CA1211363A - Trigger to initiate crystallization - Google Patents

Abstract

TRIGGER TO INITIATE CRYSTALLIZATION

ABSTRACT OF THE DISCLOSURE

A trigger to initiate crystallization of a supercoated salt solution comprises, a) a thin strip having a perimeter, b) said strip having a multiplicity of slits formed therein, each slit characterized as having opposed elongated edges which face one another in near touching relation, c) the strip further characterized as having two configurations between which it is bendable with snap-displacement causing the slit edges to initiate progressive exothermic crystallization of said salt in the solution.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to the initiation of crystallization of a superc~led salt solution; more particularly it concerns the provision of a highly advantageous trigger ~hat is ea~ily deformable and is constructed to initiate such crystallation when the trigger is deformed, and without failure or injury to a plastic container in which the txigger is confined.
Devices of the general t~pe wi~h which the present invention is concerned are described in ~S.
Patent 4,077,3~0; however, such devices have-tended to su~fer from unreliable triggering of crystallization.
For example, flexing of the actuator strips described in that patent at times will initiate crystallizakion and at other times will not. This greatly aggravates the user and reduces the practicality and utility of such devices.

S~AP~Y 0~ THE INVENTION

It is a major object o~- the present invention to provide animproved trigger which will reliablv and repeatedly produce or initiate crystallization of supercooled solutions; which is readily produced, and which will not injure or tear the plastic container in which it is incorporated.
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Fundamentally, the trigger comprises:
a) a thin s-trip having a perimeter, b) said strip hav.ing a multiplicity of slits formed therein, each slit characterized as having opposed elongated edges which face one another in near touching relation, c) the strip further characterized as havin~
two con~igurationsbetween which it is bendable with ~.nap-displacement causing the slit edges to initiate progressive exothermic crystallization of said salt in the solution.
As will appear, portions of the opposed edges o~ the slits typically touch one another, so that they may rub against one another and compress the solution trapped betwee~ those edges when the triyger is snap-deformedi the trigger is t~picall~ formed as a disc wherein the slits are spaced inwardly from the ~oundary or periphery of the disc; the disc ~ypically has a dished central portion free of sli~s and adapted to "oil can" or snap "over center" when the disc is subjected to flexing or bending; and the metal of the edges adjacent the slits is impacted during fabrication to impact orient the molecular structure so as to aid the func~ioning of the disc to produce or initiate crystallization.
These and other ob]ects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood frcm the following description and drawings, in which:

~Z~ 3 DR~WING DESCRIPTION
Fig. 1 is 2 plan view o~ a device incorpoxating the invention;
Fig. 2 is an enlarg~d section taken on lines

2-2 of Fig. 1, and showing a trigger .in one side ~levation con~iguration;
Fig. 2a is a side elevation showing the Fig. 2 trigger in a second side elevation conf.iguration, i.e.
after snap-displacement;
Fig. 3 is a further enlarged plan view o~ the trigger seen in Flg. 2;
Fig. 4 is a side elevation showing a step in ~he fabrication of the Figs. 2 and 3 trigger;
Fig. 5a is a ragmentary plan view of a slit as initially formed in the trigger blank or strip;
Fig. 5b s a fragmentaxy plan view like Fig. Sa, but showing the slit after impacting as in Fig. 4; and F.ig. 5c is an enlarged view of the slitq . ....
Fig. 6 is a view like Fi~. 3, showing a modified triggerO - -DETAILED DESCRIPTION
Referring first to Figs. 1 and 2, a llexible heat pack 10 includes a flexible plastic container 11 containing a supercooled solution 12, one example being aqueous sodium acetate as referred to in U.S. Patent 4,077,390. The container may consist of translucent or transparen~ plastic, such as polyethylene or PVC.

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The upper and lower container walls lla and llb may be peripherally bonded or heat sealed together, as indicated at 13, whereby the solution 12 is co~tained against leakage.
Located in the container is a trigger 14 adapted to be deformed to initiate exothermic crystallization of the salt in the solution, and for that purpose the concentrakion of the salt is sufficient to produce such crystallization in response to trigger bending, as will be described~ The trigger may be retained in the corner of the rectangular container by interruptedly bonded portio~ of the container walls, i~di~ated at 13ar inwardly o~ peripheral bonding 13;
at the same time, the solution has access to the trigger, at all times r via interruptions between bonded portions 13a.
Generally speakingr the .trigger comprises a thin strip, such as a metallic disc, having a perlmeter indicated at 14a in Fig. 3. ~hat perimeter isfree of sharp edges that could injure or penetrate the plastic wa~lls lla and llb. The strip has a multiplicity of - -slits 15 form~d therein, each slit characterized as ha~ing opposed elongated edges which face one another in near touching relation. Fig. 5a shows a typical slit 15 as initially fo.rmed through the disc, and with opposlte elongated edges 15a. Fig. 5b shows the slit as it finally is formed or exists, with the edges 15a so close together that they do not appear distinct;
however, there are slight gaps between and spaced along such edges, which may touch one another between th~e gaps --5-- .

Note for example the grea-tly en~arged- slit 15 in Pig. ,5c with edges lSa touching at points 16,~and with gaps 16a between the edges. Fig. 5c is representative only, and the configurations of the edges 15a ~ay vaxy, i.e. they may be less jagged for example.
The disc shaped strip 14 is characterized as having two configurations between which it is bendable with snap-displacement causing the slit edges to initiate progressive exothermic crystallization of the salt in the supercooled solution in the container., Note for example the first stable coniguration of the trigger strip 14 in Fig, 2, and its second (and relatively stable) curved configuration 14' in ~ig. 2a. The user simply applies finger pressure on the container walls lla and llb snap-deformsthe disc 14 to Fig. 2a con~iguration, in the container. This causes the edges 15a of the slit to actuate the crystallation, due to sudden deformation-(as for exa~ple sudden local compression) of the solution trapped or confined in the slit between the approximately touching edges lS~ The snap displacement of the nearly touching edges is found to initiate crystallation without ~ailure or malfunction.
These purposes are served to unusual advantage by causing the disc to have dished configuration as in Fig. 2, so as to "oil-can" when deformed, i.e. easily snap over-center into Fig. 2a configuration. Further, .
$he disc has a central portion 17 free of slits, and an outermost annular portion. The latter contains the slits t which are typically spaced inwardly from the perimeter 14a so that the latter is continuous, aiding the ~2~3~3 snap-displacement referred to. Xn Figs. 2, 2a and 3, the slits axe located in the outermost annular sec-tion 17a of the dished portion of the disci whereas in Fig. 6, the slits are located in the undished outer annular portion 18. Circles 19 in Figs. 3 and 6 generally designate the boundary between the dished and undished portions.
~Finally, the performance of the disc shaped strip to initiate crystallization is aided bv impact orientation of the molecular structure o~ the edges 15a. Fig. 4 shows a striker 20 being forci~ly urged ~ -downwardly toward blank 21, after the latter has had slits formed therein with spaced apart edges as in Fig. Sa. The bottom of the striker is protubera~t at 22 to "dish" the blank ~i.e. permanently deform it to have a central bulge as in FigO 2)~ thereafterr the trigger dis~ is stamped or cut out of the blank by a suitable die. Back up platen 23 in Fig. 4 has a recess 2~ to receive the deformed bulge of the hlank 21

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. For use in initiating crystallization of a supercooled salt solution, a trigger comprising:
a) a thin strip having a perimeter, the strip being in the form of a disc, b) said strip having a multiplicity of generally parallel slits formed therein, each slit characterized as having opposed elongated edges which face one another in near touching relation, said slits everywhere spaced inwardly from said perimeter, c) the strip further characterized as having two configurations between which it is bendable with snap-displacement causing the slit edges to initiate progressive exothermic crystallization of said salt in the solution.

2. The trigger of claim 1 wherein portions of said opposed edges touch one another.

3. The trigger of claim 1 wherein said strip is metallic and has dished configuration in one of said configura-tions characterized as stable.

4. The trigger of claim 1 wherein said strip has a central portion and an outer portion surrounding said central portion, said slits located in one of said portions.

5. The combination that includes a flexible container containing said solution, said trigger located in the container in contact with the solution, in claim 1.

6. The trigger of claim 1 wherein said strip is metallic and has molecular structure which is impact oriented.

7. The combination of claim 5 wherein said strip has molecular structure which is impact oriented.

8. The trigger of claim 4 wherein the slits are confined to said outer portion.