Abstract:
A retractable gate comprising a movable arm gate having multiple sections which nest or telescope into each other when parked (e.g. upright), and extends into a full length blocking position as it is deployed. The gate arm sections are deployed by the movement of one of the arms, e.g. the outer one section, relative to the ground or a stationary support member and is joined to the stationary support member by a pivot point or bearing, and is connected to the stationary support or ground by a cable connection (or equivalent) which powers the arm sections into extended or retracted positions by movement of the gate about the pivot bearing. A novel corresponding counterweight system provides selectable balance and torque requirements.

Description:
FIELD OF THE INVENTION 
   The present invention relates to movable arm gates, in particular to movable arm gates wherein the arm is retracted in length powered by, and in response to the gate movement. 
   BACKGROUND OF THE INVENTION 
   Movable arm gates, especially road gates for railroad crossing protection, are often required to extend over a significant expanse of horizontal surface, and to remove that gate completely to permit free travel over that surface within specified time limits. However, a long gate arm represents a considerable weight and movement inertia, which is further increased by added counter balances. Moreover, the moved gate requires a place to park when not positioned to block access. For vertically moving gates which are parked in an upright (or nearly upright) position, the upward motion is difficult especially in the initial stage of being raised from the horizontal, and significant vertical space above the gate is required. The weight and inertia and vertical space requirements of long arm style gates discourage and ultimately limit the gate arm length. Especially significant for the all gates, long or short, which are parked in the raised position is their vulnerability to wind and other weather related damage. 
   SUMMARY OF THE INVENTION 
   The retractable gate according to the present invention comprises an arm style gate having multiple sections which nest or telescope into each other when upright (or otherwise moved into a parked position), and extend into a full length deployed position as it is moved into the blocking position. The gate arm sections are extended or retracted by the movement of one of the arm sections, e.g., the outer one section, which is joined by a pivot point or bearing to a stationary support member, and by a cable connection (or other physical link) which provides the force to the arm sections as the gate is moved about the pivot bearing. 
   The retractable gate according to the present invention may be raised and lowered (or rotated) between block and park positions. While gravity provides motive forces for retraction (or extension as the gate is raised into the park position, alternate embodiments include further extension and retraction devices to broaden the applicability of the retractable gate according to the present invention. 
   Thus, the retractable gate provides reduced wind loading, less space requirement when in the park position, a reduced inertia moment arm by retractable arm sections which are deployed or retracted without requiring additional time to deploy the arm sections in the blocking position. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     These and further features of the present invention will be better understood by reading the following Detailed Description together with the Drawing, wherein 
       FIG. 1  is an elevation view of one embodiment of the present invention, showing exemplary extension elements with the gate arms in a parked upright position, an intermediate transitional position, and a blocking (deployed) position; 
       FIG. 2  is an elevation view of one embodiment of the present invention, showing exemplary retraction elements with the gate arms in a parked upright position, an intermediate transitional position, and a blocking (deployed) position; 
       FIG. 3  is an elevation view of one embodiment of the present invention, showing exemplary motor assist elements with the gate arms in a parked upright position, an intermediate transitional position, and a blocking (deployed) position; 
       FIG. 4  is an elevation view of one embodiment of the gate counterweights with the gate in the upright position; 
       FIG. 4A  is an elevation view of a first counterweight of the embodiment of  FIG. 4 ; 
       FIG. 4B  is an elevation view of a second counterweight of the embodiment of  FIG. 4 ; 
       FIG. 5A  is a plan view of one embodiment of the gate tip flexing member; 
       FIG. 5B  is a side elevation view of one embodiment of the gate tip flexing member; 
       FIG. 5C  is an end elevation view of one embodiment of the gate tip flexing member; 
       FIG. 5D  is a plan view of one embodiment of the gate tip flexing member in a tubular gate section with partial horizontal deflection thereof; and 
       FIG. 5E  is a side elevation view of one embodiment of the gate tip flexing member in a tubular gate section with partial vertical deflection thereof. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The exemplary embodiment of  FIGS. 1 ,  2  and  3  showing the gate arm  52  in lowered (blocking)  52 (D), intermediate  52 (I), and raised up (parked)  52 (P) positions. In the exemplary embodiment of  FIGS. 1 ,  2  and  3 , the retractable gate arm comprises three tubular segments,  52 A,  52 B and  52 C in which section  52 A retracts into section  52 B, which retracts into section  52 C. Alternate embodiments also include, without limitation, U-shaped, beam, rectangular planar, etc arm section cross-sections, straight or curved along the length of the sections, which may retract adjacent to, over, or any other configuration provided by one skilled in the art. The gate arm  52  includes an end portion  53  which allows the arm  52  to pivot about a pivot  54  and offsets the axis (extending through the center of the arm sections  52 A,  52 B and  53 C) centerline from the pivot  54  so as not to extend therethrough. Moreover, although the embodiment shows the gate arm  52 (P) raised substantially perpendicular to the ground  58 , other embodiments do not necessarily limit the range of or parking positions of the gate arm. Moreover, the gate arms  52 (P),  52 (I) or  52 (D) may also pivot parallel to the ground  58 , or any intermediate orientation. For clarity, each of the  FIGS. 1 ,  2  and  3  show different exemplary internal structure and devices according to the present invention, which are typically combined on and in a single structure. A counterweight system is provided as discussed, below, and illustrated in  FIGS. 4 ,  4 A and  4 B and connects to the arm  52  via offset portion  53 . 
   Cable  60  attaches to a support member  56  at a connector  62  a selected distance A from the pivot  54  and proceeds through a first pulley  64  retained by a movable collar  66  retained by and securable to the arm section  52 C. The cable  60  then proceeds along the arm section  52 C and around a second pulley  68  attached to the second end (distal to the pivot  54 ) of the gate arm section  52 C to travel through the arm section  52 C in a reverse direction until terminating at the first (proximal to the pivot) end of the second or next concentrically disposed gate arm section  52 B. As can be seen for the arm  52 (P) parked in the up position, the distance C between the cable connector  62  and the first pulley  64  is minimal, allowing the second section  52 B of the gate arm to retract into the outer section  52 C. As the gate arm is extended through the intermediate positions (e.g.  52 (I)), the distance C increases, shortening the cable and pulling the proximal end of the second section  52 B toward the distal (second) end of the first section  52 C, causing it to extend until the gate arm  52 A is finally fully deployed. 
   In the embodiment shown, the distances A and B are substantially equal to allow the cable length C to become minimized when the gate is parked. However, alternate embodiments wherein different distances A and B are within the scope of the present invention. Thus, the distance C (the third side of a triangle) is readily calculable and corresponds to the amount of extension for the arm section  52 B to which the cable terminates. 
   The typical gate cable installation proceeds as follows. With the second pulley attached, but movable along the arm section  52 C, move the pulley to the second (distal) end. Determine the extension (C′) desired of the arm section to which the end of the cable is affixed, which in the present embodiment will equal the maximum C distance ( 52 (D)) minus the minimum C distance (virtually zero for  52 (P). Pythagoras says A 2 +B 2 =C 2 , and in the present embodiment, distances B=A, so 2B 2 =C 2  and therefore B (and also A)=sqrt(½C 2 ), and the distances A and B are so adjusted, the second pulley  64  being locked or secured into position along arm section  52 A and the cable connector  62  being so affixed. For instance, if the desired extension of one section is 14 feet (C), the A and B dimensions are about 9.9 feet. In alternate embodiments where the dimensions for A and B are not the same, the geometric disposition of the cable connector  62  and the pulley  64  relative to the pivot  54  are readily determined according to the present invention by one of skill in the art. 
   A further extension device for extending the next inner section  52 A from the second section  52 B is also shown in  FIG. 1 . A second cable  70 , connected to the first (proximal) end of the outer arm section  52 C and extends forward towards the second (distal) end where a third pulley  74  is mounted on the second (distal) end of the second arm section  52 B. The second cable  70  extends around the pulley  74  and returns back toward the first end, but connects to the first (proximal) end of the third arm section  52 A. As the second arm section  52 B is extended by operation of cable  60 , the pulley  74  is moved away from the first end of the outer arm section  52 C, causing the cable  70  to pull the next inner arm  52 A out of the second arm section  52 B. 
   When the gate arms  52 A,  52 B and  52 C are moved into the park position away from the blocking position by motive devices, e.g. motors, hydraulics, etc. (not shown), the sequence of events reverses, which if the gate is raised upright to park, can occur simply by allowing the force of gravity to draw the inner sections  52 A and  52 B downward into the outer arm section  52 C. One supplemental retraction device is shown in  FIG. 2 , wherein a third cable  80  is anchored to the support  56  by connector  82  (or even directly to the ground  58 ) and extends over a slide support guide (or pulley)  84  and forward toward the second end of the outer arm section  52 C, attaching to a slide rod  85  which passes through a stop  88  and has a terminating nut  86  on the other (distal) side of the stop. The stop  88  is mounted to the first (proximal) end of the second arm section  52 B. As the retractable gate  52 (D) is moved to the park position ( 52 (P)), the total distance (in the deployed blocking position) between the stop  88 , the support guide  84  and the end of the cable  80  (e.g. at connector  82 ) increases, causing the cable  80  to pull back (to the proximal end of  52 C) on arm section  52 B. In certain alternative geometrical embodiments wherein the gate retraction or extension causes the third cable  80  to exert a force on the first cable  60 , additional resilient expandable devices, e.g. a spring (not shown), may be inserted into the third cable to accommodate any need for additional cable lengths (of either first or third cables). In horizontally moving gates, an resilient expandable device may be inserted into the first cable  60 . 
   A further retraction device is also shown in  FIG. 2 , including a fourth cable  90  connected to the second (distal) end of the outer arm support  52 C and proceeds to the first end to a pulley  94  mounted on the proximal end of the second arm support  52 B before returning distally until it is connected to the first (proximal) end of the next inner arm support  52 A. When the gate  52 (D) is retracted, as with the operation of cable  70  described above, as the second arm support  52 B is retracting and moves the pulley  94  away from the second end of the outer arm support  52 C and cable  90  being of fixed length, cable  90  will pull the next inner support arm  52 A into the second arm section  52 B. 
   A motion assist device for either extension or retraction is shown in  FIG. 3 , comprising a motor-driven pulley  102  connected to the first end of the outer arm support  52 C and a pulley  104  mounted at or near the second end of the outer arm support  52 C, and a cable or belt therearound, being fastened at a point  106  at or near the first end of the second arm support  52 B. Alternate embodiments may place the drive motor (not shown) at the pulley  104 . The force applied to the cable  100  urges the second support arm to retract or extend, and can be used to supplement or initiate the motions of the inner support arms  52 B and  52 C which become directed by the pulley-and-cable systems described elsewhere herein, and may include a releasable coupling, not shown, (e.g. on the motor, pulleys, or fasten point  106 ) so that the movement of the arm sections is not hindered by motor drag. Moreover, when combined with the operation of the first  60  or third cable  80 , alone or in combination, the motor-driven pulley, by driving the extension or retraction of the second arm support  52 B which is in turn connected to the support  56  or ground  58  according to the present invention, may provide at least some of the movement energy required to move the gate  52 (D) into the parked gate  52 (P) position and back. 
   Further details relating to the deployment of the gate arm counterweights and weight orientation is shown in  FIG. 4 , with the gate arm  52 , mounted on upper offset section  53  extends toward a counterweight arm  124  which receives the counterweights thereon, and is movable about a counterweight pivot  54  point to raise the gate into an upright position and into a blocking (down) position by movement about the pivot  54  point. The center line  126  of the telescoping gate arm  52  is offset by the section  53  in the present exemplary embodiment by 17.5 inches, or another dimension may be selected according to the present invention along with the weight and dimensions of the telescoping arm sections and the selection of and deployment of the weights as described below to achieve the desired gate torque and other characteristics. 
   The embodiment of  FIG. 4  includes 5 weights deployed at various positions along and distances from the counterweight arm vertical axis  128  (extending vertically through the pivot  54  point when the counterweight arm  124  is vertically oriented). The long axis of the rectangular (12″×36″, 65 lb.) counterweight  130  is disposed on the rear section  124  centered along the vertical axis  128  and slidably adjustable in counterweight arm slot  126  (being 18 inches in length in the present embodiment) to be spaced a greater or lesser distance relative to the pivot  54  point. Rectangular weights  132  and  134 , having a dimension of 22″×19″ and weighing 65 pounds in the present embodiment, are positioned with their longer dimension perpendicular to the axis  128 , the weight  132  with 16/22 of the weight extending to one side of the axis  128  and 16/22 of the other weight  134  extending to the other side of the axis  128 , and may be modified with the other weights and dimensions of the present invention to achieve the desired torque and other gate characteristics as described below. 
   The long axis of the rectangular (12″×36″, 65 lb.) counterweight  138  is disposed on the counterweight arm  124  with its longer dimension perpendicular to the vertical axis  128 , with 28/36 of the weight being extending away from the axis  128  and (toward axis  126 ), and slidably adjustable in counterweight arm slot  126  to be spaced a greater or lesser distance relative to the pivot  54  point. Rectangular weight  136 , having a dimension of 22″×19″ and weighing 65 pounds in the present embodiment, is positioned with its longer dimension parallel to the axis  128  and on the other side of the arm axis  126 , the weight  132  with 16/22 of the weight extending to one side of the axis through the long dimension of the weight  138 . 
   Further details of the exemplary weights  130  and  138  are shown as weight  110  in  FIG. 4A , having exemplary dimensions of 12″ wide and length (between ends  112  and  118 ) of 36″ and uniform weight distribution over the area of the weight. Holes  114 A and  114 B are used when deployed as weight  130  and mounted to arm  124  in slot  126 , and include holes  116 A and  116 B for mounting to weights  132  and  134 , (or  136 ) as described, above. Holes  114 C and  114 D are used to connect to the arm  124  via slot  126  when the weight  110  is mounted perpendicular to the axis  128  as weight  138 . The center line of holes  114 C and  114 D, and the midpoint between holes  114 A and  114 B is 8″ from the end  112 . 
   Further details of the exemplary weights  132 ,  134  and  136  are shown the weight  111  of  FIG. 4B , having an exemplary dimension of 19″ wide and 22″ long (between ends  113  and  117 ) and uniform weight distribution over the area of the weight. The center line of the holes  115 A and  115 B is 6″ from the end  113  of weight  111 , and are otherwise together centered in the other (19″) dimension. 
   Typically, governmental standards require that the gate have a down “fail” position, when the power to operate or move the gate into the upright position is lost, so that the gate arm  52  deployed down (blocking) and fully extended. Further typical requirements require a lifting force from a down position (vertical torque) of 400 to 480 ft-lbs, and a force to maintain the gate up (horizontal torque) of 80 to 120 ft-lbs. A further inventive feature of the present invention is the addition of a supplemental weight  140 , shown in  FIG. 1 , deployed along the section  52 C a distance  144  from the pivot  54 , of 12′ 5″ (center of weight) relative to the pivot  54  as measured along the axis of the gate arm  52  (not including the distance added by the offset ( 53 ) from the pivot  54 ) which may be changed according to other weight selection and deployment. Furthermore, the majority (70 to 90 percent) of the supplemental weight  140  is mounted to the gate arm section  52 C generally away from the pivot  54 , such that when the gate arm  52  is lowered, the bulk of the supplemental weight is closest to the horizontal surface  58 . It is found that since the weight of the constituent sections  52 A,  52 B and  52 C of the gate arm are generally distributed over their lengths and that the additional hardware (e.g. pulleys  68 ,  94 , etc.) do not provide a significant lumped mass, the lowering of the gate arm  52  according to the present invention is facilitated by the supplemental weight disposed as indicated, with a typical lumped weight of 69.75 pounds for the weights disposed according to the present embodiment, but may be varied according to a different selection and disposition of weights  130 ,  132 ,  134 ,  136 , and  138  made according to the present invention. 
   A further inventive concept according to the present invention provides a resilient flexure of the innermost gate section  52 A at a point thereon, as shown in  FIGS. 5A through 5E , wherein the gate section is bisected into two pieces,  52 A- 1  and  52 A- 2  which are resiliently joined with spring hinge  150  and each have flattened confronting surfaces  151 A and  151 B, respectively. As shown in  FIG. 5A  and  FIG. 5B , the spring hinge  150  has a clear ‘home’ position to which it reliably returns when surfaces  151 A and  151 B fully mate, allowing the gate arm sections  52 A- 1  and  52 A- 2  to be in axial alignment when extended or retracted. Moreover, the spring hinge  150  is retained within the gate arm sections  52 A- 1  and  52 A- 2 , which are typically tubular or otherwise having an internal opening. When the distal end of the gate section is forced out of axial alignment (e.g. by a vehicle) in either the horizontal direction as shown by  FIG. 5D  or in the vertical direction as shown by  FIG. 5E , the springs  152  allow the two pieces  154 A and  154 B of the hinge  150  to be pulled apart with increasing tension on the hinge springs  152 , and return together to the home position when the force is removed. The spring hinge  150  includes hinges  152  retained within parallel apertures within each piece  154 A and  154 B with some tension, which holds end pin  158  in place and holds the pieces  154 A and  154 B (and therefore gate sections  52 A- 1  and  52 A- 2  in axial alignment). 
   The above described embodiments are exemplary only and are not restrictive of the embodiments or scope of the present invention. For instance, additional or fewer arm sections are movable by and within the scope according to the present invention. Additional counterbalances may be added to the arm or arm connection to the support. Furthermore, the extension and retraction devices taught herein may be used alone or in combination. Also, the connections of the cables and pulleys to the particular ends of the identified age support arms may be read to include connection near to the respective ends such that the dimensions provide the desired arm section movements made according to the invention describe herein, as provided by one of ordinary skill in the art. Furthermore, the use of the reduction of the length of one section of a cable to lengthen another end as describe above, may be accommodated with other movement structures, e.g. a coupled pair of hydraulic cylinders having a constant volume of fluid, wherein shortening the piston excursion of one causing the extension of the other (and vice-versa) is within the scope of the present invention. Further modifications and substitutions by one of ordinary skill in the art are also within the scope of the present invention, which is not to be limited except by the claims which follow.