Reel-up

The invention relates to a reel-up for the continuous reeling up of a fibrous web around a reel spool into a machine reel, in which reel-up there is a reeling drum, whereby a nip load is formable between the machine reel and the reeling drum, and which machine reel is movable in relation to the reeling drum according to the growth in the diameter of the machine reel by means of a reeling carriage and locking levers of the reeling carriage.

The reel-up is a device which reels a material produced as a continuous fibrous web into the reel form as a machine reel. In the production process of the fibrous web, the reel-up is usually the first partial process in which the continuous production is broken off to be continued in sequences. The machine reel is formed around a reel spool operating as the reeling core i.e. a fibrous web being on one machine reel has a start and an end. A continuous trend in the field is the steady ihcrease in the size of machine reels, which causes a continuous development requirement for reel-ups. The dimensioning of the reel spool in practice specifies the maximum size of the machine reel. However, as the environment is dynamic and the fibrous web is a reelable material susceptible to various faults, the task of the reel-up as the maintainer of the efficiency of the paper or board machine is extremely significant. A reason for the continuous increase in the size of machine reels is the desire to obtain fewer starts and ends than earlier in the production of the fibrous web which impede or disturb the production and decrease the efficiency.

Modern reel-ups generally employ hydraulic actuators for producing motions and forces. The actuators gain their driving power from a hydraulic power unit in the form of pressure medium i.e. pressurised hydraulic oil. Typical targets are e.g. various carriage motions, levers, such as locking jaws, rotating motions, such as rotating a primary reeling device onto rails etc. In older pope reel-ups, pneumatic cylinders were also used as actuators. A disadvantage of using pneumatics is the low power level obtained from the actuators which is not usually sufficient in modern reel-ups. Also, the size of the actuator grows along the power requirement, and hydraulic actuators have in practice replaced pneumatic actuators in reel-up applications due to their small size and high power-production capacity.

An object of the invention is to further develop the technique of the reel-ups such that their operating reliability would improve from before and the maintenance re-

quirement of operations or actuators would decrease. An object is also to provide a reel-up which would be robust and durable in sudden overload situations, among others. Furthermore, an object is to provide an environmentally-friendly solution the possible environmental hazards during the operation and the environmental load produced during the lifetime of which would be particularly small.

In the conte>ct of describing this invention, the following terms are used for facilitating the description: the machine direction (MD) is referred to as the x direction, the cross direction (CD) is referred to as the y direction and the elevation is referred to as the z direction. The incoming direction of the fibrous web is referred to as the upstream direction and the outgoing direction of the fibrous web is referred to as the downstream direction. A reeling core is referred to in this context as a reel spool, but it could be called a reeling shaft as well.

It is characteristic of the invention that the position and motion of the machine reel in relation to the reeling drum are established by means of electric actuators.

In the context of this specification, an electric actuator refers to such a device in which the power and motion of the actuator is provided electrically i.e. such that electric energy is converted to power directly on the actuator. Thus, electric energy is not first converted to pressure medium and then conveyed to the actuator.

The invention will now be described in more detail with reference to the accompa- nying figures in which:

Fig. 1 shows a reel-up and an actuator embodiment of its reeling carriage and

Fig. 2-shows a locking lever embodiment of the reeling carriage;

Fig. 1 shows an embodiment in which moving a machine reel 6 being formed around a reel spool 5 is arranged by means of electric actuators. Bearing housings 57 of the reel spool 5 being the core of the machine reel 6 are gripped with locking levers 70a, 70b which are further pivotedly connected to reeling carriages 7. The reeling carriages 7 are transferred in relation to a frame 20 with the electric actuator, a reeling carriage actuator 71 , which in this figure comprises a torque motor 710 as the motor unit and a gearwheel 711 and a gear rack 712 as the transfer unit. An advantage of the electric actuator compared to the hydraulic actuator is that there are several possible ways for an electric actuator located on a moving base to convey the energy required by the actuator.

Another advantageous embodiment of the invention is arranging the operation of the locking levers 70a, 70b of the reeling carriage 7 controlling and moving the machine reel with electric actuators. As it is seen in Fig. 2, the locking levers 70a, 70b hold to the bearing housings 57 of the reel spool 5 operating as the core of the machine reel and tend to the reel spool 5 being in an exactly correct position in relation to the other structure and the reeling drum 10. An example _. of the other structure is a possible centre drive 8 (not shown in the figures) which is usually connected to a coupler 59 at the end of the reel spool 5. In such a case, the reel spool 5 and a coupler 89 of the connectable drive 8 are quite accurately coaxial, whereby their rotation axis is the same. The structure of the couplers 59, 89 has usually been designed such that they allow a little angular variation. The locking levers 70a, 70b ensure the positioning of the reel spool at the accurate point, whereby the coupler 89 can be connected to or disconnected from the reel spool.

A desired characteristic of both the first embodiment and the second embodiment is the swift, exact and precise motion of the actuator. This is an advantage of electric actuators compared to hydraulic actuators. In these embodiments, usable electric actuators most often have an integral arrangement which knows the distance travelled in each situation or the number of increments or equivalent. By comparing the equivalent actuators of the driving and tending side of the reel-up and state values received from them, a motion which remains the same on both sides can be performed with great reliability. If implemented hydraulically, there should be a relatively complex arrangement where both pressure and volume flow had to be known and additionally possibly an electric sensoring of some kind for specifying the position. With the latter is compensated an uncertainty factor caused by possi- ble leaks. Of electric actuators, this characteristic is particularly well realised with servo/stepping motors and equivalents.

According to some embodiments, the electric actuator comprises a transfer unit and a motor unit. Then, the characteristics of the unit producing power and the unit producing the motion/transfer distance can be balanced in an optimal way from the viewpoint of operation. Advantageously, said motor unit is a servo motor, a torque motor, a linear motor or equivalent motor capable of continuous torque or thrust without motion. The actual reeling-up is a relatively slow process compared to the conventional motion speeds of electric actuators, because the radius of the machine reel increases on each cycle only about the thickness of the fibrous web W. Then from the viewpoint of the motor unit, the motor unit has to be able to produce torque or thrust without motion. Furthermore, said transfer unit is a linear drive

providing a linear motion, such as a ball-race screw, a screw jack, a roller wheel or equivalent, or a drive providing a rotating motion, such as a planetary gear, a cog wheel gear, a ring gear or equivalent. Of future technologies, particularly the linear motor producing power without motion, operating at good efficiency is well suited for an actuator.

Advantageously, a resetting overload protection is arranged in these above- described embodiments into connection with the electric actuator either separately or integrated in the structure or operation. In the context of this specification, the resetting overload protection refers to such a structural arrangement which en- ables the yielding and resetting in its original position of the structure without breaking, when the load is changed in the situation from a normal load until a specific limit value of overload. Said limit value of overload is for large part a dimensioning criterion affecting the lifetime of the structure, but also a factor important from the viewpoint of functionality and the quality of the machine reel being formed. In reel-ups, overload situations are often created when the fibrous web W breaks, whereby through the nip between the machine reel 6 and the reeling drum 10 goes a bundle many times folded formed of the fibrous web W. The nature of such an overload situation is very fast, the durations of only a few milliseconds. By means of the resetting overload protection, the quality of the fibrous web already on the machine reel can be maintained good. This is because the structure yields just suitably and the force caused by the bundle cannot ruin the fibrous web on the machine reel and prevents the damaging of the mechanical structures of the reel- up.

In the first embodiment, in each reeling carriage 7 is connected the actuator 71 which advantageously comprises also the resetting overload protection. The reeling carriage 7 with its required structures, possible drives etc. is most often a unit of relatively heavy structure. Then, the great mass also provides a great inertia mass which will not easily change its position in overload cases but some other point will yield. At this point, it is then advantageous to employ an active element as the overload protection, because the active element can well be adjusted in most situations.

In the second embodiment, the locking levers 70a, 70b can only yield due to the above reason for quite a limited amount, i.e. in order not to damage the coupler 59, 89 supplying the centre moment between the reel spool 5 and the drive 8 in an overload situation. In this context, the locking lever on the upstream side is designated with reference number 70a and the locking lever on the downstream side

with reference number 70b. In this target, an arrangement is well applicable in which the open-closed motion of the actuator i.e. locking lever is performed electrically. Furthermore, in this electrically implemented motion is advantageously arranged an overload protection which enables the controlled opening of the lock- ing lever such that the structures will not be damaged in a possible overload situation. Additionally, in connection with the electric actuator there can be both a passive and an active overload protection which can be arranged e.g. with increments such that the passive element tends to small overloads and the active element to larger overloads. A construction can be e.g. choosing the actuator of the locking lever 70b on the downstream side based on a servo/torque motor, whereby the servo/torque motor itself identifies the overload and yields at the maximum for the allowed amount. In most cases when a bundle is going through the nip N, the rotation axis of the machine reel tries to go away from the reeling drum. Then, the direction is towards the locking lever 70b on the downstream side which tries to transfer in the direction of the open position. On the other hand, an equivalent situation during the return motion occurs with the locking lever 70a on the upstream side.

The overload protection according to an embodiment of the invention comprises a passive element. Most advantageously, this passive element is such that there is a clear increment between the normal load and the overload. Then, the element will not in practice yield at all from the effect of normal load but until the load exceeds a set limit value. In principle, the arrangement employs some kind of pretension force which is set to correspond the lower limit value of overload. This way, the structure has an unambiguously accurate response in the transmission of nip load but extremely fast and precise response capability in an overload situation. For providing the fast response capability, the passive element is advantageously located as close as possible to a joint surface between the reel spool operating as the core of the machine reel and the structure of the reel-up holding onto it. This embodiment is particularly well suited in connection with the locking levers 70a, 70b described in the above chapter. These locking levers 70a, 70b are directly in contact with the bearing housing of the reel spool and are thus alongside the reeling drum 10 the first part of the reel-up 'feeling' the overload. The passive element can be implemented at the end of the locking lever 70a, 70b holding the bearing housing 57 or into connection with a pivot point or actuator of the locking lever.

The overload protection according to an embodiment of the invention comprises an electric active element. This is most advantageously implemented by arranging

an electric overload protection in means keeping the machine reel in place or means responsible for the transfer of the machine reel or means producing nip load, most advantageously related to the operations of the reeling carriage 7. This can be e.g. a moment Iimiter or equivalent arranged into connection with the servo motor. When designing the structure of the overload protection connected to the means producing the nip load, the elasticities of the other structure should be considered. Often, these means responsible for the transfer are not in the immediate vicinity of the above-described joint surface, whereby the elasticities of the other structure affect the response time of the operation of the active element, which is affected by, inter alia, masses of structures, moments of inertia, various lever arms etc.

Furthermore according to an embodiment, the overload protection comprises a passive element and an electric active element connected in series. Then, the response time is at its maximum simultaneously as the ability of the structure to re- spond to different shapes of overload profiles is particularly good. In principle, the nip load of the reel-up is most often a quantity proportional to the rotational angle of the machine reel or the reeling drum. A bundle causing a load peak can go through the nip at once and fall then onto the floor, it can remain fast on the surface of the machine reel or the reeling drum. Furthermore, the shape of the bundle can be sharp-edged, gentle-edged etc. These all cause a slightly different load effect on the structure. The ability of the passive and active elements to respond to these situations is somewhat different, whereby the most optimal embodiment to the applicant's understanding is obtained by connecting said elements in series. In practice, this can be arranged e.g. such that in connection with the locking levers there is a passive element as the overload protection which enables a small motion, smaller than the elasticity allowed by the coupler 59, 89. Then, the small forced displacements caused by overload make the locking levers 70a, 70b yield. The forced displacement being larger than the one allowed by the locking levers 70a, 70b, an active element connected to the actuator 71 of the reeling carriage 7 tends to the rest of the required opening motion. The control circuit of this active element gets an advance warning as the passive element starts to operate, whereby the operation of the structure from the viewpoint of the unity is particularly well balanced.

According to a further embodiment of the invention, all hydraulic actuators of the reel-up are replaceable with electric actuators in accordance with the idea described by the invention. Then, the reel-up thus substantially comprises only elec-

trie actuators and the reel-up is thus substantially without hydraulics. Elasticity in sudden overload situation has been considered an advantage of hydraulic actuators. The elasticity is not still optimal in fast strokes, because the inertia of the system limits the amount of elasticity. Mostly, the elasticity comes from e.g. the elas- ticity of the hoses of the hydraulic circuit. A reel-up without hydraulics combines in a new way a possibility to implement engineering by means of mechanics and servo/electric motors. This makes it possible to integrate passive elastic elements in the structure for ensuring that no malfunctions occur e.g. in fast sudden overload situations. Also, the overload protection (moment limitation) of the servo/torque motors can be effectively utilised. Other possible targets replaceable with electric actuators are, inter alia, the transfer of empty reel spools from the storage towards the starting point of reeling, the motions of various rider roll constructions, the actuators of various other devices related to the machine reel change, the reel-up comprising a moving reeling drum 10 its moving devices etc.

Reference numbers used in the figures:

1 reel-up

10 reeling drum

20 frame 5 reel spool

57 bearing housing

59 coupler

6 machine reel

7 reeling carriages 70a locking lever

70b locking lever

71 reeling-carriage actuator

710 torque motor

711 gearwheel 712 gear rack

8 drive 89 coupler

F nip load W fibrous web.