SONIC DRYING OF WEBS ON ROLLS

• US 3,750,306 A
• Filed: 11/03/1970
• Issued: 08/07/1973
• Est. Priority Date: 11/07/1969
• Status: Expired due to Term

• Current Assignee: General Electric Canada (GE Aerospace)
• Original Assignee: John Gilbert Descary, Stephen Anthony Rodwin
• Inventors: Rodwin, Stephen Anthony, Descary, John Gilbert
• Primary Examiner(s): Dority, Jr., Carroll B.
• Application Number:
  US05/086,571
• Time in Patent Office: 1,008 Days
• Field of Search: 34/18,23,69,90,114,122,155,158,115,119,124
• US Class Current: 34/69
• CPC Class Codes: D21F 5/006 Drying webs by using sonic vibrations
• CPC Class Codes: F26B 13/145 on the non-perforated outside surface of which the material is being dried by convection or radiation
• CPC Class Codes: F26B 5/02 by using ultrasonic vibrations using sonic energy generated by pulse jet combustion F26B23/026

Abstract

Sonic drying as applied to conventional dryer rolls involves the provision of stem jet whistles spaced along trough-like reflectors, preferably of eliptic cross-section profile, with provision of low pressure secondary air to sweep displaced moisture clear of the travelling web.

Claims

1. Web drying apparatus for reducing the moisture content of a pervious web by the dislocation of moisture therefrom, comprising:

web support means having a substantially curved surface to receive a web for passage in surface supported relation thereover;

a plurality of mutually spaced air actuated sound generating means positioned from said surface on the side remote from the center of curvature thereof to provide sound waves directed longitudinally towards the surface and substantially normal thereto and forming a sonically energized zone of substantially uniform intensity, the actuating air exhausting from said generating means being directed in moisture displacing relation towards the outer surface of said web;

sound reflector means adjacent said sound generating means located outwardly thereof relative to said curved surface, having a cross section contour whereby in operation sound from said generating means is reflected towards said surface to enhance the sound field at the surface, and said sound reflector means comprising at least one elongated trough reflector extending in the cross machine direction and parallel with the main axis of curvature of said web support surface, having a plurality of point sound generators in mutual spaced relation therein to provide in operation sound propagation transversely to the web.

2. Apparatus as claimed in claim 1 wherein said web support means comprises a cylindrical roll.

3. Apparatus as claimed in claim 2 wherein said sound generating means comprises stem jet whistle means having gaseous fluid supply means connected thereto exhaust from the whistle means being directed in operation to pass towards said support surface in impinging relation against a web supported thereon.

4. Apparatus as claimed in claim 1 wherein said substantially curved surface comprises a rotary dryer roll of a paper drying section, said sound generating means having energizing gaseous fluid supply means connected thereto gaseous fluid from the sound generating means passing in impinging relation towards said surface, and exhaust means to receive the gaseous fluid together with moisture entrained therewith for removal from the surface of a said web.

5. Apparatus as claimed in claim 4, together with gas supply means to provide low pressure air within said sound field for resonation relative to the web to transfer sound energy thereto.

6. Apparatus as claimed in claim 4 including a heated dryer drum having said sound generating means mounted within a sound insulating hood spanning an arc of said drum.

7. Apparatus as claimed in claim 4 wherein said sound generating means comprises a plurality of stem jet whistles in spaced array, to form a plurality of rows of whistles spaced about a portion of the periphery of said support means, the respective whistles of adjacent rows being in mutual staggered relation.

8. Apparatus as claimed in claim 4 wherein said sound generating means operates in a predetermined range frequency and wave length, said reflector means and sound generating means being positioned mutually and in relation to said curved surface such that sound is beamed to the reflector from the sound center of said generating means and reflected substantially normal to said web surface, the distance thus travelled by the sound being substantially an integer multiple of one half of said wave length.

9. Web drying apparatus for reducing the moisture content of a web, comprising:

web support roll means to receive a web for drying on passage over the curved surface thereof;

sound generating means positioned from said surface on the side remote from the centre of curvature thereof to provide sound waves directed longitudinally towards the surface;

sound reflector means comprising a plurality of reflectors in side-by-side relation extending axially in relation to the drum for substantially the full width thereof, being of trough-like cross section, said sound generating means consisting of a plurality of stem jet whistles in spaced reLation located along the length of said reflectors to provide an axially overlapping field of sonic energy at the web surface, means to supply air to said whistles in sound energizing relation therewith, the air in operation impinging on the surface of a said web to displace moisture therefrom.

10. Apparatus as claimed in claim 9 wherein said roll is perforated, having means to draw air therefrom whereby percolation of air through a said web in moisture entraining relation is obtained, and web adherence to the roll surface is promoted.

11. Apparatus as claimed in claim 10 including secondary air supply means to provide low pressure air resonated by mixing, in web impinging relation whereby the mass flow of the air mixture between said reflectors and said roll surface is substantially increased.

12. Web drying apparatus as claimed in claim 10 wherein a said reflector means includes a reverberation skirt extending from one edge thereof substantially parallel to the outer surface of said roll and spaced therefrom to provide a sound reverberation zone therewith.

13. Web drying apparatus as claimed in claim 9 wherein a said sound reflector means, comprising at least one flexible blade means extending towards the surface of a said web in boundary wiping relation therewith to promote removal of moisture-containing boundary air.

14. Web drying apparatus for reducing the moisture content of a web, comprising:

web support means having a substantially curved surface to receive a web for passage thereover;

sound generating means consisting of point generators arranged in mutual spaced relation located within at least one elongated trough reflector extending in the cross-machine direction to provide sound waves directed longitudinally towards the web surface, the cross section contour of said trough reflecting sound from said generators towards said surface to enhance the sound field thereat, and an air supply manifold extending substantially the full axial extent of the reflector having nozzle means connected therewith to direct an air jet against the web within a process area extending between the reflector and the web support means.

15. Apparatus as claimed in claim 14 wherein said nozzle means is located adjacent one edge of said reflector and comprises a slit-like inclined nozzle to provide an air doctor in relation to the boundary layer of a travelling web, for exhaust displacement oppositely to the web motion.

16. Apparatus as claimed in claim 2 wherein said reflector is located relative to said web support surface to provide concentration of reflected sound waves at said point sound generators whereby said sound field is intensified.

17. Apparatus as claimed in claim 2 wherein said sound reflector means is of eliptical cross section contour, to provide direction of longitudinal sound waves normal to said roll surface.

18. Apparatus as claimed in claim 4 wherein said sound generating means comprises a plurality of stem jet whistles in spaced array to form a plurality of rows of whistles spaced about a portion of the periphery of said support means, the frequency of operation of at least one row differing from the frequency of operation of an adjacent row whereby paper vibration is reduced and runability of the web is enhanced.

19. In a web drying section having a rotatable dryer roll to carry a web on the peripheral surface thereof for drying, gas energized sonic means to enhance drying, having sound generating means positioned on the outside of said roll to provide sound waves directed longitudinally towards the roll peripheral surface, to dislocate moisture from the web boundary;

contoured sound reflector means adjacent the sound generating means located on the side thereof remote from the roll to reflect sound toward the roll surface to enhance the sound field thereat, gaseous fluid means connected in energizing relation with the sound generating means, and air curtain means directing an air curtain in web impinging relation to promote sweeping of the web boundary layer relative to the direction of web travel.

20. Web drying apparatus for reducing the moisture content of a web, comprising:

a web supporting dryer roll to receive a web for passage over the curved peripheral surface thereof;

air activated sound generating means positioned outwardly from said roll surface to provide sound waves directed longitudinally towards the surface;

sound reflector means adjacent said sound generating means located outwardly therefrom relative to said roll having a cross-section contour to reflect sound from the generating means to enhance the sound field at the drum surface in operation, air supply duct means to supply secondary air in by-pass relation with said sound generating means, to mix with air emitted by said sound generating means, a hood defining an enclosure mounted in sound attenuating and air flow control relation over a portion of said roll, including hood edge sealing means consisting of a plurality of spaced flexible baffle members adjacent the hood edge and extending axially parallel therewith, and air release control damper means intermediate at least some of the baffle members to provide controlled leakage therebetween.