Plastic article or earthenware shaping or treating: apparatus – With means lubricating cooperating apparatus parts
Reexamination Certificate
2002-08-09
2004-12-14
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
With means lubricating cooperating apparatus parts
C425S217000, C425S261000, C425S345000
Reexamination Certificate
active
06830442
ABSTRACT:
BACKGROUND OF THE INVENTION
The apparatus comprising a typical rotary tablet press includes a rotatable die table, an upper punch turret and a lower punch turret. The common design can be described generally as the turret and die table being circular in shape, and along the area near their circumferential edge, the turret and table have a number of openings machined through these parts, as depicted in
FIG. 2
a.
Fitted in the upper and lower punch turrets are cylindrical punch bars that move reciprocally within machined guide cylinders. The punch bars have a head at one end, which is suitably machined for contacting a cam or wheel, and at the other end the punch bar has a tip that goes into a die fitted into the die table. The tip is shaped for forming a tablet from powder that is fed into the die.
Typically, the turrets and the die table are joined together, so that the assembly can rotate around a central axis. As it rotates, the head of a punch bar comes into contact with a cam, which pushes the punch into the die, and there the tablet is formed by compression. As the rotation continues, the punches move off the cams, and the tablet is ejected from the die.
In the prior art presses, the punch bars and dies were removable, but that required a laborious process of taking out the punch bars from the turrets, and forcing the dies out of the die table, and in some instances, removing of the entire rotatable assembly. New dies would be hammered into the die table, and then, the other parts, such as the punches were re-installed.
Such work can be required routinely in order to change the shape of the tablet to be made, or required for major maintenance or repair of the punches, dies and other moving parts of the turrets and die table. Such maintenance to the prior art presses would be needed because the powder from which the tablets are made often has an abrasive or corrosive effect on the moving and machined parts. These dust problems, and the need to avoid that is recognized in U.S. Pat. No. 5,462,427 to Kramer and U.S. Pat. No. 4,259,049 to Willich.
REFERENCES:
patent: 3891375 (1975-06-01), Pilewski et al.
patent: 4259049 (1981-03-01), Willich
patent: 4292017 (1981-09-01), Doepel
patent: 4408975 (1983-10-01), Hack
patent: 4664173 (1987-05-01), Wolniak
patent: 4943227 (1990-07-01), Facchini
patent: 5116214 (1992-05-01), Korsch et al.
Davis Robert
Nguyen Thu Khanh T.
Thomason Charles L.
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