Joint Structure

The present invention relates to joint structures and particularly to a joint structure fastened by a self-drilling, self-tapping screw.

It is an object of the invention to provide for joint structures of the above type wherein the attachment of the self-drilling, self-tapping screw is facilitated and the engagement thereof with the joint members is improved.

It is a particular object of the invention to provide for joint structures of the above type wherein chips produced by the drill portion of the screw do not hinder operation of the screw or prevent tight mating engagement of the joint members.

Other objects and advantages will become apparent from the following description and the appended claims.

With the above objects in view, the present invention in one of its aspects relates to a joint structure comprising, in combination, first and second juxtaposed members having mating adjacent surfaces, and a screw passing through and fastening the juxtaposed members together, the screw comprising a shank having a head at one end adjacent the first member, a drilling portion at the other end, and a tapping portion between the head and the drilling portion, the screw extending through a hole in the second member formed by the drilling portion of the screw, the mating surface of the second member adjacent the first member being formed with an elongated recess intersecting the hole, the tapping portion of the screw being in threaded engagement with the second member adjacent the recess, whereby chips formed by action of the drilling portion of the screw collect in the elongated recess and the mating adjacent surfaces of the juxtaposed members are in close mating engagement.

The invention will be better understood from the following description taken in conjunction with the accompanying drawing, in which:

FIG. 1 is an elevational view of a self-drilling, self-tapping screw which may be employed in a joint structure embodying the invention;

FIG. 2 is a cross-sectional view of a joint structure embodying the invention;

FIG. 3 is a cross-sectional view of the rear joint member prior to assembly;

FIG. 4 is a front elevational view of the joint member shown in FIG. 3; and

FIG. 5 is a front elevational view of the rear joint member with screw attached showing collection of chips in the recess of the surface of that joint member.

Referring now to the drawing and particularly to FIG. 1, there is shown a self-drilling, self-tapping screw 1 of known type which may be used in the joint structure of the invention. Such screws have been extensively used heretofore for dispensing with the need to drill tap holes in metal members for the use of the screws therein. Screw 1 is formed with a shank 1a, drill portion 1b at one end, washer head 1c at the other end, and self-tapping helical threads 1d between the opposite ends of the screw.

FIG. 2 shows a joint structure which may be formed in accordance with the invention comprising a frame member 2, made for example of extruded aluminum, and a sheet metal member 3 fastened with adjacent surfaces in tight engagement by self-drilling screw 1. As seen in FIGS. 3 and 4, frame member 2 has a front surface 2a against which the rear surface 3a of sheet metal member 3 is pressed in the screw-fastened joint assembly. Member 3 has a hole 3b through which the shank of screw 1 passes and which is preferably oversized to avoid the necessity of drilling and tapping that member and the consequent production of metal chips and shavings which might fall between joint members 2 and 3. Channel 2c at the exit face of frame member 2 in the illustrated embodiment provides for insertion of screws at opposite ends to connect adjacent frame members together (not shown), and such a channel is not essential for the purposes of the present invention.

In accordance with the invention, an elongated slot or recess 2b is provided in the front surface 2a of frame member 2 into which self-drilling screw 1 is inserted in assembling the joint members. The entrance to slot 2b is beveled at top and bottom as shown. The depth of slot 2b is such that the remaining thickness of frame member 2 to be penetrated by screw 1 is less than the length of drilling portion 1b of the screw. The width of slot 2b is typically only slightly less than the diameter of the screw drilling portion, so that a minimum amount of metal is removed as that portion of screw 1 passes through slot 2b as it is rotated, and so that the threads of self-tapping screw portion 1d come into threaded engagement with the walls of slot 2b to thereby provide added thrust for drilling and firm anchoring of the screw in frame member 2. In the illustrated embodiment, the length of the tapping portion 1d is at least equal to the combined depth of slot 2b and the hole formed by drilling portion 1b.

In the fastening process, with sheet metal member 3 placed against front surface 2a of frame member 2, screw 1 is passed through clearance hole 3b of joint member 3 and is guided into slot 2b of frame member 2 by the beveled slot entrance. As the drill bit of screw 1 passes through the frame wall behind slot 2b, metal chips or shavings C are formed which are brought forward toward the entrance face of frame member 2 and collect in both directions in and along slot 2b on that surface, as seen in FIG. 5. As a result, the chips thus produced are not forced between the mating surfaces of the joint members and the possibility of sheet metal member 3 being outwardly displaced or separated from frame member 2 due to a buildup of the chips is entirely avoided.

In addition to the foregoing advantages, the provision of an elongated slot 2b as described and shown facilitates starting of screw 1 in the rear joint member, as well as locating and uniformly aligning the screws at the desired distance from the edge of the joint member to be engaged. Also, the provision of such a storage chamber for the chips produced during the fastening process avoids the possibility of the chips impeding the movement of the screw in that process or the action of the tapping portion of the screw.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the scope of the invention. Therefore, the appended claims are intended to cover all such equivalent variations as come within the true spirit and scope of the invention.