DE102006005703A1 - Molding a hollow reinforced plastic needle bar for warp knitting machine uses a thin tube which is inflated to act as core and is then left in position - Google Patents

Abstract

A needle bar is made from a pre-preg with unidirectional fiber reinforcement (10) by forming in a mold (2). The hollow space in the bar cross-section is produced by folding the pre-preg over a tube (12). Once the assembly is in the mold, the tube is inflated by air or hydraulic pressure to impose the required shape. After molding, the tube is left in position and forms part of the needle bar. An independent claim is included for a needle bar with a solid mounting section (11, 13) and a hollow section with an internal tube (12) made in this way from a pre-preg. The pre-preg includes several layers of unidirectional reinforcement, the directions changing from layer to layer.

Description

The The invention relates to a method for producing a plastic working tool bar, a first section in which a wall surrounds an interior, and a second portion, in the edge portions of the wall above each other are arranged, in which one has a flat plastic semi-finished product in a press mold and for pressing the second section pressurized. Furthermore, the invention relates to a plastic Wirkwerkzeugbarre with a first section in which a wall surrounds an interior, and a second section, in which the wall with two edge sections continues and in which the edge portions are arranged one above the other.

knitting machines usually have several bars that carry knitting tools. Under "impact tools" become simplicity half of all elements that are involved in the process of action are, for example, knitting needles, hole needles, milling plates, Polplatinen, tee boards, Etc.

If For example, if a barre wears guide needles, then she must knit in a knitting cycle in the direction of the longitudinal extent of the knitting machine to be panned once and once. It may come a pivoting transverse to the longitudinal extent add to the knitting machine. Other bars are only transverse to the longitudinal extent the knitting machine moves or in other directions. In all cases you have the Accelerate Barre from standstill and reach the final position brake the bar again in one cycle. The bigger the Mass of the barre is the bigger the forces required to accelerate and decelerate the bar.

knitting machines can Have widths that spread over extend several meters, for example, over 6 m. To be satisfactory to be able to work needed the barre a certain mechanical stability. This also applies at shorter lengths. Especially the barre should have a certain rigidity and not swing. On the other hand if possible, the mass of the barre keep low to the knitting machine with high working speeds to be able to operate.

you has long been the bars of a knitting machine made of a light metal, For example, magnesium or aluminum. One of them but Barre still has a considerable mass.

One has therefore in DE 41 11 108 C2 proposed to form a bar of a reinforced plastic by forming the hollow profile of flat overlapping superimposed bands of plastic. In the interior, a shaped body is arranged, which remains permanently in the cavity and contains nut thread pieces for the attachment of components. The shaped body is required so that you have an abutment during manufacture of the bar, against which the fiber-reinforced plastic bands can be placed. Moreover, the molded body is used for fastening nut thread pieces, which later components can be attached.

A However, such training has the disadvantage that with the molding a additional mass is introduced into the bar.

Out EP 1 600 543 A1 It is known to assemble the body of the knitting tool bar from at least two open profiles. The open profiles can each be made in a press at high pressure, so that the composite body contains a high mechanical stability. However, changing the configuration of the body always requires a change in the press shape.

Of the Invention is based on the object, the manufacture of a plastic Wirkwerkzeugbarre easy and flexible.

These Task is characterized by a method of the type mentioned by solved, that one the Interior pressure applied during pressing with internal pressure.

at This configuration can be used a press mold, the only the outer shape the barre defines. Inside the interior, however, one is free. Here you can without a change Press shape changes make reinforcements, for example accommodate or the like. When pressing takes over the internal pressure, the by a pressurized fluid, for example compressed air or a liquid, can be generated, the task of the hollow body, i. the internal pressure presses the plastic, which forms the wall surrounding the interior of inside out against the press form. Dependent on from the height the pressure prevailing in the interior pressure during pressing can be here big enough Achieve strength. By making the interior as a cavity It is not necessary to add extra mass to the bar to enter, so that one with a high stability receives a mass with comparatively low weight.

Preferably used as a plastic semi-finished product is a prepreg, in particular a UD prepreg. A prepreg is a plastic semi-finished product in a flat form, in which reinforcing fibers are embedded in a plastic matrix. In a UD prepreg (UD stands for unidirectional) have the Fibers all the same preferred direction. Such a prepreg is cured in the press mold under pressure and optionally also at elevated temperature and / or with heat release. This gives a bar with a relatively high strength.

in this connection is preferred that one insert a tube with the plastic semi-finished product into the press mold and the plastic semi-finished leads around the hose, wherein you put the hose under pressure. The hose will, however only put under pressure when the press mold is closed is. Before that he can fill easily be, if appropriate. The hose has two tasks. For one thing, he stops by Inserting the plastic the inner walls, i. the inside of the Cavity surrounding wall, away from each other, so that the inner walls are not stick together. On the other hand, the hose is pressurized, to the plastic semi-finished from the inside out against the press form press. Only the hose must be able to do so to hold the pressure building up fluid. This fluid can be a Gas, for example air, or a liquid, for example water, be. The barre must then not gas or liquid tight be. You also have to do not worry about that wear that Plastic material is compatible with the fluid. Furthermore It is easier to create a pressure chamber with the help of the hose as such a pressure space just in the press form too produce.

Preferably you leave that Hose in the interior. In many plastics, the hose is stick together with the plastic during pressing. It is much easier leave the hose in the interior rather than removing it. A significant mass increase is not connected to leaving the hose in the interior.

Preferably you use a hose made of a temperature-resistant plastic, in particular polyethylene terephthalate. The curing of the plastic semifinished product takes place usually under an elevated Temperature. It is therefore advantageous if the tube can withstand this temperature, so that during the entire process of curing inside the hose the desired Pressure can be maintained.

Preferably one uses a hose with a wall thickness of at most 0.5 mm, in particular maximum 0.05 mm. A preferred embodiment of the method used a hose whose wall thickness 0.025 mm. such hoses are available in stores, for example the production of sausages in a meat processing plant. The hose does not have to be elastic once. You can easily use a hose whose cross-section is complete inflated state is greater as the cross section of the interior. When the hose inflates Folding folds, this is not critical. It is only necessary that one with the help of the hose can apply a predetermined pressure.

Also is preferred that one used a press mold, in which an auxiliary element is inserted, the is arranged between a press cavity and a vent channel. The auxiliary element has two advantages. First, it allows in particular at sharp corners or edges of the form a vent, because the auxiliary element to the rest Components of the form can never be completely gastight. On the other hand you can use the help element to make certain minor changes also on the outer contour make. For this it is only necessary, the auxiliary element exchange. The press mold can otherwise remain unchanged.

preferably, one assigns at least in one part of the wall several layers of the plastic semifinished product one above the other at. Thus, certain areas of the wall can be specifically strengthened, if this desired or required. A gain, for example, then be expedient if arranged in this portion of the wall fasteners should be.

Also is an advantage if you look in the second section in addition to the edge sections at least one more layer of plastic semi-finished product used. The second section is often used to active elements, For example, guide needles or the like to hold. Here too can then be a reinforcement make sense.

Preferably used in the second section plastic semi-finished products with different Preferred directions. This will improve the bar's stability both in longitudinal as well as in the transverse direction.

The Task is at a plastic Wirkwerkzeugbarre the beginning solved by the type mentioned, that on the inside of the wall a hose is arranged.

As has been explained above in connection with the method, the Hose used in making the barre to a pressure to build in the interior, the plastic semi-finished from the inside Outside presses against the press mold. The hose sticks to the plastic semi-finished product, if that Plastic semi-finished cures. The tube then remains in the bar. But he wears it there not appreciable to a mass increase so that he does not continues to bother.

Preferably is the hose made of a temperature-resistant plastic, in particular Polyethylene terephthalate formed. The hose will last the temperatures that arise when curing the plastic semifinished product. This can be the pressure inside the hose when making the barre is maintained until a time when the Hardened plastic is.

Preferably the hose has a wall thickness of not more than 0.5 mm, in particular not more than 0.05 mm. In a preferred Embodiment, the hose has a wall thickness of 0.025 mm. The hose you do not have to larger mechanical Have strength. He lies down while creating the pressure of inside the plastic semi-finished, which in turn on the press mold supported. Accordingly, there is virtually no danger even with very thin wall thicknesses that the Hose is damaged by the pressure generation.

Preferably are at least in a portion of the wall several layers of a Plastic semi-finished one above the other arranged. You can selectively reinforce the wall in these areas to There, for example, to accommodate fasteners.

Also is beneficial if in the second section in addition to the edge sections arranged at least one further layer of the plastic semi-finished product is. This can be reinforce the second section, so he for the Attachment of active elements can be used.

Also is an advantage if several layers are arranged one above the other of the plastic semi-finished product at least two layers different Having preferred directions. When using UD prepregs For example, to produce the bar you will be a prepreg use, the preferred direction oriented in the longitudinal direction of the bar is, and another, the preferred direction transverse to the longitudinal direction the barre is oriented. This results in relatively high strengths. Various other angular positions can be set.

The Invention will be described below with reference to preferred embodiments described in conjunction with the drawing. Herein show:

1 half of a press mold with inserted plastic semi-finished product and inserted hose,

2 the other half of the press mold,

3 the press mold in the closed state,

4 a bar in a schematic cross-sectional view,

5 a modified embodiment of a press mold with inserted plastic semi-finished product,

6 the press shape after 5 when creating the barre,

7 the bar in cross section,

8th another embodiment of a barre,

9 the barre after 8th when producing in the press mold and

10 a schematic representation of several plastic semi-finished layers.

1 shows a first half 1 a press mold 2 ( 3 ) for making a bar 3 ( 4 ).

The first half 1 has a press cavity 4 in which an auxiliary element 5 is arranged. The auxiliary element 5 forms with the first half 1 the press mold a gap 6 coming from the press cavity 4 to a venting channel 7 leads.

The press form 2 also has a second half 8th on, which also has a press cavity 9 having.

Before the second half 8th with the first half 1 is connected, is a plastic semi-finished product 10 in the form of a multilayer prepreg, preferably UD prepreg, into the cavity 4 inserted. In a UD prepreg, the individual layers are expediently oriented in different directions, so that, for example, adjacent layers at an angle of 90 ° (other angles are possible) include. Here comes a border section 11 of the plastic semi-finished product 10 on the auxiliary element 5 to lie. The plastic semi-finished product 10 then clothes the press cavity 4 from, in this case V-shaped. In the recess formed thereby is a hose 12 filed for the sake of clarity in 1 already shown with a certain filling. In fact, the hose does not yet have to be inflated. Then it will, like this 3 it can be seen, the remaining part of the plastic semi-finished product 10 over the hose 12 placed so that the second edge portion 13 of the plastic semi-finished product 10 on the first edge section 11 to come to rest. After that, the press mold becomes 2 closed, ie the second half 8th the press shape will be on the first half 1 the press form and with the help of bolts 14 . 15 closed.

In the area of the two edge sections 11 . 13 is the clear distance between the two press halves 1 . 8th slightly smaller than twice the thickness of the plastic semi-finished product 10 in the non-compressed state, so that one by closing the press mold 2 a pressure on the two edge sections 11 . 13 can exercise. The two edge sections 11 . 13 of the plastic semi-finished are pressed together in this way. They form a second section b of the barre ( 4 ). At this second section knitting tools can be attached later.

When the press mold 2 is closed as in 3 shown, then the hose 12 Pressurized by a pressurized fluid under pressure, such as compressed air, water or oil, into the hose 12 is passed, and then presses the remaining portion of the plastic semi-finished product 10 from the inside against the press mold 2 , so that a first section a arises in which a wall 17 an interior 18 surrounds ( 4 ). A shaped body, which serves as an abutment, is not required here. After curing of the plastic, the pressure from the hose can 12 be drained and the barre 3 has the in 4 illustrated cross-sectional shape.

You can do this the hose 12 without further ado in the interior 18 leave. The hose 18 is made of a plastic material that aids in the curing of the plastic semi-finished product 10 occurring temperatures without being damaged. A suitable material for this is, for example, polyethylene terephthalate. The hose itself does not require greater mechanical stability. Accordingly, a wall thickness of, for example, 0.025 mm is sufficient. When curing the plastic semi-finished product 10 can the hose 12 without further ado with the wall 17 stick together. He then remains in the finished barre 3 , He is in for clarity in 4 not shown.

Of course it is possible the interior 18 foam with a light plastic, if necessary. In general, but you will also be a hollow Barre 3 can use.

Through the gap 6 between the auxiliary element 5 and the first half 1 The mold can be gas to the vent channel 7 escape when the hose 12 is pressurized. Accordingly, one can at the lower edge of the barre 3 produce a relatively sharp shape. At the upper right edge (referring to the illustration of the 4 ) can gas and excess resin through the gap between the first half 1 and the second half 8th the press shape 2 escape, so that there is no danger that the plastic semi-finished product 10 not completely on the inner wall of the press mold 4 . 8th can create.

The 5 to 7 show a modified embodiment in which the same parts are provided with the same reference numerals.

For the sake of simplicity, here is in the first half of the press mold 1 the auxiliary element 5 been omitted. While in the embodiment of the 1 to 4 a single plastic semi-finished product 10 in the press mold 2 inserts, one uses in the embodiment according to the 5 to 7 two separate plastic semi-finished products 10a . 10b forming an overlap zone 10c in the first half 1 the press shape 2 be inserted. If you then the hose 12 put under pressure, then creates a reinforced zone 17a the Wall 17 where you can attach, for example, holding elements for the bar.

You can such a gain zone 17a but also by forming, as in 1 to 3 shown, a single plastic semi-finished product 10 used, which is then reinforced in the region of the desired gain zone with a smaller, not shown plastic semi-finished.

If changes in the wall thickness in one or the other area are required in such ingots, then you can realize this change in wall thickness simply by that in the interior, ie between plastic semi-finished 10 and hose 12 , Introduces another plastic semi-finished, which then when pressurizing the hose 12 with the plastic semi-finished product 10 is pressed. The outer shape of the barre 3 does not change. Only inside there are different types of amplification.

8th shows a modified form of the barre 3 with a fastener 19 in a reinforced area 17a , Further, the second area b of the barre 3 reinforced, for example, to better attach knitting needles.

9 shows how to make plastic semi-finished products for insertion in the press mold 2 prepared and the individual plastic semi-finished products 20a . 20b . 20c . 20d in the press mold 2 inserts. The plastic semi-finished products 20a - 20d are then in the first area a by means of the pressurization of the hose 12 against the inner wall of the press mold 2 pressed. In the second area b are the plastic semi-finished products 20a - 20c by squeezing the two halves 1 . 8th pressed together.

The plastic semi-finished product 20a is in the form of an Ω-shaped loop around the hose 12 laid around, so that its edge portions 11 . 13 lie one above the other. These two edge sections 11 . 13 are through the other two plastic semi-finished products 20b . 20c separated from each other. This results in four layers, by the pressurization of the two halves 1 . 8th the press shape 2 be pressed together.

Below the bottom of the plastic semi-finished product 20a is the plastic semi-finished product 20d arranged with the lower wall 17b the Wall 17 by the pressurization of the hose 12 is pressed.

10 shows in a schematic representation how several UD prepregs 21a - 21e be arranged one above the other. Shown are only the fibers of the prepregs 21a - 21e , A plastic matrix present in the prepregs is not apparent here. Such a stack of prepregs provides excellent stability in virtually all directions when used as a plastic semi-finished product. Everyone in 10 "Wires" actually consists of many hundreds or many thousands of individual fibers.

Instead of the illustrated rectangular orientation of the individual prepregs can also realize other angular relationships.

By the choice of several or less superimposed prepreg layers let yourself change the thickness of the bar, more precisely the thickness of the wall thickness. So It is easy to create reinforced areas.

Claims (16)

Method for producing a plastic working tool bar having a first section (a) in which a wall ( 17 ) an interior ( 18 ) and a second section (b), in the edge sections ( 11 . 13 ) the Wall ( 17 ) are arranged one above the other, in which one comprises a flat plastic semi-finished product ( 10 ; 10a . 10b ; 20a - 20d ) in a press mold and for pressing the second section (b) pressurized, characterized in that the interior ( 18 ) subjected to internal pressure during pressing. Process according to claim 1, characterized in that a prepreg ( 21a - 21e ), in particular a UD prepreg used. Method according to claim 1 or 2, characterized in that a hose ( 12 ) with the plastic semi-finished product ( 10 ; 10a . 10b ; 20a - 20d ) in the press mold ( 2 ) and the plastic semi-finished product ( 10 ; 10a . 10b ; 20a ) around the hose ( 12 ), taking the hose ( 12 ) under pressure. Method according to claim 3, characterized in that the hose ( 12 ) in the interior ( 18 ) leaves. Process according to Claim 3 or 4, characterized in that a hose ( 12 ) made of a temperature-resistant plastic, in particular polyethylene terephthalate used. Method according to one of Claims 3 to 5, characterized in that a hose ( 12 ) with a wall thickness of not more than 0.5 mm, in particular not more than 0.05 mm. Method according to one of claims 1 to 6, characterized in that a press mold ( 2 ) into which an auxiliary element ( 5 ) inserted between a press cavity ( 4 ) and a venting channel ( 7 ) is arranged. Method according to one of claims 1 to 7, characterized in that at least in a partial area ( 17a ) the Wall ( 17 ) several layers ( 10a . 10b ; 20a . 20d ) of the plastic semi-finished one above the other. Method according to one of claims 1 to 8, characterized in that in the second section (b) in addition to the edge sections ( 11 . 13 ) at least one further layer ( 20b . 20c ) Semi-finished plastic used. Method according to one of claims 1 to 9, characterized that he in the second section (b) plastic semi-finished products with different Preferred directions used. Plastic working tool bar with a first section (a) in which a wall ( 17 ) an interior ( 18 ) and a second section (b), in which the wall ( 17 ) with two edge sections ( 11 . 13 ) and in which the marginal sections ( 11 . 13 ) are arranged one above the other, characterized in that on the inside of the wall ( 17 ) a hose ( 12 ) is arranged. Bar according to claim 11, characterized in that the hose ( 12 ) is formed of a temperature-resistant plastic, in particular polyethylene terephthalate. Bar according to claim 11 or 12, characterized in that the hose ( 12 ) has a wall thickness of not more than 0.5 mm, in particular not more than 0.05 mm. Barre according to one of claims 11 to 13, characterized in that at least in a partial area ( 17a ) the Wall ( 17 ) Several layers of a plastic semifinished product are arranged one above the other. Bar according to one of claims 11 to 14, characterized in that in the second section (b) in addition to the edge sections ( 11 . 13 ) at least one further layer ( 20b . 20c ) of the plastic semifinished product is arranged. Bar according to claim 14 or 15, characterized that at several on top of each other arranged layers of the plastic semi-finished product at least two layers have different preferred directions.