Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HIGH-START COMPACT SPRING ENERGIZED STAPLER
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a non-provisional application from which priority is based on
provisional
application number 60/943,611, filed June 13, 2007, whose entire contents are
hereby
incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to spring powered desktop staplers. More
precisely,
the present invention relates to improvements to a spring-actuated stapler
with a striker
having an initial "high start" position.
BACKGROUND OF THE INVENTION
Spring powered staplers and staple guns operate by driving a striker with a
power
spring. The striker ejects a staple by impact blow. In a desktop stapler, the
staple is
ejected into an anvil of a pivotably attached base. Two general principles are
used. In the
first design, the striker has an initial position in front of a staple track.
The striker is lifted
against the force of the power spring to a position above the staple track.
The striker is
released to impact and eject the staple. This design may be referred to as a
"low-start"
stapler.
A second design uses a "high-start" position. That is, the striker has an
initial
position above the staples loaded on the staple feed track. The power spring
is deflected
while the striker does not move. At a predetermined position of the power
spring
deflection, the striker is released to accelerate into and eject a staple.
Typical non-spring
actuated desktop staplers use a high-start design. However, in such
conventional high-start
designs, the striker is driven directly by the handle with no power spring to
store energy
that could be used to drive the striker. There is further no release mechanism
for the
striker since the striker simply presses the staples directly under handle
pressure.
In conventional high-start designs that do use a power spring, the power
spring is
either unloaded or preloaded in the rest position. Different methods are used
to reset the
mechanism. United States Patent No. 4,463,890 (Ruskin) shows a desktop stapler
with a
preloaded spring. Restrainer 42c is an element of the handle and moves
directly with the
handle. United States Patent No. 5,356,063 (Perez) shows lever 53 with tips 48
engaging
striker 24. At a predetermined position of handle 30, lever 53 is forced to
rotate out of
engagement from striker 24 and power spring 40 forces the striker downward.
Swiss
Patent No. CH 255,111 (Comorga AG) shows a high-start staple gun with the
handle
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linked to the power spring through a lever. There is no preload restrainer for
the power
spring so the spring stores minimal energy through the start of the handle
stroke. Both
references use a releasable link or release latch that is positioned behind
the striker and de-
linked by a direct pressing force from the handle. British Patent No. GB
2,229,129
(Chang) appears to show a high-start stapler design. However, no functional
mechanism
to reset the striker is disclosed. Specifically, no linkage is described to
lift the striker with
the handle in a reset stroke. The lever 3 resembles a lever used in a low-
start stapler, but
the lever does not lift the striker in any way. Instead, the striker is
somehow lifted by a
very stiff reset spring, yet no linkage is described to enable a reset spring
to lift the striker
against the force of the power spring. United States Patent No. 5,335,838
(Harris et al.)
shows a high-start pliers style stapler. A "U" shaped flat spring with arms
extending
forward engages a striker at a top arm, and a bottom arm is moved by a lever
to operate a
latch to release the striker. There is no means of pre-loading the power
spring shown.
It is desirable in a spring actuated stapler to minimize friction so that work
used to
press the handle is not wasted, but rather available substantially entirely
for ejecting and
installing staples. A further efficiency interest is to have precise timing of
the release
action. Specifically, it is desirable that the release occur at precisely the
lowest handle
position against the housing. At a higher release position, the handle is
spaced above the
housing; the housing will jump or kick back as the staple is ejected. This is
a typical
behavior in any spring actuated stapler. As the housing kicks back, the bottom
of the
stapler is spaced above the paper or other work piece. With this spacing, the
striker cannot
fully press the driven staple into the paper and anvil below. Another way to
characterize
this behavior is the energy used to kick up the stapler body is wasted and not
available for
stapling.
In normal use of a desktop stapler, papers are stacked and attached together.
It is
sometimes desirable to use the stapler as a tacker, for example, to attach
papers to a wood
post or a bulletin board. In its tacker configuration, the base must pivot out
of the way so
the staple exit area can be held against the paper and the bulletin board. But
with the base
pivoted away, the staple exit area along the striker path is exposed, and it
is possible that a
staple can be intentionally or unintentionally fired out of the device in the
direction of the
user or a bystander. To avoid such accidents, in some prior art designs, the
base is
designed in a way that it cannot pivot away from the body to expose the staple
exit area.
This prevents exposing the exit area and possible harm to the user or
bystanders, but it also
precludes the stapler from being used as a tacker.
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SUMMARY OF THE INVENTION
In a preferred embodiment of the present invention, a high-start, spring
actuated
stapler provides a compact stapler that combines enhanced handle travel for
greater
leverage with a separately movable spring/cage subassembly to preload the
power spring.
The cage may be pivotably attached to the housing at a location separate from
the
pivotable attachment of the handle. As the definition of high-start implies, a
striker
alternates between an initial rest position above a staple track (the high-
start striker start
position) and a lower-most position in front of the staple track. A power
spring is
deflected to store energy by the motion of the handle. At a predetermined
position of the
handle, the striker is released to accelerate to the lower-most position by
urging of the
power spring.
A spring/cage subassembly maintains a pre-load upon the power spring in the
upper, initial rest position of the stapler. The initial position of the
stapler is the normal
position of the stapler's components when the stapler is not being used. The
cage is
separately movable from the handle and pivotably attached at a cage rear end
in the
housing. The cage at its front end moves slightly less vertical distance than
the striker as
the power spring moves from the initial rest position above the track to the
lower release
position in front of the track. The distance is less because the front area of
the cage is
closer to pivotal attachment of the cage than the striker is to the pivotal
attachment. For
example, in a preferred embodiment the front area of the cage may move from
the initial
upper rest position and a lower most position between about 0.30" to 0.5"
inclusive of the
outer limits, with a preferred range of 0.35" to 0.4" inclusive of the outer
limits.
The spring energized mechanism is preferably nested together to provide a very
compact stapler. The housing at a location of the striker can be equal or less
than 1.1" tall
from the top of the housing to the bottom of the housing. The striker moves a
minimum
vertical distance required to drive staples while the handle, at a handle
pressing area,
moves substantially farther than the striker to achieve increased leverage and
lower
actuation force. A handle pressing area may include a portion of the handle
from a front
distal end to a position about 2.5 inches rearward. This corresponds to a
normal area a
user presses in a standard type desktop stapler. The handle at the pressing
area moves
between an initial rest position above the housing to a lower, pre-release,
position,
preferably immediately adjacent to the housing. The handle, at the pressing
area may
move between about 0.8" to 1.1" inclusive of the outer limits, with a narrower
range of
about 0.8" to 1" inclusive of the outer limits being preferred. According to
the above
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discussion, a ratio of motion between the front of the handle to the front of
the cage may
range from about 1.6 to 3.7 inclusive of the outer limits, with a preferred
range of about
2.2 to 2.9 inclusive of the outer limits.
A release mechanism uses a separately movable latch. For example, a release
latch
is pivotably fitted in the housing and is moved out of engagement with the
power at a
release point. The power spring is unstable upon the latch at least at the
release position of
the handle corresponding to a release point; in other words the power spring
presses the
latch at an off-vertical angle to cause a forward bias upon the latch. A latch
holder keeps
the latch normally engaged to the power spring to counteract the forward bias.
At the
release point the handle moves the latch holder out of the way to allow the
latch to move
forward. The latch is attached in front of the striker, at a pivot point in
front of the track
near the bottom of the stapler.
A lever links the handle to the power spring to provide enhanced leverage upon
the
power spring by the handle. The lever is pivotably attached at a front, top of
the housing.
In the preferred embodiment the lever is of a single thickness sheet metal
form; a hinge tab
is bent to one side of a lengthwise center line to create an off-center hinge
tab to engage
the housing. The rear of the lever is oppositely off center at the location
that the handle
presses the lever. An imaginary force line connecting the rear of the lever to
the hinge tab
passes over the lever-to-power spring contact location. The forces upon the
lever are thus
balanced so that the lever does not twist within the housing. For the purpose
of
explanation, for example, a contrasting design can be imagined where the front
hinge tab
and rear, handle pressing end are both to the left of the central lever-to-
power spring
contact location. In this case the lever will twist on its long axis with the
left side biased
down by the housing and handle, and the right side biased upward by the power
spring.
Optionally, a low friction linkage connects the handle to the lever rear end.
With minimal
twisting the lever does not require high force confinement within the housing,
this
minimizing friction.
The handle is connected to the striker through the lever and power spring. In
normal use, the handle presses the striker downward through these connections.
Preferably, there is also a tensile connection whereby the handle can pull up
on the striker.
This is desirable in the instance a jam or other temporary malfunction occurs
that causes
the striker to be stuck in a lower position; the handle may be used to pull
the striker back to
its upper rest position. Alternatively, a reset spring with increased
stiffness to overcome
any expected jam condition can be used. However, this is not as desirable
since the user
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must overcome this extra, normally unneeded, stiffer spring force during every
energizing
stroke. Hence, it is most preferable that the reset spring is of minimal force
as required for
a normal reset, and jams are remedied rather by the user pulling the handle up
manually.
According to the present invention, these tensile connections are simple
recess or notch
features between components that add minimal cost to the stapler.
The stapler of the present invention in the preferred embodiment includes
negligible sliding between components as the handle is depressed and the power
spring is
deflected. The striker is essentially stationary during this process, and the
geometry of the
cage, power spring, and handle are selected to maintain primarily pivoting
verses sliding
actions. This contrasts with some low-start type staplers wherein the striker
by design
slides within the housing during deflection of the power spring.
To improve the timing of the release action, the release event is actuated by
the
area of the handle directly under the pressing area. The unstable "passive"
release
described above allows a low friction action to cause the release event.
The present invention may include a simplified safety lock. Preferably, an
extension of the latch holder forms a bias arm to guide a sheet metal safety
lock. In the
rest position, the safety lock engages a bottom edge of the striker to prevent
the striker
from moving down. When the body is pressed against the base the safety lock
pivots and
slides forward and upward in front of the striker so that the striker is free
to move
downward. The striker preferably includes a tapered notch at the lower edge to
allow the
safety lock to engage the striker in the notch at a higher position than the
lower most edge
of the striker. This allows the stapler to stay compact while the safety lock
can be long
enough to be easily controlled.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side elevational view of an exemplary embodiment of a high-start
desktop stapler, excluding a base, in an initial rest position with a right
side of the housing
removed, the striker in the high rest position, and the handle partly in
section.
Fig. 2 is the stapler of Fig. 1 in a partially pressed condition with the
spring
energized and the handle in section.
Fig. 3 is a detail view of a front of the stapler of Fig. 1, in a released
condition
where the striker is in the lowered position and the handle is abutting the
housing.
Fig. 4 is an enlarged detail elevation view of the stapler of Fig. 3, showing
the body
pressed against a base and a safety lock retracted and with the striker in the
lower, released
position.
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Fig. 5 is the view of Fig. 4 in front, bottom perspective, absent the latch
and base.
Fig. 6 is the view of Fig. 4, in rear, bottom perspective, absent the base.
Fig. 7 is a perspective view of a safety lock.
Fig. 8 is a rear elevation of a striker.
Fig. 9 is a front perspective view of a latch holder.
Fig. 10 is a rear perspective view of the latch holder of Fig. 9.
Fig. 11 is the view of Fig. 5, with the striker in the upper rest position and
the
safety lock in the engaged position under the striker.
Fig. 12 is the view of Fig. 4, with the base spaced away from the body and the
safety lock in the engaged position of Fig. 11.
Fig. 13 is the view of Fig. 6, with the striker and safety lock in respective
upper and
engaged positions.
Fig. 14 is a side, slight top, perspective internal view of a left housing of
the
stapler.
Fig. 15 is a side elevation of a handle-to-lever link.
Fig. 16 is a top, side perspective view of the link of Fig. 15.
Fig. 17 is a perspective view of a sub-assembly of a power spring and cage,
with
further assembly elements of a lever, link, reset spring, striker, latch,
latch holder, and
safety lock.
Fig. 18 is an exploded perspective top view of the assembly of the power
spring,
cage and lever, with the power spring in a flat configuration.
Fig. 19 is the exploded assembly of Fig. 15, in a more side view direction.
Fig. 20 is the assembly of Fig. 17, in the upper rest position of Fig. 1.
Fig. 21 is a rear, side perspective view of a latch.
Fig. 22 is a bottom, side, perspective internal view of a handle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figures 1 to 3 show a preferred embodiment stapler of the present invention in
three representative positions of its operating cycle. Figure 1 is a rest
position, with handle
pivoted to a farthest position above housing 10. Track 500 fits within track
chamber 15
30 of housing 10. Staples (not shown) are held upon track 500 and fed toward
the front of
chamber 15 to be positioned under striker 110. Lever 20, power spring 80,
striker 110,
and cage 90 are in respective upper-most positions. Striker 110 is above track
chamber 15.
Power spring 80 is preferably an elongated flat spring. The spring 80 includes
two
elongated openings 81 separated by web 84 (Fig. 19). Power spring 80 is pre-
loaded by
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confinement in cage 90, as discussed later. Striker 110 fits slidably in slot
11 of housing
10, movable toward slot exit 11 a.
In Fig. 2, handle 30 is partly depressed toward housing 10. Power spring 80 is
deflected downward by lever 20 near the spring length center to store energy.
Cage 90 and
power spring 80, defining a spring/cage sub-assembly, rotate at pivot 94 about
hinge post
16 near the rear of housing 10. In Fig. 2, cage 90 is near, but not yet at,
its lowest most
position. Upward facing cage edge 94a engages an underside feature of the
hinge post to
confine the cage in an upward direction. Compare Fig. 2 and Fig. 3 lower front
edge 98 of
the cage. Cage 90 is spaced above ceiling rib 15a of chamber 15 in Fig. 2. In
Fig. 3, the
space is closed and cage 90 is immediately adjacent to the ceiling rib. When
the cage and
related parts reach the lowest position of Fig. 3, spring end 82 is suddenly
released, as
discussed later, to allow power spring 80 to force striker 110 to its lowest
position.
Optionally, a rear element of power spring 80 may engage the housing near post
16 (not
shown); then the assembly rotates about an element of the spring rather than
about an end
of the cage.
Between the upper position of Fig. 1 and the lower most position of Fig. 3,
including the lower intermediate position of Fig. 2, cage 90 is effectively
loose in the
assembly, pivoting about hinge post 16 and not confining power spring 80. It
is held from
rattling by its fit at notch 93 upon web 84 of power spring 80 (see also Fig.
19). In Fig. 3,
striker 110 has been released to a lowest position in front of track 500. Cage
90 and power
spring 80 are in respective lowest positions.
In Figs. 1 and 3, a subassembly of cage 90 and power spring 80 is in different
positions but in the same rest configuration. The cage/spring subassembly may
be
assembled off-line or separately, and installed later into the main assembly.
The spring is
pre-stressed against cage 90, and sits loosely in housing 10 during assembly,
allowing a
low effort process for assembly line workers or automation. This contrasts
with a power
spring that is pre-stressed against a further element of the stapler. Such an
externally
stressed spring must be forced into the assembly. For example, a power spring
that is pre-
stressed against the housing or a further linking lever would require
uncomfortable,
manual deflection of the spring by the assembly line workers, or use of high
force output
automation.
Figure 1 corresponds to the simplified view of the upper position in Fig. 20.
Power
spring 80 is in the pre-stressed rest configuration. In Fig. 2, the spring is
deflected and
energized from this pre-stressed rest configuration. Figure 3 corresponds to
the view of
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the lower position in Fig. 17. In a free position of the power spring (not
shown), the spring
is arced to a largest extent, with ends lower and center higher. In the
spring/cage rest
configuration the power spring is pre-stressed to force the ends up and center
down to form
the arc as shown in Figs. 1, 3, 17, and 20. For clarity power spring 80 is in
a flat
configuration in the exploded views of Figs. 18 and 19. Using a pre-stressed
configuration
for the power spring means that the relative change of spring force between
the rest
configuration, Fig. 1, and the pressed configuration, Fig. 2, is minimized
compared with a
non pre-stressed spring wherein the initial rest force is zero. The pre-
stressed spring
combined with varying handle leverage described later provide a relatively
constant handle
force through the stroke.
Power spring 80 is preferably held at three locations by cage 90. At the
front, cage
tip 92 supports spring end 82 from below (see Figs. 19, 20). At the rear,
notch 91 supports
a rear end of the spring from below. In the center at spring web 84, hook 93
presses the
power spring from above. Hook 93 and optionally a front portion of the cage
fit within
elongated openings 81 (see Fig. 17). Cage 90 includes a U-channel section,
wherein lever
fits within the channel. The channel is open at the front bottom to allow
lever guide tab
23 to pass below. Forward slot 81 terminates at narrow end 85 through which
passes guide
tab 23. Cage tip 92 presses upward immediately to each side of narrow slot end
85. The
assembly as described is nested together to provide a very compact mechanism,
with one
20 or both of the lever and cage being nested within slot 81 of power spring
80, and the lever
is further nested at least partially within the "U" channel of the cage. The
nesting is a great
advantage since it allows a spring actuated desktop stapler to be overall very
compact in
the vertical and horizontal directions.
Notch 91 of cage 90 includes ribs or equivalent structures to hold power
spring 80
in position lengthwise upon cage 90. Optionally, a notch or rib of the cage
can engage the
power spring at web 84 to hold the lengthwise position. Preferably, the power
spring is
not held at two separate lengthwise locations, as flexing of the spring would
cause stress
between two such fixed attaching points. Cage 90 is in turn held pivotally in
a lengthwise
position as part of the spring/cage subassembly on housing 10 at hinge post
16. In this
manner, spring end 82 is accurately held in position relative to striker 110
in the rest
position of Fig. 1. This is helpful for the release action described later.
Lever 20 is preferably made from a flat metal form. This allows the lever to
easily
fit within the channel of cage 90 and be of low cost. Lever 20 is pivotably
engaged to
housing 10 at laterally extending tab 22. Tab 22 forms an asymmetric feature
of the lever,
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engaging primarily one side of housing 10; this is the left side as
illustrated in the figures.
The force from tab 22 may be linked to the right, or opposite housing side
through a weld
or other attachment means near recess 318, whereby both sides may provide
support to tab
22. Tab 22 presses upward upon a ceiling or rib of housing at a front of the
housing, in
recess 318 (see Figs. 1, 14 as illustrated). Tab 22 presses near an uppermost
position of
housing 10 such that in the handle lowest position of Fig. 3, the handle is
immediately
adjacent to recess 318 or other surface upon which tab 22 presses. Tab 22
includes a large
surface to engage the housing, so there is minimal wear at the recess as the
lever pivots. In
addition to the above described vertical force by lever 20, there are also
horizontal or
lengthwise forces acting upon the lever. Such force is light during a reset
cycle, as striker
110 rises to the initial rest position, but larger through parts of the handle
pressing stroke
as the power spring is energized.
As handle 30 is pressed through link 130, during an energizing stroke of the
stapler, lever 20 is forced forward because of the angular orientation of the
mounting of
link 130, as discussed later regarding leverage. Link 130 imparts a forward
force vector
upon lever 20 through the upper positions of the handle stroke. It is
therefore preferred
that lever 20 is well supported against moving toward striker 110. There may
be limited
housing material for this purpose at tab 22, specifically in the preferred
compact design
striker 110 may, as illustrated, occupy the space immediately in front of
lever 20 and tab
22 that is best used for bearing forward forces of the lever. In the preferred
embodiment
lever 20, at or near tab 22, abuts and presses striker 110 through the
operating stroke of
handle 30, up to the release point of the striker. Striker 110 is
substantially stationary
during this action, and is well supported in slot 11 (Fig. 14) so it creates
an effective,
sturdy bearing surface for the lever. At the lower position of Figs. 2 and 3,
link 130 rotates
relative to handle 30 and lever 20 to be near vertical, the link therefore
presses
substantially vertically upon lever 20. The bearing surface of striker becomes
less
important. In Fig. 3, edge 28 of the lever is pressing striker 110, but gently
since Fig. 3 is
the lower position. Upon release of the striker, the force applied by the
lever quickly
decreases to near zero as the striker moves suddenly downward to the position
of Fig. 3.
Therefore, lever 20 does not require the sturdy support of striker 110 as a
front bearing at
or near the release point. To position lever 20 in this low forward force
position, edge 25
of lever 20 presses a rib at the rear of recess 318 (Figs. 2 and 14). This
engagement
operates through the reset cycle as the stapler moves from the position of
Fig. 3 back to
that of Fig. 1.
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Optionally, lever 20 may press upon the forward edge of front slot 81, behind
front
edge 82. This pressing may be instead of or in addition to the striker
pressing described
above. This forward force is transmitted through the power spring to rear
notch 91, and
finally through pivot 94 to hinge post 16 of the housing. As with the striker,
pivot 94
provides a substantial bearing surface. As with the striker, the front edge of
power spring
80 remains substantially stationary as handle 30 is pressed downward, and
there is
minimal forward bias here at the release point.
Guide tab 23 extends downward to near ceiling 15a of track chamber 15. As seen
in Figs. 1, 3, and 14, ribs 123 guides tab 23 to maintain lever 20 on-center
within housing
10. Cage 90 includes an opening in this area (Fig. 3) to allow cage 90 to
clear rib 123.
The right housing (not shown) includes a similar rib. Cage 90 extends up
through spring
opening 81 here to maintain a sturdy section to the cage. Cage 90 includes
another cut-out
at the bottom, near the length center coinciding with reset spring hole 97, to
clear lower
spring boss 12. Hook 93 preferably extends upward at this same location to
maintain a
sturdy section for cage 90.
Lever 20 presses near web 84 of power spring 80 at pressing edge 24 near a
center
of the lever length. To minimize sliding at this interface hinge post 16, edge
24, and tab 22
are substantially collinear in housing 10 from the upper to the lower
positions (Figs. 1 and
2). Being aligned, these rotation points maintain near constant relative
distance, and
therefore will operate nearly entirely by pivoting and not by sliding. Lever
20 preferably
includes notch 27 with a rib extending under the power spring whereby the
lever can pull
up upon power spring 80. As illustrated, notch 27 engages web 84 of the power
spring 80.
As further illustrated, the lever engages power spring 80 directly at web 84
or other
equivalent nearby area. Optionally, one or both of lever edge 24 and pull-up
notch 27 may
engage the power spring through the cage. For example, the area of hook 93 may
include
a notch or tab to link to edge 24 and/or notch 27 or equivalent features of
lever 20 (not
shown). If hook 93 or equivalent feature fits well to power spring 80 then
connecting the
handle to the power spring through cage 90 will provide an equivalent result
to a more
direct connection to the power spring.
For best efficiency in a compact package, cage 90 should preferably move from
an
upper most possible position (Fig. 1) to a lowest possible position adjacent
to ceiling 15a
(Fig. 3). In this manner no space is wasted. Cage 90 also should be rigid as
discussed
above. Otherwise, in the rest configuration of Figs. 1 and 3, cage 90 deflects
along with
the power spring. The energy to deflect the cage is absorbed by the cage and
wasted in
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Fig. 3 as power spring 80 resumes its load upon the cage. With the U-channel
section and
maximized section along its length, cage 90 has negligible deflection in the
assembly.
Reset spring 70 fits under power spring 80 (see Fig. 2). The reset spring
includes
upper leg 72 and lower leg 71 fitting respective hole 97 in the cage and boss
12 in housing
10. Reset spring 70 preferably includes a minimal shape change as it moves
from the
upper position of Fig. 1 to the lower position of Fig. 2 and similar lower
most position of
Fig. 3 (not shown). Therefore, with an adequate pre-load, as defined by a
large free angle
between the legs, the reset spring provides a near constant reset bias to the
assembly. This
advantageously avoids any excess force at the lower position that otherwise
occurs if the
reset has a large shape change.
Link 130 provides a low friction connection between the rear end of lever 20
and
handle 30. The length of lever 20 and related position of link 130 along
handle 30
determine the leverage of handle 30 upon power spring 80. A longer lever with
more
rearward mounting to handle 30 generally enables more leverage; the handle
moves a
greater handle travel distance and therefore requires lower user input force
acting on
handle pressing area 33. The stapler thus requires lower input effort by the
user, and hence
those who cannot generate much finger pressure such as the elderly and
children can still
easily operate the stapler.
As power spring 80 is deflected, the reaction force from the spring increases.
It is
desirable to minimize this effect at the handle so the peak force at the end
of the stroke is
not excessive. For this purpose, the leverage of handle 30 upon power spring
80
preferably varies through the pressing stroke to maintain a more constant
pressing force for
all handle positions. Preferably a low initial leverage (high spring motion
relative to
handle) becomes higher (low spring motion relative to handle) toward the end
of the
stroke. The link 130 allows this varying leverage through a changing angular
relationship
between handle 30 and power spring 80, as discussed above regarding the lever
forces at
tab 22. In the initial rest position of Fig. 1, link 130 angles downward and
forward from
the handle. Toward the lower position, as in Fig. 2, link 130 is more nearly
vertical. This
angle change provides the desired varying leverage through a cam-like action;
the handle
at link 130 moves forward relative to the lower link mount at lever rear end
26 as both
initially move downward. Link 130 thus rotates and becomes more vertical to
cause the
handle and lever end 26 to separate from each other. This wedging action
between the
handle and lever (Fig. 1) enhances the downward motion of the lever until the
link
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approaches vertical (Fig. 2). In Fig. 2, the handle and lever end 26 move
downward
directly in tandem.
The result of this action is the handle initially moves the lever
disproportionately
fast, and the relative motion becomes proportionate as the stroke proceeds.
Hence, the
leverage increases. The spring force increases through the stroke, so
increasing leverage
counteracts the increasing spring force, resulting in the input force
operating the handle
stays near constant. Again, this benefits the users who may have weak fingers
and cannot
apply great pressure to comfortably fire the stapler.
In the illustrated embodiment, housing 10 presses down upon a left side of
lever 20
by lever tab 22. Power spring 80 presses upward upon lever 20 at a center of a
width, or
centerline, of lever 20, at edge 24. This centerline is normally also a
centerline of the body
generally defined by housing 10. These two forces cause a twisting moment on
the lever,
the top of the lever biased into the page in Figs. 1 and 2. The third pressing
location, at
link 130, should counteract this moment to minimize friction. Otherwise, lever
20 must be
contained by force within housing 10. For example, tab guide 23 would slide
firmly
against rib 123 of the right housing (not shown) rather than just be guided by
the rib.
Accordingly, lever 20 preferably includes offset bend 21 to the opposite side
from tab 22.
Rear end 26 preferably includes a rear tab that extends back across the
centerline, into the
page of the figures. Link 130 includes surface 133 to engage rear end 26.
Surface 133
thereby presses lever 20 on the offset portion, opposite the centerline from
front tab 22.
With proper geometry, these forces cancel each other so lever 20 exhibits no
twisting
moment, minimizing a malfunction of the mechanism. Surface 134 opposite 133
provides
a lift surface to pull up on lever 20 at the tab of rear end 26 in a tensile
connection. The
rear end tab thereby pivotably fits into an opening or recess of link 130.
Accordingly, the present invention spring energized stapler mechanism is very
efficient, and requires minimal component travel distances resulting in both a
low user
applied force with reliable, repeatable performance. For example, based on
empirical
observations, a peak handle force of less than about 6.5 lbs., and preferably
less than about
6.0 lbs., at pressing area 33 provides effective fastening by stapling of more
than 20 sheets
of 20 pound paper using standard 26/6 staples.
Link 130 is pivotably attached to handle 30 at recess 39 (Fig. 22). Link 130
is
preferably snap fitted into its handle position whereby the link can connect
handle 30 to
lever 20 in tension. For assembly, handle 30 may be installed as a last
component. Both
left and right (not shown) housings are fitted to the internal parts including
link 130.
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Handle 30 is installed into opening 19 (Fig. 14) and moved rearward until
bosses 38 align
with recesses 13 of housing 10. The handle moves over link 130 until the link
is aligned
with recess 39 of the handle. Boss 132 then snaps into the recess, and link
130 is pivotably
held to the handle in pressing and in tension. An elongated groove 39a or
equivalent
structure at recess 39 fits link 135 as a bearing interface.
Link 130 includes resilient arm 135 to retain boss 132 in recess 39.
Preferably, the
single arm and boss form an asymmetric design for link 130 for simplicity. Arm
135
biases boss into recess 39 with enough force to provide for the required
tensile action. For
installation of the handle, ramp 34 (Fig. 22) causes resilient arm 135 to
deflect to allow
boss 132 to clear the rib that includes recess 39.
Optionally, handle 30 may be directly connected to power spring 80 and/or cage
90, without link 130 or other movable link. There can then be some sliding at
the interface
of handle 30 and lever 20, so the connection may be through a low friction
material such
as Delrin, Teflon, or the like.
Figures 1 to 3 show a latch holder 300 and latch 60, respectively, that work
in
conjunction to release striker 110 to fire the stapler. Such a release
mechanism holds
striker 110 and spring front end 82 in the upper rest position until a
predetermined release
point. The release mechanism may operate in a similar manner to that disclosed
in co-
pending U.S. patent application titled "High Start Spring Energized Stapler,"
filed on
January 20, 2006, serial no. 11/343,343, by Joel S. Marks, whose entire
contents are
hereby incorporated by reference.
In the view of Fig. 1, a rest condition of the release mechanism is shown.
Latch
holder 300 includes resilient section 302 between mounting post 301 and distal
end 303.
Specifically, latch holder 300 includes distal end 303, and a zigzag resilient
portion 302
connects distal end 303 to lower mount 301 (Figs. 9, 10). Lower mount 301
engages slot
18 of housing 10 (see Fig. 14). Latch holder 300 is at least slightly
pivotally attached at
lower mount 301. Zigzag resilient portion 302 causes distal end 303 to be
biased upward
in Fig. 1. Upward movement of distal end 303 is limited by shoulders 305 or
other
structure of latch holder 300 pressing against housing 10. Distal end 303
protrudes
through opening 310 in housing 10, and when the user presses down on handle
30,
triggering rib 31 underneath the handle (Fig. 3) engages and pushes on distal
end 303 to
begin a sequence of events that eventually releases striker 110 and fires the
stapler.
Spring end 82 extends through slot 111 of striker 110 and at least partially
into slot
62 (Fig. 21) of latch 60. Spring end 82 should be positioned accurately
relative to the latch
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for reliable release action. Latch holder 300 is constrained within opening
310 and in turn
prevents latch 60 from moving forward. Latch 60 therefore selectively
immobilizes striker
110 and limits downward motion of striker 110 as power spring end 82 presses
down
within slot 62 as power spring 82 is loaded by the user pressing down on
handle 30.
Power spring end 82 thus remains stationary at each end until its release as
handle 30 is
pressed. Latch 60 is preferably made from hardened steel.
As handle 30 is pressed, the stapler assumes the pre-release configuration of
Fig. 2.
It is seen that the front area of power spring 80 is angled upward in Fig. 2.
Therefore,
power spring end 82 engages latch slot 62 at a non-perpendicular angle,
thereby pressing
downward and forward on latch 60. Latch 60 under this power spring pressure
presses
forward against latch holder 300. This is a pre-release position, not shown,
where handle
30 is preferably near to its closest possible position toward housing 10 as in
Fig. 3, but
with the upper power spring pre-release position of Fig. 2. Power spring
center near web
84 is deflected or bent downward while the front and rear ends remain in the
initial upper
rest position. Cage 90 rotates downward.
Optionally, power spring end 82 may include a local upward bend (not shown) to
increase the forward pressing force vector on latch 60. The shape of the bend
may be
selected to optimize the release action, providing just enough forward bias to
reliably
move latch 60 forward while not so much that other components such as latch
holder 300
or housing 10 are distorted by excess biasing force from power spring 80.
In Fig. 3, as a result of the downward pressure applied by the user on handle
30,
triggering rib 31 of handle 30 has moved latch holder 300 downward. Triggering
rib 31 of
handle 30 has pushed distal end 303 of latch holder 300 below corner 311 of
housing 10,
allowing latch holder 300 to move forward under the forward bias of power
spring 80 as
transmitted through latch 60 which has also tilted forward. Once the top end
of latch 60
tilts forward, slot 62 of latch 60 no longer confines spring end 82, allowing
spring end 82
to freely accelerate downward under spring bias to fire the stapler. Since the
spring end is
captured within slot 111 of striker 110, the downward motion of spring end 82
accelerates
striker 110 in the same direction.
After its release, striker 110 rapidly moves downward to eject a staple
disposed on
staple track 500 (not shown) by impact blow, and handle 30 remains in the
lowered
position. After striker release, the power spring/cage subassembly resumes its
rest shape
of as shown in Fig. 3, but in a lower angular position relative to Fig. 1.
After release and
ejecting a staple, striker 110 is in its lowest position in front of track
500.
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As discussed earlier, latch 60 is pressed forward against latch holder 300
under bias
from the angled spring end 82. As seen in Figs. 1 and 2, the geometry of
angled portion
304, also see Fig. 9, pressing slightly upward on corner 311 of housing 10
creates a slight
downward tendency on latch holder 300, just less than the friction holding the
system in
place. This reduces the force required from triggering rib 31 to press latch
holder 300
downward to fire the stapler. Latch holder 300 is preferably made from a low
friction
material such as Delrin, acetal, nylon, Teflon, greased metal, or other low
friction
materials. These types of low friction materials help minimize wear between
latch holder
300 and housing 10 at corner 311 and improves the life of the stapler. A low
friction
interface also helps ensure the release action is reproducible and reliable.
Latch 60 is pivotably attached to housing 10 by latch tab 63 within recess 17
(see
Fig. 6). This attachment is preferably near a lowest position in housing 10 in
front of track
500. Recess 17 includes engagement with the upper edge of pivot tabs 61, so
latch 60 is
held from shifting upward. This feature is helpful during reset action as
spring end 82
slides and arcs upward along latch 60 as the power spring/cage assembly pivots
about post
16.
After striker release, spring end 82 contacts latch 60 in the position shown
in Fig.
3. Latch 60 is thus held in its forward position. Downward pressure on handle
30 is then
removed by the user so that handle 30 is biased upward in a reset action
toward the handle
rest position of Fig. 1. Striker 110 and the power spring/cage subassembly
move upward
with handle 30 under the bias of reset spring 70. Consequently, latch holder
300 is also
held in its forward position. Spring end 82 moves in an arc about hinge post
16 as
discussed above. During reset, latch 60 should remain in the forward-most
position so that
it does yet resume the latch rearward pre-release position in Fig. 1, behind
release opening
310. The forward-most latch position holds latch holder 300 out of the way. If
latch 60 is
allowed to move to the rear position, latch 60 becomes locked in the rear,
rest position by
latch holder 300 entering release opening 310. Latch 60 would then block or
obstruct the
desired movement of spring end 82, preventing it from moving up and into slot
62 of latch
60 to complete the reset action.
To ensure that latch 60 remains forward during reset, latch pivot tabs 63 and
recesses 17 receiving those pivot tabs are preferably located as low as
possible in housing
10 near the bottom of track chamber 15. The distance or torque arm as measured
between
pivot tabs 63 and spring end 82 in the after-release position of Fig. 3 is
maximized to allow
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spring end 82 to apply useful holding torque on latch 60. This ensures that
latch 60
remains forward during reset.
The preferred embodiment safety lock 280 is fitted slidably and pivotably at a
front
of the stapler. It normally extends under striker 110 to lock the striker in
the upper rest
position (Fig. 12). Preferably, a two step process moves the lock. A first
step is primarily
by rotation and provides a fast disengagement. A second step is primarily by
translation
and allows for additional motion without further disengagement. The purpose of
the two
step process is to allow for imperfect engagement with a surface such as
papers. If an
obstruction such as a fold or other installed staple (not shown) keeps the
housing slightly
spaced away from the page at exit area 11 a (Figs. 4 and 12) the safety should
still operate
to disengage to allow a striker 110 to install a staple.
Therefore, the safety immediately moves to disengage while the housing may
still
be spaced from the paper, and the safety continues to retract inward to allow
for the normal
zero spaced condition. Lower tip 284 extends downward out from housing 10 to
its lowest
relative position, as defined by a dimension labeled "H." Dimension "H" may
describe the
actual vertical motion of the safety lock, or it may describe the extended
distance of Fig.
12 relative to the bottom the body or housing 10 at striker slot exit 11 a.
The maximum
extension of safety lock 280, as defined by dimension "H" in Fig. 12, may
range
preferably from about 0.040 to 0.090 inch inclusive of the outer limits, with
the extension
more preferably ranging between about 0.050 to 0.070 inch inclusive of the
outer limits.
Based on empirical observations, such extension ranges allow for typical
obstructions
described above while not interfering too much with the space into which
papers are
inserted.
The first motion is shown in Fig. 12. The initial position is shown with
safety lock
280 in solid lines. Rib 68 (Figs. 12 and 21) provides a bearing and pivot
surface for safety
lock 280. Edge 287 of the lock moves against cam 213 of housing 10 or
equivalent cam
surface (see also Fig. 5, as the lock pivots). The lock pivots along rib 68,
guided by the
cam, at rear edge 281 in the first motion of Fig. 12. At the end of the first
motion safety
lock 280 is in the position of the dashed lines of Fig. 12, at which point it
reaches a limit of
its pivoting motion. Lower tip 284' is in the indicated position at this
point. Lock tip 283
is clear of striker 110 at 283', and the striker can move downward if it is
released from
latch 60 in normal operation. The lock is then free to begin the second motion
upward if
required.
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In Fig. 4, safety lock 280 is in its upper most position at the end of the
second
motion. Rear edge 284 has slid along the front of cam 213 until base 50 has
pressed the
lock to its upper most retracted position. This comprises the second,
primarily
translational step of the safety lock motion. Anvil 57 provides a guide to
clinch staples
behind papers to be fastened. Tip 284 presses adjacent to, but not within, the
path of
striker 110 and anvi157.
Latch holder 300 includes bias arm 308 (see Figs. 9 and 10). Bias arm 308
includes segment 309, defined by left side rib 309a and right side rib 309b.
Safety lock
280 is preferably a simple flat metal form. The left and right ribs 309a,b
partially surround
the lock to retain the distal end of bias arm 309 about the metal form of the
lock. Segment
309 presses notch 289 of safety lock 280 (Figs. 7 and 12) in a direction down
and
rearward, to the left in Fig. 12. Lock tip 283 is thereby biased to be under
striker 110 in
the raised housing position of Fig. 12. Bias arm 308 provides both the
rearward bias for
the first rotational operating step, and the vertical bias for the second
translating
operational step. The bias arm should be resilient enough allow for the full
operating
motion of safety lock 280. Bias arm 308 is preferably molded integrally as a
same part as
latch holder 300 for simplicity, but may optionally be a separate component of
the stapler.
The latch holder therefore preferably includes two resilient actions, zigzag
resilient portion
302 to operate distal end 303 to hold the latch, and bias arm 308 to operate
safety lock 280.
Safety lock 280 is preferably as long as possible within the constraints of
the
stapler to allow effective motion at tip 283 during rotation and reasonable
control of the
action of the lock. The bottom edge of the striker may be continuous near the
safety lock,
such that tip 283 is entirely below the striker. However, it is preferable to
nest the striker
over the lock to minimize the overall height of the assembly and maintain the
compact
height of the body. Striker 110 includes notch 115 (see Figs. 8 and 11). Lock
tip 283 fits
or nests into the notch to engage the upper edge of notch 115 during active
use. Notch 115
preferably includes angled sides as illustrated, with the lower notch end
being narrower
than the upper portion. A narrow bottom notch area prevents an upward lump or
distortion
in a staple wire at the notch as the striker presses the staple into position.
However, a
narrow notch requires relatively precise side alignment of the safety lock to
ensure that tip
283 can enter the notch in the rest position. Therefore, notch 115 is wide at
its upper end;
as striker 110 rises during the reset action tip 283 encounters this wide area
to provide a
generous guide into the notch.
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From the foregoing detailed description, it should be evident that there are a
number of changes, adaptations and modifications of the present invention that
come
within the province of those skilled in the art. However, it is intended that
all such
variations not departing from the spirit of the invention be considered as
within the scope
thereof as limited solely by the following claims.
