Print hammer for line printer

A print hammer having an improved head portion for striking a selected moving print character member in a line printing device is provided. The printing device prints when the print hammer strikes a print character member at a predetermined print position forcing the character member against an ink ribbon, a print paper and a platen. The head portion is formed with an inclined surface facing the direction of approaching adjacent character members to drive an adjacent character member striking the side of the print hammer around the print hammer for avoiding jamming and damage to character members and print hammers. In a preferred embodiment the head portion is substantially "V" shaped with the apex of the V disposed in a direction opposite to the movement of the print character members.

BACKGROUND OF THE INVENTION 
This invention relates generally to a print hammer for use in a line 
printing device, and particularly to the head portion of the print hammer 
for striking the print character member. In conventional line printing 
devices having a plurality of print hammers for selectively striking a 
print character member of a plurality of moving print character members, 
printing is accomplished by the impact of a print hammer on the back side 
of the selected print character member for forcing the character member 
into an ink ribbon, paper and platen. In order to avoid shadow printing 
caused by deflection of adjacent character members striking the print 
hammer, pivotally mounted print hammers have been provided with inclined 
cam surfaces on a guide arm for contacting a projecting guide surface on 
the type carrier prior to printing for laterally adjusting the print 
position of the print hammer. Such a guide surface arrangement is 
unsuitable for use with an elongated print hammer not capable of lateral 
displacement. Accordingly, it is desirable to provide an improved 
elongated print hammer of simplified construction which would avoid the 
possibility of damage to the head of the print hammer or an adjacent print 
character member which may strike the print hammer. 
SUMMARY OF THE INVENTION 
Generally speaking, in accordance with the invention, an improved print 
hammer for use in a line printing device including a plurality of print 
hammers and a plurality of print character members is provided. The device 
prints when a print hammer strikes a selected print character member of a 
plurality of print character members moving transversely across a print 
paper. When the print hammer is selectively actuated, it is displaced in a 
print direction towards the print paper striking a print character member 
into an ink ribbon against the print paper which is wound about a platen. 
The improved print hammer is an elongated member formed with guide 
surfaces for guiding travel in the print direction parallel to its longer 
dimension for striking the print character member and return travel for 
returning the print hammer to its at rest position. The head of the print 
hammer is formed with a flat end surface for striking the back of a print 
character member and an inclined side edge on the side of the print hammer 
facing the approaching print character members. In a preferred embodiment 
of the invention the print hammer head portion is formed with a 
substantially "V" shaped bend with the apex of the "V" facing the 
approaching print character members. 
Accordingly, it is an object of the invention to provide an improved print 
hammer for use in a line printing device. 
Another object of the invention is to provide an improved print hammer for 
a line printing device wherein the head of the print hammer is formed with 
an inclined surface facing approaching print character members. 
A further object of the invention is to provide an improved print hammer 
for a line printing device wherein the head of the print hammer is formed 
in a "V" shaped bend for displacing an adjacent character member striking 
the print hammer. 
Still another object of the invention is to provide an improved print 
hammer for a line printing device wherein the head of the print hammer is 
formed into a "V" by press-bending. 
Another object of the invention is to provide an improved print hammer for 
use in a line printing device which avoids damage to the print hammer and 
character members. 
Still other objects and advantages of the invention will in part be obvious 
and will in part be apparent from the specification. 
The invention accordingly comprises the features of construction, 
combination of elements, and arrangement of parts which will be 
exemplified in the construction hereinafter set forth, and the scope of 
the invention will be indicated in the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows schematically a side elevational view of the printing elements 
of a line printing device including a paper 1 wound about a platen 2, an 
ink ribbon 4 passing between paper 1 and a print character member 3 
maintained a distance S from paper 1. An elongated print hammer 5 is 
formed with a head portion 5a for striking print character member 3 and a 
body portion 5b formed with an opening 5c for mounting print hammer 5 on a 
circular guide rail 11 fixed to the printer frame (not shown). Print 
hammer 5 includes a tail portion 5d for slideably engaging a flat guide 
rail 12 also fixed to the printer frame. When print hammer 5 is actuated 
for printing by a print control means (not shown) hammer 5 is displaced in 
a print direction towards platen 2 as indicated by an arrow 6 thereby 
striking print character 3 against ink ribbon 4, paper 1 and platen 2. 
Referring now to FIG. 2, a plurality of print character members 3 and a 
series of print hammers 5 are shown in the perspective view. Print 
characters 3 are mounted on an endless belt (not shown) and are 
continuously moved transversely across paper 1 between paper 1 and print 
hammers 5 in a direction indicated by an arrow 7. A selected print hammer 
5 is disposed behind a selected print character member 3 corresponds to 
the character to be printed. Just before print character member 3 is in 
position to be printed, print hammer 5 is actuated by the printing control 
means and print hammer 5 flies in arrow direction 6 as shown in FIG. 1, 
striking print character member 3 against ink ribbon 4, and paper 1 and 
platen 2. 
In FIG. 3 print hammer 5 is shown after it has been displaced in arrow 
direction 6 distance S for printing. In this illustration a selected print 
character 3a has been displaced distance S and is shown pressing ink 
ribbon 4 against paper 1 and platen 2. When the line printing device 
functions as shown in FIG. 3, the adjacent print character members 3b 
remain in their at rest position a distance S from platen 2. When print 
character members 3b are maintained in this at rest position, print paper 
1 does not become dirty due to shadow printing caused by adjacent print 
character members 3b being driven into print paper 1. Print character 
members 3b remain in their at rest positions a distance S from print paper 
1 and printing of excellent quality can be obtained. However, when the 
return speed of print hammer 5 after printing print character member 3a is 
slow or if the printing speed of print hammer 5 and print character 
members 3 are out of phase, the condition shown in FIG. 4 occurs. 
In the condition illustrated in FIG. 4, print hammer 5 interferes with 
adjacent print character member 3b after printing print character member 
3a as print character member 3b approaches print hammer 5 in the direction 
of the moving print character members as indicated by an arrow 7. When 
this interference occurs an abnormal force is imposed between print 
character member 3b and print hammer 5 in a direction indicated by an 
arrow 8. There exists the possibility that print character member 3b or 
print hammer 5 may be broken. This condition can be avoided by 
constructing a print hammer in accordance with the invention. 
Referring now to FIG. 5, a print hammer 15 having a head portion 15a 
constructed and arranged in accordance with the invention is shown. Like 
elements of FIGS. 1-4 in FIG. 5 are represented by like reference 
numerals. Print hammer 15 is formed with a head portion 15a having an 
inclined side surface 15b on the side of print hammer 15 facing 
approaching print character members 3b. As print character member 3b 
interferes with print hammer 15, print character member 3b is moved in a 
direction indicated by an arrow 9 due to the impact and print character 
member 3b is moved in a direction substantially normal to the direction of 
movement of print character members 3 as indicated by an arrow 10, namely 
around head portion 15a without contacting print paper 1. Thus, print 
character member 3b is not deflected in the direction of arrow 8 shown in 
FIG. 4 and breaking of a print character member can be avoided. When print 
character members 3 are in phase with striking print hammers 5 in a normal 
printing condition, print hammer 15 and head 15a do not interfere with 
adjacent print character members 3b and the normal cycle is performed. 
Referring now to FIG. 6, a print hammer shown generally as 25 constructed 
and arranged in accordance with a preferred embodiment of the invention is 
shown. Print hammer 25 is formed with a head portion 25a for striking 
print character members 3 during printing and an elongated body portion 
25b for guiding displacement during printing including an opening 25c and 
a tail portion 25d. Head portion 25a is formed with a substantially flat 
front for striking print character members 3 and a "V" shaped bend 
extending to the extremity of print hammer 25 with the apex of the "V" in 
a direction opposite to the displacement of moving print character members 
3. The forward inclined surface of "V" shaped head portion 25a enables 
deflection of an approaching adjacent print character member striking the 
side of print hammer 25 about head portion 25a without causing damage to 
either print hammer 25 or print character member 3b. 
The advantages of print hammer 25 having head portion 25a constructed in 
this manner include the facts that the V-shaped head portion 25a may be 
formed from flat sheet material in a single operation by bending with a 
press. Thus, the cost of an improved print hammer constructed and arranged 
in accordance with this embodiment of the invention is not increased 
substantially over a conventional flat headed elongated print hammer. The 
defects existing with conventional flat headed print hammers can be 
avoided at little incremental cost by forming head portion 25a by bending 
with a press. Thus, a significant advantage in operating efficiency and 
avoidance of damage to print character members may be obtained at low 
cost. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are efficiently attained and, 
since certain changes may be made in the above construction without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense. 
It is also to be understood that the following claims are intended to cover 
all of the generic and specific features of the invention herein 
described, and all statements of the scope of the invention which, as a 
matter of language, might be said to fall therebetween.