Abstract:
4-bar hinge technology is applied to forward hinged mounting of a conventional cab high cover on a pickup truck load bed, so that the cover moves clear of the vehicle cab when raised to provide improved loading access. The hinge system may be integrated with upper and/or lower rails intermediately attached to the cover and load bed rails used as mounting interfaces in fixed cover installations. Use of these interfaces alone for system attachment supports universal application to conventional matched cab high covers and load beds with minimal component variation between applications. Resulting component dimensions accommodate compact packaging, and therefore convenient, efficient shipping and storage of adaptation hardware. The system concept accommodates use of readily available hardware suited to processes and equipment already in use within affected industries, and facilitates capture of dimensions for optimal function within hinge and intermediate rail assemblies, thereby minimizing reliance upon installer skills.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   This invention is based upon Provisional Application#113260 U.S. PTO 60/901,758 dated Feb. 16, 2007 entitled Short/Long Arm Hinging System for Cab-High Load bed Cover and claims benefit available to that application under 31 U.S.C. 119(e). The provisional application describes improvements over lift-roof cover concepts described under U.S. Pat. Nos. 4,756,571, 5,102,185, and 7,093,882. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   not applicable 
   NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
   not applicable 
   REFERENCE TO A SEQUENTIAL LISTING 
   not applicable 
   BACKGROUND OF THE INVENTION 
   The invention pertains to adaptation of cab high load bed covers used with pickup trucks to provide improved access to the load bed for loading/unloading and also to extend functions to new uses (where “cab high” is used to distinguish covers of approximately cab height, or greater, from load bed covers having a low profile, which are usually described as “tonneaus”). A major focus is upon achieving these benefits in a manner best accommodating processes broadly in use relative to conventional fixed mount cab high covers of the prior art (also referred to as “caps” and including covers having a height approximately matching vehicle cab height or greater, as distinct from low profile load bed covers usually described as tonneaus). Applicable US classifications include 296/100.1, 100.6 hinged load covers, 296/165 expansible or collapsible vehicle body, 296/176 expansible/collapsible from a first to a second configuration for camping. The disclosure describes a system which can be adapted for installation as part of a complete rear lifting load bed cover (similar to a lift-roof cover), or sold as a kit to be installed at a retail level. The system avoids or minimizes need for modification of the cap and ensures that aesthetic benefits are fully maintained. The application of an appropriately configured 4-bar hinging system, in combination with means for controlling associated functional geometric requirements independent of the installation process, overcomes key objections directed at lift-roof covers of the prior art. 
   (b) Description of Related Art 
   Enninga, U.S. Pat. No. 5,104,175, discloses an openable cover that is operable about an internally mounted, stationary pivot means disposed adjacent the inside top, forward end of the cover so that the cover may be rotated between open and closed positions with respect to the load bed. Limitations of the concept appear to include cost and complexity both in manufacturing and installation. A system is shown for attaching and rotating a conventional cab high load bed cover  17  to provide rear lift. The system employs hinged attachment of the cover to a frame comprising left and right side bases  21 ,  22  joined by a bridge  29  to create a frame fixedly attached to the vehicle load bed  13 . Lever members  27 ,  37  are attached to the frame by pivots  25 ,  35 . It appears that the cover  17  is attached to lever members  27 ,  67  and thereby pivots about pivots  25 ,  35 . With this arrangement, attaching locations on the cover  17  must be used other than as provided by cover side wall mounting rails normally employed for fixed mounting of a cover to a vehicle load bed. This apparently requires mountings of some form to be added to the cover forward wall. Such modifications may adversely affect the future utility and value of the cover and are avoided in the present invention. 
   Medlin, U.S. Pat. No. 5,595,418, discloses a short/long arm system for pivotally attaching a camper shell (cab high load bed cover) to a vehicle load bed, allowing rear lift while keeping the cap upper forward edge clear of the vehicle cab. However, upper and lower arm pivots are disclosed as substantially one above the other on the cap forward wall (or adjacent to it on the side walls). These upper pivot locations appear to require a prohibitively heavy and costly form of arm construction in order to achieve levels of lateral rigidity which would provide stable positioning of the cap relative to a load bed when open and also probably present difficulty with respect to completing satisfactory installation. As in Lake U.S. Pat. No. 7,093,882, attachments at the cap forward wall appear to require techniques which prevent it from being conveniently adaptable to a variety of production caps. 
   Whereas Medlin discloses a large long upper arm above a large short lower arm, each arm pivoting from an upper attachment at, or adjacent to, the cap forward wall, the present invention employs relatively small short forward and long rearward arms, each pivoting from an upper attachment at, or close to, the horizontal mounting rail at the lower edge of each side wall. In Medlin, an upper arm upper pivot resides substantially vertically above a lower arm upper pivot on or proximate the cap forward wall (cap closed), whereas in the present invention arms are positioned so that the upper pivot of each arm lies substantially on, or close to, the same horizontal plane when closed, and at no time does one arm lie above the other. Medlin discloses lengths for upper and lower arms around 48 and 30 inches, respectively, which are 6 or more times longer than needed for arms in the present invention. 
   Technology of the prior art also includes a 4-bar hinging system used in forward hinged attachment of low profile molded unit covers (e.g. Leer model 700) to pickup load beds. However, 4-bar hinges of the prior art for low profile load bed cover applications, if applied to forward attachment of a cab high cover, provide insufficient rearward travel of the cap to maintain clearance between a truck cab and a load bed cap when raised. 
   Market testing of the lift-roof cover concept defined by Lake U.S. Pat. No. 7,093,882 revealed cost issues resulting from replacement of the cap forward wall with a hinged forward wall assembly and from associated complexities of addressing multiple applications of potential customer interest. Interest has been further limited by an associated loss of availability of forward window options demanded by many users of conventional caps. The present invention provides reductions in complexity of application relative to Lake U.S. Pat. No. 7,093,882 while giving up a small degree of functionality. The improvement in loading access is provided with use of readily available caps requiring minimal or no attachment modifications. The invention is simplified relative to Lake U.S. Pat. No. 7,093,882 by avoiding need for modification of the cover forward wall, thereby more easily maintaining functional robustness and supporting customer demand for pivoting, removable, or sliding forward window options. 
   SUMMARY OF THE INVENTION 
   It is an objective of the invention to provide means for adapting a conventional cab high load bed cover to allow rear lift access as installed for use, with broad application to production pickup trucks and covers. Conventional cab high covers of the prior art vary in many details of design, as do pickup truck load beds. However, almost all load beds are built with side walls including substantially horizontal surfaces along their upper longitudinal edges which may be referred to as “bed rails”. Conventional molded caps are made with surfaces along the lower edges of their walls, usually referred to as “cap rails” and matching the load bed rail surfaces for mounting thereon. In a conventional fixed mount, cab high cover (cap) installation, weather seals are normally attached between the cap rails and load bed rails. The invention provides a lift adaptation system which is also attached between the cap rails and load bed rails, thereby supporting near-universal application with little or no modification of the cap or load bed. 
   In one embodiment of the invention, the cap rails are used as mounting surfaces for an upper intermediate rail attached to an upper link of a 4-bar hinge assembly. The hinge assembly may also be attached at a lower link to a lower intermediate rail which is, in turn, attached to the load bed. With the addition of upper and lower intermediate rails for attachment along the length of the cap rails and load bed rails, respectively, this embodiment of the invention conveniently accommodates attachment to the rails of key components needed for control of relationships between the cap and load bed. Such components include cap lift assist means (typically gas compression struts or articulating arms carrying compression struts), side retainers (to ensure correct lateral positioning of the cap relative to the load bed when closed), pivoting fixed strut means for securely holding the cap to a fixed partly raised position when needed for transporting an over height cargo), and draw latches for conveniently drawing and securing the cap to a closed position on the load bed. With pre-assembly of such a hinge and intermediate rail system, component relationships required for optimal function may be kept independent of installer skills, ensuring reliable reproduction of desired system geometry and supporting an installation process suited to the needs of most load bed cover retailers. 
   Forward pivoting of cab high covers (versus low profile covers) introduces issues beyond the obvious issue of cab interference resulting from tilting of the forward wall as a cap is lifted. A cab high cover typically has greater weight than a flat cover and, to the degree that lower edges of the side walls remain structurally unsupported, flex at hinge mountings will generally be greater. Considering flex and manufacturing costs, it is desirable to keep hinge arm lengths short. In 4-bar hinge applications of the prior art for unit-molded low profile load bed covers, pivots are longitudinally spaced so that, over much of the operating range, a long rearward arm lies vertically above a short forward arm in side view and the arms are limited in rotation, so that upper pivots only rise toward perpendicular (relative to upper surface of load bed side wall) during cover opening and only fall during closing. In the present invention, longitudinal spacing of pivots is such that a short forward arm rotates “over center” and at no point during operation lies vertically below the long rearward arm. 
   It will be recognized by one skilled in the art to which the invention pertains that application of a load bed cover to a load bed needs to fully address the effects of dynamic vehicle operation. In particular, structural flex and associated stresses will occur. The extent and effects of such stresses were inadequately addressed in some early molded cap designs with resulting fractures in extreme use cases. Although manufacturers have, in general, greatly improved structural characteristics, caps have used fixed mountings. Most caps maintain stable dimensions but, without lateral support, some early products have shown tendencies for lower edges of the rear door opening to start spreading. It is therefore necessary that, in closed condition, cap side walls are laterally constrained at the lower edges in a manner providing equivalence to mounting of conventional fixed caps. Such constraint may be conveniently integrated into the invention as will be described. Another consideration is that some manufacturers build a front to rear taper into the load bed side walls as a styling enhancement. This affects operation of a linkage as employed in the invention, resulting in flex effects which must be accommodated in system function. 
   The invention will be recognized by one skilled in the art to which the invention pertains as addressing complex issues associated with adaptation of production fixed mount cab high load bed covers to rear lift access. This is accomplished with simple structures which, in combination, provide the obvious advantages of rear lift access together with numerous advantages over technology of the prior art, including:
         Supporting near-universal application across production pickups and cab high caps;   Providing fuel economy improvement primarily due to reductions in frontal area and associated aerodynamic drag compared against on-highway use of caps exceeding cab height as means for providing improved load bed access;   Retaining all the appearance, protection and security benefits provided by a conventional, fixed mount, cab high load bed cover (cap).   Utilizing readily available hardware already in widespread use;   Providing the benefits of rear lift access with components which may be conveniently packaged, shipped and stored as a kit at low cost;   Supporting convenient adaptation to lift access of production caps already in service;   Incorporating means for conveniently and effectively accommodating dimensional variations across production caps and vehicles;   Avoiding need for reliance upon installer skills to ensure optimal system geometry (with use of upper and/or lower intermediate mounting rails);   Incorporating means of moving cover axis of rotation rearward during lift, minimizing (at cap full open) the adverse effects of compression strut low temperature effort fall-off.   Addressing structural deficiencies which may be present in some cap or pickup load bed designs relative to adaptation to lift access (with use of intermediate rails);   Ensuring high levels of cover lateral stability when open, by employing forward mounted compact dual pivot arms in conjunction with rear mounted articulating arms.   Facilitating use of forward compression struts in combination with rear mounted struts to a) facilitate installation and b) support improved reliability and lift effort modulation.   Supporting convenient adaptation to use with various load management accessory rail systems offered by pickup truck manufacturers.       

   
     DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The description refers to the accompanying drawings in which like characters refer to like parts throughout the several views. Much of what is described in the disclosure refers to one side of an installed short/long arm 4-bar hinge system. The other side may assumed to be of like, or mirror image, form and in such cases the same reference number may apply on both sides. 
       FIG. 1  is a perspective view from the rear showing a cab high cover (cap) mounted on vehicle load bed via a 4-bar hinge and intermediate rail system in raised, open position; 
       FIG. 2  is a side elevation looking left at a left side 4-bar hinge assembly with cap closed, showing forward compression strut mounting and 4-bar hinge adjustment means; 
       FIG. 3  is an enlarged fragmentary sectional view along lines  3 - 3  of  FIG. 2 , showing lateral location of longitudinal cap to load bed sealing means relative to intermediate rail, including detail of the locational capture of a lower intermediate rail to load bed attaching clamp by means of a rivet through the lower intermediate rail. 
       FIG. 4  is an enlarged fragmentary sectional view along lines  4 - 4  of  FIG. 2  showing 4-bar hinge pivot means retention relative to a lower intermediate rail and a load bed mounting rail. 
       FIG. 5  is a side elevation looking left at a left side installed 4-bar hinge assembly with cap open, showing relation of hinge system to cap forward wall; 
       FIG. 6  is a fragmentary sectional view along lines  6 - 6  of  FIG. 5  showing use of spacing means at attachment of a 4-bar hinge assembly (upper link) to upper intermediate rail plus relief/clearance requirements between a molded cap locating lip and hinge arms in an open condition. 
       FIG. 7  is an enlarged fragmentary view similar to  FIG. 6  of an alternate structure for adjustable attachment of a 4-bar hinge to an upper intermediate rail. 
       FIG. 8  is a side view of a 4-bar hinge and intermediate rail assembly folded as for shipping 
       FIG. 9  is a side view of a 4-bar hinge and intermediate rail assembly in open condition. 
       FIG. 10  is an enlarged fragmentary sectional view along lines  10 - 10  of  FIG. 9  showing attachment to an upper intermediate rail of an upper to lower intermediate rail side retainer means. 
       FIG. 11  is a side view of an alternate 4-bar hinge and lower intermediate rail assembly used in conjunction with a generally channel section bar or rail of a type offered by pickup manufacturers for attachment of load management accessories to a load bed. 
       FIG. 12  is an enlarged fragmentary view along lines  12 - 12  of  FIG. 11 , showing relationships between the 4-bar hinge and integral lower intermediate rail assembly, the channel section rail and the load bed upper inboard flange. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 : As installed on a pickup truck  10 , a cab high load bed cover (cap)  12  is mounted behind a passenger cab  14  on a load bed  16  including side walls  18  fabricated so that a side wall outside vertical surface  20  is continuous with an upper, substantially horizontal rail surface  22  of the wall  18 . The rail surface  22  likewise is continuous with an inside vertical flange  24  joined to the rail surface  22  at about 90 degrees, extending downward typically one to two inches and serving to add rigidity. The inside vertical flange  24  is generally accessible along most of the length of the load bed  16  between the load bed forward wall  26  and rear end  28 . Side walls  30  of the cap  12  are joined at their lower edges  31  to cap structural rails  32  which terminate along their length at an inner edge  34  above the load bed flanges  24  and extend from a forward wall  36  to the cap rear wall  38 . The cap rails  32  generally match contours of the load bed rails  22 . In one embodiment of the invention the cap  12  is attached at the cap rails  32  to an upper intermediate rail  40  attached to a short/long arm (SLA) 4-bar hinge assembly  42 ; the 4-bar hinge assembly  42  is in turn attached to a lower intermediate rail  44 , and the lower intermediate rail  44  is in turn attached to the inside vertical flange  24  of the load bed side wall  18 . 
   One embodiment of the invention employs articulating strut arms  46 , carrying pivotally mounted rear compression struts  47 , the strut arms  46  being pivotally attached between the upper and lower intermediate rail assemblies  40 ,  44  at a rearward, fixedly attached upper pivot  48  and at a rearward fixedly attached lower pivot  49  in such a manner as to provide assist when the cap  12  is raised or lowered from the rear  38 . For the purpose of raising or lowering the cap  12 , a handle  50  is fixedly attached to the cap  12  in a rearward location proximate a legally required central high mounted stop light (CHMSL) unit  52  connected to electrical wiring  54  routed to the vehicle  10  via an articulating strut arm  46 . Latching means  56  (such as claimed and/or disclosed in Lake U.S. Pat. No. 7,093,882), attached to a cap rail  32  or an upper intermediate rail  40 , allows latching of the cap  12  to a closed position relative to the load bed  16  by engagement with the load bed  16  or lower intermediate rail  44  attached thereto. A rear door  57  is typically hinged to the cap  12  in proximity to the cap roof rear lateral edge  58  and provides closure of the cap rear wall  38  between the (left and right) cap side walls  30 . 
   Referring to  FIGS. 1 and 2 : The 4-bar hinge assembly  42  may be understood as four links  60 ,  61 ,  62 ,  64  interconnected by pivots  66 ,  68 ,  70 ,  72 , making up a closed linkage  42  of quadrilateral form. Two links  64 ,  61  on opposing upper and lower sides incorporate attachment means  73 ,  74  and  75 ,  76 , respectively, by which major bodies may be attached. The other links, comprising a short arm  60  and long arm  62 , control relationships between links  61 ,  64  and between a cap  12  and load bed  16  fixedly attached to links  61 ,  64 , respectively. Geometric relationships (as installed for use) include location of upper pivots  66 ,  72  for arms  60 ,  62 , respectively, on or in proximity to the cap mounting rail  32  forming the base of each cap side wall  30 . The lower pivots  68 ,  70  are located in proximity to the upper edges  22  of the load bed side walls  18  (where a lower edge of the side wall inside flange  24  may be considered in proximity to the side wall upper surface  22 ) and are longitudinally spaced apart a distance greater than the spacing between the long arm upper and lower pivots,  72 ,  70 , respectively, so that under all operating conditions a short forward arm  60  remains forward of the long rearward arm  62 . The short/forward arm  60  rotates “over center” (beyond a condition where a line through upper pivot  66  and lower pivot  68  of the forward arm  60  reaches an angle perpendicular to an upper surface  22  of the side wall  18 ) so that, during later stages of opening, the short arm upper pivot  66  falls relative to the lower pivot  68 . This increases rearward movement of the forward arm upper pivot  66  sufficiently to support a maximum cover lift angle equivalent to that provided by 4-bar hinge systems of the prior art for low profile load bed covers, while employing a short arm length allowing minimal levels of lateral arm flex. 
   An upper intermediate rail  40  comprising one or more generally angle section extrusions  77  is fixedly attached toward a forward end  78  to a hinge system upper link  64  and extends rearward most of the length of the cap rail  32  toward fixedly attached upper pivot means  48  and latch means  56 . A lower intermediate rail  44  comprising one or more generally angle section extrusions  79  is fixedly attached to the hinge assembly lower link  61  and extends rearward along a load bed side wall  18  toward a fixedly attached strut arm lower pivot means  49 . The upper and lower strut arm pivot means  48 ,  49 , are engaged with the articulating strut arms  46 , and constrain the strut arms  46  to a substantially vertical orientation in front or rear view when the cap  12  is raised. 
   SLA hinge geometry causes the cap instant rotational axis (defined by intersection of force lines through pivots  66 ,  68  and pivots  70 ,  72  of arms  60  and  62 , respectively), to move from ahead of the cap forward wall  36  to a location well aft of the forward wall  36  as the cap  12  is raised. Thus, vertical rear lift force (total unaided) needed to raise the cap  12  may exceed half cap weight when lifting from closed, but decreases toward full open. This allows rear mounted lift assist compression struts  47  with relatively low force value to hold the cap  12  fully open and expands the range of geometry which allows the cap  12  to also sit closed without being separately retained in that position. 
   Whereas open cap forward lateral stability may depend primarily on lateral control provided by the hinge forward/short arms  60 ; rear mounted articulating arms  46  (as defined by Bacon, Pub. No. US2004/0084928 A1, and marketed by Bauer Products Inc. of Michigan) control cap lateral deflection of the cap rear  38  while supporting rear opening lift similar to lift achieved with some forward hinged low profile covers. To provide the desired improvement in rear loading access (as for drive-on loading of a garden tractor), rear height clearance is needed approaching double the head room of a typical cab high cover above a closed flat cover. Pivot arm geometry is defined primarily by need to offset tipping of the cap forward wall  36  toward the vehicle cab  14 , when raising the cap  12 . It will be recognized by one of ordinary skill in the art that rearward travel of the upper forward pivot  66  is limited by rotation of the forward/short arm  60 . It will also be seen that, with the forward upper pivot  66  located aft of the cap forward lower corner  82 , rearward travel may be further limited by interference of the cap forward lower corner  82  with the vehicle load bed  16 , due to downward tipping ahead of the forward arm upper pivot  66 . This requires the pivot  66  to be located close to a cap lower forward corner  82 . 
   In an embodiment of the invention employing lift assist means  47  mounted rearward only, when the cap  12  is raised at the rear  38 , the SLA 4-bar hinge upper link rearward attachment means  73  exerts force on the cap mounting rail  32  and, at the same time, lower link rearward attachment means  76  exerts opposing force on the load bed side wall inside flange  24  and/or lower intermediate rail  44  (where employed). Effects include deflection of the cap rail  32  and load bed rail  22  (plus possible bowing of hinge arms  60 ,  62 ). Loading of forward arms  60  is generally of concern only with respect to arm flex because such forces are transferred primarily via forward attachment means  75  and forward attachment means  74 , both of which are structurally well supported due to proximity to forward walls  26 ,  36 . 
   The SLA hinge arms  60 ,  62  (primarily forward/short arms  60 ) must provide reliable lateral positioning of the cap  12  with minimal bowing under load. However arms  60 ,  62  must flex sufficiently to accommodate lateral stacking of manufacturing and/or assembly tolerances and to a further degree in some applications where load bed side walls have tapered front to rear spacing for vehicle styling enhancement. Flex effects manifest as additional movement of the cap  12  toward the cab  14  when the cap rear  38  is raised, before hinge actuation causes forward cap lift-off from the load bed forward wall  26 . Flex effects can be reduced by addition of forward compression strut means  84  (as shown in  FIG. 2 ) to apply forward lift force at forward locations  88 ,  90  between the load bed  16  and cap  12 , bypassing the hinge arms  60 ,  62 , so that initial load transfer through the hinge arms  60 ,  62  is reduced when the cap  12  is raised from closed. 
   Manufacturing dimensional variation as well as flex under 4-bar hinge system operation can add significant lost motion in the form of forward tipping of the cap  12  when raised at the rear  38 , before SLA hinge actuation causes lift-off of the cap forward end  36 . This may be addressed in part via means for adjusting angle of upper or lower hinge link means  64 ,  61  relative to the cap or load bed mounting rails  32 ,  22 . With variability in thickness of the cap mounting rails  32 , adjustment of relative orientation between the SLA hinge upper link/bracket  64  and the cap side wall mounting rail  32  is needed to facilitate closed cap surface-to-surface alignment, as needed for desired seal compression. In a preferred embodiment, such adjustment may be obtained via slot vertical adjustment means  86  at a rearward attachment  73  of the hinge upper link/bracket  64 . 
   Greatest structural deflections occur in transition from zero to maximum load through the SLA hinge arms  60 ,  62  when the cap  12  is initially raised from closed. However, with addition of forward compression struts  84 , force through these struts remains present even when the cap  12  is fully closed, so that a force transition from zero to maximum levels is avoided. The forward compression strut  84  extends from an upper pivot  88  on the 4-bar hinge upper link  64  and/or intermediate rail  40  to a lower pivot  90 , attached via lower pivot mounting means  92  to the lower intermediate rail  44  and/or lower link  61 . 
   In applications where cap structural rigidity is low relative to weight, use of high force rear compression struts  47  alone may cause high levels of flex, possibly with associated functional issues. Therefore, the use of added forward lift struts  84  in combination with reduced force rear struts  47  is likely to prove more reliable, as well as supporting improved modulation of lift effort, while also avoiding compromise of the control benefits associated with use of articulating arms  46  at full rearward locations. Therefore, a preferred embodiment may incorporate adjustment means  86  to achieve optimal cap closure, in combination with forward compression struts  84  to minimize loading through the arms/links  60 ,  61 ,  62 ,  64  and pivots  66 ,  68 ,  70 ,  72 . 
   Referring to  FIGS. 1 ,  2  and  3 : Installation typically presents opportunities for error, but is simplified by use of lower intermediate angle section rails  44  clamped longitudinally against the vehicle load bed side wall inside flanges  24 , with a horizontal flange  93  between the load bed side wall upper surface  22  and cap rail  32 . Lower Intermediate rails  44  include pre-location of hinge assemblies  42  and rear strut arm lower pivot means  49  so that correct location of intermediate rails  44  relative to the load bed forward wall  26  results in automatic capture of desired hinge and lift assist system geometry. For safety, the lower intermediate rails  44  need to be securely attached to the vehicle load bed  16 . A vertical flange  94  of the lower intermediate rail  44  is clamped to a load bed side wall inside vertical flange  24 . Relying upon friction alone could be unreliable, given any possibility of error in applied clamp screw torque. In a typical embodiment, a minimum of three attachments on each side are used including clamps  75 ,  76 ,  96  on the lower intermediate rails  44  and load bed inside vertical flanges  24 . A clamp  76  has a clamping face  98  with a hole  100  engaging the projecting end  102  of a rivet  104  passing through the lower intermediate rail vertical flange  94 . With clamps  75 ,  76 ,  96  thereby positively engaged with a lower intermediate rail  44  and looped around a side wall inside flange  24 , each lower intermediate rail  44  is thereby positively retained to the load bed  16 . When clamp means  75 ,  76 ,  96  are tightened, flat rivet heads  105  are compressed against rubberized facing  106  adhesively attached to the lower intermediate rail  44 . 
   Referring to  FIG. 3 : Load bed covers are generally molded to fit on a load bed with an integrated appearance and sufficient clearance for installation of adhesive-backed strip sealing means  107  longitudinally installed between the load bed side wall upper rail surface  22  and the cap mounting rail  32 . Space between cap rail  32  and load bed side wall upper surface  22  allows outboard location of seal means  107 . The angle section lower intermediate rail horizontal flange  93 , being no more than compressed thickness of a cap to load bed strip seal  107 , may be mounted toward the inside flange  24  of the load bed side wall upper surface  22  without degrading seal function or vehicle appearance. 
   Referring to  FIGS. 2 and 4 : Hinge pivot means  66 ,  68 ,  70 ,  72  include bolts  108  with shanks  110  passing through close fitting holes  111  in the hinge links  61 ,  64  and arms  60 ,  62 . Hexagonal heads  112  of the bolts  108  passing through the lower links  61  are retained in matching hexagonal holes  113  in the lower intermediate rail  44  and protrude outward against the adhesively attached rubberized facing  106 . 
   Referring to  FIGS. 1 ,  5  and  6 : The lower edge  114  of a cap forward wall  36  forms a lateral shelf  116 , typically extending forward about two inches, to which strip seal means  107  is adhesively attached. seal means  107   a  seals against the top surface  117  of the load bed forward wall  26  when the cap  12  is closed. Where a cap manufacturer incorporates a molded lip  118  extending downward from the cap mounting rails  32  and forward wall  36  (inside the load bed side and forward walls  18 ,  26  when installed), the lip  118  will probably need to be locally relieved to provide clearance adjacent to the hinge assemblies  42 , latches  56  and/or strut arms  46 . Such material removal can generally be accomplished without compromising sealing or cap integrity. 
   Referring to  FIG. 6 : To facilitate adjustments at attachment means  73 ,  74  clearance must be provided for bolt heads  112  at upper pivot means  66 ,  72  relative to the vertical flange  119  of the upper intermediate rail  40 . When a single extrusion upper intermediate rail  40  is used, the required clearance may be achieved using spacing means  120  between the upper link  64  and upper intermediate arm vertical flange  119  at attaching means  73 ,  74 . 
     FIG. 7  illustrates an alternate method for providing bolt head clearance at upper pivot means  66 ,  72 , whereby bolt head clearance results from using an angle section intermediate rail  40   a  with a vertical flange  119   a  located outboard. A short upper link attaching bracket  121  of similar angle section is mounted toward the forward end  78   a  with an inboard vertical flange  122  between, and clear of, the hinge upper pivot heads  112   a.    
   Referring to  FIGS. 1 ,  8  and  9 : The use of an upper intermediate rail  40  mounted to the cap side wall mounting rail  32  (at each side), to which 4-bar hinge linkage upper link/bracket  64 , latching means  56  and a rear lift assist means upper pivot  48  are fixedly attached, provides further capture of geometric relationships similar to that provided by use of a lower intermediate rail  44 . Attachment of the upper intermediate rail  40  to the lower intermediate rail  44  on each side via the 4-bar hinge linkage  42  further defines relationships between components needing controlled geometric relationships for optimal function. Pre-assembly of these components provides a cap hinging system which may be installed between any cap and load bed of suited dimensions using an installation process which may be completed with minimal training requirements. 
   Upper and lower intermediate rails  40 ,  44  may be shipped pre-attached to 4-bar hinge linkages  42  at the upper and lower links  64 ,  61 , respectively, with compression struts  47 ,  84  left unmounted to facilitate shipping/storage with the rails  40 ,  44  folded. 
   Referring to  FIGS. 1 ,  4 ,  5  and  8 : System installation requires mounting of the upper intermediate rails  40  on the cap rails  32  with lateral spacing matched to that of the load bed side wall rails  22  on which the cap  12  will be mounted. This process is simplified where it can be first confirmed that spacing of cap rail inside edges  34  will correctly align with spacing of the load bed inside vertical flanges  24 . Longitudinal positioning is dependent upon clearance requirements for the cap forward wall lower edge  114  relative to the short arm  60  and lower intermediate rail  44  (or load bed side rail  22 ) with the cap  12  fully open, but may be set by positioning of the upper intermediate rail forward end  78  relative to the cap forward wall  36 . With the cap  12  suitably supported, the upper intermediate rails  40  are clamped in the desired position on the cap rails  32 . Holes  124  may be drilled in the cap rails  32  using holes  126  pre-drilled in the upper intermediate rails  40  for guidance. The lower openings  128  of holes  124  through the cap rails  32  are opened up with a countersink tool and flat head countersunk machine screws  130  are entered into the holes  124  with flat heads  132  flush with the cap rail lower face  134 . Capture of the upper intermediate rail  40  is completed with installation of locknuts  136  at the upper intermediate rail horizontal flange upper surface  138 . (In cases where the cap rails  32  are fabricated from flat plate/sheet metal, pan head or suchlike fasteners may be used in place of countersunk flat head screws  130  and nuts  136 , where the head height of such fasteners remains low relative to compressed height of sealing means  107 ). 
   The upper intermediate rail  40  may be attached to a cap rail  32 , as described above, in assembly with the SLA hinge linkage  42  and lower intermediate rail  44 . The lower intermediate rail  44  is next raised toward, and engaged with, latching means  56 , which are, thereby, used to hold the intermediate rail  44  against the cap rail  32 . Cap to load bed sealing means  107  are installed outboard of intermediate rail  44  along the cap rails  32  and cap forward wall lower face  116 . The cap  12  may then be lowered and positioned on the load bed  16 . After ensuring full seal contact along the load bed rails  22  and at the load bed forward wall  26 , the hinge upper link to upper intermediate rail attaching fasteners  73 ,  74  are tightened to hold the adjusted alignment. 
   Referring to  FIGS. 1 ,  2 ,  8  and  9 : After positioning the cap  12  on the load bed  16 , the lower intermediate rails  44  are clamped to each load bed side wall upper inboard flange  24  via clamps  75 ,  76 ,  96 . The forward compression struts  84  (if part of the application) are compressed by hand and installed with the cap  12  lowered in order to facilitate an initial cap lift prior to installation of higher force rear compression struts  47  in the open condition. Latching means  56  are disengaged from the lower intermediate rails  44  and the cap  12  is raised and supported fully open. Rear lift struts  47  are installed and the cap  12  is again lowered. Latching means  56  are adjusted to engage securely with the lower intermediate rails  44 . Installation is completed with attachment of a central rear lift handle  50  and connection of CHMSL/interior light wiring  54  routed through an articulating tubular strut arm  46 . 
   Referring to  FIGS. 1 ,  6 ,  9  and  10 : Use of intermediate rail assemblies  40 ,  44  facilitates various refinements. These refinements include the incorporation of side retainer means  142  attached to an upper intermediate rail  40  and designed to engage an inboard surface  144  of the lower intermediate rail  44  so that, in closed condition, the cap side wall lower edges  31  receive positive lateral restraint, as provided by conventional fixed cap mounting methods. A side retainer means  142  is shaped to include a ramped lower end  150  which engages an inboard edge  144  of the lower intermediate rail  44  so that the cap  12  is guided to a fully aligned position on the load bed  16  when the cap  12  is closed. Where spacing means  120  are used to provide clearance for bolt heads  112  at attachments  73 ,  74  of the upper intermediate rail  40  to hinge linkage assembly  42 , the upper intermediate rail  40  will have lateral offset relative to the lower intermediate rail  44 . Therefore, for optimal alignment of the upper and lower intermediate rails  40 ,  44 , equivalent spacing means  151  are then employed between the side retainer means  142  and an upper intermediate rail inboard face  140 . 
   Referring to  FIGS. 1 ,  8  and  10 : Another refinement is the use of a rigid strut  152  pivotally attached to a lower intermediate rail  44  toward the rail rearward end  154  so that, in emergency need for increased load clearance, the rigid strut  152  may be rotated upward to engage fastening means  156  on the opposing upper intermediate rail  40 . With appropriate retention at fastening means  156 , a cap  12  may thereby be securely supported at a slightly raised position. It will be understood by one skilled in the art that rigid  152 , also fastening means  156 , side retainer means  142 , latching means  56 , SLA 4-bar hinge assembly  42 , compression struts  47  and articulating arms  46  comprise cover to load bed relationship control components and may adequately provide their respective functions while being attached to upper and/or lower intermediate rails  40 ,  44 , respectively, instead of being attached directly to the cover  12  and/or load bed  16 . 
   Referring to  FIGS. 11 and 12 : Some truck manufacturers offer longitudinal, generally channel section rails  158  fixedly attached to the load bed side walls  18  immediately below the inside vertical flange  24 . These rails  158  are designed to provide secure attachment of cargo management accessories and comprise systems which are marketed with various descriptions such as “deck rail system”, “bed rail tracks”, “bed upper rails”, “slide-on bed rails”,“T channel load bars”, “utili-track channel system”. The presence of such rails  158  allows their use in attaching 4-bar hinge and intermediate rail assemblies  160 , thereby eliminating need for clamping means  75 ,  76 ,  96  of a type illustrated in  FIGS. 1 and 9 . Attachment of 4-bar hinge and lower intermediate rail assemblies  160  is facilitated by the incorporation of lower extensions  162  fixedly attached or integral to a lower intermediate rail  164  and designed for engagement with attaching means  166  of a type similar to those used for attaching load management accessories with which the generally channel section rails  158  were designed to be used. 
   It will be recognized by one skilled in the art that, although the presence of generally channel section cargo management system rails  158  facilitates use of an integrated lower intermediate rail and 4-bar hinge lower link  164 , the presence of such generally channel section rails (or bars)  158  also reduces need for a separate load carrying full length lower intermediate rail  164  because much of the cap system loading will be transferred more directly to load bed side wall structure  168  through the cargo management system rails  158 . Therefore, where other means can be satisfactorily employed to replace or perform the locating function of a lower intermediate rail  164 , rearward lift assist pivot means  49  and a (short) 4-bar hinge lower link  61  (shown in  FIG. 2 ) may be directly attached to the load management system rail  158 , obviating need for a separate intermediate rail  164 . 
   There have been described and illustrated what are considered alternate embodiments of the invention. However, these specifications shall not be construed as limitations upon the scope of the invention, since it will be understood that many alternate variations may be made by one who is skilled in the art without departing from the scope of the invention as defined by the appended claims.