DE102019111227A1 - Cutting knives, high speed slicers and methods of slicing food products - Google Patents

Abstract

A cutting knife for machines for slicing food products, in particular for high-speed slicers, is a sickle knife that rotates around an axis of rotation (1) during the cutting operation and that has a circular shape on its radially outer circumference, in particular in the manner of a spiral around the axis of rotation (1) has circumferential knife contour (2) which lies in a cutting plane (4) running perpendicular to the axis of rotation (1). A plurality of cutting teeth (13) with a respective cutting edge (3) is arranged along the knife contour (2), which forms the radially outer end of a cutting surface (5) of a respective cutting tooth (13) whose radially inner end passes through the transition to a throw-off surface (6) associated with the respective cutting tooth (13) is formed. The throwing surfaces (6) of the cutting teeth (13) form a throwing angle (β) with the cutting plane (4) and the throwing angles (β) of two, of several or of all cutting teeth (13) are different from one another.

Description

The invention relates to a cutting knife for machines for slicing food products, in particular for high-speed slicers, the cutting knife being a sickle knife which rotates about an axis of rotation during the cutting operation and has a circular shape deviating from a circular shape on its radially outer circumference, in particular in the manner of a spiral around the axis of rotation circumferential knife contour which lies in a cutting plane running perpendicular to the axis of rotation, a plurality of cutting teeth with a respective cutting edge being arranged along the knife contour, which forms the radially outer end of a cutting surface of a respective cutting tooth, the radially inner end of which passes through the transition is formed to a throwing surface associated with the respective cutting tooth.

The invention also relates to a high-speed slicer and a method for slicing, in particular, bar-shaped food.

Toothed cutting blades are known in principle. Both circular and sickle knives are in practice provided with serrations instead of smooth cutting edges to improve the cutting properties. There are a large number of tooth shapes, in practice the design of wavy convex teeth or saw teeth is preferred for cutting food. However, the properties of the invention described below can also be transferred to any other conceivable tooth shape. The size of the teeth is determined, among other things, by the distance from tooth to tooth, the so-called tooth pitch, and is usually between 0.5 and 20 millimeters.

According to the state of the art, teeth are incorporated either by removing material through a machining process, preferably by grinding the circumference of a knife, but it is also possible to attach preformed teeth made of harder materials to the knife circumference using a joining process such as welding, soldering or gluing. Such attached teeth must be calibrated after the joining process by means of a final grinding so that the respective cutting edges lie exactly in the cutting plane and the knife contour of the knife.

While the production of the serrations on knives by means of special machines only represents an additional effort in knife production, the re-sharpening of serrated knives often turns out to be a logistical problem. Depending on the product to be cut, both sickle and circular knives must be sharpened after each production shift. Most food companies have simply constructed, inexpensive knife sharpening machines with which smooth knife edges can be sharpened or honed on site.

The re-sharpening of serrated knives requires specially equipped and high-precision computer-controlled grinding machines, the investment costs of which are well in the six-digit euro range.

Small food companies shy away from this investment also because of the operator know-how they need. Instead, food companies have their toothed knives regrinded by specialist service providers.

The additional time and transport costs are seen as a disadvantage.

Due to the disadvantages mentioned, toothed knives are often only used in cases in which knives with a smooth cutting edge cannot deliver reliable and acceptable cutting and / or depositing results.

In the case of high-speed slicers, product bars or rods are usually clamped between an upper and lower conveyor belt and fed to the cut precisely in the direction of the knife axis. Directly in front of the cutting level there is a support bar or a so-called cutting goggle adapted to the product contour as a counter-blade for the knife. The shearbar is used to support the product bar by absorbing the cutting forces exerted on the product bar. Especially with soft or elastic products, the cutting forces lead to uncontrolled movements of the product bars. This can result in slices of inconsistent thickness or snippets, which lead to a poor and unacceptable appearance of the sliced portions. The increased friction of the knife on slightly tilted product bars also has a negative impact on the quality of the cut and placement, so that rejects are also produced. Product stability is often achieved by deep-freezing or freezing the products, but this is associated with higher costs and a loss of product quality.

The reduction of cutting forces lowers the requirements for the guidance and stability of the product bar during the cut. Due to the toothing of the knives, the overall effect of the cutting forces on the product bar can be significantly reduced. The intermittent cut from tooth to tooth cuts the product at high frequency. With high-speed slicers and blade speeds of up to approx. 2400 rpm, this frequency is in a range of upper frequencies that can still be heard acoustically, e.g. 12 kHz, well into the ultrasonic range.

Different tooth shapes are used depending on the product properties and the performance parameters of the high-speed slicer. Common geometric sizes are defined for all tooth shapes and also for smooth knife edges.

The cutting plane of a knife is perpendicular to the knife axis. The cut is made in the cutting plane when the knife rotates. The cutting plane thus defines the axial position of the cut. The cutting edge, which corresponds to the outer knife contour on smooth knives, lies in this cutting plane. With toothed knives, all cutting edges of the individual cutting teeth lie in the cutting plane; the knife contour is a kind of envelope of the cutting teeth there.

A so-called cutting wedge is created by the surface facing the product bar during the cut, which e.g. can lie in the cutting plane, and formed by the cutting surface located on the back of the knife. The parameters of the cutting wedge are the cutting angle and the cutting width of the cutting surface.

For a clear definition of these parameters, their respective position in relation to the knife contour is determined on the knife circumference. With toothless knives, a reference plane is used perpendicular to the cutting plane and in the respective normal of the knife contour. In the case of circular knives, this reference plane runs in the radial direction and contains the knife axis. In the case of sickle-shaped knives, this reference plane lies outside, but parallel to the knife axis, since the normal to the circumferential contour of the knife does not intersect the knife axis.

The cutting angle is set up within the described reference plane. One leg extends from the knife contour inwards along the normal, the other leg extends from the knife contour over the cutting width and is part of the cutting surface. The cutting surface is described by the sum of all legs in it, defined by the cutting angle and cutting width. With a constant cutting angle - 16 to 45 ° are common - and a constant cutting width, the shape of the cutting surface of a circular knife is a truncated cone.

In analogy to the definition of the geometric elements of toothless knives, the cutting surface, the cutting angle and the cutting width should also apply to teeth. For this purpose, the points on the cutting edge of the cutting tooth that lie on the knife contour are used. Through these points, the normal is dropped onto the knife contour and thus a corresponding reference plane is formed. The cutting angle is set up within the reference plane in analogy to the above procedure. This means that the cutting surface of a particular tooth can be clearly identified regardless of its shape.

In practice, knives with a constant cutting angle are used, the size of the cutting angle being a compromise for the respective product to be cut. This compromise is due in particular to a dual function of the cutting surface: on the one hand, together with the cutting edge, it is responsible for the formation of a stable cutting wedge, and on the other hand, the cutting surface indicates a force that is thrown into the just cut disc.

Depending on the cutting angle, this force is higher or lower. A small cutting angle, i.e. a relatively flat cutting surface results in gentle, gentle cuts with correspondingly low cutting forces. With a small cutting angle, however, the severed slice is pushed away from the knife significantly less over the cutting surface, so that the slice falls in an uncontrolled and therefore irregular manner. This makes it impossible to create ordered portions, such as a clapboard or a stack consisting of several slices. It is also understandable for the layman that small cutting angles together with the necessary clearance angles lead to slim knife edges, which are less stable and therefore shorter service life than knife edges with large cutting angles.

A large cutting angle leads to large cutting forces, some of which can destroy the product due to compression during the cut. Another disadvantage of large cutting angles is an excessively high ejection force between the cutting surface and the severed disk for ejecting the disk. Due to high ejection forces, the frictional force increases in the tangential direction between knife and disc and can rise to such an extent that the discs are thrown out of the machine sideways in an uncontrolled manner. The slices being thrown out of the machine to the side is also caused by an excessively large cutting width of the cutting surface.

In the DE 10 2007 040 350 A1 a cutting knife is presented as a solution for minimizing product compression and optimizing product placement, in which the cutting angle varies in the circumferential direction.

The cutting angle for each circumferential area of the cutting knife is matched to the behavior of the products. In particular, the process of immersing the knife into the product is considered with a different cutting angle, such as the subsequent cutting through of the product. In the DE 10 2017 108 841 A1 this idea is transferred to toothed knives.

As beneficial as these designs may be for some specific products, they have significant disadvantages. Varying the cutting angle also changes the rigidity and strength of the knife edge or the cutting tooth. This is particularly important in the case of hard e.g. Frozen products as well as products with a hard outer shell have the disadvantage that the cutting edge breaks out very quickly and the cutting ability of the cutting knife is lost after a few work cycles. In addition, the re-sharpening of the knives with cutting angles that vary on the teeth is even more complex and is hardly reproducible without precise knowledge of the respective cutting angle.

Coating of the cutting surface is often necessary in order to reduce the frictional forces between the product slice and the knife, as otherwise the ejection behavior is negatively influenced. The application of the coatings after the regrinding process is carried out by special companies and therefore also leads to increased logistical and time expenditure.

The object of the invention is to further develop the toothing of cutting knives of the types mentioned in such a way that, on the one hand, they meet all product or application-specific conditions and, on the other hand, the disadvantages of weakened cutting edges, complex equipment for re-sharpening and recoating are minimized, and also one to provide a correspondingly improved high speed slicer and method.

This object is achieved in the case of a cutting knife by the features of claim 1.

According to the invention it is provided that the throwing angles enclosed between a throwing surface of a cutting tooth and the cutting plane are configured differently from one another for different cutting teeth.

The definition of the throwing surface, the throwing angle and the cutting width is analogous to the definition of the cutting surface using the reference plane.

Due to the separate assignment of the cutting function to the cutting surface and the throwing function to the throwing surface, each of the surfaces can be optimally designed to fulfill the function, while according to the state of the art compromises between the two functions must be made by a surface. A blunt, i.e. large cutting angle ensures the knife's edge retention over a significantly longer working period. Also in the DE 0 2007 040 350 A1 The mentioned disadvantages of obtuse cutting angles - so-called upsets - can be completely compensated for by the optimal choice of the tooth shape and / or a gentler knife contour.

The design of the throwing surfaces is particularly advantageous with throwing angles that are variable for each tooth, since the tangential speed represents a variable over the increasing knife radius caused by the spiral shape. For example, if the throwing angle in the area of the gate is too large, the upper part of the target hurries ahead and rolls in upside down. Conversely, if the throwing angle is too small, the disc folds backwards.

The throwing angles are preferably 16 ° to 45 °. The ejection angles are preferably smaller than or equal to the associated cutting angle of a cutting tooth.

The transition between the cutting surface and the throwing surface can advantageously be formed by a transition edge in the case of one cutting tooth, in the case of several cutting teeth or in all cutting teeth, so that the cutting surface and the throwing surface are directly adjacent to one another, or it can be formed by a transition surface between the cutting surface and the throwing surface .

It is advantageous if the cutting surface and the throwing surface of each cutting tooth are arranged on the back of the knife facing away from a product to be sliced during the cutting operation.

The cutting surface width of the cutting surface is preferably between 0.2 mm and 5 mm.

It is also advantageous if the cutting surfaces of two, of more than two or of all cutting teeth form the same cutting angle with the cutting plane.

The same cutting angle is preferably between 16 ° and 45 °.

It is favorable if the discharge surface width of one, of several or of all discharge surfaces is between 0.5 mm and 12 mm.

It has proven to be particularly advantageous to coat one, several or all of the discharge surfaces with a non-stick or sliding coating made of a plastic, in particular made of PTFE. This minimizes the frictional forces and thus the tangential forces applied to the product slices in the direction of rotation of the knife. Due to the inventive design of the knife, especially when the knife is sharpened, only the cutting surfaces of the teeth are reground, while the properties of the low-friction throwing surface and its coating remain unchanged. In most cases, there is no need to recoat after the knives have been sharpened.

It can be advantageous if the tooth shapes of two, of several or of all cutting teeth are designed differently.

Two adjacent cutting teeth each define a pair of cutting teeth. It is advantageous if the tooth pitches between the two cutting teeth of two cutting tooth pairs, of several cutting tooth pairs or of all cutting tooth pairs are designed differently.

The above-mentioned object is achieved in a high-speed slicer and a method of the type mentioned in the introduction by using a cutting knife with some or all of the features described above.

• 1 eine Ansicht der Messerrückseite eines erfindungsgemäßen Schneidmessers mit Produktriegeln und einer Schneidbrille sowie mit 1A eine Detailansicht mit zwei Schneidzähnen;
• 2 einen Teilquerschnitt des erfindungsgemäßen Schneidessers in einem Schneidbereich B;
• 3 einen Teilquerschnitt des erfindungsgemäßen Schneidmessers in einem Anschnittbereich A;
• 4 eine isometrische Ansicht eines Segmentes des erfindungsgemäßen Schneidmessers;
• 5 eine isometrische Ansicht eines erfindungsgemäßen Schneidmessers mit Sägezähnen.

Embodiments of the invention are described below with reference to the drawings. Show it:

• 1 a view of the knife back of a cutting knife according to the invention with product bars and a cutting glasses and with 1A a detailed view with two cutting teeth;
• 2 a partial cross-section of the cutting knife according to the invention in a cutting area B;
• 3 a partial cross-section of the cutting knife according to the invention in a gate area A;
• 4th an isometric view of a segment of the cutting knife according to the invention;
• 5 an isometric view of a cutting knife according to the invention with saw teeth.

This in 1 The cutting knife according to the invention shown is designed as a sickle knife and comprises a spiral around an axis of rotation 1 circumferential knife contour 2 which extends approximately over an angular range of 270 ° and in a perpendicular to the axis of rotation 1 running cutting plane 3 lies. The distance of the knife contour 2 from the axis of rotation 1 , ie the radius R of the cutting knife, increases continuously with the knife angle µ, namely against a direction of rotation T, in which the cutting knife during the cutting operation about the axis of rotation 1 rotates. The cutting knife according to the invention is intended for use on a high-speed slicer, which is not specifically shown.

These high-speed slicers are equipped with a rotor, which is the axis of rotation 1 has fixing drive shaft together with storage for the cutting knife. For the centric mounting of the cutting knife on the rotor, the in 1 shown knife clearance 8th as well as the knife mounting holes 9 intended.

Along the knife contour shown in dashed lines 2 is a variety of cutting teeth 13 arranged, each via a cutting edge 3 , a cutting surface 5 and a dropping surface 6th have what the detailed view according to 1A illustrated. With each rotation, the cutting knife separates one slice from a product, in this case two product bars or product bars 10 are shown by means of cutting glasses 12th guided and supported against the cutting forces.

The back of the knife labeled C points from the product bars 10 away, the knife front marked with D faces the product bars. In 1 are the product bars 10 consequently arranged behind the plane of the paper.

The cutting knife rotating in the direction of rotation T first hits the product bars with a gate area A and the smallest radius 10 . Up to the final severing of the slices, the cut takes place over a cutting area B. The spiral shape of the cutting knife is described by the knife radius R in the respective angular position to the knife angle µ in polar coordinates.

If the knife radius R increases sharply over a comparatively small angular range, the knife pitch is large and the knife “chops” the product. If, on the other hand, the gradient of the knife radius R is small over a region of the knife angle µ, a gentle cut is made. In 1 a typical convex shaft toothing is shown. The curved cutting edge 3 each tooth touches the knife contour 2 . The normal N to the Knife contour 2 is in each case through the point of contact of the cutting edge 3 with the knife contour 2 placed.

In 2 is a partial section through the in 1 The cutting knife shown in the cutting area B is shown. The cut runs along the normal N to the knife contour 2 so that the drawing plane of the reference plane mentioned above passes through the normal N and parallel to the axis of rotation 1 corresponds. From the cutting edge 3 starting from the cutting surface extends 5 in the radial direction with a cutting surface width w at the cutting angle α. Radially inward follows the cutting surface 5 the dropping surface 6th that go to the cutting plane 4th assumes the throwing angle β and has a throwing surface width b. The knife front D is opposite the cutting plane 4th axially offset to prevent friction of the product bar 10 to avoid facing the knife.

In 3 Is analogous to 2 a partial section through the in 1 shown cutting knife in gate area A. The values of the cutting angle α and the cutting surface width w are identical to the values in 2 In this case, however, the throwing angle β is steeper and therefore the throwing surface width b is smaller. This results in higher initial accelerations of the product slices when cutting. The knife front D is less strong compared to the cutting plane 4th offset because the product bar 10 has experienced little product advance in gate area A. The throwing angle β is between 16 ° and 45 °.

In 4th is an isometric view of a segment of a modification of the knife according to the invention. Deviating from the in 1 In this case, the toothing shape shown is the discharge surface 6th in the same shape as the cutting surface 5 designed. In the first cut area A, the ejection angle β corresponds to the cutting angle α, so that there is no transition between the cutting surface 5 and dropping surface 6th is recognizable. In the further course on the circumference of the knife, the throwing angle β steadily decreases, so that the throwing surface width b increases due to the geometric conditions. The cutting surface 5 remains constant in its geometric parameters over the entire circumference of the knife. After reaching a minimum in the cutting area B, the throwing angle β increases again continuously.

In 5 is an isometric view of a further modification of the knife according to the invention with saw teeth. The cutting surface 5 and the cutting angles α are over the entire knife contour 2 uniformly executed. There are eight cutting teeth in the cutting area A of the cutting knife 13 with a flat throwing angle β, the value of which is around 17 °. This is followed by six cutting teeth ( 13 ) with a launch angle β with a value of about 23 °. The remaining cutting teeth of the cutting knife have an ejection angle β of approximately 27 °.

Through this special design of the dropping surfaces 6th becomes when cutting the product 10 only a very low acceleration force is introduced into the upper area of the cut slice, which prevents the slices from rolling in forward. Nevertheless, the cutting edge is with its cutting surface 5 and a cutting edge angle α of 34 ° is very stable, which guarantees an acceptable knife service life, especially for freshly baked meat products with a glassy surface.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102007040350 A1 [0021]
• DE 102017108841 A1 [0022]
• DE 02007040350 A1 [0029]

Claims (13)

Cutting knife for machines for slicing food products, in particular for high-speed slicers, the cutting knife being a sickle knife which rotates about an axis of rotation (1) during the cutting operation and which has a shape deviating from a circular shape on its radially outer circumference, in particular in the manner of a spiral around the axis of rotation ( 1) has a circumferential knife contour (2) which lies in a cutting plane (4) running perpendicular to the axis of rotation (1), a plurality of cutting teeth (13) with a respective cutting edge (3) being arranged along the knife contour (2), which forms the radially outer end of a cutting surface (5) of a respective cutting tooth (13), the radially inner end of which is formed by the transition to a discharge surface (6) belonging to the respective cutting tooth (13), characterized in that the discharge surfaces (6 ) the cutting teeth (13) with the cutting plane (4) include the throwing angle (β) and that the throwing angle (β) of two, of several or of all cutting teeth (13) are different from one another. Cutting knife after Claim 1 , characterized in that the throwing angle (β) is between 16 ° and 45 °. Cutting knife after Claim 1 or 2 , characterized in that the transition between the cutting surface (5) and the throwing surface (6) with one cutting tooth (13), with several cutting teeth (13) or with all cutting teeth (13) be formed by a transition edge so that the cutting surface ( 5) and the throwing surface (6) directly adjoin one another, or is formed by a transition surface between the cutting surface (5) and the throwing surface (6). Cutting knife according to one of the Claims 1 to 3 , characterized in that the cutting surface (5) and the throwing surface (6) of each cutting tooth (13) are arranged on a knife back (C) facing away from a product (10) to be sliced during the cutting operation. Cutting knife according to one of the Claims 1 to 4th , characterized in that the cutting surface width (w) of the cutting surface (5) is between 0.2 mm and 5 mm. Cutting knife according to one of the Claims 1 to 5 , characterized in that the cutting surfaces (5) of two, of more than two or of all cutting teeth (13) form an equal cutting angle (α) with the cutting plane (4). Cutting knife after Claim 6 , characterized in that the same cutting angle (α) is between 16 ° and 45 °. Cutting knife according to one of the preceding claims, characterized in that the throwing surface width (b) of one, of several or of all throwing surfaces (6) is between 0.5 mm and 12 mm. Cutting knife according to one of the preceding claims, characterized in that one, several or all of the throw-off surfaces (6) are provided with an anti-stick coating made of a plastic, in particular made of PTFE. Cutting knife according to one of the preceding claims, characterized in that the tooth shapes of two, of several or of all cutting teeth (13) are designed differently. Cutting knife according to one of the preceding claims, characterized in that two adjacent cutting teeth (13) each define a cutting tooth pair and the tooth pitches between the two cutting teeth (13) of two cutting tooth pairs, of several cutting tooth pairs or of all cutting tooth pairs are designed differently. High-speed slicer for slicing food products, characterized in that a cutting knife according to one of the Claims 1 to 11 is provided Method for cutting stick-shaped foodstuffs, in particular sausage, cheese or ham, characterized in that a cutting knife according to one of the Claims 1 to 11 is used.

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