Cutting – With randomly actuated stopping means – Responsive to tool detector or work-feed-means detector
Reexamination Certificate
2000-05-09
2004-03-02
Shoap, Allan N. (Department: 3724)
Cutting
With randomly actuated stopping means
Responsive to tool detector or work-feed-means detector
C083S062100, C083S522270
Reexamination Certificate
active
06698323
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a system for detecting when a web is not being completely perforated, cut, scored or otherwise weakened at spaced intervals along its length, and more particularly to a web perforating system that detects and indicates when a perforator in a rewinder or similar machine is operating with a broken or dull perforating blade.
2. Description of the Prior Art
During the production of paper products such as toilet tissue and paper towel rolls, a paper web is unwound from a parent roll by a rewinder as is well known in the art. As the paper web enters the rewinder, it contacts one or more rolls which deliver it to a web cutting apparatus or “perforator” that is equipped with a perforating roll. One such perforator is disclosed in U.S. Pat. No. 2,870,840 to Kwitek which is hereby expressly and completely incorporated by reference. The perforator includes a perforating roll carrying rows of perforating blades or “fly knives.” These rows are spaced from each other along the circumference of the perforating roll. The perforating blades rotate relative to and cooperate with stationary anvils that carry anvil blades. The anvils are secured in a helical pattern to a perf anvil head which extends across the path of travel of the web. The perf anvil head in such a device can rotate relative to the perforating roll between an open position and an operating position. In an open position, the perf anvil head spaces the anvils from the perforating blades so that the web will not be perforated. When the perf anvil head is rotated into the operating position, the perforating blades contact the anvil blades and perforate the passing web, thereby creating perforations at predetermined spaced intervals in the passing web. After the web passes through the perforator, it moves to a winding system which winds it onto a core.
A perforating roll can rotate at speeds typically up to 1500 feet per minute. As a result, the perforating blades experience high compressive and shearing forces when they contact the stationary anvil blades. These forces can cause a perforating blade to fail at any time during a production run. Additionally, over time, the teeth of a perforating blade can dull as a result of repeatedly impacting an anvil blade. When the perforator operates with a broken or dull blade, it may not fully perforate the web. As a result, rolls of paper products which are not fully perforated will be sent to the customer. Paper rolls with incomplete perforations are the largest complaint of perforated product customers.
Perforating machines such as that discussed above lack a system for detecting if a perforating blade has broken or become so dull that it does not perforate the passing web. Instead, perforated paper producers rely on an operator to visually inspect the perforations between sheets of a wound paper product at regularly spaced time intervals, such as every hour. Between these inspections, a broken blade may only be detected if the operator hears a noise which suggests that a blade has broken. As difficult as it is for an operator to hear when the perforator is operating with a broken blade, it is virtually impossible to detect if it is operating with a dull blade without visually inspecting the perforated rolls.
If a perforating blade breaks or becomes too dull to properly perforate the web at any time between visual inspections, the machine will continue to operate and produce incomplete perforated products until at least the next visual inspection. For example, if the operator stops and examines the results of the perforating process every hour, a blade that breaks fifteen minutes into a run will cause the perforator to produce forty-five minutes worth of improperly perforated sheet product. This can add up to a significant amount of improperly perforated product when the rewinder is operating at 1500 or more feet of paper web per minute. Additional problems associated with visual inspection are the loss of production time if the line is shut down while the visual inspection is performed, and the waste of the product that is used for the inspection.
Various machines have included systems to detect when a web has not been properly prepared. One such system is disclosed in U.S. Pat. Nos. 4,813,320 and 5,091,962 to Malloy et al. which disclose a stamping machine having an associated sensing device for determining when a stamped web has been incorrectly fed. After the web is stamped, it passes from the press to a sensing device which includes an internal coil for generating an electromagnetic flux field. The sensing device produces a waveform which is based upon the amount of metal in the web and the position of the stamped portions relative to the sensors. This waveform is compared to a reference waveform. If a deviation exists between the waveforms, this indicates that the web was incorrectly fed. The stamping machine is then stopped and the position of the web is corrected. However, since the sensing device is spaced away from the press, the press will continue to stamp the incorrectly fed web and create waste for the length of time that it takes the frame with the first perceptible amount of deviation to reach the sensor.
U.S. Pat. No. 3,339,434 to Sparling discloses a drill press including a monitoring apparatus that generates a control signal when the drill bit is broken or dull. The monitoring apparatus measures the duration of each drilling cycle and compares it with a reference cycle. Extended cycle times are caused by broken or dull drill bits taking longer to contact a reference point, such as the work piece, than a normally operating drill bit. When the measured cycle exceeds the reference cycle, a control signal is generated, indicating that a problem exists with the process. An apparatus which uses a timing cycle for monitoring a plurality of drill bits is also disclosed.
U.S. Pat. No. 2,792,833 to Pokorski discloses an automated cutting press that forces a cutting die through a sheet material until it contacts a cutting block. The reciprocating die and cutting block include electrically conductive surfaces. A detection system establishes a circuit when the die and cutting block contact each other. The circuit affects the retraction of the die to its starting position so that the cycle can be repeated. This system is designed to automate the operation of the press, not to detect the presence of a broken tool. Additionally, this system will operate with a broken tool, as long as the tool can be forced through the sheet material and at some time contact the cutting block. This can result in a substrate cut that is not properly sized or shaped.
It is an object of the present invention to overcome the drawbacks associated with the prior art rewinders and perforators.
It is also an object of the present invention to provide a perforator that detects and indicates when one of its blades breaks or becomes so dull that it cannot properly perforate a web.
A further object of the invention is to provide a method for detecting when a perforator is operating with a broken or dull perforating blade.
SUMMARY OF THE INVENTION
The present invention provides a web perforating apparatus which includes a system for detecting and indicating when a blade in the apparatus is broken, dull or otherwise not making contact with an opposing blade and thereby not perforating the web. This apparatus is typically used with rewinders or other similar machines that produce perforated sheets of products, such as paper, using sets of stationary anvil blades and rotating perforating blades. The perforating blades are typically attached to a bed roll and rotate relative to the anvil blades. These anvil and perforating blades are finely adjusted to make light, accurate contact with each other. As the perforating blades contact the web extending across the anvil blades, perforated product is produced. The anvil blades are solid in profile shape and connected to a movable mounting bar by blade holders. The blade holders secured to the rewin
Dodge Bernie
Formon John S.
Morris Andrew
Banner & Witcoff , Ltd.
Flores-Sánchez Omar
Georgia-Pacific Corporation
Shoap Allan N.
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