TECHNICAL FIELD

The present invention is concerned with an arrangement in and relating to machine tools, and then in particular to an arrangement in and relating to numerically-controlled machine tools, such as program-controlled lathes, e.g. CNC lathes.

A machine tool of the kind to which the invention refers will include means, such as a chuck for gripping and releasing unworked material (a raw material), a tool or tool arrange¬ ment for machining the material, and a stirrup-like device which is adapted so that the mutually opposing legs of said device are able to coact with the raw material in the absence of axial slip, in accordance with the conditions and propos¬ als stated in the following description.

More particularly, the invention relates to enabling raw material that has been loosened from the chuck to be moved relative to the chuck by corresponding movement of the stirrup-like device.

DESCRIPTION OF THE BACKGROUND ART

A tool arrangement of the aforedescribed kind is described and illustrated in U.S. Patent Specification 4,754,671, which describes a tool arrangement which includes a parting tool intended for parting and/or removing a machined workpiece from raw material held in the chuck.

The raw material, or unworked material, is rotated while moving the parting tool radially in relation to an axially extending centre line about which the raw material rotates, and therewith cut a channel between the machined workpiece and said raw material, wherein a stirrup-like device located

adjacent the parting tool and capable of being positioned against the outer surface of the raw material and of coacting cuttingly with the edge region of the raw material that faces the machined workpiece, either when parting of the machined workpiece is completed or during a terminating part of this parting operation, so that when the raw material is loosened and the parting tool and the stirrup-like device are moved axially, the raw material will be displaced from the chuck through an adapted distance and then again gripped by movement of the chuck jaws.

It will be particularly noticed that the construction of this known tool arrangement requires the arms 46 of the stirrup¬ like device to be sprung in a holder for both resilient radial and diametrical movement and in a direction perpendic¬ ular to said centre line.

Furthermore, each of the free ends of the arms 46 carries a respective jaw of a jaw pair 54 and the jaws are held in a desired position by screw-threaded holder means, wherein said jaw pair 54 includes mutually opposing, tool-related gripping and cutting surfaces.

The gripping surfaces are in the form of a number of saw teeth 55 which extend transversely to the centre line and which are provided with sharp edges so as to be able to saw a cut in the raw material during the workpiece parting operation and to coact grippingly with the raw material, which is in the form of rod.

In order for this combination tool to function satisfactori¬ ly, it is necessary for the distance between the saw teeth 55 to be much smaller than the diameter of the raw material, and that the sprung arms enable the saw teeth to be applied across the raw material at a moderate pressure when perform¬ ing a cutting operation.

DISCLOSURE OF THE INVENTION

TECHNICAL PROBLEMS

When considering the present standpoint of techniques as described above, in which axial movement of material to be machined from a chuck requires cutting the outer surface of the raw material, it will be seen that a technical problem resides in the provision of means which will enable the raw material to be moved easily without requiring such cutting action.

It will also be seen that a technical problem resides in the provision of means which will enable raw material which is to be worked and which has a machined and treated outer surface to be moved easily in relation to the chuck, by corresponding axial displacement of the stirrup-like device, without needing to deform the machined and sometimes highly polished outer surface.

Another technical problem is one of realizing the signifi¬ cance of and the advantages afforded by providing a stirrup¬ like device whose legs are highly rigid flexurally, at least in a direction perpendicular to said centre line.

It will also be seen that a technical problem is one of realizing the necessity of and the advantages that are afforded by permitting the distance between mutually opposed surface parts or surface sections of the flexurally rigid legs to correspond to the distance between mutually opposing parts of the raw material being worked.

It will also be seen that a technical problem is one of realizing the necessity of permitting the mutually opposed surface parts that face towards said material to have an adapted longitudinal extension which is related to and parallel with said centre line, and also to realize that the

longer the extension of said surface parts the smaller the gripping force between the legs of the stirrup-like device and the raw material to be worked, and of realizing in this regard that it is therefore necessary to adapt the length chosen to the desired gripping force between the surface parts of the legs and the corresponding surface parts of the material.

It will also be seen that a technical problem is one of realizing the advantages that are associated with and the conditions required to enable tilting of the raw material resulting from loosening said material in the chuck to generate requisite force interaction between said mutually opposed leg surface parts and the surface material parts, and that said force interaction between said surface parts shall be adaptable so that the stirrup-like device will be able to move the material relative to the chuck without plastically deforming the surface structure, even when the raw material has a smooth outer surface.

It will also be seen that a technical problem is one of realizing the significance of adapting the distance between the mutually opposing surface parts of the legs in accordance with the raw material chosen or the raw material to be worked and also in accordance with the outer dimensions and surface structure of said material, and to realize in this regard that the distance chosen should not normally be greater than the diameter of the raw material and normally equal to or slightly smaller than said diameter, for instance 0.1 mm or less than 0.2 mm smaller than said diameter.

It will also be seen that a technical problem resides in realizing the significance of providing a stirrup-like device whose legs are extremely rigid flexurally in a direction perpendicular to a longitudinal axis or centre line of the material, and to permit the legs to be far less rigid flexurally in a direction parallel with said centre line or

long axis, and to adapt the flexural rigidity of the legs to their thickness and the material chosen.

It will also be seen that a technical problem resides in realizing the significance of adapting the longitudinal extension of said surface parts in a direction relative to the longitudinal axis or centre line of the material with said extension lying within predetermined limits and being related to the dimensions and/or surface structure of the raw material.

It will also be seen that a technical problem is one of creating conditions whereby the legs of the stirrup-like device are able to coact with parts of the raw material within a very short distance from the chuck and its jaws.

Another technical problem is one of realizing the signifi¬ cance of the dimensions of the chosen raw material and that an inventive stirrup-like device finds beneficial application when said raw material has a diameter of between 4 and 60 mm.

Another technical problem is one of realizing the signifi¬ cance of enabling the raw material to be positioned obliquely with selected limitations when the chuck jaws are open, so as to adapt the gripping force between the surface parts of the legs and the mutually opposing parts of the material.

In this connection, a technical problem resides in providing means which will limit the obliqueness or tilting angle of the material when the chuck jaws are fully open.

In this regard, it will be seen that a technical problem is one of realizing the advantages that are afforded when limited tilting of the material is achieved by locating the raw material in an insert tube in the lathe, with a small clearance between the insert and the raw material.

Another technical problem is one of realizing the signifi¬ cance of taking into account the diameter of the raw materi¬ al, the longitudinal extension of the raw material in the insert tube, and the inner diameter of the tube.

It will also be seen that a technical problem resides in providing a tool arrangement, which includes a cutting tool, and a stirrup-like device in which the tool is spaced a short distance from the device, and also to provide conditions which enable the legs of the stirrup-like device and a parting tool to be positioned very close together.

Another technical problem is one of providing conditions with the aid of simple modifications which will enable a tool holder to be adapted to hold the most frequent of commercial¬ ly available parting-tool configurations, and to provide conditions which will enable such tools to be easily released and also to provide conditions which will enable a stirrup device to be attached to the tool holder with the aid of a stirrup-like device holder and an intermediate part.

A technical problem also resides in enabling the legs of the stirrup-like device to be caused to coact with the raw material adjacent a parting-off surface, for instance at a point 1-2 mm from said surface, and to be caused to coact with the raw material at a point adjacent the chuck jaws, for instance at a point located 6-10 mm from the outer surface of the chuck jaws.

Another technical problem is one of providing a stirrup- device holder which is constructed to carry either a stirrup device which has fixed legs or a stirrup device with which the distance between mutually opposing leg surfaces can be adjusted.

SOLUTION

With the intention of solving one or more of the aforesaid technical problems, the present invention takes at its starting point a tool arrangement in a machine tool, such as a CNC lathe, having means in the form of a chuck for gripping or loosening unworked material or raw material, a material parting-off tool and a stirrup-like device that has two legs, wherein the mutually opposing surface parts of said legs are adapted for coaction with mutually opposing surface parts of the raw material and, when the raw material is loosened from the chuck jaws, are able to move said material relative to the chuck by corresponding movement of the stirrup-like device.

According to the present invention, the distance between the mutually opposing surface parts of said legs will correspond to the distance between said mutually opposing surface parts of said material, and the longitudinal extension of the outer parts of said legs is adapted in relation to a centre line of the raw material, wherein tilting of the raw material caused by its release from the chuck generates increasing force interaction between the mutually opposing surface parts of the legs and the surface parts of said material, wherein the increasing force reaction is intended to provide slip- free coaction between said mutually opposing leg-surface parts and the surface parts of said material so as to enable the material to be displaced axially in relation to said chuck or said gripping or loosening device in response to corresponding displacement of the stirrup-like device.

In accordance with proposed embodiments that lie within the scope of the inventive concept, it is proposed that the distance between the mutually opposing surface parts of said legs will be only slightly smaller than the distance between the surface parts of said material.

It is also proposed that the legs are extremely rigid flexurally in a radial direction perpendicular to the longitudinal axis or centre line of the material, and that the flexural rigidity of the legs in this direction is much greater than their flexural rigidity in a direction parallel with the longitudinal axis of said material.

It is also proposed that said surface parts have a longitudi¬ nal extension of from 1-5 mm, preferably 2-3 mm, in a direc- tion relative to the longitudinal axis of the material, this extension being particularly suitable when the raw material has a diameter of between 4 and 60 mm.

It is also proposed that the legs are arranged to coact with the raw material within a distance of slightly less than 10 mm from the chuck, more particularly from the chuck jaws.

It is also proposed that tipping or tilting of the material when loosened in the chuck is limited by enclosing the raw material in a tubular insert whose inner diameter slightly exceeds the outer diameter of the raw material.

It is also proposed that the outer diameter of the raw material will be at least from 1-5 mm, preferably 1-2 mm, smaller than the inner diameter of the tubular insert.

ADVANTAGES

Those advantages that are primarily afforded by an inventive arrangement reside in the provision of simple means for axially displacing raw material to be worked, even when the material has a highly polished finished outer surface, from a loosened position in a chuck or like gripping device to a working position distanced from said chuck without needing to cut the raw material or to plastically deform the outer surface of the material to be worked to this end.

The primary characteristic features of an inventive arrange¬ ment are set forth in the characterizing clause of the following Claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplifying embodiment at present preferred and having characteristic features significant of the present invention will now be described with reference to the accompanying drawings, in which

Figure 1 is a perspective view of a computer-controlled machine tool, in the form of a CNC lathe;

Figure 2 is a sectioned view of a chuck belonging to said machine tool and functioning to grip material to be machined, and a tool arrangement including a parting tool and a stirrup-like device;

Figure 3 shows the legs of the stirrup-like device in coaction with material to be machined with the material clamped in the chuck;

Figure 4 shows the legs of the stirrup-like device in coaction with material to be machined with the material loosened in the chuck;

Figure 5 is an exploded view of a combined tool which includes a parting tool and a two embodiments of stirrup-like devices;

Figure 6 is an exploded view of a combined tool which includes a parting tool and a third embodiment of a stirrup-like device;

Figure 7 is a perspective view in larger scale of one of the stirrup-like devices shown in Figure 5;

Figure 8 is a perspective view of the tool arrangement shown in Figure 5 in a terminating sequence of a workpiece-parting operation; and

Figure 9 illustrates workpiece-parting and displacement procedures.

DESCRIPTION OF AN EMBODIMENT AT PRESENT PREFERRED

Figure 1 is a perspective view of a numerically-controlled machine tool, in the form of a CNC lathe 1, which includes a device, in the form of a chuck, which functions to grip or release raw material and in which raw material to be machined or worked can be held. The raw material 3 may be raw material that has a rough peripheral surface or raw material that has a machined or smooth peripheral surface.

The raw material 3 is normally comprised of rod material.

The raw material 3 is loosened when the jaws 2a of the chuck 2 open and is firmly gripped when the chuck jaws 2a close.

The lathe 1 also includes a holder 4 which functions to hold a plurality of tool arrangements, wherein tool arrangements are chosen in accordance with the form and surface structure of the section of raw material to be worked or machined, among other things.

The holder 4 may advantageously be comprised of a unit known as a tool revolver.

The material can be worked through the medium of a tool chosen from among several usable tool arrangements. One such tool arrangement is referenced 5 and is comprised of a shaft

or an attachment 5' and a twist drill 5, a tool arrangement according to the invention is also shown attached and is comprised of a tool 6 which includes a hardmetal cutting plate 6" and which functions as a parting or cutting-off tool, and a stirrup-like device 7 whose different properties will be described in more detail in the following.

However, the tool arrangement is illustrated with a parting tool 6 or the like, by means of which a machined workpiece or section 3a can be parted from raw material 3 gripped by the chuck jaws 2a.

This is effected by rotating the parting tool 6 and/or the raw material while moving the parting tool 6 radially inwards in relation to the raw material 3, at right angles to an axial centre line 3' of the rotary movement, and therewith cut a channel 6a between the machined workpiece 3a and the raw material 3, with the aid of the front part or cutting edge 6" of the parting tool, such as to obtain a machined workpiece 3a of given length.

The tool arrangement includes a stirrup-like device 7 which is located adjacent the parting tool 6 and its front part 6" on the side thereof nearest to the chuck 2, as explained below in more detail with reference to the drawings. The stirrup-like device 7 is adapted for mechanical coaction with that edge region 3b of the raw material 3 which faces towards the machined workpiece, at least after completion of the parting operation.

After the workpiece has been cut-off with the aid of the parting tool, the two legs 7a, 7b of the stirrup device are intended to accompany the parting tool further beyond the centre 3' in a direction at right angles to the rotational axis, so that when the raw material 3 is stationary, they can be brought into mechanical coaction with opposing outer surfaces of the raw material 3 and thereafter loosen the raw

material 3 from the chuck 2.

The raw material 3 will therewith pivot or tilt about a pivot point 40, resulting in force displacement against the edge- parts 41, 42 with a high force concentration and with plastic change in the material, primarily in the legs 7a, 7b.

When the parting tool 6 and the stirrup device 7 are moved axially in the direction of the arrow "P", the raw material 3 will be extended in the chuck 2, to a given extent.

Figure 3 shows that the material 3 is held by the jaws 2a of the chuck 2 and that the legs 7a and 7b of the stirrup device have been caused to coact equally with opposing surface parts 3c, 3d of the material 3.

The legs 7a and 7b include mutually facing surface parts 7a' and 7b', and the distance "a" between said surface parts is chosen to correspond to the distance between the surface parts 3c, 3d of the material, with selected small tolerance limits.

It is assumed in the present case that the distance "a" is smaller than the diameter "c" of the raw material by 0.1 mm.

The mutually opposing surface parts 7a' , 7b' of the legs that face towards the material have a longitudinal extension "d" related to the surface parts 3c, 3d.

Tilting of the material 3 caused by inclination 3" of the centre line 3' about the pivot point 40 as the material is loosened, shown in Figure 4, will create increasing force interactions between the mutually opposing surface parts 7a' , 7b' and the surface parts 3c, 3d, with particularly high forces acting on the laterally orientated surface sections 41, 42 of said surface parts and the material.

This increasing interaction of forces generates slip-free coaction between the surface parts 7a', 7b' and the parts 3c, 3d, so as to enable the material 3 to be moved axially in relation to the chuck 2.

Tilting or tipping of the raw material 3 will probably also result in minor lateral displacement of the legs 7a, 7b parallel with the centre line 3' .

With reference to Figure 7, it is shown that the legs 7a, 7b have a high bending resistance or flexural rigidity in a direction perpendicular to a longitudinal axis 3' on the material, although the legs are less flexurally rigid to forces acting in a direction parallel to said longitudinal axis.

The surface parts 7a' and 7b' have a longitudinal extension "d" corresponding to 1.5-5 mm, preferably 2-3 mm, in relation to said longitudinal axis 3' .

The aforesaid measurements are valid when the material 3 has a diameter of between 4 and 60 mm.

The legs 7a, 7b are adapted for coaction with the material 3 within a distance "f" of less than 6-8 mm from the chuck and its jaws.

Tilting 3" of the material 3 about a pivot point 40 as the raw material is loosened is limited by virtue of the raw material 3 being positioned inside a tubular insert 20.

The outer diameter of the raw material will be at least 1-2 mm smaller than the inner diameter of the tubular insert.

The tool 6 and the stirrup device 7 are spaced the smallest possible distance apart, which in practice means a distance of between 1-2 mm.

The basic requirements of the present invention can be illustrated thus.

The force acting between the surface parts 7a' , 7b' of the legs 7a, 7b and the mutually opposing parts 3c, 3d of the material shall be sufficiently strong to move the raw material 3 out of the chuck in response to axial movement of the stirrup device when the chuck jaws 2a are open.

The force increases with increasing inclination 3", increas¬ ing at shorter extensions "d", although the value "d" may not reach "0".

Frictional coaction is thus dependent on the chosen longitu- dinal extension "d".

The distance "a" may vary in dependence on the distance "c" between directly correspondence with one another and a difference of up to 0.2 mm with a material diameter of about 60 mm.

As shown in Figure 5, a stirrup device 7 can be screwed firmly to a stirrup holder 51 which, in turn, coacts with an intermediate part 52.

The intermediate part 52 has a portion 52a which is intended to abut the parting tool 6 when said parting tool is held in a further holder 53.

A device 7' having adjustable legs which enable the distance "a" to be varied can be substituted for the fixed stirrup device 7.

For a more detailed description of the device shown in Figure 5, reference is made to a patent application having the title "A Tool Arrangement" filed on the same day as the instant Application.

As shown in Figure 6, a stirrup device 7' ' can hold two separate legs 7a' ' , 7b' ' through apertures having a form which enable the distance "a" to be varied. The stirrup device can be screwed firmly to a stirrup holder 53.

Figure 8 is a perspective view which shows a positional setting of the tool arrangement shown in Figure 5 at the end of a workpiece-parting sequence.

Figure 9 is intended to show a sequence wherein raw material is parted and moved. Figure 9A shows the raw material 3 clamped by the chuck jaws 2a and the tool arrangement, including the parting tool 6 and the stirrup device 7, in a starting position. Figure 9B shows a stage in which the parting tool 6 has cut-off a workpiece and the chuck has stopped rotating. The tool arrangement has moved the stirrup device 7 to a position in which it coacts with the raw material. In Figure 9C, the chuck jaws 2a have been opened to release the raw material 3. Figure 9D shows that with the chuck jaws open, the raw material 3 can be moved axially to a desired position by virtue of the coaction of the stirrup device 7 with the raw material and its axial movement from the chuck 2. In Figure 9E, the chuck jaws 2a are shown gripping the raw material 3 and the tool arrangement 6, 7 is shown distanced from the raw material so that said material can be machined with another tool.

It will be understood that the invention is not restricted to the aforedescribed and illustrated exemplifying embodi- ments thereof and that modifications can be made within the scope of the inventive concept as defined in the following Claims.