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 auxiliary electric heater for automotive vehicles, comprising
a housing which is made open on longitudinal 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 layered structure being kept clamped in the housing
by the resilient element, wherein an opening is provided in a lateral
face of 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 simultaneously form a groove for guiding the resilient element
during insertion.
5. The electric heater according to claim 1, wherein the longitudinal
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 longitudinal 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
element.
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 layered
structure includes multiple PTC heating elements, and wherein the
housing further 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 an interlocking 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 longitudinal faces of the housing.
14. The electric heater according to claim 13, further comprising
respectively opposite projections provided on a 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 comprises 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 clamping forces essentially
onto reinforced longitudinal sides of the housing.
17. The electric heater according to claim 15, wherein each of
the resilient segments extends into edge portions of longitudinal
sides of the sheet member.
18. The electric heater according to claim 17, wherein the sheet
member is made integral with the resilient segments.
19. The electric heater according to claim 15, wherein the layered
structure includes multiple PTC heating elements, and wherein at
least one resilient segment is provided at each PTC heating element
position for a frictional clamping action.
20. The electric heater according to claim 19, wherein at least
two resilient segments are provided for each PTC heating element
position.
21. The electric heater according to claim 1, further comprising
at least one seal for sealing longitudinal struts relative to the
PTC heating elements.
22. The electric heater according to claim 21, wherein the longitudinal
faces of the housing are mechanically reinforced by transverse struts
having the shape of a grid structure, and wherein the seal seals
a whole grid structure.
23. The electric heater according to claim 22, wherein the seal
for a housing side is respectively made integral.
24. A housing for an auxiliary heater for automotive vehicles,
the housing comprising: a housing structure for receiving a layered
structure including at least one PTC heating element, a radiator
element, contact sheets for power supply, and a resilient element,
wherein the housing structure has a lateral opening for insertion
of the resilient element.
25. The housing according to claim 24, wherein a resilient channel
is formed in the housing structure for inserting the resilient element.
26. The housing according to claim 24, further comprising positioning
means in the housing structure for pre-fixing the elements of the
heater.
27. The housing according to claim 26, wherein the positioning
means in the housing structure form a groove for guiding the resilient
element at the same time.
28. The housing according to claim 24, wherein the housing structure
has longitudinal faces that are mechanically reinforced by at least
one transverse strut.
29. The housing according to claim 28, wherein the struts in the
longitudinal faces of the housing structure have an open configuration
and are in the form of a grid structure.
30. The housing according to claim 24, wherein the housing is made
from plastics.
31. An auxiliary electric heater for an automotive vehicle, the
electric heater comprising: a housing having open longitudinal 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 in a lateral face
of the housing for inserting the resilient element.
32. The electric heater according to claim 31, wherein a resilient
channel is formed in the housing for receiving the resilient element.
33. The electric heater according to claim 31, further comprising
positioning means for pre-fixing the elements of the heater in the
housing.
34. The electric heater according to claim 31, wherein the longitudinal
faces of the housing are mechanically reinforced by at least one
transverse strut.
35. The electric heater according to claim 31, wherein the housing
comprises positioning means for keeping the PTC heating elements
mutually spaced apart.
36. The electric heater according to claim 31, wherein the housing
comprises two half-shells.
37. The electric heater according to claim 31, wherein the resilient
element comprises a sheet member with resilient segments projecting
therefrom.
38. The electric heater according to claim 31, wherein the resilient
element is configured such that it transmits the clamping forces
essentially onto reinforced longitudinal sides of the housing.
39. An auxiliary electric heater for an automotive vehicle, the
electric heater comprising: a housing having open longitudinal 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 in a lateral face
of the housing for inserting the resilient element, wherein the
resilient element is configured such that it transmits the clamping
forces essentially onto reinforced longitudinal sides of the housing,
and 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.
40. The electric heater according to claim 1, wherein the opening
is fully enclosed about an entire perimeter thereof.
41. The housing according to claim 24, wherein the opening is fully
enclosed about an entire perimeter thereof.
42. The electric heater according to claim 31, wherein the opening
is fully enclosed about an entire perimeter thereof.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric heater, particularly
as an auxiliary heating means for an automotive vehicle.
2. Description of the Related Art
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.
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.
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.
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.
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.
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.
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.
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
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.
This object is achieved with the features of the independent claims.
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.
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.
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.
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.
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.
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.
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.
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.
The resilient element is configured such that it transmits the
clamping forces essentially to the reinforced housing sides.
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.
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.
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.
According to a particular development of the electric heater a
seal is provided between the longitudinal struts and the layered
structure.
Such a seal, particularly as a silicone seal, is preferably made
as one part and seals the whole grid structure.
Further advantageous embodiments of the invention are the subject
of the subclaims.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention shall now be explained with reference to
preferred embodiments taken in conjunction with the attached drawings,
which show in detail in:
FIG. 1 a perspective view of a half-shell of the housing of the
electric heater which is partly equipped;
FIG. 2 a perspective view of a half-shell of the housing of the
electric heater which is fully equipped;
FIG. 3 a perspective view of the electric heater;
FIG. 4 a perspective view of the electric heater in which the resilient
element is inserted;
FIG. 5 a perspective view of another embodiment of the heater according
to the invention;
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;
FIG. 7 a further detail view of the embodiment shown in FIG. 5;
FIG. 8 a perspective view of a further embodiment of the heater
according to the invention during assembly;
FIG. 9 a perspective view of the assembled embodiment according
to FIG. 8;
FIG. 10 a detail view of the inner side of a half-shell of the
housing of a further embodiment of the invention;
FIG. 11 a sectional view through the assembled housing according
to the embodiment of FIG. 10;
FIG. 12 an enlarged view of a detail of the illustration shown
in FIG. 11;
FIG. 13 an inner view of the grid structure of the elongate faces
of the housing with silicone seals;
FIG. 14 a perspective, enlarged sectional view of a half-shell
of the housing with seal;
FIGS. 15a, 15b, and 15c various views of a resilient element according
to the invention;
FIG. 16a a view of a corrugated rib element with a contact sheet
attached to said element; and
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
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.
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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 5.degree. 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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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.
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.
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. |