EP3300836A1

EP3300836A1 - Apparatus for spraying an abrasive mixture towards a delicate surface for removing writings, drawings or graffiti therefrom

Info

Publication number: EP3300836A1
Application number: EP17193107.4A
Authority: EP
Inventors: Adolfo Cristanini
Original assignee: CRISTANINI SpA
Current assignee: CRISTANINI SpA
Priority date: 2016-09-28
Filing date: 2017-09-26
Publication date: 2018-04-04
Anticipated expiration: 2037-09-26
Also published as: IT201600097204A1; EP3300836B1

Abstract

An apparatus manually transportable by an operator for spraying an abrasive mixture (M) for removing writings, drawings or graffiti therefrom, towards a delicate surface (S). The apparatus can be used with means (5) for supplying air (G) and second means (7) for supplying water (H) and comprising an inlet port (15) fluidically connectable with the first air inlet means (5), at least one tank (21) for an abrasive powder (A), a first Venturi effect mixing chamber (31) having an outlet (34) for a first air (G) - abrasive powder (A) mixture. The apparatus further comprises at least one spray lance (51) manually operable by the operator, the apparatus comprising a second mixing chamber (55) having a third inlet (56) fluidically connected with the first outlet (34) for the inflow of the air (G) - abrasive powder (A) mixture, a fourth inlet (57) fluidically connectable with the second means (7) for supplying water (H) and an outlet (58) for the abrasive mixture(M) formed by water (H) and by the first air (G) - abrasive powder (A) mixture. The spray lance (51) further comprises at least one outlet nozzle (59) fluidically connected with the outlet (58) of the second mixing chamber (55) to spray the abrasive mixture (M) towards the delicate surface (S). In particular, the second mixing chamber (55) is arranged in the proximity of the outlet nozzle (59) so as to prevent the abrasive mixture (M) from depositing upstream of the second mixing chamber (55).

Description

Field of invention

The present invention is generally applicable in the field of apparatus for removing writings, drawings or graffiti from a surface and it particularly regards an apparatus for removing writings, drawings or graffiti from a delicate surface, such as for example the surface of a monument, an artwork or a historical building.
The invention also regards a system comprising such apparatus.

State of the Art

There are known apparatus for removing writings, drawings or graffiti from a delicate surface such as for example the surfaces of a historical building, an artwork, a monument or the like, the apparatus operating by spraying a liquid, generally water, and an abrasive, generally sand, towards the delicate surface.
In particular, known apparatus generally comprise a tank with a mixing chamber inside which the water and sand are mixed, a compressor for pressurising the mixture, and a spray device connected to the tank operable by the user to suitably direct the outflowing jet.
Such apparatus generally operate with high pressures and use a high grain size abrasive. Thus, the use thereof could damage the delicate surface to be cleaned, thus making the known apparatus particularly unsuitable for cleaning monuments, artworks or delicate surfaces.
Furthermore, in such known apparatus, the water and sand mixture tend to deposit inside the mixing chamber and more generally along the line for supplying the water and abrasive mixture, with the risk of damaging the apparatus and/or jeopardising the efficiency thereof.

Summary of the invention

An object of the present invention is to at least partly overcome the drawbacks illustrated above, by providing a transportable apparatus for spraying an abrasive mixture towards a delicate surface that is highly efficient and relatively inexpensive.
Another object of the invention is to provide an apparatus transportable by an operator for spraying an abrasive mixture towards a delicate surface.
Another object of the invention is to provide a transportable apparatus for spraying an abrasive mixture towards a delicate surface, capable of maintaining the surface in question intact.
Another object of the invention is to provide a transportable apparatus for spraying an abrasive mixture containing an abrasive with particularly small grain size towards a delicate surface.
Another object of the invention is to provide a transportable apparatus for spraying an abrasive mixture towards a delicate surface, that does not clog.
Another object of the invention is to provide a transportable apparatus for spraying an abrasive mixture towards a delicate surface, having high volume capacity and small overall dimensions.
Another object of the invention is to provide a transportable apparatus for spraying an abrasive mixture towards a delicate surface, that is particularly silent.
A further object of the invention is to provide a system for spraying an abrasive mixture towards a delicate surface, for removing writings or graffiti therefrom.
These and other objects to be further clarified hereinafter, are attained by an apparatus having one or more of the characteristics described, illustrated and/or claimed herein.
The dependent claims describe advantageous embodiments of the invention.

Brief description of the drawings

Further characteristics and advantages of the invention will be more apparent in light of the detailed description of a preferred but non-exclusive embodiment of the invention, illustrated by way of non-limiting example with reference to the attached drawings, wherein:

FIG. 1 is a schematic view of a system 1;
FIGS. 2 and 3 are axonometric views of an apparatus 10;
FIGS. 4 and 5 are enlarged schematic views of some details of the apparatus 10;
FIG. 6 is an enlarged schematic view of the spray lance 51 wherein the mixing chamber 55 is separated from the support portion 53 for cleaning and/or maintenance.

Detailed description of a preferred embodiment

With reference to the attached drawings, herein described is a system 1 for removing writings, drawings or graffiti from a delicate surface S by spraying an abrasive mixture M towards the surface S. The latter may for example consist in a surface of a wall, a partition, a historical building, a monument, an artwork, an archaeological site or the like.
The system 1 may thus comprise at least one apparatus 10 for spraying such abrasive mixture M. More in particular, the abrasive mixture M may comprise a gas, for example air G, an abrasive powder A, for example sand, and a liquid, for example water H. In particular, the air G, the abrasive powder A and water H may be suitably mixed to each other to form the abrasive mixture M as better explained hereinafter.
Thus, the apparatus 10 may exploit the synergistic action of air G, abrasive powder A and water H so as to obtain a high writings removal efficiency.
Suitably, the system 1 may comprise respective means 5 for supplying air G, means for supplying abrasive powder A and means 7 for supplying water H.
In particular, the supply means 5, 7 may comprise one or more ducts, tanks, compressors and/or pumps operatively connected to each other in a per se known fashion.
For example, as schematically illustrated in fig. 1, the means 7 for supplying water H may comprise a tank while the means 5 for supplying air G may comprise one or more ducts and a compressor for pressurising the air G.
Possibly, even though not shown in the attached figures, the means 7 for supplying water H may comprise one or more ducts configured to be connected to a normal water supply system.
Thus, the apparatus 10 may be configured in a manner such that the abrasive mixture M sprayed towards the delicate surface S has low pressure, for example a pressure below 3 bars, preferably below 2.5 bars.
Thus, this may enable maintaining the delicate surface S intact during writings, drawings or graffiti removal operations.
The means 5 for supplying air G may be configured to provide a flow rate of about 450 l/min of air G at a pressure comprised between 3 and 8 bars, while the means 7 for supplying water H may be configured to provide a flow rate of about 5 l/hr of water H at a pressure comprised between 2 and 4 bars.
The apparatus 10 may comprise at least one support structure 11, for example a sheet and/or tubular metal structure.
The support structure 11 may be transportable. To this end, the latter may comprise means 12 for the transportation thereof by an operator, for example wheels and/or handles.
The support structure 11 may suitably have small overall dimensions. In particular, the same could have weight and dimensions such to enable the transportation thereof. For example, it may have a weight less than 25 kg, a height less than 1 m, a width less than 0.3 m and a depth less than 0.4 m.
The apparatus 10 may also comprise at least one spray lance 51 for spraying the abrasive mixture M towards the surface S which may be operatively coupled with the support structure 11. Suitably, as better explained hereafter, the spray lance 51 may be fluidically connected with one or more means for supplying the abrasive powder A, air G and water H.
According to a particular aspect of the invention, better described hereinafter, the apparatus 10 may comprise a single inlet port 15 fluidically connectable to the means 5 for supplying air G and a single inlet port 16 fluidically connectable to the means 7 for supplying water H.
Furthermore, for example as shown in figures 2 and 3, the spray lance 51 may have a zone 52 graspable by the user to allow the latter to operate the former, preferably with only one hand.
Such characteristic may be particularly useful in case there arises the need to remove writings, drawings or graffiti from surfaces of environments that are narrow and/or difficult to access.
The support structure 11 may comprise at least one tank 21 which may be of the per se known type suitable to contain such type of abrasive powder A.
In particular, the latter may have a particularly small grain size, i.e. a grain size smaller than 1.5 mm, preferably smaller than 1 mm and even more preferably smaller than 0.5 mm.
The tank 21 may thus comprise a duct 22 for loading the abrasive powder A which may be fluidically connected with the means for supplying the same and at least one opening 23 for the exit of the abrasive powder A.
As schematically illustrated in fig. 4, the tank 21 may have an elongated shape, preferably substantially cylindrical, and it may have dimensions such to be arranged substantially vertically inside the support structure 11. For example, the tank 21 may have an internal volume of about 10 l.
Suitably, the tank 21 may comprise a lower discharge portion 23' which includes the opening 23 and a lower portion 22' which includes the duct 22 for loading the abrasive powder A.
In particular, the duct 22 for loading the abrasive powder A may be arranged in a manner such to remain at the upper zone of the support structure 11 in a manner such to be easily accessible by the operator to load the abrasive powder A thereinto.
Suitably, the loading duct 22 may comprise a closing element 29 configured to allow the loading of the abrasive powder A into the tank 21 and prevent it from exiting therefrom. For example, such closing element 29 may be a trapdoor or a check valve.
In order to form an air G and abrasive powder A mixture, the apparatus 10 may comprise a chamber 31 for mixing the air G and the abrasive powder A. In particular, the mixing chamber 31 may comprise at least one inlet 32 for the abrasive powder A and at least one inlet 33 fluidically connected with the inlet port 15, and an outlet 34 for the air G and abrasive powder A mixture.
It is thus clear that the opening 23 of the tank 21 may be fluidically connected with the inlet 32 of the mixing chamber 31, for example by means of a duct. Preferably, the lower discharge portion 23' of the tank 21 may be configured in a manner such to define a hopper which includes the opening 23.
As illustrated in fig. 4, the mixing chamber 31 may be arranged in proximity of the opening 23. Preferably, the mixing chamber 31 may be configured in a manner such that the opening 23 and the inlet 32 may substantially coincide.
In particular, the flow of air G in the mixing chamber 31 may promote the suctioning of the abrasive powder A from the tank 21 inside the same. In other words, the mixing chamber 31 may be configured in a manner such to mix the abrasive powder A and air G by means of the known "Venturi effect".
Furthermore, the tank 21 may be pressurised in a manner such to facilitate the outflow of the abrasive powder A therefrom and prevent the entry of foreign material. In particular, the apparatus 10 may comprise pneumatic means for pressurising the tank 21 which may include a duct 24 for the fluidic connection of the upper portion 22' of the tank 21 and of the inlet port 15.
Thus, during use, the inflowing air G may feed both the spray lance 51 and such pneumatic pressurisation means. The latter, in particular, may pneumatically force the closing element 29 of the loading duct 22 to close so as to prevent the exit of the abrasive powder A and the entry of foreign bodies through the loading duct 22.
According to another aspect of the invention, there may be provided for anti-packing means, i.e. means for preventing the packing of the abrasive powder A acting on the tank 21 and/or on the abrasive powder A to facilitate the outflow thereof towards the inlet 32 of the mixing chamber 31.
Such anti-packing means may be of the pneumatic type and may comprise a duct 35 fluidically connected with the inlet port 15 which may have an outlet 36 arranged on the discharge portion 23' in proximity of the opening 23.
Thus, the inflow of air G into such discharge portion 23' may possibly break the packing of the abrasive powder A and avoid the clogging of the inlet 32 thus facilitating the inflow of abrasive powder A into the mixing chamber 31.
The apparatus 10 may further comprise valve means 37 acting on the duct 35, to control the selective inflow of air G into the duct 35.
Such valve means 37 may be controllable by the operator. For example, there may be provided for a lever or knob 37' acting on such valve means 37 that can be gripped by the operator and arranged on the upper zone of the support structure 11 so as to be easily accessible to the operator.
Suitably, the valve means 37 may be configured in a manner such to allow the selective inflow of air G into the duct 35 even during the operation of the apparatus 10.
The pneumatic anti-packing means may further comprise vibrating means 25 acting on the tank 21 to move the latter so as to shake the abrasive powder A so as to avoid the packing thereof in the tank 21 and promote the outflow towards the opening 23 of the tank 21.
Such vibrating means 25 may be of the pneumatic type. For example, they may comprise one or more pneumatic pistons operatively connected with the tank 21. Suitably, the vibrating means 25 may thus comprise a duct 26 which may be fluidically connected with the inlet port 15 in a manner such that the air G promotes the action of the latter.
Furthermore, as shown in fig. 4, the vibrating means 25 may be arranged in proximity of the tank 21 in the support structure 11 so that the overall dimensions of the apparatus 10 are particularly small.
Possibly, there may be provided a silencing element for reducing the noise of such vibrating means 25.
Thanks to such characteristics, the vibrating means 25, and the apparatus 10 more in general, may be particularly silent.
In light of the above, the means 5 for supplying air G may thus be fluidically connected with the spray lance 51, with the tank 21, with the duct 35, with the inlet 32 of the mixing chamber 31 and with the vibrating means 25. In other words, in use, the air G flowing into the apparatus 10 may feed one or more of the latter.
Preferably, all the latter may be fluidically connected to the port 15 for the inflow of air G. Thus, the energy consumption and the overall dimensions of the apparatus 10 may be particularly small.
In particular, there may be provided a plurality of ducts 38 for fluidically connecting the inlet 15 with the mixing chamber 31, in particular with the inlet 32 of the latter.
The spray lance 51 may be fluidically connected with the inlet 34 of the mixing chamber 31, for example by means of a duct 34', so as to spray an air G and abrasive powder A mixture.
Preferably, as illustrated in figs. 2 and 3, such duct 34' may be flexible, for example it may consist in one or more flexible pipes, in a manner such to facilitate the operation of transporting the spray lance 51 and/or the support structure by the operator.
Furthermore, according to a particular aspect of the invention, the spray lance 51 may comprise at least one spray nozzle 59 and it may be configured to spray an abrasive mixture M formed by air G, abrasive powder A and water H, towards the surface S.
In particular, the spray lance 51 may comprise a mixing chamber 55 substantially similar to the mixing chamber 31.
As particularly illustrated in fig. 5, the mixing chamber 55 may have an inlet 56 fluidically connected with the outlet 34 of the mixing chamber 31, an inlet 57 fluidically connected with the inlet port 16 and an outlet 58 for the abrasive mixture M fluidically connected with the nozzle 59.
In other words, as schematically shown in the attached figures, the water H and the abrasive powder A may solely come into contact in the mixing chamber 55 which may exploit the known "Venturi effect" in a manner similar to the mixing chamber 31.
As known, the water H with the abrasive powder A forms sludge which may then deposit in the apparatus 10 with the risk of at least partly clogging it thus preventing the proper spraying of the mixture M towards the surface S.
This may enable avoiding the deposit of abrasive powder A upstream of the mixing chamber 55.
Furthermore, the mixing chamber 55 may be arranged in proximity of the nozzle 59 in a manner such that the formed abrasive mixture M passes through the spray lance 51 for a brief section. Preferably, the inlet 57 of the mixing chamber 55 may be arranged in proximity of the outlet 58 thereof which may be proximal to the nozzle 59.
Thus, the abrasive mixture M may pass through only for a brief section in the spray lance 51.
Thus, the apparatus 10 may comprise an inlet 16 for the water H connectable to the supply means 7 thereof, which may be positioned on the support structure 11 in proximity of the inlet 15 for air G. Thus, the apparatus 10 may be particularly compact and comfortable to use.
Possibly, there may be provided a duct 42, fluidically connected with the inlet 16 and the mixing chamber 55 which may be at least partly arranged in proximity of the duct 34' so as to facilitate the transportation operations. For example, as shown in figs. 2 and 3, the ducts 42, 34' may be flexible pipes at least partly inserted into a protection piping 45, flexible too.
Furthermore, as schematically illustrated in FIGS. 5 and 6, the duct 42 may be fluidically connected with the inlet 57 of the mixing chamber 55. Thus, the apparatus 10 may suitably comprise valve means 49 acting on the duct 42 so as to allow the selective inflow of water H and valve means 48 acting on the duct 42 for the fine regulation of the inflow of water H to the mixing chamber 55 acting on such duct 42.
In particular, the valve means 49 may be arranged upstream of the valve means 48 and both may be upstream of the inlet 57 of the mixing chamber 55.
Suitably, the spray lance 51 may comprise knobs or levers 48', 49', that can be operated by the operator and which may act on the respective valve means 48, 49.
Suitably, there may also be provided valve means 39 for regulating the selective inflow of air G, the valve means which may preferably act on the duct 38 upstream of the mixing chamber 31.
To this end, the spray lance 51 may comprise a lever 39' acting on the regulation means 39 which may be operated by the operator in use.
In particular, the levers 39', 49' may be positioned at the handle 52 in a manner such that the operator can selectively actuate one or both without interrupting the operation of the apparatus 10 and/or without releasing the handle 52.
The valve means 39, 49, 37, may be of the pneumatic type, for example pneumatic valves such as a slide valve, and they may be operatively connected to the supply means 5 in a per se known manner, preferably to the port 15 for the inflow of air G, so that the latter promotes the actuation of the valve means 39, 49, 37.
To control the valve means 39, there may be provided suitable ducts passing through the protection piping 45 in a manner such to operatively connect the lever 39' and the regulation means 39 so that, by acting on the former, the user may promote the actuation of the latter.
More generally, by acting on the levers 39', 49' the operator may spray a mixture formed by air G and abrasive powder A, an abrasive mixture M formed by air G, abrasive powder A and water H, or just water H, for rinsing for example, towards the surface S.
Furthermore, advantageously, spraying the water H alone enables cleaning the mixing chamber 55 and the nozzle 59 thus preventing the abrasive powder A from depositing therein.
According to a further aspect of the invention, the duct 42 may have one end 42' removably coupled with the inlet 57 of the mixing chamber 55 in a manner such that the duct 42 can be removed from the latter.
On the other side, the duct 42 may be irremovably fixed to the mixing chamber 55.
Furthermore, the spray lance 51 may comprise a support portion 53, for example substantially tubular, to removably receive the mixing chamber 55.
In particular, the latter may be removably inserted into such support portion 53 to allow the operator to remove the mixing chamber 55 from the tubular portion 53 so as to facilitate maintenance and/or cleaning thereof.
Thus, the operator may access the operating chamber 55 to inspect the latter and/or clean it from potential residual abrasive powder A in a simple or quick manner.
It should be clear that the cleaning and/or maintenance operation may occur with the duct 42 connected or disconnected from the mixing chamber 55, both the duct 42 and the latter being removably or irremovably fixed with the mixing chamber 55, without departing from the scope of protection of the attached claims.
According to a particular aspect of the invention, most of the mixture M may consist in air G which may come from the operating environment.
Thus, the flow rate of the water H may be particularly lower than the flow rate of the air G. In other words, the system 1 may comprise the tank 21 for the additive A and possibly a tank for the water H fluidically connected to the inlet port 16.
Advantageously, such tank for the water H may be small in size without jeopardising the high volume spraying capacity of the apparatus 10.
For example, as schematically illustrated in fig. 1, there may be provided for a trolley or a vehicle V on which the tank for the water H and the compressor for the air G can be mounted.
Furthermore, thanks to such characteristic, the system 1, and in particular the apparatus 10 may be even easier to operate so as to allow use in particularly narrow environments such as a museum, an artwork, a historical centre or archaeological site.
Thus, the user may operatively initially position the system 1 in proximity of the area where the surface S to be cleaned is located, subsequently move within the area with the apparatus 10 and lastly grasp the spray lance 51 to spray the abrasive mixture M towards the surface S.
In light of the above, it is clear that the invention attains the pre-set objectives.
The invention is susceptible to numerous modifications and variants. All details can be replaced by other technically equivalent elements, and the materials can be different depending on the technical needs, without departing from the scope of protection defined by the attached claims.

Claims

An apparatus manually transportable by an operator for spraying an abrasive mixture (M) towards a delicate surface (S) for the removal of writings, drawings or graffiti therefrom, the apparatus being usable with first means (5) for supplying air (G) at a maximum pressure of 8 bars and with second means (7) for supplying water (H) at a maximum pressure of 4 bars, the apparatus (10) comprising:
- an inlet port (15) fluidically connectable with the first means (5) for supplying air;

- at least one tank (21) for an abrasive powder (A);

- at least one first Venturi effect mixing chamber (31) having a first inlet (33) fluidically connectable with said inlet port (15), a second inlet (32) fluidically connected with said at least one tank (21) and a first outlet (34) for a first air (G) - abrasive powder (A) mixture;

- at least one spray lance (51) manually operable by the operator comprising:
- at least one second mixing chamber (55) having a third inlet (56) fluidically connected with said at least one first outlet (34) for the inflow of said first air (G) - abrasive powder (A) mixture, a fourth inlet (57) fluidically connectable with second means (7) for supplying water (H) and a second outlet (58) for the abrasive mixture (M) formed by water (H) and by the first air (G)-abrasive powder (A) mixture;

- at least one outlet nozzle (59) fluidically connected with said at least one second outlet (58) of said at least one second mixing chamber (55) to spray the abrasive mixture (M) towards the delicate surface (S);

wherein said at least one second mixing chamber (55) is arranged in the proximity of said at least one outlet nozzle (59) so as to prevent the abrasive mixture (M) from depositing upstream of said second mixing chamber (55).
Apparatus according to claim 1, wherein said tank (21) contains a predetermined amount of said abrasive powder (A), the apparatus (10) further comprising pneumatic anti-packing means acting on said abrasive powder (A) to facilitate the outflow thereof towards said second inlet (32), said pneumatic anti- packing means being fluidically connected with said inlet port (15) so that, during use, the air (G) flowing into the apparatus feeds both said at least one spray lance (51) and said anti- packing means.
Apparatus according to claim 2, wherein said tank (21) comprises a discharge portion (23') which includes an opening (23) operatively connected with said second inlet (32), said pneumatic anti-packing means comprising at least one first duct (35) acting on said discharge portion (23') in the proximity of said opening (23), the apparatus (10) further comprising first valve means (37) acting on said at least one first duct (35) controllable by the operator to control the selective inflow of air (G) into the at least one first duct (35).
Apparatus according to the claim 2 or 3, wherein said pneumatic anti-packing means further comprise vibrating means (25) acting on said tank (21) to shake said abrasive powder (A), said pneumatic anti-packing means comprising at least one second duct (26) for the fluidic connection of said vibrating means (25) and said inlet port (15).
Apparatus according to any one of the preceding claims 2 to 4, wherein said tank (21) includes an upper portion (22') that comprises at least one duct (22) for loading the abrasive powder (A), the latter including a closing element (29), the apparatus further comprising pneumatic means for pressurising said tank (21) that include a third duct (24) for the fluidic connection of the upper portion (22') of the tank (21) and of said inlet port (15), so that, during use, the inflowing air (G), which feeds both said at least one spray lance (51) and said anti-packing means, pneumatically forces the closure of the closing element (29) of said loading duct (22).
Apparatus according to any one of the preceding claims, wherein said at least one spray lance (51) further comprises a support portion (53), said at least one second mixing chamber (55) being at least partially mutually removably connectable with said substantially tubular portion (53) to allow the operator to remove the former from the latter so as to facilitate maintenance and/or cleaning of said at least one second mixing chamber (55).
Apparatus according to any one of the preceding claims, comprising at least one fourth duct (42) fluidically connectable with the second means (7) for supplying water (H) and with said fourth inlet (57) of said at least one second mixing chamber (55), said at least one fourth duct (42) having one end (42') removably coupled with said fourth inlet (57) of said at least one second mixing chamber (55) so that the fourth duct (42) can be removable from the latter.
Apparatus according to the preceding claim, further comprising second valve means (49) acting on said at least one fourth duct (42) to allow the selective inflow of water (H) into said fourth inlet (57), said second valve means (49) being actuatable by the operator during use so as to allow the selective spraying of the abrasive mixture (M) formed by the first air (G) - abrasive powder (A) mixture or by water (H) and the first air (G) - abrasive powder (A) mixture, towards the delicate surface (S).
Apparatus according to any one of preceding claims, comprising at least one fifth duct (38) fluidically connectable with said inlet port (15) and with said first inlet (33) of said at least one first mixing chamber (31), the apparatus further comprising third valve means (39) acting on said at least one fifth duct (38) to selectively regulate the inflow of air (G) into said at least one first mixing chamber (31), the apparatus comprising a first lever (39') acting on said third valve means (39), said first lever (39') being actuatable by the operator without releasing said at least one spray lance (51).
Apparatus according to claim 8 or 9, comprising a second lever (49') acting on said second valve means (49), said at least one spray lance (51) comprising a zone (52) graspable by the operator to operate the same (51), said graspable zone (52) comprising said first lever (39'), respectively said first and second lever (39', 49'), the latter (49', 39') being selectively actuatable by the operator with the same hand that grasps said graspable zone (52) of said at least one spray lance (51).
System for spraying an abrasive mixture (M) towards a delicate surface (S) for removing writings, drawings or graffiti therefrom, comprising:
- first means (5) for supplying air (G) at low pressure;

- second means (7) for supplying water (H) at low pressure;

- a transportable apparatus (10) according to one or more of the preceding claims fluidically connected with said first and second supply means.
A spray lance (51) manually operable by an operator, the lance being suitable for use in an apparatus (10) according to one or more of claims 1 to 10 or in a system according to claim 11, the lance comprising:
- a support portion (53);

- at least one mixing chamber (55) having an inlet (56) for the inflow of an air (G) - abrasive powder (A) mixture, an inlet (57) for water (H) and an outlet (58) for the abrasive mixture (M) formed by water (H) and the air (G) - abrasive powder (A) mixture;

- at least one outlet nozzle (59) fluidically connected with said at least one second outlet (58) of said at least one second mixing chamber (55) to spray the abrasive mixture (M);
wherein said at least one second mixing chamber (55) is arranged in the proximity of said at least one outlet nozzle (59) so as to prevent the abrasive mixture (M) from depositing upstream of said second mixing chamber (55).
Lance according to the preceding claim, wherein said at least one second mixing chamber (55) is at least partially removably connectable with said substantially tubular portion (53) to allow the operator to remove the former from the latter so as to facilitate the maintenance and/or cleaning of said at least one second mixing chamber (55).
Lance according to claim 12 or 13, wherein the apparatus or system comprises at least one duct (42) fluidically connectable with the water inlet (57), the latter having means for removable connection with the end (42') of said duct (42).