Plastic article or earthenware shaping or treating: apparatus – Preform reshaping or resizing means: or vulcanizing means... – Convoluting or twisting means
Reexamination Certificate
1998-11-06
2001-02-20
Pyon, Harold (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Preform reshaping or resizing means: or vulcanizing means...
Convoluting or twisting means
C425S319000, C425S384000, C425S397000, C425S403000, C264S285000, C242S444000, C428S906000, C072S145000
Reexamination Certificate
active
06190156
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to plastic coils, and more particularly to a method for forming plastic coils and to an apparatus for carrying out this method.
BACKGROUND OF THE INVENTION
Plastic coils are well known through their several uses, for example to hingedly bind the pages of a book or booklet. The coils used this way are semi-rigid plastic wires forming a cylindroid helix of constant diameter and pitch. A particular advantage of this form of plastic coil binding element is that it is not expensive to produce, while being sturdy, offering a good aesthetic appearance and allowing an efficient and easy-to-use binding element for the book pages bound in this way.
A known method of producing plastic coils comprises using a conveyor line for a thermoplastic wire in which the wire is heated so as to achieve a semi-viscous pliable state, and then fed into a helical channel in which its selected helical form is achieved by cooling the channel so that the thermoplastic wire will solidify and recover its semi-rigidity in the form of a coil shaped according to the helical channel of constant selected pitch and diameter. The cooling is achieved by any suitable means of cooling the thermally conducting channel, whereby the plastic wire will be cooled by heat transfer therethrough.
The main problem associated with this conventional method for forming plastic coils is that the coil discharged by the helical channel is imparted with a rotative movement about its longitudinal axis, in addition to the desired output discharge translational movement along this same longitudinal axis. Thus, the plastic coil wire cannot be wound around a spool for storing and carrying purposes, because of the coiled wire rotating on itself which would result in an undesirable twisting of the plastic coil on the spool. The usual way to obviate this problem is to cut the coiled wire at regular—and relatively short—lengths, for example at every three feet. This effectively prevents the coils from twisting on themselves, but prevents the coils from being stored, carried and sold as a long, unitary coil. Not only is it less interesting to sell the coils in short lengths, but also to cut the plastic coil is likely to result in an important waste of plastic coil material. Indeed, if the length at which the coil is cut (e.g. three feet) is not a multiple of the effective used lengths of the coils (e.g. to bind books having a length of two feet), then the extra coil material (e.g. one foot long for each three feet coil) must be discarded and is wasted.
OBJECTS OF THE INVENTION
It is the gist of the present invention to provide a method and apparatus for forming plastic coils which improves on the existing methods and apparatuses, and more particularly which allows the output of the coil forming apparatus to feed a continuous, non-rotating plastic coil.
SUMMARY OF THE INVENTION
The present invention relates to a coil forming apparatus for forming an elongated continuous coil out of a straight continuous flexible wire, said apparatus comprising:
an axially rotative helical channel mounted about a fixed longitudinal axis and defining an upstream end having an inlet opening allowing the wire to be fed therein and a downstream end having an outlet opening allowing the coil to be discharged therethrough;
an injection nozzle for feeding the wire into said channel inlet opening, and integrally rotatable with said channel;
a power device, for rotating said helical channel and said injection nozzle in a common rotative movement;
wherein the wire fed into said channel will slide therealong according to a helical travelling direction upon which it will be formed into a coil, said helical channel rotating in a direction opposite the travelling direction of the wire and at a speed of rotation allowing the coil being discharged at said channel outlet opening to be imparted with an output translational displacement, while being exempt of any rotational displacement about said longitudinal axis.
The invention more particularly relates to a plastic coil forming apparatus for forming an elongated continuous plastic coil out of a straight continuous flexible thermoplastic wire, said apparatus comprising:
a helical channel mounted about a fixed longitudinal axis and defining an upstream end and a downstream end, said helical channel being formed by a stationary sleeve and an axially rotative mandrel axially extending in said sleeve in a radially adjacent fashion, said mandrel having an axially extending thread located in said sleeve, whereby the plastic wire can slide in said helical channel which defines an outlet opening at said downstream end for allowing the wire to be discharged therethrough;
an injection nozzle, having an inlet opening for allowing the wire to be fed therein, said injection nozzle being integrally connected to said rotative mandrel, thus being rotatable therewith in a common rotative movement, and allowing the wire to be fed at said helical channel upstream end;
a heating device, for heating the thermoplastic wire before it enters said helical channel so that the wire achieves a semi-viscous state;
a cooling device, for cooling the wire while it is in said helical channel, whereby the thermoplastic wire will solidify therein and will be formed into a coil due to the helical shape of said channel;
a power device, for rotating said mandrel and said nozzle; wherein the wire fed into said helical channel will slide therealong, between said mandrel and said sleeve, according to a travelling direction and be discharged at said channel outlet opening, said mandrel rotating in a direction opposite the travelling direction of the wire and at a speed of rotation allowing the coil being discharged at said channel outlet opening to move with an output translational displacement, while being exempt of any rotational displacement about its longitudinal axis.
The invention also relates to a method for forming a continuous plastic coil from a straight thermoplastic wire, comprising the steps of:
a) heating the thermoplastic wire until it achieves a semi-viscous malleable state;
b) injecting the heated wire with an injection nozzle into a helical channel formed by a rotating threaded mandrel axially extending into a stationary sleeve and being radially adjacent therewith, with the wire sliding along the channel in a helical travelling direction to an outlet opening;
c) cooling said channel during the injection of the wire therein, wherein said wire will effectively be formed into a plastic coil of a shape corresponding to said helical channel;
d) rotating in a common rotative movement the mandrel and the injection nozzle during the injection in a direction opposite the travelling direction and at a speed allowing the continuous plastic coil to be discharged at the outlet opening with an axial translational displacement, while being exempt of any rotational displacement about its longitudinal axis.
Preferably, the method further comprises the following step after step d):
e) winding around a spool the discharged continuous plastic coil in successive turns.
The invention also relates to a spooled continuous plastic coil obtained from the method described hereinabove, comprising a spool and an elongated continuous plastic coil defining a longitudinal axis, said plastic coil being wound at least several turns around said spool and being substantially free of any torsional forces relative to its longitudinal axis.
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Bedard Jean T.
Brisson Jean-Claude
Corriveau Régent
Primeau André
2751-3654 Québec Inc.
Luk Emmanuel
Martineau François
Pyon Harold
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