U.S. patent number 3,758,782 [Application Number 05/273,889] was granted by the patent office on 1973-09-11 for light pen apparatus.
Invention is credited to Robert E. Radford, Gary N. Stapleford.
United States Patent |
3,758,782 |
Radford , et al. |
September 11, 1973 |
LIGHT PEN APPARATUS
Abstract
Light pen apparatus having a small number of parts. The light
pen includes an inner barrel in which a printed circuit board is
mounted. An outer barrel surrounds the inner barrel and is arranged
for limited travel relative to the inner barrel in an axial
direction. As the outer barrel and inner barrel are moved relative
to one another a switch carried on the printed circuit board is
actuated so as to allow the circuit mounted on the board to respond
to light detected by a light responsive device also carried on the
board.
Inventors: |
Radford; Robert E. (Nashua,
NH), Stapleford; Gary N. (Londonderry, NH) |
Family
ID: |
23045848 |
Appl.
No.: |
05/273,889 |
Filed: |
July 21, 1972 |
Current U.S.
Class: |
250/552;
250/227.13; 250/239 |
Current CPC
Class: |
G06F
3/03542 (20130101) |
Current International
Class: |
G06F
3/033 (20060101); G06f 003/00 () |
Field of
Search: |
;250/217CR,227,216,229,239 ;178/DIG.2,5.4E ;350/96R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Stolwein; Walter
Claims
What is claimed is:
1. A light pen comprising:
a circuit including a light responsive device and a switch for
turning the circuit on and off;
an elongated printed circuit board with said light responsive
device mounted adjacent one end, and said switch mounted adjacent
the other end;
an elongated inner tube having
means for holding said board internally thereof with the light
responsive device adjacent one light admitting end thereof and the
switch adjacent the other end thereof;
a first spring stop located on its external surface; and
a slot in its surface at said other end;
an outer tube arranged concentrically with said inner tube and
having a second spring stop on its internal surface and a switch
actuating element on its internal surface adjacent one end thereof
and extending through said inner tube slot;
a spring element arranged concentrically with and between said
inner and outer tubes and arranged between and engaging said first
and second stops; and
an end cap which includes a fastening element adapted to be engaged
with said inner tube and which further includes an abutting edge
engaging said one end of the outer tube so as to normally maintain
said spring element in a first state of compression in which said
switch actuating element is out of the actuation range of the
switch, said inner and outer tubes being slidable relative to one
another to place said spring element in a second state of
compression in which said switch actuating element comes within the
actuation range of said switch to thereby turn said switch and
circuit on.
2. A light pen as set forth in claim 1
wherein said switch includes a source of light and another light
responsive device mounted in spaced apart relation adjacent the
other end of said circuit board; and
wherein said switch actuating element is a shutter which is
arranged to interrupt the light beam from said source when the
spring is in its second compression state.
3. A light pen as set forth in claim 2
wherein said first spring stop is located near said one end of the
inner tube; and
wherein said second spring stop is located near the other end of
said outer tube.
4. A light pen as set forth in claim 3
wherein said fastening element is a snap lock which engages an
aperture in said inner tube.
5. A light pen as set forth in claim 4
wherein said inner and outer tubes and end caps are made of plastic
material.
6. A light pen as set forth in claim 1
wherein the internal surface of said inner tube is coated with a
metallic material; and
wherein the edges of said printed circuit board are coated with
metallic material and are in electrical contact with the metallic
coating of said inner tube.
7. A light pen as set forth in claim 6
wherein said means for holding includes a pair of grooves in the
internal surface of the inner tube each holding a different one of
the two elongated edges of the printed circuit board.
Description
BACKGROUND OF INVENTION
1. Field of Invention
This invention relates to novel and improved light responsive
apparatus and in particular to a hand held light pen which is
rather inexpensive to construct and yet reliable.
Light pens are useful, for example, in information display systems
for operator selection of information items being visually
displayed on a display screen such as the screen of a cathode ray
tube. The operator selects a displayed information item by aiming
the light pen at the item. The light pen responds to the light
emitted by the selected item to produce electrical signals which
are transmitted to associated apparatus within the information
display system such as a computer.
2. Prior Art
Light pens generally include a switch operated circuit having a
light responsive device mounted within an elongated pen like
housing. In some prior art light pens, the switch, the light
responsive device and the remainder of the circuit components have
been mounted as separate units within the housing structure. This
has resulted in a relatively complex housing structure which has
been difficult to assemble as well as to service. In addition, the
switch element employed in many prior art light pens has had a
relatively short life thereby necessitating frequent service.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel and
improved light pen.
Another object is to provide a novel light pen which is
characterized by simplicity of construction whereby it can be
rapidly assembled and/or disassembled.
Still another object is to provide a novel light pen in which the
switch mechanism is extremely reliable.
In brief, light pen apparatus embodying the present invention
comprises three housing pieces, a printed circuit board assembly
and a spring. The three housing pieces, which may preferably be
injection molded thermoplastic pieces, include an inner tube an
outer tube and an end cap. The printed circuit board assembly
includes an elongated circuit board with the light responsive
device mounted adjacent one end and the switch mounted adjacent the
other end. The inner tube includes a means for holding the printed
circuit board internally of itself with the light responsive device
adjacent one end and the switch adjacent the other end. A first
spring stop is located on the external surface of the inner tube. A
slot is also located in the surface of the inner tube at the end
adjacent the switch.
The outer tube which is arranged concentrically with the inner tube
has a second spring stop on its internal surface and a switch
actuating element on its internal circuit extending through the
inner tube slot. The spring element is arranged concentrically with
and between the inner and outer tubes and between and engaging the
first and second stops.
The end cap includes a fastening element which is engaged with the
inner tube and also an abutting edge which engages one end of the
outer tube so as to normally maintain the spring in a first state
of compression in which the switched actuating element is out of
the actuation range of the switch. The inner and outer tubes are
slidable relative to one another so as to place the spring in a
second state of compression in which the switch actuating element
comes within the actuation range of the switch to thereby turn the
switch and circuit on.
In the interest of reliability and long switch life, the actuating
element is a shutter and the switch comprises a light source such
as a light emitting diode which provides a beam of light incident
upon a light responsive device such as a photo diode or photo
transistor. So long as the light is incident upon the light
responsive device (the shutter being out of the switch actuation
range) the switch is turned off. When the shutter comes within the
switch actuation range and interrupts the beam of light so that it
is no longer incident upon the light responsive device, the switch
is turned on.
BRIEF DESCRIPTION OF THE DRAWING
In the accompanying drawing like reference characters denote like
elements of structure; and
FIG. 1 is a perspective view of light pen apparatus embodying the
present invention; and
FIG. 2 is an enlarged cross sectional view taken along the line
2--2 of FIG. 1.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to FIG. 1, light pen apparatus embodying the present
invention is shown to include an inner tube or barrel 10, an outer
tube or barrel 20, an end cap 30, a spring 35 and a printed circuit
board 40. For the purpose of a clear illustration, all of these
parts are shown in FIG. 1 as disassembled with accompanying arrows
which indicate the respective location of the parts when in
assembled form. The inner tube 10 includes a pair of slots 11 and
12 (best seen in FIG. 2) in its internal surface for receiving and
holding in a secure manner the printed circuit board 40. The inner
tube 10 further includes a first spring stop 13 on its external
surface and a slot 14 at one end of the tube. The other end of the
inner tube 10 is shown to be tapered with an aperture 15 (FIG. 2)
for admitting light into the interior of the tube.
Mounted on the printed circuit board 40 at one end thereof is a
light responsive device 41. When the printed circuit board 40 is
inserted into the inner tube 10 along the grooves 11 and 12, the
ligh responsive device 41 is in substantial alignment with the
aperture 15 so as to respond to light admitted through the
aperture. The light responsive device 41 may, for example, be a
photo diode or a photo transistor. The light responsive device 41
is part of a circuit which also includes a light emitting diode 42,
another light responsive device 43 and other circuit components 44
all of which are mounted upon the printed circuit board 40. The
light emitting diode 42 and the light responsive device 43 are
mounted in spaced apart relation at the other end of the board from
the device 41. When the board 40 is fully inserted within the inner
tube 10, the space between the light emitting diode 42 and the
light responsive device 43 is in substantial alignment with the
slot 14 of tube 10. In order to provide an adequate shield for the
circuit, the printed circuit board 40 has its edge coated with a
metallic material 45 and the inner tube 10 has its interior surface
coated with a metallic material 16. Metallic material 16 and 45
may, for example, be copper.
The light emitting diode 42 and light responsive device 43 together
form a switch which is off so long as light from diode 42 is
incident upon light responsive device 43 and is on when the light
is interrupted. The switch serves to turn the circuit on and off,
i.e., make the circuit responsive and nonresponsive to light
admitted by aperture 15. When the circuit is turned on, it responds
to incident light upon light responsive device 41 to transmit a
signal via an interface cable 50 attached to one end of printed
circuit board 40. If the incident light is emitted by an
information item on a display screen in an information display
system, the cable 50 may be connected at its other end to other
apparatus in the system such as a computer.
The outer tube 20 includes a second spring stop 21 and a switch
actuating element or shutter 22. When assembled, the outer tube 20
is arranged concentrically with the inner tube with the shutter 22
extending through the inner tube slot 14.
The end cap 30 includes a pair of fastening elements 31 and 32
(snap locks in the illustrated embodiment), a pair of flange
elements 33 and 34 and an abutting edge 35. The flange and
fastening elements are positioned on the end cap 30 such that in
assembled form they extend into the interior of the inner tube 10
where the fastening elements 31 and 32 snap or lock with apertures
17 and 18, respectively, in the inner tube 10. The abutting edge 35
of the 20 end cap 30 engages the end of the outer tube 20 such that
the spring 35 is normally maintained in a first state of
compression by the first and second spring stops 13 and 21. In this
first compression state, the shutter element 22 is out of the
actuation range of the switch elements 42 and 43. That is, the
shutter element 22 does not interrupt the light emitted by diode 42
which is incident upon the light responsive device 43.
When it is desired to select an information item on the display
screen, the outer barrel is held in the operator's hand and the
tapered end of the assembled pen is aimed at the item and pressed
against the screen. This causes the outer barrel and inner barrel
to slide relative to one another so as to place the spring 35 in a
second state of compression. In this second state of compression,
the shutter 22 comes within the actuation range of the switch so as
to interrupt the light beam from the diode 42 and hence turn the
switch and circuit on. In addition, in the second state of
compression the outer barrel 20 has travelled away from the
abutting edge 35 of the end cap 30. When the operator removes the
tapered end of the assembled light pen from the screen, the outer
and inner barrels return to their initial or normal positions as
the spring 35 returns to its first state of compression.
The inner tube 10, outer tube 20 and end cap 30 are preferably made
of plastic material which may be either machined or molded into the
desired shapes. From a cost point of view, it is extremely
advantageous to employ thermoplastic material and injection molding
for these parts.
Once the circuit components have been assembled on the printed
circuit board 40, the entire light pen can be assembled very
rapidly. First, the spring 35 is slipped over the external surface
of the inner tube 10. The cable 50 is threaded through the end cap
30 and outer tube 20 and is then attached to the circuit board 40.
The circuit board 40 is then inserted along the grooves 11 and 12
into the inner tube 10. The outer tube is then slid along and over
the inner tube 10. The end cap is then placed into position with
its fastening elements 31 and 32 locking on to the inner tube 10.
The light pen assembly can also be disassembled very rapidly with
the aid of a pointed instrument (e.g., a pencil or pen) by
depressing the fastening elements 31 and 32 so as to remove them
from the apertures 17 and 18 of tube 10.
There has been described light pen apparatus embodying the
invention which employs a relatively small number of parts. The
switch in the illustrated embodiment has relatively long life since
it does not rely upon a mechanical actuating element. However, in
other embodiments the switch may take the form of mechanically
actuated switches or field (magnetic or electric) actuated
switches. In any case, the switch actuating element 22 would be
mounted upon and carried by the outer tube 20. The actual shape of
the tubes or barrels 10 and 20 and end cap 30 can vary from one
design to another and the term tube or barrel as used herein is
intended to mean not only cylindrical shapes but such other cross
sections including, inter alia, square, triangular, polygonal,
eliptical and other. Moreover, the light admitting end of the inner
tube 10 need not be tapered. If it is desirable to employ a lens
assembly to focus or magnify light emitted by an information item,
such lens assembly may be mounted (by means not shown) over or in
the aperture 15 of the inner tube 10.
* * * * *