GB2315126A - Cooking Thermometer - Google Patents

Abstract

A monitoring cooking thermometer comprises a cartridge 10 and a slidable plunger 11 supported in a removable cap 12. An active shape memory alloy element 13 forces the plunger upwards and partly out of the cartridge when the temperature inside a joint of meat, say, reaches a certain temperature. This indicates that the meat has cooked. The thermometer is easily disassembled for cleaning. Also, the element 13 can be replaced by a similar element that has different operating temperature characteristics if desired.

Description

COOKING THERMOMETER The invention relates to cooking thermometers.

The invention relates more particularly to monitoring pop-up or roast-ready thermometer indicators that have a moving plunger. The moving plunger is mounted in a cartridge that is inserted into a joint of meat before it is placed in an oven and the plunger moves out of the cartridge when a certain meat temperature is reached.

This provides a very clear visual indication that the meat is cooked. Such devices are known and widely used already and rely on the melting of wax or the like so that at the certain temperature the plunger released by the wax and forced out of the cartridge by a spring.

Currently such devices are not re-usable, are normally provided for one kind of meat (i.e. settable to one temperature range), and have relatively crude operating performance characteristics.

It is an object of the invention to reduce or overcome at least some of these problems.

According to the invention there is provided a monitoring cooking thermometer arranged to be heated with the food that is to be monitored. comprising a cartridge and a relatively slidable plunger mounted to slide out of the cartridge to visually indicate the food temperature at a certain temperature or range of temperatures, including an active shape memory alloy element inside the container which is arranged to push the plunger out of the cartridge at said certain temperature or range of temperatures, and a return spring for biassing the plunger into the cartridge.

The active element is preferably replaceably mounted in the cartridge such that different active elements that act at different temperatures can be inserted and the thermometer used for different types of food.

The plunger is preferably held and slidably mounted in a removable cap which fits to one end of the cartridge.

The cap may be a press-fit to the end of the cartridge.

A monitoring cooking thermometer according to the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows an exploded sectional side view of the thermometer; and Figure 2 shows an assembly sectional side view of the thermometer.

Referring to the drawings, the thermometer comprises a pointed cartridge 10 and a movable plunger 11. The plunger is slidably held and mounted in a cap 12 that presses and snap fits to one end of the cartridge 10. A shape memory alloy coiled element 13 is loosely mounted at the base of the cartridge and a return spring 14 surrounds the plunger. A circlip 15 is fixed adjacent a lower end of the plunger against which the element 13 and spring 14 opposingly press in use.

For monitoring the cooking operation, the cartridge is typically pressed into a piece of meat so that its pointed end is well-inside the body of the meat. At a certain temperature. or over a range of temperatures, the element 13 expands and forces the plunger 11 upwards so that it sticks well out of the one end of the cartridge to indicate clearly that the temperature of the meat around the pointed end of the cartridge has reached the certain temperature or range of temperatures. This indicates generally that the meat has fully cooked. The plunger 11 may be colour-coded or otherwise marked to indicate different levels of cooked according to how far out of the cartridge the plunger extends at any time.

Traditionally such indications relate to "rare", "medium" or "well-cooked" corresponding to different temperatures within a range of temperatures for which the element 13 is operationally set or chosen.

The described cooking thermometer is re-usable because once the temperature falls below the chosen range of temperatures, the return spring 14 urges the plunger 11 back into the cartridge to the position shown in Figure 2.

It is normally necessary to clean the thermometer from time to time or between each use. The cap 12 is removed by squeezing the top of the cartridge radially inwards to release end clips on the wall of the cartridge from engagement with the cap, and lifting the cap off. The circlip 15 can also be removed if desired to allow the plunger to be completely separated from the cap.

Importantly, the element 13 can slide out of the cartridge to allow cleaning of the inside of the cartridge. Even more importantly this enables the element 13 to be easily replaced by another shape memory alloy element, if preferred, having different operating characteristics. This provides two possible variations.

On the one hand each thermometer according to the invention can be made with the same common parts and selection for its end use is made by choosing an active element 13 having particular operational characteristics over a suitable temperature range. On the other hand, a user may be given two or more different active elements so that he can select the active element suitable for his current purpose as required. It is well-known that, say, beef and lamb are fully cooked when the meat reaches temperatures of 55 0C to 60 0C whereas poultry requires temperatures of 70C to 800C. Thus, during assembly the described thermometers may have a suitable active element 13 placed inside the cartridge for use for cooking only beef, say, or a customer/user can be given two or more active elements for each single cartridge and then select which active element to use according to what kind of meat he is about to cook.

It will also be appreciated that the described shape memory alloy elements 15 can be designed to perform reliably over selectable and accurately predicable temperature ranges. Thus overall the described thermometers are much more useful than thermometers that use wax to initially hold firm and then release a plunger in a cartridge. Further, as the described thermometers are re-usable, a normal user will be able to adjust his own assessments and may find from experience that a "medium" indication for cooked meat is exactly to his taste. He can then repeat that cooking choice because his thermometer will always produce the same results. It is simply impossible to build up any kind of reliable practical experience with much less accurate and, anyway, throw-away thermometers of the prior art.

Claims (5)

1. A monitoring cooking thermometer arranged to be heated with the food that is to be monitored, comprising a cartridge and a relatively slidable plunger mounted to slide out of the cartridge to visually indicate the food temperature at a certain temperature or range of temperatures, including an active shape memory alloy element inside the container which is arranged to push the plunger out of the cartridge at said certain temperature or range of temperatures, and a return spring for biassing the plunger into the cartridge.

2. A monitoring cooking thermometer according to claim 1, in which the active element is replaceably mounted in the cartridge such that different active elements that act at different temperatures can be inserted and the thermometer used for different types of food.

3. A monitoring cooking thermometer according to claim 1 or 2, in which the plunger is held and slidably mounted in a removable cap which fits to one end of the cartridge.

4. A monitoring cooking thermometer according to claim 3, in which the cap is a press-fit to the end of the cartridge.

5. A monitoring cooking thermometer substantially as herein described with preference to the accompanying drawings.