KNIFE ASSEMBLY

TECHNICAL FIELD

The invention relates to a knife assembly comprising a rotary axle and a plurality of knives having the shape of or comprising a ring, or are connected to a ring which is coaxial with the knife in question, the insides of the rings facing the axle, which knives together with said rings are provided on the axle where they can be positioned at distances from one another in desired positions along the axle. Particularly, the invention concerns a knife assembly intended to be employed in a slitter rewinder.

BACKGROUND OF THE INVENTION

In connection with the change of position of the knives in the assemblies of the above mentioned kind in slitter rewinders, in which the number of knives in each assembly can be very great, depending on the width of the strips which shall be produced in the slitter rewinder, the knives are moved sideways on the axle which forms part of the assembly. Conventionally the knives, more specifically the knives which have been mentioned above, are caused to slide on the axle or on longitudinal expander elements, which conventionally are used for securing the knives when desired knife positions have been reached. This, however, is not easy done. When the knives/rings slide on said expander elements it often occurs that they jam in contact with the axle or with said expander elements, so that they get caught or get wedged. If they get wedged or get directed slightly oblique, there is a risk that they will wobble as they are rotated, which impairs the cut and/or will cause a heavy wear of the knives, frequent redressing and eventually exchange of knives. It is also desirable that the displacement of the knives to new positions shall be able to be carried out automatically. It is evident that jamming in this connection is a serious complication which makes the desired automatization difficult or impossible. It is also known in the art, in connection with knife assemblies where the positioning of the knives is intended to be carried out automatically, to provide each knife/ring with a motor, which moves the knife along the axle. However, even if these motors are small, they nevertheless require so much space that they set the limit for the smallest strip width that can be achieved in the machine. As it is desirable to produce, in one and the same machine, quite wide strips as well as strips of very small width, it is of course a drawback if it would not be possible to produce strips of smaller width. It is also a drawback with many prior art knife assemblies for slitter rewinders, whether they are automatic or not, that the centering of the knives relative to the axle does not meet with high requirements.

BRIEF DISCLOSURE OF THE INVENTION

It is the purpose of the invention to address the above complex of problems. Therefore, with reference to the preamble, the invention is characterized in that at least two guide rails, which are connected to the axle, extend along the axle, that carriages are provided in each of said rings and are connected to the rings on the inside thereof facing the axle, so that each of said rings with its respective carriages forms a unit, in this text termed equipage, which, with the carriages functioning as vehicles on the guide rails, can be moved on the guide rails and be positioned in aimed knife positions.

The optimal number of guide rails is probably three, but also four may be conceived and in principle still more.

Further characteristic features are mentioned in the dependent claims or are apparent from the following description of preferred embodiments.

BRIEF DESCRIPTION OF DRAWINGS

In the following description of preferred embodiments, reference will be made to the accompanying drawings, in which

Fig. 1 shows, in the lower part of the drawing, a side view of a section of a knife assembly according to a first preferred embodiment,

Fig. 2 is a view along the line II-II in Fig. 1,

Fig. 3 is a view along the line HI-III in Fig. 2,

Fig. 4 shows an encircled detail IV in Fig. 3 at a larger scale,

Fig. 5 shows a cross-section through an axle, a knife on the axle, and a carriage holder ring, included in a knife assembly according to a modified embodiment of the invention, and

Fig. 6 shows, in a side view, four knives which are closely packed against one another on the common axle of a knife assembly according to said modified embodiment according to Fig. 5.

DESCRIPTION OF TWO EMBODIMENTS

With reference first to Fig. 1 a shear cut stand is generally designated 1. In the stand 1 there are included a bottom knife assembly 2 according to the invention, comprising a great number of bottom knives 3, of which only two are shown in the drawing, and a top knife assembly 4 comprising an equal number of top knives 5. The top knives 5 and the bottom knives 3 cooperate with one another in a mode known per se, but the top knife assembly 4 and the top knives 5 are shown only schematically. The top knife assembly

5 and the top knives 3 may also, but need not, be designed according to the principles of the invention. In this patent disclosure only the bottom knife assembly 2 will be described in detail.

In the bottom knife assembly 2, an axle is designated 10. All the bottom knives 3 are mounted on said axle 10. The axle 10 and thence all bottom knives 3 are rotated by means of only one, not shown driving motor. In the axle 10 there are three longitudinal first grooves 11 and three longitudinal second grooves 12. The three first grooves 11 are angularly spaced 120 ° from one another and so are the second grooves 12 as well, the latter ones being provided midway between the first grooves 11. The first grooves 11 , Fig. 4, have flat bottom portions 13 on both sides of a shallow, longitudinal, central groove 15, and straight walls 14, which are perpendicular to the bottom portions 13, which in turn are perpendicular to a radial plane through the axle, intersecting the centre of the central groove 15. A guide rail 16 is accommodated and is fastened with screws in the central groove and extends along the entire length of the knife assembly 2. A screw for anchoring the guide rail 16 in the central groove in the bottom of said first groove 11 is designated 17 in Fig. 4. A great number of such screws are provided along the length of the guide rail 16. The guide rail 16 has, in cross section, a pronounced waistline, due to two longitudinal depressions 18 in the sides of the guide rail, one on each side. The height of the guide rail 16 over the bottom portions 13 is slightly smaller than the height of the side walls 14.

The second grooves 12 have a shape in cross-section, Fig. 2, which is known per se and accommodates in a mode, which is also known per se, a longitudinal clamping member 21 and, under the clamping member a pneumatic hose 22 which can be inflated in order to press the clamping member 21 from a lower, passive position to the higher, active clamping position which is shown in Fig. 2.

The bottom knives 2 according to a known principle consist of circular, ring-shaped knives. Each such ring-shaped bottom knife 3 has a flat, annular shear surface 30 which is perpendicular to the axis of rotation of the axle 10 and is limited by an annular groove 29. Under the groove 29, with reference to Fig. 3, the bottom knife 3 has an annular flange 28 which protrudes in the axial direction. The shear surfaces 30 cooperate with the top knives in a mode which is conventional per se, wherein each bottom knife 3 is assigned a top knife 5 in the top knife assembly 4. The ring-shaped bottom knives 3 have a circular-cylindrical inside surface and are mounted on an inner ring 32, in this text termed carriage holder ring, the outside surface of which has the same cylindrical

shape as the inside surface of the bottom knife 3 has, so that the bottom knives 3 can be entered on and be connected snug fit to the carriage holder rings 32. In the end which is opposite the bottom knife's shear surface 30, the carriage holder ring 32 is provided with an upwards directed flange 33, which forms a support for the knife 3. The flange 33 has an axial extension, which is as large as the axial extension of the flange 28 on the opposite side of the knife. The bottom knives 3 are fastened to the carriage holder rings 32 by means of screws 38, Fig. 1. Also shrinkage fitting or other conventional fastening techniques may be conceived.

On the cylindrical inside 34 of the carriage holder rings 32, three grooves 35 are provided in the carriage holder rings , in this text termed carriage retaining grooves 35, which extend in the axial direction over the whole width of the carriage holder rings 32. The carriage retaining grooves 35 have, like said first grooves 11 in the axle 10, a flat bottom 36, which is perpendicular to a radial plane of the axle intersecting the centre line of said bottom 36, and flat side walls 37, which are perpendicular to the bottom 37 but more narrow and more shallow than said first grooves 11. Like the first grooves 11 in the axle, the carriage retaining grooves 35 are angularly spaced 120 ° from one another in the carriage holder rings 32.

In each carriage retaining groove 35 there is provided a carriage 40 having straight side walls and a flat bottom. The width of the carriage retaining grooves 35 is adapted to the width of the carriage. The carriages 40 are connected to their respective carriage holder ring 32 by means of screws 41 and are longer that the carriage holder rings 32 are wide. Therefore, an end portion 42 of the carriages 40 protrude on each side of the carriage holder rings 32 beyond the side surfaces of the carriage holder rings. The carriages 40 have been fastened to their respective carriage holder rings 32 before the carriage holder rings were fastened to their respective ring-shaped knives 3. Each set consisting of a ring-shaped bottom knife 3, a carriage holder ring 32, and three carriages 40 in combination form a unit, in this text termed equipage 44, which can be conveyed - can travel - on the guide rails 16.

The carriages 40 and the guide rails 16 thus are provided to cooperate with one another and consist of mechanical components which are known per se and available on the market-place. In combination, the carriages 40 and the guide rails 16 form assemblies, which in this text are termed ball-guide-rails, because the carriages house a great number of ball-bearing-balls 45 arranged in two ball-bearing-orbits on each long side of each carriage. When the equipage 44 is mounted on the axle 10 and is viewed as in Fig.

4, the balls 45 rest in two rows above one another against two roll-ways on each side of the guide rails, bordering the depressions 18 in the guide rails 16.

The carriages 40 extend profoundly into said first grooves 11 , which are wider than the carriages, as is seen in Figs. 2 - 4. The depths of said first grooves 11 and said carriage retaining grooves 35 are chosen in relation to the radial extension of the carriages 40 such that a carriage 40 can be received and accommodated in said first grooves 11 without touching the bottom surfaces 13 and such that an annular gap 49 is formed between the axle 10 and the carriage holder ring 32. Said gap 49 is so narrow that the pneumatic hoses 22 when inflated may press out the clamping elements 22 to the extent that they will cross the gap 49 and get into contact with the carriage holder rings 32 in order to fix the bottom knives 3 sideways, i.e. in the axial direction, in the adopted positions of the knives.

When an equipage 44 is moving along the axle 10, the balls move in said ball-bearing orbits in the carriages 40, rolling against the roll-ways, which border the depressions 18 in the sides of the guide rails 16. The ball-bearing borne equipages 44 therefore can move easily along the axle. The ball-guide-rails have a recognized great rigidity and bearing strength in all directions of bearing pressure. Also these features are utilized in the application of present invention in order to avoid any risk of jamming when the equipages 44 are moved along the axle. Moreover, the connection of the equipages 44 to the axle 10 via the ball-guide-rails implies that the bottom knives 3 are maintained centred with great accuracy during the displacement movements as well as when the knives are fixed in their aimed positions.

Normally, the bottom knives 3 are kept fixed in the sideways direction, i.e. in the axial direction of the axle 19, by means of the clamping elements 21, which are pressed against the inside surface 34 of each of the carriage holder rings 32 by means of the pneumatic hoses 22 , when the hoses are connected to a source of compressed air. The pressure of the clamping elements 21 against the carriage holder rings 32, however, has no influence on the positions of the knives 3 in the radial direction, because the carriage holder rings 32 or the bottom knives 3 can not move in any radial direction because of the stiffness and rigidity of the system consisting of a ring-shaped knive/ring 3/32 - the carriages 40 - the guide rails 16 - and the axle 10. The carriage holder rings 32 and thence the bottom knives 3 in other words are maintained permanently centred relative to the centre of rotation of the axle 10.

In the knife assembly 2 according to the invention, the equipages 44 can be brought so close against one another that the protruding portions 42 of adjacent carriages 40 will contact each other. Therefore, a free space is created between the bottom knives 3 which is wider than what is required for a tool 50, i.e. tool of a type similar to conventional shifter forks used in motor car gears, to be entered into the space and grip a knife 3 in order to move it sideways, i.e. in an axial direction of the axle. Nor does the sideways directed force which the tool 59 exerts on the knife 3 result in any oblique orientation of the knife 3, because of said stiffness and rigidity of the system consisting of the ring- shaped knive/ring 3/32 - the carriages 40 - the guide rails 16 - and the axle 10. On the other hand, the comparatively long carriages 40 means a limitation of the possibility of packing the knives 3 densely, and thence a limitation of the possibility of slicing strips of very small width. The problem could be eliminated by using shorter carriages, more specifically using carriages which are not longer than the ring-shaped knives 3 and the carriage holder rings are wide, but that would reduce the strength and stability of said system. Fig. 5 and Fig. 6 illustrates a modified embodiment of the invention, in which the problem has been solved without the employment of shorter carriages.

According to the embodiment shown in Fig. 5 and Fig. 6 of a knife assembly 2x according to the invention, the number of first grooves in the axle 10x - grooves intended for the guide rails - and the number of guide rails have been doubled. The number of guide rails and the number of grooves housing the rails thus is six and have been designated 16A and 16B, and 1 IA and 1 IB, respectively. In each of three grooves designated 1 IA there is provided a guide rail designated 16A, and in each of three grooves designated 1 IB there is provided a guide rail designated 16B. The rail housing grooves 1 IA and 1 IB and the guide rails 16A and 16B have the same design as said first grooves 11 and as said guide rails 16, respectively, in the first embodiment. The angular distance between the rail-grooves/guide rails 11A/16A is 120 °, i.e. the same as the angular distance between the rail-grooves/guide rails 11/16, and equally large is the angular distance between the rail-grooves/guide rails 11B/16B. The radial symmetry lines of the rail-grooves/guide rails 11A/16A and the radial symmetry lines of the rail- grooves/guide rails 11B/16B are designated 51A and 5 IB, respectively. The most adjacent ones of such symmetry lines 51A and 5 IB define a sector of a circle, in which the sector angle α = 40 ° , while the next adjacent ones of said symmetry lines 51A and 51 B represent a sector of a circle, in which the sector angle β = 80 ° . Symmetrically positioned in each one of the three latter sectors, there is a groove 12 housing a clamping member, said groove 12 having a shape which is identical with the shape of said second groove in the axle 10 according to the foregoing embodiment. In each one

of the three grooves there are also provided, as before, expander elements in the form of a pneumatic hose 22 and a clamping member 21.

The knife assembly 2x includes two types of knives, designated 2A and 2B, respectively. Fig. 5 shows a knife of type 2A. This type of knifes has three carriage retaining grooves 35, each of which is provided opposite to a rail-groove 1 IA and designed equally with the shape of the carriage retaining grooves according to the foregoing embodiment. In each of these carriage retaining grooves there is provided a carriage 40 which also is of identically the same type and mounted in same mode as according to the first embodiment.

Opposite to each one of the three rail-grooves 1 IA there is further, on the inside of the knife 2A, provided a carriage receiving groove 52A, which is more profound and wide than the carriage retaining grooves 35 and thence also has a depth and width which is larger than the height and width of the carriages 40. In the knives of type 2B, the carriage receiving grooves, which are designated 52B, and the carriage retaining grooves 35 have changed place. In other respects the knives of type 2 A and 2B are equal. Due to the arrangement according to the invention, the knives can be close- packed 2A-2B-2A-2B and so on, as is illustrated in Fig. 6. This is made possible because the protruding portions 42 of the carriages 40 in the knives 2 A can be brought into the carriage receiving grooves 52B in the knives 2B, while the protruding portions 42 of the carriages 40 in the knives 2B can be brought into the carriage receiving grooves 52B in the knives 2A.

When the knives 2A, 2B are maximally close-packed, Fig. 6, there is a gap 53 between each pair of adjacent knives which is sufficiently wide in order to allow the top knives 5 of the top knife assembly 4 to be moved into contact with the shear surface 30 on the bottom knife 2 A or 2B in question, and also to allow the tool 50 to enter the gap for moving any of the knives 2 A, 2B sideways.

It should be understood that the invention is not restricted to the disclosed embodiments. For example, the carriage holder rings 32 can be eliminated and the ring- shaped knives instead be provided with an inside directly facing the axle 10 or 10x, in or against which inside the carriages 40 can be directly fixed on the knife. The number of guide rails and rail housing grooves may also be varied, as well as the number of grooves assigned to the expander elements. The claimed patent therefore is neither restricted to what has been stated in the introductory part of the description nor to what

has been disclosed in the description of the embodiments, which only shall serve as illustrative examples.