[0001] The present invention relates to improvements in a method and apparatus for securing
and gripping a preceding portion of a strap such as steel band which is wound around
an article to be bound and then tightened before its ends are bonded together.
[0002] In the past the preceding portion of the strap has been gripped between a pair of
jaws as will be described in detail subsequently with reference to the accompanying
drawings. The jaws may grip the strap at a single point or may include at least one
serrated jaw to improve the grip between them and the strap. In both cases the surface
of the strap tends to be scored by the jaws which can lead to weakening and failure
of the strapping.
[0003] According to a first aspect of this invention a method of gripping a strap whilst
bonding its ends together including the steps of: winding a binding strap around articles
to be bound, gripping to secure and hold a preceding portion of the strap, taking
up the succeeding portion of the strap, and bonding overlapping strap portions of
the preceding portion and the succeeding portion to each other whilst applying tension
to them; is characterised in that the preceding portion of the strap is gripped by
grip means including a jaw and a stationary cutter which include intermeshing projections
which form the preceding portion of the strap into a serpentine shape with a number
of concave and convex portions.
[0004] According to a second aspect of this invention a strap binding machine includes a
binding head including grip means to hold a preceding portion of the strap, tensioning
means to apply tension to a succeeding portion of the strap after it has been wrapped
around an article to be bound, bonding means to bond the preceding portion and succeeding
portion of the strap together, and a cutter to sever the succeeding portion of the
strap after it is bonded, and
is characterised in that the grip means is formed by a jaw and stationary part of
the cutter and in which these include intermeshing projections which form the preceding
portion of the strap into a serpentine shape with a number of concave and convex portions.
[0005] A particular example of a method and apparatus in accordance with this invention
will now be described and contrasted with the prior art with reference to the accompanying
drawings; in which:-
Figure 1 is a side elevation of a bonded strap;
Figure 2 is a plan of the bonded strap;
Figure 3 is a side elevation drawn to a larger scale of the grip and cutter of the
binding head;
Figure 4 is a plan of the strap illustrating the grip marks formed on it;
Figure 5 is a schematic view illustrating the strap binding maching;
Figure 6(a) is a partly sectioned side elevation of a first conventional binding head;
Figure 6(b) is a partly sectioned elevation of a second conventional binding head;
Figure 7(a) is a plan of the score marks formed by the first conventional binding
head; and,
Figure 7(b) is a plan of multiple score marks formed by the second conventional binding
head.
[0006] A conventional strap binding method will be described with reference to Figures 5
to 7. A binding apparatus has a multi-functional binding head 1, to be discussed later,
which is vertically movable with respect to its frame. Articles 2 to be bound are
fed to a predetermined position under the binding head 1 in the frame. A binding strap
3 such as a steel band is fed from a dispenser by the forward rotation of reversible
rollers 4 of the binding head 1. The strap 3 is guided around articles to be bound
2 through a chute and gate (not shown). After making a round of the articles to be
bound, the preceding portion 3a of the strap 3 is returned to the binding head 1.
[0007] When the preceding portion 3a of the strap 3 comes under the succeeding portion 3b
of the strap 3 as shown in Figure 6(a), a stationary cutter 5 and a jaw 6 of the binding
head 1 are closed to grip a portion of the preceding portion 3a, so that the grip
portion of the preceding portion 3a is held and secured.
[0008] With the preceding portion fo the strap gripped, the drive rollers 4 are reversely
rotated, thereby to take up the succeeding portion 3b. This causes the winding strap
3 to come off the chute and the gate such that the articles 2 to be bound are wound
tightly with the strap 3. At the same time, the binding head 1 is lowered onto the
articles to be bound, as shown by an arrow
d.
[0009] While a high tension is being applied to the winding strap 3 by the strong reverse
rotation of the drive rollers 4, a C-sectioned seal fitment, for example, is placed
on the overlapping strap portions of the preceding portion 3a and the succeeding portion
3b, and the seal fitment is turned and crimped at its lateral edges. The lateral edges
are partially notched by the jaw 6 and notchers 9 which are lowered. This forms notches
10 which are turned in opposite directions to clamp them together to bond the overlapping
strap portions together. At the same time, the bonded strap portion is cut and separated
from the rearwardly connecting strap portion 3c, by and between the stationary cutter
5 and a movable cutter 11 which is lowered.
[0010] When the jaw 6 serving as an underlay is transversely pulled out, the bonded strap
is resiliently returned by the amount of looseness generated by the removal of the
jaw 6. However, a sufficiently high tension still remains in the binding strap to
assure a good binding effect.
[0011] In the foregoing, the most common conventional strap binding method has been described.
However a number of different bonding means may be used. For example, the overlapping
strap portions may be bonded to each other by spot welding. Further, the grip means
may also have a variety of forms. Besides the single-type grip means as shown in Figure
6a a multi-grip means is also known as shown in Figure 6b. In this the strap is gripped
by and between a sawtooth holding surface 5S formed on the stationary cutter 5 and
the flat surface of the jaw 6. Regardless of the types of the grip means and the bonding
means used the following series of steps are carried out: winding the strap 3; gripping
the preceding portion 3a; taking up and winding the succeeding portion 3b; tightening
and tensioning the strap; bonding the preceding portion 3a and the succeeding portion
3b to each other under tension; cutting and separating the bonded strap from the connecting
portion 3c; and removing the underlay.
[0012] By and between the stationary cutter 5 and the jaw 6, the strap preceding portion
3a should be gripped as tightly as possible and held in order to resist the high tension
applied to the succeeding strap portion 3b by the drive rollers 4. Even after the
strap succeeding portion 3c has been separated from the strap connecting portion 3c,
a high tension still exists between the gripped portion and the seal fitment bonding
portion. A steel-band strap having strength capable of sufficiently resisting these
tensions is typically used. For example, there may be used a steel-band strap having
a width of 3/4 to 1 1/4 inch (19 to 32 mm), a thickness of 1 mm or less, and a resistance
to tension of about 75 to 100 kgs/mm².
[0013] However, the strong gripping above-mentioned produces scores or grip marks as grip
traces on the strap preceding portion 3a at the gripped portions. Further, these gripped
portions are normally bent to some extent. Figure 7(a) shows a grip mark 12s produced
in the case of the single grip device shown in Figure 6a, while Figure 7(b) shows
grip marks 12m produced in the case of the multiple grip device shown in Figure 6b.
If the gripping force is smaller than the tightening tension applied to the strap,
the strap may be cut or slip at the gripped portions, and the binding residual tension
is considerably reduced.
[0014] The main problems encountered in the single grip are set forth below.
(I) The single grip mark 12S is relatively large and deep. Accordingly, if an excessive
tension is applied to the winding strap to enhance the binding force, the strap may
break at the scored portion.
(II) The scored portion of the strap is apt to cause slip, decreasing the tension
remaining after the strap end portions have been bonded to each other.
(III) Since the scar of grip mark is great, there is a possibility of the strap being
broken, if a binding force or an external force in the shearing direction is applied
to the binding strap during transport of the bound articles.
[0015] The main problems encountered in the multiple grips are set forth below.
(I) The gripped portions are extended in the strap longitudinal direction. Accordingly,
the distance between the strap gripped portions and the strap end portion bonded with
the seal fitment or the like is increased. This increases the looseness generated
after strap bonding, so that the drop in residual tension is increased. Thus, the
multiple gripping is not suitable for binding coil-like or small-size articles, since
the influence of such drop is considerable.
(II) It is required that for the multiple grip to be effective that a number of grip
points are arranged equidistant from the jaw and the grip conditions are equilized
along the length. Accordingly, no free space is provided in the thickness direction
of the binding strap. This requires a fine adjustment for the strap portion to be
held effectively.
(III) The bonding members of the binding head are increased in size, causing the head
to be large-sized.
[0016] In accordance with the present invention the grip means includes a jaw and a staionary
cutter of the binding head formed with intermeshing projections so that the strap
is formed into a serpentine shape with a plurality of concave and convex portions.
[0017] Figures 1 and 3 illustrate the present invention. The preceding portion 3a of the
winding strap 3 is gripped and held between and by the lower jaw 6A and an upper stationary
cutter 5A, while the strap 3 is formed into a serpentine shape by being pushed up
at first positions thereof in a direction shown by arrows U and pushed down at second
positions in a direction shown by arrows V. The first positions alternate with the
second positions. With tension applied to the strap between the gripped portions and
the portion tightened by the drive rollers, a seal fitment 7 is placed on the overlapping
strap portions of the preceding portion 3a and the succeeding portion 3b. Notches
10 are then formed to bond the overlapping strap portions to each other. The strap
portion thus bonded is cut and separated from the strap connecting portion at a cut
end 3e with a movable cutter 11A. As shown in a plan view of Fgiure 2, grip marks
are formed on the strap at its portion near the centre so that a plurality of convex
marks 12U and concave marks 12V are respectively formed on the obverse and reverse
surfaces of the strap in an adjacent manner.
[0018] The method of the present invention provides the following operations and effects.
(I) The strap preceding portion is gripped at positions on the obverse and reverse
surfaces thereof, these obverse and reverse positions alternating with each other
in the strap longitudinal direction. This eliminates a fine adjustment of the intermeshing
tips with respect to the thickness of the strap.
(II) The double-wave gripping substantially prevents the gripped portions from slipping
due to tension applied to the strap.
(III) The wave-shape gripping causes the grip marks to be convex and concave, thus
producing no scars which produce a cutting or scoring effect. Accordingly, the surface
of the strap is hardly damaged.
(IV) It is not required to grip the strap at as many points as required in the conventional
method. Accordingly, a spread of the gripped portions is small and equal to that in
the single grip according to the conventional method. This eliminates the need of
large-sized grip means. Accordingly, the drop in strap residual tension is reduced.
(V) The wave-like gripping increases the grip resistance against the strap tension.
It is therefore possible to resist the strap tension by merely gripping the centre
band area of the strap. Accordingly, both lateral edges of the strap are preserved
intact.
(VI) The grip marks are in the form of a wave. Accordingly the binding strap is hardly
scored even though an external force is applied during transportation.
[0019] The following description will discuss in more detail an example of the present invention
with reference to Figures 3 and 4.
[0020] The gripping method in accordance with the present invention includes the same steps
as those in the conventional method, of: winding a binding strap around articles to
be bound, by a binding head; and gripping, while securing and holding, the grip portions
of the preceding portion of the strap returned to the binding head.
[0021] Figure 3 is a vertical section view in side elevation of an example of the grip means
used in the gripping method of the present invention. Figure 3 shows the relative
positions of the stationary cutter 5A and the jaw 6A in a closed position.
[0022] The jaw 6A is provided on the intermeshing jaw surface thereof with a plurality of
convex portion 6A′ and concave portions 6A˝. The stationary cutter 5A is provided
on the intermeshing jaw surface thereof with a concave portion 5a˝ and convex portions
5A′. The convex portions 6A′ are opposite to the concave portion 5A˝, while the concave
portions 6A˝ are opposite to the convex portions 5A′.
[0023] Figure 4 shows, in plan, the grip marks formed on the strap preceding portions 3a
by the grip means according to the method of the present invention. The grip marks
include convex marks 12U and concave marks 12V which are formed, at a central area
of the strap, alternately in the longitudinal direction thereof.
[0024] Figure 3 also shows a movable cutter 11A, and the cut end 3e at which the strap succeeding
portion 3b is cut and separated from the connecting portion of the strap stock.
[0025] According to the present invention, when bonding the end portions of a strap wound
on articles to be bound, the preceding portion of the strap is securely gripped to
resist the tension applied to the strap at the time when the strap is tightened and
when the strap end portions are subsequently bonded to each other. Convex and concave
grip marks are formed in the vicinity of one another. This reduces the drop in strap
tension remaining after the strap end portions have been bonded to each other. Accordingly,
the binding strap is hardly scored assuring a good binding.