Cutting – Processes – With subsequent handling
Reexamination Certificate
2000-01-12
2001-05-01
Rachuba, M. (Department: 3724)
Cutting
Processes
With subsequent handling
C083S100000, C083S684000, C083S698910, C030S124000, C030S316000, C030S358000
Reexamination Certificate
active
06223637
ABSTRACT:
1. Field
This invention relates to hole cutting apparatus. It is specifically directed to hollow punches and hole cutters. It provides an improved means for ejecting and capturing discard slugs produced by such punches and cutters.
2. State of the Art
Many types of hole cutters and punches of specialized design are known. Special purpose cutters are often required for specific applications or for use with particular materials. There are various known techniques available for forming a hole in a material. A suitable hole may often be provided by punching through a material with a solid or hollow punch. In some applications, an acceptable hole is formed by applying pressure, and frequently impulse force, to a solid punch to knock out a “slug,” leaving a hole in the material. Other applications utilize a hollow punch to remove a core or slug from a piece of material. The material to be cut may be placed between the hollow punch and a supporting substrate. The punch, which is typically in the form of a hollow tube with a distal cutting edge, is pressed down upon the material, which shears along the cutting edge. A slug of material is removed with the punch, leaving a hole through the material. U.S. Pat. No. 4,010,543 to Nusbaum discloses a typical special purpose hollow tube device of this type.
Hollow punches are often round, and can thus be rotated to cut a hole. They are then typically referred to as “tube cutters.” Rotation of the cutter during hole formation reduces burrs around the edge of the resulting hole. Moreover, suitable holes can be formed with rotating cutters without the use of a supporting substrate.
Proper selection of a cutter or punch is necessarily dependent upon the nature and dimensions of the material to be cut. For example, if the material is thin and stiff, such as paper or cardboard, a hole puncher can be utilized. On the other hand, removing the core of a fruit, such as an apple, is better accomplished through use of a hole cutter.
Punch shapes vary according to specific requirements. Round shapes are most common, although oblong, elliptical, and square punches are also common. Rotating cutters are ordinarily utilized for forming substantially round holes.
Medical catheters are an example of a hole cutting operation in which proper retrieval or disposal of discard (slug) material is important. Holes are often cut through plastic catheter tubing transverse the tubing's lumen. Catheters are routinely inserted into the circulatory or respiratory systems of a patient. It is thus important that the catheter not be a source of debris. Catheters are variously used to deliver and extract fluid from the blood stream, enter the peritoneal cavity for dialysis, sense pressure inside blood vessels near the heart, and monitor contraction pressure during child birth. Slugs that are not removed from the catheter may become lodged in the body. Present practice involved in the cutting of holes in medical catheters relies upon the slug's remaining inside the hollow cutter tube through frictional engagement with the interior surface of the cutter. The slug is later pushed out of the distal (cutting) end of the cutting tube with a rod, which is inserted from the proximal (or opposite) end of the cutting tube. This slug-ejection method tends to result in a scattering of slugs in the cutting area. Occasionally, ejected slugs cling to the outside of the catheter tubing. Furthermore, the added motion required for the ejection step increases the time needed to make a hole, and increases the complexity of the machinery required for hole cutting. A slug may also remain in the lumen of the catheter because the slug is not frictionally engaged by the interior surface of the cutter.
SUMMARY
The present invention provides a hole cutting method and apparatus which avoids the shortcomings of previous devices with respect to slug disposal. The invention provides a hole cutting apparatus capable of forming holes of circular or various non-circular shapes in soft materials. A notable benefit offered by the present invention is an improved system for extracting slugs from a cutter.
The hole cutting apparatus of the present invention finds particular use in cutting plastic tubes. The present apparatus provides a slug ejection system which removes the slug through the center of the hollow hole cutter for effective transport to a filter or slug trap for convenient disposal. The apparatus of this invention may be embodied as either a punch or a rotating cutter. In any case, it may be particularly adapted for cutting holes through the sidewalls of medical catheters.
Generally, this invention provides a hole cutting apparatus comprising a hollow tube having a distal (cutting) end terminating in a cutting edge, a proximal (ejection) end, a lumen extending between the distal and proximal ends, the lumen being of smaller diameter near the distal end than at the proximal end, and ejection means constructed and arranged for urging a slug of material from the distal end towards the proximal end.
The ejection means presently preferred in practice is suction applied to the proximal end of the tube. Any mechanism effective to extract discard slugs from the proximal end of the tube could be substituted. An important characteristic of this invention is the extraction, or ejection, of discard slugs away from the cutting end of the cutter. Ideally, a moving air stream carries the slugs out of the cutting tube and transports them to a capturing or collection device, such as a filter.
Preferably, the lumen includes a first portion, extending from the cutting edge to a shoulder, and a second portion, extending from the shoulder to the proximal end. The first portion will have a cross sectional configuration substantially congruent with a preselected cross sectional shape of a discard slug. The second portion should have a cross sectional configuration which permits free travel of a slug from the shoulder to the proximal end. Assuming that the cutter is embodied as a hollow punch of circular cross sectional configuration, both the first and second portions of the lumen will typically have circular cross sectional configurations, with the second portion having a somewhat larger diameter. Usually, the two cross sections are substantially concentric, but other arrangements are operable.
To maintain unobstructed flow of ejection fluid (typically air) through the cutter, at least one aperture may be provided in the side wall of the cutter tube, communicating with the lumen near the distal end of the tube. In certain embodiments, at least one such aperture communicates with the lumen at the shoulder. The cross sectional area of the aperture(s) are typically about ⅓ the cross sectional area of the lumen of the catheter to assure adequate fluid flow through the lumen to extract the slug. The apertures are ideally located about one to about three slug thicknesses from the distal end of the cutter. The width of an aperture should be small enough, typically less than about ⅓ of a slug diameter, to avoid lodging of a slug edge in an aperture.
In an alternate and currently preferred configuration, no apertures are provided in the side wall of a cutter tube. Fluid flow is interrupted by the presence of a tube side wall, such as a catheter side wall, during the cutting operation. The fluid flow through the cutter tube is restored upon separation of the discard slug from the catheter side wall. The restored fluid flow then carries the slug away from the catheter and ejects the slug from the discard end of the cutter tube.
To form a burr-free hole on an external surface of a catheter, it is preferred to punch a partial depth hole without rotation of a cutting edge, then to rotate the cutting edge during the remainder of the cutting stroke. The initial nonrotating punch stroke cold works surface material of the catheter side wall, and prevents a surface burr. Rotation of the cutting edge on the remainder of the stroke to finish the hole cutting operation improves the cutting function of the cutter. A rotat
Pryor Sean
Rachuba M.
Trask Brian C.
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