Manufacturing container or tube from paper; or other manufacturi – Bending – Folding
Reexamination Certificate
1999-04-01
2001-10-30
Vo, Peter (Department: 3721)
Manufacturing container or tube from paper; or other manufacturi
Bending
Folding
C493S405000, C493S417000, C493S423000, C493S437000, C493S457000
Reexamination Certificate
active
06309336
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an apparatus for folding a portion of a textile length, in particular a bed sheet or similar, with a lengthwise folding device in which the portion of a textile length is folded to produce a tubular folded product with lengthwise folding edges extending substantially parallel to one another, and a crosswise folding device in which the tubular folded product is folded to produce a folded product in packet form.
BACKGROUND OF THE INVENTION
Apparatus of this type are used in particular, although by no means exclusively, for mechanically folding bed sheets so that these can be packed in packet form. After the bed sheets have been cut to size and sewn, the lengths of fabric, which are spread out flat, are fed into a lengthwise folding device in which they are folded to produce a tubular folded product with lengthwise folding edges extending substantially parallel to one another. The basic structure of folding devices of this kind is known from the prior art. The tubular folded product is then conveyed into a crosswise folding device in which it is folded with crosswise folding edges extending substantially perpendicularly to the lengthwise folding edges. The folded product is thus given the desired packet form in which it can sequently be packed.
A stop strip, against which the tubular folded product comes to lie, at least in certain regions, before being folded, is disposed in the crosswise folding device. The stop strip forms an end stop for the conveying movement of the folded product when the latter is fed into the crosswise folding device and ensures that it has a defined orientation before crosswise folding takes place.
A drawing device is disposed in the crosswise folding device in the region between the two ends of the tubular folded product in order to draw in the folded product for crosswise folding. After the folded product has been conveyed completely into the crosswise folding device and come to lie in a defined manner against the stop strip, it is drawn in by the drawing device in the central region, whereby the first crosswise fold is formed and the folded product therefore folded crosswise once.
The disadvantage of known folding apparatus lies in their inadequate folding accuracy in crosswise folding in the crosswise folding device. Since a plurality of fabric layers already lie on top of one another as a result of the lengthwise folding process in the lengthwise folding device, the folded product tends to become distorted in the drawing-in region when being drawn into the drawing device such that the free ends of the folded product, which have not yet been drawn in, are displaced horizontally. Due to this shifting of the free ends of the folded product, the lengthwise edge of the folded product no longer lies properly against the stop strip while being drawn in. As a result, the folded product is no longer drawn evenly into the drawing device parallel to the stop strip, so that considerable folding inaccuracies arise when folding crosswise, in particular in subsequent folding stages. The distortion of the folded product in the drawing-in region increases with the number of fabric layers lying on top of one another. The unwanted distortion of the folded product may be increased even further if the two lengthwise edges ofthe tubular folded product have different layer thickness, i.e. a different number of fabric layers lying on top of one another.
SUMMARY AND OBJECTS OF THE INVENTION
Taking this prior art as a starting point, the primary object of the present invention is to provide an apparatus for folding a portion of a textile length which is highly accurate when folding crosswise.
According to the invention a thrust device is disposed in the crosswise folding device, which thrust device can be brought to lie against the folded product, at least in certain regions, while the tubular folded product is being drawn into the drawing device. This thrust device exerts a thrust force directed substantially perpendicularly to the stop strip on the folded product. This thrust force causes the free ends of the folded product to be pressed with one lengthwise edge against the stop strip while the latter is being drawn into the drawing device. The thrust force must in this case be precisely of a magnitude which prevents the unwanted shifting of the free ends of the folded product and at the same time excludes the possibility of the folded product being pressed too forcefully against the stop strip, which would cause the folded product to stand up at the latter.
There are basically a large number of possibilities for constructing thrust devices for applying the desired thrust force. A construction which is particularly simple and therefore inexpensive to produce is one in which the thrust device comprises at least one pressure belt on both sides of the drawing device, which belts can be brought to lie on the tubular folded product while the latter is being drawn in and travel substantially slip-free with the folded product in the direction of the drawing device. The folded product and the pressure belts do not move in exactly parallel directions during the drawing-in process, so that reaction forces directed perpendicularly to the conveying direction arise as a result in the contact surface between the pressure belt and the folded product. Tests have shown that it is not sufficient to press the folded product onto the support with the pressure belts, which extend parallel to the direction in which the folded product is conveyed, to prevent the folded product from shifting. A thrust force component of a sufficient magnitude is only achieved if the pressure belts extend at an acute angle relative to the direction in which the folded product is conveyed, with the pressure belts being oriented such that the horizontal distance between the stop strip and the pressure belts decreases in the direction of the drawing device. Because of the angular offset between the directions of movement ofthe folded product and the pressure belts, a thrust force directed perpendicularly to the stop strip acts on the free ends of the folded product during the entire drawing-in process. This thrust force is distributed evenly over the entire contact surface between the folded product and the pressure belts and prevents the free ends of the folded product from shifting.
The magnitude of the thrust force which acts on the folded product can be varied through the angular offset between the directions of movement of the pressure belts and the folded product. The greater the angle comprised between the two directions of movement, the greater the resulting thrust force. In order to achieve a sufficiently high thrust force to prevent the free ends of the folded product from shifting and at the same time prevent the folded product from being pressed too forcefully against the stop strip, the pressure belts should preferably be disposed so as to extend at an angle of 0.01° to 10°, in particular at an angle of 0.5° to 2°, relative to the direction in which the folded product is conveyed.
A particularly simple drive, which is known per se, for the folded product when it is drawn into the drawing device can be achieved if, when being drawn into the drawing device, the folded product comes to lie on a substantially horizontal roller table with drive rollers disposed so as to extend substantially perpendicularly to the conveying direction of the folded product and is put into motion by means of the drive rollers. As soon as the folded product is to be drawn into the drawing device, the drive rollers are rotated and thus ensure that the folded product is evenly conveyed towards the drawing device.
It is of no importance whether or not the pressure belts have their own drive in order to achieve the desired action on the folded product. As the pressure belts are usually only used to prevent shifting of the free ends of the folded product and not to drive the latter, it is of advantage to drive the pressure belts passively by means of frictional contact with the surface
Erhart Guido
Muessig Karl
Huynh Louis K.
McGlew and Tuttle , P.C.
Texpa Maschinenbau GmbH & Co.
Vo Peter
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