The present invention relates to a threaded fastener and, more particularly, o a countersunk screw.
Screws are common threaded fasteners which include different types. Amid these threaded fasteners, a so-called countersunk screw means that when the screw is fastened to a workpiece, its head is level with the surface of the workpiece.
However, a plank surface around a screw head bulges easily when a common countersunk screw is screwed in the plank surface. In most cases, when a plank is screwed and fastened by a screw, waste chips, which are being cut by and removed outward through the screw thread and accumulated in gaps between the screw and the plank, get stuck in underneath of the screw head and squeezed by the screw head such that a plank surface around the screw head bulges. In addition, a conventional countersunk screw is often provided with a cone portion below the screw head thereof to facilitate the digging of the accommodating space for the screw head to be buried. However, a bulge is observed on a plank surface when the plank which is being bored invasively is squeezed and stretched outward by the cone portion.
A screw as disclosed in the U.S. Pat. No. 9,624,961 includes a shank having an insertion tip and a head end spaced from the insertion tip along a longitudinal axis. The shank has a straight portion between the insertion tip and the head end. The head end includes an upper portion and a lower portion which is adjacent to an upper end of the straight portion and tapered toward the straight portion. A plurality of anti-screw-out teeth protrude from a. circumferential surface of the lower portion. Each anti-screw-out tooth includes a guide face and a stop face, both of which intersect each other for development of a ridgeline. A recessed channel is formed between the stop face and the circumferential surface for receiving wood chips. At a bottom of the upper portion is circumferentially designed a pointed cutting portion by which wood chips or debris can be cut. A slope is provided on an inner side of the cutting portion, and a recess is formed between the cutting portion and the circumferential surface of the top end of the lower portion. When the screw is screwed into a plank for development of a drilled hole, wood chips released from the drilled hole are accommodated in the recessed channel or the recess for good flatness of a surface of the plank in which the screw is fastened. However, the recess formed between the cutting portion and the circumferential surface of the lower portion is a V-shaped groove, and is unsatisfactory in its accommodating volume. Thus, when a plank is cut by the pointed cutting portion, wood chips will still accumulate outside the recess and the squeezed plank bulges around the head end of the screw. Accordingly, the flatness of the plank surface is poor because of bulges between the head end of the screw and the plank surface.
It is an objective of the present invention to provide a threaded fastener including a head with an annular groove therein such that more waste chips can be accommodated in the annular groove and no bulge is detected on a workpiece surface when the threaded fastener is screwed in a workpiece.
To achieve this and other objectives, a threaded fastener of the present invention includes a head, a shank, and a cone portion. The shank extends from the head and defines a longitudinal axis. A thread is provided on the shank. The head includes a top portion and an annular side wall extending downwardly from a periphery of the top portion along the longitudinal axis. The cone portion is formed between the shank and the top portion and has a peripheral surface tapering from the top portion to the shank. An annular groove is created between the annular side wall of the head and the cone portion for development of an accommodating space with an opening downward. The annular groove is surrounded by an inner surface of the annular side wall, the peripheral surface of the cone portion, and a bottom wall of the top portion connected between the annular side wall and the cone portion. The bottom wall of the top portion extends in a radial direction of the head and separates the annular side wall from the cone portion.
In an embodiment, the accommodating space in the annular groove has a trapezoid cross section.
In an embodiment, the inner surface of the annular side wall is developed as a slope, and an edge portion is formed at a lower end of the annular side wall.
In an embodiment, a serrated edge portion is formed at a lower end of the annular side wall.
In an embodiment, the peripheral surface of the cone portion is provided with a. plurality of ribs extending in the radial direction.
In contrast to prior arts, a threaded fastener of the present invention features advantages as follows:
1. An annular groove is designed in a bottom of the head of the threaded fastener and characteristic of a bottom wall of the top portion of the head through which the annular side wall and the cone portion are separated from each other for development of a larger accommodating space in the annular groove. When a plank is bored by the threaded fastener invasively and downward, the accommodating space holds more waste chips in the annular groove for no bulge around the threaded fastener's head due to waste chips squeezed by the head.
2. With an approximately trapezoid accommodating space inside, the annular groove of the threaded fastener accommodates a bulge on a plank surface stretched and squeezed by the cone portion of the threaded fastener outward for no bulge around threaded fastener's head after both the threaded fastener and the plank are coupled with each other.
3. With the inner surface of the annular side wall developed as a slope and spaced from the cone portion for a larger accommodating space in the annular groove, waste chips cut by the annular side wall are held in the annular groove directly for no waste chips accumulated.
The present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings.
All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiments will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood.
Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms “inner”, “side”, “end”, “portion”, “top”, “bottom”, “annular”. “longitudinal”, “downwardly”, “radial”, “length”, and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention.
A threaded fastener 10 according to a first embodiment of the present invention is shown
The scope of the invention to be indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.