Patent Application
20110044785
The present invention generally relates to a method for manufacturing a screw with a chip discharge channel and a product thereof, and more particularly to a method for manufacturing a self-drilling screw or a self-tapping screw that is used to joint to objects and a screw manufactured with the method.
To joint two objects or to joint a steel plate and a non-ferrous material, a self-drilling screw or a self-tapping screw is often used. The advantage of the self-drilling screw or the self-tapping screw is that it can secure objects without making a hole or tapping a hole in advance so that it is often used to secure a corrugated steel plate roofing, wooden furniture, steel cabinets, fences, and aluminum doors/windows. A brief description of the self-drilling screw and the self-tapping screw will be given below.
However, although this known self-drilling screw 1 provides two symmetric chip discharge channels 142 in the drilling bit section 14, the cutting edges 144 are arranged at the intersections between the chip discharge channels 142 and the circumference of the drilling bit section 14. This makes the chip discharge channels 142 terminating at the intersection thereof with the first turn of the threads, which form ends 145 of the channels. Consequently, the remaining turns of the threads are not provided with any chip discharge space and the material chips removed by the cutting operation induced by fastening the screw may get jammed due to being blocked by the channel ends 145, which may lead to high temperature that leads to tempering and blunting of the drilling edges 143. Eventually, the drilling edges 143 are no longer capable to carry out further cutting and may even get broken. Further, most turns of the threads are not provided with chip discharge channels and thus, they cannot form a tapping edge to facilitate insertion of the screw so that the threads are often forcibly pushed into the workpiece, leading to poor fastening.
Taiwan Patent Application Nos. 96215648 and 96119066, which respectively disclose an improved structure of self-drilling screw and a method for manufacturing a self-drilling screw and a product thereof, are illustrated in FIGS. 2 and 3. The self-drilling screw 2 illustrated in these documents comprises a head 21 and a shank 22 extending from a bottom of the head 21. The shank 22 has a circumferential surface forming two sections of external threads 23 and has a free end forming a drilling bit section 24. The drilling bit section 24 has an end forming a conic surface 241, which forms in the circumference thereof two inclined chip discharge channels 242 that are symmetrically arranged and also forms a lip 243 that has a substantially square or rectangular cross-section on the circumference adjacent to one bank of each chip discharge channel 242, as shown in
To carry out fastening operation with the known self-drilling screw 2, the drilling edges 244 and the cutting edges 245 cut into and remove a portion of the material of an object so as to guide the external threads 23 of the self-drilling screw 2 to gradually penetrate into the object. Meanwhile, the material chips that are removed during the fastening operation are discharged by moving upward of the drilling bit section 24 along the inclined chip discharge channels 242. With the opposite lips 243 formed on the circumference of the drilling bit section 24, a chip discharge space is formed around the circumference of the drilling bit section 24 to facilitate discharging of chips and thus prevent over heating caused by chip jamming.
The above described structure of the known self-drilling screw 2 is effective in realizing fastening the screw. However, the opposite lips 243 are formed on the circumference of the drilling bit section 24 and the lips 243 form an outside diameter that is greater than the outside diameter of the drilling bit section 24. A fastening operation with the self-drilling screw is often carried out by manually operated power tools so that due to the vibration of the screw itself in the course of fastening and the scrapping effect induced by the cutting edges 245 of the lips 243, when the drilling bit section 24 cuts into an object, a hole, which is made in the object, must be of a slightly expanded diameter, making it substantially corresponding to the outside diameter of the threads 23 thereby leading to poor fastening result. Further, in the manufacturing of the self-drilling screw 2, two jigs are employed to respectively and securely hold an unthreaded bar-like blank and an end of the drilling bit section 24 for twisting a predetermined angle, so as to make the chip discharge channels 242 and the cutting edges 245 of the drilling bit section 24 symmetrically helical. Afterwards, the bar-like blank is subjected to formation of the external threads 23 on the circumference thereof. Consequently, the chip discharge channels 242 can only be formed to terminate at the intersection thereof with the first turn of the threads 23, which form ends 246 of the channels, and the channels do not extend to the remaining turns of the threads 23. In this method of manufacturing, if the chip discharge channels 242 are to be extended into the threads, due to the twisting operation that forms the chip discharge channels 242, the external threads 23 that are formed earlier than the chip discharge channels 242 would be deformed to change the distance between adjacent turns of the thread, or in case that the chip discharge channels 242 are formed earlier than the threads, then the formation of the threads would cause excessive material generated by rolling of the thread crest to jam the chip discharge channels 242 and thus blocking the chips to be discharged, so that the cutting edges 245 do not have sharp edges and the performance of discharging chips and tapping is reduced.
Although the self-tapping screw 3 is effective in tapping and screwing into an object to fasten the object, yet the chip discharge channel 33 is of a configuration having a 90-degree included angle 331. Due to the external diameter chord length of the milling blade, the chip discharge channel 33 is often made very short, around 12 mm, and this length of the chip discharge channel is apparently insufficient for discharging chips for long screws. Thus, when the conventional self-tapping screw 3 is applied to tap a hole of an object, the chips generated by the tapping operation will be curved by the thread 321 of the shank 32 and residual chips will be blocked by the included angle of the chip discharge channel 33 to build up or jam due to the short chip discharge channel and cannot be smoothly discharged through the chip discharge channel 33, leading poor discharging of the chips in the self-tapping screw 3, eventually affecting the screwing and tapping operation of the self-tapping screw 3 and possibly causing improper shape of the tapped thread and poor fastening.
In view of the above discussed self-drilling screws 1 and 2 and the self-tapping screw 3, it is a challenge of the mechanical part manufacturers to develop and provide a screw that may simply the manufacturing thereof, prevent the expansion of hole, and smoothly discharge chips.
The primary objective of the present invention is to provide a method for manufacturing a screw with helical chip discharge channel. The method first provides a round-bar like metal material, and uses a screw forming machine to cut the round-bar like metal material into a blank of a predetermined length. The bar is subjected to pressing operation by a pressing machine to form a head. The bar is then subjected to rolling with a thread rolling machine to form one or more sections of threads. A free end of the threaded bar is rolled or milled to form a drilling bit section and at least one helical chip discharge channel. The chip discharge channel may have any desired helical angle according to different applications. As such, a product of a screw which has a with helical chip discharge channel extending into the thread section to form tapping edges is made.
Another objective of the present invention is to provide a self-drilling screw with helical chip discharge channel. After a blank is provided, the blank is cut into a bar of a predetermined length. An end of the bar is subjected to pressing to form a head. The bar is then subjected to rolling to form one or more sections of threads. In the course of the rolling operation, a drilling bit, the threads, and the chip discharge channel are formed simultaneously with the chip discharge channel extending into the thread section. The helical drilling bit section of the screw is processed by rolling to form the one or more helical chip discharge channels and the chip discharge channels are of the length extending into the threads of the thread sections to form tapping edges. As such, the tapping edges of the threads may serve as cutting surfaces for tapping operation so as to improve the functions of chip discharging and secured fastening of the self-drilling screw.
A further objective of the present invention is to provide a self-tapping screw. After a blank is provided, the blank is cut into a bar of a predetermined length. An end of the bar is subjected to pressing to form a head. The bar is then subjected to rolling to form threads. The bar is processed to form one or more helical chip discharge channels by milling or rolling so as to form tapping edges. As such, the tapping edges of the threads may serve as cutting surfaces for tapping operation so as to improve the quality of thread tapping and the smoothness of chip discharging of the self-drilling screw, as well as secured fastening thereof.
A further objective of the present invention is to provide a self-tapping screw of which the manufacturing method is that after a blank is cut to a predetermined length, an end of the blank is subjected to pressing to form a head and a body of the blank is subjected to rolling of threads. One or more helical chip discharge channels are formed at the same time that a middle portion of the blank is carried out thread rolling. Afterwards, a milling blade further cuts the chip discharge channel that does not extend to the end of the blank to have the new cut portion jointing to and communicating the chip discharge channel. This composite machining process makes tapping edges formed by the tail end chip discharge channel effort saving and the discharging of chip smoother, and the fastening more secured.
The foregoing objectives and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts.
Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.
The following descriptions are exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims.
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To summarize, the present invention provides a method for manufacturing a screw having a chip discharge channel and a product thereof, which effectively overcome the problem of chip jamming in the conventional self-drilling screws and self-tapping screws due to the chip discharge channel being tool short and improves the smoothness of chip discharging, saves effort in tapping a hole, provides excellent shape of tapped thread, and securely fastens an object.
While certain novel features of this invention have been shown and described and are pointed out in the annexed claim, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.
