Abstract:
A rollover protection system unlocks and lowers from a raised position to a lowered position suitable for clearing a low hanging obstacle when an operator manually applies a force to an operator lever. The rollover protection system returns to the raised position when the operator ceases applying force to the operator lever.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/281,059 filed on Nov. 12, 2009 which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a rollover protection system which moves from a raised position to a lowered position suitable for clearing a low hanging obstacle. 
     BACKGROUND OF THE INVENTION 
     Numerous rollover protection systems may be found in the prior art. Various prior art rollover protection systems teach various ways for folding down, retracting or telescoping a top portion of a roll bar assembly usually in order to clear low hanging obstacles. Typically, the prior art teaches various types of joints that can be manually adjusted to lower the top portion of a roll bar assembly. A problem that arises when using prior art retractable rollover protection systems arises when an operator begins work in an area which includes low hanging obstacles. The potential exists for an operator to merely place the top portion of a roll bar assembly in a lowered position prior to working in such an area. If the same area also includes a sloped surface and the operator fails to return the top portion of the roll bar assembly to the raised position suitable for protecting the operator during a roll over, the operator will be exposed to a roll over hazard. What is needed is a rollover protection system wherein an operator may quickly and temporarily lower the top portion of a roll bar assembly to clear a low hanging obstacle and which automatically returns to a raised position when the operator is no longer acting to cause the top portion to be lowered. With such a rollover protection system, the top portion of the roll bar assembly would lower only as needed to clear low hanging obstacles and would otherwise remain in a raised position suitable for protecting the operator during a roll over. 
     BRIEF SUMMARY OF THE INVENTION 
     In order to overcome the above stated problems and limitations there is provided an improved rollover protection system for a vehicle which may be selectively lowered to clear low hanging obstacles. The improved rollover protection system includes a roll bar assembly and a lowering and raising mechanism. The roll bar assembly includes a bottom portion that is mounted to the vehicle frame and a top portion that is mounted to the bottom portion. The top portion is movably mounted to the bottom portion so that the top portion may move between a raised position and a lowered position. A lock is associated with the top portion and the bottom portion such that when the top portion is in the raised position, the lock secures the top portion sufficiently to the bottom portion so that the roll bar assembly will support the vehicle and protect the operator should the vehicle rollover. 
     The raising and lowering mechanism includes an operator lever. The operator lever may take the form of a handle, a foot pedal or any other movable element suitable for receiving a manually applied force from an operator. The raising and lowering mechanism is adapted so that when the operator of the vehicle applies sufficient force to the operator lever, the raising and lowering mechanism unlocks the top portion of the roll bar assembly and urges the top portion to move from the raised position to the lowered position. The raising and lowering mechanism is also adapted so that when the operator ceases applying force to the operator lever, the top portion moves from the lowered position to the raised position at which point the lock re-engages. 
     Accordingly, an operator using the improved rollover protection system may apply force to the operator lever to cause the top portion of the roll bar assembly to move to the lowered position to clear an low hanging obstacle. When the vehicle has cleared the low hanging obstacle, the operator can stop applying force to the operator lever thereby allowing the top portion of the roll bar assembly to return to the raised position where the lock re-engages to sufficiently secure the top portion in the raised position to protect the operator should the vehicle roll over. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view of the improved rollover protection system installed on a vehicle. 
         FIG. 2  is a side view showing an operator lever mounted to the vehicle. 
         FIG. 3  is a perspective view of a roll bar assembly. 
         FIG. 4  is a close up perspective view of one side of the roll bar assembly shown in  FIG. 3 . 
         FIG. 5  is a close up side view of the roll bar assembly showing the top portion in the upright position with the lock engaged. 
         FIG. 6  is a close up side view of the roll bar assembly showing top portion in the upright position and with the lock disengaged. 
         FIG. 7  is a close up side view of the roll bar assembly showing the top portion in a position which is between the raised position and the lowered position and showing the lock disengaged. 
         FIG. 8  is a close up side view of the roll bar assembly showing the top portion in the lowered position and the lock disengaged. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings,  FIG. 1  shows an example embodiment of the improved rollover protection system  10  installed on vehicle  5 . In this example, vehicle  5  may be any type of vehicle but will most typically be a riding lawn mower, tractor or other such vehicle which is likely to be exposed to a risk of a roll over. As can be seen in  FIG. 1 , improved rollover protection system  10  includes a roll bar assembly  12 , a raising and lowering mechanism  50  and an operator lever assembly  50 . Roll bar assembly includes a bottom portion  14  which is fixed to the frame of vehicle  5  and a top portion  30  which is pivotably mounted to bottom portion  14 . 
     As can be best seen by referring to  FIG. 3 , bottom portion  14  of roll bar assembly  12 , in this example, includes two spaced bottom members  16 A and  16 B. Each of the two spaced bottom members  16 A and  16 B have upper ends  18 A and  18 B respectively and lower ends  19 A and  19 B respectively where, in this example, may be found bolt holes  19 H for receiving bolts (shown in  FIG. 1 ) for fixing bottom members  16 A and  16 B to the frame of vehicle  5 . As can be seen in  FIG. 3 , top portion  30  includes two side members  32 A and  32 B. Each side member  32 A and  32 B includes lower ends  34 A and  34 B respectively and upper ends  36 A and  36 B respectively. A top transverse member  38  connects between upper ends  36 A and  36 B to complete a rigid upside down U shaped top portion  30 . 
     As can be best seen by referring to  FIGS. 3-8 , lower ends  34 A and  34 B of side members  32 A and  32 B are pivotably mounted to the upper end  18 A and  18 B of bottom members  16 A and  16 B respectively. The joints between the lower ends of side members  32 A and  32 B and the upper ends of bottom members  16 A and  16 B are adapted to allow top portion  30  to pivot counterclockwise as viewed in  FIGS. 3-8  between the raised position shown in  FIGS. 1 ,  3 ,  4 ,  5  and  6  to the lowered position shown in  FIG. 8 . In the alternative, relative movement between top portion  30  and bottom portion  12  as top portion  30  moves between the raised position and a lowered position could be accomplished by a translation such as with a telescoping structure or by a pivoting parallelogram structure or the like. The pivoting structure shown and described in this example is merely one way of accomplishing movement between a raised position and a lowered position. The remaining elements of the raising and lowering mechanism which will be described in greater detail below, are, out of necessity, adapted to function with a pivoting structure. 
     As can be seen in  FIGS. 3-8 , in this example, bottom portion  14  and top portion  30  include a lock which is biased to secure top portion  30  in the raised position when top portion  30  is in the raised position. As can be seen in  FIGS. 4-8  by viewing only one side of roll bar assembly  12 , the lock for securing top portion  30  in the raised position shown in  FIG. 4  is a latch mechanism  40  which includes a latch member  41  which is pivotably mounted to a bracket  20  to pivot about a shaft  41 A which is carried by bracket  20 . Bracket  20  is fixed to upper end  18 A of bottom member  16 A. As can be best seen in  FIG. 6 , latch member  41  includes a notch  41 B that is shaped to engage a rod  42 . Rod  42  is generally horizontal and oriented transversely and is fixed to a bracket  35  that is fixed to the lower end  34 A of side member  32 A of top portion  30 . Latch member  41  is biased by a spring  43  toward the latched position shown in  FIGS. 4 and 5 . Thus, latch member  41  is biased by spring  43  to secure top portion  30  in the raised position. Latch member  41  further presents a boss  41 C. A cam  44  is rotatably mounted to a bracket  35  for rotation about an axis passing through the center of shaft  36  (shown in  FIG. 4 ). Bracket  35  is fixed to the lower end  34 A of side member  32 A of top portion  30 . Cam  44  engages boss  41 C with two portions: a first recessed cam portion  44 A and a second offset cam portion  44 B. As a downward movement of cable  102  rotates cam  44  counterclockwise as viewed in  FIGS. 3-8 , boss  41 C of latch member  41  is contacted by second offset cam portion  44 B of cam  44  which has a larger radius than first recessed cam portion  44 A. This urges latch member  41  out against spring  43  and disengages latch member  41  from rod  42 . This unlatches top portion  30  from bottom portion  14  and makes it possible for top portion  30  to fold down relative to bottom portion  14 . The skilled reader should understand that the same latch and cam mechanism is preferably identically repeated on the opposite side of roll bar assembly  14  between upper end  18 B of bottom member  16 B and the lower end  34 B of side member  32 B. The skilled reader should further consider that the latch mechanism described above is merely one way to provide a lock that is biased to lock top portion  30  in the raised position. A multitude of other mechanisms well known in the art, may be selected for providing such a biased lock that can be selectively disengaged to allow top portion  30  to move to a lowered position. Just one example of an alternate locking mechanism might include a spring biased pin which engages corresponding holes in bottom portion  14  and top portion  30  which align when top portion  30  is in the raised position. The spring biased pin could be connected to the raising and lowering mechanism such that it is urged against its spring bias to unlock top portion  30  when an operator applies a force to lower top portion  30 . 
     Raising and lowering mechanism  50  includes an operator lever  100  and a spring assembly  60 . Raising and lowering mechanism  50  functions in combination with an operator lever  100  to cause the lowering and raising of top portion  30 . 
     We will first consider how raising and lowering mechanism  50  functions to lower top portion  30  from the raised position to the lowered position. In this example operator lever  100 , which may take the form of a handle or a pedal, is connected by cable  102  to cam  44 . In this example, cable  102  connects to a sliding bracket  22  shown in  FIGS. 3-8 . An upper cable portion  102 A connects between sliding bracket  22  and a pin  102 P that is mounted to cam  44 . As can be seen in  FIG. 3 , a shaft  64  extends between cam  44  and a cam  144  that is mounted to the opposite side of roll bar assembly  12 . As can be seen in  FIG. 4 , cam  44  includes two opposite, identical plates that are located on opposite sides of upper end  18 A of bottom member  16 A. As can be seen in  FIG. 3 , the same arrangement exists for cam  144  on the opposite side for bottom member  16 B. Shaft  64  is fixed to both side plates of cam  44  as well as both side plates of the cam  144  on the opposite side. Bracket  35  that is fixed to side member  32 A presents ears on both sides of side member  32 A which present co-axial bores for receiving shaft  64 . A bracket  21  is fixed to the upper end  18 A of side member  16 A supports a bushing  36  that, in turn, also receives shaft  64 . Thus cams  44 ,  144 , shaft  64  and top portion  30  are all able to rotate about an axis A shown in  FIG. 4 . Axis A is fixed in relation to bottom portion  14 . As can be seen in  FIG. 4 , bracket  35  mounted to side member  32 A of top portion  30  includes a pin  35 A which rides in a constant radius slot  44 S. Also, a tension spring  44 S 2  connects between cam  44  and pin  35 A that biases cam  44  clockwise toward pin  35 A. Slot  44 S, first recessed cam portion  44 A and second offset cam portion  44 B are arranged so that, as cable portion  102 A pulls on cam  44 , cam  44  rotates counterclockwise as second offset cam portion  44 B rotates counterclockwise to encounter boss  41 C of latch member  41 . As is shown in  FIG. 5 , and as described above, this causes latch member  41  to release rod  42 . Latch member  41  releases rod  42  before the clockwise end of slot  44 S encounters pin  35 A. Once the clockwise end of slot  44 S of cam  44  encounters pin  35 A, (which is fixed to bracket  35  which is, in turn, fixed to top portion  30 ) cam  44  ceases its rotation relative to bracket  35 . Since latch mechanism  40  is now unlatched, cam  44 , bracket  35  and top portion  30  are now free to rotate counterclockwise as seen in  FIGS. 4-8  around the axis A (shown in  FIG. 4 ) as cam  44  and bracket  35  are pulled by cable portion  102 A. Top portion  30  continues to rotates until it reaches the lowered position shown in  FIG. 8 . if cable  102  and cable portion  102 A continue to transmit sufficient force. 
     The operation described above occurs in reverse when the operator releases pressure from operator lever  100 . As can be seen in  FIG. 3 , the opposite side of roll bar assembly  12  includes a spring assembly  60  that biases top portion  30  toward the raised position. Accordingly, when the operator releases pressure from operator lever  100 , top portion  30  rotates from the lowered position shown in  FIG. 7  back to the raised position shown in  FIGS. 3 and 4  with the exception that slot  44 S and pin  35 A are in the relative positions shown in  FIG. 4  during the return stroke so that latch member  41  is in the position shown in  FIG. 4  before top portion  30  arrives in the position shown in  FIG. 4 . Accordingly, during the return stroke, pin  42 A encounters a sloped upper surface of latch member  41  to cause latch member  41  to turn out to receive pin  42 A. Also because spring  44 S 2  biases cam  44  clockwise, boss  41 C of latch assembly  40  remains in contact with first recessed cam portion  44 A thereby maintaining latch assembly  40  in the latched position. 
     Operator lever  100  is shown in  FIG. 2  as a foot pedal but can also be a hand lever or other such member for receiving force from an operator. Operator lever  100  is connected to a cable  102 . Lever  100  is biased in the position shown in  FIG. 2  by tension which is applied by cable  102 . Cable  102  routed to connect to sliding member  22  mounted to bracket  20  of roll bar assembly  12  shown in  FIG. 3 . Cable  102  is in tension because spring assembly  60  shown in  FIG. 3  pushes cam  144  in a clockwise direction as seen in  FIG. 3  which in turn applies a torque to shaft  64  which further pushes cam  44  in a clockwise direction to apply to an upper cable portion  102 A which is connected to cable  102 . When operator lever  100  is up as shown in  FIG. 2 , cable  102  is not pulling down on cam  44 . When operator lever  100  is pressed forward by an operator, cable  102  pulls on cam  44  which rotates counterclockwise as seen from the perspective of  FIG. 3  which causes the release of latch mechanism  40  and the lowering of top portion  30  as described above. 
     The skilled reader will appreciate that, for example, an actuator may be interposed between operator lever  100  and cam  44  so that the lowering and even the raising of top portion  30  may be powered in response to a switch which is activated by the rotation of lever  100 . So, for example, in an embodiment having a powered actuator, lever  100  might close a switch for activating a powered actuator and might also be biased toward the position shown in  FIG. 2 , so that when the operator ceases applying a force to lever  100 , the switch would open and the actuator would return top portion  30  to the raised position shown in  FIGS. 1 ,  3  and  4 . As is well known in the art, power may be supplied to an actuator in any one of a number of forms including, but by no means limited to, hydraulic power, electric power and pneumatic power. 
     The structures described above merely provide an example embodiment for accomplishing the objectives of the invention. To accomplish the objectives of the invention, it is essential that a top portion of a roll bar assembly unlock and move to a lowered position in response to an operator input such as applying force to an operator lever, and then return to a raised position when the operator is no longer supplying an input such as applying force to the operator lever. 
     It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto, except in so far as such limitations are included in the following claims and allowable equivalents thereof.