Doctors for Cleaning Rolls and Cylinders in Paper Machines

Doctors are essential for cleaning rolls and cylinders in paper machines, ensuring optimal performance and longevity. Each doctor is specifically constructed for a particular application in a paper machine (PM) to meet all given requirements, mainly roll cleaning. Relocating a doctor to another position is not advisable, as it can lead to improper functioning and potential roll damage.

Types of Doctors

1. Cleaning Doctors: Remove contaminants from roll surfaces.
2. Creping Doctors: Used in tissue production to create a crepe effect.
3. Breaking Doctors: Separate the paper web from the roll surface.

Design

Doctors are delivered with various blade loading mechanisms:

• Self-weight and Manual Control: Blade pressure is applied by the doctor’s own weight, manually adjustable.
• Pneumatic Cylinders: Blade pressure is controlled pneumatically.
• Hose Blade Holders: Air hoses along the blade length provide pressure and tilting.
• Pneumatic Oscillation: Enhances scraping effect using an oscillation device driven by an electric motor with an eccentric pin and gearing device. Lubrication tubes can be included.

Control Systems

• Manual Control: Pressure applied by self-weight and adjusted manually.
• Pneumatic Control: Pressure and tilting managed by air cylinders or air hoses, connected to a control box or PM control panel.
• Pneumatic Switchboard: Allows manual operation and pressure setting via a reducing valve, with pressure values indicated on the control box.

Main Parts

1. Doctor Beam (1): The main structural component.
2. Blade Holder (2): Holds the doctor blade.
3. Blade (3): The actual scraping element.
4. Pins and Bedding (4): Secure the doctor assembly.
5. PM Fixing Consoles (5): Attach the doctor to the paper machine.

Material Options

• Fully Stainless Steel: Suitable for wet parts of the machine.
• Stainless Steel Parts with Covered Carrier: For enhanced durability.
• Common Steel with Anticorrosive Paint: Used in the dry parts of the machine.

Material choice depends on customer requests or standard combinations of stainless and common steel. Oscillating electric motors can be provided with protection up to IP 68, and pneumatic control cylinders are made from standard aluminum or non-corroding steel.

Accessories

• Frequency Converter: For adjusting the speed of the oscillating device.

Scope of Delivery

• Construction design and devices as per the main parts description.
• Parts for overall control elements connection for the PM control.
• Independent control panel.

Advantages

• Efficient and Economic Scraping Function: Ensures thorough cleaning with minimal waste.
• Elimination of Roll Surface Damage: Protects roll surfaces from damage during cleaning.
• Longer Intervals for Regrinding Roll Surfaces: Reduces the frequency of maintenance.

These features ensure that doctors are highly effective in maintaining the cleanliness and functionality of rolls and cylinders in paper machines, thereby enhancing the overall efficiency and longevity of the equipment.