Classifications

• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D23/00—Control of temperature
  • G05D23/01—Control of temperature without auxiliary power
  • G05D23/12—Control of temperature without auxiliary power with sensing element responsive to pressure or volume changes in a confined fluid
  • G05D23/121—Control of temperature without auxiliary power with sensing element responsive to pressure or volume changes in a confined fluid characterised by the sensing element

Definitions

• thermostats i.a. at heating elements, in particular at water based heat radiators for controlled room heating.
• Figure 1 is a central longitudinal section through a first embodiment of the temperature sensing device according to the invention.
• the housing 2 has a sleeve portion 6 projecting axially towards the casing 4 and being enclosed by the diaphragm 7 of an elastically stretchable material, in particular a ther o- elastomer.
• the diaphragm 7 has a radially projecting flange 7a which is sealingly fitted between a shoulder 4a and a ring member 8, which encloses the sleeve portion 6 and is likewise made of a polymer material.
• the diaphragm 7 extends radially inwardly while engaging with the ring 8 and merges, via a rounded portion, with an axially extending portion 7c, which engages with the outside of the sleeve portion 6 of the housing 2.
• the sleeve portion 6 has a rounded edge portion 6a, and the diaphragm follows this edge portion with a rounded portion 7d, which merges with a planar portion 7e into a central portion 7f, which is kept in engagement with the end surface 9a of a piston 9 being slidable in the cylindrical cavity 3.
• the inner end la of the actuating rod 1 is fitted into a central recess 9b in the opposite end of the piston 9.
• the closed chamber 5 consists of an annular portion 5a located radially outwardly of the sleeve portion 6 and the portion 7c of the diaphragm, and a central portion 5b between the planar portion 7e, 7f of the diaphragm and the end portion 4b of the casing 4.
• the closed chamber 5 is prefilled with a wax-like material or a fluid, e.g. an organic ester having a high coefficient of volume expansion, so that when the temperature in the ambient air outside the casing 4 increases, heat will be transferred through the heat conducting material of the casing 4 into the fluid, whereupon the. fluid will expand and exert an increasing pressure on the diaphragm 7.
• a wax-like material or a fluid e.g. an organic ester having a high coefficient of volume expansion
• the central portion 7f of the diaphragm When the piston 9 is displaced to the left, the central portion 7f of the diaphragm will reach the plane defined by the planar portion 7e of the diaphragm and thereafter be stretched inwardly into the cavity 3 while continuously engaging with the end surface 9a of the piston 9. Since the central portion 7f of the diaphragm 7, in the illustrated embodiment, will be stretched in opposite directions in the initial stage, at a low temperature, and in the final stage, at higher temperatures, respectively, the stretchability of the diaphragm material will be used in the best possible way for achieving as large a stroke as possible for the piston 9 when the latter is being displaced within its operational region.
• the heat transfer from the outside of the casing 4 to the wax or the fluid in the chamber 5 will be particularly good in case the casing 4 is provided at the inside thereof with circum- ferentially distributed, axially extending grooves 10, which significantly enlarges the effective area of the boundary surface between the casing material and the wax or the fluid.
• the grooves 10 may alternatively be formed as inwardly projecting ridges or flanges. The essential point is that the inside of the casing has a large effective area. On the drawings only one groove 10 is shown. In practice, a plurality of such grooves are distributed circumferentially.
• the various parts are injection moulded from a polymer material, the diaphragm 7 and the ring 8 possibly being produced by double moulding.
• the ring 8 and the diaphragm 7 are joined together after the injection moulding, e.g. by ultrasonic welding.
• the unit consisting of the diaphragm 7 and the ring 8 is thereafter joined to the casing 4 in a suitable manner, e.g. by welding or gluing.
• the chamber 5 is filled with wax or fluid by inserting two fine needles through a plug 7g projecting axially through the ring 8. The fluid is fed through one of the needles, whereas air is evacuated through the other one.
• the sleeve 6' is biassed towards the position shown in figure 2a by means of a strong pressure spring 11, one end of which abuts the end wall of the housing 2 and the other end of which is inserted into an annular recess 12 in the sleeve 6 ' and abuts the bottom of the recess 12 adjacent to the end of the sleeve 6' engaging with the diaphragm.
• a radially projection flange 6 'a engages with a stop shoulder 8a on the ring 8 and holds the sleeve 6 ' in a well-defined position as shown in figure 2a.
• the second embodiment according to figures 2a, 2b and 2c has an inherent safety function which ensures that the diaphragm 7 is kept intact even at very high temperatures.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Automation & Control Theory (AREA)
• Temperature-Responsive Valves (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20396210

Family Applications (1)

Country Status (5)

Cited By (1)

Citations (1)

• 1994
  • 1994-12-02 SE SE9404199A patent/SE502895C2/sv not_active IP Right Cessation
• 1995
  • 1995-11-30 EP EP95940498A patent/EP0806000A1/en not_active Ceased
  • 1995-11-30 WO PCT/SE1995/001443 patent/WO1996017281A1/en not_active Application Discontinuation
• 1997
  • 1997-05-05 FI FI971917A patent/FI971917A/sv unknown
  • 1997-05-09 NO NO972146A patent/NO972146D0/no not_active Application Discontinuation

Patent Citations (1)

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