CN215566634U

CN215566634U - Floating sealing structure of scroll plate of oil-free scroll air compressor

Info

Publication number: CN215566634U
Application number: CN202120432930.XU
Authority: CN
Inventors: 罗小健
Original assignee: JSCC AUTOMATION (XIAMEN) Ltd
Current assignee: JSCC AUTOMATION (XIAMEN) Ltd
Priority date: 2021-02-26
Filing date: 2021-02-26
Publication date: 2022-01-18
Anticipated expiration: 2031-02-26

Abstract

The utility model provides a floating sealing structure of a scroll plate of an oil-free scroll air compressor, which comprises: a movable sealing groove is arranged on the movable scroll plate; the dynamic seal groove comprises a dynamic high-pressure seal groove and a dynamic low-pressure seal groove, and the depth of the dynamic high-pressure seal groove is greater than that of the dynamic low-pressure seal groove; the sealing strips are arranged in the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove; the static vortex disc is provided with a static sealing groove, and the static sealing groove comprises a static high-pressure sealing groove and a static low-pressure sealing groove. The utility model has the beneficial effects that: the wear degree of the sealing strip is relieved and reduced by arranging the high-pressure sealing groove and the low-pressure sealing groove, the depth of the high-pressure sealing groove is larger than that of the low-pressure sealing groove, and therefore the height of the sealing strip corresponding to the high-pressure sealing groove is relatively higher. The air pressure at the high-pressure sealing groove is large, so that the abrasion speed of the sealing strip at the high-pressure sealing groove is high, the service time of the sealing strip can be effectively prolonged by arranging the high-pressure sealing groove and the low-pressure sealing groove, and the sealing performance is improved.

Description

Floating sealing structure of scroll plate of oil-free scroll air compressor

Technical Field

The utility model relates to the technical field of sealing among scroll plates of a scroll air compressor, in particular to a floating sealing structure of a scroll plate of an oil-free scroll air compressor.

Background

The end face sealing technology between the scroll plates of the traditional oil-free scroll air compressor mainly comprises the steps that a sealing groove in a vortex shape is formed in the end face of a scroll tooth of a movable scroll plate and the end face of a scroll tooth of a fixed scroll plate, sealing strips are arranged in the sealing groove, the sealing strips are usually 0.1-0 mm higher than the sealing groove, 5mm is formed in the sealing grooves, and the end face sealing is realized through the protruding faces of the sealing strips when the scroll plates are installed in a buckled mode. The problem of the mechanism is that the sealing strip is inevitably worn along with the use of the air compressor, and a gap is generated between the movable scroll and the fixed scroll along with the wear of the sealing strip, so that gas leakage is caused, and the integral energy efficiency ratio and the service life of the compressor are influenced. To the deficiency of the traditional end face sealing technology, a floating sealing technology of arranging a flow guide seam on a sealing strip is proposed, but in the actual application process, the flow guide seam is easily blocked after the sealing strip is worn, so that high-pressure gas is prevented from entering, an ideal sealing effect cannot be achieved, and finally the reliability of the sealing technology is reduced.

Disclosure of Invention

The utility model aims to provide a floating sealing structure of a scroll plate of an oil scroll air compressor, which can reduce the abrasion of a sealing strip and effectively and automatically compensate the abrasion loss after the sealing strip is abraded.

A floating seal structure of a scroll plate of an oil-free scroll air compressor, comprising: the movable vortex disc is provided with a movable seal groove on the movable vortex tooth end surface; the dynamic seal groove comprises a dynamic high-pressure seal groove and a dynamic low-pressure seal groove, the dynamic high-pressure seal groove surrounds the center of the vortex, and the dynamic low-pressure seal groove surrounds the outer side of the dynamic high-pressure seal groove and is connected with the dynamic high-pressure seal groove; the depth of the dynamic high-pressure sealing groove is greater than that of the dynamic low-pressure sealing groove; the sealing strips are arranged in the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove; gaps are formed between the sealing strip and the inner side wall and the outer side wall of the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove, the sealing strip is higher than the dynamic high-pressure sealing groove, and the upper end face of the sealing strip is positioned on the outer sides of the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove; the static vortex disc is arranged on the movable vortex disc, and sealing strips are positioned on the static high-pressure sealing groove and the static low-pressure sealing groove; the depth of the static low-pressure sealing groove is larger than the height of the sealing strip exceeding the end face of the dynamic high-pressure sealing groove.

Further, the sealing strips comprise a high-pressure sealing strip and a low-pressure sealing strip; the high-pressure sealing strips are arranged in the dynamic high-pressure sealing groove and the static high-pressure sealing groove, and the low-pressure sealing strips are arranged in the dynamic low-pressure sealing groove and the static low-pressure sealing groove; the high-pressure sealing strip is tightly connected with the end part of the low-pressure sealing strip.

Furthermore, the inner side wall and the outer side wall of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove are non-smooth surfaces. The initial draft surface is arranged to reduce the resistance of the up-and-down floating of the sealing strip.

Furthermore, the roughness of the inner side wall and the outer side wall of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove is Ra0.8.

Furthermore, the groove depth of the dynamic high-pressure sealing groove is 1/4-1/2 higher than that of the dynamic low-pressure sealing groove; the groove depth of the static high-pressure sealing groove is 1/4-1/2 higher than that of the static low-pressure sealing groove. Preferably 1/3.

Furthermore, the inner side walls of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove are provided with drainage grooves; and the bottoms of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove are respectively provided with an air storage groove, and the air storage grooves are connected with the drainage grooves.

Furthermore, the drainage groove is semicircular, wavy, triangular or trapezoidal.

Preferably, the drainage groove is semicircular, and the diameter of the semicircle is 0.1 mm-0.2 mm.

Furthermore, the drainage grooves are uniformly distributed on the inner side walls of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove. Evenly set up a plurality of drainage grooves and can add quick drainage step-down, and can make the pressure of feeling partial position more stable.

Furthermore, the length of the air storage tank is 1/2-3/4 of the width of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove. The length of the air storage tank is preferably 2/3 the width of the sealing groove, and according to experimental data, the sealing strip can achieve the best floating effect when the length of the air storage tank is 2/3 the width of the sealing groove.

Furthermore, the sealing strips arranged on the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove are 0.2-0.3 mm higher than the dynamic high-pressure sealing groove.

After the technical scheme is adopted, the utility model has the beneficial effects that: the wear degree of the sealing strip is relieved and reduced by arranging the high-pressure sealing groove and the low-pressure sealing groove, the depth of the high-pressure sealing groove is larger than that of the low-pressure sealing groove, and therefore the height of the sealing strip corresponding to the high-pressure sealing groove is relatively higher. The air pressure at the high-pressure sealing groove is large, so that the abrasion speed of the sealing strip at the high-pressure sealing groove is high, the service time of the sealing strip can be effectively prolonged by arranging the high-pressure sealing groove and the low-pressure sealing groove, and the sealing performance is improved.

Drawings

FIG. 1 is a schematic diagram of the orbiting scroll structure of the present invention.

FIG. 2 is a schematic view of the fixed scroll of the present invention.

Fig. 3 is an enlarged schematic view of a portion a of fig. 2.

Fig. 4 is an enlarged schematic view of fig. 2 at B.

Fig. 5 is a sectional view taken along the direction C-C of fig. 2.

Fig. 6 is an enlarged schematic view of fig. 5 at D.

Fig. 7 is an enlarged schematic view of fig. 5 at F.

1. A movable scroll; 11. a movable scroll wrap; 12. a dynamic high-pressure sealing groove; 13. a dynamic low-pressure sealing groove; 14. a dynamic seal groove; 2. a sealing strip; 21. a high pressure seal strip; 22. a low pressure seal strip; 3. a fixed scroll; 31. a fixed wrap; 32. a static seal groove; 321. a static high-pressure sealing groove; 322. a static low-pressure seal groove; 323. an inner sidewall; 324. an outer sidewall; 33. a drainage groove; 34. an air storage tank.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.

As shown in fig. 1 to 7, the present embodiment discloses a floating seal structure of a scroll of an oil-free scroll air compressor, which includes a movable scroll 1, a fixed scroll 3, and a seal strip 2. The end surface of the movable spiral wrap 11 of the movable scroll plate 1 is provided with a spiral movable seal groove 14, and the movable seal groove 14 is divided into a movable high-pressure seal groove 12 and a movable low-pressure seal groove 13 according to different pressures during operation. The dynamic high-pressure sealing groove 12 surrounds the center of the vortex shape, and the dynamic low-pressure sealing groove 13 is connected with the dynamic high-pressure sealing groove 12 and surrounds the outer side of the dynamic high-pressure sealing groove. The groove depth of the dynamic high-pressure sealing groove 12 is 1/4-1/2 greater than that of the dynamic low-pressure sealing groove 13. The groove depth of the dynamic high-pressure seal groove 12 is preferably about 1/3 greater than the groove depth of the dynamic low-pressure seal groove 13.

The inner side walls 323 of the dynamic high-pressure seal groove 12 and the dynamic low-pressure seal groove 13 in roughness are respectively provided with a plurality of dynamic drainage grooves 33 (the inner side wall 323 of the seal groove is arranged on one side, close to the vortex center, of the dynamic high-pressure seal groove 12 and the dynamic low-pressure seal groove 13, and the outer side wall 324 of the seal groove is arranged on one side, far away from the vortex center), of the dynamic high-pressure seal groove 12 and the dynamic low-pressure seal groove 13, and the dynamic drainage grooves 33 can be in a series of shapes which can be used for drainage, such as semi-circular arc, wave, triangle and trapezoid. The cross-sectional shape of the preferred drainage groove 33 may be a semicircle having a diameter D of 0.1mm to 0.2mm, and a preferred semicircle having a diameter of 0.15 mm. The center of the semicircular cross section is on the vortex line of the inner side wall 323 of the seal groove. The circle center of the semicircle is arranged on the vortex line of the inner side wall 323 of the sealing groove, so that the positioning and the processing are convenient. The drainage grooves 33 are uniformly and equidistantly distributed on the inner side wall 323 of the dynamic high-pressure seal groove 12 and the dynamic low-pressure seal groove 13.

The bottom parts of the dynamic high-pressure sealing groove 12 and the dynamic low-pressure sealing groove 13 are uniformly provided with a plurality of dynamic gas storage grooves 34, and the dynamic gas storage grooves 34 are respectively connected with the drainage grooves 33 on the inner side wall 323. The width of the air storage groove 34 is equal to the diameter of the drainage groove 33, the length of the air storage groove 34 is 1/2-3/4 of the width of the dynamic high-pressure sealing groove 12 and the dynamic low-pressure sealing groove 13, and the preferable length of the air storage groove 34 is 2/3 of the width of the dynamic high-pressure sealing groove 12 and the dynamic low-pressure sealing groove 13. The air reservoir 34 has a length of 2/3 which is the width of the seal slot to achieve the best floating effect.

The sealing strip 2 comprises a dynamic high-pressure sealing groove 21 and a dynamic low-pressure sealing groove 22, and the height of the dynamic high-pressure sealing groove 21 is higher than that of the dynamic low-pressure sealing groove 22. The dynamic high-pressure sealing groove 21 is arranged in the dynamic high-pressure sealing groove 12, and the dynamic low-pressure sealing groove 22 is arranged in the dynamic low-pressure sealing groove 13. When the sealing strip 2 is installed in the dynamic high-pressure sealing groove 12 and the dynamic low-pressure sealing groove 13, gaps are reserved between the sealing strip 2 and the inner side wall 323 and the outer side wall 324 of the sealing groove. The surfaces of the inner side wall 323 and the outer side wall 324 of the dynamic high-pressure sealing groove 12 and the dynamic low-pressure sealing groove 13 need to meet certain roughness, the roughness is Ra0.8, and the resistance of the sealing strip 2 floating up and down can be effectively reduced by arranging certain roughness on the inner side wall 323 and the outer side wall 324. The movable high-pressure seal groove 21 and the movable low-pressure seal groove 22 installed in the movable high-pressure seal groove 12 and the movable low-pressure seal groove 13 are flush with each other at the top, and the installed movable high-pressure seal groove 21 and the installed movable low-pressure seal groove 22 are both higher than the upper end faces of the movable high-pressure seal groove 12 and the movable low-pressure seal groove 13, as shown in fig. 6, the preferable length a of the installed movable high-pressure seal groove 21 and the installed movable low-pressure seal groove 22 higher than the upper end faces of the movable high-pressure seal groove 12 and the movable low-pressure seal groove 13 is 0.2mm to 0.3 mm. The raised portion is for mounting in a seal groove of the fixed scroll 3.

As shown in fig. 6 and 7, a spiral static seal groove 32, which is the same as the dynamic seal groove 14, is formed in an end surface of the static spiral wrap 31 of the static scroll 3, and the static seal groove 32 is divided into two parts, i.e., a static high-pressure seal groove 321 and a static low-pressure seal groove 322, according to the pressure at the time of operation. The static high-pressure sealing groove 321 surrounds the center of the vortex, and the static low-pressure sealing groove 322 is connected with the static high-pressure sealing groove 321 and surrounds the outer side of the static high-pressure sealing groove. The static high-pressure sealing groove 321 corresponds to the dynamic high-pressure sealing groove 12, and the static low-pressure sealing groove 322 corresponds to the dynamic low-pressure sealing groove 13. The static high-pressure sealing groove 321c and the static low-pressure sealing groove 322d are deeper than the dynamic high-pressure sealing groove 21 and the dynamic low-pressure sealing groove 22 are deeper than the dynamic high-pressure sealing groove 12 and the dynamic low-pressure sealing groove 13. The groove depth of the static high-pressure sealing groove 321 is 1/4-1/2 greater than that of the static low-pressure sealing groove 322. The groove depth c of the static high-pressure seal groove 321 is preferably greater than the groove depth d of the static low-pressure seal groove 322 by about 1/3. When the static high-pressure sealing groove 321 and the static low-pressure sealing groove 322 are in the static high-pressure sealing groove, gaps b are reserved between the sealing strip 2 and the inner side wall 323 and the outer side wall 324 of the sealing groove, and the inner side wall 323 and the outer side wall 324 have certain roughness.

The inner side walls 323 of the static high-pressure sealing groove 321 and the static low-pressure sealing groove 322 are respectively provided with a plurality of static drainage grooves 33, and the positions of the static drainage grooves 33 correspond to the positions of the dynamic drainage grooves 33. The shape of the static drainage groove 33 can be a series of shapes such as semi-circular arc, wave, triangle and trapezoid which can be used for drainage. The cross-sectional shape of the preferred drainage groove 33 may be a semicircle having a diameter of 0.1mm to 0.2mm, and a preferred semicircle having a diameter of 0.15 mm. The center of the semicircular cross section is on the vortex line of the inner side wall 323 of the seal groove. The semi-circular circle center is arranged on the vortex line of the inner side wall 323 of the sealing groove, so that the static drainage grooves 33 are conveniently positioned and machined and are uniformly and equidistantly distributed on the inner side wall 323 of the static high-pressure sealing groove 321 and the static low-pressure sealing groove 322.

The bottom parts of the static high-pressure sealing groove 321 and the static low-pressure sealing groove 322 are uniformly provided with a plurality of static gas storage grooves 34, and the static gas storage grooves 34 are respectively connected with the drainage grooves 33 on the inner side wall 323. The width of the air storage groove 34 is equal to the diameter of the drainage groove 33, the length of the air storage groove 34 is 1/2-3/4 of the width of the static high-pressure sealing groove 321 and the width of the static low-pressure sealing groove 322, and the preferred length of the air storage groove 34 is 2/3 of the width of the static high-pressure sealing groove 321 and the width of the static low-pressure sealing groove 322. The difference value of abrasion of the sealing strips 2 of the high-pressure section and the low-pressure section is compensated by arranging the high-pressure sealing groove and the low-pressure sealing groove, so that the service life of the sealing strips 2 is ensured to be consistent.

The static high-pressure sealing groove 321 on the static scroll 3 is the same as and corresponds to the dynamic high-pressure sealing groove 12 on the dynamic scroll 1 in position; the static low-pressure seal groove 322 on the static scroll 3 is the same as and corresponds to the dynamic low-pressure seal groove 13 on the dynamic scroll 1. The fixed scroll 3 is provided at the same position as the drainage groove 33 and the gas storage groove 34 provided in the orbiting scroll 1. The fixed scroll 3 and the movable scroll 1 are fixedly connected by bolts.

The principle is as follows:

in the normal working process, the high-pressure sealing strip 21 is arranged in the static high-pressure sealing groove 321 and the dynamic high-pressure sealing groove 12, the low-pressure sealing strip 22 is arranged in the static low-pressure sealing groove 13 and the dynamic low-pressure sealing groove 322, high-pressure gas enters the gas storage groove 34 at the bottom of the static high-pressure sealing groove 321 through the drainage groove 33 on the inner side wall 323 and acts on the sealing strip 2 to generate pre-pressure towards the outer side wall and upwards, under the action of the pre-pressure, the sealing strip 2 is tightly attached to the outer side wall of the static sealing groove and the bottom plane of the dynamic vortex disc, the end face sealing effect of the vortex disc is better ensured, meanwhile, when the sealing strip 2 is worn, the sealing strip 2 is lifted upwards by the pre-pressure to seal the wear value, because the drainage groove 33 and the gas storage groove 34 are arranged on the vortex tooth, the risk that the drainage groove 34 is blocked due to the wear of the sealing strip 2 is effectively avoided, and the sealing reliability of the vortex disc is stably ensured for a long time, the working efficiency of the air compressor is greatly improved, the maintenance frequency is reduced, and the service life of the air compressor is prolonged.

In summary, the static scroll and the movable scroll are provided with the high-pressure sealing groove and the low-pressure sealing groove to make up the difference value of the abrasion of the sealing strips of the high-pressure section and the low-pressure section, so as to ensure the consistent service life of the sealing strips, improve the service time of the sealing strips, leave a gap between the sealing strips and the inner and outer side walls of the sealing grooves when the sealing strips are installed, and meet certain roughness requirements on the two wall surfaces of the sealing grooves. The inner side wall of the sealing groove of the movable disc and the static disc is uniformly provided with a drainage groove, and meanwhile, the bottom of the sealing groove is provided with an air storage groove and is connected with the drainage groove. The air compressor normally works to actuate, the static vortex disc is in translational engagement to form closed compression cavities with different volumes, when air is accumulated for a certain time, the volume is smaller, the pressure is higher, the drainage groove is just arranged on one side of the high-pressure cavity, high-pressure air flows to the air storage groove through the drainage groove, the high-pressure air in the drainage groove and the air storage groove acts on the side face and the bottom of the sealing strip to apply pre-pressure to the sealing strip, and under the action of the pre-pressure, the sealing strip is tightly attached to the outer side wall of the sealing groove and the end faces of the dynamic vortex disc and the static vortex disc, so that the sealing effect of the dynamic vortex disc and the static vortex disc is better guaranteed. Meanwhile, under the action of the pre-pressure, the sealing strip is always in a floating state, and the abrasion loss of the sealing strip can be automatically compensated in the working process.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims

1. The utility model provides an oilless scroll air compressor vortex dish's floating seal structure which characterized in that: the method comprises the following steps:

the movable vortex disc is provided with a movable seal groove on the movable vortex tooth end surface; the dynamic seal groove comprises a dynamic high-pressure seal groove and a dynamic low-pressure seal groove, the dynamic high-pressure seal groove surrounds the center of the vortex, and the dynamic low-pressure seal groove surrounds the outer side of the dynamic high-pressure seal groove and is connected with the dynamic high-pressure seal groove; the depth of the dynamic high-pressure sealing groove is greater than that of the dynamic low-pressure sealing groove;

the sealing strips are arranged in the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove; gaps are formed between the sealing strip and the inner side wall and the outer side wall of the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove, the sealing strip is higher than the dynamic high-pressure sealing groove, and the upper end face of the sealing strip is positioned on the outer sides of the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove;

the static vortex disc is arranged on the movable vortex disc, and sealing strips are positioned on the static high-pressure sealing groove and the static low-pressure sealing groove; the depth of the static low-pressure sealing groove is larger than the height of the sealing strip exceeding the end face of the dynamic high-pressure sealing groove.

2. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 1, wherein: the sealing strips comprise a high-pressure sealing strip and a low-pressure sealing strip; the high-pressure sealing strips are arranged in the dynamic high-pressure sealing groove and the static high-pressure sealing groove, and the low-pressure sealing strips are arranged in the dynamic low-pressure sealing groove and the static low-pressure sealing groove; the high-pressure sealing strip is tightly connected with the end part of the low-pressure sealing strip.

3. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 1, wherein: the inner side wall and the outer side wall of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove are non-smooth surfaces.

4. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 3, wherein: the roughness of the inner side wall and the outer side wall of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove is Ra0.8.

5. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 1, wherein: the groove depth of the dynamic high-pressure sealing groove is 1/4-1/2 higher than that of the dynamic low-pressure sealing groove; the groove depth of the static high-pressure sealing groove is 1/4-1/2 higher than that of the static low-pressure sealing groove.

6. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 1, wherein: the inner side walls of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove are all provided with drainage grooves;

and the bottoms of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove are respectively provided with an air storage groove, and the air storage grooves are connected with the drainage grooves.

7. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 6, wherein: the drainage groove is semicircular, wavy, triangular or trapezoidal.

8. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 7, wherein: the drainage groove is semicircular, and the diameter of the semicircle is 0.1 mm-0.2 mm.

9. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 7, wherein: the drainage grooves are uniformly distributed on the inner side walls of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove.

10. The floating seal structure of a scroll plate of an oil-free scroll air compressor according to claim 6, wherein: the length of the gas storage tank is 1/2-3/4 of the width of the dynamic high-pressure sealing groove, the dynamic low-pressure sealing groove, the static high-pressure sealing groove and the static low-pressure sealing groove;

the sealing strips arranged on the dynamic high-pressure sealing groove and the dynamic low-pressure sealing groove are 0.2 mm-0.3 mm higher than the dynamic high-pressure sealing groove.