Adjustable support frame for cup mouth foundation template

Abstract

The utility model relates to an adjustable support frame for a cup foundation template. The adjustable support frame is formed by connecting an upper back shore, a lower back shore, a central shaft, an angle brace and a wrench through pins. By adjusting the lengths of the upper adjusting lead screw and the lower adjusting lead screw of the upper back shore and the lower back shore, the cup foundation support can adapt to cup foundations of different sizes and can be repeatedly used. The central shaft is rotated to drive the upper turntable and the lower turntable of the upper back shore and the lower back shore to rotate, so that the pins in the eccentric arc-shaped holes of the upper turntable and the lower turntable drive the upper adjusting lead screw and the lower adjusting lead screw to move, and the angle brace compresses and fixes the template; when the rotating disc rotates reversely, the angle brace is pulled to be separated from the formwork, and rapid positioning, rapid supporting and lossless dismantling of the cup opening foundation formwork are achieved. The problems that in the prior art, a cup opening foundation template is difficult to manufacture, install and disassemble, and loss is large when the cup opening foundation template is used once are solved.

Description

Technical Field

[0001] This invention relates to an adjustable support frame for a cup-shaped base template.

[0002] The upper and lower adjusting screws of the upper and lower supports can be adjusted to accommodate different sizes of cup-shaped foundation templates, allowing for repeated use. Rotating the central shaft drives the upper and lower turntables of the upper and lower supports to rotate, which in turn moves the adjusting screws via pins in the eccentric arc-shaped holes of the turntables. This allows for tightening or disengaging the corner braces from the template, enabling rapid positioning, rapid support, and non-destructive removal of the cup-shaped foundation template. This solves the problems of difficult fabrication, installation, and disassembly of existing cup-shaped foundation templates, as well as high single-use losses. Background Technology

[0003] During the formwork construction of the cup-shaped foundation, the formwork is an internal formwork with a certain depth, making it difficult to support and fix, which is time-consuming and labor-intensive. In particular, the formwork removal after the concrete is poured is problematic. If the removal is done too late, the concrete will squeeze and stick to the formwork, making it impossible to remove smoothly and requiring the formwork to be chiseled away, making it usable only once. If the removal is done too early, the low strength of the concrete may damage the cup-shaped foundation concrete. Summary of the Invention

[0004] This invention provides an adjustable support frame for cup-shaped foundation templates. By adjusting the lengths of the upper and lower adjusting screws, it can adapt to cup-shaped foundations of different sizes. The upper and lower adjusting screws, along with the corner braces, reliably support the template, forming a template support system for the cup-shaped foundation. After the concrete is poured and solidified, the pins in the rectangular holes of the plate pin hole plate are pulled out. Rotating the central shaft drives the upper and lower turntables of the upper and lower top supports to rotate. This, in turn, moves the upper and lower adjusting screws through the pins in the eccentric arc-shaped holes of the upper and lower turntables, pulling the corner braces away from the template. This releases the adjustable support frame from supporting and constraining the template frame, as well as releasing the template blocks from pressing against the template. This allows the four inner template pieces of the cup-shaped foundation to continue resting independently against the concrete surface. Once the concrete reaches a certain strength, the templates can be easily removed.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: an adjustable support frame for a cup-shaped base template, comprising: an upper support (including: an upper adjusting screw, an upper turntable, and a tapered plate pin), a lower support (including: a lower adjusting screw and a lower turntable), a central shaft, corner braces, a wrench, pins, and other connecting parts.

[0006] The central shaft is made of iron rod and consists of a circular shaft body and a square pin at the top welded together. A horizontal circular hole is opened at a certain distance from the upper and lower ends of the shaft body. After the upper and lower supports are fitted onto the central shaft, pins are inserted into the horizontal circular holes so that the turntables of the upper and lower supports can rotate together with the central shaft.

[0007] The corner brace is made of angle iron. An upper connecting plate is welded between the two wings of the angle iron at a certain distance from the upper end, and a lower connecting plate is welded between the two wings of the angle iron at a certain distance from the lower end. The distance between the lower connecting plate and the lower end of the angle iron is such that when the lower adjusting screw is adjusted to its minimum length and the upper adjusting screw is adjusted to its maximum length, the bottom end of the corner brace is flush with the bottom end of the central shaft, or the bottom end of the corner brace is slightly lower than the bottom end of the central shaft. A template stop block is welded to each side of the upper and lower connecting plates for template positioning and pressing the template surface. A circular hole is opened at the geometric center of the upper connecting plate, through which a pin passes. When the turntable rotates, it drives the upper adjusting screw to move, pressing the corner brace against the template end face. When the turntable rotates in the opposite direction, it pulls the corner brace away from the template. An elongated hole is opened at the geometric center of the lower connecting plate, with semi-circular holes at both ends. The outer corner point of the corner brace, viewed from above, is on a straight line with the center line of the long side of the elongated hole and the center of the semi-circle. The lower adjusting screw is connected downwards... When the connecting plate moves in the direction of the connecting plate, the pin in the elongated hole presses against the semi-circular hole on one side of the elongated hole of the lower connecting plate, tightening the corner brace; when the lower adjusting screw moves away from the corner brace, the pin in the elongated hole leaves the semi-circular hole on one side of the elongated hole of the corner brace, releasing the pressure of the lower adjusting screw on the lower connecting plate, so that the lower end of the corner brace is in a free state, and the upper end of the corner brace moves towards the central axis and disengages from the template under the pull of the upper adjusting screw. While the lower end of the corner brace is under tension, it has a tendency to rotate towards the central axis as a fulcrum; when the adjustable support frame and the template together form a template box for the cup-shaped foundation, the outer surface of the angle iron of the corner brace is in contact with the end face of the template, and the outer corner of the angle iron coincides with the outer edge of the end face of the template, forming the four outer corners of the template box; the inner side of the template is positioned and pressed by the template blocks on the upper and lower connecting plates of the corner brace, and the outer side of the template is fixed by flexible and rigid material supports and other methods.

[0008] The upper support consists of an upper turntable, four upper adjusting screws, four tapered pins, and connecting pins. The upper turntable is circular, made of iron plate, with a central hole slightly larger in diameter than the central shaft. A central sleeve is welded to the turntable, with the hole in the sleeve having the same diameter as the central hole of the turntable and their axes coinciding, allowing the central shaft to pass through. A horizontal hole is opened on the central sleeve, through which a pin is inserted to lock the central shaft to the upper turntable, enabling synchronous rotation. Four eccentric arc-shaped holes are evenly arranged on the turntable surface, with semi-circular holes at both ends. On the horizontal projection plane, the center lines of the two semi-circular holes at both ends of the eccentric arc-shaped holes are at different distances from the center line of the central shaft, one at a greater distance and one at a closer distance. When the turntable rotates, the pins in the eccentric arc-shaped holes can move towards or away from the support direction. Four pin-hole plates are welded to the circumference of the turntable, with rectangular holes for inserting tapered pins.

[0009] The upper adjusting screw of the upper turntable consists of an inner screw and an outer screw, with the inner screw screw screwed onto the outer screw. Perforated plates are welded to the end of the inner screw facing the turntable and the end of the outer screw facing the corner brace, respectively. Pins are inserted into the holes to connect to the turntable and the corner brace connecting plates, respectively. Based on the designed upper opening dimensions of the cup-mouth base, the length of the upper adjusting screw is determined. The inner and outer screws are rotated so that the rectangle formed by the upper ends of the four corner braces is the same as the designed upper opening dimensions of the cup-mouth base. In the horizontal projection plane, the center of the central axis, the center of the far-distance semicircular hole of the eccentric arc hole of the upper turntable, and the upper corner brace... When the center of the connecting plate hole, the outer corner of the corner brace, and the four points are aligned in a straight line, the upper adjusting screw is in the state of tightening the corner brace. In this state, the angle iron surface of the corner brace is in contact with the end face of the template, the template stop block presses the template, and a tapered pin is placed in the pin hole plate to restrict the rotation of the turntable, so that the adjustable support frame and the template form a stable template system. When the tapered pin in the pin hole plate is pulled out and the upper turntable is rotated in the opposite direction, the pin in the eccentric arc hole drives the upper adjusting screw. The upper adjusting screw pulls the upper connecting plate of the corner brace to move towards the center, so that the angle iron surface of the corner brace is disengaged from the end face of the template.

[0010] The lower support consists of a lower turntable, four lower adjusting screws, and connecting pins. The lower turntable is circular, made of iron plate, with a central hole. A central sleeve is welded to the turntable, and the diameter of the hole in the central sleeve is the same as that of the central hole in the turntable, with their axes coinciding, for the central shaft to pass through. A horizontal hole is opened on the central sleeve, through which the central shaft passes, and a pin is inserted into the horizontal hole to make the central shaft drive the lower turntable to rotate. Four eccentric arc-shaped holes, identical to those on the upper turntable, are opened on the surface of the turntable.

[0011] The lower adjusting screw of the lower support consists of an inner screw and an outer screw. The inner screw is screwed onto the outer screw. Hole plates with round holes are welded to the end of the inner screw facing the turntable and the end of the outer screw facing the corner brace, respectively. Pins are inserted into the holes at both ends and connected to the turntable and the corner brace connecting plate, respectively. The length of the lower adjusting screw is adjusted in the same way as the upper adjusting screw, according to the designed lower opening size of the cup-mouth foundation. This ensures that the rectangle formed by the lower ends of the four corner braces is the same as the designed lower opening size of the cup-mouth foundation. In the horizontal projection plane, the center of the central axis, the far-distance semi-circular hole center of the eccentric arc hole of the lower turntable, and the lower connecting plate of the corner brace are all within the same dimensions. When the center line of the elongated hole of the connecting plate, the outer corner of the corner brace, and the other four points are aligned on a straight line, the lower adjusting screw is in the state of tightening the corner brace. In this state, the pin in the outer screw plate hole of the lower adjusting screw is tightened against the outer edge of the elongated hole of the lower connecting plate and the lower connecting plate, so that the angle iron surface of the corner brace is in contact with the end face of the template, and the template stop block presses against the template surface, so that the adjustable support frame and the template form a stable template system. When the lower turntable rotates in the opposite direction, the pin in the eccentric arc hole drives the lower adjusting screw to move towards the central axis, and the pin in the outer screw hole plate of the lower adjusting screw is released from the outer edge of the elongated hole of the lower connecting plate, so that the lower end of the corner brace is in a free state.

[0012] The wrench consists of a handle and a square pin head welded together. After the square pin head is fitted onto the square pin of the central shaft, turning the wrench rotates the central shaft. When the wrench drives the central shaft to rotate, the turntables of the upper and lower supports rotate with the central shaft. This causes one end of the upper adjusting screw to move within the eccentric arc-shaped hole on the upper turntable via the pin, moving the upper adjusting screw towards or away from the corner brace. The other end of the upper adjusting screw is then pressed against the corner brace via the pin, causing the corner brace surface to fit against the template end face. The template stop block of the upper connecting plate presses against the template surface. Alternatively, rotating the wrench in the opposite direction pulls the corner brace via the pin, separating the corner brace surface from the template end face, and the template stop block of the upper connecting plate releases the template surface.

[0013] The entire device is made and assembled from steel and can be used repeatedly.

[0014] Furthermore, the template can be made of steel plate or cut from wood template.

[0015] Furthermore, based on the designed cup-mouth base dimensions, the threads of the upper and lower adjusting screws of the adjustable support frame are rotated to adjust the outer frame dimensions of the cup-mouth base formed by the four corner braces. The dimensions of the single template are made according to the gap dimensions between adjacent corner braces.

[0016] Furthermore, the length of the template stop on the corner brace connecting plate extending towards the template surface can be adjusted based on the force calculation.

[0017] Furthermore, a sealing material can be added to the joint surface between each template end face and the corner brace to prevent grout leakage during concrete pouring.

[0018] Furthermore, lubricant can be applied to the contact and rotating parts of the central shaft with the upper and lower turntables to reduce friction during rotation; lubricant can also be applied to the contact parts of the upper and lower adjusting screw pins with the eccentric arc-shaped holes and the corner brace connecting plate holes to reduce friction during the movement of the adjusting screws.

[0019] Furthermore, whether or not a middle connecting plate and a template stop block on the middle connecting plate are installed in the middle section of the corner brace are determined by stress calculation based on the specific dimensions of the cup-shaped foundation.

[0020] Furthermore, when setting the middle connecting plate, the middle connecting plate is the same in form as the lower connecting plate. An elongated hole is opened on the connecting plate so that when the upper screw pulls the upper end of the corner brace to move towards the central axis, the corner brace tends to rotate towards the central axis with its lower end as the fulcrum, and the angle iron surface of the corner brace is separated from the end face of the template.

[0021] Furthermore, to prevent the pin from falling off during operation, after the pin is inserted into the corresponding part, cotter pins are inserted at both ends of the pin, or a head larger than the diameter of the pin is set at one end, and a cotter pin is inserted at the other end.

[0022] The beneficial effects of this invention are as follows: This utility model provides an adjustable support frame for cup-shaped foundation templates. The mechanism is reliable, has a strong load-bearing capacity, and its installation and disassembly are tool-based and quick. The adjustable support frame can adapt to the construction of cup-shaped foundations of different sizes by adjusting the length of the lead screws. First, the lengths of the upper and lower lead screws are adjusted according to the designed dimensions of the cup-shaped foundation. After assembly, an integral assembly structure with the same dimensions as the designed cup-shaped foundation is formed. After the adjustable support frame is installed in place, it forms a template support system together with the template. After the concrete solidifies, the lead screws are moved by rotating the central shaft and turntable, releasing the constraint of the adjustable support frame on the template, avoiding premature removal of the template, including the template within the foundation, which could easily cause concrete damage. The template is then removed after the concrete reaches a certain strength, avoiding the problem of difficult removal due to late removal, and without damaging the template, which can be reused.

[0023] This device meets the requirements of green construction and has good technical and economic benefits and promotion and application value. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Figure 1 Overall assembly diagram of the present invention.

[0026] Figure 2 Exploded view of the present invention.

[0027] Figure 3 A schematic diagram of the central axis and corner braces of the present invention.

[0028] Figure 4Schematic diagram of the upper and lower supports of the present invention.

[0029] Figure 5 A schematic diagram of the parts of this invention.

[0030] Figure 6 Schematic diagram of the top support tightening the template.

[0031] Figure 7 Schematic diagram of the top support detaching from the template.

[0032] Figure 8 Schematic diagram of the bottom support tightening the template.

[0033] Figure 9 Schematic diagram of the lower support detaching from the template.

[0034] Figure 10 Construction diagram of adjustable support frame.

[0035] Figure 11 Schematic diagram of adjustable support frame detached from cup rim base template

[0036] Figure 1 —9 In the middle, there is 1 central shaft (1), 4 corner braces (2), 4 upper adjusting screws (3), 4 lower adjusting screws (4), 1 upper turntable (5), 1 lower turntable (6), 1 wrench (7), 16 adjusting screw pins (801), 2 central shaft pins (802), and 4 tapered plate pins (9).

[0037] Figure 1 In —9, the central shaft (1) is composed of a shaft body (101) and a square pin (102) at the top, which are welded together as a whole. A round hole with the same direction as the end plane is opened at the upper and lower ends of the shaft body.

[0038] Figure 1 In 9, each corner brace (2) consists of one corner brace angle iron (201), one upper connecting plate (202), one lower connecting plate (203), and one middle connecting plate (204); two template blocks (205) are welded on both sides of the upper and lower connecting plates.

[0039] Figure 1 In section 9, each upper adjusting screw (3) consists of an inner screw (301) with a perforated plate welded to one end and an outer screw (302) with a perforated plate welded to one end; each lower adjusting screw (4) consists of an inner screw (401) with a perforated plate welded to one end and an outer screw (402) with a perforated plate welded to one end.

[0040] Figure 1In 9, the upper turntable (5) is composed of a turntable (501) with a central hole, a central bushing (502), and four pieces of plate pin hole plate (503); the central bushing (502) and the plate pin hole plate (503) are welded to the turntable (501) respectively, and the diameter of the hole in the central bushing (502) is the same as the diameter of the central hole in the turntable (501).

[0041] The lower turntable (6) consists of a turntable (601) and a central bushing (602); the central bushing (602) is welded to the turntable (601), and the hole of the central bushing (602) has the same diameter as the central hole of the turntable (601).

[0042] Figure 1 In 9, the wrench (7) consists of a handle (701) and a square pin head (702).

[0043] Figure 10 In the middle, the adjustable support frame and the template (0) together constitute the template support system.

[0044] Figure 11 In the middle, after the concrete solidifies, the corner brace (2) of the adjustable support frame is removed from the formwork (0) and taken out from the cup-shaped foundation. The formwork (0) inside the cup-shaped foundation rests independently on the concrete surface. Detailed Implementation

[0045] In the description of this invention, it should be noted that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0046] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" or "linked" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or a direct connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] The technical solution of the present invention will now be described with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0048] An adjustable support frame for a cup-mouth base template includes: an upper support (including an upper adjusting screw (3), an upper turntable (5), and a tapered plate pin (9)), a lower support (including a lower adjusting screw (4) and a lower turntable (6)), a central shaft (1), a corner brace (2), a wrench (7), a pin (801), and a pin (802).

[0049] Pass the central shaft (1) through the central holes of the upper turntable (5) and the lower turntable (6), and insert a pin (802) into the horizontal round hole on the central shaft (1) to connect the central shaft (1) to the upper turntable (5) and the lower turntable (6) respectively.

[0050] According to the designed cup mouth base size, that is, the rectangle formed by the upper ends of the outer corners of the four corner braces (2) and angle irons (201) after the adjustable support frame is assembled is the same as the upper opening size of the designed cup mouth base, and the rectangle formed by the lower ends of the outer corners of the four corner braces (2) and angle irons (201) is the same as the lower opening size of the designed cup mouth base. Draw or calculate to determine the length of the upper adjusting screw (3) and the lower adjusting screw (4), and rotate the inner and outer screws of the four upper adjusting screws (3) and the four lower adjusting screws (4) respectively to adjust the screw length.

[0051] Align the holes of the perforated plates at one end of the four upper adjusting screws (3) with the holes of the upper connecting plate (202) of the corner brace (2), and insert pins (801) to connect them. Align the holes of the perforated plates at the other end with the eccentric arc-shaped holes of the upper turntable (5), and insert pins (801) to connect them. Align the holes of the perforated plates at one end of the four lower adjusting screws (4) with the holes of the lower connecting plate (203) of the corner brace (2), and insert pins (801) to connect them. Align the holes of the perforated plates at the other end with the eccentric arc-shaped holes of the lower turntable (6), and insert pins (801) to connect them. Insert tapered plate pins (9) into the holes of the plate pin hole plate (502) of the upper turntable (5) to form an overall assembly structure of the adjustable support frame.

[0052] Align the end face of the pre-cut template (0) with the outer surface of the angle iron (201) of the two side brackets (2), and place the template (0) against the template block (205). Fix the template (0) with flexible or rigid materials on the outside of the template (0).

[0053] Place the assembled adjustable support frame on the foundation bottom formwork, so that the bottom ends of the four corner braces (2) are supported by the upper plane of the bottom formwork; after finely adjusting the position of the template support system formed by the support frame and the template (0), use the surrounding steel bars and auxiliary materials to support and fix the system as a whole.

[0054] After the concrete is poured and solidified, first pull the tapered pin (9) of the adjustable support frame out of the hole in the pin hole plate (502) of the upper turntable (5), turn the wrench (7) to drive the central shaft (1) and the upper turntable (5) and lower turntable (6) to rotate, so that the upper adjusting screw (3) moves towards the central shaft (1), and pulls the upper outer side of the corner brace angle iron (201) away from the end face of the template (0) through the upper connecting plate (202) of the corner brace (2); the lower turntable (6) Rotate and pull the lower adjusting screw (4) toward the central axis (1) so that the lower adjusting screw (4) drives the pin (801) in the elongated hole to leave the pressed edge of the elongated hole of the lower connecting plate (203), release the clamping force on the corner brace (2), so that the corner brace (2) has the tendency to rotate toward the central axis (1) with its lower end as the fulcrum at the same time. The corner brace (2) is separated from the end face of the template (0), and the template stop block (205) on the corner brace (2) is separated from the template (0) surface.

[0055] When the angle brace (2) and angle iron (201) are separated from the end face of the template (0), and the template block (205) is released from the template (0) face, the adjustable support frame can be taken out from the cup-mouth foundation; the four templates (0) become independent without connection to each other, and can be easily removed after the concrete reaches a certain strength.

[0056] After the adjustable support frame is removed, it can be reused for cup-mouth base template support of the same size; for cup-mouth bases of different sizes, it can be used after adjusting the length of the upper adjusting screw (3) and the lower adjusting screw (4); the removed template (0) can be recycled.

Claims

1. An adjustable support frame for a cup-mouth base template, characterized in that, It comprises an upper support, a lower support, a central shaft, corner braces, a wrench, and pins. The upper and lower supports are each composed of four adjusting screws and one turntable. The upper and lower adjusting screws are connected by inner and outer screws, respectively, with perforated plates having circular holes welded to both ends. Both the upper and lower turntables are disc-shaped with a central hole, and four eccentric arc-shaped holes are evenly arranged on the disc surface. A central sleeve is welded to the center of the turntable, and the diameter of the central sleeve's hole matches the diameter of the central hole. Four pin-hole plates are symmetrically welded to the sides of the upper turntable, with rectangular holes on the perforated plates for... The central shaft is composed of a circular shaft body and a square pin at the top, welded together. A horizontal circular hole is opened at a certain distance from the upper and lower ends of the shaft body. The angle bracket is mainly made of angle iron. Connecting plates are welded to the upper and lower ends of the angle iron. The plane of the connecting plate is perpendicular to the axis of the angle iron. A circular hole is opened at the geometric center of the upper connecting plate, and an elongated hole is opened at the geometric center of the lower connecting plate. The two ends of the elongated hole are semi-circular. The long side of the elongated hole and the outer corner line of the angle bracket are aligned in a straight line in the horizontal projection plane. A template block is welded to each side of the upper and lower connecting plates.

2. The adjustable support frame for the cup-mouth base template as described in claim 1, characterized in that, The central shaft passes through the central sleeves on the upper and lower turntables and the central hole of the central shaft, and a pin passes through the horizontal hole of the shaft, so that the central shaft and the upper and lower turntables form a whole that can rotate together; one end of the upper and lower adjusting screws is connected to the upper and lower turntables by pins and eccentric arc holes, and the other end of the upper and lower adjusting screws is connected to the upper and lower connecting plates of the corner brace by pins, forming the overall structure of the adjustable support frame for the cup-mouth foundation template.

3. The adjustable support frame for the cup-mouth base template as described in claim 1, characterized in that, The length of the upper and lower adjusting screws can be adjusted by rotating the inner and outer screws of the upper and lower adjusting screws respectively, which can accommodate different cup opening sizes.

4. The adjustable support frame for the cup-mouth base template as described in claim 1, characterized in that, Four eccentric arc-shaped holes are evenly arranged on the upper turntable. Each eccentric arc-shaped hole has two semicircles at its ends. The centers of the two semicircles are at different distances from the central axis. When the central axis rotates and drives the upper and lower turntables to rotate, the pins in the eccentric arc-shaped holes can drive the upper and lower lead screws to move linearly toward or away from the central axis. This causes the corner brace to move toward or away from the central axis, thereby causing the angle iron surface of the corner brace to separate from or join the end face of the template, and causing the template stop block on the connecting plate to separate from or press against the template surface.

5. The adjustable support frame for the cup-mouth base template as described in claim 1, characterized in that, The lower connecting plate of the corner brace has an elongated hole at its geometric center, with semicircular ends. The outer corner of the corner brace, viewed from above, is aligned with the center line of the long side of the elongated hole and the center of the semicircle. When the lower turntable rotates, the lower adjusting screw is driven by a pin passing through the eccentric arc hole of the lower turntable to move away from the central axis, and the pin in the elongated hole presses against the lower end of the corner brace. When the lower turntable rotates in the opposite direction, the lower adjusting screw is driven by a pin passing through the eccentric arc hole of the lower turntable to move towards the central axis, and the pin in the elongated hole leaves the semicircular surface of the corner brace on one side of the elongated hole, releasing the pressure on the lower end of the corner brace.

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