Apparatus for filling bags with bulk materials

Claim 1

In a bag-filling apparatus adapted to fill a bag with a predetermined amount of a bulk material free-flowing under the influence of gravity, said apparatus having a feed hopper, an accumulator hopper adapted to receive bulk material from said feed hopper, weighing means adapted to determine the weight of said accumulator hopper and its contents, first valve means adapted to control the passage of bulk material from said feed hopper to said accumulator hopper and second valve means adapted to transfer bulk material from said accumulator hopper into said bag, the improvement for effecting greater weight accuracy at shut-off comprising: control means associated with said weighing means and adapted to (1) sense a first predetermined weight of said accumulator hopper corresponding to near-filling of said bag and a second predetermined weight corresponding to said predetermined amount, and (2) to control the position of said first valve means in response thereto, said first valve means having a closed position corresponding to said second predetermined weight, a partially open position corresponding to said first predetermined weight and an open position, said control means including a linear fluid-drive actuator directly connected by a valve stem to said first valve means, said first valve means having a linear moving conical valve, said linear fluid-driven actuator comprising a closed cylinder, two pistons, a first and second, therein, piston rods extending from each said piston through the ends of said cylinder, the rod connected to said first piston extending to and directly connecting in line with said valve stem and the rod connecting to said second piston being adapted to permit adjustably limiting the motion of said second piston into said cylinder, and three actuator fluid connections adapted to admit and remove actuator fluid from each end of said cylinder and between said two pistons.