AU653025B2 - Method for discharging swarf from three bladed cutting tools - Google Patents

Description

I ~P/00/01I2SM AUSTALIARegulation 3.2 Patents Act 1990 ORIGINAL 2t COMPLETE SPECIFICATION STANDARD PATENT Invention Title: MMTHOD FOR DISCHARGI(G. SWARF FROM THREE BLADED CU~TTING TOOLS.

following statement is a full description of this invention, including the best .:.:method of performing it known to me:- Please see enclosed sheets and drawings I METHOD FOR DISCHARGING SWARF FROM THREE BLADED CUTTING

TOOLS

This invention relates to improvements in devices that cut sheet metal and the likes by removing a thin ribbon of swarf.

Difficulties encountered by known methods of removing swarf from three bladed hand cutting tools are: 1. An uncontrolled swarf of large diameter exits from the front of the cutting tool in the immediate path of the cutting tool and the hand of the person holding the cutting tool thereby slowing down the cutting operation due to time spent removing this unwanted swarf from the tool's path to allow for advancement of the cutting tool and for a safer area in which to use the tool, it is also possible for the swarf to re-enter the tool thereby fouling up the tool's ability to cut, 2, No consideration has been given to keeping the cutting angle between the cutting edges on the centre cutting blade and the outer opposing cutting blades constant through out the cutting operation thus causing the material to slip forwards on commencement of the cut and to cut inefficiently at the end of the cut thereby slowing down the speed and continuity of the whole cutting operation.

3. In some designs a single cutting action creates a single small piece of swauf thereby *s"e creating the possibility of jam-ups caused by a single piece of swarf that is not ejected 20 properly causing all the following swarfs to also foul up creating a time consuming job of unblocking the exit path of the swarf.

Difficulties encountered by known methods of discharging swarf though a three bladed power tool are: S. 1, A single cutting action creates a single small piece of swarf thereby creating the possibility of jam-ups caused by a single piece of swarf that is not ejected properly .causing all the following swarfs to also foul up creating a time consuming job of unblocking the exit path of the swarf.

These problems are overcome in the present invention that provides a method for discharging swarf from any three bladed outting tool that comprises of two similar hardened steel blades opposing one another and both with convex curved cutting edges at one end. A handle made from mild steel tubing, flattened at one end, is sandwiched between the two outer opposing blades at the end opposite the convex curves and riveted secure with two rivets.

In between the two outer opposing blades at the curved end are sandwiched a spacing washer at one side and a pivot pin on the opposite side, both are riveted secure with one mild steel rivet each.

A hardened steel centre cutting blade with a concave curved cutting edge at one edge and fastened to a handle, by two rivets, at the other end and with a suitably positioned pivot hole fits in between the two outer opposing blades at assembly and is positioned by the pivot hole and a pivot pin.

The outer opposing blades are kept at a fixed distance by a washer, pivot pin and the flattened portion of the handle, each being equal in thickness to the centre cutting blade plus twice the recommended cutting clearance for mild steel.

The concave curves of the centre cutting blade corresponds and works together with the convex curves of the two outer opposing blades to produce a cutting action with a constant cutting angle suitable for cutting internal and external curves and straight lines in sheet metal, corrugated sheets of both curved and angular profile and the likes in steel and plastic materials.

A spring is fitted between the handles to automatically open the cutting tool for the V. Snext cut.

By exerting pressure of one hand on the handles a cut will be taken, removing a 25 slender ribbon of material from the corrugated sheet material and by advancing the cutting tool into this cut and repeating the cutting action a sheet of corrugated material can be cut to any length and shape without distorting the original profile of the corrugated sheet and without the handles of the cutting tool ever interfering with the corrugated sheet.

In one form of the invention a hole is placed in one of the outer opposing cutting blades to allow the swarf cut from the corrugated sheets, by the cutting tool, to be discharged through it in the form of a helical spring like shape. An angle formed on the concave curved cutting edge of the centre cutting blade and biased in the direction of the swarf exit hole, directs the swarf into and through the swarf exit hole and out of the cutting tool. This angle on the centre cutting blades concave cutting edge also reduces the projected area of the swarf by twisting it slightly thereby making it narrower than the distance between the two outer opposing cutting blades, allowing a smoother passage of the swarf through the two outer opposing blades and out of the swarfhole.

The two outer opposing cutting blades and the centre cutting blade may be made of any steel suitable for hardening and can be pressed out in a press tool and then hardened and the cutting edge's ground. The two handles may be made from mild steel tubing flattened at one end to accommodate the assembling of the cutting tool. The spacer may be pressed out in a press tool. The pivot pin may be turned on a lathe from steel suitable for hardening, then hardened. The spring may be made from spring steel and formed in a press tool. The cutting tool may be assembled and fastened together with mild steel rivets.

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03 12 A J To assist with understanding the invention reference will now be made to the accompanying drawings which show one example of the invention.

In the dravings: Fig. 1 shows one example of a sheet metal hand cutting tool using the method of swarf removal according to this invention.

Fig.2 shows the cutting tool in Fig.l with one of its outer opposing cutting blades removed for clarity and a sectioned end view, Fig.3 shows a sheet metal hand cutting tool using the method described for discharging swarf whilst cutting a sheet of corrugated iron.

Referring to fig. 1 the individual components making a completed cutting tool using the method of discharging the swarf as described in the invention can be seen. Rivets 32, 33, 34, 35 and 36 and pivot pin 13 are used to fasten the completed tool.

1 and 2 being hardened steel outer opposing blades, 27 being a ball chain, 29 being a spacer washer, 31 being a spring and 13 being a pivot pin which is also used as a rivet.

spring 31 is clenched at assembly between centre blade 12 and handle Referring to fig. 2 it can be seen that the sheet metal hand cutting tool using the method for discharging swarf according to this invention comprises of two outer i: opposing blades 1 and 2 having rivet holes 3,4, 5, 6 and rivet hole 7 and convex curve 8. Handle 9 is sandwiched between outer opposing blades 1 and 2 and riveted via holes 3, 4, 10, and 11. A hardened steel centre cutting blade 12 is inserted between the two outer opposing blades 1 and 2 and kept in position and allowed to rotate by pivot pin 13 and pivot hole 14 and riveted. At one end of the centre cutting blade 12 are two rivet holes 15 and 16. A handle 30 is riveted at holes 17 and 18 on the handle 30 and holes 15 and 16 on the centre cutting blade 12, At the other end of the centre cutting 25 blade is a concave curved cutting edge 19 onto which is formed cutting angle clearance pockets 22 and 23 and clearance angle 21. On the inside edge of the swarf exit hole 7 is a counter sunk clearance angle 24. Cutting clearance 28 is maintained between blades 1, 2 and 12 by handle 9, washer 29 and pivot pin 13. A spring 31 made of spring steel is held in position by handle 30 and centre cutting blade 12.

1 4 It will be realized that the method of discharging swarf from any three bladed cutting tool according to this invention is not restricted to an exact cutting angle on the concave curved cutting edge of the centre cutting blade but can vary as long as the swarf is directed through the swarf exit hole at the side of the sheet metal hand cutting tool.

It will also be realized that the method of discharging swarf from any three bladed cutting tool according to this invention is not restricted to the form of cutting curves shown in this example but may vary using curves or multiple-flat edged shapes of any kind so as to produce a constant cutting angle between the cutting edges on the outer opposing blades and the cutting edge on the centre cutting blade.

Claims (4)

1. Means for discharging the strip of scrap in the form of a helical coil of swarf from any hand or power cutting tool which comprises of a pivotal centre cutting blade acting with two outer opposing cutting blades as to perform a cutting operation and so designed as to remove a thin ribbon of swarf, comprising of a swarf exit hole in the side of one or both the outer opposing cutting blades allowing the helical swarf, generated by the cutting action of the two outer opposing blades and the centre cutting blade, to be continuously discharged in a helical coil of small diameter and compressed length at right angles to the cutting action of the tool.

2. Means for discharging swarf as claimed in Claim 1 wherein the said swarf is directed through the swarf exit hole by an angle formed on the cutting edge of the centre cutting blade that is biased towards either of the two swarf exit holes in the side of the cutting tool thus directing the swarf to curl in that direction and by doing this the projected area of the swarf becomes less than the gap between the outer opposing cutting blades thus leading to a free exit of the swarf through the swarf exit hole.

3. Means of discharging swarf as claimed in Claim 1 or 2 wherein the outer opposing cutting blades both have a convex curved cutting edge and the centre cutting blade has a concave curved cutting edge and due to the relationship of these curves the angle created between the outer opposing cutting blades and the centre cutting blade during the closing of the handles to perform a cut, is kept constant thereby directing the swarf through the same point in the swarf exit hole at any position or at any time during the cutting action of the tool allowing the swarf exit hole to be circular and as small as possible thereby keeping maximum strength in the tool in the vulnerable areas close to the cutting action. 25 4. Means of discharging swarf as claimed in Claim 1, 2 or 3 wherein a clearance pocket is formed on the inside face of any of the outer opposing cutting blades that has a warf exit hole to enable trouble free discharge of the helical swarf through the swarf exit hole and out of the tool. oil Uy ^XJ Means of discharging swarf as claimed in Claim 1, 2, 3 or 4 wherein clearance pocket is formed on either side of the centre cutting blade and are positioned at the start of the cutting edge of the centre cutting blade allowing smooth advancement of the centre blade of the cutting tool into the slot cut by the previous cutting action.

6. A method for discharging the strip of scrap substantially as herein described with reference to the enclosed drawings. OF APPLICANT, DATE. to .00. 00 6 06*#G: too 06 ABSTRACT A method of discharging swarf whilst cutting sheet metal and the likes by using special design features incorporated into any three bladed sheet metal cutting tool is disclosed, A sheet metal hand cutting tool can have the following design features. Two hardened steel outer opposing cutting blades (1 and 2) each with convex curved cutting edges at one end and a handle sandwiched and riveted at the other end. At the curved end of these two blades and sandwiched between them are a spacing washer (29) at one side and a pivot pin (13) at the other side, The handle, spacer and pivot pin together form a parallel gap (28) between these outer opposing which allows a hardened centre cutting blade to be inserted between them and positioned by the pivot pin. One end of the centre cutting blade has a concave curved cutting edge (19) onto which is formed a cutting angle (20) and at the other end a handle (30) is riveted. The handles (9,30) are arranged as to be held and closed by the pressure exerted by one hand and opened by spring The three cutting blades (1,2,12) are so designed as to cut and discharge ribbon swarf (37) through a swarf exit hole at the side of the cutting tool. By closing the handles by hand with the corrugated sheet metal in between the cutting blades a narrow ribbon of the corrugated sheet metal is removed from the corrugated metal sheet (38) and discharged through the swarf exit hole in 0 the side of the cutting tool and by orientating the vertically positioned handles of the cutting tool it is possible to cut up and down the corrugated shapes of the corrugated sheet and by twisting ones wrist from centre to left, a left hand curve may be cut and *o by twisting ones wrist from centre to right a right hand curve may be cut, SS SS