Line printer character belt

In a line printer character belt in which characters are mounted on flexible fingers which are struck by printing hammers toward a platen in the printing operation, the fingers are flexed toward the platen by a projection on the fingers or on a character block on which the fingers are mounted. Vibration subsequent to the printing operation is eliminated, thereby providing excellent printing quality free of dirt and ghosts.

BACKGROUND OF THE INVENTION 
In a conventional character belt for use in a line printer where character 
blocks each carrying a plurality of fingers are mounted on the belt and 
characters are provided at the ends of the fingers, the character blocks 
are of such a shape that they are neither influenced by nor influence 
vibration of a finger subsequent to a printing operation. Consequently, 
when the finger is struck by a printing hammer, the finger undergoes 
vibration subsequent to striking the ribbon and paper against the platen. 
The fact that the character is at the end of the finger makes it unstable; 
resonance occurs so that the character may strike the ribbon and paper 
against the platen subsequent to the initial stroke. This phenomenon can 
result in so-called printing dirt and, the character may not stabilize 
even by the time it is next struck by a printing hammer. This type of 
operation may result in destruction of a finger as well as generation of 
printing ghosts. 
As is evident, then, it would be highly desirable to provide a construction 
in which vibration due to the printing operation itself could be 
eliminated, thereby preventing both printing dirt and printing ghosts. 
SUMMARY OF THE INVENTION 
An endless belt carries character blocks detachably mounted thereon. To 
each character block is mounted a plurality of character fingers. Each 
finger is flexible and attached at one end thereof to the character block. 
The other end of the finger carries a character. Each character block has 
a projection thereon flexing each finger in a direction in which the 
finger is to move during the printing operation, the projection preferably 
being part of the finger. The finger is struck, in the printing operation, 
by a printing hammer. The projection is so positioned as to minimize 
vibration subsequent to striking the finger with a printing hammer. 
Further to this objective the projection may be made of a resilient 
material suitable for damping vibration. Appropriate materials are rubber 
and resilient plastics. 
In a preferred embodiment the fingers are injection-molded integrally with 
the character block, the characters being of metal and being united with 
the character block during the molding process. An L-shaped retainer holds 
the block removably to the endless belt and biases the fingers toward the 
platen against which printing is to be effected. 
Accordingly, an object of the present invention is an apparatus in which 
vibration of a character finger is minimized subsequent to a printing 
operation carried out with said character finger. 
Another object of the present invention is an apparatus in which a 
projection on a character block carrying a flexible finger is positioned 
so as to minimize vibration subsequent to striking said flexible finger 
during a printing operation. 
An important object of the present invention is a character block having a 
projection of a resilient material for damping vibration in a character 
finger subsequent to a printing operation. 
A significant object of the present invention is an injection-molded 
character block in which the fingers holding characters and the metal 
characters on the fingers are integral with said block. 
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 character holder 1 mounted on an endless 
character belt 5 the face of which runs in a direction parallel with a 
line to be printed. Character block 2 holds a plurality of fingers 3 of a 
flexible material, each of said fingers 3 having mounted proximate the end 
thereof a character 4. Each of the fingers 3 is secured at the lower end 
thereof to the character holder 1. Guide rails 7 and 8 are fitted to the 
character holders 1 so as to control the motion of the character holders 
in the directions indicated by arrows 26 and 27, thereby lining up 
characters 4 in relation to the line to be printed. 
A plurality of printing hammers 13 are provided in positions such that they 
can be actuated in the direction indicated by the arrow 28. The motion of 
printing hammers 13 is controlled by guide rods 14 and 15, and the hammers 
are biased away from flexible fingers 3 by springs 16. When actuated, 
hammer 13 forces character 4 against ink ribbon 12, paper 11 and platen 
10. 
Associated with each printing hammer 13 is an electromagnet 19 and an 
armature 18, introduction of a printing signal to electromagnetic coil 20 
causing armature 18 to rotate in counterclockwise direction around axle 21 
so that end portion 18a of armature 18 drives printing hammer 13 in the 
direction indicated by the arrow 28, that is, toward platen 10. 
Platen 10 is mounted on a platen spindle 29 which is connected to a 
mechanism (not shown) for rotating same and feeding the paper 11. Frame 25 
supports guide rail 7 and axle 24 of pulley 23 which drives endless belt 
5. 
The rest position of hammer 13 is established by stop 17, and the rest 
position of armature 18 is established by stop 22. 
As can be seen from FIGS. 2a and 2b, endless belt 5 fits in channel 101 
formed in character holder 1. A boss 102 projects from the surface of 
character belt 5 and fits into and through opening 103 in character holder 
1. Boss 102 has grooves 104 and 105 therein for receiving retainer 9 to 
prevent accidental separation of character holder 1 from endless belt 5. 
Withdrawal of retainer 9, of course, makes it possible to remove character 
block 1 from endless belt 5 should such course of action be desired. 
Teeth 106 are formed on the inner periphery of endless belt 5. These teeth 
engage pulley 23 and serve for driving endless belt 5. 
As shown in FIG. 3, flexible finger 3 is removably secured to character 
holder 1 by screw 6. Character holder 1 is provided with projection 201 
which flexes finger 3 outwardly from character holder 1 and in the 
direction toward platen 10. The extent of the deflection indicated by the 
reference character .delta. is such that after striking the finger 3 with 
the printing hammer 13 the finger 3 will spring back against projection 
201 and make firm contact therewith, thereby eliminating or minimizing any 
tendency for further vibration. Preferably, finger 201 should make contact 
with flexible finger 3 at a position close to but below the character 4 
which is to be imprinted. The location of the projection 201 relative to 
character 4 and the degree of flexing which will minimize or eliminate 
vibration subsequent to a printing operation can readily be determined by 
one skilled in the art. This minimization can readily be effected to the 
point where any resonance or vibration subsequent to the printing 
operation is so small as to eliminate printing dirt or ghosts on paper 11 
due to such vibration. Further, with the elimination of such vibration, it 
becomes possible to minimize the distance between character 4 and paper 
11, thus speeding up the printing operation. An additional advantage 
accruing from the minimization of vibration is that adjacent fingers on 
the same character block are not influenced so that printing ghosts due to 
the vibration of adjacent fingers is prevented. Also breakage of fingers 
as the result of being struck by a printing hammer while still vibrating 
is eliminated. 
In a preferred embodiment, projection 201 is of a non-rigid material such 
as rubber or a non-rigid plastic, such an embodiment being shown in FIG. 
4. 
In the embodiment shown in FIGS. 1, 2a, 2b, 3 and 4, the character block 
200 is provided with a plurality of fingers 3, each having a character 4 
at the end thereof. In the preferred embodiment shown in FIGS. 5, 6a and 
6b, finger portion 200 is integrally molded at an angle of about 
90.degree. with base portion 100, said finger and base portions 
constituting character member 300. The back side of each finger 3 is 
provided with a projection 201. 
Retainer member 91 holds character base portion 100 removably to endless 
belt 5. Retainer member 91 has an upstanding portion 91 and a base portion 
93 forming a dihedral angle of about 90.degree. so that retainer member 91 
in section is L-shaped. Retainer member 91 is formed at an angle such that 
upstanding portion 91 thereof engages projection 201 on each finger 3 and 
deflects each finger in a direction away from base portion 100 and toward 
the platen (not shown) against which printing is to be effected. Base 
portion 93 of retainer 91 engages endless belt 5 for holding character 
member 300 thereto. 
In more detail, character member 300 is placed on endless belt 5 so that 
boss 102 of said belt protrudes through opening 103 in the base portion 
100 thereof. Retainer member 91 is then pushed into position so that 
interior edges 94 and 95 engage with grooves 104 and 105 respectively of 
boss 102, thereby fastening said character block to said endless belt. 
Additionally, lip 96 of retainer member 91 is inserted into opening 107 in 
base portion 100, opening 107 and lip 96 being sized to provide a selected 
degree of deflection of finger 3 away from neutral (i.e., unflexed) 
position. In assembled condition of the character member 300 and belt 5, 
fingers 3 are deflected by portion 92 of retainer member 91 toward the 
paper and platen (not shown), the degree of deflection being identical for 
all fingers in a character member, thereby guaranteeing uniform excellent 
printing quality. 
The foregoing, simple method of assembly provides for uniform alignment of 
the fingers and uniform spacing from the paper and platen against which 
printing is to be carried out. Furthermore, the engagement of the retainer 
with the projection on the fingers substantially eliminates the effect of 
external vibration so that dirt and ghosting are avoided. Moreover, the 
form of the retainer is such that it can be produced by a simple press 
operation. 
FIGS. 6a and 6b show further detail in the construction of fingers 3 in the 
preferred embodiment of FIG. 5. The fingers 3 are of a flexible, elastic 
synthetic plastic or of a flexible, elastic rubber, while the characters 4 
are of a hard, long-wearing metal. During the process of injection-molding 
the character block 200, the characters 4 are inserted and the character 
block and the characters 4 are made as a monolithic molding. 
The apparatus of the present invention is particularly advantageous with 
respect to printing speed and with respect to the fact that any defect in 
a finger or in a block can readily be eliminated due to the fact that the 
character holders and the individual fingers can easily be removed from 
the belt and replaced. Consequently, not only is printing speed increased, 
but the danger of breakage is decreased and the overall cost of operation 
is likewise decreased. 
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.