Abstract:
A bird feeder equipped with an electrically powered spinning mechanism that is triggered by the weight of a squirrel on the feeder is described. Upon detection of a squirrel on the feeder, the spinning mechanism rotates the feeder at a rate adequate to centrifugally remove the invading squirrel while resulting in a minimum loss of feed contained in the feeder.

Description:
FIELD OF THE INVENTION 
     The present invention relates to wild bird feeders and more particularly to a squirrel repellent such device. 
     BACKGROUND OF THE INVENTION 
     The feeding of wild birds is a popular pastime/hobby for many urban and suburban residents. Many bird-feeding devices have been developed to allow the convenient feeding of wild birds in easily observable exterior locations. In virtually all bird feeding environments, squirrels are a constant annoyance and pest as they invade bird feeders and compete with the birds for the available feed. Many times they drive the birds away and, in some cases, destroy or severely damage the bird-feeding device. Since squirrels are excellent jumpers, most manufacturers recommend locating the bird feeder at least ten feet from structures or other objects such as trees that squirrels can climb. This is not always possible, if the bird feeder is to remain located where the birds are readily observable from the inside of the home or office. 
     Accordingly, in order to meet and defeat the squirrel threat, many ingenious devices have been developed. Many of these remain readily defeatable by the squirrels because of their excellent jumping capabilities. Some such devices are described in the following U.S. Pat. Nos. 5,690,056, 5,535,835, 5,676,089, and 5,664,522. While the devices described in the foregoing patents all propose solutions to the problem, they are not fully satisfactory under all circumstances and are often defeated by squirrels. 
     Accordingly, there remains a need for a wild bird feeding device that is capable of repelling squirrels. 
     OBJECT OF THE INVENTION 
     It is an object of the present invention to provide a bird feeder that successfully repels squirrels attempting to feed therefrom. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a bird feeder equipped with an electrically powered spinning mechanism that is triggered by the weight of a squirrel on the feeder. Upon detection of a squirrel on the feeder, the spinning mechanism rotates the feeder at a rate adequate to centrifugally remove the invading squirrel while resulting in a minimum loss of feed contained in the feeder. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially cut-away side view of the squirrel repellent bird feeder of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1 that depicts one preferred embodiment of the squirrel repellent bird feeder of the present invention, bird feeder  10  comprises two major members, a drive module  12  and a feeder  14  vertically connected by means of a shaft or other mechanism  16  that, as described hereinafter, is capable of transmitting rotary motion from drive module  12  to feeder  14 . Drive module  12  comprises an attachment mechanism  18  for application to an overhead support such as a tree branch or other supporting structure. In the embodiment depicted in FIG. 1 attachment mechanism  18  comprises a threaded hook having a hook portion  22  for attachment to an overhead structure, tree branch or the like and A threaded shaft portion  24  securely, i.e. non-rotatably, attached directly or indirectly to top  20  and roof  26  of drive module  12 . As shown in FIG. 1, such secure attachment may be provided by the tight application of nuts  28   a  and  28   b  to threaded shaft portion  24  on the upperside and underside of roof  26  respectively as well as nuts  30   a  and  30   b  on threaded shaft portion  24  on the inside and outside of top  20 . 
     Drive module  12  comprises a housing  34  that includes top  20 , cylindrical body  36  and bottom  38 . Concentrically located within housing  34  is cylindrical support tube  40 . Slideably located within support tube  40  is motor  42  that is allowed to travel vertically within support tube  40 . Extending from the bottom of motor  42  and through bottom  38  is drive shaft  44  that transmits rotary motion to feeder  14  as described hereinafter. Retaining motor  42  in non-rotary position within support tube  40  are pins  14   a  and  14   b  that are threaded into the bottom of motor  42  but have smooth shafts in the areas thereof that pass through separate holes in bottom  38  to inhibit torque induced rotary motion of the motor relative to support tube  40  and housing  34  while permitting vertical movement of motor  42  within support tube  40  and rotation of drive shaft  44 . Attached to the outside of support tube  40  are power supplies  46 , in the embodiment depicted in FIG. 1, power supplies  46  are battery packs that are conventionally connected to motor  42  and electronic circuit board  52 . As will be clear to the skilled artisan, if an external power source is readily and locally available, battery packs  46  may be omitted entirely without affecting the successful practice of the present invention. So long as adequate power is available to activate motor  42  and cause rotation of shaft  44  as described hereinafter, the particular power source used and its location are not particularly important to the successful practice of the present invention. 
     Linear force spring  48  preferably encompasses drive shaft  44  as shown in FIG. 1, and bears against the inside surface of bottom  38 . Alternatively, linear force spring  48  could be mounted about an independent sliding shaft and engage the bottom of motor  42  and the inside surface of bottom  38  in a location remote from shaft  44 . Linear force spring  48  is connected to displacement sensor  50  that in turn is mounted to electronic circuit board  52 . Displacement sensor  50  transmits to electronic circuit board  52  signals representing the vertical displacement of motor  42  within support tube  40  induced by downward pressure on linear force spring  48  by virtue of downward pressure being applied to drive shaft  44  attached to feeder  14 . Upon attainment of a predetermined vertical displacement, commensurate to the weight of a squirrel, electronic circuit board  52  closes a circuit to cause motor  42  to operate and provide rotary motion to drive shaft  44 . The triggering weight causing engagement of motor  42  is above that of birds feeding on all of the perches as described below, but below that of an average squirrel. 
     As will be apparent to the skilled artisan, the above described motor activation circuit comprising linear force spring  48 , displacement sensor  50  and electronic circuit board  52  could be replaced with a somewhat less accurate but functional activation circuit comprising a simple contact switch (not shown) at the base of motor  42 . In this configuration, the simple contact switch would be closed when sufficient weight is placed on feeder  14  as to compress linear force spring  48  adequately to permit electrical contact in the contact switch and activation of motor  42 . The disadvantage of such a method is that it must be periodically, (perhaps daily) adjusted to account for the declining weight of the feed as it is consumed. 
     A wide variety of mechanisms may be utilized to connect drive module  12  via drive shaft  44  to feeder  14 . As long as whatever mechanism or connector is used properly imparts the rotary motion of motor  42  to feeder  14  it is contemplated as within the scope of the present invention. In the embodiment depicted in FIG. 1, connection of feeder  14  to drive shaft  44  is accomplished through the use of a shaft coupler  54  attached to drive shaft  44  using a conventional set screw arrangement. Drive shaft  44  is preferably D-shaped and includes an indentation that permits engagement of the set screw  55  with the indentation in drive shaft  44  to provide further support for the weight of pendant feeder  14 . Again, according to the embodiment depicted in FIG. 1 , a flat link chain  56 , selected because of its ability to transmit rotational torque, is connected to drive shaft  44  via bracket  58  that is in turn connected to shaft coupler  54  via connecting link  60 . Flat chain  56  allows the feeder and any clinging squirrel to rotate about their combined center of mass. Absent flat chain  56 , the drive mechanism and its support must absorb the very large radial forces resulting from the off-center rotation. Lower end  62  of flat link chain  56  is in turn connected to attachment device at the top of feeder  14 , in this case threaded eyebolt  64  that is attached to feeder roof  66  by nuts  68   a  and  68   b  threaded on threaded eyebolt  64  on the inside and outside respectively of feeder roof  66 . 
     Feeder  14  may be of any conventional design, preferably cylindrical, the only unique requirement of the present invention being that feed outlets  70  be equipped with feed collection bowls  72  that inhibit dispersion of seed through feed outlets  70  due to centrifugal force when feeder  14  is rotated by motor  42  as described hereinafter. 
     Any number of feed outlets  70  may be provided and each is preferably equipped with a matching perch  74 . Perches  74  are preferably fabricated from metal such as steel or aluminum and penetrate opposing surfaces of wall  88  for strength, as shown in FIG. 1. A feed supply hole  76  may be provided in wall  88  of feeder  14  as well as a stopper  78  that is attached to wall  88  of feeder  14  via a tether  80  for convenience. 
     According to a highly preferred embodiment of the present invention, feeder  14  includes at its bottom a conical structure  82  that prevents feed placed into feeder  14  from accumulating in the bottom thereof where it could become wet and produce fungal infections that could harm feeding birds. The presence of conical structure  82  forces the contained seed and any standing water toward the periphery of feeder  14  and the lowermost of feed outlets  70 . 
     Optionally, according to a further preferred embodiment, a dynamic stabilizing rod  84  that provides additional mass along the axis of rotation  86  of feeder  14 , thereby inhibiting horizontal motion of feeder  14  during rotation, may also be provided. 
     In use, bird feeder  10  is attached to a tree limb or other suitable overhead structural support after being filled with bird feed or seed. Upon a squirrel clinging to feeder  14  for purposes of obtaining feed therefrom, its weight on feeder  14  causes incremental compression of linear force spring  48  in direct proportion to its weight resulting in activation of displacement sensor  50  that provides a signal to electronic circuit board  52 . Upon attainment of an appropriate change in weight, i.e. an appropriate displacement signal from displacement sensor  50 , electronic circuit board  52  activates motor  42  using power from battery packs  46  thereby imparting rotary motion to drive shaft  44  and in turn feeder  14 . Feeder  14  is caused to rotate at a rate, preferably about 100 revolutions per minute, adequate to cause the trespassing squirrel to be thrown off of feeder  14 . This action can also provide entertainment for observing bird feeder owners as invading squirrels are rotationally removed from feeder  14 . Repeated repelling of invading squirrels in this fashion will result in their losing interest in the feeder as a source of food. 
     As the invention as been described, it will be apparent to those skilled in the art that the same may be varied in many ways without departing from the spirit and scope of the invention. Any and all such modifications are intended to be included within the scope of the appended claims.