US3735308A

US3735308A - Energy regulators

Info

Publication number: US3735308A
Application number: US00188125A
Authority: US
Inventors: G Shepherd
Original assignee: HARPER WYMAN COMP
Current assignee: HARPER WYMAN COMP
Priority date: 1968-09-27
Filing date: 1971-10-12
Publication date: 1973-05-22
Anticipated expiration: 1990-05-22
Also published as: GB1282524A

Abstract

An energy regulator for the intermittent supply of power to a load at high effective power levels. It includes contacts adapted to be connected in series with an electrical supply and a load, a bimetal element mechanically coupled to the contacts, and a heater for the bimetal element connected across the contacts, the contacts being closed, in use, in response to deflection of the bimetal element when it is heated.

Description

United States Patent [1 1 Shepherd May 22, 1973 [54] ENERGY REGULATORS [56] References Cited [75] Inventor: geoi'gedRonald Shepherd, Norfolk, UNITED STATES PATENTS ng an 1,840,114 1/1932 Lazich ..337/3 X Asslgneei p y p y, Hmsdale, 2,403,803 7/1946 Kearsley ..337/1 ux Ill.

Primary ExaminerRoy N. Envall, Jr. F 2, [22] fled Oct 1 1971 Attorney- Parker, Plyer 8L McEachran [21] Appl. No.: 188,125

[57] ABSTRACT [30] Foreign Application Priority Data An energy regulator for the intermittent supply of power to a load at high effective power levels. It in- Sept Great f f cludes contacts adapted to be connected in series with Oct. 15, 970 Great ntam 0 an electrical Supply and a load a bimetal element mechanically coupled to the contacts, and a heater for [52] US. Cl ..337/l3, 337/103 the bimetal element connected across the contacts, [5 II.- Cl. i the contacts being closed in in response to Fleld of Search deflection of the element when i i heated.

2 Claims, 1 Drawing Figure ENERGY REGULATORS SUMMARY OF THE INVENTION The present invention relates to energy regulators, more particularly to energy regulators for the intermittent supply of power to a load.

Energy regulators for control of heating power on domestic cooker hotplates and grill elements are well known. They usually comprise a micro-switch with normally closed contacts operated by a bimetal strip with an associated heater connected in parallel with the load; the bimetal strip deflects under the influence of its heater until the micro-switch contacts break. When the contacts break, they disconnect the bimetal heater, and also the supply to the load. The bimetal gradually cools down until the contacts reclose, and the sequence is then repeated.

The effective power fed to the load is thus varied as the ratio of the ON time to the total cycle time.

For hotplate applications it is generally desirable to achieve low effective power levels, i.e. relatively short ON periods and relatively long OFF periods, and in this respect constructions of the above known type can be said to function reasonably well. For grill and rotisserie usage, however, it is desirable to achieve high effective power levels, i.e. relatively long ON periods and relatively short OFF periods.

The thermal characteristics of known bimetal systems do not lend themselves to stable control at high effective power levels. Attempts to surmount this problem have involved the fitting of a further contact to the switch mechanism in place of the usual backstop, thus providing a single-pole changeover switch in place of the usual-pole single-throw switch. The contact which replaces the backstop is connected to the load, and connects the supply to the load whenever the thermal action of the bimetal operated the switch to the condition which disconnects the bimetal heater.

While this serves the purpose of controlling power at high effective levels, the complication of construction involved in fitting the extra contact and its associated connections makes an uneconomical arrangement for the low-cost market where such controls are needed.

An object of the present invention is to alleviate at least one of the above described shortcomings of known energy regulators.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides an energy regulator comprising contacts adapted to be connected in series with an electrical supply and a load, a bimetal element mechanically coupled to the contacts, and a heater for the bimetal element connected across the contacts, the contacts being closed, in use, in response to deflection of the bimetal element when it is heated.

The contacts may be part of a snap-action switch.

The present invention can provide an energy regulator which provides efficient and reliable control of power at high power levels without using a changeover switch mechanism, and with a simplification of installa- 2 tion wiring.

An energy regulator according to the invention will now be described, by way of example only, with reference to the accompanying drawing, which is a schematic diagram of the energy regulator.

For clarity no cam adjustment has been shown in the drawing (a cam mechanism is incorporated in the control device to allow the user to select the desired effective heating). Also for clarity, the ambient temperature compensation bimetal has not been shown.

With reference to the drawing, a bimetal l, heated by a heater 2, warps with temperature rise in the direction of an arrow 3. Numeral 4 denotes a snap-action contacts coupled to the bimetal 1, 5 a load such as the grill element of a cooker, and 6 a small isolating switch. The heater 2 is connected in series with load 5 between live and neutral terminal, 7 and 8. The direction of warp of the bimetal 1 is to close the contacts 4, i.e. the opposite from that used on known energy regulators.

Initially, current flow will be from line terminal 7 through switch 6, heater 2 and load 5 to neutral terminal 8. Heater 2 will typically have a resistance of about 13,000 ohms, and the load 5 will have a resistance of about 19 ohms for a 3kw loading value: thus almost the full supply voltage will be applied across the heater 2. The heater 2 will cause the bimetal l to warp in the direction of arrow 3 until ultimately the contacts 4 close. With the contacts 4 closed, the full supply voltage appears across the load 5, the heater 2 being shortcircuited. The bimetal 1 then cools down and when it is cooled sufficiently the contacts 4 re-open, and the supply voltage is again applied across the bimetal l with negligible power dissipated in the load 5.

This cycling condition continues indefinitely, the rate of cycling and thus the effective power fed to the load being varied by adjusting the relative positions of the bimetal and contacts 4 or that of the fixed contact of the contacts 4.

The switch 6 is provided to disconnect the heater 2 when the control dial is turned to its OFF position.

On known energy regulators with high resistance heaters, the heater for the bimetal is connected in parallel with the load being controlled, and this requires the neutral lead to be taken to the regulator; thus three leads must be taken to the regulator, LINE, LOAD, and NEUTRAL. In the described construction only two leads are required, LINE and LOAD.

I claim:

1. An energy regulator providing contacts adapted to be connected in series with an electrical supply and a load, a bimetal element mechanically coupled to the contacts, a heater for the bimetal element connected across the contacts and in series with the load, and a switch connected in series with the heater across the contacts with the switch being opened in the OFF position of the regulator, the contacts being closed, in use, in response to deflection of bimetal element when it is heated.

2. An energy regulator as claimed in claim 1 wherein the contacts are part of a snap action switch.