Printing – Rolling contact machines – Rotary
Reexamination Certificate
2002-01-14
2004-08-24
Chau, Minh H (Department: 2854)
Printing
Rolling contact machines
Rotary
C101S233000, C101S183000, C271S193000, C318S038000, C318S135000
Reexamination Certificate
active
06779447
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for registering the position of a rotor part in a transport system, in particular, for machines for processing printing material, which have a static or stationary part, such as a stator, in addition to the rotor part.
In printing-material processing machines, such as printing units, printing presses or the like, the transport of a printing material can be performed by a linear drive. A sheet transport system for transporting sheet material in a rotary printing machine is disclosed for example in the published German Patent Document DE 197 22 376 A1. This sheet transport system includes two mutually parallel extending guide rails, in each of which, respectively, an assigned forward drive element, forming the rotor part of an electric linear drive, is guided without play. The two forward drive elements are constructed as link chains having at least two individual links of magnetizable material, and are connected by a traverse or crossmember having grippers fixed thereto for holding the sheet. The drive of the forward drive elements is performed by drive stations with coils which are arranged outside the guide rails, form the stator of the linear drive and are arranged at distances from one another which are at least approximately equal to, i.e., are equal to or approximately equal to, the length of the forward drive devices.
In printing-material processing machines having at least one transport system, for example a linear drive, the rotor part or the rotor parts of the transport system are typically moved on a closed path in roundabout traffic. In order to move a drive under position control, permanent feedback of the measured position of the rotor part into a control system is absolutely required. For this reason, it is necessary to perform a registration of the position of the rotor part in the transport system.
The supplying of power to the transport system or the linear drive is typically ensured by using synchronous motors, the secondary part of which is moved, i.e., forms the rotor part. The static or stationary part includes the primary part, which is appropriately segmented in order to be able to drive a plurality of rotor parts on one track. In order to register the position of the rotor part, i.e., in order to obtain signals, diverse configurations of suitable transmitter devices for generating a signal by detection and suitable detection objects have already been proposed heretofore.
For example, a brushless linear drive supplied with direct current is disclosed in U.S. Pat. No. 5,049,676. The rotor part is driven electromagnetically forward and backward along a rail by at least one series of electromagnetic coils being activated sequentially. The position of the rotor part along the rail is determined by a transmitter that is fixed to the rotor part and detects the relative position in relation to a linear scale that is fixed to the base unit.
A drive module and a linear guide are disclosed in French Patent 92 12 321. They include a measuring system for the position of a rotor part, which has at least one transmitter on the rotor part, and a detection element on the static or stationary part of the drive module, so that the position of the rotor part can be determined. In a first embodiment, the measuring system can be an electromagnetic system including a magnetic measuring tape and a magnetic-field meter as transmitter, while, in a second embodiment, the measuring system may be an optical measuring system including an engraved straight edge or ruler that is illuminated by at least one light source, and a light-sensitive detector.
U.S. Pat. No. 4,096,384 describes a measuring transformer or transducer for picking up and measuring the relative deflection of a first part of a machine tool or a measuring machine in relation to a second part. At least two photoelectric pick-ups are accommodated on the first part, namely a rotor part, and at least two engraved straight edges or rulers are accommodated on the second part, namely a carrier element. The output signals from the photoelectric pick-ups are processed in a selection circuit, so that the relative deflection can be determined.
Furthermore, the Japanese Patent 61 292 502 describes a device for verifying the absolute position of a linear motor, which includes a primary winding and a secondary conductor, which lie opposite and at a given distance from one another, and are displaceable parallel to one another, the device being distinguished by the fact that the magnetic fields of the primary winding are laid out differently on a specified width, and a secondary conductor element is provided on a secondary conductor, the secondary conductor forming a body as a result of the addition of a plurality of verification heads, and the secondary conductor element forming a body as a result of the addition of a plurality of verification heads, in order to make it possible to verify the absolute position.
A disadvantage of mounting the transmitter or the transmitters on the rotor part is, for example, that either a permanent connection, for example, in the form of a cable dragger, or a telemetric connection, for example in the form of electromagnetic waves, between the rotor part and static or stationary part, for example, for a power supply, for a transmission of the position signal or the like, must be made to the control system. However, the use of cables to connect the moving transmitter to the control system necessitates an only limited travel distance or an only limited pivoting angle and is therefore unsuitable for the use of a rotor part on a closed path, such as is required, for example, for machines for processing printing material. In the case of a very long travel distance or in the case of many traverses of a closed path, the cable will be stressed to a great extent; furthermore, the mass of the cable which has to be dragged along is often too great. In the case of use in machines for processing printing material, in particular, sliding contacts must be dispensed with, for reasons of contamination and wear. Telemetric data transmission is very complicated when a plurality of rotor parts are used. In addition, a transmitter of electromagnetic waves on the rotor part has to be supplied with power, which makes necessary either a permanent connection for the supply of energy, or an additional mass of a power storage unit, which mass has to be moved. This is unacceptable for linear drives in printing machines. The use of a completely passive rotor part, i.e., a unit for which no power is needed to generate a position signal, is to be given preference.
A method of determining the position of an element that emits field lines in relation to sensors sensitive to field lines is described in the published German Patent Document DE 37 42 524 A1. The element that emits field lines is a position indicator, for example, a magnet which causes a voltage distribution that is typical of the position and which is used to determine the position of the position indicator, in the sensors which are sensitive to the field lines and are interrogated in multiplexed fashion. Each magnet position measured in length units corresponds to an unequivocally determined voltage distribution. Furthermore, the published German Patent Document DE 35 40 568 A1 discloses a device for the contactless determination of the position of magnets or other elements which emit field lines in accordance with the principle of position multiplexing of field-sensitive sensors.
A disadvantage in this case is that the position of only one dipole magnet or a few dipole magnets is determinable with only rather low accuracy. Moreover, complicated multiplex electronics are required in order to evaluate the signals from the sensors.
A further state of the prior art is represented by the published German Patent Document DE 35 37 384 A1, wherein a length-measuring device is disclosed which has a measuring carriage arranged to be displaceable with respect to a base bed and wherein a measurin
Frank Hendrik
Maier Stefan
Chau Minh H
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Mayback Gregory L.
Stemer Werner H.
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