CN210548589U

CN210548589U - Straight bevel gear grinding machine

Info

Publication number: CN210548589U
Application number: CN201921341914.9U
Authority: CN
Inventors: 郭新民; 姜利国; 郭华明; 史树伟
Original assignee: Liyang Tengxin Mechanical And Electrical Equipment Co ltd
Current assignee: Liyang Tengxin Mechanical And Electrical Equipment Co ltd
Priority date: 2019-08-17
Filing date: 2019-08-17
Publication date: 2020-05-19
Anticipated expiration: 2029-08-17

Abstract

The utility model relates to a straight bevel gear grinding machine, including frame, the gear carrier and the grinding subassembly that are used for the positioning gear, the gear carrier includes chassis and grudging post, the chassis rotates at the horizontal plane and sets up in the frame, the grudging post slides along the radial of chassis rotation and sets up on the chassis, be provided with the positioning shaft that is used for fixed gear on the grudging post; the grinding assembly comprises a grinding frame and a group of symmetrical grinding wheels, wherein wheel carriers are arranged on one side of the grinding frame facing the wheel carrier at intervals in the vertical direction, each wheel carrier comprises a sliding seat sliding in the vertical direction and a swinging rod hinged to the sliding seat, the swinging rods rotate on a vertical plane, and the grinding wheels are rotatably arranged at one end, far away from the sliding seats, of the swinging rods. The utility model discloses have the emery wheel through a set of symmetry, realize polishing of symmetrical flank of tooth, promote the machining efficiency's of gear effect.

Description

Straight bevel gear grinding machine

Technical Field

The utility model belongs to the technical field of the technique of gear machining equipment and specifically relates to a straight-tooth bevel gear grinding machine is related to.

Background

A gear grinding machine is a gear processing machine which uses a grinding wheel as a grinding tool to process the tooth surface of a cylindrical gear or some gears (helical gears, bevel gears and the like) processing cutter. The method is mainly used for eliminating deformation after heat treatment and improving the gear precision.

The prior Chinese patent No. CN200960606 discloses a six-axis five-linkage spiral bevel gear processing machine tool, wherein a fixed upright post and an X-direction linear guide rail are arranged on a machine body of the machine tool, an X-axis sliding table moving along the guide rail is arranged on the X-direction linear guide rail, a Y-direction linear guide rail is arranged on the X-axis sliding table, a workpiece box capable of sliding along the guide rail is arranged on the X-axis sliding table, a rotary A axis is arranged on the workpiece box, a Z-direction linear guide rail vertical to the X-axis linear guide rail and the Y-axis linear guide rail is arranged on one side surface of the upright post, a Z-axis sliding table capable of moving along the guide rail under the driving of a driving mechanism is arranged on the guide rail, a cutter box capable of rotating around the B axis and a rotary driving mechanism; in combination with the drawings of the above application, a cutter is fixed to the cutter box, and the finish machining of the gear is achieved by grinding the tooth surface of the XUE gear blank by the rotation of the cutter.

The above prior art solutions have the following drawbacks:

however, when the straight bevel gear needs to be machined actually, the tooth surfaces of the straight bevel gear are the same, but the tooth surfaces can still be ground one by one only through the rotation of a single cutter, and the machining efficiency of the straight bevel gear is low.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a straight-tooth bevel gear grinding machine through the emery wheel of a set of symmetry, realizes polishing of symmetrical flank of tooth, promotes the machining efficiency of gear.

The above utility model discloses an above-mentioned utility model purpose can realize through following technical scheme:

a straight bevel gear grinding machine comprises a rack, a gear carrier for positioning gears and a grinding assembly, wherein the gear carrier comprises an underframe and a vertical frame, the underframe is rotatably arranged on the rack on a horizontal plane, the vertical frame is arranged on the underframe in a sliding manner along the radial direction of the rotation of the underframe, and a positioning shaft for fixing the gears is arranged on the vertical frame;

the grinding assembly comprises a grinding frame and a group of symmetrical grinding wheels, wherein wheel frames are arranged on one side of the grinding frame, which faces the wheel frame, at intervals in the vertical direction, the wheel frames comprise sliding seats sliding in the vertical direction and swing rods hinged to the sliding seats, the swing rods rotate on a vertical plane, and the grinding wheels are rotatably arranged at one ends, far away from the sliding seats, of the swing rods; the grinding wheel locking device is characterized in that an installation block is arranged at one end, away from the sliding seat, of the oscillating rod, a grinding motor is arranged at the opposite end of the installation block, an installation shaft is coaxially fixed at the rotating end of the grinding motor, the grinding wheel is coaxially arranged on the installation shaft, and a locking assembly for locking the grinding wheel is arranged on the installation shaft.

Through adopting above-mentioned technical scheme, before the gear is polished, establish the emery wheel cover and be fixed in installation epaxial, start the grinding motor and drive the emery wheel rotation, then with the coaxial location epaxial that is fixed in of gear, rotate the chassis, simultaneous control location motor drives the gear and rotates to suitable angle, make the tooth portion of gear inlay locate between the emery wheel, then rotate the grinding gear through the emery wheel is high-speed, and the grudging post slides, make gear synchronous motion, realize the fine-machined feeding of gear, simultaneously through removing the sliding seat and rotating the swinging arms, change interval and inclination between the emery wheel, and then realize polishing the gear of different tooth widths.

The utility model discloses further set up to: the installation axle is including the support section and the assembly section of coaxial setting, the diameter of support section is greater than the assembly section diameter, the assembly section is located to the emery wheel cover, just emery wheel butt in the one end of supporting the section towards the assembly section, the bayonet socket has been seted up to the inboard central symmetry of emery wheel, the locking piece is including setting up in epaxial fixture block of installation and butt piece, the fixture block is fixed with the bayonet socket cooperation, radially seted up logical groove along it in the installation, the butt piece slides relatively or mutually oppositely and sets up in leading to the groove, be provided with reset spring between the butt piece, the butt piece is used for the butt emery wheel to keep away from one side of support section.

Through adopting above-mentioned technical scheme, during the installation emery wheel, locate the assembly section with the emery wheel cover on, the emery wheel slides along the assembly end and touches the butt piece until the emery wheel, then extrude the butt piece and get into logical groove completely, the emery wheel slides through the butt piece, and align between the bayonet socket of rotation emery wheel and the fixture block, make the emery wheel butt in the support section, loosen the butt piece, the butt piece stretches out under reset spring's promotion, and the butt realizes the quick installation of emery wheel at installation epaxial in one side that the emery wheel deviates from the support section.

The utility model discloses further set up to: the one end that the butt piece deviates from the support section is provided with the chamfer, chamfer and the inboard slip butt of emery wheel.

Through adopting above-mentioned technical scheme, during the installation emery wheel, locate the assembly section with emery wheel slip cap on, start the outside that the butt piece deviates from assembly section one end and be provided with the chamfer, the butt that slides between the inboard of emery wheel and the chamfer for the butt piece relative movement makes the fixture block receive simultaneously and avoids letting the groove in, the installation of the emery wheel of being convenient for promotes the installation effectiveness of emery wheel, and then reduces the equipment preparation time before the gear is polished.

The utility model discloses further set up to: the assembly section is provided with a coaxial insertion groove at one end far away from the support section, the insertion groove is communicated with the through groove, a pull rod is embedded in the insertion groove in a sliding mode, and the pull rod is provided with connecting rods hinged to the abutting blocks respectively.

Through adopting above-mentioned technical scheme, when demolising the emery wheel, outwards remove through the pull rod to the connecting rod drives the butt joint piece and the installation axle is taken in to the fixture block, demolishs the emery wheel from installing the epaxial at last, has realized the quick assembly disassembly of emery wheel promptly, reduces the preparation time promotion gear production efficiency of gear machining preceding equipment.

The utility model discloses further set up to: one end of the pull rod, which is far away from the abutting block, extends to form a pull plate positioned outside the inserting groove, and a pull hole is formed in the pull plate in a penetrating mode.

By adopting the technical scheme, when the grinding wheel is dismounted, the finger is inserted into the pull hole, the pull rod is driven to move outwards through the pull plate, and the purpose of conveniently controlling the pull rod is achieved.

The utility model discloses further set up to: the butt piece is provided with the rubber pad towards the laminating of the one end of support section.

Through adopting above-mentioned technical scheme, because there is the error in the thickness of emery wheel, after the emery wheel was installed on the assembly section, the rubber pad extrusion was fixed in between emery wheel and the butt piece, and then reduced because the emery wheel shake that the clearance between emery wheel and the butt piece caused, promoted the stability that the emery wheel was polished.

The utility model discloses further set up to: the fixture block with butt joint piece fixed connection, just it dodges the groove of dodging that the fixture block removed to open in the assembly end.

Through adopting above-mentioned technical scheme, because connect fixture block and butt piece fixed connection, when butt piece income leads to the groove in, so the synchronous income of fixture block dodges in the groove, and then when the installation emery wheel, need not to go draw-in groove and fixture block on the visual observation alignment emery wheel, after the emery wheel passes through the butt piece, rotate the emery wheel again, when bayonet socket and fixture block align, reset spring promotes the butt piece and drives fixture block back of the body removal, the fixture block inlays locates in the bayonet socket, the butt piece is injectd emery wheel butt in the support section simultaneously, realize the emery wheel and install the complete fixation between the axle.

The utility model discloses further set up to: the wedge groove has been seted up to the frame upper end, the wedge groove extends the setting along the horizontal direction, grinding frame lower extreme extends there is the wedge with wedge groove complex.

Through adopting above-mentioned technical scheme, because the size and the tooth depth of the gear of different models exist differently, start the cylinder and drive the grinding frame and remove, and then drive the removal of emery wheel for the emery wheel can cooperate the gear of grinding different models, lifting means's application scope.

To sum up, the utility model discloses a beneficial technological effect does:

1. the gear is positioned and mounted on the positioning shaft, then the bottom frame is driven to rotate and the vertical frame slides, so that the tooth part of the gear is positioned between the grinding wheels, the grinding wheels rotate at a high speed, the tooth surface is ground by the grinding wheels, and then the complete grinding of the tooth surface is realized by moving the sliding plate;

2. the emery wheel is dismantled fast and is adorned on the installation axle, is convenient for change the emery wheel to reduce owing to change the down time that the emery wheel caused, promote the production efficiency of gear.

Drawings

FIG. 1 is a schematic view of an assembly of a straight bevel gear grinding machine;

FIG. 2 is a schematic view for embodying a structure of connecting a drive bevel gear with a neutral shaft;

FIG. 3 is a schematic view for embodying a grinding wheel mounting structure;

fig. 4 is a schematic diagram for embodying the structure of the grinding wheel.

In the figure, 1, a frame; 11. a wedge-shaped groove; 2. a gear carrier; 3. a chassis; 4. erecting a frame; 41. positioning the shaft; 5. a grinding frame; 52. a cylinder; 53. a slide rail; 6. a sliding plate; 61. a pushing cylinder; 62. a chute; 63. an ear plate; 7. a sliding seat; 71. a slider; 8. a first motor; 81. a bidirectional screw; 9. a swing lever; 91. a rotating shaft; 92. a driven bevel gear; 10. a second motor; 101. a middle shaft; 102. a limiting groove; 103. a drive bevel gear; 104. a limiting block; 105. a support spring; 12. a grinding wheel; 121. a bayonet; 13. mounting a plate; 14. polishing the motor; 15. installing a shaft; 16. a support section; 17. assembling the sections; 171. a through groove; 172. an avoidance groove; 173. inserting grooves; 18. a butting block; 181. chamfering; 182. a rubber pad; 19. a clamping block; 20. a pull rod; 201. a connecting rod; 202. pulling a plate; 203. hole drawing; 21. a return spring.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

As shown in fig. 1 and 2, a straight bevel gear grinding machine comprises a frame 1, a gear carrier 2 arranged on the frame 1 and a grinding assembly, wherein a gear is positioned and mounted on the gear carrier 2, the grinding assembly comprises a group of symmetrical grinding wheels 12, and the grinding wheels 12 simultaneously grind two sides of straight teeth in the gear by moving the gear carrier 2 and the grinding assembly, so that the fine machining efficiency of the gear is improved.

As shown in fig. 1 and 2, gear carrier 2 includes underframe 3 and grudging post 4, underframe 3 is rectangular platelike, the one end of underframe 3 is rotated and is connected on frame 1, make underframe 3 drive grudging post 4 rotate at the horizontal plane, the lower extreme of grudging post 4 sets up along the radial slip of underframe 3 rotation orbit, be provided with location axle 41 and positioning motor in the upper end of grudging post 4, be fixed in the gear is coaxial on location axle 41, rotate underframe 3, control positioning motor drives the gear and rotates to suitable angle simultaneously, make the tooth of the gear portion inlay locate between emery wheel 12, then rotate the grinding gear through emery wheel 12 high speed, and slip grudging post 4, make gear synchronous motion, realize the fine-machined feeding of gear.

As shown in fig. 1 and 2, the grinding assembly further includes a grinding frame 5, a wedge-shaped groove 11 is formed in the upper end of the frame 1 along the horizontal direction, a wedge block embedded in the wedge-shaped groove 11 is fixed at the lower end of the grinding frame 5, an air cylinder 52 is fixed on the frame 1, a piston end of the air cylinder 52 extends and retracts along the extending direction of the wedge-shaped groove 11, and a piston end of the air cylinder 52 is fixed at one end of the grinding frame 5 away from the gear rack 2; because the size and the tooth depth of the gears of different models are different, the starting cylinder 52 drives the grinding frame 5 to move, and further drives the grinding wheel 12 to move, so that the grinding wheel 12 can be matched with the gears of different models to grind, and the application range of the equipment is widened.

As shown in fig. 1 and 2, one side of the grinding frame 5 facing the gear frame 2 is a vertical plane, a sliding plate 6 and a sliding seat 7 are arranged on the end face, a sliding rail 53 is arranged at one end of the grinding frame 5 facing the gear frame 2 and extends along the horizontal direction, the sliding rail 53 is perpendicular to the sliding direction of the grinding frame 5, the sliding plate 6 and the sliding rail 53 are in sliding fit, a pushing cylinder 61 for driving the sliding plate 6 to move is fixed on the grinding frame 5, so that the grinding wheel 12 is driven to slide in the horizontal direction, and the gear is ground at a high speed by the sliding of the grinding wheel 12 in the horizontal direction and the matching of the feeding direction of the gear.

As shown in fig. 1 and 2, a sliding groove 62 is formed in one end of the sliding plate 6 facing the gear rack 2, the sliding groove 62 extends in the vertical direction, a sliding block 71 embedded in the sliding groove 62 extends on the sliding seat 7, so that the sliding seats 7 can move in the vertical direction relatively or oppositely, a first motor 8 is fixed on the sliding plate 6, a first bidirectional screw 81 is fixed at the rotating end of the first motor 8, the bidirectional screw 81 is rotatably inserted into the sliding groove 62 around the axis of the bidirectional screw 81, and the sliding block 71 is respectively in threaded connection with a reverse thread of the bidirectional screw 81; when the first motor 8 is started, the bidirectional screw 81 drives the sliding seat 7 to synchronously move relatively or oppositely, so that the purpose of adjusting the distance between the grinding wheels 12 is realized, and the first motor is further suitable for processing gears with different tooth widths.

As shown in fig. 1 and fig. 2, a swing rod 9 is hinged on the sliding seat 7, a grinding wheel 12 is rotatably disposed at one end of the swing rod 9 far from the sliding seat 7, a rotating shaft 91 coaxially extends from the rotating end of the swing rod 9, a driven bevel gear 92 is coaxially fixed at one end of the rotating shaft 91 far from the swing rod 9, a driving component for driving the driven bevel gear 92 to rotate is disposed on the sliding plate 6, a pair of ear plates 63 extends on the sliding plate 6 at intervals along the vertical direction, the driving component comprises a middle shaft 101 rotatably disposed between the ear plates 63, the rotating axis of the middle shaft 101 extends along the vertical direction, a set of symmetrical driving bevel gears 103 is coaxially sleeved on the middle shaft 101, the driving bevel gears 103 are respectively engaged with the driven bevel gears 92, a limit groove 102 is disposed on the periphery of the middle shaft 101 and along the vertical direction, a limit block 104 embedded in the limit groove 102 extends in the driving bevel gears 103, two ends of the middle shaft 101 are respectively sleeved with a supporting spring 105, and two ends of the supporting spring 105 are respectively abutted against the lug plate 63 and the driving bevel gear 103, so that stable meshing between the driving bevel gear 103 and the driven bevel gear 92 is realized;

when the sliding seat 7 moves back to back or relatively, the driven bevel gear 92 pushes the drive bevel gear 103 to slide, or the support spring 105 pushes the drive bevel gear 103 to move relatively, so that the drive bevel gear 103 and the driven bevel gear 92 are always in a meshed state; and a second motor 10 for driving the middle shaft 101 to rotate is arranged on the sliding plate 6, the second motor 10 is started, the middle shaft 101 drives the driving bevel gear 103 to rotate, so that the oscillating rod 9 drives the grinding wheel 12 to rotate, the grinding angle of the grinding wheel 12 is changed, and the gear grinding machine is suitable for grinding gears of different models.

As shown in fig. 1 and 3, a mounting plate 13 is fixed at one end of the swing rod 9 far away from the sliding seat 7, a grinding motor 14 is fixed at one side of the mounting plate 13 opposite to the other side, a rotating end of the grinding motor 14 is perpendicular to the mounting plate 13, and a mounting shaft 15 is coaxially fixed at the rotating end, the mounting shaft 15 penetrates through the mounting plate 13, the mounting shaft 15 includes a supporting section 16 and an assembling section 17 which are coaxial, a diameter of the supporting section 16 is larger than that of the assembling section 17, the supporting section 16 is fixedly connected with the rotating end of the grinding motor 14, the grinding wheel 12 is coaxially sleeved on the assembling section 17 until the grinding wheel 12 abuts against the supporting section 16, and then the grinding wheel 12 is fixedly connected with the mounting shaft.

A through groove 171 is formed in the assembling section 17 along the radial direction of the assembling section, a pair of abutting blocks 18 are slidably embedded in the through groove 171, a return spring 21 is arranged between the abutting blocks 18, an inserting groove 173 is formed in one end, far away from the supporting section 16, of the assembling section 17, the inserting groove 173 extends along the axial direction of the assembling section 17 to be communicated with the through groove 171, a pull rod 20 is slidably embedded in the inserting groove 173, a connecting rod 201 is arranged between the pull rod 20 and the abutting blocks 18 respectively, two ends of the connecting rod 201 are hinged to the pull rod 20 and the abutting blocks 18 respectively, a pull plate 202 extends from one end, far away from the supporting section 16, of the pull rod 20, and a pull hole 203 is formed in the;

as shown in fig. 4, when the grinding wheel 12 is mounted, the grinding wheel 12 is slidably sleeved on the mounting section 17, the outer side of the end, away from the mounting section 17, of the abutting block 18 is started to be provided with a chamfer 181, the inner side of the grinding wheel 12 is in sliding abutting contact with the chamfer 181, so that the abutting block 18 moves relatively, the clamping block 19 is received in the avoidance groove 172, after the grinding wheel 12 passes through the abutting block 18, the grinding wheel 12 is rotated again until the bayonet 121 is aligned with the clamping block 19, the return spring 21 pushes the abutting block 18 to drive the clamping block 19 to move back and forth, the clamping block 19 is embedded in the bayonet 121, and the abutting block 18 limits the grinding wheel 12 to abut against the supporting section 16, so that the grinding wheel 12 and the mounting shaft 15 are; when the grinding wheel 12 is dismounted, fingers are inserted into the pull holes 203, the pull plate 202 drives the pull rod 20 to move outwards, the connecting rod 201 drives the abutting block 18 and the fixture block 19 to be accommodated in the mounting shaft 15, and finally the grinding wheel 12 is dismounted from the mounting shaft 15, so that the grinding wheel 12 is quickly dismounted, the preparation time of equipment before gear machining is shortened, and the gear production efficiency is improved.

Wherein the rubber pad 182 is fixed in the laminating of the one end of butt piece 18 towards support section 16, because there is the error in the thickness of emery wheel 12, after emery wheel 12 installed on assembly section 17, rubber pad 182 extrusion is fixed in between emery wheel 12 and butt piece 18, and then reduces because emery wheel 12 shake that the clearance between emery wheel 12 and the butt piece 18 caused, promotes the stability that emery wheel 12 polished.

The implementation principle of the embodiment is as follows:

the gear is positioned and installed on the positioning shaft 41, then the bottom frame 3 is driven to rotate and the vertical frame 4 slides, so that the tooth part of the gear is positioned between the grinding wheels 12, the grinding wheels 12 rotate at a high speed, the tooth surface is ground by the grinding wheels 12, and then the complete grinding of the tooth surface is realized by moving the sliding plate 6.

The embodiment of this specific implementation mode is the preferred embodiment of the present invention, not limit according to this the utility model discloses a protection scope, so: all equivalent changes made according to the structure, shape and principle of the utility model are covered within the protection scope of the utility model.

Claims

1. The utility model provides a straight bevel gear grinding machine, includes frame (1), is used for positioning gear wheel carrier (2) and grinding component, its characterized in that: the gear rack (2) comprises an underframe (3) and a vertical frame (4), the underframe (3) is rotatably arranged on the rack (1) on a horizontal plane, the vertical frame (4) is arranged on the underframe (3) in a sliding manner along the radial direction of the rotation of the underframe (3), and a positioning shaft (41) for fixing a gear is arranged on the vertical frame (4);

the grinding assembly comprises a grinding frame (5) and a group of symmetrical grinding wheels (12), wheel carriers are arranged on one side, facing the wheel carrier (2), of the grinding frame (5) at intervals along the vertical direction, each wheel carrier comprises a sliding seat (7) sliding along the vertical direction and a swinging rod (9) hinged to the sliding seat (7), each swinging rod (9) rotates on a vertical plane, and the grinding wheels (12) are rotatably arranged at one end, far away from the sliding seats (7), of each swinging rod (9); the grinding device is characterized in that an installation block is arranged at one end, away from the sliding seat (7), of the oscillating rod (9), a grinding motor (14) is arranged at the back end of the installation block, an installation shaft (15) is coaxially fixed at the rotating end of the grinding motor (14), the grinding wheel (12) is coaxially arranged on the installation shaft (15), and a locking assembly for locking the grinding wheel (12) is arranged on the installation shaft (15).

2. The spur bevel gear grinding machine according to claim 1, wherein: the mounting shaft (15) comprises a supporting section (16) and an assembling section (17) which are coaxially arranged, the diameter of the supporting section (16) is larger than that of the assembling section (17), the grinding wheel (12) is sleeved on the assembling section (17), and the grinding wheel (12) is abutted against one end of the supporting section (16) facing the assembling section (17), bayonets (121) are symmetrically arranged at the center of the inner side of the grinding wheel (12), the locking assembly comprises a clamping block (19) and an abutting block (18) which are arranged on the mounting shaft (15), the clamping block (19) is matched and fixed with the bayonet (121), a through groove (171) is arranged in the mounting along the radial direction, the abutting blocks (18) are arranged in the through grooves (171) in an opposite or reverse sliding mode, a return spring (21) is arranged between the abutting blocks (18), and the abutting blocks (18) are used for abutting against one side, far away from the supporting section (16), of the grinding wheel (12).

3. The spur bevel gear grinding machine according to claim 2, wherein: one end of the abutting block (18) departing from the supporting section (16) is provided with a chamfer (181), and the chamfer (181) is in sliding abutting connection with the inner side of the grinding wheel (12).

4. The spur bevel gear grinding machine according to claim 2, wherein: an inserting groove (173) is coaxially formed in one end, far away from the supporting section (16), of the assembling section (17), the inserting groove (173) is communicated with the through groove (171), a pull rod (20) is embedded in the inserting groove (173) in a sliding mode, and connecting rods (201) hinged to the abutting blocks (18) are respectively arranged on the pull rod (20).

5. The spur bevel gear grinding machine according to claim 4, wherein: one end of the pull rod (20) far away from the abutting block (18) extends to form a pull plate (202) located outside the inserting groove (173), and a pull hole (203) penetrates through the pull plate (202).

6. The spur bevel gear grinding machine according to claim 2, wherein: and a rubber pad (182) is attached to one end, facing the support section (16), of the abutting block (18).

7. The spur bevel gear grinding machine according to claim 2, wherein: the clamping block (19) is fixedly connected with the abutting block (18), and an avoiding groove (172) for avoiding the movement of the clamping block (19) is formed in the assembling end.

8. The spur bevel gear grinding machine according to claim 1, wherein: wedge groove (11) have been seted up to frame (1) upper end, wedge groove (11) extend the setting along the horizontal direction, grinding frame (5) lower extreme extends there is the wedge with wedge groove (11) complex.