Modular rack

The modular material rack design solves the problem of low material handling flexibility of robotic arms, enabling flexible clamping and transfer of multiple materials, and improving the versatility and loading efficiency of processing machine tools.

CN224310221UActive Publication Date: 2026-06-02LANGKUAI INTELLIGENT TECH (HANGZHOU) CO LTD

Patent Information

Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
LANGKUAI INTELLIGENT TECH (HANGZHOU) CO LTD
Filing Date
2025-02-20
Publication Date
2026-06-02

AI Technical Summary

Technical Problem

In existing technologies, robotic arms can only pick up materials from the material box one by one, resulting in low flexibility in material picking operations and making it difficult to clamp and flexibly transfer multiple materials.

Method used

A modular material rack was designed, including a base, a frame, and an adapter connector. The frame has a material clamp on the side. The base and the clamp cooperate to achieve standardized adaptation. The adapter connector is standardized to adapt to the transfer equipment. Multiple materials can be clamped and positioned through the material clamp. Combined with the clamping column and the orientation block, the orientation accuracy during the transfer process is ensured.

Benefits of technology

It enables flexible clamping and transfer of multiple materials, improves the versatility of machine tools and the flexibility of loading operations, and enhances the efficiency of cooperation with fixtures and transfer equipment.

✦ Generated by Eureka AI based on patent content.

Smart Images

  • Figure CN224310221U_ABST
    Figure CN224310221U_ABST
Patent Text Reader

Abstract

The utility model relates to the field of machine tool, specifically disclose a modular material rack. The modular material rack includes base, frame body and adaptation joint, the frame body be columnar, the lower extreme of frame body is fixedly connected with base, and the upper end is fixedly connected with adaptation joint, the base be equipped with clamping positioning unit, and the side surface distribution of frame body has a plurality of material clamps. The modular material rack can realize the clamping of multiple materials, and can cooperate with the matched clamp and transfer equipment well, has good flexibility.
Need to check novelty before this filing date? Find Prior Art

Description

Technical Field

[0001] This utility model relates to the field of machine tools, and in particular to a modular material rack. Background Technology

[0002] With the gradual increase in labor costs, automation of production and processing is an inevitable trend. In the process of realizing automated processing, the automation technology of processing equipment has become increasingly mature. The applicant's earlier Chinese invention patent application with publication number CN 115026622A discloses a general-purpose automated processing system for complex parts, which can automatically complete the loading, processing and unloading operations of products, and has the advantage of a high degree of automation.

[0003] However, in the aforementioned application, the products are transferred in the form of material boxes, and the robotic arm takes the materials one by one from the material boxes and sends them directly into the processing module. The robotic arm can only perform material picking and transfer operations one by one from the material boxes, which results in low flexibility in the material picking operation. Summary of the Invention

[0004] The technical problem to be solved by this utility model is to provide a modular material rack that can clamp multiple materials and can work well with matching fixtures and transfer equipment, thus having great flexibility.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a modular material rack, including a base, a frame and an adapter, wherein the frame is columnar, the lower end of the frame is fixedly connected to the base and the upper end is fixedly connected to the adapter; the base is provided with a clamping and positioning unit, and a plurality of material clamps are distributed on the side of the frame.

[0006] The base can be standardized to fit with matching fixtures, and the adapter connectors can be standardized to fit with matching transfer equipment. The frame can directly clamp and position the materials to be processed through material clamps. For different types and specifications of materials, standardized feeding and loading operations can be achieved by reasonably setting up material clamps, further improving the versatility of the machine tool.

[0007] Preferably, the frame is prismatic in shape, and each side of the frame is provided with a material clamp.

[0008] Preferably, each of the aforementioned material clamps includes a fixed clamping block and a movable clamping block, which are arranged sequentially, one above the other.

[0009] Preferably, the fixed clamping block and the movable clamping block on at least one side of the frame are positioned vertically opposite each other, and the fixed clamping block and the movable clamping block on at least one side of the frame are positioned horizontally opposite each other.

[0010] The quantity and type of materials to be gripped can be set according to requirements to achieve gripping in different directions and sizes.

[0011] Preferably, the adapter chuck includes a clamping column and two orientation blocks, and the clamping assembly is located between the two orientation blocks.

[0012] The clamping column head is used to connect and clamp with the matching transfer equipment, and the orientation block is used to cooperate with the matching transfer equipment to achieve circumferential positioning, thereby accurately controlling the orientation of the modular material rack during the transfer process.

[0013] Preferably, the adapter chuck includes a guide seat, and the clamping column and the orientation block are both disposed on the upper surface of the guide seat, wherein the upper surface of the guide seat is an inclined surface or a curved surface.

[0014] The inclined or curved guide seat can guide the connection and cooperation between the clamping component and the matching transfer equipment.

[0015] Preferably, the clamping and positioning unit includes a limiting hole or a limiting pin disposed on the base. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a compact production line suitable for mass production in this embodiment;

[0017] Figure 2 This is a schematic diagram of the hopper module in a compact production line suitable for mass production in this embodiment;

[0018] Figure 3 This is a top view of the hopper module in a compact production line suitable for mass production in this embodiment;

[0019] Figure 4 This is a side view of the hopper module in a compact production line suitable for mass production in this embodiment;

[0020] Figure 5 This is a partial structural diagram of the hopper module in a compact production line suitable for mass production in this embodiment. At this time, the modular rack is in a transition position.

[0021] Figure 6 This is a partial structural diagram of the hopper module in a compact production line suitable for mass production in this embodiment. At this time, the modular material rack is in the operating position.

[0022] Figure 7 This is a schematic diagram of the modular material rack structure in a compact production line suitable for mass production, as described in this embodiment.

[0023] Figure 8This is a schematic diagram of the modular rack holding materials in a compact production line suitable for mass production, as described in this embodiment.

[0024] Figure 9 This is a structural schematic diagram from another perspective of the material clamping state of the modular rack in a compact production line applicable to mass production in this embodiment;

[0025] Figure 10 This is a schematic diagram of the material storage component in a compact production line suitable for mass production in this embodiment. The chuck is in the second position at this time.

[0026] Figure 11 This is a schematic diagram of the locking mechanism in a compact production line suitable for mass production in this embodiment. The chuck is in the second position at this time.

[0027] Figure 12 This is a schematic diagram of the material storage component in a compact production line suitable for mass production in this embodiment. The chuck is in the first position at this time.

[0028] Figure 13 This is a schematic diagram of the locking mechanism in a compact production line suitable for mass production in this embodiment. The chuck is in the first position at this time.

[0029] Figure 14 This is a schematic diagram of the structure of the lifting component and the modular rack in a compact production line suitable for mass production in this embodiment;

[0030] Figure 15 This is a partial lateral schematic diagram of the cooperation between the lifting component and the modular rack in a compact production line suitable for mass production in this embodiment;

[0031] Figure 16 This is a schematic diagram of the feeding module in a compact production line suitable for mass production in this embodiment;

[0032] Figure 17 This is a side view of the feeding module in a compact production line suitable for mass production in this embodiment;

[0033] Figure 18 This is a partial schematic diagram of the feeding module in a compact production line suitable for mass production in this embodiment;

[0034] Figure 19 This is a schematic diagram of the processing module in a compact production line suitable for mass production, as described in this embodiment.

[0035] Figure 20 This is a structural schematic diagram from another perspective of the processing module in a compact production line suitable for mass production in this embodiment;

[0036] Figure 21 This is a schematic diagram of the machining fixture in a compact production line suitable for mass production, as described in this embodiment.

[0037] Figure 22 This is a schematic diagram of the structure of the machining components and tool magazine in a compact production line suitable for mass production in this embodiment;

[0038] Figure 23 This is a side view of the machining components and tool magazine in a compact production line suitable for mass production in this embodiment;

[0039] Figure 24 This is a schematic diagram of the structure of the processing components in a compact production line suitable for mass production in this embodiment;

[0040] Figure 25 This is a schematic diagram of the tool magazine and tool changing assembly working together in a compact production line suitable for mass production in this embodiment. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model. Example

[0042] like Figure 1 As shown, a compact production line suitable for mass production includes a hopper module 1, a feeding module 2, and a processing module 3.

[0043] like Figures 2-4 As shown, the silo module 1 includes a storage support 11, which is provided with a loading station 111, an operating station 112 and a transition station 113. The operating station 112 is located on one side of the transition station 113.

[0044] like Figures 2-6 As shown, the silo module 1 further includes a feeding device 12 mounted on the storage support 11. The feeding device 12 includes a feeding conveyor assembly and several material temporary storage assemblies 16. The feeding conveyor assembly drives the material temporary storage assemblies 16 to move between the loading station 111 and the transition station 113. The feeding conveyor assembly includes a circular conveyor chain, with auxiliary support units on both sides of the conveyor chain. Each auxiliary support unit includes a support plate. The feeding conveyor assembly drives the material temporary storage assemblies 16 to move, thereby achieving automated feeding.

[0045] like Figures 10-13As shown, the material storage assembly 16 includes a mounting plate 161 and a locking unit. The mounting plate 161 is provided with a material limiting unit 1611, and the mounting plate 161 is connected to the feeding and conveying assembly through the locking unit. During processing, the material is placed on the material storage assembly 16 and limited by the material limiting unit 1611.

[0046] like Figures 10-13 As shown, specifically, the locking unit includes a locking seat 1621, a locking element 162, and a locking block 1613. The locking seat 1621 is connected to the feeding and conveying assembly, and the locking block 1613 is disposed at the bottom of the mounting plate 161.

[0047] like Figures 10-13 As shown, the upper surface of the locking seat 1621 is provided with a sliding groove 1622, which extends to the side of the locking seat 1621. The locking member 162 includes a locking slider 1626, which is slidably disposed within the sliding groove 1622. A locking mechanism is provided between the locking slider 1626 and the locking seat 1621. Two claws 1623 are rotatably connected to the side of the locking slider 1626 corresponding to the opening of the sliding groove 1622. The two claws 1623 are arranged opposite each other, and an expansion elastic member 1624 is provided between the claws 1623 and the locking slider 1626. A clamping groove 1625 is formed on the inner side of the two claws 1623, which corresponds to the clamping block 1613. The claws 1623 have at least two position states: in the first position state, the two claws 1623 extend out of the slide groove 1622 and expand to both sides under the elastic force of the expansion elastic member 1624; in the second position state, the two claws 1623 are at least partially inserted into the slide groove 1622 and approach each other under the guidance and constraint of the slide groove 1622.

[0048] Operating station 112 is used by operators to operate the modular material rack 14, such as replacing the modular material rack 14 and adjusting the material clamping status. Transition station 113 is used for loading and unloading the modular material rack 14.

[0049] During the loading operation of the modular material rack 14, the jaws 1623 are initially in the first position. The mounting plate 161 is initially located at the operating station 112, and the corresponding locking unit is located at the transition station 113. The modular material rack 14 is connected to the mounting plate 161 via the clamping and positioning unit 145 and the material limiting unit 1611. A horizontal thrust is then applied to the mounting plate 161, driving it towards the locking unit. When the locking block 1613 enters between the two jaws 1623 and contacts the locking slider 1626, it pushes the locking slider 1626 to slide until the jaws 1623 enter the second position. The two jaws 1623 lock the locking block 1613, achieving a horizontal connection between the mounting plate 161 and the locking unit. The mounting plate 161 can then move between the transition station 113 and the loading station 111 under the drive of the feeding and conveying assembly.

[0050] When the modular rack 14 is removed, a reverse horizontal force is applied to the mounting plate 161 located at the transition station 113. The mounting plate 161 and the modular rack 14 move horizontally, the chuck 1623 returns to the first position, the mounting plate 161 is unlocked from the locking unit, and the mounting plate 161 and the modular rack 14 can move smoothly to the operating station 112.

[0051] like Figures 7-9 As shown, the hopper module 1 further includes a modular material rack 14, which includes a base 144, a frame 142, and an adapter 141. The frame 142 is columnar, with its lower end fixedly connected to the base 144 and its upper end fixedly connected to the adapter 141. The base 144 is equipped with a clamping and positioning unit 145, and several material clamps 143 are distributed on the side of the frame 142. The adapter 141 matches the feeding clamps. The modular material rack 14 is detachably connected to the mounting plate 161 via the clamping and positioning unit 145 and the material limiting unit 1611.

[0052] like Figures 7-9 As shown, specifically, the frame 142 is prismatic in shape, and each side of the frame 142 is provided with a material clamp 143, which can be reasonably set to clamp the quantity of materials as needed. Each material clamp 143 includes a fixed clamping block and a movable clamping block, which are arranged vertically. As a specific embodiment, the fixed clamping block and the movable clamping block on at least one side of the frame are vertically opposite each other, and the fixed clamping block and the movable clamping block on at least one side of the frame are horizontally opposite each other.

[0053] Specifically, the adapter chuck includes a clamping column and two directional blocks, with the clamping assembly located between the two directional blocks. The clamping column is used to connect and clamp with the matching feeding fixture, and the directional blocks are used to cooperate with the matching transfer equipment to achieve circumferential positioning, thereby accurately controlling the orientation of the modular material rack during transfer. The adapter chuck includes a guide seat, with both the clamping column and the directional blocks disposed on the upper surface of the guide seat, which is an inclined or curved surface. The inclined or curved guide seat guides the connection and cooperation between the clamping assembly and the matching transfer equipment.

[0054] Specifically, such as Figure 9 and Figure 10 As shown, one of the clamping and positioning unit 145 and the material limiting unit 1611 is a limiting pin, and the other is a limiting hole. Specifically, the clamping and positioning unit 145 includes a limiting hole provided on the mounting plate 161, and the material limiting unit 1611 is a limiting pin provided below the base 144.

[0055] The base 144 can achieve standardized adaptation with the material storage component 16 and the processing fixture 32, the adapter 141 can achieve standardized adaptation with the loading fixture, and the frame 142 can directly clamp and position the material to be processed through the material clamp 143. For different types and specifications of materials, standardized feeding and loading operations can be achieved by reasonably setting the material clamp 143, further improving the versatility of the processing machine tool.

[0056] like Figures 14-15 As shown, the loading station 111 is further equipped with a lifting assembly 13, which includes a lifting drive unit 131 and several lifting rods 132. The lifting drive unit 131 is located below the loading station 111, and the lifting rods 132 are vertically upward. The lifting drive unit 131 is used to drive the lifting rods to move vertically up and down. The mounting plate 161 has guide holes 1612 corresponding to the lifting rods 132, while the corresponding base 144 does not have through holes.

[0057] like Figures 14-15 As shown, the storage support 11 is also provided with a lifting and limiting unit, which includes two sets of blocking members 15. The loading station 111 is located between the two sets of blocking members 15. Limiting ears are provided on both sides of the mounting plate 161. When the material storage component 16 is located at the loading station 111, the limiting ears extend into the bottom of the blocking members 15.

[0058] During the loading operation, the lifting drive unit 131 drives the lifting rod 132 to move upward. The lifting rod 132 abuts against the base 144 of the modular rack 14 and pushes the modular rack 14 upward synchronously. Because the lifting limit unit and the limit ear cooperate to prevent the mounting plate 161 from lifting, the modular rack 14 separates from the mounting plate 161. After the modular rack 14 is lifted to the preset height, the loading module 2 clamps the modular rack 14 and performs subsequent loading operations.

[0059] like Figures 16-18 As shown, the loading module 2 includes a loading robot and a shifting assembly. Specifically, the shifting assembly includes a truss 21 and a shifting drive assembly. The truss 21 is horizontally positioned above the processing modules 3, and each processing module 3 is arranged sequentially along the extension direction of the truss 21. The shifting drive assembly includes a shifting slider 23 and a shifting power component 26. The shifting slider 23 is slidably connected to the truss 21, and the shifting power component 26 is used to drive the shifting slider 23 to move.

[0060] like Figures 16-18 As shown, specifically, the loading robot includes a robotic arm 22 and a loading fixture. The robotic arm 22 is slidably connected to a shifting slider 23, and the shifting slider 23 is also provided with a loading drive component 25 for driving the robotic arm 22 to slide up and down. The loading fixture includes a chuck 24 disposed at the lower end of the robotic arm 22.

[0061] The truss 21 type shifting component, in conjunction with the robotic arm 22, can realize the three-dimensional transfer of the modular material rack 14. Compared with the transfer device in the prior art, the flexibility of loading is greatly improved, and it can be well adapted to different processing modes.

[0062] like Figures 16-18 As shown, specifically, the shifting power component 26 includes a first motor, a first transmission gear, and a first transmission rack. The first transmission rack is fixedly mounted on the truss 21 and arranged along the truss 21. The first motor and the first transmission gear are rotatably mounted on the shifting slider 23. The first transmission gear meshes with the first transmission rack, and the first motor drives the first transmission gear to rotate. The feeding drive component 25 includes a second motor, a second transmission gear, and a second transmission rack. The second transmission rack is fixedly mounted on the robotic arm 22 and arranged along the robotic arm 22. The second motor and the second transmission gear are rotatably mounted on the shifting slider 23. The second transmission gear meshes with the second transmission rack, and the second motor drives the second transmission gear to rotate.

[0063] Specifically, such as Figures 16-18As shown, the loading fixture has at least two chucks 24, which are arranged in parallel and operate independently. By setting multiple chucks 24, multiple modular racks 14 can be gripped at once, improving loading efficiency. For example, when one of the processing modules 3 finishes processing, one chuck 24 grips the unprocessed modular rack 14, while the other chuck 24 grips the completed modular rack 14 on the processing module 3. The loading and unloading operations are completed by sequentially shifting positions.

[0064] like Figure 19 and Figure 20 As shown, the processing module 3 includes a frame 31, on which processing components 33 and clamping stations are provided. The clamping stations are equipped with processing fixtures 32. There are at least two processing modules 3, each operating independently. The shifting component drives the loading robot to move between the storage support 11 and each processing module 3. The loading robot drives the loading fixture to rotate between the loading station 111 and the clamping station, or between the clamping stations of each processing module 3.

[0065] The various processing modules 3 are linked and coordinated through the feeding module 2. This multi-machine linkage improves the overall processing capacity of the machine tool. Simultaneously, the cooperation between the feeding robot and the shifting component in the feeding module 2 enables transfers between the hopper module 1 and any two of the processing modules 3. For example, it can transfer materials from the discharge module to any processing module 3, transfer materials sequentially along each processing module 3, perform jump transfers between non-adjacent processing modules 3, and transfer materials from any processing module 3 to the hopper module 1. This allows for a wider range of processing combinations, offering advantages of high efficiency and flexibility.

[0066] Specifically, such as Figure 19 and Figure 20 As shown, the machining assembly 33 is located on one side of the clamping station. The machining assembly 33 includes a power head 331 and a feed mechanism. The power head 331 includes a cutting unit and a tool feed drive unit. The cutting unit includes a cutting drive component and a tool head. The tool head is horizontally oriented towards the clamping station. The cutting drive component is used to drive the tool head to perform cutting operations, and the tool feed drive unit is used to drive the cutting unit to feed.

[0067] like Figure 24As shown, the feeding mechanism includes a transverse feed drive unit 333 and a longitudinal feed drive unit 332. The longitudinal feed drive unit 332 includes a first mounting frame 3321 and a longitudinal feed drive component 3322. The first mounting frame 3321 is vertically movably connected to the frame 31, and the longitudinal feed drive component 3322 drives the first mounting frame 3321 to move vertically. The transverse feed drive unit 333 includes a second mounting frame 3332 and a transverse feed drive component 3331. The second mounting frame 3332 is horizontally movably connected to the first mounting frame 3321, and the transverse feed drive component 3331 drives the second mounting frame 3332 to move horizontally.

[0068] like Figure 21 As shown, the machining fixture 32 includes a fixture base 322 and a rotary drive mechanism 321. The rotary drive mechanism 321 drives the fixture base 322 to rotate. The power head 331 enables the rotary drive and axial feed of the tool, while the feed mechanism enables the transverse and longitudinal feed of the power head 331. The feed mechanism and the power head 331 work together to complete the machining operation. The orientation of the material can be adjusted by the rotational movement of the fixture base 322, thereby enabling multi-angle machining operations.

[0069] Furthermore, such as Figures 22-25 As shown, the frame 31 is also equipped with a tool magazine 35 and a tool changing assembly 34, with the tool magazine 35 located above the frame 31. The tool changing assembly 34 includes a tool changing arm 342 and a tool changing drive unit 341. The tool changing arm 342 is equipped with a tool clamping unit 343, and the tool changing drive unit 341 is used to drive the tool changing arm 342 to move between the tool head and the tool magazine 35. Specifically, the tool changing arm 342 is rotatably connected to the frame 31 around a horizontal centerline, and the tool changing drive unit 341 is used to drive the tool changing arm 342 to rotate. Tool clamping units 343 are respectively provided at both ends of the tool changing arm 342. The tool magazine 35 can store tools, and tool changing can further expand the machining capabilities of the general-purpose machine tool.

[0070] A processing method employing a compact production line suitable for mass production as described above;

[0071] At least the following steps are included:

[0072] S1. Set processing mode: Set the processing mode according to the type of product 4 to be processed and the processing procedure. The setting includes adjusting the configuration of each processing module 3, assigning the processing procedure of each processing module 3, and the feeding process of the feeding module 2.

[0073] Processing modes include at least the following types:

[0074] A. Sequential processing: According to the distribution order of each processing module 3, the processing steps of the product 4 to be processed are assigned in sequence;

[0075] B. Group processing: Each processing module is divided into several processing groups, and each processing group operates independently.

[0076] S2. Loading: Loading module 2 operates to transfer the product 4 to be processed from loading station 111 to processing module 3.

[0077] S3. Processing: Each processing module 3 performs processing operations independently according to the set procedures.

[0078] S4. Unloading: Loading module 2 operates to unload the processed parts from processing module 3.

[0079] Furthermore, sequential processing patterns include at least the following two subtypes:

[0080] A1. Single clamping: After the modular material rack 14 is loaded into the processing module 3, it only sequentially rotates between the processing modules 3 and performs processing operations accordingly;

[0081] A2. Multiple clamping: After performing some processing operations, the modular rack 14 performs at least one material clamping operation. The material clamping operation includes the loading module 2 rotating the modular rack 14 to the loading station 111 and conveying it to the transition station 113 through the feeding and conveying component. After the operator moves the modular rack 14 from the transition station 113 to the operation station 112, the material clamping adjustment operation is performed, and then it is rotated to the processing module 3 to perform the next process to continue the subsequent processing operation.

[0082] Furthermore, the group processing mode includes at least the following two subtypes:

[0083] B1. Single-machine grouping: Each group includes a single processing module 3. Each processing module 3 performs processing operations independently, and there is no sequential relationship between the processing steps performed by each processing module 3.

[0084] B2. Multi-machine grouping: Each group includes at least two processing modules 3. The processing steps performed by each processing module 3 within each group have a sequential relationship. The processing modules 3 in different groups perform processing operations independently, and the processing steps performed by each processing module 3 in different groups do not have a sequential relationship.

[0085] In summary, the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A modular rack characterized by: It includes a base, a frame, and an adapter. The frame is columnar, with its lower end fixedly connected to the base and its upper end fixedly connected to the adapter. The base is equipped with a clamping and positioning unit, and several material clamps are distributed on the sides of the frame.

2. The modular rack of claim 1, wherein: The frame is prismatic in shape, and material clamps are provided on each side of the frame.

3. The modular rack of claim 2, wherein: Each of the aforementioned material clamps includes a fixed clamping block and a movable clamping block, which are arranged sequentially, one above the other.

4. The modular material rack according to claim 3, characterized in that: The fixed clamping block and the movable clamping block on at least one side of the frame are positioned vertically opposite each other, and the fixed clamping block and the movable clamping block on at least one side of the frame are positioned horizontally opposite each other.

5. The modular rack according to any one of claims 1-4, characterized in that: The adapter includes a clamping head and two directional blocks, and the clamping and positioning unit is located between the two directional blocks.

6. The modular rack according to claim 5, characterized in that: The adapter includes a guide seat, and the clamping head and the orientation block are both disposed on the upper surface of the guide seat. The upper surface of the guide seat is an inclined surface or a curved surface.

7. The modular rack according to claim 5, characterized in that: The clamping and positioning unit includes a limiting hole or a limiting pin disposed on the base.