EP0505667A1

EP0505667A1 - A pneumatic drive means for a cleaning brush

Info

Publication number: EP0505667A1
Application number: EP91850300A
Authority: EP
Inventors: Karl-Henrik Enérus
Original assignee: BOILTEC AB
Current assignee: BOILTEC AB
Priority date: 1991-03-26
Filing date: 1991-12-03
Publication date: 1992-09-30
Also published as: SE9100903D0; SE466486B; SE9100903L

Abstract

A pneumatic drive means for propelling a cleaning brush through a tubular channel, comprising a long external casing (10) provided at one end with an attachment (16) for a cleaning brush and at the other end with a blast-air inlet (17) connectible to a blast-air hose. The drive means shows a plunger (24) displaceable therein arranged to cooperate with operating chambers (26, 27) located one on each side of the plunger (24) means being provided to cause the plunger (24) to move to and fro in said bore. The plunger (24) is therefor provided with at least one pair of longitudinal channels (28, 29) aligned with each other with outer ends facing away from each other and opening into one each of the two operating chambers (26, 27), and inner ends facing each other shaped in the form of seats (30, 31) for a valve body (32) which is movable to and fro between them in an intermediate space (33) in the plunger (24), said space communicating permanently with the blast-air inlet, and that the means is provided with at least one outlet opening (42, 43) for each operating chamber (26, 27) arranged in the casing (10) or in an element (42, 43) rigidly joined thereto, the plunger (24) being designed to alternatively close and expose said opening during its so and fro movement in the bore, the outlet openings (42, 43) pertaining to the different operating chambers (26, 27) being located at such a distance in relation to each other in the longitudinal direction of the means that only one operating chamber (26, 27) at a time is able to communicate with an outlet opening (42, 43).

Description

The present invention relates to a pneumatic drive means for propelling a cleaning brush through a tubular channel.
More specifically the invention relates to such a drive means of the type comprising a long external casing provided at one end with an attachment for a cleaning brush and at the other end with a blast-air inlet connectible to a blast-air hose and shaped with a longitudinal, cylindrical internal bore closed at both ends and containing a cylindrical plunger displacable therein and having two operating chambers located one on each side, means being provided to cause the plunger to move to and fro in said bore when blast air is supplied to the drive means via the blast-air inlet.
Previously known means of this type have been found in practice to have a number of drawbacks both as regards their design and their function.
First of all, the means required to cause the plunger to move to and fro as desired have been complicated. The plunger has usually also been spring-loaded. Furthermore, valve members in the means have been so shaped and arranged that they were easily subjected to wear and damage. Finally, the known means were relatively inefficient, nor could they usually be used to propel a cleaning brush in optional direction in a channel. However, since the channels to be cleaned by said brushes, such as boiler tubes or ventilation ducts, are often only accessible at one end, it is extremeley desirable to be able to use the drive means for propelling the cleaning brush in optional direction through a channel. The drive means must therefore be able to generate equally large surge forces in both directions.
In this connection it may be mentioned that the cleaning brush comprises an elongate central core provided with resilient, flexible bristles protruding at right angles to the core and being sufficiently long to ensure their being bent flexibly backwards when the brush is inserted into a channel, thereby permitting propulsion of the brush through the channel by the surge forces applied on the brush in one direction while effectively preventing the brush from moving in the opposite direction under the influence of the surface forces applied on the brush in other direction. However, reversal of the direction of propulsion of the brush can be achieved by subjecting the brush to sufficiently great tractive force, for instance with the aid of traction rope connected to the drive means, to cause the bristles to flexibly bend, their direction of inclination thereby being reversed so that they are inclined in the opposite direction from previously in relation to the brush's core.
The object of the invention is to provide an improved pneumatic drive means of the type described in the introduction which eliminates, or at least greatly reduces, the abovementioned drawbacks of the previously known means.
The means proposed for this purpose according to the invention is characterized primarily in that the plunger is provided with at least one pair of longitudinal channels aligned with each other with outer ends facing away from each other and opening into one each of the two operating chambers, and inner ends facing each other shaped in the form of seats for a valve body which is movable to and fro between them in an intermediate space in the plunger, said space communicating permanently with the blastair inlet, and that the means is provided with at least one outlet opening for each operating chamber arranged in the casing or in an element rigidly joined thereto, the plunger being designed to alternatively close and expose said opening during its to and fro movement in the bore, the outlet openings pertaining to the different operating chambers being located at such a distance in relation to each other in the longitudinal direction of the means that only one operating chamber at a time is able to communicate with an outlet opening.
A drive means constructed in this manner can be produced easily and at low cost. It eliminates the previous need for springs in the means, as well as substantially eliminating any risk of the valve members being subjected to any noticeable wear or damage. Furthermore, a high degree of efficiency can be obtained and the means can be constructed to produce at least substantially similar surge forces in both directions, thereby making it extremely suitable for use in propelling a cleaning brush in optional direction.
According to the invention said valve body may advantageously consist of a spherical ball. However, the valve body may also be of some other suitable shape.
With the object of permitting an increased flow of air from the blast-air inlet to the operating chambers the plunger may be provided with two or more pairs of longitudinal channels aligned with each other and distributed around the circumference of the plunger with a space between the two channels in each pair, and a valve body in said space. These pairs of channels may suitably be distributed uniformly around the circumference of the plunger to enable good balancing of the plunger and minimize the risk of it being subjected to unnecessary wear caused by asymmetry.
According to a preferred embodiment of the invention said space in the plunger can communicate with the blast-air inlet via a longitudinal air supply channel in a rod projecting into the bore from said other end of the casing and extending through a longitudinal bore in the plunger, said rod being provided with at least one air passage running transversely through the rod via which the air supply channel is in constant communication with said space by way of an air passage in the plunger running between the space and said bore in the plunger. This air passage in the plunger can suitably be formed by an inner peripheral groove in the plunger arranged in said bore which, when the plunger is provided with several pairs of longitudinal channels and with a corresponding number of spaces, can serve as a common air passage to all these spaces.
The valve seats arranged in the plunger can advantageously be formed by separately manufactured seat elements inserted in longitudinal cavities in the plunger. This simplifies manufacture of the valve seats and means that they can be manufactured from material which is particularly suitable for their intended function.
Preferably at least one of the two seat elements for a valve body is shaped as an externally threaded element which is screwed into a tapped, longitudinal hollow in the plunger. A seat element constructed in this manner enables the "stroke length" of the relevant valve body to be adjusted if necessary in order to adapt the means to a specific use.
The outlet openings cooperating with the operating chambers may be arranged in peripheral walls of these chambers. According to an alternative embodiment of the invention, however, said outlet openings may be arranged in the wall of a tubular element extending into the bore from the end of the casing provided with a brush attachment and through a longitudinal bore in the plunger, and communicating at the end nearest the brush attachment with outlet channels having their orifices at this end of the casing, the other end of the tubular element being closed. In this embodiment the air flowing out of the means can be directed towards parts of the channel wall immediately behind the cleaning brush which have been cleaned thereby, in order to blow away particles just detached from these walls by the brush.
Since, when cleaning certain types of channels, such as ventilation dicts, it is essential to avoid the risk of oil mist entering the treated channels from the compressor connected to the blast-air inlet, it may be advisable, at least if the means is intended to operate with relatively high pressure or under relatively high load to provide the plunger with peripheral seals located close to each end. This is particularly so at the outer peripheral surface of the plunger but may be justified even at the defining surfaces of any longitudinal bores arranged in the plunger by means of which the plunger is, as mentioned earlier, displaceably arranged on a rod or tube shaped element rigidly connected to the casing.
These seals may be formed by sealing rings of a material having low friction, e.g. polytetrafluroethylene, arranged in peripheral grooves in the plunger. Alternatively, however, they may consist of labyrinth seals arranged in the plunger.
To achieve the highest possible degree of efficiency in the drive means the plunger may be manufactured from a heavy metal or metal alloy, whereas the casing may consist at least primarily of a light metal or light metal alloy.
The invention will be described in more detail in the following with reference to the accompanying schematic drawings in which

Figure 1: shows a longitudinal section through a pneumatic drive means for a cleaning brush according to a first embodiment to the invention, selected by way of example,
Figure 2: shows a longitudinal section through a drive means according to a second embodiment of the invention, also selected by way of example, and
Figure 3: shows a section along the line III-III in Figure 2.

The means shown in Figure 1 comprises a long casing, generally designated 10, consisting of a cylindrical, tubular element 11 and two end pieces 14 and 15 screwed one into each internally tapped end of the element 11 and tightly joined thereto with the aid of sealing rings 12 and 13 respectively. The end piece 14 is provided at its outer end with a tapped dead hole 16 allowing it to serve as attachment for a cleaning brush, whereas the end piece 15 is provided with a hole 17 running centrally through it and serving as inlet for blast air. The hole 17 is provided with an outer, internally tapped portion by which it can be connected to a blast-air hose, and an inner portion with smaller diameter.
The end piece 15 is provided internally with a central, tapped bore 18 in which a clamping sleeve 19 with external threading is screwed to retain a rod 20 coaxially opposite the hole 17. This rod 20 has a radially protruding peripheral flange 21 by means of which it is clamped tightly to the end piece 15 with the aid of the clamping sleeve 19 and two sealing rings 22.
The space between the two end pieces 14 and 15 inside the tubular element 11 forms a cylindrical bore 23 for a cylindrical plunger 24. The plunger is provided with a longitudinal bore 25 running centrally through it, by means of which it is axially displaceable along the rod 20. An operating chamber 26 and 27, respectively, is arranged in the bore on each side of the plunger 24.
The plunger 24 is provided with two pairs of channels 28 and 29, running longitudinally and aligned with each other. Within each pair, the ends facing away from each other have their orifices in the two operating chambers 26 and 27, respectively, and the ends facing each other are shaped substantially conically to form seats 30 and 31, respectively, for a valve ball 32. This valve ball 32 can move to and fro between the two valve seats 30 and 31 in a space 33 in the plunger 24, said space communicating with the bore 25 by way of an inner peripheral groove 34 in the plunger.
According to Figure 1 the channels 28 and 29 and the valve seats 30 and 31 arranged at the ends of the channels that face each other are formed by separate, tubular elements 37 and 38, respectively, inserted in longitudinal cavities 35 and 36, respectively, in the plunger 24. It is assumed that at least the cavities 36 and elements 38 are threaded to permit adjustment of the distance between each pair of valve seats 30 and 31.
A central channel 39 runs longitudinally in the rod 20 and extends from the right end of the rod 20 in Figure 1, where it communicates with the hole 17 in the end piece 15 serving as blast-air inlet. At a point mid-way between the two end pieces 14 and 15 the rod 20 is provided with a broad recess 40 in its outer surface, produced by means of turning. Furthermore, within area of this recess 40 the rod is provided with a number of apertures 41 running radially and connecting the inner channel 29 in the rod 20 with the recess 40.
The channel 39 thus forms an air supply channel through which air can be supplied to the two spaces 33 in the plunger via the apertures 41 and recess 40 as well as to groove 34 in the plunger 24 which is movable within the area of the recess 40 upon displacement of the plunger along the bore 23.
42 and 43 designate two rows of holes running peripherally in the tubular element 11 of the casing 10 and forming outlet openings for each of the operating chambers 26 and 27, respectively. As can be seen in Figure 1, the two rows of holes are so arranged in relation to each other in the longitudinal direction of the means that only one operating chamber at a time can communicate with its outlet openings 42 or 43, repectively.
Close to each end the plunger 24 is provided with a peripheral groove in which a sealing ring 45 of a material having low friction, e.g. polytetrafluoroethylene, is arranged in order to achieve extra sealing between the bore 23 formed by the inner surface of the element 11 and the plunger 24.
The means described above operates in the following manner:
When blast air is supplied to the means through the blast-air inlet 17, it will be conveyed to the spaces 33 through the channel 39, apertures 41 and recesses 40 and 34. The two valve balls 32 will be brought into abutment with one or other of the valve seats 30 and 31, respectively. Which of these seats the valve balls will but is determined intially by in which of the two operating chambers 26 and 27 the pressure tends to build up fastest. Let us assume that the pressure build-up occurs fastest in the operating chamber 27 shown on the right in Figure 1. In this case the valve balls will be quickly brought into stable sealing abutment with the seats 30 located to their left. The pressure then increases as blast air is supplied quickly through the exposed channels 29 into the operating chamber 27, whereupon the plunger 24 will move to the left and cause compression of the air enclosed in the operating chamber 26. As soon as the plunger has moved far enough to the left to expose the righthand row of outlet openings 43, the pressure will be rapidly relieved in the operating chamber 27. The valve balls will consequently soon shift position due to the higher pressure in the operating chamber 26 achieved by compression of the air therein. Blast air thus starts to flow into this operating chamber through the channels 28. The plunger 24 will therefore shift its direction of movement and start to move to the right, continuing until the plunger exposes the outlet openings 42, thus relieving the pressure in the operating chamber 26. This in turn causes the direction of movement of the plunger to be reversed again.
As is evident from the above description of how the means functions, when the means is in operation the plunger 24 will execute an oscillating movement in the bore 23. A cleaning brush attached to the means will thus be subjected to surge forces in alternately one and then the other direction, thereby being propelled in the manner described earlier in optional direction in a channel in order to clean said channel.
The means shown in Figures 2 and 3 is in principle very similar in structure to the means shown in Figure 1. Components equivalent to those illustrated in Figure 1 have therefore been given the same designations as in Figure 1.
The means illustrated in Figures 2 and 3 also has two pairs of channels aligned with each other in the plunger 24 and having spaces between them, said spaces containing valve balls. These components are not, however, shown in detail in Figures 2 and 3. Thus only Figure 3 shows two of said channels, i.e. the two channels 29.
In this embodiment the rod 20 with air supply channel 39, and the air supply inlet, are located eccentrically. Diametrically opposite said rod a pipe 46 connected to the end piece 14, extends through a longitudinal bore 47 in the plunger 24 and is provided with outlet openings 42 and 43. This pipe 46 forms a transport channel for air conducted from the operating chambers 26 and 27, and communicates with two outlet channels 48 directed forwards and outwards in the end piece 14.

Claims

A pneumatic drive means for propelling a cleaning brush through a tubular channel, comprising a long external casing (10) provided at one end with an attachment (16) for a cleaning brush and at the other end with a blast-air inlet (17) connectible to a blast-air hose and shaped with a longitudinal, cylindrical internal bore closed at both ends and containing a cylindrical plunger (24) displaceable therein and having two operating chambers (26, 27) located one on each side, means being provided to cause the plunger (24) to move to and fro in said bore when blast air is supplied to the drive means via the blast-air inlet, characterized in that the plunger (24) is provided with at least one pair of longitudinal channels (28, 29) aligned with each other with outer ends facing away from each other and opening into one each of the two operating chambers (26, 27), and inner ends facing each other shaped in the form of seats (30, 31) for a valve body (32) which is movable to and fro between them in an intermediate space (33) in the plunger (24), said space communicating permanently with the blast-air inlet, and that the means is provided with at least one outlet opening (42, 43) for each operating chamber (26, 27) arranged in the casing (10) or in an element (42, 43) rigidly joined thereto, the plunger (24) being designed to alternatively close and expose said opening during its to and fro movement in the bore, the outlet openings (42, 43) pertaining to the different operating chambers (26, 27) being located at such a distance in relation to each other in the longitudinal direction of the means that only one operating chamber (26, 27) at a time is able to communicate with an outlet opening (42, 43).
A means as claimed in claim 1, characterized in that the valve body (32) consists of a spherical ball.
A means as claimed in claim 1 or 2, characterized in that the plunger (24) is provided with two or more pairs of longitudinal channels aligned with each other and distributed around the circumference of the plunger (24) with a space between the two channels (28, 29) in each pair, and a valve body (32) in said space (33).
A means as claimed in claim 3, characterized in that said pairs of channels (28, 29) are distributed uniformly around the circumference of the plunger (24).
A means as claimed in any of the preceding claims, characterized in that said space (33) in the plunger (24) communicates with the blast-air inlet via a longitudinal air supply channel (39) in a rod (20) projecting into the bore from said other end of the casing (10) and extending through a longitudinal bore in the plunger (24), said rod being provided with at least one air passage running transversely through the rod via which the air supply channel is in constant communication with said space by way of an air passage in the plunger running between the space and the said bore in the plunger (24).
A means as claimed in claim 5, characterized in that the plunger (24) is formed by an inner peripheral groove (34) in the plunger (24) arranged in said bore (25).
A means as claimed in any of the preceding claims, characterized in that the valve seats (30, 31) arranged in the plunger (24) are formed by separately manufactured seat elements (37, 38) inserted in longitudinal cavities (35, 36) in the plunger (24).
A means as claimed in claim 7, characterized in that at least one of the two seat elements (37, 38) for a valve body is shaped as an externally threaded element which is screwed into a tapped, longitudinal hole in the plunger (24).
A means as claimed in claim 7, characterized in that said outlet openings (42, 43) are arranged in peripheral walls of the operating chambers (26, 27) formed by the casing (10).
A means as claimed in any of claims 1-8, characterized in that the outlet openings (42, 43) are arranged in the wall of a tubular element extending into the bore from said one end of the casing (10) and through a longitudinal bore in the plunger (24) and communicating at the end nearest the brush attachment with outlet channels having their orifices at this end of the casing, the other end of the tubular element being closed.
A means as claimed in any of the preceding claims, characterized in that the plunger (24) is provided with outer peripheral seals (45) located close to each end.
A means as claimed in claim 11, characterized in that said seals (45) are formed by sealing rings of a material having low friction, e.g. polytetrafluoroethylene, arranged in peripheral grooves in the plunger (24).
A means as claimed in claim 11, characterized in that said seals (45) consist of labyrinth seals arranged in the plunger (24).
A means as claimed in any of the preceding claims, characterized in that the plunger (24) is manufactured from a heavy metal or metal alloy, whereas the casing (10) consists at least primarily of a light metal or light metal alloy.