Abstract:
A kit for assembling a backrest on a saddle-type vehicle seat selectively connected to the frame and including at least one seat passage extending therethrough. A mounting plate is adapted to be disposed between the seat and the frame. An adapter, adapted to be connected to the mounting plate or integrally formed therewith, includes at least one adapter passage having an open end facing away from the mounting plate. An inverted U-shaped seat mount includes two posts and a connection member connected between their respective first end portions. A second end portion is adapted to be selectively received in the at least one adapter passage through the open end thereof. A back support is adapted to be pivotally connected to the seat mount. At least one fastener for attaching the mounting plate to the seat. Methods for assembling the backrest onto the seat are disclosed.

Description:
CROSS-REFERENCE 
     The present application claims priority to U.S. Provisional Application No. 61/720,647 filed on Oct. 31, 2012, the entirety of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to backrests for straddle-seat vehicles. 
     BACKGROUND 
     Straddle seats are provided on many different kinds of vehicles, such as motorcycles, snowmobiles and three-wheeled vehicles. Straddle-seat vehicles may be used for touring purposes where the driver and one or more passengers remain seated on the vehicle for long periods of time. Other uses of straddle-seat vehicles may place more emphasis on maximizing performance from the vehicle and/or driver. 
     A backrest is sometimes included on a straddle-seat to increase the comfort of the driver and passengers. It is desirable to make the vehicle comfortable for different users and for different usage modes. Some drivers may like to change the configuration of the backrest for different uses of the vehicle. Some drivers may, for example, prefer not to have a backrest while others may prefer to have it be disposed at a certain angle with respect to the seat. It would also be desirable to have the ability to add a backrest to a straddle-seat after the vehicle not provided with a backrest has been purchased. 
     There is thus a need for a versatile, adjustable and removable backrest. It is desirable to have a backrest for a straddle seat that is comfortable in use, as well as easy to install and adjust according to the preferences of a driver and/or passenger. 
     SUMMARY 
     It is an object of the present invention to ameliorate at least some of the inconveniences present in the prior art. 
     In one aspect, a seat for a vehicle includes a seat base having a bottom surface adapted to be disposed on a vehicle frame and a seat cushion having a lower surface disposed on the seat base. The seat cushion has an outer surface opposite the lower surface. A seat base passage is defined in the seat base. A seat cushion passage extends in the seat cushion from the outer surface of the seat cushion and connecting to the seat base passage. Also included is a lock having a member associated with the seat base passage and a backrest. The backrest includes a post having a lower portion selectively disposed in the seat base passage, a middle portion adjacent to the lower portion, and a connection portion adjacent to the middle portion. A back support portion is pivotably mounted on the post in the connection portion. A pivot axis is defined in the connection portion. One of a notch and a hole is defined in a surface of the lower portion, and a portion of the surface of the lower portion is an angled surface. The angled surface extends at an inward angle towards a central axis of the post in a direction away from the middle portion. The one of the notch and the hole is disposed between the angled surface and the middle portion. The member is selectively disposed in the one of the notch and the hole to removably retain the lower portion in the seat base passage. 
     In another aspect, the present provides a backrest for a vehicle seat. The vehicle seat includes a seat base with a seat base passage, and a seat cushion disposed on the seat base. The backrest includes a post having a lower portion, a middle portion adjacent to the lower portion, and a connection portion adjacent to the middle portion. The lower portion is adapted to be received in the seat base passage and to be rigidly and removably retained therein by a member connected to the seat base. A back support portion is pivotably mounted on the post in the connection portion. A pivot axis is defined in the connection portion. One of a notch and a hole is defined in a surface of the lower portion. The one of a notch and a hole is adapted to engage the member. A portion of the surface of the lower portion is an angled surface extending toward a central axis of the post in a direction away from the middle portion. The one of the notch and the hole is disposed between the angled surface and the middle portion. 
     In another aspect, the present provides a seat for a vehicle. The seat includes a seat base having a bottom surface adapted to be disposed on a vehicle frame, and a seat cushion having a lower surface disposed on the seat base. The seat cushion has an outer surface opposite the lower surface. Two receptacles are connected to the bottom surface of the seat base. Two seat cushion passages extend in the seat cushion, each seat cushion passage extending from the outer surface of the seat cushion and connecting to one of the two receptacles. The seat also includes a backrest having a forked seat mount having two posts connected to each other. Each post has a lower portion selectively disposed in one of the two seat base passages, a middle portion adjacent to the lower portion, and a connection portion adjacent to the middle portion. A back support portion of the backrest is pivotably mounted on the two posts in their respective connection portions. A pivot axis of the backrest is defined in the connection portion. The lower portion of each post is selectively received in one of the two receptacles, and rigidly and removably retained therein. The middle portion of each post extends in the corresponding one of the two seat cushion passages when the lower portion is retained in the one of the two receptacles. The connection portion of the two posts and the pivot axis are disposed outside the seat cushion when the lower portion of the two posts is retained in the two receptacles. 
     In yet another aspect, the present provides a backrest for a vehicle seat. The vehicle seat has a seat base with at least one receptacle. A seat cushion disposed on the seat base has at least one passage extending through the seat cushion, from a surface of the seat cushion disposed opposite the seat base and connecting to the at least one receptacle of the seat base. The backrest includes a seat mount with at least one post. The at least one post has a lower portion, a middle portion adjacent to the lower portion, and a connection portion adjacent to the middle portion. A back support portion of the backrest is pivotably mounted on the connection portion of the at least one post. A pivot axis is defined in the connection portion. The lower portion is adapted to be received in the at least one receptacle of the seat base, and to be rigidly and removably retained therein. The middle portion is adapted to extend in the at least one passage of the seat cushion, and the connection portion and pivot axis are adapted to be disposed outside the seat cushion when the lower portion is retained in the at least one receptacle. 
     In another aspect, a kit is provided for assembly of a backrest on a saddle-type seat of a motor vehicle. The vehicle has a vehicle frame. The seat has at least one seat passage extending therethrough. The seat is selectively connected to the vehicle frame. The kit includes a mounting plate adapted to be disposed between the seat and the vehicle frame when the seat is connected to the vehicle frame. An adapter is either adapted to be connected to the mounting plate or integrally formed with the mounting plate. The adapter includes at least one adapter passage having an open end facing away from the mounting plate. An inverted U-shaped seat mount has two posts and a connection member connected between respective first end portions of the two posts. A second end portion of each of the two posts is adapted to be selectively received in the at least one adapter passage through the open end thereof. A back support is adapted to be pivotally connected to the seat mount. At least one fastener is included for attaching the mounting plate to the seat. 
     In another aspect, the mounting plate is adapted to be connected to a bottom surface of the seat. 
     In yet another aspect, at least one resilient bumper is adapted to be placed between the mounting plate and the vehicle frame to reduce transmission of vibrations from the vehicle frame to the back support 
     In another aspect, the adapter is adapted to be connected to the mounting plate. The kit also includes at least one adapter fastener for fastening the adapter to the mounting plate. 
     In a further aspect, the adapter is adapted to be disposed at least in part in the at least one seat passage when the adapter is connected to the mounting plate, and the mounting plate is disposed between the seat and the vehicle frame. 
     In an additional aspect, the second end portion of each of the two posts is adapted to be inserted through a portion of the at least one seat passage into the at least one adapter passage when the mounting plate is disposed between the seat and the vehicle frame. 
     In an additional aspect, the two posts are adapted to extend forwardly and upwardly from the second end portion to the first end portion with respect to a bottom surface of the seat. 
     In another aspect, each of the two posts defines a respective central axis, the central axes of the two posts being parallel to each other. 
     In another aspect, the second end portion of at least one of the two posts comprises an angled surface adapted to be disposed at least partly in the at least one adapter passage, the angled surface being angled toward a central axis defined by the at least one of the two posts in a direction away from the first end portion thereof. 
     In a further aspect, one of a notch and a hole is defined in a surface of at least one of the two posts in the second end portion thereof. The one of the notch and the hole is adapted to selectively receive a lock member for retaining the second end portion of the two posts in the at least one adapter passage. 
     In another aspect, the kit includes a lock having the lock member adapted to be received in the one of the notch and the hole. 
     In a further aspect, the adapter includes a slot extending into the at least one passage, and the lock member is adapted to extend through the slot of the adapter into the one of the notch and the hole. 
     In a further aspect, the lock further comprises a push-plate connected to the lock member for manipulation thereof. 
     In an additional aspect, the mounting plate has a slot extending therethrough. The lock is adapted to be fixed to at least one of the mounting plate and the adapter. The push-plate is adapted to extend through the slot of the mounting plate when the lock is fixed to the at least one of the mounting plate and the adapter. 
     In another aspect, the at least one adapter passage is two adapter passages. Each of the two adapter passages is adapted to selectively receive the second end portion of a corresponding one of the two posts of the seat mount. Each of the two adapter passages has a closed end opposite to the open end. 
     In yet another aspect, two resilient spacers are included in the kit. Each of the two resilient spacers is adapted to be placed within one of the two adapter passages near the closed end thereof. Each of the two resilient spacers is adapted to selectively receive at least a portion of the second end portion of one of the two posts. 
     In a further aspect, a seat cover included in the kit is adapted to cover the seat and has at least one opening aligned with at least one of the at least one seat passage. 
     In another aspect, at least one of the at least one opening of the seat cover is formed by an X-shaped slit. 
     In an additional aspect, a frame spacer is adapted to be placed between the mounting plate and the vehicle frame when the mounting plate is disposed between the seat and the vehicle frame. 
     In another aspect, a method is provided of installing a backrest on a saddle-type seat of a motor vehicle. The seat has a top surface, a bottom surface, and a seat passage extending upwardly and forwardly to the top surface, the method includes moving at least a portion of the seat with respect to a vehicle frame to access the bottom surface and placing a mounting assembly on the bottom surface of the seat to align an adapter passage thereof extending toward the top surface of the seat with the seat passage. The mounting assembly is fastened to the seat. A seat mount is inserted into the seat passage from a top surface of the seat and into the passage of the mounting assembly. The seat mount is locked to at least one of the seat and the mounting assembly. The at least one portion of the seat is moved with respect to the vehicle frame to reposition the bottom surface of the seat on the vehicle frame, the seat having the mounting assembly fastened thereto. 
     In a further aspect, the seat mount is inserted into the seat passage through a seat cover covering at least a portion of the seat including the seat passage. 
     In yet another aspect, the mounting assembly includes a mounting plate and an adapter. The adapter has the adapter passage. The method includes connecting the adapter to the mounting plate. 
     For purposes of the present application, terms related to spatial orientation when referring to a vehicle and components in relation to the vehicle, such as “forwardly”, “rearwardly”, “left”, “right”, “above” and “below”, are as they would be understood by a driver of the vehicle, with the vehicle in a straight ahead orientation (i.e. not steered left or right), and in an upright position (i.e. not tilted). The explanations provided above regarding the above terms take precedence over explanations of these terms that may be found in any one of the documents incorporated herein by reference. 
     Embodiments of the present invention each have at least one of the above-mentioned object and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present invention that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein. 
     Additional and/or alternative features, aspects, and advantages of embodiments of the present invention will become apparent from the following description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where: 
         FIG. 1A  is a right side elevation view of a vehicle; 
         FIG. 1B  is a top plan view of the vehicle of  FIG. 1A ; 
         FIG. 2A  is a top plan view of the seat of the vehicle of  FIG. 1A , shown in isolation; 
         FIG. 2B  is a left side elevation view of the seat of  FIG. 2A ; 
         FIG. 3A  is a front elevation view of the seat of  FIG. 2A ; 
         FIG. 3B  is a rear elevation view of the seat of  FIG. 2A ; 
         FIG. 4A  is a bottom plan view of the seat of  FIG. 2A  shown with the seat cushion removed for clarity; 
         FIG. 4B  is a bottom plan view of the seat of  FIG. 4A ; 
         FIG. 4C  is a cross-sectional view of the seat of  FIG. 4A  taken along the line  4 C- 4 C of  FIG. 4B ; 
         FIG. 5  is an exploded perspective view, taken from a rear, right side, of the seat of  FIG. 2A ; 
         FIG. 6  is an exploded perspective view, taken from a rear, right side, of the seat of  FIG. 2A  with the seat cushion removed for clarity; 
         FIG. 7  is an exploded perspective view, taken from a front, right side, of a backrest and mounting assembly of the seat of  FIG. 2A ; 
         FIG. 8A  is perspective view, taken from a front, right side, of the backrest and mounting assembly of  FIG. 7  as assembled; 
         FIGS. 8B, 8C and 8D  are respectively a rear elevation view, right side elevation view, and a bottom plan view of the backrest and mounting assembly of  FIG. 8A ; 
         FIGS. 9A and 9B  are cross-sectional views of a portion of the backrest and mounting assembly of  FIG. 8A , taken along the line  9 A- 9 A of  FIG. 8C , respectively showing a lock disposed in an open and closed position; 
         FIGS. 9C and 9D  are perspective views, taken from a rear, right side, of an adaptor of the mounting assembly of  FIG. 8A , respectively shown with the lock disposed in an open and closed position; 
         FIG. 10  is an exploded cross-sectional view of the seat of  FIG. 2A , taken along the line  10 - 10  of  FIG. 2A ; and 
         FIG. 11  is a cross-sectional view of the seat of  FIG. 2A , taken along the line  11 - 11  of  FIG. 2A ; 
         FIG. 12  is a perspective view taken from a bottom, rear and left side, of the seat and a portion of the frame of the vehicle of  FIG. 1A  with another embodiment of a backrest; 
         FIG. 13  is a top plan view of the backrest, seat and frame portion of  FIG. 12 ; 
         FIG. 14  is a cross-sectional view of the backrest, seat and frame portion of  FIG. 12  taken along the line  14 - 14  shown in  FIG. 13 ; 
         FIG. 15  is a left side elevation view of the backrest, seat and frame portion of  FIG. 12  with the seat cushion removed for clarity; 
         FIG. 16  is a top plan view of the backrest, seat and frame portion of  FIG. 15 ; 
         FIG. 17  is a cross-sectional view of the backrest, seat and frame portion taken along the line  17 - 17  of  FIG. 16 ; 
         FIG. 18  is a left side elevation view of the backrest, adaptor, mounting plate, frame spacer and frame portion of  FIG. 15 ; 
         FIG. 19  is a perspective view, taken from a top, rear and left side of the backrest, adaptor, mounting plate, frame spacer and frame portion of  FIG. 18 ; and 
         FIG. 20  is a perspective view, taken from a bottom, front and left side of the backrest, adaptor, mounting plate, frame spacer and frame portion of  FIG. 18 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will be described with respect to a three-wheeled vehicle. However, it contemplated that aspects of the embodiments of the present invention could also be used on other types of vehicles, such as all-terrain vehicles (ATVs), motorcycles, snowmobiles, and personal watercraft. 
     With reference to  FIG. 1 , the vehicle  10  has a front end  5  and a rear end  6  defined consistently with the forward travel direction. A longitudinal centerline  9  extending through the center of the vehicle  10 . 
     The vehicle has left and right front wheels  12 , and a rear wheel  14 . The front wheels  12  are equally offset from the longitudinal centerline  9 , and the rear wheel  14  is aligned with the longitudinal centerline  9 . Each of the three wheels  12 ,  14  has a tire  15 . A fairing  16  is disposed over each tire  15  to protect the driver from dirt and water which can be lifted by the tire  15  while it is rolling. Although the vehicle  10  of the illustrated embodiment has two front wheels  12  and one rear wheel  14 , it is contemplated that the vehicle  10  could also have one front wheel and two rear wheels, or a single front wheel and a single rear wheel. 
     The front wheels  12  are supported by a front suspension assembly  20 . The rear wheel  14  is supported by a rear suspension assembly  22 . The front and rear suspension assemblies  20 ,  22  are secured to a vehicle frame  24 . The front suspension assembly  20  includes a pair of suspension support arms (A-arms)  25  and a shock absorber  26  extending from each side of the frame  24  to support the wheels  12 . The rear suspension assembly  22  includes a swing arm  27  pivotally connected to the frame  24 . An engine (not shown) drives the rear wheel  14  and is secured to the vehicle frame  24 . The vehicle frame  24  is a tubular frame assembly is discussed in greater detail in U.S. patent publication No. 2004/0035623A1, published Feb. 26, 2004, the disclosure of which is incorporated specifically herein by reference. It is contemplated that other types of vehicle frames and front and rear suspensions could be used. 
     With reference to  FIG. 1 , the vehicle  10  has a straddle-type seat  30  disposed along the longitudinal centerline  9 . The seat  30  has a front seat portion  32  for accommodating a driver, and a back seat portion  34  for accommodating a passenger behind the driver. The back seat portion  34  is higher than the front seat portion  32  to permit the passenger to see in front of the vehicle  10  over the driver. It is contemplated that the straddle-type seat  30  could have only the first portion  32 . A driver backrest  36  is provided between the front seat portion  32  and the back seat portion  34 . A storage compartment  38  behind the passenger portion  34  of the seat  30  serves as backrest for the passenger. It is contemplated that a backrest similar to the driver backrest  36  could also be disposed behind the passenger portion  34  to serve as a passenger backrest. The seat  30  and the driver backrest  36  will be discussed in further detail below. 
     A driver foot board  40  is provided on either side of the vehicle  10  below the first portion  32  of the straddle-type seat  30  for a driver to rest his feet thereon. Similarly a passenger foot board  42  is provided on either side of the vehicle  10  below the back seat portion  34  of the straddle-type seat  30  for a passenger to rest his feet thereon. 
     A steering assembly, including a handlebar  44  connected to a steering column (not shown), is connected to the front wheels  12  for steering the vehicle  10 . 
     The handlebar  44  is disposed forwardly of the straddle-type seat  12  to allow a driver to steer the vehicle  10 . 
     The vehicle  10  has other features and components such as headlights and radiators. As it is believed that these features and components would be readily recognized by one of ordinary skill in the art, further explanation and description of these components will not be provided herein. 
     Turning now to  FIGS. 2 to 11 , the seat  30  and the driver backrest  36  will be described. 
     With reference to  FIGS. 2A to 6 , the seat  30  has a seat base  50  and a seat cushion  52  disposed on the seat base  50 . As mentioned above the seat  30  has a front driver portion  32  and a rear passenger portion  34 . The seat base  50  is formed as one integral piece for both the driver portion  32  and the passenger portion  34  of the seat  30 , but it is contemplated that the seat base  50  could be formed as two separate pieces. Similarly, the seat cushion  52  is formed as one integral piece for both the driver and passenger portions  32 ,  34 , but it is contemplated that the seat cushion  52  could be formed as separate pieces. 
     The seat base  50  is made of plastic. The seat base  50  has a bottom surface  67  and an upper surface  68  which engages the seat cushion  52 . The front portion  56  of the seat base  50  curves upwards. Wings  58  in the front portion  56  of the seat base  50  curve forwards on the left and right sides to wrap around the frame  24  of the vehicle  10 . Flanges  54  at the rear end of the seat base  50  serve to pivotably fix the rear end of the seat base  50  to the frame  24 . The seat base  50  is removably fixed at the front end. The seat base  50  can be lifted upwards from the front end to access the vehicle frame  24  underneath the seat  30  as well as the bottom surface  67  of the seat base  50 . It is contemplated that the seat base  50  could be removably attached to the vehicle frame  24  by its front end instead of the rear end so that it can be lifted upwards from the vehicle frame  24  by its front end. It is also contemplated that the seat base  50  could be removably attached to the vehicle frame  24  by its front end and rear ends so that the seat base could be removed from the vehicle frame  24 . 
     The seat cushion  52  is made of compressible foam material, molded such that its bottom surface conforms to the shape of the seat base  50 . The seat cushion  52  is disposed on the upper surface  68  of the seat base  50 . A seat cover  60 , placed over the seat cushion  52  and attached to the bottom surface of the seat base  50 , serves to fix the seat cushion  52  to the seat base  50 . It is contemplated that the seat cushion  52  could be formed integrally with the seat base  50 . The waterproof leather cover  60  for the foam helps to prevent the foam from becoming dusty, dirty or wet. It is contemplated that any suitably durable material could be used to cover the seat cushion  52 . It is contemplated that the cover  60  could be removable and formed of more than one part. It is also contemplated that the cover  60  could be attached to the seat cushion  52  which could be fastened to the seat base  50 . 
     As best seen in  FIGS. 10 and 11 , the seat cushion  52  is provided with a pair of passages  62  extending downward from the top surface and connected to a cavity  64  (best seen in  FIGS. 10 and 11 ) formed in the lower portion of the seat cushion  52  for installation of the backrest  36 . The seat base  50  has an opening  74  which is aligned with the seat cushion cavity  64  and seat cushion passages  62 . It is contemplated that the seat cushion cavity could be omitted and the seat base passages  62  could extend through the seat cushion  52  to the seat base opening  74 . 
     As best seen in  FIG. 5 , the seat cover  60  is provided with a pair of apertures  66  aligned with the passages  62  of the seat cushion  52  to enable installation of the backrest  36 . In the illustrated embodiment, the apertures  66  are formed by X-shaped slits  66  made in the cover  60  so that the seat cover  66  extends over the passages  62  of the seat cushion when the backrest  36  is not installed on the seat  30 . It is contemplated that the apertures  66  could not be in the form of X-shaped slits. It is contemplated that the seat cover  60  could include aperture covers to cover the apertures  66  when the backrest  36  is not installed on the seat  30 . For example, the aperture cover could be in the form a rigid plastic lid friction fit over an aperture  66 , or a flexible flap made of the same material as the seat cover  60  and fastened to the seat cover  60  adjacent the aperture  66  by means of a fastener such as a hook and loop fastener and the like. 
     With reference to  FIGS. 4C and 11 , the backrest  36  has a back support portion  80  extending above the seat cushion  52  between the driver portion  32  and the passenger portion  34 . The back support portion  80  is pivtoably attached to the seat base  50  by a seat mount  82 . The seat mount  82  extends through the passages  62  and cavity  64  of the seat cushion  52  and the opening  74  of the seat base  50 . The back support portion  80  is pivotable about a pivot axis  90  so that its angular orientation, with respect to the seat base  50  and the horizontal direction, can be adjusted according to the preference and comfort of the driver and/or passenger. 
     With reference to  FIGS. 5 and 6 , a mounting assembly  70  removably attaches the seat mount  82  of the backrest  36  to the seat base  50 . The mounting assembly  70  includes a mounting plate  71  and an adaptor  72  extending upwards therefrom. The upper surface  69  of the mounting plate  71  is fixed by the bolts  116  to the bottom surface  67  of the seat base  50 , adjacent to the seat base opening  74 . 
     Rubber bumpers  122  are inserted through the metal mounting plate  72  to prevent metal to metal contact between the bottom surface  75  (seen clearly in  FIG. 8D ) of the mounting plate  72  and the vehicle frame  24 , and to prevent vibrations of the vehicle frame  24  from being transferred to the driver/passenger if/when the seat base  50  flexes. 
     With reference to  FIGS. 4C, 10 and 11 , the adaptor  72  extends through the seat base opening  74  and above the seat base  50  into the cavity  64  of the seat cushion  52 . The seat cushion  52  extends above the adaptor  72 , with sufficient thickness of foam material between the adaptor  72  and the outer surface of the seat cushion  52 , so that a passenger sitting in the rear portion  34  or a driver sitting in the front portion  32  of the seat  30  will not feel the adaptor  72  when the backrest  36  is not installed on the seat  30 . The adaptor  72  is disposed below a line  170  (shown as a dashed line in  FIG. 10 ) passing through the highest points of the front and rear ends of the seat cushion  52  and disposed in a vertical plane containing the longitudinal centerline  9 . A line  172  (shown as a dashed line in  FIG. 10 ) passing through the lowest points of the front and rear ends of the seat cushion  52  and disposed in a vertical plane containing the longitudinal centerline  9  passes through the adaptor  72 . It is contemplated that the adaptor  72  could extend above the seat cushion  52 . 
     With reference now to  FIGS. 7 to 11 , the backrest  36  will be described in detail. 
     As mentioned above, the backrest  36  includes the back support portion  80 , configured to support the driver&#39;s back, and the seat mount  82  that attaches the backrest  36  to the seat base  50 . The back support portion  80  is pivotably attached to the seat mount  82 . 
     The back support portion  80  has a plastic frame with a compressible foam material molded onto the plastic frame. It is contemplated that the back support portion  80  could extend higher or lower than as shown in the illustrated embodiment. It is contemplated that the foam could be omitted from the back support portion  80 . The back support portion  80  is concave towards the front for supporting the driver&#39;s back. The back support portion  80  is curved forwardly in the upper portion, as well as the lateral sides. It is contemplated that the back support portion  80  could not be curved. The back support portion  80  has a plurality of apertures  81  which aid air circulation and enhance the driver&#39;s comfort during long rides. It is contemplated that the number, shape, size and arrangement of the air circulation apertures could be different. It is also contemplated that the apertures could be omitted. A pair of connection flanges  84  is provided at the lower end of the back support portion  80  for connecting to the seat mount  82 . 
     The forked seat mount  82  comprises two vertical metal posts  86  connected by a horizontal connection member  88 . The connection member  88  is in the form of a tube which is open at both ends. 
     The posts  86  have a rectangular cross-section. It is contemplated that the cross-section of the posts could be other than rectangular. The central axes  91  of the posts  86  extend perpendicularly to the tube  88 . The tube  88  is placed between the two connection flanges  84  so that the openings of the connection flanges  84  are aligned with the tube  88 . The back support portion  80  and the vertical posts  86  extend in opposite directions from the tube  88 . 
     The back support portion  80  and the seat mount  82  are pivotably connected together by a bolt  89  inserted through the openings of the connection flanges  84  and the tube  88 . The bolt  89  in the tube  88  defines the pivot axis  90  for the back support portion  80 . The back support portion  80  pivots forward and rearward about the bolt  89  thereby changing the angular orientation of the back support portion  80  with respect to the seat mount posts  86 , and the seat base  50 . 
     Each connection flange  84  on either side of the tube  88  is supported on top of the corresponding vertical posts  86  of that side. A ball bearing  92  is placed between the connection flange  84  and the vertical post  86  of each side. Each vertical post  86  has a passage  94  extending downwards from its upper surface. A spring  96  ( FIG. 11 ) placed in the passage  94  biases the ball bearing  92  against the surface of the connection flange  84 . 
     With reference to  FIGS. 7 and 11 , the outer surface of each connection flange  84  has a plurality of grooves  98  extending horizontally (parallel to the pivot axis  90 ). The ball bearing  92  is retained in a groove  98  by the spring  96  biasing the ball bearing  92  against the surface of the groove  98 . The ball bearing  92  can be moved from a first groove  98  to a second groove  98  by pushing the back support portion  82  against the seat mount  82 , so that the ball bearing  92  and spring  96  retract into the passage  94 , allowing the connection flange  84  to rotate about the pivot axis  90  until the first groove  98  slides past the passage  94 . When the second groove  98  is aligned with the passage  94  and pressure on the back support portion  80  against the seat mount  82  is released, the ball bearing  92  is retained in the second groove  98 . The ball bearing  92  held between one of the flange grooves  98  and the spring  96  in the passage  94  thus serves to lock the back support portion  80  at a particular angle with respect to the seat mount  82 . Each groove  98  of the connection flange  84  thus corresponds to a different angular configuration of the backrest  36 . 
     As mentioned above the seat mount  82  attaches the backrest  36  to the seat base  50  via the mounting assembly  70 . The posts  86  of the seat mount  82  are inserted through the seat cover apertures  66 , the seat cushion passages  62  and into the adaptor  72  of the mounting assembly  70  as shown in  FIG. 10 . With reference to  FIG. 11 , a lower portion  102  of each post  86  is received in the adaptor  72  of the mounting assembly  70 . A middle portion of each post  86 , adjacent to the lower portion  102 , is disposed in the passage  62  of the seat cushion  52  when the lower portion is disposed in the adaptor  72 . An upper portion  106 , which includes the connection tube  88  and referred to as the connection portion  106 , remains outside the seat cushion  52  when the lower portion  102  of the posts  86  are disposed in the adaptor  72 . 
     In the lower portion  102 , the posts  86  have an angled surface  103 . The angled surface  103  of the post  86  is angled away from the receptacle wall towards the central axis  91  of the post  86 . The cross-section of the posts  86  is narrower in the lower portion  102  having the angled surface  103  and therebelow. 
     A notch  105  is also defined in the lower portion  102  of the right side post  86  just above its angled surface  103 . The notch  105 , rectangular in shape, is defined in the surface of the right side post  86  facing the left side post  86 . It is contemplated that the notch could be in the form of a hole extending through the post  86 . 
     With reference to  FIGS. 7 to 9D , the mounting assembly  70  for the backrest  36 , will now be described. The mounting assembly  70  includes the mounting plate  71 , the adaptor  72  and a lock  112 . 
     The mounting plate  71  is generally flat with a raised section  119  defining a wedge-shaped slot  118 . The bottom surface  75  ( FIGS. 8D and 9A ) of the mounting plate  71  is spaced from the vehicle frame  24  in the raised section  112 . The adaptor  72  is disposed on the upper surface  69  of the mounting plate  71  on the raised section  119 , and fastened thereto by bolts  114 . 
     The adaptor  72  includes two receptacles  108 , each having a passage  107  defined therein to receive the lower portion  102  of the post  86 . The raised section  119  of the mounting plate  71  is sloped downwards towards the front so that the posts  86  incline forward with respect to the seat base  50  as best seen in  FIG. 8C . It is contemplated that the raised section could not be angled with respect to the seat base  50 . It is also contemplated that the posts  86  could be disposed perpendicular to the seat base  50 . 
     The posts  86  are retained in the receptacles  108  of the adaptor  72  by a lock  112 . The lock  112  is disposed in a gap  109  extending between the receptacles  108 . As will be explained below, the lock  112  is a quick-release type of lock that can be operated without the use of any tools. 
     With reference to  FIGS. 7 and 9A to 9D , the receptacles  108  of the adaptor  72  are formed as hollow tubular structures open at both ends, i.e. the receptacles are open at the upper surface and the bottom surfaces of the adaptor  72 . The tubular passages  107 , in which the posts  86  are received, are generally trapezoidal in shape. It is contemplated that the cross-sectional shapes of the posts  86  and the passages  107  could be other than rectangular and trapezoidal. For example, the posts  86  and passages  107  could be circular in cross-section. 
     The adaptor  72  has a front wall  132  and a rear wall  134 , each extending between the receptacles  108 . The gap  109  extends between the walls  132 ,  134  and the receptacles  108 . The front wall  132  extends between the top and bottom surfaces of the receptacles  108 . The rear wall  134  also extends upwards from the bottom surface but only part of the way to the upper surface of the adaptor  72 . The right receptacle  108  has a slot  136  extending into its tubular passage  107  from the gap  109 . It is contemplated that the gap  109  could be disposed adjacent to the one receptacle  108  which has the slot  136 . 
     The lock  112  is rotatably attached to the upper surface of the rear wall  134  by a bolt  138 . The lock  112  includes a push-plate  113  and a lock member  140  biased to extend into the slot  136  to engage the right post  86  disposed in the right receptacle  108 . The lock  112 , and thus the push-plate  113  and the member  140 , rotate about the bolt  138 . 
     The lock member  140  is in the form of a tab  140 . The height of the rear wall  134  is adapted to align the tab  140  with the slot  136 . The slot  136  is rectangular, and the tab  140  is generally rectangular in a vertical cross-section with a rounded top edge. It is contemplated that the slot  136  and the tab  140  could have a vertical cross-section that is other than rectangular in shape, for example, circular, elliptical and the like. The top edge of the tab  140  is rounded (curved downwards) to facilitate insertion of the post  86  into the receptacle. 
     The push-plate  113  (best seen in  FIG. 7 ) is rigidly connected to the tab  140 . The push-plate  113  extends downwards through the gap  109 , through the slot  118  into the space between the raised section  119  and the vehicle frame  24 . The wedge-shape of the slot  118  limits rotation about the bolt  138  of the push-plate  113  extending therein. The raised portion  119  of the mounting plate  71  ensures that the bottom end of the push-plate  113  is not in contact with the vehicle frame  24 . 
     A torsional spring  144  biases the tab  140  to extend into the slot  136  of the receptacle  108 . The helical section of the torsional spring  144  is inserted around the bolt  138  between the lock  112  and the rear wall  134 . One end of the helical coil is inserted into a hole  146  on the upper surface of the rear wall  134  while the other end is inserted into a portion integral with the tab  140  to bias the tab  140  towards the receptacle  108 . 
     Rubber spacers  110  are placed within the passages  107  of the receptacles  108  to receive the end portion of the metal posts  86 . The rubber spacers  110  surround the portion of the posts  86  with the narrower cross-section, thereby minimizing play between the posts  86  and the receptacles  108 . The rubber spacers  110  prevent metal to metal contact between the ends of the metal post  86  and the metal mounting plate  71 . 
     During installation of the backrest  36  in the seat  30 , as the post  86  is pushed into the receptacle  108  past the slot  136 , the angled surface  103  of the right post  86  sliding past the rounded top edge of the tab  140 , exerts a force on the biased tab  140  towards the slot  136 . As mentioned above, the right post  86  has a notch  105  above the angled surface  103 . The notch  105  is defined in the surface facing the slot  136 . As the post  86  slides downward into the receptacle  108 , the notch  105  slides into alignment with the slot  136 . The biased tab  140  snaps into the aligned slot  136  and notch  105 , preventing further upwards movement of the post  86  in the receptacle  108 , and thereby locking the post  86  in the receptacle  108 . The rubber spacers  110  also provide a small biasing force pushing the post  86  toward the lock  112 . 
     In order to unlock the posts  86  from the adaptor  72 , and to remove the backrest  36  from the seat  30 , the push-plate  113  is rotated about the bolt  138  in a direction away from the receptacle  108  until the tab  140  slides out of the slot  136 . 
     The push-plate  113  is rotated by accessing its bottom end by raising the front portion  56  of the seat base  50  from the vehicle  10 . 
     The lock  112  can therefore be operated, both for locking and unlocking the posts  86  in the receptacles  108 , without having to disassemble the mounting assembly  70  or the seat  30 . 
     It is contemplated that the angled surface  103  could be provided on the post  86  only on the side facing the slot  136 . It is contemplated that the shapes of the notch  105 , the slot  136  could be other than rectangular, such as, for example, circular. It is contemplated that the member  140  could be in the form of a pin, a hook or other such structure. It is contemplated that the member  140  could extend into the receptacle  108  at an angle with respect to the receptacle wall and/or the central axis  91  of the post  86 . 
     It is contemplated that both receptacles  108  could have a slot  136 . It is contemplated that each of the posts  86  of the forked seat mount  82  could be locked in the respective receptacles  108  by respective locks  112 . A gap  109  could be defined adjacent to each of the receptacle  108  for housing their respective locks  112 . It is also contemplated that the lock  112  could have two members  140 , each member  140  extending into a slot  136  of one of the receptacles  108 . The complementary slots  136  and members  140  could be configured to enable insertion and removal of the members  140  into/out of the slots  136  by rotation of the lock  112  about an axis centered between the two members  140 . 
     It is contemplated that the lock  112  could be disposed other than between the receptacles  108 . For example, the lock  112  could be disposed in front of one of the receptacles  108  with the slot  136  extending in the front wall of the receptacle  108 . 
     It is contemplated that the number of posts  86  and the corresponding number of receptacles  108  in the adaptor could be one or more than two. It is contemplated that the gap  109  could be omitted. It is contemplated that a plurality of posts  86  could be received in one receptacle  108 . The adaptor  72  is made of extruded steel. The mounting plate  71  is also made of steel. It is however also contemplated that the mounting plate  71  and the adaptor  72  could be made of other suitable materials using any suitable method. It is contemplated that the adaptor  72  and mounting plate  71  of the mounting assembly  70  could be integrally formed. It is also contemplated that the mounting assembly  70  could be integrally formed with the seat base  50 . 
     It is contemplated that a backrest kit could be provided for assembly of the backrest  36  onto the seat  30 . The kit would include the back support portion  80 , the seat mount  82  and the mounting assembly  70 . The kit could also include the seat cover  60 . 
     With reference to  FIGS. 12 to 20 , the seat  30  and backrest  36  are supported by a vehicle frame  24  which includes a seat support member  160  and a frame spacer  150 . The seat  30  and the backrest  36  of  FIGS. 12 to 20  are similar to the seat  30  and backrest  36  described above and shown in the previous Figures. As such, the components of the seat  30  and backrest  36  have been labelled with the same reference labels and will not be described again in detail below except in relation to the vehicle frame  24 . 
     The seat support member  160  extends longitudinally below the seat  30 . The rear end of the seat support member  160  is connected to another portion of the vehicle frame  24 . The front end of the seat support member  160  is also connected to another portion of the vehicle frame  24 . The support member is made of metal. The seat support member  160  is tubular and has a rectangular lateral cross-section. The tubular seat support member  160  is formed by a horizontally extending upper portion  160   a , a horizontally extending lower portion  160   a , a right side portion  160   b  extending vertically from the right edge of the upper portion  160   a  to the right edge of the lower portion  160   a , and a left side portion  160   b  extending vertically from the left edge of the upper portion  160   a  to the left edge of the lower portion  160   a . The seat support member  160  is laterally narrower than the seat base  50  and the seat cushion  52 . The upper and lower portions  160   a  include openings  168  for reducing the weight of the vehicle frame  24 . 
     The seat support member  160  has a horizontally extending front portion  162 , a middle portion  164  extending rearwardly and downwardly from the front portion  162 , and a rear portion  166  extending rearwardly and upwardly from the middle portion  164 . The rear portion  166  supports the backrest  36 , the mounting plate plate  71 , a rear portion of the front seat  32 , and a front portion of the rear seat  34 . The wings  58  of the front portion  56  of the seat base  50  extend on either side of the middle portion  164  of the seat support member  160 . The front portion  162  is disposed forwardly of the wings  56  and vertically higher than the wings  56 . The seat base  50  extends rearwardly of the rear end of the seat support member  160 . It is contemplated that the seat support member  160  could extend rearwardly of the seat base  50 . 
     It is contemplated that the portions  162 ,  164 ,  166  could be angled differently than as shown. It is contemplated that one or more of the portions  162 ,  164 ,  166  could be curved. It is also contemplated the seat support member  160  could extend horizontally through its entire length. 
     With reference to  FIGS. 18 to 20 , a frame spacer  150  is disposed on the rear portion  166  of the seat support member  160 . The frame spacer  150  is rigid and made of molded plastic. The frame spacer  150  rests on the rear portion  166  of the seat support member  160 . The upper surface of the frame spacer  150  contacts the bottom surface  67  of the seat base  50 . The mounting plate  71  attached to the bottom surface  67  of the seat base  50  is disposed on the frame spacer  150 . The frame spacer  150  prevents direct contact between the metal mounting plate  71  and the metal support member  160 . 
     The frame spacer  150  has a generally rectangular central portion with an upper surface and a bottom surface. The mounting plate  71  and the seat base, contact the upper surface. The bottom surface has reinforcement ribs  151  projecting downwardly therefrom. 
     The frame spacer  150  has a front right bracket  152 , a front left bracket  152 , a rear right bracket  154  and a rear left bracket  154  projecting outwards from the central portion. The left brackets  152 ,  154  extend leftwardly from the central portion, past the left portion  160   b  of the seat support member  160  and the left edge of the seat  30 . The right brackets  152 ,  154  extend rightwardly from the central portion, past the right portion  160   b  of the seat support member  160  and the right edge of the seat  30 . The rear right bracket  154  and the rear left bracket  154  have a portion extending rearwards of the seat  30 . The frame spacer  150  is fastened to the vehicle frame  24  by the brackets  152 ,  154 . The frame spacer  150  also has a flange  156  extending rightwardly of the seat  30  between the front right bracket  152  and the rear right bracket  154 . 
     The frame spacer  150  has an edge projecting downwardly from the periphery of the central portion and the brackets  152 ,  154 . The edges extend further downwards than the ribs  151 . A portion of the downwardly bent edges rests on the seat support member  160 . As can be seen best in  FIGS. 14 and 17 , the ribs  151  are spaced from the upper portion  160   a  of the seat support member  160 . 
     As can be seen in  FIG. 14 , a line  170  passing through the highest points of the front and rear ends of the seat cushion  52  and disposed in a vertical plane containing the longitudinal centerline  9  passes above the adaptor  72 . A line  172  passing through the lowest points of the front and rear ends of the seat cushion  52  and disposed in a vertical plane containing the longitudinal centerline  9  passes through the adaptor  72 . 
     It is contemplated that the frame spacer  150  could also be included as part of the backrest kit. 
     Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present invention is therefore intended to be limited solely by the scope of the appended claims.