Abstract:
An interlock for a skid steer vehicle with a rear engine compartment and a rear door to that compartment includes a beam that is mounted transversely to the bottom of the door and has an upward facing surface that, like the beam, extends across the entire rear engine compartment opening. An interlocking second member is fixed to the chassis and extends across the rear engine compartment opening. When the door is impacted and forced upward, the first beam engages the second interlocking member over its width and transfers the force from the door (and beam) to the chassis When the door is impacted with a forward-directed force, the first beam also contacts the second member and transfers the forward forces through the second member to the chassis. Injury to the door is reduced or eliminated by transferring door impact forces to the chassis since the first beam extends substantially the entire distance across the door and is fixed to an inner surface of the door&#39;s frame.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to skid steer vehicles. More particularly, it relates to rear doors for skid steer vehicles. 
   BACKGROUND OF THE INVENTION 
   Skid steer vehicles such as skid steer loaders are a mainstay of construction work. In their most common configuration, they have two drive wheels on each side of a chassis that are driven in rotation by one or more hydraulic motors coupled to the wheels on one side and another one or more hydraulic motors coupled to the wheels on the other side. 
   The wheels on one side of the vehicle can be driven independently of the wheels on the other side of the vehicle This permits the wheels on opposing sides of the vehicle to be rotated at different speeds and in opposite directions. By rotating in opposite directions, the skid steer can rotate in place about a vertical axis that extends through the vehicle itself. 
   The vehicles have an overall size of about 10 by 12 feet, which, when combined with their ability to rotate in place, gives them considerable mobility at a worksite. It is this mobility that makes them a favorite. 
   Skid steer vehicles commonly have at least one loader (or lift) arm that is pivotally coupled to the chassis of the vehicle to raise and lower at the operator&#39;s command. This arm typically has a bucket, blade or other implement attached to the end of the arm that is lifted and lowered thereby. Most commonly, a bucket is attached, and the skid steer vehicle is used to carry supplies or particulate matter such as gravel, sand, or dirt around the worksite. 
   As a counterbalance to the loads provided at the front of the vehicle, skid steer vehicles typically have an engine that is located behind the operator. The radiator is also commonly disposed behind the operator, usually at the center rear of the vehicle. 
   A door or other access hatch is located at the very back of the vehicle to give the operator access to the engine and radiator from the very rear of the vehicle. Other doors and hatches may be disposed down the side of the vehicle or engine compartment instead of the rear to provide additional access. 
   One difficulty with rear engine access doors is their susceptibility to impact. Skid steer vehicles typically have a restricted view to the rear, preventing the operator from seeing behind the vehicle. Skid steer vehicles also spend a substantial amount of time traveling in reverse is close quarters. Skid steer vehicles are often operated in a rapid back-and-forth movement, making what are called “Y turns” as they move material from one pile to another perhaps several hundred times a day. 
   As a result, operators often misjudge the distance between the rear of the vehicles and obstacles and occasionally back skid steer vehicles into these obstacles, albeit at very slow speeds. Whenever a skid steer with a rear engine compartment door impacts an obstacle it is the door that suffers. 
   Even when the door is not damaged, however, the door hinges an the door latch may be damaged. The forces involved may not be great enough the actually damage the door itself, but it is often significant enough to tear or bend the hinges and latch, thereby either removing the door entirely, or jamming the door shut in its closed position 
   What is needed, therefore, is an improved skid steer vehicle having a door that is resistant to being damaged. What is also needed is a skid steer vehicle with a means for protecting the door hinges from upward rear impacts. What is also needed is a skid steer door that automatically protects the hinges without requiring additional operator input. What is also needed is a means for transmitting potentially damaging forces acting against the rear door directly to the frame or chassis. It is an object of this invention to provide these advantages. While not every claimed aspect of the invention provides all these advantages, each of these advantages is provided by at least one claimed aspect. 
   SUMMARY OF THE INVENTION 
   In accordance with a first aspect of the invention, a rear door and chassis interlock for a skid steer vehicle is provided, including a first elongated and laterally-extending beam fixed to a door frame of the rear door of a skid steer vehicle, the first beam having a generally horizontal and upwardly-facing surface; and a second elongated and laterally-extending beam fixed to a rear chassis of the skid steer vehicle, the second beam having a generally horizontal and downwardly facing surface; wherein the upwardly-facing surface and the downwardly-facing surface interlock over substantially their entire lateral extent to reduce upward movement of the rear door with respect to the chassis. 
   The second beam may be fixed to and extend between two elongated chassis members disposed on either side of the engine. The first and second beams may extend substantially the entire width of a rear-facing opening of an engine compartment and may be interlocked over substantially the entire width of the opening, The first beam may have a box structure and may include an “L”-shaped angle bracket fixed to a forward surface thereof, and the angle bracket may extend laterally across the vehicle and may have the generally horizontal and upwardly-facing surface that is configured to interlock with generally horizontal and downwardly facing surface of the second beam The upper surface of the angle bracket may extend across substantially the entire width of the engine compartment. The first beam may include a generally vertical, forward-facing and laterally extending surface to which the angle bracket is fixed, the forward-facing surface may have a first surface portion that extends above the angle bracket that may be spaced closely enough to a rearward edge of the second beam to transmit the force of forward impacts to the second beam. The first and second beams may be spaced a distance apart sufficient that they engage one another when the door is lifted before hinges supporting the door on the vehicle and a latch holding the door closed are damaged. 
   In accordance with a second aspect of the invention, a rear engine compartment for a skid steer vehicle is provided, including a left sidewall, a right sidewall, and a top wall that are fixed to a chassis of the skid steer vehicle and are disposed to enclose the engine an define a rear opening to the engine compartment; a first elongated and laterally-extending beam fixed to the chassis, the first beam having a generally horizontal and downwardly facing surface extending from the rear opening; and a rear door pivotally coupled to a chassis of the vehicle, the door including a door frame and a second elongated and laterally-extending beam fixed to the door frame, the second beam having a generally horizontal and upwardly-facing surface, wherein the rear door is disposed to cover the rear opening and is supported by two hinges and a latch; wherein the upwardly-facing surface and the downwardly-facing surface interlock over substantially their entire lateral extent to reduce upward movement of the rear door with respect to the chassis. 
   The first beam may be fixed to and extend between two elongated chassis members disposed on either side of the engine. The first and second beams may extend substantially the entire width of the rear opening, and may be interlocked over substantially the entire width of the opening. The second beam may have a box structure and includes an “L”-shaped angle bracket fixed to a forward surface thereof, and the angle bracket may extend laterally across the vehicle and may have the generally horizontal and upwardly-facing surface that is configured to interlock with generally horizontal and downwardly facing surface of the first beam. The upper surface of the angle bracket may extend across substantially the entire width of the engine compartment. The second beam may include a generally vertical, forward-facing and laterally extending surface to which the angle bracket is fixed, and the forward-facing surface may have a first surface portion that extends above the angle bracket that is spaced closely enough to a rearward edge of the first beam to transmit the force of forward impacts to the first beam. The first and second beams may be spaced a distance apart sufficient that they engage one another when the door is lifted before hinges supporting the door on the vehicle and a latch holding the door closed are damaged. 
   In accordance with a third aspect of the invention, a rear chassis for a skid steer vehicle is provided, including a rear door including a door frame and a first elongated and laterally-extending energy-transmitting beam transversely fixed to the bottom of the door frame, the first beam having a generally horizontal and upwardly-facing surface; and a rear chassis including left and right longitudinally extending frame members, and a left side panel, right side panel and top panel fixed to the frame members to enclose the engine, the rear chassis also including a second elongated and laterally-extending beam, the second beam having a generally horizontal and downwardly facing surface; wherein the rear door is pivotally coupled to one side of the engine compartment with hinges, and further wherein the door is secured in a closed position by a latch; and wherein the upwardly-facing surface and the downwardly-facing surface interlock over substantially their entire lateral extent to reduce upward movement of the rear door with respect to the chassis. 
   The second beam may extend across a rear engine compartment opening that is defined between the left and right side panels and the top panel. The first and second beams may extend substantially the entire width of rear engine compartment opening and may be interlocked over substantially the entire width of the opening. The first beam may have a box structure and may include an angle bracket fixed to a forward surface thereof, and the angle bracket may extend laterally across the door frame and may define the generally horizontal and upwardly-facing surface. The upper surface of the angle bracket may extend across substantially the entire width of the opening. A portion of the first beam may be disposed slightly forward of a portion of the second beam to reduce door damage by transmitting the force of forward impacts from the door to the second beam. The first and second beams may be spaced a distance apart sufficient that they engage one another when the door is lifted before hinges supporting the door on the vehicle are damaged. 
   Numerous other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a left side view of a skid steer vehicle in accordance with the present invention. 
       FIG. 2  is a fragmentary left side perspective rear view of the vehicle of  FIG. 1  with the rear door closed. 
       FIG. 3  is a fragmentary left side perspective rear view of the vehicle of  FIGS. 1 and 2  with the rear door open showing the chassis interlock and the inner door construction including the hinges, louvers and latches. 
       FIG. 4  is a fragmentary detailed perspective view of the upper hinge area of the vehicle shown in  FIG. 3 . 
       FIG. 5  is a fragmentary cross-sectional view of the rear door and chassis of the vehicle of the foregoing FIGURES when the door is in the closed position as shown in  FIGS. 1 and 2  taken along section line  5  in  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   While the present invention is susceptible of being made in any of several different forms, the drawings show a particularly preferred form of the invention. One should understand, however, that this is just one of many ways the invention can be made. Nor should any particular feature of the illustrated embodiment be considered a part of the invention, unless that feature is explicitly mentioned in the claims. In the drawings, like reference numerals refer to like parts throughout the several views. 
   Referring now to the FIGURES, there is illustrated a skid steer vehicle  100 . The vehicle includes a chassis  102  on which are mounted four wheels (two shown)  104 . These wheels are disposed two on each side in a fore-and-aft relationship. All the wheels are drive wheels, driven by engine  106  that is disposed in a rear engine compartment  108  of vehicle  100 . 
   Engine compartment  108  encloses engine  106 , surrounding it on all four sides as well as its top. A rear engine compartment door  110  encloses the rear of the engine compartment and protects a transversely-mounted rear radiator  112  that is fixed to the chassis behind the engine. 
   The engine compartment  108  includes a top panel  114 , a left side panel  116 , and a right side panel  118 . These panels enclose not only the engine  106 , but the radiator  112  as well. The left panel is fixed to and supported by an elongated and longitudinally-extending left side chassis member  160  which can be seen best in  FIG. 1 . The right panel is fixed to and supported by an elongated and longitudinally extending right side chassis member  136  that is configured identically to left side chassis member  160 , but is disposed along the right side of the chassis and is configured as a mirror image of member  160 . Chassis members  160  and  136  extend backward along both sides of engine  106 , which is fixed to both members. 
   Door  110  seals against top panel  114  as well as side panels  116 , and  118  to provide protection both from the elements and from rigid objects that might damage the engine and radiator if the operator backs vehicle  100  backs up into them. 
   Door  110  is in the form of a rectangular frame  120  having a central rectangular opening  122 . Opening  122  is covered with louvers  124  that are disposed vertically across the aperture formed by the opening. These louvers can be pivoted about their longitudinal axes to abut one another and close opening  122 , or alternatively to open and permit air to pass therethrough. In this manner, the operator can regulate the amount of cooling provided by the radiator, which is disposed right behind door  110 . 
   Door  110  is supported by two hinges, an upper hinge  126  and a lower hinge  128 . The upper hinge includes two hinge plates  130 , 132  ( FIG. 4 ), and a pin (not shown) pivotally coupling the two plates together. Hinge plate  130  is bolted to a vertical member  134  that in turn is bolted to right side chassis member  136 . Plate  132  is fixed to door frame  120  and pivots together with the frame of the door when the door is opened. 
   Referring now to  FIGS. 3 and 4 , latch  138  is pivotally coupled to door frame  120 . It holds the door open in a first position, and permits the door to be closed in a second position. Latch  138  is pivotally mounted to door  110  by a bolt  140 . As the door is opened, hinge plate  132 , which is fixed to the door frame, pivots about hinge plate  130 , which is fixed with respect to the chassis. Latch  138  pivots together with plate  132  and the door as the door is opened, with its tang  141  sliding along the top outer edge  142  of plate  130 . 
   Latch  138  offers no resistance to this door opening, until the door is almost completely open (as shown in  FIGS. 3 and 4 ), at which point a slot  144  in plate  130  moves underneath latch  138 . Slot  144  is just wide enough to receive the outwardly extending tang  141 . The weight of tang  141  unbalances latch  138 , causing it to fall of its own weight into slot  144 . 
   Latch  138  is shown in two positions in  FIG. 4 : a first unlatched position “A” shown in phantom lines, and a second latched position “B” shown in solid lines. Position “B” illustrates how the latch would appear when it has rotated about 90 degrees clockwise under the force of gravity. The latch is configured such that it is not perfectly balanced when in position “A”, but is top heavy. The top heavy position is determined by the location of the hole in latch  138  through which bolt  140  passes. This hole is located such that latch  138  is not only top heavy, but tends to rotate in a clockwise direction (in  FIG. 3 ), supported by top edge  142  of plate  130 . 
   Lower hinge  128  similarly includes two plates  146 , 148  and a pin  149  pivotally coupling the two plates together. These plates and pin are identically arranged to those of the upper hinge. Hinge plate  146  is bolted to vertical member  134 . Plate  148  is fixed to door frame  120  and pivots together with the door frame when the door is opened. 
   The door hinges are preferably arranged so that the entire door may be removed from the vehicle by lifting the door upward until the hinge pins of the upper and lower hinges are removed from their corresponding hinge plates. The operator can stop the vehicle, open the door, lift the door upward from the bottom, and remove the door from vehicle  100 . 
   A spring loaded door latch  150  is fixed to the opposite side of the door as hinges  126 , 128 . It has a catch  152  that grasps a rod  154  extending from striker plate  156 . Striker plate  156  is bolted to vertical member  158  that, in turn, is bolted to chassis member  160 . The engagement of catch  152  and rod  154  prevents the door both from being opened and from being lifted off its hinges. When an upward force is applied to the closed door the catch and rod interengage to prevent the door from moving upward. 
   While the catch and rod are sufficiently strong to resist the force of one or two people trying to lift the closed door upward off its hinges, they may not be sufficient to prevent a substantial upward blow to the bottom of the door from lifting the door upward and either damaging the catch and rod, or damaging both the catch and rod, and the hinges, too. 
   To resist these more forceful blows or impacts from lifting the door and damaging the various door components, additional support structures are provided. These support structures include mechanically interengaging (or interlocking) members that resist the relative upward movement of the door with respect to the rest of the vehicle. These members are located at the bottom of the engine compartment opening and extend across the entire width of the opening. 
   These additional support structures are provided on both door and the chassis. They are configured to interlock automatically whenever the door is closed and disengage automatically whenever the door is opened. No additional operator activity is required to interlock these structures. 
     FIGS. 3 and 5  show these structures in particular detail. In  FIG. 3 , they are shown as they would appear when the door is open and the structures are not mutually interengaged. In the positions shown in  FIG. 3 , the door can be lifted off the vehicle without damaging the door or the vehicle itself. 
     FIG. 5  shows the additional support structures as they are positioned when the door is closed. In  FIG. 5  they are shown interlocked to resist the upward movement of the door. 
   Referring now to  FIGS. 3 and 5 , the structures include a first beam member  162  that is fixed to an inner surface of door frame  120  just below door opening  122 . Member  162  may be permanently or removably fixed to door frame  120 , such as by welding or bolting the member thereto. 
   Member  162  extends laterally, side-to-side, across the entire width of the engine compartment opening. It has the form of an L-shaped beam comprised to two major planar portions: a first planar portion  164  extending horizontally that is fixed along its laterally extending leading edge  166  to a vertically and laterally extending planar beam portion  168  having a top edge portion  169  that is fixed to edge  166 . 
   Member  162  is fixed to a second beam member  170  that also extends laterally, side-to-side and is in turn fixed to the inner surface  172  of the lower portion of door frame  120  just below opening  122 . Beam member  170  includes a first planar portion  174  that extends generally horizontally and laterally within door frame  120 . It also includes a second planar beam portion  176  that extends generally laterally and vertically within door frame  120 . Planar beam portions  174  and  176  are fixed together along a rearward and laterally extending edge  178  of beam portion  174  and along a bottom and laterally extending edge  180  of beam portion  176 . 
   Beam portion  176  generally follows the contours of the inside rear surface  172  of door frame  120  just below door opening  122 . Beam portion  176  preferably abuts and is fixed to the inside surface of door frame  120  over substantially its entire width to provide a relatively large area of support for the lower portion of the door. Since the lower portion of the door typically impacts such things as piles of dirt, sand, or rock first, it is the most prone to damage. Locating the beam members along (and fixing the beam members to) this lower portion of the door, provides particularly good protection against door damage. 
   While we describe edges  178  and  180  above as being fixed together, they need not be formed separately and then fixed together, but may be formed integrally from a single sheet of metal that is bent to form a laterally extending bend  182  that defines the junction between beam portions  174  and  176 . 
   Similarly, beam member  162  may be formed from a single sheet of metal that is bent, thereby forming a laterally extending bend  184  at the junction of beam portion  164  and beam portion  168 . 
   Beam member  162  and beam member  170  together form a generally rectangular box beam, having an internal, laterally extending, and generally rectangular hollow  186 . This arrangement enhances the individual strength of beam members  162  and  170 . 
   Beam member  162  and beam member  170  are fixed together to provide additional strength for the lower portion of door frame  120  and additional resistance to deformation when the door is impacted. As shown in  FIG. 5 , the two are fixed together by a weldment  187  that extends laterally, from side-to-side, inside door frame  120 . While a weldment is preferred, the two components may be removably fixed together with bolts, for example. This arrangement can be employed to permit each beam to be more easily mounted to the door or to permit each beam to be adjusted with respect to the other. 
   A third component of the additional support structures is an elongated and laterally extending edge member  188  that is fixed to a forward facing vertical surface  190  of beam member  162 . Edge member  188  includes a horizontally and laterally extending portion  192 , shown here as a planar and linearly extending flange, that is coupled to a vertically and laterally extending portion  193 , also shown as a planar and laterally extending flange. 
   Member  188  has a generally “L”-shaped form, commonly known as “angle iron” or “angle bracket” that is comprised of flanges  192  and  193 , the two flanges being joined at right angles to one another along an upper edge of flange  193 . Vertically extending flange  193  is fixed to vertical and forward facing surface  190  of member  162 , preferably by welding. 
   Portion  192  has an upper surface  194  that is surmounted by an elongated interlocking member  196 . Interlocking member  196  is shown in the FIGURES as a horizontally disposed planar sheet of steel that extends outward from the rear opening  198  ( FIG. 5 ) of the engine compartment. Member  196  extends laterally across the engine compartment from one side to the other. Member  196  is fixed to and between the two elongate chassis members 
   When door frame  120  is closed, member  196  is disposed immediately adjacent to and slightly above upper surface  194  of horizontally and laterally extending portion  192  of edge member  188 . In this position, member  196  cooperates with surface  194  to prevent the door from moving upward when an upward force is applied to the door and he door is closed. 
   Member  196  and portion  192  extend substantially the entire distance across the engine compartment opening  198 . This arrangement distributes the upward force of any door impact over substantially the entire width of the door, and over substantially the entire length of members  162  and  170 . 
   Just as the additional support structures reduce damage to the door from being forced upward, they also reduce damage to the door by being forced forward and inward toward the engine compartment opening  198 . When the door receives an impact that drives the door forward and generally into the engine compartment, vertically and laterally extending beam portion  168  of beam member  162  is forced forward against the rear edge  200  of member  196 . This transfers the load on the door to the member  196  which is fixed to the vehicle chassis. When this impact occurs, edge  200  engages surface  190  of beam member  162  over substantially the entire width of the engine compartment opening. 
   The door is positioned by adjusting the positions of the hinges and the latch. For this reason, a narrow gap  202  is provided between rear-facing edge  200  and the forward-facing surface  190  of beam member  162 . A similar narrow gap  204  is provided between upper surface  194  and the bottom surface of member  196 . These two gaps extend laterally across the width of the engine compartment opening. The width of each gap  202 , 204  is preferably the same across the entire width of the engine compartment. 
   From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It will be appreciated that the present disclosure is intended as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.