Threaded fastener with stabilizing threads

Claim 2

A screw-type fastener adapted to fasten a thin sheet of material to a thicker sheet spaced by a predetermined thickness of insulating material, said fastener including a shank having a work clamping head integrally formed on one extremity of the shank, a drilling tip formed on the opposite extremity of the shank, a first section of thread convolutions adjacent the work clamping head and extending for a limited axial extent along the shank, a second section of thread convolutions extending for a limited axial extent adjacent the drilling tip and axially spaced from the first section of thread convolutions, a third section of threads formed on the shank intermediate the first and second thread sections for stabilizing and controlling the drop of the fastener through the insulating material, the outer diameter of the third section of threads being greater than the outer diameter of the second section of threads and less than the outer diameter of the first section, rigid abutment means located on the shank intermediate the third section of threads and the second thread section, said rigid abutment means extending radially a distance greater than the root diameter of the convolutions of the second thread section, unthreaded means between the first and third thread sections to insure that the drilling of the thicker sheet is not impeded by restriction to axial movement of the fastener, whereby, the third section of threads controls and stabilizes the drop-through of the fastener in the insulation material prior to the engagement of drilling tip with the thicker sheet of material while allowing free drilling operation thereof.

Claim 3

A screw-type fastener as set forth in claim 1, wherein the first section of thread convolutions has a pitch and outer diameter greater than the pitch and outer diameter of the second section of threads.

Claim 4

In combination with a panel structure consisting of an inner section of insulating material of substantial thickness bounded on one side by a first relatively thin sheet of material and on the opposite side by a second sheet of thicker material, a screw-type fastener having a shank completely traversing said panel structure, a head at one extremity of the shank clampingly urged against the relatively thin first sheet of material, a first section of thread convolutions of relatively high pitch extending for a limited axial extent along the shank from the vicinity of the clamping side of the head, a drilling tip at the other extremity of the shank, a second section of thread convolutions having a pitch less than the first section adjacent the drilling tip and extending for a limited axial extent toward the first threaded section, a third section of thread convolution means for controlling the rate of entry of the fastener into the panel located between the first and second section and separated from said first and second sections by unthreaded portions of the shank the unthreaded portion extending between the second and third threaded portion including winged abutment means having a diameter greater than the outer diameter of the second threaded section and less than the outer diameter of the third threaded section, the unthreaded shank portion extending between the first threaded portion and the third threaded portion, being of an axial extent not less than the length of the drilling tip to insure unrestricted application of drilling force to be applied to the thick second sheet of material, the outer diameter of the first threaded section being greater than the second and third threaded sections as well as being greater than the abutment wings and unthreaded portions, the axial extent of the shank from the lower extremity of the drilling tip to the upper extremity of the third threaded section being substantially equal to the thickness of the insulating material, whereby a fastener is forced through the panel at a controlled rate due to the interaction of the third threaded section with thin sheets of material while the unthreaded shank portion between the first threaded section and third threaded section allows the drilling tip to proceed through the second sheet of material without limiting axial movement thereof.

Claim 5

In combination with a panel structure consisting of an inner section of insulating material of substantial thickness bounded on one side by a first relatively thin sheet of material and on the opposite side by a second sheet of thicker material, a screw-type fastener having a shank completely traversing said panel structure, a head at one extremity of the shank clampingly urged against the relatively thin first sheet of material, a first section of thread convolutions of relatively high pitch extending for a limited axial extent along the shank from the vicinity of the clamping side of the head, a drilling tip at the other extremity of the shank, a second section of thread convolutions having a pitch less than the first section adjacent the drilling tip and extending for a limited axial extent toward the first threaded section, a third section of thread convolution means for controlling the rate of entry of the fastener into the panel located between the first and second section and separated from said first and second sections by unthreaded portions of the shank the unthreaded portion extending between the second and third threaded portion including winged abutment means having a diameter greater than the outer diameter of the second threaded section and less than the outer diameter of the third threaded section, the unthreaded shank portion extending between the first threaded portion and the third threaded portion, being of an axial extent not less than the length of the drilling tip to insure unrestricted application of drilling force to be applied to the thick second sheet of material, the outer diameter of the first threaded section being greater than the second and third threaded sections as well as being greater than the abutment wings and unthreaded portions, the axial extent of the shank from the lower extremity of the drilling tip to the upper extremity of the third threaded section being substantially equal to the thickness of the insulating material, whereby a fastener is forced through the panel at a controlled rate due to the interaction of the third threaded section with thin sheets of material while the unthreaded shank portion between the first threaded section and third threaded section allows the drilling tip to proceed through the second sheet of material without limiting axial movement thereof.