DE102004033662B3 - Process to from complex leather shapes e.g. shoes, masks for theatrical props, leather furniture from wet leather with a combination of suction and pressure - Google Patents

Abstract

In a process to cover a form plug with a leather mantle, the wet leather mantle is applied and shaped under a combination of pressure and suction. The wet leather is presented to the positive or negative form with a lining and pulled taut in a vacuum bag that is then evacuated. The bag is then further placed under pressure and the leather dried in a three-dimensional form.

Description

It It is known that wet leather, if it is in a certain 3-dimensional Form after drying this form maintains.

This is used in shoe manufacturing and orthopedic technology, being wet Leather over a last stretched and with nails is held. (Expertise for Shoemaker, Sahm, 1949, page 24)

in the The field of make-up is worth mentioning the wet-shaping of leather Magnitude applied since the 16th century, in the way that during the Dehydration of the makeup artist's leather by continuous Reshaping with horn hammer, folder and bare hands the figure of an underlaid Positive form accomplished.

(The Prop Builder's mask-making Handbook, Thurston James, 1990, pages 101 ff)

The Vacuum drying already takes place during the conditioning of the leather the tanning operations, However, no shaping is done, but only the sheet dried for further use.

(Patent DE 3838370 C2 , published 7. 10. 1993)

The The principle of the vacuum press is used in the vacuum lamination of plastics and already used in gluing veneers in the furniture industry.

Furthermore, it is used for the production of leather moldings underlaid polymers that are firmly fused to the leather back. (OLS DE 10119494 A1 from 24.10.2002)

Other patents are concerned with the simplification of leather drying and also address deformation during the drying process:
Thus, the patent 52,762, Issue 20. 12. 1966 by the Office for Invention and Patenting of the GDR, describes a drying device for leather or skins under the action of heat and negative pressure by means of a vacuum. However, this is a process for flat products. A three-dimensional deformation should even be expressly prevented, so that the product is then accessible to any further use.

The publication DE 3431353 A1 From the German Patent Office in addition to the drying of the leather between an air-permeable and an air-impermeable carrier layer by means of negative pressure and heat on a deformation of the leather or sheet material. The aim of this deformation is the uniform enlargement of the surface while maintaining a flat texture.

These area stretch is by means of a domed Stamp accomplished during Drying on the leather with the adjacent support materials acts.

at Both methods do not produce end products in the sense of 3-dimensional hollow shaped body.

problem

Of the in claim the invention is based on the problem Leather without much effort working time or skill of the working person, and extremely gentle on material in reproducible to bring complex 3-dimensional shapes. Additional stabilization of resulting moldings by similar (leather) or foreign (plastic) material should not be absolutely necessary but quite possible.

solution

This problem is solved by the new process for producing molded leather articles:
Wet leather is stretched in a conventional manner to a reusable positive shape and fixed marginally. Projecting parts of the positive form are transmitted directly to the leather. By introducing the leather-taut form into a flexible evacuable bag and evacuating the same, the leather is then also pressed into recoveries and cavities. At the same time, the applied vacuum causes the leather to dry out, so that at the end of the process the dried leather retains the shape prescribed by the positive mold.

reached advantages

at The wet forming of leather can without huge Work effort and without extraordinary Skill of the working man complicated shapes are molded from leather.

leather no longer needs to be fixed in recesses and hollows with nails become what destruction of the leather at these points would.

The wet leather no longer needs to be continuous with the hands of the working people or by permanent hammering with a blunt impact tool or using Falzbein to the positive shape be pressed until it is dried out and its shape by itself holds.

It no longer comes to failure and scratches on the leather surface.

A continuous monitoring the drying process at the time of the last shape correction possibility Not to miss is no longer necessary, only the vacuum the press has to over a manometer monitored become.

A subsequent Shape correction by rewetting the leather is still possible.

The Vacuum drying is continuously distributed over the material, Spot burns of the material by heat drying e.g. with hot air or Distortions of the final product due to uneven drying do not occur more ahead.

A after time and material cost profitable possibility of wet-leather molding.

In addition is a stabilization of the molding made of leather by supporting materials or in the sense of a composite material possible, but if appropriate Texture and material thickness of the leather is not mandatory.

Process for the preparation of moldings of leather

embodiment

One embodiment The invention is illustrated in the following drawings and described in more detail.

Shown is the production of a theatrical mask made of leather.

1 shows the positive form ( 1 ) for a mask with human features in cross section. The positive mold must be sufficiently stable to withstand the pressure of the vacuum press without deformation or destruction. I used a mold made of epoxy resin.

The recesses and cavities (nostrils and eyes) are over channels ( 2 ) with the flat bottom of the mold.

2 outlines how wet leather ( 3 ) is determined by the positive form ( 1 ) is placed.

3 shows how the leather piece ( 3 ) is tightened over the edge of the mold; the fixation of the wet leather on the mold is most sensible on the bottom of the mold with nails ( 4 ). This area of the leather does not belong to the later form and is discarded at the end of the forming process. The arrows indicate the direction of pull on the leather.

protruding Part of the positive form, the wet stretchy leather hugs directly on, the leather can be in cavities and depressions are pushed in by hand, but prevails its elasticity out again. Nevertheless, you should try it once, especially to determine if the area size and material thickness as well surface finish (Error-free) of the piece of leather correct is; leaves the stretched leather piece completely create the shape, it is suitable. I have 2-3 mm thick vegetable tanned cattle leather used by the abdomen of the animal.

4 illustrates how a polyester absorbent nonwoven ( 5 ), represented by a dashed line, the wet leather ( 3 ) is launched. The size of the fleece is such that it is also around the bottom of the mold ( 1 ) and the outlets of the tubules ( 2 ) in the mold with covered. I have a Polyestersaugvlies of 150 g / m ^{2 was} used.

5 shows how a vacuum bag ( 6 ) in fleece ( 5 ) taken form ( 1 ) with the wet leather ( 3 ) is placed.

I have used both thin-walled PE tubing and alternatively PE foil. in a suitable place is a vacuum connection ( 7 ), and the openings of the vacuum bag are hermetically sealed with vacuum adhesive tape.

6 : The vacuum is applied, generated for example by a vacuum pump.

I I measured a vacuum of -900 mbar on the pressure gauge of the pump and the vacuum over 24 Hours maintained. The arrows indicate the flow direction of the Air on evacuation.

7 : The wet leather ( 3 ) is not only against the protruding parts of the positive form ( 1 ) but also pressed into the recesses and cavities and kept there continuously.

Here, the channels ( 2 ) in the form that the vacuum is fully applied even at these points. The fleece ( 5 ) absorbs the moisture of the leather and prevents air bubbles or water from arising between the vacuum bag and leather, thus causing a uniform concern of the vacuum on the leather and thereby the firm concern of the leather on the form.

About the Nonwoven layer and the vacuum is at the same time shaping Pressure causes drying of the leather by vacuum.

To For 24 hours there was a piece of vegetable-tanned cowhide about 30 by 40 cm in size from the abdominal area of the animal in a dry state and retained the predetermined by the positive shape structure.

8th shows the cross section of the demolded leather molded body after molding a face mask with human features in the center line of the face.

1

shape

2

channels

3

leather

4

nails

5

breather

6

vacuum bag

7

vacuum connection

Claims (1)

A process for the production of molded leather, which is wet under tension and pressure on a mold to be molded, characterized in that wet leather stretched under train on a positive or negative mold together with the underlying shape in a flexible evacuable bag is introduced and pressed by evacuating this bag on the mold, wherein the wet leather is simultaneously dried during this vacuum-assisted molding process by the vacuum, thus maintaining its desired 3-dimensional shape.