Electric heating – Metal heating – By arc
Reexamination Certificate
2000-02-07
2001-10-30
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
C219S121720, C225S002000
Reexamination Certificate
active
06310318
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to cutting a long glass tube into a plurality of identical short glass tube sections. More particularly this invention concerns a method and apparatus for thus cutting up a glass tube for use of the tube sections as syringe bodies.
BACKGROUND OF THE INVENTION
Glass is the preferred material for the manufacture of a syringe body since it can withstand the high heat of sterilization, is extremely dense and nonabsorbent, emits no chemicals as it ages, changes little in property as it ages, and is relatively cheap. Thus a syringe body normally is formed as a tube section having smoothed and finished ends.
Such a glass tube section is produced by cutting up an elongated glass tube. The tube itself can be relatively long and is supplied in bulk, often with somewhat damaged ends.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved system for cutting such a tube up into identical finished tube sections.
Another object is the provision of such an improved system for cutting such a tube up into identical finished tube sections which overcomes the above-given disadvantages, that is which accurately and automatically cuts from the supplied tube stock a succession of tube sections usable without further treatment as syringe bodies.
SUMMARY OF THE INVENTION
This object is attained by a method of cutting a plurality of tube sections from an elongated glass tube wherein a plurality of the tubes in a supply are fed one at a time from the supply to a station. Each of the tubes is rotated in the station about a longitudinal axis of the tube in the station and is simultaneously pressed axially against a fixed stop. A laser beam is directed at the rotating tube in the station at a location along the tube offset from the stop to melt the tube at the location and cut from the tube a section lying between the location and the stop. After cutting from the tube, the tube section is transversely displaced onto a conveyor and transported away from the station by means of the conveyor. Then the tube in the station is advanced axially into engagement with the stop and the steps of rotating, cutting, and so on are repeated until the tube is exhausted.
This system therefore automatically reduces an elongated tube into a plurality of short tube sections that are usable directly as syringe bodies. The laser cutting forms an extremely neat trailing end on the tube section and leading end on the tube, and in fact the laser can normally be used after the cut is complete to thoroughly heat the cut ends and thereby ensure that they are smooth and rounded. It is relatively easy for a controller operating the various drives and actuators to accommodate tubing stock of different diameters and to cut tube sections of different lengths, all automatically.
According to the invention the tube section and tube are urged axially in opposite directions away from the location during the cutting step. This insures that the ends will not fuse back together and that the finished ends can be perfectly smoothed.
Since the leading and trailing ends of each tube are normally somewhat imperfect and in facto often fused closed, the invention proposed transversely displacing and discarding leading and trailing end sections of each of the tubes. This is done by a separate diverter flap provided at the station. The controller can easily be set to discard the first section cut after a new piece of tube stock has been loaded in, and to discard the last piece when the pusher moves into a position spaced from the stop by a distance equal to or shorter than the desired tube-section length.
The apparatus according to the invention has a supply holding a plurality of the tubes, means for feeding the tubes one at a time from the supply to a station, means for rotating each of the tubes in the station about a longitudinal axis of the tube in the station, and an axially fixed stop in the station. A pusher is provided in the station for pressing the tube axially against the fixed stop and cutter in the station directs a laser beam at the rotating tube in the station at a location along the tube offset from the stop to melt the tube at the location and cut from the tube a section lying between the location and the stop. An unloader transversely displaces the tube section after cutting from the tube onto a conveyor which transports the tube section from the station.
The feeder according to the invention includes structure for forming a single-file row of the tubes leading to the station. It also has a selector wheel for taking the tubes one at a time from the supply and feeding them to the structure. Normally such a wheel can feed two holding and cutting units that act alternately to form tube sections that are delivered to a common conveyor. The supply is a downwardly tapering hopper above the cutting station. Thus the operator of the machine need merely keep the hopper full, and the machine will automatically produce perfect tube sections one after the other.
The rotating unit includes a pair of lower cradle-forming support rollers extending along and rotatable about parallel axes parallel to the tube and adapted to hold and support the tube in the station, at least one upper hold-down roller engageable with the tube on the support rollers, and a drive that rotates at least one of the rollers and thereby rotates the tube about its axis. Each roller has an upstream portion to one axial side of the location and a downstream portion to an opposite axial side of the station. Thus the tube is fully exposed and out of touch with all support structure at the location where the cut is made.
In accordance with the invention means is provided for urging the hold-down-roller portions downward against the tube on the support rollers with a predetermined force. This means can include individually controllable normally pneumatic biasing units that can pull back rollers as the tube gets shorter so as to let the pusher pass. In addition each of the rollers has a surface with a substantially higher coefficient of friction than glass, typically a rubber coating that also protects the glass tube from breaking.
The upper roller according to the invention has two portions axially flanking the location and canted oppositely to urge the tube away from the location so that when the tube is cut through the piece and tube are urged apart at the location. Normally the downstream piece is pressed against the stop while the upstream piece is urged oppositely against the pusher that was originally used to hold the tube against the stop.
The conveyor in accordance with the invention is underneath the station and the unloader includes means for spreading the downstream portions of the lower roller and thereby dropping the tube section onto the conveyor. Furthermore the unloading unit includes guides extending downward from the lower-roller downstream portions to the conveyor. More particularly the spreader includes respective arms pivoted about an axis parallel to the tube and underneath the station. Each arm has an outer end carrying a respective one of the lower-roller down-stream portions.
The conveyor according to the invention has prismatic seats adapted to receive the tube sections and of very low heat capacity. Furthermore means is provided for aspirating vapors produced by the cutting operation from the location. A smoothing roller is pressed against the tube at the location to round ends created in the tube by the laser beam.
The pusher according to the invention includes a pusher element axially engageable with an end of the tube in the station and means for axially displacing the pusher element and thereby axially displacing the tube through the location toward the stop which is a stop roller aligned axially with the tube in the station. This stop roller is of the same diameter as the tube being cut and is normally heated to avoid excessively cooling the tube end pressed against it.
REFERENCES:
patent: 3744690 (1973-07-01), Gray et al.
patent: 3770173 (1973-11-01), Ca
Glocker Joachim
Kavallar Günter
Rustemeier Oliver
Vetter Helmut
Arzneimittel GmbH Apotheker Vetter & Co.
Dubno Herbert
Dunn Tom
Edmondson Lynne
Wilford Andrew
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