US3858366A

US3858366A - Band grinding tool for rounding edge portions of blades for compressor and turbine plants

Info

Publication number: US3858366A
Application number: US320587A
Authority: US
Inventors: Ilia Lvovich Tashker
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-01-02
Filing date: 1973-01-02
Publication date: 1975-01-07
Anticipated expiration: 1992-01-07

Abstract

A band grinding tool for rounding the edge portions of blades for compressor and turbine plants is proposed wherein the device for fastening the workpiece to be machined and for feeding it to the grinding area comprises a support connected to the bed through an elastic link, the support being capable of moving in the direction of the transverse feeding and carrying a movable head connected to it, and containing a means to accomplish the longitudinal traverse of the tool profile along the surface of the profile cam, the means being used for rocking the head with respect to the support to accomplish the longitudinal traverse of the workpiece along the grinding band supported in the machining area by the support cam.

Description

[ Jan. 7, 1975 Unite States atent n91 Tashker Primary Examiner-A1 Lawrence Smith EDGE PORTIONS OF BLADES FOR Assistant Examiner-Nicholas P. Godici COMPRESSOR N TURBINE PLANTS Attorney, Agent, or Firm-Waters, Roditi, Schwartz &

Nissen 1 BAND GRINDING TOOL FOR ROUNDING a s .n we MU k "8 M v Tk m2 3 mm .m m .1 K E O I n e v n I 1 6 7 .l.

U.S.S.R.

ABSTRACT 22 Filed: Jan. 2, 1973 21 Appl. No.: 320,587

rein the device for fastening the workpiece to be machined and for feeding it to the grinding area comprises a support connected to the bed through an elastic link, the support being capable of moving in the di- [52] US. 51/144, 51/148 [51] Int. B2411 21/16 [58] Field of Search.......... 51/135 R,l41, 142, 143

rection of the transverse feeding and carrying a movable head connected to it, and containing a means to References Cited accomplish the longitudinal traverse of the tool profile UNITED STATES PATENTS along the surface of the profile cam, the means being 51/144 used for rocking the head with respect to the support 5 4 to accomplish the longitudinal traverse of the workpiece along the grinding band supported in the machining area by the support cam.

2,606,406 8/1952 Muel1er................................ 3,528,200 9/1970 Allen FOREIGN PATENTS OR APPLICATIONS 4 Claims, 3 Drawing Figures Patented Jan. 7, 1975 2 Sheets-Shem 1 Patented Jan. 7, 1975 2 Shoots-Sheet m BAND GRINDING TOOL FOR ROUNDING EDGE PORTIONS OF BLADES FOR COMPRESSOR AND TURBINE PLANTS The present invention relates to grinding tools, and more particularly, to band grinding tools for rounding edge portions of blades for compressor and turbine plants.

The invention can most successively be used for dimensional rounding of variable-radius spatial curves in a direction lengthwise of the edge portions of blades for gas turbines. The blades machined on the tool may contain one flange (lock), two flanges or have no flanges at all. It is also possible to machine the edge portions of blades having rectilinear generants and being in compliance with the linear law of changing the curve radius.

The tool can find a wide application in the aircraft engine building industry, as well as in general engineering for machining the edges of blades for stationary gasturbine installations, compressors, etc.

At present the machining rounding the leading and the trailing edges-is one of the most urgent problems in the engine building industry, since the engine efficiency as well as the strength of the blade proper, i.e. the service life of the engine, in the long run, depends on the quality of the edges.

The rounding of the variable-radius spatial curves in a direction lengthwise of the edge portions of blades for gas-turbine engines is carried out at present everywhere manually with the aid of grinding blocks, which fails to provide the required geometrical rounding, being often accompanied by burned edges and inflicting professional diseases on the workmen, yielding at the same time a low labour productivity.

Numerous attempts to mechanise the rounding operation by grinding the variable-radius spatial curves in a direction lengthwise of the edge portions of blades failed to produce positive results and did not find application due to the following reasons.

While machining separately the tip profile and the edges, warpage of the tip and its climb from the bases inevitably occur in the course of grinding which makes it impossible to use these bases while machining the edges (a forcible bending of the tip in order to remain the bases is not allowed).

The device for grinding the leading and the trailing edges of blades by means of an abrasive wheel shown in the book by M. F.ldzon Mechanical Machining of Blades for Gas-Turbine Engines, Moscow, 1963, FIGS. 5, 8, p. 177, has the same disadvantage, and some others, too:

a. the grinding by an abrasive wheel causes, as a rule, the burning of the blade (no matter what kind of cooling is applied), microcracks and, consequently, reduces the service life of the blade;

b. while grinding by an abrasive wheel, the workpiece sticks as it turns around the axis of the edge centres, receiving a shock and being bent.

The band grinding tools also described in the book by M. F.1dzon Mechanical Machining f Blades for Gas- Turbine Engines, Moscow, 1963, pp. 195-21 I, employing a narrow abrasive band are utilized to machine the tip of the blade together with the edges all around per one positioning of the workpiece, i.e., they are dispensed with the mentioned disadvantages, but have a complex system of two matched cutting profiles or complex spatial cutting profiles of the entire tip of the blade whose finishing is complicated, therefore the tools have so far failed to provide a suitable workpiece with machined edges. Besides, all these tools possess such essential disadvantages, as:

a. since it is impossible to maintain an uninterrupted grinding, the machining of edges on them is accompanied by a considerable wear of the abrasive band and its possible breaks; one has also to expect the sticking and bending of the blade tip by the band;

b. their efficiency is small in machining the edges while they employ a narrow band;

c. it is impossible to machine the slant edge portions of the blade having high flanges.

The machining of the edge portions of blades by blade tools (planar tool, milling cutter) described, for example, in US. Pat. No. 2,74l,l64, issued Apr. 10, 1956, Methods of and Apparatus for Working Materials does not ensure the machining of edge in a direction running the entire length of the edge and its slant portion, since for this purpose it is necessary to have a section of considerable length to accommodate the too]. This disadvantage becomes more manifest while machining blades which have high flanges (locks). Besides, due to low strength of the cutting tool, this method of machining cannot practically be used for rounding the edges of the turbine blade fabricated from heat resisting alloys, possessing a high hardness and viscosity. The quality of the machined surface obtained in the course of blade machining is of low strength and poor geometrical characteristics, and in order to improve them a finish machining is required.

The only tool producing dimensional rounding by grinding the leading and the trailing edge portions of blades for compressor and turbine plants is the blade grinding tool developed, constructed and utilized in the USSR for rounding the edge portions of the blades having rectilinear generants (Authors Certificate No. 195,922 issued in the USSR on Jan. 21, 1966).

installed on the machine bed of the known tool is a device for fastening the workpiece to be machined and for feeding it to the grinding area, and a mechanism for moving the grinding band being supported in the machining area by a support cam. The support cam is lo cated in the bed, and in the course of grinding it moved reciprocatingly in the direction perpendicular to the surface to be machined to perform the interrupted (vibrational) grinding.

The rounding of the edge portion on the known machine tool is accomplished while the blade rotates with respect to the rectilinear axis of the rounding radii, and in this case the working surface of the support cam is flat.

Since the known machine tool contains no mechanism for profiling, it cannot perform the rounding of variable-radius spatial curves in a. direction lengthwise of the edge portions of the blades having a curvilinear axis of the rounding radii.

The principal object of the present invention is to provide a band grinding machine which ensures the machining of the variable-radius spatial curves in a direction lengthwise of the edge portions of blades, including the edges with rectilinear generants.

Another object of the invention is to provide a machine tool for machining the edge portions of the blades having high locking flanges.

Still another object is to provide a tool which can use a wide abrasive band for machining the edges.

Besides, an object of the invention is to provide a tool capable of machining the edges by means of interrupted grinding which increases the strength of the band, and due to decrease of heat intensity of the cutting process, contributes to a higher quality of the machined surface.

These and other objects of the invention are accomplished by means of the band grinding tool having a bed which supports therein a device for fastening the workpiece to be machined and for conveying it to the grinding area, and a mechanism for moving a grinding band which is retained in the machining area by a support cam located in the bed. The cam, during the course of grinding, performs reciprocating movements in order to accomplish an interrupted grinding sequence wherein, according to the invention, the device for fastening the workpiece to be machined and for feeding it to the grinding area contains a support mounted on the bed and which is capable of moving in the direction of transverse feeding of the workpiece. The device carries a movable head with an attachment for fastening the workpiece and a tool profile, and includes a drive for effecting their synchronous rotation so as to be able to feed the workpiece angularly, with the tool profile for the transverse feeding of the workpiece being constantly pressed against the profiling cam mounted on the bed, the latter of which is flexibly connected to a support to ensure a longitudinal traverse of the tool profile along the surface of the profiling cam, and having a means for rocking the head with respect to the support through a movable connection therebetween for carrying out a longitudinal traverse of the edge to be machined along the grinding band while being supported in the grinding area by the support cam.

This made it possible to machine the variable-radius spatial curves in a direction lengthwise of the edges (including those with rectilinear generants) by means of a wide abrasive band while accomplishing the interrupted abrasive band grinding. The machine tool is capable of machining the edge portions of the blades having high locking flanges or without the latter.

According to the invention, it is most expedient to have a movable connection between the support and the head in the form of a common axle movable in the support and having a head and a lever fastened to it, the latter being connected to the means for rocking the head.

Such a design provides for a very simple rocking of the head and a reliable protection of the movable components and units against impurities and abrasive particles, thus contributing to improved reliability and a longer service life of the tool.

It is expedient to make provision for moving the support in the direction of the transverse feeding of the workpiece by means of a pivot connecting the support with the bed, the pivot axle being moved at some distance and held parallel to the common axle of the support and the head.

Such a design is easily protected against impurities, lends itself to be industrially produced and can be fabricated with a high degree of accuracy. This improved the accuracy of the tool and the stability of its characteristics in the process of operation.

It is advisable to construct the means for rocking the head with respect to the support in the form of a linkand-cam mechanism wherein one end of the link interacts with the lever connected through an axle to the head, the other end of the link is adapted to take up the constant-amplitude oscillations, and its rocking axle is located on the slide moving along the link for changing the rocking amplitude of the head in the course of operation according to the pre-set law to be determined by the configuration of the edge to be machined and set by the cam profile.

Owing to the fact that the said means is so constructed, a compact rigid design is obtained which provides highly accurate movements as a result of the rigid kinematic connection of its moving components and units; the small size and a low weight of such a construction make it possible to increase to a maximum the number of head rockings limited only by the inertia of its mass, thus improving the quality of the machined edge surface.

Other features and advantages of the present invention will become more apparent from the detailed description of a specific example with reference to the accompanying drawings wherein:

FIG. 1 is a kinematic diagram of the tool, according to the invention;

FIG. 2 is a basic diagram of the blade movement while rounding its edge portion on the tool, according to the invention;

FIG. 3 is a sectional view taken on line II-Il of FIG. 2.

The proposed band grinding tool for rounding the edge portions of blades for compressor and turbine plants comprises the follwing main assemblies: a bed I (FIG. I) installed on which there is the device for fastening the workpiece to be machined and for feeding it into the grinding area, and the mechanism for moving the grinding band.

The device for fastening the workpiece to be machined and for feeding it into the grinding area contains a support 2 mounted on the bed I by means of a pivot 3 making it possible for it to move in the direction of transverse feeding of the workpiece. Movable on the support 2 is the head 4. The movable connection between the support 2 and the head 4 isconstructed in the form of a common axle 5 installed in the support 2 in tapered bearings.

In this case, the axle of the pivot 3 is spaced some distance apart from the common axle 5 and is held parallel to this axle 5. Mounted on the head 4 is the device 6 for fastening the workpiece and the tool profile 7, as well as the drive for synchronous rotation of the blade 8 to be machined and the tool profile.

The mechanism for moving the grinding band contains a roller 9 leading the abrasive band 10 by means of a V-belt drive and being rotated by the electric motor II. Mounted on the bed I is the profile cam 12 supporting the grinding band 10 in the machining area. The working surfaces of the two cams l2 and 13 are cylindrical, their axes coincide in the working position, and their radii difference is equal to the difference of distances from appropriate points of the machined surface of the blade 8 and the surface of the tool profile 7 to their rotation axes O and 0,, with the thickness of the band 10 being subtracted, provided the tool profile 7 is thicker than the edge of the blade 8. If the tool profile 7 is thinner than the edge portion of the blade 8, the

thickness of the band is added (algebraically) to the difference so obtained. To compensate for the wear of the band 10, the profile cam 12 can be moved by means of the adjusting screw 14.

The support cam 13 is capable of moving reciprocatingly while grinding in the direction perpendicular to the axis of its cylindrical working surface by means of an eccentric 15 installed on the shaft 16 which is rotated by the V-belt drive from the electric motor ll connected to the band 10 performing, as a result, the interrupted grinding. The value of the eccentricity e, i.e., the displacement amplitude of the support cam 13 can be changed in the course of adjustment.

To form a transverse feeding of the workpiece, the tool profile 7 is constantly pressed against the profile cam 12 installed on the bed I by means of an elastic connection linking the support 2 and the bed I, and constructed in the form of a tension spring 17.

The blade 8 is fastened to the attachment 6 which is capable of rotation about the axle l8 and of movement along the guides 19 perpendicular to the working surface of the support cam 13. When bringing the blade 8 to the fixing pins (not shown in the Fig.) fastened to the bed I and determining the initial position of the blade 8 (they are pressed against the trough surface of the edge portion of the blade located immediately at the edge to be machined), all the movable elements of the attachment are fixed in the positions they occupy, after which the machining cycle can be started.

The shaft 20 of the attachment 6 installed on the head 4 is rigidly connected to the parallel shaft 21 which rotates the tool profile 7 by means of a steel band 22 fastened to the drums 23 of equal diameters.

For a synchronous rotation of the tool profile 7 fas tened to the shaft 21 and the blade 8 connected to the shaft 20 of the attachment 6 for fastening the blade, to forman angular feeding, use is made of the pinion 24, toothed sector 25 and pinion 26 fastened to the shaft 27. The pinion 26 is rotated by means of a rack 28 installed in the support 2. The rack 28 can move reciprocatingly under the effect of the arm 29 rotated about the axle 30 by means of the flat cam 31 (which sets the law of varying the speed of rotation of the blade 8 while machining the edge) and has for this purpose a roller pusher 32 and a spring 33 for returning the rack 28.

To form a longitudinal traverse of the tool profile 7 on the surface of the profile cam 12, the support 2 is equipped with a means which rocks the head with respect to the support for the purpose of accomplishing the longitudinal traverse of the edge portion of the blade 8 along the grinding band 10 supported in the machining area by the support cam 13.

The said means is a link-and-cam mechanism whose cam 34 is designed to vary the rocking amplitude of the head 4 and is fixed on the same shaft as the flat cam 31 and the worm wheel 35 rotated by the worm 36.

The worm 36 is fastened to the shaft 37 connected through a telescopic link 38 installed in the bed I to the reduction gear 39 of the feed and traverse drive by means of which the motion from the electric motor 40 is imparted (through the pinions Z Z Z Z Z the switch-over unit of pinions Z and Z Z and Z the shaft 41 and the pivot link 42) to the support 2.

To form the rocking amplitude of the head 4, use is made of a cam generator consisting of a drum cam 43 which is rotated through the

pinions

44 and 45, with the latter being fastened to the shaft 37, and a movable frame 46 interacting with the drum cam 43 through the pin 47 located in the curvilinear groove of the drum cam 43.

The movable frame is located in the support 2 with the aid of the journals 48 and carries the link whose end 49 is pivotably fastened to it, for the movable frame 46 to take up the oscillations of constant amplitude from the drum cam 43. The other end 51 of the link 50 has two rollers, one of them being located in the fork of the bracket 52 which serves as the lever connected to the head 4, and the other roller in the stationary guides 53 of the support 2 being used to take power load off the link 50. The connection between the bracket 52 and the head 4 is effected in the form of stationary link between the head and the common axle 5 which, in turn, is rigidly connected to the head 4 to impart the rocking of the link 50 to the head 4.

The link 50 has a movable slide 54 with its rocking axle in the form of journals 55 located in the fork 56 of the slide 57 installed on the support 2.

The slide 54 can move reciprocatingly along the link under the effect of the arm 58 rotating about the axle 30 by means of the cam 34, for which purpose the fork 56 has on its end a movable link 59 connected to the end of the arm 58, and the power circuit of the cam 34 is locked by the spring 60 supporting the slide 57.

Thus, the variation of the rocking amplitude of the head 4 takes place in the course of operation in accordance with the pre-set law which is determined by the configuration of the edges to be machined and set by the profile of the cam 34.

Employed in the tool is a mechanism for tensioning the grinding band which makes it possible:

to provide a considerable effort of tensioning the grinding band since the employed band has a width equal to or a little larger than the length of the edge to be machined, and 4 to have a minimal inertia to avoid tearing the band and to improve the conditions for the interrupted grinding.

Accordingly, the mechanism for tensioning the grinding band comprises a guiding roller 61 rotating loosely on the end of the shaft 62, a tension roller 63 rotating on the axle 64 fastened by means of a bracket 65 and held parallel to the shaft 62, an arm 66 mounted on the opposite end of the shaft 62 with a tension spring 67 fixed to one end of the shaft and with a rod 68 fixed to the other end, the rod being pivotably connected to the rack 69. A self-switchingoff oil damper 70 is fastened to the arm 66. The other end of the spring 67 is fastened to the bed I.

For tensioning the spring 67 (while replacing the band 10), the pinion Z being engaged with the rack 69 and fastened to the same shaft 71 as the pinion Z can be rotated with the help of the electric motor 40 while switching over the unit of pinions Z Z, by means of the handle 72. The rack 69 is provided with a springloaded latch 73 serving to retain the spring 67 in a tensioning position for which purpose there is a stop 74 fastened to the bed I. The handle 72 has a stop 75 which, while placing the unit of pinions Z Z to the operating position (engagement with the pinion Z8). depresses the latch 71 releasing the rack 69. The selfswitching-off oil damper 70 has a piston 76 whose rod is fastened to the arm 66, and a cylinder 77 which has two cavities: one being located under the piston 76 and the other serving as an oil tank (the cavities are interconnected by means of a non-return ball valve 78 and an orifice located at the bottom of the cylinder 77). The bottom of the cylinder 77 contains a spherical well and a bar 79 located in the middle. The bar 79 has a longitudinal hole containing a cylindrical pin 80 installed in the vertical wall of the bed I. The spherical plate 81 is mounted on the horizontal wall of the bed I under the bottom of the cylinder 77. The cylinder 77 is lifted from the horizontal wall of the bed (and, consequently, from the spherical plate 81) by the spring 82; its travel is restricted by the displacement of the pin 80 in the longitudinal hole of the bar 79,

FIG. 2 shows the diagram of machining (rounding by grinding the variable-radius spatial curve in a direction lengthwise of the edge portion of the blade to be accomplished by the tool of the proposed design.

In FIG. 2:

O is the horizontal axis of rotation of the blade 8; the rotation about the axis provides for the feeding of the workpiece to the tool profile (the direction of movement of the blade 8 about the axis is indicated by the arrows B-B);

K is the principal vertical axis of traverse about which the edge portion of the blade 8 is traversed, this being accomplished along its generant on the working surface of the support cam 13 having the abrasive band located on the latter, with the direction of the band movement being indicated by the arrow a;

N is an auxiliary vertical axis of traverse, the rocking about which is necessitated by the rocking of the blade 8 about the axis K, Le. in the course of the traverse the axis K is being displaced occupying the positions K,

. K, etc.

To provide conditions for traversing the blade 8 along the working surface of the cam 13, it is necessary that the working surface beconvex (cylindrical for the sake of simplicity, as fabrication is concerned) since the abrasive band does not fully adjoin to a concave surface (in the mid-portion of the concave support cam), and the grinding is accomplished irrespective of the'cam shape contributing to a lower accuracy of machining. As a result, the radius R of the cylindrical working surface of the support cam 13 must be selected to be of maximum size (to reduce the rocking angle of the blade 8 about the axis K in the course of traverse), but it must be smaller than the minimal curvature radius of the edge surface to be machined in the longitudinal cross-section.

Thus, the rounding of the edge is accomplished while rocking simultaneously the blade 8 with respect to the axis 0, K and N. (The positions taken up in this case by the blade 8 are indicated by the dashed line). Evidently, the amplitude of rockings of the blade 8 with respect to the axis K (the amplitude of rockings about the axis N coincides with the amplitude of rockings about the axis K) must be considerably greater than the amplitude of rockings about the axis 0, to ensure highquality machining (absence of finish, improved cooling, etc.). In this case, grinding is performed in a quickmoving point of contact (the speed of its travel depends not only on the frequency of rockings of the blade 8 about the axis K, but on the difference between the radius R and the curvature radius of the edge in its crosssection: the smaller the difference, the higher the speed of the contact point travel along the edge. In this way, it is possible to achieve such high speeds of the contact point travel (grinding) along the edge, as cannot be obtained otherwise. It means that with a similar quality of machining, for example, while obtaining a similar finish of the edge, the productivity of the proposed tool (its machining diagram is shown in FIG. 2) will be considerably higher than any others.

The tool (its kinematic diagram is shown in FIG. I) operates in the following manner.

In the tool prepared for work, the abrasive band 10 occupies the operating position on the

rollers

9, 63, 61, and on the working surface of the cam 13; the kinematic traversing circuit is closed by the handle 72, with the pinion Z being engaged with the pinion Z The blade 8 is installed in the attachment 6 and moves towards the cam 13 (turning about the axle l8 and along the guides 19) so that the surface of the edge trough would contact the two stops (not shown in FIG. I); in this position all the movable elements of the attachment 6 are fixed ensuring the positioning of the blade 8 along the edge to be machined.

In the tool prepared to start work, the spring 17 presses the tool profile against the surface of the profile cam 12 turning the support 2 on the pivot 3 with respect to the bed I.

On starting the electric motor II, the guide roller 9 sets the abrasive band 10 in motion (the direction of travel of the band is indicated by the arrow a); the motor rotating the eccentric 15 imparts reciprocating motion along the arrow B to the support cam 13 performing the interrupted grinding. The power is transmitted from the electric motor through a V-belt drive.

The electric motor 40 is switched on to provide power for the feeding and traversing. The direction of travel of the mechanisms are shown in the Figures by arrows to give a better presentation. Its rotation is transmitted to the support 2 by means of the reduction gear 39 (toothed wheels Z, Z through the pivot link 42 and the telescopic connection 38. The worm 36 and the drum cam 43 rotate therewith, the latter being set in motion by means of the

pinions

45 and 44. The worm 36 rotates the fiat earns 31 and 34 with the help of the worm wheel 35. The flat cam 31 acts by means of the roller pusher 32 on the arm 29 (rotated on the axle 30) which lifts therack 29 (it is lowered by the spring 33). The rack 28 turns the pinion 26 resulting in a simultaneous rotation (in the same direction and at the same speed) of the blade 8 and the tool profile 7, since the motion is imparted by the toothed sector 25 to the pinion 24 fastened to the shaft 21 and then further by means of the band 22 fastened to the drums 23 to the shaft 20. Thus the feeding of the blade 8 (its edge) to the cutting profile is ensured. Simultanesously, the rotating drum cam 43 rocks the movable frame 46 in the journals 48 by means of the pin 47. As a result, the end 49 of the link 50 pivotably fastened to the frame rocks together with the slide 54 about the journals 55 of the latter. The other end of the link located in the fork of the bracket 52 (fixed to the axle 5 of the head 4) while moving turns the head 4 rocking it in the bearings of the support 2 accomplishing the traverse of the edge of the blade 8 along the surface of the cam 13 (or the tool profile 7 along the surface of the profile cam 12).

The curvature of the edge surface of the blade 8 in the various cross-sections passing through the axis of rotation O is different, and while machining, it is necessary to maintain the speed of the longitudinal traverse of the blade (the speed of travel of the contact point between the abrasive band and the surface of the blade 8 to be machined).

To make provision for this, the cam 34 rotates the arm 58 about the axle 30 moving the slide 54 along the link 50, with the slide 57 supporting the slide 54 being also moved. The travel of the slide 54 changes the ratio between the arms of the link 50 whose end 49 together with the movable frame 46 performs rockings of constant amplitude and cycle.

As a result, the amplitude of the rockings of the upper end 51 of the link 50 changes, maintaining a constant cycle of rockings, i.e. the rocking speed of the head 4 changes in compliance with the change in the curvature of the surface of the blade 8 and the travelling speed along the edge of the contact point between the surface to be machined and the abrasive band 10 remains constant while the blade 8 rotates.

When the arm 29 performs one double rocking with one revolution of the cams 31 and 34, the blade 8 returns to the initial position and the tool stops indicating the end of the machining operation.

The replacement of the abrasive band 10 is carried out in the following manner. The pinion Z is brought into engagement with the pinion Z by means of the handle 72. The electric motor 40 by rotating the pinion Z by means of the pinions Z Z Z shifts the rack 69 turning the arm 66 and also the bracket 65 with the tension roller 63 and tensioning the spring 67 until the spring-loaded latch 73 passes over the stop 74. In so doing, the piston 75, 76 of the self-switching-off damper 70 comes out of the cylinder 77. Having positioned the abrasive band 10, the handle 72 is lowered; its stop 75 is pressed against the latch 73 releasing the spring 67 which strains the abrasive band 10. To avoid the tear of the abrasive band 10, use is made of the selfswitching-off damper 70. The spring 67 thrusting the piston 76 into the cylinder 77 makes the oil pass through the orifice located at the bottom of the cylinder. The excess pressure in this case shifts the cylinder 77 in the wake of the piston 76 compressing the spring 82 (which is weaker than the spring 67) until the bottom of the cylinder 77 rests on the spherical plate 81 fastened to the bed I. The travelling speed of the piston 76 is determined afterwards by the diameter of the orifice in the cylinder 77. When the tool operates, the damper 70 should not effect the mobility of the tensioning system of the abrasive band 10. This is achieved due to the spring 82 which lifts the cylinder 77 clear of the spherical plate 81 (the lift is restricted by the cylindrical pin 80 located in the longitudinal hole of the rod 79 of the cylinder 77).

To eliminate the resistance to the piston 76 while coming out of the cylinder 77 (when tensioning the spring 67), use is made of the non-return ball valve 78.

The tool constructed according to the described kinematic diagram made it possible to accomplish a dimensional rounding of the edge portions of blades rendering a high-quality surface and increasing the operational reliability and service life of the edge portion of blades.

Being rather self-contained, with no complex hydropneumatic and electropneumatic components, the tool having all the open assemblies made pivotable, with a minimal number of transitional pairs (which contributes to a better protection of the construction against 10 impurities) ensures a highly reliable operation, simple maintenance and adjustment.

The arrangement of the tool profile and the workpiece to be machined on one head with a minimal number of conjugated components ensures a high accuracy of operation irrespective of the wear of drive mechanisms and guides, and also contributes to a longer service life of the tool.

What is claimed is:

l. A band grinding tool for rounding the edge portion of workpieces, such as blades for compressor and turbine plants within a grinding area comprising: a bed; a mechanism for moving a grinding band installed on said bed; a device for fastening the workpiece to be machined and for feeding it to the grinding area, the device being installed on said bed; a support cam located in said bed retaining the grinding band in the area of machining the blade during the course of grinding, means performing reciprocating motions to said support cam to accomplish interrupted grinding; said device for fastening the workpiece to be machined and for feeding it to the grinding area comprising a movable head with an attachment for fastening the workpiece and a tool profile; a support mounted on said bed including means for moving in the direction of the transverse feeding of the workpiece and carrying said movable head, the support being connected through an elastic link to said bed; a profile cam mounted on the said bed; a drive for effecting synchronous movement of said attachment for fastening the workpiece and of the tool profile, the drive imparting angular feeding movement to the workpiece; said tool profile being constantly pressed against said profile cam to accomplish the transverse feeding of the workpiece, said drive including means to form a longitudinal traverse of the said tool profile toward the surface of the said profile cam, said last-mentioned means rocking said head with respect to said support through a movable link therebetween for the longitudinal traverse of the workpiece edge with-respect'to the grinding band.

2. A tool as set forth in claim 1 wherein the connection between the support and the head is constructed in the form of a common axle movably installed in the support with a head and a lever fastened to the axle, the lever being connected to the means for rocking the head.

3. A tool as set forth in claim 1 wherein the means for rocking the head with respect to the support is a linkand-cam mechanism wherein one end of the link interacts with a lever connected to the head through a common axle, and the other end is adapted to take up constantamplitude oscillations, with a link-rocking axle being constructed on the slide moving about it for changing the amplitude of the head rocking in the course of operation according to the configuration of the edge to be machined and adapted to be set by a cam profile.

4. A tool as set forth in claim 3 wherein said means for moving the support in the direction of the transverse feeding of the workpiece is a pivot connecting the support with the bed, the axle of the pivot being spaced at some distance and held parallel to the common axle of the support and the head.

Claims

1. A band grinding tool for rounding the edge portion of workpieces, such as blades for compressor and turbine plants within a grinding area comprising: a bed; a mechanism for moving a grinding band installed on said bed; a device for fastening the workpiece to be machined and for feeding it to the grinding area, the device being installed on said bed; a support cam located in said bed retaining the grinding band in the area of machining the blade during the course of grinding, means performing reciprocating motions to said support cam to accomplish interrupted grinding; said device for fastening the workpiece to be machined and for feeding it to the grinding area comprising a movable head with an attachment for fastening the workpiece and a tool profile; a support mounted on said bed including means for moving in the direction of the transverse feeding of the workpiece and carrying said movable head, the support being connected through an elastic link to said bed; a profile cam mounted on the said bed; a drive for effecting synchronous movement of said attachment for fastening the workpiece and of the tool profile, the drive imparting angular feeding movement to the workpiece; said tool profile being constantly pressed against said profile cam to accomplish the transverse feeding of the workpiece, said drive including means to form a longitudinal traverse of the said tool profile toward the surface of the said profile cam, said last-mentioned means rocking said head with respect to said support through a movable link therebetween for the longitudinal traverse of the workpiece edge with respect to the grinding band.

3. A tool as set forth in claim 1 wherein the means for rocking the head with respect to the support is a link-and-cam mechanism wherein one end of the link interacts with a lever connected to the head through a common axle, and the other end is adapted to take up constantamplitude oscillations, with a link-rocking axle being constructed on the slide moving about it for changing the amplitude of the head rocking in the course of operation according to the configuration of the edge to be machined and adapted to be set by a cam profile.