Abstract:
A cruiser arch moving and control mechanism includes a pair of carriage guides ( 32, 150, 188 ) fixed to opposite sides of a cruiser hull, and a pair of carriages ( 30, 170 ), each mounted to one of the opposing legs of the cruiser arch. Each of the carriage guides includes a slot ( 40, 156, 190 ) with an elongate linear track section and an adjacent arcuate track section. Each carriage includes a pair of spaced apart bearings ( 76/78, 164/176, 198/200 ) that are confined for reciprocal travel along one of the slots to support the carriage moveably relative to the associated carriage guide. Two linear actuators ( 34 ), one coupled between each carriage and its associated guide, are extendable and retractable in concert to move the arch between working and clearance positions. The carriage guides are configured to prevent any substantial rotation of the carriages until the arch is extended linearly at least a predetermined distance from the working position.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to arch or bridge assemblies used in cruisers and other watercraft for supporting radar antennas and other equipment, and more particularly to mechanisms for controlling movement of such assemblies between a generally upright position for use, and a lowered position for stowage, on-land transit or for allowing the watercraft to pass under bridges and other obstructions having low clearance. 
   For years, cabin cruisers and other watercraft have employed arch-shaped structures for supporting radar antennas, radio antennas and other electronic equipment above the normal deck level. A typical arch assembly includes an opposed pair of generally upright legs secured to the gunwales or elsewhere on opposite sides of the hull, and a transverse bridge member or transom attached to the tops of the legs and spanning the distance between them. Typically, the equipment is mounted to the bridge member. 
   While effective in supporting antennas and other equipment, the arch assembly increases the need for overhead clearance, whether the cruiser is in use or mounted on a trailer for towing. Stowage can be more difficult, and more expensive in facilities that charge by the cubic foot. While arch assemblies can be mounted in a manner that allows their detachment for the hull when the cruiser encounters a bridge or other overhead obstruction, detachment and reattachment are difficult in view of the weight and bulk of the arch assembly. An arch-shaped structure can be mounted pivotally relative to the gunwales, as shown in U.S. Pat. No. 6,986,321 (Metcalfe) in connection with a wake tower for towing a wake boarder or water skier. This still calls for manual handling, which can be difficult in view of the larger size and weight of arch assemblies as compared to the wake tower shown in Metcalfe. 
   U.S. Pat. No. 4,694,773 (Sparkes et al.) discloses a power system for raising and lowering an arch assembly. Each lower end of the arch is mounted to pivot relative to the boat through a top cover component and a lower base mounting component. A hydraulic motor within the base component is operable to extend a rod, pivoting a bracket to raise the arch. The arch can be lowered by allowing it to descend by gravity. The rod retracts, dampened by the hydraulic motor cylinder. 
   While this approach is effective from the standpoint of powering the arch assembly, it requires a bulky, unsightly housing at the base of each leg, along with an exposed pivotal coupling between separate components of the mechanism. In a competitive marketing environment where aesthetic appeal carries considerable weight, the arch assembly typically is treated as a feature of the cruiser design, either to blend in with the rest of the vessel or create its own impact on the overall appearance. Thus, the functional utility of any conventional arch assembly control mechanism is countered by the unwanted alteration in the appearance of the arch, the watercraft hull near the arch, or both. Accordingly, the present invention has several aspects directed to one or more of the following objects: 
   to provide a system for raising and lowering an arch assembly of a watercraft through linkage and motive components that are recessed into the arch assembly or hull, and are hidden from view when the arch assembly is in the generally upright working position; 
   to provide a linkage between a watercraft hull and an arch assembly adapted to guide the arch assembly through a controlled sequence and combination of linear travel and rotation as the assembly is moved from a generally upright working position to a clearance position; 
   to provide a linkage coupling an arch assembly for controlled movement relative to a watercraft hull, configured to maintain the arch assembly in a generally upright orientation for linear travel when the arch assembly is within a predetermined distance of the hull, while permitting the arch assembly to rotate relative to the hull when separated from the hull by more than the predetermined distance; and 
   to provide a mechanism for controlling movement of an arch assembly between working and clearance positions relative to a watercraft hull through a linear actuator operable to both linearly translate and pivot the arch assembly. 
   SUMMARY OF THE INVENTION 
   To achieve these and other objects, there is provided a linkage for guiding movement of a leg of an arch assembly between a raised working position and a lowered clearance position. The linkage includes a guide member adapted for mounting with respect to a watercraft hull and shaped to provide a guide track having a substantially linear first track section and an adjacent arcuate second track section. The linkage includes a carriage adapted for mounting to a leg of an arch assembly. First and second spaced-apart coupling elements are mounted to the carriage and contained for reciprocal movement along the guide track to support the carriage for alternative extension and retraction, between a retracted position corresponding to a raised arch assembly in which the coupling elements are disposed along the first track section, and an extended position corresponding to a lowered arch assembly in which the first coupling element is disposed along the second track section. A track length of the first track section is selected to provide for extension of the carriage at least a predetermined distance from the retracted position before the first coupling element reaches the second track section. 
   During initial extension, the carriage travels linearly in the direction of the first track section and cannot rotate, since both of the coupling elements are riding along the first track section. As the first coupling element (i.e. the leading coupling element during extension) enters the second track section, it travels in an arcuate path as determined by the second track section. While continuing to move linearly in the extension direction, the carriage at this stage also rotates about an axis through the second (trailing) coupling element. This causes the arch assembly leg to pivot from the generally upright working position to the lowered position for clearance. 
   The predetermined distance, over which only linear, non-rotational carriage travel can occur, is selected to provide for initial pivoting but need not be sufficient to allow complete arch pivoting to the lowered position. The predetermined distance, plus the additional linear travel that coincides with carriage rotation after the leading coupling element enters the second track section, is sufficient to allow the complete tilting of the arch assembly leg. If desired, the guide track and spacing between the coupling elements can be configured to provide a linear, non-rotational extension that completely clears the leg or tilting to the lowered position. 
   In any event, the initial non-rotational linear travel avoids the need to locate the leg/hull pivotal connection between the leg and hull outside of the leg and hull, for example as shown in the aforementioned Sparkes patent. The pivotal connection can be concealed from view when the leg and corresponding arch assembly are in the upright position for normal use. A further advantage of this arrangement is that the guide member and carriage, likewise, can be hidden from view. 
   The linkage can include an actuator adapted for mounting with respect to a watercraft hull and having a movable member adapted to be coupled with respect to the carriage. When so mounted, the actuator is operable to extend and retract the carriage. In a highly preferred arrangement, the actuator is a linear actuator aligned to reciprocate the moving member in the direction of the first track section, and the movable member is rotatably mounted to the second coupling element. This improves stability, because the nonmoving part of the actuator can be fixed rather than pivotally mounted. The linear travel of the movable member effects both linear travel and rotation of the carriage. 
   Another aspect of the present invention is a watercraft arch control system. The system includes a first guide member fixed with respect to a watercraft hull and shaped to provide a first guide track having a substantially linear first track section and an adjacent arcuate second track section, a second guide member fixed with respect to the watercraft hull and shaped to provide a second guide track having a substantially linear third track section and an adjacent arcuate fourth track section. The second guide member is spaced apart transversely from the first guide member and selectively located with respect to the first guide member to place the first and second guide tracks in substantially parallel and aligned relation. A first carriage is fixed with respect to a first leg of an arch assembly, and a second carriage is fixed with respect to a second leg of the arch assembly. First and second spaced apart coupling elements are mounted to the first carriage and contained for reciprocal travel along the first guide track, between a retracted position in which the first and second coupling elements are disposed along the first track section, and an extended position in which the first coupling element is disposed along the second track section. Third and fourth spaced apart coupling elements mounted to the second carriage and contained for reciprocal travel along the second guide track, between a retracted position in which the third and fourth coupling elements are disposed along the third track section, and an extended position in which the third coupling element is disposed along the fourth track section. The first and second carriages are operable in concert to move the arch assembly between a raised arch working position when the first and second carriages are retracted and a lowered arch clearance position when the first and second carriages are extended. A track length of the first and third track sections is selected to provide for extension of each of the first and second carriages at least a predetermined distance from the retracted position before the first and third coupling elements enter the second and fourth track sections, respectively. 
   Preferably the system further includes first and second actuators mounted with respect to the watercraft hull and having respective first and second movable members coupled with respect to the first and second carriages, respectively. The actuators are operable in concert to move the arch assembly between the raised arch and lowered arch positions. The guide members, carriages, and actuators are advantageously disposed in opposing recesses of the watercraft hull and legs of the arch assembly, and as a result are hidden from view when the arch assembly legs engage the hull in the raised arch position to close the recesses. 
   Preferably each of the first and second guide tracks comprises an elongate slot that contains its associated coupling elements for reciprocating travel. 
   Further in preferred embodiments, the second and fourth coupling elements are disposed along the first track section and third track section respectively even when the first and second brackets are in the extended position. In other words, these coupling elements remain within linear track sections, restricted to linear travel. Then, linear actuators can be employed, preferably with their moving members rotatably mounted to the second and fourth coupling elements, to linearly translate and rotate their respective carriages. 
   Another aspect of the present invention is a system for controlling a cruiser arch. The system includes a coupling mechanism for joining an arch assembly to a watercraft hull for substantially linear travel, while maintaining the arch assembly at a selected working angle, between a working position in which first and second opposite legs of the arch assembly are engaged with the hull, and an intermediate position in which the first and second legs are spaced apart from the hull by at least a predetermined distance. An arch pivoting mechanism, operable only when the legs are spaced apart from the hull by at least the predetermined distance, is adapted to pivot the arch assembly relative to the hull between the selected working angle and a selected clearance angle in which the arch assembly is lowered for overhead clearance. 
   The preferred coupling mechanism comprises first and second guide members fixed with respect to the hull and shaped to provide respective first and second guide tracks, along with first and second coupling elements mounted with respect to the first and second legs respectively and contained for reciprocal travel along substantially linear sections of the first and second guide tracks, respectively. Then, the pivoting mechanism can comprise third and fourth coupling elements mounted with respect to the first and second legs respectively and contained for reciprocal travel along respective arcuate track sections of the first and second guide tracks. 
   Thus in accordance with the present invention, linear actuators are employed in concert to move the legs of an arch assembly linearly to separate the arch from the hull of a watercraft, and then to pivot the arch assembly legs from a generally upright angle to a lowered angle for improved overhead clearance. Because the arch assembly is restricted to linear travel initially, there is no need to provide any motive or coupling components outside of the arch assembly profile. This allows these components to be hidden from view when the arch assembly is in its normal upright working position. 

   
     IN THE DRAWINGS 
     For a further understanding of the foregoing and other advantages, reference is made to the following detailed description and to the drawings, in which: 
       FIG. 1  is a perspective view showing part of a cruiser equipped with a movable arch; 
       FIG. 2  is a side elevation of an arch moving mechanism constructed in accordance with the present invention; 
       FIG. 3  is a sectional view taken along the line  3 - 3  in  FIG. 2 ; 
       FIG. 4  is a side elevation of a carriage of the moving mechanism; 
       FIG. 5  is a top plan view of the carriage; 
       FIG. 6  is an end view of the carriage; 
       FIG. 7  is a side elevation of an actuator of the moving mechanism; 
       FIG. 8  is an enlarged end view showing a bearing and part of the actuator; 
       FIG. 9  is a schematic view illustrating an intermediate actuator position; 
       FIG. 10  is a side elevation similar to  FIG. 1  illustrating the arch in the corresponding intermediate position; 
       FIG. 11  is a schematic view illustrating an extended actuator position; 
       FIG. 12  is a side elevation similar to  FIG. 10  illustrating the arch in a lowered position corresponding to the extended position; 
       FIG. 13  is a sectional view showing a guide of an alternative embodiment arch moving mechanism; 
       FIG. 14  is a side elevation of an alternative embodiment carriage; 
       FIG. 15  is a top plan view of the alternative embodiment carriage; 
       FIG. 16  is an end view of the alternative carriage; 
       FIG. 17  is an end view showing an alternative embodiment coupling of an actuator to a bearing; and 
       FIG. 18  is a side elevation illustrating an alternative embodiment carriage guide. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Turning now to the drawings, there is shown  FIG. 1  a cruiser  16  and a cruiser arch  18  mounted movable to a hull  20  of the cruiser between a working position as shown, and a clearance position ( FIG. 12 ) in which the arch is lowered to provide improved overhead clearance. In the working position, arch  18  supports radar antennas, radio antennas, and other electrical equipment (not shown) for normal use. 
   Arch  18  includes opposite legs  22  and  24  that are generally upright in the working position, although somewhat forwardly inclined. The opposite legs are joined by a horizontal transom or cross member  26 . 
   Portions of leg  22  and hull  20  near the gunwale are broken away to reveal an arch moving and controlling mechanism  28 . Mechanism  28  is housed within recesses formed in leg  22  and hull  20 , and thus is concealed from view when arch  18  is in the working position. The major components of mechanism  28  include a carriage  30  integrally mounted to leg  22 , a carriage guide  32  mounted integrally to the hull at the gunwale, and a linear actuator  34  mounted to the hull and having a moveable drive member coupled to the carriage. 
   As seen from  FIGS. 2 and 3 , carriage guide  32  has the general shape of an inverted “J” with an outer shell  36  formed of steel, e.g. 3/16 inch steel plate, and a rigid plastic interior  38  surrounded by the shell. A slot  40  is formed through guide  32  to provide a guide track that controls carriage movement relative to the guide. An elongate linear region of the slot provides a linear track section  42 , with an adjacent arcuate region providing an arcuate track section  44 . 
   As best seen in  FIG. 3 , the interior walls of guide  32  have opposed shoulders  46  and  48  to form slot  40  with a relatively narrow central region  50  and two wider opposite side regions  52  and  54 . 
   While the shape and size of carriage guide  32  can vary with the application, a suitable version of the guide has a length of about 20-25 inches, a width of about 6 inches, and a thickness of about 1½ inches. 
     FIGS. 4-6  show carriage  30 . A body of the carriage includes opposite side panels  56  and  58 , and opposite transverse panels  60  and  62  that couple the side panels and include openings  64  to receive fasteners that secure the carriage body to leg  22 . As best seen in  FIG. 5 , panels  56 ,  58 ,  60  and  62  cooperate to form an open space through which guide  32  is received for carriage/guide relative movement. 
   Further as seen in  FIG. 6 , the carriage includes two spaced apart bearing assemblies  66  and  68  mounted to side panels  56  and  58  through openings  70  for rotation relative to the side panels. The bearing assemblies further are contained in slot  40  for reciprocal motion relative to guide  32 . Respective spacers  72  and  74  are disposed between pairs of bearings  76  and  78  that ride along side regions  52  and  54  of the slot. Spacer  74  also serves as a coupler, as noted below. 
   As seen in  FIG. 7 , linear actuator  34  includes an actuator support frame  80  having frame members  82 ,  84 , and  86 . Frame member  82  is coupled directly to the hull, while frame members  84  and  86  are secured to an actuator drive housing  88  to support the housing. Frame member  84  also supports a bracket  90  used to mount a latching mechanism actuator. 
   The linear actuator includes an elongate worm  92  rotatable through a drive gear inside drive housing  88 . A gear train within a casing  94  associates the drive gear with an electric motor  96 . A conductor  98  electrically couples the motor to the cruiser battery or another suitable power supply. A tubular drive member  100  is rotatably coupled to worm  92  for linear travel as the worm rotates. 
   Annular spacer  74  is disposed at the remote end of drive member  100  and is mounted to bearing assembly  68  in surrounding relation to the assembly as seen in  FIG. 8 . Thus, the linear movement of the drive member moves bearing assembly  68  linearly along track section  42 , thus moving carriage  30  relative to carriage guide  32 . 
   With further reference to  FIG. 2 , the mounting of linear actuator  34  and carriage guide  32  to the cruiser hull is accomplished simultaneously with threaded fasteners  104  and  106  that extend through frame member  82 , a gunwale region  108  of the hull (shown in phantom, typically fiberglass) and a bottom panel  110  of shell  36 , then into the polymeric interior  38  of the guide. Thus, the carriage guide and the stationary components of the linear actuator are integral with the hull. 
   The carriage body is mounted integrally to leg  22  by threaded fasteners  112  and  114  extending through a bottom edge region  116  of leg  22  (shown in phantom, typically fiberglass) and panel  60 , together with a pair of fasteners  118  and  120  extending through region  116  and panel  62 . The incline of panel  62  relative to panel  60  is dictated by the style of the arch, particularly the shape of the leg along its bottom edge. Carriage panels used with other watercraft may well be inclined at different angles, or may be coplanar. In any event, the mechanism is preferably substantially centered within leg  22  and the adjacent region of the hull, with the carriage and carriage guide occupying a recess formed in the leg, and the majority of the linear actuator occupying a recess formed in the hull. When the arch is in the working position shown at  FIG. 1 , leg  22  is engaged with hull  20 , thus to close the recesses and hide the components from view. 
   An alignment pin  122  is mounted to gunwale region  108  through fasteners  124  and a steel plate  126 . The alignment pin extends upwardly into a recess near the forward edge of leg  22  when the leg is in the working position. When the leg is being brought downward toward the working position, the alignment pin is captured by the recess to align the leg as it is brought against the hull. 
   Near the rearward end of the leg is a latching mechanism including a latching pin  128  mounted to bottom edge region  116  via fasteners  130  extended through a steel plate  132 . Latching components mounted to the hull include a latch cam  134  mounted rotatably on a base  136  secured to gunwale region  108 . A latch arm  137  is integral with the latch cam, and is coupled to a rod  138  that reciprocates in a cylinder  140  of a latch actuator  142 . The cylinder is mounted pivotally on bracket  90 . 
   When extended as shown, rod  138  pivots latch arm  136  and cam  134  to a locking position in which the cam, bearing against latching pin  128  within a detent  144 , positively secures leg  22  against the hull. When rod  138  is retracted, the latch arm and latch cam are rotated clockwise until cam  134  no longer resides in detent  144 , thus to free leg  22  for extension away from the hull. 
   A moving mechanism substantially identical to mechanism  28  is mounted within the recesses formed in leg  24  and in hull  20  near leg  24 . The mechanisms are operated in concert to control motion of arch  18  between the working and clearance positions. 
   A salient feature of the control mechanisms is the degree of control over motion of the arch, to effect a desired sequence and combination of linear travel and rotation of legs  22  and  24 . In general, arch movement occurs in two stages between three discrete arch positions determined by the location of the carriage bearing assemblies along slot  40 . 
   In  FIG. 2 , bearing assemblies  66  and  68  are shown in a retracted position. Both of the bearing assemblies are in linear track section  42 , with bearing assembly  68  located at or near a lower end  146  of slot  40 . The retracted position corresponds to the arch working position shown in  FIG. 1 . 
   When the operator of cruiser  16  wishes to lower arch  18  to provide better overhead clearance, he or she first actuates the latching mechanism to release latching pin  128 , then operates actuator  34  to extend drive member  100  and thus move the bearing assemblies upwardly and slightly to the left as viewed in  FIG. 2 . This moves carriage  30  linearly as well. Bearing assembly  66 , captured within slot  40 , counteracts any tendency of the carriage to rotate about bearing assembly  68 . Accordingly the angle of carriage  30  remains constant during this stage of carriage travel. Linear travel continues until leading bearing assembly  66  reaches arcuate track section  44 , as illustrated in  FIG. 9 . The “linear only” travel of carriage  30  and its associated carriage in leg  24  moves arch  18  to an intermediate position illustrated in  FIG. 10 . 
   As extension of drive member  100  continues, lead bearing assembly  66  moves in the arcuate path determined by arcuate track section  44 . As a result, carriage  30  continues to move linearly but also rotates in the counterclockwise direction as viewed in  FIG. 2 . The combined linear travel and rotation continue until lead bearing assembly  66  reaches or is proximate to an upper end  148  of slot  40  as illustrated in  FIG. 11 . This corresponds to the lowered arch position shown in  FIG. 12 . Thus, the stage of motion between the intermediate and lowered arch positions is a combination of linear travel and rotation of legs  22  and  24 . The fully extended position of the bearing assemblies and the carriage corresponds to the lowered arch position. 
   After clearing the overhead obstruction, the operator returns arch  18  to the working position by rotating worm  92  in the opposite direction to retract bearing assembly  66  and the carriage. As it returns from the lowered position to the intermediate position, arch  18  is rotated back to the generally upright working angle, then is moved linearly back into engagement with hull  20 . At that stage, the latching mechanism is operated to secure latching pin  128 . 
   It can be appreciated that the linear actuator and latching mechanism could be operated independently if desired. In the preferred approach, they are coupled by a single operating program, to be effected in the required sequence by a single step, e.g. throwing a switch or pressing a button. 
   The spacing between bearing assemblies  66  and  68 , the length of linear track section  42 , and the length and radius of arcuate track segment  44  can be varied to achieve optimal performance with cruisers of different designs. In all cases, the bearing assembly spacing and linear track section length cooperate to determine a selected or predetermined distance over which the carriages, and thus the legs of the arch assembly, travel linearly from the retracted position before they are caused to pivot. Preferably the predetermined distance is selected to avoid any unnecessary or excess amount of linear travel. To this end, in the course of lowering the arch, the arch can begin to pivot well before reaching the amount of linear travel necessary to provide full clearance for tilting the arch to the position shown in  FIG. 12 . This is because linear travel continues after the arch begins to pivot, so that the arch, even if not sufficiently linearly cleared when rotation begins, is cleared by the time the arch is lowered. 
   The predetermined distance varies with a number of factors, including the size of the boat and shape of the hull, the width of each leg of the arch, and the angle of the arch (relative to the horizontal) when in the working position. For cruiser  16 , in which the working angle of arch  18  is about 65 degrees, a suitable predetermined distance is about 10 inches. If the working angle were increased to about 90 degrees in an otherwise similar cruiser and arch, the predetermined distance also would increase, e.g. to about 15 inches. 
   Slot  40  preferably is configured so that arcuate section  44  encompasses an angle of less than 90 degrees, and more preferably less than 60 degrees. In any event, the remote end of the arcuate section and the track apex should coincide, to avoid the need to generate a lifting force in order to retract the carriage. In most cruiser designs, this restriction presents no difficulty. First, due to the forward incline of many of the arch designs, lowering the arch for clearance requires pivoting over an arc in a range of only 30-45 degrees. Secondly, a given requirement for arch rotation does not translate into a corresponding requirement for the same arc in the arcuate track section, since carriage rotation depends on the spacing between bearing assemblies as well as the shape of the arcuate track segment. 
     FIG. 13  is a sectional view, similar to  FIG. 3 , showing an alternative embodiment carriage guide  150  which, when viewed in side elevation as in  FIG. 2 , has an appearance similar to carriage guide  32 . As before, guide  150  has an outer shell  152  of steel and a polymeric interior  154 . 
   In contrast to slot  40  of carriage guide  32 , a slot  156  of carriage guide  150  is defined by interior walls with projections  158  and  160  on one side to form a slot with a single region  162  of larger width to accommodate a bearing  164 , and a narrower region  166  to accommodate a shaft  168  that supports bearing  164 . 
     FIGS. 14-16  illustrate an alternative carriage  170  used with guide  150 . In this case the carriage body consists of a single upright bearing support panel  172  and a base panel  174  extending from the bottom edge of the bearing support panel. Four threaded fasteners  175  extend through a fiberglass base wall portion of an arch leg and through base panel  174  to secure the carriage body integrally to the leg. Bearings  164  and  176  are mounted rotatably on shafts  168  and  178 , respectively, which in turn are secured to panel  172  using nuts  180  and  182 . 
   The primary difference between carriage  170  and carriage  30  is that in the former does not surround the guide and therefore does not provide a symmetrical arrangement. Nonetheless, in many cases this arrangement is preferred, due to the greater ease in securing the arch to the hull using this mechanism. 
   Another difference is the manner in which the free end of a linear actuator drive member  184  is mounted rotatably to the bearing. As seen in  FIG. 17 , a bracket  186  at the end of drive member  184  has an aperture for rotatably receiving shaft  178  of bearing  176 . 
     FIG. 18  illustrates a further alternative carriage guide  188  similar in construction to guides  32  and  150 , with the exception that a slot  190  formed through guide  188  includes not only a linear track section  192  and an arcuate track section  194  as before, but further has an additional linear extension feature  196  designed to allow a trailing bearing  198  to undergo further linear travel after it enters arcuate section  194  to the position illustrated in solid lines. As compared to the guides without feature  196 , this arrangement permits further arcuate travel of a lead bearing  200  and further linear extension of trailing bearing  198 . The additional travel of both bearings causes additional counterclockwise rotation of the carriage. As before, the carriage is moved through a first stage of only linear travel followed by a second stage that combines linear travel with rotation, effected solely by linear travel of the actuator drive member acting through the trailing bearing. 
   The use of feature  196  is enabled and facilitated by the distribution of the arch weight, specifically by the forward incline through which the arch weight tends to rotate the arch counterclockwise as viewed in the figure. Forces due to the weight distribution are resolved in a downward force through bearing  200  against carriage guide  188  and an upward force through bearing  198  against the guide. Thus, when lead bearing  200  enters arcuate track section  194  during extension, it tends to stay in the arcuate section and travels to the fully extended position as shown. In contrast, as trailing bearing  198  approaches arcuate section  194  during extension, it tends to enter feature  196  rather than following the arc. 
   Thus, a carriage guide incorporating feature  196 , similar in size to another guide, can allow more rotation of the carriage and thus the arch. 
   More generally, cruiser arch moving mechanisms configured in accordance with the present invention cause the arches to move according to a controlled sequence and combination of linear travel and rotation relative to the cruiser hull as the arches are moved between generally upright working positions and lowered positions for clearance. An aspect of the sequence is the requirement for a predetermined amount of linear travel away from the working position before the arch is pivoted. This feature enables a recessed mounting of the motive and guiding components whereby they are hidden from view when the arch is in its working position.