Method of manufacturing of piston of damping fork

Abstract

This disclosure presents a method for manufacturing pistons or piston rods utilized in shock absorbers for two-wheeler vehicles. The process involves several sequential steps: initially deburring the tube by performing deburring or chamfering actions on both ends. Subsequently, a swaging operation is carried out, followed by a flaring process involving two forming operations to create a flared portion with both a straight land and a taper land. The method then proceeds to a second forming operation by inserting a second punch into the flared portion at the head end. This is succeeded by a third forming operation that involves inserting a third punch into the remaining portion at the head end of the tube, followed by executing finishing operations on the tube.

Description

[0001] “METHOD OF MANUFACTURING OF PISTON OF DAMPING FORK”

[0002] FIEUD OF THE INVENTION:

[0003] The present invention relates to method of manufacturing pistons and more particularly to method of manufacturing pistons of damping fork from a tube.

[0004] BACKGROUND OF THE INVENTION:

[0005] Shock absorbers play a crucial role in the suspension system of twowheeler vehicles, serving to absorb and dampen the impact and vibrations transmitted from the road surface to the vehicle's body thru wheels. These components are typically integrated and connected to the chassis of the two- wheeler.

[0006] In motorcycles and scooters, shock absorbers are strategically placed both at the front wheel and the rear wheel to effectively manage and minimize the impact of uneven surfaces, bumps, and vibrations encountered during the vehicle's operation. The primary purpose of these shock absorbers is to enhance ride comfort, stability, and overall handling by mitigating the effects of road irregularities on the vehicle.

[0007] The shock absorber employed for the front wheel of a motorcycle is often referred to as a damping fork. In the context of scooters and motorcycles, this crucial component, also known as the damping rod fork or the front shock absorber, serves as a pivotal element in managing the vehicle's suspension system. Typically, a shock absorber comprises several integral parts, including a mount, a bushing, a coil spring, a piston, a piston rod (also known as the damping rod), a cylinder, bolts, and other associated components. Among these constituents, the piston rod holds a significant position due to its role in regulating the damping mechanism.

[0008] The damping rod, often interchangeably referred to as the damping rod or seat pipe, plays a critical function within the front shock absorber assembly. This component serves to control the movement and absorption of the hydraulic fluid, facilitating the effective dampening of vibrations and impacts experienced by the vehicle's front wheel during operation. Its precise design and functionality significantly contribute to the overall performance and stability of the vehicle's suspension system.

[0009] In the history and contemporary practice of manufacturing damping rods, several methods have been commonly employed. Traditionally, one prevalent technique involves the manufacturing of the rod from a solid bar, shaping it through machining processes to achieve the desired specifications. Another established method entails fabricating the damping rod from a tube through cold forging, a process that involves applying compressive forces to deform and shape the material while it's at room temperature.

[0010] Additionally, there are alternative methods, such as tube end forming with the grooves, which entails shaping the tube while incorporating specific grooves or patterns to achieve desired structural attributes. Another innovative approach involves manufacturing the piston rod as a two-piece assembly with a mechanical lock, employing intricate mechanisms to secure the two components together.

[0011] These varied techniques and constructional details demonstrate the industry's continuous exploration and utilization of diverse manufacturing methodologies to create damping rods that meet stringent quality standards and performance requirements. Each method offers its unique advantages in terms of precision, durability, and efficiency, contributing to the evolution and improvement of damping rod manufacturing processes over time.

[0012] In the tube-drawing process known in the prior art, graphite powder has traditionally been applied to the blank before the drawing operation. This application aids in facilitating the drawing process. During machining processes, graphite powder gradually deposits itself in different machines, subsequently released into coolants. Over time, this accumulation creates sludge, which not only hampers machining operations but also poses environmental challenges. The formation of this sludge not only interferes with machining operations but also raises environmental concerns due to its non-biodegradable nature.

[0013] Indeed, in the prior art, the preparation of workpieces for drawing involved several techniques such as phosphating, applying soap coatings, and deep annealing of tubes. These steps were integral in facilitating the subsequent drawing operations. Moreover, manufacturing pistons in the earlier methods required specialized hardened punches for drawing operations, significantly escalating manufacturing costs. The earlier manufacturing methods involved intricate and multi-step procedures for preparing workpieces, involving chemical treatments, precise material conditioning, and specialized tooling. These preparatory steps, like phosphating, soap application, and deep annealing of tubes, were essential for facilitating subsequent manufacturing operations. Furthermore, the requirement for specialized hardened punches specifically for drawing operations significantly amplified the complexity and cost of production. The incorporation of these specialized tools added an extra layer of intricacy to the manufacturing process, contributing to increased expenses and manufacturing complexities.

[0014] Moreover, the use of high-tonnage machinery in these methods was imperative due to the extensive material movement and deformation inherent in drawing or cold forging operations. The machinery needed to exert substantial force to shape the materials accurately, resulting in higher energy consumption and operational costs.

[0015] There is a need for a method of manufacturing piston rod damping fork by a process of manufacturing that is fast and economical.

[0016] SUMMARY OF THE INVENTION:

[0017] A method of manufacturing of piston of damping fork comprising: a first step deburring a tube. The first step includes deburring or chamfering operation of both ends of the tube in the range of 0.5X45°. A second step of swaging operation, the second step includes performing swaging operation on a thread end of the tube in two sub steps. A third step of flaring operation includes a first forming operation to define a flared portion with a straight land and a taper land. A fourth step of a second forming operation, the second forming operation includes inserting a second punch in the flared portion of the head end. A fifth step of a third forming operation, the third forming operation includes inserting a third punch in the balance portion of the head end of the tube; and performing other finishing operations on the tube.

[0018] The swaged operation being performed to achieve a swaged portion with approximately 16 mm length and the outer diameter of the swaged end being around 12.7 mm. The first forming and second forming operation includes inserting a first punch in the thread end of the tube. The second forming operation defines the taper land of the flared end into a first bulge or rib. The straight land of the flared end being formed into a second bulge or rib. The swaging operation, in a first sub- step the original diameter is reduced by around 25% and in a second sub-step, the newly reduced diameter is further reduced by swaging operation by around 23 to 24%.

[0019] BRIEF DESCRIPTION OF DRAWINGS:

[0020] The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,

[0021] FIG. 1 is a front perspective view of a piston rod of damping fork in accordance with the present invention;

[0022] FIG. 2 is a side perspective view of a piston rod of damping fork of FIG. 1;

[0023] FIG. 3 is a side view of another embodiment of the piston rod of damping fork of FIG. 1; and FIG. 4.1- 4.6 are side views showing various steps of operation in accordance with the present invention.

[0024] DESCRIPTION OF THE INVENTION:

[0025] References in the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

[0026] References in the specification to “preferred embodiment” means that a particular feature, structure, characteristic, or function described in detail thereby omitting known constructions and functions for clear description of the present invention.

[0027] The foregoing description of specific embodiments of the present invention has been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed and obviously many modifications and variations are possible in light of the above teaching.

[0028] As shown in FIGS. 1 and 2, a piston rod 100 in accordance with the present invention includes a plurality of features including a head 104 and a body 108. The head 104 is positioned on one end of the body 108, and the other end includes internal threads. It is noted that the internal threads are used for holding with fork slider. The head 104 has a groove 112 for damping seal. The head 104 advantageously includes a hex i.e. a hexagonal opening 116 for arresting rotation during assembly. The head 104 also includes a seat 120 that allows a top spring to rest on the head 104.

[0029] The body includes Df holes 124 and drain holes 128 compression damping orifice. The Df holes 124 are smaller holes and the drain holes 128 are bigger holes relative to the Df holes 124. The damping rod 100 is generally made up of low carbon steel material.

[0030] In accordance with the present invention, a method of manufacturing of piston or piston rod of FIG. 1 is disclosed. In a first step a thin tube is taken. It is noted that the thin tube has cylindrical shaped construction. For example, the thin tube preferably has an outer diameter of around 22 mm and an inner diameter of around 18 mm. The length of the tube is 210 mm. Material of the tube is CEW 1 i.e. low carbon steel as per IS3074 which is a known standard used for tubes used in automobile applications. The tube 100 has two ends such that a first end defines the head end and a second end is thread end.

[0031] Accordingly, the method of manufacturing of piston or piston rod includes a first step in which deburring of the ends is performed. In this step, the ends of the tube 100 are deburred by deburring or chamfering operation in the range of 0.5X45°. It is understood, however, that the chamfering operation is performed on the both ends of the internal diameter as well as outer diameter.

[0032] In a second step, swaging operation is performed on the thread end of the tube. In this operation, the diameter of the thread end is reduced gradually such that the swaged portion is approximately 18 mm length and the outer diameter of the swaged end is around 13 mm.

[0033] In a third step, flaring operation is performed on the head end of the tube. Accordingly, a flared portion is defined by performing a first forming operation in which a first punch is inserted in the head end of the tube. As a result, a flared operation is performed. For example, in the flaring operation, the outer diameter of the tube that is 22 mm is flared to 28.6 mm in the flaring operation and the included angle of flaring is approximately 35°. The flared portion is formed such that the flared portion includes a straight land and a taper land. The straight land is a straight portion, and the taper land is a tapered portion.

[0034] In a fourth step, a second forming operation is performed. The forming operation is performed by inserting a second punch in the flared portion of the head end. In this step, the taper land of the flared end is formed into a bulge. The diameter or the bulge is 34.4 mm. This is a cold forming operation. In a next step, a chamfering operation is performed on an open end the flared portion end of the head end of the tube.

[0035] In the next step, a washer is positioned on the chamfer that is produced in the previous step. The washer is positioned by any welding process, for example, spot welding. In this embodiment the washer has a hexagonal through section, however, it may be any section such as circular, rectangular or the like. After this finishing operations on the tube are performed. The piston rod is manufactured at a low cost with high accuracy in accordance with the present invention. Now referring to FIG. 3 and 4, in another embodiment of piston or piston rod is described. Accordingly, the piston rod 300 includes a head 304 and elongated body 308. One end of the piston rod 300 has the head 304 and other end includes internal threads that are used for holding with fork slider. The head 304 has a groove 312 for damping seal. The head 304, from inside, includes a hex i.e. a hexagonal lock (i.e. not seen) for arresting rotation during assembly. The head 304 also includes a seat 320 that allows a top spring to rest on the head 304. The groove 312 of the head is defined between the first bulge or rib 328 and the second rib 332.

[0036] The body includes Df holes 324 and drain holes 328 compression damping orifice. The Df holes 124 are smaller holes and the drain holes 328 are bigger holes relative to the Df holes 324. The damping rod 300 is generally made up of low carbon steel material.

[0037] Now another method of manufacturing of piston or piston rod of FIG. 3 is disclosed. It is noted that the thin tube is preferably of cylindrical shape construction. For example, the thin tube is preferably having outer diameter of 22 mm and inner diameter of around 18.6 mm. In this embodiment the length of the tube is 225 mm. The material of the tube is CEW1 i.e. low carbon steel as per IS3074 which is a known standard used for tubes used in automobile applications. The tube has two ends. The tube 300 has two ends such that a first end defines the head end, and a second end is thread end.

[0038] In a first step, both ends of the tube are deburred by deburring or chamfering operation in the range of 0.5X45° (Ref. FIG. 4.1). After this step, a swaging operation is performed in another two sub-steps. Accordingly, in a first sub-step the original diameter is reduced by around 25% by swaging operation at the thread end (Ref. FIG. 4.3). In a second sub-step, the newly reduced diameter is further reduced by swaging operation by around 23 to 24% (Ref. FIG. 4.3). It is noted that the swaging operation in the two sub-steps is performed on the thread end of the tube. In this operation, the overall diameter of the thread end is reduced gradually such that the swaged portion is approximately 16 mm length and the outer diameter of the swaged end is around 12.7 mm.

[0039] In a third step, flaring operation is performed on the head end of the tube (Ref. FIG. 4.4). Accordingly, a flared portion is defined by performing a first forming operation in which a first punch inserted in the head end of the tube. As a result, a flared operation is performed. For example, in the flaring operation, outer diameter of the tube that is 22.1 mm is flared to 28.6 mm in the flaring operation and the included angle of flaring is about 30°. The flared portion is formed such that the flared portion includes a straight land 400 and a taper land 404 (Ref. FIG. 4.4). The straight land is a straight portion, and the taper land is a tapered portion.

[0040] In a fourth step, a second forming operation is performed (Ref. FIG. 4.5). The second forming operation is performed by inserting a second punch in the flared portion of the head end. In this step, the taper land of the flared end is formed into a first bulge or rib 328. The diameter or the bulge is about 35 mm. This is a cold forming operation.

[0041] In a fifth step, a third forming operation is performed (Ref. FIG. 4.6). The third forming operation is performed by inserting a third punch in the balance portion of the head end of the tube. In this step, the straight land of the flared end is formed into a second bulge or rib 332. The distance between the first rib and the second rib is around 4.5 mm. After this finishing operations on the tube are performed. It is understood however that the first forming operation and the second forming operation includes inserting a first punch in the thread end of the tube.

[0042] In accordance with the method of manufacturing of piston of damping fork there is not at all any use of graphite powder. Conventionally, in the tube drawing process, graphite powder is conventionally applied to the blank before drawing to facilitate the operation. However, in the present method, drawing is not utilized; instead, an end forming process is employed, distinctly different from drawing operations. This is how the method of the present invention eliminates the necessity for graphite powder, as it is unrelated to the process, and instead emphasizes end forming techniques.

[0043] The method of the present invention not only eliminates the need for graphite but also reduces the associated environmental concerns. By adopting alternative approaches like end forming, which bypasses the use of graphite, the method of the present invention is more environmentally sustainable and lessens the environmental footprint associated with machining operations.

[0044] Moreover, another notable benefit of the method of the present invention is material saving. Through the implementation of metal displacement techniques, such as forming tubes, the process requires less material compared to traditional forging operations used in previous methods. This reduction in material requirement not only contributes to cost-effectiveness but also aligns with sustainable practices by minimizing material usage, reducing waste, and enhancing the overall efficiency of the manufacturing process. It is noted that the Present method uses gross weight of around 290 gms while new method the gross wt. is 205 gms. The total material displacement method is entirely a method of drawing and cold forging which is expensive and needs heavy manufacturing equipment. The present method teaches material displacement by tube forming which needs lighter manufacturing machine and a overall cost reduction of about 25% as compared to the prior method of drawing and cold forging.

[0045] The manufacturing method of the present invention doesn’t employ any high-powered processes but instead employs operations such as flaring, which demand low-tonnage machines. This shift not only reduces the power consumption significantly but also brings down operational costs. By employing the method of the present invention that requires lower power and machinery capacity, the overall energy expenditure decreases, resulting in a more cost-effective and environmentally conscious manufacturing process.

[0046] In the prior method, the use of soap material facilitated tube drawing, often preceded by a phosphating process. However, in accordance with the present invention, tube drawing is omitted entirely, eliminating the need for phosphating or soap-coated tubes as input materials. This method bypasses the need for deep annealing the tubes, a step commonly observed in the previous method. As a result, the cost of preparing input materials is significantly reduced, with about a 15% to 25% cost reduction compared to the prior method.

[0047] Moreover, the present process offers notable energy efficiency. Unlike earlier techniques that relied on high-tonnage machines for drawing or cold forging operations, the current method replaces these with operations like flaring that demand low-tonnage machinery. This transition reduces power consumption and subsequently lowers process costs.

[0048] Additionally, the prior method necessitated specialized, hardened punches for drawing operations, an expensive and time-intensive requirement. Conversely, the present method teaches stoppers instead of punches, substantially reducing product manufacturing cycles compared to the previous method.

[0049] The advancements in the manufacturing process of the present invention not only streamline operations but also contribute to significant cost reductions, increased efficiency, and decreased energy consumption, marking a notable leap forward in production technology.

[0050] The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated.

[0051] It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention.

Claims

CLAIMS:

1. A method of manufacturing of piston of damping fork comprising: a first step deburring a tube, the first step including deburring or chamfering operation of both ends of the tube in the range of 0.5X45°; a second step of swaging operation, the second step including performing swaging operation on a thread end of the tube in two substeps; a third step of flaring operation, the flaring operation including a first forming operation to define a flared portion with a straight land and a taper land; a fourth step of a second forming operation, a second forming operation including inserting a second punch in the flared portion of the head end; a fifth step of a third forming operation, the third forming operation including inserting a third punch in the balance portion of the head end of the tube; and a performing other finishing operations on the tube.

2. The method of manufacturing of piston of damping fork of claim 1, wherein the swaging operation being performed to achieve a swaged portion with approximately 16 mm length and the outer diameter of the swaged end being around 12.7 mm.

3. The method of manufacturing of position of damping fork of claim 1, wherein the first forming and second forming operation including inserting a first punch in the thread end of the tube.

4. The method of manufacturing of position of damping fork of claim 1, wherein the second forming operation defining the taper land of the flared end into a first bulge or rib.

5. The method of manufacturing of position of damping fork of claim 1, wherein the straight land of the flared end being formed into a second bulge or rib.

6. The method of manufacturing of position of damping fork of claim 1, wherein in the swaging operation, in a first sub-step the original diameter is reduced by around 25% and in a second sub-step, the newly reduced diameter is further reduced by swaging operation by around 23 to 24%.

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