US3267625A - Latching mechanism for an extensible antenna - Google Patents

Description

Aug. 23, 1966 D. L. HOLZSCHUH ETAL 3, 67,6 5

LATCHING MECHANISM FOR AN EXTEN5IBLE ANTENNA Filed May 16, 1963 5 Sheets-Sheet l 3/ 3g I 4/ /4- V I l 35 I ,///4 5 FIG 2 v INVENTORS Donald L. Holzschuh James L. Seymour Jr:

Allan Van Horne 8" 1966 D. L. HOLZSCHUH ETAL 3,267,625

LATCHING MECHANISM FOR AN EXTENSIBLE ANTENNA Filed May 16, 1963 5 Sheets-Sheet 2 INVENTORS Donald L. Holzschuh James L. Seymour Jr Allan Van Horne BY Wk 5 M 4 z Agents 1966 D. HOLZSCHUH ETAL 3,267,625

LATCHING MECHANISM FOR AN EXTENSIBLE ANTENNA Filed May 16, 1963 5 $heets-$heet 5 44\%| & 43

4 INVENTORS Donald L. Ho/zschuh James L. Seymour Jr. Allan Van Horne BY M Agents United States Patent 3,267,625 LATCHIN G MECHANISM FOR AN EXTENSIBLE ANTENNA Donald L. Holzschuh and Allan Van Horne, Richardson, and James L. Seymour, .lr., Mesquite, Tex., assignors to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Filed May 16, 1963, Ser. No. 280,831 Claims. '(Cl. 52111) This invention pertains to extensible and retractable telescopic radio antennas and more particularly to latching devices that ensure extension and retraction in the order of arrangement of sections.

The latching mechanisms of this invention are utilized with antennas that have power erecting systems to pull upward on the respective innermost unextended telescopic tubular sections. Telescopic antennas of this type are to be extended in their order of arrangement of sections from the innermost sections to the outermost sections. As each section is fully extended, an upper stop and lower supporting stop become effective to retain the extended section fixed relative to an adjacent outer section so that both the unextended adjacent outer section and the fully extended inner section can be forced upward together.

When the retarding force of friction between two adjacent sections is less than the weight of the outer one of the sections, latching means is obviously not required to hold the outer section down until the inner section is fully extended. In practice the inner section that is being raised may develop sufiicient friction to cause the outer section to rise prior to engagement of the supporting stop and cause the inner section to fall. The excessive friction is most likely to develop when the antenna is being erected in high wind.

According to this invention, each tubular section of an antenna, except the innermost section, has an upper fastening collar that has hinged latches for engaging corresponding notches in an upper adjacent collar of an inner section, a release pin for each latch that may be forced outwardly to release the latch, a band or sleeve about each tubular section, each band engaging the release pins of the collar within which it is being guided in response to the respective section being fully extended to release the latches that are holding downwardly on the section adjacent to the section that has just been raised, each of the sections to be extended having a notch within the band or sleeve to be engaged by corresponding stop balls, and plunger and spring means operated in response to separation of the unlatched collars to position said balls inwardly into the corresponding notches to prevent downward movement of the extended sections.

An object of this invention is to provide relaible cooperating latching mechanisms for both retracted and extended positions of each section to ensure inner to outer sequence of positioning of sections during erection and outer to inner sequence of positioning of sections during retraction.

The description and the appended claims may be more readily understood by reference to the accompanying drawings in which:

FIG. 1 is a side view of a four-section telescopic antenna mounting as representative of larger structures, a portion of one of the representative intermediate collars being cut away to show latching mechanisms;

FIG. 2 shows a cross section of two adjacent telescopic sections at their guide rings to show the method of keying against rotation;

FIG. 3 is a side view of a mounting of an intermediate section within outer sections of a telescopic antenna when 3,267,625 Patented August 23, 1966 the innermost sections have been extended, the intermediate section being shown just as it is started to be pulled upward from force exerted on the innermost sections by traction rollers (not shown); and

FIG. 4 is a cross section view of a collar between two extended sections to show a ball locking mechanism.

In FIG. 1 an upper, extended, innermost section 10 is shown supported within an adjacent section 11 to which an upper fastening collar 12 is attached. Likewise, section 11 is telescoped within section 14 to which a fastening collar 13 is attached. Section 14 is mounted within an outermost section that has a fastening collar 15. This outermost section is telescoped within the base 16 that supports the antenna. The latches 17, 18, and 19 retain the outermost section and sections 14 and 11 respec- I tively in a retracted position until they are to be extended in order from the innermost section to the outermost section. Each collar has a release pin such as pin 20 that is mounted in collar 13. Each release pin is actuated by a band or a sleeve similar to sleeve 21 of section 11 shown in FIGS. 3 and 4. When section 11 is fully extended, the sleeve 21 has engaged the pin 20 and has released the latch 18 that is mounted to the lower adjacent collar 15.

Each collar also has a ball stop that is to be actuated by a spring and plunger. In FIG. 1 the plunger 22 is forced upward in opposition to its spring by its lower edge being in contact with the upper face of the adjacent collar 15. With the plunger in this position, the stop ball 23 is in an outward position relative to section 11 to permit the upper beveled portion of sleeve 21 to pass upward to a position above the ball as shown in FIG. 3. As a section 11 is lifted, the spring for forcing the plunger 22 downward forces the ball 23 into a notch on sleeve 21 as shown in FIG. 4 to prevent subsequent retraction of the section 11 until after the adjacent outer section 14 has been returned to its normal telescoped position.

In detail, each tubular antenna section except the innermost section 10 has a fastening and stop collar attached to its upper end. Obviously, a collar is not required for the section 10 because it is always the first section to be extended and is always under control of a power traction device that is not shown. Other than the collars becoming progressively larger for the outer sections, the collars are similar. The uppermost collar 12 that is attached to the section 11, next to the innermost section, requires no latch. In a preferred embodiment each collar is an aluminum casting that has two diametrically spaced hold down latches to prevent premature extension and two diametrically spaced ball stops that prevent premature retraction.

As clearly shown in FIG. 4, each collar has a lower annular lip portion 24 that is fitted into a rabbet formed within the upper edge of the inner wall of the tubular antenna section 14. The lip 24 of the collar is permanently attached within the rabbet. The inside cylindrical wall of the collar 13 has a slightly greater diameter than the aluminum stop sleeve 21 of the section 11 that is to be guided within the collar. The stop sleeve 21 is permanently attached to the outer wall of the aluminum telescopic antenna section 11 to provide a firm stop for locating the section 11 in an extended position. The stop sleeve also functions as a cam or a control surface for positioning hold-down latch 18 and stop ball 23.

A notch for receiving a stop ball is located in the vertical outer wall of the sleeve 21 at a point adjacent to the location of the stop ball 23 when the antenna section 11 is fully extended. The upper edge of the notch is slanted upwardly and outwardly from the bottom of the notch to apply force outwardly on the ball 23 when the section 11 tends to move downwardly as the upward traca tion is decreased. Although a preferred embodiment is shown using a relatively long sleeve 21, a band corresponding to only the top portion of the sleeve that extends above the top of the notch 26 may be used. The bottom of the band would have a beveled lower edge to correspond to the upper edge of the notch 26.

A cylindrical upper bearing 27 as shown in FIG. 3 lines the upper portion of the cylindrical inner wall of the collar 13. A bearing that functions very satisfactorily comprises two similar semicircular bands retained by a coil spring retainer 29. A circumferential groove that has an annular cross section for receiving the spring retainer 29, is formed by a groove in the outer surface of the bearing 27 and also a similar mating groove in the inside wall of the collar 13. The bearing pieces are preferably fabricated from a plastic material that has good wearing qualities. The inside diameter of the hearing 27 is slightly larger than the diameter of the antenna section 11 to provide a sliding fit. The lower edge 28 of the bearing 27 is beveled so that its surface contacts substantially all the surface of the beveled upper edge of the sleeve 21 to provide a stop that limits the upward motion of the section 11 relative to section 14.

The latch 18 of FIG. 1 is rotatably mounted on a horizontal bearing pin 35 that is fitted Within the U shaped bracket 30 cast into the upper outer edge of the lower adjacent collar 15. A torsion spring 31 that encircles the bearing 35 and has its ends attached to the latch 18 and the collar 15, urges the latch inwardly to bear against the wall of the collar 13. The spring is more clearly shown with reference to latch 12 that is attached to collar 13 in that the bracket for latch 19 has been cut away to show the spring 32 that urges latch 19 inwardly. A notch or seat 34 in the retaining plate 25 that is mounted by screw 36 in the outer wall of collar 13 is located to receive the tooth 33 of the latch 18 so that when a release pin 20 is free to move to its inward position, the tooth bears against the upper edge of the notch as the collar tends to travel upwardly prematurely. The cylindrical release pin 29 is a sliding fit in a bore that extends inwardly from the bottom of the notch 34 through the vertical wall of the collar 13. The pin 20 is held captive by the antenna section 11 at one end, and by the retaining plate at the other. The diameter of the outer end of the pin 20 has a smaller diameter than that of most of the pin so that it may extend through a hole in the plate 25 to contact the inner surface of the tooth 33. The length of the pin 20 is such that it extends between the wall of the antenna section 11 and the surface of the tooth 33 when the tooth is seated in the notch 34.

The stop as shown in FIG. 4 for retaining the antenna section 11 in an extended position comprises a steel ball 23, a positioning control plunger 22, and a notch 26 in the wall of the sleeve 21. The ball is contained within the hole that is located radially through an inner portion of the wall of the collar 13 at a position opposite that of the stop notch 26 during full extension of the antenna section 11. The plunger 22 is slidingly mounted vertically within a cylindrical hole that intersects the hole for ball 23. The ball 23 is also a sliding fit within its mounting hole. The'transverse distance between the surface of the plunger when it is in its lower position and the outer wall of the antenna section 11, not including the sleeve 21, is slightly greater than the diameter of the stop ball 23. As the ball is positioned inwardly toward the antenna section 11 by the plunger 22 it functions as a stop between the upper lip of notch 26 (FIG. 4) and the lower edge of its mounting hole. The vertical hole for the plunger 22 is drilled through the wall of the collar 13. As shown in FIG. 1, the plunger 22 is urged downwardly by the helical spring 37 that is mounted between the top of the plunger and a retaining cover 38 that is secured over the top of the mounting hole.

The distance of downward travel of the plunger 22, while the collar 13 is spaced above its adjacent lower collar 15, is restricted by a pin or screw 39 that is fastened radially through the outer wall of the collar 13 so that its inner end fits within a slot 40 within the outer surface of the plunger 22. The upper portion of the plunger 22 is cylindrical but the lower portion has a vertical section milled off to provide a flat surface 41 such that the stop ball 23 may be moved outwardly. The upper surface 42 of the flat surface 4-1 is gradually tapered so as to function as a cam against the surface of the ball. When adjacent collars are positioned together, the upper surface of the lower collar presses against the lower end of the milled portion of the plunger to press the plunger up wardly into its collar in opposition to the downward force of the spring 37 to permit the milled portion to be raised high enough to accommodate outward movement of the ball 23. Then, when the ball 23 is contacted by the sleeve 21, it is forced outwardly so that it does not protrude within the inner Wall of the collar to prevent passage of the sleeve.

With reference to FIGS. 2 and 4, the bearing for guiding the lower end of the antenna section 11 comprises two semicircular bands 43 and 44 that are similar to the semicircular bands comprising the upper bearing 27.

These pieces are also fabricated from a plastic or other good bearing material. The thickness of these pieces corresponds to the thickness of the bearing 27. These bearings, however, are firmly attached to the inner section 11 by countersunk screws and travel within the antenna section 14. The pieces of hearing are actually a little shorter than full semicircles so that diametric gaps 45 and 46 exist between the ends of the semicircular bearing pieces. Each of the aluminum antenna sections is extruded with diametrical, longitudinal tongues or keys 47 and 48 that travel within the gaps 45 and 46 respectively that are provided between the bearing pieces 43 and 44. Since all of the sections (except the innermost section) are provided with keys corresponding to keys 47 and 48, all the sections are restrained from rotation so that the collars are always aligned and the latches can engage the corresponding notches or seats.

Frequently, in erecting an antenna, roller traction systems are utilized. The rollers first start to raise the innermost section 10. The latches 17, 18, and 19 in FIG. 1 secure all sections to the base except the innermost section 10. Whensection 10 is fully extended, its sleeve, that corresponds to the sleeve 21 of FIG. 3, engages the pin 49 to release the latch 19. As section 11 begins to be lifted upwardly the stop ball in the collar 12, that corresponds to the stop ball 23 of collar 13, is forced inwardly by the corresponding spring and plunger to position the ball within the stop slot of the section 10. As the rollers continue to operate, they pass over the collar 12. When the rollers no longer provide an upward force on the section 1%, the stop ball, that is similar to ball 23, becomes effective to prevent retraction of the section 10. Likewise, the section 11 continues to be extended until the sleeve 21, as shown in FIG. 3, forces the pin 20 outwardly to release the latch 18. As the collar 13 starts to be separated from the adjacent collar 15, the stop plunger 22 is forced downwardly by springpressure to position the stop ball 23 in the stop slot 26 of the sleeve 21 (FIG. 4). In the same manner andin successive order, sections 11 and 14 and then lastly the outermost section are fully extended. The traction rollers are always effective to control the position of the antenna; and when they are not erecting or retracting the antenna, they are operating as brakes to maintain the antenna in an erected position. When the antenna is to be retracted, the rollers are reversed in direction of rotation and the outermost section is retracted into the base first. All other inner sections are retained in a locked position until the collar 15 is returned to the base and the corresponding stop plunger is forced upwardly so that the stop ball may be forced out of its stop notch by downward movement of the section 14 that is adjacent to the outermost section.

Obviously, the order of retraction continues from the outermost section to the innermost section until all of the sections are retracted. The operation of the hold down latches and the stop ball mechanism prevents either extension or retraction out of order because of binding, and thereby prevents any section from falling and damaging the antenna system.

Although this invention has been described with respect to a particular embodiment thereof, it is not to be so limited, as changes and modifications may be made therein which are within the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. In an extensible antenna having a plurality of telescopic tubular sections that are to be extended in an inner to outer sequence and to be retracted in an outer to inner sequence, the combination of a hold-down latch and a supporting stop for each of said sections to control sequence of extension and retraction, said latch and said stop for any of said sections being mounted on the periphery of the upper end of that section, a latch seat for each section in alignment with said latch of an adjacent section, means for urging each of said latches inwardly to engage a respective one of said seats in the immediate adjacent inner one of said sections thereby to prevent separation of said adjacent sections, a release pin extending inwardly from each of said latches to the outer surface of the adjacent inner one of said sections, means for urging said supporting stop of any one of said sections inwardly in response to the extension of that section from its fully telescoped position relative to its adjacent outer section, each of said tubular sections having an outer control surface near its lower end comprising a protruding upward facing ledge and a protruding downward facing ledge, said upward facing ledge being in vertical alignment with said release pin of the adjacent outer one of said sections, said downward facing ledge being in vertical alignment with said supporting stop of the same adjacent outer one of said sections, said upward facing ledge of any of said sections in response to substantially full extension thereof engaging said release pin of that one of said sections immediately adjacent to the outer surface of said extended section to force the respective one of said latches outwardly for unlatching said immediately adjacent outer section from the next adjacent outer section, thereby to permit extension of said immediately adjacent outer section, said supporting stop that is mounted on said immediately adjacent outer section being operated inwardly in response to upward movement of this immediately adjacent outer section to engage said downwardly facing ledge of said fully extended section to fasten said extended section to said immediately adjacent outer section, said supporting stop being operated outwardly in response to subsequent full retraction of said immediately adjacent outer section to release said extended section for permitting its retraction, and said respective release pin being forced inwardly in response to downward movement of said extended section to cause said respective latch to engage its seat for latching together said immediately adjacent outer section and said next adjacent outer section.

2. A telescopic antenna having a plurality of telescopic tubular sections with sequence control means for governing the order of extension and the order of retraction of said sections, said sequence control means comprising a collar secured to the upper edge of each of said tubular sections, each of said sections that are telescopically mounted within the outermost one of said sections being a sliding fit within the collar of its adjacent outer section, each of said sections that are mounted within said outermost section having a stop sleeve about its lower end, each of said collars having an upper portion with a smaller inside diameter than that of its lower portion so that the upper portion has a slightly smaller inside diameter than the outside diameter of adjacent inner ones of said sleeves to prevent its passage while said lower portion has sufficiently large inside diameter to accept said adjacent sleeve, the lower inside ledge of said upper portion of said collar engaging the upper edge of said adjacent sleeve to provide an upward stop as said section with said adjacent sleeve is fully extended upwardly, each of said collars that has an upper immediately adjacent one of said sections having a latch with a tooth for engaging said collar of said upper immediately adjacent section and spring means for urging the tooth of said latch inwardly against the outer surface of said upper adjacent collar, each of said collars having a notch aligned vertically with the tooth of the lower adjacent ones of said latches to receive said lower adjacent tooth when the adjacent sections are fully retracted, thereby to fasten said adjacent collars together, a release pin for each latch slidingly mounted radially with reference to said sections to extend from the bottom of said notch that receives said latch to the outer surface of the adjacent inner one of said tubular sections, the upper portion of said sleeve of said adjacent section contacting the inner end of the respective one of said release pins when said inner section is substantially fully extended as determined by said respective upward stop, said sleeve of said adjacent inner section forcing said release pin outwardly in response to said adjacent section being fully extended to release the adjacent latch, thereby to permit extension of said section with said outwardly positioned release pin.

3. In a telescopic antenna according to claim 2, a stop mounted in each of said collars, a control link for each of said stops extending between each of said stops and the lower surface of its collar, means for urging each of said stops inward and its respective link downward, said stops in their inward positions engaging said sleeves about said sections mounted within said respective collars, said stops engaging said sleeve to support said respective sections within adjacent sections, said control links extending below the lower surfaces of their respective collars while said respective stops are engaging said sleeves, each of said control links being operated by engagement with the upper portion of said lower adjacent collar in response to said adjacent collars coming together because of re traction of respective sections, and each of said stops in response to operation of said respective control links moving outwardly to release said respective sections being supported thereby.

4. In a power-driven telescopic antenna, a plurality of tubular telescopic sections, a fastening collar fixed coaxially to the top end of all of said sections except the innermost one, each of said sections having a stop sleeve fixed circumferentially near its lower end, each of said collars having an inside wall with upper and lower coaxial cylindrical portions separated by a ledge, each of said ledges being engageable with the one of said sleeves that encircles said one of said sections that is being guided within said collar to provide a limit stop with respect to extension of that section, said upper cylindrical portion of each collar having the required inside diameter to provide a sliding fit for that inner one of said sections being guided thereby, said lower cylindrical portion of each collar having a greater inside diameter than that of the corresponding one of said upper cylindrical portions to receive loosely said stop sleeve of its inner guided section, a latch rotatively mounted to each of said collars except that collar of the next to the innermost one of said sections, each of said latches having a tooth for pressing inwardly against the outer wall of the upper adjacent collar as the adjacent sections are telescoped together, spring means for urging said tooth inwardly, a notch in each of said outer walls in line with said latch of the adjacent lower one of said collars to be engaged by the tooth thereof, each of said notches being opposite the space to be occupied by said stop band of an inner adjacent one of said sections when it is extended to its upper limit, a latch release pin positioned radially within the wall of each 'of said collars, said pin for each collar being mounted slidingly to extend between said space in said lower portion of said corresponding wall and that position in said notch for receiving said corresponding tooth, each of said release pins being pressed inwardly by said tooth that is being urged inwardly within said notch, and each of said stop sleeves in response to its section being fully extended as determined by said limit stop engaging the inner end of the adjacent one of said release pins to force the adjacent one of said teeth from the corresponding notch, thereby to unlatch adjacent collars for extension of said sections in order from said innermost section to said outermost section as the sections are forced upward.

5. In a telescopic antenna as claimed in claim 4, a stop ball mounted in an opening within the vertical wall of each of said collars, a sliding plunger for each ball mounted vertically in the Wall of said respective collar to contact the surface of said ball that is facing outward relative to the one of said telescoping antenna sections that is being guided within the respective collar, each of said plungers being operated upwardly relative to its respective ball in response to the lower surface of the plunger contacting the upper surface of the outer adjacent one of said antenna sections when the adjacent sections are telescoped together, the face of each of said plungers that is in contact with said corresponding ball while said plunger is operated upwardly being recessed to permit said corresponding ball to be forced outwardly by said respective guided antenna section so that said sleeve of said section that is being guided within the collar can move freely past said ball, means for forcing each of said plungers downwardly in response to separation of the said collars of the said telescoped sections, each of said plungers during its downward travel functioning as a cam to force said respective ball inwardly so that it protrudes beyond the inner surface of said collar within which it is mounted to contact a downwardly facing ledge of said sleeve of said guided respective section while it is fully extended to prevent retraction of said extended section until the adjacent outer section is fully retracted.

References Cited by the Examiner V UNITED STATES PATENTS RICHARD 'W. COOKE, 3a., Primary Exmmner

Claims (1)

1. IN EXTENSIBLE ANTENNA HAVING A PLURALITY OF TELESCOPIC TUBULAR SECTIONS THAT ARE TO BE EXTENDED IN AN INNER TO OUTER SEQUENCE AND TO BE RETRACTED IN A OUTER TO INNER SEQUENCE, THE COMBINATION OF A HOLD-DOWN LATCH AND A SUPPORTING STOP FOR EACH OF SAID SECTIONS TO CONTROL SEQUENCE OF EXTENSION AND RETRACTION, SAID LATCH AND SAID STOP FOR ANY OF SAID SECTIONS BEING MOUNTED ON THE PERIPHERY OF THE UPPER END OF THAT SECTION, A LATCH SEAT FOR EACH SECTION IN ALIGNMENT WITH SAID LATCH OF AN ADJACENT SECTION, MEANS FOR URGING EACH OF SAID LATCHES INWARDLY TO ENGAGE A RESPECTIVE ONE OF SAID SEATS IN THE IMMEDIATE ADJACENT INNER ONE OF SAID SECTIONS THEREBY TO PREVENT SEPARATION OF SAID ADJACENT SECTIONS, A RELEASE PIN EXTENDING INWARDLY FROM EACH OF SAID LATCHES TO THE OUTER SURFACE OF THE ADJACENT INNER ONE OF SAID SECTIONS, MEANS FOR URGING SAID SUPPORTING STOP OF ANY ONE OF SAID SECTIONS INWARDLY IN RESPONSE TO THE EXTENSION OF THAT SECTION FROM ITS FULLY TELESCOPED POSITION RELATIVE TO ITS ADJACENT OUTER SECTION, EACH OF SAID TUBULAR SECTIONS HAVING AN OUTER CONTROL SURFACE NEAR ITS LOWER END COMPRISING A PROTRUDING UPWARD FACING LEDGE AND A PROTRUDING DOWNWARD FACING LEDGE, SAID UPWARD FACING LEDGE BEING IN VERTICAL ALIGNMENT WITH SAID RELEASE IN OF THE ADJACENT OUTER ONE OF SAID SECTIONS, SAID DOWNWARD FACING LEDGE BEING IN VERTICAL ALIGNMENT WITH SAID SUPPORTING STOP OF THE SAME ADJACENT OUTER ONE OF SAID SECTIONS, SAID UPWARD FACING LEDGE OF ANY OF SAID SECTIONS IN RESPONSE TO SUBSTANTIALLY FULL EXTENSION THEREOF ENGAGING SAID RELEASE PIN OF THAT ONE OF SAID SECTIONS IMMEDIATELY ADJACENT TO THE OUTER SURFACE OF SAID EXTENDED SECTION TO FORCE THE RESPECTIVE ONE OF SAID LATCHES OUTWARDLY FOR UNLATCHING SAID IMMEDIATELY ADJACENT OUTER SECTION FROM THE NEXT ADJACENT OUTER SECTION, THEREBY TO PERMIT EXTENSION OF SAID IMMEDIATELY ADJACENT OUTER SECTION, SAID SUPPORTING STOP THAT IS MOUNTED ON SAID IMMEDIATELY ADJACENT OUTER SECTION BEING OPERATED INWARDLY IN RESPONSE TO UPWARD MOVEMENT OF THIS IMMEDIATELY ADJACENT OUTER SECTION TO ENGAGE SAID DOWNWARDLY FACING LEDGE OF SAID FULLY EXTENDED SECTION TO FASTEN SAID EXTENDED SECTION TO SAID IMMEDIATELY ADJACENT OUTER SECTION, SAID SUPPORTING STOP BEING OPERATED OUTWARDLY IN RESPONSE TO SUBSEQUENT FULL RETRACTION OF SAID IMMEDIATELY ADJACENT OUTER SECTION TO RELEASE SAID EXTENDED SECTION FOR PERMITTING ITS RETRACTION, AND SAID RESPECTIVE RELEASE PIN BEING FORCED INWARDLY IN RESPONSE TO DOWNWARD MOVEMENT OF SAID EXTENDED SECTION TO CAUSE SAID RESPECTIVE LATCH TO ENGAGE ITS SEAT FOR LATCHING TOGETHER SAID IMMEDIATELY ADJACENT OUTER SECTION AND SAID NEXT ADJACENT OUTER SECTION.

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