ASYMMETRICAL THREE-BLADE SCREW-TYPE SHAFT FOR A MIXING AND KNEADING MACHINE

Abstract

A worm shaft for a mixing and kneading machine in particular for continuous preparation processes, comprising a shaft rod, on the circumferential surface of which blade elements are arranged which are spaced apart from one another and which extend outward from the circumferential surface of the shaft rod, wherein the blade elements are arranged on the shaft rod, at least in one section extending in the axial direction of the worm shaft, in three rows extending in the axial direction of the worm shaft, wherein at least one of the blade elements of one of the rows is different from one of the blade elements of one of the other rows, and/or the rows of blade elements, viewed in cross-section of the shaft rod, are distributed irregularly over the circumference defined by the outer circumferential surface of the shaft rod, and wherein the angular distance between the midpoints M of the outer circumferential surfaces of the blade elements on the circumferential surface of the shaft rod of adjacent rows differs between at least two of the three rows of the at least other two rows, and including wherein, for example, each of the blade elements of the at least one section extending in the axial direction of the worm shaft has a longitudinal extension which extends in an angle of 45° to 135° to the axial direction of the worm shaft.

Claims

1. A worm shaft (12) for a mixing and kneading machine (100) having a shaft rod (20) having a circular cross-section, on the circumferential surface of which blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) are arranged which are spaced apart from one another and which extend outwards from the circumferential surface of the shaft rod (20) wherein the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) are arranged on the circumferential surface of the shaft rod (20), at least in one section extending in the axial direction of the worm shaft (12), in three rows (40) extending in the axial direction of the worm shaft (12), wherein this section extending in the axial direction of the worm shaft (12) does not comprise any further blade elements except those arranged in the three rows (40), wherein i) at least one of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of at least one other of the both rows (40) is different from one of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of one of the other rows (40) by being shorter and/or narrower, and/or ii) the rows (40) of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v), viewed in cross-section of the shaft rod (20), are distributed irregularly over the circumference defined by the outer circumferential surface of the shaft rod (20).

2. The worm shaft (12) according to claim 1, characterized in that the angular distance between the midpoints M of the outer circumferential surfaces of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) on the circumferential surface of the shaft rod (20) of adjacent rows (40) differs between at least two of the three rows (4) of the at least other two rows (40).

3. The worm shaft (12) according to claim 1, characterized in that at least 80% of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of each row (40) of the at least one section extending in the axial direction of the worm shaft (12) are identical to one another.

4. The worm shaft (12) according to claim 1, characterized in that the length of the section of the worm shaft (12) extending in the axial direction, in which the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) are arranged in three rows (40) extending in the axial direction of the worm shaft (12), is at least 0.2 D of the length of the worm shaft (12).

5. The worm shaft (12) according to claim 1, characterized in that each of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the at least one section extending in the axial direction of the worm shaft (12) has a longitudinal extension which extends in an angle of 45° to 135° to the axial direction of the worm shaft (12).

6. The worm shaft (12) according to claim 1, characterised in that at least 50% of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the at least one section extending in the axial direction of the worm shaft (12), in the top view, has an outer circumferential surface in a form being selected from the group consisting of parallelogram-shaped, elliptical, oval, biconvex, modified elliptical, modified oval, modified biconvex, and modified rectangular.

7. The worm shaft (12) according to claim 6, characterized in that all of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of a row (40) have the same shape, wherein the shape of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of two of the three rows (40) is the same and differs from the shape of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the third row (40).

8. The worm shaft (12) according to claim 1, characterized in that the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of two of the three rows (40) of the at least one section extending in the axial direction of the worm shaft are identical to one another, and the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the third row (40) have the same or different shape as the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the other rows (40), wherein the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the third row (40) is 1 to 25% longer, shorter, narrower, or wider than the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the other two rows (40).

9. The worm shaft (12) according to claim 1, characterized in that the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of two of the three rows (40) of the at least one section extending in the axial direction of the worm shaft (12) are identical to one another, and the angular distance α between the midpoints M of the outer circumferential surfaces of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the two rows (40) on the circumferential surface of the shaft rod (20) differs from the angular distance between the midpoint M of the outer circumferential surfaces of the other row, and from each of the midpoints M of the outer circumferential surface of the two rows (40) on the circumferential surface of the shaft rod (20).

10. The worm shaft (12) according to claim 1, characterized in that the angular distance α between the midpoints M of the outer circumferential surface of the blade element (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of two of the three rows (40) of the at least one section extending in the axial direction of the worm shaft (12) on the circumferential surface of the shaft rod (20) is 124° to 146°, and the angular distances blade element between the midpoint M of the outer circumferential surfaces of the other row and each of the midpoints M of the outer circumferential surface of the two rows (40) on the circumferential surface of the shaft rod (20) are 102° to 123°.

11. The worm shaft (12) according to claim 1, characterized in that each of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of two of the three rows (40) of the at least one section extending in the axial direction of the worm shaft (12) — viewed in the cross-section of the shaft rod (20) — extends over the same angular distance of the circumferential surface of the shaft rod (20) and each of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the other row (40) extends over a shorter or longer angular section, wherein the difference between the angular distances is 1 to 20%.

12. The worm shaft (12) according to claim 1, characterized in that each of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of two of the three rows (40) of the at least one section extending in the axial direction of the worm shaft (12) — viewed in the cross-section of the shaft rod (20) — extends over an angular distance of 20° to 175° of the circumferential surface of the shaft rod (20) and each of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of the other of the three rows (40) extends over an angular distance of 20° to 120°.

13. A section for a worm shaft (12) with a shaft rod (20) having a circular cross-section, wherein spaced-apart blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) extending outward from the circumferential surface of the shaft rod (20) are arranged on the circumferential surface of the shaft rod (20), wherein the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) are arranged on the circumferential surface of the shaft rod (20) in three rows (40) extending in the axial direction of the worm shaft (12), wherein this section extending in the axial direction of the worm shaft (12) does not comprise any further blade elements except those arranged in the three rows (40), wherein i) at least one of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of one of the both rows (40) is different from at least one other of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) of one of the other rows (40) by being shorter and/or narrower, and/or ii) the rows of the blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v), viewed in the cross-section of the shaft rod (20), are distributed irregularly over the circumference defined by the outer circumferential surface of the shaft rod (20), and wherein each row (40) comprises one, two, three, or four blade elements (22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v) axially separated from one another.

14. A housing (10) of a mixing and kneading machine (100) for continuous preparation processes, wherein in the housing (10) a hollow inner space (18) is formed in which, at least in sections in the axial direction, a worm shaft (12) according to claim 1 extends, and wherein on the inner circumferential surface of the housing (10) receptacles (28) for kneading elements (24) extending at least in sections into the housing (10) are arranged, wherein the receptacles (28) on the inner circumferential surface of the housing (10) are arranged in at least three rows (29, 29′, 29″) extending in the axial direction over at least one section of the inner circumferential surface of the housing (10).

15. A mixing and kneading machine (100) for continuous preparation processes such as the production of polymer granulates, polymer extruded profiles, or polymer moulded parts, comprising a housing according to claim 14.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Below the present invention is described in more detail with reference to the drawing, wherein:

[0047] FIG. 1a shows a schematic longitudinal section of a mixing and kneading machine;

[0048] FIG. 1b shows a perspective view of the housing of the mixing and kneading machine shown in FIG. 1a;

[0049] FIG. 2a shows a perspective view of an axial section of a worm shaft according to an embodiment of the present invention;

[0050] FIG. 2b shows a top view of the axial section of the worm shaft shown in FIG. 2a;

[0051] FIG. 2c shows a lateral top view of the axial section of the worm shaft shown in FIG. 2a;

[0052] FIG. 3a shows a perspective view of an axial section of a worm shaft according to a further embodiment of the present invention;

[0053] FIG. 3b shows a top view of the axial section of the worm shaft shown in FIG. 3a;

[0054] FIG. 4a shows a perspective view of an axial section of a worm shaft according to a further embodiment of the present invention;

[0055] FIG. 4b shows a top view of the axial section of the worm shaft shown in FIG. 4a;

[0056] FIG. 5 shows the processing of the shell surface of the shaft rod of an axial section of the worm shaft with the blade elements disposed thereon and kneading elements protruding into a gap between the blade elements according to a further embodiment of the present invention;

[0057] FIG. 6 shows the processing of the shell surface of the shaft rod of an axial section of a worm shaft with the blade elements disposed thereon and kneading elements protruding into a gap between the blade elements according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0058] The mixing and kneading machine shown in FIGS. 1a and 1b and as a whole designated as 100 comprises a housing 10 and a worm shaft 12 arranged in the housing 10. The housing 10 comprises two housing halves 14, 14′, which are lined on the inside with a so-called housing shell 16. Here the housing shell 16 in the present patent application is considered as a component of the housing 10. The inner circumferential surface of the housing 10, when the two housing halves 14, 14′ are closed, delimits a cylindrical hollow inner space 18, thus an inner space 18 with circular cross-section. The worm shaft 12 comprises a shaft rod 20, on the circumferential surface of which blade elements 22 are arranged which extend radially outward on the circumferential surface of the shaft rod 20, wherein the individual blade elements 22 are arranged at a distance from one another. In the two housing halves 14, 14′, receptacles 28 are provided for kneading elements 24, i.e. for kneading bolts, kneading cogs, and the like. Here each of the receptacles 28 is a drilled hole 28, which extends from the inner circumferential surface of the housing shell 16 through the housing wall. The lower, radially inwards end of each receptacle 28 can be configured to be square in the cross-section, for example. Each kneading bolt 24 for example can have on its lower end an end which fits precisely into the squarely configured radial inner end of the receptacles 28, and is thereby fixed in a rotationally locked position into the receptacle 28 in the used state. The kneading bolt 24 is connected on its end being positioning in the receptacle 28 with a fixing element (not shown) used in the overlying end of the receptacle 28 by means of screwing. Alternatively, the kneading bolt 24 can also have an internal thread for a screw, and can be affixed with a screw instead of the fixing element and nut.

[0059] As follows in particular from FIG. 1b, the equally spaced receptacles 28 for the kneading bolts 24 extend in the form of three rows 29, 29′, 29″ into each of the two housing halves 14, 14′, viewed in the axial direction. Thus the total number of rows of receptacles 29, 29′, and 29″ of the housing is six. A row within the meaning of the present invention is understood to mean that a connecting line drawn over the axially separated receptacles 28 of a row 29, 29′, 29″ is a straight line. As shown in FIGS. 1a and 1b, the mixing and kneading machine 100 is subdivided in the axial direction into several process sections 34, 34′, 34″, wherein each process section 34, 34′, 34″ is adapted with respect to the number of kneading bolts 24 as well as the number and the extent of the blade elements 22 on the shaft rod 20 to the function of the individual process sections 34, 34′, 34″. As shown in FIG. 1b, in the section 34 and in the right section 34″ of the upper housing halves 14, there are two rows out of the three rows 29, 29′, 29″ of receptacles 28 for kneading bolts 24, namely the upper row 29 and the lower row 29″, fitted with kneading bolts 24, whereas the middle row 29′ is not fitted with kneading bolts 24. In contrast to this, of the three rows 29, 29′, 29″ of receptacles 28 for kneading bolts 24 in the centre section 34′ of the upper housing half 14 one row, namely the centre row 29′, is equipped with kneading bolts 24, whereas the upper row 29 and the lower row 29″ are not equipped with kneading bolts 24. In the middle section 34′ of the lower housing half 14′ there are two rows, namely the upper and lower row, fitted with kneading bolts, so that the middle section 34′ of the housing 10 altogether has three rows of opposing kneading bolts 24. The raw material to be mixed is added to the mixing and kneading machine 100 via the filling funnel 36, then guided through process sections 34, 34′, 34″ and finally discharged via the outlet opening 38. Instead of the depicted process sections 34, 34′, 34″, the mixing and kneading machine 100 according to the invention can also have more process sections, in particular four process sections, or fewer process sections such as two or one process section.

[0060] According to the invention, the worm shaft 12 for a mixing and kneading machine according to the present invention is designed such that the blade elements 22 on the circumferential surface of the shaft bar 20, are arranged at least in a section extending in the axial direction of the worm shaft 12, like the middle process section 34′ shown in FIG. 1b, in three rows extending in the axial direction of the worm shaft 12, i.e. the worm shaft 12 is designed in some sections to be two-bladed, and at least one of the blade elements of one of the rows is different from one of the blade elements of one of the other rows and/or the rows of blade elements, viewed in the cross-section of the shaft rod, are distributed unevenly over the circumference defined by the outer circumferential surface of the shaft rod.

[0061] Such a three-bladed section of a worm shaft 12 according to a preferred embodiment of the present invention is shown in FIGS. 2a, 2b, and 2c. The blade elements 22, 22′, 22″, 22‴, 22.sup.iv, and 22.sup.v are arranged on the cylindrical shaft rod 20 of the worm shaft 12, extending radially outwards from the circumferential surface of the shaft rod 20. Here the individual blade elements 22, 22′, 22″, 22‴, 22.sup.iv, and 22.sup.v are configured such that in a top view they have modified biconvex outer circumferential surfaces in which the two ends of the outer circumferential surfaces, viewed over the longitudinal extension of the blade elements, are configured in the form of an edge and one flank each of the two opposing end sections has a straight section 39, 39′. The longitudinal extensions L of the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, and 22.sup.v extend nearly perpendicularly to the longitudinal direction of the worm shaft 12. By longitudinal extension L, the longest possible straight line between two different points on the outer circumferential surface of a blade element 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v, i.e. the length L in this case, is to be understood. All blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v have the same form and the same dimensions. The ratio of the length L to the width B of the individual blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v is around 8.5, wherein the width B is the longest straight extension of the outer circumferential surface of the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v, which extends perpendicularly to the length L of the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v.

[0062] Here both the axially spaced blade elements 22, 22′ are arranged in an axially extending row 40 as well as the axially spaced blade elements 22″, 22‴ as well as 22.sup.iv, 22.sup.v are arranged in an axially extending row. An axially extending row 40 of blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v is present according to the present invention when — as shown in the embodiment shown in FIGS. 2a, 2b, and 2c — a connecting line drawn over the midpoints M of the outer circumferential surface of blade elements 22, 22′ being spaced apart in the axial direction is a straight line. The midpoint M of a blade element 22, 22′ here is the point which lies in the middle of the length L of the blade element 22, 22′. The ratio of the axial distance A of the adjacent blade elements 22, 22′ of the row 40 in each case is around 5.5. Here the width B of the blade element is as defined above, and the axial distance A of two axially adjacent blade elements 22, 22′ is the distance between the midpoints M of the outer circumferential surfaces of the axially adjacent blade elements 22, 22′. One of the three — viewed in the cross-section of the shaft rod 20 —adjacent blade elements 22 in the circumferential direction of the shaft rod 20 is axially displaced slightly with respect to the other two blade elements 22‴, 22.sup.iv. All of the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v extend respectively over the same angular section of 115° over the (outer) circumferential surface or shell surface of the shaft rod 20.

[0063] However, the rows 40 of the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v, viewed in the cross-section of the shaft rod 20, are distributed irregularly over the circumference defined by the outer circumferential surface of the shaft rod 20. The angular distance α of the midpoints M between the blade elements 22‴, 22.sup.iv on the circumferential surface of the shaft rod 20 is 135°, whereas the angular distances β of the midpoints M between the blade elements 22, 22‴ and 22, 22.sup.iv on the circumferential surface of the shaft rod 20 are in each case 112.5°.

[0064] FIGS. 3a and 3b show a three-bladed section of a worm shaft 12 according to a further preferred embodiment of the present invention. The outer circumferential surfaces of the blade elements 22, 22′, as in the embodiment of FIGS. 2a, 2b, and 2c, are configured to be modified biconvex, whereas the outer circumferential surfaces of the blade elements 22″, 22‴, 22.sup.iv, 22.sup.v of the other two rows have a different, likewise modified biconvex shape, wherein the outer circumferential surfaces of the blade elements 22″, 22‴, 22.sup.iv, 22.sup.v are however wider than those of the blade elements 22, 22′, and in the 22″, 22‴, 22.sup.iv, 22.sup.v the two equal ends of the lateral flanks have a straight section 39, 39′.

[0065] FIGS. 4a and 4b show a three-bladed section of a worm shaft 12 according to a further preferred embodiment of the present invention. The outer circumferential surfaces of the blade elements 22, 22′ are as in the embodiment of FIGS. 2a, 2b, and 2c, configured in a modified biconvex shape, whereas the outer circumferential surfaces of the blade elements 22″, 22‴, 22.sup.iv, 22.sup.v of the other two rows have a different, likewise modified biconvex shape, wherein the outer circumferential surfaces of the blade elements 22″, 22‴, 22.sup.iv, 22.sup.v are however wider than the blade elements 22, 22′, the end sections of the outer circumferential surfaces of the blade elements 22″, 22‴, 22.sup.iv, 22.sup.v are configured in the shape of a trapezoid which tapers toward the ends, and in the blade elements 22″, 22‴, 22.sup.iv, 22.sup.v the two opposing ends of the lateral flanks have a straight section 39, 39′.

[0066] FIG. 5 shows the design of the shell surface of a shaft rod 20 of an axial section of a worm shaft 12 with blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v arranged thereon, and the kneading elements 24 extending into the space between the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v according to an exemplary embodiment of the present invention. During operation of the mixing and kneading machine, the worm shaft 12 rotates and at the same time moves axially in translation back and forth once per rotation. The kneading elements 24 thereby move along the lateral flanks of the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v back and forth and also move back and forth in the space between the blade elements 22, 22″ or 22″, 22.sup.iv being adjacent in the circumferential direction of the shaft rod 20. The outer circumferential surfaces of the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v are in each case parallelogram-shaped, wherein the four blade elements 22, 22′, 22.sup.iv, 22.sup.v are however longer and wider than the two blade elements 22″, 22‴.

[0067] FIG. 6 shows an alternative embodiment to that of FIG. 5. In the embodiment shown in FIG. 6, the blade elements 22, 22′, 22″, 22‴, 22.sup.iv, 22.sup.v are likewise parallelogram-shaped, wherein the four blade elements 22, 22′, 22.sup.iv, 22.sup.v are however shorter and wider than the two blade elements 22″, 22‴.

TABLE-US-00001 List of reference symbols 10 Housing 12 Worm shaft 14, 14′ Housing half 16 Housing shell 18 Hollow inner space 20 Shaft rod 22, 22′, 22″, 22‴ 22.sup.iv, 22.sup.v Blade element 24 Kneading element/kneading bolt 28 Receptacle/drilled hole for kneading element 29, 29′, 29″ (Axially extending) row of receptacles for kneading elements 34, 34′, 34″ Process section 36 Filling funnel 38 Outlet opening 39, 39′ Straight section of a modified biconvex blade element 40 (Axially extending) row of blade elements 42 Lateral flank of a blade element 100 Mixing and kneading machine α Angular distance between the midpoints of two blade elements on the circumferential surface of the shaft rod β Angular distance between the midpoints of two blade elements on the circumferential surface of the shaft rod A Axial distance A of two adjacent blade elements of a row B Width (longest straight extension of the outer circumferential surface of the blade element, which extends perpendicularly to the length of the blade element) L Length (longest straight extension of the outer circumferential surface of the blade element) M Midpoint of the outer circumferential surface of a blade element