Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21H—MAKING PARTICULAR METAL OBJECTS BY ROLLING, e.g. SCREWS, WHEELS, RINGS, BARRELS, BALLS
  • B21H3/00—Making helical bodies or bodies having parts of helical shape
  • B21H3/02—Making helical bodies or bodies having parts of helical shape external screw-threads ; Making dies for thread rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
  • B23P9/00—Treating or finishing surfaces mechanically, with or without calibrating, primarily to resist wear or impact, e.g. smoothing or roughening turbine blades or bearings; Features of such surfaces not otherwise provided for, their treatment being unspecified
  • B23P9/02—Treating or finishing by applying pressure, e.g. knurling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
  • B23P9/00—Treating or finishing surfaces mechanically, with or without calibrating, primarily to resist wear or impact, e.g. smoothing or roughening turbine blades or bearings; Features of such surfaces not otherwise provided for, their treatment being unspecified
  • B23P9/04—Treating or finishing by hammering or applying repeated pressure

Definitions

• the subject of the present invention is a method and a device for finishing by burnishing a helical thread cut on a cylindrical piece, and more particularly a method and a device allowing the finishing of a helical gear screw with one or more threads. .
• the burnishing operation generally makes it possible to improve the surface condition of the parts which are subjected to it and to increase the surface resistance of the metal of which these parts are made.
• a part of which a part has a corresponding profile or a shape complementary to the surface to be finished is pressed against a surface to be finished, with a relatively high pressure, and this part of corresponding profile is rolled and possibly slid over the surface to be finished.
• surface defects due to machining are more or less flattened, and the condition of the surface to be finished is significantly improved.
• the burnishing operation is carried out using burnishing knobs comprising helical threads complementary to those for which the surface condition is to be improved.
• the drive in rotation of (or) wheel (s), on the one hand, and the workpiece, on the other hand, is carried out, in the prior art, by only one of these elements and generally by the roller (s) of burnish; the drive in rotation of the other of these elements results from the cooperation of the helical thread of the part and the corresponding profile part of the wheel (s).
• 80-06 582 in the name of the Applicant, has described a process of this type, in which the piece to be finished is clamped between a burnishing wheel, comprising a complementary helical thread of that of the part, and a counter-part, and in which the part to be finished is rotated in synchronism with the roller of burnishing.
• a burnishing wheel comprising a complementary helical thread of that of the part
• a counter-part in which the part to be finished is rotated in synchronism with the roller of burnishing.
• at least one burnishing wheel is used, so that the workpiece to be finished is clamped between several identical burnishing knobs, regularly distributed around the axis of the workpiece, the axes said knobs being parallel to the axis of the part to be finished.
• the latter can be clamped between two roller knobs, arranged on either side of the part to be finished, so that the axes of the two knobs and the axis of the part are coplanar, and the two roller knobs can be clamped against the workpiece by means of a jack, or by bringing together, by means of a jack, the two arms of a compass at the ends of which the two knobs are mounted.
• each of the roller knurling wheels used has the shape of a cylindrical roller which carries, on its lateral surface which acts on the screw, a helicoidal thread complementary to the thread cut on the screw. Therefore, in order to obtain a good surface condition of the screw thread after the burnishing operation, the complementary threads of the cylindrical burnishing knobs must be machined with very high precision, of the order of 2 microns.
• the object of the present invention is to define a method and a device for finishing by roller burnishing which makes it possible to obtain results at least as satisfactory as those obtained by the method and the machine described in French patent application 80-06 582. , but of an easier and much less costly implementation.
• the subject of the invention is therefore a method of finishing by roller burnishing a helical thread cut on a cylindrical part, in particular a gear screw with one or more threads, in which a portion of corresponding profile is introduced into the helical thread.
• a roller of rolling and one tightens one against the other the part and the wheel, one of which is driven in rotation on itself around its axis and drives the other also in rotation on itself around its axis, by cooperation of the helical thread and the corresponding profile part, and a wheel of which the periphery has, in section, a profile corresponding to the helical thread, characterized by the fact that said wheel is mounted rotatably on a support author of an axis inclined on the axis of the part; that one drives the rotating part on itself around its axis; that the roller wheel is applied resiliently against the workpiece, at one end of the thread; that the support of the wheel is allowed to move parallel to the axis of the workpiece, so that the periphery of the wheel
• the method according to the invention is preferably intended to be implemented according to a repetitive automatic cycle, comprising a predetermined number of passes of the burnishing wheel along the helical thread of the part driven in rotation; it advantageously replaces the process described in French patent application 80-06 582, according to which the burnishing is carried out in a single pass of the threaded part between at least two cylindrical burnishing knobs, one or less of which is driven in synchronism with the workpiece, because the single burnishing wheel is much less costly to make and less bulky than the two cylindrical knurls: we can, in fact, save the synchronized drive device of a knurl and the part, and a hydraulic cylinder and its supply and control circuit, which are costly and bulky components, can be replaced by application means elastic of the burnishing wheel against the workpiece, which consist, in a particularly advantageous embodiment, of a simple compression spring.
• the burnishing wheel can be mounted idle in rotation both around an axis having a fixed orientation on the support and around an orien axis table on the latter.
• the orientation of the axis of the burnishing wheel on the support can be blocked after the elastic application of part of the peripheral profile of the wheel in the helical thread of the part; but it is also possible to allow the self-adjustment of the burnishing wheel at the bottom of the helical thread of the part by letting the axis of the wheel orient itself freely, within a predetermined range of travel on the support, after the elastic application of part of the peripheral profile of the wheel in the helical thread of the part and during the movement of the wheel and its support parallel to the axis of said part.
• the invention also relates to a device intended for implementing the finishing process by burnishing a helical thread cut on a cylindrical part, as presented above;
• the device according to the invention comprises a mechanism for holding the part and a roller for roller burnishing, part of the peripheral profile of which corresponds to the thread of the part and is intended to be inserted into the latter, and it is characterized by the fact that the holding mechanism of the cylindrical part simultaneously ensures the rotational drive of this part on itself, around its axis;
• the knurling wheel is a wheel, the periphery of which has, in section, a profile corresponding to the helical thread, said wheel being mounted idly in rotation on an axis, the axis of the roller wheel being inclined on the axis of the workpiece and carried by a stressed support, in a sensitive direction perpendicular to the axis of the workpiece, by elastic means of applying the burnishing wheel against the workpiece; that the support is movably mounted on a carriage, in
• the support of the burnishing wheel is pivotally mounted on the carriage around a shaft parallel to the axis of the burnishing wheel.
• the displacement of the support of the wheel relative to the carriage, necessary for obtaining an application of the wheel against the workpiece, is then obtained by pivoting of the support urged by elastic means, these means being able to consist of at least a compression spring pressing, on the one hand, against a threaded cap screwed into the carriage and, on the other hand, against the support; very simple adjustment means, comprising for example an adjustment screw mounted on the carriage and the end of the rod of which bears against a machined plate in the support, make it possible to exert an antagonistic action on the latter at the time exerted by the spring, in order to lock the support in a position, where the engagement of the burnishing wheel in the helical thread of the part can be done in a suitable manner.
• the wheel support is slidably mounted in translation on the carriage, in a direction perpendicular to the axes of the burnishing wheel and of the part.
• the support it is advantageous for the support to be mounted sliding in translation in a bushing which is itself pivoted in the carriage, around an axis perpendicular to the axes of the part and of the wheel, and that a mechanism for locking allows the bushing to be immobilized in the desired position relative to the carriage, after introduction of the wheel into the helical thread of the part; in this way, the wheel adjusts itself in position relative to the workpiece thread at the time of its engagement in the thread and then it is locked in this position.
• FIG. 1 is a schematic view of a repetitive automatic burnishing cycle by means of a wheel mounted idly in rotation on a support which can be brought closer and away from the threaded part to be finished, in a direction substantially perpendicular to the axis of the latter, and which can also be moved parallel to the axis of this part, in one direction or the other;
• - Figure 2 is a schematic end view of a device according to the invention intended for the finishing of a gear screw carrying two reverse pitch threads;
• - Figure 3 is an elevational view, on a larger scale, of a part of Figure 2, relating to a first embodiment of the device according to the invention, this view being perpendicular to the axis of the screw to machine;
• - Figure 4 is a bottom view along IV-IV of Figure 3;
• FIG. 5 is a section along V-V of Figure 4.
• - Figure 7 is a cross-sectional view of a second embodiment of the device according to the invention, this section being perpendicular to the axis of the burnishing region; and - Figure 8 is a bottom view, along VIII-VIII of Figure 7.
• FIG. 1 represents a workpiece, which is a gear screw 10 on which a helical thread 12 with pitch turned in one direction has been cut around, on the left end portion, and a helical thread 14 with pitch turned in the opposite direction, on the right end part of the screw 10.
• This helical screw with two threads 12 and 14 was cut in a cylindrical shaft in semi-hard steel, on a work station of a multi-spindle lathe; on this lathe, after its cutting, the screw 10 is rotated on itself around its longitudinal axis by one of the pins.
• a burnishing wheel 16 is mounted idly in rotation on a support 18 around an axis inclined relative to the longitudinal axis of the screw 10; the peripheral part of the wheel 16 has a profile of shape complementary to that of the threads 12 and 14.
• the support 18 is moved relative to a carriage (not shown in FIG. 1 but which is, for example, the carriage of the lathe) towards the screw 10 in a direction substantially perpendicular to the axis of the latter, until the wheel 16 is pressed against the screw 10 at the start of the thread 12.
• the carriage is mounted to slide in translation on a rail (not shown) parallel to the axis of the screw 10; the support 18 is firstly moved towards the screw 10, according to arrow F 1 , and the wheel 16 is applied elastically against said screw 10 by elastic means which bear on the one hand against the carriage and on the other hand against support 18.
• These elastic means ensure the penetration of the peripheral part of the wheel 16 into the thread 12 of the screw 10, and the support of the wheel 16 at the bottom of the thread with a predetermined force, for example of 300 N, determined by the calibration of the elastic means.
• the wheel 16 Due to the driving of the screw 10 in rotation on itself, as soon as the wheel 16 comes into contact with the screw 10, the wheel 16 is also rotated on itself around its axis, and ensures the finish by burnishing the surface of the thread 12 by rolling on the latter. Simultaneously, the support 18 and the carriage which carries it move in translation parallel to the axis of the screw 10 up to the level of the end of the thread 12, according to arrow F 2 . Then the support 18 and the wheel 16 are moved away from the screw 10 by a displacement of the support 18 relative to the carriage, which takes place substantially in a direction perpendicular to the axis of the screw 10, according to arrow F 3 .
• This operation of removing the wheel 16, at the end of a burnishing operation is followed by a translation of the carriage parallel to the axis of the screw 10, according to arrow F 4 , in the opposite direction to the previous translation of the carriage, in order to replace the wheel 16 and the support 18 in the initial position, so that a new burnishing operation can start.
• FIGS. 1 there is shown at 10 'the position occupied by the screw 10 after the finishing by burnishing the thread 12 and at the time when the finishing by burnishing the thread 14.
• the transition from one position to the other is effected by a displacement of the screw 10 parallel to itself according to an arc of a circle, and the thread 14 is then surface using a second assembly consisting of a second roller burnishing wheel 16 ', a second support 18' and a second carriage 20 ', mounted in a similar but symmetrical manner with respect to the first assembly previously described and operating in the same way.
• a second assembly consisting of a second roller burnishing wheel 16 ', a second support 18' and a second carriage 20 ', mounted in a similar but symmetrical manner with respect to the first assembly previously described and operating in the same way.
• the roller burnishing device comprises a wheel 16, the peripheral part of which has a profile of form complementary to the thread of the screw 10; this wheel is mounted in rotation about its axis on a pivot 24.
• the pivot 24 is received in two bores located in the extension of one another and each drilled in one of the two lugs 26 of a side screed of a support 18.
• the latter is itself pivotally mounted on a shaft 28 parallel to the pivot 24 and housed in a bore with an axis inclined relative to the axis of the screw 10; said bore is drilled in the front 30 and rear 32, of a carriage body 20, the aforementioned parts 30 and 32 being connected together by an upper part 34.
• the body of the carriage 20, which therefore has the form of 'a yoke, between the two parts 30 and 32 of which the support 18 can pivot, is integral with a sliding sole 36, in the form of a square; a branch of the sole 36 is directed in a direction substantially parallel to the axis of the screw 10 and has two grooves 38 parallel to each other and to the axis of the screw 10. In each of these grooves 38, a slide is received 42 projecting from the opposite face of a branch 40 of the rail 22, which has a square section; the carriage 20, of generally external, substantially parallelepiped shape, can slide parallel to the axis of the screw 10, in the angle of the rail 22, by pressing on the slides 42.
• the shaft 28 is immobilized in a suitable position in its bore by pressing against a machined flat 44 on that of the ends of the shaft 28, which is housed in the front part 30 of the carriage body 20, of the end of the rod of a locking screw 46; the rod 46 is screwed into a threaded bore with an axis substantially perpendicular to the axis of the shaft 28, said bore being pierced in the front part 30 of the body and opening into the housing of the shaft 28, as is clearly shown in Figure 6.
• the head of the screw 46 is disposed in a pilot hole 48 of the carriage body 20.
• a threaded plug 50 is screwed into a threaded bore drilled in the upper part 34 of the carriage body 20; this bore opens out above the pivoting support 18.
• This plug 50 has a recess 52, which opens towards the support 18, opposite a recess 54 formed in the upper face of the latter.
• a compression spring 56 bears by its upper end housed in the recess 52, against the carriage body 20, and, by its lower end housed in the recess 54, against the support 18; the support 18 is thus pushed back in the direction of the screw 10, so that the roller wheel
• the maximum pivoting position of the support 18 can be adjusted by action on an adjustment screw 58, screwed in a threaded bore with an axis substantially perpendicular to the axis of the pivot 24, said bore being drilled in the rear part 32 of the carriage body 20.
• the end of the rod of the adjusting screw 58 bears against a surface plane 60 machined on the support 18, so that, by action on the screw 58, it is possible to exert on the support 18 a moment antagonistic to that exerted by the spring 56.
• FIGS. 7 and 8 there is a burnishing wheel 16 mounted idly in rotation about its axis on a pivot 24, and a carriage body 20, which is, in this example, a massive element of parallelepipedal shape slidably mounted in the angle of a rail 22 at right angles, thanks to the grooves 38 of the carriage body 20 and to the slides 42 of the branch 40 of the rail 22, as described above in connection with the first example of realization.
• the pivot 24 is mounted between the two legs 66 of a yoke carried at the lower end of a support 68, which has the shape of a cylindrical core mounted to slide axially in a socket 70 to collar 72.
• the support 68 and the socket 70 are coaxial elements integral in rotation thanks to the key 74 mounted in the support 68 and sliding in a groove 76 of the socket 70; the sleeve 70 is itself pivotally mounted in a coaxial bore of the carriage body 20.
• the collar 72 integral with the lower part of the sleeve 70 is received in another shallow coaxial bore 76 of the body 20; it pivots in this bore 76 at the same time as the sleeve 70.
• the bore, in which the sleeve 70 is received, is extended by a pilot hole 84, of diameter less than the external diameter of the sleeve 70 and greater than the diameter of the cylindrical support 68.
• This pilot hole 84 which opens onto the upper face of the body 20, is tapped in its part adjacent to this upper face, and a threaded plug 86 is screwed into it.
• a large head screw 88 is screwed into the upper end of the support 68 by tightening against the upper face of the latter a washer 90, the outside diameter of which is greater than that of the support 68 but less than that of the bore 84; a compression spring 92 bears at its lower end on the washer 90 and at its upper end against the plug 86.
• the plug 86 has a recess 94 which is open in the direction of the head 88 of the screw; this head 88 constitutes a centering element for the spring 92 and can be received in the recess 94, so that the head 88 also constitutes a high stop limiting the crushing of the spring 92 and the sliding of the support 68 inwards of the carriage body 20, when it comes into contact with the bottom of the recess 94; the peripheral part of the washer 90, which projects radially with respect to the support 68, constitutes a low stop limiting the extension of the spring 92 and the sliding of the support 68 towards the outside of the body 20, when it comes into contact with the upper end of the socket 70.
• the support 68 is thus mounted sliding in translation on the carriage 20, in a direction perpendicular laire to the axes of the burnishing wheel 16 and the screw 10; the bush 70, in which the support 68 is slidably mounted, is itself pivotally mounted in the carriage 20 about an axis perpendicular to the axes of the screw 10 and of the wheel 16.
• the compression spring 92 therefore pushes the support 68 in the direction of the screw 10 and the elastic application, with a predetermined force, of the burnishing wheel 16 against the screw 10.
• the bush 70 and the support 68 can pivot; the force of the spring 92 therefore ensures the driving of the wheel 16 at the bottom of the thread of the screw 10, even if the wheel 16 is not initially properly inclined relative to the axis of the screw 10; the wheel 16, thus mounted on a steerable axis on the carriage 20, adjusts itself in a good angular position.
• the tightening of the screws 80 then ensures the locking of the wheel 16 in this angular position suitable for the thread considered.
• roller burnishing devices have numerous advantages compared to those described in French patent application 80-06 582.
• the precision of a cylindrical wheel according to the state of the art must be obtained to within 2 microns on helicals, to give a good result
• the precision required for a burnishing wheel 16 is of the same order of magnitude but on a cylindrical surface; moreover, a wheel is much less bulky than a cylindrical wheel; in addition, the contact pressure of a wheel 16 used according to this method is much lower than for a cylindrical wheel. Consequently, the device according to the invention is much less expensive than the prior device.
• the device according to the invention functions correctly even if the thread of the screw is relatively badly cut as a result, in particular, of the malfunction of a previous operation; this device therefore also makes it possible to take account of any defect in the precision of the machine.
• roller burnishing device is much lighter and less bulky when, according to the invention, it comprises a spring instead of a hydraulic cylinder, as is the case in the aforementioned application and, ultimately, it is found that the machining time is no longer than if a device of the type described in the aforementioned application is used. It is understood that the devices and the method described above may give rise to any desirable modification, without thereby departing from the scope of the invention.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Transmission Devices (AREA)

Priority Applications (1)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9276598

Family Applications (1)

Country Status (6)

Cited By (2)

Families Citing this family (17)

Citations (2)

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• 1982
  • 1982-08-03 FR FR8213574A patent/FR2531360A1/fr active Granted
• 1983
  • 1983-08-02 GB GB08407631A patent/GB2135225B/en not_active Expired
  • 1983-08-02 DE DE3390141T patent/DE3390141C2/de not_active Expired - Lifetime
  • 1983-08-02 JP JP58502583A patent/JPS59501541A/ja active Pending
  • 1983-08-02 WO PCT/FR1983/000164 patent/WO1984000511A1/fr not_active Ceased
• 1984
  • 1984-04-03 US US06/604,654 patent/US4706483A/en not_active Expired - Lifetime
• 1991
  • 1991-11-18 JP JP102403U patent/JPH1024U/ja active Pending

Patent Citations (2)

Non-Patent Citations (2)

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