Abstrict
An electric heater including a housing having an internal bore
is provided. An electrically operated heater assembly is arranged
in the internal bore of the housing. The heater assembly includes
a resistance wire, a core and a current carrying member connected
to the resistance wire for connecting the heater assembly to a electric
source. A sleeve made of a dielectric material arranged in the internal
bore of the housing in surrounding relation to at least a portion
of the heater assembly.
Claims
What is claimed is:
1. A heater comprising: a housing having an internal bore; a core
arranged in the internal bore of the housing; a resistance wire
wound around an outer surface of the core; and a sleeve made of
dielectric material arranged in the internal bore of the housing
in surrounding relation to at least a portion of the resistance
wire to provide insulation resistance between said portion of the
resistance wire and the housing.
2. The heater of claim 1 wherein the sleeve is arranged in surrounding
relation to the entire resistance wire.
3. The heater of claim 1 further including a pair of lead pins
for connecting the resistance wire to an electric source, each of
the lead pins extending through a respective passage in the core.
4. The heater of claim 3 further including a second sleeve made
of a dielectric material that is arranged in surrounding relation
to an exposed portion of each of the lead pins which extends beyond
the core.
5. The heater of claim 3 further including a pair of lead wires
each of which is connected to a respective one of the lead pins.
6. The heater of claim 5 wherein the second sleeve is arranged
in surrounding relation to a portion of each of the lead wires.
7. The heater of claim 5 wherein the second sleeve is arranged
in surrounding relation to the connections of the lead pins to the
lead wires.
8. The heater of claim 1 wherein the heater includes first and
second cores.
9. The heater of claim 1 further including a heat transmitting
material compacted within the housing bore.
11. A heater comprising: a housing having an internal bore; a core
arranged in the internal bore of the housing; a resistance wire;
a pair of lead pins for connecting the resistance wire to an electric
source, each of the lead pins extending through a respective passage
in the core; and a sleeve made of dielectric material arranged in
the internal bore of the housing in surrounding relation to an exposed
portion of each of the lead pins which extends beyond the core to
provide insulation resistance between said exposed portions of the
lead pins and the housing.
12. The heater of claim 11 further including a pair of lead wires
each of which is connected to a respective one of the lead pins.
13. The heater of claim 12 wherein the sleeve is arranged in surrounding
relation to a portion of each of the lead wires.
14. The heater of claim 12 wherein the sleeve is arranged in surrounding
relation to the connections of the lead pins to the lead wires.
15. The heater of claim 12 wherein the heater includes first and
second cores.
16. The heater of claim 12 further including a heat transmitting
material compacted within the housing bore.
17. A heater comprising: a housing having an internal bore; a core
arranged in the internal bore of the housing, the core having an
internal passage therethrough; a plurality of current carrying components
arranged in the internal bore of the housing including a resistance
wire and a pair of lead pins for connecting the resistance wire
to an electric source, wherein a portion of the current carrying
components are arranged in the internal passage in the core and
a portion of the current carrying components are arranged outside
of the core; and a sleeve made of a dielectric material arranged
in the internal bore of the housing in surrounding relation to the
portion of the current carrying components arranged outside of the
core.
18. The heater according to claim 17 wherein the core is divided
into a hot core and a cold core.
Description CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of copending
U.S. application Ser. No. 09/854,026, filed May 11, 2001 the disclosure
of which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to electrical heaters,
and more particularly, to an electrical heater that includes a dielectric
sleeve.
BACKGROUND OF THE INVENTION
[0003] Commercial air conditioning compressors are one application
in which electrical heaters are used. In particular, an air conditioning
compressor commonly includes a sump heater that is externally mounted
in close relation to the compressor housing. The sump heater maintains
the compressor at a temperature which prevents condensation of the
refrigerating gas, namely freon, in the compressor. Otherwise, the
condensing freon will migrate to the oil in the compressor and thereby
expose the compressor parts to temperatures below that at which
they can reliably operate, creating a potential for failure.
[0004] Since such compressors often have life-time warranties,
it is important that the sump heater be adapted for long-term reliable
operation. For example, since the sump heater is a relatively inexpensive
component of an air conditioning compressor, costly service calls
and repairs associated with a breakdown of the sump heater during
operation in the field are particularly undesirable. Moreover, in
view of the long-term reliability requirements for air conditioning
compressors, they also commonly undergo extensive and rigorous reliability
testing during manufacture. Again, failure of the compressor during
such testing can impede the manufacturing processing line and is
particularly inefficient and frustrating when the failure is caused
by a relatively inexpensive component such as the sump heater.
SUMMARY OF THE INVENTION
[0005] The present invention provides an electric heater including
a housing having an internal bore. An electrically operated heater
assembly is arranged in the internal bore of the housing. The heater
assembly includes a resistance wire, a core and a current carrying
member connected to the resistance wire for connecting the heater
assembly to a electric source. A sleeve made of a dielectric material
arranged in the internal bore of the housing in surrounding relation
to at least a portion of the heater assembly to provide insulation
resistance between electrically live components of the heater assembly
and the housing.
[0006] These and other features and advantages of the invention
will be more readily apparent upon reading the following description
of a preferred exemplary embodiment of the invention and upon reference
to the accompanying drawings wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a partially cutaway side elevation view of an
illustrative electrical heater constructed in accordance with the
present invention.
[0008] FIG. 2 is an enlarged partial side elevation view of the
electrical heater of FIG. 1.
[0009] FIG. 3 is a perspective view of the hot core of the heater
of FIG. 1.
[0010] FIG. 4 is an end view of the hot core showing the resistance
coil threaded therein.
[0011] FIG. 5 is a side elevation view of the hot core tube and
hypo tubes prior to assembly of the cold core.
[0012] FIG. 6 is an end view of the hot core tube and hypo tubes
prior to assembly of the cold core.
[0013] FIG. 7 is a plan view of a spacer of the heater of FIG.
1.
[0014] FIG. 8 is a side elevation view showing the assembly of
the cold core on the hypo tubes.
[0015] FIG. 9 is a side elevation view showing the cold core assembled
relative to the hot core.
[0016] FIG. 10 is a side elevation view showing the spacers, barrel
connectors, lead wire and sleeve assembled on the hypo tubes.
[0017] FIG. 11 is an end view of the cold core of the heater of
FIG. 1.
[0018] FIG. 12 is a side sectional view of an alternative embodiment
of a heater constructed in accordance with the present invention.
[0019] FIG. 13 is a side view of a first core of the heater of
FIG. 12.
[0020] FIG. 14 is a side view of the dielectric sleeve that surrounds
the first core of the heater of FIG. 12.
[0021] FIG. 15 is a side sectional view of the assembled first
core and dielectric sleeve of the heater of FIG. 12.
[0022] FIG. 16 is a side sectional view of the heater assembly
including the first and second cores and the first and second dielectric
sleeves of the heater of FIG. 12.
[0023] While the invention will be described and disclosed in connection
with certain preferred embodiments and procedures, it is not intended
to limit the invention to those specific embodiments. Rather it
is intended to cover all such alternative embodiments and modifications
as fall within the spirit and scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Referring now to FIGS. 1 and 2 of the drawings there is
shown an illustrative electrical heater 10 constructed in accordance
with the present invention. The heater of the present invention
is particularly suited for use as a sump heater in an air conditioning
compressor. In particular, the heater can be mounted on the external
surface of an air conditioning compressor housing adjacent the bottom
of the housing. The heat produced by the heater is conducted through
the compressor housing and helps maintain the oil in the sump of
the compressor above a predetermined level so as to prevent condensation
of the refrigerant. Of course, while the present invention is described
in connection with use as a sump heater, it will be readily appreciated
that it could also be applied to heaters in other contexts which
require a very reliable and efficient electrical heating element.
[0025] The heater 10 of the present invention generally includes
hot and cold core tubes 12, 14 which are contained within a hollow
tubular housing 16. As shown in FIG. 1, a first distal end 17 of
the tubular housing 16 is closed by an end wall 18. A plug 20, in
this case, made of epoxy, seals off the opposing proximal end 19
of the housing. The plug 20 surrounds a pair of insulated lead wires
22 that supply electricity to the heater. The housing 16 is formed
with an annular indentation or groove 23 that can receive a retention
spring for securing the heater 10 to the compressor housing, in
a conventional manner.
[0026] The hot and cold cores 12, 14 are arranged in end-to-end
relation in the housing 16 with the hot core 12 being arranged closest
the end wall 18 of the housing as shown in FIGS. 1 and 2. As described
in greater detail below, in the illustrated embodiment, the entire
heater assembly, including the hot and cold cores 12, 14 and the
housing 16, is filled with a heat transmitting material such as
magnesium oxide powder 24 (partially shown in FIG. 1). The magnesium
oxide powder serves to transfer heat produced by the heater to the
housing and to electrically insulate the components of the heater
from the housing. The hot and cold cores 12, 14 can be made of any
suitable dielectric material such as, for example, an extruded and
fired steatite material or other ceramic material. Likewise, the
tubular housing 16 can be made of any suitable material such as,
for example, metal.
[0027] For receiving an electric resistance wire 26, the hot core
includes, in this case, six circumferentially spaced passages 28a-f
which extend lengthwise through the hot core. The electrical resistance
wire 26 is threaded in serpentine fashion through these longitudinal
passages as shown in FIG. 4. To facilitate assembly of the coil
within the hot core tube, the resistance wire has a conventional
coil construction, with longitudinal straight sections which define
the turning points at each end of the hot core. As shown in FIG.
4, the resistance wire 26 further includes a straight portion 30
at each end that extends outwardly from, in this case, diametrically
opposed longitudinal passages 28a, 28d at a first proximal end 32
of the hot core 12 which is nearest the cold core 14.
[0028] Each of the straight end portions 30 of the resistance wire
26 extends into a respective hypo tube 34 which, in turn, extends
through a respective longitudinal passage 36 in the cold core 14.
The end portions 30 of the resistance wire 26 are secured to the
respective hypo tube 34, which can be made, for example, of stainless
steel, via a crimp 46 in the hypo tube. A first distal end portion
38 of each hypo tube 34 extends partially into the diametrically
opposed passages 28a, 28d of the hot core 12 from which the straight
end portions 30 of the resistance wire 26 protrude. An opposing
proximal end portion 40 of each hypo tube 34 extends beyond the
cold core 14. Each lead wire 22 is connected to a respective one
of these proximal end portions 40 of the hypo tubes 34 via, in the
illustrated embodiment, an insulated barrel connector 42 that is
crimped (at 43 in FIG. 2) to the hypo tubes. In addition to the
two longitudinal passages 36 for receiving the hypo tubes 34, the
cold core 14 includes, in this instance, two additional circumferentially
spaced longitudinal passages 44 extending therethrough which facilitate
the flow of magnesium oxide through the heater assembly as explained
below (see FIG. 11).
[0029] According to one aspect of the present invention, the crimped
connections 46 between the hypo tubes 34 and the respective end
portions 30 of the resistance wire 26 are configured and arranged
so as to ensure proper orientation of the hypo tubes with respect
to the cold core 14 and the tubular housing 16. Maintaining the
hypo tubes 34 in a precise relation to the cold core 14 and the
housing 16 helps ensure reliable electrical performance of the heater
by preventing, for example, electrical leakage or sparking. In the
illustrated embodiment, the crimped connections 46 have a U-shaped
configuration and are arranged in alignment with each other adjacent
the distal ends 38 of the hypo tube 34. The U-shaped crimped portions
46 of the hypo tubes 34 extend partially into the respective longitudinal
passage 28a, 28d in the hot core 12. As a result, the upstream end
of the hypo tube 34 is oriented in a radial inward direction prior
to insertion into the cold core 12 as shown in FIGS. 5 and 6. Thus,
when the hypo tubes 34 are positioned within the diametrically opposed
longitudinal passages 28a, 28d of the cold core 14, the hypo tubes
must be pulled radially outwardly (see FIGS. 8 and 9). This biases
the hypo tubes 34 and helps maintain them in precise relation to
the cold core 14 and the housing 16.
[0030] In keeping with the invention, the hot core 12 has a recessed
end 48 for receiving the end of the cold core 14 with a spatial
separation defined by the crimped portions 46 of the hypo tubes
34 as shown in FIGS. 2, 3 and 9. In particular, the U-shaped crimped
portion 46 of each hypo tube 34 further defines a ledge which acts
as a stop surface with regard to positioning the cold core 14 with
respect to the hot core 12. The recessed end 48 of the hot core
12 facilitates reliable and rigid mounting of the cold core 14 in
axial extending relation to the hot core. During the magnesium oxide
dielectric filling process, the recessed end 48 of the hot core
12 further helps facilitate the flow of magnesium oxide from the
longitudinal passages 44 in the cold core 14 into the passages 28a-f
of the hot core 12. To allow magnesium oxide to flow into the two
passages 28a, 28d in the hot core 12 which receive the distal ends
of the hypo tubes 34, each of those passages 28a, 28d has a key-shaped
configuration as shown in FIGS. 3 and 4. The key-shaped configuration
comprises a circular portion 50 for receiving the distal end 38
of the hypo tube 34 and radially outwardly extending slotted portion
52 for receiving the magnesium oxide dielectric.
[0031] To further ensure that the hypo tubes 34 are maintained
in a precise orientation relative to each other and the tubular
housing 16, a pair of spacer plates 54 are positioned on the proximal
end portions 40 of the hypo tubes 34 that extend out of the cold
core 14. In the illustrated embodiment, the spacer plates 54 have
four openings 56a-d which extend therethrough and are configured
to abut against the interior wall of the tubular housing as shown
in FIG. 7. Two diametrically opposed openings 56a, 56c receive the
hypo tubes 34 while the other two openings 56b, 56d serve as passageways
for the flow of the magnesium oxide dielectric during the assembly
of the heater. The spacers 54 further include circumferentially
spaced recesses 58 about the perimeter for facilitating the passage
of magnesium oxide during the filling process. The spacer plates
54 are retained in axially spaced relation from each other by crimps
60 in the hypo tubes 34 disposed in closely adjacent relation to
the spacer plates as shown in FIG. 2.
[0032] Pursuant to a further feature of the invention, a sleeve
62 formed of mylar, or other dielectric material, is positioned
about the spacers 54, the proximal ends 40 of the hypo tubes 34
and the uninsulated portions of the barrel connectors 42 as best
shown in FIG. 10. The mylar sleeve 62 provides a further reliable
dielectric in surrounding relation to the proximal ends 40 of the
hypo tubes 34 so as to help ensure reliable electrical performance
of the heater 10. As described in greater detail below, such a dielectric
sleeve can be used to provide insulation resistance to any current
carrying component of an electric heater thereby protecting the
current carrying component from electrically shorting to the internal
wall of the housing.
[0033] To assemble the heater 10 of the present invention, the
components of the heater can be assembled prior to their insertion
into the tubular housing 16. In particular, the resistance wire
26 can be first threaded through the longitudinal passages 28a-f
of the hot core 12 with the straight end portions 30 left protruding
out of the first and last passages28a, 28d. Each straight end 30
can then be inserted into the respective hypo tube 34. The U-shaped
crimps 46 can then be formed in the distal ends 38 of the hypo tubes
34 to connect the resistance wire 26 to the hypo tubes. Next, the
hypo tubes 34 are inserted up to their U-shaped crimped portions
46 into the respective passages 28a, 28d of the hot core 14. At
this stage, each of the hypo tubes 34 extends in a radial inward
direction as shown in FIGS. 5 and 6.
[0034] Prior to insertion of the hypo tubes 34 into the cold core
14, any excess resistance wire 30 protruding beyond the proximal
end 40 of each hypo tube can be cut off. The hypo tubes 34 are then
pulled radially outwardly and inserted into the respective passages
36 through the cold core 14 as shown in FIGS. 8 and 9. The spacers
54 can then be placed on the hypo tubes 34 and the lead wires 22
are attached to the hypo tubes 34 by sliding the barrel connectors
42 over the proximal ends 40 of the hypo tubes. The spacers 54 and
barrel connectors 42 are secured in place via crimps and the mylar
sleeve 62 is slid over the spacers and the uninsulated portion of
the barrel connectors. This entire assembly is then inserted into
the tubular housing 16 with the lead wires 22 extending out of the
open proximal end 19 of the housing. Prior to insertion of the assembly,
a mica disk 64 can be inserted into the tubular housing 16 such
that it abuts against the end wall 18 of the housing. After insertion
of the heating assembly and the mica disk, the groove 23 can be
formed in the housing 16.
[0035] As a result of the various flow passages that are provided,
the internal spaces of the heater assembly can then be packed with
a magnesium oxide dielectric powder. The flow passages help ensure
that voids which would adversely effect the insulation provided
by the magnesium oxide are not formed. The magnesium oxide powder
is directed into the open proximal end 19 of the tubular housing
16 and passes through the diametrically opposed openings 56b, 56d
in the spacers 54 and between the circumferential recesses 58 in
the spacers and the mylar sleeve 62. The powder can pass into two
of the passages 44 through cold core 14. The magnesium oxide powder
further passes into the space between the cold core 14 and the hot
core 12, and through the four free openings 28b, c, e, f in the
hot core and the radially outwardly extending slotted portions 52
of the key-shaped passages 28a, 28d which receive the hypo tubes
34. Hence, magnesium oxide is permitted to completely fill all of
the internal spaces within the hot and cold cores 12, 14.
[0036] Magnesium oxide communicated through the outer recesses
58 in the spacer plates 54, further enables the magnesium oxide
to completely fill the space between the hot and cold core tubes
12, 14 and the outer tubular housing 16. The heater 10 can be vibrated
in order to further facilitate flow of the magnesium oxide. In one
preferred embodiment of the invention, the heater is filled with
magnesium oxide powder to the point that the powder covers approximately
half of the insulation of the barrel connectors 42. Following completion
of the magnesium oxide filling operation, the open proximal end
19 of the housing is enclosed by the epoxy plug 20.
[0037] Another embodiment of an electric heater 110 according to
the present invention is illustrated in FIGS. 12-16. As with the
FIGS. 1-11 embodiment, the FIGS. 12-16 embodiment includes an electrically
operated heater assembly 112 (shown in FIG. 16) that is arranged
within an internal bore of a tubular housing 114. The heater assembly
112 includes first and second cores 116, 118 made of an insulating
material that are arranged end-to-end within the internal bore of
the housing 114 as shown in FIGS. 12 and 16. However, in contrast
to a resistance wire that extends through the core, with this embodiment,
the heater assembly 112 includes a resistance wire 120 that is wound
around the outer surface of the first core 116 (see, e.g., FIG.
13). For connecting the resistance wire 120 to an electric source,
the resistance wire is electrically coupled to a current carrying
member, in this case, a pair of lead pins 122 that extend through
longitudinally extending passages in the two cores 116, 118. As
shown in FIG. 12, the lead pins 134, in turn, are electrically connected
to a pair of lead wires 124 via electrical connectors 126. As used
herein, the term lead pin refers to any current carrying member
that can be used to carry current to the resistance wire including,
but not limited to, pins, leads, hypo tubes, wires and the like.
As with the FIGS. 1-11 embodiment, a heat transmitting material
such as magnesium oxide is deposited in the housing 114 so as to
fill any spaces in the heater assembly as well as any spaces between
the heater assembly and the internal wall of the housing. While
the illustrated housing 114 comprises a single piece, it will be
appreciated that the housing could also consist of a plurality of
housing parts that are assembled together.
[0038] To protect the current carrying components of the heater
assembly 112 against electrically shorting to the internal wall
of the housing 114 (which is electrically grounded), a sleeve made
of a dielectric material can be arranged in surrounding relation
to at least a portion of the heater assembly 112 so as to be interposed
between the current carrying component and the internal wall of
the housing. The current carrying components of the heater assembly
112 can include the resistance wire 120, the leads or lead pins
122, the lead wires 124 connected to the lead pins and/or the electrical
connectors that couple the various current carrying components together.
[0039] In the embodiment illustrated in FIGS. 12-16, a first dielectric
sleeve 128 is arranged in the internal bore of the housing 114 and
surrounds the ends of the lead pins 122 and the connectors 126 that
couple the lead pins to the lead wires 124 (see FIGS. 12 and 16).
Thus, the first dielectric sleeve 128 provides insulation resistance
between internal wall of housing 114 and the ends of the lead pins
122 which extend beyond the second core 118 and the connectors 126.
A second dielectric sleeve 130 (shown individually in FIG. 14) is
arranged in the housing bore in surrounding relation to the resistance
wire 120 that is, in this case, wound around the outer surface of
the first core 116 (see, e.g., FIGS. 12, 15 and 16). This second
dielectric sleeve 130 therefore provides insulation resistance between
the resistance wire 120 and the internal wall of the housing 114.
In the illustrated embodiment, the first dielectric sleeve 128,
which is relatively thinner, can be made of mylar and the second
dielectric sleeve 130, which is relatively thicker, can be made
of a ceramic material. However, it will be appreciated that the
dielectric sleeve or sleeves can be made of any suitable dielectric
material.
[0040] Those skilled in the art will appreciate that the dielectric
sleeve is not limited to use in heaters having the illustrated configurations.
To the contrary, the dielectric sleeve can be used in any electric
heater having an electrically live component and an electrically
ground component. In particular, the dielectric sleeve can be used
to provide insulation resistance between the electrically live component
of the heater and the electrically grounded component of the heater.
[0041] All of the references cited herein, including patents, patent
applications, and publications, are hereby incorporated in their
entireties by reference.
[0042] While this invention has been described with an emphasis
upon preferred embodiments, variations of the preferred embodiments
can be used, and it is intended that the invention can be practiced
otherwise than as specifically described herein. Accordingly, this
invention includes all modifications encompassed within the spirit
and scope of the invention as defined by the claims. |