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(11) | EP 0 242 116 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Heat exchanger |
| (57) A header tank for a heat exchanger, e.g. a vehicle radiator, comprising a plastics
header tank shell (1) having an aperture (10) in a recess (6) in a side face (2) into
which a component, e.g. a thermostat (7), is to be push-fitted and a retaining member
(15) attachable to the shell (1) for preventing blow-out of the thermostat (7) and
having resilient arms (18) which fit into the recess (6) and which engage and snap
fit with projections (17) in the side walls of the recess (6). As no part of the shell
(1) provided for engaging the retaining member (15) projects beyond the outer surface
of the face (2), manufacture of the shell (1) by die-casting is facilitated. Several
different ways of attaching different forms of retaining members (15) to the side
walls of the recess (6) are described. |
[0001] This invention relates to a header tank for a heat exchanger, eg a motor vehicle radiator, and particularly to the fitting of a component such as a thermostat into a plastics header tank shell.
[0002] It is known to install a component such as a thermostat into a header tank shell of a motor vehicle radiator by means of a screw thread provided on the housing of the thermostat itself but this type of fitting is expensive to manufacture. It is also known to install a thermostat into a header tank shell by means of a push fit into a resilient grommet in an aperture in a side face of the shell. However, with this type of fitting it is necessary to provide some kind of security device to prevent the thermostat being pushed or blown out of the header tank shell if the pressure within the radiator rises above the level the push-fit arrangement is designed to withstand. A known security device comprises a cap which is attached by a bayonet fitting to a substantially cylindrical projection provided around the aperture in the side face of the shell.
[0003] A rib is usually provided on the header tank shell on to which a portion of a tube plate is clenched to connect the header tank shell to the rest of the radiator.
[0004] To produce the cylindrical projection, when the header tank shell is made from a plastics material by die casting, a raised area must be provided between the cylindrical projection and the rib to allow the cast shell to be removed from the die.
[0005] This raised area will prevent proper clenching of the tube plate to the rib in that area and thus weakens the connection between the header tank connection between the header tank shell and the tube plate. This is particularly disadvantageous, and would leave the connection prone to leakage if two thermostats (or other components), are installed on the header tank adjacent to each other as this would create a raised portion which may extend along the rib for a considerable percentage of its length.
[0006] According to this invention there is provided a header tank for a heat exchanger comprising: a plastics header tank shell having an aperture in a side face thereof into which a component is to be push-fitted; and a retaining member attachable to the header tank shell for limiting movement of a component out of the aperture, the retaining member having connecting means which fit into and engage with a recess in the said side face of the header tank shell, the arrangement being such that no part of the header tank shell provided for engaging with the retaining member projects beyond the outer surface of the said face.
[0007] Such an arrangement provides a simple means of fitting a component into a header tank sheel and, in the circumstances described above, the header tank shell can be formed by a die-casting method without leaving any raised portion adjacent the fitting for the component to obstruct proper clenching between the shell and a tube plate.
[0008] Preferred features of the invention will be apparent from the following description and from the subsidiary claims of the specification.
[0009] The invention will now be described, merely by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a side view of part of a prior art header tank shell;
Figure 1A is a plan view of part of a header tank shell of a first embodiment of the invention;
Figure 2 is a cross-sectional view on the line II-II of the shell shown in Figure 1A forming part of a radiator and showing a thermostat installed therein;
Figure 3 is a cross-sectional view corresponding to that shown in Figure 2 for a second embodiment of the invention;
Figure 4 is a perspective view of the retaining member shown in Figure 3;
Figure 5 is a perspective view of part of an alternative form of the header tank shell shown in Figure 3;
Figure 6 is a perspective view of an alternative form of the retaining member shown in Figure 4 for use with the header tank shell shown in Figure 5;
Figure 7 is a perspective view of part of a header tank shell of a third embodiment of the invention;
Figures 8A and 8B are perspective views from opposite side of a retaining member for the header tank shell shown in Figure 7;
Figure 9A and 9B are cross-sectional views showing how the retaining member of Figures 8A and 8B is fitted to the header tank shell;
Figure 10 is a perspective view of part of a header tank shell of a fourth embodiment of the invention;
Figure 11 is a plan view of part of the shell shown in Figure 10 in the area around the recess;
Figure 12 is a perspective view of a retaining member for the header tank shell shown in Figures 10 and 11; and
Figures 13A and 13B are cross-sectional views showing how the retaining member of Figure 12 is fitted to the header tank shell shown in Figures 10 and 11.
[0010] With reference to Figure 1 there is shown a prior art header tank shell 1A formed of a plastics material and having a side face 2A and a rib 3A. The shell 1A is also formed with a raised cylindrical water inlet 5A and a raised cylindrical boss 6A for receiving a thermostat (not shown).
[0011] To allow the header tank shell 1A to be removable from the die after it has been cast there is a raised portion 12A extending from the water inlet 5A and boss 6A to the rib 3A.
[0012] The provision of this raised portion 12A prevents the rib 3A being used as a means of securing between the points X and Y.
[0013] Figure 1A is a plan view of part of a header tank shell 1 of a first embodiment of the invention. The shell 1 is formed of a plastics material and has a side face 2 a rib 3 extending along an edge of the side face 2 to which a tube plate 4 (see Figure 2) is clenched when the shell 1 is assembled in a radiator.
[0014] Another rib 3 is provided along an edge of the opposite side face of the shell as shown in Figure 2. The shell 1 is also formed with a water inlet (or outlet) 5, which comprises an aperture surrounded by a cylindrical member which projects from the side face 2, and a recess 6 for receiving a component such as a thermostat 7 (see Figure 2). The recess 6 comprises a screw thread 8 in its side walls, a shoulder 9 and a circular aperture 10. Figure 1 also shows a bracket 11 for use in mounting the radiator in a motor vehicle.
[0015] It will be seen that there is a short raised portion 12 on the side face 2 extending from the inlet 5 to the adjacent portion of the rib 3. The raised portion 12 is provided to enable the shell 1 to be formed by a die casting process in which the die is moved away upwardly (in the orientation shown in the drawing) when the shell is removed therefrom. If the raised portion 12 were not provided, the shell I could not be formed in this way since there would be a recess between the rib 3 and the inlet 5 which would prevent the shell 1 from being withdrawn from the die. It will be appreciated that a similar raised portion has to be provided between any part of the shell I which projects beyond the outer surface of the side face 2 and the adjacent portion of the rib 3.
[0016] Figure 2 is a cross-sectional view along the line II-II through the recess 6 of the shell 1 shown in Figure 1A when forming part of a radiator and having a thermostat 7 installed in the recess 6. The shell 1 is attached by the tube plate 4 which is clenched around ribs 3 to the radiator matrix 13. A raised portion 12 on the side face 2 as shown in Figure 1A would, of course, prevent proper clenching of the tube plate 4 around the rib 3. The raised portion 12 adjacent the inlet 5 shown in Figure 1A thus weakens the connection between the tube plate 4 and the shell 1 in that area but since it extends only for the width of the inlet 5 it does not seriously threaten the water-tightness of the connection. However, when it is necessary to install a component such as the thermostat 7 adjacent to the inlet 5 or to install two such components adjacent to each other, because of restrictions on the availability of space along the length of the shell 1, it becomes necessary to avoid such raised portions since the combined width of two such raised portions adjacent one another (as shown in Figure 1) would seriously prejudice the strength of the connection between the tube plate 4 and the shell 1 in that area and so make the connection prone to leakage. The fitting illustrated in Figure 2 and the following Figures enables a component such as the thermostat 7 to be installed in the shell 1 with a security device fitted over it to prevent blow-out without the need for a raised portion extending between the fitting and the adjacent portion of the rib 3.
[0017] The thermostat 7 shown in Figure 2 is push-fitted into a resilient grommet 14 installed in the aperture 10. A flange is provided at one end of the grommet 14 to sit on the shoulder 9 and prevent the grommet being pushed into the interior of the shell 1. In this embodiment the security device for preventing blow-out of the thermostat 7 comprises a retaining member 15 provided with a thread which screws into the thread 8 in the side wall of the recess 6. The retaining member 15 is substantially cylindrical in shape to allow access to electrical terminals 16 of the thermostat 7 but has a stepped portion or flange 15A which extends over the casing of the thermostat 7 to limit the extent to which the thermostat can move out of the recess 6 if the pressure within the shell I rises to a level which overcomes the frictional engagement between the thermostat 7 and the grommet 14.
[0018] Figure 3 is a cross-sectional view corresponding to that shown in Figure 2 of a second embodiment of the invention. This embodiment is similar to that shown in Figure 2 except that the retaining member 15 engages with the recess 6 by means of a snap-fit arrangement rather than by a screw thread. The recess 6 may be circular or rectangular but again comprises a shoulder 9 and a circular aperture 10. The side walls of the recess 6 are, however, provided with saw tooth shaped ribs 17 rather than a screw thread. The retaining member 15, a perspective view of which is shown in Figure 4, has two resilient arms 18 each carrying a saw-tooth projection 19. To attach retaining member 15 to the header tank shell 1 after the thermostat 7 has been installed therein, the two arms 18 are inserted into the recess 6. As the arms 18 are pushed into the recess 6 they are elastically deformed as the saw-tooth projection 19 ride over the ribs 17 until they spring back so that the projections engage with the underside of the ribs 17 as shown in Figure 3. This type of snap-fitting is easy to assemble and less expensive to manufacture than the screw thread illustrated in Figure 2.
[0019] Figure 5 is a perspective view of an alternative form of the header tank shell shown in Figure 3. In this case, the recess 6 is substantially rectangular in shape and the ribs 17 extend along the sides of the recess which are perpendicular to the rib 3 along the edge of the shell 1. With this arrangement the side of the recess 6 adjacent the rib 3 has a cut out 20 and the side of the recess 6 opposite the rib 3 is open and so enables the recess 6 and the ribs 17 to be formed when the shell 1 is die-cast as the die can be withdrawn from the recess through its open side.
[0020] The retaining member 15 as shown in Figure 6 has part of the cylindrical wall cut away so that the retaining member can be slid with its open side leading into the recess 6 through the open side thereof until it engages the cut-out 20 in the wall of the recess 6 nearest to the rib 3. The retaining member needs to be cut away as shown to allow it to pass over the electrical terminals 16 of the thermostat as it is slid into the recess 6. The retaining member 15 shown in Figure 6 also has two arms 18 and these are preferably also resilient to assist in holding the retaining member in the recess 6 by frictional engagement with the side walls thereof. The arms 18 are, of course, each provided with a projection 19A which fit into the channels in the side wall of the recess between the shoulder 9 and the ribs 17. There is no need, however, for these projections 19A to have a saw-tooth shape as they merely have to slide into the recess 6 defined between the shoulder 9 and the ribs 17.
[0021] Figure 7 shows a header tank shell I of a third embodiment of the invention. The recess 6 in this shell is somewhat similar to that shown in Figure 5 and has two channels 21A and 21B formed in the sides of the recess 6 which lie perpendicular to the rib 3. These channels 21A and 21B start at the open side of the recess 6 but stop at shoulders 22A and 22B before reaching the side of the recess nearest to the rib 3. The recess again comprises a shoulder 9 and a circular aperture 10.
[0022] Figures 8a and 8b are perspective views of a retaining member 15 for use with the shell 1 shown in Figure 7. The retaining member is somewhat similar to that shown in Figure 4 but has a fixed projection 23 on one side and a resilient tag 24 on the opposite side. This retaining member is designed to snap-fit with the recess 6 but in this case the retaining member is inserted into the recess and then rotated to complete the snap-fit. Figures 9A and 9B illustrate how the retaining member is fitted into the recess 6. It is first positioned over a thermostat installed in a rubber bush within the aperture 10 (omitted from Figures 9A and 9B for clarity) so that it rests upon the shoulder 9. To do this it is necessary to orientate the retaining member so that the fixed projection 23 and resilient tag 24 lie along a diagonal of the recess 6, eg with the fixed projection 23 in a corner 25 of the recess between the channel 21B and the open side of the recess 6 and the resilient tag in the opposite corner 26 between the shoulder 22A and the side of the recess closest to the rib 3 as shown by the solid lines in Figure 9A. If the retaining member is then rotated clockwise from this position, the fixed projection 23 enters the channel 21B and the resilient tag 24 will be elastically deformed as it rides over the wall of the recess between shoulder 22A and the side nearest to the rib 3 as shown by the dashed lines in Figure 9A until it reaches the shoulder 22A whereupon it will spring out into the channel 21A. As the resilient tag 24 then engages the shoulder 22A, the retaining member cannot be rotated back anti-clockwise and engagement of
[0023] the fixed projection 23 with the shoulder 22B is also arranged to prevent further clockwise rotation as shown in Figure 9B. The retaining member is thus securely held within the recess by engagement of the projection 23 and tag 24 with the channels 21A and 21B and the shoulders 22A and 22B.
[0024] Figure 10 shows a header tank shell 1 of a fourth embodiment of the invention. This is similar to the shell 1 shown in Figure 7 in that it has two channels 21A and 21B in opposite sides of the recess. However, the channel 21A continues as a narrower channel 21C beyond the shoulder 22A to the side of the recess nearest to the rib 3. Figure 11 is a view of the recess 6 looking into its open side and more clearly shows the shoulder 22A at the transition between the wide channel 21A and the narrow channel 21C.
[0025] Figure 12 is a perspective view of a retaining member for use with the shell 1 shown in Figures 10 and 11. This retaining member 15 is similar to that shown in Figure 8 but has a fixed projection 23 on each side thereof. The fixed projection 23 is designed to be just able to fit into the narrow channel 21C. This retaining member is again designed to snap-fit with the recess 6 when it is inserted into the recess and then rotated. Figures 12A and 12B illustrate how the retaining member is fitted into the recess 6. It is first fitted over a thermostat installed in a rubber bush within the aperture 10 (omitted from Figures 13A and 13B for clarity) but is designed so that the stepped portion 15A thereof engages the casing of the thermostat before the end of the retaining member carrying the fixed projections reaches the shoulder 9 in the recess 6. To do this it is necessary to orientate the retaining member in a similar manner to that described in relation to Figure 9A as shown by the solid lines in Figure 13A. Simple clockwise rotation of the retaining member 15 from this position does not however permit the fixed projection 23 to enter the slots in the walls of the recess since the projection in corner 26 of the recess is not resting upon the shoulder 9 and is not therefore aligned with the narrow channel 21C. However, if the retaining member 15 is pressed further into the recess 6 against the thermostat thereby compressing the rubber grommet until the fixed projections 23 reach the shoulder 9 and is then rotated clockwise, the projections 23 will enter the channels 21C and 21B as shown by the dashed lines in Figure 13A. On further clockwise rotation, one of the projections 23 will pass the shoulder 22A and enter the wide channel 21A whereupon the rubber grommet is able to expand so that the projection 23 engages the shoulder 22A to prevent the retaining member being turned back anti-clockwise. The projection 23 on the opposite side of the retaining member 15 also then engages shoulder 22B to prevent further clockwise rotation. The retaining member is they securely held within the recess 6 by engagement of the projections 23 with the channels 21A and 21B and the shoulders 22A and 22B.
1. A header tank for a heat exchanger comprising: a plastics header tank shell (1)
having at least one recess (6) in a side face (2) thereof each recess (6) having an
aperture (10) into each of which a component is to be fitted; and a retaining member
(15) attachable to the header tank shell (1) for limiting movement of a component
out of the aperture (10), the retaining member (15) having connecting means (8, 18,
23, 24) which fit into and engage with a recess (6) in the said side face (2) of the
header tank shell (1), the arrangement being such that no part of the header tank
shell (1) provided for engaging with the retaining member (15) projects beyond the
outer surface of the said side face (2).
2. A header tank as claimed in claim 1 in which the connecting means (15) and the
recess (6) are provided with complimentary screw threads (8) by means of which the
retaining member (15) can be attached to the header tank shell (1).
3. A header tank as claimed in claim 1 in which the connecting means are a snap-fit
within the recess.
4. A header tank as claimed in claim 3 in which the connecting means comprises at
least one resilient arm (18) which is elastically deformed as the retaining member
(15) is being attached to the header tank shell (1) by a rib (17) before springing
back into engagement with the recess (6) thereby securing the retaining member (15)
to the header tank shell (1).
5. A header tank as claimed in claim 1 in which the recess (6) is substantially rectangular
in shape having on each of two opposite sides a rib 17 defining a channel and having
one of the remaining sides removed to define a T-slot into which a retaining member
(15) can be fitted.
6. A header tank as claimed in claim 5 in which the retaining member (15) has two
resilient arms (18) each having a projection 19A for engagement with the T-slot, the
retaining member 15 having one side cut away to allow it to be slid into engagement
with the T-slot even if the component is already engaged with the aperture 10.
7. A header tank as claimed in claim 5 in which the retaining member (15) has two
projections (23, 24) on opposite sides of the retaining means (15) and the retaining
member (15) is engaged with the recess (6) by orientating the two projections (23,
24) along a diagonal of the recess (6) insertion into the recess (6) and subsequent
rotation of the retaining member (15) to bring the two projections (23 and 24) into
engagement with the channels (21A, 21B).
8. A header tank as claimed in claim 7 in which each of the channels (21A, 21B) has
a shoulder (22A, 22B) against which one of the projections (23 and 24) abuts in use
to prevent disengagement of the retaining means (15) from the recess (6).
9. A header tank as claimed in claim 8 in which one of the channels (21A) has a narrower
channel (21C) extending beyond the shoulder (22A) so that when the retaining member
(15) has been inserted into the recess (6) over a component installed within a resilient
grommet in the aperture, rotation of the retaining member (15) in a first direction
and simultaneous compression of the grommet by pushing the retaining member (15) further
into the recess (6) enables one of the projections (23) to enter the narrow portion
(21C) of the channel and further rotation in the first direction of th retaining member
(15) moves the projection into the wide portion (21A) of the channel whereupon the
grommet expands to move the projection (23) into engagement with the shoulder (22A)
to prevent removal of the retaining member (15) by rotation in the opposite direction.
10. A header tank as claimed in claim 8 in which the retaining means has one rigid
projection (23) and one resilient projection (24) the resilient projection (24) be
initially deformed during engagement of the retaining member (15) with the recess
(6) before springing back to engage the shoulder (22A).