U.S. patent number 3,916,420 [Application Number 05/467,417] was granted by the patent office on 1975-10-28 for printer and display system.
This patent grant is currently assigned to NCR Corporation. Invention is credited to Robert W. Brown, James V. Cartmell, Donald Churchill, Alan J. Kresch.
United States Patent |
3,916,420 |
Brown , et al. |
October 28, 1975 |
Printer and display system
Abstract
The present invention is directed to a printer and display
system wherein the images from an optical character generator are
directed along two separate optical paths. A planar light-to-heat
transducer element is positioned in one of the optical paths to
intercept the generated character images for thermal printing a
permanent reproduction of the intercepted characters. A visual
display is positioned in the other optical path to intercept the
generated character images for forming viewable images of the
generated character images.
Inventors: |
Brown; Robert W. (Appleton,
WI), Cartmell; James V. (Kettering, OH), Churchill;
Donald (Appleton, WI), Kresch; Alan J. (Appleton,
WI) |
Assignee: |
NCR Corporation (Dayton,
OH)
|
Family
ID: |
23855608 |
Appl.
No.: |
05/467,417 |
Filed: |
May 6, 1974 |
Current U.S.
Class: |
346/17; 396/549;
347/255; 347/256; 250/316.1 |
Current CPC
Class: |
G06C
11/02 (20130101); G06C 11/04 (20130101) |
Current International
Class: |
G06C
11/04 (20060101); G06C 11/00 (20060101); G06C
11/02 (20060101); G01D 015/10 (); B41B
013/00 () |
Field of
Search: |
;346/17,76R,17R,11R,33A
;355/44,45 ;354/5,6 ;250/316,330,331,332 ;350/16LC,171,169 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hartary; Joseph W.
Attorney, Agent or Firm: Cavender; J. T. Sessler, Jr.;
Albert L. Dugas; Edward
Claims
What is claimed is:
1. Apparatus comprising, in combination:
means for forming light images;
means for directing said light images along at least two optical
paths;
transducer means intercepting the image in one of said optical
paths for transforming said image into a corresponding heat image
capable of being transferred to a heat sensitive record
material;
said transducer means comprised of:
an optically transparent substrate;
a plurality of electrodes adapted to receive an electrical
potential therebetween positioned on said optically transparent
substrate, in a pattern which outlines a desired composite
character;
a layer of photoconductive material covering said electrodes such
that a light image of a selected character impinging on the
photoconductive material in the electrode outlined pattern causes a
change in resistance of the photoconductive material on which the
light impinges thereby causing an increased temperature of said
photoconductive material in the areas on which light impinges;
and
viewing means positioned to intercept the image in another of said
optical paths.
2. The apparatus according to claim 1 wherein said means for
directing is comprised of:
a beam splitter positioned to intercept the light images from said
means for forming light images and for directing said light images
along two optical paths.
3. The apparatus according to claim 1 and further comprising:
means for activating said transducer means only when a heat image
is to be transferred to a heat sensitive material.
4. Apparatus comprising, in combination:
means for forming light images;
means for directing said light images along at least two optical
paths;
transducer means intercepting the image in one of said optical
paths for transforming said image into a corresponding heat image
capable of being transferred to a heat sensitive record
material;
said transducer means comprised of:
an optically transparent substrate;
an electrode having a plurality of openings positioned on said
substrate;
a layer of photoconductive material positioned over said electrode
and in said openings;
a second electrode positioned on said layer of photoconductive
material, said optically transparent electrode and said second
electrode adapted to receive an electrical potential therebetween
such that light impinging on said photoconductive material changes
the resistance between said optically transparent electrode and
said second electrode which in turn changes the current flow
through said photoconductive material and the temperature of said
photoconductive material; and
viewing means positioned to intercept the image in another of said
optical paths.
5. An optical display and printer system comprising in
combination:
a plurality of light sources arranged in a matrix;
means for causing selected ones of said light sources to emit
light;
means for directing the image formed by said light sources along
two optical paths;
an optical-to-thermal transducer positioned to intercept the image
in one of said optical paths, for transforming said optical image
into a corresponding heat image which image is adapted to be
transferred to a heat sensitive material, said optical-to-thermal
transducer comprised of:
an optically transparent substrate;
a plurality of electrodes adapted to receive an electrical
potential therebetween positioned on said optically transparent
substrate, in a pattern which outlines a desired composite
character;
a layer of photoconductive material over and between said
electrodes such that a light image of a selected character
impinging on the photoconductive material in the electrode outlined
pattern causes a change in resistance of the photoconductive
material on which the light impinges thereby causing an increased
temperature of said photoconductive material in the areas on which
light impinges; and
a viewing screen positioned to intercept the image in the second of
said optical paths.
6. The optical display and printer system according to claim 5
wherein said optical-to-thermal transducer is comprised of:
an optically transparent substrate;
an optically transparent electrode positioned on said
substrate;
a layer of photoconductive material positioned over said
transparent electrode; and
a second electrode positioned on said layer of photoconductive
material, said optically transparent electrode and said second
electrode adapted to receive an electrical potential therebetween
such that light impinging on said photoconductive material changes
the resistance between said optically transparent electrode and
said second electrode which in turn changes the current flow
through said photoconductive material and the temperature of said
photoconductive material.
7. The optical display and printer system according to claim 5 and
further comprising:
means for activating said optical-to-thermal transducer only when a
heat image is to be transferred to said heat sensitive
material.
8. An optical display and printer system comprising in
combination:
a light source;
character image forming means positioned to intercept the light
from said light source, said character image forming means
comprised of:
a light polarizer for receiving the light from said light source
and for polarizing the light;
a liquid crystal cell positioned to intercept the polarized
light;
means for changing the polarization characteristics of said liquid
crystal cell in selected areas so as to change the angle of the
polarized light in the selected areas;
an analyzer for passing light having a selected polarization
angle;
an optical-to-thermal transducer positioned to intercept the image
in one of said optical paths, for transforming said optical image
into a corresponding heat image which image is adapted to be
transferred to a heat sensitive material; and
a viewing screen positioned to intercept the image in the second of
said optical paths.
9. The system according to claim 8 wherein said liquid crystal cell
is further comprised of:
at least one pair of electrodes, one of which electrodes of the
pair is configured to represent a character, positioned on opposite
sides of said liquid crystal cell, said electrodes connected in
circuit to said means for changing the polarization characteristics
of said liquid crystal cell.
10. The system according to claim 9 wherein said means for changing
the polarization characteristics of said liquid crystal cell is
comprised of:
a voltage source the level of which is sufficient to change the
polarization angle of said liquid crystal cell by a desired amount;
and
select means for applying the voltage from said voltage source to
said at least one pair of electrodes.
11. The system according to claim 9 and further comprising:
a lens interposed between said analyzer and said viewing screen for
focusing the light passed by said analyzer onto said viewing
screen.
12. The system according to claim 9 wherein said means for
directing the image from said character image forming means along
two optical paths is a beam splitter positioned to intercept the
image from said character generator.
13. An optical display and printer system comprising
in-combination:
a light source;
character image forming means positioned to intercept the light
from said light source;
means for directing the image from said character image forming
means along two optical paths;
an optical-to-thermal transducer positioned to intercept the image
in one of said optical paths, for transforming said optical image
into a corresponding heat image which image is adapted to be
transferred to a heat sensitive material, said optical-to-thermal
transducer comprised of:
an optically transparent substrate;
a plurality of electrodes adapted to receive an electrical
potential therebetween positioned on said optically transparent
substrate, in a pattern which outlines a desired composite
character; and
a layer of photoconductive material covering said electrodes such
that a light image of a selected character impinging on the
photoconductive material in the electrode outlined pattern causes a
change in resistance of the photoconductive material on which the
light impinges thereby causing an increased temperature of said
photoconductive material in the areas on which light impinges;
and
a viewing screen positioned to intercept the image in the second of
said optical paths.
14. The optical display and printer system according to claim 13
and further comprising:
means for activating said optical-to-thermal transducer only when a
heat image is to be transferred to said heat sensitive
material.
15. An optical display and printer system comprising
in combination:
a light source;
character image forming means positioned to intercept the light
from said light source;
means for directing the image from said character image forming
means along two optical paths;
an optical-to-thermal transducer positioned to intercept the image
in one of said optical paths, for transforming said optical image
into a corresponding heat image which image is adapted to be
transferred to a heat sensitive material, said optical-to-thermal
transducer comprised of:
an optically transparent substrate;
an electrode having a plurality of openings positioned on said
substrate;
a layer of photoconductive material positioned over said electrode
and in said openings;
a second electrode positioned on said layer of photoconductive
material, said optically transparent electrode and said second
electrode adapted to receive an electrical potential therebetween
such that light impinging on said photoconductive material changes
the resistance between said optically transparent electrode and
said second electrode which in turn changes the current flow
through said photoconductive material and the temperature of said
photoconductive material; and
a viewing screen positioned to intercept the image in the second of
said optical paths.
Description
BACKGROUND OF THE INVENTION
In business machines, such as cash registers, there exists a need
for providing a visual display of the price of each item and of the
totals along with a sales slip for use by the vendor and the
customer. In the past the printing mechanisms which prints the
sales slips has been electromechanical in nature and has required
relatively large amounts of power to operate. Due to recent
advances in the electronic arts, there has been a trend by business
machine manufacturers towards substituting electronic circuits for
mechanical parts whenever practical. The printer section of the
business machine has been one of the mechanical units which has
been found to be difficult to replace. Although a variety of
electro-optic devices, such as gaseous discharge display panels,
have been used for the visual display, hammer type printers are
still commonly utilized for making the permanent copies. In certain
select applications thermal printers have been used to eliminate
the mechanical hammers. Because the driving requirements of
electronic display devices differ greatly from those of either the
mechanical hammer printer or the thermal printer, separate driving
systems have been required for each of these units. A system which
could merge the driving requirements of the printer and visual
display while still providing a display similar to the gas
discharge or other electro-optic type displays would be highly
desirable in that such a merging would provide not only a cost
reduction but a reduction in weight and the total number of
components used per system. Additional and significant improvement
is realized if the power requirements of the logic and control
circuitry is compatible with state of the art integrated
circuits.
Examples of prior art visual display devices can be found in U.S.
Pat. No. 3,690,745 by D. Jones, entitled "Electro-Optical Devices
Using Lyotropic Nematic Liquid Crystals," and in U.S. Pat. No.
3,703,331 by J. E. Goldmacher, entitled "Liquid Crystal Display
Element Having Storage." The devices of these prior art patents
utilize a thin cell containing a liquid crystal. The Jones patent
additionally utilizes a standard seven bar electrode arrangement
for generating numeric images. The Goldmacher device utilizes a
matrix of elements, which matrix would theoretically be capable of
generating both numeric and character images.
A prior art field effect liquid crystal shutter device is described
in U.S. Pat. No. 3,700,306 by Cartmell, et al., entitled
"Electro-Optic Shutter Having A Thin Glass Or Silicon Oxide Layer
Between The Electrodes And The Liquid Crystal," which patent is
assigned to The National Cash Register Company, the assignee of the
present application.
The present state of the art in electronic displays has been
summarized in an article entitled "Electronic Numbers" authored by
Alan Sobel, which appeared in Scientific American, June 1973,
Volume 228, Number 6, Pgs. 64-73.
A thermal type printer particularly adaptable to business machines
is disclosed in U.S. Pat. No. 3,631,512, entitled "Slave Printing
Apparatus" by J. L. Janning, which patent is assigned to The
National Cash Register Company, the assignee of the present
application. In one embodiment disclosed in that patent, a first
matrix of light sources may be selectively energized to produce a
desired character pattern. A second matrix of semiconductor areas
is positioned with respect to the first matrix such that each
semiconductor area receives the light from a corresponding light
source. Pairs of conductors, positioned on opposite edges of each
semiconductor area, sense the decrease in resistivity in a light
actuated semiconductor area, causing an increased current to flow
through the semiconductor area which increased current is used to
heat a resistance element that is positioned in proximity to a
thermal sensitive medium.
From the foregoing description of the prior art it can be seen that
the need exists for a business machine which uses low power and a
minimum number of mechanical parts to provide both a visual display
and a printout.
SUMMARY OF THE INVENTION
The present invention is directed to a system having a printer and
visual display utilizing a common optical character generator for
providing a temporary and a permanent record of the generated
characters. The system is particularly adaptable for use with low
power integrated circuits.
In one preferred embodiment of the invention, finding particular
utility in a business machine, the optical character generator is
comprised of a light source and an electro-optical cell wherein
character images are formed by changing the polarization
characteristics of a liquid crystal which is interposed between
character electrodes. A polarizer interposed between the light
source and the electro-optical cell polarizes the light from the
source before it impinges on the liquid crystal cell. An analyzer
positioned to receive the polarized light passing through the cell
provides an output (passes light) which has the correct
polarization angle and stops all other light. The polarization
angle of the light passing through the liquid crystal is controlled
by applying a potential across selected conductors in the cell. The
light beam from the analyzer is then directed to a beam splitter
element, which element provides as an output two separate beams
having identical characteristics. One of the beams is fed to a
photothermographic element, which element is used in conjunction
with a thermal sensitive material to provide a permanent copy. The
other beam is directed to a viewing screen for direct viewing.
Means are also provided for activating selected electrodes in the
electro-optical cell to form desired characters which means are
under the control of an operator.
In a second embodiment of the present invention a matrix of light
emitting diodes are connected in circuit to an operator selector
element which element activates selected diodes in response to the
operators request so as to form character light images. The light
from the activated diodes is directed to the beam splitter to
provide the two separate output beams.
From the foregoing it can be seen that it is a principal object of
the present invention to provide an improved business machine.
It is another object of the present invention to provide a printer
and visual display utilizing an optical character generator.
It is a further object of the present invention to provide a means
for activating a visual display and printer. These and other
objects of the present invention will become more apparent when
taken in conjunction with the following description and drawings,
throughout which like reference characters indicate like parts and
which drawings form a part of this application
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block schematic diagram of one preferred embodiment of
the present invention.
FIGS. 2A, 2B, and 2C are front, back and a sectioned side view of
an electro-optical cell which may be used in the embodiment of FIG.
1;
FIGS. 3A and 3B are a top view and a sectioned view of a
photothermographic element which may be used in the embodiment of
FIG. 1;
FIGS. 4A and 4B are a bottom view and a sectioned view of a second
photothermographic element which may be used with the preferred
embodiment of FIG. 1;
FIG. 5 is a top view of a photothermographic element which may be
used in the preferred embodiment of FIG. 1;
FIG. 6 is a block diagram of a second embodiment of the
invention;
FIG. 7 is the front view of an optical element which may be used
with the embodiment of FIG. 6; and
FIG. 8 is a perspective view of a business machine wherein the
embodiments of FIG. 1 and FIG. 6 find particular utility.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, a light source 10, such as a tungsten bulb,
powered by the power supply 26, provides a beam of light to a lens
12. The lens 12 focuses the provided beam of light onto a polarizer
14. The polarizer polarizes the received beam in a preferred plane.
The polarized beam is then directed to an electro-optical cell 20
which may be of the field effect twisted nematic type.
A character selector 25, connected to the power supply 26, in
response to operator-activated keys 39, provides a voltage to
selected areas of the electro-optical cell 20 so as to select a
desired character. The voltage remains applied to the selected
areas until the operator presses a "clear" key. Means for
accomplishing this function are well within the state of the art
and are not shown for purposes of clarity.
Cell 20 rotates the incident polarized light by a predetermined
angle, generally 90.degree., when there is no power applied to the
cell. Under the control of element selector 25 portions of the cell
have an electric field applied across the liquid crystal and no
longer rotate the polarized light. An analyzer 27 is positioned to
absorb the rotated polarized portions of the polarized beam from
the electro-optical cell 20 and to transmit the nonrotated portions
of the polarized beam.
The beam from analyzer 27 is directed to a beam splitting element
29, which may be a partially silvered mirror. A portion of the
transmitted beam is reflected from the beam splitter 29 on to
mirror 30, with the remaining portion of the beam passing through
the beam splitter to a lens 32. Lens 32 focuses the beam onto a
photothermographic element 33.
The character selector 25 has an output connected to a
photothermographic element power supply 37. The photothermographic
element power supply 37 is connected to the thermographic element
33 to provide an activating voltage to the element 33 in response
to a print command from the character selector 25. In operation,
power is applied to element 33 for a fixed period of time,
approximately 500 milliseconds, by the photothermographic element
power supply 37 in response to the depression of a printout key on
the character selector 25. The photothermographic element 33
provides a heated pattern corresponding to the image received from
lens 32.
A thermal sensitive material 40 is positioned adjacent the heated
areas of element 33 for recording the generated heat image. The
period of time that a voltage is applied to element 33 is dependent
somewhat on the response time of the thermal sensitive material,
but in the preferred embodiment a 500 millisecond period provided
satisfactory results.
The beam imaged onto mirror 30 is reflected to a lens 42, which
lens focuses the beam to a viewing screen 45. The viewing screen
may be made from any of a number of light scattering surfaces such
as etched glass.
Referring to FIGS. 2A, 2B and 2C for a detailed description of the
electro-optical cell 20, a glass front plate 21 has deposited
thereon sector electrodes 22 in a common numeric configuration
which electrodes are transparent to light. Conductors 23 connect
each of the electrodes 22 to conductive tabs 15a. A glass rear
plate 24 has deposited thereon a common electrode 26. formed from a
light-transparent conductive material such as tin oxide, connected
by a conductor 28 to a tab 15b. the tabs 15a and 15b are connected
in circuit to the character selector 25. The two plates 21 and 24
are positioned parallel to each other and are spaced apart by a
spacer 34. The plates and spacer are sealed together by a sealer 31
so as to form a cavity. A nematic liquid crystal material 36 fills
the cavity and is in electrical contact with the electrodes 22 and
26.
The type of liquid crystal cell used in the preferred embodiment of
this invention is of the Twisted Nematic Field Effect Type
(sometimes called Bilevel). A basic description of the liquid
crystal cell is set forth by M. Schadt and W. Helfrich, in Applied
Physics Letters 18 127 (1971).
The liquid mixture used in these cells has a positive dielectric
anisotropy -- that is when an electric field is applied across the
liquid crystal the molecules tend to line up with their long axes
parallel to the field direction.
The composition of the nematic liquid crystal mixture for the filed
effect cell used was
40% p-methoxybenzilidine-p.sup.1 -butylaniline (MBBA)
40% p-ethoxybenzilidine-p.sup.1 -butylaniline (EBBA)
20% p-butoxybenzilidine-p.sup.1 -aminobenzonitrile.
This mixture acts as a liquid crystal in a temperature range from
10.degree.C to 70.degree.C.
A field effect cell with this mixture will undergo an electro-optic
switching at about 4-12 volts of alternating field. The distance
between electrodes is about 0.5 mil. The current is in the range of
microamps per character, and the display is readily operated
directly from MOS integrated circuits with no amplification.
The size of the liquid crystal cell is not critical. For the direct
reading of a number .about.3/4 inch height is desirable, in the
display. Actual cell dimensions would be typically 1 inch height
and a width of 0.8 inch times the number of characters +1. (0.8
inch .times. (n+1) ).
In operation, selected ones of the electrodes 22 and the common
electrode 26 have a potential applied therebetween. The potential
is selected so as to either eliminate or change the amount of
angular rotation which occurs to the polarized light. Because the
field is localized between the selected electrodes 22 and the
common electrode 26, only those portions of the liquid crystal
material located between the aforementioned electrodes will be
affected. Therefore, by adjusting the angular position of the
polarizer 14 and the analyzer 27, the light transmitted through the
liquid crystal material between the electrically activated
electrodes will be of a different intensity from the light
transmitted through the electrodes where no electrical field is
applied. Depending on this adjustment, either a light digit on a
dark background or a dark digit on a light background can be
transmitted.
In the present embodiment, printing at the photothermographic
element is light activated so a light digit is the preferred
configuration.
Referring to FIGS. 3A and 3B simultaneously, the photothermographic
element 33 is shown comprised of a glass substrate 50 onto which is
formed two conductors 52 and 53. The conductors 52 and 53 are
configured to be substantially parallel to each other throughout
the plane of the element. A photoconductive material 51 is
deposited over and between the conductors. In operation, a
potential is applied to conductors 53 and 52 so as to create a
field between the conductors. Light impinging on the
photoconductive material located between the conductors causes a
decrease in resistivity which in turn causes a localized current to
flow between conductor 52 and 53, which localized current causes a
localized heating. By adjusting the spacing and the number of
parallel paths per cross-sectional area of the element the
resolution of the localized heat patterns can be increased or
decreased as desired.
Referring to FIGS. 4A and 4B, a second photothermographic element
is disclosed wherein a glass substrate 55 has deposited thereon a
mesh configured electrode 56 having a plurality of openings 59
defined thereby. A photoconductive material 57 is deposited onto
the electrode 56 and into the defined openings 59. An electrode 58
is deposited onto the photoconductive material 57. In operation, a
potential is formed between electrodes 56 and 58. Light traversing
electrode 56 and impinging on photoconductive material 57 changes
the resistivity of the photoconductive material causing current to
flow between conductors 56 and 58 in a localized pattern, which
current causes a localized heating of electrode 58. Electrode 58 is
positioned in close proximity to the thermal sensitive material 40
so as to effect a transfer of the localized heat pattern.
Referring to FIG. 5, another photothermographic element which may
be used with the preferred embodiments of the invention is shown
formed from a glass substrate 60 onto which are deposited an
electrode 62 and an electrode 63. A photoconductive material 61 is
deposited over and between the electrodes. Potentials are applied
to the electrodes 62 and 63 by means of conductors 64 and 65,
respectively. Conductors 64 and 65 are connected in circuit to the
photothermographic element power supply 37. When activated by a
printout signal from the character selector 25, a potential field
is created in the areas 66 between the electrodes 62 and 63.
Potential fields will occur in other areas, but no light should
impinge in those areas. The area 66 (between the electrodes) is a
substantial duplicate of the area formed by the seven bar elements
22 used in the electro-optical cell 20.
In operation, light transmitted through the electro-optical cell 20
impinges on the corresponding areas between the electrode 62 and
the electrode 63, causing a change in the resistivity of the
photoconductive material, which change increases the current
flowing through the photoconductive material within the areas onto
which the light impinges, thereby causing localized heating of
these areas. The thermal sensitive material 40 is positioned
adjacent the heated areas to allow the heat formed image to be
transferred to the material 40.
Referring to FIGS. 6 and 7, an array 70 of light emitting diodes 73
is used to generate a light pattern corresponding to an
operator-selected character. Conductors 74 and 75 connect each of
the diodes 73 to the character selector 25 in the well-known matrix
configuration. The operator-selected keys 39 apply the proper
potentials to the column and row conductors of the matrix so as to
cause the diodes 73 connected at the crossover points of the
selected row and column electrodes to emit light. The light image
formed by the array 70 is transmitted to the beam splitter 29. The
beam splitter 29 reflects a portion of the beam onto a mirror 30
with the remaining portion of the beam being passed through to lens
32. Lens 32 then directs and focuses the image onto the
photothermographic element 33 similar to the first embodiment.
Element 33 is activated by the photothermographic element
controller 37 for printing out the image onto the thermal sensitive
material 40. Mirror 30 reflects the other beam to lens 42. Lens 42
in turn focuses the image onto the viewing screen 45.
FIG. 8 illustrates a business machine (transaction terminal)
wherein the viewing screen 45 is mounted for easy customer viewing
and the thermal sensitive material 40, which may be a sales
receipt, is shown ready for dispensing to the customer. The
operator-selected keyboard 39 is shown mounted in an easily
accessible position on the business machine.
An amount of heat used to make the print will vary depending on the
voltage across the photothermographic element and the time allowed
for the print cycle assuming the light to be a constant. For an
interdigital photothermographic element with 3 mil. electrodes and
6 mil. spacing (FIG. 3), typical figures would be:
Voltage across element approximately 25 volts (AC)
Illumination approximately 200 foot candles
Printing cycle time approximately 500 milliseconds.
The above figures can be varied considerably but are
interdependent. Print resolutions of about 6 line pairs per
millimeter have been obtained with this type of cell.
The print size would most likely be the same as that of a
typewriter or an adding machine (approximately 1/8 inch height,
1/10 inch width, per character). Good resolution has been obtained
in prints of this size. Characters of larger sizes could be
printed. The resolution is dependent on both printing cycle time
and electrode configuration. Special purpose electrodes (FIG. 5)
should give excellent resolution and print sharpness because:
a. They are "matched" to the liquid crystal and the electrodes act
as light masks.
b. The large electrodes act as heat sinks.
While there have been shown what are considered to be the preferred
embodiments of the invention, it will be manifest that many changes
and modifications may be made therein without departing from the
essential spirit of the invention. It is intended, therefore, in
the annexed claims, to cover all such changes and modifications as
may fall within the true scope of the invention.
* * * * *