US2885711A - Long retracting soot blower - Google Patents

Description

May 12, 1959 LE ROY 5. DE MART LONG RETRACTING SOO'I BLOWER 3 Sheets-Sheet 1 Filed Aug. 28, 1956 INVENTOR. I 4625 6, ,De/Varz? if awn/2304s y 1959 LE ROY 5. DE MART 2,885,711

LONG RETRACTING soo'r BLOWER Filed Aug. 28, 1956 s Sheets-Sheet 2 INVENTOR. 46%;? J fie /7drf May 12, 195 LE ROY s. DE MART LONG RETRACTING SOOT BLOWER File d Aug. 28, 1956 3 Sheets-Sheet 3 INVENTOR.

A072} 6f 129/7472? 5 BY United State p m O LONG RETRACTING SOOT BLOWER Le Roy S. De Mart, Lancaster, Ohio Application August 28, 1956, Serial No. 606,726

3 Claims. (Cl. 15317) This invention relates to soot blowers such as are used for removing accumulations of undesired materials from heat exchanging surfaces, and more particularly to those of the type known as long retracting. soot blowers.

Soot blowers of the long retracting type commonly include a rack and pinion or a chain drive for the lance tube, with a drive motor mounted on the lance tube in order to provide rotative and longitudinal motion thereto during operation. Rack and pinion-type drive constructions are relatively expensive. When a drive motor is mounted upon a travelling lance tube, it requires a flexible power supply connection which, is subject posure, excessive wear and accidents.

Available space is relatively confined around many modern boilers and other equipment where soot blowers are. installed, and the matter of size is, therefore, also important in soot blower construction. The width of the soot blower must be minimized especially where it is desired to mount a relatively large number of soot blowers in close array. In the past, it has sometimes been necessary to ofiset alternate ones of an array of soot blowers from a desired operational line in order to provide adequate working clearance between them, and to manufacture right-hand and left-hand blowers, that is, blowers having certain unsymmetrically positioned parts projecting to the right only, or to the left only Accordingly, one object of the instant invention is to provide improved soot blowers of relatively inexpensive construction that are relatively narrow and compact in size, and substantially symmetrical and free of projecti'ng parts. Another object is to provide improved soot blowers of the long retracting type that are actuatable by a single screw which imparts both longitudinal and rotative motion to the lance tube. Still another object is to provide improved drive means for effecting simultaneous linear and rotational movement of a driven member.

These and other objects are accomplished according to the instant invention, one embodiment of which provides animproved soot blower comprising a drive screw mounted for rotation by a stationary motor. A follower nut engages the screw' to drive the lance tube longitudinally, and; a sprocket also engages the screw by means of flats formed thereon to impart rotational movement to the lance tube. Soot blowers according to the invention are relatively compact, being narrow in profile so that they may be installed in relatively confined spaces and in relatively closely packed arrays. They are inexpensive to construct relative to previous long retracting soot blowers, and, moreover, they are less subject to wear and have a longer service life.

The invention will be described in greater detail in connection with the accompanying drawings of which:

Figure l is a side elevational view of a soot blower according to the invention;

Fig. 2 is a side elevational view, partly in section and to exon a larger scale, of a portion of the soot blower shown Fig. 3 is a cross-sectional view of the soot blower shown in Fig. 1 taken along the section line 3-3 thereof;

Fig. 4 is a cross-sectional view of a part of the soot blower shown in Fig. I particularly showing the follower nut engagement with the screw; and

Fig. 5 is a longitudinal cross-sectional view of a follower nut as used in the soot blower shown in Fig. 1.

Referring now to Fig. 1, a soot blower according to a preferred embodiment of the invention comprises a longitudinal beam 6 supported between a pair of end plates 7 and 8 to which it may be welded, bolted or riveted. The beam 6 may be of any desired structural shape such as the I-beam shape shown in the drawings. A drive screw 22 is rotatably supported directly beneath the beam 6 and parallel thereto. The screw shaft 22 is journalled in a rear bearing 36 mounted upon the rear end plate 7 and in a front bearing 37 suspended beneath and attached to the beam 6. Preferably, the rear hearing 36 is a thrust bearing designed to resist axial load, the front bearing 37 being a. simple, radial type hearing or bushing. A drive sprocket 38 is rigidly secured to the screw 22 near one end thereof so that the screw may be rotatively driven by a motor 9 mounted on the beam 6 through a drive chain 11 straddling the beam 6.

The blower tube assembly comprises a travelling lance tube 10 slidably fitted on and :fed through a stationary feed tube 12, the tubes 10 and 12 being mounted below the screw 22 and vertically aligned with both the screw 22 and the beam 6. The feed tube 12 is connected to an inlet poppet-type blow valve 46 and extends forwardly through the rear end plate 7 into telescopic engagement with the lance tube 10. The lance tube 10 is equipped with a blower nozzle 14 and is slidably and rotatably supported at its forward end upon a roller assembly 15. The lance tube 10 projects forwardly of the front plate 8 through a conventional wall box 16 which may be mounted in a boiler wall. At its other end, the lance tube 10 is supported in a concentric cylindrical hanger 13 suspended from a carriage assembly generally designated 18.

Referring now to Fig. 2, the lance tube 10 and the feed tube 12 are slidably sealed together by packing 68 held within a sealing sleeve 66. The packing 68 is retained in place between the sleeve 66 and the feed tube 12 by a retaining collar 70 and a packing ring 72'. The sleeve 66 is sealed rigidly to the lance tube 10 by means including a ring 62 Welded, or otherwise bonded to the lance tube and an annular gasket 64 disposed between the ring 62 and. the sleeve 66. A reinforcing collar 69 is mounted on the lance tube beyond the ring 62, and screws 67 are passed through the collar and the ring into the sleeve 66 to hold the sleeve tightly compressed against the ring. The sleeve 66 is journalled in the hanger 13 in a pair of roller bearings 76 and a sprocket 20 is attached to the sleeve for rotational drive thereof. Thus, the lance tube is slidable both longitudinally and rotatively upon the feed tube 12 and is rigidly supported in a vertical direction by the hanger 13.

The hanger 13 is supported upon the carriage 18 which is mounted for longitudinal travel along the beam 6. The carriage 18 is provided with one pair of upper wheels 40 and two pairs of lower wheels 42 which, ride upon the upper and lower surfaces, respectively, of a plate 44 attached to the lower surface of the mainbeam 6 and extending along substantially the entire length of the beam. Two pairs of wheels are placed beneath the plate because when the lance tube 10 is projected, its weight is pivoted upon the roller assembly 15 and bears upwardly upon the carriage with substantial leverage. When the lance tube 10 is retracted, the upper wheels 40 of the carriage carry only the weight of the carriage assembly 18 and a portion of the blower tube assembly,

- gaged by a pin 56 rigidly secured to the carriage 18.

and a single pair of wheels suflices. The detailed construction of the carriage supports is not, however, critical in the practice of the instant invention. The carriage may be supported in any desired manner for smooth and rigid sliding or rolling travel along the beam '6.

If desired, a brush 21 as shown in Fig. .2 may be mountedon the carriage 18 to bear against the screw 22 to sweep it clean of dust and debris. Such an arrangement is particularly desirable when the. soot blower is operated in a relatively dirty or soot-laden atmosphere such as is commonly encountered in the vicinity of coal and oil fired boilers.

A follower nut 24 is threaded upon the screw 22 and is held within the carriage 18 upon a pair of transverse 'trunnions 25. The hanger 13 is also suspended from the carriage 18 by transverse trunnions 17, thus permitting limitedangular motion of the various parts, while holding both the nut 24 and the hanger 13 against axial rotation as well as against independent, longitudinal movement. For maximum efliciency the follower nut 24 is preferably of the circulating ball type and, as shown most clearlyin Figs. 4 and 5, includes a ball raceway 78 and aball return track 80 forming, together with the screw thread 30, a passageway for freely rollable balls 82. Preferably, the ball nut 24 is provided with three separate ball circuits so that in the event of failure of any one of the circuits the other two are still operative to retain the nut 24 in its position upon the drive screw 22. Otherwise, in the event of nut failure during operation of the blower, the air or steam pressure might force the lance tube violently forward and damage the blower and the boiler or other equipment where it is installed.

As indicated in Figs. 1 and 3, the screw 22 is provided with a pair of diametrically opposed flats 28 which extend to a depth approximately equal to the depth of the thread 30, and along substantially the entire length of the screw shaft. The flats 28 do not affect the disposition of the balls 82 in their raceway since the balls are held in the raceway by the thread of the nut 24. A sprocket 26 is fitted over the screw 22 and supported for rotational movement with the screw upon a bearing 27 which is attached by a pair of arms 29 and screws 31 to the casing of the follower nut 24. The arms 29 permit vertical, angular play between the bearing 27 and the follower nut 24, but at the same time hold the bearing 27, together with the sprocket 26, against longitudinal movement independently of the follower nut. The sprocket 26 is provided With a centrally apertured portion 33 conforming to the flattened cross section of but slidably fitted upon the screw shaft 22, so that the sprocket 26 is slidably keyed to the screw to rotate therewith. The sprocket 26 is drivingly connected to the sprocket 20 mounted on the lance tube by means of a chain 32 so that rotational movement of the screw 22 is transmitted to the lance tube 10 when the soot blower is operated.

Compressed fluid such as air or steam for operational blowing may be admitted to the feed tube 12 through a conventional poppet type valve 46 operable by means of a lever 48 and biased towards its closed position by a spring 49. A link 50 is connected between the lever 48 and a yoke-like dog 52 which is pivoted upon a pin 54 on the main beam 6. The dog 52 is positioned to be en- In operation, during projection of the lance tube, the carriage 18 moves the pin 56 into the yoke of the dog 52 and swings the latter clockwise, as viewed in Figs. 1 and 2 to swing the pivot connection 51 between the link 50 and the dog 52 over the pivot pin 54. This over center action places the dog 52 in position to hold the poppet valve open until the dog 52 is reversed by the pin 56 upon return of the carriage 18. After the lance tube has been ithe carriage 18 returns toward its starting position, the

pin 56, in passing, swings the dog 52 back to its inoperative position to close the poppet valve 46.

Soot blowers according to the invention may be con trolled by any desired means such as by conventional limit switches, or other devices for automatic cycling according to any predetermined sequence. The electric motor 9 shown in the drawing may be replaced by any other desired type of energy source such as a compressed air driven motor. It should be noted, however, that the I-beam, the screw shaft and the blowing tube assembly are vertically aligned, and the driving motor is mounted directly on top of the beam with the drive chain 11 straddling the beam. The width of the soot'blower is thus minimized and all laterally projecting moving parts are eliminated, which is of great advantage in view of the limited space available around modern boilers.

Other advantages of a soot blower according to the present invention are:

(a) Its relatively simple construction, as compared to previous soot blowers;

(b) Its use of relatively inexpensive parts;

(c) Its relatively high efliciency which permits the use of a relatively small drive motor and results in improved economy of operation;

(d) A reduction in wear on the moving parts relative to previous soot blowers; and

(e) The provision of a stationary motor for all movement of the lance tube, both longitudinal and rotative.

It should also be noted'that the drive screw 22 is preferably supported against longitudinal movement by a single thrust bearing 36, as shown in Fig. 1, at the rear end plate 7, the bearing 37 at the wall box endof the blower supporting radial load only. The effect of fluid pressure upon the lance tube 10 biases the lance tube forwardly when the blower is operated, and this forward pressure on the lance tube is transmitted to the follower nut 24 so that the screw 22 is always in tension during operation of the blower while fiuid is flowing through the tube. Since the radial bearing 37 does not oppose axial movement of the screw'shafi, the screw shaft is not subjected to compressive forces that might tend to bow or distort it, and friction and stressing of the parts are thereby minimized.

The flats 28 on the screw shaft 22 intersect the helical, round-bottomed ball track 30 at relatively large obtuse angles at all positions of meeting so that the meeting surfaces do not tend to constitute sharp edges, as would be the case if a conventional keyway were used having sides parallel to a radius. It will be understood that with no axial loading of the shaft or nut, a simple keyway, shallower than the ball track 30, would theoretically be equivalent to the flats. Under operating conditions, however, an axial load is applied to the nut so that the balls tend to roll against, and are compressed between, the rear surfaces of the nut track and the front surfaces of the screw track when, for example, the lance tube is urged forwardly by the'blowing medium. The obtuse angles at which the flats intersect the ball track are brought out in Fig. 2, and on a somewhat larger scale in Fig. 6, which illustrates a different embodiment of this driving principle, but it should be noted that if a conventional keyway were employed, the parallel sides of the keyway would intersect the ball track at relatively acute angles, which would tend, under relative axial loading of the screw and nut, to injure the balls.

What is claimed is:

l. A soot blower comprising a stationary tube and a lance tube telescopable therewith and rotatable with respect thereto, and drive means for simultaneously moving said lance tube longitudinally and rotating it with respect to said stationary tube, said drive means comprising a rotatable screw disposed parallel to said lance tube, follower means including a ball nut engaging said screw and connected to said lance tube for driving said lance tube longitudinally when said screw is rotated, said screw having a flattened longitudinal surface, and a member longitudinally slidably mounted upon said screw, said member engaging said surface for positive rotational engagement with said screw, said member also being connected to said lance tube to rotate it when said screw is rotated.

2. A soot blower comprising a stationary tube and a lance tube telescopable therewith and rotatable with respect thereto, and drive means for simultaneously moving said lance tube longitudinally and for rotating it with respect to said stationary tube, said drive means comprising a rotatable screw disposed parallel to said lance tube and having a longitudinal flat extending to a depth less than the depth of the screw thread, an angularly fixed ball nut threaded upon said screw and connected to said lance tube for driving said lance tube longitudinally inresponse to rotation of said screw, a sprocket slidably mounted coaxially upon said screw, said sprocket engaging said fiat and being thereby angularly fixed upon said screw, and coupling means to connect said sprocket to said lance tube.

3. A soot blower comprising a stationary tube and a lance tube telescopable therewith and rotatable with respect thereto, an elongated screw rotatably mounted generally parallel to said stationary tube and longitudinally fixed with respect thereto, means for driving said screw in rotation, said screw having a pair of flats thereon extendingto a depth less than the depth of the screw thread, a member longitudinally slidably mounted on said screw and in engagement with the flats thereof so that said member is angularly fixed on said screw for rotational drive thereby, means for coupling said member to said lance tube for rotating said lance tube, a ball nut threaded upon said screw, means for holding said ball nut against rotation so that it is driven longitudinally along said screw when said screw is rotated, and means for coupling said ball nut to said lance tube for longitudinal drive thereof.

References Cited in the file of this patent UNITED STATES PATENTS 196,117 Greenleaf Oct. 16, 1877 387,096 Miller et al. July 31, 1888 1,888,776 Snell Nov. 22, 1932 2,298,011 Hoffar Oct. 5, 1942 2,441,112 Hibner et a1 May 4, 1948 2,668,978 DeMart Feb. 16, 1954 2,756,964 Hogan July 31, 1956 FOREIGN PATENTS 1,026,751 France Feb. 11, 1953

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