Abstract
In recent years, development in the field of knitting tools has seen a focus on the reduction of friction and wear. A knitting tool (1) and a knitting device (27) as described herein are better able to reduce friction in knitting machines and the accumulation of dirt (23) than conventional knitting tools. For this purpose, a functional portion (5) of the knitting tool (1) has subsections (7) in which the absolute value of the gradient of a center-of-gravity line (4) is greater than zero.
Claims
1. A knitting tool (1) comprising: a shank (2), which extends essentially in a longitudinal direction (z) in which the knitting tool (1) is moved during knitting, wherein the shank (2) has, at every point along its length, a cross-sectional surface (8) which extends orthogonally with respect to the longitudinal direction (z) and along lateral (y) and elevational (x) directions, wherein each of the cross-sectional surfaces (8) has a centroid (9), through which an imaginary center-of-gravity line (4) runs that interconnects centroids (9) of all the cross-sectional surfaces (8) along the longitudinal direction (z), wherein the shank (2) has at least one functional portion (5) in which the imaginary center-of-gravity line (4) has a varying height, and in which a height dimension of the cross-sectional surface (8) in the elevational (x) direction is smaller at every point along a length of the at least one functional portion (5) than a height of the shank (6) within the at least one functional portion (5), wherein the height of the shank (6) within the at least one functional portion is a distance, in the elevational direction (x), between a lowest point of the shank (2) in the elevational direction (x) and a highest point of the shank (2) in the elevational direction (x) within the at least one functional portion (5), and wherein the at least one functional portion (5) has a length which is more than 20% of a length of the knitting tool (1), wherein the at least one functional portion (5) has subsections (7) in which an absolute value of a gradient of the imaginary center-of-gravity line (4) is between 0 and .
2. The knitting tool (1) according to claim 1, further comprising at least one butt (18).
3. The knitting tool (1) according to claim 2, wherein the at least one functional portion (5) comprises at least two sub-portions (33), each of which has subsections (7) in which the absolute value of the gradient of the imaginary center-of-gravity line (4) is between 0 and , and the at least two sub-portions (33) are spaced apart from each other in the longitudinal direction (z).
4. The knitting tool (1) according to claim 3, wherein at least one sub-portion (33) of the at least two sub-portions (33) of the at least one functional portion (5) that precedes the at least one butt (18) in the longitudinal direction (z) and at least another sub-portion (33) of the at least two sub-portions (33) of the at least one functional portion (5) that follows the at least one butt in the longitudinal direction (z).
5. The knitting tool (1) according to claim 4, wherein at least one sub-portion (33) of the at least two sub-portions of the at least one functional portion (5) adjoins the at least one butt (18) directly or is spaced apart from the at least one butt (18) only by a distance in the longitudinal direction (z) which is less than or equal to 10% of the length of the knitting tool.
6. The knitting tool (1) according to claim 1, wherein the at least one functional portion (5) has at least one local minimum or maximum elevational extreme (14, 15) of the imaginary center-of-gravity line (4), and wherein at the at least one local minimum or maximum elevational extreme, the gradient of the imaginary center-of-gravity line (4) is zero.
7. The knitting tool (1) according to claim 6, wherein a top surface (10) of the shank (2) facing a positive elevational direction (x) has a same height at positions, in the longitudinal direction (z), of at least two local maxima (14) of the imaginary center-of-gravity line (4) and/or a bottom surface of the shank (2) facing a negative elevational direction (x) has a same height at positions of at least two local minima (15) of the imaginary center-of-gravity line (4).
8. The knitting tool (1) according to claim 7, wherein the shank (2) comprises lateral surfaces facing in the lateral direction (y), and at least one of the lateral surfaces is raised laterally (y) relative to a majority of the at least one functional portion (5) at the position of at least one of the at least two local maxima (14).
9. The knitting tool (1) according to claim 1, wherein at positions of local maxima (14) of the imaginary center-of-gravity line (4), the shank (2) is spaced apart from a minimum shank height (11) of the at least one functional portion (5), and at positions of local minima (15) of the imaginary center-of-gravity line (4), the shank (2) is spaced apart from a maximum shank height (12) of the at least one functional portion (5).
10. The knitting tool (1) according to claim 1, wherein at least one sub-portion (33) of the at least one functional portion (5) forms, in an x-z plane, at least one triangular recess (19) and/or at least one wavelike recess (20).
11. The knitting tool (1) according to claim 1, wherein a top surface (10) of the shank (2) which faces a positive elevational direction (x) of the knitting tool (1) has a gradient course which, in a positive longitudinal direction (z) pointing in an extension direction of the knitting tool (1), has a local gradient maximum (40) in front of at least one local height maximum (14) of the imaginary center-of-gravity line, and/or a bottom surface of the shank (2) which faces a negative elevational direction (x) of the knitting tool (1) has a gradient course which, in the positive longitudinal direction (z), has a local gradient minimum (41) in front of at least one local height minimum (15) of the imaginary center-of-gravity line (4).
12. The knitting tool (1) according to claim 11, wherein an absolute value of the local gradient maximum (40) of the top surface (10) and/or an absolute value of the local gradient minimum (41) of the bottom surface (13) is between 0.57 and 2.75.
13. The knitting tool (1) according to claim 1, wherein a top surface of the shank (2) which faces a positive elevational direction (x) of the knitting tool (1) and a bottom surface of the shank (2) which faces a negative elevational direction (x) of the knitting tool (1) are substantially parallel to each other in the subsections (7) of the at least one functional portion (5).
14. The knitting tool (1) according to claim 1, wherein a last maximum (14), in a negative longitudinal direction (z) of the knitting tool (1) of the imaginary center-of-gravity line (4) of the at least one functional portion (5) is a global maximum (42).
15. A knitting device (27), comprising: at least one needle slot (28), which is configured to receive and, during operation, to guide a knitting tool (1), and at least one knitting tool (1) according to claim 1.
16. The knitting device (27) according to claim 15, wherein a length of the at least one needle slot (28) in the longitudinal direction (z) of the knitting tool (1), a reach of the at least one functional portion (5) in the longitudinal direction (z) of the knitting tool (1), a magnitude of a stroke (34) of a knitting movement of the knitting tool (1) during knitting are mutually coordinated such that at least 80% of the reach of the at least one functional portion (5) of the knitting tool (1), in the longitudinal direction (z), remains within the at least one needle slot (28) during knitting.
17. The knitting device (27) according to claim 16, wherein an upper edge (36) of the at least one needle slot (28) is spaced in the elevational direction (x) by a maximum of 0.5 mm from a highest point (39) of a top surface of the shank (2) facing a positive elevational direction (x) of the knitting tool (1).
18. The knitting device (27) according to claim 17, wherein: the knitting tool (1) comprises a butt (18) which is raised in a positive elevational direction (x) relative to the at least one functional portion (5), the butt (18) engages in a cam curve recess (30) of the knitting device (27), and a highest point (39), in the positive elevational direction (x), of the top surface of the shank (2) is spaced apart from the cam curve recess (30) in the longitudinal direction (z).
Description
[0041] It is also to advantage if the knitting tool of the knitting device has a butt, which is raised in the positive elevational direction relative to the functional portion and which engages in a recess of the knitting devicethe cam curve, and if the highest point, in positive elevational direction, of the shank surface facing the positive elevational direction of the knitting toolthe top surface (10) is spaced apart from the cam curve in the tool's longitudinal direction (z). In this way, the top surface of the knitting tool is prevented from accidentally engaging the cam curve at these points. Accidental engagement could cause the knitting tool to jam, with resultant damage to the knitting tool and/or the knitting device. The distance in the tool's longitudinal direction between the highest point, in positive elevational direction, and the cam curve is the safety distance. The safety distance is advantageously greater than zero.
[0042] FIG. 1 shows a knitting tool (1), which has a functional portion (5).
[0043] FIG. 2 shows the A-A section through the functional portion (5) of the knitting tool (1) at the position of a local maximum (14) in the centre-of-gravity line (4).
[0044] FIG. 3 shows the B-B section through the functional portion (5) of the knitting tool (1) at the position of a local minimum (15) in the centre-of-gravity line (4).
[0045] FIG. 4 shows a knitting tool (1), which has triangular recesses (19) in the functional portion (5).
[0046] FIG. 5 shows a knitting tool (1), which has wavelike recesses (20) in the functional portion (5).
[0047] FIG. 6 shows a knitting tool (1) whose surface in the area of local minima (15) and maxima (14) in the centre-of-gravity line (4) has dirt catches (21).
[0048] FIG. 7 shows the three sub-steps in which dirt (23) is removed from the operating area (24) of the knitting tool (1).
[0049] FIG. 8 shows a knitting device (27) comprising three needle slots (28), one of which is fitted with a knitting tool (1).
[0050] FIG. 9 shows four cam elements (29) of a knitting device (27) and a knitting tool (1).
[0051] FIG. 10 shows the top view of a knitting device (27) having three needle slots (28), each of which is fitted with a knitting tool (1).
[0052] FIG. 11 shows the section, in the x-z plane, through a needle slot (28) fitted with a knitting tool (1).
[0053] FIG. 12 shows a knitting tool (1) in the case of which the absolute value of the local gradient maximum (40) of the top surface (10) is smaller than the absolute value of the local gradient minimum (41) of the bottom surface (13).
[0054] FIG. 1 shows a knitting tool 1 having a shank 2, which extends predominantly in the tool's longitudinal direction z and has a loop-forming element 3 shaped as a hook at its first end as viewed in the tool's positive longitudinal direction z. The shank 2 has, at every point along its length in the tool's longitudinal direction, a cross-sectional surface 8 which lies in the plane defined by the lateral direction y and the elevational direction x. In the functional portion 5, the height of this cross-sectional surface 8, i.e. the cross-sectional-surface height 22, in the elevational direction x is smaller at every point than the shank height 6. The shank height 6 is the height between the minimum and maximum extension of the functional portion 5 in the elevational direction x. The cross-sectional surface 8 and the centroid 9 of a cross section are shown by way of example in FIG. 2. FIG. 1 shows a centre-of-gravity line 4, which interconnects all the centroids 9 of these cross-sectional surfaces 8 of the shank via the shortest path. In the exemplary embodiment shown in FIG. 1, this centre-of-gravity line 4 comprises three local maxima 14 and three local minima 15. Other advantageous embodiments of the knitting tool 1 may, however, have more or fewer local maxima 14 and/or local minima 15. In the area of the three local maxima 14, the top surface 10 has the same height. In the area of the three local minima 15, the bottom surface 13 has the same height in elevational direction x. In the subsections 7 of the functional portion 5, the centre-of-gravity line 4 has a gradient greater than 0. In these subsections 7, therefore, the shank 2 is tilted with respect to the tool's longitudinal direction z and, in particular, does not run parallel to the tool's longitudinal direction z.
[0055] FIG. 2 shows the A-A section, the position of which is shown in FIG. 1 and which goes through the shank 2 in the functional portion 5 at the position of a local maximum 14 in the centre-of-gravity line 4. Parts of the functional portion 5 are shown, wherein the functional portion 5, taken as a whole, extends over the entire shank height 6. The shank height 6 is delimited in positive elevational direction x by the maximum shank height 12 and in negative elevational direction x by the minimum shank height 11. The cross-sectional surface 8 is shown with hatching and has a centroid 9 which, seen in elevational direction x and lateral direction y, lies in the centre of the cross-sectional surface 8. The cross-sectional surface 8 is delimited downwardly, in negative elevational direction x, by the bottom surface 13 of the knitting tool 1. The bottom surface 13 is also visible in FIG. 2 in an area that lies outside the sectional plane and continues beneath the cross-sectional surface 8. The cross-sectional surface 8 is delimited upwardly, in positive elevational direction x, by the top surface 10 of the knitting tool 1. The top surface 10 is at the level of the maximum shank height 12. At the position of the cross-sectional surface 8, the bottom surface 13and thus the shank 2is, by contrast, spaced apart from the minimum shank height 11 by the bottom distance 16. In other words, beneath the local maximum 14, in negative elevational direction x, a clearance exists between the shank 2 and the minimum shank height 11.
[0056] FIG. 3 shows the B-B section, the position of which is also shown in FIG. 1 and which goes through the shank 2 in the functional portion 5 at the position of a local minimum 15 in the centre-of-gravity line 4. Parts of the functional portion 5 are shown, wherein the functional portion 5, taken as a whole, extends over the entire shank height 6. The shank height 6 is delimited in positive elevational direction x by the maximum shank height 12 and in negative elevational direction x by the minimum shank height 11. The cross-sectional surface 8 is shown with hatching and has a centroid 9 which, seen in elevational direction x and lateral direction y, lies in the centre of the cross-sectional surface 8. The cross-sectional surface 8 is delimited upwardly, in positive elevational direction x, by the top surface 10 of the knitting tool 1. The top surface 10 is also visible in FIG. 3 in an area that lies outside the sectional plane and continues above the cross-sectional surface 8. The cross-sectional surface 8 is delimited downwardly, in negative elevational direction, by the bottom surface 13 of the knitting tool 1. In FIG. 3, the bottom surface 13 is at the level of the minimum shank height 11. At the position of the cross-sectional surface 8, the top surface 10 is, by contrast, spaced apart from the maximum shank height 12 by the top distance 17. In other words, above the local minimum 15, in positive elevational direction x, a clearance exists between the shank 2 and the maximum shank height 12.
[0057] FIG. 4 shows a knitting tool 1 according to the invention, having a butt 18, which, during knitting, is suitable for taking up driving forces and driving movements and transmitting them to the knitting tool 1. In front of and behind the butt 18, viewed in the tool's positive longitudinal direction z, are two adjoining sub-portions 33 of the functional portion 5. Together, the two sub-portions 33 form the functional portion 5. They are spaced apart from each other in the tool's longitudinal direction z by a functional-portion distance 31, which is approximately 1.5 times as large as the butt length 32 of the butt 18. In this exemplary embodiment, the butt 18 is located between the two sub-portions 33 of the functional portion 5. The shape of the shank 2 in the sub-portions 33 of the functional portion 5 has a plurality of triangular recesses 19. These triangular recesses 19 have a substantially triangular geometry in the x-z plane and penetrate completely through the shank 2 of the knitting tool 1 in the lateral direction. The top surface 10 and the bottom surface 13 of the shank 2 are substantially parallel to each other in the functional portion 5.
[0058] FIG. 5 shows a knitting tool 1 according to the invention, which also comprises a butt 18 and a functional portion 5 having two sub-portions 33. Contrary to the shape of the embodiment of FIG. 4, the shape of the shank 2 in the sub-portions 33 has a plurality of wavelike recesses 20. These wavelike recesses 20 have a substantially wavelike or arcuate geometry in the x-z plane and penetrate completely through the shank 2 of the knitting tool 1 in the lateral directionOne of the two sub-portions 33 is disposed in front of the butt 18 in the tool's longitudinal direction z, the other of the two sub-portions 33 is disposed behind the butt 28 in the tool's longitudinal direction z. The two sub-portions 33 directly adjoin the butt 18. Accordingly, no space exists between the sub-portions 33 and the butt 18 in the tool's longitudinal direction. The last maximum in the centre-of-gravity line 4 of the functional portion 5, viewed in the tool's negative longitudinal direction z, opposite the direction of extension, is a global maximum of the functional portion 5. The knitting tool 1 is supported and guided particularly well by this global maximum in that the knitting tool 1 is prevented from tilting about an axis running in the lateral direction y.
[0059] FIG. 6 shows a knitting tool 1 according to the invention, which comprises a butt 18 and a guiding portion 5, said guiding portion 5 comprising two sub-portions 33. In its guiding portion 5, the shank 2 has subsections 7 in which the shank 2 and the centre-of-gravity line 4 are substantially linear and are tilted at a constant angle with respect to the tool's longitudinal direction zthe absolute value of the gradient of the centre-of-gravity line 4 is accordingly greater than 0. In the area of each local maximum 14, the top surface 10 of the shank 2 has a dirt catch 21. In the area of each local minimum 15, the bottom surface 13 of the shank 2 has a dirt catch 21. In the case of a dirt catch 21, which, viewed in the tool's positive longitudinal direction, is located in front of a local maximum 14 in the centre-of-gravity line 4, the top surface 10 of the shank 2 has a gradient which has a local maximum in front of the local maximum 14 of the centre-of-gravity line 4. In the case of a dirt catch 21, which, viewed in the tool's positive longitudinal direction, is located in front of a local minimum 15 in the centre-of-gravity line 4, the bottom surface 13 of the shank 2 has a gradient which has a local minimum in front of the local minimum 15 of the centre-of-gravity line 4. The top surface 10 and the bottom surface 13 are thus tilted more strongly with respect to the tool's longitudinal directionin other words, the absolute value of the gradient is greater than in the adjoining subsection 7 of the shank 2. During the reverse movement of the knitting tool 1, in the tool's negative longitudinal direction z, the dirt catches 21 increase dirt transport in the tool's negative longitudinal direction z. In this way, dirt is kept away from the part of the knitting tool 1 that comprises the loop-forming element 3. Potential soiling of the formed loops and of the textile is reduced.
[0060] FIG. 7 shows the principle according to which the self cleaning of the knitting tool works, by way of example in three steps: In the starting positionhere step a)dirt 23 has collected in the operating area 24 of the knitting tool 1. In this context, dirt 23 may be composed of large numbers of fibres, dust particles and abraded particles. The centre-of-gravity line 4, which is not shown in this drawing for reasons of better clarity, runs between local maxima 14 and minima 15 and clearly has a gradient which is greater than 0. In step b) of FIG. 7, the knitting tool 1 is shown during a forward movement 25. On account of the rising centre-of-gravity line 4 in the subsections 7, the dirt 23 is pushed during the forward movement 25 of the knitting tool 1 in the tool's positive longitudinal direction z and the elevational direction x. In step c) of FIG. 7, the knitting tool 1 is shown during a reverse movement 26. On account of the movement of the knitting tool 1 and the rising centre-of-gravity line 4, the dirt 23 is pushed in the tool's negative longitudinal direction z and the elevational direction x. In the drawing, the knitting tools 1 are arranged in a knitting machine in such a way that the tool's longitudinal direction z is upright; accordingly, gravitational acceleration g points in the tool's negative longitudinal direction z. Any dirt 23 that protrudes above the knitting tool in the elevational direction because it was pushed out of the operating area 24 will therefore fall out of the knitting machine on account of its weight, which results from the earth's acceleration g. In all embodiments of the teaching according to the invention, dirt 23 protruding from the operating area 24 will additionally be abraded by relative movement between the knitting tool 1 and the cam element 29 or a dial (in the case of horizontally disposed knitting tools). Accordingly, soiling of the knitting tool 1 and of the knitting device 27 is reduced.
[0061] FIG. 8 shows part of a knitting device 27 comprising three needle slots 28. The leftmost of the three needle slots 28 in FIG. 8 is fitted with a knitting tool 1in this case a knitting needle whose loop-forming element 3 is a hook. The middle and right-hand needle slots 28 have not been fitted with a knitting tool 1 so that the needle slots 28 can be shown better. Normally, all the needle slots 28 are fitted with a knitting tool 1 during knitting. The knitting tool 1 comprises a butt 18, which projects above the rest of the knitting tool 1 and the needle slot in elevational direction x.
[0062] FIG. 9 shows a knitting tool 1 and four cam elements 29, each of which comprises a cam curve 30. Butts 18 of knitting tools 1 are able to engage in each of the four cam curves and initiate a movement in the tool's longitudinal direction in the respective knitting tool 1, said movement resulting from a relative movement between the knitting tool 1 and the cam element 29. In order to depict the position of the cam element 29 relative to the knitting tool 1 and the shape of the cam curves more clearly, the cam element 29 is shown rotated by 90 about the tool's longitudinal axis z. In the correct installation position, the recesses of the cam curves 30 are in fact open in the negative elevational direction x, so that the butt 18 of the knitting tool can engage, in the elevational direction x, in one of the cam curves 30. The centre-of-gravity line 4 of the knitting tool 1 has two local maxima 14, at the position of which the highest points, in positive direction x, of the top surface 10 are also located. For purposes of clarity, the drawing does not show the whole centre-of-gravity line 4 but only its two local maxima 14. These highest points of the top surface 10 are spaced apart, in the tool's longitudinal direction z, from the cam curves 30 by a safety distance 38, which is greater than zero. In this way, the shank 2 of the knitting tool 1 is prevented from undesirably hooking into one of the cam curves 30 and influencing the drive motion of the knitting tool 1 or causing the knitting tool 1 to jam.
[0063] FIG. 10 is a top view of a knitting device 27 comprising three needle slots 28. In each of the three needle slots 28 is a knitting tool 1 comprising a functional portion 5, which has two sub-portions 33. The uppermost and the lowermost of the three knitting tools 1 are shown in an extended state. They show two different variants of an extended state. For one knitting movement there is only one extended state. In FIG. 10, however, both variants are shown in one drawing. In the extended state, a knitting tool has reached the furthest position of the knitting movement in the tool's positive longitudinal direction z. In the case of the first extended-state variant, shown in FIG. 10 with the uppermost of the three knitting tools 1, the functional portion 5 of the knitting tool 1 is accommodated completely in the uppermost needle slot 28 and has an edge distance 35 to the front edge of the needle slot 28. The middle knitting tool 1 of the three is shown in a retracted state. It has reached the furthest position of the knitting movement in the tool's negative longitudinal direction z. The distance, in the tool's longitudinal direction z, between the loop-forming elements 3 of the middle and uppermost knitting tools in FIG. 10 corresponds to the stroke 34 of the knitting movement. The lowermost knitting tool 1 in the drawing is shown in a second variant of the extended state. The magnitude of the stroke 34 is so large in this case that the functional portion 5 exits the needle slot 28 during knitting. At least 80% of the length, in the tool's longitudinal direction z, of the functional portion 5 of the knitting tool 1 always remains within the slot 28 during knitting.
[0064] FIG. 11 shows a sectional view of a knitting device 27. The section lies in the x-z plane and goes through a needle slot 28 fitted with a knitting tool 1. The upper edge 36 of the needle slot 28 is spaced apart from the highest point 39 of the top surface 10 of the knitting tool 1 and accordingly also from the shank 2by the elevational distance 37. In positive elevational direction x, the upper edge 36 is higher than the highest point of the top surface 10. Also advantageous for all embodiments of the invention is a needle slot 28, the upper edge 36 of which is at the same height in positive elevational direction x as the highest point of the top surface 10. In this case the elevational distance 37 would be zero.
[0065] FIG. 12 shows a further exemplary embodiment of a knitting tool 1, which has essentially the same features as the knitting tool 1 of FIG. 6. Compared to FIG. 6, the knitting tool 1 has a top surface 10 with local gradient maxima 40 having absolute values smaller than the local gradient minima 41 of the bottom surface 13. During knitting, a knitting tool 1 of this kind causes lower frictional forces in the needle slot of a knitting device because the flatter gradient of the top surface 10 makes for better guidance and more fluid motion of the knitting tool 1. The knitting tool 1 differs additionally from the knitting tool 1 shown in FIG. 6 in that the last maximum 14, viewed in the tool's negative longitudinal direction z, i.e opposite to the extension direction, of the centre-of-gravity line 4 of the functional portion 5 is a global maximum 42. Although this global maximum 42 is spaced, in the tool's longitudinal direction z, from the end of the knitting tool 1 as seen in its negative longitudinal direction z, the distance is selected to be as small as possible. In this way, the knitting tool 1 is prevented from tilting or twisting about an axis running in the lateral direction y. This measure, too, makes for better guidance and fluid movement of the knitting tool 1 during knitting. The above-described features change the shape of the dirt catches 21 formed by the top surface 10 compared to the exemplary embodiment of FIG. 6, but this form of dirt catch 21 has proved to support the self-cleaning effect already described in paragraph [0033].
TABLE-US-00001 List of reference numerals 1 Knitting tool 2 Shank 3 Loop-forming element 4 Centre-of-gravity line 5 Functional portion 6 Shank height 7 Subsection 8 Cross-sectional surface 9 Centroid 10 Top surface 11 Minimum shank height 12 Maximum shank height 13 Bottom surface 14 Local maximum of centre-of-gravity line 4 15 Local minimum in centre-of-gravity line 4 16 Bottom distance 17 Top distance 18 Butt 19 Triangular recess 20 Wavelike recess 21 Dirt catch 22 Cross-sectional-surface height 23 Dirt 24 Operating area 25 Forward movement 26 Reverse movement 27 Knitting device 28 Needle slot 29 Cam element 30 Cam curve 31 Functional-portion distance 32 Length of butt (18) 33 Sub-portion of functional portion (5) 34 Stroke of knitting movement 35 Edge distance 36 Upper edge of needle slot (28) 37 Elevational distance 38 Safety distance 39 Highest point of top surface (10) 40 Local gradient maximum of top surface (10) 41 Local gradient minimum of bottom surface (13) 42 Global maximum of centre-of-gravity line (4) x Elevational direction y Lateral direction z Tool's longitudinal direction
