WO2009098664A2 - Structured cutting - Google Patents

Abstract

An approach for producing structured cuts, which at least in part produced by an arcuate reciprocating cutting tool including an arcuate saw and a driving mechanism therefor, is disclosed. The driving mechanism is configured to facilitate the formation of arcuate slots in a substrate. A particular use of the approach in medical applications is specified.

Description

STRUCTURED CUTTING

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority from Great Britain Patent Application Serial Number GB0802166.9, filed February 6, 2008, entitled "ROTATIONALY RECIPROCATING CUTTING TOOL;" the aforementioned application is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to reciprocating mechanical cutting tool in general and more particularly to the use of such tools in arcuate cuts.

BACKGROUND OF THE INVENTION

Reciprocating saws are cutting tools in which the cutting is effected through a cyclic, mainly linear mechanical action of the blade. Power jigsaws include a power source and a reciprocating blade that cuts into the surface to be acted upon, by moving the saw into the surface from the flank of the substrate. Cuts made by the jigsaw are straight, curved, or exhibit a combined structure along the cutting line. The thickness of the blade is the distance between the two faces of the saw blade, in other words the measure of the blade perpendicular to the direction of advancement. The kerf is the width of the slot that the saw cuts and is a product of the structure and dimensions of the teeth. The teeth of the saw are usually not confined to the thickness measure of the blade. If the teeth are tilted sideways to the blade, the cut provided by the saw is thicker than the blade. Contrarily to circular or straight saw blades, core drills and hinge cup drills form a circular cut in the substrate, intended for extracting cylindrical portions of the substrate.

Several variables determine the limit of the radius of turning that a blade of a saw can provide. The narrower the blade of the jigsaw, the smaller the radius of the cut that can be made by using such a saw. In this case, the adjective narrow meaning the dimension in the direction of cutting. Additionally, a thin saw blade can provide for a smaller radius then a thick blade. Also the width of the kerf (determined by the extent of teeth sideways tilt), determines the radius of cutting. The larger the kerf is the more freedom the blade has to turn and decrease the minimal radius available.

The present invention provides an efficient mechanism for making arcuate cuts of any desired radius, as will be explained below. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an isometric description of an arcuate saw of the invention;

Fig. 2A is the geometric convention as used for describing a saw of the invention;

Fig. 2B is an isometric description of a saw of the invention with a projected cut on a flat substrate;

Fig. 2C is an isometric description of a narrow saw of the invention with a projected cut on a flat substrate; Fig. 3A is an example of an arcuate cut that can be achieved by the system of the invention or by a reciprocating linear blade saws;

Fig. 3B is an example of an arcuate cut of a small radius that can be achieved by the system of the invention or by a reciprocating linear blade saws;

Fig. 3C is an example of a linear cut that can be achieved by several types of conventional saws;

Fig. 3D is an example of a structured cut that can be obtained using saws of the invention;

Fig. 3E is an example of a structured cut that can be obtained using a saw of the invention in addition to conventional saws; Fig. 4A is a schematic description of a reciprocating rotating saw driven by eccentric wheel mechanism;

Fig. 4B is a schematic description of a reciprocating rotating saw driven by linear piezoelectric mechanism. DETAILED DESCRIPTION OF THE PRESENT INVENTION

In accordance with the present invention a rotational reciprocating cutting tool is provided which can produce arcuate cuts or slits in a substrate including in a substantially planar element. The cut made by a device of the invention is performed by a reciprocating circular movement of an arcuate saw (AS) disposed substantially in parallel to the object or substrate to be cut. Concomitant to the reciprocating rotational motion of the saw, a force is to be applied to the saw in the direction of the object in order to bring about penetration into the object.

As can be seen in Fig. 1 to which reference is now made, arcuate saw (AS) 20 having a cutting arc (CA) 22, base 24 and shaft 26. Shaft 26 is powered by an actuator (not shown) providing reciprocating rotational torque around axis 28. To define the dimensions of an arc, reference is now made to Fig. 2A. The geometrical convention relates to the size in length dimensions (L) as the length of the arc, in this example, L is subtended by an arc angle α which is about 180°. As can be seen in Fig. 2B- C, to which reference is now made, the AS of the invention can be produced in a variety of arc sizes. In Fig. 2B, AS 68 shown at a distance from substrate 70, projects a slit 72 on substrate 70. The slot is made by CA 74 rotationally reciprocating around axis of rotation 78 as indicated by double headed arrow 80. In Fig. 2C, CA 84 is somewhat narrower than the one described above, and therefore projects a narrower arc of a slot 86 than slot 72. Apart from the angular size of the AS, the angular extent of rotation (or amplitude of rotation) also can determine the size of the slit formed. Thus, a narrow CA may be caused to form a larger slit if the amplitude of rotation it performs is larger.

It should be acknowledged that the ASs of the invention, such as AS

20, can be powered by an actuator providing axial reciprocating translation along axis 28. The reciprocating axial translation is typically vibratory and preferably of ultrasonic frequencies. Provided that the actuator induces axial reciprocating translation of the AS, the angular size of the AS determines the size of the slit formed.

Uses of a system of the invention and complementary implements

Unlike core drills or hinge cup drills, which aim at producing complete circular slits for making holes in the substrate (metal, wood, masonry elements etc.), the arcuate saw of the present invention aims at producing arcuate slots in the substrate it cuts through. However, in order to form complex cuts, the arcuate saw of the invention may be used together with other cutting devices to achieve structured slits or cuts in the substrate as will be explained next. First, reference is made to Figs 3A-G. In Fig. 3A, circular cut is shown, having a certain radius, whereas in Fig. 3B, circular cut is shown, having a smaller radius. Using jigsaw type saws, a hole must first be cut in the substrate since the saw moves sideways as of the beginning of its cutting path. A circular saw on the other hand, would cut directly a slit without the need for access from the flank of the substrate or from a previously made slit. The circular saw is very non-flexible as regards deviations from the linearity of the cut. A rectangular cut as in Fig. 3C is achievable using a circular saw, without a need for a previously prepared access to the other side of the substrate. In Fig. 3D a more complex cut is shown, consisting of two opposite half- circles, joined at one end. Such a cut may be made using the system of the invention, with two different size reciprocally rotating ASs. Such a cut may be conveniently made by a tool using a single saw, with one replacement of the saw - bit, that can be replaced much in the same way as drill bits can be replaced. In Fig. 3E, a highly structured cut is shown, using a single AS of the invention to produce cut's segments 102, 104, and 106. A straight saw or a circular saw is used to make cut's segments 108, 110 and 112.

The AS of the present invention can be used to produce cuts in a variety of substrates, including such substrates having no access from a flank or an edge. Using a set of exchangeable ASs, an operator of a cutting device of the invention can produce range of cuts or slots in a substrate without the need to access the substrate from the flank, or from a pre -drilled hole.

Uses for a cutting tool of the invention are numerous, wherever a structured cut is required such as for forming a opening in an existing object. Especially, a tool implementing the present invention can be used for maintenance jobs requiring proving a structured opening for accessing into bodies or otherwise closed volumes. Medical applications for cutting into bones such as the skull or sternum are noted. Driving the AS

To achieve a rotational reciprocating motion of the AS of the invention, two driving mechanisms are plausible. An eccentric driving mechanism and a vibrating mechanism may be used to such end. These driving mechanisms are explained with reference to Figs 4A - B respectively. An eccentric driving device is described schematically with reference to Fig. 4A. AS 130 having a pivot 132 is connected via swivel joint 134, shaft 138 swivel joint 140 to driving wheel 142. Drive wheel 142 turns by the urge of motor, typically an electric motor, not shown, unidirectionally, around pivot 146. Shaft 138 transfers torque from drive wheel 142 to AS 130, but the direction of turning of the wheel is alternate, the amplitude of which is a function of the distance of both swivel joints from the respective pivots. CA 150 rotates bi- directionally as dictated by the movement of the AS 130. In Fig. 4B, piezoelectric actuator 160 vibrates to and fro along arrow 162 driving articulated shaft 164 to reciprocatingly drive AS 130 around pivot 132. Other driving mechanisms are plausible as known in the art.

In such cases in which the ASs are driven axially in reciprocating translation, the actuator therefor can be any one of the actuators known in the art, an example for which is a piezoelectric actuator. To achieve reciprocating translational movement along a line, the piezoelectric actuator provides movement back and fro along a line. Piezoelectric actuators may provide ultrasonic vibrations that can be exploited in the context of the invention to induce cutting in substrates as discussed above. It should be acknowledged that the axial reciprocating translation can be combined or used in turn with rotational reciprocating movement.

Claims

1. A method of cutting into substrates, wherein an arcuate saw is driven in a manner selected from the group consisting of: a rotational reciprocating movement in a plain substantially paralleling said substrate and an axial reciprocating translation along an axis substantially perpendicular to said substrate; and wherein a force is applied on said saw towards said substrate, whereby at least one arcuate cut is formed in said substrate; and wherein said method is characterized in that aforesaid arcuate cut is a segment forming a continuum with at least one additional cut selected from the group consisting of: an arcuate cut segment and a straight or linear cut , thereby forming at least a portion of a structured cut.

2. A method for cutting into substrates as in claim 1 wherein said substrate is a part of body of a patient.

3. A method for cutting into substrates as in claim 2 wherein said part of the body is a sternum.

4. An arcuate reciprocating cutting tool, for producing a structured cut within a substrate, comprising:

• an arcuate saw, and

• a rotational reciprocating actuating means for driving said saw; said arcuate reciprocating cutting tool is characterized in that said arcuate saw is used to produce at least one arcuate cut within said substrate, wherein said at least one arcuate cut is a segment forming a continuum with at least one additional cut selected from the group consisting of: an arcuate cut segment and a straight or linear cut segment, thereby forming at least a portion of said structured cut.

5. An arcuate reciprocating cutting tool as in claim 4 wherein said actuating means is an eccentric wheel drive mechanism.

6. An arcuate reciprocating cutting tool as in claim 4 wherein said arcuate saw is driven by a piezoelectric mechanism.

7. An arcuate reciprocating cutting tool as in claim 4 wherein said arcuate saw can replace a drill bit.