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Патент USA US2133888

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Oct. 18, 1938.
F_ G, BLQCH
2,133,888
ELECTRIC CIRCUIT ARRANGEMENT FOR CONTACT POINTER
THERMOSTATS AND LIKE INSTRUMENTS
Filed Jan. 10, 1935
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Patented on. 1a, 1938
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2,133,888
UNITED STATES PATENT OFFICE
2,133,888
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.
This invention relates to an electric circuit ar-
5
10
15
29_
25
30
Q
3
(Cl. 219-20)
voltage 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 instruments provided with a contact pointer and two
adjustable contacts, and serving for the electrical
control of temperatures,
According to the present invention, the arrangement is such that when the pointer touches
one contact a switching operation is initiated and
continues until the pointer touches the other
contact. The arrangement of the present invention differs fundamentally from the known arrangements in that both the making and the
breaking of the circuit are eiiected by the closing
of the contacts of the instrument, that is to say,
the control operation is not ail’ected when one of
the two contacts opens. On this account the
slipping or sliding contacts in general use are not
employed, these being known to possess considerable disadvantages, because the pressure needed
to establish a slip contact imposes considerable
demands on the torsional strength of the measuring unit, and the resulting friction leads to inaccurate and unreliable indications. It is also
known that, in measuring instruments, slip and
sliding contacts give rise to working troubles, also
because parts of the track traversed by the con~
tact member are scorched due to the inevitable
sparking, as a result of which the passage of the
current is impeded. Moreover, slip and sliding
change of voltage, if any, occurs in the circuit
on the contacts being opened, and consequently,
the burning of the contacts is very considerably
reduced, and in some cases practically sup
pressed. In the known circuit arrangements at
tempts were made to reduce sparking by inter
posing condensers between the contacts. Ap
plicant has found that this increases the force required to separate the contacts for instantaneous
interruption, applioant’s explanation being that
the condensers cause the contacts to be loaded
with 8 Static charge- Since this additional force
can only be generated in measuring instruments
by an increased initial voltage in the measuring
unit. the pointer jumps when the contacts are
opened, resulting in a considerable oscillation of
the pointer and ?uctuation in the conttrol opera
tion- For this reason an arrangement 0! this
kind is unsuitable where accurate control is de
sired, in which event there must be no jumping
of the Pointer
For this reason, such an arrangement is in
applicable when accurate control is required and
the pointer must not jump. According to the
present invention, condensers are provided which
serve, not for protecting the contacts of the in
strument, but to prevent disturbance being set
up by the installation, in order that the operat-
contacts necessitate a complicated construction
oft the instrument when the control is to be adjustable over the whole or a large portion of the
scale,
‘
CA
In the arrangement 01' the present invention, on
the contrary, simple mutually insulated contact
levers, with simple setting mechanism are arranged on the glass front of the instrument, enabling the adjustment to be made to any desired
40 point. Whereas, in all'the known circuit arrangements, the opening of the contacts is a
major operation, it no longer plays any part in
the arrangement of the present invention. It is
known that opening the contacts is the main
45 cause of their premature wearing out, and the
reason -for the unreliability of, present-day contact instruments. This is due to the destruction
of the contacts by the considerable liberation of
heat arising from sparking in breaking the cir59 cuit. The intensity of the sparking for a given
current strength increases with the increase in
voltage on the interruption of the current. In
circuit arrangements in which the control operation is put into action by opening the contacts,
55 an alteration in the value of the main circuit
I
10
145
20
25
30
ing of the contacts may not cause any incon
venience to neighboring broadcast receptions and
also protect the working contact. Since, on this
account, the condensers do not lie parallel to the
instrument contacts, the aforesaid inconveniences 35
also disappear. It is characteristic for the circuit
arrangement that the temperature recorder or
thermostat lies in series with the resistance of
the relay. on Contact being made with the one
limiting pointer, but parallel with the resistance 40
of the relay when in contact with the other
limiting pointer. The value of the resistance can
be so selected that the switching entails a mini
mum of current consumption in the control cir
cult, the invention accordingly also meeting prac- 45
tical requirements in respect of economy, and
constituting, in technical respects, a considerable
improvement in the sphere of arrangements for
switching contact instruments by reason of its
reliability, simplicity and ease of inspection. A 50
further advantage of the invention consists in
that the pointer instrument can be set up sepa
rately from the relay. Thus, the relay can be
situated in the immediate vicinity of the current
consumer, the heavy-current wire between them 55
2
_ 2,133,888
being unnecessary. Owing to the small control
current, the wire connecting the instrument to
pointer t1 touches the contact lever is. When
the relay may be of small cross section. More
over, in consequence of this local independence
is as follows:
of the two parts, complicated control operations
also can be performed in a simple manner.
In order more clearly to understand the in
vention reference is made to the accompanying
drawing, which illustrates by way of example, two
10 embodiments, thereof and in which
Fig. 1 is a diagrammatic representation of one
embodiment; and
Fig. 2 shows a second embodiment.
Both ?gures represent the circuit arrange
15 ment for an electric radiator, the control opera
tion of which is assumed to keep the heat of a
room within a given range of temperature. Ob
viously, any other control operation could also
be performed by means of said circuit arrange
20 ments, for example, the controlling of an elec
tromotor 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.
25
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 elec
tric switch unit, in the present case a thermo re
lay, the heavy-current contact 7c of which is
30 mounted on a bimetallic strip and is actuated
by the hot wire h and connects the electric
radiator C across the main r—s, or switches it
o? therefrom. Instead of a thermo relay, any
other relay or a corresponding electric switch
unit, may also be employed. The circuit ar
rangement consists in connecting the two con
tact 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
(Lil 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 sec
t1—t2 are in contact, the course of the current
The current from the line s ?ows through the
closed contacts t1—tz 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 ?ows
from the terminal g through we and also to the
line r.
The resistances Z01, wz and we are so 10
calculated that su?icient current for heating
the relay now ?ows 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 pro
ceeds 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
20
is now as follows:
A current ?ows 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 condi
tion so that the radiator C continues to function. 25
Consequently, the temperature of the room con
tinually increases until ?nally the contact pointer
t1 touches the contact lever t3. In these cir
cumstances a current ?ows from 1, through the
contact t:—t1, the resistance 201 and w: and the 30
contact k to s.
At the same time a current
?ows from 1', through 102, h, w; and k, to 8. How
ever, the heating current now ?owing through h
is so small that it can no longer maintain the
relay in the operative condition, the contact is 35
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 le
ver tz and the cycle recommences. Each of the
ond terminal of- the latter being connected to the
condensers 1n and 1.1.2 is connected with a contact
line 1.
lever and a line of the mains circuit and they
serve chie?y for preventing disturbance to broad 45
The second terminal of wa is connected
to the wire leading from the heavy-current ter
minal 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 arrange
50 ment of the present invention that the resistances
are switched by thevplay 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
55 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
60 so that switching requires a minimum consump
tion of current in the control circuit, and there
fore the arrangement of the present invention
also satis?es practical requirements from the
economic stand-point, whilst from the technical
65 point of view, its reliability, simplicity and ease
of supervision represent a considerable improve
ment in circuit arrangements for contact instru
ments.
When, for example, the contact lever is is set
70 on 8° of the scale, and the contact lever is on
27° of the scale, the control operation in the ex
ample represented proceeds in such a manner
that when the contact pointer t1 touches the
contact 252, current is switched on to the radiator,
75 which latter is switched o? when the contact
cast reception.
In the embodiment shown in Fig. 2, the con
tact tz, with the resistance an is applied to the
line s, whilst the contact is is applied to the ter
minal g of the energizing resistance h. The con 50
tact 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 55
u is provided in parallel therewith. In this ar
rangement, the working operation is similar to
that according to Fig. 1. 0n t1—t2 being closed,
a current fiows through 101, and t2--t1 to the point
i, where it divides. One branch of the current 60
?ows 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 ?ows from the line 3, through k, m and C, 65
to the line 1'. Said working current also passes
when the contact t1—tz is broken, because the re
sistance h still remains energized by the current
?owing, from the line 7', through 102 and h, to g,
and thence to m, by way of the contact is, to the 70
line s. On the contact t1—t3 being closed, h be
comes dead, because the contact t1—t3 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 75
2, 188,888
3
cylindrical former on the outside of which the
various resistances of the circuit arrangement
are wound. By this means the relay is protected
heater, a source of electric current, a thermostat
having an angularly movable contact member re
in a simple and reliable manner and also a sav
sponsive to temperature changes, a graduated
ing in space is eiiected in the construction of the
temperature scale on said thermostat, contacts
on said thermostat and adjustable along said
apparatus.
I claim:
1. In the controlling circuit for an electric cur
rent consuming device, a source of electric cur
10 rent, a thermostat having an angularly movable
contact member responsive to temperature
changes, a graduated temperature scale on said
thermostat, contacts on said thermostat and ad
justable along said scale, connections between
15 said current consuming device and said source of
electric current, a switch in one of said connec
tions, a thermal relay operating said switch, con
nections between said source and each of said
adjustable thermostat contacts, a connection be
20 tween said movable contact member and said
thermal relay, a current-limiting resistance in
cluded in one of said connections, a connection
between said thermal relay and one of said con
nections to said current consuming device, and a
25 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 resist
3. In the controlling circuit for an electric
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 be
tween said source and one of said adjustable
thermostat contacts, a connection between one
end of said thermal relay and the other or said
adjustable thermostat contacts, a connection be
tween said movable contact member and the op 15
posite end 01' said thermal relay, a connection be
tween the ?rst mentioned end of said thermal re
lay and one of said connections to said heater,
and a connection including a resistance between
the opposite end of said thermal relay and said 20
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 re
sponsive to temperature changes, a graduated 25
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 30
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 be 35
tween said movable contact member and the op
posite end of said thermal relay, a connection be
tween the ilrst mentioned end of said thermal re
lay and one oi.’ said connections to said heater,
a connection including a resistance between the 40
opposite end of said thermal relay and said
ance between the said end of said thermal relay
and one oi’ said connections to said heater, and a
source of electric current, and a condenser con
nected on one side thereof to said source of elec
connection including a resistance between the
opposite end of said thermal relay and said source
or electric current.
tric current and on the other side to said heater
in parallel with said switch.
FRANZ GEORG BLOCH.
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