Patent GB-1100646-A (GB)
Title: Facsimile apparatus having a magnetically biased marking stylus
Inventor: VARRARO ANGELO
IPC: H04N1/00
Filed: 1965-04-23
Abstract: 1,100,646. Copying telegraphy. COLUMBIA RIBBON & CARBON MANUFACTURING CO. INC. 23 April, 1965, No. 17215/65. Heading H4F. In a fascimile recording system of the type which operates with a pressure-responsive transfer medium such as carbon paper, the marking device or stylus which is controlled by an electromagnet is continuously pressed against the copy-producing material i.e. a copy sheet and transfer sheet, with either a positive marking pressure or a positive non- marking pressure depending on variations in an electrical signal derived from the original to be copied by means of a beam of light and a photocell which are arranged to scan the original. The original may be scanned at a point remote from the facsimile-producing apparatus or on the same apparatus which produces the facsimile copy by placing the original side by side with the copy-producing material on a drum or cylinder and scanning them simultaneously. The original may be superimposed on the copyproducing material provided the original is not so thick or stiff as to prevent the marking pressure applied by the stylus to be effective on the copy-producing material, and this arrangement facilitates location of the original with respect to the prepared material on the copy sheet. In a first embodiment illustrated schematically in Fig. 6, the original 30 is supported on a rotatable drum 31 and helically scanned by means of a light source 35 and a photocell 34 which move laterally along the drum as it rotates. A rotating chopper 39 is interposed in the light beam between the photocell and the original to cause the normal D.C. signal to have a selected frequency and this signal is fed by way of band pass A.C. amplifier 37, a rectifier 40 and a D.C. amplifier 41 (Fig. 10, not shown) to vary the amount of magnetic flux emitted from a stylus-operating electromagnet 42. Mounted adjacent the periphery of the drum is a stylus 44 having a small point 45 and a lever 46 pivoted at one end at 47. As shown the original 30 is superimposed on a pressure-responsive transfer sheet 50 and a copy sheet 49 and offset either laterally along the drum or around the drum a slight amount so as to avoid the stylus interfering with the light reflected from the original passing to the photocell. The stylus 44 forms the armature of the electromagnet 42 and the electromagnet is so adjusted that when the photocell 34 senses the background area on the original, the stylus point 45 is pressed against the original and copy-producing material so lightly that no mark is transferred from the transfer sheet 50 to the copy sheet 49, but when an image portion of the original is sensed the stylus is attracted toward the drum with a force sufficient to cause a mark to be made on the copy sheet by the transfer sheet. The photoelectric scanning means, stylus and electromagnet are arranged to move simultaneously along the rotating drum such that the polepiece of the electromagnet continuously remains opposite the stylus, Figs. 1-5, not shown. If duplicate facsimile copies are required several copy-receiving sheets and several transfer sheets may be arranged on the drum, Fig. 9, (not shown). The copy-supporting drum is made of non-magnetic material, the flux from the electromagnet passing through the drum and copy-receiving material to the armatureforming stylus to attract the stylus towards the drum when the electromagnet is energized the magnetic circuit being completed through the structural parts of the apparatus, Fig. 7, (not shown). Although the residual magnetism of the electromagnet and/or the weight of the stylus may be sufficient to maintain the stylus against the copy-producing material at all times particularly when the photo - cell senses background or " white " increments, a small positive current may be passed through the electro magnetto maintain the stylus forced against the copy-producing material with a pressure which is insufficient to produce a mark on the facsimile copy yet which is firm enough to hold the stylus from vibrating or chattering, this is explained with reference to Fig. 10, (not shown). In a second embodiment, Fig. 7a, stylus 46 which is made of magnetizable material is attracted to a permanent magnet 42a with sufficient force to make a mark and when no mark is to be made electromagnet 142 travelling with the stylus 46 counteracts the force of the permanent magnet and reduces the pressure of the stylus. In a third embodiment, Fig. 7b, the stylus may be permanently magnetized as shown and the support for the copy-receiving material may be of magnetizable material so that the stylus is held against the copy-producing material with a force insufficient to make a mark. The electromagnet 242 which is responsive to signal variations has a polepiece having the same polarity as the permanent magnet of the stylus carrier so that when a mark is called for the repelling effect of the flux will force the stylus towards the copy-producing material with force sufficient to make a mark.