Stapler for flaring staple

Details Stapler for flaring staple Stapler for flaring staple

2003-04-11

2004-08-10

Smith, Scott A. (Department: 3721)

Elongated-member-driving apparatus

With means to form member prior to penetration of work

Deflector

C227S088000, C227S123000, C227S155000

Reexamination Certificate

active

06772930

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to a stapler and, more particularly, to an improved stapler having an anvil structure that joins materials by flaring the legs of the staple outward and away from each other.
BACKGROUND OF THE INVENTION
There are numerous applications in which staplers are used to clinch materials together by diverging and curling the legs of a staple outward and away from each other. Examples of such staplers are shown and described in U.S. Pat. Nos. 4,574,992 and 3,807,619. Referring to
FIG. 1
herein, in one known application in the bedding industry, a fabric material
40
is clinched to a foam substrate
42
using a stapling process in which legs
44
of a generally U-shaped staple
46
are caused to flare or diverge and curl away from each other. The flare is accomplished with a known nose piece
20
that mounts in a known manner to a standard stapler
50
, for example, a pneumatic stapler type VA0285 commercially available from Vertex Fasteners, Inc. of Skokie, Ill. The known nose piece
20
is an assembly comprised of an anvil
22
that is mounted with respect to a retaining block
24
by means of a pin
26
and a biasing element
28
, for example, an anvil spring such as a compression spring. The retaining block
24
is attached to a backing plate
30
by means of fasteners
32
. The anvil
22
has an angled guide or wedge
34
disposed on an anvil forward surface
27
adjacent a downstream, lower end
31
of the anvil
22
. The wedge
34
has an upstream, thinner edge
52
and a downstream, thicker edge
67
. The anvil spring
28
applies a biasing force against an anvil rearward surface
29
to push the thicker edge
67
of the wedge
34
against the backing plate
30
.
In operation, a driver blade
36
has a proximal end mechanically connected to, and receiving a force from, an actuator
58
, for example, a pneumatic cylinder, in a known manner. As shown in
FIGS. 1 and 2A
, an opposite, distal end
38
of the driver blade
36
contacts a crown
48
joining common ends of the two legs
44
of the staple
46
. The driver blade
36
pushes the staple
46
between the backing plate
30
and the anvil
22
. An upstream, thinner edge
52
of the wedge
34
has corner chamfers
54
,
56
; and as the staple legs
44
contact the spaced-apart chamfers
54
,
56
, they are deflected or guided outward and away from each other as they enter the materials being stapled. As the driver blade
36
continues to push the staple crown
48
between the backing plate
30
and the anvil
22
, the staple crown
48
contacts the wedge
34
. As shown in
FIG. 2B
, continued motion by the driver blade
36
forces the anvil
22
to compress the anvil spring
28
and move from left to right, as viewed in
FIGS. 1 and 2B
, along the pin
26
. That motion permits the driver blade
36
to push the staple crown
48
past the wedge
34
and against the materials being fastened. The staple legs
44
continue to diverge and curl as they move through the foam substrate
42
(FIG.
1
).
While the above nose piece
20
works satisfactorily in many applications, it does have disadvantages. First, many pneumatic staplers use a single acting cylinder
58
to apply the longitudinal drive forces on the driver blade
36
. With a single acting cylinder
58
, pressurized air from a source
60
is ported into one end
62
of the cylinder
58
and applies a force against a piston
64
mechanically connected to the driver blade
36
. The pressurized air moves the piston
64
from left to right, as viewed in
FIG. 1
, and advances the driver blade
36
against the staple
46
. As the piston advances through the cylinder, air stored in an opposite end
66
of the cylinder
58
is compressed. At the end of the staple drive stroke, that compressed air is used to return the piston
64
and retract the driver blade
36
to their respective starting positions. The return force produced by the compressed air to power the driver blade return stroke is substantially less than the force applied by the pressurized air from the source
60
during the driver blade drive stroke.
In operation, as shown in
FIG. 2C
, after the driver blade
36
pushes the staple
46
over a downstream, larger end
67
of the wedge
34
, the driver blade
36
is then squeezed between the thicker edge
67
of the wedge and the backing plate
30
by the force of the anvil spring
28
. Thus, a longitudinal force required to retract the driver blade
36
must be sufficient to overcome the side force imposed by the anvil spring
28
. On occasion, the anvil spring
28
applies a side force against the driver blade
36
that is sufficient to overcome the compressed air return force, and the driver blade
36
is pinned or sticks between the spaced-apart chamfers
54
,
56
and the backing plate
30
.
A second disadvantage of the known nose piece
20
arises from the continuous contact between the driver blade
36
and wedge
34
as the driver blade
34
advances and retracts during a staple driving operation. Thus, the driver blade
36
and wedge
34
are parts that experience wear and, overtime, that wear can be substantial and require replacement of the anvil
22
and/or driver blade
36
. Additionally, the wear can cause the degree of curl imparted to the staple to vary from the desired curl.
Therefore, there is a need for an improved nose piece
20
that is less susceptible to driver blade sticking and has less part wear.
SUMMARY OF THE INVENTION
The present invention provides a stapler with an improved nose piece that eliminates sticking of the driver blade caused by the anvil spring and therefore operates more reliably and at less cost. Further, the improved stapler nose piece of the present invention allows the driver blade to move past the anvil with minimal or no side force imposed by the anvil spring. Thus, the driver blade advances and retracts past the anvil wedge with only minimal and inconsequential frictional forces between the anvil wedge and the driver blade. Consequently, the wear on the driver blade and anvil wedge resulting from their relative motion is substantially eliminated, thereby reducing stapler maintenance and further reducing costs. In addition, with reduced anvil wear, the flaring of the legs of the staple is more consistent and repeatable over time, thereby providing a consistently high quality clinching of the materials by the staple. Therefore, the stapler of the present invention is more reliable, requires less maintenance and, over time, provides a higher quality, more efficient, and more economical stapling process. The stapler of the present invention is especially useful in clinching materials, for example, fabric and foam, that are used to make a mattress.
According to the principles of the present invention and in accordance with the described embodiments, the invention provides a stapler for clinching materials together with a generally U-shaped staple. The stapler has an anvil with spaced-apart wedges disposed adjacent a backing plate, and the wedges have respective chamfers that contact the legs of the staple and guide the legs away from each other. A biasing element provides a biasing force pushing the wedges of the anvil against the backing plate. A driver blade is movable between the spaced apart wedges and pushes against a staple crown. An actuator is mechanically connected to the driver blade and reciprocates the driver blade through advance and retract motions extending between the backing plate and the anvil. The advance motion advances the driver blade between the spaced-apart wedges, and the driver blade pushes the staple crown over the wedges while curling the staple legs of the staple away from each other. The retract motion retracts the driver blade from between the spaced-apart wedges substantially independent of the biasing force of the biasing element.
In another embodiment, the invention provides an anvil for use in a stapler and in conjunction with a driver blade for clinching materials together with a generally U-shaped staple. The anvil has spaced-apart

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