A U-shaped clip intended to be deformed to enclose and close the mouth of a flexible tube or bag, comprising a pair of limbs of substantially constant cross-section and a web joined to the limbs, respectively at a pair of transition points, the cross-sections of the web and transition points differing from and having a higher section modulus than the cross-section of the limbs. Advantageously the limbs are round in cross-section and the web at the middle is rectangular with rounded corners, the web changing in cross-section gradually from the middle to the transition points. Indentations may be provided on the outside of the limbs near their ends to facilitate buckling of the limbs toward one another when the clip is worked upon by a closing tool. The clips are assembled one behind the other with their limbs forming two parallel lines, constituting a magazine for supply to the closing tool.

This invention relates to a U-shaped clip which is intended to close bags, 
flexible tubes or the like and has been made from a piece of wire which is 
constant in cross-section throughout its length. 
There are two basic types of clips which are intended to close bags, 
flexible tubes or the like. Clips of one kind are made in that strip 
material is shaped by embossing operations, in most cases in several 
stages, to form clips, which are joined in a strip to form a supply of 
clips, which in this form are introduced into the closing machine, in 
which each clip is severed from the strip immediately before the closing 
operation. The embossing or other shaping tools may be designed so that 
the shaped clip has a cross-sectional shape which is suitable with a view 
to the intended purpose. The clips may have different cross-sectional 
shapes in the limbs and web (see, e.g., Printed German Application No. 
1,761,616). 
Clips of the other basic kind are made from wire material, which is cut 
into pieces, which are shaped to a clip. These clips are in most cases 
U-shaped. In this shaping operation the cross-section of the piece of wire 
remains constant throughout its length, apart from the upsetting and 
stretching of the material due to the bending. The starting material is in 
most cases circular in cross-section or has other cross-sectional shapes 
with a view to special applications (see, e.g., Opened German 
Specifications Nos. 1,536,183 and 1,959,755). A supply of clips of this 
kind is formed in that a plurality of individual clips are juxtaposed with 
the same orientation and are joined by means of adhesive material or the 
like to form a "bar". 
When a flexible packaging tube is to be closed with a U-shaped clip, the 
tube is gathered and is then embraced with the clip. The two open limbs of 
the U-shaped clip are then bent inwardly on a concave die, which has one 
or more slide grooves. As a result, the end of the casing is firmly 
closed. To avoid a spontaneous opening of the clip, it must resist the 
static restoring force which is exerted by the closed end. In some cases, 
a liquid-tight, fat-tight or air-tight seal is required. 
It has now been found in practice that the clips of the last-mentioned kind 
have certain disadvantages. Particularly the behavior of said clips during 
and after the closing operation is often unsatisfactory. Filled bags and 
flexible tubes are usually closed by a machine in an operation in which a 
punch pushes the clip over the gathered end portion of a flexible tube and 
drives the clip onto the die. In this operation the limb ends in one slide 
groove or in two parallel slide grooves until the end portions of the tube 
is firmly embraced. The end faces of the limb ends may either form a butt 
joint or the grooves may be so designed that these end faces move past one 
another. 
The limbs ends will most effectively resist the restoring force exerted by 
the closed end of the casing if they extend as exactly parallel as 
possible to the web of the clip when the same is in its final position, 
and it would even be desirable to give a slight bend to the limb ends. 
Whereas it has been attempted to provide for this desired bend in that the 
U-shaped clip is slightly bent inwardly before or is beveled on the 
outside, both measures have proved unsatisfactory. Prebending results in a 
decrease of the open cross-sectional area so that larger clips, which 
involve a higher expenditure of material, are required for a given 
cross-section to be closed. The ends of such clips are often reversely 
bent inwardly to an excessively large extent so that they damage the 
gathered casing. In the use of clips having beveled limb ends it has been 
found that the inside surfaces of the limb ends were not bent inwardly to 
a sufficiently large extent opposite to the bevels so that a sufficiently 
large closing pressure often cannot be applied in this region. This may 
result in an uncontrolled opening of the closure and consequently in a 
loss or spoiling of the content. 
To ensure that the plastic deformation of the clip can be initiated without 
upsetting when the limb ends have engaged the die, that region of the 
latter which is initially engaged by the leg ends must be sufficiently 
steep, but this would result in the disadvantage that the closed clip 
would not have the desired shape. The flatter the portion of the die which 
is initially engaged by the clip, the higher is the risk that the clip is 
upset during its plastic deformation. It is not possible to adopt a 
compromise in designing the die. When prebent or beveled limb ends 
suddenly engage the die, the clips are also upset and/or improperly bent 
so that trouble arises in the operation of the closing machines and 
unsatisfactory closures result. This result has not been substantially 
improved even by the application of a suitable lubricant to the end face 
of the limb ends. 
For this reason it is an object of the invention to provide a clip which is 
of the kind defined first hereinbefore and which is improved in that its 
limbs can be bent inwardly more easily and more reliably during the 
closing operation, that perfectly tight closures are obtained, and that 
damage to the bags, flexible tubes or the like is avoided. At the same 
time, the manufacturing costs should not be increased or should not be 
substantially increased. 
Surprisingly it has been found that a clip of the kind defined first 
hereinbefore can be much improved in that it has a higher section modulus, 
as a result of a change in cross-section, in its web and at the 
transitions to the limbs. 
The clips of the kind defined first hereinbefore are made from a piece of 
wire which is constant in cross-section throughout its length although 
various portions of the shaped clip and the closed clip are subjected to 
stresses of different magnitude and intended to perform different 
functions. For a clip of a certain size, the diameter of the wire is 
selected so that its cross-section is sufficient for that portion of the 
clip which is to be subjected to the highest stress. Other portions are 
more or less excessively large in cross-sectional area so that the 
expenditure of material is higher than required. 
If the cross-sectional shape is changed in the web and its transitions to 
the limbs, in accordance with the invention, less material will be 
required to make a clip having a given size or a clip which is capable of 
exerting a stronger closing force can be made with a given expenditure of 
material. The higher section modulus provided according to the invention 
in the stated regions does not only result in the required higher 
stiffness of the clip in said regions but has also the result that those 
portions of the clip which have been changed in cross-section bear on the 
casing with an area which is narrower than the bearing area of the 
portions which have not been changed in cross-section, e.g., at the limbs. 
As a result, the local closing pressure is increased and the risk of a 
slipping of the clip from the casing is reduced. Besides, a certain 
asymmetry of the local closing pressure results because a lower local 
closing pressure is applied to those portions of the casing which face the 
limb portions that have not been changed in cross-section. Under a load 
near the highest permissible load, a slippage may begin in this area when 
the clip still adheres firmly on the opposite side of the casing. As a 
result, the clip is tilted about the center line of the clipped portion of 
the casing so that a further slippage is immediately prevented. The 
closing force exerted by the clip according to the invention has been 
ascertained in tests which have simulated practical conditions. In these 
tests it has been found that the feared slipping is absolutely avoided and 
that the application of the higher testing pressure may rather result in a 
bursting of the bags, flexible tubes or the like. 
According to a preferred feature of the invention, that portion in which 
the cross-section is to be changed is shaped to a cross-sectional 
configuration of a rectangle having rounded corners or approximately of a 
rhombus. Besides, the portion which has been changed in cross-section may 
contain less material in the neutral zone than in the regions which are to 
be stressed in tension and compression, respectively. 
Within the scope of the invention, the change in cross-section may be most 
pronounced in the middle of the web and may decrease continuously to the 
unchanged cross-section of the limbs. 
A further improvement of the clip will be obtained in that the limbs are 
provided with portions which are decreased in cross-section to define 
rated buckling points.

Referring now more particularly to the drawing, FIGS. 1a and 1b show a 
U-shaped clip 1, which has been made from a piece of wire that is circular 
in cross-section. In a web 16 and at transitions 17 between the web and 
limbs 2, this cross-section has been changed to a configuration which 
approximates a rectangle having rounded corners (Form A) by a pressing or 
embossing operation. At a certain distance from its free end, each limb 2 
is provided on its outside 8 with a rated buckling point 3, at which the 
original cross-section 7 (See FIG. 2) has been locally decreased. 
FIG. 2 shows two different rated buckling points 3 in sectional views. The 
rated buckling point 3 is provided in accordance with FIG. 2a by a 
crescent-shaped recess 4 and in accordance with FIG. 2b by a prismatic 
recess 5. It is apparent that the originally circular cross-section 7 has 
been weakened by the recess 4 or 5 in both cases. 
FIG. 3 shows how clips 1 according to the invention may be juxtaposed to 
form an assembly or magazine of such clips with their limbs forming two 
parallel lines, particularly suited for supply to a closing tool. 
FIG. 4 shows a clip (Form B) whose web at its midpoint is rhombic in 
cross-section. 
The web in FIG. 5 (Form C) is dumbbell shaped in cross-section. 
A further embodiment of the invention is shown in FIG. 6. In this 
embodiment the change in cross-section is not the same in all portions but 
is most pronounced in the middle 18 of the web 16 and decreases 
continuously to the transition 19 to the unchanged limb cross-section 20. 
FIG. 6a is a fragmentary elevation showing the clip according to the 
invention. FIG. 6b represents three different cross-sectional shapes in 
sectional views taken on lines "x", "y" and "z" in FIG. 6a. If properly 
designed tools are used, this concept may also be adopted in conjunction 
with the cross-sectional shapes as shown in FIGS. 4 and 5. Numerous other 
embodiments are possible within the concept of the invention, provided 
that the section modulus of the clip is increased by a change in 
cross-section with a view to the loads to be encountered in use. In each 
case, the selection of the changed cross-sectional shape and of the extent 
of the change will be guided by the local stresses to be expected, on the 
one hand, and the manufacturing costs involved in the change in 
cross-section. 
It will be appreciated that the instant specification and examples are set 
forth by way of illustration and not limitation, and that various 
modifications and changes may be made without departing from the spirit 
and scope of the present invention.