Controlled travel articulated linkage for waveguide and cabling support
BACKGROUND OF THE INVENTION 
     The present invention relates to microwave transmission lines, and more particularly to articulating linkages for supporting waveguide transmission lines for travel through a controlled range of movement. 
     In some microwave rf systems, one piece of equipment is required to be electrically coupled to another piece of equipment in such a way to allow relative physical movement between the two pieces of equipment. An exemplary application is a radar system comprising an extendable antenna group which is electrically coupled to a stationary radar excitation device such as a transmitter and/or receiver. The antenna system may be stowed inside a protective enclosure or silo, and raised to a position above the enclosure to an operating position. 
     Reliable RF connections must be made to the antenna group from the radar excitation device when the antenna group is in the extended, raised position. Waveguide typically comprises the desired rf transmission line. Insofar as applicants are aware, in the past the waveguide lines have been connected to the antenna system after its deployment to the operating position, and vice versa, i.e., the waveguide lines have been disconnected from the antenna system prior to its retraction to the stowed position. This requires physical access to the antenna system and has been relatively time consuming and subject to electrical discontinuity problems. 
     It would be a valuable contribution to the art to provide a system for deploying and stowing an antenna group such that the antenna group is continuously operable, and the disconnection and reconnection procedures are no longer required. 
     Thus, it is a principal object of the present invention to provide a means for maintaining electrical continuity while raising or lowering waveguide transmission and cable lines. 
     Another object is to provide an articulated linkage for supporting an articulating waveguide line through a predetermined range of movement. 
     A further object is provide an articulating linkage for supporting the waveguide through a controlled range of movement to prevent overstressing the waveguide. 
     Yet another object is to provide a relatively strong, yet lightweight, waveguide and cabling support linkage which is adapted to follow the raising and lowering of an antenna group so that disconnection of the waveguide with a resultant loss of waveguide pressure or the necessity of disconnecting cable connectors is not required. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above objects, we have developed a novel articulated linkage which can be connected between an antenna and a relative stationary point for supporting waveguide and electrical cabling, which allows for the raising and lowering of the antenna through a series of fabricated articulated joints. The waveguides are flexible at the joints, and their bend radii are controlled by the joints of the linkage, which are provided with travel limit stops to limit the bend radii. The cabling has service loops at the joints to allow for cable bending. The linkage allows the waveguide and cabling to follow the raising and lowering of an antenna group without disconnection and the resultant loss of waveguide pressure or the necessity of disconnecting cable connectors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the present invention will become more apparent from the following detailed description of a preferred embodiment thereof, as illustrated in the accompanying drawings, in which: 
     FIG. 1 is a simplified cutaway perspective view of a deployable antenna group in a stowed position within a protective silo and coupled to the articulated linkage in accordance with the invention. 
     FIG. 2 is a simplified cutaway perspective view of the antenna group and articulated linkage of FIG. 1 in an extended operating position. 
     FIG. 3 is a partial cutaway perspective view of one joint of the articulated linkage. 
     FIG. 4 is an elevation view of the articulated linkage shown in the stowed configuration (solid lines) and in the extended position (dashed lines). 
     FIG. 5 is a partial cutaway top view of one joint of the articulated linkage. 
     FIG. 6 is a side view of part of the joint of FIG. 5, shown in the straightened position. 
     FIG. 7 is a side view of the joint of the articulated linkage of FIG. 5, shown in a bent position. 
     FIG. 8 is a cross-sectional view of a pivot pin, taken through line 8--8 of FIG. 5. 
     FIG. 9 is a cross-sectional view of an elongated rigid section of the articulated linkage, taken along line 9--9 of FIG. 5. 
     FIG. 10 is a partial side view of the articulated linkage illustrating the connections to the antenna mast and silo wall, and showing in dashed lines the waveguide lines supported by the linkage. 
     FIG. 11 is an enlarged view of the structure indicated by phantom circle 11 shown in FIG. 10, showing the connection between a rigid waveguide section and a flexible waveguide section. 
     FIG. 12 is a cross-sectional view taken along line 12--12 shown in FIG. 11. 
     FIG. 13 is a cross-sectional view taken along line 13--13 shown in FIG. 10. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention comprises a novel controlled travel articulated linkage for waveguide and cabling support. The following description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiment will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications. The present invention is not intended to be limited to the embodiment shown, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 
     An application of the preferred embodiment is illustrated in FIGS. 1 and 2. These perspective cutaway drawings illustrate an antenna group 20 which is stowed within a protective silo enclosure 50 when not in use (FIG. 1), and which is deployed to a position outside the silo for operational use (FIG. 2). Antenna group 20 and mast 25 are mounted by fixtures 45 on elevator system 40 for translation movement along axis 30. Thus, fixtures 45 are adapted to carry the antenna group 20 upwardly or downwardly along axis 30, as the elevator moves up or down. The elevator system for raising and lowering the antenna system is conventional in design and the details thereof form no part of the novelty of the present invention. 
     It is necessary to electrically connect the antenna group 20 to a remotely located radar utilization apparatus (not shown) located outside the silo. The electrical connection includes waveguides for transmission of rf signals, and also typically requires basic electrical power transmission, for example, through cables. In the disclosed embodiment, the waveguide lines are made with S band rectangular waveguides, having nominal cross-sectional dimensions of 11/2 by 3 inches. The present invention overcomes the problem discussed in the Background of providing the required rf and electrical connections at both the stowed position and the extended position. 
     In accordance with the invention, an articulated linkage 100 supports the waveguide and cables necessary for continuous electrical connection of the antenna group 20 to the radar utilization device. The linkage 100 is supported at end 110 by connection to a fixed location at one wall of the silo 50, and at end 120 to the base of the mast 25 which supports the antenna group 20. The linkage 100 is adapted to follow the up and down movement of the antenna group 20 as it is deployed to or from the extended position. Thus, FIG. 1 illustrates the antenna group 20 in its stowed position, and FIG. 2 illustrates the antenna group 20 in the deployed position. It is noted that a pair of silo doors 55 are adapted to open to allow the deployment of the antenna group 20. 
     Referring now to FIG. 4, the articulated linkage 100 is disclosed in the stowed position (solid lines) and in the extended position (dashed lines). In order to accommodate the up/down travel to the antenna group, the linkage comprises three flexible joints 130,140 and 150. The three joints are connected by extended rigid sections 160,170. The drawing is not to scale, as the extended rigid sections 160,170 may typically be quite long. In the preferred embodiment, section 160 is about 181 inches in length between pivot connections to the adjacent joints, and rigid section 170 is about 71 inches in length between corresponding pivot connections. The individual links of each joint are 24 inches in length in the preferred embodiment. 
     Linkage 100 carries two extended waveguide lines (not visible in FIG. 4), each of S band size (11/2 by 3 inches in cross-section). The waveguide runs comprise lengths of rigid waveguide carried in the extended rigid sections 160,170. The waveguide runs further comprise lengths of flexible waveguide carried in the respective joints. 
     As is known to those skilled in the art, the waveguide runs may be pressurized to prevent the admission of moisture or other contaminants into the waveguides, which could otherwise lead to impairment in performance or equipment failures. To maintain pressurization the waveguide lines must be substantially airtight. Thus, in maintaining pressurization and low loss electrical continuity, it is important that the waveguide runs not be subjected to stresses which will cause the waveguide, and particularly the flexible sections, to crack or break. As will be described in greater detail below, the linkage joints are adapted to limit the amount of bend of the flex waveguide at each joint to prevent overstressing the flexible waveguide. 
     Exterior cable support channels are provided on each side of the rigid sections of the linkage to support cable bundles 250; service loops are formed at the joints of the linkage. It is noted that the respective cable bundles 250 are split into two sub-bundles 250a, 250b adjacent joint 130 as shown in FIG. 4. Each sub-bundle 250a forms an &#34;s&#34; shaped loop, and is tied to link 132 by cable fastener 251. Each sub-bundle 250b is looped free of the joint 130. Separating the cable bundles into sub-bundles facilitates connection of the cables at the antenna, and also facilitates bidirectional joint movement. 
     Referring now to FIG. 10, a side view of the articulated linkage is shown, with the antenna group in the stowed position. Two side-by-side waveguide transmission lines are supported within the linkage in the disclosed embodiment. One waveguide line comprising waveguide sections 210a, 200a, 210b, 200b, 210c is shown in FIG. 10, and is coupled at flange 63 to a feed waveguide 300 running from the radar utilization device (not shown). At the other end 120 of the linkage, the waveguide line 200c is coupled at support plate 27 of FIG. 13 near the base of the antenna mast 25 to a feed waveguide 350 which extends to the feed port 360 for the antenna group. 
     Bracket 28 moves with the elevator, carrying the linkage 100 along with it. Generally, the linkage 100 comprises flexible joints 130,140 and 150, which couple together rigid, elongated sections 160,170. In the embodiment shown, the ends of the rigid sections comprise clevises which are connected to the joints by pivot pins to allow pivotal movement. The joints themselves comprise two relatively short rigid link units which are pivotably connected by pivot pins. 
     The rigid sections 160,170 of the linkage each comprise a pair of elongated u-shaped channel members formed from extruded aluminum. These channel members define the sides of the elongated sections. A clevis member is disposed at each end of the elongated members. The clevis members are the structural elements to which the channel members are bolted. For example, clevis 166 is typical of a clevis usable in the invention, and is shown in FIG. 5, with further details thereof in FIGS. 6 and 9. Clevis 166 comprises a pair of side pieces 166a,166b, upper and lower lateral strengthening plates 166c,166d extending between the side pieces, and a lateral upright waveguide support flange 166e, all of which may be fusion welded to form the clevis. Respective ends of the side pieces are bored to accept the pivot bolts 138a connecting the joints to the rigid sections. Each side of each clevis is also provided with six bores to accept six fastening bolts 169 for fastening the channel members 164,165 to each respective side of the clevis. 
     Top and bottom plates are bolted adjacent each end of the rigid sections 160,170 to the channel members 164,165 to provide additional tortional rigidity. The fastening bolts are passed through corresponding bores formed in the plates and channel members. In the disclosed embodiment, these top and bottom plates are approximately 17.5 inches long and 8 inches wide, and are fabricated from sheets of aluminum about 0.190 inches in thickness. 
     The rigid sections are therefore fabricated to provide a rigid and strong, yet lightweight, support structure. The joints of the linkage are similarly constructed to provide lightweight, structural elements. As shown in FIGS. 3 and 10, joint 130 comprises two rigid link units 131,132. One end of link unit 131 is pivotably coupled to bracket 28 attached to the bottom of the mast 25 (FIG. 10) by a pair of pivot bolts each secured by a threaded nut. Similarly, one end of link 32 is pivotably coupled to end 171 of elongated rigid section 170 by a pair of pivot bolts each secured by a threaded nut. 
     Link 131 is typical of the link units of the joints, and comprises a pair of side members 131a, 131b, and top member 131c and bottom member 131d (not shown in FIG. 3). Each of the four members is fabricated from aluminum alloy plate material in this embodiment. The top and bottom members 131c,131d, respectively, add strength and rigidity, and are joined to the respective side members 131a,131b by conventional means, such as fusion welding. To lessen the weight of the linkage, the top and bottom members 131c,131d have circular openings formed therein. 
     Four lateral support truss members 132h are secured by fusion welding perpendicular to the side members and the top and bottom members of the link units, two adjacent each end of the link unit. For example, the truss members 132h of link unit 132 are shown in break-away view in FIG. 3. The truss members add to the strength and rigidity of the link units. A large open channel of rectangular cross-section is defined by the truss members and the bottom members of the link units, and the two flexible waveguides 210c are carried in this channel. 
     The flexible waveguide sections employed in the preferred embodiment are each six feet in length, and are available from the Airtron Division of Litton Systems, Morris Plains, N.J., as part number 123718. As will be appreciated by those skilled in the art, these flexible waveguide sections are limited in their flexibility, since they are formed from accordion-like sections of cartridge brass or similar material. The sections are subject to metal fatigue caused by undue stress and movement, which can result in breaks or other failures in the flex waveguide section. Such breaks would impair the electrical performance of the waveguide transmission link, and could lead to loss of waveguide pressurization. 
     An important aspect of the invention is the provision of a means for limiting the amount of bend of the joints of the linkage so as to prevent damage to the flex waveguide members carried by the joints. The travel limit means is illustrated, for example, in FIG. 3 with respect to joint 130. The side members 132a,b are provided with ears 132e extending from either end thereof, and are bored to form a suitably sized opening to receive pivot bolts 138a. The bolts 138a provide pivot points for allowing link unit 132 to pivot freely about the end 171 of rigid section 170 and about link unit 131. 
     The side members 131a,b of link unit 131 are provided with tapered ends 131e which extend from either end thereof and having suitably sized openings to receive corresponding pivot bolts 138a. The external width (13.54 inches) of link unit 131 is slightly smaller then the internal width dimension (13.62 inches) of adjacent link unit 132 between ears 132e, so that ends 131e of link unit 131 fit between ears 132e of link unit 132, allowing pivot bolts 138a to be passed through the corresponding openings in ends 131e and ears 132e and fastened with nuts 138b. Thus, a pivotable connection is made between the link units 131, 132 of joint 130. 
     A similar pivotable connection is provided between mounting bracket 28 coupled to the base of the antenna mast and link unit 131. Bracket 28 comprises respective side members 28a,28b which are spaced apart (13.62 inches) so as to receive the tapered ends of the side members of link unit 131. Pivot bolts 138a are passed through corresponding bores formed in the side members of brackets 28 and link unit 131. 
     Pairs of travel limit pins 131f and 131g are provided through respective sides of the tapered ends 131e of link unit 131. These pins cooperate with semicircularly relieved areas 28d,132g in the respective ear sections of the side members of bracket 28 and link unit 132 to limit the pivotal excursions about pivot pins 138a. Each of the pivots of link unit 131 is constrained for maximum excursion of about 46° in either direction from the straightened position for the joint. The maximum allowable angular excursions in one direction are illustrated in FIG. 3. It has been found that limiting the bend to less than 46° for the disclosed joint configuration results in a rugged linkage able to withstand repeated movement. 
     In the preferred embodiment, pins 131f and 131g are fabricated from 0.500 inch diameter steel pins. The pins at the maximum travel contact corresponding semicircular, relieved areas of the ends of side pieces 28a,b and 132a,b. In a similar fashion, travel limit pins 172f are placed at appropriate positions adjacent the tapered ends 171 of the sides of the clevis comprising the end of extended rigid section 170. These pins 172f limit the maximum angular excursion of the link unit 132 to about 46° from either side of the axis 173 of the rigid section 170. The pins 172f cooperatively engage semicircular relieved areas 132g formed in side members 132a and 132b adjacent ears 132e. 
     Joints 140 and 150 are similar in construction to joint 130, except that travel about the pivot points is constrained to allow travel in substantially only one direction from the straightened position. FIGS. 5-9 illustrate articulated joint 150 in further detail. In a manner similar to connection of joint 130 to mast base bracket 28, joint 150 is pivotally coupled to bracket 60, affixed to wall 52 of the silo. As shown in FIG. 6, rigid waveguide member 305 is connected to flexible waveguide 210a at flanges 211,306 by conventional connections. A support plate 63 supports the flanges at their connection. Waveguide 305 comprises a waveguide transmission line coupled to the radar utilization device (not shown). The opposite end of the flexible waveguide section 210a is terminated in a mounting flange 212. Connection is made between flex waveguide 210a and rigid waveguide 200a by bolting together the respective flanges 212,201. As will be described in connection with FIG. 10 et sequence, the connection of the two flanges is supported by waveguide support flange 166e of the clevis 166 comprising rigid section 160. 
     Joint 150 is constrained for movement in substantially only one direction away from the straightened position shown in FIG. 6, i.e., away from silo wall 52. The travel limit stop pins 151f in link unit 151 and the corresponding end sections of the adjacent link unit 152 are cooperatively configured so that very little joint movement (about 3°) is allowed in the direction toward the silo wall 52. This is accomplished by appropriate relative location of the travel limit pins 151f in unit 151 in relation to the corresponding edges of the adjacent link unit 152. 
     FIG. 7 shows joint 150 in the fully bent position away from silo wall 52. As indicated, the respective travel stop pins 151f limit the maximum angular excursion in the direction away from the wall to about 46°. In the direction toward the wall, the angular excursion is limited to about 3°, to prevent the linkage 100 from contacting the wall. This non-symmetrical travel limit is accomplished by the non-symmetrical configurations of the ends of side member 152a,152b of link unit 152. Instead of fashioning symmetrical ear members as employed in link unit 132, the corner of the ends of side members 152a,b adjacent the silo wall are squared off, while the other corners are tapered. 
     FIG. 8 is a cross-sectional view of a shoulder bolt and self-locking nut which are employed in the preferred embodiment as the joint pivot 138a and locking member 138b. The shoulder bolt is fitted with a flat washer 138c and inserted through corresponding bores formed in the overlapping ear sections of the links. As indicated in FIG. 8, the side members through which the bolt is inserted are reinforced around the pin opening. 
     FIG. 9 is a cross-sectional view of the elongated rigid section 160 of the linkage, taken along line 9--9 of FIG. 5. The flanges 201 of the rigid waveguide sections 200a (FIG. 10) are visible in the cross-sectional view, secured to the lateral support flange 166e (FIG. 5) of the clevis 166 (FIG. 5). Elongated channel members 164,165 are bolted to the outside of the respective side members 166a,166b comprising clevis 166. The channel members 164,165 provide support for electrical cable bundles 250 which are fastened in the respective channels by straps 207. It will be noted that the joints 130,140,150 are not provided with corresponding channel members for carrying the electrical cable bundles. As illustrated in FIG. 4, the cable bundles are looped free of the joints in service loops, so that the cables do not bind the joints and are not themselves overly stressed by the movement. 
     FIG. 9 shows the strapping of the cable bundle 250 into the channel defined by the channel members 164,165 of rigid section 160. A strap tightener 208 is employed to tighten the strap 207, passed through strap openings (not shown) formed in the sides of the channel member, about the cable bundle 250. 
     In the side elevation view of FIG. 10, one of the waveguide lines carried by linkage 100 is shown in dashed lines. The waveguide carried by the linkage is coupled at the silo wall to rigid waveguide 305, which is coupled to the radar utilization device (not shown). Thus, flex waveguide section 210a is mated to waveguide 305 via corresponding flanges, bolted together and to support plate 63 comprising mounting bracket 60 (see also FIG. 6). The other end of flex waveguide 210a is fastened via corresponding flanges to rigid waveguide section 200a. The connection of these two waveguide sections is supported by the waveguide support flange 165e of clevis 164,165 of the rigid section 160 (see FIG. 11). 
     Due to the length of the rigid section 160, the rigid waveguide section 200a may be comprised of a plurality of connected rigid waveguide sections; one connection between two such rigid sections is such in the cutaway section of rigid section 160 shown in FIG. 10. 
     The rigid waveguide section is in turn coupled to flex waveguide section 210b. FIGS. 11 and 12 illustrate the details of the connection between waveguide sections 200a and 210b. The waveguide members are each terminated in corresponding waveguide flanges 201,211. The flanges are of conventional design, with a fastener opening pattern formed around the periphery thereof. A plurality of threaded fasteners 203 are employed to fasten together respective mating surfaces of the waveguide flanges. The threaded fasteners also extend through a corresponding opening pattern formed in waveguide support flange 165e. 
     FIG. 12 is a cross-sectional view illustrating the support flange 165e and the fastened positions of the waveguide flanges. As shown in this figure, the support flange is provided with a T-shaped opening 165f. The two flex waveguides 210a may be inserted sideways one after the other into opening 165f and then rotated 90° to their inserted positions shown in FIG. 12 in the truss 165e. The corresponding flanges of the rigid waveguides 200a are then brought into position against the flanges 211, and the threaded fasteners inserted through the corresponding opening patterns in the flanges 201,211 and support flange 165e, and secured in position with nuts. 
     In a similar fashion as shown in FIG. 10, the flex waveguide 210b is also coupled to rigid waveguide section 200b at the waveguide support flange of the corresponding clevis 176 for the adjacent end of rigid section 170. The opposite end of rigid waveguide 200b is fastened similarly to flex waveguide 210c at a corresponding waveguide support flange of clevis 176. Finally, flex waveguides 210c are connected to rigid waveguide sections 350 which run through the antenna mast from the base to a feed port connection 360 for the antenna group (not shown in FIG. 10). 
     FIG. 13 is a cross-sectional view taken along line 13--13 of FIG. 10, and illustrates the connection of the flexible waveguide 210c to corresponding rigid waveguide 350 at the base of the antenna mast 25. Flange 27 supports the connection of the corresponding waveguide flanges for waveguides 210c and 350. It is noted that the flange 27 must be adapted to support the weight of the linkage and the supported waveguide and cables. 
     The preferred embodiment of the linkage is adapted to accommodate a maximum excursion of the antenna mast of about 496 inches above the stowed position exhibited in FIGS. 1 and 10. In this embodiment, the rigid link 160 in the stowed position is disposed approximately parallel to the antenna mast. Rigid waveguide sections 200a,200b are respectively 78.5 inches and 47 inches in length. Flex waveguides sections 200a,200b,200c are each six feet in length. The joint travel limit means are adapted to limit the minimum joint bend radius to approximately two feet, i.e., the joints are constrained to bend radii larger than two feet. This minimum bend radius is cooperatively selected in accordance with the flexibility and of the flex waveguide, to prevent overstressing the waveguide. The specific dimensions and bend radii employed in the described embodiment are, of course, specifically adapted to the particular application described herein. 
     It is understood that the above-described embodiment is merely illustrative of the many possible specific embodiments which can represent principles of the present invention. Numerous and varied other arrangements can readily be devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention.