Patent Publication Number: US-2018037097-A1

Title: Roof system for a vehicle

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to a removable roof system for a convertible vehicle and to the convertible vehicle itself. 
     BACKGROUND OF THE INVENTION 
     Vehicles which have a removable or retractable roof, often referred to as ‘convertible’ vehicles, are often two-seater vehicles in which there is no room for seated passengers behind the front vehicle seats used by the driver and his immediate passenger to one side. Early stage convertible vehicles typically included a cover or canvas hood which attached to a frame of the vehicle and which could be removed manually from the vehicle frame by the user when the weather was pleasant. The canvas was formed from a waterproof fabric which could be folded and stored in the vehicle boot or trunk once removed from the frame. Inevitably, such early designs suffered from leakage problems due to the problem of fixing the canvas to the vehicle frame in a water-tight manner. In addition, many systems made use of multiple poppers to secure the fabric to the vehicle frame once the cover was in place on the vehicle. This was a time-consuming and fiddly process for the user every time the vehicle needed to be converted. The appearance of the vehicle once the cover was removed was also prejudiced because the frame supporting the canvas remained on the vehicle and was not necessarily an attractive feature of the vehicle without the cover fitted. As car design has evolved and the aesthetics of vehicles has become an increasingly important factor in the consumer buying decision, particularly for more expensive vehicle such as sports cars, such early stage convertible vehicle designs have become outdated. 
     In more recent times, more sophisticated automated roof retraction systems have been widely used to enable the movement of a multi-layer canvas hood, or a hard-material roof, into and out of the vehicle boot to convert the vehicle from an open-top to a closed-top. The automated retraction system provides the convenience of a user in the cabin being able to control the status of the vehicle roof without leaving their seat. 
     Furthermore, in modern-day vehicles, the materials used for such canvas roofs are incredibly robust and reliable in terms of leakage. For retractable hard-top vehicles leakage problems can be avoided altogether, albeit at the expense of considerable additional vehicle weight for the roof mechanism. 
     Although such automated systems are increasingly popular, they therefore suffer from the disadvantage of high weight and large size due to the complex mechanical parts which are required for the roof retraction mechanism. These parts also introduce additional cost to the vehicle, as well as an additional factor for component reliability. Especially for sophisticated and lightweight sports cars, the increased weight factor is prohibitive as performance of the vehicle is adversely affected by the weight, and the size of the roof retraction mechanism cannot be accommodated within the limited boot space. On these vehicles in particular there remains the need for a removable or detachable roof system which substantially avoids leakage problems whilst maintaining low vehicle weight for enhanced performance. 
     It is one object of the invention to provide a roof system for a vehicle which addresses one or more of these issues. 
     STATEMENTS OF INVENTION 
     Aspects and embodiments of the invention are set out in the accompanying claims. 
     According to one aspect of the invention, there is provided a detachable roof system for a convertible vehicle having an open state in which a vehicle cabin is open at the top and a closed state in which the vehicle cabin is closed; the roof system including a front frame which is removably mountable to the vehicle at the front of the vehicle cabin; a rear frame, separate from the front frame, which is removably mountable to the vehicle at the rear of the vehicle cabin, the rear frame including an integral panel which forms a rear window of the vehicle when the rear frame is mounted on the vehicle, and wherein the roof system includes a hood for covering the cabin in the closed state; the rear frame providing a support for the hood which spans the rear frame when the hood covers the cabin. 
     The hood is conveniently permanently attached to the front frame so that, when the front frame is removed from the vehicle, the hood is removed with it and can be folded or rolled around the front frame for stowage. 
     The rear frame provides a rigid support for the hood when it is pulled back to cover the vehicle cabin, but is not permanently attached to the hood. 
     Reference to a detachable or removable roof system is intended to refer to a roof system which can be removed from a vehicle completely, and is not intended to refer to a roof which can be removed from the vehicle to expose the cabin of the vehicle with the roof merely folded back. 
     It will be appreciated that although the invention has particular benefit when applied to a relatively compact two-seater convertible vehicle, such as a two-seater sports car, it is equally applicable to vehicle having a greater number of seats. 
     The roof system may include a clamping means configured to apply a clamping force to the rear frame to clamp the rear frame to the vehicle. 
     The rear frame may comprise a plurality of separate frame sections, each of which is conveniently removable separately and independently from the vehicle when the roof system is to be removed. This allows the roof system to be removed and collapsed for storage within a relatively small storage volume. 
     In one embodiment, the clamping means may include a coupling means for coupling the frame sections together, the clamping means being configured to apply the clamping force to the coupling means so as to transmit the clamping force through one frame section to another frame section, thereby to clamp both sections to the vehicle. For example, the rear frame may include a central frame section and left- and right-side frame sections. 
     The coupling means may include a flange provided on each of the left- and right-side frame sections and a flange provided on the central frame section, the flanges being cooperable with one another when the frame sections are placed onto the vehicle so that the clamping force applied to the left- and right-side sections is transmitted to the central frame section. This provides a convenient mechanism for the user to secure the rear frame to the vehicle in a sealing manner with minimal part count, as the clamping force is applied to the central frame section via the left- and right-side sections. 
     In one embodiment, the clamping means may comprise a first latching mechanism, operable between latched and unlatched states, and a second latching mechanism, operable between latched and unlatched states, the first latching mechanism being associated with the first side frame section and the second latching mechanism being associated with the second side frame section, whereby operation of the first and second latching mechanisms serves to apply the clamping force to the side frame sections. 
     Each of the first and second latching mechanisms may include a resiliently-biased pin which, when in the latched state, engages with a latch receiver provided on the vehicle, the pin being resiliently biased into the unlatched state. 
     The first and second latching mechanisms may include a handle which is operable to cause movement of the pin between the latched and unlatched states through an intermediate linkage. The handle can be conveniently operated by a user within the cabin, or leaning into the cabin to latch/unlatch the mechanisms. 
     The rear frame may comprise a seal arrangement for engaging with an upper surface of the vehicle body under the clamping force when the roof system is mounted on the vehicle, thereby to form a substantially fluid-tight seal between the seal arrangement and the vehicle. 
     The seal arrangement may include one or more seal element mounted on each of the frame sections. The or each seal element conveniently takes the form of a bubble seal, which is a familiar component in automotive applications. 
     The rear frame may comprise means configured to prevent outward transverse movement of the roof system relative to the vehicle when the roof system is fitted on the vehicle. 
     The means may be further configured to prevent forward movement of the rear frame relative to the vehicle when the roof system is fitted to the vehicle. 
     By way of example, said means may include a foot located at an outer edge of the rear frame on the left and right sides thereof, each foot being cooperable with an upper lid of the vehicle when the roof system is fitted to the vehicle, in use, to prevent said movement. 
     The roof system may comprise at least two locating features for engagement with cooperable locating features on the vehicle to locate the rear frame in position on the vehicle. 
     Conveniently, to reduce part count the pins of the first and second latching mechanisms may form the locating features. 
     The front frame may be a foldable frame and may include a double hinge assembly configured to permit one half of the front frame to be folded double with the other half of the front frame. 
     The rear frame may be formed from a carbon fibre material, which has the benefit of being of high strength, but lightweight. 
     The integral panel may be formed from a polycarbonate material, which is a rigid material which provides better visibility than the typical plastic materials commonly used on convertible roofs. 
     The hood may include a main portion which covers the vehicle cabin when the roof system is fitted to the vehicle, and left- and right-side wings which extend rearward from the main portion for attachment to left- and right-side tethering points of the vehicle when the roof system is fitted to the vehicle. 
     In another aspect of the invention, there is provided a detachable roof system for a convertible vehicle having an open state in which a vehicle cabin is open and a closed state in which the vehicle cabin is closed; the roof system including a front frame which is removably mountable to the vehicle at the front of the vehicle cabin; a rear frame, separate from the front frame, which is removably mountable to the vehicle at the rear of the vehicle cabin and comprises at least two separate frame sections, and a clamping means configured to apply a clamping force to one of the frame sections and to transmit the clamping force through the or each of the other frame sections so as to clamp the entire frame to the vehicle. 
     In another aspect there is provided a detachable roof system for a convertible vehicle having an open state in which a vehicle cabin is open and a closed state in which the vehicle cabin is closed; the roof system including a front frame which is removably mountable to the vehicle at the front of the vehicle cabin; a rear frame, separate from the front frame, which is removably mountable to the vehicle at the rear of the vehicle cabin, wherein the rear frame may comprise means, typically in the form of left- and right-side feet for engagement with the vehicle body, in use, configured to prevent outward transverse movement of the roof system relative to the vehicle when the roof system is fitted on the vehicle. 
     In another aspect, there is provided a detachable roof system for a convertible vehicle having an open state in which a vehicle cabin is open and a closed state in which the vehicle cabin is closed; the roof system including a front frame which is removably mountable to the vehicle at the front of the vehicle cabin; a rear frame, separate from the front frame, which is removably mountable to the vehicle at the rear of the vehicle cabin, wherein the front frame may be a foldable frame and may include a double hinge assembly configured to permit one half of the front frame to be folded double with the other half of the front frame. 
     In another aspect, there is provided a detachable roof system for a convertible vehicle ( 10 ) having an open state in which a vehicle cabin is open and a closed state in which the vehicle cabin is closed; the roof system including: a rear frame ( 60 , which is removably mountable to the vehicle at the rear of the vehicle cabin, the rear frame including an integral panel ( 76 ) which forms a rear window of the vehicle when the rear frame is mounted on the vehicle, and a hood ( 34 ) attachable to the vehicle at the front of the vehicle cabin and arranged to cover the cabin in the closed state; wherein the rear frame ( 60 ) provides a support for the hood ( 34 ) which spans the rear frame ( 60 ) when the hood ( 34 ) covers the cabin. 
     In an embodiment the system comprises a front frame which is removably mountable to the vehicle at the front of the vehicle cabin and the hood ( 34 ) is attached permanently to the front frame ( 30 ). 
     According to a further aspect of the invention, there is provided a convertible vehicle provided with a detachable roof system of one of the previous aspects of the invention. 
     The convertible vehicle may have one or more fairing and/or one or more roll hoop located behind the driver and passenger seats with which the rear frame of the roof system engages in a sealing manner. 
     Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a rear view of a two-seater sports-car with a removable roof system of the vehicle in place; 
         FIG. 2  is a rear view of the sports car in  FIG. 1 , with the roof removed from the vehicle; 
         FIG. 3  is a view from the underside of the roof system for the vehicle in  FIGS. 1 and 2 ; 
         FIG. 4  is a top view of the roof system for the vehicle in  FIGS. 1 and 2 ; 
         FIG. 5  is a side view of a front frame of the roof system in  FIGS. 1 and 2 ; 
         FIG. 6  is a view, from the underside, of the front frame of the roof system in  FIG. 5 ; 
         FIG. 7  is a front view of a rear frame of the roof system in  FIGS. 3 to 6 ; 
         FIG. 8  is a rear view of the rear frame of the roof system in  FIG. 7 ; 
         FIG. 9  is an exploded rear view of the rear frame in  FIGS. 7 and 8 ; 
         FIG. 10  is an exploded front view of the rear frame in  FIGS. 7 and 8 ; 
         FIGS. 11, 12, 13 and 14  show enlarged views, in more detail, of areas of the rear frame indicated in  FIG. 10 ; 
         FIG. 15  is an isometric view of the rear frame in  FIGS. 7 and 8 ; 
         FIG. 16  is an enlarged view, in more detail, of a first latching mechanism of the rear frame shown in  FIG. 15 , with the mechanism in a locked or closed position; 
         FIG. 17  is an enlarged view, in more detail, of a second latching mechanism of the rear frame shown in  FIG. 15 , with the mechanism in an unlocked or open position; 
         FIG. 18  is a top view of a receiver for the latching mechanisms in  FIGS. 16 and 17 ; 
         FIG. 19  is an underside view of the receiver in  FIG. 18 ; 
         FIG. 20  is a rear view of the frame of the roof system, being a similar view to that shown in  FIG. 8 ; 
         FIG. 21  is a section C-C through the frame in  FIG. 20 ; 
         FIG. 22  is a section D-D through the frame in  FIG. 20 ; and 
         FIG. 23  is a perspective view of a tensioner for the hood of the roof system in  FIGS. 2 to 21 . 
     
    
    
     In the following description, references to left and right side are made from the front perspective of vehicle, but such references are not intended to be limiting. 
       FIGS. 1 and 2  show a convertible vehicle  10  in the form of a two-seater sports car having a vehicle body  12 , a front windscreen  14  having a windscreen frame  15  and left- and right-side windows (only one of which, window  16 , is visible in the figures). The vehicle  10  is manufactured with an open top but may be fitted with a roof system in accordance with embodiments of the present invention. The vehicle  10  has two seats in the form of a driver&#39;s seat and a passenger seat. A structure in the form of a fairing or ‘haunch’  18  is provided behind the driver&#39;s seat. The fairing  18  is an elongate structure which has an arc-shaped front end (identified at  18   a ) and tapers towards the rear of the vehicle to blend with the upper surface of the vehicle on the driver&#39;s side. 
     In a similar manner to the fairing  18 , a roll hoop  20  is provided behind the passenger seat which protects the passenger in the event of a vehicle roll over. The roll hoop  20  is of generally similar shape to the front end  18   a  of the fairing  18 , taking the form of an arc or ‘hoop’, but has a slightly narrower width than the fairing. The roll hoop  20  may be a deployable roll hoop which is normally hidden within the body of the vehicle. In the event that an imminent rollover is detected, the roll hoop deploys into the position shown. 
     Modifications of the vehicle with which the roof system of the invention may be used include vehicles having two roll hoops, one behind the driver and one behind the passenger, without a fairing, or vehicles including two fairings. The roof system could also be used on a vehicle without a fairing or a roll hoop, without modification to the key features of the invention. 
     Just rearward of the fairing front end  18   a  and the roll hoop  20  is a deck lid  22  forming part of the upper surface of the vehicle bodywork. The deck lid  22  provides an immovable cover for a stowage space (not visible) located beneath the deck lid. The storage volume beneath the deck lid  22  is a convenient volume to accommodate the roof system when removed from the vehicle and placed in a stowed state. Further rearward of the stowage space for the roof system is a vehicle trunk (not identified) which resides beneath an upper trunk lid  24  which also forms a part of the upper surface of the vehicle bodywork. The trunk lid  24  is flush with the deck lid  22  and is pivotally mounted to allow access to the trunk beneath in the manner of a conventional vehicle by lifting or tilting the lid  24  about its rear edge. The storage volume beneath the deck lid and the vehicle trunk are not separate compartments, so that the volume beneath the deck lid  22  is accessible by lifting the trunk lid  24  and reaching through. In a modification, the deck lid  22  could be movable and the compartments could be separate from one another. 
     The vehicle can be driven when in the status shown in  FIG. 2 , for example in fine weather conditions, with the roof system removed. In the event of bad weather or night driving, for example, if the user wants to cover the vehicle, a roof system in accordance with the invention may be fitted to enclose the vehicle cabin, as shown in  FIG. 1 , so as to provide protection from the elements. 
     With reference to  FIGS. 3 to 8 , the roof system includes three main components; a front frame or headliner component  30 , a rear frame component  60  and a waterproof cover or hood  34 . As best seen in  FIGS. 3 to 6 , when fitted to the vehicle the front frame  30  extends transversely across the upper edge of the front vehicle windscreen frame  15  and provides an anchorage for the hood  34  at the front of the vehicle cabin. The front frame  30  is formed from a lightweight material, such as carbon fibre, and is formed in two parts so that it is foldable about a centrally mounted double hinge assembly  33  (as shown in  FIG. 6 ) mounted on the central axis  35  of the frame (i.e. the axis of the frame which extends longitudinally along the vehicle axis). 
     The double hinge assembly  33  is of conventional form and includes a first hinge plate mounted on one side of the front frame  30  and pivotal about a first hinge axis  37   a  for a for a first hinge pin, and a second hinge plate mounted on the other side of the frame  30  which is pivotal about a second hinge axis  37   b  for a second hinge pin. The double hinge assembly  33  allows one half of the front frame  30  to be folded back on itself about the first and second hinge axes  37   a,    37   b,  bringing the two halves of the front frame  30  together, so that the front frame  30  can be stowed within a relatively small stowage space beneath the deck lid  22 /trunk lid  24 . 
     Referring specifically to  FIG. 5 , the front edge of the hood  34  is attached to the front frame  30  via an elongate paddle  31  which extends along the full width of the vehicle windscreen  14 . The paddle  31  is formed from a plastics material, such as ABS, to provide rigidity. The cover  34  is folded over the front edge of the frame  30  and is folded back underneath the front edge of the frame where it is stitched to the paddle  31  on its underside. The very edge of the cover  34  is double folded at the point of stitching to the paddle  31  to provide an extra secure attachment. An aluminium plate  41  completes the structure: this is sandwiched between the frame and the cover  34  to provide rigidity. At the rear edge  39  of the frame a series of bolt holes are provided (not shown) to allow fixings (also not shown) to secure the cover  34  to the frame  30  along the rear edge. The frame  30  and the cover  34  are therefore securely attached to one another so that when the frame  30  is detached from the vehicle and folded about the hinge assembly  33 , the hood  34  is detached too and can be folded with the frame  30 . 
     The hood  34  takes the form of a waterproof canvas which is easily foldable or rollable for stowage underneath the deck lid  22  with the front frame  30 . An important distinction between the hood  34  in the invention and that used in other known convertible vehicles is that the hood  34  does not incorporate a panel to provide the rear vehicle windscreen; the hood in this invention is formed from a uniform sheet of material. 
     The hood  34  is a generally rectangular sheet of material which is shaped so as to cover substantially the full length and width of the vehicle cabin when the roof system is fitted on the vehicle to provide a ceiling for the cabin. The hood  34  includes a main portion which defines the ceiling of the cabin and, at the rear of the hood  34 , is provided with left- and right-side hood wings  36 ,  38  respectively which extend rearwardly from the main portion of the hood to attach to tensioners  40 ,  42  mounted at tethering points on the left- and right-sides of the vehicle, respectively. The tensioners  40 ,  42  are mounted within the trunk of the vehicle, beneath the trunk lid  24 , as described further below. The hood takes the form of what is commonly referred to as a “bimini” hood, which is a relatively lightweight style of roof often used on boats, for example. 
     The front frame  30  can be located on the upper edge of the windscreen frame  14  by means of two location pins (not shown) carried on the frame  30 , which engage within respective recess (not shown) provided on the upper edge of the windscreen frame  14 , one on either side of the hinge assembly. A clamp assembly  44 ,  46  is provided on each side of the central axis of the front frame  30  to clamp the front frame down onto the upper edge of the windscreen frame  14  once located in place with the location pins in the recesses. Each clamp assembly  44 ,  46  includes a user-operable handle  48 ,  50 , a hook  52 ,  54  which engages within a respective recess  56 ,  58  on the upper edge of the windscreen frame  14 , and a linkage (not visible in  FIG. 3 ) between the handle  48 ,  50  and the associated hook  52 ,  54 . When the handle  48 ,  50  is operated by the user by pulling sideways, the coupling to the associated hook  52 ,  54  through the linkage causes the hook  52 ,  54  to rotate downwards into the recess  56 ,  58  to clamp the front frame  30  securely onto the windscreen frame  14 . This type of locking assembly is generally known in the art and is of the type typically used in an automated manner on electronically controlled removable vehicle roofs. 
     The rear frame  60  component of the roof system is shown in more detail in  FIGS. 7 to 10 . The rear frame  60  is a multi-section component and extends transversely across the vehicle, just rearward of the roll hoop  20  and the fairing front end  18   a,  to provide a support or fulcrum for the hood  34  at the rear of the vehicle cabin when the hood is stretched back from the front frame  30  to span the rear frame  60 . The rear frame  60  spans the vehicle width in a transverse direction and is configured to engage with the roll hoop  20  and the fairing  18 , in a sealing manner, when fitted to the vehicle. 
     The rear frame  60  includes three sections; a central frame section  62  and left- and ride-side sections  64 ,  66  which are completely detachable from the central frame section  62  and which couple to the left- and right-sides of the central frame section  62 , respectively, when the roof system is assembled on the vehicle. The frame sections  62 ,  64 ,  66  are formed for a lightweight material, such as carbon fibre, which also has high strength. The material of the frame sections is painted in the same finish as the vehicle body work to provide a coordinated appearance. 
     The central frame section  62  has a generally rectangular profile with substantially parallel upper and lower sides,  68 ,  70  respectively, and generally upright and outwardly sloping (from bottom to top) left- and right-side struts  72 ,  74  respectively. The central frame section  62  includes a translucent or tinted panel  76 , typically formed from a polycarbonate material, which forms a window to the vehicle cabin to allow the vehicle driver a rear view when the roof system is fitted to the vehicle. 
     As can be best seen in the exploded view in  FIGS. 9 and 10 , flanges  78 ,  80  are provided, one at each outer upper edge of the central frame section  62 , to form part of a coupling between the side frame sections  64 ,  66  and the central frame  62 . The coupling also forms a part of a means for clamping the frame sections together, as described in further detail below. 
     In order to mount the rear frame  60  to the vehicle  10 , the central frame section  62  is provided with a pair of pins or projection (not shown) along its lower edge  70  which form locating features for the central frame section  62 . The pins cooperate with corresponding recesses (also not shown) on the upper surface of the vehicle body, between the fairing  18  and the roll hoop  20 , to provide a means for positioning the central frame section  62  correctly on the vehicle as part of the assembly process. 
     The central frame section  62  is also provided with an elongate seal element  82  in the form of a bubble seal which extends around the lower side of the central frame section  62  and along the side struts  72 ,  74 . A bubble seal is a well-known component in general and is a familiar component in vehicles. A bubble seal includes a seal element having two channels, one on either side of the element, with one channel being of limited depth matched to the dimensions of the frame component it receives and the channel on the other side of the element being deeper. The frame components are received within the channel on the narrow side in a sealing manner whilst the edges of the deeper channel are compressible upon engagement of the seal element with a corresponding part to form a seal between the frame and the corresponding part. 
     The left- and right-side frame sections  64 ,  66  of the rear frame  60  are similar to one another, but in reverse, with each being shaped appropriately to engage with the corresponding one of the fairing  18  and the roll hoop  20  on its inner side. Each side frame section  64 ,  66  houses a translucent or tinted panel  90 ,  92  of generally triangular form to provide additional visibility for the driver and passenger. 
     Considering the left-side frame section  64 , the frame includes two generally upright struts; an inner upright strut  95  which abuts an outer side the fairing  18 , and an outer upright strut  96 . The left-side frame section  64  curves forwardly away from the central frame section  62  so that the outer upright strut  96  locates forward of the inner upright strut  95  when the rear frame is in place on the vehicle. The outer upright strut  96  therefore defines an abutment for the left side window  16  of the vehicle (as shown in  FIG. 1 ), when the window is wound-up. 
     A flange or arm region  100  extends inwardly from the upper side of the left-side frame section  64  to define an overhang which forms a coupling with the flange  78  on the left-side of the central frame section  62  and permits a clamping force to be transmitted through the left-side frame section  64  to the central frame section  62 , as described in further detail below. 
     The right-side frame section  66  is similar to the left-side frame section  64 , and thus provides an abutment for the right-side window of the vehicle at its outer upright strut, when the right side window is wound up. A flange  102  on the upper side of the right-side frame section  66  forms a coupling with the flange  80  on the right-side edge of the central frame  62  and, again, provides a means for transmitting a clamping force applied to the right-side frame section  66  to the central frame section  62 . 
     Considering again the left-side frame section  64 , a short length of seal element  104  in the form of a bubble seal is provided on the forward-facing edge of the outer upright  96 . 
     This provides a seal for the rear edge of the left side window  16  of the vehicle when the window is in a closed position, with the window being movable, vertically up and down, within a channel defined by the bubble seal. 
     In a similar manner, a longer length of seal element  104  in the form of a bubble seal extends along the lower edge of the left-side frame section  64 , to engage with an upper surface of the vehicle bodywork on the left-side of the vehicle, and then vertically upwards along the inner upright strut  94  to engage with and seal against the fairing  18 . The left-side frame section  64  therefore seals against the rear edge of the front left-side window  16 , the upper surface of the vehicle bodywork on the left-side and with the fairing  18 . The seal element  82  along the lower edge of the central frame section  62  engages with an upper surface of the vehicle body just rearward of and between the fairing  18  and the roll hoop  20  and forward of the deck lid  22 . This arrangement of seals on the rear frame  60  ensures that the rear frame  60  is sealed against the vehicle entirely to prevent ingress of any fluid into the vehicle cabin between the fairing  18  and the frame  60 , between the roll hoop  20  and the frame  60  and between the upper surface of the vehicle, along the vehicle sides and between the fairing  18  and the roll hoop  20 , and the lower edges of the frame  60 . 
     Referring in particular to  FIGS. 10 to 14 , the left- and right-side side frame sections  64 ,  66  are detachably coupled to the fairing  18  and the roll hoop  20 , respectively, by means of two identical latching mechanisms  110 ,  112  provided on the respective flange or overhang  100 ,  102 . The latching mechanisms are identical so only one will be described in detail. 
     Considering the left-side latching mechanism  110 , the mechanism  110  includes a handle  114  which is operable between a closed, latched position (as shown in  FIG. 11 ) in which a clamping force is applied to the left-side latching mechanism  110  to clamp the left-side frame section  64  to the fairing  18 , and an open, unlatched position in which the clamping force is removed from the left-side latching mechanism  110  and the left-side frame section  64  is disengaged from the fairing  18 . The unlatched position of the latching mechanism  112  on the right-side is shown in  FIG. 12 . 
     The handle  114  resides in a hollow  116  formed in the flange region  100  so that, when in the latched position, the handle  114  forms a discrete feature which does not detract from the aesthetics of the vehicle cabin. The latching mechanism  110  is convenient to operate either from within the vehicle cabin, or by leaning in through an open door of the vehicle. 
     With the left-side frame section  64  and the central frame section  62  mounted on the fairing  18 , the flange  78  on the left-side outer edge of the central frame section  62  extends beneath the flange  100  on the left-side frame section  64 . The coupling between the flanges  78 ,  100  ensures that, as the clamping force is applied to the left-side frame section  64 , pulling it down onto the fairing  18 , the central frame section  62  is pulled down with it by virtue of engagement between the flanges  78 ,  100 . 
     Referring in more detail to  FIGS. 15 to 17 , the left-side latching mechanism  100  includes a pin or projection  120  which is coupled to the handle  114  and takes the form of a quarter-turn fastener. The pin  120  includes an elongate stem and a cross bar  122  (as shown in  FIG. 14 ) which is located towards the lower end of the stem of the pin. As the handle  114  is operated, the pin is turned on its axis. Referring also to  FIGS. 18 and 19 , the pin  120  extends downwardly from the flange  100  of the left-side-frame section  64 , through an opening (not shown) in the flange  78  of the central frame section  62  to engage within a recess  130  provided in an insert, or latch receiver  132 , mounted to the fairing  18 . As the pin  120  is rotated, it engages with a cam surface (not shown) of the recess  130  of the insert  132 . As the pin rotates further and rides over the cam surface, this serves to draw the pin  120  and the insert  132  together with the pin  120  passing through the lower flange  78 . 
     A similar insert  134  is mounted to the roll hoop  20  for receiving a pin of a right-side latching mechanism mounted on the flange  102  of the right-side frame section  66 . 
     The lower end of the pin  120  engages within the recess  130  in the insert  132 . The recess  130  is provided with a sloping surface  137  and a detent  138  at the lower end which is shaped to receive the cross bar  122  at the end of the pin  120 . As the pin  120  moves rotates within the recess  130 , it rides over the sloping surface  137  until it comes towards the end of its travel and has turned sufficiently about its axis to engage the cross bar  122  in the detent  138 . This is the latched position of the mechanism  132  in which a clamping force is applied to the left-side frame section  64 , thereby applying a clamping force to the left-side frame section  64  to clamp the section to the fairing  18 . Via cooperation between the flange  100  of the left-side frame section  64  and the flange  78  on the central frame section  62 , the central frame section  62  also experiences the clamping force to clamp the central frame section  62  to that region of the vehicle body between the fairing  18  and the roll hoop  20 . 
     The pin  120  is resiliently biased upwardly from the recess  130  by means of a spring washer  140  (visible in  FIG. 14 ) so that a degree of force is required to push on the handle  114  to overcome the spring force when moving the handle  114  from the unlatched to the latched state. Once the spring force is overcome and the pin  120  is turned sufficiently to move it into the latched state within the detent  138 , the pin  120  remains in position until the handle  114  is pulled horizontally out of the hollow  116 , allowing the pin  120  to disengage from the detent  138  under the force of the spring washer  140  and unlatching the mechanism  110 . 
     One insert  132 ,  134  is provided on each of the left- and right sides of the vehicle within the fairing  18  and the roll hoop  20 , respectively, and is permanently secured thereto by means of screws (not shown) received through screw holes  136 . Once the roof system is removed from the vehicle each insert  132 ,  134  lies substantially flush with the upper surface of the respective one of the fairing  18  or the roll hoop  20 . The inserts  132 ,  134  are typically formed from a lightweight material, such as aluminium. 
     The right-side latching mechanism  112  is identical to the left-side latching mechanism  110  and operates in a similar way to clamp the right-side frame section  66  to the roll hoop  20  by operating the handle to move between the unlatched and latched states. The right-side latching mechanism  112  therefore applies a similar clamping force to the right-side frame section  66  and, hence, to the central frame section  62 , via the flange  80  on the right-side outer edge of the central frame section  62 . 
     As well as forming a part of the clamping means by which the frame sections are clamped to the vehicle, the pins of the latching mechanisms  110 ,  112  provide useful locating features to enable the side frame sections to be located in the correct position on the fairing  18  and the roll hoop  20  as part of the assembly process, by locating the pin loosely within the insert  132 ,  134  as the side frame sections are lowered onto the vehicle. 
     In addition to the pins on the side frame sections  64 ,  66  which engage in the inserts  132 ,  134 , two further locating features in the form of outwardly extending feet  150 ,  152  are provided at the outer edges of each of the side frame sections, one foot being provided on each frame section. Each foot  150 ,  152  is shaped for engagement with a corner of the deck lid  22  where it meets with the upper surface of the vehicle side, at the front of the deck lid  22 . In addition to providing a locating feature for the rear frame  60 , the feet  150 ,  152  also serve to limit any forward (i.e. towards the front of the vehicle) and outwardly transverse movement of the roof system relative to the vehicle, in use. 
     From the foregoing description it will be appreciated that with the rear frame section  60  clamped down onto the vehicle, the roof system is prevented from moving relative to the vehicle by several factors. Because the structure of the fairing  18  tapers rearwardly along the vehicle axis, and the rear frame  60  engages with the fairing  18  behind the taller front end of the fairing  18   a,  the rear frame  60  is prevented from moving forwards. Also, the clamping force provided by the latching mechanisms  110 ,  112  pulls the hood  34  securely onto the vehicle body. In addition, the feet  150 ,  152  at the outer edges of the side sections  64 ,  66  engaging with the deck lid  24  prevent forward (i.e. towards the front of the vehicle) and outwardly transverse movement of the hood  34 . Finally, friction between the seal elements  82 ,  94  and the upper surface of the vehicle body, and between the seal elements and the fairing  18  and the roll hoop  20 , also serves to prevent unwanted movement of the hood  34 . 
     A further feature of the roof system is that that once the rear frame  60  is mounted onto the vehicle body, there is no part of the frame which engages with the vehicle body, because the seal elements  82 ,  94  prevent such contact. This ensures that no damage can be caused to the vehicle body by the frame (e.g. through scratching), so that even when the roof system is detached from the vehicle the aesthetic appearance of the vehicle body work is not compromised. 
     With the rear frame  60  clamped on the vehicle, the hood  34  can be pulled back over the rear frame  60  and the wings  36 ,  38  of the hood can be secured to the tensioners  40 ,  42  located within the vehicle trunk. The upper edge of the central frame section  62  is provided with a plurality of castellations or projections  160  (four are shown in  FIG. 8 ) which extend forward from the upper edge to define a means for attachment for the hood  34 . For this purpose the hood  34  is provided with a plurality of loops on its underside (i.e. the side of the cover which forms the ceiling of the vehicle cabin when in situ) so that, when the hood  34  is laid over the upper edge of the central frame section  62  the loops can be hooked over the projections  160  to secure the hood  34  to the rear frame  60 . In another arrangement, the underside of the hood  34  may be provided with hooks or pegs which cooperate with corresponding holes provided along the upper edge of the central frame section  62 . 
       FIGS. 20 to 22  show the same embodiment as that shown in previous figures, with like parts being referred to with like reference numbers. 
     Referring to  FIG. 23 , the left-side tensioner  42  for the hood  34  includes a metal plate  170  which is securely attached to the vehicle body on the left-hand side within the vehicle trunk. A lever  172  is pivotally mounted to the metal plate  170 , and a linkage  173  couples the lever to a hook  174  at the end of the tensioner  42 . The hook  174  at the end of the tensioner  42  is cooperable with an eye  176  attached to an end of the wing  38  of the hood  34 . 
     In order to attach the wing  38  of the hood  34  to the tensioner  42 , the trunk lid  24  is raised by pivoting along its rear edge, opening a gap in the region  180  (shown in  FIGS. 1 and 23 ) defined at the rear edge of the trunk lid  24  for the wing  38  to pass through. The wing  38  is passed through the gap  180  and the lever  172  of the tensioner  42  is pulled upwardly to push the hook  174  forward, thereby enabling the eye  176  on the wing  38  to be hooked over the hook  174 . The lever  172  is then pushed down to retract the hook  174  via the linkage, with the result that the wing  38  is pulled taut. Each wing  38  of the hood at the rear is provided with a steel cable or thread along both the outboard and inboard edges so as to maintain the wing taut and substantially flat when under tension. 
     To detach the hood  34  from the tensioner  42 , the lever  172  is pulled up again, pushing the hook  174  forward to release tension in the wing  38  and allowing the eye  176  of the wing  38  to be removed from the hook  174  so the hood  34  can be detached. 
     The right-side tensioner  40  on the right-side of the vehicle is identical to the left-side tensioner  42  and can be operated in a similar manner to allow attaching and detaching of the wing  36  of the hood  34  on the right-hand side of the vehicle. 
     The sequence of steps which are performed to mount the roof system to the vehicle will now be described in further detail. 
     Initially, the front frame  30  is removed from the stowage space and is unfolded about the double hinge assembly. When stowed, the hood  34  is typically folded or rolled around the hood  34  and must be unrolled or unfolded to fit the front frame  30 . The sections of the rear frame  60  are also removed from the stowage space. 
     The front frame  30  is then placed on the upper edge of the front windscreen frame  14 , locating the pins on the front frame within the holes of the windscreen frame  14  to locate the front frame  30  correctly. The clamp assemblies,  52 ,  56  and  54 ,  58 , are then operated to pull the front frame  30  down onto the windscreen frame  14  to provide a secure attachment. 
     The central frame section  62  is positioned on the upper surface of the vehicle, between the fairing  18  and the roll hoop  20  just forward from the deck lid  22 , using engagement between the locating features and the recesses to position the central frame section  62  correctly. The left- and right-side frame sections  64 ,  66  are then placed on the fairing  18  and the roll hoop  20  respectively, using the pins  120  of the latching mechanisms  110 ,  112  to locate the frame sections  64 ,  66  correctly through cooperation with the inserts  132 ,  134 . The feet  150 ,  152  on the outer edge of each side frame section  64 ,  66  are engage with the front corners of the deck lid  22 . The handle  114  of each latching mechanism  110 ,  112  is then operated to push the respective pin  120  down into the detent  138  of the recess  130  in the insert  132 ,  134 , over-coming the force of the spring washer  140  and ‘clamping’ the side frame sections  64 ,  66  onto the central frame section  62 , and hence to the vehicle, in a sealing manner by virtue of the seal elements  82 ,  94 . 
     Once the rear frame  60  is sealed against the fairing  18 , the roll hoop  20  and the upper surface of the vehicle body, the hood  34  can be pulled back from the front frame  30 , rearwards over the rear frame  60  and further rearwards towards the vehicle boot. The rear frame  60  therefore provides a fulcrum for the hood  34 , with the loops on the underside of the hood being engaged with the projections  160  on the central frame section  62  to ensure the hood  34  remains secure and provides a taut ceiling to the cabin. The wings  36 ,  38  of the hood  34  are unravelled and can be fed through the openings  180  on each side of the trunk lid  24  with the trunk lid open. The eyes  176  on the end of the wings  36 ,  38  can then be attached to the tensioners  40 ,  42 , as described previously, before lowering the levers  172  of the tensioners  40 ,  42  to tension the wings  36 ,  38  fully. 
     In order to remove the roof system from the vehicle, the sequence of steps described above is carried out in reverse. The tensioners  40 ,  42  are released to allow the wings  36 ,  38  of the hood  34  to be unhooked. The hood  34  is removed from the rear frame  60  by releasing the latching mechanisms  110 ,  112  by pulling on the handles and moving them into the unlatched positions, and the loops on the hood  34  are unhooked from the projections  160 . Aided by the force of the spring washer  140 , the pins  120  are released from their recesses  130 , removing the clamping force from the frame sections  60 ,  64 ,  66  and allowing all three frame sections to be removed from the rear of the vehicle and place in the stowage space beneath the deck lid  22 . In a similar manner, the front frame  30  component can be removed from the front windscreen  14  by operating the left- and right-side handles  56 ,  58  to disengage each hook  52 ,  54  from its recess. Once the clamping force is removed from the front frame  30  the frame can be removed and folded into two halves, by virtue of the double hinge assembly, for stowage under the deck lid  22 . 
     A particular benefit of the roof system is its compact nature when removed from the vehicle, by virtue of the double hinge assembly on the front frame  30  and the multi-section nature of the rear frame  60 . In a sports vehicle the volume for storage within the vehicle is relatively small, and so the compact nature of the assembly is critical and allows for stowage beneath the deck lid  22 . Moreover, because the rear frame  60  is formed from a lightweight material, carriage of the roof system within the storage compartment, or when fitted to the vehicle, does not appreciably increase the overall vehicle weight. Thus, vehicle performance is not affected detrimentally by carrying the roof system. 
     A further advantage of the invention resides in the straightforward method of assembly. The rear frame  60 , whilst formed from three components, includes an integral window  76  in the central frame section  62 , rather than this being a separate part as on other known convertible vehicles. Furthermore, because the vehicle screen  76  is a polycarbonate structure, rather than being formed from a fabric as in known vehicles, the structure of the rear frame  60  which supports it can be kept relatively lightweight. In addition, the means by which the three sections are assembled together is straightforward and relies only on a simple clamping force applied through the side-frame sections  64 ,  66  to the central frame section  62 . 
     The features and advantages provided by the roof system are particularly suitable for use on sports or high performance vehicles of the type described previously. Such vehicles typically include one or two roll hoops, or a fairing and a roll hoop as described above. In a twin roll hoop version of the vehicle, the rear frame has a similar structure, but the side sections are shaped slightly differently, and substantially symmetrically, to cooperate with the overall profile of the two identical roll hoops. In a vehicle without an aerodynamic or safety structure, such as a fairing or a roll hoop, the central frame section  62  and the left- and right-frame sections  64 ,  66  of the rear frame are shaped so as the engage with one another if the rear frame  60  is formed in multiple parts. This may be beneficial compared with having a unitary rear frame structure, because it allows the roof system to be accommodated within a smaller storage volume when removed from the vehicle and disassembled. 
     It will be appreciated by a person skilled in the art that the invention could be modified to take many alternative forms without depositing from the scope of the appended claims.