Abstrict
The present invention relates to a novel constructional principle
for electric heaters, wherein the functions of frame and resilient
means are separated from one another. As a frame for an electric
heater, a housing is used that consists of two half-shells. Positioning
aids for the PTC heating elements are arranged in the housing. The
longitudinal sides of the housing are essentially made open to allow
for air throughput through the heating register. A resilient device
is additionally inserted into the housing, the resilient device
compressing the layered structure of radiator elements, PTC heating
elements and contact sheets. After the heater has been assembled,
the resilient device can be inserted through a lateral opening into
the heater.
Claims
I claim:
1. An electric heater, particularly as an auxiliary heating means
for automotive vehicles, comprising a housing which is made open
on the elongate housing faces, and a layered structure consisting
of at least one PTC heating element, a radiator element, contact
sheets for power supply and a resilient element, the layered structure
being kept clamped in the housing by the resilient element, wherein
an opening is provided laterally in the housing for inserting the
resilient element.
2. The electric heater according to claim 1, wherein a resilient
channel is formed in the housing for receiving the resilient element.
3. The electric heater according to claim 1 further comprising
positioning means for pre-fixing the elements of the heater in the
housing.
4. The electric heater according to claim 3, wherein the positioning
means in the housing simultaneously form a groove for guiding the
resilient element during insertion.
5. The electric heater according to claim 1, wherein the elongate
faces of the housing are mechanically reinforced by at least one
transverse strut.
6. The electric heater according to claim 5, wherein the struts
in the elongate faces of the housing have the shape of a grid structure.
7. The electric heater according to claim 5, wherein the grid structure
has at least one longitudinal strut in the area of the PTC heating
elements.
8. The electric heater according to claim 1, wherein said housing
is made from plastics.
9. The electric heater according to claim 1, wherein the housing
comprises positioning means for keeping the PTC heating elements
mutually spaced apart.
10. The electric heater according to claim 1, wherein the housing
comprises two half-shells.
11. The electric heater according to claim 10, wherein the half-shells
of the housing can be put together.
12. The electric heater according to claim 11, further comprising
locking pins or locking noses which, when the half-shells of the
housing are put together, effect a locking of the two half-shells.
13. The electric heater according to claim 10, wherein the half-shells
are configured such that they separate the housing approximately
in the middle between the elongate faces of the housing.
14. The electric heater according to claim 13, further comprising
respectively opposite projections provided on the separation line
of the half-shells which will engage each other when the half-shells
are assembled.
15. The electric heater according to claim 1, wherein the resilient
element consists of a sheet member with resilient segments projecting
therefrom.
16. The electric heater according to claim 1, wherein the resilient
element is configured such that it transmits the clamping forces
essentially onto the reinforced longitudinal sides of the housing.
17. The electric heater according to claim 15, wherein the resilient
element consists of a sheet member with resilient segments projecting
therefrom.
18. The electric heater according to claim 17, wherein each of
the resilient segments extends into the edge portions of the longitudinal
sides of the resilient member.
19. The electric heater according to claim 18, wherein the resilient
member is made integral with the resilient segments.
20. The electric heater according to claim 15, wherein at least
one resilient segment for generating clamping forces is provided
at each PTC heating element position for a frictional clamping action.
21. The electric heater according to claim 20, wherein at least
two resilient segments are provided for each PTC heating element
position.
22. The electric heater according to claim 1, further comprising
at least one seal for sealing longitudinal struts relative to the
PTC heating elements.
23. The electric heater according to claim 22, wherein the seal
seals the whole grid structure.
24. The electric heater according to claim 23, wherein the seal
for a housing side is respectively made integral.
25. A housing for an electric heater, particularly as an auxiliary
heating means for automotive vehicles, for receiving a layered structure
consisting of at least one PTC heating element, a radiator element,
contact sheets for power supply and a resilient element, the housing
having a lateral opening for insertion of the resilient element.
26. The housing according to claim 25, wherein a resilient channel
is formed in the housing for inserting the resilient element.
27. The housing according to claim 25, further comprising positioning
means in the housing for pre-fixing the elements of the heater.
28. The housing according to claim 27, wherein the positioning
means in the housing form a groove for guiding the resilient element
at the same time.
29. The housing according to claim 25, wherein the elongate faces
of the housing are mechanically reinforced by at least one transverse
strut.
30. The housing according to claim 29, wherein the struts in the
elongate faces of the housing having an open configuration are in
the form of a grid structure.
31. The housing according to claim 25, wherein the housing is made
from plastics.
32. A method for producing an electric heater, particularly as
an auxiliary heating means for automotive vehicles, comprising a
housing consisting of two half-shells and made open on the elongate
faces of the housing, and a layered structure consisting of at least
one PTC heating element, a radiator element, contact sheets for
power supply and a resilient element, the layered structure being
kept clamped by the resilient element in the housing, with the following
mounting steps: inserting the contact sheets, the radiator element,
and the PTC heating element into a first half-shell of the housing,
attaching the second half-shell of the housing to the first half-shell,
and inserting the resilient element through an opening of the assembled
housing to effect a clamping of the layered structure.
33. An auxiliary electric heater for an automotive vehicle, the
electric heater comprising: an open housing having elongate housing
faces; and a layered structure including of at least one PTC heating
element, a radiator element, contact sheets for power supply, and
a resilient element, the layered structure being clamped in the
housing by the resilient element, wherein an opening is provided
laterally in the housing for inserting the resilient element.
34. The electric heater according to claim 33, wherein a resilient
channel is formed in the housing for receiving the resilient element.
35. The electric heater according to claim 33, further comprising
positioning means for pre-fixing the elements of the heater in the
housing.
36. The electric heater according to claim 33, wherein the elongate
faces of the housing are mechanically reinforced by at least one
transverse strut.
37. The electric heater according to claim 33, wherein the housing
comprises positioning means for keeping the PTC heating elements
mutually spaced apart.
38. The electric heater according to claim 33, wherein the housing
comprises two half-shells.
39. The electric heater according to claim 33, wherein the resilient
element comprises a sheet member with resilient segments projecting
therefrom.
40. The electric heater according to claim 33, wherein the resilient
element is configured such that it transmits the clamping forces
essentially onto reinforced longitudinal sides of the housing.
41. The electric heater according to claim 40, wherein the sides
of the housing are reinforced by longitudinal struts, and further
comprising at least one seal for sealing the longitudinal struts
relative to the PTC heating elements.
42. A method for producing an auxiliary electric heater for an
automotive vehicle, the electric heater comprising a housing formed
from first and second half-shells and made open on elongate faces
thereof, and a layered structure including at least one PTC heating
element, a radiator element, contact sheets for power supply, and
a resilient element, the method comprising: inserting the contact
sheets, the radiator element, and the PTC heating element into the
first half-shell of the housing, attaching the second half-shell
of the housing to the first half-shell, and inserting the resilient
element through an opening of the assembled housing to effect a
clamping of the layered structure in the housing.
Description BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electric heater, particularly
as an auxiliary heating means for an automotive vehicle.
[0003] 2. Description of the Related Art
[0004] For use in automotive vehicles, particularly automotive
vehicles with new, consumption-optimized engines, in which a reduced
amount of heat energy is observed, electric auxiliary heaters are
used for heating passenger compartment and engine. Such electric
heaters are however also suited for other purposes, e.g. in the
field of building installations, particularly air conditioning,
in industrial plants, or the like.
[0005] Preferably, PTC heating elements with radiator elements
in heat-conducting communication are used for such an electric auxiliary
heater for an automotive vehicle. The heat generated by the PTC
heating elements is discharged via the radiator elements to the
air flowing therethrough. The total assembly consisting of a layered
structure of PTC heating elements, radiator elements and contact
sheets, which serve the supply of power, is kept in a clamp fit
within a frame for increasing the efficiency of the heater. Due
to clamping action a high electrical and thermal contacting of the
PTC heating elements is achieved.
[0006] The layered structure is held within a stable frame having
a preferably U-shaped cross-section. The frame is configured such
that it compresses the layered structure. The clamping action can
alternatively be effected by resilient elements arranged within
the layered structure. To enable the frame to absorb the resilient
forces, it is made particularly stable from a mechanical point of
view. Preferably, it is configured with a U-shaped cross-section.
Such a conventional heater is e.g. known from DE-A-101 21 568.
[0007] The minimum height of the longitudinal bars of such a frame
with U-shaped cross-section (or C-shaped cross-section according
to DE-A-101 21 568) is about 11 mm with respect to the necessary
clamping forces. This gives the whole heater a height of at least
22 mm that cannot be used for the passage of air. Such a constructional
shape with exterior clamping action or exterior holding frame has
therefore a large area that cannot be used for air throughput. That
is why such electric heaters are not suited for use in the case
of very small installation heights.
[0008] When electric heaters with an exterior holding frame or
exterior clamping action are assembled, troublesome measures are
needed for counteracting the contact pressure forces of the resilient
means/frame that are objectionable during assembly.
[0009] Due to these drawbacks heaters with a conventional holding
frame for modern air conditioners, especially for installation in
automotive vehicles, are less and less suited. Air conditioners
for multi-zone air conditioning in a comfort-based automotive vehicle
require more and more heaters of a large length, but small constructional
height.
[0010] Furthermore, conventional constructions with a holding frame,
particularly of metal, have a considerable weight. However, it is
desired for installation into automotive vehicles with respect to
the total weight of the vehicle that electric auxiliary heaters
should be used with a particularly low weight.
[0011] A further drawback of metal holder frames is their conductive
surface. To enhance the safety in automotive vehicles, metal surfaces
are more and more avoided so that their contact is possible without
any risk, i.e. without electrical or thermal conduction. To this
end the above-described heaters are preferably provided with a coating
of plastics, as is e.g. the case with the heater shown in DE-A-101
21 568.
OBJECTS AND SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide an electric
heater with an improved design that does not have the above-mentioned
drawbacks.
[0013] This object is achieved with the features of the independent
claims.
[0014] The electric heater of the invention and the housing for
an electric heater use a new constructional principle in which the
functions of frame and resilient means are separated from one another.
The PTC heating elements, the radiator elements and the contact
sheets are kept biased by a resilient element in a housing. The
housing has opposite openings on the longitudinal faces for allowing
air to be heated to flow therethrough. The longitudinal faces are
made particularly stable from a mechanical point of view and can
therefore absorb particularly high forces. To this end transverse
struts which absorb the clamping forces produced by the resilient
element are provided in openings of the elongate faces for the air
flowing therethrough. With the inventive structure electric heaters
can be used in many ways, particularly also in cases where the available
constructional height is small.
[0015] According to an advantageous development of the invention
longitudinal struts are provided in addition to the transverse struts
in the openings of the housing sides, so that the struts form a
grid structure. As a result, the struts as such can be kept particularly
thin, so that they will impede the air throughput only insignificantly
and nevertheless prevent deflection or bending of the housing in
an efficient way.
[0016] To minimize obstruction of the air throughput, the longitudinal
struts are particularly arranged such that they are located in the
area of the PTC heating elements. Preferably, the housing is made
of plastics. An essential advantage of a plastic housing is its
small weight, its flexible moldability and its low production costs.
[0017] In a further advantageous embodiment of the invention positioning
means are provided in the housing for keeping the PTC heating elements
mutually spaced apart in a plane perpendicular to the clamping direction.
The positioning means are preferably formed as part of the housing.
A separate positioning frame is thus no longer needed for fixing
the position of the PTC heating elements inside the heater.
[0018] According to an advantageous development of the invention
the housing has a lateral opening for insertion of the resilient
element after assembly of the heater. This makes the manufacture
of such a heater much easier because no special devices are needed
for overcoming the resilient forces during assembly. The resilient
means will only be inserted into the housing when the assembled
housing is capable of absorbing the forces produced by the resilient
means during compression of the layered structure. The resilient
means is preferably guided in a groove.
[0019] According to an advantageous embodiment the housing is composed
of two half-shells. This permits a particularly simple assembly
of the heater. To this end the half-shells are configured such that
they can be put together. A particularly fast assembly is possible
by using locking pins or locking noses effecting a locking of the
two half-shells when the half-shells of the housing are put together.
[0020] Both half-shells are preferably designed such that they
separate the housing approximately in the middle between the opposite
housing sides of an open construction. As a result, the housing
is particularly stable at the sides of an open construction, and
it is only in the middle, i.e. on the separation line of the two
half-shells that the housing can absorb either no or only small
clamping forces.
[0021] In a particular embodiment the two half-shells are provided
on their separation lines with additional projections and recesses
that engage one another when put together and interconnect the half-shells.
Thus the housing can also absorb higher forces in the central area
on the separation lines of the two half-shells.
[0022] The resilient element is configured such that it transmits
the clamping forces essentially to the reinforced housing sides.
[0023] The resilient element consists preferably of a sheet member
with obliquely projecting resilient segments. Preferably, the resilient
element is made integral with the resilient segment. The resilient
means can thus be produced as a continuous member for the first
time and supplied by a roll during production. Every resilient means
has to be manufactured separately in the prior art and produced
individually for different lengths. Since housing and resilient
means are separated, the thickness of the resilient means of about
0.8 mm in former times can be reduced to a thickness of about 0.3
mm according to the new constructional principle. As a result, the
resilient means can be produced with little effort and without any
decrease in the efficiency of the heater.
[0024] To achieve a high efficiency of the electric heater, a resilient
segment is provided for each position of a PTC heating element,
so that the clamping of the PTC heating elements is improved. A
particularly high efficiency can be achieved by enhancing the clamping
forces, and according to the invention a plurality of resilient
segments, preferably two or three, are provided in the area of a
PTC heating element.
[0025] According to a further preferred embodiment the resilient
means consist of a sheet member from which transversely inclined
individual resilient segments are projecting, the resilient segments
mechanically reinforcing the spring means such that a deflection
around the longitudinal axis of the spring means is not possible.
To this end the resilient segments extend each into the edge portion
of the resilient means so that the resilient means can be supported
on the stable outer housing edge. The housing must thus only absorb
forces on its edges and can be made less stable in the middle.
[0026] According to a particular development of the electric heater
a seal is provided between the longitudinal struts and the layered
structure.
[0027] Such a seal, particularly as a silicone seal, is preferably
made as one part and seals the whole grid structure.
[0028] Further advantageous embodiments of the invention are the
subject of the subclaims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The present invention shall now be explained with reference
to preferred embodiments taken in conjunction with the attached
drawings, which show in detail in:
[0030] FIG. 1 a perspective view of a half-shell of the housing
of the electric heater which is partly equipped;
[0031] FIG. 2 a perspective view of a half-shell of the housing
of the electric heater which is fully equipped;
[0032] FIG. 3 a perspective view of the electric heater;
[0033] FIG. 4 a perspective view of the electric heater in which
the resilient element is inserted;
[0034] FIG. 5 a perspective view of another embodiment of the heater
according to the invention;
[0035] FIG. 6 a further perspective view of the embodiment shown
in FIG. 5, in which the housing side is adapted by way of example
to a special connector geometry;
[0036] FIG. 7 a further detail view of the embodiment shown in
FIG. 5;
[0037] FIG. 8 a perspective view of a further embodiment of the
heater according to the invention during assembly;
[0038] FIG. 9 a perspective view of the assembled embodiment according
to FIG. 8;
[0039] FIG. 10 a detail view of the inner side of a half-shell
of the housing of a further embodiment of the invention;
[0040] FIG. 11 a sectional view through the assembled housing according
to the embodiment of FIG. 10;
[0041] FIG. 12 an enlarged view of a detail of the illustration
shown in FIG. 11;
[0042] FIG. 13 an inner view of the grid structure of the elongate
faces of the housing with silicone seals;
[0043] FIG. 14 a perspective, enlarged sectional view of a half-shell
of the housing with seal;
[0044] FIGS. 15a, 15b, and 15c various views of a resilient element
according to the invention;
[0045] FIG. 16a a view of a corrugated rib element with a contact
sheet attached to said element; and
[0046] FIG. 16b a view of a further resilient element which can
inter alia be inserted into the embodiment of the invention according
to FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] In contrast to conventional electric heaters for use in
automotive vehicles, the heater according to the invention is composed
of two half-shells of plastics. During production one housing half
can first be equipped in an easy way and the housing is then completed
by mounting the second housing half.
[0048] FIGS. 1 to 4 show successive assembling stages of the heater
according to the invention, the stages illustrating the structure
of the heater according to the invention. FIG. 1 is a perspective
view showing one half-shell 2a of half-shells 2a, 2b of the housing.
A contact sheet 6, a radiator element 4 and, next thereto, PTC heating
elements 3 are inserted into the half-shell 2a. For an easy assembly
guide rails and positioning means, respectively, are provided for
all components. Especially the position of the contact plate 6 with
the contact pin 6a is defined during insertion via guide 6b (and
7b, respectively, for contact plate 7 in FIG. 2). The radiator elements
4 are preferably designed in the form of corrugated rib elements.
At one side the corrugated rib element is provided with a contact
plate. Guides 4a are provided laterally in the inside of the housing
for the ends of the contact plate of the corrugated rib element
4. Said guides solely serve to facilitate the assembly. In an alternative
embodiment, they can thus be omitted as well.
[0049] To isolate the PTC heating elements 3 also in the installed
state from one another, positioning means 5 are provided in a half-shell
of the housing for keeping the PTC heating elements 3 in spaced-apart
relationship with one another. Said positioning means 5 are preferably
fastened on a longitudinal strut 10 to the lateral housing faces.
Said struts will be described in detail in the following.
[0050] As shown in FIG. 2, a radiator element 4 and a contact plate
7 with a plug contact 7a are again provided above the PTC heating
elements 3, matching the structure shown in FIG. 1. The second half-shell
2b of the housing can be attached to the first half-shell 2a equipped
in this way. Both half-shells of the housing are preferably configured
such that their separation line extends approximately in the middle
between the two elongate housing faces (which comprise the passage
openings).
[0051] The assembly of the housing can particularly be simplified
in that both half-shells 2a, 2b are provided with locking pins 18
and corresponding bores in the respectively opposite half-shell.
When the two half-shells are put together, they will lock as soon
as the second half-shell 2b has been completely attached to the
first half-shell 2a.
[0052] The assembled housing of the electric heater is again shown
in FIG. 3. As can be seen in FIG. 3, each of the housing halves
2a, 2b is provided on the elongate faces with openings for the air
flowing therethrough.
[0053] To enhance the efficiency of the heat generation by the
PTC heating elements, said elements are kept clamped within the
housing in the layered structure described with reference to FIGS.
1 and 2. This clamping action is effected by an additional resilient
element 12. Preferably, the resilient element is inserted at least
between an inner side of the housing and the layered structure.
In addition, such a resilient element may also be inserted between
the opposite inner side of the housing and the layered structure
or at a place within the layered structure.
[0054] To enable the housing to absorb the clamping forces without
deformation of the housing, the elongate housing faces are mechanically
reinforced. The housing is not capable of absorbing high clamping
forces between the mechanically reinforced housing faces, particularly
in the area of the separation line.
[0055] To be able to absorb particularly high clamping forces,
transverse struts 9 are provided inside the lateral opening for
the air to be heated. Said transverse struts make it possible for
the housing to absorb sufficiently high clamping forces without
any deflection or deformation of the housing. The half-shells with
the struts are each made integral and are preferably made from plastics.
[0056] In a particularly advantageous embodiment, the transverse
struts 9 are supplemented by one or more longitudinal struts 10,
so that the struts 9 and 10 have the shape of a grid structure.
With such a grid structure the transverse struts 9 can be made particularly
thin and do not impede the air throughput. A bending up of the housing
is efficiently prevented at the same time.
[0057] The stability of the housing between the mechanically reinforced
faces of the housing is enhanced in an advantageous embodiment by
a special design of the upper and lower sides of the half-shells.
To this end projections 16 and recesses 17 are respectively provided
on the upper and lower housing side of each half-shell 2a, 2b, and
are arranged such that they engage into one another when put together.
The mechanical stability of the upper and lower sides is thus also
enhanced between the mechanically reinforced elongate housing faces.
[0058] Since it is only after assembly that the housing is capable
of absorbing high clamping forces without any deformation of the
housing, the resilient element 12 can only be inserted after assembly
of the housing. To this end the housing 2 is provided on a housing
side with an opening 11. Such an opening is preferably provided
on the narrow sides of the housing 2. Each housing half 2a, 2b has
corresponding recesses that in the assembled state of the housing
2 supplement one another to form a slit 11 for insertion of the
resilient element 12. A special design of the inner sides of the
housing for forming a resilient channel for the insertion of the
resilient element 12 will be described in the following with reference
to FIGS. 10 to 12.
[0059] The positioning means 4a, 5, 6b, 7b, which are provided
in the housing, are arranged such that the pre-positioned elements
of the heater leave enough space for the resilient element. To be
more specific, the pre-positioned elements are fixed with a play
in the clamping direction effected by the resilient means to keep
them movable and to absorb the clamping pressure generated by the
resilient means.
[0060] As can be seen in FIG. 4, the resilient element 12 has a
plurality of individual resilient segments for producing the clamping
pressure. Preferred embodiments of the resilient element 12 will
now be discussed in connection with FIGS. 10a, 10b, and 10c.
[0061] In the illustrated embodiments, the contact plates 6 and
7 are each arranged on the outside in the layered structure, so
that the power supply takes place via the radiator elements 4 to
the PTC heating elements 3. Said structure effects an excellent
heat transition between the PTC heating elements 3 and the radiator
elements 4 which output the heat to the air flowing therethrough,
and heat conduction losses are therefore particularly small.
[0062] Thanks to the arrangement of the contact plates at the upper
and lower ends of the layered structure of the elements of the heater,
the air throughput is virtually not impeded. This makes it possible
to keep the constructional height small without any reduction of
the air passage volume.
[0063] Due to the design of the housing according to the invention
with elongate housing faces that are made particularly stable from
a mechanical point of view, the clamping forces are not received
by the side bars of the holding frame in the conventional way. The
narrow sides of the housing can thus be designed in any desired
way. Preferably, the narrow sides of the housing are designed such
that they allow for a mechanical fixation and electrical contacting
of the heater. For electrical contacting at least one narrow side
of the housing can be adapted in any desired way to the geometry
of a connector for the supply of power.
[0064] The design of the narrow sides is shown by way of example
in FIGS. 1 to 4. At the left housing side a connector shape is formed
from the projections 13a, 13b respectively formed on both housing
halves. Connector tongues 6a and 7a of the two contact plates 6,
7 project into said connector. At the opposite side, a connector
14 is formed from the projections 14a, 14b, the connector essentially
serving the mechanical fastening of the electric heater. Since the
narrow sides of the housing 2 cannot absorb great forces, they can
be designed in any desired way for mechanical and/or electrical
fastening.
[0065] FIGS. 5 to 7 show a further embodiment of a housing and
a corresponding electrical heater. FIG. 5 shows a perspective view
of an embodiment of an electric heater 20 which is made smaller
than the embodiment of FIGS. 1 to 4, but has a larger cross-sectional
area for a higher air throughput. To this end the heater comprises
PTC heating elements 3 in a plurality of planes in the layered structure.
In contrast to FIG. 1, the PTC heating elements 3 having a rectangular
shape are oriented with their longitudinal sides parallel to the
elongate housing faces of the heater.
[0066] In accordance with each layer with PTC heating elements
3 in the layered structure consisting of radiator elements 4, PTC
heating elements 3 and electrode sheets 21, 22, longitudinal struts
10 are respectively provided at the level of the layers with PTC
heating elements 3. In the illustrated embodiment, a total of four
layers with PTC heating elements 3 are present, and thus also four
longitudinal struts. Due to the larger longitudinal extension of
the heater in comparison with the heater of FIGS. 1 to 4, said embodiment
also comprises a greater number of transverse struts 9.
[0067] In contrast to the first embodiment, two resilient elements
12 are used in the illustrated heater, the two elements being inserted
at the upper end and lower end, respectively, on the narrow side
of the housing. The resilient means are each inserted in such a
way that the resilient segments 26 projecting from the resilient
element 12 protrude from the housing surface towards the layered
structure. Although this is not shown, further resilient elements
12 can also be inserted between the illustrated positions into the
layered structure.
[0068] On account of the plurality of the layers illustrated in
this embodiment with PTC heating elements 3, a correspondingly higher
number of contact sheets is needed. The uppermost and lowermost
ones of the contact sheets 22 are arranged next to the upper housing
inside and the lower housing inside, respectively. The three middle
contact sheets are each arranged next to the three lower layers
with PTC heating elements, i.e. matching the three lower ones of
the longitudinal struts 10.
[0069] Each of the contact sheets 21, 22 has contact tongues 21a,
22a projecting out of the frame. The housing side 23 from which
the contact tongues 21a, 22a are projecting may have any design.
A particular embodiment is shown in FIG. 6. The housing 23 as shown
in FIG. 5 has attached or adhered thereto an individually adapted
connector shape 25. Said adhered connector shape can be adapted
to the respective requirements, e.g. for installation of the heater
in vehicles of different car manufacturers using different types
of plug contacts. In the embodiment shown in FIG. 6, the attachable
connector attachment 25 consists of a mechanical stop with fastening
holes and a connector shoe 25a in which the contact tongues 21a,
22a are arranged.
[0070] According to a further special embodiment the housing is
laterally sealed with the help of silicone seals. The silicone seals
24 are preferably arranged on the longitudinal struts as shown in
FIGS. 5 to 7 and 11, 12. The silicone seals 24 are here arranged
on the longitudinal struts, i.e. each exactly at the level of the
PTC heating elements 3.
[0071] For an easier assembly during insertion of the seals, the
silicone seals 24 have the shape of the grid structure of the struts.
Manufacture is thereby simplified considerably because the seals
for the longitudinal struts need not be inserted individually, but
can be inserted as a whole in one step.
[0072] FIGS. 8 and 9 are perspective views showing a further embodiment.
Said embodiment differs from the embodiment shown in FIGS. 6 and
7, particularly by the number of the transverse struts. In this
embodiment, use is made of fewer, but more stable transverse struts.
[0073] Preferably, transverse struts are arranged at a distance
of 30 to 40 mm. At a distance of the transverse struts greater than
40 mm, particularly starting from about 60 mm, the clamping forces
can no longer be received to an adequate extent by the transverse
struts. By contrast, below a distance of the transverse struts of
less than 30 mm, particularly less than 20 mm, the air throughput
is considerably impeded by the elongate faces of the heater.
[0074] FIGS. 10 to 12 show a particular embodiment for the design
of the insides of the two half-shells of the housing. The inner
structure of the half-shells comprises a resilient channel into
which the resilient means 12 can be inserted after assembly of the
two half-shells of the housing. The resilient channel effects a
guiding of the resilient means during insertion, namely via laterally
extending grooves. The grooves are e.g. formed by projections 34
and either by the upper side of the housing or, like in the illustrated
embodiment, via locking tabs 32a, 32b.
[0075] The projection 34 forms not only one side of the resilient
channel for the insertion of the resilient means, but also serves
as a positioning aid of the elements of the heater. These are (pre-)fixed
by the projection 34 with a play in the housing around an insertion
channel for the resilient means to be inserted after assembly.
[0076] Furthermore, the embodiment shown in FIGS. 10 to 12 has
a higher stiffness. Such an additional stiffening may be required,
for instance for the following reasons. To achieve a high efficiency
also in the case of "large-area heaters", i.e. heaters
that are small, but formed with a large area for a high air throughput,
very high clamping forces are needed. However, at housing temperatures
of about 170.degree. C., the stiffness of the used plastic material
is decreasing. Moreover, the resilient means can transmit the force
not only to the edge of the housing because the resilient segments
used have a minimum distance of about 2 mm to 2.5 mm from the edge
of the resilient means. However, to prevent a deflection of the
upper and lower housing sides, said sides are preferably stiffened
in addition. To this end, oppositely arranged locking tabs 32a,
32b are respectively provided in both half-shells of the housing.
Each of the locking tabs projects in the direction of the opposite
housing halves, and they are interlocked via locking noses 31 during
assembly. Thanks to this toothing on the upper and lower housing
sides, the mechanical stiffness thereof is enhanced and deflection
is avoided.
[0077] A further increase in stiffness can be achieved through
an additional side wall 35, 36. Said side wall 35, 36 is respectively
arranged above the former side walls and connected thereto via supporting
elements 33. The mechanical stiffness of the upper and lower sides
can thereby be increased such that the housing can receive particularly
high clamping forces. This permits a "large-area construction",
i.e. a heater having a large number of superimposed layers of PTC
elements and interposed radiator elements.
[0078] The construction of the resilient element 12 will be described
in the following with reference to FIGS. 13a, 13b and 13c. FIG.
13a shows a top view on the resilient element 12, FIG. 13b a side
view, and FIG. 13c a perspective view of the resilient element 12.
[0079] The resilient element 12 consists of a sheet member 26 and
resilient segments 26 projecting therefrom. Preferably, the resilient
element 12 is made integral, each of the resilient segments being
punched on three sides out of the sheet member 25 and bent around
an axis 29 in the transverse direction of the sheet member 25. The
angle .alpha. around which the punched segments are bent out is
approximately between 50 and 30.degree., preferably between 15.degree.
and 20.degree.. This construction of the resilient element 12 prevents
a deflection in transverse direction and only allows one in longitudinal
direction. As a result, the resilient element only acts on the housing
edge on which it is supported during generation of the clamping
force. Thus the resilient means ideally cooperates with the housing,
which on account of its construction can only receive large forces
in the housing sides and is less capable of bearing loads in the
middle in the area of the separation line. Preferably, the lateral
ends of the resilient segments are arranged close to the edge of
the resilient element for this purpose.
[0080] The illustration in FIGS. 13a, 13b and 13c is just a schematic
one. The resilient segments 26 need not be rectangular, but may
also have areas of different width and inclination. For instance,
each resilient segment may have a broader end section which is slightly
flattened to allow the resilient element to be pushed into the housing
in an improved way.
[0081] FIG. 16a shows a radiator element 4 and a contact sheet
6 connected thereto in an elongate embodiment for a "large-area
heater" (e.g. according to FIG. 9). The corresponding resilient
element is shown in FIG. 16b. The resilient element has a number
of successively arranged resilient segments 26. Each of the resilient
segments 26 is able to exert a contact pressure force of about 15
N. For enhancing the contact pressure force the resilient segments
according to FIG. 16b are tightly positioned one after the other
such that two or more resilient segments 26 are arranged across
the surface of a PTC element. This doubles or even triples the clamping
pressure. In contrast to conventional frame mountings, the clamping
pressure is here evenly exerted over the whole length of the resilient
means.
[0082] To allow the clamping forces to be absorbed by the resilient
segments 26, the elongate faces of the housing can be equipped with
transverse struts 9 such that two to not more than five resilient
segments 26 are arranged between two successive transverse struts
9.
[0083] The embodiment according to FIG. 4 shows a resilient element
12 with two or more adjacently arranged resilient segments. This
embodiment is advantageous in the case of shapes of housings that
have a large depth.
[0084] While resilient means of a thickness of about 0.8 mm are
used in the conventional way, resilient elements having a thickness
of 0.2 to 0.5 mm, preferably about 0.3 mm, are employed in the new
constructional principle. This effects a resilient action of the
resilient segments 26 also at a small length of a resilient segment.
[0085] A special advantage of the heater of the invention is that
the resilient element can be produced as an endless member for the
first time and can thus be supplied from a roll during manufacture.
Conventionally, each resilient segment is made separately and produced
individually for all of the different heater lengths. Moreover,
it suffices to provide only one resilient element per heater.
[0086] Apart from the small constructional height, a special advantage
of the heater of the invention is that said heater can be produced
in a particularly simple way. The heater is assembled as described
in connection with FIGS. 1 to 4. According to the invention the
individual elements are assembled--in contrast to conventional heaters--without
the clamping forces acting on the layered structure. It is only
after assembly of the housing that the resilient means is slid into
the assembled housing (cf. FIG. 4).
[0087] To sum up, the invention refers to a new constructional
principle for electric heaters in which the functions of frame and
resilient means are separated from one another. A housing is used
as a frame for an electric heater, the housing consisting of two
half-shells. Positioning aids for the PTC heating elements are arranged
in the housing. The longitudinal sides of the housing are made substantially
open to allow air throughput through the heating register. In addition,
a resilient means which compresses the layered structure of radiator
elements, PTC heating elements and contact sheets is additionally
inserted into the housing. The resilient means can be slid into
the housing at a later time through an opening provided laterally
in the housing. As a result, the housing will only be exposed to
resilient forces after assembly when it can be loaded mechanically.
[0088] The new constructional principle has a number of advantages.
On the one hand the weight can be reduced considerably at the same
heating capacity with the construction according to the invention,
as no metal frame is used, i.e. up to about 50 percent. Moreover,
without additional measures and without additional weight, the heater
has no exposed metal surfaces. A further advantage is the low constructional
height that is up to about 30 percent below that of the conventional
heaters. It is thus possible to realize also much smaller heating
means than in the prior art, the heating means nevertheless achieving
a high efficiency due to the clamping principle employed for increasing
electrical and thermal contacting. Moreover, it is also possible
to produce longer heating elements that with the conventional holding
frame construction can only be realized under great efforts.
[0089] Moreover, a conventional positioning frame is not used for
keeping the PTC heating elements spaced apart and for protecting
the same, but the PTC heating elements are directly separated from
one another via housing projections.
[0090] Moreover, the manufacturing efforts are considerably reduced
in comparison with conventional heaters. The manufacture of the
heater of the invention is much easier because no special device
is needed for overcoming the resilient forces of the frame in the
production process.
[0091] The constructional principle requires no special design
of the side bars of a holding frame for absorbing the clamping force
acting on the longitudinal bars. The narrow sides of the housing
of the invention can thus be adapted in their design to any desired
connector geometry surrounding the connector tongues of the contact
sheets projecting from the housing.
[0092] In addition, the resilient means can thereby be produced
at considerably lower costs. On the one hand, the thickness of the
resilient means can be reduced and material can thus be saved. On
the other hand, the resilient element can now be produced for the
first time as a continuous member and supplied from a roll during
manufacture. Moreover, a single resilient member is sufficient.
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