Fixing device for filter screen of gas inlet system of gas turbine

Abstract

The invention discloses a fixing device for a filter screen of an air inlet system of a gas turbine, particularly relates to the technical field of fixing devices, and is used for fixing a plurality of plate-type filter screens on a frame of an air inlet channel of the gas turbine in a neat arrangement manner, a plurality of middle fixing assemblies are arranged between any two rows of adjacent plate-type filter screens, and in every two adjacent rows of plate-type filter screens, the middle fixing assemblies are fixed on the frame of the air inlet channel of the gas turbine. Two middle fixing assemblies are distributed between the pair of plate-type filter screens corresponding to each other up and down, each middle fixing assembly comprises a threaded sleeve, and a hexagonal block is fixedly arranged at the outer end of each threaded sleeve. The middle fixing assembly is arranged between the two adjacent rows of plate-type filter screens, the threaded sleeve is rotated, the middle fixing assembly can integrally stretch out and draw back under the action of threads, then the plate-type filter screens are pushed, the plate-type filter screen in the middle is clamped between the uppermost row of plate-type filter screens and the lowermost row of plate-type filter screens, punching is not needed during installation, and more convenience is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of fixing devices, and in particular to a fixing device for a filter screen of an air intake system of a combustion engine. Background Art

[0002] A gas turbine is an internal combustion power machine that converts the energy of fuel into useful work. It mainly includes two types: gas turbines and gas internal combustion engines. Gas turbines are widely used in the fields of electricity, ships, vehicles, etc. Among them, gas turbine generator sets can be used as backup power sources and mobile power sources in important places such as oil fields and power plants, and can also be used for combined heat, electricity and cooling.

[0003] The working principle of a gas engine is to inhale air through a compressor and compress it. The compressed air enters the combustion chamber and mixes with the fuel to burn, generating high-temperature combustion gas, which then flows into the turbine to expand and do work, driving the turbine impeller and the compressor impeller to rotate, thereby converting thermal energy into mechanical energy.

[0004] In the process of inhaling air, solid impurities in the air need to be filtered, so a detachable plate filter is installed at the air inlet of the engine through a fixing device, such as a fixing device for a filter of an air intake system of an engine with a publication number of CN218467718U in the prior art.

[0005] The fixing device in the prior art is divided into three parts: a top part, a middle part and a bottom part. The three parts need to be fixed by bolts and holes during installation, which is very inconvenient. Summary of the invention

[0006] The purpose of the present invention is to provide a fixing device for the filter of the gas turbine intake system. By setting a middle fixing component between two adjacent rows of plate filters and rotating the threaded sleeve, the plate filter can be pushed so that the plate filter in the middle part is stuck between the top and bottom rows of plate filters. There is no need to drill holes during installation, which is more convenient.

[0007] In order to achieve the above-mentioned object, the present invention provides the following technical solutions: a fixing device for a filter screen of a gas turbine intake system, which is used to neatly arrange a plurality of plate filter screens and fix them on the frame of a gas turbine intake passage, wherein a plurality of middle fixing components are arranged between any two adjacent rows of plate filter screens, and two middle fixing components are distributed between a pair of plate filter screens corresponding to the upper and lower positions in two adjacent rows of plate filter screens;

[0008] The middle fixing assembly includes a threaded sleeve, a hexagonal block is fixedly provided at the outer end of the threaded sleeve, and the cross section of the hexagonal block is hexagonal, which is convenient for driving it to rotate using a wrench, and longitudinal screws are provided at both ends of the threaded sleeve, and the longitudinal screws extend toward one end of the threaded sleeve to the inside of the threaded sleeve and are connected to the threaded sleeve by threads;

[0009] A push plate is fixedly provided at one end of the longitudinal screw away from the threaded sleeve. The two push plates are respectively clamped at the edges of the corresponding upper and lower plate filters. A buffer is fixedly provided on the inner side of the push plate.

[0010] Furthermore, in the highest row of plate filters, two top fixing components are provided at the top of each plate filter, and the top fixing components include a bending piece clamped at the upper edge of the plate filter, and two reinforcing ribs for reinforcement are fixed at the top of the bending piece;

[0011] An adjusting seat is fixedly arranged at the top end of the bending piece, and an adjusting screw is arranged on the adjusting seat, penetrating the adjusting seat and being connected to the adjusting seat by threads.

[0012] Furthermore, an upper mounting plate is provided at the rear side of the bending plate, an upper positioning bolt penetrating the upper mounting plate is provided at the top of the upper mounting plate, and the upper mounting plate is connected to the frame of the gas turbine air intake passage through the upper positioning bolt;

[0013] A vertical plate is fixedly disposed on the top of the upper mounting plate, and the rear end of the adjusting screw rod penetrates through the vertical plate and is connected to the vertical plate through threads.

[0014] Further, in the lowest row of plate filters, two bottom fixing components are provided at the bottom end of each plate filter, and the bottom fixing components can correspond to the top fixing components one by one, and the bottom fixing components are located directly below the corresponding top fixing components;

[0015] A reinforcement belt is provided between the bottom fixing component and the corresponding top fixing component, a connecting piece connected to the bottom fixing component by bolts is fixedly provided at the bottom end of the reinforcement belt, a fixing frame is fixedly provided on the front side of the bending piece, the top end of the fixing frame extends to the fixing frame on the front side of the corresponding top fixing component, and a fastening bolt for fixing the reinforcement belt is provided on the front side of the fixing frame through a thread.

[0016] Furthermore, the reinforcement belt is provided with a plurality of clamping assemblies, each of which corresponds to a row of plate filters, and the clamping assembly includes a positioning seat, and a sliding screw penetrating the positioning seat and connected to the positioning seat by threads is provided on the front side of the positioning seat;

[0017] A support block is fixedly provided at the rear end of the sliding screw, and the rear end of the support block contacts the plate filter at its corresponding position. The top and bottom ends of the positioning seat are fixedly provided with springs connected to the reinforcement belt. The elastic force of the spring can tighten the reinforcement belt, and the further back the support block is positioned, the longer the spring will be stretched.

[0018] Furthermore, the bottom fixing assembly includes a lower mounting plate, the lower mounting plate is provided with a lower positioning screw penetrating the lower mounting plate, and the lower mounting plate is connected to the frame of the gas turbine air intake passage through the lower positioning screw;

[0019] A horizontal support plate is fixedly provided on the top of the lower mounting plate, and the top of the support plate contacts the bottom edge of the corresponding plate filter. The support plate supports the plate filter, and two reinforcing triangular plates with a reinforcing function are provided at the joint between the support plate and the lower mounting plate.

[0020] Furthermore, a baffle is fixedly provided at the top end of the front side of the support plate, the connecting plate is installed on the front side of the baffle, the baffle is provided with a push-back screw that penetrates the baffle and is threadedly connected to the baffle, and a pressing plate in contact with the corresponding plate filter is fixedly provided at the rear end of the push-back screw. Rotating the push-back screw can push the pressing plate backward and press the plate filter backward to clamp it.

[0021] In the above technical solution, the technical effects and advantages provided by the present invention are:

[0022] 1. A middle fixing assembly is arranged between two adjacent rows of plate filters. By rotating the threaded sleeve, the middle fixing assembly can be extended and retracted as a whole under the action of the thread, thereby pushing the plate filter, so that the plate filter in the middle is stuck between the top and bottom rows of plate filters. No holes need to be punched during installation, which is more convenient and suitable for fixing plate filters of different sizes, with a wider range of applications.

[0023] 2. By adjusting the positions of the bending sheet and the pressing sheet, the top fixing assembly and the bottom fixing assembly can be used to fix plate filters of different thicknesses, which also makes the application range of the top fixing assembly and the bottom fixing assembly wider. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a front view of the present invention;

[0026] Figure 2 It is a schematic diagram of the top fixing assembly of the present invention in use state;

[0027] Figure 3 This is a schematic diagram of the middle fixing assembly of the present invention in use;

[0028] Figure 4 This is a schematic diagram of the bottom fixing assembly of the present invention in use;

[0029] Figure 5 It is a structural diagram of the top fixing assembly of the present invention;

[0030] Figure 6 This is a bottom view of the structure of the bottom fixing assembly of the present invention;

[0031] Figure 7 It is a rear view structural diagram of the bottom fixing assembly of the present invention;

[0032] Figure 8 It is a structural diagram of the middle fixing assembly of the present invention;

[0033] Fig. 9 It is a structural diagram of the clamping assembly of the present invention.

[0034] Description of reference numerals:

[0035] 1. Plate filter; 2. Top fixing assembly; 201. Bending piece; 202. Adjusting seat; 203. Adjusting screw; 204. Upper mounting plate; 205. Upper positioning bolt; 206. Vertical plate; 207. Reinforcing rib; 3. Middle fixing assembly; 301. Threaded sleeve; 302. Hexagonal block; 303. Longitudinal screw; 304. Push plate; 305. Buffer pad; 4. Reinforcement belt; 401. Connecting piece; 5. Bottom fixing assembly; 501. Support plate; 502. Lower mounting plate; 503. Baffle; 504. Lower positioning screw; 505. Reinforced triangle plate; 506. Push screw; 507. Pressing piece; 6. Clamping assembly; 601. Positioning seat; 602. Sliding screw; 603. Support block; 604. Spring; 7. Fixing frame. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] The present invention provides Figure 1-9 A fixing device for a filter screen of a gas engine intake system is shown, which is used to neatly arrange a plurality of plate filters 1 and fix them on the frame of the gas engine intake passage. A plurality of middle fixing components 3 are arranged between any two adjacent rows of plate filters 1. In two adjacent rows of plate filters 1, two middle fixing components 3 are distributed between a pair of plate filters 1 corresponding to each other in upper and lower positions.

[0038] The middle fixing assembly 3 includes a threaded sleeve 301, a hexagonal block 302 is fixedly provided at the outer end of the threaded sleeve 301, and the cross section of the hexagonal block 302 is hexagonal, which is convenient for driving it to rotate using a wrench, and longitudinal screws 303 are provided at both ends of the threaded sleeve 301, and the longitudinal screws 303 extend toward one end of the threaded sleeve 301 to the inside of the threaded sleeve 301 and are connected to the threaded sleeve 301 through threads;

[0039] A push plate 304 is fixedly disposed at one end of the longitudinal screw rod 303 away from the threaded sleeve 301 . The two push plates 304 are respectively clamped at the edges of the corresponding upper and lower plate filters 1 . A buffer 305 is fixedly disposed inside the push plates 304 .

[0040] A frame for fixing the plate filter 1 is provided on the gas turbine air intake passage. The plate filter 1 is neatly arranged and fixed on the frame, so that the gas turbine air intake passage can be blocked, so that the air is filtered when entering the gas turbine air intake passage. When fixing the plate filter 1, the top row of plate filter 1 is fixed first, and then the bottom row of plate filter 1 is fixed. After the plate filter 1 in the middle position is arranged and placed in the corresponding position, a middle fixing component 3 is provided between the two adjacent rows of plate filter 1, and the push plates 304 at both ends of the middle fixing component 3 are respectively stuck at the edges of the upper and lower plate filter 1 , then rotate the hexagonal block 302 and the threaded sleeve 301, at which time the longitudinal screw 303 and the push plate 304 are fixed. When the threaded sleeve 301 rotates, under the action of the thread, the longitudinal screw 303 will move relative to the threaded sleeve 301 and push the push plate 304 away from the threaded sleeve 301, thereby pressing and fixing the push plate 304 at the edge of the plate filter 1, so that the middle fixing component 3 is stuck in the gap between the upper and lower rows of plate filters 1, and the plate filter 1 is pushed, so that the plate filter 1 in the middle part is stuck between the upper and lower rows of plate filters 1;

[0041] Fixing the plate filter 1 in this manner, firstly, the middle fixing component 3 does not need to be punched during installation, which is more convenient and does not affect the integrity of the air intake channel frame; secondly, since the middle fixing component 3 as a whole can be retracted, the middle fixing component 3 is suitable for fixing plate filters 1 of different sizes and has a wider range of applications; thirdly, since multiple rows of middle fixing components 3 work together to clamp and fix the plate filter 1, after removing one row of the middle fixing components 3, the plate filters 1 in other middle parts will become loose, thereby reducing the complexity of disassembly.

[0042] The plate filter 1 in the top row needs to be fixed separately, such as Figure 1 , 2 As shown in FIG. 5 , in the highest row of plate filters 1, two top fixing components 2 are provided at the top of each plate filter 1, and the top fixing components 2 include a bending piece 201 clamped at the upper edge of the plate filter 1, and two reinforcing ribs 207 for reinforcement are fixed at the top of the bending piece 201;

[0043] An adjustment seat 202 is fixedly disposed on the top of the bending piece 201 , and an adjustment screw 203 is disposed on the adjustment seat 202 , penetrating through the adjustment seat 202 and connected to the adjustment seat 202 by threads.

[0044] An upper mounting plate 204 is provided at the rear side of the bending plate 201, and an upper positioning bolt 205 penetrating the upper mounting plate 204 is provided at the top of the upper mounting plate 204, and the upper mounting plate 204 is connected to the frame of the gas turbine air intake passage through the upper positioning bolt 205;

[0045] A vertical plate 206 is fixedly disposed on the top of the upper mounting plate 204 , and a rear end of the adjusting screw rod 203 penetrates through the vertical plate 206 and is connected to the vertical plate 206 by threads.

[0046] When installing the highest row of plate filters 1, the top of the plate filter 1 is flush with the top of the frame, and then the upper mounting plate 204 is fixed to the frame by the upper positioning bolt 205, and then the bending piece 201 is clamped at the edge of the top of the plate filter 1. The bending piece 201 is L-shaped and can hook the front side of the plate filter 1, clamping the plate filter 1 between the frame and the bending piece 201, and then the adjusting screw 203 is passed through the adjusting seat 202 and the vertical plate 206 in turn. By rotating the adjusting screw 203, the spacing between the adjusting seat 202 and the vertical plate 206 can be adjusted, so that the bending piece 201 moves backward, and the plate filter 1 is clamped and fixed. Moreover, since the position of the bending piece 201 can be adjusted forward and backward, the top fixing component 2 can be applied to plate filters 1 of different thicknesses, and has a wider range of applications.

[0047] The plate filter 1 in the bottom row also needs additional fixing, such as Figure 1 , 4 As shown in FIGS. 5 and 6 , in the lowest row of plate filters 1, two bottom fixing components 5 are provided at the bottom end of each plate filter 1, and the bottom fixing components 5 can correspond to the top fixing components 2 one by one, and the bottom fixing components 5 are located directly below the corresponding top fixing components 2;

[0048] A reinforcement belt 4 is provided between the bottom fixing component 5 and the corresponding top fixing component 2, and a connecting piece 401 connected to the bottom fixing component 5 by bolts is fixedly provided at the bottom end of the reinforcement belt 4, and a fixing frame 7 is fixedly provided on the front side of the bending piece 201, and the top end of the fixing frame 7 extends to the fixing frame 7 on the front side of the corresponding top fixing component 2, and a fastening bolt for fixing the reinforcement belt 4 is provided on the front side of the fixing frame 7 through a thread.

[0049] In the bottom row of plate filters 1, two bottom fixing components 5 are fixed to the bottom end of each plate filter 1, and the bottom row of plate filters 1 are fixed to the frame through the bottom fixing components 5, and a reinforcement belt 4 is provided between the bottom fixing components 5 and the corresponding top fixing components 2, and the reinforcement belt 4 blocks the front side of the plate filter 1. There are two reinforcement belts 4 in front of each plate filter 1. Once the plate filter 1 falls off, the reinforcement belt 4 can play a certain blocking role.

[0050] When fixing the plate filter 1, it is necessary to make the plate filter 1 close to the frame backwards, such as Figure 1 , 9 As shown, the reinforcing belt 4 is provided with a plurality of clamping assemblies 6, each of which corresponds to a row of plate filters 1, and the clamping assembly 6 includes a positioning seat 601, and a sliding screw 602 penetrating the positioning seat 601 and connected to the positioning seat 601 by threads is provided on the front side of the positioning seat 601;

[0051] A support block 603 is fixedly provided at the rear end of the sliding screw 602, and the rear end of the support block 603 contacts the plate filter 1 at its corresponding position. The top and bottom ends of the positioning seat 601 are fixedly provided with springs 604 connected to the reinforcement belt 4. The elastic force of the spring 604 can tighten the reinforcement belt 4, and the closer the support block 603 is to the rear, the longer the spring 604 will be stretched.

[0052] A plurality of clamping assemblies 6 are provided on the reinforcement belt 4. Rotating the sliding screw 602 can make the sliding screw 602 move relative to the positioning seat 601, thereby driving the support block 603 to move backward. After the support block 603 presses against the corresponding plate filter 1 backward, the sliding screw 602 is continued to be rotated. At this time, the sliding screw 602 will increase the distance between the positioning seat 601 and the plate filter 1. The movement of the positioning seat 601 also makes the spring 604 elongated and the reinforcement belt 4 tightened. Therefore, the elastic force of the spring 604 can drive the clamping assembly 6, so that the clamping assembly 6 has a tendency to move backward, thereby making the support block 603 push the plate filter 1 backward, so that the plate filter 1 can be tightly attached to the frame, thereby reinforcing the plate filter 1.

[0053] The plate filter 1 in the bottom row needs to be lifted while being fixed, such as Figure 1 , 4 As shown in , 6 and 7, the bottom fixing assembly 5 includes a lower mounting plate 502, on which a lower positioning screw 504 penetrating the lower mounting plate 502 is provided, and the lower mounting plate 502 is connected to the frame of the gas turbine air intake passage through the lower positioning screw 504;

[0054] A horizontal support plate 501 is fixedly provided at the top of the lower mounting plate 502. The top of the support plate 501 contacts the bottom edge of the corresponding plate filter 1. The support plate 501 supports the plate filter 1. Two reinforcing triangular plates 505 with a reinforcing function are provided at the joint between the support plate 501 and the lower mounting plate 502.

[0055] The lower mounting plate 502 is fixed to the frame by the lower positioning screw 504, and the plate filter 1 in the bottom row can be directly placed on the top of the support plate 501. The plate filter 1 is lifted by the horizontal support plate 501, and the reinforced triangular plate 505 can increase the bending resistance of the support plate 501 and improve the overall load-bearing capacity of the bottom fixing assembly 5.

[0056] A baffle 503 is fixedly provided at the top of the front side of the support plate 501, and the connecting piece 401 is installed on the front side of the baffle 503. A push-back screw 506 is provided on the baffle 503, which penetrates the baffle 503 and is threadedly connected to the baffle 503. A pressing piece 507 in contact with the corresponding plate filter 1 is fixedly provided at the rear end of the push-back screw 506. Rotating the push-back screw 506 can push the pressing piece 507 backward and press the plate filter 1 backward to clamp it.

[0057] The plate filter 1 supported on the top of the support plate 501 is located behind the baffle 503 and the pressing plate 507. At this time, rotating the push screw 506 can push the pressing plate 507 backward. While supporting the plate filter 1, the plate filter 1 is clamped backward between the pressing plate 507 and the frame, thereby improving the fixing effect of the plate filter 1. In this way, the bottom fixing component 5 can be used to fix plate filters 1 of different thicknesses, and the scope of application is also wider.

[0058] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A device for fixing filter screens of a gas turbine air intake system, used for fixing a plurality of plate filter screens (1) in an orderly manner on a frame of a gas turbine air intake passage, characterized in that: A plurality of middle fixing components (3) are provided between any two adjacent rows of plate-type filter screens (1); and in two adjacent rows of plate-type filter screens (1), two middle fixing components (3) are distributed between a pair of plate-type filter screens (1) corresponding to each other at upper and lower positions; The middle fixing assembly (3) comprises a threaded sleeve (301), a hexagonal block (302) is fixedly provided at the outer end of the threaded sleeve (301), longitudinal screws (303) are provided at both ends of the threaded sleeve (301), and the longitudinal screws (303) extend toward one end of the threaded sleeve (301) into the interior of the threaded sleeve (301) and are connected to the threaded sleeve (301) by threads; A push plate (304) is fixedly provided at one end of the longitudinal screw rod (303) away from the threaded sleeve (301), and the two push plates (304) are respectively clamped at the edges of the corresponding upper and lower plate filters (1), and a buffering (305) is fixedly provided on the inner side of the push plate (304).

2. The fixing device for the filter screen of the gas engine intake system according to claim 1 is characterized in that: In the highest row of plate filters (1), two top fixing components (2) are provided at the top of each plate filter (1), the top fixing component (2) comprising a bending piece (201) clamped at the upper edge of the plate filter (1), and two reinforcing ribs (207) for reinforcement are fixed at the top of the bending piece (201); An adjustment seat (202) is fixedly provided at the top end of the bending piece (201), and an adjustment screw (203) is provided on the adjustment seat (202) and passes through the adjustment seat (202) and is connected to the adjustment seat (202) by means of a thread.

3. The fixing device for the filter screen of the gas engine intake system according to claim 2 is characterized in that: An upper mounting plate (204) is provided at the rear side of the bending plate (201), an upper positioning bolt (205) penetrating the upper mounting plate (204) is provided at the top end of the upper mounting plate (204), and the upper mounting plate (204) is connected to the frame of the gas engine air intake passage via the upper positioning bolt (205); A vertical plate (206) is fixedly provided on the top of the upper mounting plate (204), and a rear end of the adjusting screw rod (203) passes through the vertical plate (206) and is connected to the vertical plate (206) via threads.

4. The fixing device for the filter screen of the gas engine intake system according to claim 2 is characterized in that: In the lowest row of plate filters (1), two bottom fixing components (5) are provided at the bottom end of each plate filter (1), the bottom fixing components (5) being able to correspond one-to-one with the top fixing components (2), and the bottom fixing components (5) are located directly below the corresponding top fixing components (2); A reinforcing belt (4) is provided between the bottom fixing component (5) and the corresponding top fixing component (2); a connecting piece (401) connected to the bottom fixing component (5) by bolts is fixedly provided at the bottom end of the reinforcing belt (4); a fixing frame (7) is fixedly provided at the front side of the bending piece (201); the top end of the fixing frame (7) extends to the fixing frame (7) at the front side of the corresponding top fixing component (2); and a fastening bolt for fixing the reinforcing belt (4) is provided at the front side of the fixing frame (7) by means of a thread.

5. The fixing device for the filter screen of the gas engine intake system according to claim 4 is characterized in that: The reinforcing belt (4) is provided with a plurality of clamping assemblies (6), each clamping assembly (6) corresponds to a row of plate filters (1), the clamping assembly (6) comprises a positioning seat (601), and a sliding screw (602) penetrating the positioning seat (601) and being threadedly connected to the positioning seat (601) is provided on the front side of the positioning seat (601); A support block (603) is fixedly provided at the rear end of the sliding screw (602), and the rear end of the support block (603) is in contact with the plate filter (1) at its corresponding position. The top and bottom ends of the positioning seat (601) are fixedly provided with springs (604) connected to the reinforcement belt (4).

6. The fixing device for the filter screen of the gas engine intake system according to claim 4 is characterized in that: The bottom fixing assembly (5) comprises a lower mounting plate (502), the lower mounting plate (502) being provided with a lower positioning screw (504) penetrating the lower mounting plate (502), and the lower mounting plate (502) being connected to the frame of the gas engine air intake passage via the lower positioning screw (504); A horizontal support plate (501) is fixedly provided at the top end of the lower mounting plate (502), the top end of the support plate (501) contacts the bottom edge of the corresponding plate filter (1), and two reinforcing triangular plates (505) with a reinforcing function are provided at the joint between the support plate (501) and the lower mounting plate (502).

7. A fixing device for a filter screen of a combustion engine air intake system according to claim 6, characterized in that: A baffle (503) is fixedly provided at the top end of the front side of the support plate (501), the connecting plate (401) is installed on the front side of the baffle (503), the baffle (503) is provided with a rear push screw (506) penetrating the baffle (503) and connected to the baffle (503) by means of a thread, and a pressing plate (507) in contact with the corresponding plate filter (1) is fixedly provided at the rear end of the rear push screw (506).

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