FR2495036A1 - PRECISION RECTIFIER MACHINE WITH HYDROSTATIC BEARING GUIDANCE - Google Patents

Abstract

The grinding machine for external diameters has a table 11 which slides on two pairs of hydrostatic guide bearings 41, 42 arranged on the bed and is supported by two series of hydrostatic support bearings. The grinding wheel headstock 18 also slides on hydrostatic guide bearings with which hydrostatic bearings are associated either support or opposition. (CF DRAWING IN BOPI)

Description

The present invention relates to a precision grinding machine

  precision grinding machine comprising a worktable which slides on the bench in a first direction and a portemeule doll which slides in another direction perpendicular to the first. In known grinding machines, the slides of the table and the headstock are normally made of lubricated cast iron or plastic with a low coefficient of friction. Also known are grinding machines having slides to

  rollers which subsequently lower the coefficient of friction

ment.

  These grinding machines have the disadvantage of requiring

  a laborious and precise machining is either fixed slides or movable slides, whose cooperation generates wear and, as a result, causes games that over time change the accuracy. We also proposed slides to

  hydrostatic bearings for moving parts, in which

  the contact of the movable member with the fixed slide is limited to the film of pressurized oil brought into a cavity of

  the slide. These slides, however, did not find an

  systematic use in machine tools in general and in

  grinding machines in particular.

  The technical problem which the invention proposes to solve

  dre is to create a precision grinding machine in which are eliminated the long machinings of the slides,

  as well as the wear of the slides and the game that comes from it.

  This technical problem is solved by the grinding machine

  proud according to the invention, which is characterized in that for each of the two directions of movement of the table

  and the doll there is at least one pair of

  drostatic guideways arranged along the correct direction

  corresponding to the right of two sections spaced from each other by a predetermined value .: It is clear, therefore, that a precision machining of the slide on which are arranged the two hydrostatic bearings is no longer necessary , since the machining of the surface which rests on these bearings is sufficient to obtain the perfect linearity of the slide represented by the plane

passing through the two levels.

  According to other characteristics of the invention - at each hydrostatic guide bearing is associated with at least one hydrostatic bearing support of the table and / or

the doll.

  each guide bearing and each support bearing comprises at least one pressurized oil supply pipe, a pit for the oil and a calibrated throttling mechanism.

  disposed between the pipe and the pit.

  - said pipes are fed by a hydrau-

  oil flow from the pits being recovered.

  in an interior cavity to these guide members or

  slides and being returned to said hydraulic power station.

  lic. - the right of at least one of those sections are provided

  two opposite pits for guidance and / or support.

  - the pits of the guide bearings of the table are arranged

  on the bench to the right of two sections provided for

  these equidistant from the point of application of the thrust of

the grinding wheel.

  - the pits of the support bearings of the table are arranged

  in the table and act in one direction.

  - the pits of the guide bearings and bearings corresponding to

  wheels are opposite each other in pairs and are arranged in line with two sections of the

  the movement of the doll, the recovery of the oil is

  fectuant via a cavity of said doll.

  the mandrel is guided in its rotation by two series of hydrostatic guide bearings arranged in line with two sections of the mandrel, each bearing comprising four

  distant pits angularly 900 arranged in the struc-

fixed position of the mandrel.

  the mandrel is further supported by two series of hydrostatic thrust bearings, the thrust bearings of the two

  series being opposed and being provided on an organ

axial port of the mandrel.

  the mandrel is rotated by an electric motor by

  by means of a pulley rotating on a support

  said guide bearings, an angular drive element being provided between said pulley and said mandrel.

  - the grinding headstock is likely to move longitudinally

  tudinal way by means of a DC motor, with

  inertia, specific to the control of the race of appro-

  fast, either of the working course.

  - the engine is controlled by a digital control device

  for the execution, in addition to the fast approach course and the working course, of at least one of the

  following: recovery of the consumption of the grinding wheel,

  initial registration of the wheel position and record

  really points of departure from the working race for

different diameters.

  - the engine is associated with a tachymetric dynamo and a co-

  the digital control device controlling the said

  speed and position feedback, acceleration

and controlled deceleration.

  - the motor is placed on the wheelhead, its movement is

  cement to be obtained from a fixed screw and a mother screw circulating balls rotated by the

  motor and connected longitudinally to said doll

millstone.

  Other accessory features of the invention appear

  in the detailed description given below in

  in the annexed drawing. Of course, the description and the

  drawing are given only as an indicative example and not

limiting.

  FIG. 1 is a perspective view of a precision grinding machine according to the invention; FIG. 2 is a diagrammatic plan view with partial section of the grinding machine of FIG. 1; FIG. -is a front view with partial section of the same grinding machine,

  FIG. 4 is a partial sectional view taken

  5 is a sectional view taken along the line V-V of FIG. 4,

  FIG. 6 is a sectional view taken according to the

  VI-VI of Figure 2 on an enlarged scale,

  FIG. 7 is a partial sectional view taken

  line VII-VII of Figure 6,

  FIG. 8 is a partial sectional view taken

  on line VII.-1VIII of FIG. 6 on an enlarged scale; FIG. 9 is a diagram of a different orientation;

of the grinding machine.

  Referring to Figure 1; 10 indicates in a general way

  the bench of a precision grinding machine, which is

  includes a work table It slides in the long-term direction

  on the bench 10. On the table 11 is placed a

  water 12 on which is fixed, in a manner to be described later, a workhead support 13 supporting a rotating mandrel 14. On the plate 12 may further be fixed, in variable longitudinal position, a group 15 supporting a counter-tip 16, which serves in conjunction with the mandrel 14 to hold the part 17 to grind, indicated by the dashed lines in Figure 3. On the bench 10 is disposed, further, a grinding headstock 18, which

  slides transversely to table 11 for ame-

  a rotary grinding wheel 19 in contact with the part 17.

  The plate 12 is connected to the table 11 by a central pivot

  tral 20 (Figures 2-and 3) and can rotate slightly with

  port to it to record, using a micro-screw

  metric 21 and a graduated scale 22 (Figure 2), the parallel

  lelism of the axis of the piece 17 with respect to the direction

  the table 12 is fixed rigidly.

  on the table 11 by means of two locking devices

23 (Figure 3.

  - Under the table It is fixed a lead screw 24 ball circulation preloaded double net for play catching, with which is engaged a threaded rod 26 rotating in two supports 27 fixed on a wall 28 of the bench 10. On a cylindrical end of the rod 26 is fixed a pulley 29 connected via a belt 30 to a pulley 31

  of a DC electric motor 32. This. is com.

  This apparatus is intended to control the movement of the table 11 concurrently with the plate 12 and the

room 17.

  Along the direction of movement of the table 11, the bench 10 has two fixed slides 34 and 35 (FIG. 4) with which two corresponding slides collaborate.

  36 and 37 arranged under the table 11.

  According to the invention, in correspondence of two sections 38

  and 39 fixed slides 34 and 35 (FIGS. 2 and 3) equidistant

  relative to the point of action of the wheel 19 on the

  piece 17, in each of the fixed slides 34 and 35, is dis-

  a hydrostatic guide bearing consisting essentially of

  A depression or pit 41, 42 and a corresponding calibrating throttle mechanism 43, 44 (FIG. 4) are provided by means of a line 45 to pressurized oil. This comes from a hydraulic unit generally indicated at 46 in FIG. 2, which filters the oil and switches it on via a pump.

  47 under a pressure of about 40 atmospheres.

  Each throttling mechanism 43, 44 (FIG. 4) consists of a cylindrical chamber communicating in the central part with the supply line 45 and at the end

  blind with a hole communicating with the kid 41, 42.

  Depending on the arrangement of the throttle mechanism, the supply line can also communicate with the blind end of the cylinder and the orifice with its central portion. A portion towards the end of the cylindrical chamber is threaded to receive a threaded end of a throttle piston 40 which has in correspondence of the cylindrical chamber a helical groove of square section. By more or less screwing the piston 40, between the supply line and the orifice, there is a variable length of groove, thus adjusting

  the pressure of the oil in the pit 41, 42.

  It is clear from what has been seen above that the pits 41 and 42 (see also Figure 2) of each section are opposite and the slides 34 and 35 (Figure 4) are rectangular. This is why the table 11 can slide while being perfectly balanced and the given central thrust

  by the threaded rod-26-screw-mother pair 24 (FIG.

  There is no cross-sectional component, unlike what happens with known V-shaped tables. It is clear however that the arrangement of the four pits 41 and 42 on the bench makes it possible to spare the work of the fixed slides 34

  and 35, which are obviously longer than the slides

  movable seats 36 and 37 of the table 11.

  The vertical support of the table 11 is provided by a series.

  of eight hydrostatic bearing bearings, the pits 48 and 49 are arranged in two parallel rows on the horizontal surface of the slides 36 and 37. Each pit 48, 49 is

  supplied by a pipe 50 via a

  corresponding throttle channel 51, 52 equal to that of the pits 41, 42. In the two rows of pits 48 and 49 are not opposed the other pits, the opposition made by the weight of the table It being sufficient. The arrangement of the pits 48 and 49 on the table 11 makes the position of the bearing bearings independent of the position of the wheel 19. In fact, the weight of the table 11 outweighs the action of the wheel 19, while that the number of pits provided ensures that the wheel 19 will always act in an area of the intermediate table-between

  at least two pairs of pits 48 and 49.

  The oil flowing from pits 41, 42 and 48, 49 through

  towards the respective channels is collected in a cavity 55

  delimited by the wall 28 of the bank 10. It is then completed

  mined towards the hydraulic power station 46.

  The grinding wheel 19 is fixed on a shaft 51 (FIGS. 6 and 7) which is turned on the grinding headstock 18. The shaft 51 is rotated by means of a belt 52 by means of a? electric motor 53 supported by the doll 18. The tension of

  the belt can be adjusted by means of a mechanism

  The housing 54 is provided with a manual control generally designated 150. A housing 54 covers the upper portion of the grinding wheel 19. Under the grinding head 18 is secured by means of screws 56 (FIG. each of the two sides by an L-shaped section 58,59. These two profiles form, with the respective lower surfaces 61, 62 of the doll 18, the movable slide of the carriage of the doll 18, which connects with the two fixed rectangular slides 63, 64

  supported by a carrier carriage 66 of the doll 18.

  Slides 63 and 64 are covered by a bellow hood

and telesopopic wall '76.

  According to the invention, in correspondence of the two sections 67 and 68 (FIG. 6) of the cross member 57 are provided two pairs of hudrostatic guide bearings, the pits 69 and (FIG. 8) of which are opposed in pairs, guaranteeing a sliding without friction and perfectly linear doll 18 same. Each pit 69 and 70 is fed by a pipe 71 via a throttling mechanism

corresponding 72 and 73.

  In addition, to the right of each section 67 and 68, (Figure 6)

  on the cross-member 57 are provided two pairs of

  drostatic bearing, whose pits 74 and 75 are gained on the surfaces 61 and 62 of the doll 18 and are fed by a pipe 83 via two corresponding throttling mechanisms 78 and 79. In contrast to pits 74 and 75, on the cross-member 57, are provided pits 81 and 82 of two pairs of opposing hydrostatic bearings

  powered by a conduit 83 through

  corresponding bottlenecks 84 and 85. Therefore,

  the doll 18 is perfectly guided either in the horizontal plane

  tal, ie in the vertical plane and the action of the grinding wheel 19 is

  perfectly absorbed by the opposite pits 74, 81 and 75,82.

  The oil flowing from the pits 69, 70, 74, 75 and 81, 82 through the respective channels is collected in a cavity 87 (FIG. 6) inside the carrier holder 66 and

  transported from it to the hydraulic power station 46

  to a pipe not shown in the figure.

  The grinding headstock 18 is moved on the carrier support I6.6 by means of a permanent-current electric motor 88 (FIG. 6) with permanent magnets fixed to the headstock 18. On the spindle motor 88 is fixed a pinion 89

  which, via a return gear 91, does.

  turn a toothed wheel 92 whose hub 93 rotates on rolling bearings of an appendage 94 of the wheelhead 18. Inside the hub 93 is provided a lead screw 96 with ball circulation which collaborates with a screw 97 fixed on two supports 98 of the support 66. It is clear, therefore, that the doll is rotated by means of the screw 97 and the lead screw 96 rotated by the motor 88

  and connected longitudinally to the doll 18.

  The motor 88 supports in its axis a tachometric dynamometer

  99 and an encoder 101 for the angular position, which cooperate with the digital control apparatus 33 (FIG. 2) to control the motor 88 with feedback of speed and

  position, with controlled acceleration and deceleration. The apparent

  33 is able to control the motor 88 and taking into account either the work program or the recovery of the consumption of the grinding wheel 19 following each diamonding performed periodically by a diamond 1G2 'Figure 2). The motor 88 has characteristics such that it can command under the control of the apparatus 33 either the approach run or the working run. In particular, the motor 88 has a relatively low power

  high and low inertia, to such an extent that it can

  dye, for example, a speed of 3000 rpm in

  in 30 milliseconds. Thanks to the hudrostatic bearings of

  and support of the doll 18, even the resistance of

  rage of the movement of the doll 18 is reduced. The power required by the 88 engine for fast approach races

  is of the same order of magnitude as that required for

  his work. That is why the same motor 38 can fill

  both functions. The apparatus 33 is furthermore capable of

  to request the rotation of the motor 88 for the initial recording of the position of the wheel and for the recording of the points

  starting work strokes for different diameters.

  The carriage support 66 is connected to a portion 105 of the bench 10 by a pivot 106 fixed on this portion 105. The support 66 is furthermore provided with two hollow seats 107 in which a finger 108 can be engaged. end is frustoconical which slides in a cylindrical hole of a block 109 fixed on the bench 10. The finger 108 has a toothed portion and is moved vertically by means of a pinion

  supported by a shaft 111 capable of turning by hand.

  The three seats 107 are arranged so as to locate a position of the support 66 for the front grinding of the cylindrical pieces and a position of the trolley turned by 300 in the direction of clockwise for grinding.

  simultaneous diameter and shoulder (Figure 9).

  To position the support 66, we first make

  turn the shaft 111 to disengage the finger 108 from the seat 107.

  The support 66 can then be rotated by hand around the pivot 106. When the support 66 is approximately with the seat 107 intended aligned with the finger 108, the shaft 111 is rotated again, so that the pinion 110 causes the finger 108 to engage in the seat 107 by correcting

  the position of the support 66. This is then blocked rigidly

  in this position through blockages

screw 112 (Figure 7).

  The workhead 13 (FIG. 4) is fixed on the pla--

  12 through a block 115 having an appendage

  V-slide 116. Block 115 has a tapped hole in the-

  which is screwed a threaded end of an axis 117. By screwing it, the block 15 moves to the left, so that the headstock 13 is rigidly locked on the plate 12 with a shoulder 113 of the doll 13 against a shoulder 114 of the plate 12 and with the appendix 116 of the block against a slide 118 in V of the plate 12, which makes

  that the doll 18 is urged down.

  The mandrel 14 comprises a barrel 121 (FIG. 5) rotating

  in a seat 122 of the doll 13 and adapted to receive a poin-

  te support the piece 17 between the tips or another tool, for example a clamp to pinch an end of the piece. The barrel 121 is rotated by a key 123 (Figure 4) supported by a pulley 124 which rotates on a pair of rolling bearings 126 (Figure 5) mounted on another seat 127 of the doll 13. The pulley 124 is connected by means of a channel 128 to a pulley 129 fixed to the shaft of an electric motor 131 which controls the rotation of the barrel 121 and, consequently, of the part. It is clear, therefore, that the pulley 124 rotates on a support 127 separate from the support 122 of the barrel 121, so that the traction of the belt 128 does not affect the

canon 121.

  The gun 121 rotates on the seat 122 by means of two series of four hudrostatic guide bearings arranged in line with two predetermined sections 132 and 133 of the gun 121. Each bearing of the two series comprises a pit 134 or 135 formed in the seat 122 and fed by a pipe 137 via a corresponding throttling mechanism 138, 139. The four pits 134 and 135 (Figure 4)

  of each series of bearings are arranged 900 between them.

  The oil flowing from the pits 134 and 135 is collected in a cavity 141 of the doll 13, from where it is sent

  at the hydraulic unit 46 (Figure 2).

  The barrel 121 (FIG. 5) is further provided with a flange

  142, which is supported axially in both directions by two flanges 143 and 144 opposite and fixed on the doll 13. On each flange 143 and 144 are arranged two series of four hydraulic thrust bearings each comprising

  a pit 146, 147 formed in the flange 143, 144 and food

  by means of a conduit 148, through a mechanism

  corresponding throttle 149. The pits 146 and 147 are angularly 90 apart. The oil flowing from the pits 146 and 147 is collected in the cavity 149 of the doll 13 and is sent from there to the hydraulic unit 46

(Figure 2).

  It is clear, therefore, that pits 146 and 147 (Figure 5) are opposite, so that any

  axial thrust on the barrel 121 is compensated, while

  contribute to compensate for the transversal actions of the

grinding wheel 19 on the piece 17.

  The grinding machine is equipped with a safety device

  known in itself capable of blocking the operation until the oil supplied by the hydraulic unit 46 has reached the prefixed pressure. The development of the grinding machine includes, of course, the individual casting of the hydrostatic bearings via the respective throttling mechanisms. For this purpose, the pressure in the pits is measured with special pressure gauges, while the attitude of the relative guided member is controlled by comparators with an accuracy of 1 / 1.000 millimeters. Common oil circuit facilitates pressure equalization

in the different pits.

  Of course, various modifications and various

  may be made to the grinding machine which

  has been described without departing from the scope of the

vention.

  For example, the number and position of

  or support or stop may differ from those described above. Moreover, the grinding machine can

  be equipped with a self-centering chuck

  jogging a hollow part to be corrected

  laughing. Finally, two oil circuits can be provided, or more,

instead of one.

Claims (12)

  1- Precision grinding machine comprising a table   holder (11) which slides on a bench (10) in a first   re direction and a grinding headstock sliding in another direction perpendicular to the first, characterized in that for each of said directions there is provided a pair of hydrostatic guide bearings (41-43 and 42-44) arranged   along the direction corresponding to the right of two sec-   (38 and 39) spaced apart from one another by predetermined.   2- grinding machine according to claim 1, characterized   in that at each hydrostatic guide bearing (41-   43, 42-44) is associated with at least one hydrostatic bearing   (48-51, 49-52) for supporting the table (11) and / or the doll (13).   3- grinding machine according to claim 2, characterized   characterized in that each guide bearing and each support bearing comprises at least one pipe (45-50) for supplying oil under pressure, a pit (41, 42, 48, 49) for the oil and a calibrated throttling mechanism (43, 44, 51, 52)   between the pipe (45-50) and the pit (41, 42, 48, 49).   4- grinding machine according to claim 3, characterized   characterized in that said pipes (45-50) are fed by a single hydraulic power unit (46), the oil flowing from the pits being recovered in a cavity (55) internal to these guide members or slides and being returned to said hydraulic power unit (46).   - grinding machine according to one of the claims   3 or 4, characterized in that at the right of at least one of the sections are provided two opposite pits (69 and 70) for the guidance and / or support.   6. Grinding machine according to claim 5, characterized   characterized in that the pits (48 and 49) of the guide bearings of the table (11) are arranged on the bench (10).   two sections (34 and 35) at equidistant distances   the point of application of the grinding wheel thrust (19).   7- grinding machine according to claim 6, carac-   characterized in that the pits (48 and 49) of the support bearings of the table (11) are arranged in the table (11) and act in one direction.   8- Grinding machine according to one or other of the   5 to 7, characterized in that the pits (41 and   42) of the guide bearings (69 and 70) and corresponding steps   of the doll (18) wheel holder (19) are opposed in pairs and are arranged in line with two sections (67 and 68) of the direction of movement of the doll (18), the recovery of the oil s doing through   a cavity (87) of said doll (18).   9- Grinding machine according to any one of the   1 to 8 above, including a mandrel   piece (14), characterized in that the mandrel (14) is guided in its rotation by two series of hydrostatic bearings   (134-138, 135-139) disposed at the right of two sec-   (132 and 133) of the mandrel (14), each bearing comprising   four pits (134 and 135) angularly distant 90   in the fixed structure of the mandrel (14).   - grinding machine according to claim 9,   characterized in that said mandrel (14) is further supported by two sets of hydrostatic abutment bearings (146-149, 147-149), the thrust bearings of the two series being opposed and being provided on a member (143144) of axial support mandrel (14).   11- Grinding machine according to one of the claims   9 or 10, characterized in that said mandrel (14) is rotated by an electric motor (131) via a pulley (124) rotating on a support (127) -distinct said guide bearings (134). - 138, 135-139), an element   angular drive (123) being provided between said means. lie (124) and said mandrel (14).   12- Grinding machine according to any one of the   1 to 11 above, characterized in that la-   said doll (18) wheel holder (19) is likely to move   longitudinally by means of a DC motor (88), with low inertia, suitable for the control of the race   fast approach, either from the work run.   13- Grinding machine according to claim 12, characterized   characterized in that said motor (88) is controlled by an apparatus   control wheel (33) for execution, in addition to the fast approach course and the working stroke, from   least one of the following:   summation of the grinding wheel (1d, initial recording of the position   grinding (19) and recording starting points   of the working stroke for different diameters.   14. Grinding machine according to claim 13,   characterized in that said engine (88) is associated with a tachometer dynamo (99) and an encoder (101), said   digital control (33) controlling said motor (88) with   speed and position action, with controlled acceleration and deceleration. - grinding machine according to claim 14, characterized in that said motor (88) is arranged on the   grinding wheel (18), its displacement being to be ob-   held from a fixed screw (97) and a main screw (96) circulating balls rotated by the motor (88) and   longitudinally connected to said grinding headstock (18) (19).