Abstract:
The present concept a helical antenna boom assembly includes a boom assembly, including a boom, and a plurality of rods and stays, each rod operably attached at an upper end of the boom and connected to one end of the stay. The boom assembly includes dish arms operably attached at a lower end of the boom, each dish arm connected to the other end of the stay, wherein the boom assembly moveable between an extended position, and a boom assembly collapsed position, such that in the extended position the stays are held under tension between the dish arms and the rods. The stays are also attached to a helical coil such that the tensioned stays support the helical coil in its correct helical geometry.

Description:
FIELD OF THE INVENTION 
     This application claims priority from previously filed PCT Patent Application No.: PCT/CA2011/001143, titled COLLAPSIBLE HELICAL ANTENNA filed on Oct. 13, 2011 by Patric Murphy which claims priority from previously filed U.S. Provisional Patent Application No. 61/405,694, titled COLLAPSIBLE HELICAL ANTENNA filed on Oct. 22, 2010 by Patric Murphy. 
     The invention relates generally to helical antennas and more specifically to collapsible helical antennas, which can be used in the field. 
    
    
     BACKGROUND OF THE INVENTION 
     Helical antennas are widely used and their operating characteristics are well known and understood in the art. 
     Some helical antennas are designed to remain permanently fixed in their normal operating configuration. On the other hand many applications require a deployable helical antenna that is movable between a collapsed position and extended position in the field. Examples of such deployable helical antennas are shown in U.S. Pat. Nos. 4,068,238, 3,646,566, 6,340,956, 5,977,932, 3,524,193. 
     Designing a collapsible helical antenna presents a challenge particularly with increasing wavelength. Challenges stem from the relationship between the overall helix diameter and cross-sectional diameter of the helical conductor or radiator and wavelength. In this regard it is known that the optimum overall diameter of the helical antenna is on the order of 0.3 times the central frequency wavelength. The optimum cross-sectional diameter of the helical conductor is on the order of 0.006 times the central frequency wavelength. At longer wavelengths the above relationships yield helix dimensions, which are too large for utilization of conventional helical antenna designs and deployment techniques. 
     There is a need for a collapsible helical antenna, which can be easily and quickly deployed in the field for reception of satellite signals on the ground. 
     There is a further need for a collapsible helical antenna, which is lightweight, easily carried on foot and quickly and efficiently deployed on the ground for reception of satellite signals. 
     SUMMARY OF THE INVENTION 
     The present concept a helical antenna boom assembly includes:
         a) a boom assembly, including a boom, and a plurality of rods and stays, each rod operably attached at an upper end of the boom and connected to one end of the stay;   b) the boom assembly including dish arms operably attached at a lower end of the boom, each dish arm connected to the other end of the stay,   c) wherein the boom assembly moveable between an extended position, and a boom assembly collapsed position,   d) such that in the extended position the stays are held under tension between the dish arms and the rods,   e) wherein the stays are also attached to a helical coil such that the tensioned stays support the helical coil in its correct helical geometry.       

     Preferably wherein the boom assembly including a rod holder mounted to the upper end of the boom, the rods attached at one end to the rod holder, and attached at the other end to the stays. 
     Preferably wherein the boom assembly including a hub assembly mounted to the lower end of the boom, wherein the dish arms are attached at one end to the hub assembly and attached at the other end to stays. 
     Preferably wherein the dish arms including arm pinions for engaging with a rack slidably mounted to the boom, the rack for operatively moving the dish arms from an extended position to an arms collapsed position by manually urging any one of the arms into the desired position. 
     Preferably such that the hub assembly for selectively locking the rack in a preselected position, and thereby locking the dish arms in the extended position. 
     Preferably such that the hub assembly for selectively unlocking the rack and thereby releasing the dish arms to permit folding of the dish arms into an arms collapsed position. 
     Preferably wherein the rods are resiliently biasing the straps thereby maintaining tension on the straps. 
     Preferably wherein the rods are made of resiliently flexible material thereby tensioning the straps and maintaining linear extension of the straps. 
     Preferably wherein the boom includes nested telescoping sections such that the boom is moveable between a boom extended position and a boom collapsed position. 
     Preferably wherein the boom includes an upper segment and a telescopically cooperating lower segment such that the upper segment slides into the lower segment to put the boom in the boom collapsed position. 
     Preferably further including a coupling for locking the upper segment to the lower segment when the upper section is urged into the boom extended position. 
     Preferably wherein the boom is made of nested telescoping sections such that the boom is moveable between a boom extended position and a boom collapsed position. 
     Preferably wherein the boom is made of a tubular section. 
     Preferably wherein the hub assembly includes an ejector pin slideably mounted within the lower end of a support shaft portion of the lower segment of the boom which is resiliently biased in a locked position for operably locking the rack and thereby the dish arms in the extended position. 
     Preferably wherein the hub assembly includes a key ring for manually urging the ejector pin downwardly thereby unlocking the rack and allowing the rack and dish arms to be urged into the arms collapsed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present device will now be described by example only with reference to the following drawings in which: 
         FIG. 1  is a front schematic perspective view of a helical antenna. 
         FIG. 2  is a front schematic perspective view of the antenna frame of the helical antenna. 
         FIG. 3  is a schematic side elevational view of the antenna frame of the helical antenna shown in an extended position. 
         FIG. 4  is a schematic partial side elevational view of a portion of the antenna frame showing the tripod in the tripod collapsed position and showing the motion of the dish arms being collapsed. 
         FIG. 5  is a schematic side elevational view of the antenna frame showing the tripod in the tripod collapsed position the dish arms in the arms collapsed position and the balance of the antenna frame in the extended position. 
         FIG. 6  is a schematic side elevational view of the antenna frame showing the tripod in the collapsed position the arms in the arms collapsed position and the boom in a partially collapsed position. 
         FIG. 7  is a schematic side elevational view of the antenna frame showing the tripod in the collapsed position and the boom in the fully collapsed position. 
         FIG. 8  is a schematic side elevational view of the antenna frame showing the boom assembly in the collapsed position the tripod in collapsed position and the unlocking of the cam lock for further pivoting and collapsing the tripod in the tripod collapsed position. 
         FIG. 9  is a schematic side elevational view of the frame showing the entire antenna frame in the frame collapsed position ready for storage. 
         FIG. 10  is a side elevational schematic view of the boom support shaft portion together with a portion of the boom. 
         FIG. 11  is a partial cut away schematic side elevational view of the boom support shaft portion showing the details of the ejector pin the lock balls and the spring tensioner arrangement showing the ejector pin in the locked position. 
         FIG. 12  is a schematic partial cut away side elevational view of the boom support shaft portion showing the ejector pin in the unlocked position. 
         FIG. 13  is a schematic side elevational partial cut away assembly view of the rack being placed over the boom support shaft portion and interacting with the lock balls. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present device a collapsible helical antenna is shown generally as  100  in  FIG. 1 . 
     Helical antenna  100  includes a boom assembly  102 , which further includes an antenna dish  104  and is shown in an extended position  105  in  FIG. 1 . 
     Furthermore helical antenna  100  also includes a tripod assembly  106 , which includes a tripod  108 . 
     Boom assembly  102  further includes a boom  110 , having an upper end  111  and a lower end  113 . The boom assembly includes a rod holder  112  for securely fastening one end of rods  114  thereto. Boom assembly  102  further includes an upper segment  116  a lower segment  118 , which is coupled together with coupling  120 . Boom assembly  102  also includes stays  122 , which support helical coil  124 . 
     Boom assembly  102  also includes antenna dish  104 , which further includes dish arms  130  which are connected to a hub assembly  132  and support a metalized fabric  134 . Tripod assembly  106  includes tripod  108  having a tripod mast  136  and tripod legs  138 . Referring now to  FIG. 2 , which shows schematically antenna frame  140  in an extended position  105 , and the boom assembly  102  and boom  110  in a boom extended position  109 . In the boom extended position  109  the boom  110 , rods  114 , dish arms  160  and stays  122  are fully extended and in the extended position  105  such that the stays  122  are placed in tension by being stretched between dish arms  130  and rods  114 . 
     The reader will note that antenna frame  140  includes all of the rigid components of helical antenna  100  and does not include stays  122  helical coil  124  and metalized fabric  134  for example. 
     Boom end  153  of rods  114  is securely fastened to rod holder  112  and stay end  151  of rods  114  is connected to stays  122 . The rods are preferably made of resiliently flexible material thereby resiliently biasing the straps and maintaining tension on the straps. For example plastic, fiberglass, steel, wood, aluminum and other materials known in the art may be used for the rods  114 . Rods  114  are arranged in a circular inverted conical array and extend above upper end  111  of boom  110 . as depicted in  FIGS 1 and 2 . 
     Stays  122  are connected at rod end  155  to rods  114  and at dish end  157  to dish arms  130  as depicted in  FIG. 1 . 
     Dish arms  130  further include an arm extension  142  for supporting metalized fabric  134  from the end of dish arm  130  to the outer diameter of metalized fabric  134 . 
     Referring now to  FIG. 3 , which shows schematically a side elevational view of antenna frame  140  in an extended position  105 . 
     Boom  110  further includes ball stops  150  located just below rod holder  112  and coupling  120 . Hub assembly  132  also further includes a rack  152  and each dish arm  130  includes arm pinions  154  at one end thereof. The rack is slideably mounted onto the support shaft portion  190  part of lower segment  118  of boom  110 . 
     Hub assembly  132  also includes an ejector pin  158  which is activated by pulling on key ring  156 . Referring now to  FIG. 4  which is a partial schematic side elevational view of the antenna frame  140  more specifically showing details as to how dish arms  130  are movable between an extended position  105  and an arms collapsed position  160 . 
       FIG. 4  shows that hub assembly  132  further includes arm supports  164  for pivotly attaching dish arms  130  at arm pivot  162 . Rack  152  is urged downwardly by arm pinions  154  when dish arms  130  are moved in the collapsing direction shown as  172 . 
     In order to initiate the collapsing of dish arms  130  the ejector pin  158  is manually urged outwardly by pulling on key ring  156  compressing spring  200  thereby releasing rack  152  and allowing dish arms  130  to move in the collapsing direction shown as  172 . 
       FIG. 4  also shows tripod  108  in a tripod collapsed position  168 . The collapsing of tripod  108  and the mechanism involved with this tripod is well known in the art. 
     Hub assembly  132  further includes a tripod bracket  170 , which connects tripod  108  to boom assembly  102 . 
     Referring now to  FIGS. 3 and 5 through 9  inclusively which schematically depicts antenna frame  140  being moved from the fully extended position  105  to a fully frame collapsed position  107  as shown in  FIG. 9 . 
     Referring now to  FIG. 5  with the tripod shown in the tripod collapsed position  168  and the dish arms  130  shown in the arms collapsed position  160  one further can collapse boom  110  by depressing ball stops  150  thereby lowering upper segment  116  to telescopically move over top of the lower segment  118  of boom  110 . 
     Shown in  FIG. 6  further depressing the second ball stop  150  just located below rod holder  112  one is then able to collapse the upper portion of boom  110  and retract the rod holder and the rods  114  into a boom assembly collapsed position  181  and boom collapsed position  180  as shown in  FIG. 7 . 
     Referring now to  FIG. 8  by loosening cam lock  182  of tripod bracket  170  allows tripod  108  to pivot freely about pivot  183  as shown in  FIG. 8 . 
     Pivoting tripod  108  about pivot  183  one is able to collapse tripod  108  against collapsed boom assembly  102  shown in boom collapsed position  180  into a frame collapsed position  107  as shown in  FIG. 9 . 
     Frame collapsed position  107  is the fully collapsed position of the antenna frame  140 . 
     The reader will note that the flexible portions of the helical antenna  100  such as the stays  122  the helical coil  124  and the metalized fabric  134  will easily collapse with the rigid components of boom assembly  102  and tripod  108  collapsing down into the frame collapsed position  107  as shown in  FIG. 9 . 
     For clarity of drawings we have not shown the soft components of helical antenna  100  in order that the reader is able to understand the collapsing features of antenna frame  140 . 
     The reader will note that helical antenna can be moved from the extended position  105  to the fully frame collapsed position  107  by simply reversing this procedure one can deploy helical antenna  100  by simply moving the helical antenna  100  from the frame collapsed position  107  to the extended position  105 . 
     Referring now to  FIGS. 10, 11, 12 &amp; 13  which show details of the boom support shaft portion  190 , which includes lock balls  192 , shaft threads  194 , shaft nut  166  as well as ejector pin  158  and key ring  156 . 
     Referring to  FIG. 11  ejector pin  158  is shown in a locked position  196  wherein lock balls  192  are positioned such that rack  152  not shown cannot move axially along boom support shaft portion  190 . 
     Referring now to  FIG. 12  by urging ejector pin  158  downwardly by pulling on key ring  156  this releases lock balls  192  to move inwardly thereby unlocking rack  152  and allowing it to move axially along boom support shaft portion  190 . Boom support shaft portion  190  is shown in the unlocked position  198  thereby allowing dish arms  130  to be moved into the collapsing direction  172  and finally into arms collapsed position  160 . 
       FIG. 13  shows further details in regard to the hub assembly  132  as well as the boom support shaft portion  190 . 
     Referring now to  FIG. 13  the reader will see the interaction between rack  152  and the boom support shaft portion  190 . Rack  152  is a cylindrical gear profiled rack and includes ball groove  204  for receiving lock balls  192  therein when the ejector pin  158  is resiliently biased by spring  200  in the locked position  196  when the rack  152  is in an upper locked position  159  thereby preventing rack  152  from moving axially along boom support shaft portion  190 . 
     Hub assembly  132  also includes arm supports  164 , ejector pin  158 , key ring  156 , shaft nut  166  and tripod bracket  170  as shown. 
     In Use: 
     In use helical antenna  100  is deployed into the extended position  105  as shown as  FIG. 1 . In extended position  105  stays  122  are under tension being stretched between the end of rods  114  on one end and dish arms  130  on the other end. Tension is applied to stays  122  when boom  110  is telescoped into the extended position  105  and dish arms  130  are also retracted into the extended position as shown in  FIGS. 1 and 2 . Tension on stays  122  rigidly holds helical coil  124  in place thereby defining the necessary helix required for proper functioning of the antenna. Helical coil  124  is a flexible conductor and may or may not be coated with material and/or entrained inside a material. There are a number of known materials in the art which can be used for helical coil  124  as well as stays  122 . 
     Antenna dish  104  includes metalized fabric  134  which is known in the art and is very flexible and effective in reflecting the signal back to helical coil  124 . 
     Described above is the process for collapsing helical antenna  100  from the extended position  105  to the frame collapsed position  107  shown in  FIG. 9 . In frame collapsed position  107  the entire helical antenna is put into a very compact position capable of being stored in a small bag. 
     Due to the design and construction of the helical antenna  100  in collapsed position  107  helical antenna  100  is extremely compact and light and can be easily carried on foot. 
     It will be apparent to persons skilled in the art that various modifications and adaptations of this structure described above are possible without departure from the spirit of the invention the scope of which is defined in the appended claims.