Method for drying filter rods

Abstract

The method for drying filter rods comprises the steps of providing a filter rod, providing a support surface for receiving the filter rod and guiding the filter rod on the support surface by a guide element arranged above the support surface. The method further comprises the step of supplying a gas stream of compressed gas having a pressure between 0 and 6 bar to the filter rod through the guide element when the filter rod is transported along the support surface, before wrapping the filter rod with a wrapping material.

Claims

1. A method for drying filter rods, the method comprising the steps of: providing an unwrapped filter rod comprising polylactic acid material or vapor treated filter material; providing a support surface for receiving the unwrapped filter rod on the support surface; guiding the unwrapped filter rod on the support surface by a guide element arranged above the support surface; and supplying a gas stream of compressed gas having a pressure between 0 and 2 bar to the filter rod through the guide element to remove excess moisture from the filter rod when the unwrapped filter rod is transported along the support surface, before wrapping the filter rod with a wrapping material to form a wrapped filter rod.

2. The method according to claim 1, wherein the filter rod is made of polylactic acid material.

3. The method according to claim 1, further comprising the step of arranging the wrapping material between the filter rod and the support surface.

4. The method according to claim 1, further comprising the step of supplying several gas streams simultaneously along a length of the filter rod.

5. The method according to claim 1, comprising supplying the gas stream vertically onto the filter rod.

6. The method according to claim 4, wherein the several gas streams are supplied vertically onto the filter rod.

7. The method according to claim 1, wherein the filter rod comprises cellulose acetate.

8. The method according to claim 1, wherein the filter rod is a continuous rod of filter tow.

9. The method according to claim 1, wherein the filter rod is a series of individual filter rods arranged in an end-to-end manner.

10. The method according to claim 1, wherein the gas stream has a gas temperature below 40 degrees Celsius.

11. The method according to claim 4, wherein the several gas streams have a gas temperature below 40 degrees Celsius.

12. The method according to claim 1, wherein the filter rod is contacted by a guide surface of the guide element, the guide surface having a longitudinal concave shape.

13. The method according to claim 1, further comprising applying pressure to the filter rod with the guide element to hold the filter rod against the support surface.

14. The method according to claim 1, further comprising varying a distance between the guide element and the support surface to adapt to filter rods having different diameters.

15. The method according to claim 3, further comprising holding the filter rod on the wrapping material by the guide element during supplying the gas stream to the filter rod.

16. The method according to claim 3, wherein the guide element is arranged parallel to the support surface and parallel to the wrapping material.

17. The method according to claim 1, wherein the guide element comprises a guide surface constructed to contact the filter rod, a top surface opposite to the guide surface, and two side surfaces extending between the guide surface and the top surface, each of the two side surfaces comprising a first portion having a length extending parallel to the guide surface and a second portion angled relative to the first portion and comprising a bottom edge that is angled relative to the length to form a wedge shaped front portion.

18. The method according to claim 1, wherein the unwrapped filter rod is an unwrapped hollow filter rod.

19. The method according to claim 1, wherein free moisture in the wrapped filter rod is reduced by at least 10 percent in weight compared to free moisture present in the unwrapped filter rod immediately before exposure to the gas stream.

20. The method according to claims 4, wherein the several gas streams comprise different gases, wherein the different gases differ in at least one of composition and temperature.

Description

(1) The invention is further described with regard to embodiments, which are illustrated by means of the following drawings, wherein:

(2) FIG. 1 shows an apparatus for treating a filter rod with a guide element in a retracted position;

(3) FIG. 2 shows the guide element in an operating position;

(4) FIGS. 3 and 4 are a perspective view and a longitudinal cross section of a first embodiment of a guide element;

(5) FIG. 5 shows the bottom side of the guide element of FIGS. 1 and 2;

(6) FIGS. 6 and 7 are a perspective view and a longitudinal cross section of a second embodiment of a guide element.

(7) In FIG. 1 a continuous filter rod 4 is provided from a rod supply 40, for example a rod forming device, to a support surface 2. The filter rod 4, for example a PLA filter rod, is guided along the support surface 2 to a wrapping device 3. In the wrapping device 3, the continuous filter rod 4 is wrapped with a continuous sheet of wrapping material 5, for example wrapping paper. The support surface 2 may comprise a longitudinal groove 30 in the form of a half circle for receiving the filter rod 4 and for supporting wrapping the wrapping material 5 around the filter rod 4.

(8) The wrapping material 5 is supplied from below the support surface 2, for example from a bobbin, deflected via a deflection element 21 arranged upstream of the support surface 2 such as to be transported on and along the support surface 2 into the wrapping device 3.

(9) The support surface 2 may comprise one or several rollers 20 rolling in the transport direction of the filter rod 4 and the wrapping material 5 and supporting a transport of the wrapping material 5 or the filter rod 4, respectively.

(10) The filter rod 4 is arranged on the wrapping material 5 while moving together with the wrapping material 5 along the support surface 2.

(11) A guide element 1 for guiding the filter rod 4 on the support surface is shown in FIG. 1 in a retracted position. In the retracted position of the guide element 1, free access to the support surface 2, the pre-wrapping process and the guide element 1 is available, for example for maintenance or inspection purposes.

(12) The guide element 1 is mounted to a movable positioning lever 7. By rotating the lever 7 about its hinge in the direction of arrow 500, the guide element 1 may be brought from the retracted position to an operating position. In the operating position, the guide element 1 contacts a top side 44 of the filter rod 4 and guides the filter rod 4 on the support surface 2 or on the wrapping material 5, respectively. In FIG. 2 the guide element 1 is shown in the operating position of the apparatus. In the operating position, the guide element 1 is arranged parallel to the horizontally arranged support surface 2 and parallel to the wrapping material 5 guided along the support surface 2. Filter rod 4 and wrapping material 5 are omitted in FIG. 2.

(13) The bottom side 400 of the guide element 1 is provided with a plurality of gas outlet openings 10 arranged along the length of the bottom side 400 of the guide element 1. The rear end 200 of the guide element 1 is provided with a gas supply 11.

(14) The guide element 1 is shown in more detail in FIG. 3 and FIG. 4. The rear end 200 of the guide element is provided with a gas inlet 111 connected to the gas supply 11. The gas inlet 111 is also connected via an internal channel 13 with all gas outlet openings 10. A gas source (not shown), for example a drying gas such as for example compressed air, is connected to the gas inlet 111 via a gas tube. A thread 110 may be provided for connecting the gas source via gas tube to the gas inlet 111.

(15) The internal channel 13 extends from the rear end 200 of the guide element 1 substantially along the length of the guide element 1 up to the level of the most downstream arranged gas outlet opening 10. Via this internal channel 13, gas is guided through the guide element 2 and out of the gas outlet openings 10. When in the operating position of the guide element 1, the outlet openings 10 direct eight gas streams corresponding to the number of outlet openings 10 in the bottom side 400 of the guide element 2, vertically to the top side 44 of the filter rod 4.

(16) The bottom side 400 of the guide element 2 comprises a longitudinal concave shaped guide surface 15. In FIG. 5 a view onto the concave shaped guide surface 15 of the bottom side of 400 of the guide element is shown. Preferably, the longitudinal concave form of the guide surface 15 corresponds to the circular shape of the filter rod 4. The shape of the guide surface 15 is constant along the length of the guide element 1, that is, the guide surface 15 is provided with a constant radius of curvature.

(17) The eight gas outlet openings 10 are arranged equidistantly in the guide surface 15. Preferably, the outlet openings 10 are arranged on one longitudinal line along the length of the guide element 1. However, they may also be slightly radially displaced from said longitudinal line. For example, every other outlet opening 10 may be radially displaced to one side and to the other side of the longitudinal line.

(18) The guide element 1 comprises a wedge shaped front portion 18, which is tapered laterally versus a front end 100 of the guide element. The tapered front portion 18 allows to position the guide element 1 close to the wrapping device 3 at a position, where the wrapping material 5 has already been wrapped partially around the filter rod 1. The wedge shaped front portion 18 secures a smooth passing of the wrapping material 5 next to the guide element 1.

(19) In the embodiment of the guide element of FIGS. 3 and 4, the front portion 18 extends not much further than the gas channel 13 inside the gas element or the most downstream arranged outlet opening 10, respectively. Thus, together with the wedge shaped front portion 18, gas may be provided to the filter rod until very shortly before the filter rod 4 is entirely wrapped with the wrapping material 5.

(20) The guide element 1 is provided with three bore holes or threaded holes 14 in its top side 300 for attaching the guide element 1 to the positioning lever 7. Such an attachment, for example with screws, may be provided for positioning and fixing the guide element at a predefined distance to the support surface to secure a safe guiding of the filter rod 4.

(21) In examples of a guide element 1 as shown in FIG. 3 and FIG. 4, the distances between neighbouring gas outlet openings 10 are 10 millimeter with a length of the guide element 1 of 93 millimeter and a width of 10 millimeter. A length of the front portion 18 is 15 millimeter.

(22) In FIG. 6 and FIG. 7 another embodiment of a guide element 1 for providing 12 gas streams to a filter rod 4 is shown. The guide element 1 as shown in FIGS. 6 and 7 may be used to provide more gas to a filter rod 4, either to expose the filter rod to gas for a longer period of time or over a same period of time at faster moving speed of the filter rod guided by the guide element 1. In FIGS. 6 and 7 the same reference numerals are used for the same or similar elements.

(23) The bottom side 400 of the guide element 1 is provided with 12 gas outlet openings 10 arranged equidistantly along the length of the bottom side 400. The rear end 200 of the guide element is provided with a gas inlet 111 and the gas outlet openings 10 are connected via the internal channel 13 with the gas inlet 111.

(24) The internal channel 13 extends from the rear end 200 of the guide element along the length of the guide element 1 up to the most downstream arranged gas outlet opening 10. When in the operating position, the outlet openings 10 direct 12 gas streams to the top side 44 of the filter rod 4. The outlet openings 10 are arranged to direct the gas streams vertically onto the top side 44 of the filter rod 4.

(25) The bottom side 400 of the guide element 2 comprises a longitudinal concave shaped guide surface 15. The shape of the guide surface 15 is constant along the length of the guide element 1, that is, the guide surface 15 is provided with a constant radius of curvature.

(26) The wedge shaped front portion 18 of the guide element 1 is tapered laterally versus a front end 100 of the guide element.

(27) In the embodiment of the guide element of FIGS. 6 and 7, the most downstream arranged outlet opening 10 is arranged in the guide surface 15 about 50 millimeter behind the front portion 18.

(28) The long front portion 18 allows to put pressure on a filter rod 4 until the filter rod has almost entirely entered the wrapping device 3. Thus, pressure may be applied to the filter rod 4 while a wrapping material 5 has already been, at least partially, wrapped around the filter rod. By this, sealing of the wrapping material around the filter rod, for example, by glue, may be supported, preferably, may be increased.

(29) The guide element in the embodiment shown in FIGS. 6 and 7 is provided with four bore holes or threaded holes 14 in its top side 300 for attaching the guide element 1 to a positioning lever 7 or an otherwise constructed guide holder.

(30) In the example of a guide element as shown in FIGS. 6 and 7, the distances between neighbouring outlet openings 10 are 10 millimeter with a length of the guide element 1 of 161 millimeter and a width of 10 millimeter. A length of the front portion is 43 millimeter.