Duct coating apparatus
United States Patent 3895604

A remote-controlled, self-propelled, vehicular apparatus adapted to travel tractionally within a rectangular duct and, by way of a spraying operation, coat the four walls of the duct internally with a suitable treating liquid such as a solvent, a rust or other corrosion inhibitor, paint, lacquer, or the like.

Application Number:
Publication Date:
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International Classes:
B05B13/06; B08B9/04; (IPC1-7): B05C7/02
Field of Search:
118/306,215,254,305,DIG.10 15
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Primary Examiner:
Mcintosh, John P.
Attorney, Agent or Firm:
Gerlach, Norman H.
Having thus described the invention, what I claim as new and desire to secure by Letters Patent is

1. In a self-propelled vehicular apparatus for applying a liquid coating material to the inner wall surfaces of a rectangular duct having horizontal top and bottom walls and vertical side walls, in combination, a chassis in the form of a rectangular frame having front and rear transverse frame members and a pair of side frame members, front and rear axles projecting across said side frame members, driving drums on the outer ends of the rear axle, driven drums on the outer end of the front axle, crawler treads connecting each driving drum to an associated driven drum, a reversible electric drive motor mounted on said chassis in the medial region thereof, a gear reduction drive mounted on said chassis rearwardly of the motor, means operatively connecting the gear reduction device to the motor, means operatively connecting the gear reduction device to one of said driven drums in driving relationship, a spraying device mounted on said chassis adjacent to the forward end of the latter and having a forwardly facing discharge slot designed for wide angle distribution of sprayed liquid coating material both laterally and vertically for simultaneous application thereof to the horizontal and vertical walls of the duct, a pair of outwardly diverging roller-supporting arms removably bolted to the front transverse frame member of said frame and projecting forwardly and laterally of the frame, a similar pair of roller-supporting arms removably bolted to the rear transverse frame member of said frame and projecting rearwardly and laterally of the frame, and a guide roller rotatably mounted on the distal end of each of said arms.

The present invention relates to an apparatus for internally treating the four walls of a rectangular sheet or other ducts such as are commonly used in large office buildings, factories, and other commercial establishments in connection with air conditioning or ventilating systems, hot air furnace systems, and the like. Such ducts require periodic attention in that, after a period of use, they become contaminated with dirt and other foreign material which may, under certain circumstances, give rise to unpleasant odors, as well as impair the efficiency of the ducts insofar as their air-flow characteristics are concerned. It is advisable that, immediately after any given duct-cleaning operation has been resorted to, the inner surfaces of the duct be coated with a suitable rust or other corrosion-inhibiting liquid, various commercial oils or other liquids being available for this purpose, or that such inner surfaces be freshly painted for sanitary and other purposes.

Where a rectangular duct of large size is concerned, it is possible that such cleaning and coating operations may be performed manually with the operator working within the duct while the latter is illuminated. This is a laborious procedure inasmuch as it is necessary for the operator to carry his cleaning and coating equipment with him, such equipment including open receptacles of the coating liquid which is subject to becoming spilled within the duct. Furthermore, such a manual procedure involves frequent exit and reentry of the operator from and into the duct in order to replenish his supply of the coating liquid. Where ducts of small size are concerned, both cleaning and coating operations are extremely difficult and, insofar as coating is concerned, long-handled brushes are used to spread the coating material within the duct, these brushes being introduced into the duct through adjacent access openings, utilizing internal duct illumination wherever possible.

The present invention is designed to overcome the abovenoted limitations that are attendant upon present day methods of applying a coating material to the inner wall surfaces of rectangular ducts and toward this end, the invention contemplates the provision of a fully automatic, duct-cleaning apparatus embodying a self-propelled carriage which is adapted to travel in either direction, i.e., forwardly or rearwardly, through a rectangular duct and on which there is mounted a conventional spraying unit which carries its own supply of the liquid coating material. The apparatus also embodies a caterpillar-type drive mechanism having crawler treads which make wide area frictional contact with the bottom wall of the duct in order thus to insure positive propulsion of the carriage, even in the event that the liquid coating being used by the apparatus possesses lubricating qualities which, ordinarily, would tend to reduce the coefficient of friction between the traction surface and the traction drive members. An electric motor on the carriage is operatively connected in driving relationship to the propulsion means and remote control means are provided exteriorly of the duct for regulating the movements of the carriage in either direction and also for setting the spraying unit into operation or discontinuing the spraying operation. This remote control means may assume the form of a control panel embodying a Sonar system whereby signals emitted therefrom are received by suitable electrical equipment on the movable carriage within the duct, to the end that the drive motor for the carriage may be reversed or regulated for speed. Alternatively, the control panel may be directly connected by electrical lead-out wires to such motor for the same purpose. Irrespective of the particular control mechanism which is employed, the essential features of the invention are at all times preserved.

In order to guide the carriage along the duct when traveling in either direction, novel outrigger guide rollers are provided at both the front and the rear end of the apparatus and are designed for tractional engagement with the side walls of the duct, thus enabling the apparatus to follow the contour of the latter, even when moderate curves or bends are involved.

The provision of an apparatus which is relatively simple in its construction and, therefore, may be manufactured at a low cost; one which is comprised of a minimum number of parts, particularly moving parts and, therefore, is unlikely to get out of order; one which is capable of ease of assembly and dismantlement for purposes of inspection, replacement or repair of parts; one which is smooth and silent in its operation, and one which, otherwise, is well adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

Other objects and advantages of the invention, not at this time enumerated, will readily suggest themselves as the nature of the invention is better understood from a consideration of the following detailed description.

In the accompanying single sheet of drawings forming a part of this specification, one illustrative embodiment of the invention is shown.

In these drawings:

FIG. 1 is a perspective view of a duct-spraying apparatus embodying the present invention, such view showing the apparatus operatively disposed in a rectangular duct with portions of the duct being broken away in the interests of clarity;

FIG. 2 is a vertical transverse sectional view taken on the line 2--2 of FIG. 1 and in the direction of the arrows; and

FIG. 3 is a vertical longitudinal sectional view taken on the line 3--3 of FIG. 2.

Referring now to the drawings in detail, a duct-spraying apparatus embodying the present invention is designated in its entirety by the reference numeral 10 and is shown as being operatively installed or positioned within a duct 12, the latter being rectangular in cross section and having vertical side walls 14 and 16, a top wall 18 and a bottom wall 20. The apparatus is in the form of a self-propelled vehicle or carriage which is electrically powered and carries a spraying device 22 by means of which a liquid coating material may be applied to the four walls of the duct 12 as the carriage travels through the latter. The apparatus further includes a caterpillar-type drive or propulsion mechanism 24 by means of which the carriage may be propelled in either direction longitudinally along the duct 10.

The carriage is comprised of a rectangular chassis 25 including side frame members 26 and 28, a front transverse frame member 30 and a rear transverse frame member 32. These frame members are preferably, but not necessarily, of channel shape design.

The caterpillar-type drive mechanism 24 serves tractionally to support the chassis 25 and, accordingly, it embodies a rear drive shaft 34 which carries a pair of driving drums 36, and a front driven shaft 38 which carries a pair of driven idler drums 40. Endless crawler treads 42 encompass the driving and driven drums in the usual manner of caterpillar drive construction. The two shafts 36 and 38 are rotatably carried by the side frame members 26 and 28 of the rectangular chassis 25.

The caterpillar-type drive mechanism 24 is powered by an electric motor M, the latter being fixedly mounted on a platform 44 which is supported at its ends on the side frame members 26 and 28 and is secured thereto by bolts 46. The motor M has associated therewith a gear reduction device 48, the output shaft 50 of which carries a drive sprocket 52 which is operatively connected by an endless chain 54 to a sprocket 56 which is secured to the drive shaft 34. The motor M is of the reversible type to the end that the vehicular apparatus may be caused to move in either a forward or a reverse direction. In the illustrated form of the invention, the electric motor M is supplied with energizing current by means of a branch cable 60 (see FIG. 3) which extends from a main manifold cable 62. The latter leads from a suitable control panel (not shown) which is positioned exteriorly of the duct 12 and may be of the portable type so that it may be positioned on a floor surface in the vicinity of duct-cleaning operations. A sheet metal box-like cover or casing 64 encompasses the motor M and is suitably secured on the platform 44.

The spraying device 22 may be of any suitable commercially-available type, the particular device illustrated herein being a purchased unit which is manufactured and sold by Electro Engineering Products Co. of Chicago, Illinois under the trade name "Electro-Airless." This unit bears Model No. 2400 and is in the form of a composite casing including an upper motor section 70 and a lower container section 72 which is threadedly received on the upper section as indicated at 73. The upper motor section encloses an electric motor M2, the container section 72 being adapted to receive therein a supply of the particular liquid coating material which is to be sprayed on the walls of the duct 12. The disclosure of the spraying device 22 herein is entirely schematic, the device being of the rotating centrifugal disk-type wherein liquid coating material which is deposited on a rotatable disk 74 within the upper section 70 of the casing is flung radially outwardly through a discharge slot 76 in the wall of the casing section 70. The discharge slot 76 is designed for wide angle distribution of the coating material therefrom as indicated by the diverging broken lines, the discharged liquid spray possessing wide lateral directional distribution for application of the spray to both the side walls 14 and 16 of the duct and the vertical directional distribution for application of the spray to the duct top and bottom walls 18 and 20. The lower section 72 of the composite casing of the spraying device 22 is supported within a retaining ring 78 which is secured by brackets 80 to the chassis. A pump 82 which is disposed within the lower section 72 of the sprayer casing serves to elevate the liquid coating material through a riser tube 84 for deposition on the upper surface of the rotating disk. Both the disk 74 and the pump 82 are driven by the motor M2 and the latter is supplied with energizing current through a second branch cable 86 leading from the main cable 62.

A generally L-shaped control casing 88 of the pistol grip-type contains an electrical off-on switch (not shown) which is operable under the control of a trigger member 90, the switch, when in its "on" position at the time the trigger is depressed, serving to supply electrical current to the motor M2 in order to drive both the disk 74 and the pump 82. A locking button 92 projects through one side of the control casing 88 and, when depressed, serves to maintain the trigger in its retracted position.

In order to maintain the carriage centered within the duct 12 and to guide the same therealong in either direction, a series of four outrigger guide rollers 100 are rotatably mounted at the outer ends of a series of four quadrilaterally-arranged supporting arms 102, there being a pair of such arms on the forward end of the carriage and a similar part of arms on the rear end of the carriage. The various arms are suitably bolted as indicated at 104 to the front and rear transverse frame members 30 and 32 and the arms of each pair diverge outwardly and serve to maintain their respective rollers in such spaced apart relationship that their over-all spread is slightly less than the transverse dimension or width between the side walls 14 and 16 of the duct. It is contemplated that in the commercial production of the herein described spraying apparatus 10, the diameter of the driving and driven drums 36 and 40, as well as the spread of the roller-supporting arms 102 will be varied to accommodate ducts having varying dimensions so that, insofar as practicable, the height of the discharge slot 76 may be maintained at the proper elevation for application of the sprayed liquid coating material to the four walls 14, 16, 18 and 20 of the duct 12.

In the operation of the herein described duct-spraying apparatus 10, consideration will first be given to the dimensions of the particular duct which is to be treated and, accordingly, a spraying apparatus in which the diameters of the driving and driven drums 36 and 40 will bring the height of the discharge slot 76 to an approximate mid-level position within the duct 12, and a lateral roller spread of the supporting arms 102 which will bring the rollers 100 into close proximity with the side walls 14 and 16 of the duct, will be selected and introduced into the duct. Such introduction of the apparatus 10 into the duct will, of course, be accomplished in the most expedient manner available, considering the nature of the duct. For example, where a given duct is of the overhead type, and is provided with access openings in the bottom wall thereof, the apparatus will be lifted, hoisted, or otherwise introduced upwardly and into the duct. As previously stated, remote control wireless signalling means embodying a floor-supported control box or panel (not shown) may be provided for selectively actuating the two motors M and M2, while suitable motor control solenoids may be carried by a junction box or the like (likewise not shown) which is mounted on the chassis 25, these solenoids being responsive to appropriate control switches which are associated with the floor-supported control panel. However, in the illustrated form of the invention, electric wires are employed for conducting energizing current to the motors M and M2, such wires being associated with the aforementioned main cable 62 and the branch cables 60 and 86.

Upon introduction of the spraying apparatus 10 into the duct 12, the trigger 90 will be manually depressed and locked in such depressed condition and the motors M and M2 will then be energized so as to drive the apparatus in a forward direction while simultaneously operating the spraying device 22. During travel of the apparatus through the duct, the liquid coating material which is flung peripherally from the disk 74 and emerges from the discharge slot 76 in cone-like fashion as indicated by the broken lines in FIG. 3 is deposited on all four walls 12, 16, 18 and 20 of the duct, as hereinbefore pointed out. If the bottom wall 20 of the duct 12 is provided with a series of access openings, the duct may be treated by successive operations wherein the apparatus is caused to travel in one direction from its region of introduction to an adjacent access opening and then, by reversing the motor drive, caused to return to its point of introduction. Thereafter, the apparatus may be caused to travel in the other direction to the other adjacent access opening and similarly caused to return. If dual coating operations are desired, the motor M2 of the spraying apparatus will be maintained energized during both forward and rearward movement of the apparatus. Otherwise, the motor M2 will be maintained energized only during travel in one direction. It will be understood, of course, that the pulling power which is exerted by the apparatus as it travels forwardly is adequate to pull the cable behind it. During return movement of the apparatus in a reverse direction, the cable may be drawn rearwardly by the operator or by a suitable automatic winding and reeling mechanism (not shown). Upon such return of the apparatus, and before the latter is withdrawn from the duct, the trigger 90 will, of course, be released to shut off the supply of coating material.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit or scope of the invention. Therefore, only insofar as the invention is particularly pointed out in the accompanging claim is the same to be limited.