Recently S.T. Macchine has added in its production program an innovative breast roll shaker that contributes to a more homogeneous distribution of fibres and an increased orientation of the ones in cross direction. With its precise settings, the operators easily adjust shaking stroke and frequency for a best quality production. In the past the breast roll shaker was realised by a crank and slider mechanism.
This operating principle is limited to shaking stroke and frequency, moreover it transmits very high forces to the foundations. This system leads to heavy and costly civil works. The shaker effects are strictly related to the ratio between its frequency and machine speed.
A certain relationship must be maintained between the shaking frequency and the paper machine speed. This determines that as the speed of the machine increases during the years, shaking frequencies are required to increase as well up to values which are not achievable by traditional shakers. Hence the need to create a new shaker technology based on higher dynamics.
As other manufacturers, S.T. Macchine breast roll shaker uses the principle of four eccentric masses divided in two pairs that rotates on their axes and are synchronized. Those masses are mounted on a trolley that is connected through a rod to the breast roll. This spinning creates a force that is transmitted only to the breast roll and not to the foundations.
Thanks to this technology it is possible to reach very high performances: stroke up to 25 mm; frequency from 150 to 600 Hz. Compared with conventional shaking units, the four eccentric masses system, which oscillates freely in horizontal direction, only transfers negligibly small friction and centering forces to the base thanks to the momentum conservation law. The foundation has only to support the dead weight of the unit. In this way no disruptive reaction forces are transferred to the headbox or wire section.
A unique solution
The innovation of new S.T. Macchine shaker can be resumed in three aspects: one motor to move each mass; the motors directly set the masses in motion; vertical position for the masses. There are several benefits on the adopted technical solutions. At first, having a motor per each mass no gear is needed. The direct coupling of the motor with the mass eliminates any joint.
The vertical position of the masses makes our new system independent from any gravitational problem. The whole system is installed on a static base, while the movement is guaranteed by sliding guides. And here there is an additional innovation.
The movement is guaranteed by standard ball rail system once again avoiding any need of hydraulic unit. To be considered that such system can accept some loads due to not perfect alignment between breast roll and shaker axes. A traditional hydraulic rail system does not accept such offset.
Both eccentric mass bearings and linear guides are grease lubricated and connected to an electric unit for automatic greasing. Its design allows you to eliminate any hydraulic control unit. Less moving parts and absence of hydraulic unit lead to higher reliability and less maintenance. Even with four motors, the total installed power is lower than 25 Kw.
The supply is complete with the electric cabinet containing drives and a supervision system for the synchronization of the four axes. The operator interface is by means of a touch panel that allows the local regulation and supervision of the shaker. The touch panel can be connected to the DCS for remote operation. The breast roll support can be set through the traditional, simple and reliable scotch-ply or the innovative sliding bearings.
Sliding bearing supports come together an independent electric greasing unit. As final comments we can say the following: ST Macchine has developed a unique solution where each rotating mass is moved by an independent servo motor and the synchronism between rotors is electronic. The shaker slides over standard ball rail systems.
This allows ST Macchine system to eliminate gears, special joints, oil unit for lubrication and hydrostatic support of sliding trolley and breast roll bearings. They can achieve the same performances of other manufacturers with a simpler device. Energy consumption is limited and maintenance is reduced.
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