Apparatus and method for producing knitted hook-type fastener material

A method of producing a weft knitted material having on one side a multiplicity of hook-like engaging elements suitable for repeated face-to-face engagement and disengagement with a material having a multiplicity of upstanding pile loop-like engaging elements, which includes a base knitted fabric, a plurality of upstanding hook-like engaging elements having substantially the same height, comprising:

• (a) knitting by circular knitting techniques a base fabric layer of multifilamentary yarn material and simultaneously knitting about lancets, a sequential series of monofilamentary pile loop elements upstanding from said base fabric layer, said circular knitting causing said monofilamentary loop elements to move rotationally;
• (b) applying predetermined downward forces to said fabric during the formation thereof;
• (c) maintaining said predetermined downward forces during the fabric formation to cause said monofilamentary loop elements to move downwardly along said lancets in a generally equally spaced parallel relation and to maintain substantially equal heights of said loop elements thus formed;
• (d) heating the fabric thus formed at a temperature sufficient to shrink the base fabric and loop elements to thereby provide stability to said fabric and interknitted loop elements;
• (e) selectively contacting the upper crest portions of said rotating monofilamentary loop elements with a stationary heated platen having an outwardly facing generally convex arcuate heated surface corresponding generally to the curvature of the fabric thus formed, said heated platen having a temperature sufficient to melt the crest portions of the loop elements such that substantially each of all said hook-like engaging elements are formed of a first monofilamentary member interknitted into and upstanding from said base fabric, and the relative rotary motion between said loop elements and said heated platen resulting in the formation of a second melt formed engaging member positioned at the free end portion of said first upstanding monofilamentary member interknitted into said base fabric and extending generally transversely thereof, said second melt formed transverse members each being generally asymetrically configured to have at least one end portion having a generally arcuate cross sectional configuration in a plane extending downwardly through said hook-like engaging element and an opposite tapered end portion of lesser average thickness than said arcuate end portion and being of greater flexibility than said arcuate end portion, such that the fabric may be placed in face-to-face relation with such mating loop-type material with the result that numerous engagements take place between the hook-like and loop-like elements, and separated by forces substantially normal to the interfacial plane of engagement, the asymmetric configurations of said hook-like engaging elements being such that the forces required to separate the hook-like elements from engaged loop-like elements in a direction from the arcuate end portions toward the generally tapered end portions are greater than the forces required to separate the hook-like elements in the opposite direction.

An apparatus for producing a weft knitted material having on one side a multiplicity of hook-like engaging elements suitable for repeated face-to-face engagement and disengagement with a material having a multiplicity of upstanding pile loop-like engaging elements, which includes a base knitted fabric, a plurality of upstanding hook-like engaging elements having substantially the same height, which comprises:

• (a) an upper cog wheel having a plurality of lancets secured thereto in a circular array and extending downwardly therefrom into a knitting zone;
• (b) a lower cog wheel positioned immediately below said upper cog wheel and a plurality of latch-type knitting needles positioned for rotation with said lower cog wheel for weft knitting said fabric;
• (c) means for rotating said upper and lower cog wheels at substantially the same rotational speeds;
• (d) means for reciprocating said latch needles upwardly and downwardly respectively, intermediate said lancets in an upward and downward weft knitting movement;
• (e) means for supplying multifilamentary yarn to said knitting zone for knitting the base fabric;
• (f) means for supplying monofilamentary heat-deformable yarn to said knitting zone;
• (g) means to guide said first-mentioned yarn to a position behind said lancets to form said base fabric;
• (h) means to guide said monofilamentary heat-deformable yarn to said knitting zone over said lancets to be interknitted with said base fabric simultaneously with its formation;
• (i) means for reciprocating said latch needles in an upward and downward motion and rotating said needles in a rotary motion to form in said knitting zone, a weft knit fabric having a plurality of monofilamentary loop-like elements upstanding from one surface and positioned about said lancets in generally parallel rows;
• (j) heating means positioned below said knitting zone and adapted to selectively engage the upper end portions of said rotating monofilamentary loop-like elements, said heating means having a temperature sufficient to melt the crest portions of the loop elements such that substantially all said hook-like engaging elements are formed of a first monofilamentary member interknitted into and upstanding from said base fabric, and the relative rotary motion between said loop elements and said heating means resulting in the formation of a second melt formed engaging member positioned at the free end portion of said first upstanding monofilamentary member interknitted into said base fabric and extending generally transversely thereof, said second melt formed transverse members each being generally asymetrically configured to have at least one end portion having a generally arcuate cross sectional configuration in a plane extending downwardly through said hook-like engaging elements and an opposite tapered end portion of lesser average thickness than said arcuate end portion and being of greater flexibility than said arcuate end portion, such that the fabric may be placed in face-to-face relation with such mating loop-type material with the result that numerous engagements take place between the hook-like and loop-like elements, and separated by forced substantially normal to the interfacial plane of engagement, the asymmetric configurations of said hook-like engaging elements being such that the forces required to separate the hook-like elements from engaged loop-like elements in a direction from the arcuate end portions toward the generally tapered end portions are greater than the forces required to separate the hook-like elements in the opposite direction;
• and
• (k) means positioned below said heating means for applying predetermined tension forces to said weft knitted material so as to stabilize said base fabric and upstanding loops during the application of heat and pressure to said loop members.

An apparatus for producing a weft knitted material having on one side a multiplicity of hook-like engaging elements suitable for repeated face-to-face engagement and disengagement with a material having a multiplicity of upstanding pile loop-like engaging elements, which includes a base knitted fabric, a plurality of upstanding hook-like engaging elements having substantially the said height, which comprises:

• (a) an upper cog wheel having a plurality of lancets secured thereto in a circular array and extending downwardly therefrom into a knitting zone;
• (b) a lower cog wheel positioned immediately below said upper cog wheel and a plurality of latch-type knitting needles positioned for rotation with said lower cog wheel for weft knitting said fabric;
• (c) means for rotating said upper and lower cog wheels at substantially the same rotational speeds;
• (d) means for reciprocating said latch needles upwardly and downwardly respectively, intermediate said lancets in an upward and downward weft knitting movement;
• (e) means for supplying heat-deformable yarn to said knitting zone for knitting the base fabric;
• (f) means for supplying monofilamentary heat-deformable yarn to said knitting zone;
• (g) means to guide said first-mentioned yarn to a position behind said lancets to form said base fabric;
• (h) means to guide said monofilamentary yarn to said knitting zone over said lancets to be interknitted with said base fabric simultaneously with its formation;
• (i) means for reciprocating said latch needles in an upward and downward and rotary motion intermediate said lancets to form in said knitting zone, a weft knit fabric having a plurality of monofilamentary loop-like elements upstanding from one surface and positioned about said lancets in generally parallel rows;
• (j) first heating means positioned below said knitting zone and adapted to heat said material to stabilize said base fabric and loops after formation;
• (k) heating means positioned below said first heating means and adapted to selectively engage the upper end portions of said rotating monofilamentary loop-like elements, said heating means having a temperature sufficient so as to apply heat to melt the crest postions of the loop elements such that substantially all said hook-like engaging elements are formed of a first monofilamentary member interknitted into and upstanding from aid base fabric, and the relative rotary motion between said loop members and said heating means resulting in the formation of a second melt formed engaging member positioned at the free end portion of said first upstanding monofilamentary member interknitted into said base fabric and extending generally transversely thereof, said second melt formed transverse members each being generally asymetrically configured to have at least one end portion having a generally arcuate cross sectional configuration in a plane extending downwardly through said hook-like engaging element and an opposite tapered end portion of lesser average thickness than said arcuate end portion and being of greater flexibility than said arcuate end portion, such that the fabric may be placed in face-to-face relation with such mating loop-type material with the result that numerous engagements take place between the hook-like and loop-like elements, and separated by forces substantially normal to the interfacial plane of engagement, the asymmetric configurations of said hook-like engaging elements being such that the forces required to separate the hook-like elements from engaged loop-like elements in a direction from the arcuate end portions toward the generally tapered end portions are greater than the forces required to separate the hook-like elements in the opposite direction;
• (l) means positioned below said heating means for applying predetermined tension forces to said weft knitted material so as to stabilize said base fabric and upstanding loops during the application of heat and pressure to said loop members.