GB1604660A

GB1604660A - Percussive cutting machine

Info

Publication number: GB1604660A
Application number: GB4379177A
Authority: GB
Original assignee: MACDONALD PNEUMATIC TOOLS
Current assignee: MACDONALD PNEUMATIC TOOLS
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-12-16

Description

(54) PERCUSSIVE CUTTING MACHINE (71) We, JOHN MACDONALD & COM.

PANY (Pneumatic Tools) LIM1TED, a British company of Peel Park Place, College Milton South, East Kilbride, Glasgow, G74 5LS, Great Britain; and DAVID THOMSON ALLAN, a British subject of 9 Broomhill Drive Rutherglen, Glasgow, G73 3QH, Great Britain 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 a percussive cutting machine.

Many percussion cutting machines are known for use in cutting rock, concrete or the like such as a wall groover as described in our British Patent No. 1 598 992 a scabbling machine as shown in our British Patent No.

1 056 01 1, a crack cutter for cutting grooves along the lines of cracks in concrete or a scaling hammer.

The tool bits of such machines have suffered from the disadvantages of being complex, expensive to manufacture and inefficient.

An object of the present invention is to provide a percussive cutting machine having a tool bit which obviates or mitigates the aforesaid disadvantages.

According to the present invention there is a percussive cutting machine having a tool bit comprising a solid shank portion having means at one end connecting the bit to a percussive tool driven by a percussive motor and a cutting portion at its other end, the cutting portion being an end face provided with a circular cutting edge surrounding a recess formed in said end face.

Preferably, the recess is in the form of a truncated cone.

Preferably also, the cutting portion is in the form of a tungsten carbide tip secured to the start portion and into which said recess is formed.

Preferably also, the shank portion is formed with an undercut portion on to which is secured a tungsten carbide bush which forms the outer wall of said recess and the cutting edge.

The shank portion may be made to suit either a male or a female connection to the percussive tool and may be secured thereto by a pre-stressed spring pin.

Preferably, said percussive machine comprises a block containing three or more random spaced percussion motors.

Preferably also, the percussive motors are pneumatically operated. Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is a side view, partially in section forming part of a mcahine of a tool bit according to the invention; Figure 2 is a view in the direction of the arrow A of the sectioned portion of Figure 1 to a larger scale; Figures 3 and 4 are views of the sectioned portion of a modified tool bit; Figure 5 is a sectional view of a female tool bit according to the invention; and Figure 6 is a sectional view of a further modified tool bit.

Referring to the drawings percussive cutting machine (not shown) has a tool bit comprising a shank 1 which has an enlarged portion 2 at one end which connects the tool bit to a percussive tool of the machine. The enlarged portion 2 is provided with a hole 3 which cooperates with a corresponding hole in a female portion of the percussive tool. The holes are misaligned by a few thousandths of an inch so that a spring pin can be driven through the holes to secure the tool bit to the percussive tool while forcing the surface 4 against a face on the tool so as to place the pin under stress.

The other end of the shank 1 is provided with a slightly enlarged cutting portion 5, the end face 6 of which is under cut to form a shallow recess 7 in the form of a truncated cone.

The bottom rim of the recess forms a circular cutting edge 8 which may be either sharpened to a point or may have a slight flat formed thereon (as shown in Figure 2) so as to avoid chipping of the cutting edge. The tool bit shown in Figures 1 and 2 is particularly suitable for cutting grooves in concrete or the like and a maximum efficiency of cutting is achieved because the cutting edge 8 is of a maximum length in relation to the diameter of the shank.

Furthermore, the recess 7 allows easy dispersion of the cuttings and the slightly enlarged portion 5 on the shank prevents the remainder of the shank body 9 fouling the sides of the cut groove.

In the embodiment shown in Figures 1 and 2 the shank is formed from steel with at least the tip containing the cutting edge 8 hardened by conventional heat treatment.

In a modified embodiment as shown in Figure 3 the tip of the shank which forms the slightly enlarged portion 5 may be replaced by a tungsten carbide slug 10 which is brazed into an undercut portion 11 of the shank 1. As in the embodiment shown in Figures 1 and 2 a recess 7 is formed in the slug, the rim of which forms a cutting edge 8. The slug can be parallel sided and of a slightly larger diameter to the shank in order to form the slightly enlarged portion 5 or alternatively the slug may be upwardly convergent (as shown in broken lines in Figure 3) in order to achieve the same purpose.

In a further embodiment (as shown in Figure 4) the slightly enlarged portion 5 is formed by a tungsten carbide bush 12 which is brazed on to an undercut portion 13 of the shank 1. In this embodiment the end face 6 of the shank stops short of the end of the bush, the latter being chamfered at 14 so that a recess 15 is formed to allow dispersion of cuttings. This embodiment illustrates an extremely economic method of manufacturing a tipped cutting tool due to the simplicity of the bush and the simple machining required on the shank 1.

The embodiments shown in Figures 1 to 4 illustrate male bits adapted for connection to female parts of percussive tools. The embodiment shown in Figure 5 corresponds to the embodiment shown in Figure 4 with the exception that it is a female tool bit provided with a recess 16 into which may fit the male portion of a percussive tool. As in Figure 1 a securing hole 3 is provided for co operation with a similar misaligned hole in the male portion of the tool.

The cutting edge 8 may be provided with grooves (not shown) to assist the dispersal of cuttings out of the recess 7 and any other suitable material may be used instead of tungsten carbide for forming the tip.

The tool bits described above are particularly suitable for cutting grooves in concrete such as those grooves cut across concrete in order to assist adhesion and improve water dispersal. In this case the percussive machine comprises a block containing three or more randomly spaced percussion tools driven by pneumatically operated percussive motors and bits of the type described above attached to the tools. The block is mounted on height-adjustable wheels which enable the machine to be pushed across a concrete surface thereby forming three or more randomly spaced grooves.

The tool bits described above may also be used in other percussive machines such as wall groovers, scabbling machines, crack cutters, scaling hammers and the like.

Moreover, while the tool bits have been described as being adapted for connection to the shank of a percussive tool in a modified embodiment they may be formed integrally therewith. Furthermore, while the bushes have been described above as being brazed on to the shank in an alternative embodiment as shown in Figure 6 the bushes are detachable secured, for example, by means of a spring pin arrangement as previously described orby means of an elastic locking member in the form of a flexible detent comprising a rubber plug 17 in the shank cooperating with a groove 18 in the inner periphery 13 of the bush. Alternatively, the plug 17 may be formed from steel at its ends with compressible rubber or a spring in the centre so as to allow removal and replacement of the bush.

WHAT WE CLAIM IS: 1. A percussive cutting machine having tool bit comprising a shank portion having means at one end connecting the bit to a percussive tool driven by a percussive motor a cutting portion of its outer end, the cutting portion having an end face provided with and a circular cutting edge surrounding a recess formed in said end face.

2. A machine as claimed in Claim 1, in which the recess is in the form of a truncated cone.

3. A machine as claimed in Claim 1 or 2, in which the cutting portion is in the form of a tungsten carbide tip secured to the shank portion and into which said recess is formed.

4. A machine as claimed in any preceding claim, in which the shank portion is formed with an undercut portion on to which is secured the cutting portion in the form of a tungsten carbide bush which forms the outer wall of said recess and the cutting edge.

5. A machine as claimed in any preceding claim, in which the shank portion is formed to suit a male connection to the percussive tool.

6. A machine as claimed in any one of Claims 1 to 4, in which the shank portion is formed to suit a female connection to the percussive tool.

7. A machine as claimed in Claim 5 or 6, in which the shank portion is connected to the percussive tool through a prestressed spring pin.

8. A machine as claimed in Claim 5 or 6, in which the shank portion is connected to the percussive tool through a flexible detent, the tool co-operating with a groove in the shank or vice versa.

9. A machine as claimed in Claim 10 or 11 in which the percussive tools are driven by pneumatically operated percussive motors.

10. A percussive machine substantially as hereinbefore described with reference to the accompanying drawings.

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Claims

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

5 on the shank prevents the remainder of the shank body 9 fouling the sides of the cut groove.

In the embodiment shown in Figures 1 and 2 the shank is formed from steel with at least the tip containing the cutting edge 8 hardened by conventional heat treatment.

In a modified embodiment as shown in Figure 3 the tip of the shank which forms the slightly enlarged portion 5 may be replaced by a tungsten carbide slug 10 which is brazed into an undercut portion 11 of the shank 1. As in the embodiment shown in Figures 1 and 2 a recess 7 is formed in the slug, the rim of which forms a cutting edge 8. The slug can be parallel sided and of a slightly larger diameter to the shank in order to form the slightly enlarged portion 5 or alternatively the slug may be upwardly convergent (as shown in broken lines in Figure 3) in order to achieve the same purpose.

In a further embodiment (as shown in Figure 4) the slightly enlarged portion 5 is formed by a tungsten carbide bush 12 which is brazed on to an undercut portion 13 of the shank 1. In this embodiment the end face 6 of the shank stops short of the end of the bush, the latter being chamfered at 14 so that a recess 15 is formed to allow dispersion of cuttings. This embodiment illustrates an extremely economic method of manufacturing a tipped cutting tool due to the simplicity of the bush and the simple machining required on the shank 1.

The embodiments shown in Figures 1 to 4 illustrate male bits adapted for connection to female parts of percussive tools. The embodiment shown in Figure 5 corresponds to the embodiment shown in Figure 4 with the exception that it is a female tool bit provided with a recess 16 into which may fit the male portion of a percussive tool. As in Figure 1 a securing hole 3 is provided for co operation with a similar misaligned hole in the male portion of the tool.

The cutting edge 8 may be provided with grooves (not shown) to assist the dispersal of cuttings out of the recess 7 and any other suitable material may be used instead of tungsten carbide for forming the tip.

The tool bits described above are particularly suitable for cutting grooves in concrete such as those grooves cut across concrete in order to assist adhesion and improve water dispersal. In this case the percussive machine comprises a block containing three or more randomly spaced percussion tools driven by pneumatically operated percussive motors and bits of the type described above attached to the tools. The block is mounted on height-adjustable wheels which enable the machine to be pushed across a concrete surface thereby forming three or more randomly spaced grooves.

The tool bits described above may also be used in other percussive machines such as wall groovers, scabbling machines, crack cutters, scaling hammers and the like.

Moreover, while the tool bits have been described as being adapted for connection to the shank of a percussive tool in a modified embodiment they may be formed integrally therewith. Furthermore, while the bushes have been described above as being brazed on to the shank in an alternative embodiment as shown in Figure 6 the bushes are detachable secured, for example, by means of a spring pin arrangement as previously described orby means of an elastic locking member in the form of a flexible detent comprising a rubber plug 17 in the shank cooperating with a groove 18 in the inner periphery 13 of the bush. Alternatively, the plug 17 may be formed from steel at its ends with compressible rubber or a spring in the centre so as to allow removal and replacement of the bush.

WHAT WE CLAIM IS: 1. A percussive cutting machine having tool bit comprising a shank portion having means at one end connecting the bit to a percussive tool driven by a percussive motor a cutting portion of its outer end, the cutting portion having an end face provided with and a circular cutting edge surrounding a recess formed in said end face.
2. A machine as claimed in Claim 1, in which the recess is in the form of a truncated cone.
3. A machine as claimed in Claim 1 or 2, in which the cutting portion is in the form of a tungsten carbide tip secured to the shank portion and into which said recess is formed.
4. A machine as claimed in any preceding claim, in which the shank portion is formed with an undercut portion on to which is secured the cutting portion in the form of a tungsten carbide bush which forms the outer wall of said recess and the cutting edge.
5. A machine as claimed in any preceding claim, in which the shank portion is formed to suit a male connection to the percussive tool.
6. A machine as claimed in any one of Claims 1 to 4, in which the shank portion is formed to suit a female connection to the percussive tool.
7. A machine as claimed in Claim 5 or 6, in which the shank portion is connected to the percussive tool through a prestressed spring pin.
8. A machine as claimed in Claim 5 or 6, in which the shank portion is connected to the percussive tool through a flexible detent, the tool co-operating with a groove in the shank or vice versa.
9. A machine as claimed in Claim 10 or 11 in which the percussive tools are driven by pneumatically operated percussive motors.
10. A percussive machine substantially as hereinbefore described with reference to the accompanying drawings.