Set screw

#1. Field of the Invention

#This invention relates to improvements in set screws and more particularly, but not by way of limitation, to a set screw adapted to require minimum torque in use.

#2. Description of the Prior Art

#FIG. 1 is a bottom view of a set screw embodying the invention.

#FIG. 2 is a view taken on line 2--2 of FIG. 1.

#FIG. 3 is a view taken on line 3--3 of FIG. 1.

#Referring to the drawings in detail, reference character 10 generally indicates a set screw comprising a shank 12 having a threaded portion 14 at one end thereof and a head member 16 at the opposite end thereof. The head member 16 may be of any normal or standard type, and as shown herein preferably of a substantially square cross sectional configuration for facilitating rotation of the screw 10 by engagement of the flat sides of the head 16 by a suitable tool (not shown) or manually, as desired and as is well known. The threaded portion 14 may also be of substantially any normal or standard thread construction, as desired. However, it is to be noted that the particular design of the screw 10 is such that a national course thread may be utilized for the threaded portion 14, if desired.

#The outer end of the threaded portion 14 is provided with a cutting element generally indicated at 18 which is constructed for penetrating the outer periphery of a pipe section (not shown) or the like with which the screw 10 is to be utilized. The particular cutting element 18 shown herein comprises a pair of substantially pie-shaped segments 20 and 22 extending axially outwardly from a substantially flat or planar surface 24. The inner end of each segment 20 and 22 is disposed at the center or longitudinal axis of the shank 12 and are preferably conterminous with each other, as particularly shown in FIG. 4. The outer surface of each segment 20 and 22 is of a compound taper, increasing in both a radially outward direction from the conterminous inner ends thereof and a circumferential direction about the axis of the shank 12. In this manner, the segments 20 and 22 are provided with a cutting edge or point 26 and 28, respectively. In addition, the conterminous inner ends of the segments 20 and 22, or the central portion of the cutting element 18 is recessed with respect to the position of the cutting edges 26 and 28.

#In use, the set screw 10 may be inserted into the usual threaded bore (not shown) normally provided in the sidewall of a bell fitting (not shown) such as the type hereinbefore set forth. The screw 10 may be rotated about its own longitudinal axis in the usual manner, such as by engaging the flat sides of the head member 16 with a suitable tool for rotation of the screw. When the screw has been moved through the threaded bore a sufficient distance as to bring the cutting element 18 into the proximity of or into engagement with the outer periphery of the pipe (not shown) disposed within the bell fitting, the cutting edges 26 and 28 will initially engage the pipe. Continued rotation of the screw 10 will cause the cutting edges 26 and 28 to readily penetrate the outer periphery of the pipe. The compound taper of the outer surface of the segments 20 and 22 facilitates the penetration of the cutting edge 26 and 28 into the pipe. The fact that the taper "falls away" in both a circumferential and a radial direction reduces the amount of surface engaged with the pipe during the penetration or "biting" action of the segments 20 and 22, thus reducing the friction between the segments and the pipe. The "biting" engagement of the outer periphery of the pipe may thus be achieved with considerably less torque applied to the screw 10. Thus, the stress applied to the cement lining of the pipe or fitting is considerably reduced, and the danger of damage to the cement is substantially eliminated.