end of the spring member
 up and down, opening and closing the contacts.
 Load Terminal (63)
 Pressed nickel plated steel terminal. This slides and clips into the body
 portion 22 and provides for two external electrical connections by means
 of standard 1/4" terminals. This component allows for the permanent staked
 mounting of the spring member D and the hinged mounting of the bimetallic
 strip B. It is the second part of the cycling circuit between it and the
 phase terminal 57. It also provides a connection for switching a second
 load circuit to the divided terminal 60.
 Ceramic Heater (B)
 Moulded alumina ceramic with resistive film and silver contacts screened on
 to its surface. This component clips onto and is electrically connected to
 the bimetallic strip C at one end. It provides a connection for the
 neutral connector 64 at the other end to complete a heater circuit between
 the load terminal 63 and the neutral terminal 61. This component, when
 energized, provides the heat directly to the bimetallic strip C to make
 the control cycle.
 Bimetallic Strip (C)
 Pressed bimetal. This component provides the clip mounting and electrical
 connection for the ceramic heater B, the screw mounting for the
 calibration screw 47, the hinge mounting of it to the load terminal 63 and
 the switching (cycling) of the spring member D. Heat from the ceramic
 heater 81 causes the bimetallic strip C to bend and relax pressure on the
 spring member D which allows it to spring open and break the circuit. The
 bimetallic strip C then cools and eventually returns to its original
 position causing the spring member D to snap closed again, then the cycle
 repeats. The output of the control is altered by rotating the control
 actuator 33 which changes the attitude of the bimetallic strip C.
 Cam Follower (47) (Also Used as Calibration Screw)
 Moulded thermoplastic screw. This component threads into the bimetallic
 strip 12. The nose of the screw runs on a cam ramp surface of the end of
 the control actuator 33 to allow the output of the cycling mechanism to be
 altered by the rotation of the control actuator. Adjustment of the screw
 presets the output of the cycling mechanism at predetermined settings of
 the control actuator.
 Neutral Connector (64)
 Pressed stainless steel connector. This component fits into the terminal
 cover 55. It provides electrical connection between the ceramic heater B
 and the neutral terminal 61 to complete the heater circuit.