Stapler with internal guidance of the legs of a staple

Details Stapler with internal guidance of the legs of a staple Stapler with internal guidance of the legs of a staple

1999-10-25

2001-07-10

Smith, Scott A. (Department: 3721)

Elongated-member-driving apparatus

With means to move or guide member into driving position

With means to assure correct orientation of member

C227S107000

Reexamination Certificate

active

06257477

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a stapler for driving staples into an object, such as a sheaf of papers, said stapler comprising a drive element arranged to expel a substantially U-shaped staple and drive its legs through said object.
When stapling a relatively thick sheaf of papers, a guide means is usually used for external guidance of the staple legs during the driving of the staple into the sheaf of papers. This guide means prevents the legs from bending outwards during the driving.
When stapling a thicker sheaf of papers or when stapling a sheaf of papers consisting of a comparatively small number of sheets of paper of a harder quality, e.g. sheets of paper of the type used for colour photocopies, the staple is slightly deformed in spite of the use of a guide means for external guidance of the staple legs.
When the drive element performs a driving stroke, i.e. is moved from an upper position to a lower position, its lower edge surface abuts against the web portion of the staple to press the staple legs through the sheaf of papers. When the driving resistance is too great, e.g. when the sheaf of papers is thick or when it consists of hard sheets of paper, the staple is deformed. This deformation consists in the upper portion of the staple legs sliding or creeping in under the drive element. During the continued driving stroke of the drive element, the staple then crumples up on the upper side of the sheaf of papers.
In an attempt to solve this deformation problem when stapling sheets of paper in a sheaf offering a considerable driving resistance to the staple legs, an underlying support for the web portion of the staple is used in a prior-art stapler. This support is connected with the drive element and follows it in its reciprocating movement. The support is pivotable about an axis, which is substantially parallel to the web portion of the staple, to be inserted under the web portion to form a support thereof, when the drive element abuts against the web portion of the staple during its driving stroke, and to be removed from its position under the web portion at the end of the driving stroke, before the web portion reaches the upper side of the sheaf of papers.
This solution functions fairly well and prevents a deformation of the staple of the kind described above, but it is complicated and takes up a relatively great deal of space.
In a known stapler, the deformation problem described above is solved in a considerably easier way by the drive element being provided with two protruding projections at the same mutual distance as the legs of the staple, which projections are arranged to engage the web portion of the staple just opposite a staple leg each, the projections being pointed in order to bite a distance into the web portion of the staple in the engagement therewith. By this design of the drive element, it is possible to drive the staples without deformation into sheaves of papers, which are considerably thicker than the sheaves of papers being stapable by means of prior-art staplers, which lack an underlying support for the web portion of the staple.
SUMMARY OF THE INVENTION
This stapler can be further improved to allow stapling of sheaves of papers offering a greater driving resistance to the staple legs. This can be achieved by providing the stapler with a prior-art guide means for internal guidance of the legs of the staple during the driving of the staple into the sheaf of papers. Such a guide means is movable between a first position, in which it extends into the driving path of the staple to abut against the inside of the legs during the driving of the staple, and a second position, in which it is removed against spring action from the driving path of the staple. The guide means has a ramp means for such cooperation with the web portion of the staple that the guide means is removed against spring action to its second position by the web portion as the driving of the staple proceeds. The guide means has two guide elements, which are arranged to abut against the inside of a leg each during the driving of the staple, thereby preventing the legs from bending inwards during the driving.
Two such guide elements will now be described with reference to
FIGS. 1 and 2
.
FIG. 1
shows a guide element having a ramp surface with a steep inclination, and
FIG. 2
shows a guide element having a ramp surface with a less steep inclination.
FIGS. 1 and 2
show a stapler very schematically, the drive element
1
of the stapler being shown in its driving stroke, i.e. during the driving of a U-shaped staple
2
into a sheaf of papers (not shown). The lower edge surface of the drive element
1
then abuts against the web portion
2
b
of the staple
2
.
FIGS. 1 and 2
also show one guide element
3
of a guide means intended for internal guidance of the two legs
2
a
of the staple
2
during the driving of the staple
2
. The guide element
3
is movable between a first position, in which it is inserted into the driving path of the staple
2
to abut against the inside of the corresponding staple leg
2
a,
and a second position, in which it is removed against spring action from the driving path of the staple
2
. The guide element
3
has a ramp surface
4
facing upwards. During the driving of the staple
2
, its web portion
2
b
abuts against the ramp surface
4
and then presses the guide element
3
from its first position to its second position (to the left in
FIGS. 1 and 2
) as the driving of the staple
2
proceeds.
The ramp surface
4
of the guide element
3
shown in
FIG. 1
has an inclination different from that of the ramp surface
4
of the guide element
3
shown in FIG.
2
. The steep inclination, shown in
FIG. 1
, gives the advantage of the extension of the guide element
3
in the moving direction of the guide element being fairly small, which results in the guide element
3
requiring a comparatively small space. The steep inclination gives, however, the disadvantage that a great deal of the upper portion of the staple leg
2
a,
as is clearly shown in
FIG. 1
, does not obtain an internal support from the guide element
3
. When the sheaf of papers is thick and exhibits a great resistance to the driving in of staples, it is important that the leg
2
a
be guided over as much as possible of its length. This is the reason why a guide element
3
of the type shown in
FIG. 2
must be used, i.e. a guide element whose ramp surface
4
has a less steep inclination. Such a guide element
3
offers, as is shown in
FIG. 2
, an internal support to the staple leg
2
a
substantially over its entire length. The disadvantage of the less steep inclination is that the guide element
3
is given a large extent in the moving direction and thus takes up a great deal of space, especially as a space must be available for the movement of the guide element between its two positions.
The object of the present invention is to provide a stapler, which is fitted with a guide means intended for internal guidance of the staple legs during the driving of the staple into an object, the guide means being of the type described above and its two guide elements offering an adequate support for the staple legs substantially over their entire length, while taking up a comparatively small space.
According to the present invention, this object is achieved by a stapler for driving staples into an object, such as a sheaf of papers, which stapler comprises a drive element arranged to expel a substantially U-shaped staple and drive its legs through said object, and a guide means for internal guidance of the legs of the staple during the driving of the staple into the object, which guide means is movable between a first position, in which it extends into the driving path of the staple to abut against the inside of the legs during the driving of the staple, and a second position, in which it is removed against spring action from the driving path of the staple, and which guide means has a ramp means for such cooperation with the web portion of the staple that the guid

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