Patent ID: 8573916

Claim:
A trailer comprising: a chassis; at least two lifters provided on the chassis; at least two drivers provided on the chassis and connected to the lifters; at least two locks comprising at least one detent with a first end and a second end, said first end jointly hinged with an end of the lifter and a sliding element, said second end engaged with a rack with a plurality of teeth, for locking the lifters in any intermittent upper position corresponding to the engaged tooth on the rack by the restoring force of a spring, and disengaged by a lever manually; wherein each of the lifters comprises: a first lifting unit provided on a frame of the chassis; a second lifting unit provided on the frame; at least one rod for connecting the first lifting unit to the second lifting unit; a pusher for pushing the first lifting unit directly and pushing the second lifting unit through the rod; and a contact element provided on each of the lifting units; the first lifting unit comprising: a first primary link with an end pivotally connected to the chassis; a second primary link comprising an end hinged on the sliding element of one of the locks movably provided on the chassis and another end pivotally connected to another end of the first primary link; an auxiliary link comprising an end pivotally connected to the chassis and another end pivotally connected to the contact element; the contact element includes a middle point pivotally connected to a joint between the primary links; the second lifting unit comprising: a first primary link with an end pivotally connected to the chassis; a second primary link comprising an end hinged on the sliding element of one of the locks movably provided on the chassis and another end pivotally connected to another end of the first primary link; an auxiliary link comprising an end pivotally connected to the chassis and another end pivotally connected to the contact element; the contact element includes a middle point pivotally connected to a joint between the primary links.