The present invention relates generally to the field of drilling and specifically to small bore drilling of tubular plumbing components or material.
There exist many applications requiring a hole to be made in a tube. For example, in plumbing systems, there is often a need to add an apparatus, such as a chemical cleaner dispenser, to an existing system requiring a hole to be made in the systems tubing.
Current systems typically utilize a punching mechanism that concentrates the force in a singular point on the outside wall of the tube. Other systems simply have a continuous rough cutting surface that can tear material from the outside wall, eventually producing a hole. However, such prior art methods and apparatus for creating a hole in thin walled tubing often results in distortion of the tube, the generating of metal burrs, or the generating of other defects in the hole or tubing that make mating of the hole with another tube or device difficult.
It is preferential for aesthetic purposes, and vandal-resistance purposes or reduction of inadvertent damage that the hole be made on the portion of the tube facing the wall. However, this presents difficulty due to the small clearance space between the tube and the wall. As such, prior art systems either require removal or rotation of the tube to allow the hole to be drilled or the drilling of a hole through both walls of the tube and the subsequent capping of the unneeded hole.
The present invention relates to apparatus and methods for cutting a hole in a tube or a tubular plumping component. In one exemplary embodiment, the present invention relates to an apparatus having a saddle clamp and a cutting device. The saddle clamp affixes to a tube and includes a threaded chamber for receiving the cutting device. The cutting device is preferably cylindrical and is likewise threaded to engage the chamber and includes at one end a cutting edge for engaging and cutting the tube and, at the opposite end, an actuation point for rotating the cutting device. In one embodiment, the actual thread pitch is based on the number of cutting edges and their shape. In one embodiment, the cutting edges are of a specific shape on the cutting face, with the cutting edges having a specific relief angle.
These and other objects, advantages, and features of the invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the several drawings described below.
The present invention relates to methods and apparatus for cutting a hole in a tube. In one embodiment, illustrated in
The present invention includes as part of the system 101, a cutting device 120 which is engageable with the saddle clamp 105. In an exemplary embodiment shown in profile view in
In the present invention, the cutting edge 125 is discontinuous and is formed on at least one cutting tooth 132 which protrudes from the first end 121. In an exemplary embodiment, the cutting edge 125 is formed on multiple cutting teeth 132 which serve to stabilize the cutting device 120 during cutting, as each cutting tooth 132 enters the cut, the forces of other ones of the cutting teeth 132 engaged in the cut are counterbalanced.
To effect a cut, it is required that the cutting forces be concentrated between the cutting device 120 and the tube 103 being cut; thus generating a high local stress point on the tube 103. It is generally accepted that this condition is difficult to maintain as the cutting device 120 advances into and through the tube 103 as more of the cutting edge 125 comes into contact with the tube 103. The profile of the tube 103 to be cut can further complicate the process of cutting a hole, thereby making use of the described cutting device 120 more important.
The at least one cutting edge 125 engages a portion 133 of wall 134 of the tube 103 (see
Several factors that need to be balanced in determining the size and number of cutting teeth 132. For example, the cutting edge 125 can be designed to cut a range of different tube diameters, for example tubes ranging from ¾-inch to 1½-inch outside diameter with a wall thickness of approximately 1/32-inch. In one embodiment, a thicker wall section of the tube 103 could be cut by making the cutting device 120 longer. In one embodiment, the length of the cutting edge 125 is optimized for the tube wall thickness and the minimum clearance available to access the tube 103.
To highlight the challenge in cutting through a wide variety of tube diameters, one can compare the diameter of the hole cut by the cutting device 120 to the diameter of the tube 103 through which the hole is cut. In one embodiment, in the smallest diameter the ratio of cut hole to the tube diameter is 0.333 and in the largest case this ratio is reduced to 0.167. The large tube diameter being two-times larger, and therefore the surface to be cut is flatter.
In one embodiment, the cutting device 120 comprises a “fishtail” type design having angled cutting edges (see
The “fishtail” design of one embodiment of the present invention is intended to minimize distortion of the tube 103 by directing forces inward toward the axis of the hole being cut. Material displacement takes place only on the inside of the circular cutting path; and thus the distortion occurs primarily on the discarded slug.
In one embodiment, the angle of the “fishtail” design is determined primarily by the smallest diameter tube that would be encountered. This allows the “fishtail angle” design to first engage the tube 103 with the outer edge 152. Moreover, concentration of cutting forces on the cutting point 137 and outer edge 152 also serves to quickly and easily penetrate the tube 103, of particular importance in applications such as hard-chrome plated plumbing fixtures.
For embodiments with only one cutting tooth 132, a moment is generated in the cutting device 120 perpendicular to a longitudinal axis of the cutting device 120. This moment increases the load on the cutting surface, increasing the potential to fracture the cutting device 120. Though it does not increase the difficulty to cut, it does seek to deflect the cutting edge 125 and change the course of the cutting edge 125 while exposing it to shear stress along its length. With only one tooth 132, all of the cutting forces, tensile and torsional, are concentrated in one small area. Adding a second cutting tooth 132, which is 180° from the first, results in a balanced dispersion of cutting forces, canceling this moment and directing the force axially into the tube 103. Having both the cutting teeth 132 engaged in the cut simultaneously balances and reduces the tensile and shear loads, but increases the torsional load on the cutting device 120.
In other embodiments, the cut being made is an interrupted cut increasing the chance of fracturing the cutting tooth 132. In one embodiment, three cutting teeth 132 are used to maintain a balance of the forces and manufacturability. With three cutting points there is always at least one point in contact with the tube 103; particularly in the critical early phase of starting the cut. In one embodiment, four or more cutting teeth are utilized. Four or more cutting teeth would be an improvement by reducing the feedrate or depth of cut per the cutting teeth 132, but more difficult from the perspective of cutting device manufacture.
The pitch of the threads (sidewall 123 of the cutting device 120 and inner wall 115 of the cutting chamber 113) is chosen to achieve an appropriate advance of the cutting device 120 through the cutting chamber such that the cutting device 120 would advance at such a rate so as to not damage the cutting edges, 150, 151, the cutting point 137 or the surface to be cut. Advancing too quickly could break the cutting device 120 rendering it unusable. However, an aggressive feedrate is required to penetrate some material, such as nickel chrome plating used in plumping fixtures. Advancing too slowly will allow the hard chrome to distort and dull the cutting edges, 150, 151. which also leads to the cutting device 120. In one embodiment, a standard pitch thread of, 124 threads per inch, is utilized.
In one embodiment, the cutting device 120 includes an actuation mechanism, such as the head 127 for rotating the cutting device 120, causing the cutting device 120 to pass axially through the cutting chamber 113. In an exemplary embodiment shown in
In a further embodiment, the present invention relates to a method of cutting a hole in the tube 103. The rear strap 109 and the front strap 107 of the saddle clamp 105 are positioned on the tube 103 and affixed to each other with the tube 103 disposed therebetween. The cutting device 120 is inserted into the threaded cutting chamber 113, such that the at least one cutting edge 125 is proximate the tube 103. The cutting device 120 is turned so as to interact the threads of its sidewall 123 with the threads of the inner wall 115 of the cutting chamber 113. Rotation of the cutting device 120 draws the cutting device 120 into the cutting chamber 113, and the cutting edge 125 approaches the portion 133 of the tube wall 134. As the cutting point 137 contacts the portion 133 of the tube wall 134, the cutting edge 125 traverses a circular path, cutting into the tube wall 134. The cutting edge 125 cuts a hole through the tube wall 134 as the cutting device 120 is rotated. The interaction of the threaded sections 115 and 123 advances the cutting edge 125 forward (along A-A) as the cutting device 120 is rotated. One of ordinary skill in the art will appreciate that a plurality of revolutions of the cutting device 120 may be necessary to completely cut a hole into the tube wall 134, depending in large part on the thickness of the tube wall 134.
In one embodiment, the system 101 of the present invention is engagable with a secondary tube 104 providing a connection between the secondary tube 104 and the primary tube 103. For example, in one embodiment the tube 103 is a part of a water closet fixture. After the hole is cut in the tube 103, as described above, a secondary tube 104 is inserted into the cutting chamber 113. In an exemplary embodiment shown in
In another embodiment (shown in
The foregoing description of embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the present invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the present invention. The embodiments were chosen and described in order to explain the principles of the present invention and its practical application to enable one skilled in the art to utilize the present invention in various embodiments, and with various modifications, as are suited to the particular use contemplated.
This application claims priority from U.S. Provisional Patent Application No. 60/848,431, filed Sep. 29, 2006, herein incorporated by reference in its entirety.
Number | Date | Country | |
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60848431 | Sep 2006 | US |