Mounting arrangement for wet end weight measurement system

Details Mounting arrangement for wet end weight measurement system Mounting arrangement for wet end weight measurement system

1999-08-16

2001-02-13

Silverman, Stanley S. (Department: 1731)

Paper making and fiber liberation

Apparatus

Automatic control

C162S255000, C162S262000, C162S263000, C162SDIG004, C162SDIG004, C162S199000, C248S901000, C248S904000, C277S300000, C429S100000

Reexamination Certificate

active

06187146

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a mounting and clamping arrangement for positioning sensors at the wet end of papermaking machinery.
BACKGROUND OF THE INVENTION
In papermaking machinery, determination of machine direction (MD) and cross-machine (CD) weight profiles is generally performed by scanning sensors that operate at the dry end of the paper machine. As a result, MD and CD weight control response time has been limited by the time necessary to obtain weight and moisture profiles from the scanning system. The time delay in getting the paper web to the scanning system is the total transit time through the paper machine plus the time required to thread the sheet from the wire into and through the press section, then the dryer, and finally through the calender. The accumulation of all these times often exceeds 30 minutes. It also takes an additional five minutes or so to acquire enough scans to give a reliable estimate of the MD/CD profiles. This accumulated time represents lost production time as paper manufactured during this period is discarded to the broke pit.
To address the above shortcoming of existing papermaking machinery, novel sensors have been developed to obtain rapid measurement of the MD/CD weight profile of the paper web as soon as possible after the start of the paper making process. The novel sensors are the subject of co-pending U.S. patent applications Ser. No. 08/766,864 and Ser. No. 08/789,086.
The faster the CD profile is measured and stabilized at start up, the easier the sheet threading procedure will be and the faster the time to saleable paper product with minimum loss to the broke pit. The novel sensors are positioned at the wet end of the papermaking machine at or near the dry line under the wire portion of a single wire of the machine. Alternatively, the sensors can be positioned adjacent a side of one wire of the two wires on a twin wire machine. The sensors operate by measuring the water and fiber weight on the wire portion. Each sensor comprises an array of sensor elements that measure the weight of the water on the wire by measuring the effective electrical properties of the water between individual sensor elements. The effective electrical properties are related to the water weight over each sensor element. The water weight in turn is correlated to the fiber weight. The sensor array is built into a foil-like structure that extends below the wire in the cross-machine direction. The sensor array is therefore able to simultaneously monitor the full CD width of the papermaking machine. Typically, up to 512 CD data boxes can be provided giving a 25 mm CD resolution. Full profile data can be measured at up to 600 times per second and this is used to calculate MD updates 10 times per second and CD control profiles every second.
It is important that the sensor elements reliably contact the underside of the forming wire to ensure that accurate measurements are taken. This has been a weakness of prior designs. It is necessary that the sensor arrays be removable to permit maintenance and replacement. Prior art mounting systems rely on a T-rail and T-slot arrangement to removably mount the sensor array to a base mounting beam. Relatively large clearances are required for installation and removal of such an arrangement which prevents a consistent mounting and alignment of the sensor array with respect to the wire with the result that data obtained from the sensors is not always reliable. Furthermore, the T rail/T slot arrangement limits the vertical position of the sensor array to the location of the T rail without the possibility of adjusting the sensors to ensure proper contact with the wire.
SUMMARY OF THE INVENTION
To address the foregoing problems, applicant has developed a new sensor array mounting scheme that relies on a loose fitting tongue and groove arrangement with an inflatable air bladder to lock the sensor array in position to ensure proper contact with the wire.
Accordingly, the present invention provides a mounting system for removably mounting a sensor array adjacent the wire portion of a papermaking machine comprising:
an elongate base member formed with one of a tongue and a groove;
a corresponding interlockable tongue or groove formed on the sensor array adapted to be slidably received and retained by the elongate base member, the tongue and groove being dimensioned to permit relative movement of the sensor array with respect to the base member; and
an inflatable bladder housed between the elongate base member and the sensor array adapted to be inflated to move the tongue and groove into a locked position to fix the position of the sensor array with respect to the elongate base member.
In a further aspect, the present invention provides in a papermaking machine having a wire portion and a removable sensor array mounted adjacent the wire portion by an elongate base member formed with one of a tongue and a groove, and a corresponding interlocking groove or tongue formed on the sensor array adapted to be slidably received and retained by the elongate base member, the improvement comprising:
the tongue and groove being dimensioned to permit relative movement of the sensor array with respect to the base member; and
an inflatable bladder housed between the elongate base member and the sensor array adapted to be inflated to move the tongue and groove into a locked position to fix the position of the sensor array with respect to the elongate base member.
The mounting system and apparatus of the present invention provide an arrangement that allows for easy and efficient removal of the sensor array when the bladder is unpressurized while providing reliable clamping when the bladder is inflated to hold the sensor array securely in position to ensure proper contact with the wire. In addition, the use of adjustable turnbuckles to support the base member allows for further refinement of the position of the mounted sensor array with respect to the wire.


REFERENCES:
patent: 5975532 (1999-11-01), Karttunen
Vyse, Robert et al; “Rapid MD and CD Weight Control Utilizing a New Wet End Weight Measurement System,”; Paper presented at the 84th Canadian Pulp and Paper Association Annual Meeting in Montreal Canada Jan. 1998.

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