Patent Grant
11820037
The present disclosure relates to a draw stud having a multi-start thread for use with a punch having a multi-start thread, and methods of engaging same.
In the commercial electrical contractor market, many jobs start with installing conduit runs for connecting wires between electrical boxes. During installation, holes must be formed in electrical boxes and various other sheet metal components to feed the wire and conduit therethrough. A punch system is commonly used in this operation.
Some prior art punch systems include a draw stud, a die, a punch and a nut. The punch is seated on a first end of the draw stud and secured thereto by threading the nut onto the first end of the draw stud. The die is seated on a second end of the draw stud.
The operator drills a pilot hole approximately in the center of the area where the final hole needs to be located. The draw stud, which has been attached to a driver, has the die slid over its free end until the die abuts the driver. The draw stud is then inserted with its free end first through the pilot hole until the die is seated against one side of a sheet metal. The knockout punch, which has a central hole with internal threads, is seated onto the free end of the draw stud until the knockout punch impinges onto the side of the sheet metal opposite the side on which the die is located. The nut is then attached to the draw stud to secure the punch to the draw stud. As a result, the sheet metal is snugly captured on both sides by the die and punch. Finally, the driver is actuated such that the draw stud and the knockout punch are drawn toward the driver, supplying sufficient force to the knockout punch to puncture and cut the sheet metal and produce the final hole.
The driver is operated manually or hydraulically. Overall, this punch system works well, however, the most time consuming task is attaching the knockout punch onto the draw stud, which can take as long as thirty to sixty seconds to accomplish depending on the length of the draw stud. This can be frustrating and inefficient for the operator, especially when a great number of holes need to be punched.
A punch according to some embodiments of the disclosure includes a body having a punching edge and a wall forming a passageway therethrough, the wall having a multi-start thread formed thereon, and a draw stud according to some embodiments of the disclosure includes an elongated cylinder having a multi-start thread thereon which is configured to be coupled to the multi-start thread of the punch. The number of starts provided on the punch corresponds to the number of starts provided on the draw stud. The multi-start thread on the punch is engaged with the multi-start thread on the draw stud in use.
A method of punching a hole includes forming a pilot hole in sheet metal, attaching a draw stud to a driver, sliding a die over a free end of the draw stud until the die is proximate to the driver, inserting the free end of the draw stud through the pilot hole until the die is seated against one side of the sheet metal and engaged with the driver, engaging a multi-start thread of a knockout punch with a multi-start thread of the draw stud, wherein a number of starts provided on the punch corresponds to a number of starts provided on the draw stud, rotating the knockout punch in a first direction to thread the knockout punch onto the free end of the draw stud until the knockout punch impinges onto a side of the sheet metal opposite the side on which the die is located, and actuating the driver to draw the draw stud and the knockout punch toward the die and to puncture and cut the sheet metal and produce a final hole.
This Summary is provided merely for purposes of summarizing some example embodiments so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example embodiments are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other embodiments, aspects, and advantages of various disclosed embodiments will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments.
The organization and manner of the structure and operation of the disclosed embodiments, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, which are not necessarily drawn to scale, wherein like reference numerals identify like elements in which:
While the disclosure may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that as illustrated and described herein. Therefore, unless otherwise noted, features disclosed herein may be combined together to form additional combinations that were not otherwise shown for purposes of brevity. It will be further appreciated that in some embodiments, one or more elements illustrated by way of example in a drawing(s) may be eliminated and/or substituted with alternative elements within the scope of the disclosure.
As shown in
The draw stud 22 has an elongated cylindrical body 34 and has an unthreaded cylindrical dog point 36 integrally formed therewith and extending longitudinally from a front end 38 thereof. The body 34 and the dog point 36 extending therefrom define a longitudinal centerline axis 40. The body 34 has a multi-start external thread 42, 142, 242 formed thereon which extends distally from the dog point 36, and a driver attachment 44, 44a extending proximally from a second end 46 thereof. The multi-start external thread 42, 142, 242 is configured to be coupled to the punch 26. The driver attachment 44, 44a is configured to be coupled to the driver 32, 32a. The draw stud 22 has a central section 48 extending between the multi-start external thread 42, 142, 242 and the driver attachment 44, 44a.
As shown in the embodiment of
As shown in the embodiment of
As shown in the embodiment of
In an embodiment, the multi-start external thread on the draw stud 22 has five intertwined coarse helical threads (not shown), with the start of each thread being 72° apart from each other.
The multi-start thread 42, 142, 242 limits the number of rotations required to secure the punch 26 into position on the draw stud 22 by increasing the linear distance traveled over a single rotation. A single start thread has a much smaller lead than a four-start thread per revolution, and a draw stud having a single start punch would require the punch to rotate at least four times more than the draw stud 22 having four starts as shown in
In some embodiments, the central section 48 is unthreaded section (as shown) and has an outer diameter that is the same as, or larger than, the major diameter 58, 158, 258 of the multi-start external thread 42, 142, 242. In some embodiments, the central section 48 is threaded (not shown) and has an outer diameter defined by a major diameter of the threads that is the same as the major diameter 58, 158, 258 of the multi-start external thread 42, 142, 242.
In some embodiments, the dog point 36 defines an outer diameter 64 which is less than the minor diameter 60, 160, 260. In some embodiments, the outer diameter 64 of the dog point 36 is between about 95.5% to about 99.5% of the minor diameter 60, 160, 260. A radius or chamfer 66, as defined by angle θ, may be provided extending from a front end 68 of the dog point 36.
In a first embodiment as shown in
The die 24 is conventionally formed and includes a base wall 80 and a circular side wall 82 extending from the outer perimeter of the base wall 80. A recess 84 is provided by the inner surface of the base wall 80 and the side wall 82, and the recess 84 is in communication with an unthreaded central passageway 86 extending through the base wall 80. The central passageway 86 has a diameter which is slightly greater than the outer diameter of the central section 48 of the draw stud 22.
As shown in
The threaded section 102 threadedly mates with the multi-start external thread 42, 142, 242. The cone-shaped lead-in surface 106 extends at an angle μ of 45°±5° relative to the centerline axis 98 when viewed in cross-section. Angle μ may be equal to approximately 90°−β.
The coarse helical threads 50, 52, 54, 56, threads 150, 152, 154, or threads 250, 252 on the draw stud 22 are standard Unified coarse threads which maximizes the pitch length of the threads 50, 52, 54, 56, threads 150, 152, 154, or threads 250, 252, while keeping the desired shear strength. By using coarse threads 50, 52, 54, 56, threads 150, 152, 154, or threads 250, 252, the minor diameter 60, 160, 260 of the multi-start external thread 42, 142, 242 is not reduced as occurs when fine threads are used, and as such, the shear strength of the draw stud 22 is not impacted. Typically, when reducing the number of rotations required to move an inch, a fine thread is replaced with a coarse thread to lower the threads per inch and increase the pitch length and lead of the thread. For example, one could change the draw stud 22 from a UNF 0.75-16 to an UNC 0.75-10 thread. In the present disclosure, the multi-start external thread 42, 142, 242 maximizes the distance the punch 26 travels in a single rotation, while maintaining the shear strength of an equivalent single start thread form. This allows for the lead, or linear distance traveled in a single rotation, to be equal to the pitch multiplied by the number of starts. The four-start threads 50, 52, 54, 56 move about four times as far with a single rotation as a single start thread with equal threads per inch, the three-start threads 150, 152, 154 move about three times as far with a single rotation as a single start thread with equal threads per inch, and the two-start threads 250, 252 move about two times as far with a single rotation as a single start thread with equal threads per inch. Since the threads per inch was not lowered to obtain the desired linear distance per rotation, the shear strength characteristics of a typical UNF thread is maintained. As such, the multi-start thread 42, 142, 242 reduces the number of rotations need to fully fasten the punch 26 to the draw stud 22. This coarse thread pitch increases the travel distance of its respective UNF thread equivalent, while maintaining the internal and thread shear strength. This, combined with the multi-start thread 42, 142, 242, allows for the thread lead to be more than four times the pitch travel distance (coarse pitch multiplied by the number of starts equals distance traveled) for the four-start threads, allows for the thread lead to be more than three times the pitch travel distance (coarse pitch multiplied by the number of starts equals distance traveled) for the three-start threads, and allows for the thread lead to be more than two times the pitch travel distance (coarse pitch multiplied by the number of starts equals distance traveled) for the two-start threads. For example, a four-start thread can move more than four times as far as its UNF single start equivalent, a three-start thread can move more than three times as far as its UNF single start equivalent, and a two-start thread can move more than two times as far as its UNF single start equivalent. Therefore, the speed of assembly of the punch 26 with the draw stud 22 is at least two times faster than a single start thread per hole completion, and the speed of disassembly of the punch 26 from the draw stud 22 is at least two times faster than a single start thread per hole completion.
The friction between the draw stud 22 and the punch 26, combined with the angle α of the intertwined helical threads 50, 52, 54, 56, threads 150, 152, 154, or threads 250, 252, is great enough to resist the reverse rotation of the punch 26 when the draw stud 22 and punch 26 are drawn toward the driver 32, 32a. As a result, the punch 26 and the draw stud 22 are self-locking when the punch 26 is threaded onto the draw stud 22. This prevents back-driving of the punch 26 when the draw stud 22 is being rotated.
In the embodiment which provides four intertwined coarse helical threads 50, 52, 54, 56, the start of the threading process of threading the punch 26 onto the draw stud 22 is improved over a single start thread since the four intertwined helical threads 50, 52, 54, 56 provide four starts at 90° versus one start at 360°, however, more torque is required versus a single thread. In the embodiment which provides three intertwined helical threads 150, 152, 154, the start of the threading process of threading the punch 26 onto the draw stud 22 is improved over a single start thread since the three intertwined helical threads 150, 152, 154 provide three starts at 120° versus one start at 360°, and less torque is required than in the embodiment where four intertwined coarse helical threads 50, 52, 54, 56 are used. In the embodiment which provides two intertwined coarse helical threads 250, 252, the start of the threading process of threading the punch 26 onto the draw stud 22 is improved over a single start thread since the two intertwined helical threads 250, 252 provide two starts at 180° versus one start at 360°, and less torque is required than in the embodiment where three intertwined coarse helical threads 150, 152, 154 are used.
The geometry of the dog point 36 and the counterbore 100 assists in the alignment of the draw stud 22 with the punch 26 and assists in preventing cross threading of the punch 26 and the draw stud 22. In an embodiment, the dog point 36 has a length of ¼″ for both a 7/16-14 draw stud 22 and for a ¾-10 draw stud 22. This provides sufficient length to align the draw stud 22 to the punch 26 and for part stability. Since the diameter 64 of the dog point 36 is reduced relative to the minor diameter 60, 160, 260 of the multi-start external thread 42, 142, 242 and the cone-shaped lead-in surface 62, 162, 262 is provided, this maximizes the area of the thread transition on cut thread transitions. The angle μ of the unthreaded cone-shaped lead-in surface 106 is the same as the angle β of the cone-shaped lead-in surface 62, 162, 262)(45°±5°. The combination of the transition angles and the dog point 36/counterbore 100 maximize the surface area contact of the threads 50, 52, 54, 56, the threads 150, 152, 154 or the threads 250, 252 with the threaded section 102 of the punch 26.
The provision of the dog point 36, the cone-shaped lead-in surface 62, 162, 262, and the geometry of the threads 50, 52, 54, 56, the threads 150, 152, 154, or the threads 250, 252 makes the punch 26 resistant to cross threading. The ease of function to assemble the punch 26 with the draw stud 22 is independent of the manufacturing process used to manufacture the punch 26 and draw stud 22. The threads 50, 52, 54, 56, the threads 150, 152, 154, or the threads 250, 252 can be created by forming the geometry or cutting the geometry works. Typically, internal threads are single point cut, or tapped, and external threads can be single point cut or roll threaded. The cone-shaped lead-in surface 62, 162, 262 and the counterbore 100 are machined independently of the threading operation making the mating surfaces compatible without concern of the processes utilized.
When the draw stud 22 is inserted into the punch 26, the cone-shaped lead-in surface 62, 162, 262 may engage with the central passageway 96 at the front end 92 and this causes the draw stud 22 to move inward toward the centerline axis 98 of the punch 26. As the draw stud 22 is further inserted into the punch 26, the cone-shaped lead-in surface 62, 162, 262 may engage with the cone-shaped lead-in surface 106 which causes the draw stud 22 to move until the centerline axis 40 of the draw stud 22 aligns with the centerline axis 98 of the punch 26. The cone-shaped lead-in surface 62, 162, 262 helps to align by creating a larger surface contact between the interface of the draw stud 22 and the punch 26.
Coarse threads are typically used in applications where a large torque load is generated and thread stripping or thread damage can result. This coarse pitch form is desirable for punching knockout applications, because the force used in punching are greatest in large diameter knockouts or in thicker plate steel. Coarse pitch threads have a deeper thread profile and the multi-start thread has a smaller thread start geometry. The cone shapes of the lead-in surface 62, 162, 262 and the lead-in surface 106 deter misalignment of the matching thread profiles and better expose the thread start. This allows for the multi-start lead thread starts to find the prospective mating parts start. Multi-start threads have a tendency to cross-thread, making it difficult for the operator to begin assembly. With the present geometry, the dog point 36 finds the center of the passageway 96 of the punch 26, while the cone-shaped lead-in surface 62, 162, 262 completes the thread alignment process by axially aligning the draw stud 22 and the punch 26 together.
In an embodiment as shown in
Many modifications and other embodiments of the disclosure set forth herein will come to mind to one skilled in the art to which these disclosed embodiments pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure is not to be limited to the specific embodiments disclosed herein and that modifications and other embodiments are intended to be included within the scope of the disclosure. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the disclosure. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated within the scope of the disclosure. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
While particular embodiments are illustrated in and described with respect to the drawings, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the appended claims. It will therefore be appreciated that the scope of the disclosure and the appended claims is not limited to the specific embodiments illustrated in and discussed with respect to the drawings and that modifications and other embodiments are intended to be included within the scope of the disclosure and appended drawings. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the disclosure and the appended claims.
This application claims priority to U.S. provisional application Ser. No. 63/228,339, filed on Aug. 2, 2021, the contents of which are incorporated herein in its entirety.
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