GB2103123A

GB2103123A - Apparatus for the supply of a coolant to a rotary cutting tool for the machining of metals by cutting

Info

Publication number: GB2103123A
Application number: GB08218489A
Authority: GB
Inventors: Otto Eckle
Original assignee: Komet Praezisionswerkzeuge Robert Breuning GmbH
Current assignee: Komet Praezisionswerkzeuge Robert Breuning GmbH
Priority date: 1981-07-25
Filing date: 1982-06-25
Publication date: 1983-02-16
Also published as: DE3129403C2; SE8203171L; FR2510018A1; JPS5822642A; DE3129403A1; DE8121883U1

Abstract

A drilling tool 1 having radial and axial coolant ducts is provided with a coolant ring 7 on its cylindrical shank 2, the ring 7 being connectable externally to a stationary feed pipe. Internally the ring 7 communicates through a ring duct 5 with the coolant bores 4, 5, and has a pair of wall parts 7a each adjoining the duct 5 and defining a bore 9 in which the shank 2 fits. The shank 2 has within each of the two bores 9 a screwthreadlike transport groove 12, 13, the depth t of which is greatest adjacent the duct 8 and decreases to zero towards the two outer ends of the bores 9. The coolant ring 7 is of metal. The two helical transport grooves 12 and 13 are of opposite hand. For a dextrorotatory tool shank 2 the front transport groove 12 facing the cutting tools is right-handed and the rear transport groove 13 is left-handed. Coolant is driven towards the duct 5 on rotation of the tool 1. <IMAGE>

Description

SPECIFICATION Apparatus for the supply of a coolant to a rotary cutting tool for the machining of metals by cutting The invention relates to an apparatus for the supply of a coolant to a rotary cutting tool for the machining of metals by cutting, the apparatus including a coolant ring arranged on a cylindrical shank of the tool and connectable externally to a stationary feed pipe, a ring duct provided internally of the coolant ring communicating with coolant bores in the tool shank, the coolant ring fluidtightly surrounding the tool shank with a pair of wall parts each adjoining the ring duct and each provided with a bore in which the cylindrical tool shank fits.

In a known apparatus of this Lype (United Kingdom Patent 1 366 638) the coolant ring is of plastics material, particularly nylon. Since nylon exhibits a certain elasticity, the bores of the wall parts adjoining the ring duct are able to surround the cylindrical shank closely. Good sealing is also achieved by this means initially. However, after long use wear occurs on the nylon and also on the tool shank itself. This wear is attributable to the fact that some solid suspended matter, generally ultrafine metal chips, which always remain present in the coolant, settles in the nylon and then causes wear of the tool shank in the region of the bores. This renders the seal between the bores and the tool shank leaky, and coolant escapes.

An attempt to overcome this disadvantage has been made by forming the coolant ring of metal exactly like the tool shank and arranging the bores with a comparatively snug fit on the cylindrical shank of the tool. However, there then exists a risk of seizing between coolant ring and tool shank, and also a good seal was not achieved in spite of a snug fit.

A further proposal was to effect the seal by means of felt rings. To accommodate the latter, ring grooves were recessed in the bores in the wall parts of coolant ring, and felt rings were inserted in these grooves. It was then discovered that the felt rings produce poor sealing initially, until they have become somewhat consolidated. A good seal then exists for some time, but then this deteriorates appreciably when wear of the felt rings themselves and also of the cylindrical tool shank occurs. This wear of the cylindrical tool shank is again attributable to suspended matter which settles in the felt.

The customary shaft sealing rings, also called Simmer rings, have likewise not been found successful for the purpose mentioned, because here again there is a risk of suspended matter settling on the synthetic rubber of the Simmer rings and then leading to wear of the cylindrical tool shank. The Simmer rings themselves are also subject to heavy wear due to this suspended matter. Moreover, such Simmer rings have an irreducible overall length in the axial direction, which would have detrimental effects upon the total axial overall length of the coolant ring.

It is therefore the underlying aim of the invention to develop an apparatus for the supply of a coolant to a rotary cutting tool for the machining of metals by cutting, which tool is provided with coolant ducts, which ensures good sealing between coolant ring and tool shank even over long periods, exhibits the smallest possible overall length in the axial direction, and is at the same time simple in its construction.

This is achieved according to the invention in that the coolant ring consists of metal and the tool shank has in the region of the two bores two screwthreadlike transport grooves, the depth of which is greatest in the region of the ring duct and decreases steadily to zero towards the two outer ends of the bores of the coolant ring, the grooves being arranged mutually oppositely so that in the case of a dextrorotatory tool shank the front transport groove, nearer the cutting means is dextrorotatory (like a right-handed screwthread) and the rear transport groove is levorotatory (like a left-handed screwthread), and vice versa. This means that in the case of a levorotatory tool shank the front transport groove would turn in the lefthand direction, and the rear transport groove would turn in the right-hand direction.

It has been discovered unexpectedly that such transport grooves produce extremely good sealing, even when the bores receive the cylindrical tool shank with a normal running fit of approximately 0.01 mm. Since the coolant ring and the cylindrical tool shank consist of metal, it is impossible for suspended matter to settle on either of the two parts, so that practically no wear occurs. Good sealing is therefore ensured for long periods. The apparatus according to the invention is also comparatively simple to produce with regard to the sealing between bores and tool shank. It is only necessary for the two opposite transport grooves to be machined into the tool shank. All shaft sealing rings whatsoever can be totally omitted. It is thus possible to achieve short overall length even in the axial direction.

Further advantageous developments of the invention will appear from the dependent claims hereinafter.

The invention will now be described in more detail, solely by way of example, with reference to the accompanying drawings, in which:~ Figure 1 is a side elevation of a drilling tool with a coolant ring, partly in section; Figure 2 is a partial section through the cylindrical tool shank of the tool of Figure 1 in the region of the coolant ring, in approximately tenfold enlargement.

Figure 1 shows part of a drilling tool 1 which may have at its front end (not shown) cutting means in the form of, for example, inserted hard metal plates. In Figure 1, these cutting tools would be located on the right-hand side of the illustration. The drilling tool 1 has has at its rear end a cylindrical shank 2 which merges into a holder 3. The drilling tool can be inserted by this holder 3 into the spindle of a machine tool (not shown). instead of the conical holder 3 which is shown, a cylindrical holder, or one in the form of a flange, could be provided. The drilling tool 1 has coolant ducts 4 and 5, the coolant duct 4 extending substantially axially and the coolant duct 5 extending radially. A coolant ring 7, which is stationary during a machining operation, is provided in the region of the radial coolant duct 5.

Coolant which is fed to this coolant ring 7 from the outside, as indicated by an arrow, passes through a a radial bore 6 in the ring 7 and enters a ring duct 8 of the coolant ring 7. From this ring duct 8, the coolant, which is under pressure, passes through the radial coolant duct 5 into the axial coolant duct 4. The ring duct 8 is adjoined on both sides by annular wall parts 7a, each of which defines a bore 9. This bore 9 receives the cylindrical tool shank 2 and is such that the respective annular wall part 7a surrounds and is arranged on this cylindrical tool shank 2 with a running fit. The play between the two parts 7a and 2 is approximately 0.01 mm. The coolant ring 7 is secured against axial sliding by a shoulder 10 formed on the shank 2 and a circlip 11 engaged in a groove in the shank 2.The tool shank 2 illustrated in the exemplary embodiment shown is driven in dextrorotation, indicated by the direction of an arrow R.

The cylindrical tool shank 2 has in the region of each of the two bores 9 a screwthreadlike transport groove 12, 13, machined into the cylindrical envelope surface 14 of the tool shank.

Each of the transport grooves 12 and 13 extends from the region of the ring duct 8 into the proximity of the outer ends of the bores 9. The transport grooves 12 and 13 are so formed as to have their greatest depth tin the region of the ring duct 8. This greatest depth t may be, for example, 0.6 mm. The transport grooves 12 and 13 are machined into the cylindrical envelope surface 14 helicoidally with constant pitch s like a screwthread, but so that their depth t, tl, t2, t3, t4 decreases steadily to zero towards the outer ends of the bores 9. As a result, each of the two transport grooves 12, 13 ends in the cylindrical envelope surface 14 near the outer end of the respective bore 9. The ends of these grooves should in any case still lie within the bore 9.

The coolant ring 7, and also the tool shank 2, consist of metal.

It is important that the transport grooves 12, 13 turn in a specific direction. In the case, as in the present embodiment, of a dextrorotatory tool shank, the front transport groove 12, which faces, i.e. is closer to, the cutting means arranged on the right-hand side relative to Figure 1, must turn in the right-hand direction like a right-handed screwthread. The rear transport groove 13 must then turn in the left-hand direction like a lefthanded screwthread. In the case of a levorotatory tool shank the respective transport groove must turn in the opposite directions to those just mentioned.

As may further be seen from the drawings, particularly Figure 2, the pitch s of the transport grooves 12 and 13 is such that sufficiently wide envelope surface sections 1 4a are still present between the individual turns of the transport grooves 12 and 13. These envelope surface sections 1 4a are necessary to form, conjointly with the surfaces defining the bores 9, a ring gap with an appropriate throttle action which allows only a little coolant to pass.

The transport grooves 12 and 13 conveniently exhibit the profile of a buttress screwthread, whilst the respective flank 1 2a or 1 3a oriented substantially perpendicularly to the axis D of rotation of the tool shank 2 points towards the ring duct 8 in each case, as shown in Figure 2. The second flank 1 2b or 1 3b of the transport grooves 12, 13 extends at an angle a of approximately 600 to the axis D of rotation. A particularly good transport effect is achieved by the flank 1 2a, 1 3a extending perpendicularly to the axis of rotation, since the force exerted by the flank 1 2a, 1 3a is oriented in the axial direction.

Since different coolant rings have approximately the same axial length independently of the drill diameter, approximately the same conditions as regards the length of the bores 9 are obtained for drills of different diameters. A pitch s of approximately 2 mm has been found convenient in this respect.

It may be stated generally that the ratio of pitch s to the diameter of the cylindrical shank should be approximately 1:25.

During the rotation of the tool shank 2 the two transport grooves 12 and 13 develop upon the coolant passing through between the envelope surface 14 and the surfaces defining the bores 9 a transport effect inwards towards the ring duct 8. It has been discovered that this transport effect is sufficient to prevent any escape of coolant at the two end faces of the coolant ring 7.

Preferably the pitch of the transport grooves 12 and 13 is chosen so that approximately 4 to 6 turns of each transport groove extend within the bores 9.

Claims

1. Apparatus for the supply of a coolant to a rotary cutting tool for the machining of metals by cutting, the apparatus including a coolant ring arranged on a cylindrical shank of the tool and connectable externally to a stationary feed pipe, a ring duct provided internally of the coolant ring communicating with coolant bores in the tool shank, the coolant ring fluidtightly surrounding the tool shank with a pair of wall parts each adjoining the ring duct and each provided with a bore in which the cylindrical tool shank fits, the tool shank having in the region of each of the two bores a screwthreadlike transport groove, the depth of which is greatest in the region of the ring duct and decreases to zero towards the two outer ends of the bores of the coolant ring, the grooves being arranged mutually oppositely so that in the case of a dextrorotatory tool shank the front transport groove is dextrorotatory and the rear transport groove is levorotatory, and vice versa, and the coolant ring consisting of metal.

2. Apparatus according to Claim 1, wherein the transport grooves decrease to zero depth within the bores of the wall parts, and thereby end in the cylindrical envelope surface of the tool shank.

3. Apparatus according to Claim 1 or 2, wherein envelope surface sections of the tool shank are present between the individual turns of the transport grooves.

4. Apparatus according to Claims 1 to 3, wherein the transport grooves have the profile of a buttress screwthread, and in each groove the flank thereof oriented substantially perpendicularly to the axis of rotation of the tool shank faces towards the ring duct.

5. Apparatus according to Claim 4, wherein the other flank of the respective transport groove lies at an angle of approximately 609 to the axis of rotation.

6. Apparatus according to Claims 1 to 5, wherein the depth of the transport grooves where the ring duct adjoins the bore of the wall parts is approximately 0.6 mm.

7. Apparatus according to Claims 1 to 6, wherein the pitch of each transport groove is approximately 2 mm.

8. Apparatus according to Claim 1, wherein the ratio of the pitch of each transport groove to the diameter of the cylindrical shank is approximately 1:25.

9. Apparatus according to Claim 1 , wherein the pitch of the transport grooves is chosen so that approximately 4 to 6 turns of each transport groove extend within the bores provided in the said wall parts.

10. Apparatus for the supply of a coolant to a rotary cutting tool for the machining of metals by cutting substantially as described hereinbefore with reference to the accompanying drawings.