Abstract:
A hood control apparatus comprises at least one counterbalancing spring engaged between a forward tilt hood and a top surface radiator frame mounted under the hood. The spring is chosen to have a spring rate such that, when the hood is opened, the spring supports the hood in an open equilibrium position less than fully open. A locking latch device is provided for latching the hood in the open position against unintended closure thereof.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a hood control apparatus for use on large forward tilt hoods of the type which are pivotally mounted to the frame on a horizontal axis adjacent the front bumper, such as those found on trucks and school busses, the apparatus assisting in opening and closing of the hood, requiring reduced effort on the part of the operator and further providing for capability to lock the hood in a desired open position thereof. 
     THE PRIOR ART 
     Various hood tilt assist systems incorporating counterbalance springs to reduce the physical effort required, have been proposed for use in assisting the opening and the closing of hoods on large vehicles such as trucks and busses. See, for example, U.S. Pat. Nos. 3,754,613, 4,566,552, and 4,991,675. In such systems, however, the counterbalance springs are overcome by the weight of the hood, allowing the hood to open to its maximum point as defined by a limiting cable or device or an assist spring becoming solid. Since truck hoods are relatively heavy, it still has required substantial effort on the part of the operator to open and close the hood. However, as the population of female drivers of truck and school buses has increased, it is desirable to require less effort to open and close the hood. 
     In the hood described herein, the counterbalancing is such that the hood opens to an open equilibrium position fully supported by the counterbalance springs which is less than the fully open position of the hood. Furthermore a positive locking device is provided to prevent inadvertent closure of the hood from said open position without manually releasing the locking device. Although it is known to provide a positive locking device which also functions as a limiting stop in the fully open position, it is not known to provide a locking device operable in a less than fully open position. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a primary object of the invention described and claimed herein to provide a reduced-effort control system for a hood of a truck or bus wherein the hood reaches an open position of fully supported equilibrium which is a less than fully open position. 
     A further object of the invention is to provide a reduced-effort control system for a hood of a truck or bus which incorporates structure therein for locking the hood in an open position of supported equilibrium thereby preventing inadvertent closure of the hood. 
     Yet a further object of the invention is to provide a locking device for such hood wherein the device is locked by engagement of a notch against a bracket. 
     Still a further object of the invention is to provide a locking device for such hood wherein the device has a manually engaged unlocked position for use during closure of the hood. 
     Another object of the invention is to provide a locking device for such hood wherein the device has a rearming device for automatically moving said device from said manually-engaged unlocked position upon closure of the hood. 
     These and other objects of the invention as will be seen hereinafter are specifically met in a reduced-effort hood control apparatus for a tilt hood of a mobile vehicle of the type which is pivotally mounted to the vehicle frame for rotation about a horizontal axis located adjacent the front bumper including at least one counterbalance spring disposed between said hood and a frame mounted member wherein the spring is sufficiently strong to maintain said hood in an open equilibrium position supported by said spring while permitting further movement of said hood against the force of said spring toward said open position. The apparatus further includes a locking mechanism which latches the hood and prevents closure thereof from said open equilibrium position, the locking mechanism comprising a locking bar pivotally attached to the hood and extending through an aperture in a fixed bracket, the locking bar having a notch for engaging a lower edge of the bracket when said hood is approximately in said open equilibrium position. The locking bar further may include a horizontal unlocking flange which may be manually positioned, when said hood is in said open equilibrium position, to engage a horizontal notch in said aperture and thereby prevent said notched surface of said bar from engaging said lower bracket aperture edge to permit closure of said hood. The unlocking flange terminates upon said notched surface clearing said aperture during closure and further includes a tapered rearming surface disposed on an edge facing said hood pivot to shift said locking bar laterally in said aperture during opening of said hood to ensure engagement of said notched surface with said bracket. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become more apparent upon perusal of the detailed description thereof and upon inspection of the drawings in which: 
     FIG. 1 is a side elevation illustrating diagrammatically a portion of a truck frame having a partially cut away hood mounted thereon and incorporating the hood control apparatus of the present invention with different open positions of the hood shown in phantom lines; and 
     FIG. 2 is an enlarged perspective view of the locking bar and bracket aperture in the engaged position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in greater detail, there is illustrated diagrammatically a reduced-effort hood control apparatus generally identified by the reference numeral 10 for controlling a hood 18 mounted to the forward end of a mobile vehicle 11, such as a school bus or a truck. The vehicle 11 conventionally includes parallel longitudinally extending interconnected frame rails 13 on each side of the vehicle (only one side being shown) supported on wheels 15 and a transversely extending bumper 17 supported at the front end of the vehicle by the frame rails 13. The hood 18 has a fixed rearward most point Z when closed. Further secured to each of the frame rails is an upstanding radiator support bracket 22 defining a side portion of the radiator support structure. A hood support bracket 24 is secured and adjustably fixed to the radiator support bracket 22 and extends forwardly therefrom to a hinge portion for receiving a horizontal transverse pivot pin 60 disposed adjacently above the bumper 17. A hood hinge plate 62 is pivotally mounted on the pivot pin 60 and is attached to the front reinforcement member 64 of the hood 18. Thus, the hood 18 may be opened to expose the vehicle engine (not shown) by pivoting it about pivot pin 60 so that the hood opens forwardly away from the vehicle chassis. This Pivoting causes the fixed rearward most point Z of the hood 18 to move in an arc away from the closed position. 
     To control and assist the opening and closing of the hood 18, the apparatus 10 has a primary counterbalance spring 12 on each side which is pivotably attached at one end 14 to a bracket 19 attached to a free or swing end 16 of the vehicle hood 18 and which is pivotably attached at another end 20 by a bracket 21 to a fixed element, such as the radiator support 22. To keep the hood 18 from reaching the fully open position thereof, a secondary spring 31 and cable 30 is also attached in a manner identical to that for the primary biasing-member 12. The secondary spring 31 only comes into play when the cable 30 is pulled tight should the force of the counterbalance spring 12 be overcome, such as by a gust of wind when the hood 18 is open. Thus, the secondary spring 31 is normally non-functional and only begins biasing against full opening of the hood 18 once the spring rate of the primary spring 12 is overcome, toward an undesired fully open position of the hood 18. 
     The spring rate of the counterbalance spring 12 and the locations of the attachment points respectively to the hood and radiator support is hood structure dependent, depending on the weight of the hood 18, and preferably is such that the hood opens to an equilibrium position A fully supported by the counterbalance springs 12 which is short of the completely open position B. In this position, one can be assured that the full counterbalancing force is being exerted to assist closure of the hood. Additionally, it is preferred to maintain the hood 18 less than completely open because such extreme position causes stress on hinges 62 holding the hood 18 to the front of the chassis 11. In this open equilibrium position A, the fixed rearward most point Z of the hood 18 is located forward of the pivot Din 60. 
     When the hood 18 is unlatched from a closed position thereof, the spring 12 preferably will cause the hood 18 to elevate a few inches from its closed position, unassisted, again assuring that the maximum counterbalancing force is available to assist in opening the hood 18. 
     During closure of the hood 18, the spring 12 first contracts to aid in closure to the overcenter point (center of gravity is over the pivot) and then extends again to provide a controlled closure, with the weight of the hood 18 plus a small amount of manual assistance overcoming the spring for complete closure of the hood 18 to a position permitting engagement of the conventional side latches (not shown) to secure the hood in the closed position. 
     Once the hood 18 is opened to the open equilibrium position A, it is desired to be able to releasably lock or latch the hood 18 against undesired closure, such undesirable motion being caused by a gust of wind, for example. To maintain the hood 18 open against undesired closure, a locking latch apparatus 40 is provided which comprises a notched locking bar 42 having one end 44 thereof pivotably engaged as at 25 to the lower portion of the hood 18 a small distance above the pivot pin 60 and a cooperating catch member 46 which is mounted to the radiator support member 22 to accommodate sliding engagement of the distal end 56 of the locking bar 42 within an aperture 48 therein, the aperture 48 including a cooperating lower edge 50 against which one of a plurality of teeth 52 disposed on the lower edge of the locking bar 42 can engage by operation of gravity to keep the hood 18 from closing until closure is desired. It will be seen that the locking bar 42 is only provided with one or two teeth 52 appropriately positioned along the length of the slide 42 in a manner to assure that the hood 18 is held desired open equilibrium position A while assuring that the hood 18 cannot close of its own accord. 
     To allow for closure of the hood 18, the engagement between a tooth 52 of the locking bar 42 and the flange 50 of the catch member is releasable. Such release may simply be produced by manually lifting the locking bar 42 within the vertically elongated aperture 48 and moving the hood 18 toward closure while holding the locking bar disengaged so that the notched length of the locking bar 42 merely slides above the edge 50 of the catch member 46 and thereafter permitting the unnotched portion of the locking bar to slide on the edge 50, a single locking latch member 40 being so that the operator can singlehandedly close the hood 18. 
     However, in the preferred embodiment illustrated, it will be note that the aperture 48 is further provided with a laterally extending notch 49 adjacent the upper edge thereof and the locking bar is provided with an outturned flange 51 disposed to engage the slot 49 when the locking bar is lifted sufficiently within aperture 48 to disengage the notched teeth 52 from the lower edge 50 of the aperture and the locking bar 42 is manually moved laterally in the aperture 48 to cause such engagement. Thus, in the preferred embodiment, when the hood is open, the operator may lift the locking bar 42 and move it laterally to engage the flange 51 in the slot 49 to prevent engagement of the teeth 52. Thereafter, the hood may be closed with no need for an operator&#39;s hand to remain within the hood during closure. 
     It will further be noted that the forward portion 53 of the outturned flange is tapered and terminates slightly forwardly of the forwardmost tooth 52. During closure, the flange 51 passes completely through the aperture 48 so that the flange 51 disengages from the slot 49 thereby dropping the unnotched lower edge of the locking bar 42 on the lower edge 50 of the aperture 48. Thus the locking device is rearmed to automatically engage the locking device when the hood is subsequently opened, the tapered edge 53 forcing the locking bar toward the side of the aperture opposite the slot 49 as the hood is opened. 
     As described above, the hood control apparatus of the present invention provides a number of advantages, some of which have been described above and others of which are inherent in the invention. Also modifications can be made to the hood control apparatus without departing from the teachings herein. Accordingly, the scope of the invention is only to be limited as necessitated by the accompanying claims.