U.S. patent number 3,826,167 [Application Number 05/255,243] was granted by the patent office on 1974-07-30 for sign forming apparatus, method and die for use therein.
This patent grant is currently assigned to PST Company. Invention is credited to Bernard Bouyssounouse, Fritz Haas, Pierre A. Pelet.
United States Patent |
3,826,167 |
Pelet , et al. |
July 30, 1974 |
SIGN FORMING APPARATUS, METHOD AND DIE FOR USE THEREIN
Abstract
A die heating station is supported for movement between a ready
position and a cutting position. In the cutting position a die is
brought into contact with a sheet of thermoplastic material
supported on a carrier having a suitable cutting pad against which
the die can bear to cut a letter of a word. A die cooling station
receives each die after the cutting operation and cools it to an
operator-handleable temperature. A particular die structure is used
which facilitates rapid heating and cooling of the die while
retaining the necessary thermal properties for cutting
thermoplastic sheet material. A procedure and guide is provided for
accurately spacing adjacent letters of the word being cut.
Inventors: |
Pelet; Pierre A. (Mill Valley,
CA), Bouyssounouse; Bernard (Palo Alto, CA), Haas;
Fritz (Concord, CA) |
Assignee: |
PST Company (Sausalito,
CA)
|
Family
ID: |
22967462 |
Appl.
No.: |
05/255,243 |
Filed: |
May 19, 1972 |
Current U.S.
Class: |
83/171;
83/522.26; 83/881 |
Current CPC
Class: |
B44B
5/009 (20130101); B44B 5/024 (20130101); B44B
5/028 (20130101); Y10T 83/865 (20150401); Y10T
83/293 (20150401); Y10T 83/0348 (20150401) |
Current International
Class: |
B44B
5/02 (20060101); B44B 5/00 (20060101); B26d
007/10 () |
Field of
Search: |
;83/171,8,684,522
;101/8-11 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Juhasz; Andrew R.
Assistant Examiner: Gilden; Leon
Attorney, Agent or Firm: Griffin; Roland I.
Claims
We claim:
1. In sign forming apparatus for reproducing characters or patterns
in a strip of thermoplastic sheet material, a set of dies each
having a planar configuration with a raised portion on one face
conforming to a character or pattern to be reproduced, a die
heating station including heating means for heating a die and
further including means for slidably receiving and supporting the
die with said one face thereof facing in a predetermined direction
and with the opposite face thereof positioned adjacent to said
heating means, a cutting pad for supporting the strip of
thermoplastic sheet material opposite to said one face of a die
supported by said die heating station, means for moving said die
heating station between a first, ready position at which a die
supported thereby is spaced away from said cutting pad and a
second, cutting position at which the die supported thereby is
positioned in engagement with said cutting pad to thereby cause the
heated die to thermally cut the character or pattern defined on
said one face thereof into the strip of thermoplastic sheet
material interposed between the heated die and the cutting pad, and
a die cooling station including means for slidably receiving,
supporting, and cooling a heated die from said die heating station,
said die cooling station being aligned to receive a heated die from
said die heating station when the latter is in said first, ready
position.
2. Sign forming apparatus as in claim 1 wherein each die comprises
a flat plate of relatively thin cross section made of a high
thermal-conductivity, low heat-capacity material, a raised bulb
portion disposed on said plate and integrally joined thereto, said
raised bulb portion linearly conforming to the outline of the
character or pattern to be reproduced by the die and being rounded
in cross section, a cutting bead formed on said raised bulb portion
and defining an outline of the character or pattern to be
reproduced by the die, said cutting bead being integrally formed
with said raised bulb portion and symmetrically disposed on that
side of said raised bulb portion away from said plate, said raised
bulb portion serving as a heat sink for supplying heat to said
cutting bead so that as said cutting bead is pressed into contact
with the strip of thermoplastic sheet material said cutting bead is
supplied with adequate heat to thermally cut through the
thermoplastic material.
3. Sign forming apparatus as in claim 1 further including indicia
means disposed on said opposite face of each die for indicating the
correct direction of insertion of the die into the sign forming
apparatus.
4. Sign forming apparatus as in claim 1 further including a spacing
scale marked on the sign forming apparatus alongside the path of
the strip of thermoplastic sheet material, and indicia means
carried on each die for indicating its proper character half width
and character spacing half width in the same values as said spacing
scale.
5. Sign forming apparatus as in claim 1 further including a notch
formed on one side of each die, and means forming a detent
mechanism on said die heating station for engaging said notch
whereby the position of a die can be felt by an operator when
inserting a die into the sign forming apparatus.
6. In sign forming apparatus, means forming a framework comprising
a pair of side plates including upstanding portions, a base plate
and means for connecting said base plate and said side plates into
a self-supporting structure, means, including a cutting pad carried
on said base plate, forming a carrier plane for passing a
thermoplastic material through the sign forming apparatus, means
forming guide means vertically arranged between the upstanding
portions of said side plates and interconnected therebetween, a die
heating station carried on said guide means and including a heating
plate, a heater and a thermostat for controlling the amount of heat
supplied to said heating plate within a predetermined temperature
range, and means secured to said heating plate for supporting said
die heating station for sliding movement upwardly and downwardly on
said guide means, means for moving said die heating station between
a raised, ready position and a lower, cutting position in which a
die carried on the underside of said heating plate is proximate
said cutting pad and cuts through the thermoplastic material
interposed between the die and said cutting pad, and a die cooling
station including a heat sink having cooling fins thereon and
further including fan means for moving air past said cooling fins
to cool them, said die cooling station being mounted on said
framework such that it is positioned to receive a die from said die
heating station when the latter is in its raised, ready
position.
7. Sign forming apparatus as in claim 6 wherein said means for
moving said die heating station includes a cylindrical cam
eccentrically mounted on said guide means, said die heating station
includes first follower means disposed above said cam for raising
said die heating station when a lobe defined by said cam is in an
upper position, and second follower means is mounted below said cam
for pressing said die heating station into thermal cutting
relationship against the thermoplastic material when said cam is
rotated to a lowermost position.
8. Sign forming apparatus as in claim 7 further including means for
precisely adjusting the position of said second follower means to
control the precise height of said die heating station in its
lower, cutting position.
9. Sign forming apparatus as in claim 6 further including clamp
rails positioned on each side of the thermoplastic material and
overlying said cutting pad, means for normally urging said clamp
rails into engagement with the edges of the thermoplastic material,
and means associated with said clamp rails and said die heating
station for disengaging said clamp rails from the thermoplastic
material when said die heating station is in its raised, ready
position.
10. In sign forming apparatus for reproducing characters or
patterns in a strip of thermoplastic sheet material, a set of dies
each having a planar configuration with a raised portion on one
face conforming to the character or pattern to be reproduced and
each being made of a material having a high thermal conductivity
and a low total heat capacity so that it may be readily heated and
cooled, a die heating station including die heating means for
heating a die and further including means for slidably receiving
and supporting the die with said one face thereof facing in a
predetermined direction and with the opposite face thereof
positioned adjacent to said die heating means, said die heating
means being made of a material having a high thermal conductivity
and a high total heat capacity so that its temperature is not
markedly changed by heating a die applied thereto, a cutting pad
for supporting the strip of thermoplastic sheet material opposite
said one face of a die supported by said die heating station, means
for moving said die heating station between a first, ready position
spaced away from said cutting pad and a second, cutting position in
engagement with said cutting pad thereby causing a heated die
supported by said die heating station to thermally cut the
character or pattern defined on said one face of the heated die
into the strip of thermoplastic sheet material interposed between
the heated die and said cutting pad, and a die cooling station
including means for slidably receiving, supporting, and cooling a
heated die from said die heating station, said die cooling station
being aligned to receive the heated die from said die heating
station when the latter is in said first, ready position.
11. In sign forming apparatus for forming signs in a strip of
thermoplastic sheet material by using a set of dies each of which
has a planar configuration and a raised portion on one face thereof
conforming to a character or pattern to be reproduced, a die
heating station including means for slidably receiving, supporting,
and heating a die with said one face thereof facing towards a
cutting pad for supporting the strip of thermoplastic sheet
material, means for moving said die heating station into engagement
with said cutting pad to thereby cause a heated die supported by
said die heating station to thermally cut the character or pattern
defined on said one face thereof into the strip of thermoplastic
sheet material interposed between the heated die and the cutting
pad, and a die cooling station for receiving and cooling a heated
die from said die heating station, said die cooling and heating
stations including means for removing any die positioned in said
die cooling station, remotely transferring any die positioned in
said die heating station to said die cooling station, and feeding a
die into said die heating station, whereby a plurality of dies may
be successively employed to thermally cut the characters or
patterns of a sign into the strip of thermoplastic sheet material
by cooling each heated die immediately after it is employed to
thermally cut a character or pattern of the sign while the next die
is heated and employed to thermally cut the next character or
pattern of the sign, said sign forming apparatus further including
spacing means for aiding the operator to advance the strip of
thermoplastic sheet material by an amount equal to the appropriate
sum of the half widths of the characters or patterns defined on
said one face of each of the dies in said die heating and cooling
stations and of the half widths of appropriate inter-character or
pattern spacings for each of those characters or patterns to form a
pre-spaced segment of a sign.
12. Sign forming apparatus as in claim 11 wherein said spacing
means includes a fiducial mark on the sign forming apparatus, and a
template having at least one indicium thereon corresponding to the
next character or pattern to be thermally cut, whereby said
template may be positioned over the strip of thermoplastic sheet
material such that the indicium thereon is appropriately positioned
relative to the preceding character or pattern thermally cut into
the strip of thermoplastic sheet material, the strip of
thermoplastic sheet material may then be marked to indicate the
distance from said fiducial mark on the sign forming apparatus to
the center of said cutting pad, and the strip of thermoplastic
sheet material may then be advanced so that the mark thereon
coincides with said fiducial mark.
13. Sign forming apparatus for forming characters in a strip of
thermoplastic material, said apparatus comprising a die heating
station for slidably receiving and heating a die having a planar
base with a raised portion defining a character to be formed and
facing the strip of thermoplastic material, a platen for supporting
the strip of thermoplastic material opposite the raised portion of
the die, means for moving the die heating station between a ready
position spaced away from the platen to receive the die and a
cutting position spaced closer to the platen to bring the die into
contact with the strip of thermoplastic material and thermally die
cut the character defined by the raised portion of the die in the
strip of thermoplastic material, and a die cooling station for
slidably receiving the die from the die heating station when the
die heating station is in the ready position and for cooling the
die.
14. Sign forming apparatus as in claim 13 wherein the planar base
of the die comprises a flat plate of thinner cross section than the
raised portion of the die, and the raised portion of the die
comprises a bulb of rounded cross section integrally formed on this
plate and a smaller cutting bead integrally formed on the bulb, the
bulb serving as a heat sink for supplying the bead with adequate
heat to thermally cut through the thermoplastic material.
15. Sign forming apparatus as in claim 13 wherein the die includes
an indicium for indicating the correct direction of insertion of
the die into the die heating station.
16. Sign forming apparatus as in claim 13 wherein a spacing scale
is provided on the apparatus along the path of the strip of
thermoplastic material, and an indicium is provided on the die to
indicate the half width of the character defined thereon and a
spacing therefor in the same units as the spacing scale.
17. Sign forming apparatus as in claim 13 wherein a notch is formed
on one side of the die, and a detent mechanism is provided on the
die heating station to engage this notch when the die is properly
positioned in the die heating station.
18. Sign forming apparatus as in claim 13 wherein the die heating
station includes a heating plate, a heater, and a thermostat for
controlling the amount of heat supplied to the heating plate within
a predetermined temperature range, and wherein the die cooling
station includes a heat sink with cooling fins and a fan for moving
air past these cooling fins to cool them.
19. Sign forming apparatus as in claim 18 wherein the heating plate
is made of a material having a thermal conductivity and a total
heat capacity such that its temperature is not markedly changed by
heating a die applied thereto, and the die is made of a material
having a thermal conductivity and a heat capacity such that it may
be readily heated by the heating plate and cooled by the heat
sink.
20. Sign forming apparatus as in claim 13 wherein the means for
moving the die heating station includes an eccentrically-mounted
cylindrical cam, and the die heating station includes first
follower means disposed above the cam to raise the die heating
station when a lobe of the cam is in an upper position and second
follower means disposed below the cam to limit the downward stroke
of the die heating station toward the strip of thermoplastic
material supported on the platen and thereby determine the cutting
position.
21. Sign forming apparatus as in claim 20 including means for
precisely adjusting the position of the second follower means to
adjust the cutting position of the die heating station.
22. Sign forming apparatus as in claim 13 including clamp rails
overlying each side of the platen and the sheet of thermoplastic
material supported thereon, means for normally urging the clamp
rails into engagement with the edges of the strip of thermoplastic
material, and means for disengaging the clamp rails from the strip
of thermoplastic material when the die heating station is in the
ready position.
23. Sign forming apparatus as in claim 13 wherein the die received
by the die heating station is transferred to the die cooling
station after the character defined by that die has been thermally
die cut, another similar die is then fed to the die heating
station, the strip of thermoplastic material is advanced by an
amount equal to the sum of the half widths of the characters
supported at the die cooling and heating stations and of the half
widths of the desired spacing between each of those characters and
its neighbor, the character defined by the die then supported at
the die heating station is thereupon thermally die cut, and the
foregoing steps are repeated to form a pre-spaced sign or a portion
thereof.
24. Sign forming apparatus as in claim 13 including a template
having at least one indicia thereon corresponding to the distance
between the center of the next character to be formed, when the die
on which that character is defined is at the die heating station,
and a reference mark provided on the apparatus adjacent to the
strip of thermoplastic material.
25. Sign forming apparatus as in claim 1 wherein the die comprises
a plate of thermally conductive material, a raised bulb portion of
rounded cross section integrally formed on this plate to indefine a
character thereon, and a cutting bead of smaller cross section
integrally and symmetrically formed on this bulb portion, the bulb
portion serving as a heat sink for supplying the cutting bead with
heat to thermally die cut through the sheet of thermoplastic
material.
Description
BACKGROUND OF THE INVENTION
This invention relates to sign making apparatus for successively
reproducing characters on thermoplastic sheeting to form
pre-spaced, ready-to-apply groupings of characters such as words.
It also relates to a particular die construction and to fonts of
such dies for use in the sign making apparatus.
Heretofore, several systems for so-called "instant" sign making
have been developed. In one system pre-cut letters pre-mounted on a
release sheet are selected and are arranged into an appropriate
word or other pattern at the time of making up a sign. This
requires a large inventory of pre-cut individual letters in various
fonts and sizes as well as in different materials.
In another system dies are individually used to cold cut letters or
characters at the time the sign is to be made up. Such dies must be
extremely strong and must have a relatively sharp cutting edge
which limits their useful life. In addition, the coated tapes or
materials that can be fabricated into signs using cold die cutting
are somewhat limited.
Hot die cutting is known and is found to assure uniformity and
versatility not possible in cold die cutting. Normally, a press is
equipped with a die heater maintained at a temperature adequate to
melt the sheet material from which the characters are to be formed.
Such machines, however, have been developed for mass producing
large quantities of the same character, as for use in the first
system mentioned above, and have not lent themselves to use for
properly obtaining pre-spaced, serially formed sets of characters
forming entire words or lines. There is, therefore, a need for new
and improved sign making apparatus and improved dies for use
therein.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide new sign
forming apparatus and dies for use therein which will overcome the
above-mentioned limitations and which will provide the advantages
of hot die cutting in a simple easy-to-operate arrangement adapted
for use on conventionally available thermoplastic sheet
material.
A further general object of the invention is to provide new sign
making apparatus and dies of the above character in which entire
words and phrases can be cut into thermoplastic sheet material with
the letters and characters in properly spaced positions, can then
be transferred together as a unit to an application substrate while
preserving the spacing thereof, and can subsequently be applied to
an object to form a high quality sign of hand painted appearance at
a fraction of the present cost for a hand painted sign and without
the need for skilled labor.
Another object of the invention is to provide sign forming
apparatus of the above character which is simple to construct and
reliable in operation and which permits die insertion and removal
therefrom at operator handleable temperatures.
Another object of the invention is to provide sign forming
apparatus of the above character which is readily adapted to use
dies of any font design and which requires only an inventory of
basic thermoplastic material such as a variety of rolls of
thermoplastic tape in differing appearance or color.
Another object of the invention is to provide a sign forming
apparatus and dies of the above character in which the standard
spacing of the characters is derivable from indicia carried on the
dies and read by the operator in using the apparatus, but in which
the spacing of the characters may also be varied for certain
combinations to assume a more eye-pleasing effect.
Another object of the invention is to provide sign forming
apparatus and dies of the above character in which the dies are
designed for ease of manufacture and rapid heating and cooling.
In general, the sign forming apparatus of the present invention
includes a framework defining a carrier plane for receiving a sheet
of thermoplastic material and for supporting same in a cutting
position over a platen. A die heating station is mounted in the
framework for movement between a ready position and a cutting
position and is provided with a die receiving and advancing
mechanism for sliding a die into contact with a heated plate. A die
cooling station is also mounted in the framework and is provided
with a die advancing mechanism that is aligned with the die
receiving and advancing mechanism of the die heating station when
the latter is returned to the ready position so that dies may be
sequentially inserted into the die heating station, brought to the
cutting position, returned to the ready position, and ejected
through the die cooling station. The insertion of each die into the
die heating station and its subsequent removal from the die cooling
station is performed by hand operation and by selection of the
operator.
Each die is constructed of high thermal-conductivity, low
heat-capacity material, such as an aluminum or magnesium alloy, and
has a relatively thin planar back on which is integrally formed a
raised bulb portion crowned with a bead tapering to a cutting edge
outlining a character. The bulb portion has sufficient mass to
serve as a heat sink for the cutting bead so the latter does not
become excessively cooled as it is brought into contact with the
material being cut.
The foregoing sign forming apparatus is characterized by the use of
a large capacity heated plate at the die heating station to provide
substantial stored thermal energy. Each die, being made up of a
thin section of low heat-capacity material, has low thermal
inertia. Thus, the dies being advanced through the sign forming
apparatus are rapidly heated from contact with the heated plate
without causing any substantial change in the temperature of the
heated plate and are readily cooled before being removed by the
operator.
In use, an operator selects a die and inserts it into the die
heating station after having first removed any die located in the
die cooling station and after having remotely transferred any die
from the die heating station to the die cooling station (all of
this being done while the die heating station is in the ready
position). In this way the last letter which has been cut is
located in the die cooling station and the letter to be cut is
located in the die heating station. The operator then advances the
thermoplastic sheet material a distance equalling the sum of the
half widths and spaces for the respective dies in the die heating
and cooling stations, if necessary, and then remotely manipulates
the die heating station to the cutting position bringing the die
therein into thermo-cutting relationship with the thermoplastic
sheet. The die heating station is then returned to the ready
position, and the foregoing steps are repeated until the necessary
sign is completed.
These and other objects and features of the invention will become
apparent from the following description and claims when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective exploded view, partially in schematic form
and with portions broken away or removed for clarity, of sign
forming apparatus constructed in accordance with the preferred
embodiment of the present invention.
FIG. 2 is a cross-sectional view of the sign forming apparatus
taken along the line 2--2 of FIG. 1.
FIG. 3 is a cross-sectional view of the sign forming apparatus
taken along the line 3--3 of FIG. 2.
FIG. 4 is a cross-sectional view of the sign forming apparatus
taken along the line 4--4 of FIG. 1.
FIG. 5 is a top plan view of a position indicating detent mechanism
taken generally from the plane defined by the line 5--5 of FIG.
2.
FIG. 6 is a front plan view of a die that may be used in the sign
forming apparatus of FIG. 1 and that is constructed in accordance
with the preferred embodiment of the present invention.
FIG. 7 is a rear plan view of the die of FIG. 6.
FIG. 8 is a cross-sectional view of the die taken along the line
8--8 of FIG. 7.
FIG. 9 is a detailed cross-sectional view of a die as the same is
brought into the operative cutting position in the sign forming
apparatus of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, the overall concept of the sign forming
apparatus of the present invention is shown and generally includes
a die heating station 12 having guides on its lower side for
slidably receiving a die 14 and having a gear driven advancing
mechanism 16 for advancing the die into a centrally disposed
position within the heating station and into contact with the lower
face of a heating plate 18. The die heating station is carried in a
framework provided with suitable guides and a mechanism 19 for
raising the die heating station from a lower cutting position to an
upper ready position. In the upper ready position, a die carried in
the die heating station is aligned with a die cooling station 20 so
that it can be ejected from the die heating station directly into
the die cooling station by advancing mechanism 16 and another
advancing mechanism 22 associated with the die cooling station. A
roll of thermoplastic sheet material is serially advanced together
with the insertion and removal of a respective set of dies to and
from the apparatus after each letter is cut.
Referring more particularly to FIGS. 1 through 3, the apparatus of
the present invention is generally contained within a framework
which also serves as a protective housing for the various
components. The framework generally consists of a pair of side
plates 30 and 32 held in fixed positions in spaced parallel planes
with respect to each other by a base plate 33 and by spacing and
support rods 34. The base plate consists of a single unitary
section having a flat upper surface and includes an interchangeable
resilient cutting pad or platen 37 made of silicone rubber, for
example, and located in a centrally disposed area where the cutting
pad serves as a backing against which the die of the present
invention operates, as will be hereinafter described. At one end of
the base of the framework a pair of spaced roll support rods 38 and
40 serve to support a roll 42 of thermoplastic sheet material in
the form of a strip of uniform width.
A spacing scale 43 past which the thermoplastic strip passes before
proceeding to the platen 37 is marked on one of a pair of rails 44
and 45 overlapping the thermoplastic strip from each side of the
base of the framework and is provided for the operator's use in the
spacing of letters. Rails 44 and 45 also serve to align the
thermoplastic strip into a feed position with respect to the platen
37 and the base of the framework. Spacing scale 43 is linear and
consists of numbered tens units together with subdivision marks
dividing each tens unit into units. The thermoplastic strip is
passed over the platen 37 and under a hold-down clamp 46 consisting
of a J-shaped plate 46a articulated from a pivot shaft 46b mounted
between the side plates 30 and 32 and having a lower rounded edge
lying in engagement with the upper surface of the thermoplastic
strip. Thus, a strip 47 of thermoplastic material may be drawn over
the platen 37 by being pushed into the sign forming apparatus from
the roll 42 and by being withdrawn at the other end by the
operator.
The thermoplastic sheet 47 used in the sign forming apparatus of
the present invention can be any of various kinds in which a
thermoplastic layer 47a having a pressure-sensitive adhesive
backing is bonded to a suitable heat-resistant release backing 47b
(see FIG. 9). By way of example, a 2 mil layer of vinyl plastic
with an adhesive coating on its back laid over a silicone coated
paper release liner, such as is sold by the 3M Corporation under
the trade designation Scotchcal (trademark) or Scotchlite
(trademark) is satisfactory.
The side plates 30 and 32 extend upwardly on each side of the
platen 37 and are held in spaced relation by upper and lower guide
shafts 48 and 50 which are arranged in spaced vertical relation to
each other above the platen. Guide shafts 48 and 50 carry spaced
retaining ring sets 52-53 and 54-55, respectively, in grooves
formed on the shafts. These retaining ring sets serve as lateral
guides for restraining lateral movement of die heating station 12.
The upper shaft 48 also serves as a reaction shaft for moving die
heating station 12 and for that purpose is provided with an
eccentrically mounted cam 58 having a circular shape and having a
handle 110 for rotating the cam such that the lobe 60 of the cam
moves from an uppermost position shown in FIGS. 1 and 2 to a
lowermost position in which the lobe of the cam is directed
vertically downward.
As shown particularly in FIGS. 1 and 2, the die heating station
includes a heating plate 62 having an aperture 64 therethrough for
receiving an electrical resistance heater 66 which is connected to
a suitable electrical supply through a thermostat (not shown)
mounted on the heating plate to stabilize the temperature of the
heating plate within a predetermined range. The heating plate 62
has a flat lower surface and serves to distribute heat from the
heater 66 uniformly to that surface. If desired, a visual reading
thermometer (not shown) may also be disposed on the heating plate
62 to give the operator an indication when the heating plate is
sufficiently hot. The lower surface of the heating plate 62 is
bounded back and front by side rails 68 and 70 depending downwardly
and defining a carrier plane through which a die 14 can be passed.
The upper surface of the heating plate is provided with upwardly
extending front and rear brackets 72 and 74 for supporting a gear
drive consisting of a centrally located shaft 76 supported by
bearings 78 and 80 mounted on these brackets and carrying drive
gears 82 and 84 at each end of the shaft 76.
First and second sets of resilient rollers 86a and 86b are mounted
on bearings at laterally spaced positions along the path of die
movement and may, for example, be carried at one end of shafts
extending through the downwardly depending side rails 68 and 70.
First and second sets of driven gears 90a and 90b are mounted at
the other end of these shafts. The spacing between the lower
surface of heating plate 62 and the rim of resilient rollers 86a
and 86b is made slightly less than the thickness of the die 14 to
be carried so the die can be transferred through the die heating
station by the action of these rollers, when driven, with the rear
surface of the die in sliding contact with the heating plate 62.
First and second sets of idler gears 94a and 94b are mounted on the
gear support brackets 72 and 74 in driven engagement with drive
gears 82 and 84 and in driving engagement with driven gears 90a and
90b. In this way rotation of drive gears 82 and 84 by the
operator's manipulation of knob 98 serves to drive both sets of
idler gears 94a and 94b in a similar sense and likewise to drive
both sets of driven gears 90a and 90b together with their
associated rollers 86a and 86b such that a die 14 can be carried
through the die heating station, can be remotely adjusted to any
position therein, and can be ejected if desired.
Referring to FIG. 5, there is shown a detent mechanism consisting
of an L-shaped lever 100 carrying a bearing mounted roller 102 at
one end and pivoted at an intermediate point 104. The lever 100 is
biased by a spring 106 attached between the other end of the lever
and the die heating station so as to pivot the roller 102 slightly
into the path of the die 14. Each die is provided with a notch 108
disposed along the rear edge of the die so an operator can feel
when the die is centrally disposed in the die heating station due
to the change in resistance of movement caused by the roller 102
entering the notch 108.
As shown in FIGS. 1 through 3, a mechanism is provided for moving
the die heating station 12 between and for supporting the same in a
ready position (see FIG. 1) spaced away from the platen 37 and in a
lowered cutting position at which the die 14 is impressed into
contact with the thermoplastic sheet material to cut the same by
heat melting. This mechanism includes the cam 58 and handle 110
together with a cam plate assembly 112. The cam plate assembly 112
consists of a pair of oppositely arranged cam plates 114 and 116
mounted, as with screws, on the upper surface of the heating plate
62, extending upwardly in spaced parallel planes, and terminating
at their upper ends by being bent so as to overlie the uppermost
surface 118 of the cam 58 from the front and rear sides thereof.
The portions of the cam plates 114 and 116 which overlie the cam 58
serve to support the entire die heating station 12 on the upper
surface of the cam and, hence, on the reaction shaft 48. The cam
plate assembly is constrained to follow a linear path of motion by
guide slots 120a, 120b, 122a, and 122b in the cam plates 114 and
116 through which the respective shafts 48 and 50 extend. The cam
plate assembly is also constrained to remain centrally disposed by
the rings 52-55 previously described. Thus, the die heating station
is free to move up and down following the position of the upper
surface of cam 58. A cam follower 120 is mounted immediately below
the cam 58 and consists of a cylindrical roller 122 mounted on a
shaft 124 having an axis slightly displaced from the roller axis so
that by using a knob 126 attached to shaft 124 an eccentric fine
adjustment may be made to determine the precise limit of the stroke
of the die heating station 12 as the same is moved downwardly
toward engagement with the thermoplastic material and pressed
toward the platen 37. A screw 128 serves to lock the knob 126 in
place once the desired fine adjustment is achieved. Initially, as
handle 110 is rotated, the die heating station 12 moves downwardly
under gravity while resting on cam 58 until a die 14 supported by
the die heating station comes into resting contact with the upper
surface of the thermoplastic material. Thereafter, further movement
of the handle 110 causes the lowermost surface of the cam 58 (then
on lobe 60 of the cam) to bear against the roller 122 and thereby
drive the die heating station 12 downwardly into precisely spaced
position with respect to the platen 37.
A mechanism is provided for clamping the thermoplastic strip 47
into fixed position in response to initial movement of the die
heating station towards the platen 37. This mechanism includes a
pair of clamp rails 130 and 132 having portions overlying each side
of the platen 37 and the thermoplastic strip 47 supported thereon.
Clamp rails 130 and 132 are pivoted at positions 130a and 132a
remote from the platen 37 and are biased toward the platen by
suitable springs 134 and 136. The ends of the clamp rails 130 and
132 are further provided with upstanding end portions 138
terminating in rollers 140 so positioned that when the clamp rails
are released into clamping position the rollers 140 lie in the
upward path of projections 142 formed at the ends of the heating
plate assembly and at a level such that return of the die heating
station 12 to its uppermost position causes the projections 142 to
engage the rollers 140 and thereby release the clamp rails by
pushing the rollers 140 outwardly and lifting the clamp rails off
the platen 37.
Referring to FIGS. 1 and 4, a die cooling station 150 is mounted in
the framework on brackets 152 and 154 and generally consists of a
cooling plate having a lower surface 156 of substantially the same
area as the die 14 to be passed therethrough and having a plurality
of integrally attached fins 158. Such structures are well known in
the transistor cooling art as heat sinks and, in fact, a large
transistor heat sink was utilized as the cooling plate in one form
of the present invention. A suitable fan 160 blows or draws ambient
air past the cooling fins 158. The cooling plate mounting brackets
152 and 154 are positioned so that the bottom surface of the
cooling plate is aligned to receive a die from the die heating
station 12 when the die heating station is in its raised ready
position.
A mechanism is provided for advancing the die 14 through the die
cooling station and consists of three sets of resilientlyfaced
rollers 161, 162, and 163 supported on shafts 164 which are mounted
for rotation at spaced-apart positions along the path of the die.
These resiliently-faced rollers extend upwardly to support the die
14 in sliding contact with the lower surface 156 of the cooling
plate. The roller shaft 164 nearest the die heating station 12 is
provided with a knob 168 for turning that shaft to thereby
facilitate transfer of a die from the die heating station to the
die cooling station and to also permit partial ejection of a die
from the die cooling station. The end of the die cooling station
from which the die is ejected is conveniently provided with a
tear-off bar against which the thermoplastic strip 47 is severed
after an appropriate segment of a sign has been completed.
Referring now to FIGS. 6 through 9, a suitable font of dies 14 is
provided and includes an alphabet and numeral set as well as any
other characters that may be required for sign making. Such a font
may have any particular design. Each die 14 is formed on a flat
plate 170 of relatively thin cross section. A raised bulb portion
172 is disposed on the plate 170 and integrally joined thereto, the
raised bulb portion conforming generally to the outline of the
character to be represented on the die. A bead 174 is formed on the
bulb portion 172 and converges into a broad cutting edge. The bead
174 and bulb portion 172 are integrally formed together with the
plate 170 such as by casting them in a mold. Generally, the plate
170 is made of a relatively high thermal-conductivity, low
heat-capacity material which facilitates the rapid heating and
cooling of the die. Many aluminum and magnesium alloys are
satisfactory for this purpose, such as 380 AL-Si. The bulb portion
172 is generally as thick and may be slightly thicker than the
plate 170 itself and serves as a heat sink for supplying the bead
174 with adequate heat so that as the bead is pressed into contact
with the thermoplastic material the bead will rapidly cut through
the thermoplastic material without being unduly cooled. As an
example, a die 14 for a 5 inch letter has been utilized in which
the plate 170 was 0.075 inches thick while the bulb portion 172 was
approximately 0.100 inches in depth and had a diameter of
approximately three-eighths of an inch. The bead 174 forming the
cutting edge had a depth of 0.020 inches and had a subtended angle
of convergence toward the tip of 106.degree. with a tip radius of
0.010 inches.
Each of the dies 14 is characterized by being as thin as possible,
consistent with reasonable rigidity requirements, to thereby reduce
the metal mass and thermal inertia so that rapid heating and
cooling can be achieved. In addition, the dimensions of the bulb
portion 172 and bead 174 are chosen so that due to the relatively
large mass of the bulb portion and its ability to provide adequate
heat to the bead a melting action is achieved rather than a
mechanical cutting action.
Each of the dies 14 is also provided with a suitable indicia 176
thereon for indicating its normal spacing relative to other
characters. While the spacing may vary for particular combinations,
it nevertheless is sufficiently uniform that such indicia can be
made to indicate to a sufficient degree of accuracy a generally
suitable spacing. Particular combinations may be spaced by eye or
by an auxiliary device if desired.
As shown in FIGS. 1, 2, and 4, apparatus is provided for reading
the spacing indicia from each die 14 positioned in the sign forming
machine to supply spacing indicia readings as required for both the
last die used, which is then in the die cooling station 150, as
well as the die in the die heating station 12. This apparatus
includes a light 180 and a cover 182 mounted on the rear side plate
32 to direct light inwardly across a face of the die at the die
heating station. It also includes a second light 184 and a cover
186 mounted on the rear side plate 32 to direct light across a face
of the die in the die cooling station. At the front of the sign
forming machine aperatures are provided together with mirrors 188
and 190 for permitting the operator to look upwardly onto the
illuminated faces of the dies at the die heating station and the
die cooling station. The numbers used for indicating spacing
correspond with the spacing scale 43 engraved on feed rail 45. Each
of the spacing numbers indicates the half width of its respective
character plus the half width of the appropriate space between that
character and its neighbor. The total half width and half space of
each character is added to that of the adjacent character to
provide the total center-to-center spacing of that combination.
This is used as the distance which the thermoplastic strip 47
should be advanced to properly space characters.
The operation of the device will now be described and reviewed in
detail with particular reference to FIGS. 1, 2, and 4. After the
sign forming apparatus is turned on and the correct heat range is
obtained, a strip 47 of thermoplastic sheet material is inserted
between the feed rails 44 and 45 at the right side and is fed an
appropriate distance through the sign forming apparatus and beyond
the platen 37. The first character of a word to be imprinted is
selected from a font of dies 14 of the desired size and style. That
particular die 14 is then inserted into the die heating station 12
immediately under the heated plate 62, an arrow 192 on the rear
face of the die being disposed toward the operator. The die
transfer knob 98 is rotated until the die 14 is centered under the
heated plate 62 as can be felt by the action of the detent
mechanism of FIG. 5. A reference mark should then be drawn on the
thermoplastic strip 47 at zero on the spacing scale 43.
The interval of time from insertion of the die 14 until it is
sufficiently hot may be measured with a timer (not shown). After
this time lapse, which is on the order of about 15 seconds, the
handle 110 is swung from the position shown in FIG. 1 through 180
degrees to cause the lobe 60 of cam 58 to rotate and to bear down
upon the roller 122, thereby lowering the die 14 into pressed
contact with the thermoplastic strip 47. The manner in which
thermal cutting action is effected is shown in detail in FIG. 9.
The level of the die 14 in the cutting position is adjusted by
rotating knob 126 until the cutting bead 174 of the die penetrates
the thermoplastic material 47a and presses slightly into the
release backing 47b such that the same is deformed slightly into
the resilient platen 37. As the cutting action takes place, the
thermoplastic material 47a is melted and forms a small bead of
thermoplastic material on each side of the cutting line. The depth
of the cutting bead 174 on the die 14 is at least sufficient to
accommodate this raised edge or bead of excess thermoplastic
material and to provide adequate relief therefor. It has been found
that 2 mil vinyl tape, for example, can be melted and cut in about
5 seconds using the above procedure, thereby permitting the handle
to be returned almost immediately.
The die positioning knob 98 of the die heating station 12 is then
advanced to send the die 14 to the die cooling station 150 where it
is advanced by knob 168 and rollers 161. The next die 14 required
to form the word is then inserted into the die heating station 12
and aligned. At this time both the previous half width spacing and
the present half width spacing appear in the respective mirrors 190
and 188. The sum of these half width spacings becomes the desired
inter-letter spacing. The thermo-plastic strip 47 is then advanced
the distance of that sum as by marking the thermoplastic strip
adjacent to the appropriate number on spacing scale 43 and
advancing the thermoplastic strip until that mark reaches the zero
point. The second character is then cut in the same manner as
previously described.
The first die 14 is removed from the die cooling station 150 by
advancing the first die slightly until it projects from the exit
end of the die cooling station from which it is then removed by
hand. The second die 14 is then transferred to the die cooling
station 150, and a new die 14 is inserted into the die heating
station 12. These steps are repeated sequentially until the word or
a series of words forming, for example, a segment of a sign is
completed. The thermoplastic strip 47 is then fed forward until the
desired segment of the sign is completely available, and the same
is then torn off against the tear-off bar at the exit end of the
die cooling station 150.
To facilitate handling, an arrow or other indicia 192 (see FIG. 7)
is formed on the back side of each die 14, as previously mentioned,
to indicate the correct direction of insertion of the die into the
sign forming apparatus. Either the positive or negative of the sign
can be utilized by weeding inside or outside of the die cut letters
and by transferring the resultant sign to a transfer tape by a
suitable means, such as a suitable roller and applicator, after
which the lettering may abe stripped from the paper release liner
of the transfer tape and applied by its own adhesive to any
appropriately prepared surface.
As previously described herein, the inter-character spacing is
achieved by advancing the thermoplastic strip 47 by amounts equal
to the appropriate sum of the half widths of the respective
characters to be spaced and their appropriate average
inter-character spacings, which half widths are given on the dies
14 normally located in the die cooling and heating stations 150 and
12 and are easily read from the mirrors 188 and 190. However, in
the case of a particular combination of letters, as, for example,
the letter W followed by the letter A, the intercharacter spacing
may well be such that, with reference to a vertical line, the
letters overlap when positioned for an eyepleasing appearance. In
order to facilitate use of the present sign forming apparatus and
to accommodate the freedom to space letters by eye, there is
provided a template 198 (see FIG. 1) having indicia thereon
corresponding to the more common letters requiring special spacing,
such as the letters A, O, L, T, and the like. The indicia on the
template 198 are overprinted on each other on a single reference
line, and the distance from the indicia to the right side of the
template is equal to the distance from the center of the die in the
die heating station 12 to the zero mark of the spacing scale 43,
which serves as a fiducial mark for the accurate positioning of the
thermoplastic strip 47. Thus, the operator may space letters by eye
by moving the thermoplastic strip 47 backward until the last die
cut letter appears and then positioning the template so that the
next letter is in an eye-pleasing relationship to the preceeding
letter. At that time, the operator marks the thermoplastic strip 47
at the right edge of the template and aligns that mark with the
zero fiducial mark of the spacing scale 43 to bring the appropriate
portion of the thermoplastic strip into aligned coincidence
immediately under the character defined by the die 14 in the die
heating station 12.
* * * * *