Abstract:
An inexpensive and simple-to-operate ice safety device is provided for deployment in a body of water. Once deployed, the ice safety device can be activated to check whether ice has formed to a predetermined thickness around the ice safety device. If ice has not formed to the predetermined thickness, the ice safety device indicates an unsafe condition. The ice safety device can be moored to a fixed location.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an ice safety device and, more particularly, to a device for determining when the thickness of ice on a body of water has reached a thickness prescribed as safe for supporting a selected load such as human weight. 
       BACKGROUND OF THE INVENTION 
       [0002]    Ice thickness is an important question for many types of winter sports or other load-bearing tasks. For example, pond ice is not regarded as generally safe for skating until substantially clear ice has formed to about six inches thickness. Lake ice is considered safe for ice fishing when the thickness has reached about twelve inches to allow for movement of heavy loads across the ice. In the Arctic, winter roads across bodies of water are not opened until the underlying icebed has thickened to twenty or more inches. 
         [0003]    Various apparatuses and methods have been developed for measuring ice thickness. For example, ice thickness has been measured by forming an electrical circuit with an existing ice sheet connected in series to a power supply, and then checking the resistance of the circuit, as taught by U.S. Pat. No. 4,287,472 issued to Pan. Ice thickness also has been measured by deploying two induction coils above an ice sheet, energizing one coil, and estimating the thickness of the ice sheet based on the power produced by the second coil, as taught by U.S. Pat. No. 4,418,570 issued to Warren, Jr. Ultrasonic and radar measurement devices also have been employed, for example by Clasen (US 2008/0295599). However, these electrical or non-penetrating methods have wide ranges of error—up to thirty five percent (35%) for the induction apparatuses, as reported by Pan. More simply, ice thickness has been measured by drilling a hole and lowering a ruler to the undersurface of the ice sheet, as taught by U.S. Pat. No. 4,375,721 issued to Ueda. 
         [0004]    However, all these measurement methods require expensive and complicated electronic equipment and/or physical presence of a measuring person on the ice sheet being measured. Expensive equipment is not preferred for most winter sports or other tasks, while the physical presence of a measuring person is not desirable until after safe ice thickness already has been verified. Thus, it is desirable to provide an inexpensive device that can indicate to someone at a remote location off the ice when the ice has reached a safe thickness for winter sports or other tasks. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    In accordance with the present invention, an ice safety device includes a floating base that is deployed on a body of water before the water freezes. The floating base supports a tube that houses a rod slidably movable within the tube. The tube extends from the floating base to an open distal end disposed at a predetermined distance below the waterline of the floating base. The rod has a near end housed within the tube and has a far end that protrudes from the distal end of the tube. At least a portion of the rod adjacent to the far end is exposed to the body of water outside the tube. A remotely controlled motor is connected with the rod to move the rod between extended and retracted positions. An indicator on the floating base provides an indication of the rod position. If ice has not formed around the rod in the extended position, the rod can be retracted into the tube to provide an indication that ice thickness is unsafe. If ice has formed around the rod, the rod cannot be retracted, and the ice safety device does not provide an indication of an unsafe condition. Thus, until ice forms below the tube, the ice safety device provides an “unsafe” or “no-go” indication of thin ice conditions. 
         [0006]    These and other objects, features and advantages of the present invention will become apparent in light of the detailed description of the best mode embodiment thereof, as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is an elevation view of the ice safety device deployed on a body of water, according to one embodiment of the present invention. 
           [0008]      FIG. 2  is a partial elevation view of the ice safety device including a visible indicator according to another embodiment of the present invention. 
           [0009]      FIG. 3  is an elevation view of the ice safety device according to still another embodiment of the present invention. 
           [0010]      FIG. 4  is an elevation view of the ice safety device according to still a further embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0011]    Referring to  FIG. 1 , an ice safety device  2  includes a floating base  4  having an upper surface  6  and a lower surface  8 , a circumferential surface  10 , and openings  12 ,  14  extending through the upper and lower surfaces  6 ,  8 . The floating base  4  has a known waterline  58  demarcating the portion of the base above the water and the portion of the base below the water when the device floated in a pond, stream or lake. The waterline  58  is a physical characteristic of the base  4  of the device, and not necessarily a visible line marked on the base. 
         [0012]    The floating base  4  placed in the water of the pond, stream, or lake before the water freezes, and is held in a selected location by tethers  60 . Preferably, two or more tethers  60  are used and the tethers  60  are disposed at angles outward from the vertical axis of the device  2  so as to avoid interference with the operation of the device as explained below. 
         [0013]    The floating base  4  surrounds and supports a tube  18  that is installed through the opening  14  in the lower surface  8 . The tube  18  extends from the lower surface  8  of the floating base  4  to an open distal end  20  a predetermined distance below the waterline  58 , which distance corresponds to a predetermined ice thickness considered to be safe. The tube  18  may be adjustable relative to the floating base  4  for setting a safe ice thickness for various activities. 
         [0014]    The tube  18  houses a rod  22 . The rod  22  may be hollow and closed or solid and has a near end or an upper end  24  housed within the tube  18  and a lower end or a far end  26  carrying a disc or a crossbar  28 . The rod  22  is slidably movable up and down within the tube  18 . The rod  22  is supported in the tube  18  by means of an extending and retracting mechanism including a cable  30  and a motor driven pulley  36 . The cable is disposed in an annular gap  32  defined between the rod  22  and the tube  18 . One end of the cable  30  is attached to the crossbar  28 , and the other end of the cable  30  is wrapped on the pulley  36  which is mounted on an axle  34  and driven by a motor  38 . 
         [0015]    A motor control comprises a remote control receiver  40  connected to the motor  38  for actuating the motor, and a power supply  42  connected to the motor  38  and to the remote control receiver  40 . The motorized pulley  36  is mounted to the floating base  4  at the upper surface  6 . Preferably, the motorized pulley  36  is sheltered under a weatherproof cover  44 , which can be mounted to the floating base  4 . 
         [0016]    In the embodiment of  FIG. 1 , a portion of the rod  22  adjacent to the near end  24  is painted or otherwise marked for high visibility and serves a visible indicator of the ice condition. 
         [0017]    The floating base  4 , the tube  18 , the rod  22 , and the other components may be made from a variety of materials. The floating base  4  is sufficiently rigid to withstand crushing when the water changes to ice  16  as illustrated in  FIG. 1 . It is particularly preferred that the materials for the floating base  4 , the tube  18 , and the rod  22  should be selected for durability and for low thermal conductivity. In embodiments having a hollow floating base  4 , thermal conductivity is of lesser concern for selecting the material of the base, while strength and durability are of greater concern. It is preferred that the surface of the rod  22  should not be excessively smooth or lubricious, and that the surface of the rod  22  should exhibit satisfactory friction or adhesion in contact with ice. In embodiments wherein grease is used to seal the gap  32  between the rod  22  and the tube  18 , it is preferred that grease should cling more to the tube  18  than to the rod  22 . For example, the tube  18  may be internally threaded for retention of the grease. 
         [0018]    In operation, the ice safety device  2  shown in  FIG. 1  is initially deployed on a body of water  56  before ice forms. As air temperature drops or radiation cooling begins, ice begins to form at the surface of the water and progresses downwardly to achieve increased thickness. The circumferential surface  10  of the floating base  4  interacts with the ice to keep the waterline  58  approximately at the top surface of the ice. Periodically, the thickness of the ice can be tested for safety from a remote location by means of a transmitter  62 . For example, a person standing at the shoreline of the water can operate the transmitter  62  to activate the motorized pulley  36  via the remote control receiver  40 , thereby causing the motorized pulley  36  to retract the rod  22  into the tube  18 . 
         [0019]    While the thickening ice remains thin and above the distal end  20  of the tube  18  (as shown in  FIG. 1  by the dashed line “A”), the rod  22  is freely movable and can be retracted upward in the tube  18  by the motorized pulley  36 . The extended upper end of the retracted rod is then visible from the remote location, and indicates an unsafe ice condition. Preferably, the rod  22  is painted red or orange to indicate a “thin ice” or “no-go” signal. Under such ice conditions, when the motorized pulley  36  is deactivated or reversed by the transmitter  62 , the axle  34  turns and causes the cable  30  to unwind and deploy the rod  22  downward due to the weight of the rod  22  in preparation for the next thickness test. 
         [0020]    When the thickening ice reaches a level below the distal end  20  of the tube  18  (as shown in  FIG. 1  by the double-dashed line “B”), the ice adheres to the rod  22  and prevents retraction of the rod  22  into the tube  18  in response to a test signal from the remote transmitter  62 . No “thin ice” or “no-go” signal is indicated. Thus the location of the distal end of the tube  18  corresponding to ice level “B” is set so that the absence of a visible “no-go” indication means the ice can support surface loads required for weight-bearing activities (for example, ice fishing) with a reasonable margin of safety. Typically, level “B” will be in excess of six inches below the floating base waterline  58 . 
         [0021]    Leakage of water into the necessary gap  32  between the tube  18  and the rod  22  can result in formation of ice that can bind the rod  22  in the tube  18  before the body of water  56  has frozen down to ice level “B”. To prevent such leakage, the gap  32  between the tube  18  and the rod  22  is sealed at least at the distal end  20  of the tube  18 . The gap  32  can be sealed by a variety of methods. Preferably, grease is applied uniformly to the inner surface of the tube  18 . Also, or as an alternative sealing means, an annular wiper seal can be installed at the distal end  20  of the tube  18 . Other sealing methods and devices will be apparent to those of ordinary skill. Contact with water also can also result in interruption of battery operation in the power supply  42 . Thus, all connections between the motor  38  and the power supply  42  preferably are made in a waterproof chamber  64 . 
         [0022]    Various alternate embodiments also come within the principles of the present invention. For example, referring to  FIG. 2 , wherein like reference numerals represent like parts, a second embodiment of the ice safety device  2  is provided with a separate visible indicator  46 . The visible indicator  46  is mounted to the upper surface  6  of the floating base  4  so that upward motion of the rod  22  will deploy the visible indicator  46 . The visible indicator  46  shown in  FIG. 2  is pivotally mounted to the upper surface  6 , and includes a flag  48  and a prop  50  protruding substantially perpendicularly from an inward surface  52  of the flag  48 . The flag  48  is made of stiff material, and the outward surface  54  of the flag  48  is highly visible. Preferably, the outward surface  54  is colored red or orange to indicate “thin ice” or “no-go”. Alternative structures and methods for a visible indicator  46  will be apparent to those of ordinary skill, for example, a system of electrical lights, a green light activated by the transmitter  62  when an activation signal is received by the motor control, and a red light when the rod is retracted. The dual light system provides a visible indication of device operation and ice condition. 
         [0023]    Referring to  FIG. 3 , a third embodiment of the ice safety device  102  includes a hollow floating base  104  having upper, lower, and circumferential surfaces  106 ,  108 ,  110  defining a waterproof chamber  164 . Components similar to those components shown in  FIGS. 1 and 2  are indicated by similar “100” series reference numbers. The upper and lower surfaces  106 ,  108  include upper and lower openings  112 ,  114 , respectively. The lower opening  114  is sealed by a waterproof fitting  166 . Below the lower surface  108 , and outside the hollow floating base  104 , a tube  118  is mounted to the waterproof fitting  166 . The tube  118  extends from the waterproof fitting  166  to a distal end  120 . The tube  118  houses a hollow rod  122  having a near end  124  disposed within the tube  118  and having a far end  126  extending from a distal end  120  of the tube  118 . The hollow rod  122  is slidably movable within the tube  118 . A spring  129 , disposed between the distal end  120  of the tube  118  and the far end  126  of the hollow rod  122 , draws the hollow rod  122  to an extended position outwardly of the tube  118 . The waterproof chamber  164  contains a motorized pulley  136 , from which a cable  130  extends through the waterproof fitting  166 , the tube  118 , and the hollow rod  122 . The cable  130  is fastened to the far end  126  of the hollow rod  122 . The cable  130  restrains the hollow rod  122  within the tube  118 , against the outward bias of the spring  129 . 
         [0024]    Activation of the motorized pulley  136  operates the cable  130  to retract the hollow rod  122  into the tube  118 . Rotation of the motorized pulley  136  drives a visible indicator  146  via a bevel gear  168  and pinion  170 . The visible indicator  146  includes a plurality of vanes  174  mounted on a vertical shaft  172  that is connected to the bevel pinion  170 . Rotation of the vanes indicates the rod  122  is being retracted, and therefore, the thickness of the ice has not reached the level B. Therefore, rotation of the vanes indicates “thin ice” or a “no-go” condition. When the thickening ice reaches the level B, the rod  122  remains fixed, and the vanes do not rotate, which signals a minimum or better ice condition. 
         [0025]    With ice safety device  102  shown in  FIG. 3  the entire tube  118  and the hollow rod  122  are disposed at ice level “B”. Hence, infiltration of water and ice between the tube  118  and the hollow rod  122  does not detract from the operation of the ice safety device  102 , and a seal between the two parts is not needed. The waterproof fitting  166  prevents entry of water into the waterproof chamber  164  containing the motorized pulley  136 . 
         [0026]    Referring to  FIG. 4 , a fourth embodiment of the ice safety device  202  includes a floating base  204  supporting a tube  218 . Components similar to those components shown in  FIGS. 1 and 2  are indicated by similar “200” series reference numbers. The tube  218  houses a rod  222  that has a longitudinal slot  276  cut in its near end  224  and extending toward its far end  226 . At the inward end  277  of the slot  276 , a lug  278  is formed for receiving a cable  230 . The cable  230  is connected at its other end to a motorized pulley  236  mounted on the floating base  204 . The slot  276  allows the rod to straddle the pulley  236  and cable  230  so that the rod  222  can extend above the pulley axle  234  when fully retracted. In this embodiment, sealing between the extendable rod  222  and the tube  218  is enhanced because the cable  230  does not extend through the annular gap defined between the rod and the tube. 
         [0027]    Activation of the motorized pulley  236  by a remote control transmitter causes the cable  230  to retract the split rod  222  upward into the tube  218  so that the near end  224  of the split rod  222  protrudes above the floating base  204 , providing a visible “no go” indication of ice thickness insufficient to restrain upward motion of the split rod  222 . 
         [0028]    In one working embodiment, the floating base is made from polymer foam and is about eight (8) to ten (10) inches across and about three (3) inches thick. Dimensions of the floating base are varied according to the weight of components mounted on the base. The tube is a PVC pipe about one (1) inch in diameter that extends about four (4) inches below the floating base waterline. Length of the tube is varied according to the required safe ice thickness. The rod is a plastic rod about seven-eighths of an inch (⅞″) in diameter. The near end of the rod is made highly visible by shiny orange paint so that the rod can be seen at a distance of at least about forty (40) feet. The cable is wire or heavyweight fishing string. The motorized pulley includes a remote-control toy motor, axle, remote control receiver, and power supply. Grease is used for sealing the gap between tube and rod. The remote control receiver and transmitter are operable to activate the motor a distance of at least about forty (40) feet to permit operation from the shore. Fishing lines and weights are used as tethers. 
         [0029]    Thus, the present invention provides an ice safety device for periodically checking or testing the thickness of ice on a body of water, without actually going out onto the ice. The ice safety device is easily deployed, can be tethered in place at a desired measurement location, and is relocatable. The ice safety device is simple in operation, and provides an easily understood visual indication of ice thickness. 
         [0030]    Although this invention has been shown and described with respect to the detailed embodiments shown in the drawings, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and the scope of the invention. For example, the floating base may be a hollow shell or hull, in which case the top surface is defined by the uppermost surface of the hull and the lower surface is defined by the lowermost surface of the hull. A solenoid, pivoted beam linkage, or other means for retracting the rod into the tube, can be used in place of the motorized pulley. Additionally, although a remote control receiver activates the embodiments shown in  FIGS. 1 through 4 , the means for retracting the rod also can be periodically activated by a timer or similar activating means. Furthermore, although in  FIGS. 1-4  a visible indicator is shown as being operated by linear motion of the rod, other types of indicators, such as lights or audible indicators can also be used. Accordingly, the invention has been described by way of illustration rather than limitation.