Patent Abstract:
A hinge is provided suitable for attaching a hood to a car or truck. The hinge includes generally tubular members sharing a common axis of rotation. Elastomeric elements interposed between the tubular members provide isolation between the parts of the hinge. Relative rotation between the tubular members compresses the elastomeric elements creating a spring-force opposing the relative rotation. The hood, hinge, and vehicle may be configured so that the spring-force of the elastomeric elements assists in opening and/or closing of the hood.

Full Description:
The present invention generally relates to a revolute joint or hinge, and more particularly to a revolute joint or hinge for the hood or trunk of a motor vehicle. 
   BACKGROUND OF THE INVENTION 
   Movable panels or covers, such as hoods and trunk lids, are typically attached to the body or frame of a motor vehicle by means of one or more hinges, pins, or other type of revolute joint. Such movable panels or covers provide easy access to otherwise covered and hidden parts of the vehicle, such as the engine and trunk. The panels may possess considerable weight. For example, the hood of a large truck may exceed 100 pounds. Significant effort may be required to open or close a heavy panel or cover. In addition, a heavy panel or cover may cause injury should it fall open or shut in an uncontrolled manner. 
   To reduce the effort of opening such panels and reduce the risk of injury, it is often desirable to provide a force about the pivot axis of the hinge to counteract the weight of the panel. Typically the counteracting force is provided by springs which are arranged so that they are operative at the fully opened and closed positions of the vehicle panel. For example, extension springs may be arranged so that they are stretched when the hood of an automobile is fully closed and so that the stretching of the springs creates a force about the pivot axis of the hinge which tends to assist a user in lifting the hood to an open position. Other lift assisting mechanisms may employ arrangements of compression springs, coil springs, gas-springs, torsion-bars and the like. 
   However, such mechanisms for reducing the effort needed to open or close a vehicle panel require many parts in addition to the parts needed merely to provide the hinged motion. The additional parts add to vehicle weight and complexity and may increase vehicle manufacturing, maintenance, and operating costs. Accordingly, it would be desirable to provide a simple hinged or revolute joint that provides assistance in opening or closing a panel or cover without the need for additional parts. 
   In addition to the foregoing, it is also often desirable to isolate panels and covers from other parts of the vehicle structure to accommodate relative motion between them. For example, vehicle bodies and frames flex and vibrate as the vehicle is driven over a roadway. Vehicle bodies and frames also bend and flex due to differences in the thermal expansion characteristics of various component parts of the vehicle body or frame. Flexing may cause the mounting points between a movable panel or cover and the vehicle body to move relative to each other. The relative motion of the mounting points may create significant and potentially destructive stresses in the panel. Isolating the panel from the mounting points may reduce the stresses imparted to the panel. 
   One means of isolating a panel is to provide an elastomeric resilient mount between the panel and mounting point. For example, rubber grommets may be provided around the bolts attaching a panel to a hinge. Such isolation mounts provide for limited motion between the panel and the mounting points. Another means of isolating the panel from the mounting points includes providing cylindrical elastomeric bushings located concentric with the pivot axis of the hinge. Yet another isolation method is to provide an additional hinge joint having an axis substantially aligned with the longitudinal axis of the vehicle. Combinations of these isolation techniques may also be used. 
   However, such isolation techniques also require many parts in addition to those merely needed to provide for hinged motion of the vehicle panel with respect to the vehicle body or frame. The additional parts also add to vehicle weight and complexity and may increase vehicle manufacturing, maintenance, and operating costs. Accordingly, it would be desirable to provide a hinged or revolute joint that provides isolation between the motion of the body or frame of a motor vehicle and a panel or cover attached to the vehicle. 
   SUMMARY OF THE INVENTION 
   The above and other objects and advantages of the present invention are provided by an arrangement of tubes and elastomeric bushings. The tubes generally have a square cross-section and are juxtaposed in concentric and overlapping relation to each other. Pairs of concentric tubes are rotated along their longitudinal axis relative to each other so that corners of an inner tube are adjacent to the sides of an outer tube. Elastomeric bushings are inserted between the inner and outer tubes in the spaces adjacent to the sides of the inner tube. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages of the present invention will be understood upon consideration of the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout and in which: 
       FIG. 1  is an oblique view of an illustrative embodiment of a hinge joint in accordance with the principles of the present invention; 
       FIGS. 2A and 2B  are, respectivley, end and side views of the hinge of  FIG. 1 ; 
       FIG. 3  is an an view of the hinge of  FIG. 1  in a rotated position; 
       FIG. 4  is an oblique view of a truck frame and forward tilting hood coupled by a hinge in accordance with the principles of the present invention; 
       FIG. 5  is an oblique view of the hinge assembly of  FIG. 4 , shown in more detail and with some obscuring structures removed; 
       FIGS. 6 ,  7 , and  8  are sectional views of the truck frame and hood of  FIG. 4 , showing the hood in intermediate, closed, and open positions, respectively; and 
       FIGS. 9 and 10  are, respectively, end and cut-away side views of another illustrative embodiment of a hinge joint in accordance with the principles of the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is an oblique view of a first illustrative embodiment of elastomeric hinge  10  constructed in accordance with the principles of the present invention.  FIGS. 2A and 2B , show an end view and a partial cut-away side view of elastomeric hinge  10 . Referring to  FIGS. 1 and 2  together, elastomeric hinge  10  includes inner member  12  having a generally square cross section. Outer members  14  and  16  are disposed about and overlap, but are rotated about their respective longitudinal axes by approximately 45 degrees relative to inner member  12 . As used herein, two objects overlap when at least a portion of one element extends inside a portion of the other object. 
   Preferably, inner member  12  and outer members  14  and  16  are tubes manufactured of metal, plastic, or other suitable material. Inner member  12  is shown as being a hollow tube, but may also be made of a solid bar. Outer members  14  and  16  preferably comprise square shaped tubes, but only the inner surface need be generally square in cross section and the outer surface may have other shapes as appropriate for the end use of elastomeric hinge  10 . Although, the corresponding surfaces of inner member  12  and outer members  14  and  16  are preferrably square-shaped in cross section, this need not be the case, and other geometrical shapes such as a triangle, pentagon, hexagon, and so on, may also be used. 
   Outer members  14  and  16  are prefereably approximately concentric with inner member  12 . This configuration provides the the most predictable hinge-axis behavior, in that the hinge-axis remains substantially stationary as the hinge is operated. However, under some circumstances, it may be desireable to laterally or vertically offset one or more of the tube axes when manufacturing the hinge. This may be used, for example, so that the axes become aligned when the hinge is used in a situation in which a large static load is present. 
   Elastomeric elements  18  and  18 ′ are disposed between inner member  12  and outer members  14  and  16 , respectively. Elastomeric elements  18  and  18 ′ are preferably cylindrical rods of natural rubber, but may be made of synthetic rubber or other elastomeric material and may have non-round cross sections. Elastomeric elements  18  and  18 ′ may also be composite structures in which different materials are used along their lengths or through their thicknesses. Preferably, elastomeric elements  18  and  18 ′ are pre-loaded in compression upon assembly of elastomeric hinge  10 . Advantageously, the pre-compression of elastomeric elements  18  serves to retain them in between inner member  12  and outer members  14  and  16  without the need to bond elastomeric elements  18  to the inner or outer element using adhesives or the like. 
   In use, one of outer members  14  and  16  is attached to the body or frame of a motor vehicle, while the other outer member is attached to movable panel or cover, such as the hood or trunk. Outer members  14  and  16  may be attached to their respective parts of the vehicle using clamping straps or other suitable methods of securely attaching elastomeric hinge  10  to the vehicle parts. For example, flanges with a suitable bolt hole may be welded onto outer members  14  and  16 , or may be formed when outer members  14  and  16  are manufactured, e.g., by extrusion or the like. 
   Operation of elastomeric hinge  10  is described in connection with  FIG. 3 , wherein outer member  16  remains stationary while outer member  14  is rotated counterclockwise through an angle α. As outer member  14  is rotated, the inner surfaces of outer member  14  push against and tend to compress elastomeric elements  18  against the outer surfaces of inner member  12 . This imparts a torque to inner member  12  tending to rotate it counterclockwise about its longitudinal axis through an angle β. As inner member  12  rotates, the outer surfaces of inner member  12  push against and tend to compress elastomeric elements  18 ′ against the inner surfaces of outer member  16 . Because outer member  16  remains stationary, the force arising from the compression of elastomeric elements  18  and  18 ′ tend to counteract the force tending to rotate outer member  14 , for example, the weight of a vehicle hood. 
   In  FIG. 3 , the rotation of inner member  12  is shown to be approximately half that of outer member  14 . That is, angle β is approximately one half of angle α. However, the actual relationship depends upon the relative compliance of elastomeric elements  18  and  18 ′. If elastomeric elements  18  and  18 ′ are substantially identical, then the relative rotation angles will be as shown in  FIG. 3 . A hinge so constructed would tend to have a counteracting force that increases smoothly as the hinge is operated. 
   However, if elastomeric elements  18  and  18 ′ differ significantly, then the rotation angles α and β will also differ. For example, elastomeric elements  18 ′ may be made of a material that is significantly less compliant, i.e., stiffer, than the material used for elastomeric elements  18 . In such a hinge, inner member  12  would not rotate significantly as outer element  14  is rotated, until the torque imparted on inner element  12  by elastomeric elements  18  has risen enough to begin compressing elastomeric elements  18 ′. A hinge so constructed would have a lower counteracting force during an initial rotation as the more compliant elastomeric elements  18  are compressed, and a higher counteracting force during a later portion of the rotation as the less compliant elastomeric elements  18 ′ are compressed. Similar effects may be attained by changing the dimensions, e.g., the length, of elastomeric elements  18 ′ so that they differ from those of elastomeric elements  18 . 
   An elastomeric hinge such as that shown in  FIGS. 1–3  may advantageously be used as a hinge for a truck hood as shown in  FIG. 4 , wherein hood  40  is shown coupled to frame  42  by a pair of elastomeric hinges  44  and  46 . A more detailed view of the structure of the hinge joint is shown in  FIG. 5 . 
   Brackets  52  are attached to the truck frame by suitable means such as bolts  53 . One end of each of elastomeric hinges  44  and  46  is attached to brackets  52  using clamping straps  54 , and the other end is similarly attached to brackets  55  using clamping straps  56 . Brackets  55  are attached to cross member  57  which in turn is attached to truck hood  40  of  FIG. 4 . 
   Upon consideration of  FIG. 3 , it is readily apparent that elastomeric hinge  10  is symmetrical with respect to rotation of outer member  14 . That is, rotation of outer member  14  in either a clockwise or counterclockwise direction gives rise to a counteracting force due to elastomeric elements  18  and  18 ′. This characteristic of the elastomeric hinge of the present invention may be used advantageously to provide assistance when both opening and closing truck hood  40  of  FIG. 4 . For example, in  FIG. 6  elastomeric hinge  46  and truck hood  40  are configured so that when the center of mass of truck hood  40  is vertically centered over the pivot axis of elastomeric hinge  46 , elastomeric hinge  46  is in its neutral position. In this configuration, fully closing truck hood  40  rotates elastomeric hinge  46  in one direction, whereas fully opening truck hood  40  rotates elastomeric hinge  46  in the other direction. In each case, compression of elastomeric elements  18  of elastomeric hinge  46  creates a force acting against the rotation of hood  40 , as shown in  FIGS. 7 and 8 . 
     FIG. 9  shows an alternative embodiment of an elastomeric hinge constructed in accordance with the principles of the present invention. Elastomeric hinge  90  is formed of three generally concentric tubes including inner member  92 , middle member  93 , and outer member  94 . Elastomeric elements  96  are disposed between inner member  92  and middle member  93 , and elastomeric elements  98  are disposed between middle member  93  and outer member  94 .  FIG. 10  is a side view of elastomeric hinge  90 , showing the interior components of elastomeric hinge  90  in partial cutaway. 
   In use, elastomeric hinge  90  is typically configured so that inner member  92  and outer member  94  are coupled to a vehicle hood and body. Rotation of the inner member  92  relative to middle member  93  causes compression of elastomeric elements  96  thereby imparting a torque to middle member  93 . Rotation of middle member  93  relative to outer member  94  causes compression of elastomeric elements  98 . Outer member  94  is prevented from rotating because it is fixedly attached to the vehicle body. The compression of elastomeric elements  98 , therefore, causes a torque or force tending to counteract the compression. 
   It should be noted that the different dimensions of elastomeric elements  96  and  98  may cause them to have different compliance characteristics. Accordingly, the assisting force provided by elastomeric hinge  90  may vary significantly as it is operated from fully open to fully shut. This characteristic may be advantageous in that the assisting force may be larger when a hood or other cover is fully open or fully shut, while the assisting force is near minimum when the hood is at an intermediate position. Alternatively, the dimensions or materials of elastomeric elements  96  and  98  may be chosen so that their respective compliance characteristics are similar and the assisting force varies gradually over the operating range of hinge  90 . 
   Thus, an elastomeric hinge particularly suited for use in motor vehicles has been disclosed. It will be readily apparent that the elastomeric hinge thus disclosed may be useful for other applications and that various modifications may be made to the disclosed embodiment without departing from the spirit and scope of the invention. Accordingly, one will understand that the description provided herein is provided for purposes of illustration and not of limitation, and that the invention is limited only be the appended claims.

Technology Classification (CPC): 4