Abstract:
A tonneau cover is provided which has at least one hinge-mounted latch adjacent the front of the cover, at least one support prop along the side of the cover intermediate the front and rear of the cover, and at least one latch mounted adjacent the rear of the cover, with a pair of independent side rails mounted to the vehicle, at least one of which contains a bracket for releasably receiving the hinge-mounted latch, a support prop receiving bracket cantilevered below and away from the vehicle side wall, and a rear catch bracket for receiving the rearward latch independent of dimensional variations induced from thermal forces over the cover. To facilitate release of the hinge-mounted latch within close confines of the front area of the vehicle bed, a self-contained trip handle is included in the receiving bracket. To prevent the support props from inadvertently damaging the vehicle during installation or removal of the cover, clips are provided to fix the free end of the props to the cover once it is removed from the rail mounted bracket. Dampening magnets or weights are provided to offset thermal expansion of the cover, and leveling nips are provided to offset thermal contraction of the cover. To facilitate proper alignment of the hinge-mounted latch with the rail mounted bracket during installation, a self-centering spring arrangement is provided. Further, to minimize projection of the mounting system away from the vehicle, the rails can be formed to conform to the wall portion of the vehicle portion to which they are mounted.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates generally to covers for the bed of pick up trucks, and, more particularly, to apparatus for releasably mounting tonneau covers. 
     Certain motor vehicles, such as pick up trucks and the like, are constructed with an exterior cargo area or bed, usually toward the rear of the vehicle and behind the cab portion that is for the driver or other occupants. Such cargo beds can be convenient and readily accessible. However, in the vehicle as provided by the original manufacturer, the bed is typically exposed to the elements. Thus, any cargo within the bed would also be exposed to the elements while being transported or stored in the bed. Also, it has been found that the fuel economy of pick up trucks can be adversely affected by the wind resistance or drag of the exposed cargo bed. 
     In response to such disadvantages, pick up trucks users have previously mounted rigid caps, typically molded from fiberglass, over the cargo bed. These caps appear to form an extension of the driver cab by effectively adding height and a roof to the cargo bed. Access to the bed for loading and unloading of cargo is provided by one or more doors through the cap. Often, however, caps are relatively expensive and frequently too heavy and/or bulky for quick removal if oversized cargo is to be hauled. In addition, some caps interfere with the driver&#39;s rearward visibility. As an alternative, lighterweight tonneau covers have been secured to the top area of the walls of the cargo bed. These covers are generally flush, or nearly so, with the top of the vehicle bed walls when closed on the bed and can be lifted up in whole or part on hinges to provide access to the bed. When closed, the covers are typically latched in place, and those latches can include keyed locks for cargo security. 
     A wide variety of tonneau covers are presently used within the industry for covering the bed of a pick up truck. A number of factors have determined the desirability of given tonneau cover designs. For example, it has generally been found to be advantageous for the lid to match the styling of the pick up truck and appear to be an integral part of it. In that regard, it is preferable for the lid to present as low a profile as possible to the vehicle front and side walls and tailgate surrounding the bed. 
     Some of these prior tonneau covers are permanently attached to the pick up truck. However, if cargo is to be hauled in the bed of the pick up truck that exceeds the height of the bed walls, permanently mounted tonneau covers could not be conveniently used. For that reason, some tonneau covers have been marketed that are removably mounted to the pick up truck. Among removable tonneau covers, there are rigid and flexible cover varieties. Rigid covers provide greater protection for the cargo under the tonneau cover and generally have greater durability over long periods of use. Rigid covers also can be made to require less maintenance than some flexible tonneau covers. However, rigid tonneau covers tend to be heavier and have typically required more than one person to install it on the pick up truck, primarily due to the cover weight and the alignment precision and coordination needed with prior installation or mounting systems. 
     These prior mounting systems have generally been of two types, those that penetrate a portion of the truck body or have a detachable portion that is permanently fixed to the vehicle, and those that are merely clamped to the vehicle and completely removable. Where the mounting system penetrates the side wall of the truck bed, for example, the tonneau cover can be positively located with respect to the vehicle with a minimum of sliding relative thereto during use. However, in many situations, systems that penetrate a portion of the vehicle or are permanently attached even in part are not desirable from the standpoint of preventing corrosion, maximizing truck bed usage alternatives and preserving full vehicle aesthetics. At the same time, with some prior clamping mounting systems it has been necessary to be especially careful that the clamps are properly positioned and the cover is securely mounted. If the clamps are not properly positioned, even if the cover is secure against movement off of the vehicle, the weather seals and latching mechanisms may not function properly. 
     Further, even when the clamps are properly aligned when initially installed on the vehicle, situations can arise where the weather seals and latching mechanisms may cease to function properly. For example, rigid tonneau covers have been constructed from a variety of materials, such as fiberglass and ABS plastics, or combinations of materials. Initially, these covers are typically closely mounted to the top of the bed walls of the pick up truck. However, over time and varying temperature conditions sagging and/or bulging can occur over the length and width of the cover. In addition to its impact on appearance and structural integrity, this sagging or bulging can cause misalignment of the hardware used to install and latch the tonneau covers. Thus, the cover may not close properly and/or adequately secure the tonneau to the pickup truck in certain situations. In addition, deformation of the cover and/or portions of the bed walls can occur due to uneven application of or support for the cover load by the mounting and/or latching hardware. This deformation can similarly have adverse impact upon the mounting and closing system as well as the aesthetic appearance of the vehicle. 
     Other concerns with prior removable covers arise from the procedures needed to remove the cover. For example, in many covers prop arms are used to support the cover when it is opened. The prop arms are typically fixed at one end to the cover and removably secured to a bracket connected to the vehicle at the other end. When removing the prop arm from the bracket to remove the cover from the vehicle, special care must be taken not to let the prop arm swing freely about its other end and scratch the paint off a portion of the vehicle. 
     At the same time, however, since the prop arm supports at least a substantial portion of the cover weight when the cover is opened, it is necessary that the arm be securely retained in the bracket when in use. Further, the bracket is preferably removable with the mounting system and does not need to be attached to the vehicle in a way the penetrates or damages the vehicle. Also, while it is advantageous to have a prop arm that provides as much lift assistance as possible to opening of the cover, it is important that the prop arm bracket not detrimentally affect or interfere with the mounting system. 
     In addition, some prior covers required specific elevated or inclined orientations of the cover to be maintained in order to disconnect the cover from the mounting system components. To the extent such orientations departed from the horizontal plane there is risk that a sudden gust of wind could shift the cover out of control of the user. Further, to the extent that elevation significantly above the top of the bed walls there is greater risk of injury to the user if that control of the cover is lost. It has been suggested to minimize these latter two concerns by using light but strong materials to form the cover, such as Telene, but such covers have thus far exhibited even greater thermal expansion characteristics than older, heavier materials. 
     Similarly, mounting some prior frames or support rails for the tonneau covers has been relatively awkward and complex. Typically, the cover has been supported by a U-shaped rail frame, such as the type shown in U.S. Pat. No. 5,688,017. While such frames can have minimal weight, given the width of the vehicle bed and the resulting dimensional separation of the side wall rails, lifting such frames into position and securing them to the vehicle, or later removing them, has often required the work of at least two persons. 
     At the same time, the market for tonneau covers has traditionally been highly competitive, with consumers being very cost conscious. To the extent prior systems have attempted to provide for easier cover installation, they have generally resulted in systems that are more expensive to manufacture. 
     Accordingly, it is an object of the present invention to provide an improved method and apparatus for releasably mounting tonneau covers to a pick up truck. Other objectives include the provision of a tonneau cover mounting arrangement that: 
     a. is easy to install onto a vehicle and securely retains the cover to the vehicle, 
     b. permits the cover to be readily removed from the vehicle with or without removing the mounting frame from the vehicle, 
     c. provides greater user control over the cover during cover installation and removal, 
     d. accommodates thermal induced dimensional variation in the cover without loss of weather seal or of mounting or closure latching control, 
     e. permits more consistent manufacturing process results and improved product quality, 
     f. maintains a minimal profile over the top of the bed walls, and 
     g. is easier to open and close and minimizes destructive stresses on the vehicle support. 
     These and other objects of the present invention are obtained by the provision of a tonneau cover having at least one hinge-mounted rotary latch adjacent the front of the cover, at least one support prop along the side of the cover intermediate the front and rear of the cover, and at least one rotary latch mounted adjacent the rear of the cover, with a pair of independent side rails mounted to the vehicle, at least one of which contains a bracket for releasably receiving the hinge-mounted rotary latch, a support prop receiving bracket cantilevered below and away from the vehicle side wall, and a rear catch bracket for receiving the rearward rotary latch independent of dimensional variations induced from thermal forces over the cover. To facilitate release of the hinge-mounted rotary latch within close confines of the front area of the vehicle bed, a self-contained trip handle is included in the receiving bracket. To prevent the support props from inadvertently damaging the vehicle during installation or removal of the cover, clips are provided to fix the free end of the props to the cover once it is removed from the rail mounted bracket. Dampening magnets or weights are provided to offset thermal expansion of the cover, and leveling nibs are provided to offset thermal contraction of the cover. To facilitate proper alignment of the hinge-mounted rotary latch with the rail mounted bracket during installation and usage under a variety of conditions, a self-centering spring arrangement is provided. Further, to minimize projection of the mounting system away from the vehicle, the rails can be formed to conform to the wall portion of the vehicle portion to which they are mounted. 
     Other objects, advantages and novel features of the present invention will now become readily apparent to those in the art from the following detailed description and attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a top, left exploded perspective view of a tonneau cover mounting apparatus according to the teachings of the present invention. 
     FIG. 2 shows an enlarged view of the mounting apparatus of FIG. 1 from the same perspective with the tonneau cover shell and liner omitted, with the associated vehicle shown in phantom. 
     FIG. 3 shows a further enlarged top view of the hinge-mounted rotary latch assembly of FIG. 1 with the conventional rotary latch portion shown in phantom. 
     FIG. 4 shows a side view of the hinge-mounted rotary latch assembly of FIG. 3, with elevated positions of the assembly elements shown in phantom. 
     FIG. 5 shows a further enlarged top view of the self-centering bracket for receiving the hinge-mounted rotary latch of FIG.  3 . 
     FIG. 6 shows a side view of the self-centering bracket of FIG.  5 . 
     FIG. 7 shows a further enlarged top rear left perspective view of a prop clip of FIG.  1 . 
     FIG. 8 shows a further enlarged top right perspective view of the rear catch bracket of FIG.  1 . 
     FIG. 9 shows an enlarged, bottom plan view of the underside of the tonneau cover liner of FIG.  1 . 
     FIG. 9A shows a further enlarged, cross-sectional perspective view of the rear right underside corner of the tonneau cover liner of FIG.  1 . 
     FIG. 9B shows a still further enlarged, cross-sectional perspective view of the top surface of the tonneau cover liner of FIG. 1 over the right underside corner of FIG.  9 . 
     FIG. 9C shows an enlarged, cross-sectional side view of the clamp, rail and vehicle connection of FIG. 1 along line  9 — 9 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1, which illustrates a preferred embodiment of the present invention, shows a tonneau cover  10 , including an outer cover or shell  12 , inner liner  14  and rail mounting arrangement  20 . By way of orientation, the “front” of the cover and vehicle is toward point A and the “rear” of the cover and vehicle is toward point B. Similarly, “inwardly” is toward point C within the area of the vehicle bed, and “outwardly” is away from point C. It will be understood that shell  12  and liner  14  can be formed from any conventional materials, such as fiberglass. 
     However, in especially preferred embodiments, shell  12  is formed from “Telene” material, a proprietary product of B. F. Goodyear, Inc., and liner  14  is formed from ABS plastic. Telene material could be used for liner  14  in alternative embodiments, depending upon the relative costs of ABS and Telene under current market conditions. At present, ABS is a less expensive alternative. Telene has been found to provide a better surface quality than fiberglass materials, at least in part because it can be formed to the desired shapes using closed molds. Telene also permits shell  12  to have a lower overall weight than with conventional fiberglass, thus reducing the forces which urge the cover to sag. Such Telene shells and ABS liners are then bonded together by, for example, a conventional two-part urethane adhesive. It will usually be preferable to select the particular ABS material to closely coincide with the thermal expansion characteristics of the Telene material so as to minimize the internal stresses on the composite assembly of the combined shell and liner. 
     In order to provide greater strength and rigidity for the overall tonneau cover  10 , liner  14  is preferably molded to have a pattern of ribs or ridges  15  on its underside. One such suitable pattern of ribs that provides for adequate strength without being unduly difficult or expensive to manufacture is shown in FIGS. 9,  9 A and  9 B. In effect, the pattern is a series of outer hexagons  15 A of a given height from the liner surface, each with a concentric inner hexagon  15 B of a lower height from the liner surface, with spokes  15 C projecting from each corner  15 D of the inner hexagons to the corresponding corner  15 E of the outer hexagon. Stated differently, outer hexagons  15 A of the basic ridge pattern on the bottom surface of liner  14  each include an internal “spoking trapezoid” configuration of lessor vertical projection to increase the liner rigidity and avoid complicated molding configurations. As a result, the composite Telene shell and ABS liner can present a lower overall profile to the vehicle body without increasing the risk of sagging configuration. 
     Rail mounting arrangement  20  includes, for example, two longitudinally extending rails  22 , each preferably being a mirror image of the other. These rails are, for example, formed as an extruded, stamped or roll formed length of metal, such as steel or aluminum. Each rail  22  is typically releasably secured to the side walls of the vehicle bed adjacent the top of those side walls via a plurality of clamps  24 . Preferably, rails  22  are formed to closely conform to the shape of the wall of the vehicle against which they are clamped. A variety of conventional clamps can be accommodated by rails  22 . 
     In especially preferred embodiments, rails  22  are formed with an upper flat  22 A, a recessed flat  22 B and a lower lip  22 C. Clamps  24  are then preferably formed to engage all three of these aspects of rails  22  and exert a stable force against both vertical and horizontal shifting of rails  22  with respect to the vehicle body by a “pull down” effect against the interior corner  23  of the vehicle side wall. For example, as shown in FIG. 9C, each clamp  24  includes a rail engaging portion  24 A, with upper bearing surface  24 B to abut upper flat  22 A, and a lower bearing surface  24 C to abut recessed flat  22 B and lower lip  22 C. Clamps  24  each also include a vehicle engaging portion  24 D which abuts rail engaging portion  24 A at their lower ends. The upper end of vehicle engaging portion  24 D is formed to fit into interior corner  23  and extend downwardly therefrom along the interior of the vehicle side wall for a significant length to provide an interior bearing surface for clamping engagement at that point. To facilitate that engagement with interior corner  23  and minimize the intrusion of clamp  24  into the vehicle bed area, clamps  24  are preferably formed to incline downwardly and outwardly from rails  22 . A variety of fastener elements  24 E can be used to secure rail engaging portion  24 A and vehicle engaging portion  24 D together, the hand manipulable type or “wing-nut” shown being one example. 
     The cover mounting hardware of the present invention releasably secures shell  12  and liner  14  to rails  22 . Thus, to install the tonneau cover to the vehicle, rails  22  are first secured to the vehicle and then the cover is secured to the rails. Similarly, to remove the cover, first the cover is removed from the rails and then the rails can be, if necessary, removed from the vehicle. Alternatively, in applications where there is substantial space available between the underside of the tonneau cover and the vehicle bed, the cover and rails can be preassembled to each other and then placed onto the vehicle and then the rails can be clamped in place. The latter method has the advantage of simplifying component alignment if the rails are likely to be left in place when the cover is periodically removed. In either situation, the present invention has the advantage of being able to avoid the use of fasteners that penetrate the vehicle or that require the use of special tools or complicated procedures to install. Alternatively, in applications where it is desirable to prevent unauthorized removal of the tonneau, the present invention is readily adaptable to use of security fasteners which do require special tools for removal. Further, since each of rails  22  is mounted separately and independently of the other rails, a single person can install the entire rail mounting arrangement regardless of the width of the vehicle bed. 
     The cover mounting hardware includes a hinge assembly  30 , a prop assembly  60  and a latch assembly  80 . Preferably, each of rails  22  includes a set of each of these assemblies. Each such assembly is connected to the associated rail by means of fasteners  26 , which can be conventional in nature, as described further below. Briefly, the present invention permits the cover to be pivotably hinged at the front of the vehicle bed by hinge assembly  30 , with prop assembly  60  facilitating lifting of the cover for periodic access to the bed area under the cover. The cover can be closed and locked in place by latch assembly  80 . 
     Hinge assembly includes a hinge element  32  having, for example, two side by side hinge flaps  34  and  36 . In certain embodiments these flaps can instead be vertically disposed, but in especially preferred embodiments the side by side orientation permits a more vertically compact overall assembly. Biasing spring  38  is, for example, disposed between flaps  34  and  36  so as to urge them together in a common plane. Such biasing can be helpful in preventing damage to the vehicle during installation or removal of the cover since unintended motion of the hinge assembly is reduced. Hinge flaps  34  and  36  are joined together by longitudinally extending pin  40 . In this manner, hinge element  32  can be formed as a conventional strap hinge. 
     Hinge flap  36  is mounted to the cover, such as by conventional fasteners into liner  14 . Hinge flap  34  is, thus pivotably movable with respect to the cover about the longitudinal axis  42  of pin  40 . A rotary latch assembly  44  is preferably secured to the underside of hinge flap  34 . This rotary latch assembly can be of conventional design or of proprietary designs that are commercially available. One such suitable latch assembly is the Model 240/241 Mini Rotary Latch available from Eberhard Manufacturing Co. of Cleveland, Ohio. In essence, such latch assemblies include a spring locked hook than can receive and retain a bar, post, pin or other such “latch strikers” extending below the latch. The latch assembly is preferably mounted rearwardly on the flap sufficiently to clear the front wall of the vehicle bed. Also, it is preferable to orient the latch assembly to receive the retained bar from a position vertically above the retained bar and lock onto the retained bar by downward vertical motion. Thus, the cover can be held generally horizontal during mounting, with minimal risk of loss of user control due to gusts of wind and reduced wear on the peripheral seals of the cover. 
     Typically, such latch assemblies include a release lever  46  that permits selective disengagement of the hook from the retained bar. However, it has been discovered that use of conventional release levers can be difficult when rotary latch assemblies are applied to tonneau covers because of the restricted access space available to the user at the hinge location, especially when the user is holding the cover up at a more balanced location. Accordingly, the present invention provides a self-contained trip handle  48  which is connected at one end to release lever  46  and extends rearwardly along the cover. Preferably, handle  48  passes through a guide opening  49  at an inclined end  47  of hinge flap  34 . Handle  48  is connected to release lever  46  such that pulling rearwardly on handle  48  can actuate release lever  46  to disengage the retained bar. Similarly, where a particular rotary latch assembly requires movement to a “reset” position after disengagement, handle  48  can be formed as a rigid unit to transmit pushing force for that purpose. 
     Hinge assembly  30  also includes a bracket  50  which supports and encloses a longitudinally extending hinge bar  52 , which is used for engagement and retention by rotary latch assembly  44 , through an open top  51  of the bracket. Hinge bar  52  is, for example, mounted intermediate the ends of bracket  50  and sufficiently below the open top that a significant portion of latch assembly  44  can be inserted into bracket  50  and shielded thereby during use. Hinge bar  52  includes two opposing guide discs  54  mounted on it and extending radially outward from the longitudinal axis  56  of the hinge bar, although preferably at a slight incline from a purely radially outward direction. Preferably, a spacer sleeve  57  is disposed on bar  52  between discs  54 . Springs  58  are mounted on bar  52  between each disc  54  and the adjacent side wall of bracket  52 . Bracket  50  is mounted to rail  22  by use of conventional fasteners  26 . 
     When the tonneau cover is to be attached to rail mounting arrangement  20 , the hook of each rotary latch assembly  44  is inserted into its associated bracket  50  to engage bar  52 . The incline of discs  54  is sufficient to direct and guild or funnel that hook toward the center portion of the length of bar if the hook is laterally misaligned within a predetermined range. In this manner, bracket  50  is self-centering with respect to alignment with hinge element  32  and the tonneau cover. Such misalignment can occur, for example, as a result of thermal deformation of the cover. Also, springs  58  serve to absorb torsional stresses applied to the hinge as a result of vehicle vibration and motion during use. 
     Prop assembly  60  is provided to facilitate lifting of the tonneau cover to open it for temporary access to the interior of the vehicle bed and to support the cover “hands-free” in the open position. These purposes are conventional, and a variety of suitable gas-filled props are currently on the market. The present invention improves upon the prior prop assemblies by reducing the lifting force needed for prop actuation, by minimizing the prop bracket stresses applied to the vehicle, reducing the tendency for the prop member to urge the cover off of its side wall seals and by reducing the likelihood that the prop assembly will scratch or dent the vehicle during installation or removal of the tonneau cover. 
     Prop assembly  60  includes a prop member  62 , preferably a gas filled piston of conventional design, a prop bracket  64 , a prop pad  66 , a retaining lanyard  68  and a prop clip  70 . Pad  66  is, for example, secured to the underside of liner  14 , and prop member  62  is pivotably secured to that pad at one end. The other end of prop member  62  is releasably and pivotably connected to the lower portion of bracket  64  by a conventional spring fastener  65 . To prevent fastener  65  from being misplaced, lanyard  68  is secured to the fastener at one of its ends and to prop bracket  64  at its other end. Clip  70  is secured to liner  14  by, for example, a conventional adhesive at a location that is spaced apart from pad  66 . Bracket  64  is secured at its upper portion to its associated rail  22  by conventional fasteners  26 . 
     Preferably, bracket  64  retains prop member  62  in a substantially cantilevered position with respect to rail  22 , in effect, spaced inwardly and lower than the rail within the vehicle bed area. This is accomplished in the embodiment of the drawings by use of a distinct inward bend or “dogleg”  72  in the cross-section of bracket  64  at a point intermediate its ends. Also, an outwardly extending connection pin  74  is attached to the lower portion of bracket  64  to pivotably retain prop member  62 . For increased strength and rigidity, a reinforcing rib  76  is preferably formed in bracket  64  as well. It has been found that by such a configuration of bracket  64  there is significantly less of a tendency for the prop member to warp or deflect the bracket toward the vehicle side walls. Thus, the connection of the lower end of the prop member can be further from liner  14 , permitting the use of longer, lower pressure prop members. Such longer prop members permit connection at the upper end closer to the rear of the cover, provide greater assistance to cover lifting and are less likely to urge the cover off of its side seals when the cover is closed. 
     Stated differently, bracket  64  has the advantage of being connected directly to mounting arrangement  20  so it can be removed integrally therewith from the vehicle. At the same time, bracket  64  permits the lower end of the prop member to be connected substantially below liner  14 , and thereby maximize its lifting function. In doing this, bracket  64  is formed so as to avoid both the destructive twisting effect on rails  22  and the destructive rubbing effect on the vehicle side walls that would be presented by merely elongating prior brackets. This formation of bracket  64  includes inward bend  72 , of sufficient horizontal dimension as to permit the lower end of prop member  62  to clear rails  22  in use and still terminate nearly vertically in line with the rails, and pin  74 , placed to translate at least a portion of the non vertical force from prop member  62  inwardly, rather than outwardly. 
     When the cover is to be removed from rail mounting arrangement  20 , prop member  62  is removed from pin  74  and then rotated toward liner  14  in the direction of clip  70 . Preferably, clip  70  is formed with a resilient-walled recess  77  which is sized to receive a portion of prop member  62  and an overlapping catch  78  to restrict removal of prop member  62  from recess  77  except when opening force is applied by the user to clip  70  via catch  78 . According to preference in a given application, clip  70  can be secured to liner  14  such that recess  77  opens outwardly or inwardly. 
     Latch assembly  80  preferably includes elements that are mounted on and adjacent to each of rails  22  and simultaneously actuated by a central squeeze handle  82  mounted on the top rear portion of cover  12 . Rear latches  84  are positioned under liner  14  at each of the rear corners. These latches can be of any conventional or commercially available proprietary design and are intended to releasably engage a bar or pin attached which serves as a latch catch. In especially preferred embodiments, these latches can be of the same type as rotary latches  44 . Cables or rods of conventional nature operably connect handle  82  and rear latches  84 . In general, the rear latches are spring biased to receive and retain the latch catches and thereby fix the tonneau cover with respect to each of the latch catch. Since each latch catch is fixed with respect to the vehicle body, this allows the rear latches to hold the cover in a closed position over the vehicle bed. To open the tonneau cover, handle  82  is actuated to cause the rear latches to release the latch catch, permitting the cover to be lifted by pivoting about hinge assembly  30 . 
     However, due to thermal expansion and contraction of the cover in various weather conditions, tending, for example, to cause bowing or sagging of the cover as well as variation in overall length and width, the relative position of the rear latches and latch catches can vary over time. Since the hinge assembly fixes the cover at one end, the dimensional variance can be most noticeable at the vehicle rear. As a result, the cover may not always be properly latched in place. To remedy this, the present invention includes rear catch brackets  86 , one mounted to each of rails  22 , for example, by conventional fasteners  26 . Brackets  86  include a base plate  88  with a length of catch bar  90  extending therefrom and formed with an inclined U shape. Catch bars  90  extend inwardly of the vehicle bed and are inclined in the direction that cover deformation will move the position of the rear latches. Thus, as the position of the rear latches changes in changing temperature, each rear latch will engage a different portion of its associated catch bar  90 , but still achieve secure retention of the cover to the vehicle. 
     To counteract certain of the effects of thermal deformation on the sides of the cover, the present invention can include dampening or weight load bars  92  mounted to liner  14  intermediate the front and rear of the cover and adjacent the vehicle sides. Alternatively, load bars  92  are formed from magnetic material so as to encourage retention of the cover to the vehicle at that point. These load bars can be secured between liner  14  and cover  12 . In effect, these load bars serve to exert a pull down force on the cover intermediate the front and rear. 
     Further thermal deformation effects can be countered by use of leveling projections or nibs  94  that are attached to or molded into the underside liner  14  at adjacent its sides to engage the top surface of the vehicle side walls at spaced apart locations. In effect, these nibs tend to push the sides of the cover upward intermediate the front and rear. 
     Although the present invention has been described above in detail with respect to particular embodiments, this was done only by way of illustration and example. Those of ordinary skill in the art of designing tonneau covers will now recognize that various modifications of these examples can be readily constructed for particular applications. For example, rails  22  have been shown as each being a unitary construction over the length of the vehicle bed side. Alternatively, rails  22  could be sectioned into portions only of sufficient length along the vehicle bed side to support the rail mounting arrangement, perhaps saving rail material in exchange for additional clamps. Similarly, rotary latch mechanisms have been suggested for the hinge and rear latch functions, but gate and hook/eye latches can be substituted in given applications. Accordingly, the spirit and scope of the present invention are limited only by the terms of the claims defined below and in any related patent applications.