Thermal switch adapter

Details Thermal switch adapter Thermal switch adapter

2002-07-16

2004-08-24

Vortman, Anatoly (Department: 2835)

Electricity: electrothermally or thermally actuated switches

Thermally actuated switches

With bimetallic element

C337S398000, C337S415000

Reexamination Certificate

active

06781504

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to mounting adapters, and in particular to snap on mounting adapters for thermal sensing switches.
BACKGROUND OF THE INVENTION
Thermal sensing electrical switching devices, or thermal switches, of various configurations are generally well known. For example, thermocouples, resistive thermal devices (RTDs) and thermistors are used for measuring temperature in various applications. Such sensors provide an electrical analog signal, such as a voltage or a resistance, which changes as a function of temperature. Monolithic temperature sensors are also known. For example, a diode connected bipolar transistor can be used for temperature sensing. More specifically, a standard bipolar transistor can be configured with the base and emitter terminals shorted together. With such a configuration, the base collector junction forms a diode. When electrical power is applied, the voltage drop across the base collector junction varies relatively linearly as a function of temperature. Thus, such diode connected bipolar transistors have been known to be incorporated into various integrated circuits for temperature sensing. Such devices are useful in providing relatively accurate temperature measurements; however, they are generally not used in control applications to control electrical equipment.
Precision thermostats are generally used in such control applications. The thermal switch is one form of precision thermostat used in control applications to switch on or off heaters, fans, and other electrical equipment at specific temperatures. Such temperature switches typically consist of a sensing element which provides a displacement as a function of temperature and a pair of electrical contacts. The sensing element is typically mechanically interlocked with the pair of electrical contacts to either make or break the electrical contacts at predetermined temperature set points. The temperature set points are defined by the particular sensing element utilized.
Various types of sensing elements are known which provide a displacement as a function of temperature. For example, mercury bulbs, magnets and bi-metallic elements are known to be used in such temperature switches. Mercury bulb thermal sensors have a mercury filled bulb and an attached glass capillary tube which acts as an expansion chamber. Two electrical conductors are disposed within the capillary at a predetermined distance apart. The electrical conductors act as an open contact. As temperature increases, the mercury expands in the capillary tube until the electrical conductors are shorted by the mercury forming a continuous electrical path. The temperature at which the mercury shorts the electrical conductors is a function of the separation distance of the conductors.
Magnetic reed switches have also been known to be used as temperature sensors in various thermal switches. Such reed switch sensors generally have a pair of toroidal magnets separated by a ferrite collar and a pair of reed contacts. At a critical temperature known as the Curie point, the ferrite collar changes from a state of low reluctance to high reluctance to allow the reed contacts to open.
Bi-metallic thermal switch elements typically consist of two strips of materials having different rates of thermal expansion fused into one bi-metallic disc-shaped element. Precise physical shaping of the disc element and unequal expansion of the two materials cause the element to change shape rapidly at a predetermined set-point temperature. The change in shape of the bi-metal disc is thus used to activate a mechanical switch. The bi-metallic disc element is mechanically interlocked with a pair of electrical contacts such that the rapid change in shape can be used to displace one or both of the electrical contacts to either make or break an electrical circuit. The electrical contacts may be provided as individual components mounted in a base structure, commonly known as a “header,” or integrated into a conventional microswitch such that the necessity of assembling discrete components is substantially obviated. Examples of such of formations are described in U.S. Pat. Nos. 3,748,888 and 3,933,022, each of which is incorporated herein by reference in its entirety, wherein a thermally responsive, snap-action bi-metallic disc is provided.
FIG. 1
is a cross-sectional view that illustrates one known modular bi-metallic thermal switch device
10
having a bi-metallic disc actuator
12
positioned to drive relatively movable electrical contacts
14
and
16
. The bi-metallic disc actuator
12
is embodied as a thermally responsive, snap-action bimetallic disc actuator that provides a snap force F generated during transit between bi-stable states at a predetermined set-point temperature. The electrical contacts
14
,
16
are mounted on the ends of a pair of spaced-apart, electrically conductive terminal posts
20
,
22
that are mounted in a header
24
such that they are electrically isolated from one anther. For example, terminal posts
20
,
22
are mounted in the metallic header
24
using a glass or epoxy electrical isolator (not shown).
As illustrated in
FIG. 1
, the movable contact
16
is affixed to an electrically conductive carrier
28
that is embodied as an armature formed of an electrically conductive spring material. The armature
28
is affixed in turn in a cantilever fashion to the electrically conductive terminal post
22
such that a spring pressure S of the armature
28
operates to bias the movable contact
16
toward the fixed contact
14
to make electrical contact therewith. The electrical contacts
14
,
16
thus provide an electrically conductive path between the terminal posts
20
,
22
such that the terminal posts
20
,
22
are shorted together.
The disc actuator
12
is spaced away from the header
24
by a spacer ring
30
interfitted with a peripheral groove
32
. A substantially cylindrical case
34
fits over the spacer ring
30
, thereby enclosing the terminal posts
20
,
22
, the electrical contacts
14
,
16
, and the disc actuator
12
. The case
34
includes a base
36
with a pair of annular steps or lands
38
and
40
around the interior thereof and spaced above the base
36
. The lower edge of the spacer ring
30
abuts the upper case land
40
. A peripheral edge portion
42
of the disc actuator
12
is captured within an annular groove created between the lower end of the spacer ring
30
and the lower case land
38
. The disc actuator
12
operates the armature spring
28
to separate the contacts
14
,
16
through the distal end
44
of an intermediary striker pin
46
fixed to the armature spring
28
. Separation of the contacts
14
and
16
creates an open circuit condition.
FIG. 2
is a cross-sectional view that illustrates another known modular bi-metallic thermal switch device
50
having the bi-metallic disc actuator
12
positioned to drive relatively movable electrical contacts (not shown) within a conventional microswitch
52
. The closing and opening of the contacts respectively shorts together terminal posts
54
,
56
to create a closed circuit condition or separates the contacts to create an open circuit condition. The disc actuator
12
is mounted on the annular step or land
38
around the interior thereof and spaced above the base
36
of the cylindrical case
34
. According to one embodiment, a lower edge of a spacer ring
58
abuts the upper case land
40
and captures the peripheral edge portion
42
of the disc actuator
12
within an annular groove created between the lower end of the spacer ring
58
and the lower case land
38
. The spacer ring
58
spaces the microswitch
52
away from the disc actuator
12
to an extent that the disc actuator
12
is positioned in operational relationship with the electrical contacts through the distal end
60
of an intermediary striker pin
62
projecting from the casing of the microswitch
52
. An adhesive joint
64
fixes the microswitch
52
within the case
34
and secures the operational relationship with the disc actuator

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