 |
Description  |
|
|
BACKGROUND OF THE INVENTION
This invention relates to a resetting device for a thermostat. The
thermostat is of the type that has a switch housing, electric contacts, an
arcuate bimetal disc which, upon reaching a predetermined temperature,
abruptly changes its arcuate height, an actuating pin which transmits the
change in path of the bimetal disc to the movable switch contact and a
resetting pin which is displaceably arranged in the housing and by means
of which the bimetal disc or the switch contact, as the case may be, can
be reset into the original, closed position to re-establish current flow
subsequent to the shutoff operation.
In known arrangements of the above-outlined type the thermostat is reset by
applying a manual pressing force directly to the resetting pin. The manual
force exerted on the resetting pin is, in these arrangements, directly
transmitted to the bimetal disc or to the switch contacts.
It is a disadvantage of these prior art arrangements that upon
intentionally depressing the resetting pin and maintaining it in the
depressed position by the operator, the thermostat is not capable of
normal operation because the bimetal disc is forcibly held in its
"electric circuit closed" position and thus the thermostat will not
interrupt the electric current when the predetermined temperature is
reached. This constitutes a dangerous situation for the user of the
electric appliance with which the thermostat is associated and therefore
in various household appliances it is a requirement to provide the
thermostat with a circuit breaking arrangement which provides for a
current shutoff even in the depressed state of the manually engaged
resetting button.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved thermostat
resetting device which ensures that the thermostat resumes its normal
operation immediately after the resetting pin is actuated, regardless of
the position of the push button.
This object and others to become apparent as the specification progresses,
are accomplished by the invention, according to which, briefly stated, the
resetting device coupled to a thermostat which has a resetting pin
actuated by depressing the same comprises a body arranged to be movable
towards and away from the resetting pin; a propelling device for launching
the body in the direction of the resetting pin for depressing the
resetting pin by the body in an impact-like manner; and an operating
arrangement movable into an actuating position for actuating the
propelling device. The resetting pin is freely movable subsequent to the
impact-like engagement by the body irrespective of the momentarily-assumed
position of the operating arrangement.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view of a preferred embodiment of the
invention, showing the structure in its position of rest, prior to
operation.
FIGS. 2 and 3 are longitudinal sectional views of the embodiment, showing
the latter in successive phases of operation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to FIG. 1, the thermostat resetting device shown therein
comprises a housing 1 in which there is held a tubular retaining member 2.
The latter is provided with a plurality of longitudinally extending
parallel slots 3 arranged in a circumferential array to divide the tubular
portion of the retaining member 2 into a plurality of parallel-arranged
resilient fingers 4. The fingers 4 are connected to one another at one end
to form a socket structure 5 immobilized inside the housing 1, for
example, by means of recesses 19 which are provided in the housing 1 and
into which the socket 5 may be snapped. The opposite end 6 of the fingers
4 is free and thus this terminus is adapted to resiliently move in a
direction transverse to the length dimension of the fingers. At
approximately the middle of their length dimension, the resilient fingers
4 have, at their inwardly-oriented wall 7, inwardly projecting detents 8.
A spherical body 9 is disposed in the space surrounded by the resilient
fingers 4. A hollow, generally thimble-shaped push buttom 10 is slideably
secured to the housing 1 for a motion generally parallel to the length
dimension of the resilient fingers 4. The push button 10 has a floor 11
from the central portion of which there extends, towards the sphere 9, a
post 12 which supports one terminus of a coil spring 13. The other
terminus of the coil spring 13 cooperates with the spherical body 9. The
inner wall of the push button 10 has a conical portion 14 which tapers
towards the floor 11.
Within the housing 1 there is further slidably arranged a return sleeve 15
which surrounds the resilient fingers 4 and which is in engagement with a
terminal face of the push button 10. The return sleeve 15 has a plurality
of inwardly directed lifting lugs 16 which project into the slots 3 and
extend behind the sphere 9. A coil spring 20 is in engagement with the
fixed socket member 5 and, with its other, opposite terminus, engages a
flanged portion of the return sleeve 15, thus urging both the return
sleeve 15 and the push button 10 into their limit position (position of
rest) shown in FIG. 1.
The end portion of the housing 1, remote from the push button 10, has
recesses 17 which receive one part of a thermostat 18 shown only in
phantom lines. The recesses 17 permit a mechanical connection with the
housing 1 without any additional securing means. A resetting pin 21
forming part of the thermostat 18 projects in the zone of the socket
member 5 into the space defined by the resilient fingers 4.
In the description which follows, the operation of the above-described
thermostat resetting device will be discussed, particularly in conjunction
with FIGS. 2 and 3.
Prior to starting the resetting operation, the device is in its normal
position (position of rest) as shown in FIG. 1.
It is now assumed that the thermostat 18 has just responded to a
temperature limit and, as a result, by means of its snap-type bimetallic
member, has opened an electric circuit, as outlined above. The resetting
pin 21 is now in an advanced position; for closing the circuit it is
necessary to reset the thermostat by depressing the resetting pin 21; for
this purpose the push button 10 is manually depressed.
As the push button 10 travels into the housing 1, it displaces the return
sleeve 15 against the force of the coil spring 20. The lifter lugs 16,
forming part of the return sleeve 15, thus move further away from the ball
9, liberating a path of motion therefor. At the same time, the coil spring
13 starts to exert a force on the sphere 9 in the direction of the
resetting pin 21. A motion of the sphere 9 towards the resetting pin 21,
however, is resisted by the detents 8 of the resilient fingers 4.
As the push button 10 is moved further into the housing 1, the end of the
post 12 engages the sphere 9 and thus a rigid force path between the push
button and the sphere 9 is established. As a result, the sphere 9 is now
positively moved against the detents 8 and the resiliency of the fingers
4, whereupon the latter gradually spread apart by the wedging effect of
the advancing sphere 9. This forced downward motion of the sphere 9
proceeds until the equator of the sphere 9 passes the spreading detent.
This moment is depicted in FIG. 2 which also shows that by this time the
lifter lugs 16 of the return sleeve 15 have travelled sufficiently far as
to entirely clear the path for a movement of the sphere 9 to the resetting
pin 21. The obstruction (that is, the detents 8) in the path of motion of
the sphere 9 spring-biases ("loads") the latter by virture of the
resilient force exerted on the sphere 9 by the coil spring 13 and the
resilient fingers 4. Stated differently, in this operational phase, a
potential energy is imparted to the sphere 9 at a distance from the
resetting pin 21. This potential energy reaches its maximum value as the
equator of the sphere 9 reaches the detents 8.
As it may be further observed in FIG. 2, the laterally outward displacement
of the resilient fingers 4 in response to the wedging (spreading) effect
of the travelling sphere 9 is stopped by the conical wall portion 14 of
the push button 10; this arrangement results in an increased resilient
resistance of the fingers 4 to the laterally outwardly-directed force
component of the sphere 9 moved with the push button 10.
As the equator of the sphere 9 has passed the detent 8, their retaining
effect ceases and the ball 9 is forcefully launched -- like a projectile
-- by the accumulated potential energy in the direction of the projecting
resetting pin 21.
The downwardly propelled sphere 9 engages the resetting pin 21 in an
impact-like manner and with sufficient force to reset the thermostat into
its operative, current conducting condition. This phase of operation is
illustrated in FIG. 3 from which it is seen that the push button 10 is in
its fully depressed position, the resilient fingers 4 have assumed their
normal state and the coil spring 13, being out of contact with the floor
11 of the push botton 10, is in a fully relaxed state. Thus, after the
sphere 9 has spent its kinetic energy, no forces act thereon and thus the
resetting pin 21 is not retained in a depressed condition even if the push
button 10 is retained in its fully depressed state.
Thus, should the temperature which the thermostat is designed to monitor,
reach the predetermined maximum value, the thermostat is capable of again
breaking the electric circuit even if the push button 10 is still in its
depressed position.
Upon removing the manual force from the push button 10, the coil spring 20
moves the retaining sleeve 15 and the push button 10 outwardly towards
their normal position. As the return sleeve 15 executes this motion, its
lifter lugs 16 arrive into engagement with the sphere 9 and raise the
latter into the normal position of rest as shown in FIG. 1. It is to be
understood that the force of the coil spring 20 should be so designed that
it is adapted to overcome the resilient resistance of the spring fingers 4
and thus, acting under the force of the coil spring 20, the return sleeve
15, with the lifter lugs 16, is capable of forcing the sphere 9, by
wedging effect, beyond the detents 8 into the position shown in FIG. 1,
whereupon the thermostat resetting device is ready for a successive
operation.
It is noted that the force of the resilient fingers 4 and the shape of the
detent members 8 may be so designed that, as the sphere 9, during the
depression of the push button 10, passes with its equator the detent 8,
the resilient force of the spring finger 4 imparts a sufficiently large
launching force (potential energy) to the sphere 9 to depress the
resetting pin 21 without needing the force of the coil spring 13. Thus, in
such cases it is feasible to omit the coil spring 13 altogether.
It is to be understood that the resetting device described above can be
associated with other types of thermostats where similar resetting
problems occur.
It will be understood that the above description of the present invention
is susceptible to various modifications, changes and adaptations, and the
same are intended to be comprehended within the meaning and range of
equivalents of the appended claims.
* * * * *
|
|
 |
|
 |
Description |
|
