GB2255079A

GB2255079A - Device for floatingly guiding and/or conveying webs or sheets

Info

Publication number: GB2255079A
Application number: GB9208960A
Authority: GB
Inventors: Hilmar Vits
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1991-04-25
Filing date: 1992-04-24
Publication date: 1992-10-28
Anticipated expiration: 2012-04-24
Also published as: DE4113465A1; GB9208960D0; DE4113465C2; GB2255079B

Description

2 2 -) so -,) Device f or f loatingly guiding and/or conveying webs or

sheets ' The invention relates to a device f or f loatingly guiding and/or conveying webs or sheets, said device comprising a plurality of blowing nozzles provided in the boundary wall facing the webs or sheets, for the blowing-A-ir supply each of said blowing nozzles featuring a guiding surface, said guiding surface being inclined towards the 10lowing-air source and cut around a tongue-shaped segment in a semicircular-like manner.

SucIr., a device is known from the German Patent 19 07 083.

By mea-ns of such a device the web or the sheet is held at a very small distance away from the boundary wall, when being guided and/or ccnveyed, as the flow of the air source has a strong sucking influence on the web or the s.n.eet, thus reducing sa-Ld distance to a min-imL= as a result of the discharge of the blowing air.

G.Iven a unilateral arrange=nent either above or below the material web or sheet plane, such a device is able to hold the web or the sheet in a very stable position, as depending on the distance of the web the blowing air which escapes in a fan-like diverging -manner has either an attracting or a repelling eff feet on the material web until the forces are balanced. The direction of the e-scaping blowing-air stream has a stabilizing effect on the distance of the material web or the sheet f rom the boundary wall; in arddition, it exerts a force on the plane of the web or the sheet, a force which can be used for laterally tensioning the web or for conveying the sheet.

Disadvantageous w:Lt'-r- this device is the risk that sharp edges of the tongue-shaped segment may tear the web or the sheet to be conveyed. True, the sucking force and the pressure are balanced; however, they are not evenly distributed. The tongue-shaped segnient is also the segment which has the greatest vacuum. Friction, braking or adhesion effects of the web or the sheet on the tongue-shaped segment may sometimes prevent the conveyance starting from a standstill.

Therefore it is the object of the invention to improve a device of the type mentioned above in order to achieve a reliable guidance w-d/or conveyance of the web or the sheet, without damaging thke material. Moreover. it is aimed at reducing the energy cc-nsumption.

According to the invention this object is achieved in that the center of the curvature of the tongue-shaped segment lies in the center of the guiding sur.,.ace and that said guiding surface is concentr -f-- ally surrounded by a circular depression.

The combination of features according to the invention favourabLy influences the rel-Jabi-14A. ty of the web or the sheet in two ways. Cn the one hand, the tongue-shaped segment extending up to center of the guiding surface creates a guiding-surface region which permits the discharge of the blowing air around said tcngue-shaped segment, which represent region of more thar_ 180 degzees, without turbulences occurring at the beginning and at the end of the (manufacturing-caused) cutting edge considerably!Limiting the angle of the escaping blowing air, as _Js the case in the state of the art. The edge region of thae tongue-shaped segment of the state-of-the-art a device, which causes problems when contacting the material web, c moved away from said material web. On the other hand, moving the active blowing- air area, formed by the tongue-shaped segment and the guiding surface, into the depression ensures a safety zone with. respect to the material web so that the risk of tearing is elimiinated, without limiting the blowing-air effect.

The sucking effect is increased if the depression is designed as a recess having the shape of a truncated cone the marginal inclinat-io.-- of which is flatter than the inclination of the guiding surface. This produces a sufficient distance of the active area of the blowing nozzle with respect to the material web and, at the same time, guarantees a good transfer of the blowing-air jet from the guiding surface to the plane of the boundary wall.

Preferably the inclination of the guiding surface is appoximately double the inclination oil the depression.

The invention is hereinafter explained with reference to the drawing representing a specimen embodiment.

Fig. 1 is a cross-section through the device of the invention in the area of a blowing nozzle, and Fig. 2 is a top view of the detail shown in Fig. 1.

The blowing-air box of Fig. 1, shown in cross-section, comprises a boundary wall 1 above which, and at a slight distance thereto, there is provided the web material to be guided and the sheet material to be conveyed, respectively. The boundary wall is provided with a blowingnozzle orifice (reference numeral 2). Said blowing nozzle features a recess 5 having the shape of a truncated cone and a diameter d (Fig. 2). The outer cylindrical surface of the truncated cone and the plane of the boundary wall 1 form an angle V The distance between the bottom of the recess 5 and the boundary wall 1 is v.

A semicircular-like segment 3, in its function as a guiding surface, Is cut into the circular area of the center part of the depression 5 the diameter of which is m, thus producing a aped segment 4 in the center of said depression. The tongue-s... 0 the tongue-shaped segment 4 bears the reference symbol wi dth oA i. As appears from Fig. 1, the semicircular-like segment 3 surrounding the manufacturing-caused cutting edge is sloped with respect to the flat tongue-shaped segment 4 so that the thus formed gulding surface describes an angle of inclination ry with res-Dect to the boundary wall 1.

The thickness of the tongue-shaped segment 4 is s. Below said tongueshaped segment 4 there is provided a slitted orifice resulting from the blanking the width of which bears the reference symbol w.

Fig. 1 s.--cws that the angle of inclination 0 of the guiding surface --is double the magnitude oil the angle p which is formed by the ou--er cylindrical surface of the truncated-cone recess 5 and the boundary wall 1. The width i of the tongue-shaped the segment 4 is smaller than one f if th of the diameter d ol depressicn; it is approximately half the diameter m of the guiding-surface area.

The thickness s of the tongue-shaped segment 4 is selected such thaz it is as great at most as the depzh of the depression v and the depth of the guiding-surface area w, respectively.

Or. the cne hand, the embodiment of the blowing nozzle permits the guiding of the web and/or the conveying of the sheet without the risk of a direct contact between the web or the sheet and the edges of the tongue- shaped segment 4; on the other hand, it ensures a reliable aerodynamic operation as the blowing-air jet - leaving t"te slitted orifice having a width w floods approximately half cr riore than half of the outer edge of the depression, on all sf-des thereof, in direction of the boundary wall 1, a vacuum ex-isting in said depression, and the blowing-air stream of the adjacent blowing nozzle reaches up to the outer edge of the depression where said blowing-air stream and the vacuum are balanced if-, viewed from center to center, the distance t of the blowing nozzles is approximately five times as great as the width of the tongue-shaped segment.

It will be appreciated that the above invention has been described by way of example only and that changes may be made without departing from the scope of the inventiop.

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Claims

A device for f loatingly guiding and/or conveying webs or sheets, comprising a plurality of blowing nozzles provided in a boundary wall facing the webs or sheets, each of said blowing nozzles having a guiding surface for the blowing-air supply inclined towards a blowing-air source and cut around a tongue-shaped segment in a semicircular- like manner; and in which the center of curvature of said tongue- shaped segment lies in the center of said guiding surface, said guiding surf ace being concentrically surrounded by a circular depression.
2. A device according to Claim 1, in which the depression has the shape of a truncated cone the marginal inclination of which is f latter than the inclination of the guiding surface.
3. A device according to claim 1 or 2, in which the inclination of the guiding surface is double the magnitude of the inclination of the depression.
4. A device according to one of claims 1 to 3, in which the width of the tongue-shaped segment is smaller than one 25 fifth of the diameter of the depression.
5. A device according to any one of Claims 1 to 4, in which the width of the tongue-shaped segment is approximately half the diameter of the guiding surface.
6. A device according to any one of Claims 1 to 5, in which the thickness of the tongue-shaped segment is smaller than the depth of the depression.
7. A device according to any one of Claims 1 to 6, in which the thickness of the tongue-shaped segment is smaller than the depth of the guiding surface.

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8. A device substantially as described, with reference to the drawings.