DE9210737U1 - Upper knife single holder for a high-speed rewinding cutting machine for longitudinal cutting of material webs - Google Patents

Description

6387/I/ac

Upper knife single holder for a high-speed rewinding cutting machine in particular for longitudinal cutting of material webs

The invention relates to an upper knife single holder for a cutting device for longitudinally cutting material webs, in particular paper webs, according to the scissor-cutting system by flying cutting, e.g. in a high-speed rewinding cutting machine.

The scissor cutting system works with two circular knives, namely an upper and a lower knife. The upper knife is arranged in an upper knife head of an upper knife single holder. The lower knife has a cutting edge with a relief ground, whereby the upper knife dips slightly into the lower knife. During flying cutting, the paper web is guided straight through the cutting zone and separated in the contact area between the upper and lower knives. The upper knife is usually - seen from the inlet side of the material web - slightly inclined to the lower knife; on the outlet side, however, a small amount of play is provided.

The lower blade shaft is driven. The upper blade head can be easily rotated and is driven by the pressing of the upper blade against the lower blade with a lead of about 5%.

For high-speed rewinding cutting machines with large working widths, high running speeds and a large number of cuts (rewinders), individual holders for the upper blades are known, which have a pneumatic switching mechanism for moving the upper blade vertically and horizontally in the direction of the lower blade, whereby the engagement depth of the upper blade (lowering of the upper blade head) as well as the lateral upper blade contact pressure

and the inclination (position of the upper blade to the lower blade) can be adjusted.

It is known that, particularly in the case of compressed air-loaded shear cutting knife holders, high vibration loads or dynamic loads act on the cutting tools as a result of high cutting speeds and can impair their function, the service life of the knives and the quality of the cutting edges. The cutting edges of the knives break off in particular due to the special cutting geometry of the upper knives of this type, which results in the knife service life being too short, the cutting quality being poor and the amount of dust being generated. The rapid wear of the knives requires frequent retooling and thus high downtimes of the cutting machine.

To solve the problem, attempts were made, for example, to provide larger damping masses on the upper knife holder, an anti-twisting device on the holder axis and better ball bearing conditions on the knife head. In addition, a ball guide bush was used to guide the bearing axis for the axial positioning movement of the upper knife.

The service life of the blades depends essentially on the lateral contact pressure between the upper and lower blades during operation. For example, a minimum pressure of 4 bar is required for the vertical and axial adjustment movements, which is reduced to 3 bar during operation using a known method, which is intended to reduce wear.

Although these known means lead to improvements in the service life of the ball bearings and in the wear of the blades, if continuous lubrication is also provided for the sliding parts, it has been found that the improvements are not sufficient; to solve the problem, it has therefore been proposed to also eliminate the causes of the vibrations in the machine concept by lubricating the entire cutting section of the cutting machine in

a separate system with damping units.

The wear of the upper blades occurs due to material removal in the overlap area. The cause of the material removal is also due to the slip between the upper and lower blades. However, slip between the upper and lower blades is desirable in order to create a regrinding process. If the contact pressure is set too high, the cutting tools will fail prematurely.

The object of the invention is to create a pneumatically switched upper knife single holder for a high-speed rewinding cutting machine in particular, which guarantees with simple means long service life of the knives with correspondingly long regrinding intervals, so that in particular perfect cutting edges with low cutting dust generation over a long work cycle, i.e. in particular with low downtimes due to knife changes, and higher output rates at lower costs can be guaranteed.

This object is achieved by the features of claim 1. Advantageous further developments of the invention are characterized in the subclaims. The invention is explained in more detail below using the embodiment shown in the drawing. They show:

Fig. 1 shows a schematic side view of an upper knife single holder ;

Fig. 2 a longitudinal section through the upper cutter head; Fig. 3 a pressure/force diagram for explanation

the function of the adjusting device according to the invention;

Fig. 4 shows another pressure-Z-force diagram to explain the function of the adjusting device according to the invention.

-A-

The upper knife single holder according to the invention (hereinafter referred to as knife holder) consists essentially of a lowering device 1 and a knife head device 2. The lowering device 1 is not part of the subject matter of the invention; it is constructed as usual and has, for example, a vertically aligned lowering piston rod 3 and a lowering piston guided in the pressure chamber of a pressure housing 4 against a return spring and acted upon by a pressure medium. The pressure chamber of the pressure housing 4 is supplied with pressure medium via a pressure medium supply device 5. A holding block with, for example, a prism guide for holding and adjusting the knife holder on a knife bar of a roller cutting machine (not shown) is usually located on the pressure housing 4.

The knife head device 2 is located at the knife-side lower end of the lowering piston rod 3. It has a support shaft 7 that is guided horizontally in a setting housing 6 in the direction of the double arrow 14, the setting housing 6 being arranged so as to be fastened to the lowering piston rod 3.

A hub 10, which can freely rotate about an axis of rotation 36 that passes through the support shaft 7, is mounted on the end area of the support shaft 7 on the knife side via ball bearings 9. The hub-side annular groove wall 11a has a radially external, conical inclined surface 11a to which the upper knife 11b is arranged and fastened in a replaceable manner. The inclined course of the surface 11a means that the upper knife 11b rests on the hub 10 over a larger area than in the case of a groove wall that runs continuously perpendicular to the wheel shaft 7. The advantage of the larger contact surface for the upper knife 11b is that there is a reduction in fretting corrosion, i.e. less abrasion between the hub 10 and the upper knife 11b.

An elastic, ring-shaped rubber element lld is arranged on the wall lic opposite the groove wall lla, the thickness of which is selected such that it borders on the upper blade 11b.

The rubber element lld compensates for the lateral runout of the upper blade 11b, reduces fretting corrosion and dampens vibrations.

The support shaft 7 guided in the bearing chamber 13 of the adjustment housing 6 is supported radially on, for example, two support rings arranged at an axial distance from one another, e.g. Teflon rings 15. In the area between the support rings 15, a vertical threaded hole 16 is made in the wall of the adjustment housing 6, in which a grub screw 17 is located that is accessible from the outside. The lower end area of the grub screw 17 freely engages in a longitudinal groove 18 made in the outer surface of the support shaft 7 and extending parallel to the axis in such a way that the movement of the support shaft 7 in the direction of the double arrow 14 is not hindered. The function of the grub screw 17 is explained further below.

The end of the support shaft 7 facing away from the hub 10 is connected to the front end of an adjusting piston rod 19, which extends freely through a hole 23 in the rear wall 20 of the adjusting housing 6 and axially into the adjusting housing 6 and is guided with its piston 8 in the pressure chamber of a pressure cylinder 37 of a double-acting piston-cylinder device 21. The pressure cylinder 37 sits axially in a pressure-medium-tight manner above the hole 23 on the rear wall 20 of the adjusting housing 6 and has a buffer pressure chamber 22 and a adjusting pressure chamber 43.

Preferably, an elastic coupling is arranged on the end of the adjusting piston rod 19 on the cutter head side, which extends into the bearing chamber 13 of the adjusting housing 6, which has an elastic buffer 25 between two coupling heads 26, 27 made of a rigid material, with the piston rod 19 being located on the rear coupling head 26 and a fastening pin 28 on the front coupling head 27. The fastening pin 28 is detachably fastened in an axial blind bore 29 in the rear end area of the support shaft 7. The detachable fastening consists of an annular groove 30 provided in the fastening pin 28, into which a grub screw 31 engages, which sits in a wall threaded bore 32 of the support shaft 7.

A bore 33 is provided in the wall of the adjusting housing 6, axially aligned with the threaded bore 32, so that the grub screw 31 is accessible from the outside using a tool.

The purpose of the elastic buffer 25 is to provide an elastic coupling of the support shaft 7 to the adjusting piston rod 19, in particular with the aim of compensating for misalignment between the support shaft 7 and the piston rod 19 and thus preventing damage to the seals of the cylinder 37. The elastic coupling also serves to transmit the force generated in the pressure chamber 43 to the support shaft 7.

The rear wall 20 is expediently detachably attached to the housing side walls 35 of the adjustment housing 6 using screws 34 parallel to the axis. By loosening the grub screws 17, 31, the support shaft 7 with the hub device can be pulled forwards out of the adjustment housing 6. By loosening the screws 34, the rear wall 20 with the piston-cylinder device 21 can also be removed from the adjustment housing 6.

The pressure chambers 22, 43 of the piston-cylinder device 21 are also supplied with pressure medium by the pressure medium supply device 5, whereby the buffer pressure chamber 22 is sealed off from the bearing chamber 13 of the actuating housing 6 in a pressure medium-tight manner. For this purpose, the base 38 of the pressure cylinder 37 adjacent to the rear wall 20 has a sealing ring mounted in an annular groove 39 on the rear wall, which rests on the piston rod 19, which freely passes through a passage 41 adapted to the diameter of the piston rod 19. The piston 8 sits firmly on the free end of the piston rod 19 and is located in the area of the cylinder cover 42, whereby the actuating pressure chamber 43 is formed between the cylinder cover 42 and the piston 8. A connection bore 44 leads to the buffer pressure chamber 22 and a connection bore 45 leads to the setting pressure chamber 43, through which pressure medium can be fed from the pressure medium supply device 5 into the pressure chambers 22, 43 via a pressure medium line 46 or 47 (see Fig. 1).

The end face of the piston 8 opposite the cylinder cover 42 is chamfered (at 48) so that pressure medium can be applied to the rear of the piston via the connection bore 45.

The function of the adjusting device according to the invention will now be explained in more detail with reference to Figs. 3 and 4.

According to the invention, the contact force F _A is set as a differential pressure between the pressure applied in the actuating pressure chamber 43 and in the buffer pressure chamber 22 in order to ensure a control of the driving force which is independent of the friction force F _R and the mass inertia force F _M which counteract the driving force F _Ä .

If the adjusting device is initially considered to be ideally frictionless and massless, the contact force F _A generated by pressure application in the adjusting pressure chamber 43 is determined as follows:

F _A = &Rgr;,«, A ₁ (1),

where P ₍₄₃₎ is the pressure prevailing in the adjustment chamber 43 and A ₁ is a constant. A pressure/force curve based on formula (1) is shown in the diagram in Figs. 3 and 4 by the characteristic curve Kl.

Contrary to the assumed idealized conditions, in the real case, as stated above, a friction force F _R and a mass inertia force F _M must be expected, which counteract the setting force F _A and must be overcome to generate a positive setting force F _A as follows:

Fa ⁺ _FR + _FM = P ₍₄₃₎ -A ₁ (2).

Under these conditions, it is no longer possible to control the contact pressure F _A in the required precise manner, since the friction force F _R is present as non-constant static and sliding friction, whereby the mass inertia force F _M is also influenced by the friction force F _R.

By introducing an additional force F, which can be precisely defined and is generated in the buffer pressure chamber 22, an exact control of the contact pressure can be achieved. A corresponding pressure/force curve is shown as characteristic curve K2 in Fig. 3 and 4. The force F is significantly greater than the friction force F" and the mass inertia force F _M . The condition for the force F is:

F >> F _R , F _M (3).

In other words, it is necessary that the additional force F is significantly greater than the friction force F _R and the mass inertia force F _M . By applying the additional force F in the buffer pressure chamber 22, the friction force F _R and the mass inertia force F _M can be compensated to such an extent that these forces can be neglected. When setting the characteristic curve K2, it is important to ensure that the slope of this characteristic curve is not chosen to be too steep in order to ensure that the required contact force F _A can be adjusted over a large pressure range (see Fig. 3).

The derivation of the contact force F _A is explained below, taking into account the additional force F due to pressure applied in the buffer pressure chamber 22. The following diagram can be drawn up vectorially:

The following equation corresponds to this diagram:

Fi ⁺ F _R + F _M + F _A = F ₂ (4),

where the following equations apply to the forces F _R , F _M , F ₁ and F ₂ :

F _R = m ■ g ■ u (5)

F _M = m ■ a (6)

F ₁ -Jc ₁ -X (7)

F ₂ = k ₂ · χ (8),

where the constants mentioned in these equations are defined as follows:

k: spring constant

u: friction factor

m: mass

&khgr;: Path

g: gravitational constant.

The forces F ₁ and F ₂ are path-dependent, i.e. dependent on the path x. Such a path dependence is unfavorable and is eliminated by the following agreement:

F ₁ = Ic ₁ · X ₁ - A ₁ · P ₁ (9)

F ₂ = k ₂ · X ₂ = A ₂ · P ₂ (10).

Since F _R ; F _M << F ₁ ; F ₂ , F _R and F _M (11)

holds, equations (9) and (10) can be shortened as follows:

F ₁ + F _A = F ₂ (12)

F _Ä = F ₂ - F ₁ (13).

If the piston diameter,

di the piston rod diameter

P ₁ and P ₂ denote the pressure in the chambers 22 and 43, the formula (13) can be written as follows:

₁ (14) · P ₁ ) (15) P ₁ ) (16).

F _A = Ir ■ &ngr; " ^k i ^x i = _A2 P ₂ -A ₁ I F _A - «4 · (since ² ■ _P2 - (since ² - Tuesday ² ) F _A = *4 &bull; (since ² ( _P2 - Pi) + Tue ²

Preferably, the piston diameter da and the piston rod diameter di should be selected so that the contact force F _A can be adjusted over the largest possible pressure range.

Claims (18)

6387/I/ac claims 1. Upper knife single holder for a cutting device with two circular knives for longitudinal cutting of material webs, in particular paper webs according to the scissor cutting system by flying cutting in a roll cutting machine, in particular in a high-speed rewind cutting machine with a preferably pneumatically switched lowering device (1) and a pneumatically switched knife head device (2),
marked by a) a double-acting piston-cylinder unit (21) having a buffer pressure chamber (22) and a setting pressure chamber (43) in a pressure cylinder (37) for setting the knife of the knife head device (2) and b) a pressure medium supply device (5) suitable for generating and maintaining different pressures in the two pressure chambers (22,43) during the setting state of the knife of the knife head device (2). 2. Upper knife single holder according to claim 1,
characterized, that the knife head device (2) has a hub (10) which is freely rotatable on a support shaft (7) which is mounted in a support housing (6) and can be pushed back and forth, on which the circular disk-shaped upper knife (lib) is seated, the end of the support shaft (7) facing away from the hub (10) being connected to a piston rod (19) of the piston-cylinder unit (21). 3. Upper knife single holder according to claim 2,
characterized, that the piston-cylinder unit (21) is arranged on the rear wall (20) of the support housing (6), wherein the piston rod (19) freely passes axially through a hole (23) in the rear wall (20). 4. Upper knife single holder according to one or more of claims 1 to 3, characterized,
that the buffer pressure chamber (22) of the piston-cylinder unit (21) is sealed in a pressure-tight manner to the bearing chamber (13) of the adjusting housing (6). 5. Upper knife single holder according to claim 4,
characterized, that a base (38) adjacent to the rear wall (20) is provided in the pressure cylinder (37) of the piston-cylinder unit (21), which has a sealing ring (40) mounted in an annular groove (39) on the rear wall, which rests on the piston rod (19) which freely passes through a passage (41) in the base (38) adapted to the diameter of the piston rods (19). 6. Upper knife single holder according to one or more of claims 2 to 5, characterized,
that the piston (8) of the piston-cylinder unit (21) sits firmly on the free end of the piston rods (19) and is located in the region of the cylinder cover (42) of the piston-cylinder unit (21), wherein the actuating pressure chamber (43) is formed between the cylinder cover (42) and the piston (8) and the buffer pressure chamber (22) is located between the bottom (38) and the piston (8). 7. Upper knife single holder according to claim 6,
characterized, that a connection bore (44) penetrating the cylinder wall of the pressure cylinder (37) leads to the buffer pressure chamber (22) and a connection bore (45) penetrating the cylinder wall of the pressure cylinder (37) leads to the setting pressure chamber (43), through which pressure medium is fed from the pressure medium supply device into the pressure chambers (22, 43) via a pressure medium line (46 or 47). 8. Upper knife single holder according to one or more of claims 1 to 7, characterized,
that the adjusting housing (6) is located at the lower end of a lowering piston rod (3) of the lowering device (1). 9. Upper knife single holder according to one or more of claims 1 to 8, characterized,
that the support shaft (7) carries the hub (10) on the end region protruding from the adjustment housing (6) via ball bearings (9), which has an annular groove (11) in which the circular disk of the upper blade is arranged in a replaceable manner. 10. Upper knife single holder according to claim 9,
characterized, that the support shaft (7) guided in the bearing chamber (13) of the adjusting housing (6) is supported radially on support rings (15) arranged at an axial distance from one another, e.g. made of Teflon. 11. Upper knife single holder according to claim 10,
characterized, that in the area between two support rings (15) a vertical threaded hole (16) is made in the wall of the adjusting housing (6), in which an externally accessible Grub screw (17) is seated, the lower end region of which freely engages in a longitudinal groove (18) extending parallel to the axis in the outer surface of the support shaft (7) in such a way that the movement of the support shaft (7) in the direction of the double arrow (14) is not hindered. 12. Upper knife single holder according to one or more of claims 9 to 11, characterized,
that the end of the support shaft (7) facing away from the hub (10) is connected to the front end of the adjusting coupling rod (19) via a flexible coupling (24). 13. Upper knife single holder according to claim 12,
characterized, that the elastic coupling (24) has an elastic buffer (25) between two coupling heads (26, 27) made of a rigid material, with the piston rod (19) located on the rear coupling head (26) and a fastening pin (28) on the front coupling head (27). 14. Upper knife single holder according to claim 13,
characterized, that the fastening pin (28) is detachably fastened in an axial blind bore (29) in the rear end area of the support shaft (7). 15. Upper knife single holder according to claim 14,
characterized, that for the detachable fastening in the fastening pin (28) an annular groove (30) is provided, into which a grub screw (31) engages, which is seated in a wall threaded hole (32) of the support shaft (7), wherein a hole (33) is made in the wall of the adjusting housing (6) axially aligned with the threaded hole (32), so that the grub screw (31) is accessible from the outside with a tool. 16. Upper knife single holder according to one or more of claims 2 to 15, characterized,
that the rear wall (20) of the support housing (6) is releasably fastened to the housing side walls (35) of the adjustment housing (6) with screws (34) arranged parallel to the axis. 17. Upper knife single holder according to one or more of claims 2 to 16, characterized,
that the hub (10) has an inclined upper knife support surface (Ha). 18. Upper knife single holder according to one of claims 2 to 17, characterized in that that the upper blade (Hb) is braced against the hub (10) by means of an elastic rubber element (Hg).