Abstract:
A hook cable support assembly is arranged to support a hook cable above a runway surface for arrestment of an aircraft having a tail hook. The operating mechanism of the support assembly is mounted to the detachable cover of an enclosure. A cable support block holding the hook cable can be rotated to lower the cable into a runway slot for non-arrested landings and can be depressed downward upon impact by an aircraft wheel. Support block rotation is controlled by a pneumatic cylinder and compression spring combination acting via a four-bar linkage. Support block upward recovery following depression is controlled by torsion springs. The cylinder and compression and torsion springs are mounted to the lower surface of the cover and function as a self-contained mechanism isolated from mechanical contact with the enclosure. With this cover-mounted configuration, the operating mechanism of the cable support assembly is removable for service or replacement by detachment of the cover.

Description:
SEQUENCE LISTING 
     (Not Applicable) 
     RELATED INVENTIONS 
     (Not Applicable) 
     FEDERALLY SPONSORED RESEARCH 
     (Not Applicable) 
     BACKGROUND OF THE INVENTION 
     This invention relates to arresting systems arranged to arrest the travel of aircraft during landing and, more particularly, to arrangements for supporting and lowering a cross-runway cable provided for engagement by the tail hook of an aircraft while landing. 
     A variety of aircraft arresting systems have been proposed and implemented. Systems particularly suited for arresting of military aircraft equipped with an integral tail hook typically provide a cable stretched across a landing surface for engagement by the tail hook. In some applications a runway is used for both arrested landings and non-arrested landings. For such use, cable support assemblies have been adapted to enable the cable, while stretched across the runway, to be alternatively positioned a few inches above the landing surface or lowered below the landing surface into a slot formed across the runway. When positioned above the runway, the cable is subjected to being run over by the wheels of aircraft and depressed downward. Also, the support members or blocks which position the cable above the landing surface may themselves be impacted by aircraft wheels and provision is typically made to permit the support blocks to be depressed upon impact. 
     Thus, for a retractable cable system, the support blocks must be implemented in a manner permitting both automated lowering of the cable into a runway slot, and resilient depressing of the support blocks while the cable is in its raised condition, Prior systems have employed cable support assemblies located in enclosures sunk below the landing surface and having covers which are flush with the landing surface and cable support blocks extendable upward through openings in the covers. Arrangements of springs and support block positioning and lowering members of significant complexity have typically been mounted within the enclosures and arranged for remote activation via fluid controlled piston configurations. 
     FIGS. 1 and 2 illustrate basic components of a previous support block assembly produced by the assignee of the present invention. The components of the assembly are mounted to the sides and base of an enclosure, which is not shown. As represented in FIG. 1, the support arm assembly mounted within the enclosure beneath the landing surface is urged upward by the torsion spring, so as to cause the support block to protrude above the landing surface. The support block is constructed of durable rubber material and has a hole for cable insertion and a cut enabling the cable to be pulled from the support block when hooked by a landing aircraft. When an aircraft wheel strikes the support block, the torsion spring permits the support arm and support block to be depressed downward during passage of the wheel and then returned to the position shown in FIG.  1 . FIG. 2 shows the support block lowered for non-arrested landings. Upon activation of the air cylinder the shaft of the piston overcomes the pressure provided by the torsion spring, so as to tilt the support arm downward from horizontal. At the same time, a short control cable is pulled around a pulley and trips a latch arrangement to permit springs to tilt the support block so that an arresting cable held by the support block is lowered into a slot extending across the runway. From the FIG. 2 lowered-cable position, the support block may be returned to its FIG. 1 position by release of piston pressure in the air cylinder, to permit the torsion spring to move the support arm to a horizontal position. At the same time, the support block is returned to its former upright position and latched in place. While the mechanism of FIGS. 1 and 2 continues to provide excellent performance in runway installations, it is desired to provide improved configurations. 
     Objects of the present invention are, therefore, to provide new and improved hook cable support assemblies and such assemblies having one or more of the following advantages and characteristics: 
     operating mechanism of support assembly mounted to hinged enclosure cover for ease of servicing and removal; 
     support arm assembly rotatably mounted to detachable enclosure cover; 
     all other active components of support assembly mounted to support arm assembly; 
     control of support block depression during aircraft roll over, by torsion spring carried on enclosure cover; 
     control of support block tilt for cable raising, by compression spring carried on enclosure cover; 
     increased time between repairs by use of separately functioning torsion spring and compression spring assemblies; and 
     long term cost reduction by ease of installation, maintenance, and component and assembly replacement. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a hook cable support assembly, for an aircraft arresting system, comprises the following: 
     an assembly enclosure having a detachable cover with a pivot structure mounted to the cover; 
     a support arm supported below the cover by the pivot structure and rotatable about an axis thereof; 
     a torsion spring device concentric to the pivot axis and arranged to rotate the support arm upward to a static alignment; 
     a cable support block mounted to the support arm and rotatable between raised and lowered positions; 
     a four-bar linkage coupled between the support arm and the support block and operable to rotate the support block; 
     a cylinder/piston device coupled between the support arm and the four-bar linkage and operable on the four-bar linkage to rotate the support block to its lowered position; and 
     a compression spring device mounted between the support arm and the four-bar linkage and arranged to cause the linkage to rotate the support block to its raised position in the absence of action by the cylinder/piston device to rotate the support block to its lowered position. 
     Pursuant to the invention, the detachable cover and subsequent components referred to above form an operating mechanism removable from the enclosure by detachment of the cover and associated air supply hose. 
     For a better understanding of the invention, together with other and further objects, reference is made to the accompanying drawings and the scope of the invention will be pointed out in the accompanying claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a prior cable support mechanism with cable support block raised. 
     FIG. 2 shows the FIG. 1 mechanism with cable support block lowered. 
     FIG. 3 is a side view of an embodiment of a hook cable support assembly in accordance with the invention, with cable support block raised. 
     FIG. 4 is a side view of the FIG. 3 embodiment with the lower enclosure removed and cable support block lowered. 
     FIG. 5 is a plan view of the FIG. 3 embodiment with the lower enclosure removed. 
     FIG. 6 is an end view of the FIG. 3 embodiment with the lower enclosure removed. 
     FIG. 7 corresponds to FIG. 3, with the cable support block displaced downward. 
     FIG. 8 shows the enclosure cover partially opened, raising the operating mechanism. 
    
    
     DESCRIPTION OF THE INVENTION 
     FIG. 3 is a side view of a hook cable support assembly  10  in accordance with the invention. Upon arresting system installation, assembly enclosure  12  is sunk into the runway or other landing surface, with the upper surface of cover  14  level with the landing surface represented by dashed line  18 . As shown, assembly enclosure  12  has a detachable cover  14 . Enclosure  12  and cover  14  are shown in section, with the portion toward the viewer removed for purposes of illustration. Cover  14  is hinged via hinge pins  16  to permit the main portion  14  to be rotated upward to the left, as shown in FIG.  8 . Cover portion  14   a , shown to the left, remains bolted to enclosure  12  when the main portion is rotated upward as in FIG.  8 . For removal of the cover from the enclosure  12 , main cover portion  14  and portion  14   a  may be detached by removal of bolts, of which bolt  15  is typical (the openings for placement of the bolts are represented in the top view of FIG.  5 ). To the right in FIGS. 3 and 8 is shown an additional cover section  17 , which is separate from cover portions  14  and  14   a.    
     In FIG. 3 cable support block  20  is in a raised position suitable for supporting an arresting cable or pendant (not shown) by insertion in the circular opening  22  in the block. Cable support block  20  may be formed of a neoprene rubber compound or other suitable material and includes a cut or slit  24  which permits removal of the cable when engaged by the tail hook of an aircraft during landing. Block  20  also includes a structural base  26  to be described further below. FIG. 4 is similar to FIG. 3, except that cable support block  20  has been rotated to a lowered position and the cover  14  has been detached from enclosure  12 , which is not shown. With block  20  in its lowered position of FIG. 4, an arresting cable inserted into opening  22  would be lowered into a cross-runway slot  34 , shown in cross section in FIG.  3 . FIGS. 5 and 6 are respective plan and end views of the FIG. 3 support assembly with block  20  rotated to its raised position and cover  14  detached from enclosure  12  and shown transparent. 
     Cover  14  has a pivot structure mounted to (e.g., attached to or formed integrally with) its lower surface. The pivot structure as illustrated includes horizontal shaft  30  and pivot support brackets  32  visible in FIG. 6, which extend downward from the lower surface of cover  14  to support shaft  30 . Shaft  30 , which at each end has a portion removed to form a flat, is bolted to cover  14  by bolts  31  extending through brackets  32  into shaft  30 . 
     Support assembly  10  includes support arm  40  which is supported below cover  14  by the pivot structure  30 / 32 . Support arm  40  is arranged to be rotatable about an axis  42  extending horizontally through the center of shaft  30 . Axis  42  is represented in FIGS. 5 and 6. Support arm  40  is a structural member configured to support movable components of the support assembly, excepting the cover  14  itself. As shown in end view in FIG.  3  and top view in FIG. 5, assembly  10  includes a torsion spring device  46  comprising two torsion springs positioned concentric to shaft  30 . The springs  46  are arranged (e.g., pre-tensioned upon installation) to rotate support arm  40  upward to a static alignment, which is the horizontal alignment illustrated in FIG.  3 . Cable support block  20 , previously referred to, is mounted to the support arm and rotatable between raised and lowered positions respectively shown in FIGS. 3 and 4. As will be described further with reference to FIG. 7, support arm  40  (together with all components mounted on it) is rotatable downward in response to an aircraft wheel contacting support block  20  while in its raised position. Torsion springs  46  are arranged to permit support arm  40  to rotate downward, and then return it to its static horizontal position when downward pressure on support block  20  is removed. 
     Components mounted on support arm  40  and arranged to rotate cable support block  20  between its raised and lowered positions will now be considered. As illustrated, there are mounted to support arm  40  the following: four-bar linkage  50 , cylinder/piston device  60  and compression spring device  70 . Support block  20  is rotatably mounted to support arm  40  via shaft  48 , which is fixed to the support arm. Support block  20 , formed basically of rubber material, includes a structural support member or base  26  affixed to the bottom thereof. Base  26  is attached to and arranged for rotation around shaft  48 , and also supports an additional shaft  28 . 
     Four-bar linkage  50  includes an upper bar  52  rotatable about shaft  28  of base  26  and a lower bar  54  rotatably attached to upper bar  52  via shaft  56 . Base  26  of block  20  acts as a third bar rotatably fixed to support arm  40  via shaft  48 . As shown, the lower end of lower bar  54  is rotatably fixed to a downward extending structural portion  40   a  of support arm  40 , via shaft  58 . With extremities of both lower bar  54  and base  26  (the “third bar”) thus fixed to support arm  40  at separated points, support arm  40  itself is effective to act as a fourth bar, extending between shafts  48  and  58 . As will be described further, with this configuration movement of shaft  56  to the left in FIG. 3 is effective to rotate support block  20  to its lowered position as illustrated in FIG.  4 . The four-bar linkage  50  of support assembly  10 , as thus configured, actually comprises two four-bar configurations arranged to function in parallel. As partially visible in the end view of FIG. 6, there are respective sets of upper and lower bars  52  and  54  at each side of support block  20 . For each set, the upper bar is rotatably fixed to shaft  28 , the lower bar is rotatably fixed to a separate shaft  58 , and the upper and lower bars are commonly rotatably fixed to shaft  56 . Third and fourth bars for each of the two parallel four-bar configurations are thus provided by base  26  and support arm  40 . 
     Cylinder/piston device  60  typically comprises a pneumatic cylinder arranged to be remotely activated in known manner by application of compressed air via one or more flexible air hoses (not shown). Compressed air of suitable pressure can be controllably provided via air supply tubes from a central pressurized tank (not shown) by application of known techniques. In a currently preferred embodiment device  60  is a pneumatic cylinder with a 3 inch bore and 5 inch piston stroke. A suitable hydraulic cylinder may be used in other embodiments. As shown in FIG. 3, in this embodiment when device  60  is not actuated the piston rod  60   a  is in an extended position. The piston rod  60   a  is rotatably fixed at its far end to shaft  56  at a position between the attachments of the respective bars of the two parallel four-bar configurations. As shown, the cylinder portion of cylinder/piston device  60  is rotatably fixed to a downward extending structural portion  40   b  of support arm  40 , via shaft  62 . FIG. 4 illustrates the state of support assembly  10  when cylinder/piston device  60  is actuated to cause the piston rod  60   a  portion to be retracted into the cylinder portion. 
     As illustrated, the support assembly  10  further includes a compression spring device  70  comprising two compression springs arranged to function in parallel. As shown in FIG. 3, one end of the compression spring  70  which is visible in this view is attached to a spring guide  72  which is rotatably fixed to shaft  56  and the other end is attached to a spring guide  74  which is rotatably fixed to shaft  62 . A guide rod, which is visible in FIG. 4, is fixed at one end to spring guide  74 . Spring guide  72  is free to slide over guide rod  76 , which keeps the spring guides  72  and  74  from rotating about their respective shafts  56  and  62 . The second compression spring  70 , which is partially visible in the view of FIG. 5, is similarly supported between shafts  56  and  62 . The compression springs  70  and cylinder/piston device  60  are thus effectively arranged for parallel counter action. That is to say, when device  60  is actuated its piston rod  60   a  is retracted, thereby compressing springs  70  as illustrated in FIG.  4 . In the absence of actuation of device  60  the springs  70  drive the piston rod  60   a  out to its extended position as illustrated in FIG.  3 . The four-bar linkage is thereby operable to rotate support block  20  to its respective raised and lowered positions of FIGS. 3 and 4. Other physical details of the illustrated embodiment can be provided as shown or in modified form by skilled persons once having an understanding of the invention. Dimensions are not necessarily accurate as shown, as certain dimensions may be changed for clarity of illustration. 
     As illustrated and described, hook cable support assembly  10  provides two modes of operation. In a first mode, a hook cable inserted in the opening  22  in cable support block  20  is suspended above detachable cover  14 , whose upper surface is level with a landing surface  18  (see FIG.  3 ). In this mode, for non-arrested landings the hook cable can be positioned below the landing surface by actuating cylinder/piston device to cause rotation of support block  20  to its lowered position (see FIG.  4 ). In a second mode, when an aircraft wheel impacts the support block while in its raised position, as in FIG. 3, downward pressure from the aircraft wheel causes support arm  40  to rotate or tilt downward so that support block  20  is displaced to a lower position, as illustrated in FIG.  7 . With block  20  in this displaced position, a hook cable (not shown) held in opening  22  would lie across the landing surface of a runway. Passage of the aircraft wheel is thus facilitated, without destruction of the support block. When an aircraft wheel impacts the supported hook cable without directly impacting the support block, the cable is forced downward toward the landing surface and an adjacent support block may or may not be displaced downward to some degree. As will be apparent from the following more detailed discussion of the mechanical action involved in each such mode of operation, an important feature of the invention is that all interacting mechanical components are mounted to cover  14 . As a result, for servicing, repair or replacement the entire operative mechanism may be rotated upward about hinge pins  16  or removed by detaching cover  14  from enclosure  12 . FIG. 8 shows the cover partially opened to provide servicing access. A flexible air line attachment (not shown) connected to cylinder/piston device  60  requires detachment when detaching the cover, however, in the illustrated embodiment all other operative components are attached to the cover and not to the walls or base of the enclosure. 
     Operation of the support assembly can be further considered in view of FIGS. 3 and 7. In FIG. 3 support block  20  is in its raised position. Four-bar linkage  50  has its shaft  56  in its furthest position to the right in FIG.  3 . Pressure from compression springs  70  pushes shaft  56  to the alignment illustrated in FIG.  3 . In this alignment, arms  52  and  54  are in an “over center” position, with the centerline of shaft  56  displaced slightly to the right relative to a line joining the centerlines of shafts  28  and  58 . In this position, shaft  56  is physically prevented from moving further to the right by a suitable stop or other means. Pursuant to the first mode of operation, with shaft  56  in this position downward pressure on support block  20  during roll over by an aircraft wheel has the effect of causing downward rotation of support arm  40  about the axis of shaft  30 , thereby displacing support block  20  downward relative to the landing surface represented by dashed line  18 . This downward displaced configuration is shown in FIG.  7 . With the over center positioning of shaft  56 , relative to shafts  28  and  58 , downward pressure on support block  20  does not result in movement of shaft  56  to the left in FIG. 3 (which would produce rotation of support block  20  as in the second mode of operation to be further described). When no downward pressure is applied to support block  20 , torsion springs  46  are effective to rotate support arm  40  (and thereby support block  20 ) upward to the static alignment shown in FIGS. 3 and 5 (and also FIG.  6 ). The first operational mode thus comprises two configurations of the mechanism. In one configuration support arm  40  is forced downward by pressure upon support block  20 , causing rotation downward around shaft  30  while overcoming counter-rotational force from springs  46  (FIG.  7 ). In the second configuration of the first mode support arm  40  is returned to its static position as illustrated, by action of torsion springs  46  (FIG.  3 ). 
     The second operational mode of support assembly  10  also comprises two configurations of the mechanism. In the first configuration, compression springs  70  are effective to move the bars of four-bar linkage  50  to the alignment shown in FIG. 3, and thereby to provide the over center alignment described above. In the second configuration, cylinder/piston device  60  is actuated by application of compressed air to retract the piston rod  60   a  and thereby move the bars of the four-bar linkage  50  to the alignment shown in FIG.  4 . As illustrated, this alignment of the four-bar linkage is effective to rotate support block  20  from its raised position of FIG. 3 to its lowered position of FIG.  4 . An important operational fail/safe feature is that unless cylinder/piston device  60  is actuated, compression springs  70  are effective to position support block  20  in its raised position, and thereby suspend an associated hook cable above the landing surface in position to provide aircraft arrestment. 
     As already discussed, hook cable support assembly construction pursuant to the invention permits all of the mechanical elements necessary to implement both described configurations of each of the first and second operational modes to be mounted to the cover  14  of the support assembly. And to thereby enable ready access by tilting the cover as in FIG.  8  and removal of the entire mechanism by detaching the cover. This result is obtained via the novel combination of four-bar linkage  50 , compression springs  70  and torsion springs  46 , each acting between points carried on support arm  40  or between arm  40  and cover  14 , with no operative connection to the sides or bottom of the enclosure  12 . 
     While there have been described the currently preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made without departing from the invention and it is intended to claim all modifications and variations as fall within the scope of the invention.