Patent Publication Number: US-5829268-A

Title: Multi-chamber expansion device for a vehicle cooling or heating circuit

Description:
FIELD OF THE INVENTION 
     This invention relates to an expansion device for a heat transfer fluid flowing in a circuit, in particular a circuit for cooling and/or heating purposes in a motor vehicle, and the like. The device comprising at least one first chamber and a second chamber. These chambers are connected together through a first duct open into the upper part of the first chamber, in such a way as to enable liquid or gas to be transferred into the second chamber as a result of expansion of the liquid in the circuit. A pressure-limiting safety valve is adapted to open, to allow the liquid or gas to escape from the second chamber, when the pressure in the latter reaches a predetermined value. 
     BACKGROUND OF THE INVENTION 
     Such an expansion device is designed to absorb the variations in volume in the heat transfer fluid that occur during the operation of the circuit. These variations in volume are due to variations in the temperature of the fluid and, where appropriate, to its changes of state when it is a fluid of a kind that operates in both the liquid and gaseous states. The gaseous phase which is present above the liquid in the first chamber, and which can pass into the second chamber, consists of air and/or, where appropriate, the heat transfer fluid in its gaseous state. The presence of the second chamber enables the height available in the first chamber above the minimum level of liquid to be reduced. This has the effect of reducing the overall height of the system, because the minimum liquid level has to be situated above the whole of the cooling or heating circuit. 
     It is also known to provide a third chamber, with at least one second duct connecting the second and third chambers through the above mentioned safety valve (referred to herein as the first safety valve), together with a second pressure-limiting safety valve which is arranged to open, in order to allow the gas to escape from the third chamber, when the pressure in the third chamber reaches a predetermined second value higher than the above mentioned first value. The third chamber enables heat transfer fluid in the gaseous state that has escaped from the second chamber to be recovered and condensed. The opening pressure of the first safety valve corresponds to the maximum normal operating pressure of the circuit, and the opening pressure of the second safety valve corresponds a pressure that must not be exceeded for safety reasons. 
     In known multi-chamber expansion devices, each one of the various chambers has its own separate casing. These casings are connected together through ducts in the form of separate pipes. 
     DISCUSSION OF THE INVENTION 
     The object of the invention is to simplify the structure and manufacturing operations of the expansion device, and to reduce its size. 
     According to the invention, an expansion device for a heat transfer fluid flowing in a circuit, especially a cooling and/or heating circuit in a motor vehicle, the device comprising: at least one first chamber and a second chamber which are connected together through a first duct open into the upper part of the first chamber, in such a way as to enable liquid or gas to be transferred into the second chamber as a result of expansion of the fluid in the circuit. A first pressure-limiting safety valve is adapted to open so as to allow the liquid or gas to escape from the second chamber when the pressure in the latter reaches a predetermined first value, is characterised in that the first and second chambers and the first duct are defined by a common rigid casing. The first duct extends along the outer wall of the casing, the first safety valve being fixed to the latter. 
     According to a preferred feature of the invention, the first duct is defined within a thickened portion of the outer wall of the casing. 
     According to another preferred feature of the invention, the casing consists of at least two hollow moulded casing members which are assembled together in sealing relationship edge to edge, in particular by adhesive bonding or welding. A groove is formed along the assembly edge of at least a first one of the casing members, so as to constitute the first duct. 
     According to a further preferred feature of the invention, the casing defines a third chamber and at least one second duct. The second duct connects the second and third chambers through the first safety valve, and the casing carries a second pressure-limiting safety valve. The second safety valve is adapted to open in order to allow gas to escape from the third chamber when the pressure in the third chamber reaches a predetermined second value greater than the first predetermined value. 
     Preferably, the casing defines second and third ducts which connect the second and third chambers, respectively, to the first safety valve, together with a fourth duct which connects the third chamber to the second safety valve, all of these ducts being formed within thickened portions of the outer wall of the casing. 
     Preferably, the casing has a horizontally elongated form having a substantially uniform transverse cross-section, the three chambers being aligned between a first and a second end of the casing, and being separated from each other by two transverse bulkheads. 
     According to yet another preferred feature of the invention, the casing comprises two casing members which are assembled together along a longitudinal junction plane, with the four ducts extending in the junction plane. This junction plane is preferably substantially vertical, and the first duct preferably extends in the form of a groove formed along the edge of the said first casing member, from a junction zone in which it is open into the first chamber, and which is situated on the upper side of the edge, to a further junction zone in which the groove is open into the second chamber, and which is situated on the lower side of the edge, the groove passing through the first end of the casing, and the third chamber being adjacent to the second end of the casing. 
     The first and second safety valves are preferably disposed on the outside of the second end of the casing, on either side, respectively, of the junction plane. 
     The first, second and third chambers are preferably aligned in that order between the first and second ends of the casing. 
     According to a still further preferred feature of the invention, the second and third ducts extend in the form of a first groove formed along the assembly edge of the first casing member. The second duct extends from a junction zone in which it is open into the second chamber and which is situated on the upper side of the assembly edge, to the second end of the casing. The third duct extends from the second end of the casing, below the second duct, to a junction zone in which the third duct is open into the third chamber and which is situated on the lower side of the assembly edge. The groove is interrupted by an integral bridge formed by molding to separate the second and third ducts from each other at the second end of the casing. The groove being connected to the inlet and outlet of the first safety valve, above and below the bridge respectively, through respective cavities which are formed in the wall of the casing. 
     Preferably, the fourth duct is defined by a second groove in the edge of the first casing member at the second end of the casing. This second groove being juxtaposed, towards the interior of the casing, to that region of the first groove that defines the second duct, the first duct being in communication with the third chamber at its upper end and being closed at its lower end, the lower end being connected to the inlet of the second safety valve through a cavity formed in the wall of the casing. 
     According to yet another preferred feature of the invention, the first groove extends over substantially the whole peripheral length of the edge of the first casing member to define the first, second and third ducts(and which is constituted for example by the above mentioned integral bridge), the first groove having, apart from the interruption at the second casing end that separates the second and third ducts, at least one interruption on the upper side between the upstream ends of the first and second ducts, together with a least one further interruption on the lower side between the downstream ends of the first and third ducts. 
    
    
     The various features and advantages of the invention will appear more clearly on a reading of the following detailed description of a preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view in longitudinal cross section of the casing of an expansion device in accordance with the invention. 
     FIG. 2 is an end view as seen from the left hand side of FIG. 1. 
     FIG. 3 is a view in cross section taken on the line III-III in FIG. 1. 
     FIG. 4 is a detail view showing on a larger scale a detail from FIG. 3. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     The casing shown in the drawings has the general form of a cylinder of revolution having a tubular side wall 2 and two end walls, or casing end portions, 3 and 4, seen on the right hand side and left hand side, respectively, of FIG. 1. The central regions of the end walls 3 and 4 are flat and lie at right angles to the axis 5 of the casing. The end walls 3 and 4 are joined to the side wall 2 through rounded regions. The casing consists of two substantially semi-cylindrical hollow casing members 6 and 7 of moulded plastics material, having respective thickened peripheral edges 8 and 9 through which they are joined together by thermo-welding so as to form a vessel which is sealed to liquids and gas. The vessel is divided, considered from right to left in FIG. 1, into three chambers 10, 11 and 12, by means of transverse bulkheads 13 and 14. The bulkheads 13 and 14 are also formed by the welded assembly of the two components, the bulkhead 14 being bowed towards the chamber 12. 
     The two thickened edges 8 and 9, also referred to in this description and in the Claims as junction edges or assembly edges, are abutted together in a vertical junction plane P1, which is almost coincident with the vertical plane P2 that passes through the axis 5. The edges 8 and 9 of the members 6 and 7 define a strap element 15 which projects outwardly from the adjacent regions of the casing, and which extends right around the casing over its upper and lower sides and its end walls 3 and 4. On the upper and lower sides, the strap element 15 projects from respective horizontal flats 16 and 17, and lies within the circular profile of the tubular wall 2. The junction edge 8 has a fork-shaped profile, each of the two branches 18 and 19 of which has a width equal to the general thickness of the walls of the casing. The inner branch 18 is disposed within the alignment of the adjacent regions of the wall of the casing, and in particular that of the flats 16 and 17 on the upper and lower sides, while the outer branch 19 is substantially parallel to the inner branch 18. The gap between the two branches 18 and 19 of the thickened portion 8 defines a groove 20. The junction edge 9 of the member 7 has a thickness equal to that of the junction edge 8, and makes sealed contact, secured by welding(see FIG. 4), with the free ends of the branches 18 and 19, thus closing off the groove 20. 
     Four notches are formed in the inner branch 18 of the junction edge 8, namely two notches 21 and 22 on the upper side of the casing, and two notches 23 and 24 on its lower side. The notch 21 lies in line with the bulkhead 13, the notch 22 between the bulkheads 13 and 14, the notch 23 again between the bulkheads 13 and 14, and the notch 24 to the left of the bulkhead 14 (with reference to FIG. 1). In addition, the groove 20 is interrupted locally by five integral bridges which are formed during the moulding of the casing member 6. Four of these bridges, 25 to 28, lie, respectively: to the left of the notch 21; immediately to the right of the notch 22; immediately to the left of the notch 23; and immediately to the right of the notch 24. The fifth bridge, 29, lies at mid-height in the end portion 4 of the casing. 
     These five bridges define three ducts within the peripheral length of the groove 20, namely a first duct 31, a second duct 32, and a third duct 33. With reference to FIG. 1, the first duct 31 extends towards the right along the upper side of the casing, from the bridge 25, and then downwardly along the end portion 3 and towards the left along the lower side as far as the bridge 27. The first duct 31 is in upstream communication with the chamber 10 through the notch 21, and in downstream communication with the chamber 11 through the notch 23. The second duct 32 extends to the left with reference to FIG. 1, along the upper side of the casing from the bridge 26, and then downwardly along the end portion 4 as far as the bridge 29. It is in upstream communication with the chamber 11 through the notch 22. The third duct 33 extends downwardly along the end portion 4 from the bridge 29, and then continues towards the right along the lower side, as far as the bridge 28. The third duct 33 is in downstream communication with the chamber 12 through the notch 24. 
     The ducts 32 and 33 are completed by two cavities 34 and 35 (see FIG. 2), which are again formed in a thickened region of the wall of the casing, in its end portion 4. The cavities 34 and 35 put the groove 20 into communication, above and below the bridge 29, with the inlet and outlet, respectively, of a pressure-limiting valve 36, (referred to here for convenience as the first safety valve). The valve 36 consists of known components, not themselves shown, and is adapted, in particular, to enable gas to pass from the duct 32 to the duct 33 only when the pressure in the first of these exceeds a predetermined value. In this example this value is 0.4 bar. 
     The components of the valve 36 are accommodated within a space which is defined by an annular wall portion 37 and a removable cover 38. The wall portion 37 is formed integrally with the casing member 7, and projects on the outside of the casing from its end wall 4. The portions 39 and 40 of the groove 20, shown in FIG. 1, are disposed respectively between the bridges 25 and 26, and between the bridges 27 and 28, and constitute isolated cavities. 
     In the upper half of the end wall 4, the. profile of the junction edge 8 of the casing member 6 includes a third branch 41 which is parallel to the inner branch 18. This third branch 41 is offset towards the interior of the casing with respect to the branch 18, which is separated from it by a groove 42. The groove 42 is closed in the same way as the groove 20, by means of a region of the junction edge 9 of the casing member 7, the edge 9 having a thickened region accordingly. The groove 42 is in communication with the chamber 12 at its upper end, and is interrupted at mid-height of the end wall 4 by an integral bridge 43 which is effectively an extension of the bridge 29. The groove 42 is in communication with the inlet side of another valve 44 for limiting pressure, through a cavity 45 which is similar to the cavities 34 and 35, but which is situated towards the interior of the casing with respect to the general plane of the end wall 4. The valve 44 is a safety valve and is of similar construction to the valve 36, but is adjusted for an opening pressure of 0.7 bar. The valve 44 is located in symmetrical relationship with the safety valve 36 about the plane P2, and its output communicates with the atmosphere. 
     In the conventional way, the casing 1 has a filler pipe 46, which communicates with the chamber 10 and which is provided with a filler cap 47. The chamber 10 also communicates, through an inlet orifice and an outlet orifice, neither of which is shown, with the cooling and heating circuit with which the expansion device is associated. 
     Modifications can be applied to the device described above and shown in the drawings, without departing the scope of the present invention. Thus, the grooves which define the various ducts may be formed in both the casing members at once, with the junction plane P1 then being coincident the with plane of symmetry P2. The two bridges 25 and 26, which terminate the neutral portion 39 of the groove 20, may be replaced by a single bridge disposed between the notches 21 and 22, and the same can be done with the bridges 27 and 28.