[0001] The invention relates to an apparatus for blasting dry ice comprising a compressed
air supply, an ice pellet supply, a mixer for mixing ice pellets and compressed air
and an outlet to which a blasting pistol can be connected, which mixer comprises a
disc, rotatably disposed between two non-rotatable plates, and wherein the compressed
air supply and the ice pellet supply each debouch in a first of the non-rotatably
disposed plates, and wherein the outlet connects to the oppositely disposed second
non-rotatable plate, and wherein the rotatable disc has one or several holes which
during rotation of the disc alternatingly align with the ice pellet supply on the
one hand and the compressed air supply and the outlet on the other hand, wherein the
compressed air supply has at least two outlets in the first non-rotatable plate.
[0002] Such an apparatus is known from the Dutch patent NL-C-1015216, and is used for blasting
solid frozen carbon dioxide granules, also called pellets, with great force onto a
surface to be cleaned.
[0003] It is the object of the invention to improve the known apparatus such that a more
powerful and more even blast is obtained. To this end the apparatus according to the
invention is characterised, in that the outlet is provided with at least two inlet
openings in the second non-rotatable plate, arranged in pairs opposite to the outlet
openings of the compressed air supply in the first non-rotatable plate, so as to form
through-passages when the hole or holes in the disc are aligned with the outlet openings
of the compressed air supply.
[0004] Surprisingly, it has been shown that by doubling the number of inlet openings of
the outlet, a dry ice blast twice as powerful is produced, while the amount of ice
pellets supplied is the same as with an apparatus of the prior art. A further increase
of the number of inlet openings of the outlet will even better this result. Referring
to the foregoing, the person skilled in the art will be able to choose the number
of inlet openings, so that a further explanation with regard to its implementation
is not necessary.
[0005] A further advantage obtained with the apparatus according to the invention is that
the blast is not only more powerful but also more even and free of pulsation in the
discharged dry ice blast.
[0006] The above-mentioned advantages are achieved while maintaining the favourable properties
of the apparatus known from the cited prior art. In brief these advantages are as
follows.
[0007] A small amount, from 1m
3/min., of compressed air enables the apparatus according to the invention to produce
a powerful blast at a dry-ice consumption ranging from only 5 kg/hour up to a maximum
of 40 kg/hour.
[0008] When in use, the apparatus according to the invention produces a sound pressure of
approximately 79 dB(A) at a standard operating pressure of 5 bars.
[0009] The working performance of the apparatus according to the invention is further advanced
by the disc being provided with a series of holes positioned at regular distances
from each other and equidistanced from the centre of the disc.
[0010] The invention will now be further elucidated with reference to the drawing of a non-limiting
exemplary embodiment of the apparatus according to the invention.
[0011] The drawing shows in:
- Fig. 1 a schematic cross section of the active components of the apparatus according
to the invention.
- Figs. 2 and 3, respectively, a cross-section of the non-rotatable upper plate and
lower plate of the apparatus according to the invention.
[0012] Identical reference numbers in the figures refer to similar components.
[0013] Referring first to Fig. 1 showing the active components of the apparatus according
to the invention. These include a dual compressed air supply 1 generally connected
to a common compressed air source (not shown), an ice pellet supply 2 embodied as
a hopper, a mixer 3, 4, 5 for mixing the ice pellets and compressed air, and an outlet
6 to which a blasting pistol can be connected. The mixer 3, 4, 5 comprises a rotatable
disc 5 disposed between non-rotatable plates 3 and 4. As can be seen in the figure,
both the compressed air supply 1 and the ice pellet supply 2 each debouch in one of
the non-rotatably disposed plates 3, 4, in the case illustrated this is the upper
plate 3. These outlet openings are clearly shown in Fig. 2 carrying the reference
numbers 1', 1'' and 2', respectively.
[0014] Referring partly also to Fig. 3, the other non-rotatably disposed plate, i.e. the
lower plate 4, is provided with two inlet openings 6' and 6" for the outlet 6. In
a manner quite clear to the person skilled in the art and therefore not further illustrated
in the drawing, the rotatable disc 5 is provided with one or several holes which during
rotation of the disc 5 alternatingly align on the one hand with the ice pellet supply
2 and on the other hand with the compressed air supply 1 and the outlet 6. As clearly
shown in connection with Fig. 2 and Fig. 3, the inlet openings 6' and 6" of the outlet
6 are disposed in pairs in the extended direction of the outlet openings 1' and 1''
of the compressed air supply 1, such that when the hole or the holes align with the
outlet openings 1', 1'' of the compressed air supply 1 they form through-passages.
In a manner that is obvious to the person skilled in the art, the disc 5 is preferably
provided with a series of holes at regular distances from one another and equidistanced
from the centre of the disc, so that when the disc is being rotated, such a through-passage
can be realised at high frequency.
[0015] Both Fig. 1 and Fig. 2 show that the compressed air supply 1 comprises two outlet
openings 1' and 1'' positioned diametrically in relation to one another. In this way
the compressed air load on the rotatable disc is symmetrical, allowing it to rotate
with the least possible friction between the non-rotatably disposed plates 3 and 4.
Fig. 1 further shows that the non-rotatably disposed plates 3 and 4 are fixed in relation
to one another by means of fixing pins 7. These pins further serve to fasten the plates
3 and 4 to each other. The pins 7 are further provided with spring rings 8 exerting
a slight upward pressure that pushes the non-rotatably disposed plates 3 and 4 toward
each other, so as to avoid leakage loss between these non-rotatable plates 3 and 4
and the rotatable disc 5. Fig. 1 further schematically shows that the rotating disc
5 is coupled with an air-operated engine 9. In this connection the Figs. 2 and 3 show
slots 10 provided in the upper plate 3 and the lower plate 4, for venting excess driving
air. The apparatus according to the invention produces an excellent, constant blast
that is virtually free of pulsation.
1. An apparatus for blasting dry ice comprising a compressed air supply (1), an ice pellet
supply (2), a mixer (3, 4, 5) for mixing ice pellets and compressed air and an outlet
(6) to which a blasting pistol can be connected, which mixer (3, 4, 5) comprises a
disc (5), rotatably disposed between two non-rotatable plates (3, 4), and wherein
the compressed air supply (1) and the ice pellet supply (2) each debouch in a first
of the non-rotatably disposed plates (3), and wherein the outlet connects to the oppositely
disposed second non-rotatable plate (4), and wherein the rotatable disc (5) has one
or several holes which during rotation of the disc (5) alternatingly align with the
ice pellet supply (2, 2') on the one hand and the compressed air supply (1) and the
outlet (6) on the other hand, wherein the compressed air supply (1) has at least two
outlets (1', 1'') in the first non-rotatable plate (3), characterised in that the outlet (6) is provided with at least two inlet openings (6', 6'') in the second
non-rotatable plate (4), arranged in pairs opposite to the outlet openings (1', 1'')
of the compressed air supply (1) in the first non-rotatable plate (3), so as to form
through-passages when the hole or holes in the disc (5) are aligned with the outlet
openings (1', 1'') of the compressed air supply (1).
