THE BLADE

The invention relates to the field of reciprocating bread slicer devices for slicing loaves into sliced loaves.

Reciprocating bread slicer devices for slicing loaves are widely used worldwide and exist in many different embodiments. In rather simple embodiments primarily destined for small scale bakeries where vending to individual consumers takes place the loaves are to be placed manually in the device, to slice each loaf on demand of the individual consumer. In embodiments suitable for industrial bakeries the loaves are commonly supplied to the slicer device by a conveyor mechanism in a continuous, high volume stream. Known high volume slicing devices are able to slice more than 2000 loaves per hour.

An example of a reciprocating bread slicer device is disclosed in W098/41368. In this device a plurality of cutting blades is held in the device and moved in reciprocating manner to slice the loaves that are fed through the device over a support for the loaves.

As discussed in W098/41368 the cutting process of the loaves entails that bread material contaminates the cutting blades, in particular bread material adheres to the side surfaces of the cutting blades. This contamination is detrimental to the cutting process and also impairs the service life of the cutting blades.

It is known, in particular for high volume slicing devices in industrial bakeries, to provide a bread slicing device with cleaning means that allow to clean the cutting blades during the cutting process. Commonly such cleaning means are disposed outside the path of the loaves so as to not interfere with the passage of the loaves. In W098/41368 examples of such cleaning means are disclosed.

In particular in industrial bakeries it is observed that problems with the slicing of the loaves still occur. In particular it has been observed that if the loaves have not been cooled sufficiently when they arrive at the bread slicer device, e.g. as the room temperature in the bakery is elevated during the summer period, the cutting may be problematic. It is observed that - even with the cleaning means in operation - a problematic built-up of contamination on the cutting blades occurs. The present invention aims to solve the above-mentioned problem.

The present invention achieves this goal by providing a bread slicing device for slicing loaves provided with a plurality of reciprocating bread slicer cutting blades, which is characterised in that - over at least a part of the length of the cutting section - the width of the cutting blade body, that is measured in said part between the peak line on the one hand and the rear edge of the blade body on the other hand, is reduced at least 25% with respect to the greatest width of each of the securing portions of the cutting blade body.

The invention thus proposes to provide the cutting blade body with a waist over at least a part of the length of the cutting section, preferably over the entire length of the cutting section, whereas known reciprocating bread slicer cutting blades have a uniform width over their length, corresponding to the width of the strip material from which the blade is manufactured.

It has been found that by effectively reducing the width of the cutting blade in the region of the cutting section, the problem of adhering contaminants is significantly reduced. As a result the slicer device is less sensitive to the temperature of the breads to be sliced. The invention envisages that the securing portions have a significantly greater width than the waistlined portion of the blade, preferably a width that is equal to prior art design cutting blades of this type to ensure that these securing portions remain able to counter the tendency of the blade to twist with respect to its longitudinal axis.

The blade according to the invention is in a possible embodiment of the method according to the invention made with a production device and a method as disclosed in EP-A-888847, the production device then at least having the features of claim 1 of said document, wherein the additional step is performed of removal of a portion of the blank such that - over at least a part of the length of the cutting section - the width of the cutting blade body, that is measured in said part between the peak line on the one hand and the rear edge of the blade body on the other hand, is reduced at least 25% with respect to the greatest width of each of the securing portions of the cutting blade body.

This additional step is preferably performed later than the machining of the front edge region. In this manner the original width of the steel strip starting material is maintained during the front edge machining, so that the blank is stable and can withstand the forces exerted thereon during this machining process, e.g. during the grinding of the teeth. Also maintaining the width of the blank during this machining process enhances the control of the temperature of the blade, and allows to avoid overheating and detrimental effects on the structure of the metal of the blade. It is noted that the additional step can also be included in other production methods and associated production devices for bread slicer cutting blades according to the preamble of claim 8.

As is common, and preferred, the steel strip material from which the blade body is made is supplied as strip-steel coils, and the production device includes an unwinding station where strip steel is uncoiled and fed as a continuous strip intro the production device.

The strip steel may in a practical embodiment have a thickness between 0.25 and 0.5 millimeter.

The strip steel may in a practical embodiment have a width between 9 and 14 millimeter.

Preferably a grinding operation is carried out on both sides of the front region of the blank, so that the tips of the teeth lie accurately in a centre plane of the blade and each tooth has bevelled tooth faces that are symmetrical with respect to the centre plane of the blade.

The teeth may be scallop shaped, but also other shapes are envisaged, e.g. with a semi- elliptical, substantially U-shaped, or substantially V-shaped recess between two adjacent tooth tips.

The invention also relates to a reciprocating bread slicer cutting blade adapted for use in a bread slicing device for slicing loaves with a plurality of reciprocating bread slicer cutting blades and to such use. The present invention also relates to a production device for production of the inventive blades, said production device including at least one machining station for machining the front edge of the blade, e.g. including one or more grinding devices, and the production device further including a station for removal of the portion of the blade to create the waist, preferably said station including a spark erosion device, e.g. a wire spark erosion device.

The invention will now be explained with reference to the drawings. In the drawings:

figure 1 shows an example of a prior art reciprocating bread slicer cutting blade, figure 2 shows a first example of a reciprocating bread slicer cutting blade according to the invention,

figure 3 shows a second example of a reciprocating bread slicer cutting blade according to the invention, and

figure 4 shows an example of a reciprocating bread slicer.

The figures 1 - 3 each show a reciprocating bread slicer cutting blade 20, 40, 60 that is adapted for use in a device for slicing loaves. The figure 1 prior art embodiment is shown to facilitate the understanding of the invention.

As is known in the art a bread slicing device for slicing loaves wherein such cutting blades are used comprises:

- a frame, which is provided with a support for the loaves to be sliced, which support defines a path for the loaves through the device,

- cutting-blade attachment and tensioning means, which are adapted to hold each blade at axial ends thereof in an arrangement wherein said blades are parallel to and spaced from one another and wherein each blade is held in axial tension, at least during the cutting operation of the device,

- drive means adapted to effect a reciprocating movement of the plurality of cutting blades with respect to the support means for the loaves, which reciprocating movement is parallel to the longitudinal direction of the cutting blades.

A non-limitative example of such a slicing device is disclosed in W098/41368. Figure 4 shows an embodiment of said known slicing device, corresponding to figure 2 of said prior art document.

In this figure 4 reference numeral 1 denotes the stationary frame (to be placed on the ground) and parts thereof. The frame is provided with a support 8 for the loaves through the device.

Reference numeral 2 denotes a top holding member of the device for a top bar 3 of a cutting blade carrier with cutting blades 20 (here of prior art design), whereas reference numeral 4 denotes a bottom holding member of the device for a bottom bar 5 of the cutting blade carrier. Tensioning means (e.g. hydraulic or with one or more tensioning bolts) allow to alter the distance between the top and bottom holding member in order to tension the blades. Reference numeral 7 denotes the drive means to effect the reciprocating movement of the cutting blades. Reference numeral 9 denotes the top cleaning member for the blades, and reference numeral 10 the bottom cleaning member for the blades, e.g. each embodied as scraper member, e.g. as in the preferred embodiment of W098/41368. In a possible embodiment of the slicer device no cleaning members for the blades are present, at least no cleaning members that are in frictional contact with the blades during operation of the slicer device.

For each of the blades in figures 1 - 3 the cutting blade has an elongated, strip shaped and monolithic cutting blade body that is made of resilient steel material. As is preferred, and as is common, the blades are produced in a production device (preferably based on the device disclosed in EP 888 847) starting from coiled strip steel material supplied by a strip steel manufacturer.

The cutting blade body of each of the blades 20, 40, 60 has axial ends, as well as a front edge 20a, 40a, 60a, a rear edge 20b, 40b, 60b opposite the front edge, and parallel, opposite side surfaces 20c, 40c, 60c.

The distance between the opposite side surfaces defines the thickness of the blade body. In practical embodiments the thickness lies between 0.25 and 0.5 millimeter. The front portion of the blade body has been machined over part of its length to a cutting section having a multitude of cutting formations having peaks and valleys for cutting the loaf, said peaks lying on an imaginary peak line of the blade body.

The blade body has a securing portion 21 , 22; 41 , 42: 61 ,62 at each axial end of the blade body, which securing portion is adapted to secure the cutting blade with respect to the cutting blade attachment and tensioning means of the device.

As is preferred the securing portions have no cutting teeth at their front edge side. Their function is to attach the blade to the slicer device. The width of the securing portions is kept as great as possible to enhance the stability of the securing portion. In most slicer devices the securing portions are each received in a corresponding slot of the attachment means,

(see e.g. figure 4 of WO 98/41368) so that twisting of the blade during the cutting operation is prevented by the securing portion being received in the mating slot. The width of the securing portion enhances the stability of the blade against twisting during the cutting process of the loaves. The securing portions are basically planar tabs.

In these examples the securing portions are each provided with a securing feature embodied as a closed contour hole, here a circular hole 2; 43; 63, said hole extending from one side surface to the other side surface through the blade body, said hole allowing connection of the blade body to said cutting-blade attachment and tensioning means. As explained other securing features are also possible. In figure 1 it can be observed that the width of the cutting blade body 20 is generally uniform over its length, as the imaginary peak line substantially coincides with the front edge portions of the securing portions 21 , 22, and as the rear edge 20b is straight and parallel to the front edge. In figures 2 and 3 it can be observed that - over at least a part of the length of the cutting section - the width of the cutting blade body 40; 60, that is measured in said part between the peak line on the one hand and the rear edge of the blade body on the other hand, is reduced at least 25% with respect to the greatest width of each of the securing portions of the cutting blade body.

As is preferred in the invention, the figures 2 and 3 show that the peak line of the teeth is aligned with the front edges of the securing portions, so similar to the prior art blade 20. The rear edge 20b is recessed in said reduced width part with respect to the rear edge portions of the securing portions 41 , 42; 61 , 62 to obtain the significant waist of the blade.

As is preferred in the invention, the figures 2 and 3 show that the width of the cutting blade body, that is measured in said part between the peak line on the one hand and the rear edge of the blade body on the other hand, is reduced between 25% and 50% with respect to the greatest width of each of the securing portions of the cutting blade body.

As is preferred in the invention, the figures 2 and 3 show that - over at least 50% of the length of the cutting blade body - the width of the cutting blade body, that is measured in said part between the peak line on the one hand and the rear edge of the blade body on the other hand, is reduced at least 25% with respect to the greatest width of each of the securing portions of the cutting blade body.

In figure 2 the waist extends over the entire length of the cutting section, whereas in figure 3 the waist extends over less than the entire length of the cutting section. As is preferred the blades in figures 2 and 3 have been provided with the recessed rear edge 40b, 60b, by removing from the rear a portion of the material of the blank. As is preferred the removal of said portion is performed after the provision of the cutting teeth section, so that the blank remains stable during the machining of the cutting teeth, e.g. during the grinding. As is preferred the removal of said portion is effected by wire spark erosion cutting as this is beneficial for the quality of the blade and its service life due to the very high quality edge that is then provided. Grinding away said substantial portion has been found to be detrimental, in particular due to the heat input into the blade. Water jet cutting of the blade is another option, yet the results are not as good as wire spark erosion cutting.

In a preferred embodiment the production device for the blades includes a wire spark erosion cutting station to remove said portion of the blade, preferably downstream of one or more grinding stations where the cutting teeth are grinded.

The production method may include the step of coating of the blade (in particular the sides and the teeth) with a hard surface coating, e.g. 70 Rockwell C, which coating step is performed later than the machining of the front edge and preferably prior to the removal of said portion to obtain the reduced width. The coating can be for example Chromium-nitride (CrN), Titanium-Aluminum Nitride (TiAIN), Titanium-nitride (TiN), Aluminum-Chromiumnitride (AICrN), Titanium-Carbo-Nitride (TiCN), Chromium-Carbo-Nitride (CrCN), Wolfram Carbide- Cobalt (WCCo), a Ni-PTFE, or a DLC (diamond like) coating.