WO2020126355A1

WO2020126355A1 - Cutting tool and method for setting a target weight

Info

Publication number: WO2020126355A1
Application number: PCT/EP2019/082616
Authority: WO
Inventors: Bernd SEIDENPFENNIG
Original assignee: Arlanxeo Deutschland Gmbh
Priority date: 2018-12-20
Filing date: 2019-11-26
Publication date: 2020-06-25

Abstract

The present invention relates to a cutting tool (30) for cutting out a core (34) from an elastomer body (14) made from an elastic material, in particular synthetic caoutchouc, comprising a cutting tube (38) for driving into the elastomer body (14), the cutting tube (38) having, at a cutting end (42), a circumferentially continuous, substantially circular cutting edge (44), and comprising at least one cutting blade (52), projecting radially inwards from the cutting tube (38), for cutting, at least partly, into the core (34). Owing to the geometry of the cutting tool (30), a predefined core (34) can be conveyed out of the interior of the elastomer body (14) in an automated process as a result of a pressure force applied from inside via the cutting blade (52), such that it is made possible to set a desired target weight of an elastomer body (14) in an inexpensive and precise manner.

Description

Cutting tool and method for setting a target weight

The present invention relates to a cutting tool and to a method for setting a target weight, which tool and method can be used, in the case of an elastomer body, to cut off a portion to enable the desired target weight of the elastomer body to be set.

In the production of an elastomer body made from an elastic material, in particular a synthetic caoutchouc such as, for example, butyl caoutchouc (HR), the elastomer body may exist as a ball-shaped semifinished product that, following transport, can be processed to form a particular end product. For the subsequent production steps, it is important for the elastomer body to have a particular target weight, which must be within a predefined tolerance range. For this purpose, it is known to weigh the elastomer body before the elastomer body is packaged and transported away. If the weight of the elastomer body is within the tolerance range around the target weight, the elastomer body is forwarded for packaging, without further processing steps. If the weight of the elastomer body is at the lower limit of the tolerance range, below a minimum weight that is still allowable, the elastomer body is separated out as reject. In this case, adding additional elastic material to the elastomer body is usually too difficult and cost-intensive. If the weight of the elastomer body is at the upper limit of the tolerance range, above a maximum weight that is still allowable, some material is manually cut off from the outside of the elastomer body, by means of a blade, in order to achieve the desired target weight of the elastomer body. In the case of an elastomer body made from synthetic caoutchouc, however, setting a particular target weight for this procedure is laborious and cost-intensive.

It is the object of the invention to indicate measures that enable a desired target weight of an elastomer body to be set in an inexpensive manner. The object is achieved according to the invention by a cutting tool having the features of Claim 1, and by a method having the features of Claim 11. Preferred designs of the invention are specified in the dependent claims and the description that follows, which each individually or in combination may represent an aspect of the invention.

Provided according to the invention is a cutting tool for cutting out a core from an elastomer body made from an elastic material, in particular synthetic caoutchouc, comprising a cutting tube for driving into the elastomer body, the cutting tube having, at a cutting end, a circumferentially continuous, substantially circular cutting edge, and comprising at least one cutting blade, projecting radially inwards from the cutting tube, for cutting, at least partly, into the core.

By means of the cutting tube, the cutting tool can be driven into the interior of the elastomer body. This makes it easier, particularly in dependence on the insertion depth, to part-off a portion of the elastomer body that has a defined weight, for example approximately 200 g. The target weight of the elastomer body can thereby be achieved with a high degree of accuracy. In this case, use is made of the knowledge that, for production reasons, the outer form of the elastomer body may be irregular and varying, such that cutting off an outer portion of the elastomer body involves particularly stringent tolerances with respect to the weight of the parted-off portion. Parting-off a portion of the elastomer body from the interior of the elastomer body involves lesser weight tolerances, and is therefore better suited to automation. Moreover, owing to the elastomer body's own weight, the core of the elastomer body that is separated out of the interior can be filled back automatically as a result of cold-flowing of the elastomer material of the elastomer body, such that a closed elastomer body, having the desired target weight, is again obtained after a certain time. Preferably, the cutting tool is driven into the elastomer body substantially in the centre of a lateral surface of the elastomer body, in particular substantially in the surface centroid of the lateral surface. The cutting tool may part-off a substantially cylindrical core, having a defined length and a defined diameter, which, the density of the elastomer body being known, may correspond to a particular desired weight by which the elastomer body is to be made lighter in order to achieve the target weight.

The cutting tool in this case may take account of the viscoelastic nature and the adhesiveness of the elastomer body made, in particular, from synthetic caoutchouc such as, for example, butyl caoutchouc. The cutting tube can be driven into the elastomer body, and in the process may locally compress the elastomer body and compact it somewhat as a result. The cutting tool in this case can rotate, such that the at least one cutting blade can screw into the material and spirally cut the core, which is cylindrical as a result of the driving-in of the cutting tube. The cutting blade can penetrate into the core or an outer radius region of the core and, in particular, spirally cut, at least in the outer radius region, the cylindrical core that penetrates into the cutting tube. If there is a sufficiently large core present inside the cutting tube, the cutting tool may be withdrawn without rotation, the at least one cutting blade in this case being able to engage behind the core to be parted-out. A flat side of the cutting blade, in particular a wedge surface or lateral surface of the cutting surface, may serve as a stop that, from the interior of the elastomer body, can impinge on the core in the axial direction of the cutting tube in order to move the core out of the elastomer body. The cutting blade can thus exert a pressure force upon the core, contrary to the original direction of advance of the cutting tube, when the cutting tube is being withdrawn from the elastomer body, such that the core can be withdrawn concomitantly. This makes it possible to part-off, as a core, a portion having a predefined weight, even in the case of particularly soft and particularly elastic materials. Owing to the geometry of the cutting tool, a predefined core can be conveyed out of the interior of the elastomer body in an automated process as a result of a pressure force applied from inside via the cutting blade, such that it is made possible to set a desired target weight of an elastomer body in an inexpensive and precise manner.

In particular, the cutting blade is oriented with a bevel towards the cutting end, in particular an angle of inclination a of 15° < a < 90°, in particular 20° < a < 45°, and preferably a = 30° ± 3°, being enclosed between the cutting blade and a radial plane of the cutting tube. The cutting blade thus has an angle of inclination that is sufficient to enable the cutting blade to cut into the interior of the elastomer body as the cutting tube is advanced axially. The cutting blade may cut spirally into the material of the elastomer body, in particular in a manner comparable to a corkscrew. At the same time, the angle of inclination imparts an axial stop function to the cutting blade when the cutting tool is withdrawn from the elastomer body, in particular substantially without rotation.

Preferably, at least two cutting blades are provided in a substantially common axial region of the cutting tube, in particular the cutting blades being arranged in a substantially uniformly distributed manner in the circumferential direction of the cutting tube. The cutting blades may each serve as an axial stop for the core as the core is being withdrawn, such that a correspondingly high axial pressure force can be exerted upon the core. In addition, the situation is avoided in which the core deflects laterally past the individual cutting blade. The plurality of cutting blades may significantly reduce the clear diameter region within the cutting tube, such that it is correspondingly easier to part-off a core having a predefined shape, and a weight associated therewith, from the elastomer body. Particularly preferably, the cutting blade has a cutting wedge facing in the tangential direction and/or in the circumferential direction of the cutting tube. The cutting blade can thus easily cut into the material of the core as a result of being rotated and advanced in the axial direction. In addition, if rotated without being advanced axially, the cutting blade can cut off at least some, preferably most or the entirety, of an inwardly facing end of the core, from the rest of the material of the elastomer body.

In particular, the radial extent of the cutting blade, from an inner side of the cutting tube, is less than a distance of the inner side in relation to a central axis of the cutting tube. Complete cutting of the core upon a full rotation of the cutting blade is thus avoided. Instead, it is ensured that the core remains centrally joined to the rest of the material of the elastomer body via a rod-shaped residual stump extending in the axial direction. However, the diameter of this residual stump may be so small that, upon the cutting tool being withdrawn axially from the elastomer body, the residual stump becomes waisted-in in a substantially defined manner, and is ultimately severed. At the same time, the spirally distributed regions of the core are still joined to the residual stump, such that the core can be parted-off as a single-piece body from the elastomer body.

The cutting tube preferably has a tapering conical surface, at least in a partial region of an outer side, in particular the conical surface merging into the cutting edge of the cutting tube. Owing to the tapering conical surface, the outer diameter of the cutting tube can increase in the axial direction. The cutting end of the cutting tube may have a minimum outer diameter in the region of the circular cutting edge, and penetrate with this minimum outer diameter into the material of the elastomer body. The further the cutting tube penetrates into the material of the elastomer body, the greater the outer diameter of the cutting tube becomes, such that a correspondingly high bearing pressure is obtained, by which the cutting tube acts upon the elastomer body. The elastomer body can thus be compressed and compacted around the core that is to be parted out, as a result of which the incision of the cutting edge at the cutting end of the cutting tube, and/or the incision of the cutting blade within the cutting tube, can be improved.

Particularly preferably, the cutting tube, at least in a partial region, has an inner side having inner diameters that increase in the axial direction, beginning at the cutting end, the various inner diameters increasing abruptly via steps, and/or continuously via a tapered form of the inner side. Owing to the increasing inner diameter, the core inside the cutting tube can separate from the inner side of the cutting tube, such that a frictional contact of the core with the inner side with of the cutting tube can be avoided, or at least reduced. Preferably, the inner diameter of the cutting tube is of such a magnitude, at least in a partial region, that contact with the inner side of the cutting tube is avoided, even in the case of deformation of the core as a result of the pressure force applied by the cutting blade. The basically tapering inner side of the cutting tube can ensure that the core is conveyed axially as a result of slow, further rotation of the cutting tool, with the result that the core can be conveyed rapidly out of the cutting tube without adhering to the inner side of the cutting tube. Conveying of the core out of the interior of the elastomer body by means of the cutting tool is thus facilitated. In particular, it is easily possible for the core to come easily out of an outlet opening at the axial end of the cutting tube that is other than the cutting end. In this case, it is possible in principle for the core to be pressed out of the interior of the cutting tube by the next core to be parted-out, if necessary with a component contrary to the direction of gravity.

In particular, the cutting tube is provided with an anti-adhesion coating on an inner side and/or on an outer side. The anti-adhesion coating may comprise, for example, a Teflon and/or a silicone layer. A anti-adhesion coating is described, for example, in DE 199 63 670 Al, reference to the content of which is hereby made as part of the invention. Owing to the anti-adhesion coating, the core can easily be conveyed out of the cutting tube, despite the high degree of adhesiveness of the elastomer material.

The invention additionally relates to a test device for checking a target weight of an elastomer body made from an elastic material, in particular synthetic caoutchouc, comprising a weighing scale for measuring the weight of the elastomer body, an evaluation unit for comparing the measured weight with a target weight, and a cutting device for cutting out a core from the elastomer body, the cutting device having a cutting tool, which may be realized and developed as described above, that can be driven into the elastomer body. Owing to the geometry of the cutting tool, a predefined core can be conveyed out of the interior of the elastomer body in an automated process as a result of a pressure force applied from inside via the cutting blade, such that it is made possible to set a desired target weight of an elastomer body in an inexpensive and precise manner.

In particular, a receptacle, for collecting the at least one cut-out core, is arranged in the direction of gravity beneath an outlet opening of the cutting tube of the cutting tool that faces away from the cutting end. The core removed from the interior of the elastomer body can be pushed automatically out of the cutting tube and received in the receptacle. In particular, the core can be displaced by the next removed core. The cores received in the receptacle can easily be recycled, in particular in order, with a sufficient number of cores, to press an elastomer body of which the weight corresponds substantially to the target weight.

The test device may have, in particular, a conveyor belt, by means of which the elastomer body can be supplied. In particular, a part of the conveyor belt that can be separated off may be connected to the weighing scale, such that it is possible to transport the elastomer body automatically onto the weighing scale and subsequent transport it away from the weighing scale. Preferably, the test device has a holding device, by means of which the elastomer body can be held while the cutting tool is being driven in. The holding device can thus provide a sufficient counter-force to enable the forces applied by the cutting tool to be removed without the elastomer body being able to be forced away by the cutting tool. The holding device may have, for example, clamping arms that can be swivelled by an actuating cylinder. Particularly preferably, at least one of the clamping arms has, on a holding plate that can be placed against the elastomer body, a through-opening for lead-through of the cutting tool. Mutually opposite holding plates of the holding arms may already compress the elastomer body, thereby making it easier for the cutting tool to be driven into the interior of the elastomer body. The holding device is preferably coupled to a frame via a positioning unit, in particular a linear drive. If necessary, the holding device can thus convey the elastomer body down from the conveyor belt, for example if the elastomer body should be too light. The cutting tool may be connected to a drive unit, which, in particular, can effect both an axial motion and a rotatory motion of the cutting tool. The cutting tool may be screw-connected, for example, to a rotatable sleeve of the drive unit.

The invention additionally relates to a method for setting a target weight for an elastomer body made from an elastic material, in particular synthetic caoutchouc, in which the weight of the elastomer body is measured, the measured weight is compared with a target weight and, if the weight is greater than a still allowable maximum weight that is above the target weight, a core is cut out of the elastomer body by means of a cutting tool, which may be realized and developed as described above, and/or a test device, may be realized and developed as described above. Owing to the geometry of the cutting tool, a predefined core can be conveyed out of the interior of the elastomer body in an automated process as a result of a pressure force applied from inside via the cutting blade, such that it is made possible to set a desired target weight of an elastomer body in an inexpensive and precise manner.

In particular, an insertion depth of the cutting tool into the elastomer body is set in dependence on a difference of the measured weight in relation to the target weight or in relation to the maximum weight. The length, and the therewith associated weight, of the core can thus easily be adapted, such that the weight of the elastomer body can be particularly close to the target weight without the necessity of fully utilizing an allowable tolerance range.

Preferably, the cutting tool is rotated simultaneously while being driven axially into the elastomer body. The cutting blade of the cutting tool can thus screw into the core and reach the end of the core that is to be parted-off.

Particularly preferably, the cutting tool, in an axial relative position in relation to the elastomer body that corresponds to a predefined insertion depth, is temporarily exclusively rotated, before withdrawal of the cutting tool from the elastomer body. The cutting blade can thus execute a substantially circular cut in a common plane, enabling the core to be cut off fully or partly, on its axial side that is to be parted-off, from the rest of the elastomer body.

In particular, a production weight of the elastomer body is selected so as to be greater than the target weight, in such a manner that the weight of the elastomer body, with production tolerances taken into account, in particular with a probability of > 98 %, preferably > 99 %, and particularly preferably = 100 %, is above a still allowable minimum weight. The weight of the elastomer body after the production process is thus deliberately greater than the target weight, such that an elastomer body of too low a weight can be avoided in a substantially reliable manner. Owing to the easy and inexpensive reduction of the weight of the elastomer body by means of the cutting tool, excessively heavy elastomer bodies can be avoided, and rejects of excessively light elastomer bodies can be minimized.

The invention is explained exemplarily in the following, on the basis of preferred exemplary embodiments, with reference to the appended drawings, wherein the features presented in the following each both individually and in combination may represent an aspect of the invention. There are shown: Fig. 1 a schematic side view of a test device,

Fig. 2: a schematic top view of an elastomer body in the test device from Fig. 1, at a first time point,

Fig. 3: a schematic top view of an elastomer body in the test device from Fig. 1, at a second time point,,

Fig. 4: a schematic top view of an elastomer body in the test device from Fig. 1, at a third time point,,

Fig. 5: a schematic top view of an elastomer body in the test device from Fig. 1, at a fourth time point,,

Fig. 6: a schematic top view of an elastomer body in the test device from Fig. 1, at a fifth time point,,

Fig.7: a schematic sectional view of a cutting tool of the test device from Fig. 1, and Fig. 8: a schematic top view of the cutting tool from Fig. 7.

The test device 10 represented in Fig. 1 has a conveyor belt 12, by means of which an elastomer body 14 that is made, in particular, of synthetic caoutchouc, for example halogenated butyl caoutchouc, can be transported onto a weighing scale 16 (Fig. 2). If the weighing scale 16 determines an excessively high weight of the elastomer body 14, the elastomer body 14 can be held by a holding device 18 (Fig. 3). The holding device 18 has articulated holding arms 20, which can impinge on the elastomer body 14 via holding plates 22. The holding arms 20 may be actuated by means of an actuating cylinder 24. The holding device 18 may be attached to a frame 28 in a relatively movable manner, via a traversing unit, such that, if necessary, the holding device 18 can raise an excessively light elastomer body 14, as reject, from the conveyor belt 12.

In the case of an excessively heavy elastomer body 14, a cutting tool 30 can be driven helically into the elastomer body 14 held by the holding device 18 (Fig. 4). For this purpose, the cutting tool 30 can be displaced in the axial direction by means of a linear drive 26, and/or rotated in the circumferential direction by means of a drive unit 32. The cutting tool 30 can take out from the interior of the elastomer body 14 a core 34 (Fig. 5) which, at the end that faces away from the elastomer body 14, can come out of the cutting tool 30 and fall, under force of gravity, into a receptacle positioned beneath the cutting tool 30. The elastomer body 14 can then be weighed again by the weighing scale 16 and, if the weight of the elastomer body 14 is sufficiently close to the target weight, within a predefined tolerance range, can be conveyed onwards by the conveying belt 12, for example to a packaging station, after the holding device 18 has again released the elastomer body 14 (Fig. 6).

The cutting tool 30, represented in detail in Fig. 7 and Fig. 8, has a cutting tube 38, which on its inner side 40 may be provided with an anti-adhesion coating. In addition, the inner side of the cutting tube is stepped, such that the portion of the core 34 that is parted-off from the elastomer body 14 by the cutting tube 38 can lift off from the inner side 40, and does not adhere to the inner side 40. The core 34 can thus be conveyed axially backwards by a slow rotation of the cutting tool 30. At a cutting end 42, the cutting tube 38 has a circular cutting edge 44, by means of which the cutting tube 38 can cut into the elastomer body 14, and in particular the cutting edge may be serrated. The cutting tube 38 has a tapering outer side 46, which widens radially outwards, starting from the cutting edge 44. The tapering outer side 46 is bevelled, for example by 4 ± 1°, relative to a central axis 48 of the cutting tube. The cutting tool may be coupled to the drive unit 32 via a threaded end 50. Projecting radially inwards from the inner side 40 of the cutting tube 38 there are, for example, two cutting blades 52, the cutting wedges 54 of which are oriented substantially tangentially. In addition, the cutting blades 52 are inclined by an angle of inclination a of approximately 30° in relation to a radial plane of the cutting tube 38, such that, upon the cutting tool 30 being advanced into the elastomer body 14 and the cutting tool 30 being simultaneously rotated, the cutting blades 52 can screw into the core 34 that is to be parted out. If the cutting tool 30 is withdrawn axially, without rotation of the cutting tool 30, flat sides 56 of the cutting blades 52 that face towards the core 34 can serve as stops, by means of which the core 34 can be withdrawn from the elastomer body 14. A residual stump of the core 34 remaining between the cutting blades 52 becomes waisted-in as the core 34 is withdrawn, and severs automatically. The parted-out core 34 can then come out of the cutting tool 30 via an outlet opening 58 that faces away from the cutting end 42.

In the embodiment represented, the cutting tube 38 also has, in particular, at least one mounting opening 60, into which, for example, a tool can be inserted for the purpose of screw-connecting the cutting tool 30. Changing of the cutting tool 30 is thus simplified.

Claims

1. Cutting tool for cutting out a core 34 from an elastomer body (14) made from an elastic material, comprising a cutting tube (38) for driving into the elastomer body (14), the cutting tube (38) having, at a cutting end (42), a circumferentially continuous, substantially circular cutting edge (44), and comprising at least one cutting blade (52), projecting radially inwards from the cutting tube (38), for cutting, at least partly, into the core (34), the cutting tube (38), at least in a partial region, having an inner side (40) having inner diameters that increase in the axial direction, beginning at the cutting end (38), the various inner diameters increasing abruptly via steps, and/or continuously via a tapered form of the inner side (40).

2. Cutting tool according to Claim 1, characterized in that the cutting blade (52) is oriented with a bevel towards the cutting end (42), in particular an angle of inclination a of 15° < a < 90°, in particular 20° < a < 45°, and preferably a = 30° ± 3°, being enclosed between the cutting blade (52) and a radial plane of the cutting tube (38).

3. Cutting tool according to Claim 1 or 2, characterized in that at least two cutting blades (52) are provided in a substantially common axial region of the cutting tube (38), in particular the cutting blades (52) being arranged in a substantially uniformly distributed manner in the circumferential direction of the cutting tube (38).

4. Cutting tool according to any one of Claims 1 to 3, characterized in that the cutting blade (52) has a cutting wedge (54) facing in the tangential direction and/or in the circumferential direction of the cutting tube (38).

5. Cutting tool according to any one of Claims 1 to 4, characterized in that the radial extent of the cutting blade (52), from an inner side (40) of the cutting tube (38), is less than a distance of the inner side (40) in relation to a central axis (48) of the cutting tube.

6. Cutting tool according to any one of Claims 1 to 5, characterized in that the cutting tube (38) has a tapering conical surface, at least in a partial region of an outer side (46), in particular the conical surface merging into the cutting edge (44) of the cutting tube (38).

7. Cutting tool according to any one of Claims 1 to 6, characterized in that the elastic material is a synthetic caoutchouc.

8. Cutting tool according to any one of Claims 1 to 7, characterized in that the cutting tube (38) is provided with an anti-adhesion coating on an inner side (40) and/or on an outer side (46).

9. Test device for checking a target weight of an elastomer body (14) made from an elastic material, in particular synthetic caoutchouc, comprising a weighing scale 16) for measuring the weight of the elastomer body (14), an evaluation unit for comparing the measured weight with a target weight, and a cutting device for cutting out a core (34) from the elastomer body (14), the cutting device having a cutting tool (30), according to any one of Claims 1 to 8, that can be driven into the elastomer body (14).

10. Test device according to Claim 9, characterized in that a receptacle (36), for collecting the at least one cut-out core (34), is arranged in the direction of gravity beneath an outlet opening (58) of the cutting tube (38) of the cutting tool that faces away from the cutting end (42).

11. Method for setting a target weight for an elastomer body (14) made from an elastic material, in particular synthetic caoutchouc, in which the weight of the elastomer body (14) is measured, the measured weight is compared with a target weight and, if the weight is greater than a still allowable maximum weight that is above the target weight, a core (34) is cut out of the elastomer body (14) by means of a cutting tool (30) according to any one of Claims 1 to 8 and/or a test device (10) according to Claim 9 or 10.

12. Method according to Claim 11, in which an insertion depth of the cutting tool (30) into the elastomer body (14) is set in dependence on a difference of the measured weight in relation to the target weight or in relation to the maximum weight.

13. Method according to Claim 11 or 12, in which the cutting tool (30) is rotated simultaneously while being driven axially into the elastomer body (14).

14. Method according to any one of Claims 11 to 13, in which the cutting tool (30), in an axial relative position in relation to the elastomer body (14) that corresponds to a predefined insertion depth, is temporarily exclusively rotated, before withdrawal of the cutting tool (30) from the elastomer body (14).

15. Method according to any one of Claims 11 to 13, in which a production weight of the elastomer body (14) is selected so as to be greater than the target weight, in such a manner that the weight of the elastomer body (14), with production tolerances taken into account, in particular with a probability of > 98 %, preferably > 99 %, and particularly preferably = 100 %, is above a still allowable minimum weight.