SUCTION DEVICE FOR DRYING AT LEAST ONE PLASTIC STRAND

Abstract

A suction device for drying at least one plastic strand, incorporates a suction housing having a top side, a bottom side and several lateral surfaces, the top side having an inlet opening and one of the other surfaces having an outlet opening for the flow of a drying medium therethrough, and a screening element which has through apertures a base area with a maximum length and a maximum width. Each through aperture has an aperture cross-sectional area, and the sum of the aperture cross-sectional areas of all through apertures together forms a total aperture cross-sectional area. The screening element is on the top side and has its drying area above the inlet opening of the suction housing. The at least one plastic strand is moved in a process direction on the screening element, wherein the process direction is in a longitudinal direction of the screening element. The length of the drying area is at least 150 mm, and a ratio of the total aperture cross-sectional area of the through apertures to the base area of the drying area is between 30% and 45%, in particular 35% and 40%.

Claims

1. A suction device for drying at least one plastic strand, comprising a suction housing, consisting of a top side, a bottom side and a several lateral surfaces, the top side having an inlet opening and one of the other surfaces having an outlet opening made therein for the flow of a drying medium therethrough, a screening element with a drying area which has through apertures made therein in a distributed manner and which has a base area of a maximum length and a maximum width, each through aperture having an aperture cross-sectional area, and the sum of the aperture cross-sectional areas of all through apertures of the screening element together forming a total aperture cross-sectional area, wherein the screening element is arranged at the top and with its drying area above the inlet opening of the suction housing, wherein the at least one plastic strand is moved in a process direction on the screening element, wherein the process direction is aligned in a longitudinal direction of the screening element, wherein the length of the drying area is at least 150 mm and a ratio of total aperture cross-sectional area of the through apertures to the base area of the drying area is in the range of at least one of between 30% and 45%, and between 35% and 40%, of the drying area.

2. A suction device according to claim 1, wherein the length of the drying area is at least 200 mm, and the ratio of the total aperture cross-sectional area of the through apertures to the base area of the drying area remains to be in the range of at least one of between 30% and 45%, and 35% and 40%.

3. A suction device according to claim 1, wherein the base area of the drying area of the screening element and a base area of the screening element are identical or nearly identical.

4. A suction device according to 1, wherein the through apertures are slot-shaped and have a greater length than width.

5. A suction device according to claim 4, wherein the length of the through apertures is perpendicular to the process direction.

6. A suction device according to claim 4, wherein the length of a through aperture is smaller than the width of the drying area.

7. A suction device according to claim 4, wherein the width of the through apertures is from 2 mm up to 5 mm.

8. A suction device according to claim 4, wherein the through apertures are aligned side by side perpendicular to the process direction.

9. A suction device according to 4, wherein several rows of through apertures are provided, which are aligned parallel to each other in their longitudinal direction.

10. A suction according to claim 8, wherein a distance between through apertures arranged next to each other is between 8 mm and 30 mm.

11. Suction device according to claim 9, wherein the rows of through apertures are arranged at a distance from one another of between 0 mm up to 50 mm.

12. A suction device according to claim 1, wherein the screening element is made of sheet metal.

13. A suction device according to claim 12, wherein the screening element is formed of corrosion-resistant steel, stainless steel or hardened steel.

14. A suction device according to claim 1, wherein a laser is used for making the through aperture into the screening element.

15. A suction device according to claim 1, wherein the screening element is formed in several parts and its parts are placed on top of each other in a sandwich-like manner.

16. A suction device according to claim 1, wherein a cover element covering the entire drying area of the screening element is provided on the side of the screening element remote from the inlet opening, the cover element being arranged above the screening element and at a predetermined distance from the screening element.

17. A suction device according to claim 16, wherein the cover element has its long sides connected to the suction housing in an airtight manner.

18. A suction device according to claim 16, wherein a ventilation slot extending perpendicular to the process direction is provided in the cover element centrally with respect to a length of the cover element, so that the drying medium can flow into the drying area at one end of the cover element between the cover element and the screen element, and at the other end of the cover element between the cover element and the screening element and via the ventilation slot.

19. A suction device according to claim 18, wherein the ventilation slot has an opening cross-section corresponding to 35% to 45% of the base area of the drying area of the screening element and the cover element has a width of between 4 mm and 5 mm, and a length of between 40 mm and 50 mm.

20. A suction device according to claim 1, the base area of the top side of the suction housing is larger than the base area of the bottom side of the suction housing.

21. A suction device according to claim 1, a suction unit is provided which conveys drying medium, in particular ambient air, into the suction housing through the inlet opening and out of the suction housing through the outlet opening.

22. A suction device according to claim 21, the suction unit is arranged outside of the suction housing.

23. A suction device according to claim 21, the suction housing is connected to a water separator downstream in the flow direction.

Description

[0040] Throughout the description, the claims and the drawings, those terms and associated reference signs are used as are stated in the list of reference signs below. In the drawings,

[0041] FIG. 1 is a perspective view of the suction device according to the invention, taken at an angle from above;

[0042] FIG. 2 is a side view of the suction device of FIG. 1, with lines indicating its internal structure;

[0043] FIG. 3 is a top view of the suction device of FIG. 1;

[0044] FIG. 4 is a front view of the suction device of FIG. 1 with section line A-A;

[0045] FIG. 5 is a sectional view along section line A-A of the suction device of FIG. 4, and;

[0046] FIG. 6 is a top view of the screening element of the suction device according to the invention.

[0047] FIGS. 1 to 5 each are views of a suction device 10 having a suction body 14, a suction channel 28, a conveyor element 22 for conveying plastic strands, a cover 20 and a screening element 32.

[0048] FIG. 1 is a perspective view of the suction device 10, taken at an angle from above.

[0049] The suction body 14 has a front wall 14a, a rear wall 14b and two sidewalls 14c. The screening element 32 is arranged on the top side of the suction body 14 and is fluidically connected to the suction body 14 via an aperture in the top side. The suction body 14 has a larger cross-sectional area on its top side than on its bottom side.

[0050] The conveyor element 22 for conveying plastic strands is arranged on a sidewall 14c of the suction body 14. The conveyor element 22 rotates about an axis of rotation 22a. The conveyor element 22 is cylindrical in shape, with the cylindrical surface 22d extending along the axis of rotation 22a in each case. The conveyor element 22 includes a plurality of circumferential partitions 22b arranged side by side on the cylinder surface 22d spaced from the nearest partition. As a result, several plastic strands introduced into the conveyor element 22 will be separated from each other and moved separately in a process direction 12. The conveyor element 22 is surrounded in part by a housing 22c.

[0051] Below the conveyor element 22, a connection receptacle 36 is provided on the sidewall 14c adjacent to the conveyor element. More precisely, the connection receptacle 36 has a fastening element 36a. The fastening element 36a can be used to fix in place a connecting element inserted into the connecting receptacle 36. This allows the suction device 10 to be connected to a production line. The connection receptacle 36 is connected to the suction body 14 via several screw connections.

[0052] The cover 20 is pivotally connected to the rear wall 14b by a hinge 20b. The cover 20 has a cover opening 20b. The cover opening 20b is formed as a slot that is orthogonal to the process direction 12. More precisely, the cover opening 20b is arranged centrally along the process direction 12 with respect to the length and width of the screening element 32. In the area of the sidewalls 14c, the cover 20 is formed at an angle in such a way that it is inclined upwards away from the screening element 32.

[0053] The cover 20 forms a flow channel together with the channel sidewalls 26 and the screening element 32. The cover 20 covers at least the surface area of the screening element 32 and is arranged substantially parallel to the screening element 32. The flow channel has a first inlet opening 16 and a second inlet opening 18 for the plastic strands. Ambient air is sucked through both openings 16, 18 as well as through the cover opening 20b through the screening element 32 into the suction body 14.

[0054] In the area of the channel sidewalls 26, the cover 20 rests on the channel sidewalls 26 in an airtight manner.

[0055] The surface area of the screening element 32 corresponds to a drying area. The latter is at least 150 mm long, i.e. along the process direction 12.

[0056] The cover opening 20b has an opening cross-section corresponding to between 35% and 45% of the surface area of the drying area. The width of the cover opening 20b is between 4 mm and 5 mm and its length is between 40 mm and 50 mm. The width extends along the process direction 12 and the length is orthogonal to the process direction 12.

[0057] The suction body 14 has a cylindrical suction channel 28 on its front wall 14a. Pipes or tubes can be attached to the suction channel 28. The suction channel 28 is connected to a suction device not shown here, and ultimately to a water separator.

[0058] FIG. 2 is a front view of the suction device 10. This drawing has lines in it that indicate a sectional view of the components behind it. The suction channel 28 is arranged in the bottom portion of the suction body 14. In the bottom portion of the suction body 14, the connection receptacle 36 with the fastening element 36a is also arranged on the sidewall 14c. Above the suction channel 28, the suction body 14 is wider than compared to its bottom portion. The walls 14a, 14b, 14c are each connected to one another in a secure and airtight manner by means of fasteners 24.

[0059] FIG. 3 is a top view of the suction device 10. The cover 20 is shown cut open in some parts, see below left. As a result, the screening element 32 located under the cover 20 can be seen.

[0060] The screening element 32 has slots 34 made therein. The slots 34 are formed orthogonally to the process direction 12. The slots 34 are designed to be of different lengths. The width of the slots 34 is the same across the screening element 32. The width extends along the process direction 12 and the length is orthogonal to the process direction 12.

[0061] The width of the slots 34 is 4 mm.

[0062] The screening element 32 is preferably formed in several parts.

[0063] A ratio of the total aperture cross-sectional area of the slots 34 to the base area of the drying area, in this case the area of the screening element 32, is in the range of between 30% and 45%, in particular between 35% and 40%, of the drying area.

[0064] The cover 20 has a handle 20c in the area of the front wall element 20. The handle 20c can be used to pivot the cover 20 via the hinge 20b and open it so as to make the screening element 23 accessible from above. When the cover 20 is closed, it is connected to the front wall 14a and the rear wall 14b in an airtight manner.

[0065] FIG. 4 is a side view of a sidewall 14c with section line A-A drawn in, and with the cover 20 being shown in its closed state.

[0066] FIG. 5 is a sectional view along section line A-A of the suction device 10 of FIG. 4.

[0067] FIG. 6 is a view of the screening element 32. The slots 34 are each arranged in rows side by side, with each row extending from one long side 32a to the other long side 32b. The distance between the rows is the same along each of the long sides 32a, 32b. More precisely, there is an equal distance from the laterally outer ends of the slots 34 to the edge of the long sides 32a, 32b. Furthermore, the distance from the longitudinally outer ends of the slots 32 to the edge of the short sides 32c, 32d is the same in each case.

[0068] The distance between the rows of slots 34 along the process direction 12 is consistently between 20 mm and 50 mm. Side by side, perpendicular to the process direction 12, the slots 34 are each arranged with a distance of between 8 mm and 30 mm between them.

[0069] The screening element 32 is made of corrosion resistant sheet steel, i.e. of stainless steel. A laser is used for making the through apertures 24 into the screening element 32.

[0070] A suction unit (not shown) is provided, which conveys the ambient air through the inlet opening 16 into the suction body 14 and through the suction channel 28 out of the suction body 14 into a water separator. The suction unit is arranged outside the suction body 14.

[0071] The geometric design of the suction body 14, the area ratios of the opening cross-section of the slots 34 to the surface area of the screening element 32 and the design of the cover 20 increase the effectiveness of the drying performed in the suction device 10 in a simple manner.

LIST OF REFERENCE SIGNS

[0072] 10 suction device [0073] 12 process direction [0074] 14 suction body [0075] 14a front wall [0076] 14b rear wall [0077] 14c sidewall [0078] 16 first inlet opening [0079] 18 second inlet opening [0080] 20 cover [0081] 20a cover opening of cover 20 [0082] 20b hinge of cover 20 [0083] 20c handle of cover 20 [0084] 22 conveyor element [0085] 22a axis of rotation of conveyor element 22 [0086] 22b partition wall of conveyor element 22 [0087] 22c housing of conveyor element 22 [0088] 22d cylinder surface [0089] 24 fasteners [0090] 26 channel sidewall [0091] 28 suction channel [0092] 32 screening element [0093] 32a first long side of screening element 32 [0094] 32b second long side of screening element 32 [0095] 32c first short side of screening element 32 [0096] 32d second short side of screening element 32 [0097] 34 slot [0098] 36 connection receptacle [0099] 36a fastening element of connection receptacle 36