Abstract:
A clamp for use in attaching a cap or other accessory to the bed of a pickup truck comprising a receiving member forming a receiving pocket and a received member having a leg insertable into the pocket of the receiving member. The received leg is contacted on both sides by the receiving pocket to maintain alignment of the two members to keep the clamping surfaces parallel to one another. Single point contact is provided between the received leg and the walls of the pocket to reduce friction. The two sided contact with the received leg eliminates bending stress in the attaching bolt.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to a mounting clamp and in particular to a mounting clamp for attaching accessories such as a pick-up truck cap to the bed of a pick-up truck. 
     Several clamps have been developed for use in securing accessories such as a pick-up truck cap, a tonneau cover, a cab spoiler, bed rails, etc., to a pick-up truck bed. One type of truck bed clamp includes two clamping parts pivotally connected to one another and adjustable by a threaded bolt. However, depending upon the thickness of the parts being clamped together, the two clamping surfaces may not be parallel to one another in the clamped position, compromising the clamping strength. This is due to the relative rotation of the clamp parts. 
     The disadvantage of pivotally connected clamp parts has been overcome by another clamp that provides two parts having a pair of engaging surfaces. During adjustment of the clamp, the two parts slide relative to one another along the engaging surfaces to securely fasten items to the truck bed. The sliding motion between parts allows the clamping surfaces to remain parallel to one another over a range of material thicknesses being clamped together. However, with such a clamp having only one pair of engaging surfaces between the two parts, the bolt used to hold the clamp parts together experiences high bending loads in addition to the tensile loads necessary to produce the clamping load. 
     Accordingly, it is an object of the present invention to provide an improved truck bed clamp configured to avoid bending loads in the attaching bolt and to maintain the clamping surfaces parallel to each other. 
     It is a feature of the clamp of the present invention to provide two clamp members in which one member is formed with a pocket into which a leg of the other member is slidably received. The result is two pairs of engaging surfaces between the two members which enables the received leg to be contacted on two sides by the receiving member. Contact on both sides of the received leg enables the internal bending moment in the clamp to be carried by the clamp members themselves rather than being carried through the securing bolt. 
     It is a further feature of the clamp of the present invention that the contact between the engaging surfaces is in the form of point contact rather than surface to surface contact. This results in less friction between the members. To further reduce the friction, the contact points are formed by bushings made of ultra-high molecular weight polyethylene which is self lubricating. When clamping loads are applied to the clamp members, resulting in internal bending stresses, the low friction between the clamp members facilitates relative movement of the clamp members. 
     It is a further feature of the clamp of the present invention that one or both of the clamping surfaces are formed with rubber bushings to avoid damage to the surfaces engaged by the clamp. 
     The two clamp members are attached to one another by a bolt slidably carried by one member and threadably received by the other. In a preferred embodiment of the clamp, the two clamp members are made of extruded aluminum. To provide increased strength to the threaded bolt attachment, a captured nut is mounted to the member receiving the bolt and both the bolt and the nut are made of steel. Steel has greater strength than the extruded aluminum for a threaded attachment. 
     One or both of the clamp members can be formed with means for mounting additional accessories to the clamp itself separate from the accessory mounted to the truck bed between the two clamping surfaces of the clamp members. 
     Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a pick-up truck showing the clamp of the present invention being used to attach accessories to the truck bed; 
     FIG. 2 is a vertical sectional view of one embodiment of the truck bed clamp of the present invention shown in use attaching a cap to a truck bed; 
     FIG. 3 is a sectional view of the clamp as seen from the line 3--3 of FIG. 1; and 
     FIG. 4 is a sectional view of an alternative embodiment of the clamp of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The truck bed clamp 10 of the present invention is shown in FIG. 1 in use attaching accessories to the bed 6 of pick-up truck 7. The clamps 10 are used to attach a cab spoiler 8 and a rear wing 9 to the truck bed. Other accessories such as a truck cap, tonneau cover etc., can be attached to the truck bed with clamps 10. 
     Clamp 10 is shown in greater detail in FIGS. 2 and 3 and includes two principal components, a receiving member 12 and a received member 14. The terms &#34;receiving&#34; and &#34;received&#34; will be further described below. The clamp 10 as shown in FIG. 2 is in use securing a truck cap 16 to a truck bed 18. This is accomplished by securing a horizontal lower flange 20 of the cap to a horizontal upper flange 22 of the truck bed with a resilient gasket 24 therebetween. 
     The received member 14 is generally U-shaped including a base portion 36 and a pair of generally parallel legs 32 and 34 extending therefrom. Leg 32 ends in a clamping pad 56 which faces in the same direction which leg 34 extends from the base portion 36. 
     The receiving member 12 is generally an F-shaped member having a base portion 30 from which extends a pair of generally parallel legs 26 and 28 The distal end of base portion 30 forms a clamping pad 31 which faces in the direction of extension of the legs 26 and 28 for engagement with one of the two objects being clamped together. The two legs 26 and 28 of the receiving member 12 form a pocket 38 therebetween for receiving the leg 34 of the received member 14. Hence the labels &#34;receiving&#34; and &#34;received&#34; for the two members 12 and 14 respectively. 
     The two clamping pads 31 and 56 are positioned in confronting juxtaposition relative to one another by insertion of the leg 34 of member 14 into the receiving pocket 38 of the receiving member 12. As the leg 34 is inserted further into the pocket, the two clamping pads 31 and 56 are brought closer together. The spacing between the two clamping pads is determined by the amount of insertion of the leg 34 into the pocket 38. As a result, the length of the shortest leg, leg 28, determines the operating range of the clamp 10. 
     The received leg 34 is formed near its distal end 40 with a groove 42 into which a bushing 44 is seated. The bushing 44 engages the flat engagement surface 46 of the leg 28. Likewise, the leg 26 of the receiving member includes, at its distal end 48, a groove 50 similar to the groove 42 which mounts a bushing 52. The bushing 52 contacts the flat engagement surface 54 of the leg 34 of the received member. Surface 46 of the leg 28 is parallel to flat engagement surface 54 of the leg 34. As a result, the two clamping pad surfaces remain parallel to one another regardless of the adjusted position of the two clamp members. 
     The two bushings 44 and 52 are made of ultra-high molecular weight polyethylene which has a low coefficient of friction and which is self-lubricating. This provides smooth operation of the clamp as the two members are moved relative to one another while clamping loads are present. This is in contrast to clamp members engaging in surface to surface engagement where the clamp loads can produce high friction forces at the sliding engagement surfaces. 
     Clamping pad 56 is formed with a pair of grooves 58 for mounting resilient rubber rods 60 to provide a &#34;no damage&#34; clamping surface. The clamping pad 31 is shown with integral grooves forming the clamping surface but can alternatively be made identical to the clamping pad 56 with rubber rods. 
     The leg 34 mounts a nut 62 or other insert with a threaded bore 64. The insert is mounted in a manner which prevents rotation of the nut 62 about the axis of its threaded internal bore. The nut can be mounted to the leg 34 by a punching operation, adhesive or the like, or the nut could be free until held by the bolt 68. The receiving member 12 includes a non-threaded bore 66 through the base portion 30 at the closed end of the pocket 38 for passage of a shaft 68 of a bolt 70. The lower portion 72 of the shaft 68 is threaded to enable the bolt to be threadably received by the nut 62. The bolt 70 positions the two clamp members relative to one another to provide the clamping force at the two clamping pads 31 and 56. Clockwise rotation of the bolt 70, as viewed at the bolt head, draws the nut 62 further onto the bolt. This draws the leg 3 further into the pocket 38 and draws the clamping pad 56 of the received member toward the clamping pad 31 of the receiving member. 
     As the two clamping pads bear against the objects being clamped together, a load is applied to the clamp members 12 and 14 at the clamping pads. This load is carried through the clamp members and a side load is developed at the contact points of the two bushings 44 and 52 with the smooth walls they engage. The side loads balance the internal moments within the clamp members produced by the clamp loads. As the distance between the two clamping pads decreases, the bushings 44 and 52 are moved further away from one another and the magnitude of these side loads is reduced. 
     By sliding the leg 34 into a pocket with contact points on both sides of the leg 34, the two clamp members will remain aligned with one another upon the application of a clamping load. The side loads produced between the clamp members balance the internal moments such that the bolt 70 will not experience bending loads. 
     The clamp members 12 and 14 can be made of any of several materials. In a preferred embodiment, they are made from extruded aluminum bars which have been cut to a predetermined thickness. Aluminum has a high strength to weight ratio resulting in a light weight clamp. After cutting, the bore 66 is machined into the receiving member 12 and the nut 62 is secured in the received member 14. The bushings 44 and 52 and the rubber rods 60 are also installed. The use of a steel nut 62 or other threaded steel insert within the aluminum clamp member provides greater clamping strength as compared to forming the screw threads directly in the extruded aluminum. If the added strength of the steel nut is not needed, a threaded bore can be formed directly in received leg 34. 
     The received member 14 also includes a lateral passage 74 formed therein which can be used as a tie-down hole for securing objects within the truck bed. Additionally, other attaching features can be formed into the two clamp members for mounting other accessories to the truck bed. An alternative embodiment of the clamp 10 is shown in FIG. 4 and designated as Clamp 10a shows an accessory mount in a clamp member. In clamp 10a, similar elements to elements of clamp 10 have been given the same reference numeral with the suffix &#34;a&#34;. The clamp 10a is functionally identical to the clamp 10 described above. The primary difference in the configuration of clamp 10a is that the leg 32 of clamp 10 has been moved from clamp member 14 to clamp member 12a forming a leg 32a. This positions the clamping pad 31a at a distance from the arm or base portion 30a of the number 12a. Conversely, the clamping pad 56a of member 14a is mounted directly to the base portion 36a. 
     Like the clamp 10, clamp 10a includes a tie down hole 74 to enable objects to be tied to the clamp 10a. In addition, the clamp 10 includes a second nut 78 mounted to the member 14a in a manner that prevents rotation of the nut about the axis of its internally threaded bore. The nut 78 threadably receives a threaded bolt shaft 80 used to attach the cab spoiler 8 to the clamp 10a and thereby attaching the cab spoiler to the truck bed 6. The bolt 80 passes through a horizontal mounting flange 82 on the inside of the cab spoiler 8. 
     As shown in FIG. 4, the clamp is only used to mount the cab spoiler 8, that is, no other accessory is mounted to the bed 6 between the clamping surfaces of the clamp. If desired, the clamp can also be used to clamp an object or other accessory to the pick-up bed 6 between the two clamping pads 31a and 56a as shown with the clamp 10 of FIGS. 2 and 3. 
     The clamp of the present invention thus provides numerous features as described above which improve upon previously available truck bed clamps. These features include contact of the received member on both sides of the received leg to eliminate bending stresses in the clamping bolt; low friction bushings at the contact points; a steel nut and bolt for holding the two extruded aluminum clamp members together and the addition of tie down holes or other accessary attachment means to the clamp members. 
     It is to be understood that the invention is not limited to the exact construction illustrated and described above, but that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.