Abstract 1. In combination with apertured workpiece means, the provision of a thread forming fastener device particularly suitable for use with power drivers comprising: A. SHANK AND WORK-ENTERING END PORTIONS, B. A CONTINUOUS ROLLED TYPE THREAD ON BOTH SAID SHANK AND END PORTIONS, C. MEANS ON THE FASTENER FOR APPLYING AN OUTWARDLY ACTING AXIAL LOAD THERETO WHEN INSTALLED, D. THE THREAD ON SAID END PORTION BEING PROVIDED WITH A PITCH SURFACE WHICH IN CROSS SECTION IS OF ARCUATE TRIANGULAR LOBULAR CONFIGURATION HAVING ARCUATE SIDES WITH INTERMEDIATE ARCUATE LOBES AND EACH TRANSVERSE CROSS SECTION OF SUCH SURFACE IS OF EQUAL WIDTH THROUGHOUT 360*, E. THE THREAD ON SAID END PORTION BEING PROVIDED WITH A SERIES OF CIRCUMFERENTIALLY SPACED APART LOBES WITH THE LEADING SIDE OF EACH LOBE PROGRESSING FROM A POINT OF MINIMUM RADIAL DIMENSION FROM THE AXIS BETWEEN LOBES WHICH IS LESS THAN THE MAXIMUM RADIAL DIMENSION OF THE PRECEDING LOBE TO A MAXIMUM RADIAL DIMENSION AT THE CREST THEREOF WHICH IS GREATER THAN THAT OF THE PRECEDING LOBE DEFINING A SERIES OF PROGRESSIVE THREAD SWAGING SURFACES OF INCREASING RADIUS, THEREBY PROVIDING A RELATIVELY LOW DRIVING TORQUE FOR SAID DEVICE, F. THE DIFFERENCE BETWEEN THE MINIMUM AND MAXIMUM RADIAL DIMENSIONS OF ANY CROSS SECTION OF THE PITCH SURFACE OF THE THREAD ON SAID SHANK BEING NOT SUBSTANTIALLY MORE THAN TWOTHIRDS THE MAXIMUM DEPTH OF THE THREAD, WHEREBY WHEN SAID DEVICE IS AXIALLY LOADED, THE CONTINUOUS THREAD OF SAID SHANK PORTION MAY ENGAGE THROUGHOUT 360* WITH THE COMPLEMENTARY MATING THREAD FORMED DURING DRIVING OF SAID DEVICE INTO THE WORKPIECE MEANS TO PROVIDE A RELATIVELY HIGH STRIPPING STRENGTH FOR THE DEVICE, AND G. WHEREIN THE APERTURE IN THE WORKPIECE MEANS IS OF A SIZE RELATIVE TO THE SIZE OF FASTENER SUCH THAT THE EXTENT OF SWAGING ENGAGEMENT BETWEEN THE SWAGING SURFACES OF SUCCESSIVE LOBES WITH THE WORKPIECE MATERIAL AMOUNTS TO APPROXIMATELY 25% OR LESS OF THE PERIPHERAL EXTENT OF ONE TURN OF THE SCREW THREAD TO PROVIDE THE RELATIVELY LOW DRIVING TORQUE.
In combination with apertured workpiece means, the provision of a thread forming fastener device particularly suitable for use with power drivers comprising: a. shank and work-entering end portions, b. a continuous rolled type thread on both said shank and end portions, c. means on the fastener for applying an outwardly acting axial load thereto when installed, d. the thread on said end portion being provided with a pitch surface which in cross section is of arcuate triangular lobular configuration having arcuate sides with intermediate arcuate lobes and each transverse cross section of such surface is of equal width throughout 360*, e. the thread on said end portion being provided with a series of circumferentially spaced apart lobes with the leading side of each lobe progressing from a point of minimum radial dimension from the axis between lobes which is less than the maximum radial dimension of the preceding lobe to a maximum radial dimension at the crest thereof which is greater than that of the preceding lobe defining a series of progressive thread swaging surfaces of increasing radius, thereby providing a relatively low driving torque for said device, f. the difference between the minimum and maximum radial dimensions of any cross section of the pitch surface of the thread on said shank being not substantially more than twothirds the maximum depth of the thread, whereby when said device is axially loaded, the continuous thread of said shank portion may engage throughout 360* with the complementary mating thread formed during driving of said device into the workpiece means to provide a relatively high stripping strength for the device, and g. wherein the aperture in the workpiece means is of a size relative to the size of fastener such that the extent of swaging engagement between the swaging surfaces of successive lobes with the workpiece material amounts to approximately 25% or less of the peripheral extent of one turn of the screw thread to provide the relatively low driving torque.
Claim 2
Dependent Claim
328 words
In combination with apertured workpiece means, the provision of a thread forming fastener device particularly suitable for use with power drivers comprising: a. shank and work-entering end portions, b. a continuous rolled type thread on both said shank and end portions, c. means on the fastener for applying an outwardly acting axial load thereto when installed, d. the thread on said end portion being provided with a pitch surface which in cross section is of arcuate triangular lobular configuration having arcuate sides with intermediate arcuate lobes and each transverse cross section of such surface is of equal width throughout 360*, e. the thread on said end portion being provided with a series of circumferentially spaced apart lobes with the leading side of each lobe progressing from a point of minimum radial dimension from the axis between lobes which is less than the maximum radial dimension of the preceding lobe to a maximum radial dimension at the crest thereof which is greater than that of the preceding lobe defining a series of progressive thread swaging surfaces of increasing radius, thereby providing a relatively low driving torque for said device, f. the difference between the minimum and maximum radial dimensions of any cross section of the pitch surface of the thread on said shank being not substantially more than twothirds the maximum depth of the thread, whereby when said device is axially loaded, the continuous thread of said shank portion may engage throughout 360* with the complementary mating thread formed during driving of said device into the workpiece means to provide a relatively high stripping strength for the device, and g. wherein the aperture in the workpiece means is of a size relative to the size of fastener such that the extent of swaging engagement between the swaging surfaces of successive lobes with the workpiece material amounts to approximately 25% or less of the peripheral extent of one turn of the screw thread to provide the relatively low driving torque.
Claim 3
Dependent Claim
42 words
The combination of claim 1, wherein there is left approximately 75% of the screw thread out of engagement with the workpiece material during threading, whereby permissive stripping torque to driving torque ratios of the order of 6 to 1 may be attained.