GB2354725A

GB2354725A - Rotary cutterblock grinding arbor

Info

Publication number: GB2354725A
Application number: GB9918748A
Authority: GB
Inventors: Paul Bailey; Carl Quirke
Original assignee: WADKIN Ltd
Current assignee: WADKIN Ltd
Priority date: 1999-08-10
Filing date: 1999-08-10
Publication date: 2001-04-04
Also published as: GB9918748D0

Abstract

An arbor for mounting a rotary cutterblock in a cradle of a grinding machine includes a hydraulically expansible shaft (1,11) which can be expanded to clamp a rotary cutterblock in place for and during grinding. The hydraulic pressure can be increased by means of a pressure grease gun or by mechanically moving a piston (26) to decrease the working volume of a hydraulic chamber (27) so as to expel hydraulic grease from that chamber (27).

Description

2354725 TITLE Rotary Cutterblock Grinding Arbor 01

DESCRIPTION Field of the Invention

The invention relates to the grinding and re-grinding of the blades of a rotary cutterblock, and provides a novel and inventive arbor for holding those blades during the grinding process.

Background Art

When a rotary cutterblock has its blades ground or reground, it is mounted on a grinding arbor on which it is carried to a grinding machine. The arbor has shaf t end portions extending one from each axial end of the cutterblock, and on those arbor shaf t end portions are bearings on which the arbor is mounted on a cradle of the grinding machine so as to lock the arbor against all movement other than rotary movement. With the arbor thus mounted on the cradle, the cutterblock is positioned axially of the arbor to bring it into the correct alignment with a grinding wheel, and is then locked onto the arbor using whatever locking means are provided on the rotary cutterblock.

Some cutterblocks incorporate hydraulic locking means such as that disclosed in our European Patent No. EP-B-325577. Such a cutterblock is conventionally locked onto the arbor by injecting hydraulic grease at high pressure through a grease nipple on the cutterblock so as to contract the central bush of the cutterblock onto the arbor shaft. other cutterblocks utilize mechanical locking means in the form of a locknut on the end of the arbor exerting an axial load, pushing the block against a shoulder on the arbor or against a spacer or shim to adjust the axial position. The hydraulically locked cutterblocks are self-centring onto the arbor shaft, but the manually locked cutterblocks have no centring facility and are therefore subject to centring inaccuracies as they are moved from the grinding machine to the processing machine such as a moulding machine. The hydraulically locked cutterblocks have the disadvantage that in order to lock the cutterblock on the arbor shaft the cutterblock itself must be physically handled. That physical handling can result in the axial displacement of the cutterblock on the arbor shaft, which is something that must then be corrected before grinding can take place.

It is an object of the invention to provide a novel grinding arbor for a rotary cutterblock which is universal in the sense that it accepts both hydraulically and mechanically locked cutterblocks and permits automatic self-centring together with locking of those cutterblocks onto the shaft with minimal need for handling the cutterblock.

The Invention The invention provides an arbor for mounting a rotary wordworking cutterblock in a cradle of a grinding machine, the arbor being sized to pass through a central bore in the cutterblock and to protrude from opposite ends of that central bore, and carrying bearings on those protruding end portions for mounting the arbor and cutterblock on the grinding machine cradle, characterized in that means for locking the cutterblock on the arbor are provided on the arbor and comprise a flexible sleeve around at least a portion of the arbor, a hydraulic chamber within the arbor in communication with an inner cylindrical surface of the flexible sleeve, and means for increasing the hydraulic pressure within the hydraulic chamber to cause expansion of the sleeve until its outer circumference clamps against the central bore of the cutterblock. The hydraulic chamber may be filled with any suitable hydraulic fluid, but high pressure grease is particularly suitable. The hydraulic chamber may be a variable volume chamber, with the means for increasing the hydraulic pressure being a plunger associated with screw-threaded means for mechanically advancing the plunger in a direction to decrease the volume of the chamber in order to increase the hydraulic pressure therein. The use of a variable volume hydraulic chamber has the advantage of cleanliness in use, but as an alternative the hydraulic chamber may be a fixed volume chamber and the hydraulic pressure can be increased using an external grease gun applied to a grease nipple.

Drawings Figure 1 is a partly sectional side view of an arbor according to the invention; and Figure 2 is a partly sectional side view of the arbor of Figure 1 with the bearings, hand wheel and outer sleeve removed.

The arbor illustrated in the drawings comprises a solid machined shaft 1 carrying at one end bearings 2,3 separated by a spacer 4 and at the other end a single bearing S. The bearings 2, 3 and 5 f it into cooperating location supports 6,7 of a cradle of grinding machine. The location supports 6,7 are shown only in phantom line in Figure 1 because they form part of the grinding machine and not of the arbor itself.

Fast to one end of the shaft 1 is a hand wheel 8 which is locked onto the shaf t 1 by two dog point grub screws 9 During grinding the hand wheel 8 is used to control the rotation of a cutterblock mounted on the arbor, as the blade edges are brought against the edge of the rotating grinding wheel.

At the other end of the shaf t 1, remote from the hand wheel 8, the shaft 1 is formed with a ribbed projecting end 10 designed as a hand grip making it easier to carry heavy cutterblocks when mounted on the arbor.

Around a mid-portion of the shaft 1 is secured a flexible sleeve 11 made of mild steel. The wall thickness of the sleeve 11 is such as to give the sleeve the required elastic flexibility in use without creating distortion in the arbor.

The shaft I (Figure 2) has four lands 12, 13, 14 and 15 of the same diameter as the internal diameter of the sleeve 11, separated by three portions 16, 17 and 18 of slightly smaller diameter. The sleeve 11 thus fits over the shaft 1 to define three annular hydraulic chambers 161, 17, and 181 between the sleeve and the portions 16, 17 and 18. A greater or lesser number of hydraulic chambers may be chosen, depending on the axial length of the arbor, its diameter, the strength and flexibility of the materials used and the design pressure to be applied to the hydraulic medium in the chamber or chambers. The three chambers are linked hydraulically by arcuate grooves 19, 20 milled into the lands 13 and 14. The sleeve 11 is welded to the shaft 1 at its opposite ends.

An axial blind stepped bore 21 is formed in the shaft 1 from the righthand end portion 10. The bore 21 comprises a screw-threaded portion 22 of the largest diameter, leading to a smaller diameter cylindrical portion 23, leading in turn to the smallest diameter portion 24 which communicates via a cross-bore 2S with the chamber 181.

In the cylindrical portion 23 of the bolt 21 is received a screw-threaded actuator piston 26 which can be moved axially of the shaft 1 by advancing a shaft portion of the piston along the screw-thread of the portion 22. Between the plunger 26 and the inner end of the stepped bore 21 is formed a hydraulic chamber 27 the volume of which can be varied by the mechanical advancement of the plunger in either direction axially along the shaft 1.

An axial blind stepped bore 28 is formed in the shaft I from the lefthand end. The bore 28 comprises a screw-threaded portion 29 and a nonthreaded portion 30. The portion 30 communicates with the chamber 161 via a cross-bore 31. The screw-threaded portion 29 retains a grease inlet valve 32, which can be used as a grease top-up valve.

In use, the intercommunicating bores 21, 25, 28 and 31, the chambers 27, 161, 171 and 181 and the grooves 19,20 are filled with hydraulic grease by pumping in the grease through the valve 32 until the cylindrical portion 23 receives grease. The actuator piston 26 is then inserted into the cylindrical portion 23 of the stepped bore 21 so as to define the movable wall of the hydraulic chamber 17.

A cutterblock (not illustrated) is then threaded onto the arbor, and the arbor/cutterblock assembly is placed in a grinding machine cradle where the bearings 2, 3 and 5 are clamped. The arbor is then held fast against translational movement but is freely rotatable. The cutterblock, however, is axially slidable along the sleeve 11.

The cutterblock is then moved, as necessary, axially to a position which corresponds to the axial position of a master pattern (not shown) in the form of the blade shape to be ground in the cutterblock. To anchor the cutterblock on the arbor, the actuator piston 26 must be advanced along the screw-threaded portion 22 of the stepped bore 21 so as to decrease the volume of the hydraulic chamber 27. Because the valve 32 is closed, the hydraulic pressure of the grease in the chambers 161, 171 and 181 increases as the grease is displaced from the hydraulic chamber 17. At about 100 bar, the hydraulic pressure beneath the sleeve 11 causes the sleeve to expand elastically to a larger diameter, until it frictionally grips the internal bore of the cutterblock.

In contrast, the hydraulic pressure that can be attained using an external grease gun is about 450 bar.

There is no need to handle the rotary cutterblock during the step of clamping it to the arbor, so the possibility of accidentally moving the cutterblock during set-up is avoided. Moreover the clamping of the cutterblock onto the arbor is quick, efficient and simple, using as it does only the single screw-threaded actuator piston 26 to vary the hydraulic clamping pressure.

Claims

1. An arbor for mounting a rotary wordworking cutterblock in a cradle of a grinding machine, the arbor being sized to pass through a central bore in the cutterblock and to protrude from opposite ends of that central bore, and carrying bearings on those protruding end portions for mounting the arbor and cutterblock on the grinding machine cradle, characterized in that means for locking the cutterblock on the arbor are provided on the arbor and comprise a flexible sleeve around at least a portion of the arbor, a hydraulic chamber within the arbor in communication with an inner cylindrical surface of the flexible sleeve, and means for increasing the hydraulic pressure within the hydraulic chamber to cause expansion of the sleeve until its outer circumference clamps against the central bore of the cutterblock.

2. An arbor according to claim 1, wherein the hydraulic chamber is filled with grease.

3. An arbor according to claim 2, wherein the means for increasing the hydraulic pressure within the hydraulic chamber comprises a piston for increasing or decreasing the volume of the hydraulic chamber and a screwthreaded means for mechanically advancing the piston in a direction to decrease the volume of, and thereby to increase the hydraulic pressure in, the hydraulic chamber.

4. An arbor according to claim 3, wherein the screw-threaded means comprises a threaded shaft portion of the piston aligned axially of the arbor and accessed from one axial end of the arbor.

5. An arbor according to claim 4, wherein the hydraulic chamber communicates with hydraulic passages extending continuously through the arbor from the hydraulic chamber at the one axial end of the arbor to a grease inlet valve at the other axial end.

6. An arbor according to claim 1 or claim 2, wherein the means for increasing the hydraulic pressure within the hydraulic chamber comprises an external grease gun.

7. An arbor according to any preceding claim, wherein the flexible sleeve is a mild steel sleeve.

8. An arbor for mounting a rotary woodworking cutterblock in a cradle of a grinding machine, substantially as described herewith with reference to the drawings.