GB1579333A

GB1579333A - Percussive power tool with a flexible blade

Info

Publication number: GB1579333A
Application number: GB2481276A
Authority: GB
Original assignee: Kango Electric Hammers Ltd
Current assignee: Kango Electric Hammers Ltd
Priority date: 1976-06-15
Filing date: 1976-06-15
Publication date: 1980-11-19
Also published as: AU507749B2; DE7718583U1; ES237301U; CA1064253A; ES237301Y; FR2354855A1; IT1083834B; AU2610677A; FR2354855B3

Description

(54) PERCUSSIVE POWER TOOL WITH A FLEXIBLE BLADE (71) We, KANGO ELECTRIC HAM MERS LIMITED, a British Company, of Lombard Road, Morden Road, South Wimbledon, London SW19 3XA, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to percussive power tools.

According to this invention there is provided a percussive tool having a tool bit holder, power-operated means for applying impact forces to the holder, and a cutting bit comprising a shank held by one end in the holder and a flexible blade secured to the other end of the shank, said blade being made from a springy metal.

Bainitic steel and phosphor-bronze have been found to be particularly suitable materials for the blade. The thickness of the blade is preferably 5mm. or less if a single thickness of material is used, but the blade may be of laminated form in some cases. 1.5mm has been found to be a particularly effective thickness for the tip portion of the blade.

Such a percussive tool has been found to be remarkably effective in removing dropped plaster and concrete, paint, caked oil and other deposits, and tiles from floors, walls and ceilings.

In certain applications the blade may be inclined to the shank, e.g. at an angle of 30 , to provide a clearance for the body of the cutting tool, as where the bit is used to cut silage and hay disposed in a stack.

The blade may be brazed or welded to the shank but it is preferred to make the blade detachable from the shank. For this purpose, the said one end of the shank may be formed as a yoke to embrace an edge of the blade, the blade being secured by one or more rivets or threaded bolts extending through the blade and the yoke. Thus one blade may be exchanged for another and a gasket or gaskets may be disposed between the blade and the yoke to reduce the risks of fatigue failure and high-frequency noise. In order to avoid the gasket or gaskets becoming lost it or they may be adhesively secured to tlae blade.

to embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows in elevation a cutter bit for a percussive tool according to the invention, Figure 2 is a side elevation of the bit partly sectioned on line 2-2 of Figure 1, and Figures 3 and 4 are respectively front and rear end views of the bit shown in Figures 1 and 2.

The bit shown in the drawings is intended to be mounted in the tool holder of a percussive power tool of the well-known kind in which power-operated means is provided for applying impact forces to the holder.

Referring to the drawings, the bit comprises a shank 10 having a blade 11 secured to one end thereof. To hold the blade a yoke 12 is secured on a self-locking tapered spigot 13 on the end of the shank, the spigot being driven into a correspondingly tapered socket in the yoke. In the illustrated construction the blade is rectangular and is clamped in a rebate in the yoke by a plate 14, two bolts 15 extending through holes in the plate, blade and yoke and being secured by nuts 16. Heavy duty gaskets 17 are adhesively bonded to both sides of the blade between the plate 14 and the yoke to reduce the risks of fatigue-failure and highfrequency noise.

The blade is made from bainitic steel or from phosphor-bronze and is thus relatively springy by comparison with the usual type of cutting or chisel bit where the shank and a heavy rigid blade are forged integrally with each other from a tough steel.

In an alternative construction, the yoke has instead of the rebate and plate 14 a slot into which the back edge portion of the blade fits. In this construction also, heavy duty gaskets are secured by an adhesive to the faces of the blades where it fits in the slot. The blade is secured in the slot by bolts and nuts as in the illustrated arrangement.

The releasable attachment of the yoke to the shank enables different lengths and types of shank to be used interchan eably, but the yoke may be formed integrally with the shank or may be brazed or welded or press-fitted to the shank. The yoke may be a steel forging or a spheroidal graphite iron casting.

A percussive tool equipped with the bit may be used for removing concrete and plaster droppings, tiles, paint and caked oil from floors, walls and ceilings, and if the blade is sharpened may be used for cutting such materials as silage and hay for feeding farm animals. The bit can be used with any type of percussive tool including those, known as buzz drills, which employ high frequency, low energy vibrations.

Where the tool is to be used for cutting silage or hay disposed in a stack the blade of the bit may be inclined to the general lengthwise dimension of the shank, i.e. to the direction of the percussion or vibration, at an angle which should not exceed 30 , to provide a clearance for the body of the per cussive tool. The blade can be so disposed for example by forming a bend in the shank near its forward end, by arranging the yoke at an angle to the shank, or by inserting packing pieces of appropriate form between the yoke and the blade.

WHAT WE CLAIM IS: 1. A percussive tool having a tool bit holder, power-operated means for applying impact forces to the holder, and a cutting bit comprising a shank held by one end in the holder and a flexible blade secured to the other end of the shank, said blade being made from a springy metal.

2. A percussive tool as claimed in claim 1, wherein the blade is made from bainitic steel.

3. A percussive tool as claimed in claim 1, wherein the blade is made from phosphor-bronze.

4. A percussive tool as claimed in any one of claims 1 to 3, wherein the blade has a thickness not exceeding 5mm.

5. A percussive tool as claimed in claim 4, wherein the tip portion of the bit has a thickness of 1 .5mm.

6. A percussive tool as claimed in any one of claims 1 to 5, wherein the plane of the blade is inclined to the lengthwise axis of the shank.

7. A percussive tool as claimed in any one of claims 1 to 6, wherein the blade is made separately from and is secured to the shank.

8. A percussive tool as claimed in claim 7 wherein one end of the shank carries a yoke to which is secured the rear edge of the blade.

9. A percussive tool as claimed in claim 9, wherein a gasket or gaskets are interposed between the rear edge of the blade and the yoke.

10. A percussive tool substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. In an alternative construction, the yoke has instead of the rebate and plate 14 a slot into which the back edge portion of the blade fits. In this construction also, heavy duty gaskets are secured by an adhesive to the faces of the blades where it fits in the slot. The blade is secured in the slot by bolts and nuts as in the illustrated arrangement. The releasable attachment of the yoke to the shank enables different lengths and types of shank to be used interchan eably, but the yoke may be formed integrally with the shank or may be brazed or welded or press-fitted to the shank. The yoke may be a steel forging or a spheroidal graphite iron casting. A percussive tool equipped with the bit may be used for removing concrete and plaster droppings, tiles, paint and caked oil from floors, walls and ceilings, and if the blade is sharpened may be used for cutting such materials as silage and hay for feeding farm animals. The bit can be used with any type of percussive tool including those, known as buzz drills, which employ high frequency, low energy vibrations. Where the tool is to be used for cutting silage or hay disposed in a stack the blade of the bit may be inclined to the general lengthwise dimension of the shank, i.e. to the direction of the percussion or vibration, at an angle which should not exceed 30 , to provide a clearance for the body of the per cussive tool. The blade can be so disposed for example by forming a bend in the shank near its forward end, by arranging the yoke at an angle to the shank, or by inserting packing pieces of appropriate form between the yoke and the blade. WHAT WE CLAIM IS:

1. A percussive tool having a tool bit holder, power-operated means for applying impact forces to the holder, and a cutting bit comprising a shank held by one end in the holder and a flexible blade secured to the other end of the shank, said blade being made from a springy metal.