Electric mechanical clamping jaw
By using electric mechanical jaws in the clamp and using the electric spindle assembly and driving mechanism to achieve electric drive, the existing mechanical jaws are solved, and the service life and effect are improved.
Patent Information
- Application Number
- CN202421668666.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-15
- Publication Date
- 2025-04-22
- Estimated Expiration
- 2034-07-15
AI Technical Summary
The existing two-finger mechanical jaws are prone to leak air or liquid due to wear during long-term use, which affects the service life and effect of the clamp.
Electric mechanical jaws are used to realize electric drive through the combination of electric spindle assembly, driving mechanism, connecting screw, wedge block and slider to avoid pneumatic or hydraulic air or liquid leakage problems.
It realizes reliable electric drive of the jaws, extends the service life, and improves the use effect and reliability of the gripper.
Smart Images
Figure CN222779615U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of clampers, in particular to an electric mechanical clamp. Background Art
[0002] A gripper is a device that holds an object and manipulates it. It can clamp and release the object while performing certain actions. In a typical robotic processing process, the workpieces must be clamped, positioned, sorted and transported by a gripper. At present, the gripper is generally installed at the end of a robotic arm as a grasping tool. The object is grasped and clamped by the gripper, and then transferred from the initial position to the target position or other operations are performed as needed. The two-finger mechanical grippers in the prior art are mostly pneumatically or hydraulically driven. During long-term use, it is difficult to avoid air or liquid leakage due to wear, which affects the service life and use effect of the gripper. Therefore, a device to solve the above problems is needed. Utility Model Content
[0003] In order to solve the problem that two-finger mechanical grippers in the prior art are mostly pneumatically or hydraulically driven, and it is difficult to avoid air or liquid leakage due to wear during long-term use, which affects the service life and use effect of the gripper, an electric mechanical gripper is invented.
[0004] The technical solution of the utility model is to include an upper shell body, wherein the upper shell body is connected with a lower shell body, a lower mounting groove is provided in the lower shell body, an electric spindle assembly is connected in the lower mounting groove, a middle mounting groove connected with the lower mounting groove is provided in the lower shell body, an upper mounting groove connected with the middle mounting groove is provided in the upper shell body, a driving mechanism is provided in the middle mounting groove and the upper mounting groove, a rotating shaft of the electric spindle assembly extends into the middle mounting groove and is connected with the driving mechanism, a connecting screw is threadedly connected with the driving mechanism in the upper mounting groove, the connecting screw is connected with a wedge block, a sliding groove connected with the upper mounting groove is provided in the upper shell body, the wedge block is arranged in the sliding groove, a pair of sliding blocks for connecting clamping claws are movably connected in the sliding groove, and the ends of the two sliding blocks approaching each other are slidably connected with the wedge block, forming a structure in which the wedge block moves up and down to drive the two sliding blocks to slide in the sliding groove.
[0005] Preferably, the driving mechanism includes, from top to bottom, an upper ball bearing, a transmission trapezoidal nut, an upper bearing washer, an upper needle bearing, a lower needle bearing, a lower bearing washer, a thrust bearing pressure ring, a coupling, and a lower ball bearing, the upper ball bearing is interference-connected in the upper mounting groove, one end of the transmission trapezoidal nut is interference-connected in the upper ball bearing, a limiting ring is extended when viewed from the outer end surface of the transmission trapezoidal nut, an upper needle bearing and a lower needle bearing are respectively provided on the upper and lower sides of the limiting ring, the upper bearing washer is arranged between the upper ball bearing and the upper needle bearing, the thrust bearing pressure ring is arranged below the lower needle bearing, and the lower The bearing washer is arranged between the thrust bearing pressure ring and the lower needle bearing, the lower ball bearing is interference connected in the middle mounting groove, the coupling is interference connected in the lower ball bearing, the end face of the coupling close to the electric spindle assembly is provided with a non-circular plug-in hole, the rotating shaft of the electric spindle assembly is non-circular and plugged into the plug-in hole, the end of the coupling close to the transmission trapezoidal nut is provided with a plurality of connecting holes, the end of the transmission trapezoidal nut close to the coupling is extended with a plurality of connecting blocks, the connecting blocks are plugged into the connecting holes, the axis of the transmission trapezoidal nut is provided with a transmission threaded hole, and the connecting screw is threadedly connected in the transmission threaded hole.
[0006] Preferably, wedge-shaped grooves are formed at the adjacent ends of the two sliding blocks, and the two ends of the wedge block are respectively slidably connected in the wedge-shaped grooves on the two sliding blocks.
[0007] Preferably, guide grooves are provided on the two inner side walls of the sliding groove, and guide strips are extended from the two side end faces of the two sliding blocks. The guide strips are slidably connected in the guide grooves, and the vertical sections of the guide strips and the guide grooves are both isosceles trapezoids. The angles between the side end faces of the guide grooves and the side end faces of the sliding grooves, and between the side end faces of the guide strips and the side end faces of the left sliding block or the right sliding block are 20°.
[0008] Preferably, an upper cover plate is connected to the end surface of the upper shell away from the lower shell.
[0009] Preferably, a lower cover plate is connected to the end surface of the lower shell away from the upper shell and corresponding to the lower mounting groove.
[0010] Preferably, one side of the lower housing is connected to an electric control housing, an electric control installation slot is provided in the electric control housing, and an electric control module assembly electrically connected to the electric spindle assembly is provided in the electric control installation slot.
[0011] Preferably, the lower shell is connected to a position sensor receiving module extending into the upper shell, the slider is mounted with a position sensor transmitting module, and the position sensor receiving module and the position sensor transmitting module are electrically connected to the electronic control module assembly.
[0012] The following beneficial effects can be achieved by adopting the technical scheme of the utility model: (1) the electric spindle assembly is powered on and operated by means of the electric spindle assembly, the driving mechanism, the connecting screw, the wedge block and the slider, and the driving mechanism rotates, the connecting screw is driven to move, and then the wedge block is driven to move along the length direction of the upper mounting groove, and then the two sliders are driven to move in the sliding groove in a direction perpendicular to the wedge block, so that the clamping claws connected to the two sliders can clamp or release objects; (2) the sliding of the slider in the sliding groove can be limited by means of the guide groove and the guide strip; (3) the sliding position of the slider in the sliding groove can be detected by means of the electric control module assembly, the position sensor receiving module and the position sensor transmitting module, and then the electric control module assembly can be used to control whether the electric spindle assembly is powered on and whether it rotates clockwise or counterclockwise; the technical scheme of the utility model has broad application prospects in the field of clamp technology. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 It is a cross-sectional view of the electric mechanical clamp of the utility model.
[0014] Figure 2 for Figure 1 Enlarged view of point A in the middle.
[0015] Figure 3 This is a diagram showing the matching structure of the transmission trapezoidal nut and the coupling of the electric mechanical clamp of the utility model.
[0016] Among them, 1. lower housing, 2. electric spindle assembly, 3. lower cover, 4. electric control housing, 5. electric control mounting groove, 6. upper housing, 7. upper mounting groove, 8. coupling, 9. plug-in hole, 10. lower ball bearing, 11. thrust bearing pressure ring, 12. lower bearing gasket, 13. lower needle bearing, 14. transmission trapezoidal nut, 15. connecting hole, 16. connecting block, 17. limiting ring, 18. upper bearing gasket, 19. upper needle bearing, 20. upper ball bearing, 21. transmission threaded hole, 22. connecting screw, 23. wedge block, 24. sliding groove, 25. slider, 26. wedge groove, 27. limiting pin, 28. limiting groove, 29. position sensor receiving module, 30. upper cover, 31. lower mounting groove, 32. middle mounting groove. DETAILED DESCRIPTION
[0017] The following will clearly and completely describe the technical solutions of various embodiments of the utility model in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the utility model. In the description of the utility model, it should be noted that the orientation or position relationship indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the utility model.
[0018] In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In the description of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.
[0019] like Figure 1-3 The electric mechanical clamp shown includes an upper shell 6, and a lower shell 1 is detachably fixedly connected to the upper shell 6 by bolts, so that the upper shell 6 is connected to the lower shell 1. A lower mounting groove 31 is provided in the lower shell 1, and an electric spindle assembly 2 is detachably fixedly connected to the lower mounting groove 31 by bolts, so that the electric spindle assembly 2 is isolated from the outside world through the lower shell 1, and then the electric spindle assembly 2 is powered on to provide power for the pick-up and placement of the clamp. The electric spindle assembly 2 includes a drive spindle and a reducer. The drive spindle is a common forward and reverse bidirectional electric spindle on the market, so that the electric spindle assembly 2 provides power for the pick-up and placement of the clamp. The lower shell 1 is detachably fixedly connected to the lower cover plate 3 at the end surface away from the upper shell 6 and corresponding to the lower mounting groove 31 by bolts, so that the opening of the lower mounting groove 31 is blocked by the lower cover plate 3 to prevent external dust and other debris from entering the lower mounting groove 31 and affecting the normal operation of the electric spindle assembly 2, while facilitating the maintenance of the electric spindle assembly 2 in the lower mounting groove 31.
[0020] like Figure 1-3The electric mechanical clamp shown in the figure has a middle installation groove 32 connected to the lower installation groove 31 in the lower housing 1, and an upper installation groove 7 connected to the middle installation groove 32 in the upper housing 6. A driving mechanism is arranged in the middle installation groove 32 and the upper installation groove 7. The rotating shaft of the electric spindle assembly 2 extends into the middle installation groove 32 and is connected to the driving mechanism. The driving mechanism is threadedly connected with a connecting screw 22 in the upper installation groove 7, so that the output shaft of the spindle assembly drives the driving mechanism to rotate, and then the connecting screw 22 is moved axially along the upper installation groove 7 through the driving mechanism and the connecting screw 22 of the lead screw structure. .
[0021] like Figure 1-3The electric mechanical clamp shown in the figure has a driving mechanism which includes, from top to bottom, an upper ball bearing 20, a transmission trapezoidal nut 14, an upper bearing washer 18, an upper needle bearing 19, a lower needle bearing 13, a lower bearing washer 12, a thrust bearing pressure ring 11, a coupling 8, and a lower ball bearing 10. The upper ball bearing 20 is interference-connected in the upper mounting groove 7, and one end of the transmission trapezoidal nut 14 is interference-connected in the upper ball bearing 20, so that the transmission trapezoidal nut 14 is connected to the upper shell 6 through the upper ball bearing 20 without affecting the rotation of the transmission trapezoidal nut 14 relative to the upper shell 6. In addition, the upper ball bearing 20 can also reduce the friction between the transmission trapezoidal nut 14 and the upper mounting groove 7 when rotating, thereby avoiding wear. The outer end face of the transmission trapezoidal nut 14 extends with a limit ring 17, and the upper and lower sides of the limit ring 17 are respectively provided with an upper needle bearing 19 and a lower needle bearing 13, so that the friction force of the transmission trapezoidal nut 14 during rotation is reduced by the upper needle bearing 19 and the lower needle bearing 13, and the transmission trapezoidal nut 14 can be limited to avoid the transmission trapezoidal nut 14 from being deflected during rotation. The upper bearing washer 18 is arranged between the upper ball bearing 20 and the upper needle bearing 19, and the upper ball bearing 20 and the upper needle bearing 19 are isolated by the upper bearing washer 18, so as to reduce vibration transmission and wear. The thrust bearing pressure ring 11 is arranged below the lower needle bearing 13, so that the lower needle bearing 13 is limited by the thrust bearing pressure ring 11, so as to avoid the upper bearing washer 18, the upper needle bearing 19, the lower needle bearing 13, and the lower bearing washer 12 from axially moving in the upper mounting groove 7. The lower bearing washer 12 is arranged between the thrust bearing ring 11 and the lower needle bearing 13, so that the thrust bearing ring 11 is isolated from the lower needle bearing 13 by the lower bearing washer 12, and the lower needle bearing 13 and the thrust bearing ring 11 are prevented from directly contacting each other and causing wear. The lower ball bearing 10 is interference-connected in the middle mounting groove 32, and the coupling 8 is interference-connected in the lower ball bearing 10, so that the coupling 8 is connected to the lower housing 1 through the lower ball bearing 10, and the rotation of the coupling 8 relative to the lower housing 1 is not affected, and the friction between the rotation of the coupling 8 and the lower housing 1 is reduced by the lower ball bearing 10. The coupling 8 has a non-circular plug hole 9 at the end face close to the electric spindle assembly 2. The rotating shaft of the electric spindle assembly 2 is non-circular and plugged into the plug hole 9, so that when the electric spindle assembly 2 is powered on, the rotating shaft rotates to drive the coupling 8 to rotate. At the same time, the non-circular plug hole 9 and the non-circular rotating shaft are used to prevent the rotating shaft and the coupling 8 from slipping, which affects the rotating shaft driving the coupling 8 to rotate together. The coupling 8 has a plurality of connecting holes 15 at one end close to the transmission trapezoidal nut 14. The transmission trapezoidal nut 14 has a plurality of connecting blocks 16 extending from one end close to the coupling 8. The connecting blocks 16 are plugged into the connecting holes 15, so that the coupling 8 and the transmission trapezoidal nut 14 are connected together by plugging the connecting blocks 16 into the connecting holes 15, and then the transmission trapezoidal nut 14 is driven to rotate simultaneously by the rotation of the coupling 8.A transmission threaded hole 21 is opened at the axis of the transmission trapezoidal nut 14, and the connecting screw 22 is threadedly connected in the transmission threaded hole 21, so that the transmission trapezoidal nut 14 and the connecting screw 22 form a screw structure, and then the transmission trapezoidal nut 14 rotates to drive the connecting screw 22 to move along the axial direction.
[0022] like Figure 1-3 In the electric mechanical clamp shown, the connecting screw 22 is welded or detachably fixedly connected with a wedge block 23 by bolts, so that the connecting screw 22 and the wedge block 23 are connected together to achieve simultaneous movement. At the same time, the connecting screw 22 is limited by the wedge block 23 to prevent the connecting screw 22 from rotating relative to the upper housing 6, thereby forming a screw structure between the connecting screw 22 and the transmission trapezoidal nut 14. A sliding groove 24 is provided in the upper housing 6, which is vertical and connected to the upper mounting groove 7. The wedge block 23 is arranged in the sliding groove 24, so that the connecting screw 22 is driven to move by the rotation of the driving mechanism, thereby driving the wedge block 23 to move in the sliding groove 24 along the axial direction. A pair of sliders 25 for connecting the clamping jaws are movably connected in the sliding groove 24. The two sliders 25 are slidably connected to the wedge block 23 at the ends that are close to each other, so that the wedge block 23 moves up and down to drive the two sliders 25 to slide in the sliding groove 24. Specifically, wedge grooves 26 are provided at the ends of the two sliders 25 that are close to each other, and the two ends of the wedge block 23 are respectively slidably connected in the wedge grooves 26 on the two sliders 25, so that the wedge block 23 can move axially along the upper mounting groove 7 by utilizing the cooperation of the wedge groove 26 and the wedge block 23 to realize the sliding of the two sliders 25 in the sliding groove 24, thereby adjusting the opening and closing of the clamping jaws connected to the two sliders 25.
[0023] like Figure 1-3 The electric mechanical clamp shown in the figure has guide grooves on the two inner side walls of the sliding groove 24, and guide bars are extended on the two side end faces of the two sliders 25, and the guide bars are slidably connected in the guide grooves, so that the movement of the slider 25 in the sliding groove 24 is limited by the guide bars and the guide grooves, so that the slider 25 can move along the length direction of the guide bars and the guide grooves, and avoid the slider 25 from moving randomly in the sliding groove 24, which affects the movement of the slider 25 driven by the wedge block 23. The vertical sections of the guide bars and the guide grooves are both isosceles trapezoids, and the angles between the side end faces of the guide grooves and the side end faces of the sliding grooves 24, and between the side end faces of the guide bars and the side end faces of the sliders 25 are 20°, which is convenient for the slider 25 to slide in the sliding grooves 24, and convenient for processing, and reduces processing costs. The end surface of the upper shell 6 away from the lower shell 1 is detachably fixedly connected to the upper cover plate 30 by bolts, so that the movement of the wedge block 23 is limited by the upper cover plate 30 to prevent the wedge block 23 from escaping from the sliding groove 24. At the same time, the moving space of the wedge block 23 is sealed by the upper cover 30 to prevent foreign objects from entering the moving space of the wedge block 23 and affecting the sliding.
[0024] like Figure 1-3The electric mechanical clamp shown in the figure has a limit pin 27 detachably fixedly connected to the lower shell 1 by bolts, and a limit slot 28 is provided on the slider 25. One end of the limit pin 27 passes through the upper shell 6 and extends into the limit slot 28, so that the movement distance of the slider 25 in the sliding slot 24 is limited by the cooperation of the limit pin 27 and the limit slot 28, thereby preventing the slider 25 and the wedge block 23 from detaching from the sliding slot 24.
[0025] like Figure 1-3 In the electric mechanical gripper shown, an electric control housing 4 is detachably connected to one side of the lower housing 1 by bolts, so that the electric control housing 4 is connected to the lower housing 1. An electric control installation slot 5 is provided in the electric control housing 4, and an electric control module assembly electrically connected to the electric spindle assembly 2 is provided in the electric control installation slot 5. The electric control module assembly is a common single-chip control circuit board module on the market, so that the electric control module assembly controls whether the electric spindle assembly 2 is powered on and rotates clockwise or counterclockwise. A position sensor receiving module 29 extending into the upper shell 6 is detachably fixedly connected to the lower shell 1 by bolts, and a position sensor transmitting module is installed on the slider 25 corresponding to the position sensor receiving module 29. The position sensor receiving module 29 and the position sensor transmitting module are electrically connected to the electronic control module assembly. The position sensor receiving module 29 and the position sensor transmitting module are both common position detection modules on the market, so that the position of the slider 25 in the sliding groove 24 is monitored by the position sensor receiving module 29 and the position sensor transmitting module, and the signal is then transmitted to the electronic control module assembly. The electronic control module assembly receives and processes the signal, and then controls the working state of the electric spindle assembly 2.
[0026] Unless otherwise specified, the device elements involved in the above embodiments are all conventional device elements, and the structural settings, working modes or control modes involved are all conventional settings, working modes or control modes in the art unless otherwise specified.
[0027] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.
Claims
1. An electric mechanical gripper, comprising an upper housing (6), characterized in that: The upper shell (6) is connected to a lower shell (1); a lower mounting groove (31) is provided in the lower shell (1); an electric spindle assembly (2) is connected in the lower mounting groove (31); a middle mounting groove (32) communicating with the lower mounting groove (31) is provided in the lower shell (1); an upper mounting groove (7) communicating with the middle mounting groove (32) is provided in the upper shell (6); a driving mechanism is provided in the middle mounting groove (32) and the upper mounting groove (7); a rotating shaft of the electric spindle assembly (2) extends into the middle mounting groove (32) and is connected to the driving mechanism; the driving mechanism A connecting screw (22) is connected to the inner thread of the upper mounting groove (7), and the connecting screw (22) is connected to a wedge block (23). A sliding groove (24) connected to the upper mounting groove (7) is provided in the upper shell (6), and the wedge block (23) is arranged in the sliding groove (24). A pair of sliders (25) for connecting the clamping claws are movably connected in the sliding groove (24), and the two sliders (25) are slidably connected to the wedge block (23) at their ends close to each other, so that the wedge block (23) moves up and down to drive the two sliders (25) to slide in the sliding groove (24).
2. The electric mechanical gripper according to claim 1, characterized in that: The driving mechanism comprises, from top to bottom, an upper ball bearing (20), a transmission trapezoidal nut (14), an upper bearing washer (18), an upper needle bearing (19), a lower needle bearing (13), a lower bearing washer (12), a thrust bearing pressure ring (11), a coupling (8), and a lower ball bearing (10); the upper ball bearing (20) is interference-connected in the upper mounting groove (7); one end of the transmission trapezoidal nut (14) is interference-connected in the upper ball bearing (20); a limiting ring (17) extends from the outer end surface of the transmission trapezoidal nut (14); an upper needle bearing (19) and a lower needle bearing (13) are respectively provided on the upper and lower sides of the limiting ring (17); the upper bearing washer (18) is arranged between the upper ball bearing (20) and the upper needle bearing (19); the thrust bearing pressure ring (11) is arranged below the lower needle bearing (13); and the lower shaft A bearing washer (12) is arranged between the thrust bearing pressure ring (11) and the lower needle bearing (13); the lower ball bearing (10) is interference-connected in the middle mounting groove (32); the coupling (8) is interference-connected in the lower ball bearing (10); a non-circular plug-in hole (9) is provided on the end surface of the coupling (8) close to the electric spindle assembly (2); the rotating shaft of the electric spindle assembly (2) is non-circular and plugged into the plug-in hole (9); a plurality of connecting holes (15) are provided on one end of the coupling (8) close to the transmission trapezoidal nut (14); a plurality of connecting blocks (16) extend from one end of the transmission trapezoidal nut (14) close to the coupling (8); the connecting blocks (16) are plugged into the connecting holes (15); a transmission threaded hole (21) is provided on the axis of the transmission trapezoidal nut (14); and the connecting screw (22) is threadedly connected in the transmission threaded hole (21).
3. The electric mechanical gripper according to claim 1, characterized in that: The adjacent ends of the two sliders (25) are provided with wedge-shaped grooves (26), and the two ends of the wedge-shaped block (23) are respectively slidably connected in the wedge-shaped grooves (26) on the two sliders (25).
4. The electric mechanical gripper according to claim 1, characterized in that: The two inner side walls of the sliding groove (24) are provided with guide grooves, and the two side end surfaces of the two sliding blocks (25) are extended with guide strips, and the guide strips are slidably connected in the guide grooves. The vertical sections of the guide strips and the guide grooves are both isosceles trapezoids, and the angles between the side end surfaces of the guide grooves and the side end surfaces of the sliding grooves (24), and between the side end surfaces of the guide strips and the side end surfaces of the left sliding block (25) or the right sliding block (25) are 20 degrees.
5. The electric mechanical gripper according to claim 1, characterized in that: An upper cover plate (30) is connected to the end surface of the upper shell (6) away from the lower shell (1).
6. The electric mechanical gripper according to claim 1, characterized in that: A lower cover plate (3) is connected to the end surface of the lower shell (1) away from the upper shell (6) and at a position corresponding to the lower mounting groove (31).
7. The electric mechanical gripper according to claim 1, characterized in that: An electric control housing (4) is connected to one side of the lower housing (1), an electric control installation slot (5) is provided in the electric control housing (4), and an electric control module assembly electrically connected to the electric spindle assembly (2) is provided in the electric control installation slot (5).
8. The electric mechanical gripper according to claim 7, characterized in that: The lower housing (1) is connected to a position sensor receiving module (29) extending into the upper housing (6), the slider (25) is mounted with a position sensor transmitting module, and the position sensor receiving module (29) and the position sensor transmitting module are electrically connected to the electronic control module assembly.
9. The electric mechanical gripper according to claim 1, characterized in that: The lower shell (1) is connected to a limit pin (27), the slider (25) is provided with a limit slot (28), and one end of the limit pin (27) passes through the upper shell (6) and extends into the limit slot (28).