Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an improved design
of type-carrying fingers used in belt printer applications
and particularly a design which minimizes the breakage of
flexible type fingers during impact printing.
United States Patent No. 3,605,610, issued June 4, 1968
to Earle B . McDowell, Clifford M. Jones and Seymour M. DePuy
discloses a printing apparatus utilizing a type-carrying
belt that carries a number of flexible fingers each of
which has a type face for a particular character on one
end thereof. United States Patent No. 3,605,613 issued
June 4, 1968 to Seymour M. DePuy and Donald G. Hebert discloses
such a t~vpe-carrying belt and the general design of the
flexible type fingers. These type fingers are preferably
made of metallic material and have a shank provided with means
for vertically positioning or locating the fingers within
slots on the belt.
It will be appreciated that such type fingers must be
designed with certain criteria in mind. For instance, the
shank portion of the type finger must exhibit a degree of
resilience and be rather accurateIy dimensioned. The type
face portion must be suitable for continuous impacting with-
out damage. Such type fingers when struck by hammers are
caused to deflect and impact a record medium. During
impact the fingers develop compression and tension stresses
both due to deflection in response to the hammer force, as
well as edgewise bending or deflection due to friction forces
deveIoped at the point where the type face impacts the
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;~l record medium while the beIt continues its movement. The
` finger, when exposed to repeated stresses over a long period
of time, can develop cracks which lead to breakage and
termination of finger life. With the trend to higher printing
rates, a need has developed for improving the life of type
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ingers used in impact printing,
An object of the present invention is to provide im-
proved type fingers capable of longer operation a~ high
speeds,
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' Another object of this invention is to improve the
life of flexible type fingers which are stressed during
impact printing,
A further object of this invention is to minimize
breakage of flexible type fingers used in a belt printer,
A still further object of this invention is to provide
' fingarA which can withstand the continuous stressing during
- impact printing while being provided with means for movable
' locating the type fingers in a type finger belt,
'~l A further object of this invention is to minimize
~ breakage which occurs at a shoulder provided on a flexible
type finger to enable the finger to be locked in a position
,: in the slots provided in a type finger carrying belt,
In accordance with a preferred embodiment of the
,j invention, there is provided a removable type face carrying
`" 20 finger ~hich can be inserted into a finger slot extending
I through the width of an elastic belt, The belt when rotated
`, causes the inserted finger to be moved past a hammer whexe
` ` it can be struck to cause impact printing against the
s; record medium, The finger comprises a substantially flat
elongated member bearing a type face near one end thereof,
The type finger is adapted to be inserted into one of the
slots with the plane of its length and width substantially
:'
,, parallel to the plane o the belt, In order to fix the
,' finger with respect to the edge surface of the belt nearest
30 the type face7 a shoulder is provided in the member ex-
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i tending orthogonally in the direction of the width of the
'~ finger and dimensioned to abut the edge surface of the
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belt, The ~inger is made o~ Elexible material and adapted
to deflect in ~e direction substantially orthogonal to
'~ the plane of its width and length when struck by said
hammer, The struck finger develops tension and compression
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stresses at the shoulder location on the member during im-
pact by the finger against the record medium, To minimize
breakage of the finger due to said stresses developed in
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,'j the finger at said shoulder location, the shoulder is
,,'` located on the traillng edge of the finger as defined by its
movement by the belt past a hammer for impact printing,
~- This corresponds to the region of the finger where the
~,j member is under compression,
The matters discussed above as well as further objects
; and features of the present invention will be more clearly
', understood and appreciated following a consideration of the
~, accompanying drawings,
,'. FIGURE 1 illustrates schematically a printing mechanism
~' employing removable type ~ingers,
FIGURE 2 illustrates how the fingers are provided with
~' 20 a shoulder to facilitate proper location of the removable
;~
finger within the belt.
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.. ` FIGURE 3 illustrates schematically and diagramatically
'~ the stress forces developed on the finger during impact
printing.
FIGURE 4 is a stress diagram illustrating the various
;~ forces developed at the shoulder location,
` FIGURE 5 illustrates the force diagram when the finger
has not been impacted against the paper,
.,
FIGURE 6 illustrates the forces developed when the
`~ 30 type finger impacts the record medium; and
FIGURE 7 illustrates in greater detail the shoulders
~ provided on a type finger to facilitate location within an
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elastic helt carri~r.
The perspective sketch of FIGURE 1 illustrakes the
principal components of an impact printing apparatus of the
;~ type shown in the aforecited U S Patent 3,605,610 dated
; ~une 4, 1968~ This sketch shows a type carrier or belt
10 adapted to be driven at a constant speed around pulleys
or reels 13, 14 in a counterclockwise direction as viewed
from above. The direction of movement of the belt 10
relative to a record medium 12 is such that it traverses a
line of print on the record medium Interposed between
~- type carrier 10 and the record medium 12 is an inking
ribbon 11 It will be understood that any suitable material
may be used for recording medium 12 and inking ribbon 11.
Type carrier 10 carries a plurality of flexible type fingers
~; 20 which are attached to the belt 10 and extend through it
' at pxecisely located positions. At the upper external end
o the ~lexible fingers, a type ace 21 is provided for
cooperation with the ribbon 11 in order to impress particular
characters on the recording medium. Fingers 20 are pre-
ferably equally spaced along the length of the belt Only
a few typical fingers are shown in the sXetch. One or
more complete Eonts of type formed characters may be provided
and as explained hereinafter, the particular characters ~;
may be changed by changing the fingers 20 They may take
the form of numerals, letters, marks or other symbols in
accordance with the desire of the particular users.
` A row of hammers 30 is disposed across the entire usable
width of the record medium 12, a separate hammer being
provided for each position at which a character may be
`j 30 printed on the recording medium. The hammers are located
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~ behind the type carrier 10 and are controlled by circuitry
:
to move orward when a character is to be impressed on the
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record medium, The hammer is designed to strike a finger 20
and drive it into ribbon ll and the sur~ace of recording
medium 12. The fingers are formed of material highly
.
resistant to taking a set, A plurality of electromagnets
,, .~
32 is illustrated to show the general method o~ actuating
hammers 30. It will be understood that the harnmers pivot
about an axis 31 and spring means not shown are provided
for returning them to the position shown, As previously
noted, as the type carrierlO moves at a continuous velocity
across the ~ace of the record medium, hammers 30 are sel-
ectively actuated to impress the various characters at
desired locations on the record medium, As a result of
each hammer impact, the flexible fingers are urged in the
direction transverse the motion oE the belt and into the
ribbon and recording medium and they must return in time
to permit the possible subsequent impacting o~ a succeeding
hammer, The dynamic characteristics required to satis-
factorily permit this functioning place stringent re-
quirements on the design oE the type carrier belt and the
fingers employed with it.
A more complete understanding of -the specific features
of the invention will be available upon consideration of
FIGURE 2 which illustrates a short segment of belt in an
enlarged and somewhat exaggerated form, This segment
illustrates two flexible finger members 20 properly mounted
in the belt lO, It also shows a slot 17 as it appears prior
to insertion of a flexible finger. Fingers 20 are pre-
ferably made of metallic material and are provided with
upper and lower shoulder portions 22 and 23 respectively,
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;~ 30 The belt itself is made of an elastic material such as
urethane or the like, In order to insert a type finger 20
into the belt 10, the lower portion 24 is simply forced
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through a preform~d slot 17 and the lower should~r 23 acts
to expand th~ slot as the ~inger traverses it, When the
I finger member is in the correct position~ upper shoulder
22 and lower shoulder 23 reside on th~ upper and lower
surfaces of the belt respectively. The shoulders maintain
the alignment of the type along a desired line by assuring
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the rigid, vertical positioning of the fingers and re-
' straining the fingers within their respective slots until
' su~ficient pressure is applied to purposely remove the
fingers from their position.
. The upper portion of each finger 20 carries a type face
21, These type faces may be fastened to or formed as an
integral part of the upper portion of the fingers~
By using polyurethane as the elastic material for the
body lO of the carrier belt, it is possible to manufacture
the belt by casting techniques. Thus, the belt is cast
having the desired peripheral dimensions and including an
interprojecting portion 18 for engagement with the pulley
i rneans 13 and 14 that drive the belt so that the type fingers
can traverse a line on a record medium.
Refexence is now made to FIGURE 3 for discussion o the
principal foces involved in developing the tension and com-
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pression stresses developed at the location where the type
~, finger enters the belt and where the positioning shoulder
22 is located. The forces acting at the point where the
type ace impacts the record medium is the hammer force due
to hammers striking the type finger and driving it forward
into the record medium and the pinching force resulting
~i from the fact that the type finger is moving in the dir- -
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ection of belt travel while the portion of the type finger
' containing the type face is in impact contact with the record
medium. The result is that the type finger is caused to bend
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eag~wise opposlte the dir~ction oE travel as the result of
the resultant force developed by the hammer striking the
type finger and the pinching force developed when the type
fa~e impacts the stationary record mediumO FIGURE 4 ill-
ustrates that ~or the belt motion indicated and the pinching
force developed upon impact, the leading edge of the type - :
finger is stressed in tension while the trailing edge is
stressed in compression, Under the circumstances~ if a
~, discontinuity is provided in the type finger in the
;~ 10 vicinity where the tension and compression stresses are
maximum, this discontinuity becomes a site now for possible ~ -~
finger cracking and rupturing due to fatigue failure, Under
.'l the circumstances where it is necessary to provide a shoulder
i! such as 22 shown in FIGURE 2 to the finger in order to help
' locate it and position it fixedly within the belt, this
:~ shoulder introduces sufficient discontinuity in the type
; ~inger structure to provide a point of rupture when exposed
~ to the tension stresses described. Experience shows that
flexible material such as a type finger made of maraging
steel is more susceptible to rupture when exposed to
1, tension stresses, Accordingly~ in accordance with the present
invention a shoulder is provided on the type finger for
positioning and locking purposes on the edge of the type
finger exposed to compression~ This corresponds to the
trailing edge of the type finger when referenced against the
.. ' direction of belt motion, Since the type finger material
' can withstand greater compression than tension, the result
is a type finger provided with the shoulder for locating or
' locXing purposes with minimum opportunities for breakage of
,;~ 30 the flexible type finger due to edge bending caused by the
' pinching forces when the type finger impacts the record
.~r~ medium.
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Referring to FIGURE 5, there i9 shown a back view and
side view of the type finger before impact, Under the
, circumstances~ no forces are shown being developed which
could lead to stresses in the type finger, FIGURE 6 shows,
however, that upon contact of the type ~inger with the
record medium, a pinching force is developed at the type
' face in response to the hammer holding the type face against
~ the record medium, The belt continues to move the type
; finger even during the impact period when the hammer is
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-I lO contacting the type face, ~his motion of the supported
c end of the finger while the motion of the end of the finger
is temporarily arrested, causes a stress in the leading
edge of the finger in the vicinity of the emergence of the
type face carrying end of the finger from the slot in the
belt, FIGURE 7 illustrates in greater detail the pair of
shoulders used at the bottom to align the type finger with
the bottom edge of the belt and the single shoulder located
, on the trailing edge of the type finger for aligning the
finger with respect to the top edge of the belt,
The embodiment disclosed and discussed here and above
may be modified by those skilled in the art, It i3
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`~, contemplated in the appended claims to include all such
modifications which come within the spirit and scope of
~ the teachings herein,
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