Winding – tensioning – or guiding – Tension control or brake – Supply controlled
Reexamination Certificate
1999-07-14
2003-08-19
Marcelo, Emmanuel M. (Department: 3653)
Winding, tensioning, or guiding
Tension control or brake
Supply controlled
Reexamination Certificate
active
06607157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to air bearings, novel constructions using air bearings, and novel methods using the air bearings and the constructions using them. In particular, the present invention relates to air cylinder systems, web dancer systems, and idler rolls using air bearings as an essentially frictionless implementation of movement between mechanical elements.
2. Background of the Invention
Friction between moving parts still provides one of the underlying engineering problems in the construction of mechanical elements. Friction not only induces wear on parts and materials in apparatus, but also decreases the accuracy and consistency of many mechanical devices. For example, in laser printing apparatus, even though the focus of the laser beam can be reduced in size and time controls are available for accuracy less than milliseconds, the mechanical movement of elements is hampered by friction and the attendant vibrations and irregularities introduced onto the apparatus and writing surfaces. Additionally, friction causes wear in moving parts and the variations in mechanical accuracy significantly increase with time. Wear on moving parts or on parts in contact with a moving part can necessitate regularly part replacement and down time for the equipment while the part is being replaced.
Many different contributions have been made over the years towards reducing friction between moving elements. The earliest efforts were directed towards providing smoother surfaces in contact with each other, either by improved mechanical milling, grinding or lapping, or by the application of lubricant between moving surfaces. The use of the wheel or ball bearing is another way used to reduce friction between surfaces. Mechanical bearings have ball or barrel rolling elements which have a lower friction than a bearing with elements which slide relative to each other on low friction materials such as bronze, lead, Teflon, polyethylene, or other materials. Roller bearings still require lubrication to protect the point or line contact between the spherical or cylindrical elements and their associated raceways. The lubricant is progressively squashed as a roller passes by and the shearing action present here creates friction forces and generates heat that can decompose the lubricant and/or damage the bearing surface. Some precision bearings have oversized balls installed into runways to eliminate the gaps between the ball and the raceway. This reduces the looseness of the bearing device. Each compressed ball generates friction forces due to the material damping characteristics of the ball construction material.
U.S. Pat. No. 5,810,236 (Yoshida) describes a web accumulator using a dancer roller which is mounted on a single linear ball bearing slide assembly to replace conventional support systems which use two pivot arms or two vertical guide rods. The weight of the rolls provides the web tension which is not controlled. As compared to a near zero friction air bearing pivot arm dancer roller support, this system has substantial friction in the arm support system. Nothing is taught about the use of air bearings in a roller or any other part of the system including the use of an air bearing air cylinder to control the web tension.
U.S. Pat. No. 3,995,791 (Schoppee) describes a web accumulator system which holds a sufficient amount of web material in storage that the web may continue entering the accumulator even though it is stopped momentarily to splice another roll of web. The system consists of idler rolls and driven rolls and web tension is provided by counterweights on web roll arms and also provided by friction clutch devices. Idler rolls are supported on traveling slides but no concern is expressed for the friction introduced by the slides or the rollers or the residual friction which is present in the adjustable clutch even when the activation electrical signal is turned off.
U.S. Pat. No. 4,188,257 (Kirkpatrick) describes a web splicing mechanism which uses drive motors to accelerate the web from a new roll of material to speed match the web from a near exhausted roll of material so that the two webs may be joined with adhesive tape and the old web cut away from the new. This splicing function is done on-the-fly without the use of a web accumulator system. Many web idler rolls are used in this mechanism but no concern is expressed about the amount of friction that exists in any of these idler rolls.
U.S. Pat. No. 4,028,783 (Buck) describes a system of many abrasive coated idler rolls typically used in a printing press machine which have to be changed frequently to replace the old ink contaminated abrasive surface with new clear material. Buck uses a system of telescoped abrasive sleeves which are locked on mandrels with a keyway which allows the roll replacement to be accomplished much faster than the old system. Even though the printing press has many rolls in contact with the printed web, no concern is expressed in controlling the turning friction of each of these rolls or of the total cumulative friction of all of the rolls.
U.S. Pat. No. 4,643,300 (Morrison) describes an idler roll which has antifriction bearings to reduce the rolling friction of these rolls as used in a conveyor system to allow small diameter bearings to be used without deflection of the roll shaft by making a shaft with a hollow large diameter in the middle of the roll but where the largest bending forces take place and yet using a small diameter at the ends to allow the continued use of small bearings. The dirt seals on small diameter bearings have less frictional drag than large diameter bearings so an advantage in low friction is retained with these small bearings. This beneficial feature is not discussed as the primary focus is on maintaining low cost of the idler roll. Use of extraordinary low friction air bearings in these idler rolls is not discussed.
U.S. Pat. No. 4,645,071 (Faulkner) describes a low friction idler roll where the lubricated roller bearings are replaced with solid plastic bearings which eliminates the lubrication material which is a potential contamination source to the process where the idler roll is used. Thin roll shells are used with these rolls. When foreign material enters the lubrication passageways within the roller bearing body, these bearings tend to lock up and prevent the roll from turning. Use of low friction air bearings which tend not to contaminate and also are low friction are not considered.
U.S. Pat. No. 5,709,352 (Rogers) describes a zero web tension unwinder for gossamer web material used in cigarette manufacturing which is simpler than commercial machines which are available to accomplish unwinding of fragile web material. A web is loosely stretched horizontally under a pulsed sensor with an air jet blower nozzle which applies some windage downward force on the web to stabilize it for successful position measurement of the web. A feedback control system uses the sensor output to control an unwind motor to advance the unwind roll sufficient to obtain the desired droop of the web under the sensor. Rogers is concerned about the tension effects on the fragile web but he does not address elimination of friction within the machine components such as with the use of zero friction air bearings on idler rolls, web dancer arms and within air cylinders.
U.S. Pat. No. 5,791,541 (Jitsuishi) describes a web tension control system for paper printer machines that has two dancer systems that are force activated by air cylinders. Sensors indicate the position of the dancer pivot swing arms and send signals to web brakes and to drive motors to stabilize the web tension upstream of both a web in-feed roller and the nipped print heads. A control system monitors and controls the web tension during start-up, normal operation, web break events and shut-down. No discussion is made of the friction present in the standard air cylinders, the mechanical bearings of the dancer pivot arms and the bearings in the many web rollers present in the sy
Keltech Engineering, Inc.
Marcelo Emmanuel M.
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