Patent Application
20240261935
The present invention relates to a shot blasting machine having a metallic conveyor belt for the treatment of metal pieces and the related shot blasting system.
In particular, the invention relates to a shot blasting machine having a belt provided with a special support device to improve the operation of its conveyor belt, so as to overcome technical drawbacks that are rather common in conventional metal belt shot blasting machines.
It is well known that shot blasting systems are used for the surface treatment of metal pieces of various weights and sizes in order to remove rust, oxides, foundry residues and other undesirable materials from their surface.
The surface treatment can be aesthetic (satin-finishing technique) or aimed at creating the surface roughness required for other applications, such as painting or electroplating. In a shot blasting machine, tiny iron balls, the so-called ‘shots’, are generally used to hit the metal pieces to be treated at high speed, thereby achieving the desired effect (cleaning, etc.).
A shot blasting machine generally consists of a projecting member that produces the high-speed stream of shots. The projecting member can be a nozzle if compressed air is used to impart high speed to the shots, or alternatively, the projecting member is a turbine that uses centrifugal force to project the shots against the metal pieces.
There are different types of shot blasting machines, such as belt, hook, continuous drum, and horizontal wire mesh belt shot blasting machines. Belt shot blasting machines, which are equipped with a conveyor belt made of special anti-abrasive rubber or metal material, are the most commonly used among them. The metal pieces to be treated are placed on top of this conveyor belt and are mixed inside it while receiving the high-speed shot blast.
Rubber belt shot blasting machines are ideal for treating aluminium die castings, small metal pieces in general, and also screws.
Metal belt shot blasting machines are suitable for machining heat-treated pieces, such as cast iron and brass castings. In addition, they lend themselves advantageously to the treatment of large, heavy pieces with burrs from heat treatment or the foundry industry.
The method of loading the conveyor belt with metal pieces can be automatic by means of a hydraulic tipping bucket, except for smaller models that make use of manual loading. An inverter is used to vary the speed of the conveyor belt during the step of treating the metal pieces, and also to arrange the unloading of the pieces: in fact, shot blasting systems are equipped with automatic unloading with reversal of the belt's rotation direction.
Generally, the path of the conveyor belt is designed so that in a defined portion thereof, it takes on a concave shape provided to contain and move the metal pieces to be cleaned. The conveyor belt is supported by a series of shafts, one of which transmits movement to the belt.
The continuous advancement of the conveyor has the effect of mixing the metal pieces inside it, so that they uniformly present all their surfaces to the action of the abrasive streams launched by the centrifugal turbines. An effective dust removal system, consisting of a self-cleaning cartridge filter, provides suction and abatement of the dust formed inside the blasting machine during treatment.
In more detail, the metallic conveyor belt is generally composed of a sequence of horizontal steel slats, held together by two side support chains to which they are bolted. The lateral chains are connected to the drive shaft and this connection allows the continuous movement of the belt.
One of the main technical drawbacks encountered in a metal-belt shot blasting machine is that the abrasive launched by the turbines affects both the metal pieces to be blasted and the different mechanical components of the shot blasting machine equally, thus contributing to significant wear of the machine over time. The belt conveyor is certainly the component most subject to heavy wear and tear over time, as it is directly hit by the high-speed stream of shots.
The lateral chains of the belt consist of a succession of pins and links that keep the horizontal slats hinged. In particular, it is the pins and links of these chains that wear quickly: wear leads to gradual thinning of the lateral chain pins and, at the same time, to gradual widening of the link openings, which creates unwanted play between the pins and links, resulting in increased conveyor extension. The formation of play between pins and links is particularly pronounced at the concave part of the conveyor belt: this is due to the combined effect of the force of gravity and the centrifugal force of the shots. Excessive ‘slackening’ of the concave portion of the belt can give rise to jamming of metal pieces at the gaps created between pins and links. When these interlocks occur in large numbers, they can cause the conveyor belt to stop moving and, in the worst case scenario, breakage of the shot blasting system.
Therefore, the main problem to be solved for users of metal-belt shot blasting machines is the risk of an interruption of the treatment, caused by possible jamming of pieces in the lateral chains of the conveyor belt.
At present, the only valid system for trying to avoid the formation of unwanted play in the lateral chain links is a manual adjustment, which an operator must carry out during maintenance of the system: the operator acts on a tensioning slide of the lateral chains to restore their smooth running.
Unfortunately, if this maintenance is not carried out with due frequency, this leads to considerable degradation of the conveyor belt and its malfunctioning for the reasons stated above due to wear on the pins and links of the lateral chains.
In recent years, efforts have been made to limit the wear of critical conveyor components by using very hard and abrasion-resistant materials: however, the aforementioned drawbacks have only been partially alleviated with the disadvantage of significantly increasing the operating costs of these shot blasting systems.
In light of the above, there is a need for a system capable of counteracting the formation of play between the links and pins of the belt lateral chains, so as to avoid the risk of metal pieces getting jammed inside the conveyor belt.
The Applicant has found that the technical problem outlined above can be easily solved by the use of support devices, appropriately placed inside a belt shot blasting machine.
A first purpose of the present invention is to provide support devices within a belt shot blasting machine to counteract wear on the metal components that make up the conveyor belt.
A second purpose of the invention is to provide the industry in question with a belt shot blasting system, in which the maintenance operations of the conveyor belt are considerably reduced compared to the case of currently commercially available shot blasting machines.
The Applicant has devised, tested and embodied the present invention to overcome the above-mentioned shortcomings of the state of the art and to obtain these and other objects and advantages.
The present invention is expressed and characterized in the independent claims, while the dependent claims set forth other preferred and non-essential features of the present invention, or variants of the main solution idea.
A first object of the present invention is a metal belt shot blasting machine for the treatment of metal pieces comprising:
The shot blasting machine of the present invention ensures more reliable operation of its conveyor belt over time, the components of which, in particular the lateral chains, are subjected to fewer technical drawbacks caused by mechanical wear and tear, thanks to the presence of support devices positioned below the lateral chains of the belt.
A further advantage of the belt shot blasting machine according to the present invention lies in the fact that the support devices used are simple to use and can be mounted easily below the lateral chains of the conveyor belt. In addition, these support devices can be adapted and installed without any problems inside shot blasting machines of different sizes and treatment capacities.
The conveyor belt of the shot blasting machine is suitably shaped to comprise a concave portion inside which the metal pieces to be treated are hit by a stream of abrasive material (shot blast) at high speed.
According to a preferred embodiment of the present invention, the support devices installed inside the belt blast machine are positioned below the lateral chains of the conveyor belt at its concave portion: this is due to the fact that this concave portion is subject to greater stresses than the rest of the conveyor belt, also due to the action of the force of gravity which comes from the weight of the metal pieces themselves.
Support devices for belt shot blasting machines in accordance with the invention comprise a sequence of rollers, which are inserted into a support frame mounted below the concave portion of the conveyor belt.
The term “rollers” in this description and appended claims means rollers of small dimensions and having a cylindrical shape.
A second object of the present invention is the use in a metal belt shot blasting machine of at least two support devices comprising a sequence of rollers inserted into a support frame, these support devices being positioned below the concave portion of the conveyor belt of the metal belt shot blasting machine.
These and further advantages of the shot blasting machine in accordance with the invention will be highlighted more clearly in the following description of embodiments with reference to the appended figures.
The metal belt shot blasting machine for the treatment of metal pieces of the invention will now be described in detail with reference to the appended
With reference to
The belt shot blasting machine 2 comprises a closed-loop conveyor belt 4 for the movement of metal pieces 3 to be cleaned, this conveyor belt 4 being composed of a sequence of horizontal metal slats hinged onto two lateral chains 5.
The conveyor belt 4 of the shot blasting machine 2 is shaped in a closed loop so as to comprise a concave portion 6 within which metal pieces 3 are hit by a stream of abrasive material (shots) at high speed.
The lateral chains 5 are connected to a drive shaft 7 and this connection allows the continuous movement of the conveyor belt 4. A centrifugal turbine 8 is used to project the shots at high speed against the metal pieces 3 in the concave portion 6 of the conveyor belt 4. The turbine 8 is an integral part of the belt shot blasting machine 2.
The continuous advancement of the conveyor belt 4 has the effect of mixing the metal pieces 3 within its concave portion 6, so that the metal pieces 3 evenly present all their surfaces to the action of the abrasive streams launched by the centrifugal turbine 8.
In the shot blasting system 1 shown in
A gear motor 10 is used to appropriately adjust the speed of the conveyor belt 4 during the treatment of the metal pieces 3. The gear motor 10 also has the function of reversing the direction of travel of the conveyor belt 4, once the blasting treatment has been completed: in this way, the metal pieces 3 can be easily unloaded and recovered after the cleaning treatment in the shot blasting system 1.
The conveyor belt 4 consists of a continuous sequence of metal slats 11 hinged to the links 12 of two chains 5 located on either side of each metal slat 11. The lateral chains are set in motion by the drive shaft 7 shown in
The concave portion 6 of the conveyor belt 4 encloses the metal pieces 3 inside it for the time strictly necessary for the shot blasting treatment. The abrasive launched by the centrifugal turbine 8 hits equally both the metal pieces 3 to be treated and the metal slats 11 of the conveyor belt 4, which are subject to heavy wear over time as they are directly hit by the high-speed stream of shots.
The most critical components of the conveyor belt 4 are the two lateral chains 4, consisting of a continuous succession of links 12 and pins 13, which keep the metal slats 11 hinged. As already explained in the section on the state of the art, it is mainly the links 12 and pins 13 that wear out quickly, resulting in gradual thinning of the pins 13 and, at the same time, gradual widening of the openings of the links 12.
As a result, unwanted play is created over time between pins 13 and links 12, and the formation of this play is particularly pronounced at the concave part 6 of the conveyor belt 4 due to the joint action of the force of gravity of the metal pieces 3 and the centrifugal force of the shots hitting the links 12 and pins 13. Metal pieces 3 can get jammed at the gaps created between pins 13 and links 12. This jamming of metal pieces 3 can cause the conveyor belt 4 to stop moving and, in the worst case scenario, breakage of components inside the shot blasting machine 2.
The present invention solves the above technical problem by counteracting the formation of unwanted play between links 12 and pins 13 of the two lateral chains 5. The technical problem is solved by inserting into the shot blasting machine 2 at least two support devices having the characteristics of the present invention at the lateral chains 5 of the conveyor belt 4.
The frame 15 has the function of supporting the sequence of rollers 16 and comprises a support base 17, from which perforated walls 18 branch out parallel to each other and perpendicular to the support base 17. Each wall 18 is provided with a sequence of holes 19 of a suitable size to accommodate the rollers 16.
The perforated walls 18 can vary in number, but are generally present in a number comprised between two and five. In particular, in the embodiment of the invention shown in
The rollers 16 are inserted into the holes 19 in the perforated walls 18 in such a way that they can rotate unrestrained within these holes 19. A variable number of rollers 16 can be inserted into the holes 19 and this number depends on the extension in length of the concave portion 6 of the conveyor belt 4 of the shot blasting machine 2. In general, the support devices 14 of the present invention comprise a sequence of rollers 16 in a number generally comprised between 8 and 30, preferably comprised between 10 and 20.
The material constituting the support device 14 shown in
The support device 14 of the present invention is inserted at the concave portion 6 of the conveyor belt 4. In particular, the support device 14 is positioned below the lateral chains 5 of the conveyor belt 4.
The support device 14 is positioned so that the rollers 16 are in close contact with the links 12 and pins 13 of the lateral chains 5 of the conveyor belt 4. As a result, the continuous movement of links 12 and pins 13 is transferred to the sequence of rollers 16, so as to determine their rotation about their axes.
As there are two lateral chains 5 at the edges of the conveyor belt 4, at least two support devices 14 are required: each is inserted below each lateral chain 5 to support their movement at the concave portion 6 of the conveyor belt 4.
The rollers 16 are supported in their rotational movement by a frame 15 having the construction characteristics described with reference to
The presence of the support device 14 and rollers 16 in close contact with the links 12 and pins 13 inhibits a “slackening” of the lateral chains 5 and prevents the formation of unwanted and deleterious play between pins 13 and links 12. As a result, the risk of jamming of metal pieces in the concave portion 6 of the conveyor belt 4, a rather frequent risk in conventional shot blasting machines of the prior art, is prevented. The metal belt shot blasting machine can therefore run for a long time without incurring any stoppage of the movement of its conveyor belt 4.
The present invention is not limited to the particular embodiments previously described in relation to
| Number | Date | Country | Kind |
|---|---|---|---|
| 102023000001986 | Feb 2023 | IT | national |
