US2133888A - Electric circuit arrangement for contact-pointer thermostats and like instruments - Google Patents

Description

Oct. 18, 1938. BLQCH 2,133,888

ELECTRIC CIRCUIT ARRANGEMENT FOR CONTACT POINTER THERMOSTATS AND LIKE INSTRUMENTS Filed Jan. 10, 1935 L Z2 Z:

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UNITED STATES PATENT OFFICE ELECTRIC CIRCUIT ARRANGEMENT FOR CONTACT-POINTER THERMOSTATS AND LIKE INSTRUMENTS Franz Georg Bloch, Leitmeritl, Clechoslovakia Application January 10, 1935, Serial No. 1,238 In Czechoslovakia January 10, 1034 4 Claims. (Cl. 219-20) This invention relates to an electric circuit arvoltage occurs. With the arrangement of the rangement for thermostats having pointers present invention, on the contrary, only a slight adapted to act as contacts and for like instruchange of voltage, if any, occurs in the circuit ments provided with a contact pointer and two on the contacts being opened, and consequently,

5 adjustable contacts, and serving for the electrical the burning of the contacts is very considerably I control of temperatures, reduced, and in some cases practically sup- According to the present invention, the arpressed. In the known circuit arrangements atrangement is such that when the pointer touches tempts were made to reduce sparking by interone contact a switching operation is initiated and posing condensers between the contacts. Ap-

continues until the pointer touches the other plicant has found that this increases the force re- 10 contact. The arrangement of the present inquired to separate the contacts for instantaneous vention differs fundamentally from the known arn er pti n, pp i a e p n n being ha rangements in that both the making and the the condensers cause the contacts to be loaded breaking of the circuit are eiiected by the closing h 8 Static c S n e th s additional force 5 of the contacts of the instrument, that is to say, a o ly e e at in measuring str ents 145 the control operation is not ailected when one of by an increased initial voltage in the measuring the two contacts opens. On this account the unit. th p in r jumps when the contacts are slipping or sliding contacts in general use are not opened, resulting in a considerable oscillation of employed, these being known to possess considthe pointer and fluctuation in the conttrol operaerable disadvantages, because the pressure needed tion- For t s reason an arrangement 0! his to establish a slip contact imposes considerable kind is unsuitable where accurate control is dedemands on the torsional strength of the measursired, in which event there must be no jumping ing unit, and the resulting friction leads to inacof the P curate and unreliable indications. It is also For this reason, such an arrangement is inknown that, in measuring instruments, slip and applicable when accurate control is required and 25 sliding contacts give rise to working troubles, also the pointer must not jump. According to the because parts of the track traversed by the conpresent invention, condensers are provided which tact member are scorched due to the inevitable serve, not r pr e n the ntact f the insparking, as a result of which the passage of the strument, but to prevent disturbance being set current is impeded. Moreover, slip and sliding up by the installation, in order that the operat- 30 contacts necessitate a complicated construction ing of the contacts may not cause any inconoft the instrument when the control is to be advenience to neighboring broadcast receptions and justable over the whole or a large portion of the also protect the working contact. Since, on this scale, account, the condensers do not lie parallel to the In the arrangement 01' the present invention, on instrument contacts, the aforesaid inconveniences the contrary, simple mutually insulated contact also disappear. It is characteristic for the circuit levers, with simple setting mechanism are ararrangement that the temperature recorder or ranged on the glass front of the instrument, enthermostat lies in series with the resistance of abling the adjustment to be made to any desired the relay. on Cont t be ad w th the o e point. Whereas, in all'the known circuit arlimiting pointer, but parallel with the resistance 40 rangements, the opening of the contacts is a of the relay when in contact with the other major operation, it no longer plays any part in limiting pointer. The value of the resistance can the arrangement of the present invention. It is be so selected that the switching entails a miniknown that opening the contacts is the main mum of current consumption in the control circause of their premature wearing out, and the cult, the invention accordingly also meeting prac- 45 reason -for the unreliability of present-day contical requirements in respect of economy, and tact instruments. This is due to the destruction constituting, in technical respects, a considerable of the contacts by the considerable liberation of improvement in the sphere of arrangements for heat arising from sparking in breaking the cirswitching contact instruments by reason of its 59 cuit. The intensity of the sparking for a given reliability, simplicity and ease of inspection. A current strength increases with the increase in further advantage of the invention consists in voltage on the interruption of the current. In that the pointer instrument can be set up sepacircuit arrangements in which the control operarately from the relay. Thus, the relay can be tion is put into action by opening the contacts, situated in the immediate vicinity of the current an alteration in the value of the main circuit consumer, the heavy-current wire between them 55 (Lil being unnecessary. Owing to the small control current, the wire connecting the instrument to the relay may be of small cross section. Moreover, in consequence of this local independence of the two parts, complicated control operations also can be performed in a simple manner.

In order more clearly to understand the invention reference is made to the accompanying drawing, which illustrates by way of example, two embodiments, thereof and in which- Fig. 1 is a diagrammatic representation of one embodiment; and

Fig. 2 shows a second embodiment.

Both figures represent the circuit arrangement for an electric radiator, the control operation of which is assumed to keep the heat of a room within a given range of temperature. Obviously, any other control operation could also be performed by means of said circuit arrangements, for example, the controlling of an electromotor driving a compressor, a pump, a fan, a valve, slide or the like. Moreover, a magnet or other electrical apparatus can be controlled instead of an electromotor.

In Fig. 1, A denotes the contact instrument or thermostat with the contact pointer t1 and the two contact levers 152 and fig. 18 denotes an electric switch unit, in the present case a thermo relay, the heavy-current contact 7c of which is mounted on a bimetallic strip and is actuated by the hot wire h and connects the electric radiator C across the main rs, or switches it ofi therefrom. Instead of a thermo relay, any other relay or a corresponding electric switch unit, may also be employed. The circuit arrangement consists in connecting the two contact levers t2 and is to separate lines, s or r of the electric mains, whilst the contact pointer h is connected to the resistance w. The other terminal of an is connected at g to the hot wire h and the resistance 103. The second terminal of h is connected with the resistance wz, the second terminal ofthe latter being connected to the line 1. The second terminal of wa is connected to the wire leading from the heavy-current terminal through the radiator C to the line 1'. The second terminal of the heavy-current contact It leads to the line s.

It is a characteristic feature of the arrangement of the present invention that the resistances are switched by the play of the contacts so that in all cases two resistances alternately are connected in parallel, one of which then serves as a joint series resistance, for example, 72 and 202 in the drawing being regarded as one resistance. Only when the contact pointer is open and the heavy-current contact closed, are the resistances wz and an in series. The rational values of the resistances are a matter of simple calculation so that switching requires a minimum consumption of current in the control circuit, and therefore the arrangement of the present invention also satisfies practical requirements from the economic stand-point, whilst from the technical point of view, its reliability, simplicity and ease of supervision represent a considerable improvement in circuit arrangements for contact instruments.

When, for example, the contact lever is is set on 8 of the scale, and the contact lever is on 27 of the scale, the control operation in the example represented proceeds in such a manner that when the contact pointer t1 touches the contact 252, current is switched on to the radiator, which latter is switched ofi when the contact pointer t1 touches the contact lever is. When t1t2 are in contact, the course of the current is as follows:

The current from the line s flows through the closed contacts t1tz and by way of the resist-' ance 7.01 to the terminal 9 where it divides. The heating current flows through h and we to the line 1. The other branch of the current flows from the terminal g through we and also to the line r. The resistances Z01, wz and we are so calculated that sufiicient current for heating the relay now flows through h. By this means, the contact k is closed, and a current now flows from the line 3 through the radiator C and to the line r. The heating of the room now proceeds and, in consequence, the contact pointer t1 moves towards the right, thus separating from the lever t2 and breaking the contact t1--t2. The path taken by the current in the control circuit is now as follows:

A current flows from s through the contact k, resistance wz, h and on to the line 1'. In this case also, the heating current is so calculated as to maintain the relay in the operative condition so that the radiator C continues to function. Consequently, the temperature of the room continually increases until finally the contact pointer t1 touches the contact lever t3. In these circumstances a current flows from 1, through the contact t:t1, the resistance 201 and w: and the contact k to s. At the same time a current flows from 1', through 102, h, w; and k, to 8. However, the heating current now fiowing through h is so small that it can no longer maintain the relay in the operative condition, the contact is being consequently interrupted and the radiator C disconnected from the main. The temperature of the room becomes cooler, and the contact pointer t1 moves away in the dead circuit from the lever t3. As the room becomes colder the contact pointer t1 bears against the contact lever tz and the cycle recommences. Each of the condensers 1n and 1. .2 is connected with a contact lever and a line of the mains circuit and they serve chiefly for preventing disturbance to broadcast reception.

In the embodiment shown in Fig. 2, the contact tz, with the resistance an is applied to the line s, whilst the contact is is applied to the terminal g of the energizing resistance h. The contact t1 is connected to the common terminal i of h and on, this latter being applied to the line 1'. The point g is in electrical connection with the terminal 112. of the resistance C. For the protection of the contact is, a condenser u is provided in parallel therewith. In this arrangement, the working operation is similar to that according to Fig. 1. 0n t1t2 being closed, a current fiows through 101, and t2--t1 to the point i, where it divides. One branch of the current flows through L02, the other through h and the loading resistance C to the line T. The second branch current energizes the resistance h and closes the contact is, so that a working current now flows from the line 3, through k, m and C, to the line 1'. Said working current also passes when the contact t1tz is broken, because the resistance h still remains energized by the current flowing, from the line 7', through 102 and h, to g, and thence to m, by way of the contact is, to the line s. On the contact t1t3 being closed, h becomes dead, because the contact t1t3 is now in parallel with h. By this means, the contact A: is opened and the working current interrupted.

The relay may be housed in the interior of a cylindrical former on the outside of which the various resistances of the circuit arrangement are wound. By this means the relay is protected in a simple and reliable manner and also a saving in space is eiiected in the construction of the apparatus.

I claim:

1. In the controlling circuit for an electric current consuming device, a source of electric current, a thermostat having an angularly movable contact member responsive to temperature changes, a graduated temperature scale on said thermostat, contacts on said thermostat and adjustable along said scale, connections between said current consuming device and said source of electric current, a switch in one of said connections, a thermal relay operating said switch, connections between said source and each of said adjustable thermostat contacts, a connection between said movable contact member and said thermal relay, a current-limiting resistance included in one of said connections, a connection between said thermal relay and one of said connections to said current consuming device, and a connection through a current-limiting resistance between said thermal relay and said source of electric current.

2. In the controlling circuit for an electric heater, a source of electric current. a thermostat having an angularly movable contact member responsive to temperature changes, a graduated temperature scale on said thermostat, contacts on said thermostat and adjustable along said scale, direct connections between said heater and said source 0! electric current, a switch in one of said connections, a thermal relay operating said switch, direct connections between said source and each or said adjustable thermostat contacts, a connection including a resistance between said movable contact member and one end or said thermal relay, a connection including a resistance between the said end of said thermal relay and one oi said connections to said heater, and a connection including a resistance between the opposite end of said thermal relay and said source or electric current.

3. In the controlling circuit for an electric heater, a source of electric current, a thermostat having an angularly movable contact member responsive to temperature changes, a graduated temperature scale on said thermostat, contacts on said thermostat and adjustable along said scale, direct connections between said heater and said source of electric current, a switch in one of said connections, a thermal relay, operating said switch, a connection including a resistance between said source and one of said ustable thermostat contacts, a connection between one end of said thermal relay and the other or said adjustable thermostat contacts, a connection between said movable contact member and the opposite end 01' said thermal relay, a connection between the first mentioned end of said thermal relay and one of said connections to said heater, and a connection including a resistance between the opposite end of said thermal relay and said source of electric current.

4. In the controlling circuit for an electric heater, a source of electric current, a thermostat having an angularly movable contact member responsive to temperature changes, a graduated temperature scale on said thermostat, contacts on said thermostat and adjustable along said scale, direct connections between said heater and said source of electrtic current, a switch in one or said connections, a thermal relay operating said switch, a connection including a resistance between said source and one of said adjustable thermostat contacts, a connection between one end oi said thermal relay and the other of said adjustable thermostat contacts, a connection between said movable contact member and the opposite end of said thermal relay, a connection between the ilrst mentioned end of said thermal relay and one oi. said connections to said heater, a connection including a resistance between the opposite end of said thermal relay and said source of electric current, and a condenser connected on one side thereof to said source of electric current and on the other side to said heater in parallel with said switch.

FRANZ GEORG BLOCH.

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