DE2856120A1 - THERMOSTAT DEVICE - Google Patents

Description

Applicant: R.J. Hodges - 36

German ITT Industries GmbH DITTI 0217

Freiburg

Thermostat equipment

The invention relates to a temperature-responsive control device, e.g. for use in thermostatically controlled water mixers.

The most important requirements for the sensing element in such control systems consist in the following.

a) preferably have a linear expansion in the temperature range from ⁰ C to 10O ⁰ C with a minimum of hysteresis should.

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b) The force generated should be sufficiently large for the actuating movement of the control valve against a water pressure of about 10 bar, the curvature or deflection should be about 2 mm.

c) The thermal conductivity should be good so that there is a total time constant of about 1 second.

d) The establishment should be durable without its distinctive features Change properties when the water conditions change at a temperature range between 0 ° C and 100 ° C and the various water pressures between 0.5 and 10 bar.

e) The device should be protected from the corrosive conditions of the water and the excretions from the water (mainly Calcium compounds) are not attacked.

f) The dimensions of the facility should be as small as possible be.

g) The sensing element should be cheap, compatible and the dispersion of the characteristics between the different devices should be reduced to a minimum.

For this purpose it is known to use bimetallic devices or devices filled with wax To use elements that meet part of the requirements listed above. In the case of biraetallic fittings however, a specialized manufacture is required that makes the bimetallic device not insignificantly expensive, in addition, they can be attacked by the corrosion effect of the water. Specialized production is also required for the wax-filled capsules, as well as careful production Construction so that undesired hysteresis is eliminated and a required time constant is achieved.

The invention is therefore based on the object of a temperature-sensitive To create element that meets the requirements listed above and is relatively inexpensive to manufacture is.

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This object is achieved according to the invention with the in the characterizing Part of claim 1 listed features solved. Further embodiments of the invention are set out in the subclaims set out.

In the proposed solution, the change in the modulus of elasticity used depending on the ambient temperature. The change in the modulus of elasticity relates to the thermoelastic one Effect that is inherent in all materials and includes the change in elasticity of the material with temperature. This Module is one of three elastic modules,

G = the shear modulus

B = the compression modulus

E = the modulus of elasticity,

which all have a relation to the Poisson's ratio μ . For most metals, the Poisson's ratio is between 0.25 and 0.3, so the shear modulus is about 0.4 of the elastic modulus and the compression modulus is about 0.67 of the elastic modulus. The modulus of elasticity of metals changes with temperature, and for most nickel-iron alloys the thermoelastic coefficient (ie the change in elasticity with temperature) is negative. For a metal with 65% Fe (Invar) the thermoelastic coefficient is positive.

To understand how this effect can be used it is necessary to relate stress and strain to the modulus of elasticity to put. If, for example, a rod which is attached to the upper end is loaded with a weight W, then the

a '

Stress in the rod S = /, where a denotes the cross-sectional area of the rod. The elongation in the rod is T = ^Χ / τ, where χ denotes the extension of the original rod length L produced by the weight W. The elastic modulus is thus the elastic modulus E with the following relationship

S WL
E - _ = -
T ax.

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If now E changes with temperature and the weight W is constant remains and if it is assumed that the cross-section a does not change, then χ changes with temperature. The direction the change depends on the sign of the thermoelastic coefficient away. If the thermoelastic coefficient is negative, as is the case with most metals, then it increases the length of the rod.

If two rods are now assembled with their ends against each other, whereby one rod has a positive coefficient, the other rod has a negative coefficient and the rods are prestressed to allow for a corresponding pre-deformation of x- and χ _? the change in χ with temperature is twice as great as for a single rod.

The last-described system is explained in a below Device used, wherein the sensing element is formed by a column of Belleville washers. In the enclosed Drawing is shown as an exemplary embodiment of a thermostatically controlled mixing valve in section, which is shown below is described in more detail.

Such valves are used in the sanitary sector, e.g. as part of a shower device. The mixer tap has one each Inlet opening 1 for cold water and 2 for hot water and an outlet 3 for mixed water. The temperature can be adjusted with the help of a Adjusting button 4 can be preselected.

The temperature sensor element is of two packages or columns 5 and 6 formed, each stack consisting of about forty Belleville washers. A package consists of disks with a positive coefficient, the other from disks with negative coefficients of the Thermoelasticity. The inner end of each package rests there at a stop 7 of the battery housing. The outer end is each with the help of snap rings 8.9 or the like with a Coupled valve rod 10, which is passed centrally through the discs and the stop 7. This valve rod 10 controls the balanced control valves 11 and 12, one valve being the cold water inlet and the second valve being the hot water inlet regulates. The two valves are also pushed against the ends of the valve rod 10 with the aid of the helical springs 13, 14.

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The hot and cold water is after passing the two valves 11 and 12 mixed in the outlet area of the cold water valve 11, and the mixed water then reaches a central one Temperature sensing chamber in which the disk spring washer packs are arranged are. These spring packages respond to a change in the water temperature at the two inlets and thus regulate the Valves so that the mixed water produced has a constant temperature.

The temperature sensing chamber is preferably made of a material which has a very low specific heat, for example made of plastic material, so that the temperature sensing device has as low a time constant as possible.

As soon as the modulus of elasticity of the two disc materials changes with the temperature, the valve rod 10 is deflected until the force acting on it is in equilibrium with that on the adjusting knob 4 is selected water temperature. The regulation by this adjustment knob 4 causes the temperature sensing elements with respect to the two valve seats, whereby the equilibrium point of the system is changed and thus the temperature of the emerging mixed water changes accordingly.

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Claims (4)

Applicant: R.J Hodges - 36 German ITT Industries GmbH DITTI 0217 Freiburg 2856120 EXPECTATIONS [l. J Temperature control device for use in fluid control devices, consisting of a number of temperature sensing elements lined up and one or more valves coupled to the temperature sensing elements, characterized in that the temperature sensing elements are designed as springs whose modulus of elasticity changes depending on the temperature, and the individual temperature sensing elements are arranged so that, depending on the fluid temperature, the flow of which is regulated, a regulating element being linked to one or more of the temperature sensing elements, which generates a corresponding actuating movement as a function of a change in the temperature of the fluid. 9Θ9827 / 0938 2858120 2. Temperature control device according to claim 1, characterized in that that the temperature sensing elements are designed as disc spring washers in a stack of washers in pairs are summarized, wherein the control element is passed as a valve rod (10) centrally through the discs. 3. Temperature control device according to claim 2, characterized in that that the valve rod (10) penetrates two sets of Belleville washers, one set of the washers one positive and the other set of washers has a negative thermoelastic coefficient and the two sets of cup washers are arranged with respect to the valve rod (10) so that a dimensional change is added. 4. Temperature control device according to claims 1 to 3, characterized characterized in that the control device is arranged in a mixer tap for mixing cold and hot water, such that cold and hot water are mixed in a mixing room and then passed into a temperature sensing chamber is, in which two stacks of Belleville washers are arranged adjacent to one another, with the one stack of the washers one positive and the other stack has a negative thermoelastic coefficient, and that the disks of one common valve rod (10) are penetrated, with which the outer ends of the two disk spring washer stacks are coupled are, while the two inner end parts of the plate spring washer stack abut a stop (7), the ends the valve rod (1.0) on the two valves (11.5 2) act as an actuator, and that the control range with the help of a Temperature preselection device is adjustable by changing the position of the Belleville washers. 9Θ9827 / 0938