Electromechanical mechanism fitted on truck vehicles for loading and unloading

Claim 1

In a truck including a platform, an elongated parallelogram linkage having two longitudinal members and two transverse members at the respective longitudinal end portions of said linkage, one of said end portions being fastened to said platform for arcuate movement of the other end portion, a gate mounted on said other end portion for pivoting movement between a substantially upright position and a normally horizontal position, said gate moving between a raised position at the level of said platform and a lowered position during said arcuate movement, and drive means for arcuately moving said other end portion, the improvement which comprises: a. compression spring means interposed between said gate and the transverse member of said linkage at said other end portion for biasing said gate toward said upright position; b. said drive means including 1. an electric motor, mounted on said platform, said motor having a series winding and a shunt winding, 2. an elongated tension member, 3. a rotatable drum member having an axis drivingly connected to said motor and secured to one longitudinal end of said tension member for retracting and releasing the tension member when said drum member rotates about said axis thereof, 4. securing means Securing the other longitudinal end of said tension member to said other end portion of said linkage for moving said gate between said raised and lowered positions during said rotation of said drum member, 5. a spur gear transmission operatively interposed between said motor and said drum member, 6. brake means connected to said transmission and spring-biased toward a locking position for preventing rotation of said drum member, 7. electrically operated brake release means, 8. a source of direct current, 9. respective contactors in circuit with said windings and said source, 10. means connected to said contactors for energizing said series winding for movement of said gate from said lowered toward said raised position and for energizing said shunt winding for movement of said gate from said raised toward said lowered position, 11. said brake release means being connected in circuit with said contactors for releasing said brake when either of said contactors energizes said motor, 12. said source of current being a rechargeable battery and being charged by current generated in said shunt winding during movement of said gate by gravity from said raised to said lowered position.