|Title of Invention||
'PORTABLE COMPUTER PRINTER '
|Abstract||A Portable Computer Printer consisting of the following parts: 1. An inner frame which contains the assembly as herein specifically described provided to impart x-direction movement to the Printer head. 2. An Outer frame which contains the assembly as herein specifically described provided for moving the inner frame in y-direction. 3. A Printer head mounted on Head-carrier, the Printer head is capable of moving in two directions namely the x-direction and the y-direction. 4. Printer Control Card (PCC) with a parallel port to control the elements placed on the PCC. 5. PCC to control the degree and direction of rotation of the stepper motors. 6. PCC to control the pins of the Printing head. 7. Two stepper motors to provide the drive along with mechanisms to transfer this drive to the Printer head. 8. Software driver for the Printer.|
|Full Text||The present invention relates to a novel Portable Computer Printer that can print on any
plane surface. For the purpose of description we describe this plane in terms of two
perpendicular axes. We call these axes as x-axis and y-axis and these directions as the x-
direction and y-direction respectively.
The conventional portable computer printers are desktop printers. The conventional
desktop printers suffer from two handicaps. Firstly, the printing surface, which is
generally paper, is required to be fed into the printer. Secondly, the printing surface is
required to conform to the standard sizes and shapes such as A-3, A-4 etc. Further the
conventional desktop printer can not be used to print on any particular part of a large size
printing paper as may be required. The conventional desktop printer also can not be used
to print on a printing surface which can not be conveniently detached such as the page of
a book or notebook. For example, the conventional desktop printer can not be used for
printing of accession number, date and other details on the books as required in the
It is an object of the present invention to design and develop a Portable Computer Printer
which can be used to print on a printing surface of any dimensions.
It is a further object of the present invention to design and develop a Portable Computer
Printer which can be used to print on a printing surface which can not be conveniently
detached for example the page of a book or notebook.
Accordingly the present invention provides a Portable Computer Printer consisting of the
1. An Inner frame which contains the assembly as herein specifically described
provided to impart x-direction movement to the Renter head.
2. An outer frame which contains the assembly as herein specifically described
provided for moving the Inner frame in v-direction.
3. A Printer near mounted on Head-carrier the Printer head is capable of moving in
two directions namely the x-direction and the y-direction.
4. Printer Control Card (PCC) with a Parallel Port to control the elements placed on
5. PCC to control the degree and direction of rotation of the Stepper motors.
6. PCC to control the pins of the Printing head.
7. Two Stepper motors to provide the drive along with mechanisms to transfer this
drive to the Printer head.
8. Software driver for the printer.
The Outer frame contains an assembly comprising a stepper motor (Motor .#1), fixed to the outer frame which provides the drive to move the entire inner frame in the y-direction, stands for the printer to be placed firmly on the print surface and the rods on which the inner frame is mounted.
The Inner frame contains an assembly comprising a stepper motor (Motor #2) fixed on the inner frame which provides drive to move the head carrier along the x-direction. The head carrier is mounted on the rods fixed on the inner frame.
The Portable Computer Printer, according to the present invention, is illustrated in the
accompanying drawings wherein
Figure 1, shows the Assembly contained in the Inner frame for imparting x-direction
movement to the Printing head. Figure 2 shows the assembly contained in the Outer frame for moving the Inner
frame in the y-direction.
Figure 3 shows the Diagram of atypical Stepper motor.
Figure 4 Shows the Block diagram of electrical element of the circuit for the
Printer Control Card.
Figure 5 shows the parts of the Software architecture.
The Portable Computer Printer, according to the present invention, consists of two Frames namely an Inner frame (1) and an Outer frame (2). The Inner frame contains the assembly which is needed to provide the x-direction movement to the Printer head. Thus the Inner frame is capable of printing a row of dots. The Inner frame assembly consists of Stepper Motor #2 (4) , head carrier (5), the printer head (6) and the ribbon (7). The Ribbon Cover (13) is fixed on the Inner frame. The Outer frame contains the assembly needed to move the Inner frame in the y-direction. The Outer frame consists of Stepper Motor #1 (3), rods (8) on which the Inner frame is mounted and the stands (9) which are
used to place the printer on the print surface. Thus a matrix of dots can be printed. The inner assembly prints a row of dots, then the outer assembly moves the inner assembly to the position of next row. The process is repeated to get the second row of dots and similarly the third row and so on till the entire matrix of dots is printed. As any monochrome image can be represented in terms of a matrix of black and white dots the image can be printed.
The entire Framework has been manufactured using light weight metal, such as Aluminium sheet. This is done to keep the weight low and maintain strength. PRINTER HEAD
The Printer head is fixed rigidly on a Head carrier and can be made of cut out of any light weight and strong material such as. persex. The motion and geometrical position of Printer head, is controlled by the Head carrier. In order to provide the x-direction movement, a Stepper motor (motor # 2) is used. This motor drives a belt using a pair of gears (10), one of which is coupled with the shaft of the Stepper motor. So when the motor rotaies, the belt moves. In one step the motor rotates by a fixed degree controlled by the printer driver and as a result the belt moves by a specific length. For example when the printer driver rotates the stepper motor by 7.5° the belt moves by 0.41 mm. This belt is tied to the Head carrier which rests on a pair of horizontal MS rods (12) used to guide the Head carrier. Thus when the belt moves, the Head carrier moves in the x-direction along the guide rods and with it the Printer head moves, This entire assembly is placed in Inner frame to print in the x-direction motion. The Inner frame rests on two MS rods (8) fixed on the Outer frame along the y-direction. Thus the Inner frame can glide on these rods in the y-direction. The Outer frame rests on the paper surface on four stands (9). These stands can move up and down to adjust the Printer head distance from the print surface. The y-direction motion is provided using rack and pinion arrangement (11). A Stepper motor (motor # 1) is used to provide the drive. This motor is fixed on the Outer frame. A double gear is coupled to shaft of Motor # 1. The gear which is coupled with the shaft provides a reduction depending on the radii of the gears, in the prototype we have chosen the radii so that the reduction ratio is same as 1:6. The other gear acts as a pinion. In one step Motor # 1 rotates by a specific angle which is controlled by the printer drive let us say a and therefore the pinion rotates by (a/6)°, the
rack is fixed on the inner frame with its length along the y-direction. Thus when Motor
#1 rotates, the inner frame moves in the y-direction and thus the y-direction motion is
The Printer head generally has 9 pins or 24 pins. In the prototype we have used a 9 pin
printer head. An individual pin is controlled and fired by the printer driver.
In order to prevent the Printer head from hitting the boundaries, two microswitches are
used. These switches are used to detect the boundary along x-direction and the boundary
along the y-direction and provide feedback to the printer driver running on the computer.
Thus by using these switches the Printer head can be placed on the one corner of the print
area. Since the x-direction length and the y-direction length of the print area are known,
with precise control over the Stepper motors, the Printer head can be placed at any
desired location in the print area.
The printer ribbon for the Printer head is cut from a standard ribbon. A small sheet of
steel is fixed at the bottom of the Head carrier to prevent any smears of ribbon being put
on the paper as the Printer head moves.
The Stepper motors are the standard stepper motors available in the market. The diagram
of a typical stepper motor is shown in Figure 3.
PRINTER CONTROL CARD
The Printer Control Card employs many circuit elements as latches, multiplexers, inverters, power amplifiers and voltage regulators. In order to drive the Stepper motors and the Printer head, the digital input values are stored in the latches.
Power amplifiers are used as switches. These switches are used to provide current to the electrical elements i.e. Stepper motors and Printing head. The switches are controlled by the digital signals stored in the latches and depending on this value current is allowed or prevented to flow in the motors and head.
All the digital signals needed to control the latches, multiplexers and inverters come from the parallel port.
For providing the driving current to the motors and the Printer head, voltage regulators are used.
The Parallel port in this document refers to the Centronix Printer Parallel Port. The Parallel port will allow the input of upto 5 bits or the of 8 bits at any one given
lime, thus requiring minimal external circuitry to implement many simpler tasks; The port is composed of 4 control lines, 5 status lines and 8 data lines. It's found commomy on the back of a PC as a D-type 25 Pin female connector.
The output of the Parallel Port is normally TTL logic levels. The voltage levels are the easy part. The current you can sink and source varies from port to port. Most Parallel Ports implemented in ASIC, can sink and source around 12mA. Source 12mA/Sink 20mA, Sink 16mA/Source 4mA, Sink/Source 12mA. As can be seen they vary quite a bit. The best bet is to use a buffer, so the least current is drawn from the Parallel Port. The Parallel Port has three commonly used base addresses. The 3BCh base address was originally introduced used Ibr Parallel Ports on early Video Cards. LPT1 is normally assigned base address 378h, while LPT2 is assigned 278h.
The base address usually called the Data Port or Data Register is simply used for outputting data on the Parallel Port's data lines (Pins 2-9). This register is normally a write only port.
The Data 0 - Data 6, i.e. Pin 2-8 are used for controlling the stepper motors and the printer head. Data 7 i.e., Pin 9, is used for the feedback.
The Status Port (base address + 1) is a read only port. Any data written to this port will be ignored. The Status Port is made up of 5 input lines (Pins 10,11,12,13 and 15), a IRQ status register and two reserved bits. Bit 7 (Busy) is a active low input, e.g. if bit 7 happens to show a logic 0, this means that there is +5v at pin 11. Likewise with Bit 2, (nlRQ) if this bit shows a then an interrupt has not occurred.
Any 2 of the five input lines can be used to take feedback from the printer through the microswitches. SOFTWARE
The software consists of printer driver. It works as shown in Figure 5 of the accompanying drawings. The application (it can be any program which wants to print a monochrome image using the printer) uses the printer driver to print the monochrome image. The driver depending on the image calculates a sequence of values to be dumped on the parallel port.
Based on these values the Printer Control Card (PCC) effects the Stepper motors and the Printer head. The printer driver is also getting feedback from the Parallel port regarding the status of the microswitches.
The following arc the salient features of the Portable Computer Printer according to the present invention.
1 . The Printer has very small size. The total dimensions of the Printer prototype that we have manufactured are 170 mm x 80 mm x 120 mm. The print area is 100 mm x 40 mm. The design is flexible so that it can be used to make printers of different dimensions and hence different print areas.
2. The Printer is of light weight and handy. It can be easily held in one hand and can
be carried easily.
3. The Stepper motors and the Printing head are easily available in the market which
means that they can easily be replaced when needed. The Printer head is the dot
matrix printing head
4. Since it is handy and rests on paper on simple stands, it can be used to print on
vertical or inclined surfaces also. The surface is not constrained to be horizontal.
5. It can print any black and white image, for the dimensions used in the prototype it
can print any image of the size in 10 cm x 4 cm.
6. The text it can print has no restrictions on the fonts, it can print any font.
7. It only uses a parallel port connection from the computer.
8. Since all the procedures of putting the paper in the printer, adjusting and then
tearing it off are made redundant, the printing also becomes pretty fast.
9. It can be used in Libraries to print accession numbers, dates and other details on
books. Similarly it can be used on notebooks. It can be used for similar purposes
10. It can be a direct replacement of rubber stamps.
11. It can be used for Block printing.
12. It can be used to print on vertical surfaces also.
Since many apparently different embodiments of the present invention could be made without departing from the spirit and scope thereof, it is intended that the description of the invention herein be interpreted as illustrative only and not limiting in any manner whatsoever.
1. A Portable Computer Printer consisting of the following
a. An Inner frame which contains the assembly as
herein specifically described provided to impart
x-direction movement to the Printer head.
b. An Outer frame which contains the assembly as
herein specifically described provided for moving
the Inner frame in y-direction.
c. A Printter head mounted on Head-carrier, the Printer
head is capable of moving in two directions namely
the x-direction and the y-direction.
d. Printer Control Card (PCC) with a Parallel Port to
control the elements placed on the PCC.
e. PCC to control the degree and direction of rotation
of the Stepper motors.
f. PCC to control the pins of the Printing head.
g. Two Stepper motors to provide the drive along with
mechanisms to transfer this drive to the Printer head, h. Software driver for the Printer.
2. A Portable Computer Printer substantially as herein
described and illustrated in the accompanying drawings.
|Indian Patent Application Number||1521/DEL/1999|
|PG Journal Number||01/2008|
|Date of Filing||06-Dec-1999|
|Name of Patentee||PROF. K.A. PADMANABHAN|
|Applicant Address||THE DIRECTOR, INDIAN INSTITUTE OF TECHNOLOGY, KANPUR-208016|
|PCT International Classification Number||G06F 1/16|
|PCT International Application Number||N/A|
|PCT International Filing date|