Abstrict
An insulator for an electric heater employs a central elongated
slot and two guide surfaces. Below each guide surface is a notch
for receiving an outer convolution of a heater coil, while the central
slot terminates in a notch for receiving an intermediate convolution
of the heater coil. The slot engages the central convolution of
the heater coil before outer convolutions engage the guide surfaces
to facilitate installation of the insulator. As the insulator is
inserted into the heater coil, the guide surfaces engage the outer
convolutions and direct them to respective notches for securely
holding the heater coil. The insulator may support a single pass
of the heater coil or may be arranged to have these surfaces and
notches on opposite ends to support two passes of the heater coil.
Claims
What is claimed is:
1. An electric heater comprising a helical heater coil and an insulator
supporting said heater coil, said insulator comprising a body of
electrically insulating material having one end engaging individual
convolutions of said heater coil, said one end having a slot extending
in a first direction from an upper edge of said one end downwardly
into said body, said slot terminating in a first notch and receiving
a convolution of said heater coil, a first guide surface sloping
away from said slot in a second direction which forms an acute angle
with said first direction, a second notch extending inwardly from
a side of said body adjacent a lower terminus of said first guide
surface and receiving a second convolution of said heater coil,
the distance between an upper portion of said guide surface and
said slot being less than the distance between said first and second
notches, a second guide surface sloping away from said slot in a
third direction which forms an acute angle with said first direction,
wherein said first and second guide surfaces are on opposite sides
of said slot, and a third notch extending inwardly from a location
adjacent the lower terminus of said second guide surface in a second
side of said body and receiving a third convolution of said heater
coil, wherein the distance between an upper portion of said second
guide surface and said slot is less than the distance between said
third and first notches.
2. The heater of claim 1 wherein said second and third notches
extend in respective directions oblique to said first direction.
3. The heater of claim 1 further comprising a first flat surface
perpendicular to said first direction between the upper terminus
of said first guide surface and the upper terminus of said slot
and a second flat surface perpendicular to said first direction
between said upper terminus of said slot and the upper terminus
of said second guide surface.
4. The heater of claim 3 further comprising a third flat surface
substantially parallel to said first direction and extending from
the lower terminus of said first guide surface to said second notch,
and a fourth flat surface parallel to said first direction and extending
from the lower terminus of said second guide surface to said third
notch.
5. The heater of claim 4 further comprising means for receiving
means for grasping said body to support said body and said heater
coil.
6. The heater of claim 4 further comprising a second end engaging
individual convolutions of a heater coil and having a second slot
extending from said second end in a direction opposite to said first
direction and terminating in a fourth notch, and third and fourth
guide surfaces extending from locations adjacent the outer terminus
of said second slot to locations adjacent respective fifth and sixth
notches.
7. The heater of claim 4 wherein each of said first and second
guide surfaces is planar.
Description TECHNICAL FIELD
This invention relates to the art of electric heaters, particularly
the art of insulating support members for a coiled heater element.
BACKGROUND ART
A known electric heater employs a coiled element attached to a
source of electric current. As current is passed through the electric
coil, it is heated and radiates energy. Also, the coil may be placed
in the flow of air to transfer energy by conduction.
It is common to provide a support structure for holding the coiled
heater element, and this structure typically includes a ceramic
insulator which engages the heater coil and is attached to the support
structure.
U.S. Pat. No. 4,363,959 (Cottrell et al.) shows an electric heater
having a coiled heating element. The heating element is supported
by insulators which are in turn attached to a frame. Several forms
of the insulator are illustrated, and each relies upon a notch engaging
an individual convolution of the heater coil. Embodiments shown
in FIGS. 3, 4, and 5 employ slanted surfaces to direct adjacent
convolutions of the heater coil into respective notches. FIG. 7
shows an embodiment wherein rounded ears direct convolutions into
respective notches while another notch receives an intermediate
convolution.
U.S. Pat. No. Des. 262,285 (Janning) discloses an insulator having
upstanding ears and an intermediate broad notch. The upstanding
ears form notches for receiving outer convolutions of a heater coil
and an intermediate convolution is received in the central notch
between the ears. Since this is a design patent, there is no disclosure
regarding the operation of the device; however, it would appear
that the rounded ears are intended to separate the convolutions
of the heater coil during installation of the insulator.
SUMMARY OF THE INVENTION
Major factors in choosing an insulator in an electric heater of
the type having a heater coil are the ability of the insulator to
properly support the heater coil and the ease in applying the insulator
to the heater coil.
The above-noted prior art insulators fail in one or both of these
aspects, and it is an object of the invention to provide an electric
heater having an insulator for a heater coil which securely holds
the heater coil and is very easy to install.
The insulator of the electric heater according to the invention
has a supporting end with a rather long central slot for receiving
a central one of three adjacent convolutions of the heater coil.
Adjacent the vertical slot are two guide surfaces which are much
longer than the guide surfaces of prior art insulators. This structure
produces an elongated tip which allows the installer to easily engage
the central convolution of the heater coil without necessarily engaging
the guide surfaces with the outer convolutions. After the central
convolution is securely engaged in the central slot, the insulator
is pushed into the coil so that the guide surfaces engage the outer
convolutions to thus spread them. Below each guide surface is a
notch for receiving a single convolution of the heater coil, and
this notch extends inwardly and upwardly from a location below the
lower end of each guide surface. As the insulator is pushed into
the heater coil, the guide surfaces separate the outer convolutions
until they move over the ends of the guide surfaces and into the
notches. During this motion, the central convolution moves down
the central slot. When the central convolution engages a notch at
the bottom of the central slot, it is not possible to push the insulator
further into the heater coil, and the outer convolutions then assume
their positions in ends of the other two notches because of the
resiliency of the heater coil. While the three notches are preferably
colinear, this is not necessary.
In order to support two passes of the heater coil, a similar arrangement
is used on the opposite end of the insulator, and the heater coil
is applied to this opposite end in the manner described above.
A portion of the insulator also has parallel notches for receiving
means to hold the insulating support. In the preferred embodiment,
the holding means is a single wire which at least partially encircles
the central portion of the insulator and engages the parallel notches.
This wire is then secured to a main frame of the heater element.
It is an object of this invention to provide an electric heater
having an insulating support for a coiled heater element which securely
holds the heater element and is easy to install.
It is a further object of this invention to provide an electric
heater having an insulating support element having an elongated
central slot for receiving an intermediate convolution of the heater
coil and adjacent notches for receiving outer convolutions of the
heater coil wherein the outer convolutions are directed to the outer
notches by means of elongated guide surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a portion of a heater unit showing the
preferred embodiment of an insulator.
FIG. 2 is a side view of the preferred embodiment illustrating
the manner of installation.
FIG. 3 is a side view of the insulator of the electric heater according
to the invention.
DETAILED DESCRIPTION
In FIG. 1, an insulator 2 is shown in an operative environment
supporting a first pass 4 of a heater coil and a second pass 6 of
the heater coil. The insulator 2 is held by a wire 8 which at least
partially encircles the central portion of the insulator 2 and engages
parallel notches 10 and 12. The wire 8 is in turn supported by a
frame 14 as is known in the art.
The features of the preferred insulator 2 are clearly shown in
FIGS. 1 and 2. One end of the insulator 2 has an elongated slot
16 therein which extends along the longitudinal axis of the insulator
2. This elongated slot receives a central convolution 18 of a set
of three adjacent convolutions of the heater coil. The slot 16 terminates
in a first notch 20 which has a width slightly greater than that
of the slot 16. The arrows in FIG. 2 indicate the path which the
central convolution 18 follows during installation of the insulator.
On opposite sides of the elongated slot 16 are guide surfaces 22
and 24. These guide surfaces are oriented at an angle to the direction
of the elongated slot 16. The guide surface forms an acute angle
with the slot 16, and in the preferred embodiment this angle is
42.5 degrees. The angle may, however, vary from the preferred angle
and, for example, be 40 to 45 degrees.
A second notch 26 extends inwardly from one side 28 of the insulator
and is below a lower end of the guide surface 22. A third notch
30 extends inwardly from an opposed side 32 and is below the lower
end of guide surface 24. The second and third notches 26, 30 are
adapted to receive outer convolutions 34 and 36 respectively of
the heater coil and are aligned with notch 20. The heater coil is
usually linear and notches 20, 26 and 30 are, thus, preferably colinear.
In the preferred embodiment, the entrances to the notches 26 and
30 are spaced from the lower edges of respective guide surfaces
22 and 24 by surfaces 38 and 40, and notches 26 and 30 extend in
directions oblique to that of slot 16.
Also, in the preferred embodiment, the upper ends of guide surfaces
22 and 24 are separated from the entrance to elongated slot 16 by
top surfaces 42 and 44 respectively.
The insulator shown in FIGS. 1 and 2 is adapted to receive a heater
coil at each end. The lower end has surfaces and notches identical
to those described with respect to the upper end, and corresponding
elements have been identified by corresponding, primed numbers.
It should be noted that use of the insulator 2 with a single end
adapted to receive a heater coil is within the concept of the invention.
An important feature of the insulator of the electric heater of
the invention is that the distance between the upper ends of the
guide surfaces 22 and 24 is smaller than the distance between outer
convolutions 34 and 36 and the distance between bottoms of notches
26 and 30. This allows the central convolution 18 to be firmly placed
within the elongated slot 16 before the guide surfaces 22, 24 engage
outer convolutions 34, 36. It will be appreciated that it is not
necessary for guide surfaces 22 and 24 to be perfectly flat, even
though in the preferred embodiment these surfaces are planar. After
the central convolution 18 has been engaged in slot 16, the insulator
is inserted into the heater coil until the outer convolutions 34
and 36 engage respective guide surfaces 22 and 24. As the insulator
is inserted into the coil, the guide surfaces 22, 24 urge outer
surfaces 34 and 36 outwardly as they slide down respective guide
surfaces 22 and 24. After the outer convolutions 34 and 36 have
reached the lower ends of guide surfaces 22 and 24, they engage
edge surfaces 38 and 40 and then enter the notches 26 and 30. As
the outer convolutions 34, 36 enter the notches 26, 30, the resiliency
of the heater coil causes them to move into the notches until each
convolution engages the bottom of a respective notch. At this point,
the central convolution 18 has engaged the notch 20 and the insulator
is fully in place to support the heater coil. Parallel notches 10
and 12 are flanked by angled surfaces 46 and 48 to facilitate engaging
the wire 8 with the notches 10 and 12.
Protuberances 50 aid in stacking the insulators after manufacture
and perform no function in supporting the heater coil.
This installation procedure is very efficient and allows the installer
to easily align the insulator with the three convolutions 18, 34,
and 36 because of the elongated nature of the slot 16.
Modifications of the above-described structure within the scope
of the appended claims will be apparent to those of skill in the
art. |