Counting and quantitative concentration device for algae in water

Abstract

The utility model relates to the technical field of quantitative concentration devices, and provides an in-water algae counting and quantitative concentration device which comprises a silicone tube, a big-bellied pipette and a cylindrical separating funnel, a first filter bolting-silk net is mounted at a tube opening of one end of the silicone tube, and the big-bellied pipette is fixedly connected to a tube opening of the other end of the silicone tube; a first bolting silk is bound at the position of a pipe opening at the bottom of the big-bellied pipette, and an upper double-layer filtering bolting silk net and a lower double-layer filtering bolting silk net are arranged at the position of the pipe opening at the bottom of the big-bellied pipette. Finally, the algae on the wall of the cylindrical separating funnel and the first filter bolting-silk net can be flushed, and the liquid is slowly sucked through the double-layer filter bolting-silk net while being kept flush with the liquid level, so that the situation that the detection data of the final algae is influenced by the fact that the bottom pipe of the big-belly pipette is inserted into the high-concentration algae liquid on the bottom layer to suck out part of the high-concentration algae at the bottom is avoided; therefore, the data accuracy of algae detection is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of quantitative concentration devices, in particular to a quantitative concentration device for counting algae in water. Background Art

[0002] Since algae in surface water cannot be tested alive, the existing algae counting is done by fixing with Lugol's iodine solution, staining the flagella, cilia, nuclei and intracellular starch in the algae, using a quantitative concentration device to transfer the algae to a 50mL conical centrifuge tube, and counting the number of cells and individuals under a microscope to determine the distribution of algae in the water.

[0003] Typically, during algae counting, 1L of water sample is taken, 10mL of Lugol's iodine solution is added, and the sample is allowed to settle in a cylindrical separatory funnel for more than 24 hours. The supernatant is then aspirated using a quantitative concentrator, leaving 50mL of the lower layer containing algae, which is transferred from the lower end of the separatory funnel to a 50mL conical centrifuge tube. During the operation, most of the algae are transferred to the 50mL conical centrifuge tube. However, due to limitations of the method itself or slight improper operation by the experimenter, some algae may be lost, affecting the algae detection data.

[0004] At present, among the existing algae quantitative concentration devices, some of the algae quantitative concentration devices use a simple silicone tube plus a siphon tube to perform quantitative concentration when in use.

[0005] The existing algae counting and quantitative concentration device suffers from serious algae loss because the smallest algae is less than 1 micron. A siphon tube connected to a silicone tube is used. A sieve silk with a pore size of 64 microns is tied to the bottom of the siphon tube to suck out the upper clear liquid in the cylindrical separatory funnel, leaving 50 ml of algae water sample with sediment at the bottom and transfer it to a 50 ml conical centrifuge tube 10. During the operation, some algae will stick to the wall of the cylindrical separatory funnel. The deeper the sieve silk at the bottom of the siphon tube is inserted into the liquid surface, the more algae will be sucked out. At the other end, the silicone tube mouth will also suck out some algae, all of which ultimately affect the accurate number of algae. Utility Model Content

[0006] In view of this, the utility model provides a device for counting and quantitatively concentrating algae in water. The first filter screen at the tube mouth of one end of the silicone tube can prevent algae from flowing out of the silicone tube mouth. Part of the algae will be trapped on the first filter screen and finally rinsed into a 50mL conical centrifuge tube. Using a large-bellied pipette for siphoning can leave more liquid in the large-bellied pipette, and finally the algae on the wall of the cylindrical separatory funnel can be rinsed. Through the upper double-layer filter screen, it can be kept level with the upper liquid surface at any time to control the siphoning speed, avoid the generation of bubbles during rapid siphoning, reduce the contact area with the algae liquid, and avoid the loss of algae. Through the lower double-layer filter screen, it can be kept level with the liquid surface when finally absorbing the bottom liquid, and the liquid can be absorbed slowly to avoid the bottom tube of the large-bellied pipette being inserted into the bottom layer of high-concentration algae liquid to absorb part of the high-concentration algae at the bottom, affecting the final algae detection data, thereby improving the data accuracy of the algae.

[0007] The technical solution is as follows: A device for counting and quantitatively concentrating algae in water, comprising a silicone tube, a large-bellied pipette and a cylindrical separatory funnel, wherein a first filter screen is installed at the tube mouth of one end of the silicone tube, and a large-bellied pipette is fixedly connected to the tube mouth of the other end of the silicone tube, the tip of the bottom tube mouth of the large-bellied pipette is cut off, and a first screen is tied to the bottom tube mouth of the large-bellied pipette, an upper double-layer filter screen and a lower double-layer filter screen are provided at the bottom tube mouth of the large-bellied pipette, and the bottom tube mouth of the large-bellied pipette is inserted into the cylindrical separatory funnel.

[0008] During use of the above technical solution: the first filter screen silk at the tube mouth at one end of the silicone tube can prevent algae from flowing out of the silicone tube mouth. Some algae will be retained on the first filter screen silk and finally rinsed into the conical centrifuge tube. Using a large-bellied pipette for siphoning can leave more liquid in the large-bellied pipette, and finally the algae on the wall of the cylindrical separatory funnel can be rinsed. Through the upper double-layer filter screen silk, it can be kept level with the upper liquid surface at any time to control the siphoning speed, avoid the generation of bubbles during rapid siphoning, reduce the contact area with the algae liquid, and avoid algae loss. Through the lower double-layer filter screen silk, it can be kept level with the liquid surface when finally absorbing the bottom liquid, and the liquid can be absorbed slowly to avoid the bottom tube of the large-bellied pipette being inserted into the bottom layer of high-concentration algae liquid to absorb part of the high-concentration algae at the bottom, affecting the final algae detection data, thereby improving the data accuracy of algae detection.

[0009] Preferably, the first filter screen is welded with 64um screen silk, and the upper layer has a maximum inner diameter of 5mm.

[0010] During use, the above technical solution can prevent algae from flowing out of the silicone tube opening.

[0011] Preferably, the connection between the silicone tube and the large-bellied pipette is curved.

[0012] During use, the above technical solution facilitates the downward diversion of water flow.

[0013] Preferably, the first sieve silk is tied from the bottom tube opening of the big-bellied pipette to 8 cm above the tube opening.

[0014] Preferably, the upper double-layer filter screen is installed 4 cm above the bottom nozzle of the big-bellied pipette.

[0015] Preferably, the upper double-layer filter screen mesh comprises a lower layer and an upper layer, the upper layer of the upper double-layer filter screen mesh is a 20-mesh national standard 304 silk filter mesh, and the lower layer of the upper double-layer filter screen mesh is a 64um screen mesh.

[0016] Preferably, the lower double-layer filter screen is installed at the bottom nozzle of the big-bellied pipette.

[0017] Preferably, the lower double-layer filter screen mesh comprises a lower layer and an upper layer, the upper layer of the lower double-layer filter screen mesh is a 20-mesh national standard 304 silk filter mesh, and the lower layer of the lower double-layer filter screen mesh is a 64um screen mesh.

[0018] Preferably, a glass rod is fixedly installed at the connection between the large-bellied pipette and the silicone tube.

[0019] During use, the above technical solution enables the bottom tube of the large-bellied pipette to be vertically inserted into the upper layer of liquid in the cylindrical separating funnel.

[0020] Preferably, a Robert clamp is installed on the silicone tube, and the silicone tube crosses the openings at both ends of the Robert clamp.

[0021] During use of the above technical solution: when the supernatant is sucked to the scale line position of the cylindrical separating funnel, the Robert clamp can be pressed at any time to immediately stop sucking the supernatant.

[0022] Preferably, the cylindrical separating funnel is mounted on a mounting frame, a support frame is provided on the mounting frame, a clamping block is slidably mounted on the support frame, the support frame is transmission-connected to the clamping block through an adjustment mechanism, and the adjustment mechanism is operated to move along the mounting frame through the clamping block.

[0023] Preferably, an adjusting screw is rotatably mounted on the adjusting mechanism, a rotating handle is fixedly mounted on the adjusting screw, the clamping block is mounted on the sliding block, the sliding block is slidably mounted on the support frame, a first screw hole is opened on the sliding block, and the adjusting screw is threadedly mounted in the first screw hole.

[0024] Preferably, an arc-shaped frame is fixedly provided on the sliding block, a second screw hole is opened on the arc-shaped frame, a limiting bolt is rotatably installed on the clamping block, and the limiting bolt is threadedly installed in the second screw hole.

[0025] During use of the above technical solution: operating the rotating handle drives the adjusting screw to rotate, the adjusting screw drives the arc frame to move along the support frame, the arc frame drives the glass rod to move, and the glass rod drives the large-bellied pipette to move along the cylindrical separating funnel, thereby improving the stability of the movement of the large-bellied pipette and thus improving work efficiency.

[0026] After adopting the above technical scheme, the beneficial effects of the utility model are as follows: the first filter screen silk at the tube mouth of one end of the silicone tube can prevent algae from flowing out of the silicone tube mouth, and some algae will be trapped on the first filter screen silk, and finally rinsed into the conical centrifuge tube. Using a large-bellied pipette for siphoning can leave more liquid in the large-bellied pipette, and finally the algae on the wall of the cylindrical separatory funnel can be rinsed. Through the upper double-layer filter screen silk, it can be kept level with the upper liquid surface at any time, and the siphoning speed can be controlled to avoid the generation of bubbles during rapid siphoning, reduce the contact area with the algae liquid, and avoid the loss of algae. Through the lower double-layer filter screen silk, it can be kept level with the liquid surface when finally absorbing the bottom liquid, and the liquid can be absorbed slowly to avoid the bottom tube of the large-bellied pipette being inserted into the bottom layer of high-concentration algae liquid to absorb part of the high-concentration algae at the bottom, affecting the final algae detection data, thereby improving the data accuracy of algae detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 It is a three-dimensional diagram of the utility model;

[0029] Figure 2 This is an exploded view of the utility model;

[0030] Figure 3 It is a partial cross-sectional view of the utility model;

[0031] Figure 4 For this utility model Figure 3 Enlarged view of point A in the middle;

[0032] Figure 5 This is a perspective view of the second embodiment of the present utility model;

[0033] Figure 6 It is a cross-sectional view of the adjustment mechanism of the utility model;

[0034] In the figure, 1. Silicone tube; 2. First filter screen; 3. Pipettes; 4. Glass rod; 5. Robert's clamp; 6. Cylindrical separatory funnel; 7. First screen; 8. Upper double-layer filter screen; 9. Lower double-layer filter screen; 10. Conical centrifuge tube; 11. Control valve; 12. Mounting bracket; 13. Fixing bracket; 14. Support bracket; 15. Rotating shaft; 16. Rotating handle; 17. Sliding groove; 18. Sliding block; 19. Adjusting screw; 20. Curved bracket; 21. Second screw hole; 22. Limit screw; 23. Clamping block; 24. First screw hole. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figures 1 to 4 As shown, a device for counting and quantitatively concentrating algae in water includes a silicone tube 1, a large-bellied pipette 3 and a cylindrical separating funnel 6. A first filter screen 2 is installed at the tube opening of one end of the silicone tube 1, and the large-bellied pipette 3 is fixedly connected to the tube opening of the other end of the silicone tube 1. The tip of the bottom tube opening of the large-bellied pipette 3 is cut off, and a first screen 7 is tied to the bottom tube opening of the large-bellied pipette 3. An upper double-layer filter screen 8 and a lower double-layer filter screen 9 are provided at the bottom tube opening of the large-bellied pipette 3. The bottom tube opening of the large-bellied pipette 3 is inserted into the cylindrical separating funnel 6.

[0038] Specifically: the capacity of the large-bellied pipette 3 is 10 mL, and the capacity of the cylindrical separating funnel 6 is preferably 1000 mL.

[0039] The first filter screen mesh 2 is welded with 64um screen silk, and the upper layer has a large inner diameter of 5mm, which can prevent algae from flowing out of the silicone tube 1.

[0040] The connection between the silicone tube 1 and the large-bellied pipette 3 is curved, which is convenient for leading the water flow downward.

[0041] The first sieve silk 7 is tied to the bottom tube mouth of the big-bellied pipette 3 to 8 cm above the tube mouth, and the upper double-layer filter sieve silk mesh 8 is installed 4 cm above the bottom tube mouth of the big-bellied pipette 3. The upper double-layer filter sieve silk mesh 8 includes a lower layer and an upper layer. The upper layer of the upper double-layer filter sieve silk mesh 8 is a 20-mesh national standard 304 silk filter mesh, and the lower layer of the upper double-layer filter sieve silk mesh 8 is a 64um sieve silk.

[0042] The lower double-layer filter screen silk mesh 9 is installed at the bottom tube mouth of the big-bellied pipette 3. The lower double-layer filter screen silk mesh 9 includes a lower layer and an upper layer. The upper layer of the lower double-layer filter screen silk mesh 9 is a 20-mesh national standard 304 silk filter mesh, and the lower layer of the lower double-layer filter screen silk mesh 9 is a 64um screen silk.

[0043] A glass rod 4 is fixedly installed at the connection between the large-bellied pipette 3 and the silicone tube 1. The length of the glass rod 4 is 30 cm, which enables the bottom tube of the large-bellied pipette 3 to be vertically inserted into the upper liquid of the cylindrical separating funnel 6.

[0044] A Robert clamp 5 is installed on the silicone tube 1, and the silicone tube 1 crosses the openings at both ends of the Robert clamp 5. When the supernatant is sucked to the scale line position of the cylindrical separating funnel 6, you can hold the Robert clamp 5 and press it at any time to stop sucking the supernatant immediately.

[0045] Specifically: the bottom tube of the cylindrical separating funnel 6 is provided with a control valve 11, the bottom tube of the cylindrical separating funnel 6 is inserted into a 50mL conical centrifuge tube 10, the upper end of the cylindrical separating funnel 6 sucks out the upper layer liquid without algae, and the lower end releases the lower layer liquid containing algae.

[0046] The upper double-layer filter mesh 8 and the lower double-layer filter mesh 9 are hard and soft, and can be easily inserted into the 1000 mL cylindrical separatory funnel 6 while keeping the surface level.

[0047] The working steps of the algae counting and quantitative concentration device are as follows:

[0048] Step 1: Before quantitative concentration, first remove the first filter screen silk mesh 2 on the silicone tube 1, connect the tube end to the pure water tap, and let the water flow out from the other end of the silicone tube 1. At this time, immediately close the tap, remove the silicone tube 1 at this end, and insert the first filter screen silk mesh 2. The other end of the large-bellied pipette 3 is gently inserted 4 cm below the surface of the supernatant in the cylindrical separating funnel 6. The other end of the large-bellied pipette 3 is lowered to the first filter screen silk mesh 2 of the silicone tube 1. Through the liquid level difference and liquid drainage, the upper layer of liquid begins to be absorbed;

[0049] Step 2: When absorbing the upper layer of liquid, hold the silicone tube 1 and glass rod 4 at Robert's clamp 5 with one hand, and gently move down the 10mL big-bellied pipette 3 with the tip cut off at the bottom, so that the upper double-layer filter screen 8 is always level with the upper liquid surface. Use one hand to control the lowering of the first filter screen 2 at the other end of the silicone tube 1, release the sucked-out upper layer of liquid, and when it is almost at the mark position, keep the lower double-layer filter screen 9 level with the upper liquid surface of the bottom liquid, and gently absorb the upper layer of the bottom liquid to prevent the bottom of the 10mL big-bellied pipette 3 from being inserted into the algae liquid, causing the loss of algae. When it reaches the mark position, quickly press the Robert clip 5, quickly move the lower end of the bottom tube of the large-bellied pipette 3 tied with the first sieve silk 7 away from the liquid surface, shake the lower layer liquid of the cylindrical separatory funnel 6 and put it into the 50mL conical centrifuge tube 10, and use part of the 10mL liquid left in the large-bellied pipette 3 with the tip cut off to rinse the algae on the wall of the cylindrical separatory funnel 6, and part of it to rinse the algae on the first filter sieve silk 2, the first sieve silk 7, the upper double-layer filter sieve silk 8 and the lower double-layer filter sieve silk 9. All the liquid after rinsing is transferred to the 50mL conical centrifuge tube 10.

[0050] Example 2

[0051] Based on the first embodiment, Figure 5 and Figure 6 As shown, the cylindrical separating funnel 6 is mounted on a mounting frame 12, a support frame 14 is provided on the mounting frame 12, a clamping block 23 is slidably mounted on the support frame 14, the support frame 14 is transmission-connected to the clamping block 23 through an adjusting mechanism, and the operating adjusting mechanism moves along the mounting frame 12 through the clamping block 23.

[0052] An adjusting screw 19 is rotatably mounted on the adjusting mechanism, a rotating handle 16 is fixedly provided on the adjusting screw 19, the clamping block 23 is mounted on the sliding block 18, the sliding block 18 is slidably mounted on the support frame 14, a first screw hole 24 is opened on the sliding block 18, and the adjusting screw 19 is threadedly mounted in the first screw hole 24.

[0053] Specifically: the cylindrical separating funnel 6 is detachably mounted on the fixing frame 13, the fixing frame 13 is fixedly mounted on the mounting frame 12, a sliding groove 17 is provided on the supporting frame 14, the sliding block 18 is slidably mounted in the sliding groove 17, a rotating shaft 15 is fixedly provided on the adjusting screw 19, the rotating shaft 15 is rotatably mounted on the supporting frame 14, and the rotating handle 16 is fixed on the rotating shaft 15.

[0054] An arc frame 20 is fixedly provided on the sliding block 18 , and a second screw hole 21 is opened on the arc frame 20 . A limiting bolt 22 is rotatably installed on the clamping block 23 , and the limiting bolt 22 is threadedly installed in the second screw hole 21 .

[0055] Specifically: the number of the clamping blocks 23 is two, and the two clamping blocks 23 are symmetrically distributed on the arc frame 20;

[0056] In actual operation: the limiting bolt 22 is operated to rotate along the second screw hole 21, thereby driving the clamping block 23 to move along the arc frame 20, and the glass rod is fixed by the two clamping blocks 23, and the rotating handle 16 is operated to drive the adjusting screw 19 to rotate, and the arc frame 20 is driven to move along the support frame 14 through the adjusting screw 19, and the glass rod is driven to move through the arc frame 20, and the large-bellied pipette is driven to move along the cylindrical separating funnel through the glass rod, thereby improving the stability of the movement of the large-bellied pipette, thereby improving work efficiency.

[0057] The working principle of the utility model is as follows: a first filter screen 2 is installed at the tube mouth of one end of the silicone tube 1 to prevent algae from flowing out of the tube mouth of one end of the silicone tube 1. Part of the algae will be trapped on the outer surface of the first filter screen 2 and finally rinsed into a 50mL conical centrifuge tube 10. A Robert clamp 5 is installed at the connection between the silicone tube 1 and a 10mL large-bellied pipette 3 with a tip cut off at the bottom. When the lower layer liquid remains nearly 40mL, the upper layer liquid can be stopped immediately to avoid sucking out too much algae liquid. The 10mL large-bellied pipette 3 with a tip cut off at the bottom is used for siphoning, so that more liquid can be left in the 10mL large-bellied pipette 3. Finally, the wall of the cylindrical separatory funnel 6 can be rinsed. For the algae on the surface, a double-layer filter screen mesh 8 is installed 4 cm away from the bottom nozzle of a 10 mL pipette 3 with a tip cut off at the bottom, which can keep it level with the upper liquid surface at any time, control the siphon speed, avoid bubbles during rapid siphoning, reduce the contact area with the algae liquid, and avoid algae loss. A double-layer filter screen mesh 9 is installed at the bottom horizontal nozzle surface of the 10 mL pipette 3 with a tip cut off at the bottom, so that it can keep it level with the liquid surface when the upper liquid is finally sucked out, and the liquid can be sucked out slowly to avoid the siphon tube being inserted into the bottom high-concentration algae liquid, sucking out part of the high-concentration algae at the bottom, and affecting the final algae detection data. This improvement improves the accuracy of the algae data.

[0058] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements shall fall within the scope of the present invention to be protected. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A device for counting and quantitatively concentrating algae in water, comprising a silicone tube (1), a large-bellied pipette (3) and a cylindrical separating funnel (6), characterized in that: A first filter screen (2) is installed at the tube mouth of one end of the silicone tube (1), and a large-bellied pipette (3) is fixedly connected to the tube mouth of the other end of the silicone tube (1). The tip of the bottom tube mouth of the large-bellied pipette (3) is cut off, and a first screen (7) is tied to the bottom tube mouth of the large-bellied pipette (3). An upper double-layer filter screen (8) and a lower double-layer filter screen (9) are provided at the bottom tube mouth of the large-bellied pipette (3), and the bottom tube mouth of the large-bellied pipette (3) is inserted into a cylindrical separating funnel (6).

2. The device for counting and quantitatively concentrating algae in water according to claim 1, characterized in that: The first filter screen mesh (2) is made of 64um screen silk welded together, and the upper layer has a maximum inner diameter of 5mm.

3. The device for counting and quantitatively concentrating algae in water according to claim 2, characterized in that: The connection between the silicone tube (1) and the large-bellied pipette (3) is curved.

4. The device for counting and quantifying algae in water according to any one of claims 1 to 3, characterized in that: The first sieve silk (7) is tied to the bottom tube mouth of the big-bellied pipette (3) to 8 cm above the tube mouth, and the upper double-layer filter sieve silk net (8) is installed 4 cm above the bottom tube mouth of the big-bellied pipette (3).

5. The device for counting and quantitatively concentrating algae in water according to claim 4, characterized in that: The upper double-layer filter screen silk mesh (8) comprises a lower layer and an upper layer, the upper layer of the upper double-layer filter screen silk mesh (8) is a 20-mesh national standard 304 silk filter mesh, and the lower layer of the upper double-layer filter screen silk mesh (8) is a 64um screen silk.

6. The device for counting and quantitatively concentrating algae in water according to claim 5, characterized in that: The lower double-layer filter screen silk mesh (9) comprises a lower layer and an upper layer, the upper layer of the lower double-layer filter screen silk mesh (9) is a 20-mesh national standard 304 silk filter mesh, and the lower layer of the lower double-layer filter screen silk mesh (9) is a 64um screen silk.

7. The device for counting and quantitatively concentrating algae in water according to claim 5 or 6, characterized in that: The silicone tube (1) is provided with a Robert clamp (5), and the silicone tube (1) is passed through the openings at both ends of the Robert clamp (5).

8. The device for counting and quantifying algae in water according to any one of claims 1 to 7, characterized in that: A glass rod (4) is fixedly installed at the connection between the large-bellied pipette (3) and the silicone tube (1), and the cylindrical separating funnel (6) is installed on the mounting frame (12). A support frame (14) is provided on the mounting frame (12), and a clamping block (23) is slidably installed on the support frame (14). The support frame (14) is transmission-connected to the clamping block (23) through an adjusting mechanism, and the adjusting mechanism is operated to move along the mounting frame (12) through the clamping block (23).

9. The device for counting and quantitatively concentrating algae in water according to claim 8, characterized in that: An adjusting screw (19) is rotatably mounted on the adjusting mechanism, a rotating handle (16) is fixedly mounted on the adjusting screw (19), the clamping block (23) is mounted on the sliding block (18), the sliding block (18) is slidably mounted on the support frame (14), a first screw hole (24) is opened on the sliding block (18), and the adjusting screw (19) is threadedly mounted in the first screw hole (24).

10. The device for counting and quantifying algae in water according to claim 9, characterized in that: An arc frame (20) is fixedly provided on the sliding block (18), a second screw hole (21) is provided on the arc frame (20), a limiting bolt (22) is rotatably installed on the clamping block (23), and the limiting bolt (22) is threadedly installed in the second screw hole (21).

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