CN112879428B - Pre-tightening device of linear rolling guide rail based on mechanical-hydraulic control system - Google Patents

Abstract

The invention discloses a pre-tightening device of a linear rolling guide rail based on a machine-liquid control system, which comprises a movable base, a ball, a groove, a movable block and an upper rail, wherein the movable base is connected with a scrap scraping plate through a first screw, the scrap scraping plate is arranged at the top of a lower rail, a wedge block is arranged at the top of the lower rail, the left end part of the wedge block of a support guide rail is connected with a hydraulic cylinder piston rod through a second screw, the hydraulic cylinder piston rod penetrates through and is hermetically connected into a hydraulic cylinder body, the inner side of the top of the hydraulic cylinder body is connected with a slide valve body, the middle of the slide valve body is sleeved with a slide valve core, the outer side of the top of the hydraulic cylinder body is connected with a quantitative pump, and the inner side surface of a scrap collecting box is fixedly provided with a sleeve block. This preloading device of linear rolling guide based on machine liquid control system can control the pretension volume, can clean the oil stain on the pneumatic cylinder piston rod simultaneously.

Description

A preloading device of linear rolling guide based on mechanical-hydraulic control system

technical field

The invention relates to the technical field of machine tool equipment, in particular to a preloading device for a linear rolling guide rail based on a machine-hydraulic control system.

Background technique

With the continuous development of modern manufacturing technology, numerical control technology, mechatronics and industrial robots are more widely used in production. The positioning, guiding accuracy, cutting speed, and rapid feed of the mechanical transmission mechanism are constantly improving, so that the linear rolling guide pair replaces the previously widely used sliding linear guide, the control system centralized lubrication replaces manual oil supply, and the linear rolling guide can be used in high loads. The preload is a very important parameter of the rolling guide. By adjusting the preload, the flexibility and rigidity of the slider can be changed, thereby improving the accuracy of the rolling guide. However, the existing linear rolling The preloading device of the guide rail has the following problems:

The existing preloading device for linear rolling guides preloads the rolling guides through interference preloading or adjusting screws, but it is very difficult to control the preloading amount of the interference preloading. The adjusting screw preloading needs to be threaded at the front end of the main shaft. , poor craftsmanship, the use of the preloading device of the linear rolling guide based on the machine-hydraulic control system can solve this problem very well. The machine-hydraulic control system itself has the advantages of compact structure, small size, light weight, good rigidity, reliable control and response At the same time, the existing preloading device of the linear rolling guide based on the machine-hydraulic control system is easy to adhere to the waste debris on the piston rod of the hydraulic cylinder to form oil scale, which requires Carry out cleaning process.

Therefore, we propose a preloading device for linear rolling guides based on the machine-hydraulic control system, in order to solve the above problems.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preloading device for a linear rolling guide based on a mechanical-hydraulic control system, so as to solve the problem that the preloading device of the existing linear rolling guide on the market proposed by the above-mentioned background technology is inconvenient to control the amount of preload , and at the same time it is inconvenient to clean the oil dirt on the piston rod of the hydraulic cylinder.

In order to achieve the above purpose, the present invention provides the following technical solutions: a preloading device for a linear rolling guide rail based on a mechanical-hydraulic control system, comprising a moving base, a ball, a groove, a movable block and an upper rail, and the moving base passes through the first A screw is connected with the scraper board, and the scraper board is installed on the top of the lower track, and the top of the lower track is equipped with a support rail wedge block, and the top of the lower track is installed with a connecting block, and the connecting block is installed on the top of the upper track. bottom, and the upper rail is located above the lower rail, the left end of the support rail wedge is connected with a hydraulic cylinder piston rod through a second screw, and the hydraulic cylinder piston rod is connected to the hydraulic cylinder body through the seal, and the hydraulic cylinder piston rod It is sleeved in the scraper, and the hydraulic cylinder body is installed on the top of the mobile base through a fixed tripod, and the hydraulic cylinder piston rod is connected to the middle of the hydraulic cylinder body through the seal, and the top inner side of the hydraulic cylinder body is connected with a slide valve The middle part of the spool valve body is sleeved with a spool valve spool, and the end of the spool valve spool is connected with a lever handle, and a scale is installed on the front side of the upper part of the lever handle, and the top outer side of the hydraulic cylinder body is connected with a Quantitative pump, and the quantitative pump is connected with the motor, and an overflow valve is installed above the motor, a wedge adjustment plate is installed on the left end of the upper rail, and an installation port is opened on the top of the scraper plate, and A cleaning ring is connected in the installation port, and a guide plate is fixed under the outer side of the installation port, and a chip collecting box is installed under the guide plate, and a sleeve block is fixed on the inner end surface of the chip collecting box, and the sleeve block is connected to. In the insertion slot, and the insertion slot is opened on the side of the fixing plate, and the fixing plate is fixed on the outer middle part of the scraper board, the middle part of the fixing plate is connected with a clamping rod through the second return spring, and the clamping rod is located in the middle part of the scraper board. below the fixing plate.

Preferably, the support rail wedge is connected to the lower rail through balls, and a standard rail block is connected through the middle of the lower rail, and the ball is connected between the support rail wedge, the standard rail block and the lower rail.

Preferably, the balls are distributed at equal intervals on the outside of the standard guide rail block, and the support guide rail wedge blocks form a relative movement structure through the balls, the lower rail and the piston rod of the hydraulic cylinder.

Preferably, the movement direction of the piston rod of the hydraulic cylinder is opposite to that of the slide valve body, and the piston rod of the hydraulic cylinder and the slide valve body form a structure in which the front is tightened and the back is loose.

Preferably, the slide valve body forms a horizontal sliding structure between the slide valve valve core, the lever handle and the hydraulic cylinder body, and the displacement of the lever handle is equal to the preload amount of the preload device.

Preferably, a groove is formed on the outer side of the cleaning ring, and a movable block is connected to the groove through a first return spring, and the end of the movable block is connected to the card groove, and the card groove is opened on the inner wall of the installation hole superior.

Preferably, the end of the movable block and the card slot are designed in a triangular structure, and the movable block forms an engaging structure through the first return spring and the card slot.

Preferably, the guide plates correspond to the positions of the chip boxes one-to-one, and the chip boxes are symmetrically distributed on both sides of the scraper.

Preferably, the clamping rod forms an elastic movement structure between the second return spring and the insertion slot, and the clamping rod is designed as a "U"-shaped structure as a whole, and the bottom of the clamping rod is designed as a rectangular frame.

Compared with the prior art, the beneficial effects of the present invention are: the preloading device of the linear rolling guide rail based on the machine-hydraulic control system;

1. Through the hydraulic cylinder piston rod, slide valve, slide valve spool, lever handle, scale, quantitative pump, motor and relief valve, the motor drives the quantitative pump to the slide valve through an initial displacement of the given slide valve. Supply oil, push the spool valve spool through the lever handle to drive the spool valve to move, and then drive the piston rod to move to achieve the purpose of pre-tightening the slider. There is a scale on the lever handle, and the displacement of the lever handle will be fed back to the scale. Thereby, the preload amount can be known. The most important thing is that it is an innovation to use the hydraulic control system to preload the rolling guide. The hydraulic control system itself has the advantages of compact structure, small size, light weight, good rigidity, reliable control and response. It has the characteristics of high speed and high precision, so it has been widely used, so as to realize the control of the preload;

2. Through the set support rail wedges, balls, standard rail blocks, connecting blocks and wedge adjustment plates, the support rail wedges can move relatively between the balls and the lower rail, and then preload the device. The standard rail block , connecting block and wedge adjustment plate make the internal connection of the device stable, and the ball can reduce friction and wear, so that the stability and reliability of the machine tool are greatly improved, and the temperature rise, noise, vibration and other performance are significantly improved. So as to avoid wear and affect the machining accuracy and machining quality of CNC machine tools;

3. Through the set installation port, cleaning ring, groove, first return spring, movable block and card groove, the cleaning ring can clean the waste chips adhering to the piston rod of the hydraulic cylinder, and when the cleaning ring is replaced , Pull the cleaning ring to the outside of the installation port, and the movable block outside the cleaning ring will compress the first return spring and separate from the card slot for replacement. The installation can be done in the same way, so that the cleaning ring is easy to disassemble and wash;

4. Through the set guide plate, sleeve block, insertion slot, fixed plate, second return spring and clamping rod, the guide plate can guide the cleaned waste into the dust collecting box, and pull the clamping rod, the clamping rod will be closed. The second return spring is compressed and slides in the insertion slot, so that the insertion slot and the sleeve block are separated, so that the dust collection box for collecting waste is disassembled for subsequent processing.

Description of drawings

Fig. 1 is the overall frontal structure schematic diagram of the present invention;

Fig. 2 is the front view structure schematic diagram of the quantitative pump of the present invention;

Fig. 3 is the front view structure schematic diagram of the guide plate of the present invention;

4 is a schematic side view of the cleaning ring of the present invention;

Fig. 5 is the enlarged schematic diagram of the structure at A in Fig. 4 of the present invention;

6 is a schematic top view structure diagram of a movable block of the present invention;

Fig. 7 is the enlarged structural schematic diagram at B in Fig. 3 of the present invention;

FIG. 8 is a schematic top view of the structure of the clamping rod of the present invention.

In the figure: 1. Mobile base; 2. The first screw; 3. Scraper board; 4. Supporting guide rail wedge; 5. Ball; 6. Standard guide rail block; 7. Lower rail; 8. Connecting block; 9. The second screw; 10, the piston rod of the hydraulic cylinder; 11, the body of the hydraulic cylinder; 12, the fixed tripod; 13, the body of the spool valve; 14, the spool of the spool valve; 15, the lever handle; 16, the scale; 17, the quantitative pump; 18, electric motor; 19, relief valve; 20, wedge adjustment plate; 21, installation port; 22, cleaning ring; 23, groove; 24, first return spring; 25, movable block; 26, card slot; 27, guide plate; 28, chip box; 29, sleeve block; 30, insertion slot; 31, fixed plate; 32, second return spring; 33, clamping rod; 34, upper track.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

1-8, the present invention provides a technical solution: a pre-tightening device for a linear rolling guide based on a mechanical-hydraulic control system, including a moving base 1, a first screw 2, a scraper 3, and a support guide rail wedge Block 4, ball 5, standard rail block 6, lower rail 7, connecting block 8, second screw 9, hydraulic cylinder piston rod 10, hydraulic cylinder body 11, fixed tripod 12, spool valve body 13, spool valve spool 14 , lever handle 15, scale 16, quantitative pump 17, motor 18, relief valve 19, wedge adjustment plate 20, installation port 21, cleaning ring 22, groove 23, first return spring 24, movable block 25, The card slot 26, the guide plate 27, the chip box 28, the sleeve block 29, the insertion slot 30, the fixing plate 31, the second return spring 32, the clamping rod 33 and the upper rail 34, the mobile base 1 is connected to the scraper through the first screw 2. The chipboard 3 is connected, and the chipboard 3 is installed on the top of the lower rail 7, and the support rail wedge 4 is installed on the top of the lower rail 7, and the connecting block 8 is installed on the top of the lower rail 7, and the connecting block 8 is installed on the The bottom of the upper rail 34, and the upper rail 34 is located above the lower rail 7, the left end of the support rail wedge 4 is connected with the hydraulic cylinder piston rod 10 through the second screw 9, and the hydraulic cylinder piston rod 10 is connected to the hydraulic cylinder through the seal In the main body 11, the hydraulic cylinder piston rod 10 is sleeved in the scraper plate 3, and the hydraulic cylinder body 11 is installed on the top of the mobile base 1 through the fixed tripod 12, and the hydraulic cylinder piston rod 10 is connected to the hydraulic cylinder body 11 through sealing. In the middle of the hydraulic cylinder body 11, a slide valve body 13 is connected to the top inner side of the hydraulic cylinder body 11, and a slide valve spool 14 is sleeved in the middle of the slide valve body 13, and a lever handle 15 is connected to the end of the slide valve spool 14, and the lever A scale 16 is installed on the front side of the upper part of the handle 15, a quantitative pump 17 is connected to the top outer side of the hydraulic cylinder body 11, and the quantitative pump 17 is connected with the electric motor 18, and a relief valve 19 is installed above the electric motor 18, and the left side of the upper rail 34 is installed. A wedge adjustment plate 20 is installed at the side end, an installation port 21 is opened on the top of the scraper 3, and a cleaning ring 22 is connected in the installation port 21, and a guide plate 27 is fixed under the outer side of the installation port 21. Moreover, a chip collecting box 28 is installed under the guide plate 27 , a sleeve block 29 is fixed on the inner end surface of the chip collecting box 28 , and the sleeve block 29 is connected to the insertion slot 30 , and the insertion slot 30 is opened in the fixing plate 31 . On the side, and the fixing plate 31 is fixed on the outer middle part of the scraper 3, the middle part of the fixing plate 31 is connected with the clamping rod 33 through the second return spring 32, and the clamping rod 33 is located below the fixing plate 31;

The support rail wedge 4 is connected with the lower rail 7 through the ball 5, and the middle of the lower rail 7 is connected with the standard rail block 6, and the ball 5 is connected between the support rail wedge 4, the standard rail block 6 and the lower rail 7 , so that the ball 5 can reduce the friction force and wear when the relative movement between the support guide rail wedge 4 and the lower rail 7 is performed;

The balls 5 are equally spaced on the outside of the standard guideway block 6, and the support guideway wedge 4 forms a synchronous movement structure between the lower track 7 of the balls 5 and the hydraulic cylinder piston rod 10, so that after the hydraulic cylinder piston rod 10 moves, it will drive the The support rail wedge 4 moves in the same direction, so as to form relative movement with the lower rail 7 .

The movement directions of the hydraulic cylinder piston rod 10 and the spool valve body 13 are opposite, and the hydraulic cylinder piston rod 10 and the spool valve body 13 form a structure in which the front is tightened and the latter is loosened, so that a backward displacement of the spool valve body 13 will push The hydraulic cylinder piston rod 10 moves in the preload direction, on the contrary, a forward displacement of the spool valve body 13 will push the hydraulic cylinder piston rod 10 to move in the opposite direction;

The sliding valve body 13 forms a horizontal sliding structure through the sliding valve spool 14, the lever handle 15 and the hydraulic cylinder body 11, and the displacement amount of the lever handle 15 is equal to the preloading amount of the preloading device, so that the value after the lever handle 15 moves It will be directly reflected on the scale 16, so that it is convenient for people to adjust the preload;

The outer side of the cleaning ring 22 is provided with a groove 23, and a movable block 25 is connected to the groove 23 through the first return spring 24, and the end of the movable block 25 is connected to the card groove 26, and the card groove 26 is opened in the installation hole. on the inner wall of the port 21, so that after the cleaning ring 22 is installed in the installation port 21, the movable block 25 will engage with the card slot 26;

Both the end of the movable block 25 and the card slot 26 are designed in a triangular structure, and the movable block 25 forms an engaging structure through the first return spring 24 and the card slot 26, so that when disassembled, the movable block 25 squeezes the first return spring. 24 is separated from the card slot 26, so as to realize convenient disassembly;

The positions of the guide plates 27 and the chip collecting boxes 28 correspond one-to-one, and the chip collecting boxes 28 are symmetrically distributed on both sides of the scraper plate 3, so that the guide plates 27 can guide the cleaned waste into the chip collecting boxes 28, and Each chip box 28 has a corresponding guide plate 27 to form a group with it;

The clamping rod 33 forms an elastic movement structure between the second return spring 32 and the insertion slot 30, and the clamping rod 33 is designed as a "U"-shaped structure as a whole, and the bottom of the clamping rod 33 is designed as a rectangular frame, so that the clamping rod 33 passes through. The second return spring 32 slides between the insertion grooves 30 , so that the chip box 28 can be easily disassembled and assembled without affecting its normal operation.

Working principle: When using the preloading device of the linear rolling guide based on the hydraulic control system, as shown in Figure 1-2, first, push the lever handle 15, and the lever handle 15 will pass the spool valve spool 14 to the spool valve. An initial displacement of the main body 13 is recorded as the initial position, and then the motor 18 is started, and the motor 18 will provide power to the quantitative pump 17, and the quantitative pump 17 will start to supply oil to the hydraulic control system. The oil will be transported to the hydraulic cylinder body 11 through the slide valve body 13, and then push the hydraulic cylinder piston rod 10 to move horizontally. After the hydraulic cylinder piston rod 10 moves, it will drive the support rail wedge 4 through the second screw 9. During the movement of the support rail wedge 4, the ball 5 is connected between the support rail wedge 4, the standard rail block 6 and the lower rail 7, so that there will be relative movement between the support rail wedge 4 and the lower rail 7 , and then achieve the purpose of preloading the slider, and the ball 5 can reduce the friction and wear during the movement process, thereby making the machining accuracy and machining quality of the CNC machine tool better. The lever handle 15 is provided with a scale 16. The displacement of the handle 15 will be fed back to the scale 16, so that the preload amount can be known, and a backward displacement of the spool valve body 13 will push the hydraulic cylinder piston rod 10 to move in the preload direction. A forward displacement of the body 13 will push the hydraulic cylinder piston rod 10 to move in the opposite direction, the moving base 1 is fixedly connected with the scraper 3 through the first screw 2, and the fixed tripod 12 can be the hydraulic cylinder body 11 and the moving base. The identification support is provided between the seats 1, so that it is convenient for people to control the preload, and the operation is convenient;

As shown in Figures 3-8, during the working process of the hydraulic cylinder piston rod 10, the hydraulic cylinder piston rod 10 is sleeved in the scraper plate 3, and the waste generated by the machine tool during processing will adhere to the hydraulic cylinder piston rod 10. It needs to be cleaned up. The cleaning ring 22 installed in the installation port 21 opened by the scraper 3 can clean the outside of the hydraulic cylinder piston rod 10, so that the adhering waste is scraped off and the falling The waste chips will fall into the chip collecting box 28 through the guide plate 27 for collection. After a period of use, the cleaning ring 22 and the chip collecting box 28 need to be disassembled and cleaned. When the cleaning ring 22 is pulled from the outside of the opening 21 , the movable block 25 on the outer side of the cleaning ring 22 will be squeezed with the slot 26 , so that the movable block 25 compresses the first return spring 24 along the oblique edge and retracts into the groove 23 Then, the cleaning ring 22 can be disassembled for cleaning. When installing, insert the cleaning ring 22 into the installation port 21, and the movable block 25 will be engaged with it when it moves to the position of the card slot 26, and then the installation is completed. When processing the chip container 28, manually pull the clamping rod 33, the clamping rod 33 will compress the second return spring 32 and slide in the insertion slot 30, and after completely withdrawing from the sleeve 29, the chip container can be removed. 28 is separated from the fixing plate 31, and then the dust collecting box 28 is subjected to subsequent cleaning treatment, and then the clamping rod 33 is pulled again to insert the sleeve block 29 into the insertion slot 30, and then let go, and the clamping rod 33 will be in the first position. Under the elastic force of the second return springs 32, it is reset, and then the dust collecting box 28 is stably fixed on the outside of the scraper plate 3 for continued use, so as to realize the collection and cleaning of waste and complete a series of tasks.

Contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still possible to modify the technical solutions described in the foregoing embodiments, or to perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. The utility model provides a preloading device of straight line rolling guide based on machine liquid control system, includes removal base (1), ball (5), recess (23), movable block (25) and last track (34), its characterized in that: the scrap removing device is characterized in that the movable base (1) is connected with the scrap scraping plate (3) through a first screw (2), the scrap scraping plate (3) is installed at the top of the lower rail (7), the supporting guide rail wedge block (4) is installed at the top of the lower rail (7), the connecting block (8) is installed at the bottom of the upper rail (34), the upper rail (34) is located above the lower rail (7), the left end of the supporting guide rail wedge block (4) is connected with the hydraulic cylinder piston rod (10) through a second screw (9), the hydraulic cylinder piston rod (10) is connected to the hydraulic cylinder body (11) in a penetrating and sealing mode, the hydraulic cylinder piston rod (10) is sleeved in the scrap scraping plate (3), the hydraulic cylinder body (11) is installed at the top of the movable base (1) through a fixed screw (12), and the hydraulic cylinder piston rod (10) penetrates through and is connected to the middle of the hydraulic cylinder body (11) in a sealing mode, the inner side of the top of the hydraulic cylinder body (11) is connected with a slide valve body (13), the middle of the slide valve body (13) is sleeved with a slide valve core (14), the end part of the slide valve core (14) is connected with a lever handle (15), the front side of the upper part of the lever handle (15) is provided with a graduated scale (16), the outer side of the top of the hydraulic cylinder body (11) is connected with a constant delivery pump (17), the constant delivery pump (17) is connected with a motor (18), an overflow valve (19) is arranged above the motor (18), the end part of the left side of an upper track (34) is provided with a wedge adjusting plate (20), the top of the scraping plate (3) is provided with an installation through hole (21), the installation through hole (21) is connected with a cleaning ring (22), a guide plate (27) is fixed below the outer side of the installation through hole (21), and a scrap collecting box (28) is arranged below the guide plate (27), the inner side end face of the scrap collecting box (28) is fixedly provided with a sleeve block (29), the sleeve block (29) is connected into an insertion groove (30), the insertion groove (30) is arranged on the side face of a fixing plate (31), the fixing plate (31) is fixed to the middle of the outer side of the scrap scraping plate (3), the middle of the fixing plate (31) is connected with a clamping rod (33) in a penetrating mode through a second return spring (32), and the clamping rod (33) is located below the fixing plate (31).

2. The pretensioning device for the linear rolling guide rail based on the mechanical-hydraulic control system as claimed in claim 1, wherein: the supporting guide rail wedge block (4) is connected with the lower rail (7) through a ball (5), the middle of the lower rail (7) is connected with a standard guide rail block (6) in a penetrating mode, and the ball (5) is connected among the supporting guide rail wedge block (4), the standard guide rail block (6) and the lower rail (7).

3. The pre-tightening device for the linear rolling guide rail based on the mechanical-hydraulic control system is characterized in that: the balls (5) are distributed on the outer side of the standard guide rail block (6) at equal intervals, and the support guide rail wedge block (4) forms a relative movement structure through the balls (5), the lower rail (7) and the hydraulic cylinder piston rod (10).

4. The pretensioning device for the linear rolling guide rail based on the mechanical-hydraulic control system as claimed in claim 1, wherein: the moving directions of the hydraulic cylinder piston rod (10) and the slide valve body (13) are opposite, and the hydraulic cylinder piston rod (10) and the slide valve body (13) form a structure with a tight front and a loose back.

5. The pretensioning device for the linear rolling guide rail based on the mechanical-hydraulic control system as claimed in claim 1, wherein: the slide valve body (13) forms a horizontal sliding structure through the slide valve core (14), the lever handle (15) and the hydraulic cylinder body (11), and the displacement of the lever handle (15) is equal to the pre-tightening amount of the early warning device.

6. The pretensioning device for the linear rolling guide rail based on the mechanical-hydraulic control system as claimed in claim 1, wherein: the outside of clean ring (22) is seted up flutedly (23), and is connected with movable block (25) through first reset spring (24) in flutedly (23) to the tip of movable block (25) is connected in draw-in groove (26), and draw-in groove (26) are seted up on the inner wall of installation opening (21) moreover.

7. The pretensioning device for the linear rolling guide rail based on the mechanical-hydraulic control system as claimed in claim 6, wherein: the end part of the movable block (25) and the clamping groove (26) are designed to be triangular structures, and the movable block (25) forms a clamping structure through the first reset spring (24) and the clamping groove (26).

8. The pretensioning device for the linear rolling guide rail based on the mechanical-hydraulic control system as claimed in claim 1, wherein: the guide plates (27) are in one-to-one correspondence with the positions of the chip collecting boxes (28), and the chip collecting boxes (28) are symmetrically distributed on two sides of the chip scraping plate (3).

9. The pretensioning device for the linear rolling guide rail based on the mechanical-hydraulic control system as claimed in claim 1, wherein: the clamping rod (33) forms an elastic moving structure through the second return spring (32) and the insertion groove (30), the clamping rod (33) is integrally designed to be of a U-shaped structure, and the bottom of the clamping rod (33) is designed to be a rectangular frame.

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