GB2107905A

GB2107905A - Temperature regulating apparatus for an installation, for example, a refrigeration plant

Info

Publication number: GB2107905A
Application number: GB08229995A
Authority: GB
Inventors: Gilbert Waldemar Jessen
Original assignee: Danfoss AS
Current assignee: Danfoss AS
Priority date: 1981-10-21
Filing date: 1982-10-20
Publication date: 1983-05-05
Also published as: DK445482A; IT1156000B; IT8268222A0; DE3141736C2; GB2107905B; DE3141736A1; JPS5880713A

Abstract

In a temperature regulating apparatus for an installation, particularly a refrigeration plant, there is a mains voltage part (12) comprising an appliance switch (7) which is actuated directly by a thermostat (8) for switching on a working appliance depending on the temperature control departure. A low voltage part 13 is connected free of potential to the mains voltage part (12) by way of a mains transformer (15) and comprises an electronic circuit (14) for monitoring and/or controlling operations of the installation. This circuit is fed with operating signals (Sg, So, St) from the mains voltage part by way of at least one coupling position (16, 20, 22) free from potential, eg, optical couplings. <IMAGE>

Description

SPECIFICATION Temperature regulating apparatus for an installation, for example, a refrigeration plant The invention relates to a temperature regulating apparatus for an installation, for example a refrigeration plant, comprising a mains voltage part having an applicance switch which is actuated directly by a thermostat for switching a working appliance on in dependence on the temperature control departure.

In refrigerator and freezer chests one nowadays uses temperature regulating apparatus in which the conductor at mains voltage leads to the refrigerant compressor by way of an appliance switch actuated by a thermostat. The thermostat and applicance switch are disposed in the refrigerated chamber and often form a constructional unit together with a lamp for illuminating the refrigerated chamber. This mains voltage part requires official approval in most countries so that all safety regulations are complied with.

It is already known (DE-OS 28 41 783) to provide an electronic circuit which is energised by low voltage and comprises a temperature responsive resistor to detect the temperature of the existing value of the refrigerated chamber and adjustable resistors for determining the desired value. The control line of a thyristor disposed in the mains lead of the refrigerant compressor is operated by way of a comparator. Luminous diodes included in the low voltage part indicate that a control voltage is present for operating the compressor, that the electronic circuit is functioning normally or that there is an excess temperature. Since the temperature sensor is accommodated in the low voltage part, the luminous diodes can be operated comparatively easily.However, one has to sacrifice the proven arrangement of an appliance switch which is actuated by a thermostat and is disposed directly in the mains voltage line. In addition, the mains voltage part and low voltage part are conductively interconnected, for which reason the low voltage part must conform to the same high safety requirements as does the mains voltage part.

The invention is based on the problem of providing a temperature regulating apparatus of the aforementioned kind wherein operations of the installation can be monitored and/or controlled whilst retaining the mechanical applicance switch which is actuated by a thermostat and is disposed in the mains lead to the working appliance.

This problem is solved according to the invention by a low voltage part which is connected free of potential to the mains voltage part by way of a mains transformer and comprises an electronic circuit for monitoring and/or controlling operations of the installation, operating signals being feedable to the electronic circuit from the mains voltage part by way of at least one coupling device free from potential.

The present invention provides: A regulating apparatus for a temperaturecontrolled installation, the apparatus comprising a mains voltage part having a switch which is actuated directly by a thermostat for switching on an operating unit in dependence on the temperature control departure, and a low voltage part isolated from the mains voltage part by way of a mains transformer and comprising an electronic circuit for monitoring and/or controlling operations of the installation, operating signals being in use, fed to the electronic circuit from the mains voltage part by way of at least one potential-free coupling device.

In this arrangement, the low voltage part is galvanically separate from the mains voltage part.

Since the low voltage is harmless, no safety requirements have to be met for the entire apparatus other than for the appliance switch alone. Outlet lines for monitoring and/or control elements are at a low voltage and can therefore be placed where desired. Consequently, the user of such temperature regulating apparatuses can, without the need for obtaining permission from the authorities, individually design his installation such as a refrigerator or freezer chest. Since the applicance switch is actuated directly from the thermostat, it is not necessary to transmit an appropriately strong signal from the low voltage part to the mains voltage part. Conversely, only very small energies have to be transmitted as operating signals so that correspondingly simple and cheap coupling devices free from potential will result. The arrangement can therefore be made comparatively cheaply.

With particular advantage, the thermostat, the appliance switch, the mains transformer, the at least one coupling device free from potential, and the electronic circuit are combined as one constructional unit. This constructional unit can be placed directly in the chamber of which the temperature is to be monitored. This constructional unit is, as is usual for an appliance switch, connected to a mains conductor for which the usual safety requirements apply. All other connecting lines are at low voltage and can therefore be installed where desired.

It is also desirable if the constructional unit includes the lamp for illuminating the refrigerated chamber because in that case still more connections can be made within the constructional unit.

In a preferred embodiment, the coupling device free from potential comprises a light transmitter and a light receiver. The light transmitter may be a mains voltage glow lamp and the light receiver a low voltage phototransitor. Compared with a coupling device with a luminous diode and a phototransistor, the latter provides a solution which consumes very little energy.

Advantageously, one appliance operating signal is tapped between the appliance switch and working appliance. This appliance operating signal indicates that voltage is applied to the compressor.

Further, the thermostat may comprise a second switch which is operable at a higher temperature than the appliance switch and from which an excess temperature operating signal can be tapped. This excess temperature operating signal is produced only when an excess temperature obtains.

It is also possible to tap a door operating signal between the door contact of a refrigerated chamber and the lamp for illuminating the refrigerated chamber. This door operating signal obtains whenever the illumination for the refrigerated chamber is switched on, i.e. when the door is open.

In a preferred embodiment, the low voltage part comprises optical and/or acoustic signal generators. These signal generators can be applied to the outside of a refrigerator or the like so that they will be visible at all times or can be well heard.

In a preferred embodiment, the low voltage part comprises a relay coil which switches on an auxiliary switch in shunt with the appliance switch when a freeze signal and an appliance operating signal are present simultaneously. This auxiliary switch allows the refrigerant compressor to continue to run even if the appliance switch opens again. It can, however, be designed to be comparatively weak because it will never carry the full switching on current. This is because the appliance switch is already on in the presence of the appliance operating signal. A very low rated relay will therefore suffice.

The freeze signal is preferably supplied with the aid of a switch in the low voltage part.

Freezing can therefore be started at will.

Desirably, the electronic circuit comprises a timer which switches the relay off after a predetermined freezing period. The apparatus will thereafter operate normally.

The freezing period is preferably set with the aid of a potentiometer.

The low voltage part preferably comprises a switch for switching off the signal generators and/or the relay. In this way an alarm or the freezing process can be switched off.

In a preferred embodiment, the electronic circuit comprises a change-over switch which, on the occurrence of an excess temperature operating signal, actuates a first type of signal and, on the disappearance of this operating signal, actuates a second type of signal. The second type of signal indicates that an excess temperature has existed and that the food may therefore be spoilt.

Another way of monitoring is for the electronic circuit to comprise a timer which is actuated on the occurrence of the door operating signal and allows a signal generator to respond after a predetermined period. The user is therefore made aware that the door has been opened for too long, for example more than 20 seconds.

Further, the electronic circuit may comprise a timer which, in the absence of the appliance operating signal, switches on the relay beyond a predetermined period. The absence of the applicance operating signal indicates that the appliance switch is no longer functioning. Its function is then taken over by the relay and the working appliance is operated continuously to keep the damage to a minimum. If this should damage the relay switch, this is unimportant because the appliance switch has to be repaired anyway.

Preferably, a transparent plastics socket comprises two receptacle apertures extending from both ends for the light transmitter and the light receiver and the dividing wall left therebetween is in the form of a convex lens. This gives a compact and simple unit for the light coupling position, both the light transmitter and light receiver being well centred and no separate component being necessary for the lens.

The plastics socket with inserted light transmitter and light receiver may be surrounded by a tube of shrink film which is somewhat longer than the socket. The shrunk-on tube keeps all the parts securely in position.

A temperature regulating apparatus as constructed in accordance with the invention will now be described by way of example only with reference to the accompanying drawings in which: Fig. 1 is a circuit diagram of the temperature regulating apparatus according to the invention; Fig. 2 shows a freezer unit with the temperature regulating apparatus built-in and Fig. 3 shows one embodiment of a light coupling device.

According to Fig. 1, a double pole main switch 1 is provided which connects a conductor 2 at mains line voltage and a mains neutral conductor 3 to appropriate leads 4 and 5 of the motor 6 of a small freezer unit. Switching on of the motor is performed with the aid of an appliance switch 7 actuated by a thermostat 8. As usual, the thermostat 8 comprises a temperature sensor and a desired value setting knob 9. Further, there is a door contact 10 which closes when the door is opened and energises a lamp 11 for illuminating the freezer chamber. The arrangement as described thus far is nowadays conventional for freezer units. The arrangement described thus far is designated as the mains voltage part 12. In addition, there is a low voltage part 13.The latter comprises an electronic circuit 1 4 which is coupled to the mains voltage part 12 by way of a mains isolating transformer 1 5 providing a potential-free coupling. The low voltage part 14 is supplied with DC voltage by way of this mains transformer 15, rectifiers, smoothing components and voltage limiters. By way of a potential-free coupling device 16, an appliance operating signal Sg/ derived from the point 17 between the appliance switch 7 and motor 6, is fed to the electronic circuit 14 when the appliance switch 7 is closed. The coupling device 16 comprises a neon glow discharge lamp 18 and a phototransistor 19.

An excess temperature signal 5a is fed to the circuit 1 4 by way of a similar potential-free coupling device 20 when an excess temperature switch 21, which the thermostat 8 also controls, is switched on. By way of a third potential-free coupling device 22, a door open signal St derived from the point 23 between the door contact 10 and lamp 11 is fed to the circuit 14 when the door contact 10 is closed, that is when the door is open. A relay 24 is arranged to actuate a switch 25 which bridges the appliance switch 7, so that the motor 6 continues to run even when the appliance switch 7 opens. Further, three signal lamps are provided, namely a green signal lamp 26, a red signal lamp 27 and a yellow signal lamp 28.There is also an acoustic alarm generator 29, a switch 30 for initiating a freeze signal Se/ and a switch 31 which delivers a switching off signal Sa for switching off the light and sound signal devices 27 to 29 and for switching off the relay coil 24.

The broken outline shown in Fig. 1 indicates a constructional unit 32 which contains the thermostat 8 with appliance switch 7 and the additional switch 21, the mains isolating transformer 13, the potential-free coupling devices 1 6, 20, and 22, the relay 24 with its contact 25, and the electronic circuit 14. This constructional unit 32 can, if desired, include also the chain-dotted part 33 so that the lamp 11 for illuminating the chamber is additionally included.

All the conductors extending from the mains voltage part to the coupling devices and to the transformer 15 are included in the constructional unit. This constructional unit 32 is built into a conventional freezer cabinet 35 (Fig. 2) of which the door 36 operates the door contact 10 (not shown). The desired value setting knob, the three signalling lamps 26, 27, 28, the acoustic alarm generator 29, the main switch 1, the freeze switch 30 and the switch 31 for switching the individual operations off are accommodated in an upper console 37. As shown in Fig. 2, it is also possible to combine the mechanical parts in a first group 32a and the electrical parts in a second group 32b and to accommodate them at different locations of the freezer cabinet.

This temperature regulating apparatus can perform the following operations: a) When the appliance switch 7 is switched on, the appliance operating signal S9 causes the green signalling lamp 26 to light to indicate operation.

b) If an excess temperature occurs and the switch 21 is closed, the excess temperature signal SO causes also the red signalling lamp 28 to light up and the acoustic signal generator 29 to respond.

c) When the excess temperature recedes, that is the excess temperature operating signal SO disappears, the acoustic alarm generator 29 nevertheless remains switched on. The red signalling lamp 28 is caused to change to a second type of signalling, namely a flashing light. The user will therefore know that an excess temperature had occurred in the meantime and that the goods in the freezer could possibly be spoilt.

d) For freezing; the switch 30 is depressed. The freeze signal 5e causes the relay 24 to respond if the appliance switch 7 is already switched on and an appliance operating signal S, is present. The switch 25 need therefore not switch the full switching-on current and can be designed with a correspondingly low switching capacity. The freeze condition is indicated by the yellow signal lamp 27. A timer (not shown) in the electronic circuit, e.g. an electronic timer operated by a pulse generator, keeps the relay 24 energised during the whole of a predetermined switching-on period. The switch 25 will open only after the predetermined period, for example 24 hours, so that the thermostat can again operate normally. If desired, the freezing period can be varied by a potentiometer at the operating panel 37.

e) If the door is opened, the door operating signal St ensures that a timer in the electronic circuit 14 is again set in operation to switch the acoustic signal generator 29 on after a predetermined period, for example 20 seconds.

f) Every time the appliance switch 7 opens and the appliance operating signal S, disappears, a further timer is set in motion which causes the relay 24 to respond after a predetermined period, for example 10 hours, so that the switch 25 starts the motor 6 independently of the appliance switch 7, a possible sacrifice being damage to the switch 25. Such emergency operation is indicated by flashing of the yellow signal lamp.

g) Upon actuation of the switch 31, the switching-off signal Sa causes the giving out of signals and/or the freezing process to be switched off. Thus the switch 31 resets all functions and stops freezing if freezing has been selected. Modifications can be made in this respect, for example so that, in the presence of the excess temperature, only the acoustic alarm will be switched off but not the optical indication.

Fig. 3 shows a socket 37 of transparent plastics material containing a first receptacle 38 for the diagrammatically illustrated glow lamp 18 and a second receptacle 39 for the diagrammatically indicated phototransistor 1 9.

The dividing wall 40 between the two receptacles 38 and 39 is in the form of a convex lens. A shrink film tube 41 which is longer than the socket 37 surrounds the whole and at the same time the shrunk ends 42 and 43 secure the glow lamp 18 and phototransistor 1 9 in their positions.

The construction of the electronic circuit 14 is well within the scope of a man skilled in the art because we are here merely concerned with simple interlinking of input and output signals or storage and delay procedures. The appropriate circuits are simple to design.

Claims

1. A regulating apparatus for a temperaure controlled installation, the apparatus comprising a mains voltage part having a switch which is actuated directly by a thermostat for switching on an operating unit in dependence on the temperature control departure, and a low voltage part isolated from the mains voltage part by way of a mains transformer and comprising an electronic circuit for monitoring and/or controlling operations of the installation, operating signals being, in use, fed to the electronic circuit from the mains voltage part by way of at least one potential-free coupling device.

2. Apparatus according to claim 1, wherein the thermostat, the switch, the mains transformer, the at least one potential-free coupling device, and the electronic circuit are physically combined as a constructional unit.

3. Apparatus according to claim 2, for a refrigeration apparatus wherein the constructional unit includes a lamp for illuminating the refrigerated chamber

4. Apparatus according to any one of claims 1 to 3, wherein the at least one potential-free coupling device comprises a light transmitter and a light receiver.

5. Apparatus according to clairr 4, wherein the light transmitter is a mains voltage glow lamp and the light receiver is a low voltage phototransistor.

6. Apparatus according to any one of claims 1 to 5, wherein, in use, one appliance operating signal is derived from a point between the switch and the operating unit.

7. Apparatus according to any one of claims 1 to 6, wherein the thermostat comprises a second switch which is arranged to operate at a higher temperature than the first-mentioned switch and from which, in use, an excess temperature operating signal is tapped.

8. Apparatus according to any one of claims 1 to 7, for a refrigeration apparatus wherein, in use, a door operating signal is tapped between the door contact of a refrigerated chamber and a lamp for illuminating the refrigerated chamber.

9. Apparatus according to any one of claims 1 to 8, wherein the low voltage part comprises optical and/or acoustic signal devices.

1 0. Apparatus according to any one of claims 1 to 9, for a refrigeration apparatus wherein the low voltage part comprises a relay coil which, in use, switches on an auxiliary switch in shunt with the first-mentioned switch when a freeze signal and an operating signal are present simultaneously.

11. Apparatus according to claim 10, wherein the low voltage part comprises a switch for delivering a freeze signal.

12. Apparatus according to claim 10 or claim 11, wherein the electronic circuit comprises a timer arranged to switch the relay off after a predetermined freezing period.

1 3. Apparatus according to claim 12, further including a potentiometer for setting the freezing period.

1 4. Apparatus according to any one of claims 9 to 13, wherein the low voltage part includes a switch for switching off the signal generators and/or the relay.

1 5. Apparatus according to any one of claims 1 to 14, wherein the electronic circuit comprises a change-over circuit which, in use, on the occurrence of an excess temperature operating signal, actuates a first type of signal and, on the disappearance of this operating signal, actuates a second type of signal.

1 6. Apparatus according to any one of claims 1 to 15, for a refrigeration apparatus with a door wherein the electronic circuit includes a timer which, in use, is actuated on the occurrence of a door operating signal and allows a signal generator to respond after a predetermined period.

1 7. Apparatus according to any one of claims 10 to 16, wherein the electronic circuit comprises a timer which, in use, in the absence of the appliance operating signal, switches on the relay (24) when a predetermined period is exceeded.

1 8. Apparatus according to claim 4 or claim 5, wherein a transparent plastics socket comprising a respective receptacle opening extending from each end is provided for the light transmitter and the light receiver and the dividing wall left between the openings is in the form of a convex lens.

1 9. Apparatus according to claim 18, wherein the plastics socket with inserted light transmitter and light receiver is surrounded by a tube of shrink film which is somewhat longer than the socket.

20. A regulating apparatus for a temperaturecontrolled installation, the apparatus being substantially as herein described with reference to, and as illustrated by, Figure 1 of the accompanying drawings.

21. Apparatus as claimed in claim 20 including a light coupling device substantially as herein described with reference to, and as illustrated by, Figure 3 of the accompanying drawings.

22. A temperature controlled installation including apparatus as claimed in any preceding claim.

23. An installation as claimed in claim 22 comprising a freezer unit substantially as herein described with reference to, and as illustrated by, Figure 2 of the accompanying drawings.