CN1382414A - Control unit - Google Patents

Abstract

A control member (2) for an electric water heater incorporating an electric heating element, the control member comprising a thermally responsive bimetallic element (12) responsive to boiling of water, electrical conductors (40, 42, 50, 54) providing live and neutral conductive paths, a pair of live switch contacts (41, 44) having a movable contact (41) in said live conductive path, a pair of neutral switch contacts (58, 59) having a movable contact (59) in said neutral conductive path, first actuating means (16) adapted to act on said movable contacts to sequentially open said switches one after the other in response to said thermally responsive element when water boils.

Description

control parts

technical field

The invention relates to a control part for an electric water heater, in particular to a control part for an electric water pot and a kettle.

Background technique

Electric kettles are required to have a control unit to allow the user to heat the water to a predetermined temperature, usually to a boil, at which point the kettle automatically turns off. Of the various existing controls that perform this function, most typically employ a thermally sensitive element, such as a bimetallic element, which acts indirectly on an electrical contact to de-energize the heating element.

An example of this type of control is that described in British Patent GB1470364 to Otter Controls Ltd, in which a bimetallic element is positioned over an opening which receives steam from the kettle body. The bimetal element acts on an over center lever which in turn acts to break a pair of contacts connected to the heating element.

For safety reasons, domestic kettles also need to include controls when there is no water in the kettle being heated, or when the kettle is boiled dry, for example, if the water is boiled because the kettle lid is not closed or the eccentric lever is deliberately turned off by the user. When it is prevented from working so that it boils dry. In addition, for the sake of kettle safety, control components are also required if this "boil dry" or "no water switch closed" protection fails or does not work under experimental conditions.

In order to provide this "boil dry" protection, various control components have been proposed. For example, in British Patent 2204450 of Strix Ltd., a detachable thermal fuse is provided, which can release a spring mechanism when it melts or does not melt at a predetermined temperature, and the spring mechanism opens a pair of wires connected in series with the heating element. The switch contacts, so that the kettle is permanently disconnected.

In another class of control components, British Patent 2185857 to D H Haden Ltd is the subject of an invention of a pair of bimetallic discs having different switching temperatures arranged to act on a pair of switch contacts, One disc switches reversibly at about 130°C to provide basic boil-dry protection, the other disc has a higher switching temperature and provides irreversible switching as a backup.

There is also a kind of control part, which improves safety by switching between two states with electrodes and without electrodes. For example, in UK Patent 2112209 to Strix Ltd, the "polarity" switching between boil and dry is provided by a sliding link.

All of the above solutions suffer from a specific disadvantage. Those using thermal fuses or a single secondary bimetal have very slow control action, allowing substantial excessive temperatures to occur within the control components, which can have unpredictable results on live working internal parts and can cause damage to the kettle.

Simultaneous switching operations on both poles also present problems with arcing when they are switched off. The breakdown problem is particularly prone to kettles using a heating element consisting of a long coil formed from relatively low resistance windings and thus having a relatively high inductance. Said switching of the control unit with such a highly inductive heating element can lead to dangerously high potential differences.

Contents of the invention

The present invention aims to provide a control unit which overcomes the above-mentioned disadvantages.

According to a first aspect of the present invention, there is provided a control unit for a water heating appliance having an electric heating element, the control unit comprising a heat responsive element responsive to boiling of water, electrical conductors providing charged and non-charged conduction paths, a pair of A live pair of switch contacts in said live conduction path has a movable contact, a pair of dead switch contacts in said dead conduction path has a moveable contact, and is adapted to operate on all The first actuating means acting on said movable contact responds to said thermally responsive element to sequentially open said switches one by one as the water boils.

This sequential switching reduces the potential of live and dead components, thereby reducing the risk of arcing of the contact pair controlling a second contact pair which can be used as basic dry-out protection . Furthermore, by switching between live and non-charged electrodes, the control unit can be controlled substantially equally smoothly even if the electrical connections of the control unit are reversed.

Sequential transformations can be implemented using various structures. The first actuating device may include an actuating lever, one end of which is set to be acted on by the thermally responsive element, and the other end rests on the first pair connected to the live contact pair and the dead contact pair respectively. actuating levers, wherein said other end of the lever is configured to engage one of the actuating levers before the other actuating lever provides said sequential disconnection. Optionally, the actuating device may consist of an actuating lever, one end of which is set to be acted on by the thermal response element, and the other end rests on the live contact pair and the neutral contact pair respectively. A first pair of actuating linkages, wherein the pair of contacts are disposed relative to the actuating lever such that one pair is closer to the actuating lever than the other to provide said sequential opening. Optionally, the actuating device may be composed of an actuating lever, one end of which is set to be acted on by the thermal response element, and the other end rests on the charged contact pair and the neutral contact pair respectively. A first pair of actuating rods connected, wherein the actuating rods have different lengths to ensure the sequential disconnection as described.

The thermally responsive element may be a bimetallic element that changes shape at a predetermined temperature. The actuating lever may be a bistable spring biased over-center lever.

The control unit may further provide overheating protection, in which case the overheating protection means comprises first and second thermally responsive elements responsive to the overheating, and the actuating means is arranged on said first and second thermally responsive elements and comprising rotatably mounted lever arms each having one end connected to said thermally responsive element and the other end respectively acting on the movable contacts to open the switch under overheating conditions.

In another aspect, the present invention provides a control unit with overheating protection for use in a water heating appliance incorporating an electric heating element, the control unit comprising an electrical conductor having live and non-carrying conduction paths, where the live A live switch contact pair has a movable contact in a conductive path and a dead switch contact pair has a movable contact in said dead conductive path; a first contact in response to an overheat condition and a second thermally responsive element; an actuating device disposed between the first and second thermally responsive elements, the actuating device comprising rotatably mounted lever arms, each lever arm having one end connected to the thermally responsive element , and the other ends respectively act on the movable contacts to open the switch in an overheating condition.

The lever arm may be rotatably mounted such that its pivot point is located at the end of the lever that is closer to the thermally responsive element than the other end, so that displacement of the other end corresponds to the thermally responsive element Movement of the end of the lever arm to which it is attached is amplified, for example the lever can be rotated about a third of its length.

This structure switches the live side and the dead side through a very compact and simple and reliable structure under overheating conditions. The movement amplification provided by the lever arranged in this way enables a sensor structure with very little movement to be used.

More specifically, the first and second thermally responsive elements each consist of a disc-shaped bimetallic disc which switches when its temperature exceeds a predetermined value, and wherein the actuating means comprises A respective actuator rod extends between the bimetal disc and the end of the lever. The bimetallic discs may be arranged substantially parallel to each other, the second disc located closest to the end of the lever has a central hole, the actuator rod consists of a hollow sleeve, and the first disc Having an actuator rod which extends through said central hole of the second disc and said sleeve to the end of said lever provides a particularly compact arrangement.

The control means may be adapted to sequentially open said switch contacts in an overheating condition. The first and second bimetallic discs may be supported by a metal ring at intervals around their periphery so that in use there is a thermal gap between heat reaching said second disc and heat reaching said first disc. hysteresis, and these discs may have substantially the same transition temperature, so that the first bimetallic disc transitions before the second bimetallic disc under overheating conditions, so by its corresponding levers and actuators in relation to the first Two bimetallic discs connect the changeover contacts before opening their changeover contacts.

The movable switch contacts may be provided on respective leaf springs. A third bimetallic disc may be provided with a switching temperature much higher than said first and second bimetallic discs, which acts on the sleeve actuator to open the changeover contacts of both . Under overheating conditions, this is an irreversible switch to effectively disable the appliance.

Description of drawings

An embodiment of the present invention will now be described with reference to the following drawings.

Fig. 1 is the perspective view of the control part of an embodiment of the present invention;

Figure 2a is a side view of the control member of Figure 1 in the off position;

Figure 2b is a side view of the control part of Figure 1 in the on position;

Figure 3 is a view of the rear of the control switch;

Fig. 4 is a rear perspective view;

Fig. 5 shows the front part of the control part with the thin plate on the cover removed;

Figure 6 shows a bimetallic element of a "dry boil" conversion part;

Figure 7 is an exploded view of the working parts of the control unit; and

Fig. 8 is an exploded view of the electrically conductive components of the control unit.

Detailed ways

Referring to the drawings, and first to Figures 1 and 2, these figures illustrate a control unit 2 according to an embodiment of the present invention. The control unit is of the general type used on electric water heaters, such as kettles or jugs, which include a recessed heating element. When installed, such a heating element projects laterally into the water-carrying jug from a top plate which is received in an opening in the side wall of the water-carrying jug near the bottom. The cold tails of the heating elements extend through the top plate and are electrically connected to the control components, as will be discussed further below.

When the water has reached the desired temperature, generally boiling, the control part can automatically disconnect the kettle, and when the automatic disconnection fails or when there is no water in the kettle but it is still heating, the control part provides overheating protection. This is the so-called "dry boil" protection.

The lower part of the control part has a substantially cylindrical cup-shaped hollow casing 4, which is made of injection molding material, and a plate-shaped support 6 protrudes upward from the casing 4. The housing 4 contains or supports most of the conversion components and is closed by an annular cover 8 with two screws 9 .

In front of the cover 8 is provided with a part of the conversion part that provides dry boil protection, that is to say, many bimetallic elements are fixed under a metal cover 10 with an annular opening (this will be discussed further below), through this annular opening The foremost bimetal element 62 can be seen. In use, the control unit is positioned so that the cover 10 is adjacent or close to a thermal contact having a hot spot at the tip of the heating element, as is known in the art.

A bimetal switching element 12 is arranged in front of the control switch 2 on the upper part of the support 6 . In this assembled kettle, the element 12 is arranged in a steam channel which communicates with the interior of the kettle so that steam flows through the element 12 . The element 12 is of known construction and is contained on a thin bimetallic disc which is slightly dished so that it can be dished back when it cools, this element 12 also has a A generally U-shaped opening forms a central tongue 14 . At a predetermined temperature, the element is snapped to an opposite position in which the element is reverse recessed. The perimeter 12 of the element is fixed so that the central tongue 14 moves rearwardly relative to the support 6 at a given temperature.

At the rear of the support 6 is a bistable lever 16, which can be seen very clearly in FIG. In a shallow groove in the rearwardly protruding claw 20 on the support 6, more specifically, in order to switch between the first (on) position (FIG. 2b) and the second (off) position (FIG. 2a) The first position refers to the position where the upper end of the lever is closest to the support 6, and the second position refers to the formation that the lower end of the lever leans against the housing 4 things. A C-shaped spring 22 is captured in compression between a shoulder 24 on the support 6 and under a pawl 26 at the upper end of the lever 16 . The upper end of the lever 16 also has a nose 28 which extends towards the element 12 so that when it is quickly switched to its hot position, the central tongue 14 of the element 12 engages with the nose 28, thereby allowing the eccentric lever to move from the The on position shown in 2b moves to the off position shown in FIG. 2a. The lower end of the lever has a bridge portion 30 with an actuating face 31 which bears on the ends of a pair of actuating rods 32, 33 which pass through the housing respectively. 4 Corresponding holes in the rear. The function of the actuation levers 32, 33 is described further below.

The control unit 2 provides an electrically conductive path between live, neutral and ground pins 34, 36, 38 protruding rearwardly, and when the control unit is installed in the kettle, these pins extend into the socket slot and, when When using the socket outlet, an accompanying plug or power cord is connected to the mains power source (not shown). In FIGS. 7 and 8 it is clearly seen that the pins 34, 36 and 38 have T-shaped ends.

Utilize the movable charged contact spring bar 40 to be provided with a switch at the charged side of this control part, contact piece 41 is arranged at the upper end of charged contact spring 40, fixed charging bar 42 has contact piece 44. The two opposing contact pieces 41, 44 may be discs made of silver or other electrical contact alloys. The fixing strip 42 extends near a flat portion of the contact piece 44 where the strip 42 is located in the housing 4 and the fixing strip 42 also has an upright arm terminating in a curved region 46 for use in the housing 4. , the strip 42 is secured at this region 46 to the live cold end of a heating element (not shown).

The movable live contact spring bar 40 has a lower rectangular hole through which the live pin 34 extends and at which the contact spring bar 40 is supported as a cantilever. An enlarged actuating surface 48 is located at a distance from pin 34 approximately two-thirds of the length of the contact spring bar.

A switch is also provided on the neutral side of the control part by means of a neutral fixed contact strip 50 having a structure similar to that of the contact strip 42 with a bent end 52, A contact strip is secured to the opposite neutral cold end of the heating element at end 52 and extends through the head of the element (not shown). The movable neutral contact spring strip 54 has a similar structure to the contact strip 40, with an enlarged actuation surface 56, and the opposite ends of the neutral contact strips 50, 54 have silver contact pieces 58, 59. The lower end of the movable spring contact strip 54 is secured to a dead pin 36 which extends through a rectangular hole therein.

The ground pin 38 is connected by a conductor 60 which is connected to the component head (not shown).

As shown in Figure 6, the dry-boil conversion element consists of a series of bimetallic discs, as is known, secured within a housing 10, which are recessed when cold. , with its concave surface facing the rear of the switch, which is to the right in Figure 6, and will quickly switch to the opposite configuration at a predetermined temperature. These discs provide a large force (typically 500gf) though only a relatively small distance of motion (typically about 1mm). Specifically, there is a first bimetal disc 62 which can be selected to switch rapidly at about 140°C and automatically return to its original state when cooled to a lower temperature, typically below 70 to 100°C. The second bimetallic disc 64 is separated from the first disc by a metallic heat conducting spacer ring 66, which is switched at a similar temperature as the first disc 62, and is likewise reversible when cooled. An optional third disc 68 may be inserted between the first and second discs 62, 64, it is selected to be switchable at a relatively high temperature, typically around 260°C, the third disc 68 acts as A backup switch, but it's not the type that snaps back automatically when it cools down, leaving the kettle essentially inoperable. However, disc 68 may be omitted if not desired. A bimetallic disc is operatively connected to the pair of changeover contacts by the actuating means now described. The first bimetal disc 62 acts on a push rod 70 which extends through the center hole of the second and third discs and through the opening of the push rod sleeves 72 of the second and third discs. Axial opening. Both the push rod 70 and the sleeve 72 protrude into the interior of the housing 4 through the opening in the cover 8 . Figure 7 shows the position of the push rod 70 and the sleeve 72 relative to the other work switching components. Between the push rod 70 and the sleeve 72 and the conversion contacts, there are charged and non-charged dry boiling conversion levers 74, 76. Both levers 74, 76 are rotatably mounted on a shaft 78, which is located near the lower ends of the two levers connected to the push rod 70 and the sleeve 72, generally at a third of the length of the lever. The live switching lever 74 has at its lower end a flat surface at 80 against which an end of the push rod 70 engages, and at its upper end 82 a ring which bears against the contact 40 The rear side of the actuation face 48 and the actuation rod 32 pass through the ring without hindrance so that the rear portion of the actuation face 48 can also be engaged. The lower end of the uncharged lever 76 has a ring 83 which is sized to allow the push rod 70 to pass therethrough without hindrance to an end 80 of the charged lever 74, but prevents the push rod sleeve 72 from passing through . There is a small gap between this ring 83 and the face 80 in order to allow the independent movement of the rod 76 when the contact pair 41, 44 cannot break. The upper end 85 of the lever 74 is engaged in the lower area 56 of the dead contact, and there is also an upper ring through which the actuating rod 33 extends unhindered to rest against the dead movable Contact elastic strip 54. Rotation of the lever near the lower end has the effect that a small distance of movement of the push rod and sleeve causes a larger displacement of the upper end of the lever engaging the contact spring bars 40, 54, a ratio of about 2:1. If the movement is confined to a welded live contact pair 41, 44, then additional movement is used to compensate for the loss of movement of the rod at the lower end.

In normal use of a kettle equipped with such a control unit 2, from the disconnected position (as shown in the figure), the user manually moves the button on the outside of the kettle, which is effectively connected to the lever 16, causing the lever to quickly eccentric Transition to the on position, in which the top of the lever is located near the bimetallic tongue 14 . When boiling, the bimetal 12 detects the steam and switches quickly to its hot position, the tongue 14 switches the lever 16 off-centre quickly to its off position, in which the lower end of the lever urges the actuating lever 32, 33 bears against the actuating faces 48, 56 and opens the contact pair. According to an aspect of the invention, the contact pairs are arranged to break sequentially, that is to say, the uncharged contact pair breaks momentarily before or after the live contact pair, thereby disengaging the kettle element sequentially from the uncharged and live contacts. On the one hand, to reduce the potential change at any moment of switching, thereby reducing the risk of arcing at the second contact. This can be achieved by configuring the lower end regions of the different rods on opposite sides, with the actuating surface 31 positioned slightly forward of the other actuating surface, so that the end of the rod 32 is slightly forward or slightly ahead of the rod 33. was joined afterwards. Alternatively, one of the actuating rods 32, 33 could be made longer than the other. Alternatively, the actuating rods 32, 33 may be of the same length, but the charged contact spring bar 40 is at a different distance from the end of the rod 32 than the uncharged spring bar 54 at the end of the rod 33. distance. Combinations of these methods or other methods with simple modifications can be used to ensure sequential opening of contact pairs.

In the boil-dry state, the steam detection bimetal 12 does not switch when there is no steam. In this case, the temperature of the heating element will rise above the normal operating temperature. The first bimetal 62 of the dry-boil switching element closest to the element head will switch first, causing the central area of the bimetal to move backwards, pushing the push rod 70 backwards and causing the lever 74 to rotate, opening the live contact pair 41,44 , thus disconnecting the power supply connected to the live terminals of the component. After a short time the bimetal 64 switches, moving the push sleeve 72 to the rear, causing the lever 76 to rotate and open the neutral pair of contacts 58,59. The time delay is determined by the precise transition temperature of the second bimetal 42 relative to the first bimetal and the heat transfer path between the disks 62 and 64 via the ring 66 and the outer shield 10 and the third bimetal disk 68. Determined by thermal conductivity.

Upon cooling, the bimetal 62, 64 returns to its cooled position, movable contact spring bars 40, 54 of the resiliently closed contact pair.

In case bimetallic 62 or push rod 70 or lever 74 or contact pair 41,44 welding went wrong, any one will transform shape in its corresponding temperature in bimetallic disk 64 or 68, move lever 76 And open contact pair 58,59, to close kettle.

Thus, the control unit can increase safety and has a very compact overall design.

Claims (20)

1. control assembly that is used to be equipped with the electric heater of electrical heating elements, this control assembly comprises the heat responsive element of response water boiling, and it is levied and is, and also comprising provides charged and electric conductor uncharged conducting path; The a pair of charged switch contact that has a movable contact in described charged conducting path is right; The a pair of uncharged switch contact that has a movable contact in described uncharged conducting path is right; Be suitable for acting on first actuating device on the described movable contact, respond described heat responsive element and when water seethes with excitement, sequentially disconnect described switch one by one.

2. control device according to claim 1, it is characterized in that, described first actuating device comprises an actuation lever, the one end is arranged to be worked by described heat responsive element, the other end bears against respectively and described charged and the first pair actuator lever of uncharged contact to linking to each other, and the described other end of this lever is configured to make it to engage an actuator lever before engaging another actuator lever to disconnect so that described order to be provided.

3. control device according to claim 1, it is characterized in that, described first actuating device comprises an actuation lever, the one end is arranged to be worked by described heat responsive element, the other end bears against respectively and described charged and the first pair actuator lever of uncharged contact to linking to each other, and described contact contrasts another contact is disconnected so that described order to be provided more close described actuator lever being arranged to wherein pair of contact.

4. control device according to claim 1, it is characterized in that, described first actuating device comprises an actuation lever, the one end is arranged to be worked by described heat responsive element, the other end bears against respectively and described charged and the first pair actuator lever of uncharged contact to linking to each other, and described actuator lever has different length and disconnects to guarantee described order.

5. control device according to claim 1 is characterized in that, described heat responsive element is a bimetal piece that changes its shape under predetermined temperature.

6. control device according to claim 1 is characterized in that, described actuation lever is the eccentric lever of a bistable spring biasing.

7. control device according to claim 1, it is characterized in that, also further comprise first and second heat responsive elements that respond overheated condition, and be arranged on actuating device between this first and second heat responsive element, this actuating device comprises first and second lever arms of installing rotationally, each lever arm has an end to link to each other with described heat responsive element, and the other end acts on respectively on the movable contact to disconnect this switch when responding overheated condition.

8. control assembly that overtemperature protection is provided that is used to be equipped with the electric heater of electrical heating elements, this control assembly comprise provides charged and electric conductor uncharged conducting path; The a pair of charged switch contact that has a movable contact in described charged conducting path is right; The a pair of uncharged switch contact that has a movable contact in described uncharged conducting path is right; Respond the first and second overheated heat responsive elements; Be arranged on the actuating device between this first and second heat responsive element, comprise first and second lever arms of installing rotationally, each lever arm has an end to link to each other with described heat responsive element, and the other end acts on respectively on the movable contact to disconnect this switch when responding overheated condition.

9. control device according to claim 8, it is characterized in that, described lever arm is installed rotationally, make their run-on point be positioned at a end than the more close lever that links to each other with this heat responsive element of the other end, thereby mobile being exaggerated of the displacement of the described other end pair this lever arm one end that links to each other with this heat responsive element.

10. control device according to claim 9 is characterized in that this lever is to rotate around the distance along its length 1/3rd,

11. 9 or 10 described control device according to Claim 8,, it is characterized in that, each comprises the bimetallic disk of depression described first and second heat responsive elements, when their temperature surpasses predetermined value, change, and cut this actuating device and comprise separately the actuator rod that between this bimetallic disk and this lever end, stretches.

12. control device according to claim 11, it is characterized in that, described bimetallic disk is arranged to be parallel to each other basically, the second bimetallic disk of close described lever end has a centre bore, this actuator rod comprises the sleeve of a hollow, and the described first bimetallic disk has an actuator rod, and described centre bore and described sleeve that it passes the second bimetallic disk are stretched over described lever end.

13. control device according to claim 12, it is characterized in that, this lever end that links to each other with this bimetallic disk overlaps mutually, that lever end overlapping with another lever end has an opening, the actuator rod of first disk stretches by this opening and can move unobstructedly, but described actuator sleeve can not be passed through.

14. control device according to claim 8, the contact that is suitable for sequentially disconnecting described switch under overheated condition is right.

15. control device according to claim 12 is characterized in that, the described second bimetallic disk supports on its peripheral intervals ground with a becket, thereby has a heat lag in use when heat arrives second and first disk.

16. control device according to claim 11, it is characterized in that, this bimetallic disk has same inversion temperature basically, thereby the first bimetallic disk was changed before the second bimetallic disk under overheated condition, thus the first bimetallic disk with switch contact that the second bimetallic disk links to each other before disconnect its switch contact by its corresponding lever and actuator.

17. control device according to claim 8 is characterized in that, described removable switch contact is arranged on the corresponding sheet spring.

18. control device according to claim 11, it is characterized in that also further comprise one the 3rd bimetallic disk, its inversion temperature is more much higher than the inversion temperature of the described first and second bimetallic disks, it acts on this sleeve actuator, disconnects both switch contacts.

19. control device according to claim 18 is characterized in that, described the 3rd bimetallic disk is irreversibly conversion under overheated condition, so that this electrical equipment can not be worked.

20. control device according to claim 8, it is characterized in that, also further comprise the heat responsive element and the actuating device that is suitable for acting on described movable contact of another response water boiling, respond described heat responsive element often in the water boiling and sequentially disconnect described switch one by one.

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