Handheld Brush Positioner with Retraction Stop Sensing

The present invention relates to tube cleaning machines for cleaning tubes and pipes having a brush assembly fitted to a spinning flexible shaft contained in a sleeve, and means for an operator to extend and retract the flexible shaft and brush into a tube or pipe.

Tubes and pipes of power plant equipment and machines such as boilers, chillers, condensers, heat exchangers, and other similar machines need periodic cleaning. For example, tubes and pipes installed in power plant equipment and machines become coated with deposits such as soot (in the fire tubes of boilers) or boiler compound (used to inhibit scale and corrosion in the water tubes of boilers) which over time reduce heat transfer efficiency. In the same way, chillers often accumulate scale which is typically an accumulation of mineral salts such as calcium carbonate and calcium phosphate. Therefore, periodic tube cleaning is required.

Tube cleaning systems provided by Applicant have a brush assembly fitted to one end of a spinning flexible shaft. The flexible shaft is typically a woven metal cable jacketed with a plastic sleeve. The flexible shaft typically has a metal connector at its end. The brush assembly includes a metal shaft which can be mounted and locked into a socket in the metal connector, and an elongated, generally cylindrical spiral brush at the forward end of the brush assembly. The flexible shaft can be rotated in clockwise and counterclockwise directions by a reversible motor to provide the spinning movement of the flexible shaft and brush. The rotational speed of the spinning flexible shaft and brush can be controlled by a speed controller that has a dial for setting speed.

A reversible drive motor uses drive rollers that engage with the plastic sleeve jacketing the flexible shaft to extend and retract the flexible shaft and brush assembly into and out of each tube being cleaned. Preferably a water flow is provided via the plastic sleeve to flush removed deposits out either end of the tube after cleaning by the brush.

Preferably, the reversible motor which provides the spinning movement of the flexible shaft and brush and the reversible drive motor and drive rollers that cause the flexible shaft and brush assembly to extend and retract are located in a housing.

The operator of the tube cleaning system positions the brush to clean a particular tube and controls the extension and retraction of the rotating flexible shaft and brush into and out of the particular tube. Although in some systems the operator may simply position a brush by gripping the plastic sleeve and positioning the brush as desired, in preferred embodiments, the operator positions and controls the tube cleaning system using a handheld brush positioner. In some embodiments, the handheld brush positioner is a feed gun. A feed gun has a pistol grip, and a barrel which provides a passageway for the flexible shaft and brush assembly as they are positioned adjacent each tube during a cleaning operation. In preferred embodiments, the brush positioner is connected to the housing with a protective casing such as a hose, and the flexible shaft and brush assembly extend through the protective casing from the housing to the brush positioner.

Various control embodiments may be provided to activate and control the tube cleaning system. In some embodiments, the control system is activated by a pneumatic air switch system which is linked to the reversible drive unit, and to a source of pressurized air. In some embodiments the feed gun includes a finger-operated trigger to activate the tube cleaning system. In other embodiments, a foot operated pedal switch can be provided to activate the tube cleaning system.

One embodiment of a finger-operated trigger is a pneumatic rocker switch trigger positioned vertically in the feed gun pistol grip, and the two ends of the switch provide the operator with control of extension and retraction of the casing, flexible shaft, and brush. The pneumatic rocker switch trigger is fed two continuous streams of control air; one to a port located behind the upper end of the rocker switch trigger, and one to a port located behind the lower end of the rocker switch trigger. In its default neutral position, the control air is vented out through the two ports and no action is actuated. When the rocker switch trigger is squeezed on its upper end, the inner face of the upper end of the switch bears against and closes an upper vent opening, causing an increase in air pressure in the forward air line, which line connects to a forward air switch. The increase in air pressure is a pneumatic signal that is received by the forward air switch. The forward air switch activates the reversible drive motor, causing it to operate the drive rollers to extend the flexible shaft and brush assembly into a tube. When released, the trigger returns to a neutral position, stopping movement of the brush. The operator can then squeeze the rocker switch trigger at its lower end, so that the inner face of the lower end of the switch bears against and closes a lower vent opening, causing an increase in air pressure in the reverse air line, which line connects to a reverse air switch. The increase in air pressure is a pneumatic signal that is received by the reverse air switch. The reverse air switch activates the reversible drive motor, causing it to operate the drive rollers to retract the flexible shaft and brush assembly from the tube. Each of the forward and reverse air switches operates the drive motor (i.e., turns “on”) with buildup of air pressure in its air line and turns “off” when the air line is vented. Accordingly, the feed gun is connected by separate (i.e., forward and reverse) air lines to the forward and reverse air switches. By squeezing the upper part of the rocker switch trigger, the air lines to the forward air switch are pressurized and the drive motor operates to advance the brush into a tube. At the same time the switch trigger vents the reverse air line and the reverse air switch remains in the “off” position. By squeezing the lower part of the rocker switch trigger, the forward air line is vented and the forward air switch goes to its “off” position, while the reverse air line is pressurized and the reverse air switch is activated.

A foot operated pedal switch operates in the same way as described above for a rocker switch trigger and allows the operator to use a foot control instead of a finger control.

Examples of tube cleaning systems as described above are disclosed in U.S. Pat. Nos. 5,235,718; 5,426,807; 5,636,403; 7,055,203; and 7,827,647; the disclosures of which are hereby incorporated by reference.

An issue which has been experienced by operators of tube cleaning systems is that when the brush is retracted from a tube that the position of the brush on retraction is dependent on the operator's skill, specifically, position of the brush on retraction is dependent on the timing of the operator's release of the trigger. Consequently, sometimes the brush is not fully retracted, and in other cases, may be retracted into the feed gun barrel or into the protective casing. This inconsistency in retraction typically adds to the time required to complete the cleaning of the tube to be cleaned when positioning error requires the operator to reposition themselves or the brush.

A previous effort to provide for a brush retraction stop mechanism is disclosed in U.S. Pat. No. 5,235,718 at Col. 7, line 23-55. The disclosed mechanism, a hard stop provided by a lever which is held in position to catch on the lip of a brake collar located on the flexible shaft and to stop the retraction of the flexible shaft and brush. However, this approach has not been satisfactory as the frequent hard stops of the brake collar on the lever leads to metal fatigue and eventual deformation and the breaking of the lever and the brake collar, as well as general wear and tear on the flexible shaft, connectors, and motors. It is to be appreciated that metal fragments are an undesirable item to be included in a tube cleaning process, so this stop mechanism is disfavored and is not in commercial use.

Desirably, upon retraction of the rotating brush from a tube, the retracted brush is stopped at a position that is most efficient for the operator to move from tube to tube without wasted movement. Tube cleaning and maintenance is a critical step to maintaining and operating equipment and machinery. Yet the downtime involved in tube cleaning, particularly if it requires the shutdown of the entire plant, can have substantial opportunity costs as a plant that is not operating is not generating revenue. Thus any improvement in the efficiency and effectiveness of the tube cleaning process is extremely valuable to the plant owner.

The present invention provides an apparatus for improving efficiency in the cleaning of tubes and pipes.

The present invention provides a handheld brush positioner with retraction stop sensing for use in a tube cleaning machine as described above. The retraction stop sensing detects when a flexible shaft and brush are retracted back to the brush positioner and terminates the operation of the drive motor. The handheld brush positioner with retraction stop sensing provides a consistent retraction of the flexible shaft and brush and an automatic stop of retraction so that the operator can move the brush positioner to a next position without requiring any axial correction or adjustment of the axial position of the brush. In addition, automatically stopping a cleaning brush with a consistently protruding brush section that can be placed into the next tube to be cleaned provides the operator with a positioning aid so that the brush is in the correct position and in line with the next tube to be cleaned.

One embodiment of the invention provides a tube cleaning apparatus comprising a brush assembly, for cleaning the interior surfaces of tubes, which is affixed to an elongated flexible shaft. The brush assembly may include a plastic bristle brush, and a metal rod connector between the bristle brush and the flexible shaft. The flexible shaft is encased in a flexible plastic sleeve. A handheld brush positioner is used to position the brush, and includes a guide tube and a forward end and a stop sensor. The stop sensor can sense when the brush assembly is retracted to a position so that the brush assembly is located in the forward end of the brush positioner with at least some of the brush assembly extending out from the forward end of the brush positioner.

A reversible drive motor powers a drive unit. The drive unit has powered rollers that engage with the flexible shaft and sleeve to thereby extend and retract the sleeve, flexible shaft and brush assembly from the guide tube into the interior surfaces of tubes.

One embodiment of a control system for controlling operation of the drive unit includes a continuously operating pump providing a supply of control air operably connected to a forward control valve and a reverse control valve. Closing the forward control valve causes an increase in air pressure in a forward air switch and activation of a forward electrical switch to provide current to the drive motor to cause the drive motor to operate the drive unit to extend the sleeve, flexible shaft and brush. Closing the reverse control valve causes an increase in air pressure in a reverse air switch and activation of a reverse electrical switch to provide current to the drive motor to cause the drive motor to operate the drive unit to retract the sleeve, flexible shaft and brush. When the stop sensor senses that the brush assembly is retracted to a position where it is located in the forward end of the brush positioner with at least some of the brush assembly extending out from the forward end of the brush positioner, a vent valve operably connected to the reverse air switch is opened, causing a decrease in air pressure in the reverse air switch and deactivation of the electrical switch providing current to the drive motor and thereby terminate operation of the drive motor and drive unit and stopping retraction of the sleeve, flexible shaft and brush.

In one embodiment, the stop sensor comprises a mechanical linkage which includes a roller contacting the sleeve, flexible shaft, and brush assembly, the linkage pivoting to keep the vent valve closed when a larger diameter component is (e.g. the flexible shaft and surrounding plastic sleeve) contacting the roller, the linkage pivoting to bear against and open the vent valve when a smaller diameter component (e.g. the flexible shaft core section or a connector between the flexible shaft and the brush) is contacting the roller. The vent valve is operably connected to an exhaust port; manually blocking the exhaust port overrides the stop signal and permits operation of the reverse control valve.

Another embodiment of a control system uses a low voltage microcontroller (for example, a 5 volt/20 mA controller) to enable a similar control logic wherein closing a forward control switch causes the microcontroller to activate a forward electrical relay to provide current to the drive motor to cause the drive motor to operate the drive unit to extend the sleeve, flexible shaft and brush; and closing a reverse control switch causes the microcontroller to activate a reverse electrical relay to provide current to the drive motor to cause the drive motor to operate the drive unit to retract the sleeve, flexible shaft and brush. A stop sensor senses that the brush assembly is retracted to a position where it is located in the forward end of the brush positioner with at least some of the brush assembly extending out from the forward end of the brush positioner, causing a signal to be sent to the microcontroller to cause the microcontroller to terminate the reverse electrical relay and thereby terminate operation of the drive motor and drive unit, stopping retraction of the sleeve, flexible shaft and brush. An override may be programmed into the microcontroller such that when both the forward and reverse control switches are pressed at the same time when the reverse stop is activated, the flexible shaft can be retracted further past the stop position into the protective casing.

In one embodiment, the brush positioner comprises a feed gun with a pistol grip, and the forward control valve and reverse control valve are actuated by a finger-operated rocker trigger provided in the pistol grip. In another embodiment, the finger-operated rocker trigger is replaced or supplemented by a foot-operated pedal switch.

Other and further objects of the invention will become apparent with an understanding of the following detailed description of the preferred embodiment of the invention or upon employment of the invention in practice.

Referring now to, a schematic pneumatic control systemof a tube cleaning machine including a handheld brush positioner with retraction stop sensing is shown. Pressurized air is delivered from a compressorto a forward control valveand a reverse control valve. Valvesandare normally open valves that vent to the atmosphere. The two valvesandare preferably controlled by a rocker or other manual control that allows only one valve,to be closed at a time. Closing forward control valveincreases pressure in lineand then in forward air switch. When pressure reaches a certain level, air switchactivates an electrical switch to provide current to drive motorto cause the drive motor to extend a flexible shaft and brush of a tube cleaning machine. Closing reverse control valveincreases pressure in lineand then in reverse air switch. When pressure reaches a certain level, reverse air switchactivates an electrical switch to provide current to drive motorto cause the drive motorto turn in the opposite direction and retract the flexible shaft and brush of a tube cleaning machine. When the flexible shaft and brush is retracted to a desired position in the handheld brush positioner, the retraction is detected by a stop sensor, which then causes vent valvein the brush positioner to open. The opening of vent valvereleases pressure from lineand reverse air switch, stopping drive motor, and preventing further retraction of the flexible shaft and brush. If it is desired to further withdraw the flexible shaft and brush, the stop signal from the stop sensor can be overridden by blocking the exit of air from valveat exhaust port. Blocking exhaust portprevents venting of air pressure, so that closing reverse control valvewill cause an increase in pressure in lineand then in reverse air switch, to activate the electrical switch to provide current to drive motorto cause the drive motorto further retract the flexible shaft and brush.

Referring to, the forward endof a handheld brush positioneris shown.show the forward endmounted on a rear endwith includes a pistol gripto provide the complete brush positioner. Brush positioneris a handheld unit desirably controlled by holding the pistol gripand the lower part of the bodyof forward endas seen in.

The forward endof brush positionerhas at its forward enda brush assembly. The brush assemblyincludes a plastic bristle brushmounted to a connector. The brush assemblyis mounted to a flexible shaftwhich is contained in a plastic sleeve. The forward endof the brush positioner includes a resilient conical bumperthat helps to prevent damage to tubes to be cleaned in the event the operator loses control of or grip on the brush positioner. A drain hoseis provided in the body of the brush positionerto divert any water and cleaning liquids that may be flushed from the tubes of the equipment being cleaned and which flows backwardly into the body of brush positioner. Drain hosemay be provided with a nipple, and in use nipplecan be connected to a longer hose to send wastewater to an appropriate catch basin for wastewater processing. A guide tubeextends through the body of the brush positionerwhich provides a passageway for the flexible shaft and brush assembly. Guide tubemay be connected via portto a hose that is connected to the housing of the tube cleaning machine and through which the flexible shaft and brush assembly extend.

Referring to, a finger-activated pneumatic trigger switchfor controlling the pneumatic control systemof a tube cleaning machine ofis shown in the brush positioner. Trigger switchis positioned vertically in the feed gun pistol grip, and the two ends of the switch provide the operator with control of extension and retraction of the casing, flexible shaft, and brush. The trigger switchis fed two continuous streams of control air; one to a port located behind the upper end of the rocker switch trigger, and one to a port located behind the lower end of the rocker switch trigger. In its default neutral position, the control air is vented out through the two ports and no action is actuated. When the rocker switch trigger is squeezed on its upper end, the inner face of the upper end of the switch bears against and closes an upper vent opening, causing an increase in air pressure in the forward air line, which line connects to a forward air switch. The increase in air pressure is a pneumatic signal that is received by the forward air switch. The forward air switch activates the reversible drive motor, causing it to operate the drive rollers to extend the flexible shaft and brush assembly into a tube. When released, the trigger returns to a neutral position, stopping movement of the brush. The operator can then squeeze the rocker switch trigger at its lower end, so that the inner face of the lower end of the switch bears against and closes a lower vent opening, causing an increase in air pressure in the reverse air line, which line connects to a reverse air switch. The increase in air pressure is a pneumatic signal that is received by the reverse air switch. The reverse air switch activates the reversible drive motor, causing it to operate the drive rollers to retract the flexible shaft and brush assembly from the tube.

In an optional alternative embodiment, shown in, the trigger switchis replaced with or can be supplemented with a foot-activated pedal switch. A foot-activated pedal switchoperates in the same way as described for the trigger switchto operate the extension and retraction of a rotating flexible shaft and brush of a tube cleaning machine. The foot activated pedal switch includes a forward pedal, a neutral position, and a reverse pedal. Pressure from an operator's foot on the forward pedal closes a normally open port, increasing air pressure in the forward pedal line and activating a forward air switch, which activates the reversible drive motor, causing it to operate the drive rollers to extend the flexible shaft and brush assembly into a tube. When released, the pedal switch returns to the neutral position, stopping movement of the brush. Pressure from the operator's foot on the reverse pedal closes a normally open port, increasing air pressure in the reverse pedal line and activating a reverse air switch, which activates the reversible drive motor, causing it to operate the drive rollers to retract the flexible shaft and brush assembly into a tube.

In an alternative embodiment of a feed gun, shown in, the pneumatic control systemofis replaced with a low voltage microcontroller, operating, for example, at 5 volts/20 mA. Triggering is controlled by two separate push button switches,. Instead of a closing a vent opening, the pushing of the forward control push button switchcauses the microcontroller to emit a forward control activation signal, which is amplified by a transistor to 12 V, and the amplified signal activates a forward electrical relayto provide current to the drive motor to cause the drive motor to operate the drive unit to extend the sleeve, flexible shaft and brush. Pushing on the reverse control push button control switchcauses the microcontrollerto emit a reverse control activation signal, which is amplified by a transistor to 12 V, and the amplified signal activates a reverse electrical relayto provide current to the drive motor to cause the drive motor to operate the drive unit to retract the sleeve, flexible shaft and brush until stopped by the stop sensor as described below.

Referring now to, a cross-section of forward endis shown. Flexible shaftis contained in the guide tube. A forward guide tubeis positioned inside the forward endnear endand is spaced part from guide tube, leaving a space therebetween for a retraction stop sensor as described hereafter.

Flexible shaftwith its plastic sleeveis connected to connectorand brushis mounted on connector. Flexible shaftand plastic sleevehave a greater diameter than the diameter of the flexible shaftor connector. The difference in diameter is sufficient that it can be detected by a stop sensor. The stop sensor is a sensing means which may include a mechanical mechanism as described hereafter or an electronic sensor such as a proximity sensor.

In one embodiment, the stop sensor is a mechanical linkage. Referring now to, mechanical linkageincludes an L-shaped pivot armincludes a sufficient framework to retain a lower rollerat the lower endof pivot arm. Rolleris positioned perpendicularly to the line of travel of the flexible shaftand plastic sleeve. The plastic sleeverides on the roller, causing the upper endof pivot armto be held away from the brush positioner vent valve, such that brush positioner vent valveis closed. The L-shaped pivot arm pivots around pin, and has spring tension applied to it by spring, so that when lower rollerrides on the smaller diameter flexible shaftor the connector, the upper endof pivot armis pulled rearwardly.

A yokeprovides adjustment so that the mechanical linkagewill be operable as a stop sensor for a range of differently sized flexible shaftsand plastic sleeves. Yokeaccommodates a range of different diameters of flexible shaftsand plastic sleevesby providing a threaded thumbscrewmounted in a nut in the yoke, and by having an upper rollerplaced above and opposite the lower rollerto maintain an appropriate spacing between the rollers,so that that there is a slight tension thereon. By providing this, the lower rollercan appropriately ride on flexible shaftand plastic sleeve, and the smaller diameter flexible shaftor the connector, to enable the operation of the pivot armin stopping the retraction of the flexible shaftand plastic sleevefor a range of different diameters. The adjustability provided by yokepermits the upper rollerto be moved up and down to account for shaft wear as well as different size shafts. In general, the step down from the flexible plastic sleeve to the core of the flexible shaft is fairly consistent between most flexible shaft sizes, so the yokeallows setting of a “neutral” position so that the mechanical linkage detects the step down no matter the particular flexible shaft being used.

In a pneumatic control system shown in, the retraction stop sensing provided by mechanical linkagemechanically opens brush positioner vent valvewhich corresponds to valvein. Brush positioner vent valvereceives air pressure via line. Brush positioner valveis normally closed. Brush positioner valveis opened by lateral force and/or a stem or probe applied to one side to allow air to be vented from lineto exhaust line. For example, brush positioner valvecan be a check valve or a linear valve. In mechanical linkage, when lower rollerrides on the smaller diameter flexible shaftor the connector, the upper endof pivot armis pulled by springtowards vent valveto cause vent valveto open and vent air to exhaust line, stopping the retraction of the flexible shaftand plastic sleeve. Vent valveis operably connected via exhaust lineto an exhaust port. Blocking the exhaust port(or in, the exhaust port), for example with a thumb or finger, overrides the stop signal by allowing pressurization of the control system air lines, and permits operation of the reverse control valve by trigger switchto cause retraction of the flexible shaft

In an electronic control system, shown in, the stop sensoris a magnetic or mass or proximity sensor which senses when the upper endof L-shaped pivot armhas been positioned near the stop sensor, which happens when the brush assembly is sufficiently retracted that the lower rollerrides on the smaller diameter flexible shaftor the connector, causing the upper endof pivot armto be pulled rearwardly by spring, and positioning the upper endnear the stop sensor. When the microcontrollerdetects that the stop sensor has sensed the upper endof pivot arm, microcontrollerterminates its signal to the reverse electrical relayand thereby terminates operation of the drive motor and drive unit, stopping retraction of the sleeve, flexible shaft and brush. An override may be programmed into the microcontrollersuch that when both the forward and reverse control push button switches are pressed at the same time when the reverse stop is activated, the flexible shaft can be retracted further past the stop position into the protective casing and back to a storage reel.

Accordingly, the present invention provides an improved tube cleaning apparatus and brush positioner, which provides the user with a consistent retraction of the brush, with a sufficient extending brush that makes it easier for the operator to consistently guide the brush and brush positioner into a correct position to clean the next tube in a series. By using the protruding brush as a guide the operator can visually align and then insert the brush into the tube to be cleaned, thus minimizing errors in the alignment or positioning, and thus providing greater efficiency and a cost savings.

It is within the scope of the invention to utilize other control systems for the tube cleaning apparatus. For example, the pneumatic air pulses or signals issued from the control handle through air links to the air switches are illustrative embodiments and other specific, analogous means such as electric, mechanical or radio pulses or signals can be used through appropriate links to turn the drive motor “on” and “off” and to form part of the arresting gear described.