Abstract:
An electro-mechanical dual linear drive system for adjustably power moving a watercraft seat along a linear travel path. A pair of elongate extruded hollow aluminum rails are mounted in parallelism to a fixed seat support structure. An elongate extruded aluminum hollow slide is non-rotatably and slidably mounted within each rail and driven in a linear travel path for moving the seat load. A lead screw is rotatably mounted within each slide and rail and a traveling nut on each lead screw moves the associated slide. A gear reduction drive mounted on each rail is driving coupled for rotating the associated lead screw. A single electric motor is rotationally drivingly coupled to both gear drive units for synchronously rotating the lead screws in response to motor rotation. Each rail and slide are non-circular and complementary for restraining relative rotation therebetween. A laterally protruding flange along one side edge of the rail bottom wall provides an exteriorly accessible mounting flange on the rail. Likewise, each slide has a planar mounting platform protruding laterally in offset relation to the associated rail to provide seat load fastening access clearance. At least two glides are fixedly carried adjacent longitudinally opposite ends of each slide and each have a generally rectangular cross-sectional configuration generally complemental to that of the slide and rail and generally forming a slide bearing therebetween. Each glide is molded from low friction plastic and has a free-state configuration flex stressed when in assembly on the associated slide and providing peripherally spaced slide bearing zones. A dual rail single lead screw system second embodiment is also disclosed, along with a swivel seat mounting third embodiment.

Description:
This is a regular utility patent U.S. patent application filed pursuant to 37 U.S.C. §111 (a) and claiming the be nefit under 35 U.S.C. §119 (e) (1) of United States Provisional Patent Application Serial. No. 60/118,456 filed Feb. 3, 1999 pursuant to 35 U.S.C. §11 (b). 
    
    
     FIELD OF THE INVENTION 
     This invention relates to electric motor lead screw driven linear actuators, and more particularly to such actuators for adjustable seat mechanisms particularly adapted for marine use on recreational watercraft such as cabin cruisers, speed boats, sport boats, fishing skiffs and the like. 
     BACKGROUND OF THE INVENTION 
     The continued development and upgrading of recreational watercraft has seen the introduction of various power driven convenience accessories including power actuated adjustable seats for helmsman, passenger and aft trolling/fishing station use. There also is a continuing need to improve such systems from the standpoint of such parameters as ease of installation on standard marine seating, vertical profile, load carrying capacity, non-binding operation, economy of manufacture, reliability, and service life under adverse marine environmental conditions. 
     Typically, the gear drive and associated heavy-duty slide and rail used for mounting the seats are provided as separate assemblies, which in turn leads to additional costs both in manufacture and in assembly and installation on the watercraft. In addition, in some prior art the load of the seat is impressed gravitationally on the gear drive and/or motor as well as on the associated dual slides and rails, thereby leading to track and/or carriage binding and even lock-up from stress-induced distortion, excessive wear, premature system failure and seat load limitations. Some systems now incorporate metal to metal contact in the carriage or slide assembly which leads to sticking and jamming from salt water corrosion and dirt. Other systems suffer from excessive play and rattling creating irritating noise when under way in the watercraft as they vibrate harmonically with the engine vibration imparted to the watercraft. Typically, the seat slide assemblies are installed as dual parallel tracking rails and carriage/slides wherein cocking is a problem, particularly when supporting extra-wide dual person side-by-side type seats, leading to drive jamming, motor failure and/or fuse blowing. Prior art assemblies also often require excessive vertical clearance between the seat bottom and the seat mounting area in order to fit the seat slide drive assembly, rendering the unsightly drive unduly visible and less stable in use. 
     OBJECTS OF THE INVENTION 
     Accordingly, among the objects of the invention are to provide an improved electric seat slide and actuator system that overcomes one or more of the foregoing problems of prior art marine electric seat slide and actuator systems and that is improved from the standpoint of (1) economy of manufacture, (2) versatility and flexibility in design, different travel lengths, thrust capacities and carriage travel speed, (3) overall height as installed, (4) ease of installation on standard marine seating, (5) unitization of gear drive and heavy duty slide and rail, (6) isolation of the weight load of the seat and the passengers sitting on the seats from the gear drive and/or motor for actuating the same, (7) reduction of frictional resistance to seat slide travel, (8) reduction or elimination of excessive play in the seat mounted on the actuator system, (9) dual seat carriage tracking capability along slightly misaligned parallel tracks, (10) ability to handle off-center loading without hang-up and jamming, (11) ease of installation as a complete assembly for mounting of the seat on the actuator system, (12) capability to resist lock-up or racking when a seat is moved against a travel resistance force applied unevenly or to one side only, or when weight-loaded unevenly and off-center as by an occupant sitting on either extreme end of the seat, (13) elimination of the need to cut holes in the mounting seat box on the watercraft in order to accommodate an excessively high system assembly profile, and/or (14) elimination of the need for a special mounting system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing as well as additional objects, features and advantages of the present invention will become apparent from the following detailed description, appended claims and accompanying drawings (which are to engineering scale except where indicated otherwise) illustrating improved apparatus provided and organized for a marine seating system application in accordance with preferred but exemplary embodiments of the invention constructed pursuant to the best mode presently known by the inventors of making and using the same, and wherein: 
     FIG. 1 is a simplified CAD line drawing illustrating in top plan view a first embodiment of an electric seat slide and actuator system of the invention, and shown as a complete assembly as manufactured and provided to the watercraft manufacturer for installation on suitable seat mounting structure and adapted to receive a seat mounted thereon. 
     FIG. 2 an end view projection of the port side rail and slide subassembly of FIG. 1, assuming for convenience that the assembly of FIG. 1 is watercraft mounted to provide fore and aft seat travel with the motor mounted aft. 
     FIG. 3 is a simplified sectional view taken on line  3 — 3  of FIG. 1, the drive lead screw and associated traveling nut being deleted form FIGS. 1-3 for simplification. 
     FIG. 4 is a simplified cross sectional view of the port side lead screw drive, track and slide subassembly taken generally on the line  4 — 4  of FIG.  5 . 
     FIG. 5 is a cross sectional view taken generally on the line  5 — 5  of FIG.  4 . 
     FIG. 6 is a fragmentary top plan view of the port side rail and slide subassembly with associated gear reduction unit and motor, with a portion broken away to illustrate details of the traveling nut of the subassembly. 
     FIGS. 7,  8 , and  9  are respectively port side elevational, frontal elevational and starboard side elevational views of mounting bracket for the gear reduction unit of the subassembly of FIGS. 4 and 6. 
     FIGS. 10,  11  and  12  are respectively cable-end view, side elevation view and gear-reduction-end view of the motor drive cable lead-in ferrule provided for reinforcing the flexible drive coupling to the associated gear reduction drive unit and to the motor armature shaft. 
     FIG. 13 is a cross sectional view of the port rail and slide subassembly, but with the slide reversely mounted relative to its mounting in FIGS. 1-6, taken in a cross sectional plane perpendicular to the rotational axis of the lead screw (and to the longitudinal axes of the rail and slide), and illustrating a slide glide in cross section in an imaginary view thereof as it would appear if not assembly stressed to conform to the clearance space between the slide and rail that is normally occupied by the glide in assembly, i.e., illustrating glide in its free state cross sectional configuration. 
     FIG. 14 is an end view of the glide shown by itself in its unstressed or free state condition, i.e., as originally de-molded and unstressed, and illustrating schematically with force arrows those zones of the glide that resiliently press against the adjacent surface area of the rail as the glide is preloaded in assembly on the slide and the slide/guide subassembly slidably inserted into the rail. 
     FIG. 15 is another end view of the glide shown by itself in free state condition. 
     FIG. 16 is a side elevational view of the glide of FIG.  15 . 
     FIGS. 17,  18  and  19  simplified end views of the port and starboard slide and rail subassemblies respectively illustrating both the slide and rail mounting flanges oriented inwardly of the assembly (FIG.  17 ), both slide and rail mounting flanges oriented outwardly of the assembly (FIG.  18 ), and the slide mounting flange oriented inwardly of the assembly whereas the rail mounting flange oriented outwardly of the assembly (FIG.  19 ). 
     FIG. 20 is an end elevational view of one of the rail end cap plates shown by itself. 
     FIG. 21 is a simplified CAD drawing top plan view of a second embodiment electric seat slide and actuator system of the invention. 
     FIG. 22 is a simplified end elevational view projected off the port side slide and rail subassembly of the assembly of FIG.  21 . 
     FIG. 23 is a simplified CAD drawing cross sectional view taken generally on the line  23 — 23  of FIG.  21 . 
     FIG. 24 is a top plan view of the port rail of the port slide/rail subassembly in FIG. 21 (assuming a fore and aft travel mounting with motor aft). 
     FIG. 25 is an end projection of the port rail shown in FIG.  24 . 
     FIG. 26 is a top plan view of the aft one of the two slides shown on the port rail of the assembly FIG.  21 . 
     FIG. 27 is end elevation projection of the slide of FIG.  26 . 
     FIG. 28 is a side elevational view of the slide shown in FIG.  26 . 
     FIG. 29 is a simplified end elevational view illustrating the assembled relationship of the slide and rail of FIGS. 24-28 without lead screw, lead screw nut and slide bearing glides. 
     FIG. 30 is a perspective view of an actual experimental prototype assembly looking forward from the motor end of the assembly of the components generally as shown in FIG. 1 but with the components reoriented such that the mounting flanges of the slides and rails are both oriented inboard, as in the FIG. 17 orientation, and with the gear reduction brackets and associated gear reduction drives rotated 180° from their orientation in the system assembly FIGS. 1-6 such that the dual tandem drive cables from the motor are trained beneath the inboard arm of the associated mounting bracket. 
     FIG. 31 is a fragmentary side elevational view of the aft end of the outboard side of the starboard rail and slide subassembly of FIG. 30 with the gear reduction drive removed from the mounting bracket. 
     FIG. 32 is a reproduction from a photo print of the actual parts of a subassembly of a slide, lead screw and lead screw nut of the system of FIGS. 21-23, with a bearing glide mounted on the slide, these parts having been constructed as actual operating parts in experimental prototype of the system of FIGS. 21-23. 
     FIG. 33 is a reproduction of a photo print showing the slide part of FIG. 32 with the slide bearing glide mounted thereon but with the lead screw removed, the lead screw nut along with the gear reduction drive mounting bracket being shown separated, and another slide bearing glide shown on end in its free state condition. 
     FIG. 34 is a reproduction of a photo print of the gear reduction drive, a connecting stubshaft and a lead screw of FIG.  32  and shown separated before being welded in assembly together, with these parts being shown laid out separately from one another. 
     FIG. 35 is a reproduction of a photo print of the subassembly of the gear reduction unit and lead screw of FIG. 34 coupled in driving relation. 
     FIG. 36 is a fragmentary perspective view of the aft end of the starboard slide and rail subassembly and a portion of the drive motor and drive cable connection thereto of the system assembly show in FIG. 30, as reproduced from a photo print of the actual prototype parts thereof. 
     FIG. 37 is an elevational view of the forward end, looking aft, of the starboard rail and side subassembly of FIG. 30 showing the end cap fastened to the rail in elevation. 
     FIG. 38 is a fragmentary top plan view reproduced from a photo print of the components shown in FIG. 36 (minus the slide). 
     FIG. 39 is a fragmentary split view, looking aft, of the components shown in FIG. 36 as reproduced from a photo print of actual prototype parts constructed and arranged as shown in FIG.  30 . 
     FIG. 40 is a front elevational view of a molded plastic single seat body mounted on a third embodiment electric seat slide and actuator system of the invention that in turn is mounted on a conventional cast swivel mount spider support. 
     FIG. 41 is a perspective view of the assembly shown in FIG. 40 as the subassembly is viewed looking aft and to port. 
     FIG. 42 is a bottom plan view, as reproduced from a photo print of prototype parts in assembly, of the third embodiment electric seat slide and actuator system removed from the seat but with the swivel spider still mounted on the actuator assembly. 
     FIG. 43 is a perspective view in front elevation of the subassembly shown in FIG. 42, but oriented upright, and 
     FIG. 44 is a bottom plan view of the bottom side of the seat slide and actuator system of FIG. 42 shown mounted to the bottom of the seat shown in FIGS. 40 and 41, but with the swivel spider removed from the cross braces of the assembly, FIGS. 40-44 being drawings reproduced from photo prints of these parts as actual working parts so oriented in an actual experimental prototype. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring more particularly to the accompanying drawings, FIGS. 1-20 are CAD drawings to engineering scale of an exemplary first embodiment system and apparatus of the invention. FIG. 1 illustrates in plan view the system set-up for a single motor/dual tandem drive for a dual rail/slide seat actuator assembly. Assuming that the desired seat travel is fore and aft and that a single drive motor  100  is to be mounted at the aft end of the assembly, a first rail and slide subassembly  102  will be herein designated the “port-side” subassembly, and a second rail and slide subassembly  104  will be herein designated the “starboard side” subassembly. The two principal components of subassembly  102  is a “rail”  106  and a “slide”  108  mounted for sliding motion longitudinally along the rail. Subassembly  104  likewise has a rail  110  and a slide  112  identical to rail  106  and slide  108  respectively. It will also be understood that components  106  and  110  function a fixed guide tracks and are herein each termed a “rail”, whereas components  108  and  112  function as load bearing carriages slidingly mounted in the rails for motion longitudinally therealong, and are herein each termed a “slide”. 
     In accordance with one feature of the invention, rails  106  and  110  may be cut from the same extruded length of structural aluminum alloy stock having the as-extruded cross sectional configuration seen in FIGS. 2,  5 ,  13  and  17 - 19 , and as best seen in FIG.  13 . For further clarification at this point, it is to be understood that the rail and slide components in FIG. 13 are oriented as set forth in FIG. 19, whereas in the system assembly of FIGS. 1-6 the rail and slide components are assembled and oriented relative to one another as shown in FIG.  17 . 
     Rails  106  and  110  are thus identical to one another and assembled as mirror image components for economy of manufacture. Likewise, slides  108  and  112  are cut from the same extrusion and machined for fastener openings in an identical manner so that they can be made as identical components and mounted in mirror image fashion in the assembly of FIG. 1 to economize on manufacture. 
     Each slide  108 ,  112  has a mounting platform portion  114  of rectangular configuration in plan view (FIGS. 1 and 6) integrally joined to the upper edge of a laterally off-center web  116  (FIG. 13) extending perpendicularly to the major plane of platform  114  and integrally joined a E its opposite, lower edge to a shoulder wall  118  of slide  108 . A pair of laterally spaced parallel side walls  120  and  122  are integrally joined at their upper edges to shoulder wall  118  and depend therefrom to free lower edges  124  and  126 . Each of these lower edges  124 ,  126  is provided with an inwardly offset toe portion  128  and  130  respectively and each of which is hollowed out by a longitudinally extending downwardly-opening groove  132  and  134  respectively. The upper region of each of the dependent side walls  120  and  122  of slide  108  has an outwardly bowed curved section of constant radius of curvature, thereby defining laterally opposite concave interior surfaces  136  and  138  dimensioned for loosely cradling therebetween a drive lead screw  140  of subassembly  102  (FIGS. 4,  5 ,  6  and  13 ). 
     Each slide  108 ,  112  is preferably provided with a pair of identical slide bearings, herein termed “glides”  142  and  144 , of identical construction and located one adjacent each of the opposite longitudinal ends of each slide as illustrated in FIG. 4, Glides  142 ,  144  are preferably injection molded but alternatively may be sections cut from a single extrusion of lubricant-filled plastic material, such as that sold under the trademark ACETRON by DSM Company, which is a filled Delrin plastic material. Other compositions of polyolefin and polyethylene or polypropylene filled with self-lubricating material to provide good lubricating properties are also usable as materials for glides  142 ,  144 . In any event the plastic material selected should have a high elastic modulus or spring rate for developing suitable spring frictional retention grip when stressed to develop a pre-load in assembly of the glide on the slide. 
     More particularly, and referring to FIGS. 15 and 16, glide  142  is shown in end view and in side view in its free state, and in an as-molded or as-extruded and cut condition. FIG. 14 is an enlargement of FIG. 15 also showing glide  142  in its free state or unstressed condition. It will be noted that the cross sectional contour of glide  142  generally conforms to the configuration of the design clearance space provided between rail  106  and slide  108  in their operative assembled relationship (see FIGS.  17 - 19 ). Thus glide  142  has a pair of laterally space d side walls  150  and  152  integrally interconnected by a bottom wall made up of coplanar wall portions  154  and  156  respectively integrally joined to the bottom edges of side walls  150  and  152  and extending toward one another. (“Integral” as used herein means joined or united into one piece as and when molded or extruded). Bottom wall portions  154  and  156  are interconnected by a raised rib portion  158  that functions as a folded spring to compensate for dimensional variations in glide  142  and/or in the aluminum extrusions from which rail  106  and/or slide  108  are cut. A pair of top leg walls  160  and  162  extend toward one another and are integrally joined one to each upper edge of side walls  150  and  152  respectively. The free ends of leg walls are spaced apart to define a gap  164  therebetween to accommodate web  116  of slide  108  in assembly therewith. 
     It is to be noted that, in their free state as-molded condition, leg walls  160  and  162  incline downwardly from one another at a slight angle rather than being coplanar. The interior dimension and resilience of glide  142  is designed to enable a flexing slide-on snug fit of the glide  142  endwise onto slide  108  as shown in FIGS. 13 and 17. The top leg walls  160  and  162  during this fit-on have a slight interference fit with the top surfaces of shoulder wall  118  of the slide. Therefore leg walls  160  and  162  must bend upwardly to assume a coplanar orientation as seen in FIG.  17 . This stress places the resilient plastic material of the glide under preload and thus helps the frictional grip retention of glide  142  on side walls  120  and  122  and shoulder wall  118  of slide  108 . 
     The free state as-extruded cross-sectional configuration of glide  142  is also purposely made slightly non-conforming to the cross-sectional configuration of the internally uniform clearance space between the exterior surfaces of slide walls  118 ,  120  and  122  and the juxtaposed interior surfaces of rail  106 . Thus, as best seen in FIG. 14, side wall  150  is provided with a s hallow angle outwardly crowned (with straight wall sections) portion  170  having an apex at  172 , a bowed outwardly convexly curved portion  174  and an upper very slightly crowned (with straight wall sections), portion  176  having an apex at  178  and integrally joined at its upper edge to the outer edge of leg wall  160 . The opposite side wall  152  of glide  142  is contoured in identical fashion but in mirror image and thus has a lower crowned portion  179  with a crown apex  180  corresponding to apex  172 , an outwardly convex bowed portion  182  opposite portion  174 , and a slightly crowned upper portion  183  with an apex at  184  and integrally joined to leg wall  162  at its upper edge. 
     Glide bottom walls  154  and  156  also each respectively have upwardly protruding longitudinally extending mounting rib  186  and  188  that respectively fit snugly into the longitudinally extending slots  132  and  134  formed in the lower toe edges  124  and  126  of the slide walls  120  and  122 , as best seen in FIG.  13 . 
     It is to be further understood that in FIG. 13 glide  142  is shown (with artistic license) in imaginary assembly with slide  122  and rail  106 , glide  142  being shown in its free state contour to better illustrate the nature of the overlapping interference relationship it has relative to the geometric cross sectional configuration of the clearance space defined between the slide as nested in the rail. In actuality, glide  142  is resiliently deformed upon assembly between these components to be pre-stressed and preloaded so as to essentially fill this slide-to-rail clearance space. Therefore in assembly glide  142  would appear more as shown in the left hand figure of FIG.  17 . This bearing preload deformation feature will be better understood after explaining the construction in detail of rail  106 . 
     Rail  106  will be described in detail with reference to the right hand view of FIG. 18 to avoid crowding of reference numerals in FIG.  13 . Rail  106  has a bottom wall  200  with an integral coplanar mounting flange extension  202 . A pair of laterally spaced upright side walls  204  and  206  are integrally joined at their lower edges to bottom wall  200 . Each side wall  204 ,  206  is respectively capped at its upper end by a leg wall  208 ,  210  and these are laterally spaced apart at their inner free edges to permit passage therebetween of web  116  of slide  108 . The outboard, longitudinally extending edges of leg walls  208 ,  210  each have a re-entrantly curved lip  212 ,  214  respectively which present a smooth rounded outer, longitudinally extending edge to the upper longitudinal edges of rail  106 . Lips  212 ,  214  also each define a curved channel  216 ,  218  respectively that opens at both longitudinally opposite ends of the rail. Rail side walls  204 ,  206  also each have downwardly and outwardly sloping ribs  220 ,  222  respectively protruding from their exterior surfaces at an elevation slightly above the upper surface of bottom wall  200 . Rib  220  has a re-entrant curvature to define another open-ended channel  224 . Rib  222  has a slight re-entrant curvature to define with the upper surface of extension  202  still another open-ended channel  226 . (As noted in more detail hereinafter it will be seen that the centers of the four open-ended channels  216 ,  218 ,  224  and  226  are by design spaced at the four corners of a square, i.e., equidistant from one another on X and Y Cartesian coordinates.) Each side wall  204 ,  206  of rail  106  has an outwardly bowed portion  230 ,  232  respectively that matches the outwardly bowed curvature of the bowed portions  120  and  122  respectively of slide  108 . It thus will be seen that the exterior cross sectional geometry of slide  108  in the portion of web  116  and walls  120  and  122  defines a uniform clearance space with the juxtaposes interior surfaces of rail walls  204  and  206 , rail bottom wall  200  and the rail top leg walls  208  and  210 . 
     Returning again to the slide-in-rail assembly procedure and the fit of glide  142  between the rail and slide described previously in conjunction with FIGS. 13-16, it will seen from FIG. 13 when compared to the showing in FIG. 17, left hand view, that the slide-assembled glide  142  as stress-slip-fitted on slide  108  is further squeezed and conformed to the exterior surfaces of the slide as the glide is inserted into the confines of the hollow interior of rail  106 . The glide deforms resiliently to make this conformation fit. However, sticking and jamming of this guide slide bearing during its sliding engagement with the rail interior wall surfaces is prevented by the low coefficient of friction of the lubricant-filled plastic material of the glide. Frictionally drag is also reduced by the bowed portions  174  and  182  of glide  142 , as best seen in FIG. 14, being made thinner in cross section so that there is a clearance remaining between these portions of the glide and the adjacent surfaces of the rails and slide after assembly of the three parts together. 
     The drive of slide  108  fore and aft along rail  106  is produced by corresponding bi-directional rotation of lead screw  140 , which in turn is driven by a conventional commercially available reversible electric motor  100 . The rotational output torque of motor  100  is transmitted by a conventional flexible cable drive shaft  250  encased in a flexible cable shroud  252  (FIG. 1) that is drivingly coupled into the input end  254  of a conventional right angle gear reduction drive unit  256 . The output shaft of gear unit  256  is drivingly affixed as by welding to the adjacent end of lead screw  140 . Gear reduction drive unit  256  is supported by a bracket  258  that carries a support bolt  260  that in turn extends through a mounting bore in the housing of the gear reduction drive unit  256 . 
     The construction of bracket  258  is best seen in FIGS. 7,  8  and  9 . The port and starboard side walls  261  and  262  of the bracket are cut away to provide clearance for the tubular input shaft protuberance  254  of the housing of drive unit  256 . The end wall  264  of bracket  258  mounts in abutment against the end surfaces of rail  106  and is centrally slotted at  266  to provide assembly clearance for passage therethrough of the lead screw  140  and the forward end of the drive unit housing. As shown in FIG. 4, drive unit  256  contains an input worm gear drivingly engaged with a mating helical gear  272 , preferably pitched for a 20 to 1 reduction drive ratio, thereby providing a high mechanical advantage for driving the slide as well as a self-locking gear drive mechanism to securely hold the associated slide against travel on the rail when rotation of motor  100  is stopped. 
     A lead screw drive nut  280  (FIGS. 4,  6  and  13 ) is threadably received on lead screw  140  and is loosely received in a complementally shaped opening  282  milled through the walls  120  and  122  of the slide and extending partially into web  116  of the slide. Nut  280  is generally rectangular shaped in cross section with its width dimension extending parallel to the side walls of the rail and its thickness dimension extending perpendicularly thereto. The opposite lateral sides of drive nut  280  have a loose sliding fit between the juxtaposed inner surfaces of the rail side walls  204  and  206 . The outline of nut  280  can be seen in FIG. 1 where it will be understood that the rectangular configuration of the nut in cooperation with the flanking rail side walls  204  and  206  prevents rotation of the nut. Hence rotation of lead screw  140  will threadably advance or retract the nut along the lead screw. The protrusion of the nut front and rear faces in overlapping abutment with the slide opening faces formed by milling opening  282  in the slide side walls provides the driving engagement between the nut and the slide, as best seen in FIG.  4  and in the cut-away portion of FIG.  6 . 
     As best seen in FIG. 13 lead screw  140  is generally journal supported loosely by the cradling of the concave surfaces  136  and  138  of slide side walls  120  and  122  in conjunction with the bearing support provided by nut  280  loosely riding on the edges of the nut opening  282  milled into the slide side walls. Because of this assembly clearance between the subassembly of lead screw  140  with its traveling drive nut  280  relative to slide  108 , weight loads and any other loading on the slide and/or rail by forces acting in a plane perpendicular to the lead screw axis are not transmitted to the lead screw and nut subassembly. Hence the lead screw and nut as well as the gear reduction  256  and motor  100  are substantially isolated from seat loadings imposed vertically or in any direction in such plane perpendicular to the axis of the lead screw. Lock up and/or binding of the slide drive otherwise typically resulting from such adverse forces is thus prevented. The lead screw drive reaction forces exerted in tension and compression on lead screw  140  in response to operationally generating driving forces on the slide, or in exerting a holding braking force, are taken in the gear reduction housing by conventional thrust bearing structures provided in such conventional commercial units. 
     As a further feature to enhance system installation versatility, the forward ends of rails  106  and  110  are closed by an end cap plate  290  shown assembled on the rail in FIGS. 4 and 6, and shown by itself in FIG.  20 . Four mounting holes  292 ,  294 ,  296  and  298  are provided, one in each of the four corners of end plate  290 , for individually receiving therethrough self-tapping screws  300 . Screws  300  individually self-thread into the aluminum material of the extrusion as they are received in the associated open ends of rail channels  216 ,  218 ,  224  and  226  Due to the previously-mentioned equidistant X-Y coordinate spacing of the open ends of these rail channels, and likewise as to the mounting openings  292 - 298  of the head plate  290 , and plate  290  can be mounted in any one of four 90° rotated positions. Likewise, mounting bracket  258  is provided with four mounting openings  300 ,  302 ,  304  and  306  (FIG. 8) in the end wall  264  of the bracket that also are located on equidistant X-Y coordinate centers to line up with the four open ends of the rail channels  216 ,  218 ,  224  and  226  at the opposite longitudinal ends of the rail. Self-threading screws are again provided through these openings to mount bracket  258  to the rail end. Again, any one of four quarter turn installation positions may be utilized because of the mounting hole equidistant spacing. The holes  308  (FIG. 7) and  310  (FIG. 9) in side walls  262  and  261  of the bracket receive the drive unit mounting bolt  260  therethrough for mounting the drive unit in the bracket after the mounting screws have been inserted into the rail end. 
     From the foregoing description it will be seen that the electric seat slide and actuator system of the first embodiment of FIGS. 1-20 combines the components as a complete factory pre-assembly of the dual spaced-apart rails and slides, the dual lead screw drives, dual gear boxes and single electric motor. Typically, a boat seat is mounted on top of the assembly by fastening it to the two laterally spaced slides  108  and  112 , utilizing preassembled machine screw fastening lugs  320 ,  322  on slide  108  and  324  and  326  on slide  112  (FIG.  1 ). These fastening lugs are provided in the offset extension mounting flange  115  of the mounting platform  114 , and hence are spaced outwardly and clear of the rail upright wall structure regardless of the assembled orientation of the rail and slide, as will be evident by comparing the various orientations shown in FIGS. 17,  18  and  19 . The seat, with the electric seat drive rails and motor assembly attached, can then be mounted on a seat box or other attachment structure in the watercraft by utilizing mounting fasteners  330  and  332  provided in the lateral mounting flange  202  of bottom wall  200  of rail  106  (FIG.  1 ), and fasteners  334  and  336  in the like lateral extension mounting flange  203  of rail  110 . 
     The entire assembly and its various components are preferably designed for use in marine applications that require resistance to salt water. The exposed surfaces are therefore made of marine grade materials. However, it is to be understood that this assembly, drive and mounting slide can be used for other non-marine applications. However the slide and rail are preferably made of aluminum material as extrusions that best lend themselves to marine application. The extrusion cross sectional configuration of the rail incorporates integrally the lateral mounting flange extension or legs  202  and  203  of the respective rails, and likewise the extrusion cross sectional configuration of the slide incorporates integrally the lateral mounting flange extensions  115  of the mounting platforms  114  of the slides. In addition, the rail extrusion configuration provides for the four self-tapping screw openings in each of the opposite longitudinal ends of the rail. 
     Glides  142  and  144  for each slide can be made by extrusion but preferably are injection molded of filled Delrin material to provide bearing surfaces that are self-lubricating and thereby insure a good sliding action. The stiff but resilient nature of this glide material, as configured in the slides as described previously and when fit on the slide and inserted in the rail to be stressed in the clearance space therebetween, has been found to eliminate play between the slide and rail that otherwise would cause an undesirable wobble or rattle of the seat assembly. 
     The slide extrusion with the toes  128  and  130  providing the glide mounting slots  132  and  134  for receiving the ribs  186  and  188  of the glide enables each glide to be easily fastened securely in a selected position on the slide. This is done by striking in and thereby permanently deforming a portion of the toe wall adjacent to but just beyond the axially opposite end faces of the glide. Thus, slots  132  and  134  and the tabs thereby formed in slide wall toes  128  and  13 ) that are designed into the extrusion configuration enable this material to be easily crimped to form tabs in-situ that hold the two glides in place on the slide after the same has been stress slip-fitted and slid into desired location on the slide. 
     In the first embodiment system of FIGS. 1-20 motor  100  is remotely mounted from each rail and slide sub assembly, and a pair of flexible drive shafts couple each end of the motor output shaft to drive in tandem each of the dual lead screws via each associated gear box  258 . A conventional automotive type electric motor  100  thus can be utilized that will allow connecting two conventional flexible drive shafts  250  and  350 , one to each of the output ends of the motor, so that shaft  250  drives lead screw  140  and shaft  350  drives lead screw  141  (FIG.  1 ). Connecting both drive shafts  250  and  350  in tandem advantageously enables the drive of the port and starboard slide and rail assemblies  102  and  104  to be synchronized. Typically, the carriage or the slide of each of these port and starboard slide and rail subassemblies is mounted one on each side of the seat. Hence with this driving system the load is applied to both sides of the seat. With the slides so synchronized and driven in unison, there is very little or no tendency to lock up or rack the drive system, such as that which typically occurs in prior constructions when a seat is moved with a load that is applied unevenly or to one side only. 
     Preferably drive screws  140  and  141  and drive shafts  250  and  350  are made of high tensile steel, which, of course, is not a marine-grade material. However, drive shafts  250  and  350  are covered with a plastic sheath  252  and  352  to protect them from the marine environment. A special corrosion resistant coating is put on each of the drive screws  141  and  142 , and a special marine-grade grease is used to coat the drive screw and drive shafts to insure that they can withstand salt water conditions. 
     Due to the spacing or clearance between the exterior surfaces of the slide and the interior surfaces of the rail, typically 0.100 inches, and which is maintained in operation by the slide bearing glides  142  and  144 , compensation is thereby provided for any misalignment that might occur when deflection-magnitude loads are applied to the seat assembly, or rail misalignment is imparted by improper mounting surface structure. Glides  142 ,  144  also eliminate metal-to-metal contact or torque twist from the screw drive mechanism that drives the slides on the rails. The folded spring provided by the raised bow rib  158  in the bottom will portions  154  and  156  of glides  142 ,  144  fills the gap between the slide and rail, and this bow rib flexes if there is side-to-side misalignment therebetween. This bow rib thus acts as a spring to eliminate noise or rattle that would occur if there were a free gap between the slide and rail. This folded spring also compensates for dimensional vacations in the plastic or aluminum extrusions. 
     As best seen or visualized in the illustration of FIG.  13  and FIG. 14, each plastic glide  142 ,  144  has bearing points at each of its four corners to transmit loads applied between the rail and slide in any direction at a plane perpendicular to the screw axis. This is important inasmuch as such loads are applied in all directions, up, down or sideways. Seat testing has shown that the greatest loads are downward and upward, as occurs when the seat occupant rocks back and forth, or when the occupant leans back against the back of the seat. The slide bearing system provided by the pair of spaced glides  142  and  144  thus insures that all such loading can be taken adequately by this system without frictional lock up or damage to the system. 
     The lateral extension provided by the asymmetric cross-sectional geometry of the mounting platform  114  of the slide, i.e., its laterally offset mounting flange  115 , and likewise the laterally offset mounting flange  202  of the bottom wall  200  of the rail, as described previously, provides convenient offset mounting flanges for mounting the assembly to the seat or seat box or to other mounting structure in the watercraft. These offset mounting flanges extend beyond the associated upright structure of the slide and rail and thus act both as beam stiffeners and readily accessible platforms for ease of inserting and removing mounting fasteners. The assembly thus accommodates the preference of boat builders who prefer an assembly that lets them flush mount to the flat surface of the seat and the flat surface of the seat box. 
     In the illustrated embodiment the slide and rail assembly with gear box accomplishes a low profile seat mounting and power drive system assembly which, for example, may be only 1¾ inches in vertical dimension. 
     Typically, motor  100  is operably electrically coupled in a conventional travel control system that utilizes the gear reduction bracket  250  at one end of the rail and the end bracket or plate  290  at the other end of the rail as limit stops against which the juxtaposed end of the slide abuts attach end limit of travel in the rail. This obstruction increases motor current load that, through a thermistor in the motor circuit, de-energizes the motor, thereby providing a typical limit switch motor control type operation for this system. If desired, an adjustable stop  354  can be fastened to the lateral extension  202  of rail  106  (FIG. 2) and a stop abutment  356  fastened to the lateral extension  115  of slide  108  to thereby serve as an adjustable stop system to suitably adjust travel of the actuator assembly. 
     Use of aluminum extrusions to manufacture the rail and slide components facilitates modular design and manufacturing. These extrusions can be cut to varying lengths to suit various applications. Thus, two basic extrusion cross sectional configurations and the associated simplified extrusion die and tooling can be used to create a large number of different assemblies, thereby reducing manufacturing costs. Further versatility is achieved because the pitch of the lead screw can be readily changed by appropriate selection of lead screws to give faster traverse, or slower traverse with greater torque. The lead screws can be standard automotive drive screws for power seats in vehicles, and thus such are readily commercially available in standard lengths. Custom lengths can be created economically by using cut down or using stub drive screws and welding different drive screws on to provide different lengths and pitches. Drive motor  100  is also readily and economically available from automotive suppliers and may be low profile, i.e., a vertical dimension of only 1¾ inches. The plastic glides  140  and  142  are preferably made of lubricant-filled Delrin or a polyolefin-polyethylene or polypropylene that have good lubricating properties. Whatever plastic material is used to meet this parameter should have a high elastic modulus or spring rate inasmuch as the high spring rate of the plastic mate rial of each glide as intended to assist the glide functionally gripping and staying in place on the slide initially as a workpiece subassembly during manufacture, i.e., until the final tab staking operation is performed. 
     The electric seat slide and actuation system may be used in applications to move the watercraft seats fore and aft, or to move these seats up and down, or to tilt seats up and down. The system can also be used to move bolster seats up and down and in an arc. This system is also adaptable to be used as a lift mechanism for imparting motion either vertically or in an arc, such as a hinge-mounted pivoted hatch. For this purpose the mounting surface on the slide and rail can be modified to accept a clevis. The rail and slide subassembly substantially limits relative rotation between the slide and rail about their center line axis, which assists in maintaining good vertical and horizontal rail and slide alignment and parallelism in operation. 
     FIGS. 10,  11  and  12  illustrate an injection molded plastic ferrule  251  that is preferably utilized to receive the flexible drive cables  252  and  352  therein at their ends to limit bending stress on the cables at these terminations in accordance with conventional flexible drive cable practice. 
     Second Embodiment 
     FIGS. 22-29 illustrate components of a second embodiment electric seat slide and actuator system of the invention. The second embodiment system utilizes essentially the same components as employed in the first embodiment system, but provides a greater length dimension in the rail and greater slide bearing range by the use of two longitudinally spaced slides on each rail to thereby accommodate a greater load carrying dimension longitudinally of the rail. Also, as seen in FIG. 21, the port and starboard rail/slide subassemblies  400  and  402  are widely spaced laterally from one another, and this is accommodated by utilizing suitable extended lengths of shrouded drive shafts  404  and  406 . Note that the drive reduction units  256  are mounted with brackets  258  inverted or rotated 180° from their mounting shown in the first embodiment system of FIGS. 1 and 3, thereby fur her illustrating the versatility of the system design in this regard. 
     Each of the rail/slide assemblies  400  and  402  utilizes one rail  408  and  410  respectively that may be economically made in the same extrusion dies as rails  106  and  110 . In addition, each of the rail/slide assemblies  400  and  402  utilizes two slides instead of one, namely an aft slide  412  and a forward slide  414  mounted longitudinally spaced apart on rail  408  but operable in same manner as in the first system of FIGS. 1-20. Each slide thus has its own lead screw drive nut  280  associated therewith threadably received on a common lead screw  140  so that the two slides are driven for synchronized travel in unison. Likewise, the tandem hook-up of motor  100  to the port and starboard rail/slide subassemblies insures synchronized drive of both sides of the entire system, similar to that described in conjunction with the first embodiment system. 
     FIGS. 24 and 25 illustrate rail  408  of the port side rail/slide assembly  400 . As will be evident from FIG. 21, the starboard side rail  410  is identical and turned around as a mirror image in assembly but constructed identically during manufacture of this component. Likewise as to each of the slides  412  and  414 , one of the slides  412  being illustrated in FIGS. 26,  27  and  28 . The same component is made identically and used as the slide for slides  414  of the port assembly  400  and for each of the slides  414  and  420  of the starboard rail/slide assembly  402  It will be understood that the slide  412  as shown in FIGS. 26 and 28 is turned around ends for end from its showing in FIG.  23 . 
     Experimental Prototype Hardware 
     FIGS. 30-39 illustrate, by graphic line drawing reproductions of photographic prints, various features and facets of experimental operational prototype hardware constructed in accordance with the foregoing description as referenced in conjunction with FIGS. 1-29 and hereby incorporated by reference to these photo print reproductions. Thus, FIG. 30 illustrates a system assembly set up like FIG. 1 but with the port and starboard rails and associated slides assembled and oriented as shown in FIG.  17 . Note that the reduction drive brackets are mounted as shown in the second embodiment system for tandem drive off the single motor  100 . Reference numerals from FIGS. 1-29 are thus applied to FIGS. 30-39 and therefore the description of the illustrated components not repeated. 
     Third Embodiment System 
     FIGS. 40-44 illustrate a third embodiment system of the invention wherein a single side drive is employed to activate and actuate a power adjustable and dual rail/slide supported single-person seat that is also mounted for swivel action, i.e., rotation about a vertical axis. As shown in FIGS. 40 and 41 the seat is a conventional one-piece molded member in the style of a captain&#39;s chair  500  having a back  502 , a head rest portion  504 , a seat portion  506  and side arm portions  508  and  510 . In FIG. 40 the third embodiment power seat adjustment and swivel mechanism  512  is partially visible below the seat bottom  506 . In FIG. 41 this mechanism and associated swivel mounting structure is essentially hidden by the seat. 
     FIGS. 42 and 43 illustrate the third embodiment electric seat slide and actuator system de-mounted from seat  500 , the system components being shown upside down in FIG.  42  and in vertical right-side-up front elevation in FIG.  43 . Note that the port slide and rail assembly utilizes the same rail  106  and slide  108  as in the first embodiment system (FIG.  1 ), but with the mounting flange extensions of the rail and slide facing inboard as in the orientation of FIG.  17 . Likewise, the starboard rail and slide subassembly utilizes the starboard rail  110  and starboard slide  112  components of the FIG. 1 system, as well as the mounting bracket  258  to operably mount a right angle drive unit  514 . However drive unit  514  is part of a combined motor and drive unit and thus mounts the associated drive motor  516  of a commercially available combination motor and reduction drive unit. Hence, motor  516  also receives its support from the mounting bolt  260  of bracket  258  that supports the gear reduction unit to  514 . This third embodiment system thus does not employ a flexible drive cable, and also only employs one lead screw driven off the motor mounted directly on the port side rail and slide subassembly  110 / 112 . As another difference, note that the starboard side slide  108  is slave-driven off of slide  112  by fastening a pair of two rigid cross piece plates  520  and  522  at their ends to the mounting platform of the slides  108  and  112 , as shown in FIG.  42 . The fastenings of the ends of the plates and their width dimension may be used to rigidity the dual rail and slide assembly and make it possible to transmit driving force from slide  112  over to slide  108  without undue cocking or lock up forces being developed for medium rated loads. 
     In order to provide sea swivel capability, a standard conventional cast swivel spider  524  is mounted as shown in FIG. 42 with two of its legs bolted to cross brace  520  and the other two legs bolted at their ends to cross brace  522 . The center of rotation of swivel fixture  524  is centered between the two cross braces  520  and  522  and likewise centered laterally between two slides  108  and  112 . Note that the four legs of the swivel casting, by their attachment to the two cross braces  520  and  522 , serve to maintain the parallelism of these two cross braces  520  and  522  independently of their mounting support fastening arrangement on slides  108  and  112 . Hence, only one mounting bolt is needed to attach each end of each cross brace to the associated slide, as will be evident from FIGS. 42 and 43, as well as FIG.  44 . 
     The third embodiment system of FIGS. 40-44 thus consists of a seat for one person that is mounted on a pedestal for swivel rotation about a vertical axis. A single motor attached to one of the rail/slide assemblies drives both assemblies together by slave driving the non-lead screw slide-rail assembly through the cross-over bridge plates  520  and  522 . Preferably the port and starboard rail/slide assemblies are laterally spaced apart no greater than 22 inches to prevent undue racking or lock up forces being exerted. On the other hand, the two rail assemblies are spaced preferably at least 8 inches apart in the example shown in order to limit wobble and flexing of the seat on the dual rail slide mounts. Within these constraints the third embodiment system provides a power actuated, swivel-type single person eat system at reduced cost due to the elimination of one lead screw, one drive nut, one gear reduction unit and one drive shaft. However, it is believed that for most applications the single motor tandem dual drive employed in the first and second embodiment systems is preferred since it enables much more flexibility in rail spacing and load driving capability without lock up or undue racking from unbalanced resistance forces and/or weight loading forces. Preferably drive screw  140  utilizes an Acme thread and, as indicated previously, is made of high strength steel or stainless steel, whereas lead screw drive nut  280  is preferably made of a plastic material such as nylon or may be made of a non-ferrous material such as brass. 
     From the foregoing description and appended drawings, it will now be evident to those of ordinary skill in the art that the electric seat slide and actuator system embodiments of the invention amply fulfill one or more of the aforestated objects and provide many advantages and features over the prior art, such as those stated previously. However, it will also be understood that the invention has many equivalent features and applications other than those illustrated which will be apparent and useful to those skilled in the art without departing from the spirit and scope of the invention and as set forth in the appended claims.