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Browse Prior Art Database

Hammer Unit Alignment Indicator for Bar Code

IP.com Disclosure Number: IPCOM000122227D
Original Publication Date: 1991-Nov-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 6 page(s) / 179K

Publishing Venue

IBM

Related People

Clark, WD: AUTHOR [+3]

Abstract

The invention allows the easy determination of hammer unit and print band alignment. Technical considerations related to the hammer geometry, balancing, and center of mass often limit the height of the hammer face to about 0.200 inches. However, the printing of bar code has led to characters that have elements as high as 0.186 inches leaving a total possible misalignment between the band and hammer face of 0.014 inches. Typical misalignment tolerances built into the printer assembly are as much as plus or minus 0.030 inches. There is clear exposure of having the hammers and band misaligned with the result that characters do not print properly.

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This is the abbreviated version, containing approximately 37% of the total text.

Hammer Unit Alignment Indicator for Bar Code

      The invention allows the easy determination of hammer
unit and print band alignment.  Technical considerations related to
the hammer geometry, balancing, and center of mass often limit the
height of the hammer face to about 0.200 inches. However, the
printing of bar code has led to characters that have elements as high
as 0.186 inches leaving a total possible misalignment between the
band and hammer face of 0.014 inches.  Typical misalignment
tolerances built into the printer assembly are as much as plus or
minus 0.030 inches.  There is clear exposure of having the hammers
and band misaligned with the result that characters do not print
properly.  In the final inspection of a machine, it is necessary to
establish the hammer and character alignment to determine if a
potential printing problem exists and to correct the machine if
necessary.  The method described in this article presents an easy
means of determining the character and hammer alignment.

      When printing characters on an impact printer there is the
concern that the characters are too high relative to the height of
the hammer faces with the result that top or bottom character cut-off
may result.  Although the machine may be designed such that at a
nominal condition characters are always acceptably printed,
tolerances may allow misalignment between the print band and the
hammer unit. The problem is particularly severe when bar code or
other abnormally high foreign language characters are printed.

      In the past, the check for proper alignment has been to print
on the hammer faces, that is print without any paper and look at the
impression of the character left on the hammer.  This presents two
problems.  First, in a machine without a swing casting an
investigator cannot see the hammer faces without removing the front
unit, and, second, if the alignment is critical, a measurement is
required.  A common method used is to print the bar code or other
questionable characters and simply view them for cut-off. This works,
but only tells the inspector if the machine is good or bad, not how
good or how bad.  As this test is most often needed in a production
environment, a faster solution is required.

      According to the method described in this article, there is
provided a print band having a character consisting of two horizontal
segments nominally spaced apart a vertical distance equal to the
nominal height of the hammer.  See Fig. 1.  If this character were
printed in a perfect printer, the horizontal segments would both be
completely printed as they would just fall within the boundaries of
the hammer face.  In a real printer, however, either the top or
bottom character would not print as the print band and hammers might
not be perfectly aligned and the centerline of the band might be
higher or lower than the center line of the hammer faces.  The
printing of a single of the aforementioned characte...