Sheet-material associating – Associating or disassociating – Signature associating
Reexamination Certificate
1998-11-09
2001-03-06
Skaggs, H. Grant (Department: 3651)
Sheet-material associating
Associating or disassociating
Signature associating
C270S052060, C270S058030, C271S263000
Reexamination Certificate
active
06196537
ABSTRACT:
TECHNICAL FIELD
This invention relates to an apparatus for the measurement of the thickness of flat products such as sheets or signatures and is particularly directed to an apparatus for measuring the thickness of sheets or signatures being fed by a feeding mechanism from a pile of signatures to a transport device such as a pocket feeder, in order to detect a malfunction of the feeding mechanism.
BACKGROUND OF THE INVENTION
In the technology of building books including booklets, magazines, periodicals, and so on, the use of collating systems is well known. These systems typically have a transporting device on which individual signatures are gathered to build a book-block set, which then is finished and bound. Typically a number of hoppers is arranged along the transporting device where each of the hoppers comprises a feeding mechanism for feeding an individual signature from a pile of signatures onto the transporting device, in order to progressively build up the book-block set. Such feeding mechanisms typically employ callipering devices for detecting a malfunction of any of the feeding mechanisms on a given line. Such a malfunction may, for example, result in a delivery of more or less than the intended number of sheets onto the transporting device.
To alleviate these problems some efforts have previously been made to design collating systems having callipering devices for measuring the thickness of sheets being delivered from a pile of signatures to a transporting device. These calipers typically employ a mechanical feeder gauge which is calibrated to measure the thickness of the sheets being fed from a hopper to a transporting device. Such a thickness measurement device is, for example, known from U.S. Pat. No. 4,471,954, the disclosure of which is hereby incorporated by reference. This document discloses a transporting device in the form of a pocket feeder having a plurality of sheet loading pockets. Each of the pockets is associated with a sheet ejector for ejecting single sheets into a common sheet conveyor path from the respective pocket. A photo-electric sheet passage detector is mounted between each pocket and the common sheet conveyor path which generates a transparency or reflectivity signal of the sheet and which is compared to a stored averaged signal representative for a single sheet.
Another apparatus for measuring the thickness of sheets being fed from a hopper to a pocket feeder is known from U.S. Pat. No. 5,213,318, the disclosure of which is hereby incorporated by reference. The apparatus of U.S. Pat. No. 5,213,318 comprises a plurality of hoppers for holding signatures where the plurality of pockets is movable past the plurality of hoppers. Each of the pockets has a first fixed roller and a second movable roller being in contact with each other when no sheet is fed between the two rollers. When a flat product passes between the two rollers the second roller is deflected, where the amount of the deflection corresponds to the thickness of the product passing. In order to measure the thickness the deflection of the second roller is measured. The second roller therefore is mounted on a movable shaft which comprises a plate on one of its ends. The plate is rotatable and arranged within a gap between a light source and a light sensor. Depending on the degree of rotation of the shaft the plate has a corresponding angular position and depending on this angular position it interrupts more or less light from the light source where the amount of interrupted light corresponds to the deflection the rollers.
The accuracy of this method however is limited due to shadow-effects and due to the limited resolution of the light sensor. Furthermore, every pocket has to be provided with a separate light source.
SUMMARY OF THE INVENTION
It is an object of the present invention to increase the accuracy of the thickness measurement and to provide an improved apparatus for measuring the thickness of flat products.
In summary, according to one aspect of the present invention, an apparatus for measuring the thickness of flat products such as sheets or signatures is disclosed, where the flat products are fed by a feeder from a pile of signatures to a receiving location. The feeder includes a first and a second roller where the first roller is arranged against the second roller to form a nip therebetween for receiving the flat product, wherein the first roller is deflectable when a flat product enters the nip. The apparatus comprises a first proximity target being arranged on the first roller and a second proximity target being fixedly arranged on the transporting device. The apparatus furthermore includes at least one proximity switch which is arranged apart from the transporting device for monitoring at least one of the first and second proximity targets.
Solutions according to the present invention are advantageous, since the present invention can measure the thickness of the flat products with high accuracy. Furthermore, the present invention can magnify the very slight movement of the first roller which corresponds to the thickness of the flat product by measuring the distance in the appearance of the first and second proximity targets.
According to further details of the present invention, the first and second proximity targets can be arranged on a movable transporting device, including movable receiving units, so-called compilers, which have a pocket and a pocket feeder. The proximity switch and a calculating unit can be arranged stationary apart from said movable transporting device. This separation of the components leads to the advantage that only one proximity switch is needed to detect the appearance of a plurality of receiving units or compilers.
According to another detail of the present invention, the first proximity switch can be arranged stationary apart from the movable receiving unit at a location where it can monitor the first and second proximity target. When the proximity switch detects the first proximity target a microcomputer begins to count the pulses generated by an encoder. The microcomputer stops counting as soon as the proximity switch detects the second proximity target. As the number of counts refers to the thickness of the flat product, the thickness can be calculated from the number of counts.
According to a further aspect of the present invention the thickness measurement apparatus includes a plurality of hoppers for holding stacks of sheet material, a plurality of receiving units or compilers having a receiving location and a feeding mechanism for performing sheet feeding operations to feed sheet material from said hoppers to said receiving locations. The apparatus further includes driving means for sequentially moving each of said receiving units past each of said hoppers in turn and comprises a plurality of first and second proximity targets. Each of said first proximity targets is movable and attached to each of said feeding means and each of said second proximity targets is attached fixedly to each of said receiving units. A first proximity switch for sensing one of the plurality of the first and second proximity targets is arranged stationary, apart from the receiving units. An encoder for generating pulses is stationary apart from the receiving units and a microprocessor unit is arranged stationary apart from the receiving units which monitors the pulses of said encoder and said first and second sensor signal.
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patent: 5967503 (1999-10-01), Newsome
Conner Charles Jeffrey
Farr Alan Scott
Schlough James Richard
Burns Doane , Swecker, Mathis LLP
Heidelberger Druckmaschinen AG
Mackey Patrick
Skaggs H. Grant
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