This invention relates to blast apparatus.
BACKGROUND TO THE PRESENT INVENTION
The invention is concerned with blast guns for discharging a mixture
of abrasive material and fluid, for example air, whereby surfaces may be polished,
scoured or mechanically plated. As used herein the term abrasive material' includes
In our patent specification No. 2065514 B we have disclosed a blast
gun comprising a body having an internal mixing chamber, a discharge nozzle, and
internal passageways for introducing into the mixing chamber separate flows of
air and water from tubular inlets which are connected in use to supply hoses. When
a series of discharge nozzles are required several of these blast guns can be mounted
alongside one another, but a problem with such an assembly of blast guns is that
there is a large number of external hoses which all need to be connected separately
to the air and water supplies.
SUMMARY OF THE PRESENT INVENTION
According to the present invention a blast gun assembly comprises
a plurality of body sections which are clamped in face to face contact with one
another, at least some of the body sections being In the form of head sections
carrying respective discharge nozzles, the sections being formed with duct means
for supplying in use the nozzles with separate flows of abrasive material and the
duct means extending through the mating faces of the adjacent sections to provide
communication between the sections.
The provision of duct means communicating with the adjacent body section
avoids the need for each discharge nozzle to be provided with individual hose
Preferably each head section comprises an internal mixing chamber
and passageways for introducing separate flows of the abrasive material and fluid
into a common end of the said mixing chamber.
The blast gun assembly may comprise an alternating arrangement of
head sections carrying discharge nozzles being separated by sections without discharge
nozzles acting as spacer sections.
Preferably an end section comprises duct means for the transportation
of abrasive material and fluids between the separate duct means of one head section.
Preferably the duct means comprises circular holes with axes of which
are perpendicular to a flat plane of the section.
Preferably the blast gun assembly is provided with a supply connection
and a return connection for the abrasive material.
Preferably for at least some of the head sections the common axis
of the circular holes used for conveying the abrasive material to the mixing chamber
is in alignment with the axis of the supply connection. Also preferably for at
least some of the head sections the common axis of the circular holes used for
introducing the abrasive material is in alignment with the axis of the return connection.
The provision of the abrasive material being conveyed from the supply
connection and the return connection provides a consistent supply of abrasive
material and fluid to each nozzle whereby a uniformity of blasting results.
Preferably the blast gun assembly comprises an air supply connection.
Preferably the blast gun assembly is provided with at least one fluid
rinse supply connection. Also preferably the blast gun assembly is provided with
at least one air drying supply connection.
Preferably the head sections comprise fluid rinse nozzles.
Preferably the head sections comprise air drying nozzles.
Preferably the head section is made out of abrasive-resistant material.
Also preferably the head section is made out of a resilient plastics material,
eg a urethane elastomer.
Preferably the spacer section is made out of abrasive-resistant material.
Also preferably the spacer section is made out of a resilient plastics
material, eg a urethane elastomer.
Preferably the blast gun assembly is made out of abrasive-resistant
Also preferably the blast gun assembly is made out of a resilient
plastics material, eg a urethane elastomer.
BRIEF DESCRIPTION OF THE DRAWINGS
The various aspects of the invention will now be further described,
by way of example only, with reference to the accompanying drawings wherein:
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
- Figure 1 is a schematic view of a blast gun assembly in accordance with
- Figure 2 is a side view on a larger scale of a head section of the assembly
of Figure 1,
- Figure 3 is a side view of a spacer section of the assembly of Figure
- Figure 4 is a perspective view of a return end section of the assembly
of Figure 1.
With reference to Figure 1 a blast gun assembly 1 of cylindrical form
is shown thereby. The assembly 1, which is for discharging a pressurised mixture
of abrasive material (in slurry form) and air, and for discharging rinsing and/or
drying fluid, comprises a plurality of identical head sections 2 and identical
spacer sections 3, a supply end section 4 and a return end section 5, all held
together, by tie rods 36, in face to face engagement.
The supply end section 4 comprises a plate 10 having substantially
flat inner and outer faces. Projecting from the outer face of section 4 is a tubular
slurry supply connection 6, a tubular slurry return connection 7, a tubular blast
air supply connection 8 and two tubular fluid rinse/air dry supply connections
9. Respective supply tubes are attached in use to the different connections 6 to
9. The connections 6 to 9 connect with ducts in the plate 10 in the form of circular
holes having axes perpendicular to the plane of the plate 10.
Figure 2 shows one of the head sections 2 comprising a circular disc
28 having substantially flat side faces, and formed with a radial bore 13' the
inner end of which provides a cylindrical mixing chamber 11, duct means comprising
internal passageways 12 and 13 for introducing separate flows of an abrasive material
and air into the mixing chamber 11, and a mixture discharge (blast) nozzle 14 demountably
disposed within the outer part of bore 13'. The substantially flat side faces may
have raised sections protruding from the surface. The said raised section may house
resilient O-rings in abutment with the adjacent section, the O-rings surrounding
the respective holes in the sections.
The passageway 13 is disposed in substantial alignment with an axis
15 of bore 131. Passageway 12 is disposed at an angle to the axis 15
of approximately 60°.
Mixture discharge nozzle 14 is of tubular form and has a convergent
entry portion 16 merging with a substantially parallel outlet portion 17. Such
nozzles are as described in patent specification No. GB 2065514. The nozzle 14
is prevented from being blown out of the disc 28 by stop means comprising an abutment
formed by an inwardly extending flange portion 18. The flange portion 18 defines
a frusto-conical outlet orifice. The disc 2, being resilient and deformable, allows
the nozzle 14 to be replaced, when necessary, by distortion of the disc 2, whereby
a nozzle can be removed from or inserted, into bore 131.
The duct means also comprises a plurality of circular holes 19, 21,
22, 23 and 24 all of which have their axes perpendicular to the discos flat faces
and extend through the full thickness of the disc 2.
Passageway 12 connects hole 19 with the mixing chamber 11. Projecting
from the bore walls of holes 19 and 22 are sector-shaped baffles 20. The baffles
20 comprise structure operable to create fluid flow turbulence within the duct
means formed by the aligned holes 19, 22.
Passageway 13 connects the hole 21 with the mixing chamber 11.
Protruding from the edge of the disc 28 are two nozzles 26. Internal
passageway 25 connects holes 23 with nozzle 26 mounted symmetrically with respect
to axis 15.
Figure 3 shows a spacer section 3 comprising a circular disc 27 having
substantially flat side faces. The same reference numerals have been used in Figure
3 for holes corresponding to those in head sections 2. The circular disc has a
plurality circular holes 19, 21, 22, 23 and 24 the locations of which correspond
to the holes in the head section 2 and their axes are all perpendicular to the
flat faces of disc 27. the holes 19 to 24 all extending through the full thickness
of disc 27.
When head sections 2, spacer sections 3 and end sections 4 and 5 are
assembled as shown in Figure 1, holes 24 (not shown in Figure 1, but in Figures
2, 3 and 4) are aligned to receive stainless steel tie rods 36 with securing nuts
37 and washers 38. The axes of the tie rods are shown at 35.
The axis of the air supply connection 8 is then in alignment with
the axis of the circular holes 21, and the axis of the fluid rinse/air dry nozzles
9 is in alignment with the axis of the circular holes 23.
The head sections 2 are substantially symmetrical about the axis 15
with the exception of the passageway 12. The axes of the holes 19 are aligned
respectively with the slurry supply connection 6 and with the slurry return connection
The aligned holes 19, 20, 21 and 23 form four ducts which extend for
substantially the length of the blast gun assembly. As shown in Figure 4, the
return end section 5 is formed with two transverse pockets 30, 31. Pocket 30 providing
for a return flow from hole 22 to hole 20 in the adjacent section 2, and optional
pocket 31 connecting holes 23 in that section 2 when the holes 23 are to convey
the same fluid.
It will be appreciated that it is possible to provide spacer sections
3 of different thicknesses in order to provide a different spacing of the discs
2 and accordingly of the nozzles 14.
In use the air supply connection 8 is constantly supplied with air
to keep the circular holes 21 and passageways 13 pressurised. This helps to stop
slurry from entering the aforementioned holes and passageways.
The outer circular shape of the blast gun helps to prevent the build-up
of abrasive material on the outside of the gun, as there is a lack of flat surfaces
for the material to accumulate.
Typically the assembly of Figure I comprises up to about fifteen head
sections 2 before the flow through the conduits connected to connections 6, 7
becomes restricting. In order to provide more head sections 2, in a modified assembly,
a supply end section 4 is provided at both ends of the stack, and a special centre
section is provided at the midpoint of the stack, the special centre section being
provided in the opposed side faces thereof with a respective pocket similar to
the pocket 30 of Figure 4.
In a yet further modification, there are supply end sections 4 at
both ends of the stack, some fluids being supplied through one of the end sections
4, whereas other fluids are supplied through the other end section 4.