TANGENTIAL GRINDING MACHINE, PARTICULARLY FOR RAILWAY RAILS

Abstract: A tangential grinding machine, particularly for railway rails, comprising a rotating member (4), a plurality of abrasive sectors (5) mounted on supports radially movable on said rotating member, elements which radially move said supports in order to move said abrasive sectors outwards by an extent which compensates their wear, and a plurality of sensors which when a predetermined degree of wear of the abrasive sectors is attained are activated to act under the control of an electronic unit on the radially movable supports, in order to restore the original grinding surface of the abrasive sectors which have undergone wear, characterised in that between the rotating member (4) provided with abrasive sectors (5) and the machine structure (1) slidable on the rail (3) there is interposed an articulated frame (8) provided with means (15, 16, 17) which cause said rotating member (4) to undergo transverse oscillations about a longitudinal axis substantially coinciding with the axis of curvature of the corresponding band of the rail (3) to be ground.

Description: Tangential grinding machine, particularly for railway rails This invention relates to a tangential grinding machin particularly for railway rails. EP-A2-0 318 521 describes a tangential grinding machin comprising a rotating member, a plurality of abrasive sector supported by supports radially movable on said rotatin member, elements which radially move said supports in orde to move said abrasive sectors outwards by an extent whic compensates their wear, and a plurality of sensors which whe a predetermined degree of wear is attained are activated t act under the control of an electronic unit on the radiall movable supports, in order to restore the original grindin surface of the abrasive sectors which have undergone wear. Because during working the grinding wheels wear i accordance with the deformation of the rail profile to b ground, and hence in a non-uniform manner, a grinding manne consisting essentially of a diamond-set tool is provide which, during the working of the machine, automaticall recreates the profile of the abrasive sectors which i altering due to their wear. This known grinding machine has proved effective in tha it combines the merits of high operability and precis results with the merits of considerable compactness and high degree of safety. In particular, it has bee advantageously used in the case of tramway rails in which th limited vehicle speed, the weights and the stresses concerne are such as not to produce large deformation of the rai profiles. However in the case of railway rails th requirements are of a different kind, both because of th extent of the rail profile deformations and because of th nature of these deformations, which involve the formation o the top of the inner side of the rail of a substantiall pronounced longitudinal projection, resulting in rapid an non-uniform wear of the abrasive sectors and a likewise rapi wear of the diamond-set tool used to restore their origina profile. Based on the fact that a rail profile comprises central band with a curvature of 300 mm connected to tw further lateral bands of 13 mm curvature, the tangentia grinding machine according to the invention, of the typ described in the cited EP-A2-0 318 521 , is characterised i that between the rotating member provided with abrasiv sectors and the machine structure εlidable on the rail ther is interposed an articulated frame provided with means whic cause said rotating member to undergo transverse oscillation about a longitudinal axis substantially coinciding with th axis of curvature of the corresponding rail band to b ground. The present invention is further clarified hereinafte with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view showing the priσipl on which the grinding machine of the invention i based; Figure 2 is a cross-section through a rail portion to a enlarged scale; Figure 3 is a schematic side view of the grinding machin according to the invention; Figure 4 is a plane view thereof on the line IV-IV of Figur 3; Figure 5 is a cross-section therethrough; and Figure 6 is a cross-section on the line VI-VI of Figure 4. As can be seen from the figures, the machine accordin to the invention comprises a structure 1 provided with wheel which run on the rail 3 to be ground. The tangential grindin device, indicated overall by 4, is of the type described i the cited EP-A2-0 318 521, none of the constructional detail given in this latter having however been included in th present description, for reasons of clarity. It need merel be stated that this grinding device is provided with plurality of abrasive sectors 5 rotated simultaneously by a electric motor 6 and mounted on supports (not shown) whic are movable radially outwards to ensure that th circumferential grinding surface remains rigorously constan as the wear to which said sectors 5 are subjected durin working varies. The outward movement of these supports an the relative abrasive sectors 5 is controlled by a pluralit of sensors (not shown) which are normally "covered" by th sectors when they operate on the rail to be ground, but ar uncovered when the sectors 5 wear beyond the predetermine amount - In addition to the wheels 2, the structure 1 is als provided lowerly with a plurality of rollers 7 which overal form a roller table for supporting and guiding the entir machine on the rail 3 to be ground, to overcome th inevitable longitudinal undulations by virtue of thi distributed support, or at last to attenuate their effect- The structure 1 supports an intermediate frame indicated overall by 8 and comprising two shoulders 9 joine by two longitudinal members 10- The entire assembly i supported at its ends by two tubular supports 11, 11 slidable along transverse guides 12, 12' provided in t structure 1. More specifically, one of the two tubul supports 11 is hinged to the corresponding guide 12 about t axis of this latter, whereas the other tubular support 11 consists in reality of a portion 13 rigid with the frame and slidable along a vertical support 14, which is itsel vertically slidable along the guide 12'. In each of the two shoulders 9 of the frame 8 there is curved slot 15 in which there engage a pair of rollers 1 supporting a saddle 17, which supports the grinding device and its drive motor 6. The radius of curvature of the slot 15 is such that when the rollers slide on them the abrasiv sectors 5 of the grinding device 4 describe, in the region o contact with the rail 3 to be ground, a transverse curve surface having the same radius of curvature as th corresponding rail band to be ground- A pair of geared motors of worm type, schematicall shown with 18, are interposed between a longitudinal membe 10 of the intermediate structure to the rail 3, in the manne described hereinafter. A further geared motor 19 is interposed between the structure 1 and a longitudinal member 10 of the intermediate frame 8 to adjust, in the manner described hereinafter, the rest inclination of the grinding device 4 to the rail to be ground. Further geared motors 20, 20' are interposed between the structure 1 and the two tubular structures 11, 11 ' , and a further geared motor 21 is interposed between the two portions 13 and 14 of the tubular structure 11' . On the drawing the structure 1 is shown for a single rail 3, although in a practice it preferably extends from one rail to the other to form a single trolley slidable along the track. As gaps exist between the rails and the wheels of the grinding machine which could result in an inclination of the longitudinal axis of the machine to the track axis, with inevitable negative consequences for the grinding work, the invention in order to preserve perfect mutual parallelis provides two pairs of rollers 22, 23 by which the machine bears laterally against the rails- The roller 22 of each pai is rigid with the structure 1 and bears laterally against on rail 3; the other roller 23 is connected to the end of an ar 24 which is hinged to the structure 1 and is associated at its other end with a pneumatic cylinder-piston unit 25 whic causes said roller 23 to adhere laterally to the other rail- In this manner the axis of the machine according to th invention always remains parallel to the track axis. The operation of the machine according to the inventio is as follows: having defined the extent of interference between th grinding device 4 and rail 3 to be ground by operating th geared motor 21 and hence by adjusting the portion of th support 11' rela ive to the vertical guide, and having als defined the amplitude of oscillation of the saddle 1 relative to the intermediate frame 8, the electric motor and the geared motor 18 are powered- The electric motor rotates the grinding device 4 to thus produce the grindin effect on the rail 3- The geared motors 18 cause the grindin device to undergo a series of transverse oscillations guide by its rollers 16 within the guide slots 15. Because of the particular shape of said slots, th abrasive sectors 5 of the grinding device 4 on the one en restore the original curvature of the rail 3, eliminating i particular the internal longitudinal projection which i develops with use, and on the other hand wear uniformly t preserve their original profile, notwithstanding their wear- The wear compensation takes place in accordance with th known principle, described in detail in EP-A2-0 318 521- The aforesaid presupposes that the abrasive sectors originally have a curved transverse profile conforming to th original profile of the rails 3- However, as the abrasiv sectors usually obtainable commercially in practice have straight transverse profile, the sectors must be initiall shaped to conform to the transverse profile of the rail to b ground- This can be done either by operating the machine for a few metres along the rail portion to be ground so that the transverse oscillations of the grinding device give these sectors the desired transverse curvature, or by associating with the grinding device 4 a diamond-set tool 26 comprising a ip 27 oscillating transversely to describe a circular arc with a curvature corresponding to that to be formed in the abrasive sectors 5- Aε stated, a railway rail 5 has a transverse profile comprising a central band with a radius of curvature of 300 mm connected to two lateral bands of 80 mm radius of curvature, these being connected to two outer bands of 13 mm radius of curvature- Thus whereas the grinding of the central band is done in the described manner, the grinding of the lateral bands requires the shoulders 9 to be previously replaced by others in which the slots 15 have the curvature corresponding to that of the lateral bands to be ground, and the replacement of abrasive sectors 5 by others of a like curvature. Then operating the geared motors 19 the grinding device is inclined to the central plane of the lateral band to be ground, and as this inclination inevitably involves a lateral movement of the device, the geared motors 20, 20' ar operated to cause the entire intermediate frame to slid along the transverse guides 12, 12' of the structure 1, t thus make the central plane of the band to be ground. At this point the grinding operation is performed in th initially described manner. Instead of operating with a single grinding device wit interchangeable parts corresponding to the position an curvature of the rail bands to be ground, it is possible t operate with several devices in succession, each acting on different longitudinal band of the rail- In this case it i no longer necessary either to adjust the lateral inclinatio of the grinding device or to adjust its lateral movement, however an oscillatory movement of each grinding device is still required about its neutral position, whether this is vertical or inclined. These transverse oscillations are always obtained by the geared motors 18. It should be noted that there are five different- curvature bands on a railway rail, and it would therefore seem at first sight that five grinding devices would be required. However as the deformation of the rails 3 generally involves their inner part, only three grinding devices are required, one acting on the central band of 300 mm curvature, another on the inner lateral face of 80 mm curvature, and the third on the inner end face of curvature 13 mm- From the aforegoing it is apparent that the tangentia grinding machine according to the invention is particularl advantageous, in that: - it enables the profiles of railway rail to be totally an perfectly ground, however deformed; - it combines the merits of the tangential grinding whee with those of the traditional cup grinding wheel while a the same time eliminating the drawbacks of this latter, i the large number of tools and the resultant "flats" on th ground rai1 ; - using a single grinding wheel for every rail radius o curvature results in easy control of the work hig productivity and substantially quiet operation; - it maintains a constant abrasive sector profile and in fac restores it in a virtually perfect manner.

Claims: CLAIMS 1- A tangential grinding machine, particularly fo railway rails, comprising a rotating member (4), plurality of abrasive sectors ((5) mounted on support radially movable on said rotating member, elements whic radially move said supports in order to move said abrasiv sectors outwards by an extent which compensates their wear, and a plurality of sensors which when a predetermine degree of wear of the abrasive sectors is attained are activated to act under the control of an electronic unit on the radially movable supports, in order to restore the original grinding surface of the abrasive sectors which have undergone wear, characterised in that between the rotating member (4) provided with abrasive sectors (5) and the machine structure (1) slidable on the rail (3) there is interposed an articulated frame (8) provided with means (15, 16, 17) which cause said rotating member (4) to undergo transverse oscillations about a longitudinal axis susbantially coinciding with the axis of curvature of the corresponding band of the rail (3) to be ground. 2. A tangential grinding machine as claimed in claim 1, characterised in that the intermediate frame (8) is hinged to the structure (1) about two coaxial longitudinal pins and is provided with an actuator (19) connected to said structur (1) to define the central position of the rotating membe (4). 3- A tangential grinding machine as claimed in claim 1, characterised in that the structure (1) is provided wit transverse guides (12, 12') for supports (11, 11') of th intermediate frame (8), the positioning of this latter alon said guides being obtained by actuators (20, 20'). 4. A tangential grinding machine as claimed in claim 3 characterised in that the intermediate frame (8) is hinged a one support (11) to a transverse guide (12) of the structur (1) and has its other support (11') vertically adjustable t adjust the interference between the rota ing member (4) an the rail (3) to be ground. 5. A tangential grinding machine as claimed in claim 2 characterised in that the rotating member (4) is hinged t the intermediate frame (8) about a longitudinal axi coinciding with the axis of curvature of that band of th rail (3) to be ground. 6- A tangential grinding machine as claimed in claim 2 characterised in that the intermediate frame (8) is provide with two shoulders (9) in which curved slots (15) ar provided having their center of curvature lying on the axi of curvature of that band of the rail (3) to be ground, i each slot there being engaged a pair of guide rollers (16) rigid with a saddle (17) supporting the rotating member (4), said saddle being connected to the intermediate frame (8) via at least one actuator (18), which impresses transverse oscillations on it during the rotation of the rotating member (4). 7- A tangential grinding machine as claimed in claim 1, characterised in that the intermediate frame (8) comprises two pairs of rollers (22, 23) for laterally bearing against the two rails (3) of the track in order to eliminate any clearance between the wheels (2) of said structure (1) and said rails. 8- A tangential grinding machine as claimed in claim 7, characterised in that each pair of rollers (22, 23) comprises a first roller (22) of vertical axis rigid with the structure (1) and adhering to the inner side of a rail (3) and a second roller (23) also of vertical axis, mounted at the end of an arm (24) hinged to the structure (1) and urged at its other end by an actuator (25) to press said roller (23) against the inner side of the other rail (3). 9. A tangential grinding machine as claimed in claim 1, characterised by comprising a diamond-set tool (26) consisting of a rod hinged to the intermediate frame (8) such that the tool tip (27) describe a transverse circular arc having a radius of curvature corresponding to the radius of curvature of that band of the rail (3) to be ground. 10. A tangential grinding machine as claimed in one or more of claims 1 to 9, characterised in that several rotating members (4) acting on different bands of the rail (3) to be ground are mounted on the structure (1), each rotating member oscillating transversely about a central position coinciding with the longitudinal central plane of the correspondin band.

Inventors: FAVARON CLAUDIO, FAVARON, CLAUDIO
Applicants: ROTRAFER S R L, ROTRAFER S.R.L.
Application year: 1991
Main classification: E01B31
IPC codes: E01B31