Stoves and furnaces – Heaters – Chemical
Patent
1987-04-21
1989-05-16
Yeung, James C.
Stoves and furnaces
Heaters
Chemical
F24J 100
Patent
active
048299804
DESCRIPTION:
BRIEF SUMMARY
This invention concerns improvements in and relating to trigger or activator devices for so-called `heat packs`.
In the so-called `heat packs` latent heat of crystallisation is stored in a supercooled solution of a crystalline material. It is known that such packs can be stored in a stable condition and used as a heat source as and when required, by triggering or initiating crystallisation of the supercooled solution whereby the latent heat of crystallisation is given up in the resulting exothermic reaction. British Patent Specification No. 1585808, for example, describes a self-contained heat pack comprising a flexible container incorporating the appropriate supercooled solution, together with an activator device in the form of a fissured activator strip capable of being flexed to initiate crystallization of the solution.
U.S. Pat. No. 2,220,777 describes a heat pack comprising a container, which may have rigid or flexible walls, for the supercooled solution and an activator device which may take the form of a rod having one end which is attached to a flexible wall portion and is manipulable to cause the other end to scrape the inside of the container wall; in another embodiment opposed wall portions of a flexible container are provided with metal inserts which may be manipulated so that their internal surfaces come come into scraping contact. In yet another, rather conjectural, embodiment `various pieces of metal` may be placed within the container and crystallisation initiated merely by shaking the container.
Although various activator devices for initiating such crystallisation have hitherto been proposed, the mechanism whereby crystallisation is initiated is not fully understood.
It is an object of the present invention to provide a reliable activator device for initiating crystallisation of a supercooled solution, for example in a so-called `heat pack`.
An activator device in accordance with the invention is characterised in that it comprises one or more convoluted metallic filaments to disposed that flexing of the filamentary metallic material, and consequent rubbing contact of contacting metallic surfaces, is effective to initiate crystallisation of a supercooled solution within which the activator device may be immersed.
According to a first preferred form of the invention the activator device comprises two or more resilient helical filaments nested one within the other, optionally with a flexible core. Each helix may be wound in a sense the same as or opposed to that of its immediate neighbours; moreover the diameter of the filaments may decrease in a radially inward direction. According to a second preferred form of the invention the device comprises a helical spring fitted with a cap or terminal insert, the surface of which is brought into rubbing contact with that of the spring on compression, extension or flexing thereof. In a third preferred form the device comprises a body of flexible convoluted filament which may be random or woven.
In each form of the invention flexing of the convoluted flexible metallic filaments, for example the one or more springs, causes the rubbing contact which triggers crystallisation. In the case of the first and third forms of the invention the contact is between surfaces of convoluted flexible filament and in the second form between the surface of the convoluted flexible filament (the spring) and the insert or cap.
An activator device in accordance with the invention may take a variety of forms, some specific examples of the invention being illustrated in the accompanying drawings, in which
FIG. 1 is a side elevation of one embodiment of device according to the invention;
FIG. 2 is a part sectional elevation corresponding to FIG. 1;
FIG. 3 is a plan view corresponding to FIG. 1;
FIGS. 4, 5 and 6 are views corresponding to FIGS. 1 to 3 respectively and illustrating another embodiment of the invention;
FIGS. 7, 8 and 9 are corresponding views of a yet further embodiment of the invention, and;
FIGS. 10, 11 and 12 are each an elevation of a yet further embodiment of
REFERENCES:
patent: 1915523 (1933-06-01), Ferguson
patent: 2220777 (1940-11-01), Othmer
patent: 4077390 (1978-03-01), Stanley et al.
patent: 4379448 (1983-04-01), Kapralis et al.
patent: 4460546 (1984-07-01), Kapralis et al.
patent: 4580547 (1986-04-01), Kapralis et al.
patent: 4587950 (1986-05-01), Mack et al.
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