WO1997049914A1

WO1997049914A1 - Wax motor

Info

Publication number: WO1997049914A1
Application number: PCT/US1997/009547
Authority: WO
Inventors: Andre Teisser-Ducros
Original assignee: Metex Corporation
Priority date: 1996-06-24
Filing date: 1997-06-03
Publication date: 1997-12-31
Also published as: AU3296397A

Abstract

A wax filled metal capsule housing (4) is coupled to a piston (20) through a flexible diaphragm (14) and a rubber plug (16). A spring (38) normally urges the piston (20), diaphragm (14), plug (16) and wax (12) to a quiescent position. A copper wire mesh (40) comprising flattened wires is distributed throughout the cavity (10) of the housing (4) and soldered or brazed to the housing (4) at a location (42) distal the diaphragm (14) to permit the diaphragm (14) and mesh (40) to flex. The wire mesh (40) distributes heat input from the housing (4) substantially uniformly and instantly throughout the wax (12) so that the wax (12) exhibits a relatively rapid expansion response to the heat input for operating a valve device coupled thereto.

Description

WAX MOTOR This is a complete application of prior provisional application Serial No. 60/020,295 filed June 24, 1996

This invention relates to devices referred to as wax motors wherein wax is coupled to a prime mover such as a piston for displacing the piston in response to temperature cycling which causes the wax to expand and contract.

In the valve and faucet industry and in particular, the thermostatic valve industry, wax motors actuate a thermostatic valve employing wax in various formulations, called poly-eutectic wax compounds. These waxes have relatively high thermal expansion coefficient wherein the expansion is derived from a change of phase in various eutectics compounded to achieve a maximal expansion within a certain temperature range.

Wax motors are used in thermostatic valves to regulate fluid flow through a nozzle. A wax capsule is in contact with the fluid. The wax has a high thermal expansion coefficient. If the temperature changes, the wax of the capsule expands or contracts, i.e. pushes or pulls a piston which is the valve actuator. A copper powder filler is used in some cases to increase the thermal conductivity of the wax capsule, which increases the response speed, without interfering with the thermal expansion properties of the wax. These wax motors are used in the aerospace industry for the regulation of the temperature of a- fuels, b- liquid coolants, and c- lubricants and in thermostatic industry for the regulation of the temperature of a- fuels, b- liquid coolants, and c- lubricants and in thermostatic operated valves and faucets. Mass produced wax motors are also used in the cooling circuit of automobiles. The copper filler in the wax is a copper powder. The present inventor recognizes that the powder permits the expansion of the wax, but is not an adequate thermal conductor since the particles are isolated and effectively insulated from each other by the wax. Furthermore, the handling of the copper powder constitutes a nuisance and a hazard in a manufacturing environment.

Waxes used in wax motors, like all waxes, are poor heat conductors, or very good heat insulators. Therefore, the larger a wax capsule, the longer it will take to raise the capsule core temperature. As a result, large wax motors are used only in applications where the time delay in observing the expansion is not significant: for example, in valves for coolant, e.g.,water, temperature control in the refrigeration circuit of large Diesel engines. In applications needing a relatively large fluid flow, typically greater than a few gallons of water per minute, water being distributed in an array of bathrooms, showers, kitchens, etc., wax motors cannot be used. For large fluid flow, other technologies, using more complex and costly devices, such as bi-metal devices, liquid/bellows systems, bi-metal plus hydraulic relays, and recently, memory alloys, marketed in 1995 by Toto Ltd., are employed

Various devices have been tried to improve heat conductivity: e.g., metal inserts or metal powder. These were sufficiently unsuccessful to allow a substitution in favor of wax motors in larger valves, and to permit the use of wax cartridges in thermostatic faucets to replace pressure balance mixing valves. Even in smaller sizes, using metal inserts, no wax motor could demonstrate a reaction to pressure or temperature changes sufficiently rapidly to comply with the anti-scalding standard ASSE 1017. The best prior art proposed designs were sufficient to show performances comparable, or almost, to pressure balance valves. In Europe and Japan, the wax cartridge valve is considered superior to the pressure balance valve because of accuracy and thermostatic control for individual faucets.

A thermostatic material driven actuator according the present invention comprises a housing having a cavity. A mass of thermostatic temperature responsive material having a relatively high coefficient of thermal expansion fills the cavity. Piston means are coupled to the cavity for displacement in response to expansion and contraction of the thermostatic material in the presence of temperature cycling of the material. At least one thermally conductive elongated filament is in the cavity for distributing heat to the mass in a region interior the cavity.

In one aspect, the filament comprises copper wire.

The filament may be any metal and is tortuous.

The housing in a further aspect is thermally conductive and the filament is thermally conductively connected to the housing at at least one connection point. In a still further aspect, the filament comprises at least one thermally conductively interconnected and mechanically interconnected wire filament loops.

Preferably, the filament comprises compressed knitted wire mesh.

Further, the filament is preferably thermally conductively coupled to the housing. In a further aspect, the filament is located substantially throughout the cavity and throughout the mass and thermally connected to the housing.

In a further aspect, the piston means comprises a flexible diaphragm enclosing the cavity and mass, a bore, a resilient plug in the bore next adjacent to the diaphragm, a piston in the bore next adjacent to the plug and a spring for normally urging the plug against the diaphragm and against the mass.

IN THE DRAWING: FIGURE l is a diagrammatic sectional elevation view of a thermostatic material, e.g., wax, operated actuator in the quiescent state according to one embodiment of the present invention;

FIGURE 2 is a diagrammatic sectional elevation view of the actuator of Fig. 1 after the piston has been displaced by expansion of the thermostatic material in response to a heat input;

FIGURE 3 is a plan view an embodiment of a knitted wire mesh used in the embodiments of Figs. 1 and 2;

Fig. 4 is a chart of response curves illustrating curves for a prior art actuator and an actuator according to the present invention; and Fig. 5 is a diagrammatic sectional elevation view of a capsule containing wax and a knitted wire heat conductor soldered or connected to the metal capsule,

In Fig. 1, an actuator 2 comprises a preferably metal capsule or housing 4 secured to a preferably metal cylinder 6 having a piston circular cylindrical bore 8. The cavity 10 of the housing 4 is filled with a thermostatic hydrocarbon material 12, preferably wax of a known composition. A flexible elastomeric or rubber diaphragm 14 is clamped between the cylinder 6 and housing 4 sealing the cavity 10 and the wax in the cavity. An elastomeric preferably rubber or other elastic material plug 16 is in the bore 8 abutting the diaphragm 14. The bore 8 preferably has a diameter in region 18 preferably larger than the rest of the bore distal the diaphragm 14. The cavity 10 particular shape, shown cylindrical, and relative size to the bore 8 is determined in accordance with a given implmentation. The enlarged cavity 10 is given by way of example as are the particular piston elements such as the bore 8 and mating piston 20 described below. The actuator and its relative dimensions may take the form of any suitable arrangment as needed according to a given implementation.

A piston 20, preferably metal or other material, is in bore 8 and axially displaces in directions 22. An annular disc-like flange 24 is secured to the piston by a retaining ring 26. An annular disc-like flange member 28 is arranged to be secured to a support represented by symbols 30. The capsule or housing 4 is also secured to a support represented by symbols 32. The flange member 28 has an opening 36 through which the piston 20 passes. The actuator housing 4 is secured to support 32 so that the piston 20 in its acquiescent position of Fig. 1 is preferably in the opening 36. A compression coil spring 38 is intermediate the flange member 28 and flange 24. The piston 20 end in the opening 36 is coupled to a device (not shown) for actuating such a device, such as a valve or the like, typically which may be commercially available. The attachment of the actuator 2 to supports 30 and 32 for operating such a device is by known elements in a known manner as employed in prior art wax motors. The housing 4 is thermally coupled to a fluid whose temperature is to be controlled by actuation of the valve (not shown) via the piston 20.

A preferably knitted wire mesh 40, preferably copper wire, Fig. 3, is inserted into the housing 4 cavity 10. The mesh 40 comprises a plurality of continuous wire filaments interconnected by loops 41. Preferably, the mesh 40 is brazed or soldered at various points 42 to the housing 4. In the alternative, the mesh is preferably connected by any suitable thermally conductive coupling devices in thermal conductive contact with the housing 4. The points 42 at which the mesh is connected to the housing 4 are on a base wall 44 of the housing distal the diaphragm 14. The mesh may also be thermally conductively and mechanically connected to the side walls of the cavity remote from the diaphragm. However, the mesh need not be directly thermally and mechanically conductively connected to the housing 4 according to a given implementation, and in the alternative, may be adjacent thereto for receiving thermal energy for the purpose described below herien. The wire mesh 40 is attached to the housing in the cavity 10 first. Prior to attaching the housing 4 to the cylinder 6, the cavity 10 is then filled with the thermostatic mass material 12 and the wire mesh 40 impregnated with the thermostatic material compound such as wax, filling the cavity 10. The knitted mesh 40 is preferably distributed uniformly as possible through out the material 12 filled capsule cavity. This provides a good heat input to an optimum volume of the material 12. The mesh 40 is preferably of uniform wire size, but may have different sizes as needed for a particular implementation. The mesh 40 wire diameter is determined to optimize heat transfer to the wax in the cavity 10.

The wire mesh 40, preferably fine copper wire, is interspersed in the mass of material 12 and allows the material 12 to expand and displaces as the material 12 expands since the knitted metal mesh 40 is flexible. The thermal conductivity of the mesh 40 is much greater than prior art copper powder interspersed in the preferred wax material 12 since the mesh provides a substantially continuous path of thermal conductivity to the wax distributed throughout the cavity 10. In contrast, the prior art metallic powder comprises a plurality of discrete particles each spaced by insulating wax providing discontinuous thermal conductivity in the wax mass.

The copper knitted mesh conducts heat substantially instantaneously to the entire mass of the material 12 based on wire diameter, contact points with the housing 4 and density of the mesh in the cavity 10. This results in relatively rapid expansion of the material 12.

The brazing or soldering, if used, of the mesh 40 to the housing 4 at the points 42 is preferably only to the lower part of the mesh at wall 44 distal the flexible diaphragm 14, This permits the portion of the mass material 12 and the mesh 40 adjacent to the diaphragm 14 to be free to expand with the material 12.

The density, i.e., the volume, of the metal mesh 40 in the capsule cavity as compared to that of the density of the thermostatic material 12 is preferably minimal, so as to benefit as much as possible from the expansion properties of the material 12. That is, the volume of the wax material such as material 12 is optimum so as to provide maximum expansion volume in response to a given heat input to the housing 4.

Knitting machines for producing the wire knitted mesh have the effect of flattening the wire, which is beneficial to the operation of the actuator 2. A flat wire is a wire section; a flat wire is more flexible than other shapes, and therefore will offer less resistance to the expansion of the wax material.

A metal mesh does not cause a health hazard while being handled by manufacturing operators, while a copper powder does.

This combination of properties of the mesh in a wax motor does not result obviously from the use of knitted metal and allows an improved performance, resolving problems which until now prevent a wider use of wax motors. First tests showed an expansion speed higher by about 20% to one observed on best copper powder motors, and yet the mesh was not soldered in this embodiment to the housing capsule, the contact between the mesh and the housing capsule was not optimized, and the metal density had been rated at too high a level to comply with specifications which did not consider the properties of this technology. In one embodiment, knitted copper metal wire, Fig. 3, (7.5xl0³ inches in diameter) was flattened during knitting. The knitted metal preferably had a 10% density in the mass of wax in the housing and was soldered or brazed to the housing capsule of a standard wax motor. This low density metal filler replaced the copper powder with approximately 80% density used in current units, increasing performance (higher thermal density conductivity for same thermal expansion) and eliminating health and safety hazards in the manufacturing process.

The product may be used in several applications such as Aerospace and anti-scalding valves for thermostatic faucets.

The housing 4, FIG 1, of the present invention has a relatively rapid response time for use in anti-scalding applications and is preferably useful for large Diesel engines providing a relatively high precision thermostatic valve for the cooling circuit thereof.

The actuator 2, Figs. 1 and 2, provides a relatively fast acting thermostatic response or, a relatively high force and relatively long travel displacement for the effective control of water and oil temperatures. The actuator 2 withstands the vibration and pressure changes that exist in liquid-cooled diesel powered units. The plug-and-diaphragm, solid wax charge type of actuators of Figs, l and 2 are preferably used.

The thermostatic material 12 used may be a pellet mix of hydrocarbons that expands as temperature increases. The chemical composition of the material is varied to create desired operating temperature ranges. The increase in the volume of the thermostatic material can be as high as 10% within a selected temperature range. The knitted copper wire heat conductor of mesh 40 is thermally conductively connected to the capsule housing 4 at spaced locations and is dispersed throughout the thermostatic material to conduct heat approximately uniformly to the thermostatic material 12.

The thermostatic material 12 is sealed from the piston area by the molded synthetic rubber diaphragm 14. Above this in the piston cylinder 6 the piston-like, oversize plug 16 is of similar material. When the thermostatic material expands, as a result of a temperature increase input to the housing 4, the plug 16 is forced into a reduced diameter section of the cylinder bore 8. This amplifies the relative movement of the piston 20. That is, a relatively small increase in volume of the wax in the cavity 10 amplifies the displacement of the piston 20.

The piston 20 displacement creates sufficient power, even when the temperature change is small, to operate a valve disc, mechanical linkage, electric switch, or other mechanical device (not shown) . The piston 20 moves against the force of the spring 38, which, as the material 12 cools, returns the piston 20 to its former acquiescent position, Fig. 1, from the displaced position of Fig. 2, and reforms the thermostatic material 12 to its original shape in cavity 10. The diaphragm 14 and plug 16 are made from synthetic compositions that are stable with respect to compression and hygroscopic absorption and are ductile at subfreezing temperatures.

The piston 20 travels smoothly throughout its full stroke. Rapid temperature fluctuations do not cause chattering and temperature extremes will not damage any of the components or cause variation in calibration. Changes in barometric or static pressures do not affect operation of the actuator 2. The response time is enhanced by the presence of the copper knitted wire mesh.

For example, reference is made to Fig. 4. Curve a shows the response time of a prior art wax motor employing copper powder in the wax mass. Curves b and c show response ranges for wax motor actuators constructed according to the present invention. The actuators of the present invention displace greater displacements more rapidly than the prior art wax motors.

In Fig. 5, the wire mesh 40 is soldered or brazed to housing 4' at points 50 and 52 on the respective bottom wall 44' and side walls 45 and 47. While a single connection point is shown for each wall, in practice, numerous connection points are preferred. However, these connection points are all distal the flange 54 of the housing. The flange 54 is secured to the piston cylinder such as cylinder 6, Fig. 1, and diaphragm 14, not shown in Fig. 5. These connection points are all distal the flange 54 to permit the mesh 40' to flex at the diaphragm as described previously.

While knitted wire mesh is preferred, it will occur to one of ordinary skill that random wire loops may also be used. That is, wire may be merely coiled randomly into loops or, in the alternative, wire loops may be formed from flattened coil springs and used as heat conductors in the housing cavity 10. The more uniform the coil or wire distribution in the cavity, the more uniform and, thus, rapid heat transfer to the thermostatic material 12. While it is preferred that the wire mesh heat conductors are interconnected, this is not essential. Relatively long conductors that are closely spaced will still perform more desirably than powder by thermal conductive coupling to the housing 4. The optimum condition, however, is interconnected wire loops thermally conductively connected directly to the housing.

It will occur to one of ordinary skill that various modifications may be made to the disclosed embodiments, given by way of illustration and not limitation, without departing from the scope of the invention as defined in the appended claims.

Claims

What is claimed is.-

1. A thermostatic material driven actuator comprising.- a housing having a cavity; a mass of thermostatic temperature responsive material having a relatively high coefficient of thermal expansion filling the cavity; piston means coupled to the cavity for displacement in response to expansion and contraction of the thermostatic material in the presence of temperature cycling of the material; and at least one thermally conductive elongated filament in the cavity for distributing heat to said mass in a region interior said cavity.

2. The actuator of claim l wherein the filament comprises copper wire.

3. The actuator of claim 2 wherein the filament is a metal wire and is tortuous.

4. The actuator of claim 1 wherein the housing is thermally conductive and the filament is thermally conductively connected to the housing at at least one connection point.

5. The actuator of claim 1 wherein the filament comprises at least one thermally conductively interconnected and mechanically interconnected wire filament loops.

6. The actuator of claim 1 wherein the filament comprises knitted wire mesh and the material is wax.

7. The actuator of claim 6 wherein the filament is thermally conductively coupled to the housing.

8. The actuator of claim 1 wherein the filament is located substantially throughout the cavity and throughout the mass and thermally conductively coupled to the housing.

9. The actuator of claim 1 wherein the thermostatic material is a hydrocarbon.

10. The actuator of claim 1 wherein the thermostatic material is wax.

11. The actuator of claim 1 wherein the piston means comprises a flexible diaphragm enclosing the cavity and mass, a bore, a resilient plug in the bore next adjacent to and responsive to the displacement of the diaphragm, a piston in the bore next adjacent to the plug responsive to displacement of the plug and a spring for urging the plug against the diaphragm and the diaphragm against the mass.

12. The actuator of claim 11 wherein the filament is a wire, the housing is a metal capsule and the wire is thermally conductively connected to the housing distal said diaphragm and is dispersed throughout said cavity including a region adjacent to the diaphragm.

13. The actuator of claim 1 wherein the filament comprises flexible interconnected loops of a metal wire.

14. An actuator comprising: a thermally conductive housing having a cavity; a mass of thermostatic temperature responsive material having a relatively high coefficient of thermal expansion filling said cavity; piston means coupled to the cavity for displacement in response to expansion and contraction of the thermostatic material in the presence of temperature cycling of said material; and at least one thermally conductive elongated tortuous elongated filament in said cavity for distributing heat to said mass interior said cavity from a region adjacent to the housing.

15. The actuator of claim 14 wherein the housing is metal and the filament is a wire mechanically and thermally conductively connected to the housing.

16. The actuator of claim 15 wherein the wire is copper and is bonded to the housing.

17. The actuator of claim 14 wherein the piston means includes a piston and a diaphragm enclosing the cavity, the piston for displacement in response to flexure of the diaphragm, said filament being flexible in a region at least adjacent to the diaphragm to permit the diaphragm to flex in response to thermal expansion and contraction of said mass of material.