FLOW GUIDES

TECHNICAL FIELD

[0001] The present invention relates to plastic extrusion for producing double wall plastic pipes. Specifically, the present invention relates to a die head and die tooling spider with spider legs.

BACKGROUND

[0002] A conventional mandrel of a die head and die tooling used in extruding double wall plastic pipe is made of a plurality of concentric mandrel tubes that are centered and stabilized relative to one another through the use of a device known in the industry as a "spider". The spider provides a spacer to allow the flow of plastic along the tubes past the spider. The spider has a plurality of internal plastic flow passages extended axially and "spider legs" (supports) between each flow passage.

[0003] In the prior art, as shown in FIGURES 1A to IE, the spider legs have an upstream part and a downstream part at opposite ends. The upstream part splits a flow of plastic (stream A) into independent plastic streams that flow around the spider leg and reunite at the downstream end of the spider as streams El and E2. The shape and

configuration of the spider legs affects the welding lines created between streams El and E2. [0004] FIGURE 1A shows prior art spider legs with a downstream part that does not have split legs staggered or offset from each other. FIGURES IB to ID show prior art spider legs with a downstream part that has two staggered or offset legs that increase the turbulence and disruption to the plastic streams. However, the prior art spider legs shown in FIGURES IB to ID direct the plastic streams through straight channels (shown in FIGURE ID ) .

[0005] The straight channels shown in FIGURE ID direct the

streams of plastic to meet and be pressed together, resulting in a right-angled welding bond (shown in FIGURE IE ) . The wall thickness of the pipe is thinner along the weld lines and thicker in the regions between the weld lines. There is however a need in the field for stronger bonds at these weld lines.

SUMMARY

[0006] The present invention as detailed in this document is

advantageous over known spider legs in that the spider legs of the present invention produce non-right-angled bonds in the weld lines of the double wall plastic pipe. These spider legs provide bonds with acute or obtuse angles that tend to be stronger and more secure than right-angled bonds.

[0007] In a first aspect, the present invention provides a spider for a die head and die tooling, wherein said spider comprises: a plurality of internal plastic flow passages extending axially through said spider; and a spider leg between each of said plurality of internal plastic flow passages, wherein said spider leg comprises: an upstream portion; a center portion; and a downstream portion;

wherein said upstream portion has a front apex for

dividing a stream of plastic in said die head and die tooling into a first stream on a first side of said spider leg and a second stream on a second side of said spider leg; wherein said downstream portion further comprises an upper curved flow guide and a lower curved flow guide; and wherein said upper curved flow guide and said lower curved flow guide direct said first stream and said second stream towards each other to bond with one another after flowing around said spider leg.

[0008] In a second aspect, the present invention provides a

spider leg for use in a spider in a die head and die tooling, said spider leg comprises: an upstream portion; a center portion; and a downstream portion; wherein said upstream portion has a front apex for dividing a stream of plastic in said die head and die tooling into a first stream and a second stream; wherein said center portion separates said upstream portion from said downstream portion; wherein said downstream portion further comprises an upper leg portion and a lower leg portion staggered at different radial depths from each other, said upper leg portion having an upper curved flow guide and said lower leg portion having a lower curved flow guide; wherein said lower curved flow guide directs at least a portion of said first stream towards a vertical plane along a longitudinal axis of the spider leg and said upper curved flow guide directs at least a portion of said second stream towards said vertical plane; wherein said at least a portion of said first stream and said at least a portion of said second stream are directed towards each other to bond with one another after flowing around said spider leg.

[0009] In a third aspect, the present invention provides a spider for a die head and die tooling, wherein said spider comprises: a plurality of internal plastic flow passages extending axially through said spider; and a spider leg between each of said plurality of internal plastic flow passages; wherein said spider leg comprises: a front apex; a first leg and a second leg coupled to said front apex, each of said first leg and said second leg being angled away from each other and each of said first leg and said second leg being angled away from a vertical plane along a longitudinal axis of said spider leg; wherein a flow of plastic is divided into a first flow, a second flow, a third flow and a fourth flow by said front apex, said first flow flowing along a first side of said first leg, said second flow flowing along a second side of said first leg, said third flow flowing along a first side of said second leg and said fourth flow flowing along a second side of said second leg; wherein the first flow and the third flow are adjacent to one another and said first flow and said third flow are directed by said spider leg to flow towards each other; wherein said second flow is directed to flow away from said second leg and said fourth flow is directed to flow away from said first leg; wherein a portion of the first side of the first leg is distal to the front apex and said portion of the first side of the first leg slants towards the second leg; and wherein a portion of the first side of the second leg is distal to the front apex and said portion of the first side of the second leg slants towards the first leg.

[0010] In a fourth aspect, the present invention provides a

spider leg for use in a spider, wherein said spider leg comprises: a front apex; a first leg and a second leg coupled to said front apex, each of said first leg and said second leg being angled away from each other and each of said first leg and said second leg being angled away from a vertical plane along a longitudinal axis of said spider leg; wherein a flow of plastic is divided into a first flow, a second flow, a third flow and a fourth flow by said front apex, said first flow flowing along a first side of said first leg, said second flow flowing along a second side of said first leg, said third flow flowing along a first side of said second leg and said fourth flow flowing along a second side of said second leg; wherein the first flow and the third flow are adjacent to one another and said first flow and said third flow are directed by said spider leg to flow towards each other; wherein said second flow is directed to flow away from said second leg and said fourth flow is directed to flow away from said first leg; wherein a portion of the first side of the first leg is distal to the front apex and said portion of the first side of the first leg slants towards the second leg; and wherein a portion of the first side of the second leg is distal to the front apex and said portion of the first side of the second leg slants towards the first leg. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will now be described by reference to the following figures, in which identical reference numerals refer to identical elements and in which:

FIGURE 1A shows a top view of a prior art spider leg;

FIGURE IB shows a top view of another prior art spider leg;

FIGURE 1C shows a top view of the prior art spider leg shown in FIGURE IB, with the direction of the flow of plastic in the extrusion process;

FIGURE ID shows a downstream view of the prior art spider leg shown in FIGURES IB and 1C;

FIGURE IE shows the weld lines that result from the prior art spider leg shown in FIGURES IB to ID;

FIGURE 2 is a side cross-sectional view of an extrusion die mandrel fitted with a spider according to an

embodiment of the present invention;

FIGURE 3A is a front cross-sectional view along lines 2-2 of FIGURE 2, showing a spider according to one embodiment of the present invention within the extrusion mandrel;

FIGURE 3B is a cross-sectional view of a spider according to another embodiment of the present invention within the extrusion mandrel;

FIGURE 4A shows a top view of a spider leg according to a further embodiment of the present invention; FIGURE 4B shows a downstream view of the spider leg according to the further embodiment;

FIGURE 4C shows the acute angle welding lines in the plastic pipe resulting from the spider leg according to the further embodiment;

FIGURE 5 is a perspective view of the spider leg according to the further embodiment;

FIGURE 6 is a top view of the spider leg according to the further embodiment;

FIGURE 7 is an upstream view of the spider leg according to the further embodiment;

FIGURE 8 is a first side view of the spider leg according to the further embodiment;

FIGURE 9 is a second side view of the spider leg according to the further embodiment;

FIGURE 10 is a bottom view of the spider leg according to the further embodiment;

FIGURE 11 is a cross-sectional downstream view of the spider leg according to the further embodiment, viewed along lines 7A-7A of FIGURE 10;

FIGURE 12 is a cross-sectional view of the spider leg according to the further embodiment, viewed along lines

7B-7B of FIGURE 10;

FIGURE 13A shows a top view of a spider leg according to an alternative embodiment of the present invention; FIGURE 13B shows a downstream view of the spider leg according to the alternative embodiment;

FIGURE 13C shows the obtuse angle welding lines that result from the spider leg according to the alternative embodiment ;

FIGURE 14 is a perspective view of the spider leg

according to the alternative embodiment;

FIGURE 15 is a top view of the spider leg according to the alternative embodiment;

FIGURE 16 is an upstream view of the spider leg according to the alternative embodiment;

FIGURE 17 is a first side view of the spider leg according to the alternative embodiment;

FIGURE 18 is a second side view of the spider leg

according to the alternative embodiment;

FIGURE 19 is a bottom view of the spider leg according to the alternative embodiment;

FIGURE 20 is a cross-sectional view of the spider leg according to the alternative embodiment, viewed along lines 14B-14B of FIGURE 19;

FIGURE 21 is a cross-sectional view of the spider leg according to the alternative embodiment, viewed along lines 14A-14A of FIGURE 19. DETAILED DESCRIPTION

[0012] As described above, FIGURES IB and 1A show prior art

spider legs with and without staggered or offset legs in the downstream part, respectively. FIGURE 1C shows the direction of the flow of plastic in the extrusion process with the prior art spider leg shown in FIGURE IB. FIGURE ID shows a downstream view of the prior art spider leg shown in FIGURE IB. The prior art spider leg has angular flow guides with straight channels. Specifically, FIGURE ID shows the downstream end of the spider leg with right angle flow guides. FIGURE IE shows the right-angle welding lines of the plastic after the split independent streams of plastic have converged as the final streams El and E2 at the downstream end of the spider leg.

[0013] FIGURE 2 shows an exemplary mandrel 1 of an extruder that may incorporate the present invention. The tubes of the mandrel 1 are centered and stabilized relative to one another by means of a spider located at position 3. Cross- sectional views of the intersection at lines 2-2 (i.e., the spider at position 3) are shown in FIGURES 3A and 3B. The mandrel 1 is used for the molding of double wall plastic pipes. The outer wall of a double wall plastic pipe is produced by a stream of plastic that flows along plastic flow path 4, terminating at the mandrel orifice 5. The mandrel orifice 5 is upstream of the spider at position 3. The mandrel 1 further includes a second plastic flow path 9, terminating at a second mandrel orifice 7. The plastic flows along this second plastic flow path 9 to the second mandrel orifice 7 to form the inner pipe wall. The second mandrel orifice 7 is located downstream of the spider at position 3; accordingly, the plastic flowing along second plastic flow path 9 must pass through the spider at the downstream position 3.

[0014] FIGURE 3A is a front cross-sectional view of a spider 12

along lines 2-2 of FIGURE 2. As shown in FIGURE 3A, the spider 12 is formed of a plurality of concentric tubes.

The spider 12 (located at position 3 of FIGURE 2) is provided with a plurality of axially extending spider plastic flow paths 13 to allow the passage of the plastic through the spider 12. The plastic flows through the second plastic flow path 9 (shown in FIGURE 2) and through the spider plastic flow paths 13. The plastic flows through the spider 12 and exits the mandrel 1 at second mandrel orifice 7 (shown in FIGURE 2) . The spider plastic flow paths 13 run between the different diameter ring portions of the spider 12. The ring portions are held together by spider legs 15. In one embodiment, the spider 12 may further include air and/or utility passages 17 for an air opening and/or utility. The air and/or utility passages 17 extend radially from the hollow center to the outside edge of the spider 12 through the spider legs 15. The spider legs 15 separate the air and/or utility

passages 17 from the plastic flow paths 13.

[0015] FIGURE 3B shows a cross-sectional view of a spider 51

according to another embodiment of the present invention. The spider 51 may be used in an extruder and is

particularly suited for use in a die head and die tooling mandrel 1 (shown in FIGURE 2) of a pipe forming apparatus used for making double wall plastic pipes. The spider 51 may be located at the downstream position 3 of FIGURE 2.

[0016] When producing a double wall plastic pipe, the outer wall of the pipe exits the mandrel 1 at the mandrel orifice 5 (shown in FIGURE 2), which is located upstream of the spider 51. The inner wall of the pipe exits the mandrel 1 at the second mandrel orifice 7, which is located

downstream of the spider 51. Accordingly, the inner wall of the double wall pipe is formed by plastic that flows through axially extending plastic flow passages 52 of the spider 51.

[0017] The spider 51 is made from two separate and distinct

rings. The inner ring 53 and the outer ring 55 are separated by the plastic flow passages 52. The spider legs 15 act as both spacers and connectors between the inner 53 and the outer rings 55.

[0018] FIGURE 4A shows a top view of a further embodiment of a spider leg 15 for use in a spider. FIGURE 4A shows the direction of the flow of plastic along the spider leg 15. FIGURE 4B shows a downstream view of the spider leg 15. As shown in FIGURE 4B, the downstream portion of the spider leg 15 does not contain straight and right-angled

channels. The downstream end of the spider 15 has curved flow guides that produce a stronger welding bond between the streams of plastic.

[0019] FIGURE 4C shows the acute angle of the welding lines that result from plastic flowing through a spider with spider legs 15. Different configurations of the curved flow guides produce different welding lines. The plastic flows through the mandrel 1 (shown in FIGURE 2) to the

downstream end of the spider legs 15. The spider legs 15 separate the flow of plastic into multiple streams. The multiple streams reunite as the final streams El and E2 at the downstream end of the spider leg 15. As shown in

FIGURE 4C, the final streams El and E2 join in an acute angled welding line that provides a stronger bond than the right-angled welding lines produced by the prior art spider legs.

[0020] FIGURE 5 shows a spider leg 15 according to the further embodiment. The spider leg 15 comprises an upstream portion 19, a widened center portion 21, and a downstream portion 23. The upstream portion 19 has a front apex 25 that separates a first side surface 26 and a second side surface 27. The front apex 25 divides an incoming flow of plastic (stream A) that flows along the second plastic flow path 9 of the mandrel 1 (shown in FIGURE 2) . The flow of plastic stream A is divided into the independent streams B1 and B2. The independent stream Bl flows along the first side surface 26 and the independent stream B2 flows along the second side surface 27. After the

independent streams Bl and B2 flow past the widened center portion 21, the independent stream Bl is split into further streams Cl and C2 and the independent stream B2 is split into further streams D1 and D2 (shown in FIGURE 9) . The further streams Cl and C2 and the further streams D1 and D2 each flow along one side of the downstream portion 23 and reunite at the downstream end of the spider 15 as the final streams El and E2, respectively. [0021] The downstream portion 23 is comprised of an upper leg portion 29 and a lower leg portion 31. The upper leg portion 29 includes a first upper surface 33, a second upper surface 34, a third upper surface 35 and a fourth upper surface 37. The second upper surface 34, the third upper surface 35, and the fourth upper surface 37 are not visible in FIGURE 5. Similarly, the lower leg portion 31 includes a first lower surface 39, a second lower surface 41, a third lower surface 43, and a fourth lower surface 45. The first lower surface 39 is not visible in FIGURE 5. Accordingly, the first upper surface 33, the second lower surface 41, the third lower surface 43, and the fourth lower surface 45 comprise a first side of downstream portion 23 (i.e., the visible side in FIGURE 5) . The first lower surface 39, the second upper surface 34, the third upper surface 35, and the fourth upper surface 37 comprise a second side of downstream portion 23 (i.e., the non- visible side in FIGURE 5) . Accordingly, the independent stream B1 flows along the first side surface 26, past the widened center portion 21 and then along the first side of the downstream portion 23. Similarly, the independent stream B2 flows along the second side surface 27, past the widened center portion 21 and then along the second side of the downstream portion 23.

[0022] The upper leg portion 29 (i.e., the first 33, the second

34, the third 35, and the fourth upper surfaces 37) may be rotationally symmetrical or substantially rotationally symmetrical to the lower leg portion 31 (i.e., the first 39, the second 41, the third 43 and the fourth lower surfaces 45) along the longitudinal axis (see 600 of FIGURE 6) of the spider leg 15. In other words, if the spider leg 15 was divided into two pieces by a horizontal center plane (see 120 of FIGURE 11) along the longitudinal axis (see 600 of FIGURE 6), the two resulting pieces would be identical. However, a skilled artisan would understand that the spider leg 15 could still create strong acute angled weld lines with non-rotationally symmetrical upper 29 and lower leg portions 31.

[0023] In a preferred embodiment, the first upper surface 33 and the first lower surface 39 are flat. The second upper surface 34 and the second lower surface 41 may also be flat. Alternatively, the second upper surface 34 and the second lower surface 41 may blend and curve smoothly into the third 35 and the fourth upper surfaces 37 and the third 43 and the fourth lower surfaces 45, respectively. The first upper surface 33 converges with the third upper surface 35 at an angle of less than 90° at the downstream end of the spider leg 15. Similarly, the first lower surface 39 converges with the third lower surface 43 at an angle of less than 90° at the downstream end of the spider leg 15. The edges where the first upper surface 33 and the first lower 39 converge with the third upper surface 35 and the third lower surface 43, respectively, are

preferably in line with a vertical center plane (see 110 of FIGURE 11) .

[0024] The third 35 and the fourth upper surfaces 37 collectively form a concave shape on the upper leg portion 29.

Similarly, the third 43 and the fourth lower surfaces 45 collectively form a concave shape on the lower leg portion 31. The third lower surface 43 is sloped radially outwards in a downward direction from the lower edge of the first upper surface 33 towards the lower edge of the fourth lower surface 45. The fourth lower surface 45 is sloped in a downward direction towards the lower edge of the third lower surface 43. Accordingly, the third 43 and the fourth lower surfaces 45 are abutting and sloped towards each other to create a concave flow guide that widens at the downstream end of the spider leg 15. In a preferred embodiment, the channel created at the junction of the third 43 and the fourth lower surfaces 45 is along an axis parallel or near parallel to the first upper surface 33.

[0025] Similarly, the third upper surface 35 is sloped radially outwards in an upward direction from the upper edge of the first lower surface 39 towards the fourth upper surface 37. The fourth upper surface 37 is sloped inwards towards the upper edge of the third upper surface 35. Accordingly, the third 35 and the fourth upper surfaces 37 are abutting and sloped towards each other to create a concave flow guide that widens at the downstream end of the spider leg 15. In a preferred embodiment, the channel created at the junction of the third 35 and the fourth upper surfaces 37 is along an axis parallel or near parallel to the first lower surface 39.

[0026] The upper and the lower surfaces are configured such that the further stream Cl flows along the first upper surface 33 to converge with the further stream D1 flowing along the second 34, the third 35, and the fourth upper surfaces 37. Similarly, the further stream C2 flows along the second 41, the third 43, and the fourth lower surfaces 45 to converge with the further stream D2 (see FIGURE 9) flowing along the first lower surface 39.

[0027] The spider leg 15 is optionally fitted with an air and/or utility passage 17 that extends radially through the spider leg 15 at the widened center portion 21. When the spider leg 15 is fitted in the spider 12 (shown in FIGURE 3A) , the air and/or utility passage 17 extends radially from the hollow center of the spider 12 to the outside edge of the spider 12. The air and/or utility passage 17 may also be bordered on either side by dowel holes 47. The dowel holes 47 are for receiving dowel pins to secure the spider leg 15 to the spider 51 (shown in FIGURE 3B) . Specifically, the dowel pins hold the inner ring 53 and the outer ring 55 of the spider 51 together. The dowel pins may be accessible to enable the quick release of the spider leg 15 from the inner ring 53 and the outer ring 55. The quick release function enables the spider 51 to be dismantled if the spider leg 15 becomes damaged or

requires servicing.

[0028] FIGURE 6 shows a top view of the upstream portion 19, the widened center portion 21, and the downstream portion 23 of the spider leg 15. The downstream portion 23 shows that the upper leg portion 29 and the lower leg portion 31 are staggered or offset from each other. The upper leg portion 29 and the lower leg portion 31 act as guides to direct the flow of plastic towards the longitudinal axis 600 of the spider leg 15. The lower leg portion 31 shows a flat second lower surface 41 and a curved third lower surface 43 and a curved fourth lower surface 45 that collectively direct the flow of plastic towards the longitudinal axis 600 of the spider leg 15.

[0029] FIGURE 7 shows an upstream view of the spider leg 15. The stream A, after flowing through the mandrel 1 (shown in FIGURE 2) , is split by the spider leg 15 into the

independent streams B1 and B2 by the front apex 25. The independent stream B1 is diverted along the first side surface 26 and the independent stream B2 is diverted along the second side surface 27.

[0030] FIGURE 8 shows a view of the flow path of the independent stream B1 (i.e., a view of the spider leg 15 along the first side surface 26 and the first side of the downstream portion 23) . The spider leg 15 divides the independent stream B1 into the further streams Cl and C2 after the independent stream B1 flows past the widened center portion 21. While the plastic flows in slightly different directions, the further streams Cl and C2 may still be one stream of plastic that has portions flowing along

different surfaces.

[0031] A portion of the independent stream B1 is redirected along the first upper surface 33 of the upper leg portion 29

(further stream Cl) . The further stream Cl is directed towards the junction where the third upper surface 35 (see FIGURE 10) abuts the fourth upper surface 37. By flowing towards the junction between the third upper surface 35 and the fourth upper surface 37, the further stream Cl is directed towards the further stream D1. The further streams Cl and D1 converge at or near a vertical center plane (see 110 in FIGURE 11) at the downstream end of the spider leg 15. In a preferred embodiment, the further streams Cl and D1 converge at or near the longitudinal axis 800 at the downstream end of the spider leg 15.

[0032] The remaining portion of the independent stream B1 flows along the second 41 and the third lower surfaces 43 (see FIGURE 5) towards the fourth lower surface 45 (further stream C2) . The fourth lower surface 45 (see FIGURE 5) directs the further stream C2 inwards towards a vertical center plane (see 110 in FIGURE 11) . Accordingly, the further stream C2 is directed towards the further streams D1 and D2. In a preferred embodiment, the further stream C2 converges with the further streams D1 and D2 at or near the longitudinal axis 800 at the downstream end of the spider leg 15.

[0033] FIGURE 9 shows a view of the flow path of the independent stream B2 (i.e., a view of the spider leg 15 along the second side surface 27 and the second side of the

downstream portion 23) . The spider leg 15 divides the independent stream B2 into the further streams D1 and D2 after the independent stream B2 flows past the widened center portion 21. While the plastic flows in slightly different directions, the further streams D1 and D2 may still be one stream of plastic that has portions flowing along different surfaces.

[0034] A portion of the independent stream B2 flows along the

second 34 and the third upper surfaces 35 (see FIGURE 10) towards the fourth upper surface 37 (further stream Dl) . The fourth upper surface 37 (see FIGURE 10) directs the further stream Dl inwards towards a vertical center plane (see 110 in FIGURE 11) at or near the longitudinal axis 800 at the downstream end of the spider leg 15.

Accordingly, the further stream Dl is directed towards the further streams Cl and C2 (see FIGURE 12) . In a preferred embodiment, the further stream Dl converges with the further streams Cl and C2 at or near the longitudinal axis 800 at a downstream end of the spider leg 15.

[0035] Referring again to FIGURE 9, the remaining portion of the independent stream B2 flows along the first lower surface 39 of the lower leg portion 31 (further stream D2). The further stream D2 is directed towards the junction where the third lower surface 43 abuts the fourth lower surface 45 (see FIGURE 5) . By flowing towards the junction between the third lower surface 43 and the fourth lower surface 45, the further stream D2 is directed towards the further stream C2 (see FIGURE 12) . The further streams C2 and D2 converge at a vertical center plane 110 (see 110 in FIGURE 11) at the downstream end of the spider leg 15.

[0036] The further streams Cl and C2 collectively form the final stream El (see FIGURE 8) at the downstream end of the spider 15 and the further streams Dl and D2 collectively form the final stream E2 (see FIGURE 9) at the downstream end of the spider 15. The turbulence caused by the further streams C2 and Dl flowing towards each other provides a strong welding bond between the plastic streams. Further turbulence is caused by directing the further streams Cl and D2 towards the further streams Dl and C2 ,

respectively. The turbulence results in the final streams El and E2 joining each other in an overlapping bond or welding at an acute angle. Specifically, the final streams El and E2 converge at a vertical center plane (see 110 in FIGURE 11) at a downstream end of the spider leg 15. In a preferred embodiment, the final streams El and E2 converge at or near the longitudinal axis 800 at the downstream end of the spider leg 15. Accordingly, the final streams El and E2 bond together to form the acute angled welding lines shown in FIGURE 4C.

[0037] FIGURE 10 is a bottom view of the spider leg 15 showing plastic stream A divided into the independent streams B1 and B2 that flow along the first side surface 26 and the second side surface 27 (see FIGURE 5), respectively. The upper leg portion 29 has a flat second upper surface 34, a curved third surface 35 and a curved fourth upper surface 37 that direct the flow of plastic. FIGURE 10 also shows intersecting lines 7Ά-7A and 7B-7B, to illustrate the flow passages of the spider leg 15 in FIGURES 11 and 12,

respectively .

[0038] FIGURE 11 shows a downstream cross-sectional view of the spider leg 15 along lines 7A-7A of FIGURE 10. FIGURE 11 divides the spider leg 15 into four (4) sections by a vertical center plane 110 and a horizontal center plane 120. As can be seen, the third upper surface 35 and the third lower surface 43 each begin to form a concave shape at lines 7A-7A (shown in FIGURE 10) .

[0039] FIGURE 12 shows the downstream cross-sectional view of the spider leg 15 along lines 7B-7B of FIGURE 10. As can be seen, the spider leg 15 has an upper concave shape formed by the third 35 and the fourth upper surfaces 37 and a lower concave shape formed by the third 43 and the fourth lower surfaces 45.

[0040] FIGURE 13A shows a top view of an alternative embodiment of the present invention. FIGURE 13A shows the direction of the flow of plastic along the spider leg 115. FIGURE 13B shows a downstream view of the spider leg 115. As shown in FIGURE 13B, the downstream portion of the spider leg 115 does not contain straight and right-angled channels. The downstream end of the spider 15 has curved flow guides that produce a stronger welding bond between the layers of plastic.

[0041] FIGURE 13C shows the obtuse angle of the welding lines that result from plastic flowing through a spider with the spider legs 115 according to the present invention. As shown in FIGURES 4C and 13C, different configurations of the curved flow guides produce different welding lines.

The spider leg 115 separates the flow of plastic into multiple streams. The multiple streams reunite as the final streams El and E2 at the downstream end of the spider leg 115. As shown in FIGURE 13C, the final streams El and E2 join in an obtuse angled welding line that provides a stronger bond than the right-angled welding lines produced by the prior art spider legs.

[0042] FIGURE 14 shows a spider leg 115 according to an

alternative embodiment. The spider leg 115 comprises an upstream portion 119, a widened center portion 121, and a downstream portion 123. The upstream portion 119 has a front apex 125 leading to a first side surface 126 and a second side surface 127. The front apex 125 divides an incoming flow of plastic, stream A, into independent plastic streams B1 and B2. The independent stream B1 flows along the first side surface 126 and the independent stream B2 flows along the second side surface 127. After the independent streams B1 and B2 flow past the widened center portion 121, the independent stream B1 is split into further streams Cl and C2 and the independent stream B2 is split into further streams D1 and D2 (see FIGURE 18) . The further streams Cl and C2 and the further streams D1 and D2 each flow along one side of the downstream portion 123 and reunite at the downstream end of the spider 15 as two final streams El and E2, respectively.

[0043] Referring again to FIGURE 14, the downstream portion 123

is comprised of an upper leg edge 129, a middle point 131 and a lower leg edge 133 that collectively separate a first side and a second side of the spider leg 115. The upper leg edge 129, the middle point 131 and the lower leg edge 133 collectively form a substantially twisted C-shape at the downstream end of the spider leg 115. The upper leg edge 129 is the intersecting edge between the first upper surface 135 and the second upper surface 137. The middle point 131 is the intersecting point between the first middle surface 139 and the second middle surface 141.

Lastly, the lower leg edge 133 is the intersecting edge between the first lower surface 143 and the second lower surface 145.

[0044] The first side of the downstream portion 123 includes a first upper surface 135, a first middle surface 139, and a first lower surface 143. In a preferred embodiment, the first upper surface 135 is flat and the first middle surface 139 and the first lower surface 143 collectively form a concave flow guide. The lower edge of the first upper surface 135 abuts the upper edge of the first middle surface 139. The first middle surface 139 curves radially outwards in a downward direction towards the upper edge of the first lower surface 143. The first lower surface 143 curves radially inwards in an upward direction towards the first middle surface 139, the middle point 131, and the lower leg edge 133. Specifically, the first lower surface 143 abuts the first middle surface 139 on the upstream side and converges with the middle point 131 and the lower leg edge 133 on the downstream side to form a lower ramp. Accordingly, the first middle surface 139 and the first lower surface 143 are curved in opposite directions and towards each other in a manner that directs the further stream C2 upwards towards the middle point 131.

[0045] Similarly, the second side includes a second upper surface

137, a second middle surface 141, and a second lower surface 145. In a preferred embodiment, the second lower surface 145 is flat and the second middle surface 141 and the second upper surface 137 collectively form a concaved flow guide. The upper edge of the second lower surface 145 abuts the lower edge of the second middle surface 141. The second middle surface 141 curves radially outwards in an upward direction towards the lower edge of the second upper surface 137. The second upper surface 137 curves radially inwards in a downward direction towards the second middle surface 141, the middle point 131, and the lower leg edge 133. Specifically, the second upper surface 137 abuts the second middle surface 141 on the upstream side and converges with the middle point 131 and the lower leg edge 133 on the downstream side of the spider leg 115 to form an upper ramp. Accordingly, the second middle surface 141 and the second upper surface 137 are curved in opposite directions and towards each other in a manner that directs the further stream D1 (see FIGURE 18) downwards towards the middle point 131.

[0046] The first side of the downstream portion 123 may be

rotationally symmetrical or substantially rotationally symmetrical to the second side of the downstream portion 123 around a longitudinal axis (see 150 of FIGURE 15) of the spider leg 115. However, a skilled artisan would understand that the spider leg 115 could still create strong obtuse angled weld lines with non-rotationally symmetrical first and second sides of the downstream portion 123.

[0047] Referring again to FIGURE 14, after stream A is diverted into two independent streams B1 and B2, the independent stream B1 is further diverted into further streams Cl and C2. The further stream Cl flows along the first upper surface 135 and the further stream C2 flows along the first middle surface 139 and the first lower surface 143. Similarly, the independent stream B2 is further diverted into further streams D1 and D2 (see FIGURE 18) . The further stream D1 flows along the second middle surface 141 and the second upper surface 137 and the further stream D2 flows along the second lower surface 145. A skilled artisan will understand that while the two independent streams B1 and B2 flow independently of each other, the further streams Cl and C2 and the further streams D1 and D2 may form single streams of plastic, respectively, that flow along different surfaces.

[0048] The further streams Cl and C2 converge at a downstream end of the spider leg 115, collectively becoming the final stream El (see FIGURE 17) . The further streams D1 and D2 converge at a downstream end of the spider leg 115, collectively becoming the final stream E2 (see FIGURE 18) . The final streams El and E2 converge along the upper leg edge 129, the middle point 131 and the lower leg edge 133 at the downstream end of the spider leg 115. Preferably, the final stream El and the final stream E2 converge at the middle point 131. The first and second sides of the downstream portion 123 each have concave shapes that act as curved flow guides to direct the flow of the further streams Cl and C2 towards the other side's further streams D1 and D2. These curved flow guides cause turbulence in the streams of plastic. When the final streams El and E2 converge at the upper leg edge 129, the middle point 131 and the lower leg edge 133, the final streams El and E2 bond to form the obtuse angle welding line shown in FIGURE 13C .

[0049] The spider leg 115 is optionally fitted with an air and/or utility passage 17 that extends radially through the spider leg 115 at the widened center portion 121. When the spider leg 115 is fitted in the spider 12 (shown in FIGURE 3A) , the air and/or utility passage 17 extends radially from the hollow center of the spider 12 to the outside edge of the spider 12. The air and/or utility passage 17 may also be bordered on either side by dowel holes 147.

The dowel holes 147 are for receiving dowel pins to secure the spider leg 115 to the spider 51 (shown in FIGURE 3B) . Specifically, the dowel pins hold the inner ring 53 and the outer ring 55 of the spider 51 together.

[0050] FIGURE 15 shows a top view of the upstream portion 119,

the widened center portion 121, and the downstream portion 123 of the spider leg 115. FIGURE 15 sho.ws that the downstream end of the upper leg edge 129 and the lower leg edge 133 are staggered or offset from each other. The upper 129 and the lower leg edges 133 act as guides to direct the streams of plastic inwards towards the

longitudinal axis 150 of the spider leg 115.

[0051] FIGURE 16 shows an upstream view of the spider leg 115. As previously described, the stream A is split at the front apex 125 into two independent plastic streams B1 and B2. The independent streams B1 and B2 are diverted along the first side surface 126 and the second side surface 127, respectively .

[0052] FIGURE 17 shows a view of the flow path of the independent stream B1 (i.e., a view of the spider leg 115 along the first side surface 126 and the first side of the

downstream portion 123) . The independent stream B1 is divided into the further streams Cl and C2 after flowing past the widened center portion 121. The further stream Cl flows alongside the first upper surface 135 and is directed towards the further stream D1 (see FIGURE 18) . The further stream C2 flows along the first middle surface 139 and is directed towards the first lower surface 143. The first lower surface 143 directs the further stream C2 radially inwards in an upward direction towards the middle point 131. Accordingly, the curved flow guide formed by the first middle surface 139 and the first lower surface 143 directs the further stream C2 to converge with the further stream D1. The final stream El converges with the final stream E2 along the upper leg edge 129, the middle point 131 and the lower leg edge 133. Preferably, the final stream El converges with the final stream E2 at or near the middle point 131.

[0053] FIGURE 18 shows a view of the flow path of the independent stream B2 ( i . e . , a view of the spider leg 115 along the second side surface 127 and the second side of the

downstream portion 123) . The independent stream B2 is divided into the further streams D1 and D2 after flowing past the widened center portion 121. The further stream D1 flows along the second middle surface 141 and is directed towards the second upper surface 137. The second upper surface 137 directs the further stream D1 radially inwards in a downward direction towards the middle point 131. The further stream D2 flows along the second lower surface 145 and is directed towards the further stream C2 (see FIGURE 17) . Accordingly, the curved flow guide formed by the second upper surface 137 and the second middle surface 141 directs the further stream D1 to converge with the further stream C2 [0054] FIGURE 19 is a bottom view of the spider leg 115 showing the stream A divided into two independent streams B1 and B2 that flow along the first side surface 126 and the second side surface 127, respectively. FIGURE 19 also shows intersecting lines 14B-14B and 14A-14A, to

illustrate the flow passages of the spider leg 115 in

FIGURES 20 and 21, respectively.

[0055] FIGURE 20 shows a downstream cross-sectional view of the spider leg 115 along lines 14B-14B of FIGURE 19. FIGURE 20 divides the spider leg 115 into four (4) sections by a vertical center plane 210 and a horizontal center plane 220. The upper left section shows that the first upper surface 135 extends from the vertical center plane 210 across to the widened center portion 121. Similarly, the second lower surface 145 extends from the vertical center plane 210 across to the widened center portion 121, shown in the bottom right section.

[0056] The bottom left section shows the downward slope of the first middle surface 139. The interior portion 230 shows that the upward slope of the first lower surface 143

directs the further stream Cl in an upward direction towards the center of the spider leg 115, indicated at the intersection of the vertical center plane 210 and the horizontal center plane 220. Similarly, the upper right section shows the upward slope of the second middle surface 141. The second interior portion 240 shows that the downward slope of the second upper surface 137 directs the further stream D1 in a downward direction towards the middle of the spider leg 115. [0057] FIGURE 21 shows a downstream cross-sectional view of the spider leg 115 along lines 14A-14A of FIGURE 19. The first upper surface 135 extends across the vertical center plane 210 and directs the further stream Cl towards the junction between the second upper surface 137 and the second middle surface 141. Similarly, the second lower surface 145 extends across the vertical plane 210 and directs the further stream D2 towards the junction between the first middle surface 139 and the first lower surface 143. The interior portion 230 and the second interior portion 240 show the slopes of the first lower surface 143 and the second upper surface 137, respectively. Accordingly, the first lower surface 143 and the second upper surface 137 direct the further streams C2 and Dl, respectively, towards the middle point 131 (see FIGURE 14) . The middle point 131 is located at the intersection of the vertical center plane 210 and the horizontal center plane 220. As such, the further streams Cl and C2 (collectively the final stream El) and the further streams Dl and D2 (collectively the final stream E2) are directed towards each other and converge at the downstream end of the spider leg 115.

[0058] A skilled artisan will understand that the spider leg 15

(FIGURES 4 to 12) or the spider leg 115 (FIGURES 13 to 21) can be used in either embodiment of the spider 12 (FIGURE 3A) or the spider 51 (FIGURE 3B) . Furthermore, either spider leg 15 or 115 may have air and/or utility passages 17 to provide an air opening and/or utility opening.

Furthermore, either embodiment of the spider leg 15 or 115 may have dowel holes 47 or 147, respectively. Accordingly, either embodiment of the spider leg 15 or 115 may be operatively or mechanically coupled to the spider 51 by inserting dowel pins in the dowel holes 47 or 147, respectively .

[0059] As a result of all of the above, there is substantial turbulence caused by a spider using the spider legs 15 or 115 of the present invention in mandrel 1. Specifically, the original stream A flows through the spider 12 or 51 and is split into multiple smaller streams. The smaller streams are redirected towards each other at the

downstream end of each spider leg 15 or 115 prior to exiting the spider 12 or 51. This turbulence and

subsequent convergence greatly improves bonding of all of the streams, over and above the standard butt welding or right angle welding lines provided for in the prior art.

[0060] A person understanding this invention may now conceive of alternative structures and embodiments or variations of the above all of which are intended to fall within the scope of the invention as defined in the claims that follow .