US 3328896 A
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Description (OCR text may contain errors)
July 4, 1967 H. HANF 3,328,896
CONDENSATE REMOVAL SCOOP FOR ROTARY DRYER CYLINDERS Filed May 12. 1965 2 Sheets-Sheet l INVENTOR HUBERT HANF ATTORNEY H. HANF July 4, 1967 CONDENSATE REMOVAL SCOOP FOR ROTARY DRYER CYLINDERS 2 Sheets-Sheet 2 Filed May 12. 1965 INVENTOR HUBERT HANF BY VWQ United States l atent C 3,328,896 CONDENSATE REMOVAL SCOOP FOR ROTARY DRYER CYLINDERS Hubert Hanf, Grenoble, Isere, France, assignor to Ateliers Neyret-Beylier & Piccard-Pictet (Neyrpic) and Societe Grenobloise dEtudes et dApplications Hydrauliques (Sogreah), both of Grenoble, Isere, France, both corporations of France Filed May 12, 1965, Ser. No. 455,173 9 Claims. (Cl. 34-125) ABSTRACT OF THE DISCLOSURE A condensate removal scoop for rotary dryer cylinders having a body formed to provide a fluid passage including in succession an intake slot, a weir, a pocket for collecting condensate flowing over the weir, and an outlet for the pocket located at a restricted portion of the fluid passage and below the level of the weir.
This invention relates to steam heated rotary dryer cylinders such as are used for example in paper making machines, and more particularly to the scoops which are employed in such cylinders for the removal of condensate therefrom.
Rotary dryer cylinders are usually mounted for rotation about a horizontal axis and are heated by introducing steam inside the same. The steam forms a condensate inside the cylinder and at low rotational speeds of the cylinder, this condensate tends to gather along the length of the cylinder at the bottom thereof, and can be evacuated without difiiculty by one or more revolving scoops turning at the same rotational speed as the cylinder. These scoops are arranged along the internal periphery of the cylinders and pick up the gathered condensate when in the low position of their revolutions. The condensate thus picked up by a scoop flows away by gravity through a tube connecting the scoop to the hollow shaft of the cylinder when the scoop is in the high position of its revolution. However, as the rotational speed of the cylinder is increased, the condensate is subjected to centrifugal force which initially causes the condensate to form a film over part of the inside of the cylinder, and then as the speed continues to increase, a film over all of the inside of the cylinder. Nowadays,'these dryer cylinders are usually op erated at high rotational spteds because of the high output of the machines with which they are used, so that the formation of a condensate film on the interior walls of these cylinders is a common occurrence. The conventional types of scoops heretofore employed in removing condensate that gathered at the bottoms of cylinders revolving at low speeds, cannot satisfactorily remove the condensate film which forms on the interior walls of the cylinders at high rotational speeds.
It is important that any condensate film which forms on the interior wall of a dryer cylinder be removed or evacuated since it results in a considerable rise in power consumption when the film covers only part of the inside surface of the cylinder, and in a lower heat transfer efficiency as between the steam and the wall of the cylinder when such film covers all of the inside surface of the cylinder. Further, at the high speeds at which such film is formed, the centrifugal force so counteracts the effect of gravity on any condensate which is gathered by the scoop, that the condensate cannot flow by gravity away from the scoop and through the tube connecting the scoop to the hollow shaft of the cylinder when the scoop is in its high position during its revolving movement. The prior art tried to increase the eifectiveness of the operation of the scoop in removing the film at high speeds by causing a 3 ,328,896 l atented July 4, 1967 certain amount of the drying steam in the cylinder to be sucked through the revolving scoop with the aim of drawing the condensate with the steam into the scoop and through the tube to the hollow shaft of the cylinder. This method however, did not prove satisfactory because the steam in the scoop has a tendency to blow some of the condensate back into the cylinder through the scoop intake slot so that under steady operating conditions the removal of the condensate is not complete enough to get rid of the film on the inside of the cylinder.
It is the principal purpose of the present invention to provide an improved scoop capable of satisfactorily removing the condensate at all rotational speeds of the drying cylinder.
Another object of the invention is to provide an im proved scoop capable of removing practically all of a condensate film formed on the interior wall of a dryer cylinder at high speeds.
A still further object of the invention is to provide an improved scoop capable of more efiiciently removing condensate while using an amount of steam substantially reduced from that required by known scoops for condensate extraction.
The aforesaid objects are attained in accordance with the invention by providing in the scoop adjacent to the intake slot thereof a weir forming the outer wall of a pocket narrowing from the weir to an outlet set below the level of the weir. The Weir prevents the condensate being blown back into the cylinder by the steam entering the scoop, thereby ensuring practically total removal of the condensate film inside the dryer cylinder. By arranging the outlet of a pocket in the form of a restriction placed below the level of the weir, an ejection eflect is achieved and the discharge of steam required to draw the condensate into the extraction tube is kept to a minimum.
For a better understanding of the invention, as well as the advantages and features thereof reference is made to the following description which should be read in connection with the accompanying drawings which illustrate by way of example a scoop embodying the invention incorporated in a high speed paper machine dryer and in which FIG. 1 is a diagrammatic view showing in vertical section a dryer cylinder provided with a scoop in accordance with the invention;
FIG. 2 is a perspective view of the working end of a scoop embodying the invention; and
FIG. 3 is a diagrammatic view showing in vertical section the construction of the working end of the scoop depicted in FIG. 2.
In the drawings, the reference numeral 10 indicates generally the rotary cylinder which forms part of the usual high speed paper machine dryer and which rotates about a horizontally disposed, hollow shaft 11 as is customary. The cylinder 10 rotates in the direction of the arrows 12, 12 and is supplied with steam in the customary manner to heat the cylinder. On the inside of the cylinder 10 is the condensate removal system composed of a scoop mounted on the outer end of a supporting arm 14 and located against the inner surface of the cylinder 10. The arm 14 is connected by a nut and counter-nut arrangement 15 to the hollow shaft 11; the arrangement 15 being manipulative to wedge the scoop 13 against the interior surface of the cylinder 10. The scoop 13 is connected to the interior of the hollow shaft 11 by a tube 16 in such a way that when the scoop turns with the cylinder in the direction of the arrows 12, the condensate picked up from the inside wall of the cylinder is drawn into the tube 11 by a controlled quantity of steam flowing in the direction indicated by the arrows 17 to the interior of the hollow shaft 11 into which it is discharged with the ex- 3 haust steam. Suction means are connected to the hollow shaft 11 in a manner well known to the art to draw into the scoop a given amount of the drying steam supplied to the cylinder.
As is shown more clearly in FIGS. 2 and 3 of the drawings, the scoop 13 is composed of two side walls having front sections 20, 20 which diverge from the front or entry end of the scoop to a point spaced from the latter approximately one half the length of the scoop having intermediate sections 21, 21 which converge from such point towards the rear end of the scoop body, and having rear sections 38 which extend from the sections 21 to a coupling flange 39. The front side wall sections 21 support a transverse rod 22 to which the outer end of the supporting arm 14 is connected. The outer longitudinal edge 23 of each side wall, throughout the lengths of at least the sections 2%), 21 thereof preferably has an arc of curvature corresponding to the curvature of the inner surface of the cylinder 10, so that when the scoop is wedged thereagainst by the adjustable supporting arm 14, it will seat securely on such surface and such longitudinal edges will be in tight engagement therewith.
The two side walls support a series of transverse wall sections which form a fluid passageway through the scoop. Thus there is supported by the front side wall sections 20 and extending from the entry end of the scoop to a point approximately two thirds the length of such front sections, a transverse wall section 24 which is disposed in converging relation with said outer longitudinal edges 23 so that it forms with the inner cylinder surface a funnel-shaped intake passage 25 which terminates in a relatively narrow transverse intake slot 26. Adjoining the rear end of transverse wall section 24 and also supported at its ends by the side wall sections 20 is a transverse wall section 27 which is disposed in diverging relation with a transverse wall section 28 supported at its ends by the side wall sections 20 and extending inwardly from the longitudinal edges 23 at the intake slot 26 to a transverse ridge 29 forming a weir in the scoop. Disposed at about 100 to transverse wall section 28 is a transverse wall section 30 which extends outwardly from ridge 29 to a point adjacent to or at the longitudinal edges 23 and is then joined with a transverse wall section 31 which inclines inwardly and rearwardly beyond the ends of the side wall sections 21. Associated with the transverse wall sections 30 and 31 are transverse wall sections 32 and 33, respectively, which incline generally rearwardly and outwardly to a point approximately midway of the intermediate side wall sections 21 where the rear edge of transverse wall section 33 forms a transverse restricted opening 34 with transverse wall section 31. It will be noted that the transverse wall sections 30 and 31 form with the side walls of the scoop a pocket 35 in rear of the weir 29 and that the outlet of such pocket is the restriction 34 which is located below the weir 29. The restricted outlet 34 is followed by a diverging passage portion 36 formed by the transverse wall section 31 and a transverse wall section 37 extending from the rear edge of transverse wall section 33 at the outlet 34 to the rear edge of transverse wall section 31. The transverse wall sections 24, 27, 32, 33 and 37 constitute the inner wall sections, and the transverse wall sections 28, 30 and 31 constitute the outer wall sections of the longitudinally extending fluid passageway which is formed to provide the intake slot 26, the weir 29, the pocket 35, the restricted opening 34- and the diverging portion or section 36. It will be noted more clearly from FIG. 2 that the rear converging side wall sections 38 beyond the side wall sections 21 close the sides at the rear end portion of the diverging section 36 up to the coupling flange 39 which encircles the tubularly-shaped end of such diverging section 36. The flange 39 connects the discharge tube 16 to such tubularly-shaped'end of the scoop.
It will be understood that when the cylinder revolves at high speed in the direction of the arrow 12, a film of condensate 40 (note the left hand side of FIG. 3) is formed on the inside surface of the cylinder by centrifugal force. The scoop 13 revolves in the same direction 12 and at the same speed as the cylinder and during such movement the condensate 40 is fed into the intake slot 26 by the converging section 24. The condensate flows through the slot 26 into the scoop as indicated by the arrow 17 and over the weir 29 to collect in the pocket 35. The steam which is drawn from the interior of the cylinder and also enters the scoop through the intake slot 26 is prevented by the weir 29 from blowing back into the cylinder any of the condensate accumulated in the pocket 35. The condensate removal from the cylinder therefore is almost complete, there being only left inside the cylinder an extremely thin film of condensate which from a practical standpoint is not detrimental to the heat transfer between the steam and the cylinder wall, and does not result in any increase in the power required to drive the dryer.
The steam entering the scoop 13 escapes through the restricted orifice 34 and in doing so produces an ejection effect which draws the condensate into the cylinder shaft and thus insures its discharge. Owing to the fact that the restricted orifice 34 is below the level N of the condensate in the pocket 34, it is always drowned, thereby producing an ejection effect which is increased by the escaping steam, while at the same time limiting the flow of steam required to attain the desired end.
It will be understood that while the scoop of this invention has been described in connection with a dryer cylinder for a paper machine dryer, it may be used to equal advantage in dryer cylinders for machines making other things than paper, and that the construction thereof may be modified to suit a particular technical application without departing from the basic principles of the invention. Hence, it is intended to cover all forms of the invention coming within the scope of the appended claims.
What is claimed is:
1. A condensate removal scoop for rotary dryer cylinders com-prising a scoop body formed to provide a fluid passage therethrough, said passage including in succession an intake slot, at weir, a pocket for collecting condensate flowing through said intake slot and over said weir, and an outlet for said pocket located at a restricted portion of said fluid passage and below the level of the weir.
2. A scoop as defined in claim 1, in which said intake slot is spaced from the entry end of said scoop, and said fluid passage includes a converging intake section extending from the entry end of said scoop to said intake slot.
3. A scoop as defined in claim 1, in which said restricted outlet is spaced from the rear end of said scoop, and said fluid passage includes a diverging section extending from said outlet to the rear end of said scoop.
4. A condensate removal scoop for rotary dryer cylinders comprising a scoop housing, and means for maintaining said housing against the interior wall of a dryer cylinder, said scoop housing comprising side walls and inner and outer wall sections forming in said scoop housing a longitudinally extending passageway, said wall sections forming at a place spaced from the entry end of said passageway a transverse restricted intake slot, and forming in succession after such slot, a transverse weir extending across the passageway, a pocket for collecting condensate flowing through said intake slot and over said weir, and a transverse restricted outlet for said pocket located outwardly of the level of the weir so as to be submerged in the condensate collected in said pocket in back of the weir.
5. A scoop as defined in-claim 4, in which said intake slot is formed by said side walls, said inner wall sections and the interior wall of the cylinder.
6. A scoop as defined in claim 4, in which said outer wall sections start at said intake slot, and in which said inner wall sections start at the entry end of said scoop and include a front section extending in inclinedrelation from such entry end to said intake slot so as to form with the interior wall of the cylinder a converging intake passage section leading to said intake slot.
7. A scoop as defined in claim 4, in which said weir is formed by two outer wall sections disposed at an angle to each other to form a transverse ridge forming said weir and the front end of said pocket.
8. A scoop as defined in claim 4, in which said inner and outer wall sections beyond said restricted outlet are disposed in diverging relation to form a diverging passage section at the discharge end of the scoop.
9. A scoop as defined in claim 4, including a transverse rod supported by said side walls and extending across said scoop inwardly of said inner wall sections, and a supporting arm connected to said transverse rod and supporting said scoop in the cylinder, said supporting arm being adjustable to wedge said scoop against the interior wall of the cylinder.
References Cited UNITED STATES PATENTS FREDERICK L. MATTESON, JR., Primary Examiner. A. D. HERRMANN, Assistant Examiner.