Abstract:
A monitoring cooking thermometer includes a shape memory alloy activated probe for entering into food being cooked. A clockwork mechanical mechanism in a body fits to the top of the probe. When the food reaches a predetermined temperature a mechanical bell is sounded and a flag is exposed outside the body.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to cooking thermometers. 
     2. Description of Prior Art 
     The invention relates more particularly to a cooking thermometer that monitors the temperature of roasting meat. Such a thermometer is described in U.K. Patent Application No. 2315126. The main disadvantage of that described thermometer is that the visual indication may be overlooked, especially if the roasting meat is behind an opaque closed oven door, and so the meat may easily be overcooked in practice. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to overcome or at least to reduce this problem. 
     According to the invention there is provided a monitoring cooking thermometer arranged to be heated with food that is to be monitored including an elongate probe that has first end and for entering into the food and second end to fit to a wind-up audible alarm mechanism, including an SMA actuator inside the first end of the probe and a latch mechanically coupled to the actuator to release the wind-up mechanism and causes the ball to ring when the end of the probe rises to a predetermined temperature. 
     The latch is preferably arranged to be moved away from the winding mechanism by the SMA actuator to release the mechanism. 
     The monitoring cooking thermometer may include a movable flag mounted to the mechanism that provides a visual indication that the alarm has been initiated. 
     The alarm mechanism may include a coilable spring that provides stored mechanical energy for operating the alarm, in which the flag is spring biased against an external coil of the spring so as to move towards and away from the spring when it is wound up and unwinds respectively. 
     Most of the components of the alarm mechanism are preferably made of stainless steel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A monitoring cooking thermometer according to the invention will now be described by way of example with reference to the accompanying drawings in which: 
     FIG. 1 is an isometric view of the thermometer; 
     FIG. 2 is a sectional front view of the thermometer in one operative position; 
     FIG. 3 is a sectional front view of the thermometer in a second operative position; 
     FIG. 4 is a schematic top plan view of the thermometer in the one operative position; and 
     FIG. 5 is a schematic top plan view of the thermometer in the second operative position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, in FIG. 1 the thermometer has an elongate probe  10  that is pointed at one end  11  and is held at its other end by a screwed flange  12  to a body  13  that contains mechanical mechanism. A flag  14  is shown extending out of a side of the body  13 . In use, the probe  10  is plunged into a joint of meat and placed in an oven with the meat. When the meat is properly cooked, an audible alarm is initiated, driven by the mechanical mechanism, and the flag  14  moves out of the body  13  to the position shown in FIG.  1 . 
     In FIGS. 2 and 3, it can be seen that the probe contains a shaped memory alloy (SMA) actuator in the form of a coiled spring  15 . A mechanical latch  16  is provided in the form of an end of a rod  17  that extends down inside the probe  10 . The rod  17  is biassed upwards by a coil spring  18  and mechanically coupled to the actuator  15  by bearing against a circlip  19 . When the actuator  15  rises to a predetermined temperature it expands, as shown in FIG. 2, to move the rod downwards and away from the mechanical mechanism to release the latch  16 . The actuator  15  is prevented from moving upwards by a cylindrical sleeve  20  inside the probe that surrounds the rod  17 . 
     The body  13  contains the mechanical mechanism that comprises a generally conventional clockwise type arrangement with a coil spring  21 , gearing (including a gear  22 ), and a U-shaped pivoted clockwork-escape racket  23 . The racket extends along one side  23 A where it can engage the latch  16  and along another side  23 B to loosely support at its remote end a circular striker  24 . A bell housing  25  forms a top of the body  13  and the striker  24  is positioned to vibrate against the inside surface of the housing  25  to provide an audible alarm when the clockwork mechanism unwinds. 
     In order to wind up the clockwork mechanism, the housing  25  is rotated relative to the base of the housing  13 . The spring  21  becomes therefore coiled up more tightly, as required. The latch  16 , when it is in the position shown in FIG. 1, prevents the spring unwinding because the latch holds the racket  23  to prevent any reverse movement of the gear  22 . If the latch  16  is withdrawn, as in FIG. 2, the gear  22  is freed to move and allow the coil spring to unwind. As the gear moves it rocks the racket  23  in conventional manner so that the striker  24  hits against the housing  25 . 
     It was mentioned earlier that the flag  14  also provides a visual indication of when a joint of meat has been properly cooked. The operation of the flag is better shown in FIGS. 4 and 5. The flag  14  is pivotably mounted in the body  13  and biassed by a wire spring  26  towards a central axis of the body  13 . An upstanding tongue  27  on a top surface of the flag bears against an outer coil of the spring  21 . In FIG. 4 when the coil spring  21  is fully wound up, the flag lies wholly inside the body  13 . In FIG. 5 when the coil spring is nearly or fully unwound, the flag  14  lies predominantly outside the body  13  as required. 
     The described monitoring cooking thermometer thus provides an audible alarm and a visible alarm that cooking has been completed. As the actuator is formed by an SMA element, it automatically resets for repeated use and allows the clockwork mechanism to be wound up for each cooking cycle. The probe  10  is easily removed by unscrewing the flange  12  which means that the probe can be cleaned separately. It also enables other probes of different length and/or containing different SMA actuators to be fitted to the body  13 . This may be necessary as different kinds of meat (beef, pork and chicken, or even fish) are properly cooked only when reaching different respective temperatures. 
     It is most preferable to make the components of the clockwork mechanism at least predominantly of stainless steel, but other high temperature-stable materials may be used.