Core temperature probe for a cooking appliance

Abstract

Core temperature probe (10) of a cooking appliance (12), comprising a hollow, elongated tube (18) with a longitudinal axis (X), a plate-shaped circuit board (20) located inside the tube (18) and extending in its longitudinal direction (A) along the longitudinal axis (X) of the tube (18), the circuit board having a strip-shaped form, wherein the circuit board (20) is in particular an antenna circuit board, and comprising at least one temperature sensor (40) attached to the circuit board (20), wherein the circuit board (20) has a side wall (34) extending in the longitudinal direction (A) and the side wall (34) and the circuit board (20) are curved at least in sections when viewed in the direction (B) towards the side wall (34).

Description

[0001] The invention relates to a core temperature sensor for a cooking appliance.

[0002] These core temperature probes are inserted into the food being cooked and indicate the instantaneous temperature inside the food. Typically, core temperature probes are designed to detect not only the temperature at the tip, i.e., the end of the probe, but also temperatures in other areas of the probe.

[0003] There are different types of core temperature probes, namely wired and wireless, i.e., radio-based core temperature probes. The invention preferably relates to such wireless core temperature probes, i.e., those that transmit data via radio transmission. For this purpose, a control unit is provided in the cooking appliance itself, which communicates preferably bidirectionally with a radio module in the core temperature probe.

[0004] From DE 10 2004 047 758 B4, for example, a temperature sensor device with a temperature probe for wirelessly measuring the internal temperature of food being cooked is known, which includes an energy storage unit and a communication unit, wherein the energy storage unit can store vibrational energy in at least two temperature-dependent frequencies and the communication unit communicates a microwave signal.

[0005] So-called SAW (Surface Acoustic Wave) sensors are also used as temperature sensors, which operate using acoustic or elastic surface waves. The temperature measurements achieved by these sensors are based on the fundamental principle that surface waves propagate at different speeds at different temperatures, or that the path length changes due to thermal expansion, or more generally, that they have different wave properties.

[0006] DE 10 2005 015 028 A1 describes a method for measuring temperature in a household appliance, in particular an oven, in which a temperature measuring probe with an integrated surface wave element is used.

[0007] The corresponding sensors are mounted on a printed circuit board (PCB), which is elongated and located inside the tube. Such PCBs are rigid, flat, and thin bodies that can easily break under bending stress, especially pressure on their sides.

[0008] However, core temperature probes can also bend, or even deform, due to improper handling, for example, if the food is not sufficiently thawed and the probe is inserted with too much force. Users then simply bend these probes back into shape. This excessive bending can cause the circuit boards inside the probe to break or at least develop cracks.

[0009] DE 10 2012 217 357 A1 discloses a core temperature sensor with a tubular sensor tube into which an elastically bendable circuit board, on which at least one temperature sensor is mounted, is inserted. Since the circuit board preferably has a width greater than the diameter of the sensor tube, it is first rolled or bent. Once inserted into the sensor tube, the circuit board attempts to return to its original position, i.e., to unroll, so that it fits snugly against the inside of the sensor tube.

[0010] The object of the invention is therefore to create a core temperature sensor which has an internal circuit board that is more stable against lateral bending.

[0011] This problem is solved by a core temperature sensor of a cooking appliance, comprising a hollow, elongated tube with a longitudinal axis, a plate-shaped circuit board located inside the tube and extending in its longitudinal direction along the longitudinal axis of the tube, which has a strip-shaped form, wherein the circuit board is in particular an antenna circuit board, and with at least one temperature sensor located on the circuit board, in particular a surface acoustic wave sensor, wherein the circuit board has a longitudinally extending side wall and the side wall and the circuit board are curved at least section by section in the tube when viewed towards the side wall.

[0012] The present invention utilizes the effect that bending caused by a compressive force applied to the side wall of the strip-shaped or plate-shaped circuit board results in lower mechanical stresses in the circuit board if it is already curved perpendicular to the direction of force application.

[0013] As previously mentioned, the core temperature sensor according to the present invention is in particular provided with one or more SAW sensors, and the circuit board is designed as an antenna board, i.e. a radio module with corresponding antenna structures is formed on the circuit board.

[0014] Preferably, the side wall is curved in a wave-like pattern and housed within the tube. The wave shape is also evident in a view of the side wall of the strip-shaped or plate-shaped circuit board, with the side wall essentially running along the longitudinal axis of the tube. "Essentially" means that, of course, due to the curvature, the circuit board no longer has a linear shape in this view.

[0015] The curvature is not achieved by a raised surface on the outside of the circuit board, but rather by the fact that the opposite sides with the largest area (hereinafter referred to as the top and bottom surfaces) are essentially parallel to each other, with one side having a convex curvature and the other side having a concave curvature at the corresponding point, the curvature extending over the entire height of the circuit board, so that the circuit board has a cylindrical shape in the area of ​​the curvature, since the generating line of the top and bottom surfaces is a straight line.

[0016] Preferably, the curvature is present in the area of ​​the middle third, with respect to the longitudinal direction, but it can of course also extend over the entire length of the circuit board, so that no linear sections would be present when looking towards the side wall.

[0017] The SAW sensor(s) each have a housing that is in electrical contact with conductors on the circuit board via electrical contact conductors and can communicate with each other and / or with the antenna structure.

[0018] To ensure the flexibility of the circuit board in the area of ​​the sensors, these are preferably only attached to the circuit board in sections on their underside facing the board.

[0019] The fastening points between the circuit board and the SAW housing are limited, for example, to the electrical contact areas. A full-surface connection between the underside of the housing and the top side of the circuit board is therefore excluded, so that no sandwich or composite construction can be created over large areas, which would lead to a stiffening of the overall structure.

[0020] Preferably, several temperature sensors are arranged longitudinally in a series one behind the other on the elongated, strip-shaped circuit board.

[0021] The circuit board can be installed in the tube in an elastically bent state, meaning it has a flat, plate-like initial state. However, in its installed state, i.e., inside the tube, the circuit board is then elastically bent to achieve the curvature or wave shape.

[0022] To achieve the curvature in the simplest way possible, a lateral spacer can be placed between the circuit board and the tube, which causes the circuit board to bulge at the desired point.

[0023] The spacer can be pre-mounted on the circuit board and thus inserted into the inside of the tube along with it.

[0024] Examples of such spacers are adhesive dots that are applied to the front and / or back of the circuit board and cure before the board is inserted into the tube.

[0025] As previously explained, an antenna structure is preferably applied to the circuit board.

[0026] The circuit board can be firmly mounted laterally in the tube at its front and / or rear end sections and may have a wave-like curvature in the area between the end sections.

[0027] To secure the circuit board, a fastening element, such as a wire or silicone, can be placed between the underside of the board and the tube. The wire can also be inserted later into the space between the tube and the circuit board. Other options, such as elastic leveling elements, are also possible.

[0028] The core temperature sensor according to the invention does not require an electrical energy storage device, which significantly improves its service life and maintenance.

[0029] Further features and advantages of the invention will become apparent from the following description and from the following drawings, to which reference is made.

[0030] The drawings show: - Fig. 1 a schematic longitudinal sectional view through a core temperature sensor according to the invention, - Fig. 2 a very schematic representation of the core temperature sensor according to Fig. 1 installed circuit board in installed state, - Fig. 3 a cross-sectional view through a core temperature sensor along line III-III in Fig. 1, and - Fig. 4 an enlarged schematic cross-sectional view through the core temperature sensor Fig. 1 inserted circuit board including adjacent sensor.

[0031] In Fig. Figure 1 shows a core temperature probe 10 of a cooking device 12 depicted with dashed lines. The core temperature probe has a handle 14 and a probe rod 16 protruding from the handle 14, which is to be inserted into the food being cooked. The probe rod has a tube 18. The tube 18 extends into the handle 14 and is, for example, glued or molded into it.

[0032] The tube 18 has a circular cylindrical outer shell and defines a longitudinal axis X with the cylindrical shell, whereby the tube 18 can also have a different shape, e.g. oval or polygonal.

[0033] The electronics and sensors for temperature measurement are at least partially housed inside the tube 18. For this purpose, a plate-shaped, or more precisely in this case strip-shaped, circuit board 20, originally designed in a single plane, is provided, on which conductive traces are applied.

[0034] In Fig. Figure 2 shows the strip-shaped circuit board 20.

[0035] In the area of ​​the handle 14, the circuit board 20 is anchored at its handle-side end. The reference symbol 22 indicates an anchoring point. This anchoring point 22 is symbolically represented in Fig. 2 shown.

[0036] In Fig. Figure 1 shows that the circuit board 20 extends significantly beyond the anchoring point 22 into a recess 24 in the handle and can project freely in this area.

[0037] The handle 14 is, for example, designed in two parts in this area, with a base part 26 and a finishing part 28 inserted into a rear opening in the base part 26, which has the recess 24 inside.

[0038] As in Fig. As can be seen in Figure 1, the strip-shaped circuit board 20 extends with its longitudinal direction A along the longitudinal axis X.

[0039] The circuit board 20 has two opposite end faces 30, 32, representing the short sides, two opposite side faces 34 representing the long sides, and a top face 36 and a bottom face 38, which are oriented in opposite directions and represent the largest surfaces of the circuit board. The terms "top" and "bottom" are used here purely symbolically to distinguish the sides, since the core temperature sensor does not have a defined top and bottom.

[0040] On the upper surface 36, several sensors 40 are mounted one behind the other in longitudinal direction A, of which only two are in Fig. 2 are shown.

[0041] These sensors 40 are temperature sensors that detect the temperature of the core temperature sensor 10 at their measuring point.

[0042] In this case, so-called surface acoustic wave (SAW) sensors are used as sensors 40, each of which is housed in its own casing 42 (see Fig. 4) The sensors 40 are chip-like and are glued to the inside of a shell-like housing base 44.

[0043] Electrically, the sensor 40 is connected via one or more contact conductors 56 and a conductor guide 57 through the lower housing part 44 to a contact surface 58 on the underside of the lower housing part 44. This contact surface 58 is connected to a corresponding contact surface 60 on the upper side 36 of the circuit board 20 via a conductive layer 62. This layer can be, for example, a silver sintered paste.

[0044] As in Fig. As can be seen in Figure 4, the housing 42 is only connected to the circuit board 20 via this layer 62 and is therefore not fully attached to the underside of the circuit board 20.

[0045] The circuit board 20 is elastically bent and installed in the tube 18, facing the side surface 34, i.e. in the direction of arrow B according to Fig. 2, i.e. in the non-bent, flat initial state, this viewing direction would be parallel to the top and bottom surfaces 36, 38 and additionally perpendicular to the longitudinal direction A.

[0046] Due to the slight curvature, the strip-shaped circuit board 20 has a curved profile, at least in sections, over its entire height; in this case, it has a wave-like curvature in sections. The wave-like curved section bears the reference numeral 70.

[0047] The curved area can, this is not to be understood as restrictive, lie in the middle third of the circuit board 20 with respect to the longitudinal direction A.

[0048] To ensure that the circuit board 20 is held in the tube 18 in addition to the anchoring point 22, one or more fastening means 72 can be provided at various points or locations in the longitudinal direction A, which are Fig.Figure 3 is symbolically represented. For example, a thin wire extending in longitudinal direction A is shown, but a spherical part can also be used. Furthermore, it is possible to pre-attach this part to the back of circuit board 20. The use of silicone gel in this area, possibly as a potting compound, is also conceivable.

[0049] To achieve the wave shape or curvature, the circuit board 20 preferably has a laterally projecting spacer 76 on its underside 38 opposite the sensors 40, which is preferably already pre-assembled before the circuit board 20 is inserted into the tube 18.

[0050] This spacer 76 can, for example, be a solidified adhesive dot that forms a bump on the underside 38. For further stabilization of the circuit board's position, it can, for example, also have a spacer 82 at its end near the tip 80 of the core temperature sensor 10 in the area of ​​the top side 36, so that the circuit board 20 is fixed in position perpendicular to the top or bottom side 36 or 38.

[0051] The curvature of the circuit board 20, which deviates from its original flat shape, reduces its bending stress when a force F is applied to the board parallel to direction B. Such a force occurs, for example, when the tube 18 is bent or plastically deformed in direction B. Due to the reduced bending stress, the breaking load for the circuit board material and also for the electronic components on the circuit board 20 is not exceeded; rather, the deformation remains within the elastic range.

[0052] Of course, more than one wave-shaped curved area 70 can be provided.

[0053] The core temperature probe 10 has no energy storage inside and works exclusively via radio, communicating bidirectionally with a control unit 90 in the cooking appliance 12.

[0054] For this purpose, antenna structures 92 are formed on the circuit board 20. These antenna structures 92 can be implemented only in the area of ​​the recess 24 or also in the remaining section of the circuit board 20, which may also have electrical connecting lines between the individual sensors 40, depending on the circuit.

[0055] These connecting lines allow the number of antenna structures 92 to be reduced; if necessary, only one antenna structure 92 may be sufficient, through which signals from all sensors 40 are then introduced and transmitted.

Claims

[1] Core temperature probe (10) of a cooking appliance (12), comprising a hollow, elongated tube (18) with a longitudinal axis (X), a plate-shaped circuit board (20) located inside the tube (18) and extending in its longitudinal direction (A) along the longitudinal axis (X) of the tube (18), the circuit board having a strip-shaped form, wherein the circuit board (20) is in particular an antenna circuit board, and comprising at least one temperature sensor (40) attached to the circuit board (20), wherein the circuit board (20) has a side wall (34) extending in the longitudinal direction (A) and the side wall (34) and the circuit board (20) are curved at least in sections in the direction (B) towards the side wall (34). [2] Core temperature sensor (10) according to claim 1, characterized by , that the circuit board (20) is curved in a wave-like manner, as seen with direction (B) towards the side wall (34). [3] Core temperature sensor (10) according to claim 1 or 2, characterized by, that the curvature is located in the area of ​​the middle third of the circuit board (20), with respect to the longitudinal direction (A). [4] Core temperature sensor (10) according to any one of the preceding claims, characterized by , that the temperature sensors (40) have housings (42) which are in electrical contact with conductors on the circuit board (20) via electrical contact conductors (56). [5] Core temperature sensor (10) according to claim 4, characterized by , that the housings (42) are only partially attached to the circuit board (20) on their underside facing the circuit board. [6] Core temperature sensor (10) according to claim 5, characterized by , that fastening points between circuit board (20) and housings (42) are limited to electrical contact areas. [7] Core temperature sensor (10) according to any one of the preceding claims, characterized by , that the temperature sensors (40) are arranged in a row along the longitudinal direction (A) of the circuit board (20) on the circuit board (20). [8] Core temperature sensor (10) according to any one of the preceding claims, characterized by , that the circuit board (20) is installed in the tube (18) in an elastically bent manner and the curvature is created by the elastic bending in the installed state. [9] Core temperature sensor (10) according to any one of the preceding claims, characterized by , that to achieve the curvature, at least one laterally projecting spacer (76) is provided between the circuit board (20) and the tube (18). [10] Core temperature sensor (10) according to claim 9, characterized by , that before mounting the circuit board (20) in the tube (18) the spacer (76) is attached to the circuit board (20), in particular a dried adhesive dot. [11] Core temperature sensor (10) according to any one of the preceding claims, characterized by , that the circuit board (20) is mounted and supported at its front and / or rear end sections on the tube (18) and has a wave-like curvature between the end sections. [12] Core temperature sensor (10) according to any one of the preceding claims, characterized by , that the circuit board (20) is held on the tube (18) by at least one fastening element (72) positioned between the underside (38) of the circuit board (20) and the tube (18). [13] Core temperature sensor (10) according to any one of the preceding claims, characterized by that the sensors (40) are surface acoustic wave sensors. [14] Core temperature sensor (10) according to any one of the preceding claims, characterized by that it is designed as a wireless core temperature sensor and can transmit data wirelessly. [15] Core temperature sensor (10) according to claim 14, characterized by , that at least one antenna structure (92) is provided on the circuit board (20) via which data exchange via radio is possible.

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