GB2147723A - Data printer - Google Patents

Abstract

A portable radio paging device 2 provides a printout of the messages it receives, it has a dot matrix printer 24 and a photocell 22 sensing perforations for detecting the movement of paper 16 past the printer. The user is warned of the receipt of a message by a bleep and draws the paper from the paging device. The message is printed evenly along the length of the paper despite variations in the speed at which it is pulled, as a result of the photocell and control circuitry 10. A second bleep indicates that the whole message has been printed and the user can then tear off the paper strip to examine the message. The photocell 22 may be replaced by an optical disc driven by one of two idler rollers gripping the paper. <IMAGE>

Description

SPECIFICATION Data printer The present invention relates to data printers in which data in the form of electronic signals is fed to a print head for printing on a strip of paper guided past the head.

Data printers of many kinds are known for a wide variety of uses. They commonly use dot matrix printing devices of which there are three types namely impact, thermal and electrosensitive. An earlier data printer of the present applicants comprises a mobile data printer intended for use in road vehicles to print out messages and information transmitted by radio. While this is small enough to fit conveniently into a motor car it has basic constructional features which are common to the majority of data printers namely a print head, a drive device for traversing the print head across the paper to produce a line of print, a paper feed mechanism for advancing the paper between successive lines, and an electronic control unit.

It is an object of the present invention to provide a data printer which can be of smaller size than existing printers and which has lower power consumption.

In accordance with the invention there is provided a data printer comprising a print head, a source of data to be printed, means coupling the data source to the print head, a paper store for holding paper in strip form, means for guiding the paper strip from the store past the print head, said print head being arranged to print parallel to the length of the strip when the strip is manually drawn past the print head, a paper movement detector and control means coupling the movement detector to the print head to control the printing of data in accordance with the movement of the paper.

In a printer in accordance with the invention the print head remains stationary and the power for moving the paper is provided by the user. If the message is in more than one line the lines are printed simultaneously by a number of print heads.

Elimination of the paper feed mechanism and the print feed drive greatly reduces the space requirement and also the power consumption. Power is only required to control the feed of the data to the print head.

The invention thus enables the size and weight of the printer to be substantially reduced, to the extent that in one embodiment the printer is incorporated in a paging device ("bleeper") which can be carried in the pocket. Known bleepers receive a coded radio signal and generate an audio signal to alert the wearer when the wearer's code is recognized. With the addition of a printer it is possible for the wearer then to receive a simple message telling him, for example, where he is wanted. In this device the print head could use any of the three known dot matrix printing techniques referred to above but it is preferred to use a thermal technique. The paper supply is preferably stored in the device as a fan-fold which is more compact than a roll of paper.The end of the paper strip projects through a slot in the casing of the device so that when the user hears the conventional audio tone he can draw the paper smoothly out of the casing.

Movement of the paper can be detected by the passage of perforations in the paper past a detector, for example, a photo cell. Alternatively a roller in contact with the paper is caused to rotate as the paper is drawn past it and movement is detected by means of an optically coded disc driven by the roller. When movement commences printing is initiated by the supply of data to the print head and the speed of printing is then controlled in accordance with the detected movement of the paper to achieve a regular print-out. When the message is complete a further audio signal is given to the user, who then stops pulling and tears off the paper strip to examine the message. These control functions are carried out by the electronic control unit using conventional techniques.The printed message may be one which is transmitted by radio with the coded user signal or one which is stored locally in the unit and selected by a coded section signal accompanying the user signal.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of a paging device ("bleeper") according to the invention; Figure 2 is a flow chart showing the operation of control circuitry used in the paging device of Figure 1; and Figure 3 shows in schematic form an alternative movement detector to that employed in the embodiment of Figure 1.

The bleeper shown in Figure 1 has a casing 2 which contains a battery 4 connected to a radio receiver 6, decoder 8, control unit 10 and thermal print head driver 12. It also contains a compartment 14 at its lower end which contains a fanfolded (zig-zag) paper strip 16. The paper strip has perforations along its length adjacent one edge.

The perforations are evenly spaced from one another, by a distance corresponding to the required character spacing of the printed message (10 per inch in this embodiment).

The opposite end of the casing to the compartment is formed with a slot 18 through which the paper strip is drawn from the bleeper. Between the compartment 14 and slot 18, and aligned with the slot, are a guide roll 20 at the compartment end, a paper position detection device 22, and, downstream of the device 22, a print head 24.

The paper position detection device 22 is a photocell with light source detector components 26 and 28 respectively. The photocell is connected to the control unit 10. The paper pathway is between the components 26 and 28 and the row of perforations in the paper is aligned with them.

The print head 24 is of the thermal dot matrix type. On the opposite side of the print head 24 is a spring biassed pressure pad 30 to maintain the required contact between the print head 24 and the paper strip. The print head 24 is connected to the thermal print head driver 12.

The bleeper also has message indicating components in the form of a sound-emitting element 32 and an LED 34, operating in response to signals from the control unit 10.

The battery 4 powers the receiver, decoder, control unit, driver, the paper position detection device and the print head. There is no motor to feed the paper or drive the print head over the paper. Instead, when an incoming message is signalled, the user draws the paper strip out as the print head prints the message on it.

The signal transmitted to the bleeper is a direct carrier modulation of a differential phase shift keyed (DPSK) signal, and consists of a header to identify the bleeper for which the message is intended, followed by the message itself. The receiver 6 demodulates the signal and passes it to the decoder, which decodes the DPSK signal and passes it to the control unit 10. The control unit 10 compares the signal header with the bleeper code and, if they are different, ignores the message. The bleeper then returns to its original state and awaits the new message (Fig. 2). However, if they are the same, the incoming message is stored and the user is informed that a message has been received, by the sounding of the element 32 and illumination of the LED 34 which continues until the user starts to draw the paper strip from the bleeper.When the whole message has been printed an indication is given, either printed on the strip of paper, or as a second bleep, and1or flash from the LED, and the user can tear off the strip carrying the printed message.

After the printing of each character in the message, other than the final character, information as to the position of the paper strip is sent to the control unit by the photocell 22, detecting the perforations as they are drawn past it. The time taken for successive perforations to pass the photocell is used to determine when the next character is printed. On printing of the final message the user is informed that the message is complete and the system returns to its original state, awaiting a new message.

The signal for printing is given by the change in output of the thermal print head driver 12, in response to the control unit 10.

In this embodiment a single dot matrix printer is used and so the message printed along the strip dot matrix printer is used and so the message printed along the strip of paper is on a single line.

In other embodiments a pluraiity of dot matrix printers are used, arranged transverse to the length of the paper, and messages with a corresponding number of lines can be printed.

In the bleeper described above the thermal print head 24 is Texas Instruments type EPN 3390. The print head driver 12 is Texas Instruments type 75270, whilst the photocell 22 is Texas Instruments Type TIL 147. The control unit 10 is a masked programmed microprocessor type 6805 manufactured by, among others, Motorola. The other parts- the battery 4, element 32, LED 34, receiver 6 and decoder 8 are all used in existing paging devices, such as those manufactured for British Telecom PLC by Multitone PLC, and are entirely standard.

In another embodiment a different paper position detection method is employed (see Fig. 3). The paper 35 no longer has perforations but instead causes an optically encoded wheel 36 to rotate between source and detector elements of a photocell 38. The paper is drawn between two idler rollers 40 and 42 mounted on axles (not shown). The roller 40 causes the encoded wheel to turn. The encoded wheel 36 may be mounted on a common shaft with the idler roller 40, as shown, or mounted rim to rim with the idler roller. In the embodiment shown it is desired to print 10 characters per inch.

The idler wheel 40 has a circumference of one inch and the encoded wheel has ten opaque spokes 46 and transparent segments between the spokes.

If it is be desired to detect the position of the paper more than once for every character spacing the optical wheel technique is particularly useful and it is possible, for example, to encode the wheel such that the separation of adjacent spokes corresponds to the dot spacing within a character rather than the spacing between characters.

Claims (8)

1. A data printer comprising a print head, a source of data to be printed, means coupling the data source to the print head, a paper store for holding paper in strip form, means for guiding the paper strip from the store past the print head, said print head being arranged to print parallel to the length of the strip when the strip is manually drawn past the print head, a paper movement detector and control means coupling the movement detector to the print head to control the printing of data in accordance with the movement of the paper.

2. A data printer according to claim 1, wherein the print head is of the thermal dot matrix type.

3. A data printer according to claim 1 or 2, wherein the paper is stored as a fan-fold.

4. A data printer according to any of claims 1 to 3, wherein the paper movement detector comprises a light-sensitive cell aligned with perforations formed along the length of the paper.

5. A data printer according to any of claims 1 to 3, wherein the paper movement detector comprises an optically encoded wheel rotated on movement on the paper, and means for sensing the movement of the wheel.

6. A paging device comprising: a data printer according to any preceding claim, in which the source of data is a radio receiver; means for generating an alerting signal when a message is received; and means coupling the receiver to the print head to print out a message.

7. A data printer substantially as hereinbefore described with reference to the accompanying drawings.

8. A paging device substantially as hereinbefore described with reference to the accompanying drawings.