DEVICE FOR REDUCING THE ROUGHNESS

Abstract: Device for reducing the roughness of plane or cylindrical surfaces of a body (12) machined on machine tool, provided with grinding wheel (6) having suitable granulometry on saddle (5) fastened to the fixed part (8) of said machine in a translatable way in respect of said body and with means (1, 2, 3, 4) suited to push the wheel-carrying saddle (5) constantly during the operations of polishing so that the grinding wheel (6) adheres on the surface to be polished uniformly on all its parts, thus following the technical surface and not the ideal one of the body.

Description: Device for reducing the roughness The new device in conformity with the present invention refers to a device for reducing the roughness, which operation shall be indica_ ted for shortness in text and claims only with the word polishing, and specifically of the roughness of plane or cylindrical surfaces of a body machined by means of a tool respectively on a planer or a lathe or a grinder or machine tools of this type, roughness being intended as the whole of the unevennesses, that is the most part of the m icro_ geometrical errors, which make the real surface of a body different from the technical one, opposed to the macrogeomet ical form errors which make the technical surface different from the ideal one. Treatments exist up to now suited to reduce the roughness after the said machining on the machine tool, the amount of which roughness we shall indicate with the value Ra and namely the mean arithme_ tical val.ue adopted by the DIN standardization as well as by UNI, and which after said machining generally amounts respectively to Ra = 1 micrometer, unit of measure which we shall indicate in the folk? wing for shortness with the symbol used in the techniques of "μm", after machining with the planer, Ra = 0,25 μm after machining with the lathe, Ra = 0,1 μm after machining on the grinder. The treatments up to now employed allow at the most to bring the roughness to a value of Ra of about 0,004 Pin, limits which are a_ tained only with the operations of polishing with very fine-grained grinding wheels on ground surfaces. But for carrying out finishing operations with so low Ra values many machining hours are required. In addition, as the present means available for regulation of the wheels against the surface to be polished allow only a practically fixed position of their saddle, and as the surfaces have after machining operations with the planer, the lathe and also after grinding, especially in the case of very long cylindrical bodies, still macro geometric a I form errors, it follows that the action of the wheel cannot be perfectly equal in all the po_ tions subjected to polishing with the consequence that the roughness cannot be reduced everywhere to the required values and namely unj^ for ly over the whole surface to be polished, as well as particularly after special treatments of the surfaces as for instance after chrome plating, the higher pressure in some portions can cause injuries related to the previously occurred treatments. In other polishing operations as those effected on the lathe, after the relevant machining, wheels and brushes and lubricators are used which heavily soil machines and surrounding room with both the draiv backs of having the operators working in dirty places and of having to provide for heavy cleaning operations and restoring of machines and rooms. Aim of the device in conformity with the present invention is to eliminate the aforesaid drawbacks and to carry out an operation of reduction of the roughness perfectly homogeneous in any portion of the surface to be polished and so to attain much more lower values of the residual roughness, even lower than 0,001 μm, and with times of processing much lower than the present ones and without the risk of causing injuries to the eventual previous treatment of the p I is he d surfaces. The device for reducing the roughness of plane or cylindrical surfa_ ces of a body machined on a machine tool, in conformity with the present invention, is composed of a wheel having cylindrical form and granulometry suited to the required reduction of the roughness, mounted with rotary motion according to its axis on a sliding saddle having very low friction on a fix guide which is made directly or indirectly integral to the base of the machine whereon the tool ma chining has been effected or of a similar one, said saddle being provided in addition to the usual means to control approaching of the wheel to the surface of the body, which must be disconnectable from the saddle when the wheel reaches with its peripherical working su_ face near the surface to be polished, with means suited to push it during the whole polishing operation in such a way that the wor_ king surface of the wheel remains in contact with the surface to be polished with a perfectly constant pressure uniformly all over the said surface. In a preferred solution the device is composed of one or more coun_ terweights i. e. one or more cables fastened at one of their ends to the said wheel-carrying saddle and at the other end respectively to one or more heavy free bodies, and of one or more sets of trans_ mission pulleys, the axis of which is fastened to the fix part of the device and hence of the base of the machine tool so that the cable, or cables, owing to the action of the weight of the aforesaid heavy bodies, cause the saddle and as a consequence the wheel to adhere to the surface to be polished constantly in a uniform way, the value of the weights of said bodies, the arrangement of the pulleys and the direction of the sections of said cable or cables being so dete_ mined as to achieve the required value of the said pressure, which of course can be subsequently modified on the same device by rn _ difying the weight of the bodies acting as counterweights. In an improvement of the previous solution the counterweight or coun_ terweights are connected to the wheel-carrying saddle in such a way that the resultant of their thrusts on the saddle act practically accor_ ding to the longitudinal axis of the guide of the saddle. In a further improvement the motor operating the wheel is connec_ ted to the wheel-carrying saddle and eventually also to the wheel with means suited to avoid transmitting its eventual vibrations. In a further improvement of the previous solutions the device is provided with one or more lightening cables namely directly or indj_ rectly connectable to the wheel-carrying saddle at one of their ends and to a fix structure in respect to the machine tool base at the other end and with eventual means to bring the cable or cables under stress, the sizes and resistance of cable or cables being such that when the wheel-carrying saddle is in working position it is stressed by a vertical resultant force upward such as to reduce the force which its mass discharges on the guide and consequently to reduce propor_ tionally the friction between saddle and guide so that the action of the pressure of the wheel of the device against the surface to be polished occurs with still more uniformity. In another solution the device includes only the means suited to push the saddle during the whole phase of polishing and eventually the lightening cable or cables,- being such means directly connected to the saddle of the wheel which the machine tool whereon polishing is effected is equipped ith, and namely usually a grinding machine, and thus such means directly acting on said saddle and hence on the w hee I . The above exposition evidences the important advantage of the new device as with it the action of the wheel is constant and uniform independently from the macrogeometr ical form errors, the working sur_ face of the wheel always remaining adhering with the same pressure on the whole surface to be polished. In order to explain better the device according to the present invention an embodiment shall be described, as an example only, with reference to the enclosed diagram drawings wherein: - figure 1 is a plan view; - figure 2 is a side view; - figure 3 is a perspective view from F. The device for reducing the roughness of the example is composed only of the means for automatical continuous approaching, including two sets of elements a and b, each one composed of a cable 1, of a vertical axis pulley 2 and of a horizontal axis pulley 3 as well as of a weight 4- The two sets of elements are applied symmetrically one on one side and the other one on the other side of the saddle 5 which carries the very fine-graned wheel 6 of a grinding machine 7, of which the figure shows very schematically the base 8, the slide 9 which is moved w ith alternate movement along its guide 10, integral with the base 8. Of the two sets a and b of the automatical approa_ ching means the drawings practically show only the one arranged on the left when looking to the plan of figure 1, where also part of the cable lb and of the weight 4b and the pulley 3 are seen; not all of the motors and the transmissions of the general movements of the grinding machine are shown on the drawings, for easiness and. also because they are well known to the prior art. The saddle 11 carrying the work piece 12 composed of a steel cylinder, which peripherical surface has already been ground, is made integral with the slide 9. The saddle 11 is provided with the motor 13 which transmits the r£ tary movement through its shaft 14 and the two cross members 15, made integral with the cylinder 12. At the other end the cylinder is supported in free rotation by the saddle 16 of the tailstock through the pin 17 and two cross members similar to the previous ones but not in view. The wheel-carrying saddle 5 has a sliding coupling with minimal friction with the guide 18 integral to the side extension 19 of the base 8, to said saddle is integral the casing of the motor 20 which transmits the rotary movement to the wheel 6. The saddle 5 can be shifted manually until the peripherical surface 6p of the wheel 6 adheres to the peripherical surface 12p of the cylinder to be po_ lished 12, then the saddle is pushed automatically and constantly by the resultant thrust of the actions of the counterweights 4a and 4b, which thanks to the symmetrical arrangement of said means acts practically according to the axis of longitudinal symmetry of the -guide 18 of the saddle 5, said counterweights 4a and 4b are connec ted to the free end of the cables la and lb, while the other end o said cables is connected to the shaped flat bars 21a and 21b, each one composed of three parts, of which the two external 22a and 22b and 23a and 23b are reciprocally parallel and vertical while the intermediate one is horizontal, the first upper parts 22a and 22b are respectively fastened to the two sides of the saddle by means of the screws 25a and 25b, and the parts 24a and 24b are so sized as to keep the subsequent parts 23a and 23b off from the sides of the base 19, the said parts 23a and 23b being connected to the cables la and lb„ w.hich pass then in the peripherical grooves of the two pulleys 2a-2b and 3a-3b. The pins 2ap and 2bp supporting in free rotation the pulleys 2a and 2b are vertical and their lower ends are fastened to the horizontal upper surface of the parallelepiped lateral extensions 26a and 26b of the base 19, while the pins 3pa and 3bp supporting in free rotation the pulleys 3a and 3b are horizontal and are fastened at one end to the lateral surface of the extensions 27a and 27b o the base 19 of the wheel-carrying saddle, the positions of the pulleys 2a-2b and 3a-3b being such that the first two sections of the cables la and lb are horizontal, while the third sections of the cables la and lb ace vertical as their free ends are connected to the counter weights 4a and 4b. The wheel-carrying saddle 5 is provided in ad dition with the ring 28, which is fastened on the upper surface 5s of the same, to said ring can be fastened through the slip hook 29 the lower end of the cable 30 which is fastened at the other end to a structure 31 which is fix in respect to the grinding machine base, said cable is provided with the turnbuckle 32 which allows, after con nection of the cable with the slip hook 29 to the ring 28j to be so stretched as to transmit to the wheel-carrying saddle 5 such a vertj cal stress upward as to reduce the force with which the mass of sai saddle presses on its guide 18, and so to allow a considerable r duction of the friction of said coupling and hence a much more unj form operation of the device of counterweight in pushing the wheel against the technical surface of the cylinder 12.

Claims: [received by the International Bureau on 13 March 1987 (13.03.87); original claim 1 amended; other claims unchanged (1 page)] . . 1. Device for reducing the roughness of plane or cylindrical surface of a metallic body of large dimensions, that is of surfaces greate 2 even than 250 m , machined on machine tool to value of Ra even les than 0,001 μ m characterized in that it is composed of a wheel (6) h ving cylindrical form and granulometry suited to the required reductio of the roughness, mounted with rotary motion according to its axi on a sliding saddle (5) having very low friction on a fix guide (18) which is made directly or indirectly integral to the base (8) oF th machine (7) whereon the tool machining has been effected or of a simj lar machine, said saddle (5) being provided in addition to the usual means to control approaching of the wheel to the surface of the body, which must be disco nnectable from the saddle (5) when the wheel (6) reaches with its peripherical working surface near the surface (1) t be polished, with means suited to push it during the whole polishin operation in such a way that the working surface of the wheel (6) r ains in contact with the surface (12) to be polished with a perfectl constant pressure uniformly all over the said surface. 2. Device as claimed in claim 1 characterized in that it consist of one or more counterweights (a, b) i. e. of one or more cables (la, lb) fastened at one of their ends to the said wheel-carrying saddl (5) and at the other end respectively to one or more heavy fre bodies (4a, 4b) and of one or more sets of transmission pulley (2a, 2b, 3a, 3b), the axis (2ab, 2bb, 3ab, 3bb) of which is fastene to the fix part of the device and hence of the base (8) of the machine tool so that the cable, or cables (la, lb), owing to the action of th weight of the aforesaid heavy bodies (4a, 4b), push the saddle (5 and as a consequence the wheel (6) to adhere to the surface (12 to be polished constantly in a uniform way, the value of the weight of said bodies (4a, 4b), the arrangement oF the pulleys (2a, 2b, 3a, 3b) and the direction oF the sections oF the cable or cables (la, lb being so determined as to achieve the required value oF the sai

Inventors: MAGNI GIULIO, MAGNI, GIULIO
Applicants: MAGNI GIULIO, MAGNI, GIULIO
Application year: 1986
Main classification: B24B47
IPC codes: B23Q5, B24B47