Measuring device for trailing edge curved edge of aero-engine turbine blade

Abstract

The utility model relates to a device for measuring the curved edge of the trailing edge of a turbine blade of an aero-engine. The device comprises a clamping structure and a measuring structure. A reference sliding seat is installed on the flat plate, the positioning chuck assembly is provided with an inclined reference surface, and the blade body positioning block is installed on the inclined reference surface. The curved-edge reference block is installed on the side face of the support, the side, away from the support, of the curved-edge reference block is provided with a curved surface, the zero-setting standard part is installed at the end, away from a chuck, of the positioning chuck assembly, the two zero-setting surfaces of the zero-setting standard part face the reference sliding seat, the curved-edge gauge stand assembly is movably installed on the reference sliding seat, and the axial face of the measuring rod abuts against the curved edge of a blade body. The measuring head and the abutting pin abut against the curved surface of the curved edge reference block, and the measuring head has a telescopic function. By means of the structure, the problem that continuous measurement and accurate measurement data reading cannot be achieved in existing aviation blade curved edge measurement is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of turbine blade processing and detection, in particular to a device for measuring the curved edge of a turbine blade trailing edge of an aero-engine. Background Art

[0002] The measurement of the structural characteristics of aircraft engine turbine blades is relatively complex. Among them, the more conventional measurement is the measurement of the blade plane characteristics, but the special characteristics of the blade structure require more than that. There may also be measurement of some curved surfaces. Curved surface measurement is a relatively complex research topic in the field of tooling design.

[0003] In the previous measurement of the turbine trailing edge boundary, the method adopted was the push gauge measurement method with a matching surface measuring tool. Its characteristic is that the "go" and "stop" of the push gauge are used to complete the qualified or unqualified judgment of the trailing edge boundary of a specific section. This method is simple to judge, cannot achieve continuous measurement, and is prone to judgment errors. Utility Model Content

[0004] The utility model provides a device for measuring the curved edge of the trailing edge of an aircraft engine turbine blade, which solves the problem that the existing aircraft blade curved edge measurement cannot realize continuous measurement and accurately read measurement data.

[0005] The technical solution of the utility model to solve the above technical problems is as follows:

[0006] The clamping structure includes a base plate, a flat plate, a support, a positioning chuck assembly, a blade positioning block and a reference slide. The flat plate is installed on one side above the base plate, and the support is installed on the other side. The reference slide is installed on the flat plate. The positioning chuck assembly is installed above the support. The positioning chuck assembly has an inclined reference surface, and the blade positioning block is installed on the inclined reference surface near the chuck position of the positioning chuck assembly.

[0007] The measuring structure includes a zeroing standard part, a curved edge table frame assembly and a curved edge reference block. The curved edge reference block is installed on the side of the support and is located below the blade positioning block. The side of the curved edge reference block away from the support has a curved surface. The zeroing standard part is installed at the end of the positioning chuck assembly away from the chuck. The zeroing standard part has two upper and lower zeroing surfaces, and the two zeroing surfaces face the reference slide. The curved edge table frame assembly is movably installed on the reference slide. The curved edge table frame assembly has a table frame, a measuring rod, a measuring head, a clamping pin and a micrometer. The axial surface of the measuring rod is abutted against the curved edge of the blade, and the measuring head and the clamping pin are abutted against the curved surface of the curved edge reference block. The measuring head has a telescopic function.

[0008] The beneficial effects of the utility model are as follows: the head of the standard part is clamped on the positioning chuck assembly, and the blade positioning block is abutted against the tail of the standard part to prevent the standard part from rotating and skewing. First, move the curved edge meter frame assembly to the zero standard part, and adjust the dial indicator to zero. Then move the curved edge meter frame assembly to the measuring area, the measuring rod is abutted against the curve of the standard part, the measuring head is abutted against the curved edge of the curved edge reference block, and the curved edge meter frame assembly moves on the reference slide along the direction of the curved edge of the standard part, and the measuring head will telescope and move at different heights of the curved surface. Observe the value of the dial indicator. When the value of the dial indicator is always zero, the test standard is qualified. Continuous measurement of the curved edge boundary of the trailing edge of the blade is achieved, and continuous control of the dimensional fluctuation of the curved edge of the trailing edge of the blade is achieved, making it less likely for measurement errors to occur.

[0009] On the basis of the above technical solution, the present invention can also be improved as follows.

[0010] Furthermore, one side of the blade positioning block is provided with a boss, and the bottom of the boss has an oblique angle.

[0011] The beneficial effect of adopting the above further solution is that the bottom of the blade body is supported on the boss, and the bevel on the boss fixes the tail of the blade body to prevent the blade body from moving.

[0012] On the basis of the above technical solution, the present invention can also be improved as follows.

[0013] Furthermore, the upper part of the meter frame is U-shaped, and a rotating shaft is provided at the two ends of the U-shape, the two ends of the measuring rod are rotatably mounted on the rotating shaft, the lower part of the meter frame is provided with a measuring head and a tightening pin, and the dial indicator is installed at the rear end of the measuring head.

[0014] The beneficial effect of adopting the above further scheme is that the upper part of the meter frame is U-shaped, and the two ends of the measuring rod are rotatably installed on the rotating shaft of the U-shaped meter frame. Because the thickness of the blade body is relatively thick, a measuring rod with a long length is used to roll and measure the curved edge of the blade body, so that all dimensions of the curved edge can be measured, thereby achieving the measurement purpose.

[0015] On the basis of the above technical solution, the present invention can also be improved as follows.

[0016] Furthermore, a center line connecting the measuring rod and the measuring head is perpendicular to the bottom surface of the table frame.

[0017] The beneficial effect of adopting the above further solution is that the center line connecting the measuring rod and the measuring head is perpendicular to the bottom surface of the table frame, so that the measuring rod and the measuring head are kept on the same axis, ensuring the accuracy of the measured value.

[0018] On the basis of the above technical solution, the present invention can also be improved as follows.

[0019] Furthermore, the axial surface of the measuring rod contacts the upper zeroing surface of the zeroing standard part, the measuring head contacts the lower zeroing surface of the zeroing standard part, and the end surfaces of the upper zeroing surface and the lower zeroing surface are flush.

[0020] The beneficial effect of adopting the above further scheme is that, because the end faces of the upper zero surface and the lower zero surface are flush, the axial surface of the measuring rod contacts the upper zero surface of the zero standard part, and the measuring head contacts the lower zero surface of the zero standard part, so that the measuring contacts of the measuring rod and the measuring contacts of the measuring head remain on the same plane.

[0021] On the basis of the above technical solution, the present invention can also be improved as follows.

[0022] Furthermore, the chuck of the positioning chuck assembly comprises an upper chuck and a lower chuck, and both the upper chuck and the lower chuck have locking teeth.

[0023] The beneficial effect of adopting the above further solution is that the head of the blade body is clamped by the clamping teeth of the upper clamp and the lower clamp so as to position the blade body.

[0024] On the basis of the above technical solution, the present invention can also be improved as follows.

[0025] Furthermore, a crank handle is provided on the upper clamp, and the crank handle is rotatably connected to the upper clamp.

[0026] The beneficial effect of adopting the above further solution is that by turning the crank, the upper clamp and the lower clamp are separated, so that the blade body can be easily clamped between the upper clamp and the lower clamp. Then, by turning the crank, the blade body is clamped and fixed to prevent the blade body from rotating and moving.

[0027] On the basis of the above technical solution, the present invention can also be improved as follows.

[0028] Furthermore, the upper chuck and the lower chuck clamp the head of the blade, the blade positioning block abuts against the tail of the blade, and the axial surface of the measuring rod abuts against the curved edge of the blade.

[0029] The beneficial effect of adopting the above further scheme is that the blade body is installed on the measuring area, the upper chuck and the lower chuck clamp the head of the blade body, the blade body positioning block is against the tail of the blade body, and the axial surface of the measuring rod is against the curved edge of the blade body. The blade body is tightened and fixed by the upper chuck, the lower chuck and the blade body positioning block to prevent the blade body from rotating and moving. Then, the curved edge of the blade body is slidingly measured using the curved edge table frame assembly, so that the curved edge table frame assembly moves on the reference slide along the direction of the curved edge of the standard part, and the value of the dial indicator is observed. When the value of the dial indicator is always zero, the size of the blade body is qualified. When the value of the dial indicator is non-zero, the size of the blade body is unqualified. Continuous measurement of the curved edge boundary of the trailing edge of the blade is achieved, and continuous control of the dimensional fluctuation of the curved edge of the trailing edge of the blade is achieved, making it less likely for measurement errors to occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of a device for measuring the curved edge of a trailing edge of a turbine blade of an aero-engine according to the utility model when it is working;

[0031] Figure 2 It is a schematic diagram of the structure of the utility model when it is not working;

[0032] Figure 3 This is a schematic diagram of the structure of the curved edge table frame assembly of the utility model;

[0033] Figure 4 It is a structural schematic diagram of the clamping structure of the utility model;

[0034] Figure 5 It is a top view of the clamping structure of the utility model;

[0035] Figure 6 It is a front schematic diagram of the clamping structure of the utility model;

[0036] Figure 7 It is a side view schematic diagram of the clamping structure of the utility model;

[0037] Figure 8 Another side view of the clamping structure of the utility model;

[0038] Fig. 9 It is a schematic diagram of the percentage-to-zero structure of the utility model.

[0039] In the attached drawings, the parts represented by each reference numeral are listed as follows: 100-clamping structure; 110-base plate; 120-flat plate; 130-support; 140-positioning chuck assembly; 141-inclined reference surface; 143-upper chuck; 1431-crank handle; 145-lower chuck; 1451-grip; 150-blade positioning block; 151-boss; 160-reference slide; 300-measuring structure; 310-zero standard part; 311-upper zero surface; 313-lower zero surface; 330-curved edge table frame assembly; 331-table frame; 3311-rotating shaft; 333-measuring rod; 335-measuring head; 337-tightening pin; 339-dial indicator; 350-curved edge reference block. DETAILED DESCRIPTION

[0040] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0041] Example 1

[0042] like Figure 1-9 As shown, the clamping structure 100 includes a base plate 110, a flat plate 120, a support 130, a positioning clamp assembly 140, a blade positioning block 150 and a reference slide 160. The flat plate 120 is installed on one side above the base plate 110, and the support 130 is installed on the other side. The reference slide 160 is installed on the flat plate 120. The positioning clamp assembly 140 is installed above the support 130. The positioning clamp assembly 140 has an inclined reference surface 141. The blade positioning block 150 is installed on the inclined reference surface 141 at the clamp position close to the positioning clamp assembly 140.

[0043] The measuring structure 300 includes a zero standard part 310, a curved edge table frame assembly 330 and a curved edge reference block 350. The curved edge reference block 350 is installed on the side of the support 130 and is located below the blade positioning block 150. The side of the curved edge reference block 350 away from the support 130 has a curved surface. The zero standard part 310 is installed at the end of the positioning chuck assembly 140 away from the chuck. The zero standard part 310 has two upper and lower zero surfaces, and the two zero surfaces face the reference slide 160. The curved edge table frame assembly 330 is movably installed on the reference slide 160. The curved edge table frame assembly 330 has a table frame 331, a measuring rod 333, a measuring head 335, a tightening pin 337 and a micrometer. The axial surface of the measuring rod 333 is abutted against the curved edge of the blade, the measuring head 335 and the tightening pin 337 are abutted against the curved surface of the curved edge reference block 350, and the measuring head 335 has a telescopic function.

[0044] Specifically, the head of the blade is clamped on the positioning clamp assembly 140, and the blade positioning block 150 is against the tail of the blade. First, the curved edge gauge frame assembly 330 is moved to the zero standard part 310, the measuring rod 333 is against the upper zero surface 311, the measuring head 335 is against the lower zero surface 313, and the dial indicator 339 is adjusted for zero. Then the curved edge gauge frame assembly 330 is moved to the measurement area, the measuring rod 333 is against the curve of the blade, the measuring head 335 is against the curved edge of the curved edge reference block 350, and the curved edge gauge frame assembly 330 moves on the reference slide 160 along the direction of the curved surface of the curved edge reference block 350, and the measuring head 335 will telescope and move at different heights of the curved surface. Observe the value of the dial indicator 339. When the value of the dial indicator 339 is always zero, the size of the blade is qualified. When the value of the dial indicator is non-zero, the size of the blade is unqualified.

[0045] like Figure 1-9 As shown, one side of the blade positioning block 150 has a boss 151 , and the bottom of the boss 151 has an oblique angle.

[0046] Specifically, the head of the blade is clamped into the clamping teeth 1451 of the upper clamp 143 and the lower clamp 145, the tail of the blade is supported on the blade positioning block 150, and the bevel on the boss 151 is clamped on the blade to clamp and fix the blade to prevent the blade from rotating and moving.

[0047] like Figure 1-9 As shown, the upper part of the meter frame 331 is U-shaped, and a rotating shaft 3311 is provided at the two ends of the U-shape, and the two ends of the measuring rod 333 are rotatably mounted on the rotating shaft 3311. The lower part of the meter frame 331 is provided with a measuring head 335 and a tightening pin 337, and a dial indicator 339 is installed at the rear end of the measuring head 335.

[0048] Specifically, the measuring rod 333 rotates as the curved edge table frame assembly 330 moves on the reference slide 160 along the direction of the curved edge of the standard part. The measuring head 335 and the clamping pin 337 are abutted against the curved surface of the curved edge reference block 350. The measuring head 335 will telescope and move at different heights of the curved surface, and the value of the dial indicator 339 is observed. When the value of the dial indicator 339 is always zero, the size of the standard part is qualified.

[0049] like Figure 1-9 As shown, the center line connecting the measuring rod 333 and the measuring head 335 is perpendicular to the bottom surface of the table frame 331.

[0050] Specifically, the measuring rod 333 and the measuring head 335 are arranged on the same vertical plane to ensure that the measuring contact of the measuring rod 333 and the measuring contact of the measuring head 335 are kept on the same plane from top to bottom.

[0051] like Figure 1-9As shown, the axial surface of the measuring rod 333 contacts the upper zero surface 311 of the zero standard 310 , the measuring head 335 contacts the lower zero surface 313 of the zero standard 310 , and the upper zero surface 311 is flush with the end surface of the lower zero surface 313 .

[0052] Specifically, the axial surface of the measuring rod 333 is brought into contact with the upper zeroing surface 311 of the zeroing standard 310, and the measuring head 335 is brought into contact with the lower zeroing surface 313 of the zeroing standard 310, and the dial indicator 339 is zeroed. Ensure that the measuring contact of the measuring rod 333 and the measuring contact of the measuring head 335 are kept in the same plane from top to bottom.

[0053] like Figure 1-9 As shown, the clamp of the positioning clamp assembly 140 includes an upper clamp 143 and a lower clamp 145 , and both the upper clamp 143 and the lower clamp 145 have locking teeth 1451 .

[0054] Specifically, the head of the blade is clamped into the clamping teeth 1451 of the upper clamp 143 and the lower clamp 145 to clamp and fix the blade to prevent the blade from rotating and moving.

[0055] like Figure 1-9 As shown, a crank 1431 is provided on the upper clamp 143 , and the crank 1431 is rotatably connected to the upper clamp 143 .

[0056] Specifically, the crank handle 1431 is turned to separate the upper clamp 143 and the lower clamp 145, and then the head of the blade body is clamped into the clamping teeth 1451 of the upper clamp 143 and the lower clamp 145. Then, the crank handle 1431 is turned in the opposite direction to bring the upper clamp 143 and the lower clamp 145 together to clamp and fix the blade body.

[0057] like Figure 1-9 As shown, the upper clamp 143 and the lower clamp 145 clamp the head of the blade, the blade positioning block 150 abuts against the tail of the blade, and the axial surface of the measuring rod 333 abuts against the curved edge of the blade.

[0058] Specifically, the blade is mounted on the measuring area, the upper chuck 143 and the lower chuck 145 clamp the head of the blade, the blade positioning block 150 abuts against the tail of the blade, and the axial surface of the measuring rod 333 abuts against the curved edge of the blade. The blade is tightened and fixed by the upper chuck 143, the lower chuck 145 and the blade positioning block 150 to prevent the blade from rotating and moving. Then, the curved edge meter frame assembly 330 moves on the reference slide 160 along the direction of the curved surface of the curved edge reference block 350, and the value of the dial indicator 339 is observed. When the value of the dial indicator 339 is always zero, the size of the blade is qualified. When the value of the dial indicator is non-zero, the size of the blade is unqualified.

[0059] The beneficial effects of this embodiment are: the curved edge table frame assembly 330 is moved to the measurement area, the measuring rod 333 is pressed against the curve of the standard part, the measuring head 335 is pressed against the curved edge of the curved edge reference block 350, the curved edge table frame assembly 330 moves on the reference slide 160 along the direction of the curved surface of the curved edge reference block 350, and the measuring head 335 moves telescopically at different heights of the curved surface. Observe the value of the dial indicator 339. When the value of the dial indicator 339 is always zero, the size of the standard part is qualified. When the value of the dial indicator is non-zero, the size of the blade body is unqualified. Continuous measurement of the curved edge boundary of the trailing edge of the blade is achieved, and continuous control of the dimensional fluctuation of the curved edge of the trailing edge of the blade is achieved, so that measurement is less prone to errors.

[0060] The working process of this embodiment is as follows: the head of the standard part is clamped on the positioning chuck assembly 140, and the blade positioning block 150 is pressed against the tail of the standard part. First, the curved edge gauge frame assembly 330 is moved to the zero standard part 310, the measuring rod 333 is pressed against the upper zero surface 311, the measuring head 335 is pressed against the lower zero surface 313, and the dial indicator 339 is adjusted for zero. Then the curved edge gauge frame assembly 330 is moved to the measurement area, the measuring rod 333 is pressed against the curve of the standard part, the measuring head 335 is pressed against the curved edge of the curved edge reference block 350, and the curved edge gauge frame assembly 330 moves on the reference slide 160 along the direction of the curved surface of the curved edge reference block 350, and the measuring head 335 will telescope and move at different heights of the curved surface. Observe the value of the dial indicator 339. When the value of the dial indicator 339 is always zero, the test standard is qualified. When the value of the dial indicator is not zero, the blade size is unqualified. This test standard is used as the standard to measure the processed blades in the future.

[0061] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0062] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0063] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0064] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0066] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in the field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A device for measuring the curved edge of the trailing edge of an aircraft engine turbine blade, characterized in that: include A clamping structure (100), the clamping structure (100) comprising a base plate (110), a flat plate (120), a support (130), a positioning chuck assembly (140), a blade body positioning block (150) and a reference slide (160); the flat plate (120) is mounted on one side above the base plate (110), and the support (130) is mounted on the other side; the reference slide (160) is mounted on the flat plate (120); the positioning chuck assembly (140) is mounted above the support (130); the positioning chuck assembly (140) has an inclined reference surface (141); and the blade body positioning block (150) is mounted on the inclined reference surface (141) at a chuck position close to the positioning chuck assembly (140); A measuring structure (300), the measuring structure (300) comprising a zero standard component (310), a curved edge table frame assembly (330) and a curved edge reference block (350), the curved edge reference block (350) being mounted on a side of the support (130) and located below the blade body positioning block (150), the curved edge reference block (350) having a curved surface on a side away from the support (130), the zero standard component (310) being mounted on an end of the positioning chuck assembly (140) away from the chuck, the zero standard component (310) having two upper and lower zero standard components. The two zero surfaces face the reference slide (160), the curved edge table frame assembly (330) is movably mounted on the reference slide (160), the curved edge table frame assembly (330) comprises a table frame (331), a measuring rod (333), a measuring head (335), a tightening pin (337) and a micrometer, the axial surface of the measuring rod (333) is pressed against the curved edge of the blade body, the measuring head (335) and the tightening pin (337) are pressed against the curved surface of the curved edge reference block (350), and the measuring head (335) has a telescopic function.

2. The device for measuring the trailing edge curve of an aircraft engine turbine blade according to claim 1, characterized in that: One side of the blade positioning block (150) is provided with a boss (151), and the bottom of the boss (151) is provided with an oblique angle.

3. The device for measuring the trailing edge curve of an aircraft engine turbine blade according to claim 1, characterized in that: The upper part of the meter frame (331) is U-shaped, and a rotating shaft (3311) is provided at the two ends of the U-shape. The two ends of the measuring rod (333) are rotatably mounted on the rotating shaft (3311). The lower part of the meter frame (331) is provided with the measuring head (335) and the tightening pin (337), and the micrometer is installed at the rear end of the measuring head (335).

4. The device for measuring the trailing edge curve of an aircraft engine turbine blade according to claim 3, characterized in that: The center line connecting the measuring rod (333) and the measuring head (335) is perpendicular to the bottom surface of the meter frame (331).

5. The device for measuring the trailing edge curve of an aircraft engine turbine blade according to claim 4, characterized in that: The axial surface of the measuring rod (333) contacts the upper zeroing surface (311) of the zeroing standard part (310), the measuring head (335) contacts the lower zeroing surface (313) of the zeroing standard part (310), and the end surfaces of the upper zeroing surface (311) and the lower zeroing surface (313) are flush.

6. The device for measuring the trailing edge curve of an aircraft engine turbine blade according to claim 1, characterized in that: The chuck of the positioning chuck assembly (140) comprises an upper chuck (143) and a lower chuck (145), and both the upper chuck (143) and the lower chuck (145) have latching teeth (1451).

7. The device for measuring the trailing edge curve of an aircraft engine turbine blade according to claim 6, characterized in that: The upper clamp (143) is provided with a crank (1431), and the crank (1431) is rotatably connected to the upper clamp (143).

8. The device for measuring the trailing edge curve of an aircraft engine turbine blade according to claim 6, characterized in that: The upper clamp (143) and the lower clamp (145) clamp the head of the blade, the blade positioning block (150) abuts against the tail of the blade, and the axial surface of the measuring rod (333) abuts against the curved edge of the blade.

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