GB2437933A

GB2437933A - Machining tool with internal fluid delivery system

Info

Publication number: GB2437933A
Application number: GB0609057A
Authority: GB
Inventors: Vladimir Gviniashvill
Original assignee: LIVERPOOL INNOVATIVE TECHNOLOG
Current assignee: LIVERPOOL INNOVATIVE TECHNOLOG
Priority date: 2006-05-09
Filing date: 2006-05-09
Publication date: 2007-11-14
Also published as: WO2007129122A1; GB0609057D0

Abstract

A rotary machining tool, comprises ```a rotatable hub (10) carrying a plurality of tool elements (14) around its outer periphery for machining a work-piece at a predetermined contact region of the tool. A plurality of passages (26) extend outwardly from an inner chamber (22) of the hub (10) at a non-orthogonal angle to the hub axis (12) so as to emerge at the outer periphery of the hub between respective pairs of adjacent tool elements (14). A nozzle (28) is disposed within the inner chamber (22) adjacent to the rotary path of the inner ends of the hub passages (26) and adapted to direct fluid lubricant into no more than two of the passages (26) at any time when the hub is rotated, such that the fluid lubricant is ejected between tool elements (14) substantially only at the predetermined contact region of the tool.

Description

I

DESCRIPTION

MACHINING TOOL HAVING AN IMPROVED

INTERNAL FLUID DELIVERY SYSTEM

The present invention relates to a machining tool and, in particular, a tool having means for delivering a fluid to a contact zone with a work-piece. More particularly the present invention relates to grinding or milling tools.

It is common in the machine tool industry to use abrasive grinding wheels to shape and finish work-pieces, and to use milling wheels to cut work-pieces. In almost all machine tool operations, the friction between the tool and work-piece generates tremendous amounts of heat energy which, if left uncontrolled, can lead to significant damage of the tool and the work piece. Accordingly, tool life is shortened, and machine tool operations are less productive and expensive.

It is therefore common in the industry to use a coolant, particularly a fluid coolant, to reduce the temperature in the region of the contact area between the tool and the work-piece. Typically, the coolant is delivered by spraying to ensure that there is a constant supply of fluid to the tool and to seek to direct the fluid towards the grinding or cutting zone, where the tool engages the work-piece.

Whilst the fluid can be delivered to the grinding or cutting zone, it is often difficult to ensure that the necessary quantity of such fluid actually arrives at the interstices between the tool and the work-piece and therefore large volumes must generally be continuously supplied to the grinding or cutting zone for the tool to operate effectively. This need to keep a continuous supply of coolant fluid between the grinding wheel and work-piece becomes even more problematic where the coolant fluid cannot be introduced in close proximity to the grinding or cutting zone while the tool is engaged with a work-piece due to, for example, the depth of the grinding or cutting action in the work-piece.

Known machining tools include those having a grinding wheel where fluid coolant is supplied to the grinding wheel through the spindle of the machine by way of a central hole. The fluid coolant is pumped out through slots towards the periphery of the wheel. These known tools suffer from the disadvantage that fluid coolant exits the wheel around the whole periphery of the wheel. However, the fluid coolant need only be supplied to the contact zone between the tool and a work-piece where material grinding or cutting occurs. Therefore, most of the fluid coolant is wasted. Furthermore, a wheel loaded with liquid tends to burst at high rotational speeds and a special spindle is required to ensure that the fluid coolant is delivered, whereby the wheel can not be used on other machines.

Another known tool, having a grinding wheel and a "through wheel" fluid coolant delivery where fluid is supplied from the nozzle into the wheel chamber using a flooding method, has a chamber disposed in the wheel, from which fluid coolant is pumped out through slots towards the cutting zone by the centrifugal effect of the rotating grinding wheel. In this system, fluid coolant is intended to exit the wheel in the area of material removal rather than the whole periphery of the wheel. However, in the use of this flooding method, fluid enters many holes at once and fluid coolant is wasted. As a consequence, fluid coolant caimot be directed accurately towards the small area of the cutting zone. A further disadvantage is that delivery of the fluid coolant of the cutting zone in this system mostly depends on the wheel speed and cannot be efficiently increased if necessary. In addition, this type of tool cannot make use of non-liquid coolants, such as a gas.

It is the object of the present invention to overcome or alleviate one or more

of the problems associated with the prior art.

In accordance with the present invention, there is provided a rotary machining tool, comprising a rotatable hub carrying a plurality of tool elements around its outer periphery for machining a work piece at a predetermined contact region of the tool; a plurality of passages extending outwardly from an inner chamber of the hub at an angle to the hub axis so as to emerge at the outer periphery of the hub between respective pairs of adjacent tool elements; and a nozzle disposed within said inner chamber adjacent to the rotary path of the inner ends of the hub passages and adapted to direct fluid lubricant into no more than a predetermined number of said passages at any time when the hub is rotated, such that the fluid lubricant is ejected between tool elements substantially only at the predetermined contact region of the tool.

Preferably, the predetermined number is two only.

Preferably, the inner chamber has a peripheral surface at which the inner ends of the passages emerge and which is of part-circular or angled section, the outlet nozzle being shaped so as to match the curvature or angled profile of said peripheral surface of the inner chamber and being mounted so as to be closely spaced therefrom.

Advantageously, the passages through the hub are of circular section and extend at the same, non-orthogonal angle to the hub axis, whereby they emerge at the peripheral surface of the hub chamber with elongated, substantially elliptical mouths, the mouth of the nozzle being shaped substantially to match.

The use of passages extending at a non-orthogonal angle to the hub axis, as opposed to being radial in the known system described hereinbefore, has the advantage of enabling the centrifugal pumping effect to be maximised.

The tool elements can comprise arcuate abrasive elements when the rotary tool is a grinding wheel and cutting elements when the rotary tool is a milling wheel.

Advantageously, the angular position of the nozzle within the hub chamber can be adjusted to enable the lubricating fluid to be supplied to different selected contact regions to the tool periphery.

In some embodiments there can be two or more nozzles for supplying different fluid lubricants, which can be liquids and/or gases, into the hub passages and thence to the predetermined cutting zone at the tool periphery.

The invention is now described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a partially cut-away side elevation of a grinding wheel in accordance with one embodiment of the present invention; Fig. 2 is a partially cut-away front elevation of the grinding wheel of Fig. 1; Fig. 3 is a partial sectional view of a fluid delivery means; Fig. 4 is a partial cut-away view of part of a milling tool in accordance with a second embodiment of the grinding wheel of Fig. 1; and Figs. 5, 6 and 7 are partial front elevations illustrating grinding wheels having abrasive sections of three different forms.

The grinding wheel of Figs. 1, 2 and 3 comprises a hub 10 mounted on a spindle (not shown) for rotation about a horizontal central axis 12 and having a plurality of arcuate abrasive sections 14 disposed around its periphery which are spaced apart circumferentially by gaps 16 forming respective radially extending channels disposed between adjacent arcuate abrasive sections 14. The grinding wheel hub 10 is formed on one side with a large circular recess 18. As best seen in Fig. 3, the recess 18 has an outer peripheral surface 24 which is of part-circular (or angular) transverse section whereby effectively to define an annular chamber 22 internally within the hub 10.

Extending between the peripheral surface 24 of the recesses 18/chamber 22 and the outer peripheral surface of the hub 10 is a plurality of passages/holes 26 which in this embodiment comprise straight bores of uniform circular section. The radially outermost end of each passage 26 communicates with a respective one of the radial gaps 16 between adjacent pairs of the arcuate abrasive sections 14.

As best seen in Fig. 1, in this embodiment the passages 26 are each disposed at the same (non-radial) angle relative to the hub axis 12 (and to tangents to the hub periphery) whereby the distances between the radially inner (inlet) ends of the passages 26 when they reach the surface of the internal chamber 18 has reduced substantially to zero as seen in Figs. I and 2.

Disposed within the hub recess 18 is a fluid dispensing nozzle 28 having a nozzle outlet 30 facing, but spaced slightly inwardly of the curved peripheral surface 24 of the recess 18. The outlet 30 is shaped so as to conform closely to the shape of the curved peripheral surface 24 of the hub recess 18 so that there is a substantially uniform radial spacing between the periphery of the nozzle outlet 30 and the adjacent portion of the peripheral surface 24 of the recess 18.

The nozzle 28 itself lies in a plane perpendicular to the rotational axis of the grinding wheel 10 but has a connecting tube 32 at its inlet end which extends perpendicularly away from the wheel 10 for connection, in use, to a cooling fluid supply (not shown).

As shown in Figs. I and 3, the fluid delivery outlet 30 of the nozzle 28 is positioned very close to the inlet ends of the passages 26. The distance between the nozzle edge and the peripheral surface 24 of the internal chamber 18 is reduced to the minimum practically possible, consistent with physical contact between the nozzle and the rotating hub being avoided.

The shape of the mouth of the nozzle 28 conforms to that of the curved internal peripheral surface of the hub internal chamber 18.

The cross-sectional area of the nozzle is equal or substantially equal to the cross-sectional area of each of the passages 26.

When the hub 10 is rotated about the hub axis 12, the axis of the nozzle is arranged to coincide sequentially with the axis of each of the opposed passages 26 and also with its angular direction whereby there is momentary alignment between fluid ejected by the nozzle 28 and each of the passages 26 in turn.

The passages 26 act as conduits between the nozzle 28 and the gaps 16 between the arcuate abrasive sections 114 for delivering fluid coolant to the outer periphery of the grinding wheel 10.

Because of the angle at which the circular sectioned passages 26 emerge at the curved peripheral surface 24 of the recess 18, their shape at the interface with the surface 24 is generally elliptical. Thus, in order to overlap accurately with the passages 26, the nozzle outlet 30 is similarly elliptical in shape..

As will be best seen from Fig. 1, in this embodiment, the length of the elliptical nozzle outlet in the circumferential direction of the hub corresponds substantially to the length of the elliptical inlets of the passages 26 whereby at any one time the nozzle is supplying fluid, in this embodiment, to a maximum of two passages 26 depending on the instantaneous overlap of the nozzle therewith. Thus, cooling fluid is restricted to a correspondingly short circumferential length of the grinding wheel.

As showii in Figs. 1 and 2, the abrasive sections 14 are adhered to the wheel hub 10 around its periphery. As shown in Fig. 5, the abrasive sections 14 can have two central grooves 34, preferably of semi-cylindrical shape, at its two opposed ends whereby each adjacent pair of abrasive sections 14 form outlet channels of cylindrical shape midway, in this case, along the gaps 16.

Fig. 6 shows an embodiment where the gaps are arranged at an angle to the hub axis 12, but parallel to each other. Fig. 7 shows a similar arrangement but where only every other gap 16 is mutually parallel.

Fig. 4 shows how exactly the same practical effect can be achieved to form a milling wheel 10 if the arcuate abrasive sections 14 are replaced by metal segments 14a carrying cutting plates 40.

The cutting plates 40 are located closely adjacent to the outlets of the passages 26, whereby to guide the fluid flow from the passages 26 onto their surface and onto the work-piece during a milling operation.

In use, fluid coolant is delivered by a pump (not shown) from the supply tank to the nozzle 28 by way of a conduit. The hub 18 is caused to rotate by a drive motor (not shown) in the direction B indicated in Fig. 1. By means of the pump action and the centrifugal effect acting on the fluid due to the rotation of the hub, the fluid coolant leaving the nozzle is caused to flow outwardly towards the periphery of the hub by way of the maximum of two passages 26 (in this embodiment) which are sequentially aligned therewith at any given time, the nozzle being positioned within the hub 10 so that the coolant fluid flow is directed specifically to the desired contact region between the wheel 10 and work-piece (not shown).

In other embodiments, the nozzle length could be greater so as to overlap with an arrangement of three or more passages 26 at any given time. However, the preferred arrangement is that shown in the drawings where the nozzle can communicate with a maximum of two passages 26.

In still further embodiments, and depending upon the particular requirements, two nozzles can be employed for the delivery of two types of fluid (liquid or gas) The actual position at which the nozzle 28 is disposed within the hub chamber 18 can be selected by rotating the nozzle 28 around the chamber 18 to a new fixed position, thus enabling fluid to be supplied at any required location around the external surface of the grinding wheel where a working zone is located.

Claims

CLAIMS

1. A rotary machining tool, comprising a rotatable hub carrying a plurality of tool elements around its outer periphery for machining a work-piece at a predetermined contact region of the tool; a plurality of passages extending outwardly from an inner chamber of the hub at an angle to the hub axis so as to emerge at the outer periphery of the hub between respective pairs of adjacent tool elements; and a nozzle disposed within said inner chamber adjacent to the rotary path of the inner ends of the hub passages and adapted to direct fluid lubricant into no more than a predetermined number of said passages at any time when the hub is rotated, such that the fluid lubricant is ejected between tool elements substantially only at the predetermined contact region of the tool.

2. A rotary tool as claimed in claim 1, wherein the predetermined number is two.

3. A rotary tool as claimed in claim I or 2, wherein the inner chamber has a peripheral surface at which the inner ends of the passages emerge and which is of part-circular or angled section, the outlet of the nozzle being shaped so as to match the curvature or angled profile of said peripheral surface of the inner chamber and being mounted so as to be closely spaced therefrom.

4. A rotary tool as claimed in claim 3, wherein the passages through the hub are of circular section and extend at the same, non-orthogonal angle to the hub axis, whereby they emerge at the peripheral surface of the hub chamber with elongated, substantially elliptical mouths, the mouth of the nozzle being shaped substantially to match.

5. A rotary tool as claimed in any of claims I to 4, wherein the inner chamber of the hub is formed by a recess on one side of the hub.

6. A rotary tool as claimed in any of claims 1 to 5, wherein said tool elements comprise arcuate abrasive elements when the rotary tool is a grinding wheel and cutting elements when the rotary tool is a milling wheel.

7. A rotary tool as claimed in any of claims I to 6, wherein the angular position of the nozzle within the hub chamber can be adjusted to enable the lubricating fluid to be supplied to different selected contact regions at the tool periphery.

8. A rotary tool as claimed in any of claims 1 to 7, wherein there are two or more nozzles for supplying different fluid lubricants, which can be liquids and/or gases, into the hub passages and thence to the predetermined cutting zone at the tool periphery.

9. A rotary machining tool substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.