GB2059609A

GB2059609A - Contact printing

Info

Publication number: GB2059609A
Application number: GB8027256A
Authority: GB
Original assignee: HANSA TECHNIK GmbH
Current assignee: HANSA TECHNIK GmbH
Priority date: 1979-09-26
Filing date: 1980-08-21
Publication date: 1981-04-23
Also published as: GB2059609B; IT8009543A0; DE2938906A1; IT1136062B; FR2466036A1

Abstract

In a contact printing process in which an original 22 and photosensitive material 18 are passed in wet form (with the original on the inside) between a cylinder 6 and endless belts 7 supported on drive rolls 1-4, cylinder 6 having at one end a toothed ring 5 which meshes with gear wheels at the end of drive rolls 1-4, the transmission ratio is such that the surface of the cylinder has a slightly higher angular velocity than the surface of the belts facing the cylinder, such that relative displacement of the original and photosensitive material is prevented. The original is withdrawn under tension between leaf-springs 10 and rubber rings 11 of a driven roll 12, the pressure provided by the leaf-springs being adjustable. <IMAGE>

Description

SPECIFICATION Photo-copying machine In a known photo-copying machine, in accordance with the pre-characterising clause of Claim 1 (German Auslegeschrift 1,182,070), the cylinder and the transport belts, which run around this cylinder, are driven in such a manner that their opposing surfaces posess the same velocity. In spite of this, it is found that the longitudinal dimensions of the copy are larger than those of the original. This effect cannot be adequately explained in terms of the comparatively slight difference between the radii of the circular paths of the two lengths of material. There are specific applications, in which the inadequate superimposition uniformity of original and copy, resulting from this effect, is disadvantageous, for example when producing copies of patterns, which are transferred to the material to be cut out.

Although it is possible to achieve superimposition uniformity by passing the photo-copying material through the photo-copying section whilst keeping it flat, this nevertheless results in poor utilisation of the illumination devices and larger machine dimensions.

The object of the invention is accordingly to produce a photo-copying machine of the type cited in the pre-characterising clause of Claim 1, which enables copies with superimposition uniformity to be produced.

The object is achieved, according to the invention, on the basis of the fact that the cylinder is driven at a higher angular velocity than the transport belts. By this means, the original, lying on the inside, is arranged to be transported at a slightly higher velocity. This leads, in general, to a circumferential displacement relative to the copy, which is surprising insofar that painstaking efforts are made in copying technology to avoid any displacements between the original and the copy.

The degree of the displacement is, however, obviously extremely small, for no appreciable lack of sharpness is apparent. This fact, in association with the observation that the lack of superimposition uniformity occurring in known machines is not completely explicable in terms of the geometric relationships pertaining to the cylinder rotation, allows the conclusion that the effect of the invention does not reside only in a different transport velocity of the two continuous lengths of material. Possibly, a negative slip, hitherto undetected, is also being compensated, this slip being attributable to the occlusion of air between the two lengths of material and non uniform increase of temperature under the incident light.

The drive-connection between the cylinder and the rolls driving the transport belts is advantageously effected, as known per se, by means of gear wheels. Moreover, it is advantageous, according to the invention, to provide means for the more positive application of the original to the cylinder, or for increasing the friction between the original and the cylinder, these means advantageously consisting of a device for applying a longitudinal tension to the length of material comprising the original.

According to the invention, this device can consist of a roll, driven at a somewhat higher circumferential velocity than the cylinder, rubbing on the continuous material of the original.

In the following text, the invention is explained in greater detail with reference to the drawing, which illustrates an advantageous illustrative embodiment and in which: Fig. 1 shows a vertical section and Fig. 2 shows a plan view of the photo-copying machine.

The transparent cylinder 6 is mounted to allow rotation about its longitudinal axis inside a machine frame and casing, the latter not being represented in detail. The rolls 1, 2, 3 and 4 for guiding the transport belts 7 are located parallel to the cylinder and spaced around its circumference.

At its end, the cylinder carries a cap, provided with a toothed ring 5, which meshes with corresponding gear wheels on the ends of the rolls 1-4. Synchronised running of the cylinder, of the rolls and of the transport belts is thereby assured.

According to the invention, the transmission ratio of these gear wheels is chosen such that the cylinder rotates at a somewhat higher angular velocity than the transport belts which lie on it.

A winding-up device for the continuous length of original material is located in front of the exit opening for the original material 22, this windingup device being formed by rolls 12, 13 having superposed rubber rings 11 and a row of spiral winding-up springs 1 5. Beside the rubber rings 11 of the roll 12, leaf-springs 10 are attached, by means of a fixture 9, to a fixed part 8 of the casing, the ends of these leaf-springs rubbing under preload against the rubber rings.As the continuous length of original material 22 emerges from the photo-copying machine, it is gripped between the rubber rings and the springs 10 and is transported in this manner, in the direction of the arrow, by the driven roll 1 2. At the same time, the circumferential velocity of the rings 11 is somewhat higher than that of the cylinder 6, so that a frictional force is exerted on the length of continuous material in the transport direction, which imparts a tension to the material. Due to this tension, the continuous material is pressed, the more firmly against the surface of the cylinder and, according to the laws of circumferential friction, is carried along the more securely by the cylinder, without slipping. The attachment fixture 9 for the leaf-springs 10 is constructed in a known manner which accordingly is not described in detail herein, in such a way it can be vertically displaced in the direction of the arrow, in order to alter the pressure with which the continuous length of material is pressed against the rubber rings of the roll 12.

1. A photo-copying machine with a rotatable drum, around which the photo-copying material is

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Photo-copying machine In a known photo-copying machine, in accordance with the pre-characterising clause of Claim 1 (German Auslegeschrift 1,182,070), the cylinder and the transport belts, which run around this cylinder, are driven in such a manner that their opposing surfaces posess the same velocity. In spite of this, it is found that the longitudinal dimensions of the copy are larger than those of the original. This effect cannot be adequately explained in terms of the comparatively slight difference between the radii of the circular paths of the two lengths of material. There are specific applications, in which the inadequate superimposition uniformity of original and copy, resulting from this effect, is disadvantageous, for example when producing copies of patterns, which are transferred to the material to be cut out. Although it is possible to achieve superimposition uniformity by passing the photo-copying material through the photo-copying section whilst keeping it flat, this nevertheless results in poor utilisation of the illumination devices and larger machine dimensions. The object of the invention is accordingly to produce a photo-copying machine of the type cited in the pre-characterising clause of Claim 1, which enables copies with superimposition uniformity to be produced. The object is achieved, according to the invention, on the basis of the fact that the cylinder is driven at a higher angular velocity than the transport belts. By this means, the original, lying on the inside, is arranged to be transported at a slightly higher velocity. This leads, in general, to a circumferential displacement relative to the copy, which is surprising insofar that painstaking efforts are made in copying technology to avoid any displacements between the original and the copy. The degree of the displacement is, however, obviously extremely small, for no appreciable lack of sharpness is apparent. This fact, in association with the observation that the lack of superimposition uniformity occurring in known machines is not completely explicable in terms of the geometric relationships pertaining to the cylinder rotation, allows the conclusion that the effect of the invention does not reside only in a different transport velocity of the two continuous lengths of material. Possibly, a negative slip, hitherto undetected, is also being compensated, this slip being attributable to the occlusion of air between the two lengths of material and non uniform increase of temperature under the incident light. The drive-connection between the cylinder and the rolls driving the transport belts is advantageously effected, as known per se, by means of gear wheels. Moreover, it is advantageous, according to the invention, to provide means for the more positive application of the original to the cylinder, or for increasing the friction between the original and the cylinder, these means advantageously consisting of a device for applying a longitudinal tension to the length of material comprising the original. According to the invention, this device can consist of a roll, driven at a somewhat higher circumferential velocity than the cylinder, rubbing on the continuous material of the original. In the following text, the invention is explained in greater detail with reference to the drawing, which illustrates an advantageous illustrative embodiment and in which: Fig. 1 shows a vertical section and Fig. 2 shows a plan view of the photo-copying machine. The transparent cylinder 6 is mounted to allow rotation about its longitudinal axis inside a machine frame and casing, the latter not being represented in detail. The rolls 1, 2, 3 and 4 for guiding the transport belts 7 are located parallel to the cylinder and spaced around its circumference. At its end, the cylinder carries a cap, provided with a toothed ring 5, which meshes with corresponding gear wheels on the ends of the rolls 1-4. Synchronised running of the cylinder, of the rolls and of the transport belts is thereby assured. According to the invention, the transmission ratio of these gear wheels is chosen such that the cylinder rotates at a somewhat higher angular velocity than the transport belts which lie on it. A winding-up device for the continuous length of original material is located in front of the exit opening for the original material 22, this windingup device being formed by rolls 12, 13 having superposed rubber rings 11 and a row of spiral winding-up springs 1 5. Beside the rubber rings 11 of the roll 12, leaf-springs 10 are attached, by means of a fixture 9, to a fixed part 8 of the casing, the ends of these leaf-springs rubbing under preload against the rubber rings.As the continuous length of original material 22 emerges from the photo-copying machine, it is gripped between the rubber rings and the springs 10 and is transported in this manner, in the direction of the arrow, by the driven roll 1 2. At the same time, the circumferential velocity of the rings 11 is somewhat higher than that of the cylinder 6, so that a frictional force is exerted on the length of continuous material in the transport direction, which imparts a tension to the material. Due to this tension, the continuous material is pressed, the more firmly against the surface of the cylinder and, according to the laws of circumferential friction, is carried along the more securely by the cylinder, without slipping.The attachment fixture 9 for the leaf-springs 10 is constructed in a known manner which accordingly is not described in detail herein, in such a way it can be vertically displaced in the direction of the arrow, in order to alter the pressure with which the continuous length of material is pressed against the rubber rings of the roll 12. CLAIMS

1. A photo-copying machine with a rotatable drum, around which the photo-copying material is to run, said photo-copying machine having endless guide-belts which run on four rolls and enclose the cylinder on three sides, and said machine having drive devices and interacting drive-connections between the cylinder and at least one roll, these drive-connections assuring synchronised movement, characterised in that the transmission ratio of the drive-connections is chosen such that the surface of the cylinder has a higher angular velocity than the surface of the belts facing the cylinder.

2. A photo-copying machine according to Claim 1, characterised in that the drive-connection is formed by gear wheels.

3. A photo-copying machine according to Claim 1 or 2, characterised in that a device is provided for applying a tension to the continuous length of paper in contact with the cylinder, as the paper leaves the cylinder.

4. A photo-copying machine according to Claim 3, characterised in that a driven roll and means for pressing the continuous material against the roll surface are provided on the exit path of the continuous material.

5. A photo-copying machine according to Claim 4, characterised in that the means for pressing the continuous material against the roll surface are formed by leaf-spring.

6. A photo-copying machine according to Claim 5, characterised in that the roll is driven somewhat faster than would correspond to the nominal design velocity of the continuous length of paper.

7. A photo-copying machine according to Claim 5, characterised in that the spring tension can be varied.

8. A photo-copying machine substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.