Patent Application
20150050865
This application claims priority to German Application No. 10 2013 013 498.6 filed Aug. 16, 2013, the contents of which are incorporated herein by reference.
The invention relates to an apparatus for sharpening rotating blades which have a cutting edge running in the circumferential direction.
Blades of this kind are used, for example, in machines for slicing product loaves, which are also called slicers. The cutting edge of the rotating blades is not concentric with the blade axis, but rather has the shape of an eccentric circle or a spiral.
When the cutting edge is worn, it must be reground in a sharpening apparatus. This grinding apparatus has a grinding head which, in known machines, is adjusted radially according to the geometry of the cutting edge (radially with respect to the blade axis).
The different sections of the cutting edge have markedly different distances from the axis of the rotating blade, and accordingly a device for adjusting the grinding head must be constructed with a corresponding size.
An apparatus for sharpening rotating blades which is distinguished by a compact construction is to be specified by the present invention.
This object may be achieved by a sharpening apparatus for sharpening rotating blades which have a cutting edge running in the circumferential direction and bounded by a rear cutting-edge surface and a front conical cutting-edge surface running in a manner inclined with respect to the rear cutting-edge surface having a blade carrying part, to which a rotating blade can be fastened and by which the rotating blade is rotated, and a grinding head for regrinding the front conical cutting-edge surface, which has a rotating cutting tool. The relative position between a cutting head or a grinding head with respect to the rotating blade is chosen such that the location of engagement between the rotating cutting tool and rotating blade travels in a direction of an axis of the grinding tool on its lateral surface in dependence on the angular position of the rotating blade.
The sharpening apparatus according to the invention has small dimensions because the change in the position of the cutting edge is accommodated by the fact that the grinding tool, which is inclined according to the setting angle of the conical front cutting-edge surface, is moved axially with respect to the blade axis. Thus, the area of engagement of the cutting edge with the grinding tool travels on the lateral surface of the latter in the axial direction. The adjusting distance of the grinding head required for this can be small because the movement of the grinding tool upon small movements of the grinding tool axis can even cope with large radial differences in the position of the cutting edge, since the angle between the rear cutting-edge surface and a surface line of the front cutting-edge surface is small, and typically lies in the range from 15 to 25°.
According to one aspect of the invention, it is ensured by structural features that the grinding tool is moved in the desired preset direction.
According to another aspect of the invention, the sharpening apparatus is of small construction. The reduction of the cutting speed, caused thereby, compared with conventional grinding discs with a large radius can be compensated by increasing the rotational speed of the drive for the grinding work.
According to another aspect of the invention, movement of the grinding head is achieved in the axial direction of the grinding tool in the manner of a cam gear can be directly derived from the shape of the cutting edge of the blade. The force with which the tool lies against the cutting-edge surface to be reground is always the same. As a result, all regions of the conical cutting-edge surface are reground equally.
According to another aspect of the invention, simple and reliable possibilities of how the contact pressure of the grinding tool against the cutting surface is kept constant may be provided.
According to yet another aspect of the invention, the orientation of the rotating blade and of the grinding head during the grinding operation can be chosen in a manner that is favourable as regards small space requirement and ergonomic mounting and demounting of the rotating blade on the sharpening apparatus. A deflection of the weight, which thus becomes necessary, is obtained with simple and reliable means.
According to a further aspect of the invention, the transmission of the prestressing force to the grinding tool is also carried out simply and reliably.
According to another aspect of the invention, a linear guide distinguished by particularly simple and reliable mechanical construction may be provided. Those cooperating surfaces which provide the guidance are small and environmentally sealed, so that impurities are kept away from the guide surfaces.
According to another aspect of the invention, the grinding tool may remain in the immediate vicinity of the cutting-edge surface also in such angular positions in which the rotating blade has a cutout.
The cutting edge of a rotating blade to be resharpened is preset, on the one hand, by the conical front cutting-edge surface already mentioned above and, on the other hand, by a rear cutting-edge surface which can lie in a plane transverse to the blade axis, but can also form with this plane an angle of a few degrees (e.g. about 3 degrees) in both directions. The rear cutting-edge surface can be reground with a sharpening apparatus together with the conical front cutting-edge surface.
According to another aspect of the invention, it is ensured that the grinding tool is always supported by the rotating blade, also in those regions of a spiral blade which is free from a cutting edge and where the cutting edge jumps back again to a small distance from the axis of rotation.
In an advantageous aspect of the invention, the grinding tool passes over the connecting edge substantially parallel to this edge.
Other advantages and aspects of the present invention will become apparent upon reading the following description of the drawings and detailed description of the invention.
The invention is explained in more detail below using exemplary embodiments with reference to the drawing, in which:
While this invention is susceptible to embodiments in many different forms, there is described in detail herein, preferred embodiments of the invention with the understanding that the present disclosures are to be considered as exemplifications of the principles of the invention and are not intended to limit the broad aspects of the invention to the embodiments illustrated.
In
The sharpening apparatus has a base plate 14, in which a blade carrier 16 is mounted rotatably about a horizontal axis, e.g. by ball bearings (not shown specifically). Acting on the blade carrier 16 is a drive motor 18, which preferably comprises a geared motor, here a belt drive 19.
As can be seen from
24 designates a cutting edge in the drawing. In the exemplary embodiment according to
The rear cutting-edge surface 28 can also be the shape of a truncated cone with a very large opening angle (e.g. 174 degrees), the vertex of which points forwards, or a truncated cone with a very large opening angle (e.g. 179 degrees), the vertex of which points rearwards.
In the spiral blade shown in the figures, a radially outer rear end of the spiral blade 12 and a, in the direction of rotation, front radially inner end of the spiral are connected to one another by a secant-shaped connecting section 30. Other geometries of the connecting section are also frequent, particularly when the total angular extent of the cutting edge 24 is greater than in the exemplary embodiment shown. The connecting section 30 can then also have the shape of an asymmetrical V.
In the claims and the present description, “conical” is to be understood in connection with the front cutting-edge surface 26 as a surface whose surface lines encloses an angle to a transverse plane which lies in practice between 15 and 25°, in the exemplary embodiment considered here about 17°. This conical surface is additionally curved in the circumferential direction.
In connection with the rear cutting-edge surface 28, the angle mentioned can be between 0 degrees and a few degrees, e.g. about 3 degrees.
The conical cutting-edge surface 26 can, in the case of a genuine eccentric blade (circular blade which is mounted off-centre), have exactly the shape of a conical surface. It can, however, as in the case of the spiral blade shown, also have the shape of a conical surface whose circumferential curvature changes in the circumferential direction.
To sharpen the cutting edge 24, both the front cutting-edge surface 26 and the rear cutting-edge surface 28 are reground. This is carried out by a first grinding head 32 and a second grinding head 34, respectively.
The first grinding head 32 has a rod-shaped grinding tool 36 and is driven by an electric motor 38.
The electric motor 38 is seated on a parallelogram linkage, designated as a whole by 40. This linkage has a first link 42, which is pivotably mounted at a free, in
The support 46 has at its free end a pivotable axial rotary bearing 48 for an adjusting spindle 50, the thread of which runs in an adjusting nut 52, which is pivotably supported by a lower section of the link 42.
By rotation of the adjusting spindle 50, the angle between the link 42 and the support 46 can thus be adjusted. As a result, the setting angle of the cutting-edge surface 26 is preset.
The link 42 carries, at a place which is spaced about a third of the total length from an end bearing 44, a first bearing 56 of the parallelogram linkage 40. A second bearing 58 is situated at the lower end of the link 42. The second bearing 58 supports one end, located on the left in the drawing, of a second link 60 of the parallelogram linkage 40. This link carries, at its end located on the right in
The four links all have the same length and thus form a parallelogram linkage. The third link 64 is always parallel to the first link 42. The same applies to the links 68 and 60.
The drive motor 38 is fastened at the centre of the third link 64 such that the axis of the grinding tool 36 is perpendicular to the link 64.
A rope pulley 72 is connected in a rotationally fixed manner to the fourth link 68 by means of pins 70. Over this pulley runs a rope 74 (not shown in
For the second grinding head 34, a second parallelogram linkage 80 is provided. This linkage comprises a support 82 which is perpendicular to the base plate 14 and corresponds to the support 46. The links 84, 86, 88, 90 and bearings 92, 94, 96, 98 therebetween are the components of the parallelogram linkage 80.
The centre of the link 88 carries the second grinding head 34. The centre of the link 88 thus carries the drive motor 98 of this head and the grinding tool 100 driven by it.
The link 96 is connected via pins 102 again to a rope pulley 104, over which a rope 106 runs (not shown in
By the mechanism just described, it is ensured that the grinding tool 100 bears against the cutting-edge surface 28 always under a constant force. Again it is the case that the area of engagement between grinding tool and blade disc travels in the axial direction of the grinding tool when the rotating blade 12 rotates during sharpening. Again it is the case that the grinding tool 100 is supported by the rotating blade 12 in all angular positions of the latter.
From
Typically, spiral blades and eccentric blades, as used in slicers, have a maximum radius of 20 to 40 cm. The radial dimension of the cutting surfaces 26 and 28 is in practice about 20 mm. An outermost section of the conical cutting-edge surface 26 can be set a little steeper, as shown in
Typically, the pressure with which the grinding tools 36, 100 are pressed against the cutting-edge surfaces 26, 28 is about 50 to about 100 p.
From the above description and the drawing, it can be clearly seen that the sharpening apparatus has compact dimensions overall. The total dimension of the sharpening apparatus in the vertical direction in
Instead of a weight, it is also possible to use a pneumatic cylinder connected to a constant pressure source to prestress the grinding tools 36, 100 against the cutting-edge surfaces 26, 28.
While in the foregoing there has been set forth various embodiments of the invention, it is to be understood that the present invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. While specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the characteristics of the invention and the scope of protection is only limited by the scope of the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 013 498.6 | Aug 2013 | DE | national |
