Smooth blade sharpening device

Abstract

The invention provides a smooth knife sharpening device, relates to the field of knife sharpening equipment, and aims to solve the problem that the machining precision is reduced due to poor stability when a smooth knife is sharpened at present, a moving path of a clamp and a smooth knife on the clamp is established by utilizing the matching of an arc-shaped sliding block and an arc-shaped sliding groove, and the stability of the clamp and the clamped smooth knife during knife sharpening is ensured. The swing rod assembly serves as a linkage mechanism for driving the arc-shaped sliding block, tangential guiding is provided for movement of the arc-shaped sliding block relative to the arc-shaped sliding groove, the accuracy and smoothness of movement of the arc-shaped sliding block relative to the arc-shaped sliding groove are improved, the response speed of adjusting the sharpening position of the smooth knife is increased, and therefore the machining precision is guaranteed.

Description

Technical Field

[0001] The invention relates to the field of blade sharpening equipment, and in particular to a light knife blade sharpening device. Background Art

[0002] In the machining industry, some precision, low-roughness workpieces are often turned by light knives (turning instead of grinding) to improve machining accuracy, which can improve machining efficiency and surface residual compressive stress, thereby improving its wear resistance. Light knife machining usually uses low cutting depth and large feed rate, so that the light knife cutting edge is projected as a continuous arc on the base surface; the arc radius is determined by the surface roughness and feed rate after machining. According to r = (4Ra 2 +f 2 ) / 8Ra, where r is the tool arc radius (unit: mm), Ra is the surface roughness value to be achieved (unit: mm), and f is the feed rate (unit: mm / r). If the surface roughness of the workpiece after processing is to reach Ra0.4, and the feed rate is 1.5 mm / revolution, then r should be 468.875 mm, which means that the arc radius of the light knife should not be less than 469 mm to achieve the surface quality.

[0003] A Chinese patent (publication number: CN103567817A) discloses a shaft cutting tool sharpening machine, on which the grinding assembly and the tool feed assembly are connected and arranged for transmission, and the grinding wheel on the grinding assembly feeds in the vertical and vertical directions and adjusts the angle, and the tool clamped in the chuck on the slide plate rotates and deflects the shaft neck of the tool feed assembly to form a ball-line transmission deflection, and the spherical edge, front edge, and rear edge of the tool are subjected to forming sharpening. However, it is not suitable for the arc sharpening process of the light knife. During the sharpening process of the light knife, the vibration of the light knife body will be transmitted back to the fixture, and the vibration of the fixture will easily affect the movement accuracy of the fixture, resulting in the deviation of the arc trajectory during sharpening, resulting in a large deviation in the radius of the light knife arc, which affects the accuracy of the workpiece being processed during cutting, and also causes the force deviation of the light knife, accelerating the wear of the light knife. Summary of the invention

[0004] The purpose of the present invention is to provide a polishing knife sharpening device in response to the defects of the prior art, which utilizes the cooperation of an arc-shaped slider and an arc-shaped slide groove to establish the moving path of the fixture and the polishing knife thereon, thereby ensuring the stability of the fixture and the clamped polishing knife during sharpening, and using a rocker arm assembly as a linkage mechanism to drive the arc-shaped slider, thereby providing tangential guidance for the movement of the arc-shaped slider relative to the arc-shaped slide groove, thereby improving the accuracy and smoothness of the movement of the arc-shaped slider relative to the arc-shaped slide groove, and improving the response speed of adjusting the polishing position of the polishing knife, thereby ensuring processing accuracy.

[0005] In order to solve the above problems, the following solutions are adopted:

[0006] A light knife sharpening device, comprising:

[0007] The guide mechanism includes an arc-shaped slide groove and an arc-shaped slider that are slidably matched. The track of the arc-shaped slide groove is in an arc shape. A clamp is provided on the arc-shaped slider. The arc-shaped slide groove is connected to the winding wheel through a traction rope. The arc-shaped slide groove is installed on the slider through a translation mechanism.

[0008] The rocker assembly includes a rocker and a connecting rod. The two ends of the connecting rod are respectively hinged with rockers. The rocker is rotatably connected to the slide plate to form a double rocker mechanism with the slide plate as a frame. The connecting rod is connected to the arc-shaped slider. The connecting rod constrains the slider to keep tangential movement along the slide track.

[0009] The grinding tool is facing the clamping part of the clamp and is used for sharpening the light knife on the clamping part.

[0010] Furthermore, the arc-shaped slide groove includes a support plate and relatively spaced guide plates. The two guide plates are connected to the support plate to form a groove body for accommodating the arc-shaped slider. The arc-shaped slider is located in the groove body. The support plate supports the bottom surface of the arc-shaped slider, and the side surface of the guide plate slides in sliding cooperation with the side surface of the arc-shaped slider.

[0011] Furthermore, the side of the guide plate that fits the arc-shaped slider is an arc surface, and the side of the guide plate away from the support plate is connected to a pressure plate, which slides and fits the top surface of the arc-shaped slider to keep the arc-shaped slider in the arc-shaped slide groove.

[0012] Furthermore, the winding wheel is rotatably mounted on the slide plate, one end of the traction rope is connected to one end of the arc-shaped slide groove, and the other end of the traction rope is connected to the other end of the arc-shaped slide groove after passing around the winding wheel and the driven wheel. The winding wheel, traction rope and driven wheel together form a translation drive mechanism.

[0013] Furthermore, the axle of the winding wheel is rotatably mounted on the slide plate, and the axle of the winding wheel is connected to the winding drive element.

[0014] Furthermore, the rocker is mounted on the slide plate via a rotating seat, and the connecting rod is fixed to the arc-shaped slide block via a connecting seat, so that the connecting rod moves along the arc slide groove following the slide block.

[0015] Furthermore, a limiting member is provided on the slide plate, and the limiting members are respectively arranged at the starting point and the end point of the rocker arm's running track to abut against the rocker arm.

[0016] Furthermore, the translation mechanism includes a translation slider and a translation rail that match each other, and the translation rail is distributed along the length direction of the light knife grinding.

[0017] Furthermore, the slide plate is mounted on the base plate via a feed sliding mechanism, the feed sliding mechanism comprises a matching feed slider and a feed slide rail, the base plate is mounted with a feed mechanism, and the feed mechanism drives the slide plate to move relative to the base plate along the feed slide rail direction.

[0018] Furthermore, the distribution directions of the feed slide rail and the translation slide rail are vertical in space, and the mold is installed on the bottom plate.

[0019] Compared with the prior art, the present invention has the following advantages and positive effects:

[0020] (1) In view of the problem that the machining accuracy is reduced due to the poor stability of the polishing knife during the current grinding, the movement path of the fixture and the polishing knife thereon is established by using the coordination of the arc-shaped slider and the arc-shaped slide groove to ensure the stability of the fixture and the clamped polishing knife during the grinding. The rocker assembly is used as the linkage mechanism to drive the arc-shaped slider to provide tangential guidance for the movement of the arc-shaped slider relative to the arc-shaped slide groove, thereby improving the accuracy and smoothness of the movement of the arc-shaped slider relative to the arc-shaped slide groove, and improving the response speed of adjusting the polishing position of the polishing knife, thereby ensuring the machining accuracy.

[0021] (2) A pressure plate is configured for the arc-shaped slide to constrain the position of the arc-shaped slider to prevent the arc-shaped slider from falling out of the arc-shaped slide due to the vibration during grinding of the mold. Combined with the constraining effect of the rocker assembly, the stability of the movement of the arc-shaped slider is improved.

[0022] (3) The slide plate is installed on the base plate through a feed sliding mechanism, which can make the base plate and the corresponding light knife close to or away from the grinding tool, making it easier to control the grinding amount and improve the grinding accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 Schematic diagram of the optical knife sharpening device in Example 1 of the present invention.

[0025] Figure 2 This is a schematic diagram of the main working parts of the optical knife sharpening device in Example 1 of the present invention.

[0026] Figure 3 Schematic diagram of the coordination of the arc-shaped slider and the arc-shaped slide groove in Example 1 of the present invention.

[0027] Figure 4 It is a structural schematic diagram of the translation mechanism in Example 1 of the present invention.

[0028] In the figure, 1. mold, 2. polishing knife, 3. fixture, 4. arc-shaped slider, 5. arc-shaped slide groove, 6. translation mechanism, 7. translation drive mechanism, 8. bottom plate, 9. double rocker mechanism, 10. winding wheel, 11. rocker, 12. rotating seat, 13. connecting rod, 14. translation slide rail, 15. translation slider, 16. slide plate, 17. connecting seat, 18. limiter, 19. feeding mechanism, 20. feeding slider, 21. traction rope, 22. pressure plate. DETAILED DESCRIPTION

[0029] Example 1

[0030] In a typical embodiment of the present invention, Figure 1-Figure 4 As shown, a light knife sharpening device is provided.

[0031] During the sharpening process of the optical knife 2, the vibration of the optical knife 2 body will be transmitted back to the fixture 3. This vibration not only affects the movement accuracy of the fixture 3, but also causes the arc trajectory during sharpening to be offset, thereby causing a large deviation in the radius of the arc of the optical knife 2. The deviation of the arc working position of the optical knife 2 will directly affect the accuracy of the workpiece being processed during cutting, reduce the overall processing quality, and increase the wear rate of the optical knife 2. Based on this, the present embodiment provides a optical knife sharpening device, which ensures the stability and accuracy of the optical knife 2 during the sharpening process through the precise matching of the arc slider 4 and the arc slot 5, as well as the guiding effect of the rocker assembly, and reduces the influence of vibration on the sharpening accuracy.

[0032] like Figure 1 As shown, the light knife sharpening device mainly includes a clamp 3, a guide mechanism, a rocker assembly and a grinder 1, wherein the guide mechanism includes a sliding arc groove 5 and an arc slider 4, the trajectory of the arc groove 5 is arc-shaped, the arc slider 4 is fan-shaped, the arc groove 5 is also fan-shaped, and the length of the arc groove 5 along its arc trajectory is greater than the length of the arc slider 4, so that the arc slider 4 can slide along the arc trajectory of the arc groove 5, and the sliding of this arc trajectory drives the clamp 3 to form the trajectory required during sharpening.

[0033] In order to clamp the optical knife 2, a clamp 3 is provided on the arc-shaped slider 4, and a clamping part for clamping the optical knife 2 is provided on the clamp 3. The clamping part is provided with a positioning structure matching the optical knife 2, such as a positioning groove, a positioning block, etc. The clamping part can also be configured according to the structure and size of the optical knife 2.

[0034] Different from the conventional method of directly driving the arc-shaped slider 4, in this embodiment, the arc-shaped slide 5 is used as the active part, and the arc-shaped slide 4 is driven to move by the movement of the arc-shaped slide 5. The arc-shaped slide 5 is connected to the winding wheel 10 through the traction cable 21, and the arc-shaped slide 5 is installed on the slide plate 16 through the translation mechanism 6. When the winding wheel 10 rotates, the arc-shaped slide 5 is driven to translate relative to the slide plate 16 through the traction cable 21, and the moving direction of the arc-shaped slide 5 is based on the movement direction established by the translation mechanism 6.

[0035] Among them, Figure 3 and Figure 4 As shown, the traction rope 21 can be a steel wire rope, a metal ribbon, etc. Due to the flexibility of the traction rope 21, it can bypass obstacles or be arranged along a complex path, and is suitable for a light knife sharpening device with limited space or requiring flexible layout. The flexible traction rope 21 can effectively transmit power, so that the power source winding wheel 10 is connected to the actuator arc chute 5, thereby driving the actuator arc chute 5 to perform various movements, including forward and backward movement of the arc chute 5.

[0036] The traction rope 21 can pass through the winding wheel 10 and the driven wheel, and connect the two ends of the arc chute 5 to form a driving chain. When the power source (such as a motor) drives the winding wheel 10 to rotate, the traction rope 21 will move accordingly, thereby driving the arc chute 5 to move forward or backward along a predetermined path.

[0037] like Figure 2 As shown, the rocker assembly includes a rocker 11 and a connecting rod 13, the two ends of the connecting rod 13 are respectively hinged with the rockers 11, the rocker 11 is rotatably connected to the slide 16, forming a double rocker mechanism 9 with the slide 16 as a frame, the connecting rod 13 is connected to the arc-shaped slider 4, and the connecting rod 13 constrains the slider to keep moving tangentially along the slide track. When the double rocker mechanism 9 moves, the two rockers 11 rotate relative to the slide 16, and the two ends of the connecting rod 13 rotate relative to the connected rockers 11.

[0038] like Figure 3 As shown, the two rockers 11 in the double rocker mechanism 9 are respectively hinged at the two ends of the connecting rod 13, and are rotatably connected to the slide plate 16. The rotation of the rocker 11 transmits force through the connecting rod 13, and the connecting rod 13 connects the two rockers 11 and the arc-shaped slider 4. Its design ensures that the arc-shaped slider 4 always maintains a tangential direction along the slide track when moving, thereby improving the accuracy and smoothness of movement.

[0039] The double rocker mechanism 9 uses the slide plate 16 as a frame, and realizes complex motion conversion through the mutual cooperation of the rocker 11 and the connecting rod 13. When the arc chute 5 moves, since the movement direction of the arc chute 5 is not completely consistent with the direction of the arc slider 4 constrained by the double rocker mechanism 9, when the arc slider 4 moves horizontally, the arc slider 4 constrained by the double rocker mechanism 9 follows the connecting rod 13 of the double rocker mechanism 9 and rotates while moving. This process is exactly the same as the movement direction of the arc slider 4 along the arc chute 5, so that the arc slider 4 can form a circular arc trajectory along the mutual chute, ensuring the stability and accuracy of the arc slider 4 during the grinding process. The arc slider 4 can also drive the light knife 2 on the fixture 3 to form an arc motion trajectory, thereby forming the required grinding path relative to the grinder 1.

[0040] By ensuring the stability and accuracy of the optical knife 2 during the sharpening process and accurately controlling the sharpening parameters, the surface roughness and precision of the processed workpiece are significantly improved. The force deviation and wear of the optical knife 2 during the sharpening process are reduced, and the service life of the optical knife 2 is extended.

[0041] The coordination of the arc-shaped slider 4 and the arc-shaped slot 5 is utilized to establish the moving path of the fixture 3 and the polishing knife 2 thereon, resist the uncontrollable deviation generated during the vibration process, ensure the stability of the fixture 3 and the clamped polishing knife 2 during sharpening, and use the rocker assembly as the linkage mechanism to drive the arc-shaped slider 4 to provide tangential guidance for the movement of the arc-shaped slider 4 relative to the arc-shaped slot 5, thereby improving the accuracy and smoothness of the movement of the arc-shaped slider 4 relative to the arc-shaped slot 5, and improving the response speed of adjusting the sharpening position of the polishing knife 2, thereby ensuring the processing accuracy.

[0042] like Figure 3 and Figure 4 As shown, the structure of the arc chute 5 and the arc slider 4 in this embodiment is described in detail. The arc chute 5 is composed of a support plate and relatively spaced guide plates, and the two guide plates are connected to the support plate to form a slot body for accommodating the arc slider 4.

[0043] The support plate bears the bottom surface of the arc-shaped slider 4, and the side surface of the guide plate slides with the side surface of the arc-shaped slider 4 to ensure that the slider slides stably in the slide groove. A stable sliding path is provided, so that the arc-shaped slider 4 can move smoothly along a predetermined arc track, improve the accuracy and stability of the movement, and reduce friction and wear.

[0044] The side of the guide plate that contacts the arc-shaped slider 4 is an arc surface, such as Figure 4 As shown, the arc slider 4 is fan-shaped, the guide plate on one side of the arc slider 4 has an outward convex arc surface, and the guide plate on the other side of the arc slider 4 has an inward concave arc surface, and the two arc surfaces are coaxially distributed to match the arc structures on both sides of the arc slider 4.

[0045] A pressure plate 22 is connected to the side of the guide plate away from the support plate. The pressure plate 22 slides and fits with the top surface of the arc-shaped slider 4. The support plate constrains the bottom surface of the arc-shaped slider 4 to keep the arc-shaped slider 4 in the arc-shaped slide groove 5, preventing the arc-shaped slider 4 from leaving the slide groove during movement, thereby increasing the stability and safety of the system, ensuring the stable operation of the slider under high-speed or complex working conditions, and reducing the failure rate.

[0046] In order to realize the movement of the arc chute 5 and the arc slider 4, a translation drive mechanism 7 is configured, and the translation drive mechanism 7 includes a winding wheel 10, a driven wheel and a traction rope 21, wherein the winding wheel 10 is rotatably mounted on the slide 16, and the two ends of the arc chute 5 are connected by the traction rope 21. The traction rope 21 bypasses the winding wheel 10 and the driven wheel, connects the two ends of the arc chute 5, and forms a driving chain. The driven wheel cooperates with the winding wheel 10 to drive the traction rope 21 to move. The translation movement of the arc chute 5 is realized, and a power source is provided for the movement of the arc slider 4, which can efficiently and accurately drive the arc chute 5 to translate.

[0047] The axle of the winding wheel 10 is rotatably mounted on the slide plate 16 and connected to the winding drive element, which can be a servo motor, a hand wheel, etc., to provide a power source for the rotation of the winding wheel 10, thereby realizing the retraction and release of the traction rope 21. This makes the control of the translation drive mechanism 7 more flexible and can adapt to different work requirements.

[0048] like Figure 2 and Figure 3 As shown, the rocker 11 is mounted on the slide 16 through the rotating seat 12, and the connecting rod 13 is fixed to the arc-shaped slider 4 through the connecting seat 17, so that the connecting rod 13 moves along the arc slide groove following the slider. The mechanical linkage between the rocker 11 and the arc-shaped slider 4 is realized, and the movement of the rocker 11 is converted into the arc movement of the arc-shaped slider 4. The flexibility and controllability of the mechanical structure are increased, and it is easy to realize complex motion trajectories.

[0049] The limiter 18 is arranged on the slide plate 16, at the starting point and the end point of the running track of the rocker 11, and is used to abut the rocker 11. The rocker 11 is prevented from exceeding the predetermined range during the movement, and the safety and stability of the system are ensured. In this embodiment, the limiter 18 can be a limit screw, and the threaded portion of the limit screw matches the preset threaded hole on the slide plate 16. The end of the limit screw is divided into an abutment end that contacts the rocker 11, which can abut the rocker 11 to prevent the rocker 11 from getting closer, thereby improving the reliability and durability of the system and reducing the damage caused by exceeding the range of motion.

[0050] Specifically, Figure 2As shown, the translation mechanism 6 is composed of a translation slider 15 and a translation rail 14, which are distributed along the length direction of the light knife 2. The translation slider 15 is installed on the bottom surface of the arc-shaped slide 5, and the translation rail 14 is arranged on the slide plate 16. The translation slider 15 and the translation rail 14 form a sliding fit, so that the entire arc-shaped slide 5 moves along the direction of the translation rail 14.

[0051] The feed slide mechanism is composed of a feed slider 20, a feed rail and a feed mechanism 19, and drives the slide plate 16 to move along the feed rail relative to the bottom plate 8. The distribution direction of the feed rail and the translation rail 14 is vertical in space, forming a two-axis adjustment in the horizontal plane, realizing the precise movement of the slide plate 16 in the first horizontal direction and the second horizontal direction, meeting complex processing requirements.

[0052] Among them, the feeding mechanism 19 can adopt a screw slider mechanism, the two ends of the screw of the screw slider mechanism are installed on the base plate 8 through supports, the slider of the screw slider mechanism is connected to the slide plate 16, the slider cooperates with the screw, when the screw rotates, the slider can drive the slider to move along the axial direction of the screw, and the moving direction of the slider can be adjusted by adjusting the rotation direction of the screw to achieve feeding or retreat.

[0053] The mold 1 is mounted on the bottom plate 8 and cooperates with the translation mechanism 6 and the feed sliding mechanism on the slide plate 16 to complete the processing task. It ensures that the movement of the slide plate 16 in different directions does not interfere with each other, improves the stability and reliability of the system, makes the entire mechanical structure more compact and reasonable, and improves the processing efficiency and accuracy.

[0054] The grinding tool 1 is selected according to the polishing knife 2 to be sharpened. The grinding tool 1 is driven by a corresponding rotating element, and the rotating element can be a motor, a stepping motor, etc. In this embodiment, a grinding wheel can be used. The grinding wheel is one of the most common grinding tools, which is made of abrasives and binders, has different particle sizes, hardnesses and shapes, and is suitable for grinding various materials. When sharpening a tool such as a polishing knife 2, a diamond grinding wheel or a CBN (cubic boron nitride) grinding wheel is often used, which has high hardness and wear resistance and can maintain sharpness for a long time.

[0055] The grinding tool 1 can also be a sanding belt. Sanding belt grinding is an efficient and flexible grinding method suitable for processing flat surfaces, curved surfaces and complex-shaped workpieces. Sanding belts are composed of abrasives, substrates and binders, and have a wide range of particle sizes and different material options to meet different processing requirements.

[0056] The grinding tool 1 can also be a grinding disc, which is usually used for precision machining, such as mirror polishing, etc. It uses fine-grained abrasives to perform micro-machining on the surface of the workpiece by rotating and applying pressure to achieve extremely high surface finish and flatness.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A light knife sharpening device, characterized in that: include: The guide mechanism includes an arc-shaped slide groove and an arc-shaped slider that are slidably matched. The track of the arc-shaped slide groove is in an arc shape. A clamp is provided on the arc-shaped slider. The arc-shaped slide groove is connected to the winding wheel through a traction rope. The arc-shaped slide groove is installed on the slider through a translation mechanism. The rocker assembly includes a rocker and a connecting rod. The two ends of the connecting rod are respectively hinged with rockers. The rocker is rotatably connected to the slide plate to form a double rocker mechanism with the slide plate as a frame. The connecting rod is connected to the arc-shaped slider. The connecting rod constrains the slider to keep tangential movement along the slide track. The grinding tool is facing the clamping part of the clamp and is used for sharpening the light knife on the clamping part.

2. The optical knife sharpening device according to claim 1, characterized in that: The arc-shaped slide groove includes a support plate and guide plates that are relatively spaced apart. Two guide plates are connected to the support plate to form a groove body that accommodates the arc-shaped slider. The arc-shaped slider is located in the groove body. The support plate supports the bottom surface of the arc-shaped slider, and the side surface of the guide plate slides in a sliding fit with the side surface of the arc-shaped slider.

3. The optical knife sharpening device according to claim 2, characterized in that: The side of the guide plate that fits the arc-shaped slider is an arc surface, and the side of the guide plate away from the support plate is connected to a pressure plate, which slides and fits the top surface of the arc-shaped slider to keep the arc-shaped slider in the arc-shaped slide groove.

4. The optical knife sharpening device according to claim 1, characterized in that: The winding wheel is rotatably mounted on the slide plate, one end of the traction rope is connected to one end of the arc-shaped slide groove, and the other end of the traction rope is connected to the other end of the arc-shaped slide groove after passing around the winding wheel and the driven wheel. The winding wheel, the traction rope and the driven wheel together form a translation driving mechanism.

5. The optical knife sharpening device according to claim 4, characterized in that: The wheel axle of the winding wheel is rotatably mounted on the slide plate, and the wheel axle of the winding wheel is connected to the winding driving element.

6. The optical knife sharpening device according to claim 1, characterized in that: The rocker is mounted on the slide plate via a rotating seat, and the connecting rod is fixed to the arc-shaped slide block via a connecting seat, so that the connecting rod moves along the arc slide groove following the slide block.

7. The optical knife sharpening device according to claim 6, characterized in that: The slide plate is provided with a limiter, and the limiters are respectively arranged at the starting point and the end point of the rocker operation track to abut against the rocker.

8. The optical knife sharpening device according to claim 1, characterized in that: The translation mechanism comprises a translation slider and a translation rail that match each other, and the translation rail is distributed along the length direction of the light knife grinding.

9. The optical knife sharpening device according to claim 8, characterized in that: The slide plate is installed on the bottom plate through a feed sliding mechanism. The feed sliding mechanism includes a matching feed sliding block and a feed slide rail. The bottom plate is installed with a feed mechanism, which drives the slide plate to move relative to the bottom plate along the feed slide rail direction.

10. The optical knife sharpening device according to claim 9, characterized in that: The distribution directions of the feed slide rail and the translation slide rail are vertical in space, and the mold is installed on the bottom plate.

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