Abstract:
A bird feeder has telescopically aligned inner and outer cylindrical housings with opposed surfaces of complementary shape that are reverse tapered in a substantially vertical direction to enable guided vertical movement of the housings with respect to each other. The housings have openings in their side walls which are substantially in alignment when the outer housing is in an upper position and misaligned when the outer housing is in a lower position. A compression spring centrally located about the vertical axis of the feeder is confined within a lower portion of the feeder and biases the outer housing to its upper position. When the outer housing is moved to its lower position by the weight of a squirrel overcoming the biasing force of the compression spring, the housing openings are substantially misaligned such that no significant through opening exists, thereby preventing access to the birdseed.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present, invention is generally directed to an improved bird feeder of desirably simple and economic construction and, more specifically, to a bird feeder that is squirrel proof and that can be adapted to a wide variety of uses so as to be fairly characterized as a general purpose bird feeder. 
   2. Description of the Prior Art 
   There have been numerous attempts over the years to design a bird feeder that is squirrel proof. Certain of these feeders are designed for a specific purpose or installation and are relatively squirrel proof when so used. As a general purpose bird feeder, however, such designs have proven inadequate. Conversely, general purpose bird feeders have been found lacking with regard to their squirrel proof capability. 
   The above-described problem is known in the prior art and several patents disclose feeders which accomplish the squirrel proof objective in ways different from each other and from the invention described in detail hereinafter. For example, U.S. Pat. No. 4,646,686 to Fulani discloses a selective bird feeder having a cylindrical, transparent feed container located inside a concentric, coaxial, transparent shroud. The upper end of the shroud is supported above a shoulder near the upper end of the container by a compression spring which permits the shroud to move between an upper bird feeding position and a lower feed blocked position caused by the weight of a squirrel or large birds resting on the shroud. 
   U.S. Pat. No. 5,720,238 to Dracos discloses a bird feeder having an inner housing fixed vertically and an outer housing telescopingly received about the inner housing and movable between upper and lower positions. The housings have openings that are aligned when the outer housing is in its upper position so that the openings serve as feed ports. When the outer housing is in its lower position, the openings are misaligned to close the feed ports. External tension springs are provided to bias the outer housing toward its upper position, but allow the outer housing to move downwardly to its lower position under the weight of a squirrel or the like. 
   There is, therefore, a need for a general purpose squirrel proof bird feeder that can be readily manufactured at a reasonable cost, and that is reliable, sturdy, and long-lasting. 
   SUMMARY OF THE INVENTION 
   An object of the present invention, therefore, is to provide a bird feeder that is suitable for general purpose feeding of birds, and that is also squirrel proof. More particularly, it is an object of the present invention to provide a squirrel proof bird feeder having inner and outer housings capable of structural cooperation so as to provide access to birdseed through aligned openings in the cooperating housings when birds are present, and to restrict access to birdseed when a squirrel is present. 
   In accordance with one embodiment of the present invention, a compression spring operated squirrel proof bird feeder has an inner tubular housing and an outer tubular housing or shroud telescopically surrounding the inner housing. The opposed surfaces of the housings have a complementary shape for structural mating purposes. The outer housing or shroud includes a perch assembly associated therewith, and is vertically slidable on and about the inner housing between an upper position and a lower position. A bird seed storage container is mounted above the inner housing to feed bird seed to the inner housing by gravity. When the outer housing is in its upper position, the housings are in their structurally mating position; when the outer housing is in its lower position, the housings are not mated. 
   The complementary shape of the opposed surfaces of the cooperating housings are preferably reverse tapered with respect to each other in a substantially vertical direction so as to enable telescopically guided movement of the housings both toward and away from the complementary surfaces. The mating housings are preferably substantially cylindrical in shape and have an associated hanging wire assembly for supporting the inner housing in a fixed substantially vertical position. Preferably, the hanging wire passes through the birdseed storage container and holds the inner housing so that the mating housings may be suspended from a tree limb or the like in a spaced relationship therebeneath. 
   Each of the housings has at least one opening in a side wall thereof, with the openings in the two housings in substantial alignment and in communication so as to provide a through opening or feed port when the outer housing or shroud is in its upper position and mated with the inner housing. With the outer housing in its lower position, the openings in the two housings are substantially misaligned and in substantial non-communication such that no significant through opening exists. A bottom wall closes off the bottom of the inner housing to support birdseed therewithin for access through the through opening when the two housings are mated and their openings are in aligned communication. 
   A generally vertical compression spring is operatively connected between the inner housing and the outer housing to urge the outer housing toward its upper position in mating relation with the inner housing. The compression spring is also selected so as not to be overcome by a predetermined weight, such as the weight of an average or typical bird (or of several such birds), but readily overcome by the weight of an average or typical squirrel. Thus, the presence of a squirrel on the perch assembly will cause the outer housing to move to its lower position and close the through opening, thereby restricting access to the birdseed. 
   In a preferred embodiment, the feeder has a plurality of pairs of cooperating feed openings in the two housings for opening and closing operation, as described, when the outer housing is in its upper and lower positions, respectively. 
   The compression spring is preferably supported around the base of a spring socket centrally located with respect to the vertical axis of the feeder and adjacent the bottom thereof. The spring socket is supported in a downwardly facing cylindrical opening in the center of the inner housing. The compression spring is retained in position around the spring socket by two radial flanges, one projecting inwardly from the outer housing and the other projecting outwardly from the base of the spring socket. As indicated, the compression spring is selected to maintain the outer housing in its upper position despite the presence of a load on the perch assembly that is less than a predetermined weight. But, the spring force is insufficient to sustain a load on the perch assembly greater than the predetermined weight, whereupon the outer housing descends to its lower position, the through openings are substantially closed, and access to birdseed is restricted until the load is removed. 
   It is, therefore, another object of the present invention to provide a squirrel-proof birdfeeder which utilizes a single compression spring centrally located in the base of the feeder to urge the outer housing toward its upper position in mating alignment with the inner housing. 
   Yet another object of the present invention is to provide a squirrel-proof birdfeeder in accordance with the preceding object in which the centrally located compression spring is supported around the base of a spring socket assembled centrally in a downwardly facing cylindrical opening in the inner housing. 
   A further object of the present invention is to provide a squirrel-proof birdfeeder in accordance with the preceding objects in which the compression spring supported around the base of the spring socket is protected from contact with birdseed in the birdfeeder and other contaminants which might interfere with operation of the compression spring to bias the outer housing toward its upper mating position with the inner housing. 
   Still a further object of the present invention is to provide a squirrel-proof birdfeeder in accordance with the preceding objects in which the opposed surfaces of the inner and outer housings have reverse tapered complimentary shapes in a substantially vertical direction so as to enable telescopically guided movement of the outer housing with respect to the inner housing. 
   Yet a further object of the present invention is to provide a squirrel-proof birdfeeder in accordance with the preceding objects which includes a hanging wire assembly connected to the inner housing adjacent its base at substantially its axial center and passing upwardly through a birdseed storage container in communication with and supported above the inner housing for hanging the birdfeeder in spaced relation below a tree limb or other hanging support. 
   A final object to be recited herein is to provide a squirrel-proof birdfeeder in accordance with the preceding objects, which can be easily manufactured from readily available and known components for ease and economy of manufacture and which will be sturdy and long lasting in operation and use. 
   These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like reference numbers refer to like parts throughout. The accompanying drawings are intended to illustrate the invention, but are not necessarily to scale. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a compression spring operated squirrel proof bird feeder according to one embodiment of the present invention, and illustrates the feeder suspended from a tree limb. 
       FIG. 2  is an exploded perspective view of a lower portion of the embodiment of the bird feeder illustrated in  FIG. 1 , and shows a portion of a birdseed storage container, inner and outer housings, the perch assembly, the spring socket, the compression spring, the hanging wire assembly and related assembly components. 
       FIG. 3A  is a perspective view of the inner and outer housings shown in  FIGS. 1 and 2 , and illustrates the mating cooperation of the housings in an upper position of the outer housing. 
       FIG. 3B  is a perspective view of the inner and outer housings shown in  FIGS. 1 and 2 , and illustrates the positions of the housings when the outer housing is in its lower position. 
       FIG. 4  is a side elevational view of the bird feeder of  FIG. 1  with the outer housing in the upper position. 
       FIG. 5  is a partial sectional view of the bird feeder taken along line  5 - 5  of  FIG. 4 . 
       FIG. 6  is a side elevational view of the bird feeder of  FIG. 1  with the outer housing in its lower position, and with the bird feeder rotated 90° with respect to the position shown in  FIG. 4 . 
       FIG. 7  is a partial sectional view of the bird feeder taken along line  7 - 7  of  FIG. 6 . 
       FIG. 8  is a bottom view of the bird feeder of  FIG. 1 , and illustrates the location of the compression spring between an exterior surface of the spring socket and an interior surface of a hub of the perch assembly that is attached to the outer housing. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Although only preferred embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. 
   Also, in describing the preferred embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art, and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
     FIGS. 1 and 2  illustrate a compression spring operated squirrel proof bird feeder, generally designated by reference numeral  10 , in accordance with a preferred embodiment of the present invention. The bird feeder  10  includes a birdseed storage container  12  having a removably mounted lid  14 . A hanging wire assembly  16  passes through the container  12  and the lid  14 , and is secured at its lowermost end within a bird feeder housing assembly, generally designated by references numeral  18 . 
   An upper end  20  of the hanging wire assembly  16  preferably has a loop and is secured by a crimped metal strap  22  to form a loop opening  24 . According to a preferred embodiment, the opening  24  is used to suspend the bird feeder  10  from a support structure, such as a tree limb  26 , by a strap  28 . Alternatively, in one of many possible variations, the opening  24  may be threaded onto a small branch of sufficient size to provide support for the bird feeder  10 , or any other support structure. Alternatively, the feeder  10  can be mounted on a post. 
   As illustrated in  FIG. 2 , the housing assembly  18  includes an inner housing, generally designated by reference numeral  30 , telescopically received in an outer housing, generally designated by reference numeral  32 . The outer housing includes a perch assembly, generally designated by reference numeral  34 , having radially outwardly extending vane portions  34   a ,  34   b ,  34   c , and  34   d  extending from a central hub  34   e . Threaded fasteners such as, for example, screws  36 ,  38  (see also  FIG. 7 ), extend through a radially inwardly extending rim  32   a  of the outer housing into threaded passageways  34   f  of the perch assembly  34  for securing the hub  34   e  of the perch assembly  34  into the outer housing  32 . 
   The inner housing  30  includes a spring socket, generally designated by reference numeral  40 , having a cylindrical wall section  42  terminating at its upper end in horizontal top plate  44 . At the bottom end of the cylindrical wall section  42  is a radially outwardly extending support flange  46 . Flange  46  preferably includes a plurality of radially extending ribs  54  for strengthening the flange  46  and for supporting one end of a compression spring, generally designated by reference numeral  56 , as described in more detail below, on the flange  46 . As illustrated, the compression spring  56  is positioned around the vertical axis of the feeder  10  and adjacent its lower end. 
   Top plate  44  includes holes  44   a ,  44   b  for receiving threaded fasteners  47  and  48 , respectively, and central hole  44   c  for receiving a lower end  50  of the hanging wire assembly  16 . A crimped metal band  52  and washer  52   a  (as shown in more detail in  FIGS. 5 and 7 ) on the lower end  50  of the hanging wire assembly  16  prevent the lower end  50  from passing upwardly through the hole  44   c  in the top plate  44  of the spring socket  40 . 
   The body of spring  56  surrounds the cylindrical wall section  42  of spring socket  40 . The lower end  56   a  of spring  56  is seated on top of flange  46  of spring socket  40 . The spring socket  40 , with the spring  56  surrounding the cylindrical wall section  42 , extends through a central opening  34   g  of the hub  34   e  of the perch assembly  34  and the central opening  32   b  of the outer housing  32 . The upper end  56   b  of spring  56  engages radially inwardly extending rim  32   a  of the outer housing  32  as will be described in greater detail with reference to  FIGS. 5 and 7 . 
     FIG. 5  shows a partial sectional view of the bird feeder  10  in an uncompressed state. As illustrated, the spring  56  extends only approximately one-half way along the exterior length of the cylindrical wall section  42  of spring socket  40 . The remainder of the cylindrical wall section  42  extends into a downwardly facing cylindrical opening defined by the cylindrical body portion  58   a  of a receptacle, generally designated by reference numeral  58 , centrally located within the inner housing  30 . The threaded fasteners  47  and  48  are assembled through the interior of cylindrical wall section  42  of spring socket  40  and extend through holes  44   a  and  44   b , respectively, of top plate  44  of spring socket  40  into engagement with holes  58   b ,  58   c  in a top surface  58   d  of receptacle  58  (see  FIGS. 2 and 7 ). A bottom flange portion  58   e  extends radially from the bottom of receptacle body portion  58   a  and is seated on top of annular flange portion  32   c  of the lower housing  32 . The lower end  50  of the hanging wire assembly  16  passes through aperture  58   g  of anchor block  58   f.    
     FIG. 3A  is a perspective view of the inner and outer housings  30 ,  32  illustrating the mating cooperation of the housings in the upper position of the outer housing.  FIG. 3B  is another perspective view of the housings  30 ,  32  illustrating their positions when the outer housing is in its lower position. As shown, the inner housing  30  and the outer housing  32  cooperate with each other by mating opposed surfaces including a plurality of tapered recesses  30   c  formed into the exterior surface of the inner housing  30 , and a plurality of complementary shaped tapered projections  32   c  forming the upper surface of outer housing  32 . The tapered recesses  30   c  guide the tapered projections  32   c  when the outer housing moves from its lower position to its upper position so that the two housings  30 ,  32  are aligned and structurally mated. 
   When the two housings  30 ,  32  are aligned and structurally mated, an outer housing opening  32   d  of outer housing  32  aligns with an inner housing opening  30   d  of inner housing  30  so as to provide a through opening  33  that enables passage of birdseed therethrough. When the outer housing  32  moves to its lower position, as shown in  FIG. 3B , due to the presence of a squirrel on the perch assembly  34 , the opening  32   d  moves out of alignment with the opening  30   d  and prevents access to the source of birdseed through opening  30   d  of inner housing  30 . 
   As shown in  FIGS. 2 and 5 , the seed storage container  12  has a feed section  12   a  with vertically extending slots  12   b  positioned to cooperate with gussets  30   a  of the inner housing  30 . When the gussets  30   a  are positioned in the slots  12   b , threaded fastener holes  12   c  in the side of the feed section  12   a  are aligned with the threaded fastener holes  30   b  in the inner housing  30 . Threaded fasteners  70 ,  72  initially pass through holes  30   b , then through holes  12   c , and are finally secured by nuts  74  contained within the anchor block  58   f  located on top of receptacle  58  to assemble the seed container  12  onto the top of the inner housing  30 . 
   Two of projections  32   c  of the outer housing  32  preferably include flared portions  32   e . These flared portions  32   e  allow the projections  32   c  to pass over the heads  70   a ,  72   a  of the threaded fasteners  70 ,  72  when the outer housing  32  is in its upper position. 
     FIG. 4  is a side elevational view of the bird feeder  10  with the outer housing  32  in its upper position. As shown, the upper housing  30  and lower housing  32  are in position to allow access through the through openings  33  to birdseed in compartments  12   a ,  12   b ,  12   c  of the container  12  formed by vertical dividers  13   a ,  13   b .  FIG. 6  is a side elevational view of the bird feeder  10  with the outer housing  32  in its lower position, and with the bird feeder  10  rotated 90° with respect to the position shown in  FIG. 4 .  FIG. 7  is a partial sectional view of the bird feeder  10  taken along line  7 - 7  of  FIG. 6 .  FIG. 8  is a bottom view of the bird feeder  10 , and illustrates the central location of the compression spring  56  around the vertical axis of the feeder and between the exterior surface of the spring socket  40  and the interior surface of the hub  34   e  of the outer housing perch assembly  34 . 
   In a preferred embodiment the container  12  is formed as two substantially identical molded half shells  15   a , 15   b . The half shells preferably include half partitions molded into the half shells to form partitions  13   a , 13   b , when the half shells are assembled. Passageway openings  12   d  are provided in the half shells  15   a , 15   b  to accommodate a fastening assembly, such as a bolt and nut set, for joining the two half shells together to form the container  12 . 
   Compression spring  56  is operatively connected with the outer housing  32  to urge the outer housing  32  toward its upper position in mating relation with the inner housing  30 . The compression spring is selected so as not to be overcome by the weight of an average bird (or of several average birds), but readily overcome by the weight of an average squirrel, typically about 9.5 ounces. Thus, the presence of a squirrel on the perch assembly  34  will cause the outer housing  32  to move to its lower position, and thus eliminate the through openings  33 . Conversely, removal from the perch assembly  34  of the load heavier than the predetermined weight causes the compression spring  56  to uncompress, moving the outer housing  32  from its lower position to its upper position, thereby again to provide access to the birdseed. 
   That is, as shown in  FIGS. 6 and 7 , when a squirrel is present on the perch assembly  34 , the outer housing  32  separates from the inner housing  30  due to the weight of a squirrel overcoming the force of compression spring  56 . In the position shown in  FIG. 6 , the projection  32   c  includes two inwardly tapering sidewalls  100 ,  102 . The sidewalls terminate in a horizontal upper surface  104 . When the outer housing  32  moves from its lower position (shown in  FIG. 6 ) to its upper position (shown in  FIG. 4 ), the tapered sidewalls  100 ,  102  engage outwardly tapered sidewalls  106 ,  108  defined by the recesses  30   c  of the inner housing  30 . To provide the desired amount of engagement, the sidewalls  100 ,  102 ,  106 , and  108  are preferably tapered at an angle of from approximately 60° to approximately 80°, and still more preferably at an angle of approximately 70°. 
   Therefore, if there is any twisting or torquing of the lower housing  32 , such as by example, the movement of a squirrel leaving the perch assembly  34 , the sidewalls  100  engage the sidewalls  106 , or the sidewalls  102  engage the sidewalls  108 , depending upon the direction of twisting of the perch assembly  34 , so as to guide the projections  32   c  of the outer housing  32  into the recesses  30   c  of the inner housing  30 . The openings  32   d  of the outer housing  32  thereby align with the openings  30   d  of the inner housing  30  so as to once again structurally mate the housings and provide the through opening  33 . 
   When the squirrel leaves the perch assembly  34 , the compressed spring  56  (as shown prior to unloading in  FIG. 7 ), expands to a less compressed or uncompressed state (shown in  FIG. 5 ), and thereby returns the outer housing  32  to its original upper position in engagement with the inner housing  30 . Birds are thereby again permitted access to the birdseed conveyed from container  12  to the opening  30   d  of the inner housing  30 . 
   In a preferred embodiment, the compression spring  56  has an uncompressed length of approximately 4.25 inches, and a fully compressed length of approximately 0.30 inches. When the compression spring  56  is compressed to 1.35 inches, the measured spring force is approximately 16+/−1 ounces. The compression spring  56  can, however, have characteristics different from those described herein, such as a different spring force, depending upon the particular service in which the feeder  10  is to be used. 
   The mating housings  30 ,  32  are preferably made of die cast zinc or other durable and sturdy metals or materials. The mating housings  30 ,  32  are preferably substantially cylindrical in shape and have the associated hanging wire assembly  16  for supporting the same. 
   Further, by positioning the compression spring  56  around the cylindrical wall section  42  of the spring socket  40  on flange  46 , and inside the perch assembly hub  34   e  and flange  32   a  of the outer housing  32 , the compression spring  56  is insulated from contact with birdseed or other contaminants which might interfere with its operation. 
   The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes may readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation described and shown. For example, one embodiment of the feeder  10  has been described above as including the hanging wire assembly  16  for maintaining the feeder in a substantially vertical orientation. In another possible embodiment of the invention, however, the feeder can be supported from below, such as mounting the inner housing on top of a pole or post. Accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the invention as defined by the following claims.