Lifting device with swinging arms

Claim 1

A swinging arm type lifting device comprising a base member, a horizontal cross shaft carried by said base member, a first swinging arm, means pivotally mounting said first swinging arm intermediate its length to said cross shaft, a counter-weight carried at one end of sAid shaft first swinging arm, said counter-weight being sized to balance at least in part weight which bears on the other end of said first swinging arm, a second swinging arm, means pivotally mounting said second swinging arm to the other end of the first swinging arm on an axis parallel to the axis of the cross shaft, second counter-weight means balancing at least in part the said second swinging arm, said second counter-weight means being pivotally mounted on said cross shaft, and force transmission means connecting the second counter-weight and said second swinging arm to establish the angular position of the second counter-weight in respect to the angular position of the second swinging arm and the base member, independent drive means for pivoting the first swinging arm about the cross shaft and for pivoting the second swinging arm about its pivotal connection to the first swinging arm, a cabin, means pivotally mounting the cabin to the free end of the second swinging arm, and control means associated with the pivotal axis between the first and second swinging arms and the first swinging arm and the base member to maintain orientation of said cabin.