Patent Application
20080311824
This invention relates preferably to ceramics technology for the manufacture of ceramic products by casting a suspension in water of a clayey raw material (known as “slip”) in porous moulds to obtain semi-finished sanitaryware such as washbasins, bidets and similar articles.
The invention relates in particular to an apparatus for finishing these products by smoothing their surfaces during the manufacturing process while they are still in “states” that allow abrasive means to be used on them with the aid of liquids to facilitate their machinability, that is to say, when they are in the “green” and “leather hard” states.
This specification refers to this particular technology. It will be understood, however, that the description is provided purely by way of non-limiting example, since the characteristics of the invention are such that further, advantageous applications of it are possible in sectors other than the reference sector.
The surface smoothing of semi-finished ceramic products obtained by slip casting is preferably performed when the products are in the “green” state (that is to say, solid but still having a water content of between 17% and 20% by weight—and hence still subject to plastic deformation) or in the “leather hard” state (with a water content normally less than 13%, where the product, although rigid, can still be worked with a wet smoothing tool). However, under certain conditions, smoothing can also be performed when the product is already in the “dry” state, that is, having a water content normally below 2%.
A prior art apparatus—described in document EP 640.450—comprises a finishing tool that can be automatically regenerated continuously while working.
The tool comprises a power-driven endless abrasive belt trained around three pulleys positioned in space in such a way as to subtend the belt to a form closed, three-sided figure comprising an active section, a passive section and a transmission section.
The passive section is associated with a tank containing a liquid through which the passive section moves and remains permanently dipped.
The semi-finished product to be smoothed, held by a robot-controlled mechanical manipulator, is suitably oriented in space and moved into contact with the active belt section which slides tangentially over the surface of the semi-finished product to remove burs and other surface irregularities.
The particles of ceramic material removed are trapped in the material structure of the abrasive belt's active section and are washed away when the active section moves on to become the passive section and is dipped into the tank.
The method described above has inherent disadvantages, one of which is the fact that it involves moving the semi-finished product and keeping the smoothing apparatus stationary, the apparatus being much lighter in weight than the product.
The negative consequences of this are not difficult to imagine. The heavy weights that the robot is required to handle are reflected in the high cost of installation and in the equally high costs of running and maintenance, not to mention the extended process times.
Another disadvantage is that smoothing using the method described above is relatively easy if the surfaces to be smoothed are convex but, on the contrary, is considerably difficult, or even impossible, if the surfaces are concave.
Another disadvantage is that the robots must be provided with a different end effector for each different product to be manipulated, the wider the range products, the higher the number of different effectors required.
Moreover, the patterns of motion involved in the manipulation of the product may be very complicated, which means that the parts of the product that come into contact with the robot are subjected to stress that is not always negligible and are therefore liable to damage.
This makes it problematical to handle relatively large products such as articles of sanitaryware, which are heavy and fragile, and which cannot be held suspended in the air without the risk of breaking them.
Yet another disadvantage, connected with the regeneration of the abrasive belt in a tank of water, is that the tank can have only one, predetermined and invariable orientation in space: this places considerable limitations on the versatility of the installation in terms of providing the best operating conditions for the finishing operations.
To overcome the above disadvantages, rotary tools (such as cylindrical sponges) can be used. These tools are rotated while the product (especially “greenware”) is held stationary in a predetermined position.
These tools, too, are not free of disadvantages, however. They have to be cleaned frequently to restore their effectiveness after just a few runs, which means their productivity is not very high. Above all, the inherent characteristics of the tools and of the rotary drive system require make it impossible to withhold the material removed from the products which ends up being splashed on the surrounding area and on the products themselves.
It is therefore an aim of this invention to provide a finishing and surface smoothing apparatus which can overcome the disadvantages inherent in prior art smoothing belts while at the same time offering the advantages of rotary tools.
In accordance with the above mentioned aim, this result is achieved by a smoothing apparatus whose technical characteristics may be easily inferred from the contents of the appended claims, especially claim 1, and any of the claims that depend, either directly or indirectly, on claim 1.
The advantages of the invention are more apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate preferred embodiments of the invention provided merely by way of example without restricting the scope of the inventive concept, and in which:
With reference to
The apparatus 1 basically comprises an abrasive tool 3 in the form of an endless belt 4 which (in the embodiment illustrated) is trained around at least one pair of pulleys 5 and 6, at least one which is power-driven (by a respective motor 5m), and which defines an active section 7 and a passive section 8 of the belt 4:
the first, active section 7 identifies the part or branch of the belt 4 that is designed to remove material from the product 2; while
the second, passive section 8 is designed to receive a continuous regenerating treatment that restores the abrasive capacity of the tool 3 making it suitable for smoothing purposes when that section of the belt 4 becomes the active section again.
The apparatus 1 also comprises:
drive means 20 acting on the belt 4 in such a way as to enable the belt 4 itself to move in the space surrounding the product 2;
means 10, located in the vicinity of the belt 4, for spraying a liquid on the belt 4 itself, which has liquid absorption properties;
suction means 9 associated with the passive section 8 of the belt 4 and operating in such a way as to remove the liquid and the process waste materials retained by it, that is to say, the materials removed from the product 2 during the smoothing process and retained by the belt 4.
The means 20 enable the apparatus 1 to be associated with a manipulator 21, preferably robot-controlled (partly illustrated since it is of known type).
The association of the apparatus 1 with a manipulator 21 controlled by a robot or even manually by an operator, enables the belt 4 to move in the space surrounding the product 2 in such a way as to orient its active section 7 relative to the lateral surfaces of the product 2 as required for smoothing.
In particular, again with reference to
The lower pulley 6 of the belt 4 is rotatably connected to the first arm 22, at the lower end of the first arm 22.
The upper end of the arm 22 is associated with a counterweight 25 for balancing the center of gravity of the first arm 22 itself, and hence of the belt 4: in this way, the belt 4 is kept in a neutral positional configuration independent of the position adopted by the apparatus 1 as a whole. In other words, the belt 4 and the first arm 22 remain in a static, substantially stationary, configuration, especially during movements towards and away from the product 2.
The first arm 22 is also provided with adjustable limit stop and contact means 26 acting between the first arm 22 and the support 23 and designed to permit adjustment of at least one stable end position where the first arm 22 is angularly closest to the support 23 and where movement towards the belt 4 is stopped when the belt 4 comes into contact with the product 2.
As regards the force of contact which the active section 7 of the belt 4 must possess to operate on the product 2, the invention contemplates the provision of pushing means 100 composed of a cylinder 101 mounted on the support 23 and acting on a roller 102 that is keyed to the first arm 22 and positioned eccentrically with respect to its pivot point 22a: in this way, the active section 7 of the belt 4 may apply a predetermined contact force on the product 2, even in combination with the manipulator 21, according to the pushing force exerted by the cylinder 101 (see arrow F101) on the eccentric roller 102.
The numeral 103 indicates a block (see
The limit stop and contact means 26 are located at two different points of the first arm 22 and each consists of a threaded rod 27 protruding transversally from the first arm 22 and screwed into a respective hole 28 made in the first arm 22.
Each of the rods 27 has an end head 29 designed to come into contact, in use, with respective zones of the support 23.
The above mentioned lower pulley 6 is connected by its mounting shaft 6a, to the inside of a slot 30 made in the first arm 22 and in such a way that, when required, it can be moved (arrow F30) to adjust the tension of the belt 4 by slackening the shaft 6a from the slot 30 and, if necessary, to change the belt 4 itself.
As clearly shown in
As stated earlier, in order to enable the abrasive properties of the belt 4 to be regenerated continuously while working, the belt 4 is made of a material that absorbs liquid—for example water—which is sprayed on the belt 4 by the above mentioned spraying means 10 which the apparatus 1 is equipped with.
More specifically (see also
In one example embodiment, shown in
In particular, the spray means 10 may consist of a plurality of nozzles 10a, fed by a respective source 10b, positioned upstream of the negative pressure means 9 relative to a direction of rotation (indicated by the arrow S) of the belt 4 in such a way that they face a portion of the passive section 8 of the belt 4.
As just mentioned, the apparatus 1 also comprises negative pressure means 9 which are associated with the passive section 8 of the belt 4 and which are designed to remove from the belt 4 the liquid sprayed onto it by the spraying means 10 together with the process waste material removed and retained by the belt 4 during the active stage of the smoothing process and transferred to the passive stage of the smoothing process.
The negative pressure means 9 include, in particular, a roller 11 which rotates freely about its axis of rotation 15 and which is in direct, tangential contact with the passive section 8 of the belt 4.
The roller 11, cylindrical in shape, is rotatably coupled coaxially with a hollow pin 17 that defines a cavity 12 inside it.
The roller 11 also has a cylindrical outside lateral operating surface 11a provided with a plurality of through holes 11b designed to allow the outside and the inside of the cavity 12 to communicate through a slot 17c formed on the hollow pin 17 in such a way as to face the passive section 8 of the belt 4.
The lateral surface 11a of the roller 11 has shoulders 16 having an enveloping shape matching the opposite longitudinal edges of the belt 4.
The cavity 12 inside the hollow pin 17 is designed to suck the liquid and the smoothing process waste material out through the roller 11, that is to say, through the holes 11b in the lateral surface 11a and through the slot 17c; the suction being produced by: the negative pressure created inside the cavity 12 by the fluid connection of the cavity 12 with vacuum generating means 31m such as, for example, a vacuum pump, represented as a block in
In other terms, the roller 11 turns freely together with the belt 4 and when the portion of the roller 11 surface with the holes 11b comes into contact with the passive section 8 and the holes coincide with the slot 17c, the process waste material is removed from the passive section 8 by the suction produced.
More specifically, the roller 11 is held in direct, forced contact with the belt 4 by contact means 18 which include a mounting arm 18a and elastic elements 19 interposed between the roller 11 and the first arm 22 and which operate in such a way as to compress the roller 11 against the belt 4 so as to maximize the effect of the seal and, hence, the effectiveness of suction.
Obviously, the products sucked into the cavity 12 and consisting, as already stated, of liquid and process waste, once they reach the interior of the cavity 12, are then carried by the negative pressure along a conveyor 31 circuitally connected with the vacuum pump 31m (see arrow F31m).
In this specific case, the belt 4 mounting structure 20 comprises:
a box-shaped frame 33 equipped at the top of it, with flange means 34 for connection to the above mentioned manipulator 21 and mounting the above mentioned spraying means 10 inside it, the negative pressure means 9 acting (in this case) at an arc-shaped passive section 8 of the belt 4 passing over the upper pulley 5 that is rotatably mounted inside the frame 33 and equipped with a respective drive 5m;
a rigid support 35 associated with the box-shaped frame 33 and extending downwardly from the latter as far as the bottom end of the lower pulley 6 of the belt 4.
The support 35 also has in the middle of it an auxiliary idle wheel 36 that is rotatably connected to the support 35 and in bilateral contact with a protruding internal profile of the belt 4 in such a way as to enable the latter to slide more easily.
The spraying means 10, the negative pressure means 9, the upper pulley 5 and the related drive 5m are mounted on a first member 60 located inside the frame 33 and pivoted at end of it and at 60a to the frame 33 itself.
The member 60 is acted upon by tensioning means 61, composed of a cylinder 62 located at the bottom of the frame 33, protruding vertically inside the frame 33 and acting on an idle roller 63 connected, at 63a, to the member 60 and positioned eccentrically with respect to the pivot point 60a of the member: in this way, moving the member 60 up or down (see arrow F60,
The numeral 64 indicates a block (see
As regards the spraying means 10 and the negative pressure means 9, the latter are made in a portion 37 of the member 60 that is pivoted at 37a to the member 60 itself, in such a way as to enable the portion 37 to rotate between:
a lowered operating position, where the spraying and negative pressure means 10, 9 are in contact with the passive section 8 of the belt 4 (arrow F37,
a raised, non-operating position where the spraying and negative pressure means 10, 9 are away from the upper pulley 5 and from the belt 4 in such a way that the latter can be substituted (see arrow F37a,
In this case, the negative pressure means 9 (see
The negative pressure is generated in the chamber 65 using suitable means 65b which, in this case, purely by way of example, are embodied by a Venturi unit, partly illustrated in
The spraying means 10 comprise two sets of nozzles 10a made on the portion 37 on opposite sides of the cylindrical chamber 65: the liquid supply means 10b are, obviously, activated by one or the other of the sets of nozzles 10a depending on the rotation direction S of the belt 4 and in such a way that the belt 4 is always sprayed before it moves past the cylindrical chamber 65: that means the belt 4 can operate in both directions of rotation.
Means 38 are provided between the portion 37 and the member 60 for locking the containing portion 37 in the lowered operating position so that it can be positioned stably over the belt 4.
The locking means 38 comprise a vertical lever 39 pivoted at one of it, at 39a, to the member 60 and snappingly engageable, at it its free opposite end, with a pin 40 that protrudes laterally from the portion 37 and that can be positioned near the lever 39 when the portion 37 is in the lowered operating position.
An elastic element 41 is interposed between the lever 39 and the member 60 so as to keep the lever 39 constantly in contact with the pin 40.
In other words, when the portion 37 is lowered towards the belt 4, the pin 40 comes into contact with the rounded head of the lever 39 which in turn withdraws to allow the passage of the portion 37 and of the pin 40, thus extending the elastic element, or spring, 41; once the pin 40 has passed, the lever 39, under the pulling action of the spring 41, returns to the advanced position, thereby locking the pin 40 under it and thus holding the portion 37 in place: this keeps the portion 37 correctly positioned against the passive section 8 of the belt 4, allowing the cylindrical chamber 65 to remove the material from the belt 4 by suction.
For obtaining the optimum position of the portion 37 at all times, adjustable limit stop means 70 (see also
Screwing or unscrewing the bolt 70a thus moves the portion 37 towards or away from the belt 4, according to the thickness of the belt 4 and its state of wear, and, hence, according to the need to move the cylindrical suction chamber 65 towards or away from the passive section 8 of the belt 4.
The belt 4 may have a quadrangular cross section and regular thickness, or a quadrangular cross section and regular thickness with an internal protruding profile running along the middle of it (see
The apparatus 1 made as described above makes it possible to smooth a generic product 2 of any shape held stationary while only the tool 3 moves.
This offers numerous advantages.
Since the moving part of the apparatus is the tool 3, which is considerably lighter than the product 2 (at least when the latter is a semi-finished ceramic product), the robot-controlled manipulator required to drive the tool 3 may be relatively small and inexpensive.
Also, the possibility of orienting the belt 4 quite freely makes it possible to expose the product 2 not only to the active sections 7 of the belt 4 but also to the portions of it, for example, close to the curved area where the belt 4 moves around the pulleys.
That means the tool 3 can work also on small and/or, if necessary, even concave, parts of the surface of the product 2.
Further, the belt 4 is regenerated by a forced suction system that not only has no influence on the structure of the apparatus 1 but also has the advantage of being very effective in removing process waste material and thus provides high regenerating performance.
Another advantageous aspect of the invention is due to the fact that the two drive units described above can be used for a plurality of products 2 of different shapes and sizes, with obvious advantages in terms of versatility because the apparatus 1 is applicable to a wide range of generic products 2.
In the second embodiment described, the special structure of the rigid support 35 allows the belt 4 to be positioned even horizontally to be able to work even on parts of the product 2 that are difficult to access, which is added to the fact that use of the curved belt section at the upper pulley 5 as the regeneration area makes it possible to have two active sections of the belt 4 available at all times.
In the first preferred embodiment of the invention as described above, the roller 11 is mounted laterally of the two pulleys 5 and 6 around which the belt is trained and acts as a tensioner of the belt 4 thanks to the compression it exerts on the passive section 8.
It will be understood, however, that numerous variants of this embodiment are possible, the easiest one to imagine being that the roller 11 could be integrated into one of the pulleys 5 or 6 around which the belt 4 is trained, the belt being in this case a Moebius belt (as clearly illustrated in
The invention described above is susceptible of industrial application and may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted by technically equivalent elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| BO2007A000411 | Jun 2007 | IT | national |
