Stump out safety leg system for dock levelers

Abstract

A pit dock leveler having a base frame secured to a loading dock pit and a dock platform pivotally connected at one of its ends to the base frame and pivotally connected at its opposite end to a dock platform lip that pivots between a downward hanging position when the dock leveler is not in use and an extended position substantially co-planar with the dock platform when the dock leveler is in use, whereby the dock platform lip spans and compensates for the space and height differentials between the loading dock and a transport vehicle, the dock leveler having at least one safety leg pivotally mounted directly to the underside of the dock platform near its pivotal connection to the dock platform lip, the safety leg manually pivotal between a first position and a second position, until it is substantially not perpendicular to the underside of the dock platform.

1 . A pit dock leveler having a base frame secured to a loading dock pit and a dock platform pivotally connected at one of its ends to the base frame and pivotally connected at its opposite end to a dock platform lip that pivots between a downward hanging position when the dock leveler is not in use and an extended position substantially co-planar with the dock platform when the dock leveler is in use, whereby the dock platform lip spans and compensates for the space and height differentials between the loading dock and a transport vehicle, the dock leveler having at least one safety leg pivotally mounted directly to the underside of the dock platform near its pivotal connection to the dock platform lip, the safety leg manually pivotal between a first position perpendicular to the underside of the dock platform and a second position in which the safety leg is pivotal away from the dock platform lip, until it is substantially not perpendicular to the underside of the dock platform, the safety leg, when in its first position, is of sufficient length to prevent the dock platform from pivoting below horizontal after loss of transport vehicle support for the in-use dock platform lip; wherein the improvement comprises, 
 a first moment arm extending between each safety leg and the safety leg pivotal mounting on the underside of the dock platform, whereby when the dock platform is horizontal the moment of the first moment arm pivots the safety leg away from its first position towards its second position to a position therebetween in which the safety leg is not perpendicular to the underside of the dock platform;    a second moment arm for each first moment arm, each second moment arm having a weight at one end and a safety leg contact point at the other end, and each pivotally mounted to the underside of the dock platform about a point between the weight and the contact point, whereby the contact point is pivotal into contact with the safety leg by the moment of the second moment arm from its pivotal mounting to the weight, which is greater than the moment of the first moment arm, whereby when the dock platform is horizontal the safety leg is pivoted by the moment of the second moment arm to the safety leg's first position, perpendicular to the underside of the dock platform; and    a linkage pivotally mounted at one end to the dock platform lip and pivotally mounted at the other end to each second moment arm between its pivotal mounting and the weight, whereby when the dock platform lip is in the extended position, or when the dock platform lip is in the downward hanging position, the linkage does not affect the moment of the second moment arm, but when the dock platform lip is therebetween, the linkage pivotally moves the second moment arm against the moment between the pivotal mounting and the weight, reducing the moment of the second moment arm to less than the moment of the first moment arm, whereby the moment of first moment overcomes the moment of the second moment arm and pivots the safety leg from its first position toward its second position to a position therebetween in which the safety leg is not perpendicular to the underside of the dock platform.    
   
   
       2 . A pit dock leveler having a base frame secured to a loading dock pit and a dock platform pivotally connected at one end of its ends to the base frame and pivotally connected at its opposite end to a dock platform lip that pivots between a downward hanging position when the dock leveler is not in use and an extended position substantially co-planar with the dock platform when the dock leveler is in use, whereby the dock platform lip spans and compensates for the space and height differentials between the loading dock and a transport vehicle, the dock leveler having at least one safety leg pivotally mounted directly to the underside of the dock platform near its pivotal connection to the dock platform lip, the safety leg manually pivotal between a first position perpendicular to the underside of the dock platform and a second position in which the safety leg is pivotal away from the dock platform lip until it is substantially not perpendicular to the underside of the dock platform, the safety leg, when in its first position, is of sufficient length to prevent the dock platform from pivoting below horizontal after loss of transport vehicle for the in-use dock platform lip; wherein the improvement comprises, 
 a first movement arm extending between each safety leg and the safety leg pivotal mounting on the underside of the dock platform, whereby when the dock platform is horizontal the first movement arm pivots the safety leg away from its first position towards its second position to a position therebetween in which the safety leg is not perpendicular to the underside of the dock platform;    a second movement arm for each first movement arm, each second movement arm having a safety leg contact point at one end thereof, and each pivotally mounted to the underside of the dock platform, whereby the contact point is pivotal into contact with the safety leg by the second movement arm, the force of which upon the safety leg is greater than the force of the first movement arm upon the safety leg, whereby the safety leg is pivoted by the second movement arm to the safety leg's first position, perpendicular to the underside of the dock platform; and    a linkage pivotally mounted at one end to the dock platform lip and pivotally mounted at the other end to each second movement arm, whereby when the dock platform lip is in the extended position, or when the dock platform lip is in the downward hanging position, the linkage does not affect the movement of the second movement arm, but when the dock platform lip is therebetween, the linkage moves the second movement to reduce its force upon the safety leg, reducing the force upon the safety leg of the second movement arm to less than the force upon the safety leg of the first movement arm, whereby the first movement arm overcomes the second movement arm and pivots the safety leg from its first position toward its second position to a position therebetween in which the safety leg is not perpendicular to the underside of the dock platform.    
   
   
       3 . The loading dock leveler of  claim 1  in which the first moment arm and second moment arm pivot about a common axis.  
   
   
       4 . The loading dock leveler of  claim 2  in which the first movement arm and second movement arm pivot about a common axis.  
   
   
       5 . The loading dock leveler of  claim 1  and further comprising a damper connected between the dock platform lip and the dock platform, whereby the pivotal movement of the dock platform lip between the extended position and the downward hanging position is slowed.  
   
   
       6 . The loading dock leveler of  claim 2  and further comprising a damper connected between the dock platform lip and the dock platform, whereby the pivotal movement of the dock platform lip between the extended position and the downward hanging position is slowed.  
   
   
       7 . A pit dock leveler having a base frame secured to a loading dock pit and a dock platform pivotally connected at one of its ends to the base frame and pivotally connected at its opposite end to a dock platform lip that pivots between a downward hanging position when the dock leveler is not in use and an extended position substantially co-planar with the dock platform when the dock leveler is in use, whereby the dock platform lip spans and compensates for the space and height differentials between the loading dock and a transport vehicle, the dock leveler having at least one safety leg pivotally mounted directly to the underside of the dock platform near its pivotal connection to the dock platform lip, the safety leg manually pivotal between a first position perpendicular to the underside of the dock platform and a second position in which the safety leg is pivotal away from the dock platform lip until it is substantially not perpendicular to the underside of the dock platform, the safety leg, when in its first position, is of sufficient length to prevent the dock platform from pivoting below horizontal after loss of transport vehicle support for the in-use dock platform lip; wherein the improvement comprises, 
 means to pivot each safety leg from its first position in which it is positioned when the dock platform lip is in the extended position, or when the dock platform lip is in the downward hanging position, and towards its second position to a position there between when the dock platform lip is between the extended and downward hanging positions.    
   
   
       8 . The loading dock leveler of  claim 7  wherein the means to pivot each safety leg includes a cam mounted to the dock platform lip that controls the pivotal movement of each safety leg.  
   
   
       9 . The loading dock leveler of  claim 7  wherein the means to pivot each safety leg includes a control arm assembly mounted at one end to the dock platform lip and received at its other end within a sliding tube that is pivotally mounted to each safety leg.  
   
   
       10 . The loading dock leveler of  claim 9  wherein the means to pivot each safety leg pivots the safety leg towards a second position that is forward of its vertical position.  
   
   
       11 . The loading dock leveler of one of claims  7 - 10  and further comprising a damper connected between the dock platform lip and the dock platform, whereby the pivotal movement of the dock platform lip between the extended position and the downward hanging position is slowed.  
   
   
       12 . The loading dock leveler of one of claims  9 - 10  wherein the control arm assembly includes means to dampen its movement.