Abstract:
An extendable column consisting of a plurality of axially elongated rigid structural sections nested within one another. Each section includes a plurality of screws running the length thereof and rotatably attached therein. The next inner section includes threaded lugs oriented to threadingly engage the screws thus resulting in extension or retraction of the column upon rotation of the screws. The screws of each section are selectively rotated by a motor and an engagement mechanism.

Description:
ORIGIN OF THE INVENTION 
     The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat. 435; USC 2457). 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an extendable column and more particularly to an extendable column utilizing screws to extend and retract a plurality of axially elongated sections which telescope within each other. 
     In the design of a large deployable parabolic antenna for space application a need arose for an extendable column capable of extending up to ten times its initial length. This capability is necessary to enable the antenna to be collapsed for transport aboard the space shuttle. 
     A variety of extension designs were investigated, including systems using cables, hydraulics and airjacks, but proved inadequate. In space application the use of hydraulic or airjack systems is precluded by the risk of leaks and subsequent system failure. Cable systems are complex and prone to failure especially in a weightless environment where opposing sets of cables are required. 
     The present invention utilizes screws to extend sections which telescope within each other. Each section includes a set of screws interconnected by a chain and sprockets to enable simultaneous rotation thereof. Rotation of the screws in one section results in telescoping the next inner section having threaded bosses engaging the screws. The section screws are driven by a common motor being selectively engaged therewith by clutch mechanisms to extend the column to the desired length. 
     The use of screws to interface the extended section provides excellent structural integrity, low compliant joints, and zero backlash since once extended, the sections are bolted tightly together. Also, the column is capable of supporting both compressive and tensile loads during extension and retraction affording a high degree of safety in operation under loaded conditions. 
     An object of the present invention is an extendable column capable of extending up to ten times its original length. 
     A further object of the invention is an extendable column with low compliant joints and zero backlash. 
     A further object of the invention is an extendable column capable of supporting loads during extension and contraction. 
     A further object of the invention is an extendable column having a plurality of structural sections which telescope within each other having screws threadingly engaging an adjacent section to extend or retract the column by rotation of the screws. 
     Another object of the invention is an extendable column which yields the foregoing advantages and which utilizes a single motor and a plurality of clutches to selectively extend or retract the structural sections of the columns. 
     Another object of the invention is an extendable column which yields the foregoing advantages and which utilizes chains and sprockets to drivingly connect the motor with the clutches. 
     Other objects and advantages of the present invention will be readily apparent from the following description and drawings which illustrate preferred embodiments of the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention involves a power operated telescoping column. The column consists of a plurality of axially elongated rigid structural sections which nest within one another including an outermost, an innermost and a plurality of intermediate sections. The outermost and each intermediate section includes a plurality of screws extending longitudinally therealong and attached thereto. Each screw is rotatable about its axis of symmetry. Sprockets are rigidly attached to the screws and interconnected by a chain to provide simultaneous rotation of the screws of a single section. Threaded lugs are attached at the base end of the section and oriented to engage the screws of the next outer section. The column is extended and rotated by selectively rotating the screws of a section with a motor and an engagement mechanism. As the screws rotate, the next inner section, being threadingly engaged thereto, is extended. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary side view of an extendable column according to the present invention; 
     FIG. 2 is a fragmentary side view similar to FIG. 1 showing the motor and engagement mechanisms of the present invention; 
     FIG. 3 is a perspective view of a screw engager of the present invention; 
     FIG. 4 is a fragmentary base end view similar to FIG. 1 showing a motor, sprocket and chain arrangement of the present invention; 
     FIG. 5 is a fragmentary side view of an intermediate section of the present invention; 
     FIG. 6 is a tip end view of the intermediate section of FIG. 5; 
     FIG. 7 is a base end view of the intermediate section of FIG. 5; 
     FIG. 8 is a detail view showing the corner of the interface of two sections in the fully extended position; and 
     FIG. 9 is a cutaway view of the engager of FIG. 3. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the nesting arrangement of the axially elongated sections of the preferred embodiment is shown. For clarity portions of innermost section 30, intermediate sections 31 and 33, and outermost section 34 have been omitted from FIG. 1. Also, the motor and clutch mechanism, being shown in detail in FIG. 2, have been deleted from FIG. 1 for clarity. As shown, sections 30 and 31 are in the fully extended position while sections 32 and 33 are in the fully retracted position. Section 34 is the outermost section composing the base of the column and section 30 is the innermost section composing the tip of the column. 
     The preferred embodiment, and each section thereof, is equilaterally triangular in cross-section and forms a right triangular configuration. FIG. 1 views one side or face of the column. Diagonal braces 49 extend diagonally across each face of each section, however, for clarity are shown only on section 32 of FIG. 1 and section 31 of FIG. 5. 
     Referring now to FIG. 2, the drive motor and clutch mechanism of the preferred embodiment are shown. The outer section 34 and the intermediate sections 31, 32, and 33, each are associated with a separate set of chains and sprockets and a clutch and receiver similar in construction from section to section. Similar parts are hereinafter and in the drawings assigned identical numbers plus a letter to associate them to the corresponding section. The letters a, b, c, and d correspond to sections 31, 32, 33 and 34, respectively. For example, part 12a, a clutch, is similar to part 12c, but part 12a is associated with and acts upon section 31 and other &#34;a&#34; parts, whereas part 12c is associated with and acts upon section 33 and other &#34;c&#34; parts. Hereinafter reference to a numeral without the corresponding letter is reference to all the similar parts, e.g., &#34;clutches 12&#34; refers to &#34;clutches 12a, 12b, 12c and 12d.&#34; 
     Drive motor 10 turns motor shaft 11 and shaft sprockets 15 attached thereto. Clutch sprockets 14 are rotatably attached to clutches 12 and are drivingly interconnected to shaft sprockets 15 by primary chains 16. Engagers 13 are drivingly connected to clutches 12. 
     Screws 17, 21, and 24 are positioned at the corners of and extend the length of each section. Sprockets 18, 19 and 27 are fixedly attached at the base end of and share axes of symmetry with screws 17, 21 and 24 respectively. Sprockets 19 and 27 are drivingly interconnected to sprockets 18 by chains 20. Screws 17 extend past the base end of the section to mate with engagers, 13. As shown in FIG. 2, screws 17 extend to meet receivers 23 of engagers 13. 
     Refer now to FIG. 3 which shows screw 17 removed from receiver 23. Receivers 23 are hollow for receiving the end of screws 17 and have tapered edges 24 and slots 25 for receiving pins 22 protruding from screws 17. When screw 17 and receiver 23 are mated, the rotation of engager 13 causes screw 17 to rotate through the engagement of receiver 23 and pins 22. 
     Refer now to FIG. 9, a cutaway view of an engager 13 is shown. Receiver 23 is attached to plate 37 which may slide but not rotate with respect to engager 13 to compress spring 38 positioned inside engager 13. The spring affords the system a degree of flexibility to account for possible variations in screw 17 length or position. Additionally upon retraction of a section, initially, pins 22 may not line up with slots 25 and may contact receiver 23 at the upper edge thus depressing spring 38. Subsequently, upon rotation of engager 13 and receiver 23 relative to screw 17, pins 22 will slip into slots 25 to mate screw 17 with receiver 23. 
     Referring back to FIG. 2, note that as shown, all screws 17 are mated with engagers 13 and the column is fully retracted except for the innermost section 30 which is partially extended. 
     Screw 17a is drivingly connected to screw 21a by drive sprocket 18a, driven sprocket 19a and secondary chain 20a. Screws 17a and 21a engage threaded lugs 45 of section 30. Similarly, the innermost and each intermediate section in the column has threaded lugs 45 to engage the screws of the corresponding next outer section. 
     Refer now to FIG. 4 which shows a base end view of the sprockets, chains, and drive motor 10. Motor 10 may be positioned at any convenient location either inside or outside the boundaries of the column. Drive chains 16 drive sprockets 14. The other chains shown are secondary chains 20 which interconnect the sprockets of each of sections 31, 32, 33 and 34. 
     Refer now to FIG. 5, there being shown intermediate section 31. Intermediate sections 32 and 33 are similarly constructed to section 31. Innermost section 30 is similarly constructed to section 31, but lacks screw mechanisms. Outermost section 34 is similarly constructed to section 31, but lacks threaded lugs 45. 
     Framing members 61a, 62a, and 63a are semicircular tubes concave toward the geometric center of the section. Framing members 64a, 65a and 66a are angle beams rigidly attached to framing members 61a, 62a and 63a of the tip end of section 31 by riveting, welding, or other suitable means. Similarly framing members 67a, 68a and 69a are angles riveted or welded or otherwise rigidly attached to framing members 61a, 62a, and 63a at the base end of section 31. The above mentioned framing members are connected to form a right triangular configuration. 
     Plates 46a (FIG. 6) and lugs 45a (FIG. 7) are attached to framing members 61a, 62a and 63a at the tip and base ends respectively to provide plane surfaces perpendicular to the framing members 61a, 62a and 63a. 
     Threaded screws 17a, 21a, and 24a extend the length of section 31 and extend through and are rotatably attached at the tip end to plates 46a and extend through and are rotatably attached at the base end to lugs 45a. 
     Sprockets 18a, 19a, and 27a are rigidly attached to and share an axis of rotation with screws 17a, 21a and 24a respectively and are interconnected by chain 20a. 
     FIG. 6 shows a tip end view of section 31. Note the triangular configuration of framing members 64a, 65a and 66a. Also note the orientation of the semicircular framing members 61a, 62a and 63a concave toward the center of section 31. Recirculating ball nuts 48 enable low friction rotation of screws 17a, 21a and 24a within plates 46a and preclude the slipping of said screws therethrough. 
     FIG. 7 shows a base end view of section 31. Note threaded holes 52a in lugs 45a. Holes 52a of lugs 45a threadingly engage screws 17b, 21b and 24b of the next outer section, intermediate section 32. Base end bushings 50a enable low friction rotation of screws 17a, 21a and 24a within lugs 45a. Screws 12a, 21a and 24a are precluded from sliding through lugs 45a. 
     FIG. 8 illustrates the engagement of hole 52 of lug 45 of section 31 with screw 21b of section 32. Here, section 31 is shown in its fully extended position relative to section 32 and lug 45 is held tight against plate 46. A polished rubbing block 55 is attached to plate 46 to provide a low friction contact and alignment between sections 31 and 32. 
     Referring back to FIG. 2, in operation of the preferred embodiment of the invention, the column initially is in the fully collapsed position. This is the configuration of FIG. 2 except with lugs 45 of section 30 being in contact with lugs 45 of section 31. Motor 10 turns motor shaft 11 and drive sprockets 15 connected thereto thus, sprockets 14 are turned via chains 16. 
     Initially, clutches 12 are not engaged and screws 17 are mated with receivers 23. To initiate extension of the column clutch 12a is engaged thus turning screws 17a via engager 13a, receiver 23a and pins 22. Drive sprocket 18a turns chain 20a which turns sprocket 19a and screw 21a. 
     As screws 17a and 21a are turned, lugs 45 and section 30 are raised. When section 30 becomes fully extended, similar to the configuration of FIG. 8, clutch 12a is disengaged. Clutch 12b is now engaged resulting in the raising of section 31 in the above described fashion. Note that as section 31 is raised, screw 17a, being prohibited from sliding relative to section 31 by nuts 48a, is withdrawn from receiver 23a. When section 31 becomes fully extended, clutch 12 is disengaged. Each of the sections is thus raised in this fashion until the desired degree of extension is obtained. The selective clutch engagement may be accomplished manually or by the utilization of switches (not shown) positioned to activate clutch engagement and disengagement upon reaching a desired section extension. 
     The preferred embodiment of the invention as described hereinbefore includes five sections of equal length and being triangular in cross-section. These characteristics are illustrative only and do not limit the invention thereto. Any number of sections of any length may be used and the utilization of ten columns of equal length will accomplish an object of the invention of extensibility to ten times the original length. Any cross-section is possible, i.e., square, circular, rectangular, etc. In addition, the size of the sprockets may be varied to obtain the desired speed of erection or appropriate torque to supply desired lifting force. Recirculating ball type lugs and bushing and ball threaded screws may be used in place of conventional threads within the scope of the invention. 
     Semicircular tubing and angles were used as structural members for purposes of illustration. The invention is not limited thereto and any suitable shape, size or material of structural member may be used. 
     The above described description and drawings are only illustrative of a preferred embodiment which achieves the objects, features and advantages of the present invention, and it is not intended that the present invention be limited thereto. Any modifications of the present invention which come within the spirit and scope of the following claims are considered part of the present invention.