Patent Application
20080157916
The present invention relates to a thermostatic element which, by using a heat-expandable material, converts a calorific energy into a mechanical energy. It also relates to a method for manufacturing such an element.
These elements are routinely used in the field of fluid regulation since they make it possible to distribute a fluidic supply channel into one or more distribution channels, according to the heat of the fluid to be regulated and/or of another heat source. These elements are therefore arranged in cooling circuits in which a cooling fluid flows, particularly the cooling circuits associated with an internal combustion engine of a motor vehicle or similar element.
Typically, a thermostatic element comprises a metal cup of generally cylindrical shape and containing a heat-expandable material such as a wax. The element also comprises a piston substantially coaxial with the cup and able to be moved in translation relative to this cup under the effect of the expansion of the heat-expandable material contained in the cup, when this material is heated. By expanding, the heat-expandable material partially expels the piston, so that the latter is deployed outside the cup while, when the heat-expandable material cools, the piston may be retracted into the cup, usually under the action of a return spring associated with the thermostatic element. To guide the movements in translation of the piston, the thermostatic element comprises a bored metal guide inside which the piston slides, this guide being firmly attached to the cup. In addition, to prevent the heat-expandable material from escaping from the cup during the movements of the piston, this material is sealed relative to the outside, the sealing means used often being provided to transmit to the piston the thrust of the heated material.
Conventionally, the sealing of the heat-expandable material is provided by a composite structure interposed between the expandable material and the end of the piston plunging into the cup. This structure usually comprises a flexible diaphragm for the retention of the wax, firmly immobilized on the guide, a deformable pad housed in the bore of the guide and in contact with the surface of the diaphragm opposed to the weight of the wax, and a shim inserted between the pad and the piston in a manner adjusted to prevent the material forming the pad from creeping around the piston. This “sandwich” design is well suited to the use of a highly expandable wax for causing an ample movement of the piston.
However, this composite sealing structure is tricky to assemble since each of its constituent parts must be handled in turn, put in place and, where necessary, immobilized within the thermostatic element. These handling operations are all the more complex because these parts have small dimensions, which increases, on the one hand, the time for assembling the thermostatic elements and, on the other hand, the cost of the assembly lines whose robots have to be precise. The result of this is that the unit price of the thermostatic elements is relatively high if elements with good reliability are desired.
Through U.S. Pat. No. 3,080,756, U.S. Pat. No. 3,712,053 and FR-A-1 232 776, thermostatic elements are known in which the heat-expandable wax is sealed by a one-piece composite assembly including a metal insert to guide the piston of the thermostatic element, sunk into a flexible and sealed casing. In U.S. Pat. No. 3,080,756 and U.S. Pat. No. 3,712,053, this casing is interposed between the insert and, on the one hand, the piston and, on the other hand, the cup of the thermostatic element, while, in FR-A-1 232 776, a woven sheath covers most of the piston of the thermostatic element, which makes the latter difficult to assemble, particularly on an automated assembly line. In any case, the inserts of these one-piece assemblies have, on the side of the wax, a totally flat face, between which and a portion facing the collar a matching portion of casing is provided. This portion of casing is critical from the point of view of the sealing of the wax because, in service, the high pressure that exists inside the cup tends to damage its seal. In practice, the dimensioning and the production of this portion of casing are decisive from the point of view of the seal of the thermostatic elements envisaged in the aforementioned three documents, so that the assembly of these elements along automated lines is incompatible with a high level of reliability.
The object of the present invention is to propose a novel thermostatic element which, while being as reliable as the existing elements, is easier, quicker and less costly to manufacture, particularly with automatic assembly lines.
Accordingly, the subject of the invention is a thermostatic element comprising:
The use of a one-piece assembly as aforementioned, which ensures both the guidance of the piston relative to the cup and the sealing of the heat-expandable material relative to the outside of the thermostatic element, prevents the use and handling of the various corresponding parts of the existing thermostatic elements, such as the guide, the diaphragm, the pad and the shim mentioned above. On an automatic assembly line, the installation of this one-piece assembly represents only one operation. In addition, unlike the aforementioned various small dimension parts, this assembly has a relatively large overall dimension, which makes it easier to handle by robots or similar programmable controllers, whose operating constraints are less than those associated with high precision programmable controllers. The result of this is that the thermostatic element according to the invention has a lower manufacturing cost than the existing elements.
In addition, the presence of the protruding abutment makes it possible, during the assembly of the thermostatic element according to the invention, to rigorously control both the positioning of the one-piece assembly relative to the cup and the squashing of the portion of filler: since this portion of filler occupies the angled space delimited by the abutment, the user controls the degree of squashing of this portion of filler when the abutment is positioned and brought to bear against the corresponding bearing portion of the cup, this pressing action being easily carried out by a robot or a programmable controller along an automated assembly line. By ensuring in this way a minimal degree of squashing of this portion of filler, the user ensures a predetermined level of seal in a zone of the casing subjected to significant internal pressure stresses. The angled shape of the protruding abutment advantageously makes it possible to absorb a portion of this internal pressure.
In addition, the rigid insert may advantageously withstand the mechanical stresses resulting from swaging together the cup and the insert during the manufacture of the thermostatic element according to the invention.
Other features of this thermostatic element, taken in isolation or in all the technically possible combinations, are set out in dependent claims 2 to 15.
A further subject of the invention is a method for manufacturing a thermostatic element in which are provided:
The invention will be better understood on reading the following description, given solely as an example and made with reference to the drawings in which:
For convenience, the rest of the description will be oriented by considering that the terms “lower” and “down” indicate a direction directed toward the bottom portion of
The cup 2 comprises a tubular barrel 2A centered on the axis X-X which, at its bottom end, is closed off by a bottom wall 2B, while at its top end, the barrel is open to the outside while forming an end collar 2C. The wax 3 is stored in the closed bottom portion of the barrel 2A, the top portion of the barrel being closed off by the end portion 4A of the piston 4 and by the assembly 5. The collar 2C is made up of an annular body 2C1 centered on the axis X-X which, in the bottom portion, is made of the same material as and in one piece with the barrel 2A while forming a shoulder 2C2 and which, in the top portion, is folded upward in a convergent manner toward the axis X-X, forming an inclined end edge 2C3.
The assembly 5 essentially comprises a rigid insert 51, particularly metallic, and a flexible casing 52, made in a single piece that totally shrouds the insert 51. This casing 52 is made of a material that is sealed against wax 3, for example rubber, nitrile, hydrogenated nitrile or a mixture of these materials. In
The insert 51 and the casing 52 have respective shapes of revolution about a longitudinal axis Y-Y indistinguishable from the axis X-X in
More precisely, the insert 51 comprises, as it gets further away from the axis Y-Y, a top ring 51A coaxial with the axis Y-Y, an intermediate flange 51B that is substantially flat and that extends in a plane substantially perpendicular to the axis Y-Y, and an annular bottom edge 51C coaxial with the axis Y-Y. This edge 51C therefore extends in protrusion downward from the periphery of the flange 51B, in a direction substantially parallel to the axis. The ring, the flange and the edge form one and the same part, centered on the axis Y-Y. The ring 51A has a slightly larger internal diameter than the external diameter of the piston 4 so that, in the assembled state of the element 1, the piston is received inside the ring with interposition of a corresponding portion 52A of the casing 52 which covers the ring internally. In the assembled state of the element 1, the flange 51B extends, as it gets further away from the axis X-X, almost to the annular body 2C1 of the collar 2C, so that the external portion of the bottom face of this flange extends substantially parallel to the internal portion of the top face of the shoulder 2C2 of the collar. The edge 51C has a slightly smaller external diameter than the internal diameter of the annular body 2C1, so that the insert 51 is centered inside the collar 2C with radial interposition of a corresponding portion 52B of the flexible casing 52. Similarly, a portion 52C of the casing 52 is axially interposed between the edge 51C of the insert 51 and the external portion of the top face of the shoulder 2C2 of the collar 2C.
The bottom space delimited between the edge 51C and the flange 51B is filled with a portion 52D of the casing 52. In the free state of the assembly 5, this portion of casing 52D extends in protrusion downward relative to the adjacent portion of casing 52C, as shown in
Advantageously, in the squashed zone of the portion of casing 52D, the top face of the shoulder 2C2 is hollowed out with an annular groove 2C4 centered on the axis X-X and filled with the portion of casing 52D when the assembly 5 is assembled, in order to improve the seal.
On either side, along the axis Y-Y, of the insert 51, the casing 52 forms a bottom protrusion 52E and a top protrusion 52F. These protrusions 52E, 52F extend in the extension of the portion of casing 52A, respectively downward and upward, so that the wall delimiting the passageway 53 is made up entirely of the material of the casing 52, this passageway being delimited in turn by, from bottom to top, the protrusion 52E, the portion of casing 52A and the top protrusion 52F. When the piston 4 is received in this passageway 53, the bottom protrusion 52E seals the wax 3 relative to the piston 4, the pressure existing in the wax being able to reach 200 bar, while the top protrusion 52F seals the piston relative to the outside of the thermostatic element, particularly relative to a fluid in which the thermostatic element 1 can be bathed, in particular when the temperature of this fluid is relatively low, which makes it easier to insert fluid between the piston and the wall of the passageway 53.
In order to reinforce their seal, the protrusions 52E and 52F are furnished with respective annular ribs 52E1, 52F1, which extend in protrusion from the rest of the wall delimiting the passageway 53, toward the axis Y-Y.
The thermostatic element 1 is manufactured as follows.
First, the assembly 5 is manufactured independently of the other components of the thermostatic element 1. To do this, the insert 51 is preferably obtained by stamping a metal sheet. As variants, the insert is formed by machining or drop-forging. The insert 51 is then sunk into the casing 52, particularly by using a mold which confers on the casing 52 its contours in the free state as shown in
Secondly, after the cup 2 has been filled with wax 3, the assembly 5 is assembled to the cup 2, the installation of this assembly being easily obtained by the interaction of shapes between the edge 51C of the insert 51 and the annular body 2C1 of the collar 2C. It can therefore be understood that the edge 51C forms a positioning abutment of the assembly 5 relative to the cup 2 and ensures that the assembly 5 is centered on the cup 2 while making the axes X-X and Y-Y substantially indistinguishable.
The assembly 5 is installed while the top edge 2C3 of the annular body 2C1 is not bent as in
During the swaging, the portion of casing 52D is axially squashed against the shoulder 2C2 of the collar 2C, as indicated by the arrow F, until it takes the configuration of
The wax 3 is therefore reliably and repetitively sealed.
The piston 4 is then inserted into the passageway 53 of the assembly 5 already positioned on the cup 2, until its end portion 4A is immersed in the wax 3.
The element 1′ of
With respect to the bottom zone of the casing 52′, the variant of
The addition of the glove finger 52G′ in the variant of
In addition, optionally, the grease 6′ designed to make the piston 4′ slide more easily in the passageway 53′ may then be stored in an annular recess 52H′ hollowed out in the wall of the casing 52′ delimiting the passageway 53′, beneath the level of the insert 51′.
With respect to the zone of junction between the insert 51′ and the cup 2′, unlike the collar 2C of the cup 2 of the element 1, the collar 2C′ does not extend the barrel 2A′ of the cup 2′ upward via an annular body such as the body 2C1 of the collar 2C, but consists only of a shoulder 2C2′ similar to the shoulder 2C2 of the cup 2C. The end edge 2C5′ of this shoulder 2C2′ is tapered while converging downward.
In addition, unlike the edge 51C of the insert 51 of the element 1, the edge 51C′ of the insert 51′ extends radially beyond the cup 2, as it gets further away from the axis X-X, since this insert 51′ has a downward angled shape whose internal diameter is substantially equal to the maximum external diameter of the shoulder 2C2′ of the cup 2′ and whose free end portion 51D′ is folded toward the axis X-X, against the edge 2C5′ of the shoulder 2C2′. Before the assembly 5′ is assembled to the cup 2′, this end portion 51D′ has an annular shape which extends in the axial extension of the downward angle of the edge 51C′. In this pre-assembly state (not shown), the portion of casing 52D′ is substantially dimensioned like the portion of casing 52D of the casing 52, that is to say that this portion of casing 52D′ extends in protrusion from the flange 51B′ lower than the bottom face of the edge 51C′. On the other hand, unlike the corresponding zone of the casing 52 of the thermostatic element 1, no portion of casing covers this bottom face of the edge 51C′. In other words, the casing 52′ includes no portion similar to the portions of casing 52B and 52C of the casing 52 of the element 1. On the other hand, as for the element 1 of
Assembling the assembly 5′ to the cup 2′ is similar to assembling the assembly 5 to the cup 2: the assembly 5′ is fitted to the collar 2C′ of the cup 2′ by inserting the shoulder 2C2′ of this collar inside the angled edge 51C′ of the insert 51′, ensuring that the assembly 5′ is centered relative to the cup 2′; then the end portion 51D′ of the angled portion of the edge 51C′ is swaged around the shoulder 2C2′, while being guided by the rounded end edge 2C5′ of this shoulder, until it occupies the configuration inclined downward and in the direction of the axis X-X represented in
It will be noted that the arrangements of the element 1′ relative to the glove finger 52G′ and to the swaging of the insert 51′ to the cup 2C′ are independent of one another and may therefore, as a variant, be applied separately to the element 1 of
The element 1″ of
To ensure a sufficient mechanical hold between the casing 52″ and the insert 51″, the flat flange 51B″ is advantageously traversed axially from one side to the other by several through-holes 54″, preferably distributed in a substantially uniform manner along the periphery of this flange. These holes 54″ are for example 6 in number, two diametrically opposed holes being represented in the plane of
Assembling the assembly 5″ to the cup 2″ is similar to assembling the assembly 5 to the cup 2.
Various arrangements and variants to the thermostatic elements 1, 1′ and 1″ described hereinabove, and to their method of manufacture, can be envisaged. As examples:
| Number | Date | Country | Kind |
|---|---|---|---|
| 05 03296 | Apr 2005 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2006/000728 | 4/3/2006 | WO | 00 | 9/25/2007 |
