Tube cutter

Details Tube cutter Tube cutter

2000-08-15

2002-05-28

Payer, Hwei-Siu (Department: 3724)

Cutlery

Pipe and rod cutters

Rotary

C030S101000

Reexamination Certificate

active

06393700

ABSTRACT:

The present invention relates to the field of tube cutting and more particularly to a tube cutter having an automatic feed as the cutter is rotated for the purpose of cutting through the tube.
BACKGROUND OF THE INVENTION
A large number of devices exist for rotating a cutter around a tube to cut the tube at the desired position. The present invention relates to a tube cutter wherein the cutter wheel is a wheel biased against the outer surface of the tube to automatically advance or feed the cutter into the tube as the cutter is rotated. A common arrangement for accomplishing this objective is shown in Condon U.S. Pat. No. 2,448,578 and Collier U.S. Pat. No. 5,903,980. A cutter or cutters are carried on a clam shell type frame by a spring element so the clam shell can be assembled over a tube with the cutter biased against the outside surface of the tube. By rotating the frame, the cutter or cutters automatically advances into the tube until the tube is severed. Such devices do not specifically relate to the present invention, but are incorporated by reference herein as background information. Another mechanism for tube cutters having an automatically advanced cutter is illustrated in McDaniel U.S. Pat. No. 5,206,996. A cutter wheel is mounted on a spring biased lever system or is spring biased from one side of a fixed C-shaped frame. This patent is incorporated by reference herein as further background information, even though it does not even disclose the general feeding arrangement used in the present invention.
The invention involves a tube cutter wherein a housing, frame, or jaw supports and forms a cradle for the tube to be cut. An opposite frame, jaw, or arm carries the rotary cutter wheel and slides toward the tube being cut during the cutting operation. The sliding jaw concept for tube cutters is illustrated in Myers U.S. Pat. No. 1,945,949 and Kritchever U.S. Pat. No. 5,495,672 both of which are incorporated by reference herein as teaching the general concept to which the present invention is directed. This general concept is an automatic tube cutter wherein the cutter includes two linearly slidable frames movable together to define the cutting action. The rotary cutting wheel is biased against the tube so that it is automatically advanced as the cutting depth increases during the rotary cutting action.
BACKGROUND OF INVENTION
Tube cutters are well known in the field and are generally constructed to allow movement of the cutting wheel into the tube by manually advancing the cutting wheel inwardly during the cutting operation. Such devices are awkward to use and require constant operator attention, as well as skill. Consequently, it has become somewhat common to provide a tube cutter in which the rotating cutting wheel is automatically fed into the tube as it is being cut. This provides a tube cutter that is easily and quickly positioned for use. Such tube cutter only requires turning of the cutter around the tube in order to complete the cutting operation once the cutter has been positioned on the tube. This rotating action can be manual or can be by a power drive as shown in Kritchever U.S. Pat. No. 5,495,672. The difficulty is that the various structures for accomplishing the automatic feeding of cutting wheel into the tube during the rotating cutting action have advantages, but present distinct disadvantages. For instance, when the automatic advancing cutter is in a clam shell frame, as shown in Condon U.S. Pat. No. 2,448,578 or Collier U.S. Pat. No. 5,903,980, the size of the frame is dictated by the size of the tube being cut. Consequently, each tube size requires its own cutter. The amount of spring force exerted during the cutting operation is dictated by the size of the clam shell frame. Minor differences in the diameter of the tube can not be accommodated in such fixed frame rotary tube cutters. These cutters are thus dedicated tools and can not be used universally. Another type of tube cutter that is generally size specific is shown in McDaniel U.S. Pat. No. 5,206,996. The diameter of the tube being cut dictates the size of the U-shaped frame for carrying the support rollers and the spring biased cutter. With this fixed frame tube cutter, there is no easy way to accommodate different tube sizes. As the spring loses its spring force during long-term use or in temperature changes, the cutting action is drastically affected. This is also true of the encircling frame type of tool. Each of these cutters is tube size specific and susceptible to changes in the spring biased cutter to alter the efficiency and effectiveness of the cutting action. McDaniel recognizes the disadvantage of fixed frame tube cutter by suggesting a tube cutter involving a spring biased lever system wherein one blade of the system carries the support rolls and the other blade carries the rotating cutter wheel. This attempt to rectify the problems associated with a fixed frame tube cutter is not successful for many reasons. It includes protruding handles and a pivoting infeed of the rotating cutter wheel that changes the cutting action and spring force according to the diameter of the tube being cut.
The disadvantages of tube cutters that automatically feed the cutter wheel into the tube during cutting, but are size specific, was generally solved in 1934. In Myers U.S. Pat. No. 1,945,949, a first frame carries the two tube support rollers. The other frame rotates the rotating cutter wheel about a fixed axis and is pulled toward the first frame by a threaded shaft. To load the cutter for automatic feeding, the shaft is connected between the two frames through a coil spring. Movement of the second frame stops when the cutter wheel engages the surface of the tube positioned adjacent the support rollers in the first frame. Thereafter, rotation of the threaded shaft compresses the coil spring to bias the second frame toward the first frame. During the cutting action, as the tool is rotated about the tube, the second frame advances toward the first frame as the depth of cut increases. This action creates automatic feeding for the rotating cutter blade. The tool is not size specific. Sliding of one frame with respect to the other frame with the spring loaded threaded shaft has heretofore proved an extreme benefit over the fixed frame tube cutters described above. Another version of the cutter shown in Myers is illustrated in Kritchever U.S. Pat. No. 5,495,672. The movable jaw or frame carrying the rotating wheel is moved toward the tube cradled by the support rollers on the other frame. The rotating threaded shaft moves the one jaw until it engages and clamps the tube in the cutter. Additional rotation of the threaded shaft compresses an encircling spring to determine the amount of force exerted by the cutter wheel against the tube. After the force has been applied one jaw is biased toward the other jaw to load the rotating cutter wheel for automatic feeding as the cut progresses. This type of cutter can be operated manually or by a power rotating device. Even though there is an advantage for the movable frame type pipe cutters they still have certain disadvantages. The cutting action is controlled by a Belleville spring or a coil spring surrounding the shaft used for sliding one jaw toward the other jaw. Such spring indirectly affects the moving action of the cutter wheel. The wheel movement is also affected by sliding of the two frames together. Dirt and environmental contamination can adversely affect the cutting action. Indeed, in some instances, dirt and contamination in the slide mechanism between the two frames renders this type of cutter inoperative. Since the jaw must be moved by an intermediate spring, it is difficult for the threaded shaft to overcome irregularities in the sliding mechanism. The second frame may be movable into the cutting position, but during the cutting action, it can jerk, freeze or otherwise affect the smoothness and repeatability of the tube cutting operation. Friction irregularities causes jerks, which can affect the uniformity of the cut being made on the tube. All

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