EP2578356B1

EP2578356B1 - Appartus for machining the surface of bars.

Info

Publication number: EP2578356B1
Application number: EP12187517.3A
Authority: EP
Inventors: Cesare MANGILI
Original assignee: Projetman Macchine Srl
Current assignee: Projetman Macchine Srl
Priority date: 2011-10-07
Filing date: 2012-10-05
Publication date: 2016-09-14
Anticipated expiration: 2032-10-05
Also published as: EP2578356A1; ITMI20111830A1

Description

The present invention relates to a device for the surface processing of a bar. In particular, the present invention relates to a device for carrying out the surface finishing of a metal bar with solid or hollow round section, as per the preamble of claim 1. An example of such a device is disclosed by DE 38 41 916 A .
Bars or rods with round or polygonal section are made by processing plastic or metal materials. The bars obtained by means of metallurgy operations, such as drawing or plastic deformation processes in general, have a not perfectly smooth surface that requires further finishing treatments. Despite the possibility of obtaining the planarity of the bar surface, or the regularity of the same if referring to circular section products, this will have a surface roughness due to microscopic irregularities.
In order to reduce the sliding friction or improve the efficacy of sealing members (such as seals) or still, for preparing the surface with the suitable roughness degree for galvanic processes it is necessary to reduce micro-irregularities (roughness), thus improving the functional features from the mechanical viewpoint.
Moreover, while the surface planarity macroscopically defines the evenness of the reflected light ray direction, the same surface roughness causes several micro-reflections in random directions, thus subtracting intensity to the reflected light. For this reason, a less rough surface is more reflecting, in other words more polished, than a rougher surface.
Several finishing treatments for surface polishing are known. This may be carried out by brushing the outer surface of bars and tubes. Such brushing is obtained by means of rotating brushes in contact with the products to be processed. In these systems, the tube is generally brushed by rotation or not of the same. While the cost of such finishing operation is moderate, the brushing is not accurate and thus such treatment cannot be used when a high finishing accuracy is required.
In order to obtain a polished surface and carry out more accurate surface finishing, metal bars are treated with a different process called glazed finish polishing. This is carried out by a controlled abrasion of the surface by means of very fine and even grain abrasives, which reduce the extent of the surface roughness, obtaining the polishing of the same. In particular, the polishing consists in using abrasive tapes with different, basically decreasing grains, whereby the surface roughness is reduced with a limit tolerance equal to the dimension of the same grain.
Known devices comprise an idle roller bed, a pushing roller and a support for the abrasive tape. The idle roller bed allows the bar to advance and rotate about its axis by means of the force impressed by the motor driven pushing roller. The abrasive tape is mounted on a support which usually consists of a device with two opposite pulleys that allow the tension and rotation of the tape wound thereon. In particular, one of the two pulleys is coated with rubber and presses the abrasive tape against the bar to be polished. Such finishing operation is generally carried out by working on the bar with a consecutive series of supports, each provided with finer grain abrasive tapes.
Devices like the known ones described above have significant drawbacks. A problem of such devices relates to the considerable overall dimensions they have if it is necessary to use a plurality of supports provided with different grain abrasive tapes. Moreover, it is necessary to calculate the cost and time required for processing the bar on consecutive stations, as well as the cost related to the change of several abrasive tapes when only partly used.
A further problem of known devices is not to be able to correct any roundness defects related to the same bar. In fact, if the bar is ovalized it is polished while keeping the roundness defect.
Finally, known devices can generate linearity defects during the processing operation. In fact, the support pressure on the bar may cause a bending of the same, with the result of deforming the thinner bars or achieving different processing on different portions of the bar. Moreover, since known devices do not have an even contact by the entire tape width, the produce a clear helical impression at the edge with the greatest contact.
It would therefore be desirable to have a device for the surface processing of a bar or the like capable of achieving an accurate surface polishing without causing damage or deformation to the processed products. In particular, it would be desirable to have a device capable of preventing the bar deformation while polishing.
Moreover, it would be desirable for such device to achieve the surface polishing of the bar at moderate costs, limiting the use of the amounts of abrasive tape.
It would also be desirable for such device to allow the processing time and the number of supports to use for bar processing to be minimized. In particular, it would be desirable for such device to be flexible in processing bars having different dimensions and heterogeneous surface finish.
Moreover, it would be desirable for such device to minimize the occupied space while keeping the required features.
Finally, it would be desirable for such device to have the capability of minimizing, or eliminating, the roundness defects of the products to subject to surface finishing processes. Within the scope of the above task, an object of the present invention is to provide a device capable of minimizing the occupied space while ensuring the required functions.
A further object of the present invention is to provide a device capable of minimizing the processing time and costs, achieving the desired result with the smallest amount of abrasive tapes and the smallest number of operations.
Yet another object falling within the scope of the above task is to provide a device capable of ensuring the processing evenness while having a high flexibility in the use of different bars with a heterogeneous surface finish. In particular, an object of the present invention is to provide a device capable of minimizing, or eliminating, any roundness defects of the bars without producing further defects or deformation in the processing.
The above objects are achieved by a device for the surface processing of a substantially round bar having the features of claim 1.
In the present invention, the term "operating mode" refers to the mode in which the device carries out the bar processing achieving the surface polishing of the same. In particular, in the operating mode the abrasion means place the abrasive tape in contact with the bar to be processed, during the rotation of the same.
Likewise, in the present invention the term "non operating mode" refers to the stand-by condition of the device or at least of the abrasion means. The latter, in fact, do not achieve the contact of the abrasive tapes with the bar to be processed, nor the rotation.
With the above features, the device according to the invention provides to the surface processing of bars or the like by exerting a greater pressure, and thus a greater removal, where the bar diameter is larger, thus achieving an even diameter on the entire length.
The use of two opposite supports, in fact, allows roundness defects to be eliminated by the fixed distance between centres between the same two supports, which are provided with abrasive tape, thus determining an accurate and constant diameter.
Moreover, the device allows the reduction of the abrasive tape use thanks to the even use of the tape on the entire width thereof.
The movable supports in operating mode are in contact with the bar with symmetry axes substantially parallel to the symmetry axis of the bar. The movable supports in operating mode provide to the rotation of the abrasive tapes.
In this way, the surface abrasion is controllable by the control of the same support.
The movable supports in operating mode are opposite and in contact with two different portions of the bar surface with symmetry axes substantially parallel to the symmetry axis of said bar.
In this way, the two supports ensure an equal and opposite pressure on the bar surface, preventing the deformation of the same. Moreover, the presence of two opposite supports improves the processing, making it more even and speeding it up. Moreover, the compensation of the working pressure on two opposite generatrices of the bar prevents the forming of impressions due to temporary deformations (deflections) of the same bar. Preferably, the device further comprises support means for coupling with the movable supports. In particular, the coupling also makes the rotation fulcrum for the same supports. Even more preferably, the support means comprise means for spacing the supports from the bar for changing the distance between centres between the two supports.
In this way, the adjustment in rotation of the supports allows the fine adjustment of the removal of material to be carried out on the bar surface, defining the working distance between centres.
Preferably, the spacing means comprise a ball recirculation screw for spacing the supports. Even more preferably, the spacing means further comprise a pneumatic system and/or a hydraulic system for controlling the supports. In particular, the pneumatic system and/or the hydraulic system in operating mode allow at least one of the two supports to exert a constant pressure on the bar surface.
In this way, the system ensures a high flexibility in the processing of bars having a different dimension and an optimal control of the finish that can be obtained.
Preferably, the device further comprises means for the dimensional control of the bar.
In this way it is possible to carry out a control of the processed bars and optionally subject them to a new process.
A significant reduction in the overall length dimensions is obtained with a system as described thanks to the possibility of halving the number of stations.
Further features and advantages of the present invention will appear more clearly from the description of preferred embodiments, made by way of an indicative non-limiting example in the annexed figures, wherein:

Figure 1 shows a perspective view of the preferred embodiment of the device for the surface processing of a bar according to the present invention, in operating mode;
Figure 2 shows a schematic view of the embodiment of the device of Figure 1, in non operating mode;
Figure 3 shows a schematic view of the embodiment of the device of Figure 1, in operating mode;
Figure 4 shows a schematic view of a system comprising a plurality of devices of the embodiment of Figure 1.

With reference to Figures 1-3, a device 10 is shown for the surface processing of a bar 200. In particular, such device allows the polishing of bar 200 or similar products to be carried out by the surface abrasion, minimizing the roughness of the same.
Device 10, in particular, allows the surface finish processing of a substantially round bar 200. Such device 10 comprises support and advance means 120', 120" and abrasion means for bar 200.
Such means 120', 120" comprise two pairs of motor driven rotating discs placed at the two opposite ends of device 10. These allow the support of bar 200 to be polished and at the same time, the rotation of the same on its axis. Such pairs of rotating discs may be equally replaced with different means achieving the same result. Device 10 further comprises a motor driven pressure roller which closes the bar onto supports 120', 120" with the function of supporting, rotating and advancing bar 200 being processed.
The abrasion means comprise two opposite movable supports 110', 110" comprising each a cylindrical rotor 112', 112" provided with abrasive tape 250', 250".
In the embodiment described herein, rotors 112', 112" are made with rubber coated pulleys for favouring the driving of tapes 250', 250", according to the grain to use. These do not cover the entire surface of rotors 112', 112" but about half a turn thereof, the same tapes 250', 250" being tensioned by means of further idle pulleys 118', 118", entirely metal, whereon they wound by the remaining portion, corresponding to about half a turn of the same pulleys 118', 118". Rotors 112', 112" therefore allow the rotation of tapes 250', 250" applied thereto by the actuation of motors 114.
In a further embodiment, supports 110', 110" may each comprise a cylindrical rotor 112', 112" of metal material, whereto the abrasive tape 250', 250" is applied, according to the grain to be used, so that the latter covers the entire surface of the same rotor 112', 112".
The two rotors 112', 112" need not be both provided with abrasive tape 250', 250". If device 10 is used in roughing stations, in order to have a greater removal both rotors 112', 112' will be provided with abrasive tape 250', 250", acting as working rotors, therefore both supports 110', 110" will carry out the process. On the other hand, when device 10 is used in the finishing step a smaller removal is more convenient. In that case, only one of the two supports 112', 112" will be provided with the abrasive tape whereas the other will act as contrast keeping all the advantages illustrated above with reference to roundness correction, dimensional control and compensation of the forces acting on bar 200.
The rotation movement of tapes 250', 250" is imparted by means of a toothed pulley and belt drive by the two motors 114 arranged on the median beam of the adjustment means 130', detailed hereinafter.
The two supports 110', 110" are positioned so as to be in contact with bar 200 in two opposite portions of the same. In this way, the symmetry and rotation axis of rotors 112', 112" is substantially parallel to the symmetry axis of the same bar 200.
In the preferred embodiment, device 10 further comprises support means 130, consisting of a metal framing fastened to the machine base. The adjustment means 130' obtained by a metal plate provided with side ball recirculation guides controlled by a ball recirculation screw may slide vertically on such framing. The coupling of supports 110', 110" with said support means 130 is obtained by means of the adjustment means 130' whereto the same are coupled. In particular, said supports 110', 110" are pivoted on the plate of the adjustment means 130' by means of rotation fulcrums 132', 132" for supports 110', 110" arranged between rotors 112', 112" and pulleys 118', 118". Such coupling forms the fulcrum for the rotation of supports 110', 110", allowing the fine adjustment of the removal of material to be carried out on the bar surface, defining the working distance between centres while ensuring the vertical movement of the plate of the adjustment means 130'. Such vertical movement is intended to bring the symmetry axis of rotors 112', 112" in line with the symmetry axis of bar 200, so that the three axes lie on the same plane, preventing asymmetric processing. As the diameter of bar 200 varies, therefore, the vertical translation and the rotation of supports 110', 110" allow the adjustment of the amount of material to be removed, and at the same time the correct distribution of the forces acting on bar 200.
In order to achieve the adjustment of supports 110', 110" and ensure the suitable adjustment of the distance between centres of rotors 112', 112" accordingly, the adjustment means 130' comprise means for spacing supports 110', 110" from bar 200. In particular, in the embodiment described herein they comprise a ball recirculation screw 140 adapted to ensure the translation of supports 110', 110". Such screw, as known, comprises steel screws inserted in a spiral space between the threaded portion 116', 116" of supports 110', 110" and the nut screw. The balls allow the grazing friction to be transformed into rolling friction and thus, the rotational motion of the nut screw to be transformed into a translating motion of supports 110', 110". The use of the ball recirculation screw 140 compared to a screw-nut screw system allows a greater accuracy to be achieved, as well as a high efficiency and duration, high wear resistance, significant axial rigidity and reduction of the friction between contacting parts.
Moreover, device 10 is provided with diameter control means (not shown) arranged in the back portion of the same, downstream of the process. Such means allow an accurate control of the diameter and thus, of the amount of material removed.
Moreover, in an embodiment not shown, the spacing means may comprise a pneumatic system or a hydraulic system for controlling supports 110', 110". In particular, such systems in operating mode allow at least one of the two supports to exert a constant pressure on the bar surface. In this way, the correction and determination of the diameter and roundness of bar 200 are not obtained but a constant pressure is exerted so as to obtain an even removal on the surface of the same bar 200.
In a further embodiment, not shown, the abrasion means may comprise a single support for the cylindrical rotor, minimizing the dimensions of the same device 10.
Figure 2 shows device 10 in non operating mode, wherein it is not actuated and the abrasion means do not achieve the contact of the abrasive tapes with the bar to be processed, or the rotation.
Bar 200 is statically resting on the two pairs of motor driven rotating discs 120', 120" since the latter are not actuated. The two supports 110', 110" are arranged so as to not be in contact with bar 200. Finally, rotors 112', 112" are not placed in rotation and accordingly, the abrasive tapes 250', 250" are stationary as well.
Before proceeding with the finishing operations it is necessary to adjust the distance between the two rotors 112', 112", and distance of the same from the ground, in relation to the dimensions of bar 200 to be processed and in relation to the amount of surface material to be removed from the same. This happens by adjusting the distance between centres of the same rotors 112', 112" and by the vertical translation of the adjustment means 130'. The adjustment of the distance between centres is obtained by means of the spacing means acting on screw 140, translating the threaded portions 116', 116" of supports 110', 110" relative to the nut screw. By rotating the latter in one direction or in the opposite direction, a concurrent approach or spacing apart is obtained for supports 110', 110" from bar 200 arranged centrally relative to device 10, in relation to the rotation of the same supports 110', 110" relative to fulcrums 132', 132". Moreover, in relation to the diameter of bar 200, it is necessary to adjust the position of supports 110', 110" by acting on the vertical translation of the same by the guides of the adjustment means 130', as described above.
Moreover, with device 10 not yet operating, it is necessary to place the abrasive tapes 250', 250" on rotors 112', 112", according to the finish to make, so that they are also arranged on pulleys 118', 118" and tensioned.
Figure 3 shows device 10 in operating mode, wherein the same carries out the processing of bar 200 achieving the surface polishing thereof. In particular, in the operating mode the abrasion means place the abrasive tape 250', 250" in contact with bar 200 to be processed and at the same time the motor driven pressure roller 114' closes the bar onto supports 120', 120", supporting, rotating and advancing bar 200 being processed.
The movable supports 110', 110" provide to the rotation of the abrasive tapes 250', 250" by the rotation of rotors 112', 112" and of the idle mounted return pulleys 118', 118". Supports 110', 110" therefore are approached at the same time to bar 200 up to contacting the same with the abrasive tape 250', 250" in rotation, according to the distance between centres defined with the ball recirculation screw 140. In particular, supports 110', 110" are self-centring thanks to a pair of gears relative to bar 200 being processed with an action and reaction of the one relative to the other, relieving equal and contrary pressures along the opposite contact generatrices of rotors 112', 112" with bar 200. In this way, the effect of annulling the forces that may cause an even temporary deformation of bar 200 is obtained. Moreover, the symmetry axis of the same rotors 112', 112" is arranged substantially parallel to the symmetry axis of bar 200.
The surface processing of bar 200 is achieved by the removal of material by abrasion, in relation to the grain of the abrasive tapes 250', 250". During the process, supports 110', 110" are constantly in contact with bar 200 through rotors 112', 112", interposing the abrasive tapes 250', 250" in rotation thereinbetween. The mobility of supports 110', 110", relative to the coupling fulcrums 132', 132", allows the distance between centres to be defined in relation to the working needs. In this way, a greater pressure is exerted, and thus a greater removal, where the diameter of bar 200 is larger, thus achieving an even diameter on the entire length. Moreover, the opposition of the two supports 112', 112" allows roundness defects to be eliminated, thus determining a precise and constant diameter. A homogeneous polishing results therefrom.
Therefore, the determination of the distance between supports 110', 110" and bar 200 determines the pressure that the same must exert on bar 200 accordingly, also eliminating the heterogeneity of the surface roughness.
Supports 110', 110" are separate from each other but are in contact with two different portions of the surface of bar 200. In particular, they are in contact with two opposite portions of bar 200, with symmetry axis substantially parallel to the symmetry axis of said same bar 200, and exerting a same but opposite pressure so as to balance the efforts and prevent deformations of the same bar 200. In particular, the distance of supports 110', 110" from the ground allows the symmetry axes of the same to be placed on the same plane as the symmetry axis of bar 200.
As the end of the process, an accurate control of the amount of material removed and thus an accurate measurement of the new diameter of bar 200 is obtained by the dimensional control means (not shown).
If the diameter obtained still has larger dimensions than what required, the operator decreases the separation distance between supports 110', 110" and bar 200, reducing the distance between centres of the same. In particular, the reduction of the distance between centres is obtained by acting on screw 140 with a suitable rotation. Therefore, a new process is necessary to reduce the diameter as required.
The above description envisages the use of a device the rotors 112', 112" whereof are both provided with the abrasive tapes 250', 250". The operation is the same if the abrasive tape is provided on only one of the supports whereas the opposite one acts as contrast in the process.
Finally, figure 4 shows a system 500 for processing substantially round bars. This consists of a plurality of devices for the surface processing of the bars according to the above description, arranged in a sequence. Such system 500 forms a complete finishing station for bar polishing, being provided with five devices 10', 10", 10' ", 10"", 10""" with abrasive tapes having a different grain, finer in the devices arranged downstream of the process.
The device for the surface processing of a bar according to the present invention therefore allows the occupied space to be minimized while ensuring the required functions.
Advantageously, the use of two opposite supports allows roundness defects to be eliminated by the fixed distance between centres between the same two supports, thus determining an accurate and constant diameter while having a high flexibility in the use of different bars with heterogeneous surface finishes. In particular, an advantage of the present invention is to exert a greater pressure and thus a greater removal, where the diameter of the bar is larger, achieving an even abrasion on the entire length.
A further advantage of the device according to the present invention is the flexibility of use. In fact, the device is capable of minimizing the processing time and costs, achieving the desired result with the smallest amount of abrasive tapes and the smallest number of operations, thanks to the tape wear evenness on the entire length thereof.

Claims

Device (10) for the surface processing of a substantially round bar (200) comprising support and/or advance means (120', 120") and abrasion means for said bar (200),
wherein
said abrasion means comprise a first movable working support (110') and a second movable working and/or contrast support (110"), at least said first working support (110') being provided with abrasive tape (250' 250"); said two movable supports (110', 110") being opposite and in operating mode being constantly in contact with said bar (200), optionally interposing said abrasive tapes (250', 250"), and keeping a fixed distance between centres between said movable supports (110', 110"), characterized in that
said movable supports (110', 110") each comprising a cylindrical rotor (112', 112") having the symmetry and rotation axis substantially parallel to the symmetry axis of said bar (200), said fixed distance being the distance between their symmetry axis, said cylindrical rotors (112', 112") being vertically movable to bring in operating mode their symmetry axis in line with the symmetry axis of bar (200), so that said axes lie in the same plane, preventing asymmetric processing.
Device (10) according to claim 1, characterized in that said movable supports (110'; 110") in operating mode provide to the rotation of said abrasive tapes (250', 250").
Device (10) according to one or more of claims 1 or 2, characterized in that it comprises support means (130) for coupling with said movable supports (110', 110"); said coupling forming the rotation fulcrums (132', 132") for said supports (110', 110").
Device (10) according to claim 3, characterized in that said support means (130) comprise means for spacing said supports (110', 110") from said bar (200) for modifying said distance between centres.
Device (10) according to claim 4, characterized in that said spacing means comprise a ball recirculation screw (140) for spacing said supports (110', 110").
Device (10) according to claim 4 or 5, characterized in that said spacing means
comprise a pneumatic system and/or a hydraulic system for controlling said supports (110', 110"); said pneumatic system and/or said hydraulic system in operating mode allowing at least one of said two supports (110', 110") to exert a constant pressure on the surface of said bar (200).
Device (10) according to one or more of claims 1 to 6, characterized in that it further comprises means for the dimensional control of said bar (200).
System (500) for processing substantially round bars characterized in that it comprises at least one device for the surface processing of said bars according to one or more of claims 1 to 7.