Enclosed horizontal wheel set fixation device

Abstract

The closed horizontal wheel group fixing device comprises an upper panel, a lower panel, a sleeve, an upper heavy plate, a lower heavy plate and an end cover. The upper panel is provided with a first hole, and the lower panel is provided with a second hole opposite to the first hole. The sleeve is a hollow cylinder, and the sleeve penetrates the upper panel and the lower panel through the first hole of the upper panel and the second hole of the lower panel, and the sleeve is sleeved outside the horizontal wheel shaft. The upper heavy plate is arranged above the first hole, and the upper heavy plate is provided with a third hole matching the shape and size of the first hole. The lower heavy plate is arranged below the second hole, and the lower heavy plate is provided with a fourth hole matching the shape and size of the second hole. The end cover is arranged above the upper heavy plate, and the end cover is connected with the second end of the horizontal wheel shaft to form an assembly. The closed horizontal wheel group fixing device can better ensure the accuracy of the final horizontal wheel position while ensuring the structural strength.

Description

Technical Field

[0001] This invention relates to the field of horizontal wheel structures for sliding trolleys, and more specifically to a closed horizontal wheel assembly fixing device. Background Technology

[0002] The horizontal wheel structure of the skid steer trolley is a crucial component of quay crane products. Its main function is to suppress lateral displacement of the skid steer trolley, ensuring the stable operation of the pulley block in the container lifting and winding system. Due to the limited space in the horizontal wheel structure of the skid steer trolley, multiple factors need to be considered during the design process, including requirements for structural strength, stability, and safety.

[0003] To meet structural strength requirements, numerous reinforcing ribs were used at the fixed positions of the horizontal wheels, forming a closed box structure to provide sufficient rigidity and strength. However, this closed box structure makes it difficult to ensure the final accuracy of the horizontal wheel position, posing significant construction challenges. Summary of the Invention

[0004] To address the aforementioned problems, this invention designs a reasonable enclosed horizontal wheel assembly fixing device, which ensures structural strength while effectively guaranteeing the accuracy of the final horizontal wheel position. A corresponding construction method is also designed to reduce construction difficulty.

[0005] This invention provides a closed-type horizontal wheel assembly fixing device for fixing the horizontal wheel assembly of a sliding trolley. The horizontal wheel assembly includes a horizontal wheel axle and a horizontal wheel sleeved on the first end of the horizontal wheel axle. The closed-type horizontal wheel assembly fixing device includes:

[0006] The upper panel has a first hole at the horizontal wheel axle mounting position;

[0007] The lower panel is disposed opposite to the upper panel, and the lower panel has a second hole at the horizontal wheel axle mounting position, the second hole being disposed opposite to the first hole;

[0008] The sleeve is a hollow cylinder. The outer diameter of the sleeve matches the diameter of the first hole and the second hole. The sleeve passes through the first hole on the top plate and the second hole on the bottom plate, penetrating the top and bottom plates. The sleeve is fitted onto the outside of the horizontal wheel axle.

[0009] The upper weighing plate is positioned above the first hole in the upper panel, and a third hole is formed on the upper weighing plate, the shape and size of which match the shape and size of the first hole;

[0010] The lower weighing plate is located below the second hole in the lower panel, and a fourth hole is opened on the lower weighing plate, the shape and size of the fourth hole matching the shape and size of the second hole;

[0011] An end cap is disposed above the upper weighing plate. The bottom of the end cap is inserted into the gap between the sleeve and the second end of the horizontal wheel axle. The end cap and the second end of the horizontal wheel axle are connected to form an assembly.

[0012] In one embodiment, the sleeve includes a first processed section, a non-processed section, and a second processed section. The inner diameters of the first processed section and the second processed section are equal, the inner diameter of the non-processed section is smaller than the inner diameter of the first processed section, the lower bottom surface of the first processed section is connected to the upper bottom surface of the non-processed section, and the lower bottom surface of the non-processed section is connected to the upper bottom surface of the second processed section.

[0013] The upper weighing plate is fitted onto the outside of the first processing section, and the lower weighing plate is fitted onto the outside of the second processing section.

[0014] In one embodiment, a first processed section, a non-processed section, and a second processed section are combined by welding to form a sleeve. The non-processed section is made of seamless pipe profile directly cut into shape. The ends of the non-processed section are processed with butt weld bevels. The first processed section and the second processed section are made of CNC-cut steel plates.

[0015] In one embodiment, the inner diameters of both the first and second processing sections have machining allowances, and the inner diameters of the first hole in the upper panel and the second hole in the lower panel also have machining allowances.

[0016] The process involves machining the inner diameters of the first and second machining sections, as well as the inner diameters of the first hole in the upper panel and the second hole in the lower panel, using a marking method. This marking method includes:

[0017] After the main structure of the sliding trolley is formed, the center position of the horizontal wheel is marked for the first time according to the overall center of the sliding trolley. The machining allowance left in the inner diameter of the first and second holes is trimmed in order to install the sleeve, upper weight plate and lower weight plate.

[0018] After the sliding trolley is fully installed, the centers of the first and second machining sections inside the sleeve are marked a second time according to the overall center of the sliding trolley. The machining allowance left for the inner diameter of the first and second machining sections is then machined to confirm the centers of the first and second machining sections. The centers of the first and second machining sections are the machining centers of the horizontal wheel shaft hole.

[0019] In one embodiment, the gap between the unprocessed section and the horizontal wheel axle is more than 5mm on one side.

[0020] In one embodiment, the sliding trolley has N horizontal wheel sets, then the top plate has N first holes and the bottom plate has N second holes. Each first hole is provided with an upper weight plate above it and each second hole is provided with a lower weight plate below it. N+1 reinforcing ribs are provided between the top and bottom plates, and the reinforcing ribs are used to separate each horizontal wheel set.

[0021] In one embodiment, the horizontal wheel axle is an eccentric shaft, which includes a first shaft segment and a second shaft segment. The second end of the first shaft segment is connected to the first end of the second shaft segment. The second shaft segment is used to fix the horizontal wheel. The first and second shaft segments are designed as an eccentric structure. By rotating the horizontal wheel axle, the distance between the horizontal wheel and the running track can be adjusted.

[0022] The second end of the second axle segment is the first end of the horizontal wheel axle, and the first end of the first axle segment is the second end of the horizontal wheel axle.

[0023] In one embodiment, the end cap includes an upper top plate and a connector disposed below the upper top plate, the connector being hollow to accommodate a second end of a horizontal wheel axle.

[0024] In one embodiment, the end cap is provided with a plurality of bolt through holes, and the top plate is provided with a plurality of threaded holes, the number of threaded holes being greater than the number of bolt through holes;

[0025] The bolt through-holes on the end cap are rotated to correspond with the threaded holes on the upper panel. The bolt through-holes on the end cap and the threaded holes on the upper panel are connected by fasteners to fix the end cap to the upper panel.

[0026] In one embodiment, the end cap is provided with 4 bolt through holes, and the top plate is provided with 12 threaded holes. The assembly formed by the end cap and the horizontal wheel axle rotates within the sleeve to align the bolt through holes on the end cap and the threaded holes on the top plate. Every 30° rotation of the assembly formed by the end cap and the horizontal wheel axle aligns the bolt through holes on the end cap with the next threaded hole.

[0027] The enclosed horizontal wheel assembly fixing device of the present invention has the following beneficial effects:

[0028] 1. This invention designs a through-tube structure, utilizing the stability of a circular tube to enhance structural strength. This invention also designs a reinforcing weight plate at the horizontal wheel axle fixing position, increasing structural strength and the effective thread length of the horizontal wheel axle fixing bolts.

[0029] 2. This invention designs upper and lower panels with allowances in the inner holes. The final horizontal wheel axle center can be determined by marking the center line of the sliding trolley structure. The accurate position of the sleeve is ensured by trimming the corresponding opening allowances of the upper and lower panels. The sleeve in this invention is manufactured in sections, retaining the inner hole machining allowances (i.e., the machining allowances left for the inner diameter) of the first and second machining sections at both ends. This ensures the final position of the horizontal wheel axle hole (i.e., the inner holes of the first and second machining sections) and the perpendicularity of the center line of the horizontal wheel axle hole to the entire closed horizontal wheel assembly fixing device.

[0030] 3. This invention designs a marking construction method for the horizontal wheel structure of a sliding trolley. This marking method allows for machining allowances in the inner diameters of the first and second machining sections, as well as in the inner diameters of the first hole in the upper panel and the second hole in the lower panel, thus reducing construction difficulty. This marking construction method involves two marking processes: the first marking confirms the installation positions of the sleeve and the weight plate, and the second marking confirms the machining center of the horizontal wheel axle hole.

[0031] 4. In this invention, an eccentric horizontal wheel axle is used, and the distance between the horizontal wheel and the running track can be adjusted by rotating the horizontal wheel axle. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a closed horizontal wheel assembly fixing device according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the internal structure of the sleeve according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of a horizontal wheel axle according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the segmented fabrication of the sleeve according to an embodiment of the present invention.

[0036] Figure Labels

[0037] 1. End cap; 2. Upper weighing plate; 3. Upper panel; 4. Sleeve; 5. Horizontal wheel axle; 6. Lower panel; 7. Lower weighing plate; 8. Horizontal wheel. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention 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 for illustrative purposes only and are not intended to limit the invention.

[0039] like Figure 1As shown, this invention provides a closed-type horizontal wheel assembly fixing device for fixing the horizontal wheel assembly of a sliding trolley. The horizontal wheel assembly includes a horizontal wheel axle 5 and a horizontal wheel 8 sleeved on the first end of the horizontal wheel axle 5. One embodiment of the closed-type horizontal wheel assembly fixing device includes: an upper panel 3, a lower panel 6, a sleeve 4, an upper weight plate 2, a lower weight plate 7, and an end cap 1. The upper panel 3 has a first hole at the mounting position of the horizontal wheel axle 5. The lower panel 6 is opposite to the upper panel 3 and has a second hole at the mounting position of the horizontal wheel axle 5, which is opposite to the first hole. The upper panel 3 and the lower panel 6 are components of the main structure of the sliding trolley and are the main supporting structures for the horizontal wheel assembly. The sleeve 4 is a hollow cylinder, and its outer diameter matches the diameter of the first and second holes. The sleeve 4 passes through the first hole on the upper panel 3 and the second hole on the lower panel 6, and is sleeved on the outside of the horizontal wheel axle 5. The upper weighing plate 2 is positioned above the first hole in the upper panel 3. A third hole is formed on the upper weighing plate 2, the shape and size of which match the shape and size of the first hole. The lower weighing plate 7 is positioned below the second hole in the lower panel 6. A fourth hole is formed on the lower weighing plate 7, the shape and size of which match the shape and size of the second hole. The upper weighing plate 2 and the lower weighing plate 7 are reinforcing structures designed on the upper panel 3 and lower panel 6, increasing the contact pressure-bearing area between the horizontal wheel axle 5 and the closed horizontal wheel assembly fixing device. The end cap 1 is positioned above the upper weighing plate 2. The bottom of the end cap 1 is inserted into the gap between the sleeve 4 and the second end of the horizontal wheel axle 5, and the end cap 1 is connected to the second end of the horizontal wheel axle 5 to form an assembly. Preferably, in this embodiment, the end cap 1 and the horizontal wheel axle 5 are connected as an assembly using pins.

[0040] Furthermore, such as Figure 2 As shown, the inner diameter of the sleeve 4 has a stepped structure, which avoids the problem of excessive depth in the middle part during internal machining, which would make machining difficult. Specifically, the sleeve 4 includes a first machining section, a non-machining section, and a second machining section. The inner diameters of the first and second machining sections are equal, while the inner diameter of the non-machining section is smaller than that of the first machining section. The lower bottom surface of the first machining section is connected to the upper bottom surface of the non-machining section, and the lower bottom surface of the non-machining section is connected to the upper bottom surface of the second machining section. The upper weight plate 2 is fitted onto the outside of the first machining section, and the lower weight plate 7 is fitted onto the outside of the second machining section. The sleeve 4 is a covering structure for the outside of the horizontal wheel axle 5, utilizing the stability of the circular tube to enhance structural strength.

[0041] Furthermore, such as Figure 4As shown, the first processed section, the unprocessed section, and the second processed section are combined by welding to form the sleeve 4. The unprocessed section has a large diameter and is made from seamless tubular material directly cut to size. The ends of the unprocessed section are machined with butt weld bevels. The first and second processed sections are made from CNC-cut steel plates. In this embodiment, after the components are welded, the inner diameters of the first and second processed sections can be machined by scribing to ensure the final position of the horizontal wheel axle hole and the perpendicularity of the center line of the horizontal wheel axle hole inside the sleeve to the entire sleeve. The horizontal wheel axle hole here refers to the hollow part inside the sleeve used to accommodate the horizontal wheel axle.

[0042] Furthermore, both the inner diameters of the first and second processing sections have machining allowances, meaning that the inner diameters of these two parts can be further processed or adjusted in the final product. The inner diameters of the first hole in the upper panel and the second hole in the lower panel also have machining allowances. The sleeve 4 penetrates the upper and lower panels of the sliding trolley, facilitating accurate sleeve positioning by trimming the corresponding opening allowances on the upper and lower panels. The fixing weld of the sleeve 4 can also be completed outside the housing. Specifically, the machining allowances in the inner diameters of the first and second processing sections, as well as the inner diameters of the first hole in the upper panel and the second hole in the lower panel, are processed using a scribing method. This scribing method includes:

[0043] After the main structure of the sliding trolley is formed, the center position of the horizontal wheel is marked for the first time according to the overall center of the sliding trolley. The machining allowance left in the inner diameter of the first and second holes is trimmed in order to install the sleeve, upper weight plate and lower weight plate.

[0044] After the sliding trolley is fully installed, the centers of the first and second machining sections inside the sleeve are marked a second time according to the overall center of the sliding trolley. The machining allowance left for the inner diameter of the first and second machining sections is then machined to confirm the centers of the first and second machining sections. The centers of the first and second machining sections are the machining centers of the horizontal wheel shaft hole.

[0045] Furthermore, the gap between the unmachined section and the horizontal wheel axle is more than 5mm on each side, which means that no additional machining is required between these two parts.

[0046] Furthermore, since the sliding trolley has N horizontal wheel sets, the upper panel 3 has N first holes, and the lower panel 6 has N second holes. Each first hole has an upper weight plate 2 above it, and each second hole has a lower weight plate 7 below it. To increase structural strength, N+1 reinforcing ribs are installed between the upper panel 3 and the lower panel 6. These reinforcing ribs separate each horizontal wheel set, forming an internally enclosed box structure.

[0047] Furthermore, the horizontal wheel axle 5 is an eccentric shaft, comprising a first axle segment and a second axle segment. The second end of the first axle segment is connected to the first end of the second axle segment, and the second axle segment is used to fix the horizontal wheel. For example... Figure 3 As shown, the first and second axle segments are designed as eccentric structures, and the distance between the horizontal wheel and the running track is adjusted by rotating the horizontal wheel axle. Specifically, the second end of the second axle segment is the first end of the horizontal wheel axle, and the first end of the first axle segment is the second end of the horizontal wheel axle.

[0048] Specifically, such as Figure 1 As shown, the end cap includes an upper top plate and a connector disposed below the upper top plate, the connector being hollow to accommodate the second end of the horizontal wheel axle.

[0049] Furthermore, the end cap 1 has multiple bolt through holes, and the upper panel 3 has multiple threaded holes, with the number of threaded holes exceeding the number of bolt through holes. The bolt through holes on the end cap 1 align with the threaded holes on the upper panel 3 by rotation, and a fastener connects the bolt through holes on the end cap 1 with the threaded holes on the upper panel 3 to fix the end cap to the upper panel 3. Preferably, in this embodiment, the end cap has four bolt through holes, and the upper panel has twelve threaded holes. The assembly formed by the end cap and the horizontal wheel axle rotates within the sleeve to align the bolt through holes on the end cap with the threaded holes on the upper panel. Every 30° rotation of the assembly, the bolt through holes on the end cap align with the next threaded hole. The upper weighing plate 2 increases the depth of the threaded holes on the upper panel 3, which improves the bolt fixing strength between the end cap and the shaft assembly.

[0050] The specific application process of the enclosed horizontal wheel assembly fixing device according to an embodiment of the present invention is as follows:

[0051] sleeve Figure 4 The process is divided into three sections. The middle section has a large inner diameter and is made by directly cutting seamless tubing. The ends are machined with butt weld bevels. The two ends are made by CNC cutting steel plates. The inner diameter is reserved for machining allowance. The three sections are welded together to form an integral sleeve structure.

[0052] After the main structure of the sliding trolley is formed, the center position of the horizontal wheel is marked for the first time according to the overall center of the sliding trolley. The machining allowance left in the inner diameter of the first and second holes is trimmed to install the sleeve, upper weight plate and lower weight plate. Then all welds are completed on the outside of the box.

[0053] After the sliding trolley is fully installed, the centers of the first and second machining sections inside the sleeve are marked a second time based on the overall center of the sliding trolley. The machining allowance left for the inner diameter of the first and second machining sections is then machined to confirm the centers of the first and second machining sections, which are the machining centers of the horizontal wheel axle holes. Subsequently, the machining of the threaded holes on the top plate is completed.

[0054] When installing the horizontal wheel, measure the distance between the horizontal wheel and the running track. Adjust the distance between the horizontal wheel and the running track by rotating the horizontal wheel axle until the requirements are met. Then, fix it by connecting the bolt through holes on the end cover and the threaded holes on the top panel through the bolt group connection.

[0055] The enclosed horizontal wheel assembly fixing device of the present invention has the following beneficial effects:

[0056] 1. This invention designs a through-tube structure, utilizing the stability of a circular tube to enhance structural strength. This invention also designs a reinforcing weight plate at the horizontal wheel axle fixing position, increasing structural strength and the effective thread length of the horizontal wheel axle fixing bolts.

[0057] 2. This invention designs upper and lower panels with allowances in the inner holes. The final horizontal wheel axle center can be determined by marking the center line of the sliding trolley structure. The accurate position of the sleeve is ensured by trimming the corresponding opening allowances of the upper and lower panels. The sleeve in this invention is manufactured in sections, retaining the inner hole machining allowances (i.e., the machining allowances left for the inner diameter) of the first and second machining sections at both ends. This ensures the final position of the horizontal wheel axle hole (i.e., the inner holes of the first and second machining sections) and the perpendicularity of the center line of the horizontal wheel axle hole to the entire closed horizontal wheel assembly fixing device.

[0058] 3. This invention designs a marking construction method for the horizontal wheel structure of a sliding trolley. This marking method allows for machining allowances in the inner diameters of the first and second machining sections, as well as in the inner diameters of the first hole in the upper panel and the second hole in the lower panel, thus reducing construction difficulty. This marking construction method involves two marking processes: the first marking confirms the installation positions of the sleeve and the weight plate, and the second marking confirms the machining center of the horizontal wheel axle hole.

[0059] 4. In this invention, an eccentric horizontal wheel axle is used, and the distance between the horizontal wheel and the running track can be adjusted by rotating the horizontal wheel axle.

[0060] The embodiments described above are merely further illustrations of the present invention and are not intended to limit the present invention in any other way. The present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding modifications and changes based on the present invention, but all such modifications and changes should fall within the protection scope of the present invention.

Claims

1. A closed-type horizontal wheel assembly fixing device for fixing the horizontal wheel assembly of a sliding trolley, the horizontal wheel assembly comprising a horizontal axle and a horizontal wheel sleeved on the first end of the horizontal axle, characterized in that, The enclosed horizontal wheel assembly fixing device includes: The upper panel has a first hole at the horizontal wheel axle mounting position; The lower panel is disposed opposite to the upper panel, and the lower panel has a second hole at the horizontal wheel axle mounting position, the second hole being disposed opposite to the first hole; The sleeve is a hollow cylinder. The outer diameter of the sleeve matches the diameter of the first hole and the second hole. The sleeve passes through the first hole on the top plate and the second hole on the bottom plate, penetrating the top and bottom plates. The sleeve is fitted onto the outside of the horizontal wheel axle. The upper weighing plate is positioned above the first hole in the upper panel, and a third hole is formed on the upper weighing plate, the shape and size of which match the shape and size of the first hole; The lower weighing plate is located below the second hole in the lower panel, and a fourth hole is opened on the lower weighing plate, the shape and size of the fourth hole matching the shape and size of the second hole; An end cap is disposed above the upper weighing plate. The bottom of the end cap is inserted into the gap between the sleeve and the second end of the horizontal wheel axle. The end cap and the second end of the horizontal wheel axle are connected to form an assembly.

2. The enclosed horizontal wheel assembly fixing device according to claim 1, characterized in that, The sleeve includes a first processed section, a non-processed section, and a second processed section. The inner diameters of the first processed section and the second processed section are equal, and the inner diameter of the non-processed section is smaller than the inner diameter of the first processed section. The lower bottom surface of the first processed section is connected to the upper bottom surface of the non-processed section, and the lower bottom surface of the non-processed section is connected to the upper bottom surface of the second processed section. The upper weighing plate is fitted onto the outside of the first processing section, and the lower weighing plate is fitted onto the outside of the second processing section.

3. The enclosed horizontal wheel assembly fixing device according to claim 2, characterized in that, The first processed section, the unprocessed section, and the second processed section are combined by welding to form a sleeve. The unprocessed section is made of seamless pipe profile directly cut into material. The ends of the unprocessed section are processed with butt weld bevels. The first processed section and the second processed section are made of CNC cutting steel plates.

4. The enclosed horizontal wheel assembly fixing device according to claim 2, characterized in that, The inner diameters of the first and second processing sections are both left with machining allowances, and the inner diameters of the first hole in the upper panel and the second hole in the lower panel are both left with machining allowances. The process involves machining the inner diameters of the first and second machining sections, as well as the inner diameters of the first hole in the upper panel and the second hole in the lower panel, using a marking method. The marking method includes: After the main structure of the sliding trolley is formed, the center position of the horizontal wheel is marked for the first time according to the overall center of the sliding trolley. The machining allowance left in the inner diameter of the first and second holes is trimmed in order to install the sleeve, upper weight plate and lower weight plate. After the sliding trolley is fully installed, the centers of the first and second machining sections inside the sleeve are marked a second time according to the overall center of the sliding trolley. The machining allowance left for the inner diameter of the first and second machining sections is then machined to confirm the centers of the first and second machining sections. The centers of the first and second machining sections are the machining centers of the horizontal wheel shaft hole.

5. The enclosed horizontal wheel assembly fixing device according to claim 2, characterized in that, The gap between the unmachined section and the horizontal wheel axle is more than 5mm on one side.

6. The enclosed horizontal wheel assembly fixing device according to claim 1, characterized in that, The sliding trolley has N horizontal wheel sets, with N first holes on the top plate and N second holes on the bottom plate. Each first hole has an upper weight plate above it and each second hole has a lower weight plate below it. There are N+1 reinforcing ribs between the top and bottom plates, which are used to separate each horizontal wheel set.

7. The enclosed horizontal wheel assembly fixing device according to claim 1, characterized in that, The horizontal wheel axle is an eccentric shaft, which includes a first shaft section and a second shaft section. The second end of the first shaft section is connected to the first end of the second shaft section. The second shaft section is used to fix the horizontal wheel. The first shaft section and the second shaft section are designed as an eccentric structure. By rotating the horizontal wheel axle, the distance between the horizontal wheel and the running track can be adjusted. The second end of the second axle segment is the first end of the horizontal wheel axle, and the first end of the first axle segment is the second end of the horizontal wheel axle.

8. The enclosed horizontal wheel assembly fixing device according to claim 1, characterized in that, The end cap includes an upper top plate and a connector disposed below the upper top plate, the connector being hollow to accommodate the second end of the horizontal wheel axle.

9. The enclosed horizontal wheel assembly fixing device according to claim 1, characterized in that, The end cap is provided with multiple bolt through holes, and the top plate is provided with multiple threaded holes, the number of which is greater than the number of bolt through holes; The bolt through-holes on the end cap are rotated to correspond with the threaded holes on the upper panel. The bolt through-holes on the end cap and the threaded holes on the upper panel are connected by fasteners to fix the end cap to the upper panel.

10. The enclosed horizontal wheel assembly fixing device according to claim 9, characterized in that, The end cap has four bolt through holes, and the top plate has twelve threaded holes. The assembly formed by the end cap and the horizontal wheel axle rotates within the sleeve to align the bolt through holes on the end cap with the threaded holes on the top plate. Every 30° rotation of the assembly formed by the end cap and the horizontal wheel axle aligns the bolt through holes on the end cap with the next threaded hole.

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