Patent Application
20210009394
This disclosure relates generally to robotic grippers and, in particular, to grippers that tighten caps or lids on containers.
The use of robotic devices with end effectors to perform routine manufacturing tasks is widespread. For example, putting a cap on a container is just such a routine task.
Placing a cap on a container and twisting it to seal the container is important. The product inside the container may have a shelf life that may be compromised by a cap that is loose or not tight, or the contents may be harmful, even dangerous, if the contents spill because the cap was not properly sealed. An example of a group of products that are sold in carefully sealed containers is pharmaceutical medications.
To seal a container with a cap, the top of the container and the inside of the cap may be threaded to permit a tight closure. The cap may be placed on the container and either the cap, the container, or both may be rotated. The threads of the cap advance as the cap is threaded to the container until the cap will advance no further. Containers may be capped by a robotic end effector. A robotic end effector is a device on an electro-mechanical arm that picks up a cap, orients it so the cap's open end is toward the top of the container and, with both cap and container coaxially aligned, advances the cap onto the container. Relative rotational movement between the cap and the container in the appropriate direction advances the cap onto the container. When the force to rotate the cap causes the prior art grippers holding the cap to slip, the cap is deemed to be tight, and the prior art grippers will then open to allow the container to be removed from its cap-tightening position and the process then repeats by fetching another cap for the next container.
The prior art grippers, made of aluminum, which are on the end effector, are able to grip the cap with enough pressure to hold the cap while the container rotates relative to the cap. That level of pressure on the cap is set to allow the cap to slip when the resistance of the cap to the pressure of the prior art grippers indicates that the cap is tight enough to meet specifications.
In an automated production facility, containers are filled as fast as possible and as many containers as can be filled properly are capped and advanced to the next step in the process, such as labeling, packaging and shipping. Productivity depends on the speed of the process as well as the number of units of product that can be capped before parts such as prior art grippers become worn by friction. When prior art grippers are worn, they are discarded and replaced with new prior art grippers.
A reliable, high-performance gripper for end effectors used in capping pharmaceutical containers would be an advantage.
According to its major aspects and briefly described, herein is disclosed a gripper for use in tightening a cap onto a container. The present device includes at least two grippers on an end effector of a robotic arm. The two or more grippers cooperate to grip a cap selected from an advancing supply of caps, to position the gripped cap over the next container on the conveyor, and then to thread the cap to the container once the cap makes contact with the container. The end effector rotates the cap as the conveyor holds the container, thereby threading the rotating cap onto the stationary container. When the cap has reached the end of its threaded path, the grippers that were holding the cap will slip because the torque force on the container exceeds the frictional force exerted by the grippers on the cap, and thereby signaling that the cap is tight. The end effector releases the cap and the conveyor removes the capped container.
The improved grippers are attached to the end effector, and are spaced apart. A gripper has an exterior face that is oriented to face the curved side of the cap, and curved to conform to the curved side of the cap, and has a compartment formed in the interior of the gripper. At least two apertures and as many as five narrow, parallel apertures formed in the face of the gripper lead to the compartments, one aperture for each compartment. The compartments may be shaped like partial, right cylindrical compartments, each spaced apart from the other. A resilient material—a natural or synthetic rubber such as a fluoropolymer—is inside each compartment and extends through the apertures, bulging out of the curved face of the gripper as a series of resilient ribs. When the gripper engages the cap, the resilient ribs contact the cap and holds it frictionally as the cap is threaded to the container.
The gripper itself is made of steel, such as stainless steel and has a removable bottom wall secured to the balance of the gripper by at least one steel screw. Removing the screw and then the wall provides access to the compartments in the interior of the gripper to allow replacement of the resilient material, which saves time and money. The steel gripper can be used indefinitely and the resilient material is inexpensive.
These and other features of the disclosure will be apparent to those skilled in end effectors used in manufacturing processes from a careful reading of the Detailed Description accompanied by the following drawings.
In the figures,
Herein is disclosed a device for use in threading a cap to a container as part of an automated system. The container may be formed to receive a cylindrical cap. The device includes at least two grippers on an end effector of a robotic arm, for example, two opposing grippers that cooperate to take the next cap from an advancing supply of caps, position the next cap over the container, and then lower the next cap so it makes contact with the container. While rotating the cap, the end effector continues to lower the rotating cap onto a container, which is on a stationery surface. The cap is thus quickly threaded to the container.
When the cap has reached the end of its threaded path, the grippers that were rotating the cap up to that point will start to slip as the torque force required rises sharply when the cap is fully threaded. The slipping of the grip on the cap signals that the cap is tight. The end effector releases the cap and the conveyor resumes its march on the conveyer with the capped container.
As shown in these figures, a conveyor 10 brings a series of containers 14 near to a series of caps 18 that are advancing toward conveyor 10 in a feed tray 22. A robotic arm 26 extends from a vertical shaft 30, shown in broken lines so that conveyor 10 and other components are not obscured.
Vertical shaft 30 moves up and down in a programmed sequence, as best seen by comparing
End effector 42 has two positions. It has an open position wherein its grippers 54 are farther apart and a closed position wherein its grippers are closer together. Grippers 54 move to their closed position when end effector 42 is about to lift next cap 46 and then move to their open position to release next cap 46 after next cap 46 has been tightened onto container. End effector 42 has at least two grippers 54 but may have more, operating in a synchronized, opposing manner to grip portions of the side of next cap 46.
There may be more than two grippers 80. If two grippers 80, they will be opposing they will be centered 180 degrees apart. Three grippers 80 would be centered 120 degrees apart, and so forth, and the curve of their width would cover a smaller and smaller arc of a circle
Gripper 80 has at least two compartments 94, best seen in
Resilient material 108 provides the friction to hold and rotate next cap 88 while next container 14 is held securely with respect to next cap 88. When next cap 88 is tight, gripper 80 will slip. In time, resilient material 108 may be warn and need to be replaced by removing bottom 104 and inserting new resilient material 108 into compartments 94. Removable bottom 104 is then reattached to gripper 80 by screws 100, and gripper 80 can be put back into operation.
Those skilled in the art of robotic manufacturing and in end effectors configured to attach caps and lids will appreciate many modifications and substitutions can be made to the present end effector as shown and described without departing from the scope of the present disclosure.
