Patent Application
20060225589
1. Field of the Invention
This invention relates generally to doctors used to doctor rolls in web handling and processing operations, and is concerned in particular with an improvement in doctors that are reciprocated in the cross machine direction during the doctoring process.
2. Description of the Prior Art
The journals of reciprocating doctors are conventionally supported for both axial and rotary motion in sleeve bearings. There are several disadvantages with such arrangements, especially when the doctor journals are subjected to heavy loads and only minimum axial movement is required, which is often the case with doctors employed in paper malting machines. Sleeve bearings normally have coefficients of friction ranging from 0.15 to 0.3, with 0.25 being the most common for a wide variety of sleeve materials. Using this value as an example, the force required to axially shift a journal within its sleeve bearing would be calculated as 0.25 multiplied by the applied load. Thus, a doctor with an applied load of 10,000 lbf would demand an elevated force on the order of 2500 lbf to effect axial reciprocating movement. Under these conditions, sleeve bearings exhibit significant wear over time, thus requiring expensive maintenance or replacement.
Linear ball bearings are also used to support doctor journals. Ball bearings offer less frictional resistance to axial movement of the journals. However, they require constant lubrication and can also exhibit significant wear over time, particularly when the axial displacement is relatively small, causing depletion of the lubricant at the contact zones between the balls and the bearing races.
In accordance with the present invention, a reciprocating doctor is provided for doctoring the cylindrical surface of a roll rotating about a first axis. The doctor includes a doctor back with a blade holder carrying a doctor blade. The doctor back has journals aligned on a second axis parallel to the first rotational axis of the roll. The journals are rotatably supported in sleeve bearings, and the sleeve bearings are in turn supported by diaphragms spaced along the second axis. The sleeve bearings are fixed axially on their respective journals. The diaphragms have hub portions surrounding and fixed relative to the sleeve bearings, and peripheral portions surrounding the hub portions and fixed relative to a support structure. The diaphragms are configured to resiliently accommodate reciprocating movement of their hub portions and associated sleeve bearings relative to their peripheral portions and associated support structure. A first operating mechanism serves to rotate the doctor back about the second axis between an unloaded position at which the doctor blade is removed from roll surface, and a loaded position at which the doctor blade is applied to the roll surface. A second operating mechanism serves to impart reciprocating movement to the journals and their sleeve bearings along the second axis.
The reciprocating support provided by the diaphragms is both rigid in directions transverse to the second axis, and flexible in the axial direction. Axial movement is accommodated solely by the flexibility of the diaphragms, without sliding or rolling contact between coacting elements. This eliminates wear associated with axial motion.
These and other features and advantages of the present invention will now be described in greater detail with reference to the accompanying drawings, wherein:
With reference initially to
The doctoring apparatus includes a doctor back 14 having journals 16 aligned on a second axis A2 parallel to axis A1. A doctor blade 18 is supported by a blade holder 20 carried on the doctor back. The journals 16 are supported in bearing assemblies 22 fixed to the support structure 24 of the machine.
As can best be seen by further reference to
As shown in
The intermediate spacer assemblies 32 each comprise a hub spacer element 44 surrounded by a peripheral spacer element 46. As shown in
As shown in
As shown in
One and perhaps more of the spacer assemblies, as indicated for example at 32′, may be thickened. The peripheral spacer of thickened spacer assembly 32′ and/or the thickened end plates 58 receive external cap screws 76 (shown in
Flexible seal elements 68 may be incorporated at each end of the bearing assembly to prevent contaminants from infiltrating into the sandwiched components.
As can best be seen in
The flexure beams 42 are thus free to flex about the support edges 50, 56 to accommodate axial movement of the journal 16, sleeve bearing 26 and hub spacer elements 44 relative to the peripheral spacer elements 46, the latter being fixed relative to the support structure 24.
With reference to
It will be seen from
As shown in
An oscillator 74 of known design, examples being pneumatic, hydraulic and mechanical linear motion devices, is connected to an end of one of the journals 16. The oscillator serves as a second operating mechanism for imparting axial reciprocating movement to the journals 16 and their sleeve bearings 26 along axis A2. This axial reciprocating movement, which typically ranges up to ±⅜ inch about the stroke center, is accommodated exclusively by the resilient flexure of the beams 42 in the diaphragms 30. The diaphragms provide rigid support against transverse deflection of the journals under loads applied transversally with respect to axis A2, yet the beams 42 offer relatively light resilient resistance to an oscillating force applied in the direction of axis A2. Thus, in the example described previously, a relatively modest oscillating force on the order of only about 1500 lbf would be required to axially reciprocate the heavily loaded doctor.
