WO2008103513A1

WO2008103513A1 - System and method for acoustically detecting ice

Info

Publication number: WO2008103513A1
Application number: PCT/US2008/051601
Authority: WO
Inventors: Terrence J. Knowles; Brian J. Truesdale
Original assignee: Illinois Tool Works Inc.
Priority date: 2007-02-22
Filing date: 2008-01-22
Publication date: 2008-08-28
Also published as: EP2122342A1; US20080202142A1

Abstract

A system for detecting ice of a particular thickness includes a structure from which ice forms, and an ice detection assembly movably secured to the structure. The ice detection assembly includes a transducer operatively connected to a sensing medium. The transducer generates a trapped acoustic wave in the sensing medium, wherein ice of a particular thickness is detected when the ice that forms from the structure contacts the sensing medium and dampens the trapped acoustic wave within the sensing medium.

Description

SYSTEM AND METHOD FOR ACOUSTICALLY DETECTING ICE

RELATED APPLICATIONS

[0001] This application relates to and claims priority benefits from U.S. Provisional Patent Application No. 60/902,797 entitled "System And Method For Detecting The Presence Of Ice," filed February 22, 2007, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] Embodiments of the present invention generally relate to a system and method for detecting the presence of ice, and more particularly to a system and method of detecting the presence and thickness of ice through the use of trapped acoustic waves.

BACKGROUND OF THE INVENTION

[0003] Typical systems for detecting the presence of ice use capacitive sensing systems that determine impedance from a sensor electrode to ground. A conventional ice forming machine includes an ice grid. As water flows over the grid, the water freezes. With continued freezing, the layer of ice continues to grow outward. When the ice layer grows far enough, the water cascading over the ice layer contacts the capacitive electrode or sensor. If the water makes continuous contact with the electrode for an extended period of time, the ice forming machine transitions to a harvest mode and heats the grid so that the layers of ice break off.

[0004] Conventional ice forming machines, however, are susceptible to detrimental effects caused by "scale" build-up on the electrode and/or spurious conducting paths to ground due to contaminants, fluids and the like. SUMMARY OF THE INVENTION

[0005] Certain embodiments of the present invention provide a system for detecting ice of a particular thickness. The system includes a structure from which ice forms, and an ice detection assembly movably secured to the structure. The ice detection assembly includes a transducer operatively connected to a sensing medium. The transducer generates a trapped acoustic wave in the sensing medium, wherein ice of a particular thickness is detected when the ice that forms from the structure contacts the sensing medium and dampens the trapped acoustic wave within the sensing medium.

[0006] The sensing medium may include a substrate having an acoustic wave cavity. Optionally, the sensing medium may include a sensor strip. A support plate may be used to support the sensor strip and shield the transducer from the structure. The sensor strip may include an extension beam integrally connected to an ice contacting portion through a curved intermediate portion.

[0007] The system may also include a heating element configured to heat the sensing medium. Additionally, the system may include a control unit operatively connected to the ice detection assembly.

[0008] The structure may be an ice grid having a plurality of ice forming compartments. In this case, the system may also include an ice collection bin, wherein the ice grid may be heated to form ice cubes when the ice contacts the sensing medium, thereby breaking the ice cubes off from the ice grid. The ice cubes then fall into the ice collection bin.

[0009] The system may also include a bracket that pivotally connects the ice detection assembly to the structure. The bracket is configured to adjustably position the ice detection assembly with respect to the structure.

[0010] Certain embodiments of the present invention provide an ice forming system that includes an ice grid, an ice detection assembly, an ice collection bin and one or both of a processing unit and/or a detection circuit operatively connected to the ice detection assembly. The ice grid includes a plurality of forming compartments configured to form ice cubes, wherein water flows over the ice grid and into the plurality of forming compartments to form outwardly growing ice.

[0011] The ice detection assembly is pivotally secured to the ice grid and includes a transducer operatively connected to a sensing medium. The transducer generates a trapped acoustic wave in the sensing medium, wherein ice of a particular thickness is detected when the outwardly growing ice from the ice grid contacts the sensing medium and dampens the trapped acoustic wave within the sensing medium.

[0012] The ice grid may be heated to detach the ice cubes from the compartments when the outwardly growing ice contacts the sensing medium. The ice detection assembly pivots away from the ice grid as falling ice cubes contact the ice detection assembly. The ice cubes are then collected in the ice collection bin.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0013] Figure 1 illustrates an isometric view of an ice forming system according to an embodiment of the present invention.

[0014] Figure 2 illustrates a simplified lateral view of an ice forming system according to an embodiment of the present invention.

[0015] Figure 3 illustrates an isometric view of an ice detection assembly according to an embodiment of the present invention.

[0016] Figure 4 illustrates a rear view of an ice detection assembly according to an embodiment of the present invention.

[0017] Figure 5 illustrates a lateral view of an ice detection assembly according to an embodiment of the present invention.

[0018] Figure 6 illustrates a front view of an ice detection assembly according to an embodiment of the present invention.

[0019] Figure 7 illustrates a simplified lateral view of an ice forming system according to an embodiment of the present invention. [0020] Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Figure 1 illustrates an isometric view of an ice forming system 10 according to an embodiment of the present invention. The ice forming system 10 includes an ice grid 12, an ice detection assembly 14 and an ice collection bin 16. The ice grid 12 and the ice detection assembly 14 are connected to a source of power (not shown). Additionally, the ice detection assembly 14 and the ice grid 12 may also be in electrical communication with a control system, such as a processing unit (not shown in Figure 1).

[0022] The ice grid 12 includes a main housing 18 having a top surface 20 integrally connected to side walls (not shown in Figure 1), which are, in turn, integrally connected to a base (not shown in Figure 1). An ice forming chamber 22 is defined between the top surface 20, the side walls and the base. A plurality of forming compartments 24 are positioned with the ice forming chamber 22. The plurality of forming compartments 24 are configured to form ice cubes.

[0023] The ice detection assembly 14 includes a deflection arm 26 pivotally connected to the top surface 20 of the ice grid 12 through a bracket 28. The deflection arm 26 is configured to pivot in the directions of arrows A and A' about an axis defined by rods 30 that secure the deflection arm 26 to the bracket 28. A sensor housing 31 having a transducer 32 operatively connected to an acoustic wave cavity 34 is secured to the deflection arm 26. The transducer 32 and acoustic wave cavity 34 may be distally located from the deflection arm 26, as shown in Figure 1. The transducer 32 is on one side of the acoustic wave cavity 34, the other side of which is exposed to water and ice proximate the ice grid 12. The transducer 32 is electrically connected to the source of power.

[0024] In operation, water cascades over the ice forming chamber 22 and into the individual compartments 24. As the ice grid 12 cools, the water collected within the ice compartments 24 freezes and grows outwardly towards the ice detection assembly 14. As discussed below, the ice detection assembly 14 senses when the ice bonds to the acoustic wave cavity 34, at which point the cooling process stops and an ice harvest mode begins. In particular, the ice grid 12 may be heated to break the ice off from the compartments 24. As the ice breaks off, the ice may hit the deflection arm 26 as it falls toward the collection bin 16. As the ice hits the deflection arm 26, the deflection arm 26 is pushed back in the direction of arrow A' so that the ice falls into the collection bin 16.

[0025] Figure 2 illustrates a simplified lateral view of the ice forming system 10 according to an embodiment of the present invention. As noted above, the ice detection assembly 14 includes the transducer 32 operatively connected to a rear of the acoustic wave cavity 34. The ice detection assembly 14 utilizes one or more acoustic waves trapped in the acoustic wave cavity 34 to detect the presence of ice on the outer surface 36 of the acoustic wave cavity 34. To detect the presence of ice, a trapped acoustic wave, such as a trapped shear acoustic wave, is generated within the acoustic wave cavity 34 by the transducer 32, as described in United States Patent No. 7,026,943, entitled "Acoustic Wave Ice and Water Detector," which is hereby incorporated by reference in its entirety.

[0026] As shown in Figure 2, the acoustic wave cavity 34 is defined by a raised area 38 of a substrate 40. The acoustic wave cavity 34 is formed on the substrate 40 by an area of increased mass such that the mass per unit surface area of the acoustic wave cavity 34 is greater than the mass per unit surface area of the substrate 40 immediately adjacent the acoustic wave cavity 34. The acoustic wave cavity 34 may also be defined by an area of increased mass that is not raised above the substrate 40. Such cavities may be formed, for example, by depositing a thin layer of material on the surface of the substrate 40 in an area defining the acoustic wave cavity 34. Such cavities may also be formed with material of greater mass than the substrate 40 throughout the cavity or in a portion thereof.

[0027] The raised area 38 defining the acoustic wave cavity 34 may be square, rectangular or other shapes. The raised area 38 may have a circular circumference or peripheral edge. The raised area 38 may have a flat surface or may have a curved, dome-like surface, as shown in Figure 2.

[0028] The height and geometry of the acoustic wave cavity 34 that will support a trapped or resonant acoustic wave is the same as the height and geometry requirements of an acoustic wave cavity supporting a trapped shear wave as described in United States Patent No. 7,106,310, entitled "Acoustic Wave Touch Actuated Switch," which is hereby incorporated by reference in its entirety.

[0029] Embodiments of the present invention use the transducer 32 to generate a trapped resonant acoustic wave within the acoustic wave cavity 34, as described in United States Patent No. 7,026,943. The transducer 32 is electrically connected to a processing unit 41. When no ice contacts the raised area 38 of the acoustic wave cavity 34, a known amplitude, impedance or decay rate of a trapped acoustic wave cavity is sensed by the processing unit 41 (or detection circuit 42). Thus, the processing unit (or detection circuit 42) determines that no ice is contacting the acoustic wave cavity 34. When ice contacts the acoustic wave cavity 34, however, the sensed amplitude, impedance or decay rate changes. That is, when the ice 44 contacts the acoustic wave cavity 34, the acoustic energy trapped in the acoustic wave cavity 34 is dampened. As such, the processing unit 41 or detection circuit 42 is able to determine that ice is bonding to the acoustic wave cavity 34.

[0030] When the processing unit 41 or detection circuit 42 determines that ice is contacting the acoustic wave cavity 34, the processing unit 41 may transition the ice grid 12 into a heating mode, in which the compartments 24 may be heated in order to break off the formed ice 44 protruding therefrom. As the ice breaks off from the compartments 24, the ice falls into the collection bin 16. As noted above, ice that hits the ice detection assembly 14 forces it to swing backward in the direction of A'. As such, ice above the ice detection assembly 14 is allowed to fall into the collection bin 16.

[0031] The ice detection assembly 14 may also include a heating element 43, such as a coil heater, operatively connected to a rear surface of the substrate 40. The heating element 43 may be used to slightly heat the acoustic wave cavity 34 so that water condensation does not freeze on the acoustic wave cavity 34. Condensation that freezes to ice could produce an ice detection reading (i.e. the processing unit 41 or detection circuit 40 may detect the presence of ice through a change in amplitude, impedance or decay rate of a trapped acoustic wave) before the growing ice 44 from the compartments 24 contacts the acoustic wave cavity 34.

[0032] The ice detection assembly 14 may be spaced from the ice grid 12 at a desired distance, depending on the size of ice to be formed. As such, the system 10 is able to determine a desired thickness of ice. That is, when the ice contacts the acoustic wave cavity 34, the processing unit 41 or detector circuit 42 determines that ice of a particular thickness (as determined by the spacing of the detection assembly 14 from the ice grid 12) has formed. If larger chunks of ice are desired, the ice detection assembly 14 may be moved away from the ice grid 12. If smaller chunks of ice are desired, the ice detection assembly 14 may be moved closer to the ice grid 12. The bracket 28 may be adjustable through directions denoted by arrows B and B'. For example, the bracket 28 may include a telescoping neck 46 that allows it to move through the directions B and B'.

[0033] As shown in Figure 2, the transducer 32 may be in close proximity to the ice 44 and flowing water over the ice grid 12. Thus, the transducer 32 and associated electronics may be sealed to prevent adverse effects that may arise from water contacting electronic components. A sealing compound may be applied over the transducer 32 and associated electronics to prevent water ingress. Moreover, the transducer 32 and the acoustic wave substrate 40 may be integrally formed and connected to one another, thereby providing an improved seal therebetween. [0034] Figures 3 and 4 illustrate isometric and rear views, respectively, of an ice detection assembly 50 according to an embodiment of the present invention. The ice detection assembly 50 includes a planar support plate 52 having upturned lateral walls 54. The plate 52 may be formed of plastic. Pivoting rods 56 are located at proximal ends of the lateral walls 54 and allow the ice detection assembly 50 to be pivotally attached to a bracket of an ice grid.

[0035] The support plate 52 securely supports a sensor strip 58, which may be formed of metal. One end of the sensor strip 58 is secured to the plate 52 proximate a top portion of the plate 52. The secured end of the sensor strip 58 is connected to a transducer 60. That is, the transducer 60 is operatively connected to an end of the sensor strip 58 to produce a trapped acoustic wave within the sensor strip 58. The sensor strip 58 includes an extension beam 62 that extends from the transducer 60 over a length of the plate 52. That is, the extension beam 62 is part of the sensor strip 58, itself. The extension beam 62 of the sensor strip 58 may be secured in place by one or more securing clips 64 that extend from the plate 52. For example, the securing clips 64 may snapably secure to edges of the extension beam 62 of the sensor strip 58. An ice contacting hook 66 extends from the extension beam 62 past the lower edge of the plate 52. While the extension beam 62 is generally coplanar with the planar portion 67 of the plate 52, the hook 66 extends inwardly past the plane 67 of the plate 52. The sensor strip 58 may be, for example, a 5" long, 0.4" wide and 35 mm thick strip of stainless steel operating in shear mode at 1.2 MHz.

[0036] Figure 5 illustrates a lateral view of the ice detection assembly 50. As shown in Figure 5, the hook 66 curves inwardly in the direction of arrow C from the extension beam 62. A flattened ice contacting portion 68 of the hook 66 is connected to an inwardly curved portion 70 extending from the extension beam 62. An upturned tip 72 is, in turn, integrally connected to the flattened ice contacting portion 68. The plane x of the flattened ice contacting portion 68 is inwardly-offset in the direction of arrow C from the plane y of the extension beam 62. As shown in Figure 5, the flattened ice contacting portion 68 extends past the plate 52 in the direction of arrow C. [0037] Figure 6 illustrates a front view of the ice detection assembly 50 according to an embodiment of the present invention. The plate 52 provides a shield that protects the transducer 60 (shown, e.g., in Figure 5) from direct contact with ice and water.

[0038] Figure 7 illustrates a simplified lateral view of an ice forming system 80 according to an embodiment of the present invention. The ice forming system 80 includes the ice detection assembly 50 pivotally connected to an ice grid 82 through a bracket 84, and operates similar to the ice forming system 10 shown and described in Figures 1 and 2. In particular, water 86 flows over the ice grid 82 to form ice 88 that grows and eventually contacts the ice contacting portion 68 of the hook 66. The transducer 60 is connected to a processing unit, which detects changes in amplitude, impedance, wave decay rate or the like. That is, the processing unit (or detecting circuit) detects when ice contacts the ice contacting portion 68 and transitions the system 80 to an ice harvesting mode, as discussed above with respect to Figures 1 and 2.

[0039] Referring to Figures 3-7, it has been found that the sensor strip 58, which may alternatively be a tube or rod, is an efficient medium for propagating certain types of acoustic waves. The transducer 60 generates an acoustic wave within the sensor strip 58 that travels all the way to the hook 66, reflecting back and forth, and which is confined by the sides and ends of the sensor strip 58. That is, the generated acoustic wave is trapped within the sensor strip 58. It has been discovered that confined or trapped shear waves within the sensor strip 58 (and by extension, torsional waves in rods and tubes) may be significantly absorbed by ice bonded to the ice contacting portion 68, as opposed to the length of the sensor strip 58. Water flowing on the sides of the sensor strip 58 does not materially absorb wave energy. As such, the system 10 is able to discriminate between the presence of water and ice. Moreover, the sensor strip 58 is insensitive to mineral deposits (scale), in stark contrast to conventional sensing devices.

[0040] The sensor strip 58 is long enough to displace the transducer 60 and associated electronics out of the path of the water 86. As such, the water 86 is not able to infiltrate the transducer 60 or the associated electronics, thereby alleviating a need to provide additional sealing. The sensor strip 58 is easier to manufacture than conventional ice sensing devices. In general, it has been found that the sensor strip 58 may be bent, twisted and folded in various shapes without affecting performance. In general, the curvature radii of the sensor strip 58 are large in relation acoustic wavelengths of generated waves within the sensor strip 58.

[0041] Embodiments of the present invention sense and detect the presence and thickness of ice through acoustic waves, particularly trapped acoustic waves within an acoustic wave cavity. It has been found that embodiments of the present invention, in stark contrast to conventional ice forming machines, are not affected by scale build up (presumably because the wave motion couples through the calcium carbonate (scale) layer), water and other contaminants.

[0042] Embodiments of the present invention do not use propagating waves. Instead, embodiments of the present invention utilize trapped wave motion, as described in United States Patent No. 7,106,310 and United States Patent No. 7,026,943. Detecting ice through trapped wave motion provides a detection system that is more sensitive to the presence of ice and greatly simplifies signal processing. Plastic acoustic wave sensing systems may be advantageous over metal acoustic wave sensing systems because their thermal conductivity is less than typical metals, which allows for better thermal insulation from the ice generating surfaces.

[0043] Embodiments of the present invention may be used in various settings and applications. The ice cube forming devices described above are just examples. Embodiments of the present invention may also be used to detect the presence and thickness of ice forming on condensation coils and pipes, which is a known problem for refrigeration units, and, for example, to determine the ice buildup on the outer surfaces of skyscrapers, which may pose safety hazards (e.g., falling ice from skyscrapers hitting pedestrians).

[0044] While various spatial and directional terms, such as upper, bottom, lower, mid, lateral, horizontal, vertical, and the like may used to describe embodiments of the present invention, it is understood that such terms are merely used with respect to the orientations shown in the drawings. The orientations may be inverted, rotated, or otherwise changed, such that an upper portion is a lower portion, and vice versa, horizontal becomes vertical, and the like.

[0045] Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.

[0046] Various features of the invention are set forth in the following claims.

Claims

1. A system for detecting ice of a particular thickness, comprising: a structure from which ice forms; and an ice detection assembly movably secured to said structure, said ice detection assembly comprising a transducer operatively connected to a sensing medium, said transducer generating a trapped acoustic wave in said sensing medium, wherein ice of a particular thickness is detected when the ice that forms from said structure contacts said sensing medium and dampens the trapped acoustic wave within said sensing medium.

2. The system of claim 1, wherein said sensing medium comprises a substrate having an acoustic wave cavity.

3. The system of claim 1, wherein said sensing medium comprises a sensor strip.

4. The system of claim 3, further comprising a support plate that supports said sensor strip, said support plate shielding said transducer from said structure.

5. The system of claim 1, wherein said sensor strip comprises an extension beam integrally connected to an ice contacting portion through a curved intermediate portion.

6. The system of claim 1, further comprising a heating element configured to heat said sensing medium.

7. The system of claim 1, wherein said structure is an ice grid having a plurality of ice forming compartments.

8. The system of claim 7, further comprising an ice collection bin, wherein said ice grid is heated to form ice cubes when the ice contacts said sensing medium, the ice cubes being collected in said ice collection bin.

9. The system of claim 1, further comprising a bracket that pivotally connects said ice detection assembly to said structure.

10. The system of claim 1, wherein said bracket is configured to adjustably position said ice detection assembly with respect to said structure.

11. The system of claim 1 , further comprising a control unit operatively connected to said ice detection assembly.

12. An ice forming system, comprising: an ice grid having a plurality of forming compartments configured to form ice cubes, wherein water flows over said ice grid and into said plurality of forming compartments to form outwardly growing ice; and an ice detection assembly movably secured to said ice grid, said ice detection assembly comprising a transducer operatively connected to a sensing medium, said transducer generating a trapped acoustic wave in said sensing medium, wherein ice of a particular thickness is detected when the outwardly growing ice from said ice grid contacts said sensing medium and dampens the trapped acoustic wave within said sensing medium.

13. The system of claim 12, wherein said sensing medium comprises a substrate having an acoustic wave cavity.

14. The system of claim 12, wherein said sensing medium comprises a sensor strip having an extension beam integrally connected to an ice contacting portion through a curved intermediate portion.

15. The system of claim 14, further comprising a support plate that supports said sensor strip, said support plate shielding said transducer from said ice grid, wherein said ice contacting portion is exposed to said ice grid.

16. The system of claim 12, further comprising a heating element configured to heat said sensing medium.

17. The system of claim 12, further comprising a bracket that pivotally connects said ice detection assembly to said ice grid, wherein said bracket is configured to adjustably position said ice detection assembly with respect to said ice grid.

18. An ice forming system, comprising: an ice grid having a plurality of forming compartments configured to form ice cubes, wherein water flows over said ice grid and into said plurality of forming compartments to form outwardly growing ice; an ice detection assembly pivotally secured to said ice grid, said ice detection assembly comprising a transducer operatively connected to a sensing medium, said transducer generating a trapped acoustic wave in said sensing medium, wherein ice of a particular thickness is detected when the outwardly growing ice from said ice grid contacts said sensing medium and dampens the trapped acoustic wave within said sensing medium; an ice collection bin, wherein said ice grid is heated to detach the ice cubes from said compartments when the outwardly growing ice contacts said sensing medium, said ice detection assembly pivoting away from said ice grid as falling ice cubes contact said ice detection assembly, the ice cubes being collected in said ice collection bin; and one or both of a processing unit and/or a detection circuit operatively connected to said ice detection assembly.

19. The system of claim 18, wherein said sensing medium comprises a substrate having an acoustic wave cavity, said acoustic wave cavity having a greater mass per unit surface area than that of said substrate adjacent said acoustic wave cavity.

20. The system of claim 18, wherein said sensing medium comprises a sensor strip having an extension beam integrally connected to an ice contacting portion through a curved intermediate portion.

21. The system of claim 20, further comprising a support plate that supports said sensor strip, said support plate shielding said transducer from said ice grid, wherein said ice contacting portion is exposed to said ice grid.

22. The system of claim 18, further comprising a heating element configured to heat said sensing medium.

23. The system of claim 18, further comprising a bracket that pivotally connects said ice detection assembly to said ice grid, wherein said bracket is configured to adjustably position said ice detection assembly with respect to said ice grid.