The present invention relates to a cleaning device for dry ice blasting of objects such as machines, walls and so on.

Dry ice blasting is a dry cleaning technique wherein dry ice particles arc directed at an object for cleaning using compressed air. Dirt is removed from the object as a result of such an impact of the dry ice on the object, a temperature difference between the dry ice and the object and/or forces exerted on the object as a result of the conversion of dry ice particles to gas. Devices known in practice for dry ice blasting make use of rotating discs to mix dry ice with compressed air. This requires a relatively costly device which is not very flexible.

The present invention has for its object to reduce or wholly obviate the existing problems.

The invention comprises for this purpose a cleaning device for dry ice blasting of objects, the device comprising:

a frame provided with a cylinder which comprises a piston provided with a number of piston chambers and arranged movably in the cylinder housing; and

a first air feed for feeding air to the cylinder;

a dry ice feed for feeding dry ice to the cylinder;

a discharge for discharging air with dry ice; and

control means for controlling the movement of the cylinder in the cylinder housing such that in use, during a stroke of the piston, a chamber is filled with dry ice from the dry ice feed and subsequently carried by air from the air feed to the discharge of the cleaning device.

By providing a cylinder the mixing of the dry ice with air, particularly compressed air, is performed using a preferably reciprocal stroke of the piston. Arranging or providing a volume in the piston in the form of a number of piston chambers, i.e. for instance 1, 2, 4, 6, 8 or other number of piston chambers, achieves that these chambers can be successively filled with dry ice from the dry ice feed and carried with air from the air feed to the discharge. From the discharge the dry ice mixed with air can then be blasted onto an object using for instance a spray gun or blasting lance.

The dry ice feed preferably comprises a hopper with which the dry ice can be carried into a piston chamber. The air feed is preferably connected operatively in use to a compressor for supplying compressed air. The compressed air blows out the piston chambers filled with dry ice, whereby the mixture of compressed air and dry ice is guided to the discharge of the device.

The control means provide for the movement of the piston in the cylinder housing whereby a reciprocal movement is realized. In a currently preferred embodiment the control means make use here of compressed air to move the piston by successively filling and emptying two cylinder chambers on either side of the piston, wherein the chambers are alternately filled and emptied. The desired piston movement is hereby realized in effective manner.

An object for cleaning is for instance a machine, installation, component of such a machine or installation, wall, ceiling or floor. Dry ice blasting of such objects has the advantage, among others, that an effective cleaning can be realized without addition of chemical additives or other cleaning agents and whereby a relatively effective cleaning is achieved.

An additional advantage of the use of a cylinder in the device according to the invention is that it can be set into and held in motion with a relatively low energy consumption relative to conventional dry ice devices. Not only the dry ice blasting as process but also the device as such can hereby be operated in effective and environmentally-friendly manner.

In an advantageous preferred embodiment according to the invention the cylinder further comprises a second air feed for feeding air.

Providing a second air feed achieves that a mixture of compressed air with dry ice is delivered in both directions of movement of the piston in the cylinder housing. In a currently preferred embodiment the dry ice feed is positioned here between the first and second air feeds, as seen in the direction of movement of the piston in the cylinder housing. Dry ice is hereby provided at the discharge of the device in effective manner.

In an advantageous preferred embodiment according to the invention the cylinder housing is provided with pressure relief openings for discharging pressure from the chambers prior to filling of the chambers with dry ice.

Pressure which may be present in the piston chambers can be discharged prior to filling of the piston chambers with dry ice by providing the cylinder housing with a number of openings. This prevents the dry ice being pressed back to the feed, and therefore not arriving with the compressed air at the discharge, as a result of pressure present in the piston chamber.

In an advantageous preferred embodiment according to the invention, the invention further comprises an air bypass connection for carrying air past the cylinder to the discharge.

The cylinder can be bypassed by providing a bypass connection, i.e. a bypass, for the air between the feed and discharge. This achieves a continuous flow of air to the discharge of the device at the spray gun or blasting lance such that air pulses are avoided and a continuous dry ice blasting process is possible.

In an advantageous preferred embodiment according to the invention the cylinder housing is provided with at least one detector for detecting the position of the piston in the cylinder housing.

The position of the piston can be detected in use by providing one, preferably two, detectors, for instance in the form of a reed contact, in the cylinder chambers. By placing the detectors preferably on or in the outer ends of the chambers it is detected whether the piston makes the full stroke and whether the control from the control means is therefore being performed correctly. The device according to the invention can hereby be controlled in effective manner, wherein a correct operation is realized. An additional advantage is that it is relatively easy to set the frequency of the piston, and thereby the number of dry ice portions processed per minute. An adjustable dry ice device is hereby obtained with which the quantity of dry ice used can be set and thereby adapted to the conditions and/or the object for cleaning.

In an advantageous preferred embodiment according to the invention the control means are configured to realize a number of strokes of the piston in the cylinder housing in the range of 0-500 strokes per minute, preferably 10-300 strokes per minute and most preferably 100-200 strokes per minute.

Through the adjustability of the cleaning device according to the invention a device is obtained which can be deployed in flexible manner and with which a dry ice blasting process can be applied in effective and flexible manner to a range of objects for cleaning. In a preferred embodiment the piston is provided with 6 or 8 piston chambers so that 6 or 8 portions of dry ice are provided at the discharge per stroke. This makes it possible to process about 90 kg of dry ice per hour, for instance in 600 (6 chambers and 100 strokes) to 1600 (8 chambers and 200 strokes) portions per minute.

In an advantageous preferred embodiment according to the invention the chambers of the piston are provided with rectangular inlet openings.

It has been found that the wear of piston springs/seals is reduced by providing rectangular inlet openings for the air inlet and/or the dry ice inlet to the cylinder. When passing such an opening the piston spring/seal will only be able to expand to limited extent and the force with which the spring/seal comes up against the edge of the opening will remain limited. This increases the lifespan of piston springs/seals, thereby increasing the availability of the device according to the invention.

In an advantageous preferred embodiment according to the invention the device further comprises a battery.

A so-called stand-alone device for which no mains voltage is required during use is obtained by providing a battery. This is possible in that the device according to the invention can be driven with a relatively limited power since the piston can be moved using less force compared to for instance the rotating discs of conventional devices. This is particularly advantageous in the case of installations wherein mains voltage, for instance 220 V, may not be used, such as in some furnaces.

In an advantageous preferred embodiment according to the invention the cylinder housing is provided with cylinder chambers provided with at least one sub-chamber positioned at the outer end of the cylinder with a reduced cross-sectional area and/or wherein the piston is provided at the outer end with at least one sub-chamber with a reduced cross-sectional area. The force exerted at the beginning of the stroke is limited to some extent by providing the outer end of the cylinder chambers in use with a sub-chamber with a reduced cross-sectional area. Alternatively or additionally, a sub-chamber can also be provided in the outer end of the piston. A better controllable movement of the piston in the cylinder housing can hereby be realized.

The invention further also relates to a method for dry ice blasting of objects, comprising of providing a cleaning device as described in the foregoing.

The stated methods provide the same effects and advantages as described for the device. Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawing, in which: - Figure 1 shows a view of the device according to the invention;

Figure 2 shows a view of the cylinder of figure 1 ;

Figure 3 shows a view of the cylinder housing of figures 1 and 2;

Figures 4A-B show views of the piston of the cylinder housing of figure 3; and

Figures 5 A-C show schematic views of the movement of the piston.

Dry ice device 2 (figure 1) comprises a frame 4 in which cylinder housing 6 is placed. In the shown embodiment frame 4 is provided with a number of uprights 9, girders 10 and connecting beams. For the sake of clarity the finishing plates on the outer side of frame 4 are not depicted in the shown embodiment.

Cylinder 6 (figure 2) is provided with a first air inlet 8 with a first feed 10, a second air inlet 12 with a second feed 14 which in the shown embodiment are connected operatively to a central air feed conduit 16, which is in turn connected operatively via valve 18 to a compressor (not shown). In the shown embodiment the dry ice is fed from hopper 20 provided with vibrating unit 21, via dry ice inlet 22 to the interior of cylinder 6.

The mixture of compressed air and dry ice leaves the interior of cylinder 6 via first outlet 24 with first discharge conduit 26 or via second outlet 28 with second discharge conduit 30. First discharge conduit 26 and second discharge conduit 30 are then combined to form central discharge conduit 32, which carries the mixture to the blasting lance (not shown). A first bypass 34 and second bypass 36 are further provided with which compressed air can bypass cylinder 6.

Cylinder 6 is provided at the outer ends of cylinder housing 38 with air connections 40 for pneumatic control of cylinder 6. Housing 38 is also provided with a number of air outlets 42 (figure 3) for discharging pressure.

Piston 44 is arranged in cylinder 6 (figures 4A and B). Piston 44 is provided with a number of piston chambers 46, wherein chambers 46 are separated airtightly using piston springs (not shown) provided in grooves 48. In the shown embodiment piston 44 is provided with six chambers 46. It will be apparent to the skilled person that a different number of chambers 46 is likewise possible according to the invention. Piston 46 is also provided with a number of sub-chambers 50 for reversing the direction of movement of piston 46 in controlled manner.

Piston 46 (figures 5A-C) moves through a stroke length during use by controlling valves 52. The end position of piston 46 is detected with reed contact 54 and magnet 56 on piston 46. Air is carried alternately into first cylinder chamber 58 and second cylinder chamber 60 using valves 52.

In the shown embodiment frame 4 is provided in the form of a cube with a length of the edges of about 525 mm. The length of cylinder housing 38 amounts to about 420 mm, with an internal diameter of about 40 mm. The length of piston 44 amounts to about 280 mm, with a stroke length of about 135 mm. Piston chambers are about 12 mm wide and provided at a mutual centre- to-centre distance of about 27 mm. It will be apparent to the skilled person that other dimensions are likewise possible according to the invention, for instance subject to the specific application and the desired quantity of dry ice processed per minute.

For the purpose of cleaning objects with device 2 the compressor is activated, whereby in the shown embodiment piston 44 can be set into motion by controlling valves 52. The correct operation can be monitored using reed contacts 54 arranged in the outer ends of cylinder chambers 58, 60.

The compressor is also used to supply compressed air to first and second feeds 8, 12. As soon as a piston chamber 46 is located in front of the dry ice inlet 22, dry ice will be carried into chamber 46. Through further movement of piston 44 the piston chamber is closed and moved further to air inlet 8, 12 and the associated outlet 24, 28. In this position the compressed air presses the dry ice out of piston chamber 46 to outlet 24, 28 and further to finally the blasting lance (not shown). As soon as piston 44 has arrived at the end of the stroke, this is detected by reed contact 54, 56. The control for piston 44 is regulated such that the direction of movement of piston 44 reverses and moves in the opposite direction. Use is made here in the shown embodiment of a controlled reversal with sub-chambers 50.

Device 2 is optionally provided with a display screen which shows for instance the strokes per minute of piston 44 and the quantity of processed dry ice in kg/minute. The display is preferably combined with setting options for setting a number of parameters of device 2, such as the number of strokes per minute and the pressure in feed conduit 16 and/or cylinder chambers 58, 60. It is possible here to combine the settings with the display via a touchscreen.

The present invention is by no means limited to the above described embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.