Note: Descriptions are shown in the official language in which they were submitted.
~040600
~ This invention is concerned with a unitary hol~ing strip
made of plastics material for retaining a plurality of screws in
a row, of the type including a plurality of screw holding sleeves
and lands interconnecting the sleeves which extend along a portion
of the threaded length of the respective screw in the axial direc-
tion thereof.
It is a known to connect screws to each other by a
retaining belt of breakable plastic material. The screw strip
formed in this way is placed in the known manner in the flat maga-
zine of a screwing appliance in which the first screw togetherwith a part of the retaining belt is separated from the screw strip
in the workpiece direction by a screw blade and is then screwed
into the workpiece. Parts of the cut off retaining belt then
drop onto the workpiece surface and from there get partly
underneath the head of the screw which presses them into the work-
piece surface. The parts lying loosely on the workpiece surface
can be pressed into the surface when the screwing appliance moves
onwards and can make their presence felt very inconveniently
especially on planed and sanded surfaces of furniture and may even
damage the surface. The cut off particles of the retaining belt
can moreover settle in the guide channel of the screwing applicance
and in the front part of the magazine and can noticeably impede ;~
the operation of the screwing appliance.
Another disadvantage of these known screw strips
results from the fact that the screw is no longer guided safely
in the cylindrical guide channel of the screwing appliance and
/ can tilt and is then screwed into the workpiece at an angle.
j~ To prevent this disadvantage guide jaws are required near the
, guide channel which make the screwing appliance more expensive
{ 30 and can also lead to trouble.
It is an object of this invention to provide a screw
holding strip as well as a process for its production, in which
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rh~ section surrounding the screw to be separated is not cut off
from the remaining retaining belt with the screw and in which
the screw is guided securely until it reaches the workpiece.
In accordance with the invention, there is thus provided
a unitary holding strip made of plastics material for retaining
a plurality of screws in a row, the screws having longitudinal axes
and a threading with a given outer thread diameter. The unitary
holding strip of the invention includes a plurality of screw
holding sleeves and lands interconnecting the sleeves which extend
along a portion of the threaded length of the respective screw
in the axial direction thereof, the lands and sleeves having a
wall thickness substantially smaller than the outer thread dia-
meter, and is characterized in that the sleeves comprise inwardly
facing screw threads for receiving the screw threading and that
they further comprise along one side thereof, substantially
between the lands, an area of reduced strength such that a screw
which is being threaded into a workpiece is automatically separated
from its sleeve while simultaneously maintaining the length of
the strip substantially intact and while guiding the screw by the
inwardly facing threads of the respective sleeve.
When the first screw is separated it turns in the
inwardIy facing screw threads of the sleeve in the direction of
the workpiece and is securely guided by the sleeve in the screwing
direction. If the screw is provided with a head it can expand the
sleeve when it reaches the sleeve during the screwing operation,
in such a way that the screw can be screwed completely into the
workpiece without damaging the retaining belt or strip. It is
best if the retaining belt is made of a flexible plastic material,
but other materials e.g. suitable metals or paper can also be used.
In a preferred embodiment of tlle invention, the sleeves
have a given wall thickness on one side and a thinner wall
thickness on the opposite side thereof, whereby the thinner wall
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rhickness provides the area of reduced strength. Alternatively,
the sleeves may only partially surround the screws to form the area
of reduced strength. The sleeve can thus be pressed sideways by
- the screw head transversely to the screwing appliance, and it is
then fractured at the area of reduced strength.
The undamaged empty retaining belt may leave the screwing
appliance through a suitable opening and no residues canaccumulate
on the workpiece surface.
According to another preferred embodiment, the area of
reduced strength of the sleeve comprises gap means in the sleeve
on one side thereof, whereby each sleeve surrounds its screw
along the entire length of the sleeve and circumferentially outside
the gap means. Preferably, the gap means comprises a longitudinal
slot on the aforesaid side of the sleeve.
According to a further preferred embodiment, the sleeves
enclose the screw threading with a peripheral angle within the
range of about 210 to about 270, whereby the sleeves have
longitudinally extending slots. Advantageously, all of the longi-
tudinal slots extend on the same side of the strip.
The construction of a retaining belt with lands the
wall thickness of which is smaller than the outer thread diameter
of the screw and with sleeves having one side thinner than the
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other side thereof helps on the one hand the retaining belt
to bypass the screwing appliance and, on the other hand,enables
the reduction of costs of the screwing appliance itself, by not
requiring the use of guiding jaws.
The screw strip in accordance with the invention provides
the further advantage that due to its flexibility, and the
arrangement of the ribs in the center plane of the screw strip,
the screw strip may be spirally wound or angularly. As a result,
it is possible to employ the screw strip not only in flat
magazines, but also in other forms of magazines. This provides
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the advantage that, when a differently ~ormed magazine is provided,
a larger number of screws can be processed in a screwing appliance,
without the necessity of frequent reloading of the magazine.
The invention also relates to a process for the
production of a unitary screw holding strip of the above type.
The process comprises arranging the screws in a row and in spaced
parallel relationship with one another; extruding plastics
~aterial on said row of screws to form a strip engaging the screw
threads; forming, with at least one pair of forming rollers, a
screw retaining strip having sleeves interconnected by lands with
a wall thickness substantially smaller than the outer thread
diameter of the screws, and controlling feeding of said plastics
material so that the sleeves comprise, along one side thereof with
respect to said lands, an area of reduced strength. Such forming
rollers are axially parallel, face one another on either side of
the strip and are formed, at their periphery, with longitudinally
extending grooves located so that one groove of one roller faces
a groove of the other roller when said screws pass therebetween.
Preferred embodiments of the invention will now be des-
cribed in greater detail with reference to the appended drawings,
whrerein:
Figure 1 is a side view of a screw strip according to
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the invention;
Figure 2 shows a cross-section through the screw strip
according to Fig. 1 along the line II-II;
Figures 3-5 illustrate the process of producing a screw
strip according to the invention, Figures 3 and 4 representing
the type of roller utilized; and
Figure 6 shows a modification of the screw strip of the
invention, where the sleeves completely surround the screws.
The screw strip 1 contains a nul~er of screws 2 which ~ h
are provided with bodies 3, a screw thread 4 and in the present
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~04~690
embodiment with screw heads 5. The screw strip according to the
: invention can equally contain screws without he~ds or with scre~
bodies and screw threads which differ from the _
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embodiment. 1040600
The screws 3 are connected to each other by a retaining
belt 6 of flexible plastic material which in the embodiment runs
vertically to the longitudinal axis of the screws. However, in
the case of screw strips the screws of which are in staggered
arrangement, it can be slightly inclined towards the longitudinal
axis of the screws.
The screw threads 4 are enclosed by sleeves 7 of the
retaining belt 6 with a peripheral angle of 270 so that longitu-
dinal slots 8 result in the sleeves 7 on one side of the screw
strip 1. The sleeves 7 have a counter-thread 9 on their inside,
which forms a mating thread to the screw thread 4. The wall thick-
ness 10 of the sleeve 7 outside the screw thread 4 is smaller than
the depth 11 of the screw thread 4.
; The sleeves 7 are connected to each other by integrated
ribs 12 connected to the sleeves, the ribs 12 being arranged in
the centre plane or the screw strip 1. The wall thickness 13 of
the ribs 12 is smaller than the outside diameter 14 of the screw
threa~ 4.
The right end of the sleeve of the screw strip illustra~
ted in F gs. 1 and 2 is shown without a screw in position. This
depicts the undamaged form of the empty retaining belt or strip 6
as it leaves the screwing appliance by way of a suitable opening.
A conventional machine for the manufacture of fastener
strips, known as a collator, may be employed in the formation of
the screw strip in accordance with the invention. In the process
of forming the screw strips, the screws 2 are suspended by their
heads and arranged in a row ~or feeding to a forming device. In
the forming device, they are entrained by the grooves of a
circulating conveyor chain. In accordance with the inVention,
when the strip 6 is formed of a flexible plastic material, the
plastic material is extruded from a nozzle only onto one side of
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T~ row of screws, to engage the screw threads of the screws.
The strip 6 is then formed into the shape illustrated in Figs. 1
and 2, by the use of at least one pair of forming rollers. As
illustrated in Figs. 3 and 4, a forming roller 20 for this
purpose is provided with one or more longitudinally extending
semi-circular grooves 21. These grooves have radii greater than
the radius of the screw thread, so that the plastically molded
plastic material can be forced to penetrate into the threads of
the screw thread 4 and also to surround the screw threads to form
the sleeves. The rollers 20 may also be provided with an annular
groove 22, or alternatively, with angular ribs, intersecting
the longitudinal grooves 21, for forming the ribs 12.
The process in accordance with the invention is shown
generally in Fig. 5, wherein the extruded unformed portion 25 of
the strip is shown as being disposed only on one side of a screw
2. The strip and the screws 2 are advanced to the right, as indi-
cated by the arrow 26, to pass between a pair of rollers 27 of
the type illustrated in Figs. 3 and 4. The semi-circular longi-
tudinally extending grooves 28 of these rollers are positioned to
be in alignment as the screw 2 passes therebetween. As a
consequence, the grooves 28 form the sleeves, by pressing the
material of the strip 6 into the threads of the screws, and by -
plastically forcing the material to partially surround the oppo-
site side of the screw.
It is, of course, apparent that the amount of plastic
material extruded onto the sides of the screws is metered, such
that a sufficient amount of plastic material is provided to
enable the sleeve to be formed to surround the screw to the desired
extent. Thus, as discussed above, it is preferred that the sleeve
surrounds the screw through an angle of between 210 and 27~.
In the modification of the screw strip in accordance with
the invention as illustrated in Fig. 6, the sleeves 30 of the
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screw strip are formed to completely surround the screws. In
this arrangement, the portion 31 of the sleeves on one side of the
screw strip is thicker than at least a portion 32 of the sleeve
on the other side of the screw strip. The interconnecting ribs 33
are formed, as in the previously described embodiment of the
invention, to have thicknesses less than the diameter of the
threads of the screw 34.
In this embodiment of the invention, since one side of
the sleeve is thinner than the other side thereof, the thinner
side is broken by the advancement of the head of the screw in a
screwing operation. Due to the flexibility of the strip, however,
the other side of the sleeve is not broken, so that the plastic
strip may be fed from the screwing appliance, through a suitable
opening as in the above example, without leaving portions thereof
on the surface of the workpiece.
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