JPH0631434A - Post treatment of casting work and apparatus therefor - Google Patents

Abstract

PURPOSE:To provide the method and apparatus for automatically and continuously executing heat treatment and cleaning a work obtd. by a metallic mold casting. CONSTITUTION:While conveying the work W after completing the casting by a conveyor C, the heat treatment is executed, and the work is transfered to a cleaning conveyor D provided so as to travel in parallel by a transfer machine 20 provided at a work sweep-away position H of the conveyor. The work is cleaned by a cleaning device 24 provided at the first half part of the cleaning conveyor and the work after cleaning is conveyed at the latter half part of the cleaning conveyor, and at the sweep-away position, the work after the heat treatment is swept away. A work stock part E is arranged on the extending line of the conveying direction of a heat treatment conveyor to stock the work after the treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for continuously and automatically heat treating and polishing a cast work obtained by die casting.

[0002]

2. Description of the Related Art Conventionally, post-treatment such as heat treatment and blasting of a die-cast casting work is conventionally performed by arranging a casting die device, heat treatment, blasting device, etc. independently of each other. The casting, heat treatment, and blasting work were performed separately. Further, in the past, in order to convey the cast work between the apparatuses, a conveyer dedicated to the conveyance is installed, or the apparatus is conveyed by a motor vehicle or the like.

[0003]

SUMMARY OF THE INVENTION The above-mentioned prior art is such that when heat-treating a cast work, it is necessary to put it in a heat treatment apparatus.
Since it is done after a while, it requires stock space for casting work and stock equipment, which is disadvantageous in space efficiency. In addition, since the time for heat-treating the work is not constant after the casting, there is a possibility that the heat-treatment effect varies, which may cause deterioration in quality.

Next, the work after the heat treatment is ground and swept. However, since the heat treatment time and the polishing time are different, a waiting time for the work is generated, or a stocking place for the waiting time is required. There is. In addition, since heat treatment and blasting are performed by a single device, each work is separate, and at least one or more workers are required for each device. Furthermore, work transfer, transfer, storage, etc. A worker is required, and a lot of workers are required for the post-processing as a whole.

The present invention has been made to solve the above problems. The object of the present invention is to make it possible to carry out post-treatment of a casting work in a consistent process from casting, to fully automate the post-treatment and save labor. It is an object of the present invention to provide a post-processing method and apparatus for casting work, which can eliminate stock space between processes and improve the quality of casting work.

[0006]

[Means for Solving the Problems] Means for solving the above-mentioned problems are as follows: a step of carrying a cast work after completion of casting by a conveyor, and heat treating the cast work in the carrying process; With the transfer machine provided at the payout position, the work is transferred onto the work polishing conveyor provided so as to run in parallel with the conveyor, and the transfer is performed with the polishing apparatus provided in the first half of the work polishing conveyor. The step of blasting the cast work conveyed by the conveyor, and the cast work after the blast is carried in the latter half of the above-mentioned blast sweep conveyor, and the cast work after the blast is finished by the transfer machine at the transfer position. And a post-treatment method for the cast work, comprising the steps of paying out and delivering the work to the cast work stock part after the post-treatment, which is arranged on the extension of the conveying direction of the heat treatment conveyor. , The post-processing method of a cast work according to claim 1, wherein the casting of the work is performed in synchronization with each other.
Means for solving the above problems of the present invention is a heat treatment apparatus for performing heat treatment while conveying a casting work after completion of casting,
And a heat treatment conveyor, a transfer machine disposed on the payout side of the heat treatment conveyor for transferring and discharging the cast work after the heat treatment is completed, and a transfer machine arranged to be partially parallel to the payout side of the heat treatment conveyor. It is installed endlessly, and has a blasting device for blasting the casting work in the first half part, and a part of it is placed on the blasting conveyor facing the transfer machine and on the extension of the heat treatment conveyor in the conveying direction. A post-treatment device for a cast work consisting of a stock part of the work after the completion of the blast cleaning, and further, at the transfer and delivery positions of the blast cleaning conveyor, a mechanism for changing the direction of the work transfer hanger of the conveyor is provided. It is provided.

[0007]

According to the above means, the heat treatment and the post-cleaning treatment of the cast work are carried from the casting to the heat treatment conveyer, and the heat treatment is continuously carried out from the casting. After heat treatment, the work is transferred to the equipped cleaning conveyor,
Carry out blasting with a conveyor, and the work after blasting is
It will be paid out by the transfer machine and will be stocked. Therefore, casting, heat treatment, and polishing can be performed continuously and synchronously, and the above processes can be fully automated, which is extremely advantageous in terms of labor saving, work efficiency improvement, and space saving. is there.

[0008]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows a layout of an apparatus for carrying out the method according to the present invention, and is a plan view including the polishing and cleaning device and the conveyor. FIG. 2 is a plan view of a hanger turning mechanism provided on the polishing and cleaning conveyor. FIG. 3 shows 3-3 of FIG.
A line sectional view, FIG. 4 is a view showing a hanger of the polishing conveyor,
4 is an enlarged sectional view taken along line 4-4 of FIG. 1, FIG. 5 is an explanatory side view of the heat treatment conveyor, and FIG. 6 is an enlarged sectional view of a main part of the heat treatment conveyor.
FIG. 7 is an enlarged cross-sectional view of an essential part of a heat treatment conveyor, and FIG. 8 is an explanatory plan view showing the layout of each device showing the integrated work from casting to post-treatment.

FIG. 8 is an explanatory plan view showing the layout of each device showing the integrated work from casting to post-processing, and is indicated by A in the drawing.
Denoted by 3 are casting dies arranged around the transfer machine B, for example. A work W such as a knuckle arm is cast by the mold A. The work W sequentially cast by the dies A is transferred by the transfer machine B to the upstream side of the heat treatment conveyor C having the upstream end adjacent thereto, and the work W is conveyed to the downstream side by the conveyor C and then transferred to the conveyor C. Heat treatment is performed by the attached heat treatment device. The work W conveyed by the heat treatment conveyor C and subjected to the heat treatment faces the downstream end of the conveyor C, is sent to the polishing and sweeping conveyor D by the transfer machine, and is conveyed endlessly by the polishing and sweeping conveyor D while being polished by the front half thereof. The workpiece W that has been swept and finished after polishing and cleaning returns to the transfer position and is transferred to the stock section E, for example, a conveyor or the like that is conveyed to the next process.

FIG. 5 shows a heat treatment conveyor C provided in the upstream process of the post-treatment. The heat treatment conveyor C is arranged on the endless belt 3 wound between the driving roller 1 and the driven roller 2, and on the lower surface on the conveying side of the belt 3. The guide rollers 4, ..., Tension rollers, auxiliary rollers 5, ...
It is composed of a motor 7 and the like driven via The belt 3 of the conveyor C conveys the work W from the left side to the right side in FIG. 5, and the transfer end position F of the work W after casting the upstream end on the left side of the belt 3.
Then, the transfer machine B takes out the cast work W from the mold A, and pays out the work W to the transfer position F of the belt 3,
It suffices if it has a function of being placed on the belt 3.

A furnace frame 8 is provided on the conveyor portion of the belt C of the conveyor C, a heater 9 is provided on the ceiling, and the workpiece W is conveyed in the process of conveying the workpiece W from the upstream side to the downstream side of the belt 3. Is heated to perform heat treatment. This constitutes the heat treatment apparatus 10 for the transported work W.

As the work W conveying belt 3 of the heat treatment conveyor C, a mesh belt conveyor which moves on the base frame 11 is used as shown in FIG. The mesh belt conveyor is composed of a core metal 12 and a mesh belt 13 spirally wound around the core metal 12. The mesh belt 13 is heated in the process of passing through the heat treatment apparatus 10 described above, and since the mesh belt 13 is made of wire, the coefficient of thermal expansion greatly differs from that of the cast work W, the knuckle arm in the embodiment, Therefore, as shown in FIG.
If the workpiece W has corners W1 and W2 facing downward, the corner W
1 and W2 may get into the space between the eyes 14 of the mesh belt 13. When the heat treatment is performed under such a condition, the mesh belt 13 is greatly stretched by heating, the corners W1 and W2 of the work W are caught in the eyes 14 of the mesh belt 13, and the work W may be stretched more than a set amount. There is. Therefore, in the heat treatment process, the dimensional accuracy of the work W may be deviated.

Therefore, as shown in FIG. 7, the R portion W of the work W is
3 is directed downward, and the R portion W3 is loaded so as to abut on the mesh belt 13. By doing so, only the corner W4 of one end is placed on the eyes 14 of the mesh belt 13,
Even if the mesh belt 13 is caught in this portion and the mesh belt 13 is stretched, the other contact portion W3 is the R portion, so the mesh belt 13 slips on the mesh belt 13, and even if the belt 13 stretches, it is not restricted by this. It is possible to prevent deformation and excessive elongation of the work W during heat treatment. Therefore, as shown in FIG. 6, it is preferable that the work W is loaded, conveyed, and heat-treated so that the R portion W3 faces downward and the R portion W3 contacts the upper surface of the mesh belt 13.

A polishing and sweeping conveyor D is arranged on the downstream side of the above heat treatment conveyor C. As shown in a plan view in FIG. 1, the polishing / conveying conveyor D is adjacent to the downstream side of the conveyor C, has an oval endless shape in a direction parallel to the conveyor C, and is outside the middle portion of the polishing / cleaning conveyor D. The downstream side of the heat treatment conveyor C faces adjacent to. On the downstream side of the payout position G at the downstream side of the heat treatment conveyor C, the heat treatment conveyor C is provided on the polishing conveyor D.
A transfer machine 20 is provided to transfer the heat-treated work W that has been conveyed in step S1 and to transfer the work W that has been completely cleaned by the cleaning / conveying conveyor D to the stock section E.

The transfer machine 20 has an arbitrary structure, but FIG.
As shown in the plan view of FIG.
2 is swung to the left and right, and the arm 22 has gripping arms 23 and 23 for gripping the work W at the tip thereof, and grips the work W after the heat treatment of the heat treatment conveyor C at the payout position G in the downstream portion and pays it out. Rotate to the transfer position of the polishing / conveying conveyor D, and face the loading position H (which is also the position for discharging the workpiece W after the cleaning / cleaning of the polishing / conveying conveyor D and the loading position to the stock section E). It only needs to have a function of gripping, transferring, and loading the work W, and is configured by a robot or the like.

The polishing / conveying conveyor D circulates and moves in an endless manner in the direction of arrow a in FIG. The polishing / cleaning device 24 is configured to perform a cleaning / polishing treatment on the surface of the work W that has been heat-treated by, for example, shot peening. In the drawing, the polishing / cleaning chamber 25 is formed by covering the front half of the conveyor C. The work W is configured to be cleaned in the process in which the work W is transported inside. The blasting / cleaning device 24 may be a general surface blasting / cleaning means, and may blast / clean the surface of the heat-treated work W, or other means such as sandblasting.

As shown in FIG. 4, the scouring and cleaning conveyor D is composed of a carrier rail 30 which is an I-shaped rail and a hanger 31 which is suspended from the carrier rail 30, and the upper part of the hanger 31 is a bifurcated support portion 32. On the left and right of the upper part of the rollers
3 are provided, and rollers 33, 3 are provided on the left and right mounting portions of the rail 30.
3 is mounted and the hanger 31 is moved. A chain 34 that moves the hanger 31 along the rail 30 is locked between the lower portions of the support portions 32, and a suspension bar 36 can be swung by a bearing 37 via a joint 35 at the lower end portion of the support portions 32. Suspended and supported by.

An umbrella-shaped cover 37 is installed at an intermediate portion of the suspension bar 36, a positioning plate 38 is suspended below the cover 37, and a hanger bar is provided at a lower end of the suspension bar 36. 39 is swingably suspended around a shaft 40 as a fulcrum. Around the hanger bar 39,
In the embodiment, four hanger members 41 are vertically projected at equal angular intervals, and the work W is attached to each hanger member 41. In the embodiment, the knuckle arms are as described. It hangs vertically through a hole etc. to fit and support it. Therefore, four works W are supported by the hanger bar 39 at 90 ° intervals for convenience.

The above hangers 31 are hung and supported on the rails 30 at a predetermined pitch, are pulled by one endless chain 34, are guided by the rails 30 and move to carry the works W .... The above hanger 31 is conveyed and faces the above-mentioned loading position H of the cleaning / conveying conveyor D. However, before the loading position H of the polishing / cleaning conveyor D, the opposite side of the transportation direction is widened and an interval is provided in the transportation direction. A pair of guide plates 42, 42 which are gradually narrowed are arranged.
Is set to a height including the positioning plate 38 described above.

The guide plates 42, 42 of the polishing conveyor D
A hanger direction changing mechanism 50 is arranged on the downstream side close to. As shown in FIGS. 2 and 3, the hanger direction changing mechanism 50 is configured so that a spur gear-shaped gear 53 is driven and rotated by a vertical shaft 54 between plate-shaped base frame plates 51 and 52 arranged vertically. 3, the shaft 54 is driven by a motor (not shown) to drive the gear 53, and 55 and 55 in FIG. 3 are bearings that rotatably support the shaft 54. The base frame plates 51 and 52 are supported by columns 56 at the four corners. At the parts of the base frame plates 51 and 52 that are closer to the chain 34 of the conveyor, one guide portion 57, the other faces the upper surface and the other faces the lower surface. 57 is projected, and the guide portion 5
As shown in FIG. 2, 7 and 57 are arranged on a circular arc and three are arranged in a land shape, but the guide portions 57 and 57 may be continuously formed in a protruding rail shape.

A portion of the outer periphery of the switching plate 58 is fitted so as to be sandwiched between the base frame plates 51 and 52 near the chain 34, and the gear 53 is attached to the outer periphery of the switching plate 58.
2 and 3 are formed in the shape of a spur gear by providing teeth 59 that mesh with the guide plate 57, 57 on the upper and lower surfaces of the switching plate 58. As shown in, the concave grooves 60, 60 engage with the guide portions 57, 57 provided between the base frame plates 51, 52 so as to guide the rotation of the switching plate 58. The switching plate 58 passes vertically through a part of the outer circumference to the middle part in the radial direction, and further up to a part close to the outer circumference end on the opposite side. The guide slit 61 is open to a part of the outer circumference. The slit 6 is formed by cutting out the inlet 6 of the slit 61.
2 is formed by expanding in a taper shape and is configured to guide the entry of the positioning plate 38 of the hanger 31 described above.

The switching plate 58 described above is provided at the same level as the positioning plate 38 of the hanger 31 described above. The switching plate 58 has a small thickness, while the positioning plate 38 has a large vertical thickness and the positioning plate 38 has a large thickness. Is set in the guide slit 61 of the switching plate 58 as shown in FIGS. 2 and 3 so that the upper and lower sides of the positioning plate 38 project above and below the switching plate 58. Switching plate 58
I kept it from coming off. The positioning plate 38 is shown in FIG.
As clearly shown in FIG. 3, it is formed with a length so as to correspond to the guide slit 61 in a plan view.

Next, the post-treatment of the casting work will be described according to steps. As described above, the casting work W cast by the mold A ... Is transferred to the upstream portion F of the heat treatment conveyor C by the transfer device B, and the work W is on the downstream side as described by the belt 3 of the conveyor C. Then, the work W is heat-treated by the heat treatment apparatus 10. The work W that has passed through the heat treatment apparatus 10 reaches the downstream portion G of the conveyor C, is received by the transfer machine 20 provided on the extension of the downstream portion G, and is discharged.

The work W gripped by the transfer machine 20 is transferred to the loading position H of the polishing / conveying conveyor D by the turning motion of the transfer machine 20. On the other hand, the hanger 31 that has been conveyed through the polishing conveyor D faces the expansion upstream portion a of the pair of guide plates 42, 42 provided in front of the loading position H of the polishing conveyor D, and the guide plates 42, 42 are Since the upstream side b is widened and the interval is set to be gradually narrowed to the downstream side c, the hanger 31 is moved and the guide plate 42 from the upstream part b enters into the space between the guide plates 42, 42, and thus the positions are not uniform. The positioning plate 38 is the guide plate 4
When the posture is changed by being guided by the slit between the guide plates 42 and 42, and when the guide plate 42, 42 exits from the downstream portion c, the chain 3
The posture is converted substantially in parallel with 4.

The above-mentioned hanger direction changing mechanism 50 is disposed downstream of the outlets of the guide plates 42, 42 at the downstream side c, and a switching plate 58 of this mechanism is faced, and the switching plate 58 has a guide slit 61. The positioning plate 38 is positioned on the same locus as the position 34 and the slit 61 engages with the positioning plate 38. This state is shown in FIG. 1, FIG. 2 and FIG. 3, and the slit 61 is the inlet 6 on the upstream side.
Since 2 is expanded, the positioning plate 38 can be guided and engaged smoothly and surely while being guided.

In this state, the hanger 31 is held, and the work W gripped by the transfer machine 20 is put into the hanger member 41 closest to the transfer machine 20 among the four hanger members 41. The work W is hooked on and supported. Next, the transfer machine 20 is returned to the original position, the next work W on the downstream side of the heat treatment conveyor C is gripped, and is brought to the loading position H. On the other hand, the switching plate 58 is rotated by, for example, 90 ° in FIG.
6 and below rotate, the next hanger member 41 faces the loading position H, and similarly loads and supports the work W, and further the gear 5
3 is rotated by 90 ° and the work W is loaded and supported in the same manner, and the work W is attached to the four hanger members 41 by this operation.
Add one by one and support it.

On the other hand, the work W suspended from the hanger 31 and having undergone the polishing and cleaning process is transferred to the stock section E by gripping, retreating, and swinging the work W by the transfer machine 20.
At the above-mentioned loading position H, the transfer machine 20 is used to load the work W of the heat treatment conveyor C onto the polishing / cleaning conveyor D, dispense the work W from the polishing / cleaning conveyor D, and transfer the work W to the stock section E.
Done in. In the hanger 31, the switching plate 58 is rotated, the positioning plate 38 is opened at a position where the slit 61 is rotated 180 ° with respect to FIG. 2, and the hanger 31 is conveyed by the chain 34 in the direction of arrow a in FIG. And the switching plate 58
The positioning plate of the next hanger will be engaged with this. By repeating the above, the hanger and the work W supported by the hanger face the polishing / cleaning device 24 provided on the conveyor D, and the polishing / cleaning process is performed. The above hangers 31 ... Are sequentially transferred to the downstream side of the endless loop conveyor D, and as described above, the transfer machine 20 loads the stock section E at the loading position H or the hanger. In the above description, it is explained that the switching plate 58 is rotated by 90 °. However, for example, two gripping claws of the transfer machine 20 are provided so that two workpieces are simultaneously dispensed or loaded, and the switching plate 58 is rotated by 180 °.
The transfer may be performed by rotating the rotation, which is optional.

By the way, casting in the above-mentioned mold A,
Heat treatment of work W Heat treatment of conveyor C, conveyance, work W
Of the conveyor cleaning D, the transfer of the work W to the cleaning conveyor C by the transfer machine 20, and the delivery speed are synchronized with the casting by the mold, the transfer speed of each conveyor, and the transfer of the transfer machine. Adjust the speed etc. to be the same. Therefore, the work W is subjected to the heat treatment and the post-casting post-casting treatment between the casting and the heat treatment conveyor C by adjusting the speeds of the steps after the casting by the die, the heat treatment conveyor C and the polishing conveyor D. Between the cleaning conveyor D and the transfer machine 20,
There is no need to stock the work W between them, and no stock space or stock equipment is needed.

[0029]

As is apparent from the above, according to the present invention,
For heat treatment and post-cleaning of cast workpieces, the casting is transferred from the casting to the heat treatment conveyor, and heat treatment is performed continuously from casting.
After the heat treatment, the transfer machine is used to transfer the workpieces to the cleaning conveyor equipped with a polishing and cleaning apparatus, and the workpieces are conveyed and conveyed to perform the cleaning and cleaning. As a result, casting, heat treatment, and blasting can be performed consistently and continuously, and there is no temporary interruption of work between each conveyor, heat treatment, and blasting as in the past, and post-treatment is possible. Can be performed continuously and consistently.
Therefore, since there is no interruption of each work, stock of work, etc., there is no need for transportation and transfer work from interruption to the next process, stock space and stock equipment are not required, and the number of workers is also minimal, and labor saving is drastically reduced. This is extremely advantageous in utilizing the space in the factory.

As described above, casting, heat treatment, and blasting treatment are carried out while being conveyed by each conveyor, so that casting, heat treatment, and blasting are consistently and continuously synchronized at the same speed. It is possible to perform post-processing of casting work fully automatically, further labor saving, work efficiency improvement, space stock and space equipment are unnecessary, and space saving can be surely achieved effectively. it can.

Further, according to the present invention, the cast work is heat-treated while being conveyed by the conveyor, and the work to be blasted and hung by the conveyor is hung at the downstream of the conveyer and is blasted by the blasting and sweeping device provided in a part thereof. Since the endless conveyor is installed and the transfer machine is installed between them, each post-processing device can be easily configured,
Since the sweeping conveyor is installed downstream of the heat treatment conveyor so that part of it is parallel, transfer between conveyors is easy and reliable, and a simple transfer machine is sufficient. It is also possible to construct an economical post-treatment system, which is extremely advantageous in terms of space efficiency.

When a transfer machine for loading and unloading works is installed between the heat treatment conveyor and the polishing conveyor, the polishing conveyor is provided with a mechanism for changing the direction of the work transfer hanger, so that a plurality of works are suspended on the hanger. Support
It is possible to reliably and easily perform the individual payout and loading of each work. In addition, this allows the hanger to support and support multiple workouts and to individually dispense and load the entire post-processing cycle. There is also the effect that an optimal line can be constructed that matches the time.

[Brief description of drawings]

FIG. 1 is a plan view showing the layout of an apparatus for carrying out the method according to the present invention, and including the blasting apparatus and the conveyor.

FIG. 2 is a plan view of a direction changing mechanism of a hanger provided on the above-mentioned polishing conveyor.

FIG. 3 is a sectional view taken along line 3-3 of FIG.

FIG. 4 is a view showing a hanger of a cleaning conveyor, which is shown in FIG.
― Enlarged sectional view of line 4

FIG. 5 is an explanatory side view of the heat treatment conveyor.

FIG. 6 is an enlarged cross-sectional view of the main part of the heat treatment conveyor.

FIG. 7 is an enlarged cross-sectional view of a main part of an unfavorable example of a heat treatment conveyor.

FIG. 8 is an explanatory plan view showing the layout of each device showing the integrated work from casting to post-treatment.

[Explanation of symbols]

A ... Casting die for casting work W, B ... Transfer machine, C ... Heat treatment conveyor, D ... Abrasive sweep conveyor, E ... Stock section, 10 ... Heat treatment apparatus, 20 ... Transfer machine, 24 ... Abrasive sweep apparatus, 50 … Hanger turning mechanism.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location // C21D 5/00 Z

Claims (4)

[Claims] 1. A step of transporting a cast work after casting is completed by a conveyor, and a step of heat-treating the cast work in the transporting step, and a transfer machine provided at a work delivering position of the heat-treating conveyor, which is parallel to the conveyor. A step of transferring the work to a work polishing conveyor provided so as to run, and polishing and cleaning a cast work conveyed by the conveyor with a polishing device provided in the first half of the work polishing conveyor; The cast work after blasting was conveyed in the latter half of the blasting conveyor, and the cast work after blasting was discharged by the above-mentioned transfer machine at the above-mentioned transfer position, and it was arranged on the extension of the conveying direction of the heat treatment conveyor. A post-treatment method for a cast work, comprising the steps of: paying out the work to a cast work stock portion after the post-treatment. 2. The post-processing method for a cast work according to claim 1, wherein the post-processing of the work and the casting of the work are performed in synchronization with each other. 3. A heat treatment apparatus and a heat treatment conveyor for heat-treating a cast work after completion of casting, and a heat-treatment conveyor, which is arranged on the delivery side of the heat-treatment conveyor, transfers and casts the work after completion of heat treatment. A transfer machine to be put out and a part of the heat treatment conveyor are arranged so as to be parallel to the payout side, endless, and a blasting device for blasting the cast work is provided in the first half part, part of which is A post-treatment device for a cast work, comprising: a polishing conveyor facing the transfer machine; and a stock portion of the work after the cleaning, which is arranged on an extension of the heat treatment conveyor in the conveying direction. 4. The post-treatment device for cast work according to claim 3, wherein a direction changing mechanism for the work transfer hanger of the conveyor is provided at the transfer / delivery position of the polishing / conveying conveyor.