Mounting arrangement for wet end weight measurement system

A mounting system for removably mounting a sensor array adjacent the wire of a papermaking machine. The mounting system comprises an elongate base member formed with a tongue or groove with a corresponding interlocking groove or tongue formed on the sensor array adapted to be slidably received and retained by the elongate base member. The tongue and groove are dimensioned to permit relative movement of the sensor array with respect to the base member. An inflatable bladder is housed between the elongate base member and the sensor array and the bladder is 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. This arrangement allows for easy and efficient removal of the sensor array when the bladder is unpressurized while providing reliable clamping when the bladder is inflated. Adjustable fasteners associated with the base are also provided to allow for fine tuning of the height of the sensor array and the tilt of the array to accommodate the wire of the papermaking machine.

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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Referring to FIG. 1, there is shown a preferred embodiment of a mounting
 system 2 according to the present invention for removably positioning a
 sensor array 4 below the wire 5 at the wet end of a papermaking machine.
 In the illustrated embodiment, the sensor array is a conventional foil
 array. It will be appreciated by those skilled in the art that other
 sensor arrays can be used with the mounting system of the present
 invention.
 As is conventional, papermaking equipment includes a foundation rail 6 to
 which is clamped at 8 a mounting beam 9 that extends across the width of
 the papermaking machine in the cross-direction (CD). A global jacking
 screw 10 is provided at each end of the mounting beam 9 to provide coarse
 adjustment of the mounting beam below the wire 5.
 In the mounting system of the present invention, mounting beam 9 supports,
 via a plurality of adjustable fasteners 12, an elongate base member 15
 that extends across the papermaking machine in the cross-direction. As
 best shown in FIG. 2, base member 15 is formed with a dovetail groove 20
 adapted to slidably receive in the cross-machine direction a
 correspondingly shaped dovetail tongue 22 formed on the lower edge of the
 sensor array 4. Groove 20 and tongue 22 are dimensioned so that the
 resulting interlocking tongue and groove joint between base member 15 and
 sensor array 4 permits relative movement of the sensor array with respect
 to the base member in the vertical direction. This free play allows for
 easy insertion of the sensor array into position beneath the wire. It will
 be appreciated that the tongue and groove arrangement specifically
 illustrated in FIG. 2 can be reversed without changing the general
 operating principle of the mounting system of the present invention. For
 example, sensor array 4 can be formed with a groove and base member 15
 with a tongue.
 Sensor array 4 comprises a plurality of sensors 28 housed in a generally
 rectangular box with a leading ceramic edge 29.
 An inflatable bladder 25 is provided between elongate base member 15 and
 sensor array 4. When bladder 25 is inflated, tongue 22, and hence sensor
 array 4, are moved upwardly until the sloped walls of tongue 22 and groove
 20 engage and interlock to fix the sensor array 4 into a stable position
 with respect to the elongate base member.
 Preferably, as illustrated in FIG. 2, bladder 25 is housed in groove 20
 formed in base member 15. Inflatable bladder 25 is preferably generally
 dome shaped in cross-section and formed with a substantially flat base 30
 that extends substantially the length of the base member in the
 cross-machine direction. Flat base 30 engages against base member 15 while
 tongue 22 is formed with a concave cavity 32 dimensioned to accommodate
 the domed surface of the bladder.
 To further refine the adjustability of the mounting system of the present
 invention, base member 15 is provided with adjustable fasteners 12 in the
 form of turnbuckle assemblies 35 that extend between the base member and
 mounting beam 9. Preferably, turnbuckle assemblies 35 are arranged in
 pairs at intervals along the length of base member 15. Each pair is
 positioned on opposite sides of the longitudinal axis of the base member
 as best shown in FIG. 2. By adjusting the length of the turnbuckle
 assemblies, the sensor array already locked into position with respect to
 base member 15 by inflatable bladder 25 can be aligned with the existing
 drainage table of the wire to ensure reliable contact with the wire. The
 turnbuckles allow for adjustment of the position of the sensor array in
 both the machine direction and the cross-machine direction. In particular,
 the turnbuckles can be adjusted to fine tune the position of the sensor
 array by adjusting the height and tilt angle of the sensor array. Height
 adjustment is useful to control the contact pressure of the sensor array
 with the wire. Adjustment of the tilt angle accommodates variations in the
 wire.
 Although the present invention has been described in some detail by way of
 example for purposes of clarity and understanding, it will be apparent
 that certain changes and modifications may be practised within the scope
 of the appended claims.