Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND TOOLFOR ATTACHING PRINT ELEMENTS TO THE
BAN D
OF A DOT BAND PRINTER.
DESC~IPTION.
Technical Field.
The invention described and claimed herein relates to a method
and a tool for attaching print elements to a print band in a dot
printer.
Background of the Invention.
Prior known methods for attaching print elements to a metal band
include resistance spot welding, laser welding and brazing. In
all these processes the thin printband is subjected to extreme
heat which causes stresses in the material. Thus, further heat
treatment processes are needed in order to remove said stresses
in the band material. Also a laser heat treatment of each indi-
vidual print element to harden them is needed. In summary, this
manufacturing processes are very complicated, time consuming and
as a consequence thereof very expensive.
It is further prior known from US Patents 4.299.519 and 4.233.879
in combination with 3.645.125 to secure two plates together by
riveting or swaging using a two part member. These patents de-
scribe a two piece fastener and an installation tool for securing
two thin plates together using a pin and a swageable collar. The
tool exerts an axial pulling force on the pin and reaction force
on the collar so as to swage the collar into engagement with the
i
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pin. This method is not applicable for attaching print elements
to a thin print band as the axial forces will cause dammages to
-the print band.
Summary of the Invention.
The invention as claimed is intended to remedy the above mentioned
drawbacks. It solves the problem of how to attach print elements
to a thin steel band of a dot matrix printer without causing
damages to the print band or changing the metallurgical proper-
ties of the parts by means o a special tool which exerts an en-
tirely radial force to swage a collar inwardly to conform to a
recess of the print element.
The advantages offered by the invention are mainly that by the
use of the new tool the print elements can be attached to the thin
steel print band in a fast and economical way without exposing
the band to heat or stress which can cause irreparable damages
and causes need of further process steps to get rid of stresses
in the band. Further, with the new method the print band is not
subjected to axial forces from the tool.
Brief Desription of the Drawings.
l`he invention, which is defined in the attaced claims, is de-
scribed in detail below with reference to the drawings in which:-
Figure 1 shows a typical print band for à dot band printer andan exploded view of a print element and a collar;
Figure 2 shows a first alternative attachment of a print element
to a print band;
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Figure 3 shows a second alternative attachment of a print element
to a print band;
Figure 4 shows a schematical view of a tool for fastening a print
element to a print band and
Figure 5 shows enlarged pictures of crosscuts of a print element
fastened to a print band.
Detailed Desription of the Invention.
Figure 1 shows a typical print band 1 made in thin hardened steel.
The print band is provided with openings 2 and 3 forming tongues
4 having holes 5 for attachment of print elements 6. The print
band is also provided with timing slots 8 and 9. Figure 1 also
shows an exploded view of the print element 6 and the collar 7
for attaching the print element to the print band.
Figure 2 A shows a first alternative form of a print element 6.
The print element, which is made of hardened steel, is provided
with a cylindrical part 26 having a necked-down portion 23, a
flange 24 and an anvil surface 22 and a dot impactor part 25.
The cylindrical part 26 of the print element is inserted into the
hole 5 of the print band 1 and held in a fixed position with
flange 24 slightly pressed against the print band. A swageable
collar 27 of unhardened steel is threaded over the cylindrical
part 26 to contact with the print band 1 and thereafter radially
pressed against the cylindrical part 26 so that the material flows
into the necked-down portion 23 and thereby mechanically locks
the print element to the print band. Figure 2 B shows a sche-
matical cross-sectional wiew of such a print element fastened to
the printbelt.
~%~7~
Figure 3 A shows a second alternative form of a print element 6
In this embodiment the print element consists of a dot impactor
part 34, a cylindrical part 36 with a necked down portion 33 and
an anvil part 31 with an anvil surface 32. The diameter of the
anvil part 31 is greater than the diameter of the cylindrical part
36 and therefore the anvil part also serves as a flange. ~le print
element is mechanically attached to the print band in the same
way as described above in connection with figure 2. Figure 3 B
shows a schematical cross-sectional view of a second type print
element fastened to the print band.
Figure 4 shows in schematic form a tool for fastening the print
elements 6 to the print band 1. The tool comprises an outer cy-
lindrical collet 41, a trisectional jaw 42 and an axially movable,
cylindrical wedge 43. The cylindrical collet 41 is provided with
an inwardly extending annular flange 41' having an annular pivot
edge 44. The trisectional jaw 42 comprises three parts separated
from each other by slots and forming a rotational body comprising
an upper portion 45~ an intermediate portion 46 and a lower por-
tion 47. The upper cylindrical portion 45 of the body has an
outer diameter substantially less than the inner diameter of the
cylindrical collet 41 and an inner diameter d and a lower inwardly
sloping surface 48. The intermediate portion 46 of said body has
an outer cylindrical surface 49 which together with the sloping
surface 48 forms an annular nip 46', a first inner cylindrical
surface Sl having a diameter d and a heigth of d/2 and a second
inner cylindrical surface 52 having a smaller diameter. The two
cylindrical surfaces Sl and 52 are joined by a plane surface 53.
The lower portion 47 of the body forms a tapered cone having a
cylindrical cavity 54 with a diameter slightly greater than the
outer diameter of the swageable collar 7. The trisectional jaw
42 is pivotally journalled in the annular nip 46' around the pivot
edge 44. The three parts of the jaw are held in a spaced re-
lationship and in contact with the annular pivot edge 44 by a
s~
spherical steel member 58 having a diameter equal to the inner
diameter d of the upper portion 45 of the body and its centre in
the plane containing said annular pivot edge 44. The three jaw
parts are separated from each other by equal slots 62a, 62b and
62c (Fig. 4B) by means not shown. ~urther, the jaw parts held
in the position shown in figure 4A by resilient means (not shown).
A cylindrical wedge 43 is axially movable via a piston 59 by a
linear motor 55, e. g., a hydraulic or pneumatic motor, which is
fixedly mounted to the cylindrical collet 41 by means of a plate
57. When the wedge 43 is moved downwards from the start position
shown in figure 4A it presses the upper portions of the jaw parts
apart. Then, by the lever effect the jaw tips 60 is moved in-
wardly.
Figure 4B is a cross-sectional view along line A-A i figure 4A
with the spherical member 51 remowed showing the three parts 42a,
42b and 42c of the jaw 42 separated by the slots 62a, 62b and 62c.
The function of the tool 40 is as follows: A swageable collar 7
is inserted into the cavity 54 of the jaw 42 and the linear motor
55 is acttivated and moves the wedge downwards a short distance
thereby gripping the swageable collar 7. The tool 40 is than
moved so that the swageable collar 7 is threaded over the cylin-
drical part 26 of a print element 6 which has been inserted in a
hole 5 of print band 1. The swageable collar is moved so that
it slightly contacts the print band 1. With the tool in this
position the linear motor 55 is again activated and moves the
wedge 43 further downwards. By the lever effect the jaw tips 60
presses the swageable collar 7 radially inwards so that the ma-
terial of the collar as described above flows into the necked-down
portion 23 of the cylindrical part 26 of the print element 6.
Excess material of the swageable collar 7 flows into the slots
62a, 62b and 62c between the jaw parts 42a, 42b and 42c. Thus,
the print element 6 is mechanically secured to the print band 1
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without exposing the print band to axial forces that may damage
the print band.
Figure SA is an enlarged picture of a cross-section of a collar
7 fastened to a print element 6 in accordance with the invention.
The picture shows how material has flown out into the space be-
tween the jaw tips. Figure 5B is an enlarged picture of a
cross-section of a print element 6 fastened by a collar 7 to the
print band 1 in accordance with the invention. The picture shows
how material has flown into the necked-down portion 23 of the
print element 6.
The invention is not to be limited by the embodiments shown in
the drawings and described in the specification which are given
by way of example and not of limitations.
