WO1999015285A1

WO1999015285A1 - Ultrasonic cleaning and vibrating conveyer therefor

Info

Publication number: WO1999015285A1
Application number: PCT/GB1998/002853
Authority: WO
Inventors: Duncan John Mcdonald
Original assignee: Maysonic Ultrasonics Limited
Priority date: 1997-09-20
Filing date: 1998-09-21
Publication date: 1999-04-01
Also published as: GB9719961D0; AU9174598A

Abstract

Apparatus for cleaning elongate workpieces (9) such as shafts, tubes or rollers comprises an ultrasonic cleaning bath having an inlet, an outlet and a conveyor for successively transporting the workpieces through the bath. The conveyor includes first (6A) and second (66) elongate transport members forming a V-shaped trough for receiving the workpieces, each of the transport members having a multiplicity of upstanding bristle members (7) and being arranged to be vibrated in a reciprocal manner such that a workpiece supported thereon advances along the length of the transport members.

Description

ULTRASONIC CLEANING AND VIBRSTING CONVEYER THEREFOR

The present invention relates to ultrasonic cleaning, and apparatus therefor and more specifically to the ultrasonic cleaning of machine parts such as shafts, tubes and rollers etc.

Machine parts or other workpieces (such as, for example, bearing rollers), can often become contaminated with polishing dust, oils and general debris, and are typically cleaned by a high pressure jetting system. Bearing rollers, for example, generally must be cleaned at two stages during a manufacturing process, namely: a) at a post grinding and pre-polishing stage; and b) at a post polishing, pre- inspection stage.

Ultrasonic cleaning generally comprises several successive stages. Machine parts can be transferred from one stage of the cleaning operation to the next. In a production line, this transfer can be carried out automatically, but it is generally necessary to gather a batch manually before moving on to a further stage. Also, when components are cleaned as a batch, mechanical damage to the components is common because they tend to collide with one another. Other disadvantages include mechanical unreliability of the parts due to inadequacy of cleaning, rinsing and drying. The parts then require frequent replacement which can prove costly and time-consuming.

It is the aim of the present invention to provide an automated ultrasonic cleaning process which can alleviate some of the aforementioned problems .

Bearing rollers form part of an assembly known as a bearing comprising rollers, cage and inner and outer case. The present invention is especially applicable for use with bearing rollers, but is equally applicable to ultrasonic cleaning of various other elongate machine parts (hereinafter referred to as workpieces) . The present invention is broadly concerned with workpiece cleaning apparatus, which comprises: (i) an ultrasonic cleaning bath; (ii) an inlet for permitting a succession of workpieces to enter the bath; (iii) an outlet for permitting the succession of workpieces to exit the bath; and (iv) conveyor means for conveying the succession of workpieces, in order, to the inlet, to traverse the bath while immersed therein, and then through the outlet to a recovery zone.

According to the invention, the conveyor means comprises :

(a) a first elongate transport member;

(b) a second elongate transport member inclined relative to the first member with the axes of the members substantially parallel to one another, the transport members being arranged to support a workpiece in the angle between the transport members, each of the transport members having a workpiece support surface comprising a multiplicity of upstanding bristle members; and

(c) means for reciprocatingly vibrating each of the transport members such that an elongate workpiece supported thereon advances along the length of the transport members .

It is a preferred feature of the present invention that the transport members comprise stainless steel.

The upstanding bristle members (which may themselves be of stainless steel) are preferably approximately 3 to 10mm in length.

Bearing rollers and other workpieces of a variety of sizes (typically ranging from 13 to 100mm diameter) can traverse the cleaning bath in a sequential fashion in the apparatus according to the invention; this permits the ultrasonic cleaning of a succession of workpieces in a substantially continuous manner . The present invention further comprises a method of ultrasonically cleaning a workpiece, which comprises advancing the workpiece through an ultrasonic cleaning station while the workpiece is jointly supported by a first elongate transport member and a second elongate transport member inclined relative to the first transport member, with the axes of the members substantially parallel to one another, wherein the transport members each have support surfaces comprising a multiplicity of upstanding bristle members, and wherein the workpiece is advanced through the ultrasonic cleaning station by reciprocal vibration of the transport members.

The transport members used in the apparatus and method according to the invention may enable the workpieces to proceed silently and substantially smoothly along the length of the transport members whilst (in the case of substantially round workpieces) the workpieces simultaneously rotate about their longitudinal axes. Substantially the entire surface of each of the workpieces can be subjected to ultrasonic cleaning thereby. This may eliminate the need to subject the workpiece to more than one ultrasonic cleaning operation, thereby providing better production rates than previously used methods, and providing an overall more efficient process (which may, as indicated above, be operated in a continuous manner) .

Furthermore, each workpiece may be individually cleaned in the method according to the invention, which alleviates the problems associated with batch cleaning. Each workpiece may be cleaned to a higher standard according to the invention than when carrying out batch cleaning.

In addition, the method according to the invention may be integrated with a manufacturing or forming process, and thereby avoid the need to gather or collect workpieces at each manufacturing stage before moving on to the next stage.

The ultrasonic cleaning bath may be part of an ultrasonic cleaning station, which may comprise a plurality of different stages or zones, which generally include a washing stage or zone, a rinse stage or zone, a dewatering stage or zone, and a drying stage or zone. Each stage or zone is preferably segregated from the adjacent stage or zone thereby preventing transfer of liquid from one stage or zone to the next.

According to the present invention, each stage in an ultrasonic cleaning station used according to the invention may be separated from the adjacent stage by means of weirs (typically of polypropylene) , air knives or the like. These weirs and air knives facilitate "sealing" of the respective stage, to substantially prevent liquid loss or leakage from a respective stage into an adjacent stage.

It is preferred to provide a liquid seal with an aperture of up to approximately 100mm and 150mm head of liquid after a respective stage.

When a washing stage is employed, washing may be carried out with a detergent or the like. A different or the same detergent may then be sprayed onto the workpieces during a subsequent rinse stage. A dewatering oil can be sprayed onto the rollers during the dewatering stage. This may help prevent corrosion of the workpieces, the oil being generally applied as a low pressure flush, followed by warm air drying.

The drying stage may be employed to ensure that the cleaned workpieces are substantially liquid-free or condensation- free . The drying stage is generally carried out by means of fan jets which serve to blow air over the workpieces.

It is important to control spent air from the drying stage, particularly if oil is present as a mist. According to the present invention, the air temperature may be controlled by means of a blower which is arranged to convert some of its work energy into heat instead of into air compression.

Various methods may be used to seal the ultrasonic bath, for example, a spray directed at a specific angle and location toward the inlet and outlet can substantially reduce liquid flow requirements to maintain the ultrasonic cleaning bath in flooded condition. Liquid flow should generally be minimised as much as possible, because large flows sometimes have the effect of reducing the efficiency of the ultrasonic cleaning apparatus and method according to the invention. The apparatus according to the invention may include a transducer with geometric construction which helps in the even and efficient focussing of the ultrasonic pressure waves onto the workpiece to be cleaned.

Each stage of the overall ultrasonic cleaning method according to the invention typically lasts up to approximately 5 minutes. The cleaning stage is unlikely to exceed 40 seconds although the time spent by any one workpiece within the entire process may be as long as 5 minutes. However, the cleaning stages and treatment times can be altered depending on the nature of the workpiece to be cleaned.

The flow of water during the washing stage is typically controlled by a manual valve and monitored by a pressure sensor or the like.

The rinse stage may involve a spray wash using at least one fan jet nozzle from a manifold distributor. Again, the flow control can be by a manual valve and can be monitored by a pressure sensor, the jet pressure being typically controlled by a valve . The rinse stage can involve the use of the same or a different detergent to that used during the wash stage. The temperature at which the wash and rinse stages are carried out may be the same or different.

The dewatering stage is essentially the same as the rinse stage except that the detergent used during the rinse stage may be replaced by a dewatering oil . This stage can take place in a dewatering tank. The temperature of the liquid in the tank can be controlled by a thermostat and is generally maintained at about 20°C (or ambient temperature) .

The drying stage can involve use of an air pump and fan jets which may be fed from a manifold distributor. The air supply used is generally filtered atmospheric air.

It is preferred that all liquids are controlled by manually set valves and switched by servo valves. It is preferred that the dewatering stage includes a pump and control . The pump and blower may be controlled by operators and switched automatically as required. The transport members, when caused to vibrate, can initiate movement of a workpiece placed on the transport members and also cause initiation of the ultrasonic cleaning process. The transport members may be made to vibrate in the method according to the invention by means of a driver or vibrator.

The speed and amplitude at which the transport members are made to vibrate can be adjusted, thereby controlling the speed at which the workpieces proceed along the conveyor and the time they are subjected to ultrasonic cleaning.

The individual stages of the ultrasonic cleaning process may be segregated. An advantage of the present invention is that oil mist discharge may be substantially eliminated and the passage of liquid along the transport members may also be substantially eliminated.

The washing medium, in the ultrasonic bath, which typically comprises water, can, if necessary, be heated (preferably to a maximum of 50°C) . If the water is heated, then a secondary water rinse stage will generally be required.

Different chemicals and different temperatures can be used for the different stages of the ultrasonic cleaning method according to the invention. Secondary storage facilities can be used to contain the liquids. These can be linked to factory primary supplies. The liquids which are provided to the cleaning stages may be treated by filtration, heating or chilling, and replenishment, etc. within the plant.

Although the apparatus according to the invention has been described for ultrasonic cleaning, one can also apply other treatments to workpieces traversing the apparatus, for example, chemical treatments etc.

The invention will now be described, by way of example only, with reference to the accompanying drawings, which are given by way of illustration only. Referring to the drawings: Figure 1 is a schematic representation of the different stages of an ultrasonic cleaning method according to the invention;

Figure 2 is an end view of a conveyor for use in apparatus according to the present invention;

Figure 3 is a schematic representation of a weir assembly for use in apparatus according to the present invention;

Figure 4 is a representation of the driver assembly in apparatus according to the present invention;

Figure 5 is a representation of a wash stage in a method according to the present invention;

Figure 6 is a representation of the wash, rinse and dewater stages in a method according to the present invention;

Figure 7 is a schematic representation of a dryer suitable for use in apparatus according to the present invention; and

Figure 8 is a schematic representation of a plant assembly in apparatus according to the invention.

Referring initially to Figure 1, there is shown a schematic representation of an ultrasonic cleaning method comprising a wash stage 1, a rinse stage 2, a dewatering stage 3, a drying stage 4 with the sequence of operations taking place in a left to right direction 5.

Figure 2 is an end view of a conveyor and illustrates a pair of elongate transport members 6a and 6b with a bristle finish 7, with the transport members positioned on a support block 8 and defining a V-shaped trough. The workpiece 9 to be cleaned is placed in the angle between the transport members 6a and 6b and excess liquid is allowed to pass through a drain 10 at the lowermost apex of the V-shaped trough.

Figure 3 is a representation of a weir assembly for use according to the invention, and illustrates the weir 11, a spray 12, a brush 13 and a flexible seal 14.

Figure 4 is a representation of a conveyor assembly illustrating the conveyor 15 being positioned on supports 16 and also partly supported by a vibrator 17. Figure 5 is a schematic representation of a wash stage, illustrating a section flooded with liquid 18 and a liquid drain 19 arranged to remove excess liquid, with the flooded sections being separated by a weir assembly 20.

Figure 6 is a schematic representation of the wash, rinse and dewatering stages, illustrating a distribution manifold 21 with attached sprays 22.

Figure 7 is a schematic representation of a dryer stage comprising a filter 23 to filter atmospheric air before the latter is passed into a blower 24, after which it reaches an air manifold 25 and is separated by air knives 26.

Figure 8 is a schematic representation of the plant assembly and illustrates the flooded section 27 and the wash, rinse and dewater stage 28 and the drying stage 29. Storage tanks for the wash liquid 30, rinse liquid 31 and dewatering liquid 32 are positioned adjacent one another; a frame 33 contains the assembly which is operated by a pump 34.

Claims

Claims :

1. A workpiece cleaning apparatus, which comprises:

(i) an ultrasonic cleaning bath;

(ii) an inlet for permitting a succession of workpieces to enter said bath;

(iii) an outlet for permitting said succession of workpieces to exit said bath;

(iv) conveyor means for conveying said succession of workpieces, in order, to said inlet, traversing said bath while immersed therein, and then through said outlet to a recovery zone, wherein said conveyor means includes:

(a) a first elongate transport member;

(b) a second elongate transport member inclined relative to said first member with the axes of said members substantially parallel to one another, each of said transport members having a workpiece support surface such that a workpiece can be supported in the angle between said transport members, each of said workpiece support surfaces comprising a multiplicity of upstanding bristle members; and

(c) means for reciprocatingly vibrating each of said transport members such that an elongate workpiece supported on said support surfaces advances along the length of said transport members .

2. Apparatus according to claim 1, wherein said transport members comprise stainless steel .

3. Apparatus according to claim 1 or 2, wherein said upstanding bristle members are approximately 3 to 10mm in length.

4. Apparatus according to any of claims 1 to 3 , wherein said ultrasonic cleaning bath is part of an ultrasonic cleaning station comprising a washing zone, a rinse zone, a dewatering zone and a drying stage .

5. Apparatus according to claim 4, wherein each said zone is separated from an adjacent zone by means of a weir or air knife .

6. Apparatus according to any of claims 1 to 5, wherein said means for vibrating is also arranged to cause ultrasonic cleaning in said bath.

7. A method of ultrasonically cleaning a workpiece, which comprises advancing said workpiece through an ultrasonic cleaning station while said workpiece is jointly supported by a first elongate transport member and a second elongate transport member inclined relative to the first transport member, with the axes of the members substantially parallel to one another, wherein the transport members each have support surfaces comprising a multiplicity of upstanding bristle members, and wherein the workpiece is advanced through said ultrasonic cleaning bath by reciprocal vibration of said transport members.

8. Method according to claim 7, wherein said cleaning station comprises a washing stage, a rinse stage, a dewatering stage and a drying stage.

9. Method according to claim 8, wherein said detergent is sprayed onto the workpieces during said rinse stage.

10. Method according to claim 8 or 9 , wherein a dewatering oil is sprayed onto the rollers during said dewatering stage.

11. Method according to any of claims 8 to 10, wherein said drying stage is carried out by means of fan jets which blow air over the respective workpieces.

12. Method according to any of claims 8 to 11, wherein each stage of the ultrasonic cleaning process lasts up to approximately 5 minutes. lS . Method according to any of claims 8 to 12, wherein the flow of water during the washing stage is controlled by a manual valve and monitored by a pressure sensor.

14. Method according to any of claims 8 to 13 , wherein said rinse stage comprises a spray wash using at least one fan jet nozzle from a manifold distributor.

15. Method according to any of claims 8 to 13, wherein said ultrasonic cleaning station includes spray means directed towards said inlet and/or spray means directed towards said outlet .