Abstract:
Structure is provided for joining and bonding together two halves of a plastic upper body member which in turn are joined and bonded to a fiber reinforced lower member to comprise a monocoque vehicle assembly. The joint designs facilitate side-to-side and fore-and-aft alignment for quick and easy assembly of the upper body member to the lower member. Spacer surfaces are provided for controlling adhesive reservoirs between adjoining surfaces to facilitate positive bonding.

Description:
This application is a continuation of application Ser. No. 07/715,204, filed Jun. 14, 1991, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to lower and upper body structures for a vehicle, and more specifically to a three-piece monocoque body assembly for use in small vehicles, such as lawn and garden tractors. 
     2. Description of the Related Art 
     Lawn and garden ride-on vehicles utilize a main frame that is typically manufactured from many individual pieces. Those pieces have traditionally been made of metal to withstand the various loads and deflections encountered by the vehicle. The pieces are either cut and/or stamped and then welded or bolted together. Subsequently, some type of body enclosure is attached to the main frame to cover the mechanical components, such as the engine, wheels, control linkages and battery. 
     The expenses associated with the materials, and the manufacturing and assembly operations in producing vehicle frames and bodies is substantial and, therefore, some manufacturers have utilized alternative materials, including fiber reinforced plastics. 
     To obtain the stiffness needed to withstand the types of loads and deflections associated with vehicle operation, metal frame members have been used as skeletal supports with the plastic panels which may be bonded together then being bolted to the metal members. Subsequently, other plastic panels are bolted or bonded to the first panels to complete the vehicle and its body structure. 
     Some fiber reinforced plastic vehicle bodies have also been made without the use of a metal skeletal structure. Accordingly, the panels are relatively rigid and bonding of the panels into a vehicle structure requires tight tolerances and careful assembly procedures to assure that the bonded joints have the desired dimensions and appropriate strength. 
     SUMMARY OF THE INVENTION 
     It would therefore be desirable to provide a plastic-type upper and lower body vehicle assembly which does not necessarily require metal skeletal members, yet one which has the resiliency and durability to withstand the loads encountered by a vehicle, such as a lawn and garden tractor. 
     It would additionally be desirable to provide a multi-piece plastic-type upper and lower body having parts which can quickly and positively be positioned with respect to one another during assembly operations. Further, the tolerances required for adhesive gaps at the bonding joints should be maintained to assure that the joint develops the desired strength and that the joints can accommodate differential thermal and moisture expansion and contraction of the plastic parts. 
     Towards these goals, there is provided a plastic-type vehicle assembly which includes a top body structure made from plastic without reinforcing fibers, this body shell or top member being assembled from left and right section halves. 
     The assembly further includes a lower member produced from fiber reinforced plastic. The assembled monocoque structure provides the rigidity necessary to carry the loads encountered by the vehicle. 
     The structural joints between the upper and lower members and between the two halves of the upper body member creates the monocoque body. Vehicle loads are carried throughout the skin of the body. The bond joints therefore are essential in continuously transferring the loads among body elements and are essential to avoid the stress concentrations that originate at mechanically fastened joints. 
     A bonding joint design is provided between the upper and lower members that enables them to be quickly and easily assembled. The joints are configured to positively align and locate the upper member halves relative to the lower member as they are assembled, then snap into place and lock them together to positively provide the appropriate adhesive gap between mating surfaces for bonding the two parts together. The upper plastic body structure is further able to flex as it is joined to the lower member without incurring fractures, cracks or other damage, thereby allowing its joint members to snap into place with the lower member joints. 
     The joint designs also provide an adhesive gap dimension that can be maintained at the desired configuration to accommodate differential thermal and moisture expansion and contraction of the bonded assembly of plastic materials with dissimilar coefficients of thermal and moisture expansion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates the monocoque body assembly with the two upper body portions assembled to the lower structure. 
     FIG. 2 illustrates the lower structure. 
     FIG. 3 is a view taken along lines 3--3 of FIG. 1 and illustrates the upper and lower joints between the upper and lower members. 
     FIG. 4 is a view taken along lines 4--4 of FIG. 1 and illustrates the two joints in the hollow steering column enclosure formed between the left and right upper body portions. 
     FIG. 5 is a view taken along lines 5--5 of FIG. 1 and illustrates the joints in the center and forward portion of the body assembly. 
     FIG. 6 is an enlarged view of the left end portion of FIG. 5 and illustrates in detail the bonding joint between the upper and lower members. 
     FIG. 7 is a view taken along lines 7--7 of FIG. 1 and illustrates the forwardly located and laterally extending joints between the upper and lower structures. 
     FIG. 8 is a view taken along lines 8--8 of FIG. 1 and illustrates the rear joint between the two upper body portions. 
     FIG. 9 is a front right perspective view of a lawn and garden vehicle utilizing the monocoque body assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Looking first to FIGS. 1 and 2, it will be seen that the monocoque vehicle assembly 10 is comprised of three parts. Two of these parts are joined to form the upper structure and include similar left and right body portions or halves, designated 12 and 14. The third part is the lower frame structure 16, best illustrated in FIG. 2. The structure and manner of joining these three members 12, 14 and 16 to form a monocoque vehicle assembly 10 comprises the subject of this invention. 
     Returning now to FIG. 1, it will be noted that the upper body portions 12 and 14 include a fore-and-aft extending seam or joint along which they are bonded. This bonding joint is designated 18 in FIG. 9. FIGS. 8, 5 and 4 illustrate respectively the rear, center and forward joints 20, 22 and 24 between the two body portions 12 and 14. 
     Looking first at FIG. 8, it will be noted that the rear sections of the upper body structure or member 26 are joined by overlapping members including a first flap or tab, designated 28, carried by the right body portion 14. The second flap or tab, designated 30, is carried by the left body portion 12. A satisfactory adhesive gap 32 is provided between the two tabs 28 and 30 to allow the desired amount of adhesive for joining the portions 12 and 14 and for allowing differential thermal and moisture expansion and contraction of the plastic portions 12 and 14. Spacer bumps similar to those bumps 33 (see FIG. 2) located along the forward center joint 22 are included between the tabs 28-30 to provide the desired adhesive reservoirs between them. 
     Looking now to FIG. 5, there is illustrated the center joint 22 between the two body halves 12 and 14 and the U-shaped channel 34 formed in the lower member 16. Prior to inserting the legs or leg portions 36 of the L-shaped edges of the upper body halves 12 and 14 into the channel 34, adhesive would be applied to their adjacent vertical surfaces and the channel 34. This joint 22 assists in locking the upper body member 26 and lower frame members 16 against side-to-side movement. 
     The four fore-and-aft extending surfaces 38 of the lower member 16 will also receive adhesive and therefore bond to the lower corresponding and center surface 40 of the assembled upper body 26 (see FIGS. 2 and 5). The two center fore-and-aft surfaces 38 will also include the spacer bumps 33 which when joined with the upper body 26 serve to provide adhesive reservoirs that define the amount of adhesive contained in the joint. The outer two surfaces 38 preferably include fore-and-aft extending U-shaped channels 39 that serve as adhesive reservoirs to control the adhesive bead retained between those surfaces 38-40. 
     The forward joint 24 between the steering column halves would come together into a steering column structure as illustrated in FIGS. 1 and 4. This joint includes overlapping and abutting tab structures or surfaces 42 and 44 which are also provided with a gap 46 therebetween for receiving the appropriate amount of adhesive to permanently secure them together. Spacer bumps could also be provided in this joint if desired. 
     Looking again to FIG. 2, the lower member surfaces which would be bonded to the upper member body 26 include the rearwardly located and generally laterally extending upper surfaces 48 and 50, the fore-and-aft, left and right running board-type surfaces, designated 52 and 54, the upper, generally vertical, fore-and-aft extending operator area surfaces designated 56 and 58, the fore-and-aft extending center U-shaped channel area designated 34, the fore-and-aft extending surfaces 38, and the forwardly located and transversely extending surfaces designated 60, 62 and 64. These surfaces 60-62 would also include spacer bumps 61-63 (FIG. 2) that serve to regulate the adhesive between the mating surfaces of the upper and lower members 26-16. 
     To join the body portions 12 and 14, a fixture can be provided wherein adhesive is applied and the portions are held together until the joints 20, 22 and 24 bond. U-shaped clips may be of assistance in positioning and securing the legs 36 together if desired. Once the rear, center and steering column joints 20, 22 and 24 have been bonded, the body 26 is positioned for receiving the lower member 16 illustrated in FIG. 2. While various assembly techniques can be utilized to position the upper structure 26 within the lower structure 16, one believed satisfactory is to invert the upper structure 26 and provide the adhesive beads along the appropriate joint surfaces of the upper member 26 in anticipation of positioning the lower member 16 therein. 
     The procedure for quickly and easily assembling the upper body 26 and lower member 16 follows. Assuming that the upper member 26 is inverted and that the lower member 16 is lowered therein, beads of adhesive would be placed along the body surfaces that would be joined with the lower member 16. Those body surfaces would include the left and right lower fore-and-aft extending edge surfaces 66 and 68 and the left and right, generally vertical, upper fore-and-aft extending operator surfaces 70 and 72 (best shown in FIG. 3). Further, body surfaces receiving adhesive would include the vertical edges of the fore-and-aft extending center leg surfaces 36 (FIG. 5), the left and right laterally extending upper surfaces 74 and 76 (FIG. 1), the fore-and-aft extending forward surface 40 (FIG. 5) and the laterally extending forwardly located first, second and third surfaces 60, 62 and 64 (FIG. 2). 
     Subsequently, the lower member 16 would be inverted and lowered into the upside down upper body 26 held in a fixture. As the lower member 16 is lowered, the left and right fore-and-aft extending upper and lower guide surfaces 52-54 and 56-58 respectively of the lower member 16 contact their respective complementary joint follower surfaces 66-68 and 70-72 of the upper body 26 and slidingly move therealong (see FIG. 3). Simultaneously, the vertical and laterally extending rear surfaces 48-50 of the lower member 16 slidingly contact the body surfaces and the legs 36 begin to seat into the U-shaped channel 34. As the pairs of fore-and-aft extending guide and follower surfaces 52-66, 54-68, 56-70 and 58-72 come together, they will be snapped or locked in place. Since the spaced apart pairs of fore-and-aft extending surfaces 52-66 and 54-68 have essentially identical bonding surface configurations, only the enlarged view illustrated in FIG. 6 need be discussed in detail. 
     As the surfaces 52 and 66 (or 54 and 68) slidingly contact, movement of the upper body surface 66 may be limited as its end portion by the stop means or dam 78. As the surfaces or legs 52 and 66 of the V-shaped upper body structures 66-80, 68-83 and V-shaped lower body structures 52-82, 54-85 engage and the lower member 16 continues to be lowered, the resilient or flexible locking members 80 become engaged with their respective latching or locking shoulder member 82 and the resilient locking or hook member 80 flexes outwardly with the end thereof snapping or locking into the recess 84 provided in the shoulder member 82. Because the snap joint parts and in the preferred embodiment the upper body 26 and snap joint parts are plastic, they can flex without incurring cracking or fracturing as the V-shaped guide means 80-66 of the body member and means 82-52 of the frame member position and align the upper body member 26 with the lower frame member 16 (see FIGS. 5-16). 
     The recess 84 in shoulder 82 also serves to retain a designated amount of adhesive to bond them together. In the preferred embodiment, the gap provided between all the surfaces, except 64-88 (FIG. 7), is approximately 30/1000 once the parts are locked into place. Similarly, an adhesive bead will be applied to the surfaces 52-66 and, as they slidingly engage, adhesive will be squeezed outwardly towards the edge and fill the space or area between the edge of 66 and the dam 78 (see FIG. 6). This bead of adhesive 79 will then flow around the end 81 of flap 66 and over it to seal it against the tendency for it to peel loose. The adhesive bead 79 will seal the end of the flap 66 and help insure that the higher forces necessary to shear the bond joint at the end 79 of flap 66 be exceeded before any peeling of the flap 66 can occur. 
     While the fore-and-aft pairs of surfaces are being joined, the notch 87 and slot 86 and upper rear surfaces 48-50 assist in positioning and locking the upper body 26 and lower member 12 in the fore-and-aft direction (see FIG. 1 and 2) and the laterally extending upper body and lower member surfaces 60, 62 and 64 come into contact with the front portion of the upper body 26. Looking to FIG. 7, there is shown the transverse edge of ledge 64 which mates with transverse lip 88 of the upper member to position the two members 26-16 in a vertical orientation and lock them fore and aft. To limit downwardly movement of the lower member 16 into the upper body 26, the forwardly extending surfaces 38 and 40 and transverse lip 88 contact and are bonded. 
     From the foregoing, it can be seen that there is provided a monocoque assembly structure that can quickly, easily and positively be joined and fixed together, yet retain the bonded joint configurations required to enable the structural elements to appropriately transfer loads and to expand or contract as temperature and moisture variations occur.