GB2114428A - Egg boiler - Google Patents

Abstract

An egg boiler comprises a separable egg-holder which engages a reciprocable member 4 within an electrically heated cooking vessel. An electrical circuit is provided with a thermal switch, external but in intimate contact with the vessel, to effect at a set temperature an attenuation of the heating simultaneously with a commencement of a timing cycle through an electronic timer. In addition this circuit has means of self adjustment to compensate for a possible change of the initial starting temperature. <IMAGE>

Description

SPECIFICATION Pop-up egg boiler The invention herein described has been designed to to cook an egg to a preferred degree of consistency by electrical heating of water in which it is immersed for a set period of time; to then terminate the cooking process by raising the egg from the hot water and disconnect the electrical power at the same time. Furthermore, the design incorporates means for maintaining the same degree of consistency if the cooking of a second egg closely follows the first, irrespective of the higher initial temperature of the containing water.

A detailed account of the essential parts of one embodiment of this invention will now be described with reference to accompanying drawings: Figure 1 shows an external view of the device. The egg (1 ) is held in a holder (2) of folded sheet aluminium in which there is a hole whose diameter is just sufficient to prevent the egg passing through.

This holder is a separate part but in operation it is placed astride the water vessel or tank (3) with its sides supported by the metal lugs of a movable cradle (4) (only the far - side support is shown in this figure). This cradle is caused to slide vertically down the outer sides of the tank when the handle (5) which is linked to it, is pushed downwards; so causing the supported egg to be lowered into the tank.

Figure 2 shows the tank (3) removed from the main body so as to show its spout (6) and thermal switch (7) integral with its bottom. Normally the tank is held in position, as shown in Figure 1, by the fixture at each end of electrical immersion heaters (8 & 9) shown here in broken line form. These two heaters are sufficiently separated apart to allow the lower portion of the egg to lie between them when the cradle is fully lowered. Also shown in Figure 1 is the toggie of a three position switch (10). Positions are designated 'S', 'H' or 'M' as reference to the desired degree of cooking viz. Soft, Hard or Medium respectively.

Figure 3 shows the body of the device when stripped of its outer covering and with tank and immersion heaters removed. This reveals how the lugs of the cradle (4) slide down the bars of a cage forming the enclosure forthe tank and are held together by a barwhich locates in slots cut vertically in the body. (Please note that this end view depicts the opposite end to that shown in Figure 1).

Attached to the cradle through one of the slots is a short arm (11). Vertical downward movement of the cradle also results in downward movement of the arm and in the lowest position the extremity of the arm impinges upon the insulated top face of a double lever switch (12) causing it to close its contacts. Also shown in Figure 3 is (a) a hole (13) through which the spout (6) passes (b) Electronic components board (14) (c) Small transformer (15) attached to the body.

Figure 4 shows a view of the exposed body turned up-side-down. (the end view depicted here is the same as that shown in Figure 1). This reveals the inner mechanism of the handle (5) and its attachmentto the catch (16) and spring (17) via an arm which slides down a rod thus raising and lowering the cage through slots in the body. In the lowest position the spring is extended and the catch will latch with a hinged armature of the solenoid (18) when it is in the unenergised state. In the energised state magnetic movement of the solenoids armature causes the catch to release, so freeing the cradle and allowing it to rise under the pull of the spring. Also shown in Figure 4 are (a) the three position switch (10) and (b) the thermal switch (7).

The operaton of the electrical circuit will now be described with reference to the schematic diagram shown in Figure 5.

Before plugging in to the mains, water must be poured into the tank until it reaches a level just below the inner port of the spout. Having plugged in and switched on and with an egg placed in the holder, positioned astride the ta.nk, the handle is depressed to the lowest position where it should hold latched down. The egg will now be completely immersed in the water and the neon signal lamp will glow brightly, indicating that the mains A.C. power is connected. This is because as explained earlier switch (12) has been closed by the action of lowering the cradle (4) with attached arm (11). Current now flows via contacts Al of unenergised relay 'A' to power the immersion heater (9) and also through the contacts of the thermal switch (7) to power the immersion heater (8) causing the water to rapidly heat up.Note that the transformer (15) is not active at this stage because its primary windings are shorted by the thermal switch contacts. However when the water reaches a temperature of approxi mately 95 C the action of the thermal switch causes these contacts to open and current is diverted through the transformers primary windings thus greatly reducing the amount of current passing through immersion heater (8). The low voltage A.C.

current now flows from the secondary of the trans formerthrough rectifiers D2a & D2b to charge the reservoir capacitor C1 with a D.C. voltage, which is applied via restor R2 to the coil of relay 'A'. This has three physical effects:- (1 ) Changeover contacts Al break causing immersion heater (9) to be fed via diode rectifier D1 at half power (2) Contacts A2 will break, thus freeing capacitor C3 from its previously shorted state (3) The glow from the neon will halve showing a rectified A.C. condition. The half power - now applied to the immersion heater (9) is just sufficient to maintain simmering. At the same time voltage is applied to the solid state timer ZN 1034 E which immediately starts its timing cycle.The length of time period between the input of power to the solid state timer and an output from it is dependent upon the value of the capacitor C3 together with the associated resistances R4, R5, R6, R8 & T1. The capacitor value is fixed but the resistance value may be changed. The change is effected by means of the three position switch and its associated resistance network. Notethatthe FETtransistorT1 is in a passive state and will have a fairly low resistance; s largely bipassing R4 at this stage. When the predetermined period of delay has expired the solid state timer will output a current via R9 to energisethe relay 'B'.This, inturn closes contact B1 so allowing A.C. current to energisethe solenoid (18) which immediately trips the catch (16) releasing the cradle (4) which rises and in so doing allows the lever switch (1 2j to separate thus disconnecting the main electrical power.

With the boiled egg now raised clear of the water further cooking is suspended. It will, however remain under warm conditions for sometime until the recipient lifts the holder from the cradle and transfers the boiled egg to their plate. If now or soon afterwards a second egg is required to be cooked the described procedure may be repeated but it would not result in the same degree of cooking unless certain compensations are made. This is because in the first place the cooking of the egg would now start in hot water and in the second place if its temperature was in the range 90"C to 100'C the thermal switch (7) would already be open and the timing period would start immediately.

In practice it has been found that the second effect outweighs the first and it is necessary to extend the timing period by a variable amount in order to achieve consistent results.

Referring back to Figure 5 it will be recalled that the solid state timer's output changed state when the predetermined period of delay had expired. Now diode D3 is connected to an output which is complementary to that formerly described and at the moment of termination its anode, (which had previously been at line potential) is switched to ground potential causing it to be foreward biased. This allows the capacitor C2 to charge to full potential and D3 isolates the charge when power is cut off. Now this charge becomes instrumental when cooking is repeated soon after the first application because it activates the FET transistor T1 causing its effective resistance to be greatly increased. Moreover T1 now acts as a variable resistance whose resistance change is dependant upon the value of the charge in the capacitor C2.Therefore the duration of the time delay is increased by an amount which is related to the value of charge in capacitor C2. If the rate of decay of the charge with time is arranged to be substantially similar to the rate of cooling of the water, (over the limited range 90"C - 98"C) consistency of cooking is achieved. The introduction of this compensation does not affect the correct variations of time for Soft, Medium or Hard boiled eggs.

On completion the water may be retained in the tank or emptied away as follows: First disconnect the device from the electricity supply and then by gently tilting towards the spout allow the water to flow out as with a kettle or tea-pot.

CLAIMS (Filed on 20 Dec 1982) I declare that what I claim is: 1. A culinary utensil in which a sliding platform is arranged to move in a vertical plane relative to a secured tank and also a separate but related holder or egg-rack so constructed that when positioned upon the raised platform, so as to lay astride the tank, the contained egg or eggs will be lowered into the tank as the sliding platform is moved downwards.

2. A culinary utensil as claimed in claim (1) in which the sliding platform is spring-loaded so as to cause the platform to be biased towards the raised position. So that if the sliding platform is moved down to the lowest position and held by a latch, it will rise under the action of the spring if the latch is released.

3. A culinary utensil as claimed in claim (1) and (2) in which the latch may be released by means of an energised electrical solenoid.

4. A culinary utensil as claimed in claim (1), (2) and (3) in which the energising of the solenoid is delayed for a variable period of time under control from an electronic timer under programmable supervision.

5. A culinary utensil as claimed in claim (1) and (2) in which the sliding platform is caused to impinge with and actuate an electrical switch when in the lower position.

6. A culinary utensil as claimed in claim (1) in which water held within the tank may be heated to boiling point by means of electrical immersion heaters.

7. A culinary utensil as claimed in claims (1) and (6) in which a thermal-switch is attached to the external surface of the tank so as to detect a specific temperature of the water within the tank.

8. A culinary utensil as claimed in claims (1, 2, 3, 4, 5, 6, and 7) in which the action of the thermalswitch should simultaniously reduce the heating power and initiate the timing cycle.

9. A culinary utensil as claimed in claims (1,2,3, 4,5,6 and 7) in which the control programme of the electronic timer adjusts for the discrepancy initial temperature condition when a second boiling operation closely follows that of the first.

10. A culinary utensil as claimed in claims (1-9) constructed and arranged substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. relay 'B'. This, inturn closes contact B1 so allowing A.C. current to energisethe solenoid (18) which immediately trips the catch (16) releasing the cradle (4) which rises and in so doing allows the lever switch (1 2j to separate thus disconnecting the main electrical power. With the boiled egg now raised clear of the water further cooking is suspended. It will, however remain under warm conditions for sometime until the recipient lifts the holder from the cradle and transfers the boiled egg to their plate. If now or soon afterwards a second egg is required to be cooked the described procedure may be repeated but it would not result in the same degree of cooking unless certain compensations are made. This is because in the first place the cooking of the egg would now start in hot water and in the second place if its temperature was in the range 90"C to 100'C the thermal switch (7) would already be open and the timing period would start immediately. In practice it has been found that the second effect outweighs the first and it is necessary to extend the timing period by a variable amount in order to achieve consistent results. Referring back to Figure 5 it will be recalled that the solid state timer's output changed state when the predetermined period of delay had expired. Now diode D3 is connected to an output which is complementary to that formerly described and at the moment of termination its anode, (which had previously been at line potential) is switched to ground potential causing it to be foreward biased. This allows the capacitor C2 to charge to full potential and D3 isolates the charge when power is cut off. Now this charge becomes instrumental when cooking is repeated soon after the first application because it activates the FET transistor T1 causing its effective resistance to be greatly increased. Moreover T1 now acts as a variable resistance whose resistance change is dependant upon the value of the charge in the capacitor C2.Therefore the duration of the time delay is increased by an amount which is related to the value of charge in capacitor C2. If the rate of decay of the charge with time is arranged to be substantially similar to the rate of cooling of the water, (over the limited range 90"C - 98"C) consistency of cooking is achieved. The introduction of this compensation does not affect the correct variations of time for Soft, Medium or Hard boiled eggs. On completion the water may be retained in the tank or emptied away as follows: First disconnect the device from the electricity supply and then by gently tilting towards the spout allow the water to flow out as with a kettle or tea-pot. CLAIMS (Filed on 20 Dec 1982) I declare that what I claim is:

1. A culinary utensil in which a sliding platform is arranged to move in a vertical plane relative to a secured tank and also a separate but related holder or egg-rack so constructed that when positioned upon the raised platform, so as to lay astride the tank, the contained egg or eggs will be lowered into the tank as the sliding platform is moved downwards.

2. A culinary utensil as claimed in claim (1) in which the sliding platform is spring-loaded so as to cause the platform to be biased towards the raised position. So that if the sliding platform is moved down to the lowest position and held by a latch, it will rise under the action of the spring if the latch is released.

3. A culinary utensil as claimed in claim (1) and (2) in which the latch may be released by means of an energised electrical solenoid.

4. A culinary utensil as claimed in claim (1), (2) and (3) in which the energising of the solenoid is delayed for a variable period of time under control from an electronic timer under programmable supervision.

5. A culinary utensil as claimed in claim (1) and (2) in which the sliding platform is caused to impinge with and actuate an electrical switch when in the lower position.

6. A culinary utensil as claimed in claim (1) in which water held within the tank may be heated to boiling point by means of electrical immersion heaters.

7. A culinary utensil as claimed in claims (1) and (6) in which a thermal-switch is attached to the external surface of the tank so as to detect a specific temperature of the water within the tank.

8. A culinary utensil as claimed in claims (1, 2, 3, 4, 5, 6, and 7) in which the action of the thermalswitch should simultaniously reduce the heating power and initiate the timing cycle.

9. A culinary utensil as claimed in claims (1,2,3, 4,5,6 and 7) in which the control programme of the electronic timer adjusts for the discrepancy initial temperature condition when a second boiling operation closely follows that of the first.

10. A culinary utensil as claimed in claims (1-9) constructed and arranged substantially as described with reference to the accompanying drawings.