U.S. patent number 3,684,858 [Application Number 05/155,948] was granted by the patent office on 1972-08-15 for thermal printing head.
Invention is credited to Iwar H. Buck.
United States Patent |
3,684,858 |
Buck |
August 15, 1972 |
THERMAL PRINTING HEAD
Abstract
A thermal printing head comprises a vitreous plate through which
a plurality of wires extend, the forward face, including the free
extremities of the wires, constituting a planar continuum, and a
plurality of vapor deposited sections selectively extending between
selected free extremities of wires. The arrangement is such that
the thermal coefficient of expansion of the wires and the vitreous
plate are alike so that permanent integration of the wires and the
plate is effected and bonding of the wires to the vapor deposited
sections is assured.
Inventors: |
Buck; Iwar H. (Hudson, MA) |
Family
ID: |
22557426 |
Appl.
No.: |
05/155,948 |
Filed: |
June 23, 1971 |
Current U.S.
Class: |
347/208; 219/543;
347/206 |
Current CPC
Class: |
B41J
2/3355 (20130101); B41J 2/3351 (20130101); B41J
2/33545 (20130101); B41J 2/3357 (20130101); B41J
2/33525 (20130101); B41J 2/3353 (20130101); B41J
2/33515 (20130101); H05B 3/00 (20130101) |
Current International
Class: |
B41J
2/335 (20060101); H05B 3/00 (20060101); H05b
001/00 () |
Field of
Search: |
;219/216,538,543,552
;346/76R ;40/28R ;340/166EL |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Albritton; C. L.
Claims
What is claimed is:
1. A thermal print head comprising a vitreous plate, electrical
leads extending through said plate from a rear face to a front
face, said front face including the free extremities of said
electrical leads and the surrounding regions of said vitreous plate
disposed in a planar continuum, and a vapor deposited pattern on
said front face composed of a metal containing, as its
characteristic ingredient, a member selected from the class
consisting of chromium and tantalum, said pattern including
resistive elements of waveform configuration and conductive
elements of solid configuration, selected ones of said resistive
elements being connected between selected pairs of said conductive
elements.
2. The thermal print head of claim 1 wherein said plate is composed
of glass and said leads are composed of a nickel-iron alloy, said
glass and said alloy having the same thermal coefficient of
expansion.
3. The thermal print head of claim 1 wherein said free extremities
of said selected ones of said electrical leads are in contact with
selected ones of said conductive elements.
4. The thermal print head of claim 1 wherein the thickness of said
resistive elements and said conductive elements ranges from 500 to
10,000 angstrom units.
5. The thermal print head of claim 1 wherein said resistive
elements are eight in number and generally discrete from each
other, being arranged in the form of a figure 8, together with a
succeeding decimal point.
6. The thermal print head of claim 1 wherein certain of said
conductive elements generally surround said resistive elements.
7. The thermal print head of claim 1 wherein certain of said
conductive elements generally are surrounded by said resistive
elements.
8. A thermal print head comprising a vitreous plate, electrical
leads extending through said plate from a rear face to a front
face, said front face including the free extremities of said
electrical leads and the surrounding regions of said vitreous plate
disposed in a planar continuum, and a vapor deposited pattern on
said front face composed of a metal containing, as its
characteristic ingredient, a member selected from the class
consisting of chromium and tantalum, said pattern including
resistive elements of waveform configuration and conductive
elements of solid configuration, selected ones of said resistive
elements being connected between selected pairs of said conductive
elements, said plate being composed of glass and said leads being
composed, of a nickel-iron alloy, said glass and said alloy having
the same thermal coefficient of expansion, said free extremities of
said selected ones of said electrical leads being in contact with
selected ones of said conductive elements, the thickness of said
resistive elements and said conductive elements ranges from 500 to
10,000 angstrom units, said resistive elements being eight in
number, being generally discrete from each other and being arranged
in the form of a figure 8, together with a succeeding decimal
point.
9. The thermal print head of claim 8 wherein certain of said
conductive elements generally surround said resistive elements.
10. The thermal print head of claim 8 wherein certain of said
conductive elements generally are surrounded by said resistive
elements.
Description
DETAILED DESCRIPTION
The present invention relates to thermal printing heads of the type
that are capable of producing characters, symbols, or the like in a
heat sensitive paper and, more particularly, to a thermal print
head comprising a vitreous substrate, a series of electrically
resistive sections thereon and a series of electrical leads
therethrough. Difficulties have been encountered in connection with
unduly rapid wear of the electrically resistive elements, adequacy
of the substrate as a heat sink for enabling repetition of the
printing cycle, and accumulation of dust in interstices of the
print head as a result of abrasion.
The object of the present invention is the provision of a novel
printing head in which a vitreous plate support, a plurality of
electrically resistive elements, and a plurality of electrical lead
elements present a totally integrated planar continuum for contact
with a heat sensitive paper, by which friction, abrasion and dust
are minimized, risk of mechanical failure is decreased, and the
resistive elements are sufficiently thin to enable very rapid rise
and fall times thermally with respect to input electrical pulses.
Preferably, the substrate is composed of glass and the leads are
composed of a glass sealing alloy, such as Kovar sold by
Westinghouse, so as to ensure an absolute seal between the
substrate and the leads. Preferably, the resistive elements are
composed of a chromium or tantalum metal, which combines good
electrical resistivity and excellent mechanical wear
resistance.
Other objects of the present invention will in part be obvious and
will in part appear hereinafter.
The invention accordingly comprises the product and system,
together with their parts, components and interrelationships, which
are set forth in the following disclosure the scope of which will
be indicated in the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
Further details of the present invention will be understood in
connection with the following detailed disclosure, together with
the accompanying drawings, wherein:
FIG. 1 is a perspective view of a printing element embodying the
present invention;
FIG. 2 is an enlarged broken-away view, in cross-section, of the
printing head of Fig. 1, the cross-section being along lines 2--2
of Fig. 1;
FIG. 3 is a resistive and conductive element pattern, typically
associated with the printing element of Fig. 1;
FIG. 4 is an alternative resistive and conductive element pattern,
typically associated with the printing element of Fig. 1; and
FIG. 5 is a schematic view of the system embodying a series of
print heads of the type shown in Fig. 1.
DETAILED DESCRIPTION
Fig. 1 illustrates a preferred printing element of the present
invention as comprising a substrate base 10, a plurality of
electrical leads 12 which project from the rearward face 14 of the
base to its forward face 16, and a plurality of electrically
resistive elements 18 which are vapor deposited upon forward face
16. Resistive elements 18, which are electrically discrete, include
(1 ) three cross elements and four vertical elements that generally
give the appearance of a figure 8 and (2 ) an additional element to
the lower right of the figure 8 which constitutes a decimal point.
As shown in FIG. 2, substrate 10 and leads 12 are perfectly flush
with each other at front face 16 and leads 12 electrically
communicate with certain of the vapor deposited sections 18.
Preferably substrate base 10 is composed of a vitreous material,
particularly glass, and metallic leads 12 are composed of a metal
such as Kovar, which has substantially the same coefficient of
expansion as glass. Typically, such a glass sealing alloy is a
nicke-iron alloy containing, by total weight, 20 %- Ni, 17 %- Co,
0.2 %- Mn, and balance -Fe. Face 16 is polished so as to produce a
planar continuum. Preferably, the resistive elements, which are
composed of a metal containing chromium or tantalum as its
characteristic ingredient, ranges in thickness from 500 to 10,000
angstrom units. It will be appreciated that at the same time heat
resistive elements 18 are formed, electrical communication between
the resistive elements and leads 12 also is established.
The thermal print head consists of seven heat generating metallic
resistive elements arranged in a Figure 8 configuration and a
additional heat generating resistive element at the lower right of
the Figure 8. By selectively energizing the heat resistive
elements, all numbers from 0 to 9 can be generated and printed on a
heat sensitive paper in contact with the print head. The vitreous
substrate also serves as insulation for the heat elements. Thus the
thermal print head consists of a glass plate with glass to metal
sealed wires in connection with the heat resistive element that are
formed by vacuum vapor deposition. The above method of forming heat
generating character elements is not limited to the seven segment,
numeric font shown. Other print characters can be formed to print
alphanumeric symbols, letters and numbers. For example, a 16 -line
element would cover all numbers and letters and some symbols, and a
5 .times. 7 or 35 dot matrix would cover all types of numbers,
letters and characters.
By virtue of the fact that the coefficient of expansion of kovar
and the coefficient of glass are identical virtually, there is no
physical interface between the kovar and the glass so that
continued increase and decrease of heat in the vicinity of the
kovar glass interface does not have the defect of breaking open the
seal between the two. Preferably, the diameter of any kovar
electrical lead ranges between 5 to 50 mils.
Fig. 3 illustrates a preferred pattern of resistive elements in
accordance with the present invention. This pattern includes a
plurality of resistive elements each in the form of a square wave,
including horizontal elements 20, 22 and 24, vertical elements 26,
30, 32 and displaced element 34. Each of these elements, because of
its extended length and small cross section, is capable of
generating heat rapidly and intensely when subjected to an applied
voltage. Control leads for the resistive elements are connected to
wide area conductive elements 36, 38, 40 42, 44, 46, 48, 50, 52,
54, 56. Of these conductive elements, all are positioned externally
of the figure 8 configuration, except conductive element 44 which
is inside the figure 8 configuration. More specifically: resistive
element 20 is connected between conductive element 36, 38;
resistive element 28 is connected between conductive elements 40,
42; resistive element 22 is connected between conductive element 54
on one side and conductive elements 42, 44 on the other side;
resistive element 32 is connected between conductive elements 42,
48; resistive element 24 is connected between conductive elements
50, 48; resistive element 30 is connected between conductive
elements 44, 52; and resistive element 26 is connected between
conductive elements 56, 36. It will be appreciated that, with the
proper logic circuitry, any number from 0 to 9 with or without a
decimal point following, can be presented.
FIG. 4 illustrates an alternative vapor deposited pattern including
horizontal resistive elements 58, 62, 66 and vertical resistive
elements 60, 70, 64, 68, there being an additional adjacent
resistive element 72 at the lower right. As in Fig. 3, each
resistive element is in the form of a square wave, which has an
extremely small cross-section whereby current flow establishes
large heat generation. The electrical leads, which are 11 in number
are connected to conductive sections, of which sections 74, 76, 78,
80, 82, 84, 86, 88 are external of the figure 8 configuration and
sections 90, 92, 94 are internal of the figure 8 configuration. As
shown: resistive element 60 is connected between conductive
elements 76, 90; resistive element 64 is connected between
conductive elements 78, 82; resistive element 58 is connected
between conductive elements 74, 90; resistive element 64 is
connected between conductive element 90, 92; resistive element 66
is connected between conductive elements 84, 94, resistive element
70 is connected between conductive elements 88, 90; and resistive
element 68 is connected between conductive elements 94, 86.
Fig. 5 illustrates a system embodying a series 96 of print heads of
the type shown in Fig. 1. Each of these print heads, one of which
is shown at 98, is capable of creating numeric characters on a heat
sensitive paper strip 100, which is advanced by feed rollers 102,
and pressed against print heads 96 by a pressure pad 98. The
character imparted depends upon an electronic circuit and power
supply, which includes electronic switches and decoder 106 capable
of imparting pulses in a train to selected conductive sections of
the vapor deposited pattern on the print head. Electronic switches
and decoder 106 are energized from a power supply 108, under the
control of the print command and pulse generator 110 and is
programmed by a print logic circuit 112. In practice the duration
of a pulse ranges between 2 and 100 milliseconds. The foregoing
arrangement has the advantages of solid state reliability, quiet
operation, fast printing capability, and economical price. It is
designed for application to such instruments as electronic desk
calculators, computer output printers, electronically operated
instruments, teletypewriter, digital display units, etc. Thermal
printing eliminates the major mechanical and electromechanical
parts of a printer, thus avoiding in mechanical complexity and
reducing mechanical motion to paper advance only.
EXAMPLE
The following non-limiting example further illustrates the present
invention:
Typically, the print head of Fig. 1 measures 0.200 inch high, 0.140
inch wide and 0.100 inch thick. The character dimension is 0.120
inch high and 0.080 inch wide. Electrical specifications are:
resistance per segment -- 100 ohms; power requirement -- 18 volts;
pulse duration -- 20 milliseconds. Electrical contacts to segments
are made by 11 leads on which three are common.
The present invention thus provides a novel thermal printer of
improved solid state reliability, unusually quiet operation,
unusually fast printing capability and unusually economical price.
It is to be understood that all matter contained in the foregoing
description and shown in the accompanying drawings are to be
interpreted in an illustrative and not in a limiting sense.
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