Font segment front loading device

A plurality of outwardly and radially extending font segment support arms are coupled to a central hub which is rotated to sequentially present the letters formed upon the segments to an optical imaging station which selectively projects optical images of the letters upon a photosensitive medium. Vertical shoulder portions are precision machined upon outer portions of the radially extending support members for precisely positioning the arcuate character tracks on the segments with respect to the imaging station. Horizontal plates are affixed to the radially extending support members to support the segments against gravity and centrifugal force is employed to precisely seat the segments against the vertically oriented shoulder portions upon rotation of the hub. A stationary stage plate together with a ramp element provide for easy and rapid insertion and removal of font segments from the front of the phototypesetter.

BACKGROUND OF THE INVENTION 
Most manufacturers of phototypesetting machines place several fonts on one 
disc or film strip carrier with the entire disc or film strip being 
replaceable when it is desired to change fonts. It is known in the art 
that it is advantageous to separate a unitary disc into segments such as a 
number of pie-shaped disc portions so that each may be replaced on an 
individual basis upon the selection of a new font. Several manufacturers 
have employed such a segmental font system with the individual font 
segments being accurately located by expensive alignment pins and holes. 
However, since the mounting accuracy should be typically less than one 
mil, very little clearance exists between the holes and the guide pins 
which makes the segments difficult to replace and expensive to 
manufacture. Difficulty in replacement increases operator burdens and 
slows down such replacement. 
It is highly desirable to effect rapid and easy insertion and removal of 
font segments from the front of the phototypesetter with a minimum of 
visual operator guidance, in contrast with the loading arrangement 
disclosed in patent application Ser. No. 747,761 filed Dec. 6, 1976 and 
assigned to the same assignee as the present invention. 
SUMMARY OF THE INVENTION 
In accoreance with an embodiment of the present invention, a plurality of 
outwardly and radially extending arms or support members are coupled to a 
central rotatable hub and a vertical reference shoulder portion is 
precision machined at outer portions of the support members so that upon 
rotation of the hub, centrifugal force is employed to accurately seat the 
segments against the shoulder portions. First and second sets of 
horizontally oriented retaining plates are affixed to the support members 
for supporting the segments against gravity and a stationary stage plate 
is positioned below the retaining plates for guiding the leading edge of 
the font segment and causing it to traverse a ramp member for positioning 
upon the rotatable retaining plates. This simple and highly reliable 
arrangement provides for extremely easy and rapid insertion and removal of 
the segment from the front of the phototypesetter.

DETAILED DESCRIPTION 
In accordance with the prior art, outwardly extending arms are provided, 
which are coupled to hub 2 and have outer portions which terminate in 
members 3 which have the above-mentioned vertically oriented reference 
shoulder portions machined in each member. Horizontal plates 4 are 
illustrated which support pie-shaped font segments 6 against gravity. The 
three degrees of translational freedom, x, y, and z, are illustrated by 
orthogonal vectors. Since the plane of the segments are perpendicular to 
the optical projection axis, character focus is affected only by z 
variations. Since the depth of focus at the font plane is about plus or 
minus 5 mils, alignment accuracy in the z axis is not critical. Alignment 
in the y axis is a function of flash timing and is independent of font 
segment position since the clock track on the segments control flash 
timing. Thus, only alignment in the radial direction represented by the x 
vector is critical. The above-mentioned vertically oriented reference 
shoulder portions 9, shown in FIG. 2, are formed by grinding, after the 
mounting of the assembly on the drive shaft 7, and may be readily 
controlled very accurately with respect to its radial position. This 
procedure minimizes any "radial run out" of the surface and establishes 
excellent radial alignment of the font segments. The retaining plates 4 
are thereafter attached to create a land on which the font segments rest. 
Font segments 6 are rapidly and easily placed upon the above-mentioned 
horizontally oriented support plates 4 as illustrated. Centrally located 
support plates 4' are coupled to the hub portion to fully support the font 
segments. Upon the rotation of hub 2, typically at a speed of 1800 rpm, 
centrifugal force causes the segments to be firmly seated against the 
inwardly facing vertically oriented precision machined shoulder portions 9 
as illustrated in FIG. 2. 
When it is desired to change a font segment, the machine is stopped and the 
segment is easily and rapidly lifted out of the assembly and a replacement 
segment is readily dropped into the assembly. The actual prior art 
prototype produced very accurate radial alignment of the font tracks and 
excellent results were obtained. This prototype employed an assembly 
having an overall diameter of 9 inches and which was rotated at a speed of 
1800 rpm. Each segment was made of plexiglass and had an approximate 
weight of 1/8 pound. 
In FIG. 4, a preferred embodiment of the present invention is illustrated, 
employing similar numbers to represent similar parts of the structure 
described hereinabove in connection with the prior art font segment 
support device. A rotatable shaft 10 supports hub member 2a and outwardly 
extending arm 1a. A stationary stage plate 5 is affixed to the machine 
frame and is positioned adjacent a first horizontal segment support plate 
4a attached to the outer portion 3a of arm 1a in the neighborhood of the 
vertical precision machined segment referencing wall or shoulder portion 
9a. The upper surface 11 of horizontal support plate 4a lies in a first 
font segment support plane which also includes the upper surface 12 of the 
second segment support plate 4'a which is coupled to rotatable shaft 10. 
The upper surface 13 of stationary stage plate 5 lies in a second font 
segment support plane below the first font segment support plane including 
upper surfaces 11 and 12 of support members 4a and 4'a respectively. In 
the most preferred embodiment there are four members 4a and four members 
4'a as in FIGS. 1-3. The assembly of FIG. 4 is positioned adjacent an 
opening 14 defined by enclosure members 16 and 17. Enclosure members 16 
and 17 are vertically oriented so that opening 14 faces the operator 
seated in front of the phototypesetting machine. Preferably a door (not 
shown) is employed to close off the opening of the machine. Font segment 
6a is easily and rapidly inserted into the machine by sliding the leading 
edge portion 17 along the upper surface 13 of stationary stage plate 5. 
The leading edge 17 as it continues in its forward motion represented by 
arrow 18 "rides up" ramp portion 19 of the support member 4'a and 
thereafter rests upon the upper surface 12 of member 4'a. After the 
segment 6a is fully inserted, trailing edge portion 21 of font segment 6a 
just clears horizontal support plate 11. The operator thereafter pulls the 
segment toward her in the direction of arrow 22 so that trailing edge 21 
slides over upper surface 11 of outer support plate 4a and rests thereon. 
A second segment may thereafter be loaded if desired, by rotating arm 1a 
so that the next sector is positioned adjacent opening 14 and the 
above-mentioned process is repeated. 
A segment is easily and rapidly removed from the phototypesetter by first 
pushing the segment forward in the direction of arrow 18 so that the 
trailing edge 21 clears plate 11 and rests upon stationary stage plate 5. 
The leading edge 17 of the segment at this time assumes the extreme 
innermost position upon the upper surface 12 of support plate 4'a. Segment 
6a is thereafter pulled toward the operator in the direction of arrow 22 
and the trailing edge 21 slides across the stationary stage plate 5 along 
its upper surface 13 and clears horizontal support plate 11 and is removed 
from the machine. Spring element 20 may be employed to bias segment 6a 
downwardly against upper surfaces 11 and 12 of the horizontal support 
plates. 
Thus it should be appreciated that the present invention provides a simple 
and highly reliable device for easily and rapidly inserting and removing 
font segments to and from a rotatable font segment support device, from 
the front of the machine. The need for operator "eye balling" with respect 
to visual alignment is maintained at a minimum. 
The ramp element 19 preferably is formed upon rotatable horizontal support 
plates 4'a, in the interest of simplicity and ease of manufacture. 
However, it is possible to form the ramp element upon the upper surface 13 
of the stationary stage plate 5 or for that matter provide a separate ramp 
element if desired. While the stage plate may have numerous shapes, a 
pie-shaped plate is conducive to the above described design. 
While preferred embodiments of the invention have been described, the 
teachings of this invention will readily suggest many other embodiments to 
those skilled in the art and thus the invention is to be limited only by 
the permissible scope of the following claims.