Note: Descriptions are shown in the official language in which they were submitted.
r' 210~7
Ro341/7028
WAL/DMD,-
11/13/9,
1550w
POWER STAPLER
Field of the Invention:
This invention relates to a power stapler and more
particularly to an improved clinching head for use in a
power stapler.
Backqround of the Invention:
Power staplers operated by pneumatic and/or
electric actuators are widely used in document handling
and document creation applications. Photocopiers and
laser printers often incorporate a power stapler or
"stitcher" in their mechanism to provide optional
binding of completed documents.
Fig. 1 is an example of a typical implementation
for a stitcher 10. A set of printed sheets 12 are fed
either one at a time or as a group (as shown) to the ~ :
stitcher 14.
The stitcher 14, itself, comprises àn
electromechanical and/or pne~matic stitcher shown
schematically. A known stitcher such as the Hohner
Universal 52/8 is contemplated. However, the
principles of this invention are applicable to
virtually any known stitcher mechanism. The stitcher
14 forms wire staples or "stitches" 16 as shown from a
fed coil 18 of staple wire 20 in a conventional
manner. The staple 16 is driven as shown by the arrows
22 by a reciprocating stitcher head 24 into a
predetermined point on the stack of sheets 12 such as
an upper corner as shown in Fig. 1.
,
, ",",," , ~ ", ~ ,",.. ,i."~, ;;",~ .. "~
- 2~088o~
Positioned opposite the stltcher head 24 is a
clinching head 26 operated by pneumatic pressure in
this example. The clincher head 26 bends the ends of
the staple 16 inward upon themselves once the staple is
forced completely through the stack. The resulting
stapled stack is output to an output point 28 as shown
in Fig. 1. As will be described further below, this
invention has as an object the formation of improved
staples by providing an improved clincher head, This
invention also has as an object the stitching of
variable thickness stacks of pages without requiring
adjustment of the staple length.
SummarY of the Invention
A power stapler according to this invention
provides an improved clincher head for use in
conjunction with a stitcher that drives staples through
a stack of sheets. The clincher head includes
clinchers that abut a stop that limits travel of the
clinchers into the clincher head. Accordingly, as the
staple is driven through the stack of sheets, its ends
are brought into contact with the partially retracted
clinchers. The angle at which the clinchers are
positioned in their partially retracted, stopped, state
is chosen so that the driven staple ends plastically
deform inwardly toward themselves as they contact the
grooved faces of the clinchers. The grooves within the
faces of the clinchers are arranged at angles so that
the guided ends of the staples moving therealong miss
each other. This enables the use of a constant length
staple in which ends would normally strike each other.
The plastic deformation results in permanent inwardly
disposed bends in each of the staple ends. When the
final clinching step occurs and the clinchers are
extended, the inwardly directed bends are driven into
- 2 -
~10~8~7
the face of the sheet stack. The finished staple,
therefore, more closely resembles a conventional
manually formed staple and is less likely to grab onto
clothing and skin and more firmly binds the sheets
together.
In a preferred embodiment in which a clincher bar
is utilized to activate the clinchers, a stop can be
mounted in the clincher head that interacts with a slot
in the bar. The slot is sized and arranged to prevent
retraction of the bar so that the clinchers rest on the
bar in a partially retracted state and both the bar and
the clinchers are prevented from full retraction into
the head, thus forming the desired angle for forming
inwardly directed bends in the staple ends.
Brief Description of the Drawings
The foregoing and other objects and advantages of
the invention will become more ciear with reference to
the following detailed description of the preferred
em~odiments as illustrated by the drawings in which:
Fig. 1 is a schematic perspective view of a
stitcher mechanism and the stapling process according
to this invention;
`~ Fig. 2 is a more detailed cross-sectional side view
of a clincher head according to the prior art;
Figs. 3A-C are somewhat more detailed schematic
~`; side views of the clinching process according to the
prior art;
Fig. 4 is a cross-sectional side view of a clincher
head according to this invention;
Fig. 4A is a top view of the clincher head
according to Fig. 4i
Fig. 4B is a perspective view of a staple formed in
a thin stack of sheets using the clincher head
according to Figs. 4 and 4A; and
. '~
2 ~ o ~
Figs. sA-D are somewhat schematic side views of the
clinching process according to this invention.
Detailed Description
As discussed above, a stitching implementation
according to Fig. 1 can be utilized according to this
invention in order to bind sheets in 2 stack together
using staples 16. The stitcher head 24 forms and
drives staples 16 through the stack and the clinching
head 26 subsequently, by means of a pneumatic actuator
30, bends the ends of the staple 16 passing through the
stack 12 to bind the staple 16 to the stack 12. While
the stitcher 14 in this example is located above the
clincher head 26 in this implementation, it can be
preferred in some embodiments to locate the clincher
head 26 above the stack 12. As used herein "above" and
"below" will refer to orientation of components
relative to the clincher head surface 54 and not to the
orientation of components relative to the ground.
Fig. 2 and Figs. 3A-C further detail a prior art
clincher head. The head 26 comprises a block 32 that
can include two core pieces 34 along the sides of the
head 26 and outer plates 36 bolted to the core pieces
to form a hollow interior channel 38. The lower
portion of the channel 38 is substantially rectangular
and allows a clincher bar 40 constructed, generally, of
hardened steel to slide therein. The bar 40 can move
along the channel 38 as shown by the double arrow 41.
The bar 40 is connected to a pneumatic actuator 30 that
advances and retracts the bar 40 upon application of
pressure. The stitcher according to this invention
includes timing circuitry (not shown) that controls the
timing of staple formation, staple driving and
clinching respectively. Clinching, in general, is the
final step in the process. A valve 42 on the actuator
;`
,,
- 4 -
: 21 ~07
air line 44 that is connected to the timing control
cir~uitry governs the application of air pressure to
the actuator 30.
The bar 40 acts to move a pair of clincners 46
located at the uppermost end of the clincher head 32.
The clinchers 46 are seated between the outer plates 36
on pivots 48. The clinchers 46 have flattened upper
surfaces 50 that, according to this embodiment, include
grooves 52 for guiding a staple wire therealong. The
clinchers 46 rotate on the pivots 48 between a fully
retracted position in which the clincher upper surfaces
50 define an angle A with the flat upper surface 54 of
the clincher head 32~ and a fully extended position in
which the upper surfaces 50 pass out of the clincher
head (as shown in phantom). The clinchers 46 according
to this embodiment can be pivoted upwardly out of the
head surface for removal by aligning the rear slots 56
of the clinchers 46 with the thinner cross section of
their rectangular pivot 48. However, removability of
the clinchers 46 is not necessary according to this
invention.
In a fully retracted state (shown by solid lines),
the bar 40 is substantially out of contact with the
clinchers 46 so as to allow them to retract fully into
the clincher head 32, hence defining the angle A. The
bar 40 can be extended upon actuation as shown by the
extended bar (in phantom) to force the clinchers 46
beyond the upper surface 54 of the head 32.
Practically, the opposing stitcher head 24, as shown in
Fig. 1, limits ~he outward extension of the clinchers
46. This is further illustrated in Figs. 3A-C which
will now be described.
In Fig. 3A, the staple 16 is driven (arrow 60)
through the sheet stack 12 by the stitcher head 24
until the staple ends 62 pass out of the opposing side
,
~ ~ 5 ~ ~
., ................ . , , .. ~ . ~ , . . -,, ~... . .
2~0~7
of the stack and into contact with the upper surfaces
50 of the clinchers 46. Since the clinchers 46 are
retracted and the clincher bar 40 is not extended into
contact with the clinchers 46, the staple ends 62
remain relatively straight at this time.
Fig. 3B illustrates the step following driving of
the staple 16 by the stitcher head 24. The ~ar 40 is
then extended upwardly (arrow 63) so as to rotate the
clinchers 46 toward the staple ends as shown by the
arrows 64. ~ccordingly, the staple ends 62 rotate
about the bottom face 66 of the stack 12 until the ends
are brought into parallel alignment with the bottom
face 66 of the stack 12.
At this time, the stack 12 has been firmly bound by
the staple 16 as shown in Fig. 3C and is ready for
output from the stitcher mechanism.
The extreme retraction of the clinchers 46 as shown
in Figs. 2 and 3A-C causes the ends 62 of the staple to
bend into virtually parallel alignment with the stack
bottom face 66 (see Fig. 3C). The bent ends 62 of the
staple 16 are, thus, somewhat unlike those formed by
the manual staplers in which the tips 68 of the bent
ends 62 are driven back into the lower face of the
stack and often dig into the face. As a practical
matter, the parallel ends 62 generated by a power
stitcher can catch on clothing, often include burrs
that abrade skin causing cuts and are more prone to
become unbent and allow the stack to unbind.
Fig. 4 illustrates an improvement to the clincher
head 26 of Fig. 2 in which a clincher head 70 is
- provided that limits retraction of the clinchers 46.
Hence, the angle Al defined between the upper surfaces
50 of the retracted clinchers 46 and the surface 54 of
the clincher head 70 is reduced from the angle A of
Fig. 2. Such a reduction is facilitated according to
::
,
: .
:"
210~7
. ,
- this embodiment by forming a channel 72 in the clincher
bar 74 and inserting through-passlng bolt or stake 76
in which the channel 72 rides. The stake 76 is held by
the outer head plates 78 which include holes for
retaining the stake 76. The length channel 72 is
chosen so tha~ the lower end 80 of the channel 72 still
allows maximum extension of the bar 74 ~as shown in
phantom), but the upper end 82 of the channel 72 limits
retraction of the bar 74. Retraction of the bar 74 is
limited so that the clinchers 46 remain in contact with
the upper end 84 of the bar 74 and define therewith an
angle Al.
While the bar 74 in this embodiment is used to
limit retraction of the clinchers 46 so as to define
the angle Al, other methods of limiting clincher 46
retraction are expressly contemplated according to this
invention. For example, each clincher 46 can have
associated therewith its own stake or bolt that limits
retraction. The clinchers can also be formed so that
lower ends 86 thereof contact the central blocks 34 of
the clincher 46 upon a certain predetermined degree of
retraction. The blocks 34 would have to be lengthened
- or the lower ends 86 of the clinchers 46 would have to
be extended to limit retraction to the appropriate
angle Al. These alternatives are not shown but are
expressly contemplated.
The angle Al is chosen, according to this
embodiment, based upon usually trial and srror so that
an optimum shape for the staple end 62 is generated.
The angle Al causes formation of staples with ends 62
as illustrated in Figs. 5A-D which will be described
further below.
As stack thicknesses vary, it is normally desirable
~`~ to vary the length of the staple. In this manner, the
`~ ends of the staple are spaced from each other when the
~. ~ 7 ~ ~
:: :
: ' ~
`
2lass~
staple is clinched as shown by the space 75 in Fig,
3C. Otherwise, the ends of the staple, which are
normally collinear (i.e. bo~h along the same line which
in this example is perpendicular to the axes of the
clincher pivots 48), tend to strike each other causing
a defective stitch.
The clinchers 46 according to this embodiment
include grooves 52a that are angled relative to ~ach
other as illustra~ed in Fig. 4A. Each groove 52a is
offset by an acute angle B to grooves define
noncollinear lines that are parallel to each other.
Thus, staple ends riding within the grooves 52a tend to
pass each other even if they are long enough to meet.
Fig. 4B illustrates a stack 87 that would be
considered too thin for the length of staple 89
chosen. Accordingly, in a conventional clincher
embodiment in which grooves are aligned along a single
common line (i.e. "collinear"), the staple ends 91
would collide. Conversely, however, by utilizing
angled grooves 52a according to this embodiment, the
ends 91, upon clinching, pass by each other and do not
interfere with each other.
Referring now to the operation of the stitcher
according to this embodiment, Fig. 5A illustrates the
driving of a staple 16 through a stack of sheets 12.
The stitcher head 24 is still in the process of driving
(arrow 60) the staple when the ends 62 contact the
retracted clinchers 46 that are shown resting on the
clincher bar 74 in a less retracted state than in Figs.
3A-C. As such, the staple ends 62 begin to bend toward
each other (arrows 88) along the slightly downwardly
angled slopes of the clincher upper surfaces 50.
As the staple 16 is fully driven into the stack as
shown in Fig. 5B, the tips 68 of the staple end 62 have
bent inwardly slightly toward the lower stack face 66.
i~
- - 8 -
~:'
2~088~7
The clinchers 46 have no~ yet moved upwardly under the
force of the bar 74, but are at this time only resting
on the bar 74. The reason the tips 68 bend in slightly
is that, unlike the example of Fig. 2, the angle Al of
the less retracted clinchers 46 of this embodiment are
chosen so that the bending of the staple end tips 68
imparts a force on the ends 62 that is greater than the
elastic limit of the staple wire. The fully retracted
clinchers 46 of Fig. 2 can cause slight bending of the
ends 62, but this bending does not impart a force that
exceeds the elastic limit of the staple wire. Hence,
only the final clinching step (Fig. 3B) results in
plastic deformation of the staple wire. This final
clinching step (Fig. 3B) thus, causes a full 90 bend
in the staple ~6 proximate its exit point from the
lower s~ack face 66. Conversely, plastic deformation
of the staple ends 62 according to this example begins
before any movement of the clinshers 46 in the
clinching step. The angle Al insures that the bending
of the ends 62 orients the tips 68 of the staple back
inwardly toward the lower stack face 66.
When the clinching 46 step occurs as shown in Fig.
5C, the inwardly bent tips 68 are forced back into the ~-
lower stack face 66. The tips, thus, form a more ~ ~ -
traditional curled-in staple end 62 as shown in Fig. ~ '
5D. The inwardly directed tips 68 are not as prone to
grab on clothing or skin and serve to more firmly bind
the stack of sheets together. ~
While the clinchers 46 according to this embodiment : ;
are angled to form as large a curve in the staple end
62 as possible, certain types of staple wire may be
more resistant to plastic deformation than others.
Thus, the angle Al should be at least sufficient to
cause the ends 62 of the staples to plasticly deform
slightly. The inward curl of the staple 16 need not be
' '
'
2 ~ 0 8 ~ ~ l
pronounced to attain a desired result. Even a slight
inwardly projected bend in the ~taple end 62 will
prevent grabbing and enhance grip of the staple 16 on
the sheet back 12. The staple 16 can still carry a
shape substantially similar to that of more
conventional power stitchers except that the tips are
now directed toward the stack face and are generally
aligned along parallel angled lines.
The foregoing has been a detailed description of a
preferred embodiment. Various modifications and
equivalents can be made withou~ departing from the
spirit and scope of this invention. This description
is, therefore, meant to be taken only by way of example
and not to otherwise limit the scope of the invention.
What is claimed is:
1 0 -
-
.
:-: - , - ,
. , , , -, .. :, : .. ~, . ~ , .
