CA1119082A - Thermally-responsive indicating device - Google Patents

Abstract

ABSTRACT
This invention relates to thermally responsive indicating devices. More particularly it relates to thermally responsive indicating devices which employ a class Or nitrogen-containing organic materials as a fusible locking means. The fusible locking means is solid at 20° C
and is adapted to fuse at a predetermined temperature so as to release an indicating means which signals the attainment of the predetermined temperature. The class or organic materials utilized eliminates the need to employ toxic and expensive metal alloys as the locking means. The devices Or the invention are particularly useful in the preparation Or roods such as meats.

Description

l~lgO8Z

THERMALL~-RESPONSIVE I~DICATING DFVICE
This invention relates to thermally-responsive indicating devices. More particularly, it relates to de-vices which indicate the attainment of predetermined temperatures.
Thermally-responsive indicating devices are especially useful in preparing foods, particularly meats and fowl. ~y providing means by which the device indicates the attainment of predetermined temperatures, such devices can signal the degree of "doneness" of the food.
Such devices are, of course, known as exempli-fied by the number of patents issued thereon. Thus, see, for example, U. S. Patent Nos. 3,140,611; 3,280,629:
3,479,876; 3,548,780; 3,559,615; 3,626,897; 3,656,452;
3~682,130; 3,693,579; and 3,965,849. The devices des-15 cribed in these patents employ fusible latching means for normally securing the indicating means in a non-indicating position relative to the housing of the device. Typically, the latching means employed in these devices comprise metal alloys or waxes.
While devices employing such latching means have proven useful, they have certain drawbacks. For example, the metal alloys are high density materials. Thus, in addition to being expensive, relatively large quantities of alloy must be utilized in order to provide a given volume 25 f latching means thereby adding to the expense of such means. Moreover, such alloys are typically prepared from toxlc substances such as bismuth, lead, cadmlum, tin, etc.

- ill90~32 Waxes have been suggested as replacements for metal alloys. However, they have not proven entirely sat-isfactory Typically, waxes fuse over a relatively wide temperature range (5C or more). Thus, they do not provide a ~uick response when a predetermined temperature has been attained. Moreover, some of such waxes can be extracted from the indicating device during preparation of the food.
The present invention overcomes these disadvan-tages. It provides a thermally-responsive indicating device which employs a locking means that comprises a class of nitrogen-containing organic materials. This locking means is substantially less dense and less expensi~e than a corresponding volume of the metal alloys. Thus, devices of the inventlon require significantly less of the locklng means per unit volume and thereby afford substantial cost savings. Moreover, the toxic alloys are replaced with materlals which are considered nontoxic and, in the most preferred case, exhibit essentially no acute oral toxicity.
Furthermore, the organic locking means employed in the present invention typically fuse over a narrow temperature range (3qC or less) and are generally resistant to extraction from the devlce by water and cooking fats and oils. Thus, devices of the present invention are safe and provide a quick and accurate response upon attainment of a predeter-mined temperature.
In accordance with the present invention, thereis provided a thermally-responsive indicatlng device com-prising a housing which defines a cavity closed at one end and open at the other end, an indicating means within said cavity for movement relative to said houslngS a biasing means within said cavity for urging the movement of said O~Z

indicating means relative to said housing, and a fusible locking means within said cavity which is solid at about 20C. and is adapted to fuse at a predetermined temperature and wherein said locking means has the formula Rl -N - R2 (I) [H]n wherein Rl is selected ~rom ~ C and R3 - C/
C
o R2 is selected from saturated aliphatic radicals; aryl radicals and aryl-substituted aliphatic radicals; R3 is a saturated aliphatic radical containing ~rom about 1 to 20 carbon atoms; and n is O or l; provlded that (i) when is o C , n is O and R2 is a saturated aliphatic radical C ~
o /
and ~i) when Rl is R3 - C~ , n is 1, and R2 is selected from saturated aliphatic radicals, aryl radicals and aryl-substituted aliphatic radicals; and provided further that the sum of the number o~ carbon atoms in Rl and R2 is at least about 10 and pre~erably is at least about 14.
The present invention is described in more detail hereinafter with reference to the accompanying drawings wherein like re~erence characters re~er to the same parts throughout the several views and in which:

~lgO~2 Figure 1 is a cross-sectional view of a preferred embodiment of the invention having an indicator rod in a lowered position relative to the body Or the device~
Figure 2 is a cross-sectional view of the em-bodiment o~ Figure 1 having the indicator rod in a raised position relative to the body of the device.
Figure 3 is a cross-sectional view of the upper portion of an alternative embodiment of the invention.
The detailed devices of the invention employ a class of compounds of formula I as the locking means. The locking means has a relatively sharp trigger temperature (defined hereinafter). Thus, while it may trigger over a range of temperatures that range is no greater than about 3C. Moreover, the locking means is stable under severe storage and use conditions (100 percent relative humidity and 50C). Thus, when expo~ed to severe conditions for a period of 30 days, it does not exhiblt any substantial change in trlgger temperature (a change of less than about 6C
and preferably a change of less than about 3C). Long chain compounds of formula I (those containing at least about 14 carbon atoms) are particularly stable under severe storage and use conditions.
Additionally, the preferred locking means are also virtually impossible to extract from the indicating device when exposed to conditions which simulate the cooking environment. Thus, the danger of accidental oral ingestion by humans ls very remote.
As used herein, the term "trigger temperature"
refers to that temperature, or range of temperatures, at l~gO~Z

which the indicating devices signal the attainment of their predetermined temperature. The trigger temperature may be easily determined. Thus, flve gauges are suspended in an appropriate liquid bat~h so that the tip and most of the body of each of the devices (but not the top), is sub-merged, The temperature of the bath is controlled so that it cycles within a + 0.55C temperature band. The bath is held in each band for two minutes after which the tempera-ture i5 raised in 0.55C increments to the next band. The number of devices that fire in each band is recorded.
Extraction tests are performed on separate gauges in separate water and heptane baths. Devices con-tainlng a 50 percent by weight excess of the locking means and having a nylon 6 (food grade) body are used. The water bath simulates the effect of water on the device during cooking. The heptane bath simulates the effect of fats and oils on the device during cooking. Water extraction tests are performed at 118C under sufficient pressure to prevent the water from boiling off. Heptane extraction tests are performed at a temperature of about 3C above the melting point of the locking means belng tested. The tests are run by submerging the tip and lower portion of each of the devices in the appropriate bath at said temperature for two hours. The water or heptane is then evaporated to deter-mine the amount of locking means extracted thereby.
One class of compounds coming within formulaI are the aromatic amides of the formula ~ R4 H2b+lCb C7 ~' ( II) H
wherein R4 is a lower alkyl group containing from about 1 to 4 carbon atoms; b is an integer of from about 4 to 20;

~ll90~Z

and d ls 0 or 1.
In formula II when d is 1, R4 is preferably a methyl group which i5 ortho or para to the amide group.
Additionally, b is preferably from about 7 to 17 and most preferably about 13.
The most preferred compound of formula II is myristanilide. This compound exhlbits essentially no acute oral toxicity. Consequently, there is virtually no danger from its accidental oral ingestion by humands.
Another class of useful compounds coming within formula I are the aliphatic amides of the formula , ll 5 R3-C-N-R (III) H

wherein R3 is as described above and R5 is selected from saturated aliphatic radicals and aryl-substituted allphatic radicals containing from about 1 to 20 carbon atoms, provided that the sum of the number of carbon atoms in R3 and R5 is at least about 13.
Yet another class of useful compounds coming within formula I are the N-alkyl phthalimides of the formula ~ (IV) wherein R6 is a saturated aliphatic radical of at least about 6 carbon atoms.

z Representative examples of compounds o~ formula I, their melting points, and their average trlgger tem-peratures are set forth in Table I below. The meltlng points were determined by the Fisher-Johns ~ethod.

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o ~ C~ o C~ o a~: o ~ o a o o v z z æ æ z ltl9~32 The compounds of formula I may be easily prepared by, for example, combining the necessary reactants in a suitable vessel in the presence of a solvent (e.g., xylene) and reacted at atmospheric pressure in an inert at-mosphere untll substantlally all of the llberated water hasbeen azeotropi¢ally removed. The reactlon mixture may be heated to facllltate the reactlon. However, certain of the reactlons may be exothermic so that coollng may be necessary.
Typically the reaction temperature ls ln the range of 140C
to 210C. Upon completion of the reactlon, the mixture may be cooled tlf necessary) and slmultaneously diluted with alcohol to precipitate the compound. The precipitate may then be filtered from the mixture, washed with alcohol and air dried.
Typlcally reactants used in preparing the compounds of formula I are H2N ~ d (V) H N-(CH ~ CH (VI)

2 2 0-20 3 2b+1 b (VII) Il ~ ~ 0 (VIII) Reactants of formulae V and VII are useful in preparing compounds of formula II. Reactants of formulae VI and VII
are useful ln preparing compounds of formula III. Reactants of formulae VI and VIII are useful in preparing compounds of formula IV.

l~lsoaz Specific examples of preparations of compounds of formula II, III, and IV are now set forth. 0 H
A. Preparation of Myristanllide [27cl3_C_l ~ ]
A three liter flask equipped with a stirrer, 5 thermometer, nitrogen inlet, Barrett trap and condenser was used. Myristlc acld (commercially available from Emery Chemicals, 97 percent purity, 685 grams, 3.0 moles), aniline (300 ml., 3.2 moles) and 120 ml xylene were charged to the flask. The mixture was stirred and heated for approxlmately 6-1~2 hours at a temperature of from about 170C-220C.
The reaction was conducted in a nitrogen atmosphere. The reaction mixture was then cooled to 140C and poured into a 4 liter beaker. About 1. 8 liters of denatured alcohol were slowly added to the reaction solution. After standing over-night, the slurry of semi-solid myristanilide was collected by filtration. The filter cake was washed thoroughly with two portions of denatured alcohol and then air dried at about 22C. The resultant white crystalline solid weighed 706 grams and had a meltlng point of 83.5C-84.5C.
B. Preparatlon of N-dodecylpalmitamide ¦ H3lcl5-c-N-cl2H~
A 250 ml fla~k equipped with a stirrer, thermo-meter, nitrogen inlet, Barrett trap and condenser was used.
Palmitic acid (commercially available as "Emersol" 144 from Emery Chemicals, 95~ purity, 51.3 grams, 0. 2 moles) 3 dodecylamine (commercially available as "Armeen" 12D from Armak Chemicals, 97% purity, 37.1 grams, 0.2 mole) and 50 ml xylene were charged to the flask. The mixture was stirred and heated for approximately 2-1/4 hours at a temperature Of from about 150C to 220C. The reaction was conducted in a nitrogen atmosphere. The reaction mixture was cooled 9V~Z

to 140C and added slowly to 250 millil~ters of denatured alcohol. The resulting slurry of semi-solid N-dodecyl-palmitamide was then heated on a steam bath untll the solid dissolved. The bath was then cooled to room temperature (22C) and the resulting slurry was filtered The collected solid was washed on the filter with 2 portions of alcohol and air dried at room temperature. The resultant white crystalline solid weighed 80 grams and had a melting point of about 79.5 - 81.5.
C. Preparation of N-octadecylphthalimide _ _ ~ ~NC18H37 _ _ A 250 ml flask equipped with a stirrer, thermometer, nitrogen inlet, Barrett trap and condenser was used.
Octadecylamine (commercially available as "Kemamine" P99OD
from Humko-Sheffield, Division of Kraftco Corporation, 90% purity, 53.9 grams, 0.2 moles), phthalic anhydride 20 (99.5% purity, 29.6 grams, 0.2 mole), and 50 ml of xylene were added to the flask. The initial reactlon of the phthalic anhydride and octadecylamine was moderately exothermic. The reaction was carried out in a nitrogen atmosphere. The mixture was reacted for approximately 1-1/2 25 hours at a temperature of from about 140C to 200C. The reaction mixture was then cooled to 140C and was added to approximately 250 ml of denatured alcohol. The resulting slurry of semi-solid N-octadecylphthalimide was then heated oaz on a steam bath to dissolve the solids. After cooling to room temperature the precipitated solid was filtered off and washed with 2 portions of alcohol. The yleld of white crystalline solid was 72.1 grams which had a melting point of about 78-79C.
Referring now to Figure 1, there ls shown thermally-responsive signaling device 10 comprising a housing 12 de-fining a cavity 14 and indicating means 16 within said cavity, a biasing means 18 within said cavity and a locking means 20 within said cavity.
Housing 12 has a closed end 22 and an open end 24.
Closed end 22 is preferably pointed, as shown, although it i9 not necessary that it be so. Additionally, said end is preferably provided with a flange 26 which may either circumscribe housing 12 or pro~ect from only a portion thereof. In this iatter case, flange 26 may also be referred to as a barb. In either event, flange 26 permits penetra-tion of device 10 into the food to be prepared while preventing the tendency of the food to urge the device outwardly during preparation.
Open end 24 is provided with a reverse curl lip 28 which is adapted to slideably receive indicating means 16 and form a mating seal with shoulder 30 of said indicating means. (See Figure 2).
Alternatively open end 24 may be provided wlth a cap 32 (See Figure 3) rather than the reverse curl lip. In this embodiment, cap 32 is received within open end 24 of the housing 12. Cap 32 has a passage 34 therethrough which i~ in registry with the lndicating means (not shown) and ~lsoa2 adapted to slideably receive said indicating means. Addi-tionally, it is preferred that cap 32 have tapered shoulder 36 to form a mating seal with the shoulder of indicating means The material of construction of housing 12 must be capable of (i) wlthstanding the rigors of the environ-ment to which it is subJected and (ii) conducting the internal temperature of the article being cooked to the locklng means relatively quickly. Moreover, it is preferred that the material be chemically inert. Representative of useful materials are metals (e,g~, aluminum~, glass? polymers (e.g., nylon, polypropylene, etc.).
The shape of housing 12 may vary. Circular cross-sections are preferred, but any shape, symmetrical or asymmetrical, may also be used.
Indicatihg means 16 is preferably axially dis-posed within cavity 14. In the embodiment shown, it is adapted so as to be substantially within said cavity prior to the attainment of a predetermined temperature and sub-stantially outslde of said cavity after the attainment ofsaid predetermined temperature~ However, it may also be adapted to operate in the opposite manner (e~g., raised prior to attainment of a predetermined temperature and lowered at the attainment of a predetermined temperature).
Moreover, said indicating means may be disposed so as to rotate to an indicating position without changing its height relative to the housing. In any event, the exact type of movement of the indicating means relative to the housing is not critical to the invention.
Indicating means 16 may be constructed from the same materials used for housing 12. Additionally, it may have a variety of cross-sectional areas, although circular 1:1190~32 cross-sections are preferred.
The movement of indicating means 16 relative to housing 12 so as to indicate the attainment of a predeter-mined temperature is brought about by biasing means 18.
In the embodiment shown~ such movement is between lowered and raised positions 9 although, as pointed out above, other movements are also possible, Typically, said biasing means comprises a spring. Said spring is generally held in com-pression until such time as locking means 20 fuses, although it may be held in any configuration such that it can urge the indicating means to an indlcating position Locking means 20 may either secure indicating means 16 directly to housing 12, or alternatively, it may directly restrain biasing means 18 (e.g., by ~oining said means to itsel~ or encasing said means wlthin the locking means). Moreover, a quantity of the locking means may be provided around the lower end of the indicating means so as to hold the biasing means in compression (or other config-uration) between such point and the shoulder of the indicating means. Still other arrangements are also possible as will be understood by those skilled in the art and are included within the scope of the inventlon.
Thermally-responsive signaling devices of the invention may be easily assembled. For example, the em-bodiment shown in the figures may be assembled by forming apellet of pre-determined size of the material of the locking means; inserting it into the closed end of the housing;
inserting the biasing means and indicating means into the housing; forming the reverse curldown lip at (or inserting the cap in) the open end; and heating the material of the locking means until it fuse~s. Methods o~ forming the reverse curldown lip are described in U. S. Patent No.

~90~2

3,965,849. The indicating means may then be urged toward the closed end of the device (thereby compressing the biasing means) and held in that position until the fused locking means material solidifies.
The assembled signaling devices are then preferably quality assurance tested by heating them at a temperature slightly below the trigger temperature of the device for 2 hours. This test causes those devices which have received an insufficient amount of the material of the locking means to fire prematurely. Those devices which have received a sufficient amount of the material of the locking means do not fire prematurely in this test.
The trigger temperature of the devices of the invention may be affected by the reactants used to prepare the compounds of formula I. Commercially available starting materials frequently contain minor amounts of impurities.
These impurities are usually closely related compounds which persist in the compound of formula I. The effect which these impurities have upon the trigger temperature is dependent upon the nature and amount of the impurities present.
The trigger temperature of the devices of the invention may also be slightly varied by the intentional incorporation of impurities into the locking means. Thus, for example, the trigger temperature of a myristanilide locking means may be lowered by the incorporation of a minor amount of myristic acid therein.
The thermally-responsive signaling devices des-cribed in the figures represent but two embodiments o~ the present invention. Still other embodiments are possible, as ~ill be understood by those skilled in the art and are in-cluded within the scope of the following claims.

Claims (21)

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

1. A thermally-responsive indicating device comprising a housing which defines a cavity closed at one end and open at the other end, an indicating means within said cavity for movement relative to said housing, a biasing means within said cavity for urging the movement of said indicating means relative to said housing, and a fusible locking means within said cavity for resisting movement of said indicating means by said biasing means, wherein said locking means is solid at about 20°C, and is adapted to fuse at a predetermined temperature and wherein said locking means has the formula wherein R1 is selected from R2 is selected from saturated aliphatic radicals, aryl radicals and aryl-substituted aliphatic radicals; R3 is a saturated aliphatic radical containing from about 1 to 20 carbon atoms; and n is 0 or 1; provided that (i) when R1 is , n is 0 and R2 is a saturated aliphatic radical and (ii) when R1 is R3 , n is 1, R2 is selected from saturated aliphatic radicals, aromatic radicals and aryl-substituted aliphatic radicals; and provided further that the sum of the number of carbon atoms in R1 and R2 is at least about 10.

2. A thermally-responsive indicating device com-prising a housing which defines a cavity closed at one end and open at the other end, an indicating means within said cavity for movement relative to said housing, a biasing means within said cavity for urging the movement of said indicating means relative to said housing, and a fusible locking means within said cavity for resisting movement of said indicating means by said biasing means, wherein said locking means is solid at about 20°C and is adapted to fuse at a predetermined temperature and has the formula wherein R4 is a lower alkyl group containing from about 1 to 4 carbon atoms; b is an integer of from about 4 to 20; and d is 0 or 1.

3. A thermally-responsive indicating device according to claim 2 wherein d is 0.

4. A thermally-responsive indicating device ac-cording to claim 3 wherein b is from about 7 to 17.

5. A thermally-responsive indicating device according to claim 4 wherein b is 13.

6. A thermally-responsive indicating device according to claim 2 wherein d is 1.

7. A thermally-responsive indicating device according to claim 6 wherein R4 is a methyl group.

8. A thermally-responsive indicating device according to claim 7 wherein said methyl group is ortho or para to the amino group.

9. A thermally-responsive indicating device according to claim 8 wherein b is from about 7 to 17.

10. A thermally-responsive indicating device according to claim 9 wherein b is 8.

11. A thermally-responsive indicating device comprising a housing which defines a cavity closed at one end and open at the other end, an indicating means within said cavity for movement relative to said housing, a biasing means within said cavity for urging the movement of said indicating means relative to said housing, and a fusible locking means within said cavity for resisting movement of said indicating means by said biasing means, wherein said locking means is solid at about 20°C, and is adapted to fuse at a predetermined temperature and has the formula wherein R3 is a saturated aliphatic radical containing from about 1 to 20 carbon atoms and R5 is selected from saturated aliphatic radicals and aryl-substituted aliphatic radicals containing from about 1 to 20 carbon atoms, provided that the sum of the number of carbon atoms in R3 and R5 is at least about 13.

12. A thermally-responsive indicating device according to claim 11 wherein R5 contains 12 carbon atoms.

13. A thermally-responsive indicating device according to claim 12 wherein R3 contains 15 carbon atoms.

14. A thermally-responsive indicating device according to claim 12 wherein R3 contains 17 carbon atoms.

15. A thermally-responsive indicating device according to claim 11 wherein R5 contains 8 carbon atoms.

16. A thermally-responsive indicating device according to claim 15 wherein R3 contains 17 carbon atoms.

17. A thermally-responsive indicating device according to claim 11 wherein R5 contains 18 carbon atoms.

18. A thermally-responsive indicating device according to claim 17 wherein R3 contains 9 carbon atoms.

19. A thermally-responsive indicating device according to claim 17 wherein R3 contains 11 carbon atoms.

20. A thermally-responsive indicating device comprising a housing which defines a cavity closed at one end and open at the other end, an indicating means within said cavity for movement relative to said housing, a biasing means within said cavity for urging the movement of said indicating means relative to said housing, and a fusible locking means within said cavity for resisting movement of said indicating means by said biasing means, wherein said locking means is solid at about 20°C, and is adapted to fuse at a predetermined temperature and has the formula wherein R6 is a saturated aliphatic radical of at least about 6 carbon atoms.

21. A thermally-responsive indicating device according to claim 20 wherein R6 contains 18 carbon atoms.