Abstract The embodiment of the invention disclosed herein is directed to a push type fastener and method of using the same in the securing of a workpiece to a member formed of pliable plastic having substantial amounts of resiliency. The fastener has a head portion which can receive a driving tool for pushing the fastener into the pliable plastic material until the head portion of the fastener abuts the surrounding wall of the workpiece. A threaded shank has a leading guide portion including substantially circular, reduced diameter threads formed therealong and a trailing portion including substantially non-circular, multilobular enlarged diameter threads which extend from the leading guide portion to the head portion. The threads have a front flank sloping toward the leading end of the shank at an angle to allow the pliable, resilient material to slide easily over the threads while the fastener is being inserted. The rear flank of the threads are disposed at a more abrupt angle to resist pull out. During seating of the fastener, which by pushing or driving the fastener into the plastic material without turning said fastener, the non-circular thread form on the trailing portion will form the recess wall to a corresponding slope, i.e. non-circular. Accordingly, upon rotation of the fastener a quarter turn after seating, two results are obtained; first the lobes on the fastener will be firmly engaged in the relatively flat portions of the aperture wall to provide a locking action, and secondly, the fastener will seat more firmly.
A push-type threaded fastener designed to be driven into an opening formed in pliable resilient material without rotation thereof, and when seated, rotated to provide a locking action which resists inadvertent rotation thereof, said fastener comprising in combination; a head portion to abut the material around the opening receiving the fastener, a threaded shank having a leading guide portion adjacent the work-entering end of said fastener and a trailing locking portion intermediate said guide portion and said head portion, said leading guide portion including a plurality of thread turns of a generally circular configuration with a crest diameter of said thread turns increasing in a direction away from said work-entering end; said trailing portion including a plurality of thread turns of a noncircular, multilobular configuration, said non-circular threads having a maximum crest height at the lobe portions thereof which is greater than the maximum crest height of said circular thread turns on said leading guide portions, both said circular and noncircular threads having a sloped front flank surface facing toward the leading end of said threaded shank to allow the pliable, resilient material easily to slide thereof as the fastener is driven into the opening formed in said material, and a sloped rear-flanked surface facing toward head portion, said front flank defining a flank angle from about 40* to 60*, with said rear flank defining a flank angle from about 20* to 0*, such that the included angle is approximately 60*, with said flank surfaces merging smoothly to define a crest apex over which said resilient material will flow and conform to the shape of said crest apex to be disposed on opposite sides thereof thereby providing means which resists pullout, wherein said fastener may be rotated a fractional part of a revolution to cause said lobular portion on the trailing non-circular thread to bite into the resilient material and afford a locking action which resists inadvertent rotation.
Claim 2
Dependent Claim
318 words
A push-type threaded fastener designed to be driven into an opening formed in pliable resilient material without rotation thereof, and when seated, rotated to provide a locking action which resists inadvertent rotation thereof, said fastener comprising in combination; a head portion to abut the material around the opening receiving the fastener, a threaded shank having a leading guide portion adjacent the work-entering end of said fastener and a trailing locking portion intermediate said guide portion and said head portion, said leading guide portion including a plurality of thread turns of a generally circular configuration with a crest diameter of said thread turns increasing in a direction away from said work-entering end; said trailing portion including a plurality of thread turns of a noncircular, multilobular configuration, said non-circular threads having a maximum crest height at the lobe portions thereof which is greater than the maximum crest height of said circular thread turns on said leading guide portions, both said circular and noncircular threads having a sloped front flank surface facing toward the leading end of said threaded shank to allow the pliable, resilient material easily to slide thereof as the fastener is driven into the opening formed in said material, and a sloped rear-flanked surface facing toward head portion, said front flank defining a flank angle from about 40* to 60*, with said rear flank defining a flank angle from about 20* to 0*, such that the included angle is approximately 60*, with said flank surfaces merging smoothly to define a crest apex over which said resilient material will flow and conform to the shape of said crest apex to be disposed on opposite sides thereof thereby providing means which resists pullout, wherein said fastener may be rotated a fractional part of a revolution to cause said lobular portion on the trailing non-circular thread to bite into the resilient material and afford a locking action which resists inadvertent rotation.
Claim 3
Dependent Claim
21 words
The push type threaded fastener according to claim 1, wherein said non-circular, enlarged diameter threads are tri-roundular in the cross section.