Forklift fork frame welding process

Abstract

This invention discloses a welding process for forklift fork frames. First, the upper and lower crossbeams, uprights, and vertical plates are precisely spot-welded together using tooling. Then, all splicing edges are fully welded to form the fork frame. After welding, a press and hydraulic straightening fixture are used to straighten the crossbeams and vertical plates, ensuring the flatness and perpendicularity of the workpieces. Subsequently, using specialized tooling, the longitudinal roller shaft and composite roller shaft are positioned and welded, with strict control over the coaxiality and positional accuracy of the two shafts. Post-weld inspection and secondary correction of dimensional deviations are performed. Before painting the finished product, protective devices are installed to protect the outer diameter of the shafts, screw holes, and inner holes from spray paint damage. The painting process includes shot peening, degreasing and washing, silane treatment, drying, and powder coating curing. This invention, by first straightening and then precisely welding the shaft system, avoids workpiece deformation errors caused by secondary welding, effectively ensuring the geometric accuracy of the roller assembly. Simultaneously, the silane treatment enhances coating adhesion, meeting environmentally friendly production requirements.

Description

Technical Field

[0001] This invention relates to the technical field of welding forklift fork frame bodies, and more particularly to a welding process for forklift fork frame bodies. Background Technology

[0002] Forklifts are wheeled vehicles used for moving goods. Modern forklifts all use a mast system for loading and unloading goods. The mast system is the working device of the fork carriage. The welding of the fork carriage body is a key component of the mast system, playing a crucial role in the operation of the forklift. The quality of the fork carriage body welding directly affects whether the forklift can work properly. Poor welding will directly lead to fork carriage jamming, severe mast wear, mast shaking during operation, and ultimately, the forklift malfunctioning.

[0003] Existing forklift fork carriages such as Figure 1 As shown, it includes an upper crossbeam 1 and a lower crossbeam 4. The two ends of the upper crossbeam 1 and the lower crossbeam 4 are connected by a pair of columns 2. Two connecting plates 3 are provided between the upper crossbeam 1 and the lower crossbeam 4. A vertical plate 5 is provided on each of the two connecting plates 3. Two pairs of stiffening plates 8 are provided on the inner sides of the two vertical plates 5. The two pairs of stiffening plates 8 are fixed to the lower crossbeam 4 and the upper crossbeam 1 respectively. A hanging chain plate 6 is provided on each of the two vertical plates 5 near the lower crossbeam 4. Two pairs of composite roller shafts 10 and a pair of longitudinal roller shafts 9 are provided on the outer sides of the two vertical plates 5. The longitudinal roller shafts 9 are located at the end of the vertical plate 5 near the upper crossbeam 1, and the composite roller shafts 10 are located at the other end and the middle of the vertical plate. A limiting block 7 is provided on one of the vertical plates 5.

[0004] The fork carriage body is welded as a single welded component. If it is assembled and welded as a whole in a conventional one-time process, the material deformation caused by welding makes it difficult to guarantee the parallelism of the two vertical plates on the fork carriage body, the equal height of the roller shafts welded on the two vertical plates, and the parallelism of the line connecting the roller shaft centers. The roller shafts on the vertical plates of the fork carriage body are the carriers for installing longitudinal rollers and compound rollers. The rollers and compound rollers on the vertical plates of the fork carriage body move in close contact with the sides of the left and right column slots and the cover plate surface of the mast during lifting and lowering. The manufacturing precision of the fork carriage body welding directly affects the stability of the mast during operation. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to improve the precision of welding and manufacturing of forklift frames.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] A forklift fork frame welding process includes the following steps: Step 1): Forklift frame assembly welding: Assemble and position the upper crossbeam, lower crossbeam, 2 connecting plates, 2 uprights, 2 vertical plates, 4 stiffening plates, 2 chain hangers, and limit blocks on the forklift frame assembly welding fixture; weld multiple spot welds to the edges of the upper crossbeam, lower crossbeam, connecting plates, and vertical plates for assembly; weld multiple spot welds to the edges of the upper crossbeam, lower crossbeam, and uprights for assembly; weld multiple spot welds to the edges of the upper crossbeam, lower crossbeam, and stiffening plates for assembly; weld multiple spot welds to the edges of the vertical plates and chain hangers for assembly; weld multiple spot welds to the edges of the vertical plates and limit blocks for assembly. Step 2): Fork frame welding: Full welding is performed along the splicing edges of the upper crossbeam, lower crossbeam, connecting plate, vertical plate, column, stiffening plate, hanging chain plate, and limit block to form the fork frame weld; Step 3): Fork frame welding and straightening: Use a press to press and straighten the upper and lower crossbeams welded to the fork frame until they are level and flush. Use a hydraulic straightening fixture to straighten the two vertical plates welded to the fork frame until the vertical surfaces of the two vertical plates are parallel and the width distance between the outer sides of the vertical surfaces of the two vertical plates meets the requirements. The vertical surfaces of the two vertical plates are perpendicular to the plane where the upper and lower crossbeams are located. Step 4): Welding of longitudinal roller shafts and composite roller shafts: On the welding fixture for welding roller shafts on the fork frame, the longitudinal roller shafts and composite roller shafts are spliced ​​and positioned; multiple spot welds are made to the edge of the vertical plate where the longitudinal roller shafts and composite roller shafts are spliced, and the two longitudinal roller shafts are spot welded to be coaxial and meet the positional dimension requirements, so that the axes of the two longitudinal roller shafts are on the same straight line and parallel to the plane of the upper and lower crossbeams and perpendicular to the vertical plane of the vertical plate. The corresponding composite roller shafts are coaxially distributed one by one and meet the positional dimension requirements, and the axes of the corresponding composite roller shafts are on the same straight line and parallel to the plane of the upper and lower crossbeams and perpendicular to the vertical plane of the vertical plate. Step 5): Welding of longitudinal roller shaft and composite roller shaft: Full welding is performed along the longitudinal roller shaft, composite roller shaft and the edge of the vertical plate splicing to form a fork frame welded product; Measure the distance between the outer side of the vertical plane of the vertical plate. If there is a discrepancy, the two vertical plates are corrected again by hydraulic straightening fixture until the vertical planes of the two vertical plates are parallel and the width distance between the outer side of the vertical planes of the two vertical plates meets the requirements. Step 6): The welded forklift frame can then be painted.

[0008] Preferably, in step 6), a coating protection device is installed on the welded assembly of the fork frame before coating.

[0009] More preferably, the coating protection device is used to prevent the coating spray from damaging the outer circle, inner hole, and screw hole of the component. The specific installation positions are: the outer circle and end face of the longitudinal roller shaft and the composite roller shaft, the screw hole of the column, the screw hole of the vertical plate, and the inner hole and screw hole of the hanging chain plate.

[0010] Preferably, in step 6), post-treatment is performed after coating, including: shot peening, pre-degreasing, degreasing, secondary washing, silane treatment, secondary washing, drying, powder coating, leveling and curing, and strong cooling. After the welded fork frame assembly is transferred to the coating line, shot peening removes the oxide scale from the surface of the welded fork frame assembly and eliminates welding stress. Silane treatment (including cleaning) followed by powder coating increases the adhesion of the cured powder coating and meets environmental protection requirements.

[0011] This invention utilizes the correction after welding of the fork carriage body. During the subsequent welding of the longitudinal roller shaft and composite roller shaft of the fork carriage, it can effectively avoid the error caused by the deformation of the upper and lower crossbeams and the vertical plane of the vertical plate due to the welding between the vertical plate and the crossbeam after the longitudinal roller shaft and composite roller shaft are welded. This ensures the geometric accuracy of the longitudinal roller and composite roller after they are installed on the longitudinal roller shaft and composite roller shaft. Attached Figure Description

[0012] Figure 1 This is a structural diagram of a forklift fork carriage; Figure 2 This is a schematic diagram of the forklift frame assembly welding process; Figure 3 This is a schematic diagram of the upper and lower crossbeams during correction. Figure 4 This is a schematic diagram of the vertical board correction process; Figure 5 This is a schematic diagram of the welding process between longitudinal roller shafts and composite roller shafts. Figure 6 This is a schematic diagram showing the installation location of the coating protection device.

[0013] Figure 1-6 In the middle, 1-upper crossbeam, 2-column, 3-connecting plate, 4-lower crossbeam, 5-vertical plate, 6-chain plate, 7-limiting block, 8-stiffening plate, 9-longitudinal roller shaft, 10-composite roller shaft, 11-fork frame welding fixture, 12-fork frame welding, 13-press machine, 14-upper straightening die, 15-lower straightening die, 16-hydraulic straightening fixture, 17-vertical surface, 18-plane, 19-fork frame welding roller shaft welding fixture, 20-protective workpiece one, 21-protective workpiece two, 22-protective workpiece three, 23-protective workpiece four, 24-protective workpiece five, 25-protective workpiece six, 26-protective workpiece seven, 27-protective workpiece eight. Detailed Implementation

[0014] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0015] Example A forklift fork carriage welding process includes the following steps: S1, such as Figure 1 Each of the following is provided: one upper crossbeam (panel 1), one lower crossbeam (panel 4), two vertical plates (panel 5), two columns (panel 2), two connecting plates (panel 3), four stiffening plates (panel 8), two hanging chain plates (panel 6), one limiting block (panel 7), two longitudinal roller shafts (bar material 9), and four composite roller shafts (bar material 10). S2. Process each part blank into a finished product: 1. Upper crossbeam 1 machining process: CNC cutting – leveling – milling – transfer and welding; 2. Lower crossbeam 4 machining process: CNC cutting – straightening – flame cutting – drilling and tapping – transfer and welding; 3. Vertical plate 5 processing technology: CNC cutting – leveling – milling – drilling and tapping – transfer and welding; 4. Machining process for column 2: CNC cutting – leveling – drilling and tapping – transfer and welding; 5. Processing technology of connecting plate 3: CNC cutting - gas cutting beveling - transfer welding; 6. Rib plate 8 processing technology: CNC cutting – transfer and welding; 7. Chain plate 6 processing technology: CNC cutting - milling - drilling and tapping - transfer and welding; 8. Limiting block 7 machining process: CNC cutting – transfer welding; 9. Longitudinal roller shaft 9 machining process: sawing - tempering - turning - pickling and phosphating - transfer and welding; 10. Composite roller shaft 10 processing technology: sawing - heat treatment - turning - drilling - pickling and phosphating - transfer and welding; S3. Forklift frame assembly welding: such as Figure 2 As shown, the upper crossbeam 1, lower crossbeam 4, two connecting plates 3, two uprights 2, two vertical plates 5, four stiffening plates 8, two chain plates 6, and one limiting block 7 are spliced ​​and positioned on the fork frame welding fixture 11; multiple spot welds are made to the edges of the upper crossbeam 1, lower crossbeam 4, connecting plates 3, and two vertical plates 5, multiple spot welds are made to the edges of the upper crossbeam 1, lower crossbeam 4, and two uprights 2, multiple spot welds are made to the edges of the upper crossbeam 1, lower crossbeam 4, and four stiffening plates 8, multiple spot welds are made to the edges of the two vertical plates 5, two chain plates 6, and multiple spot welds are made to the edges of the vertical plate 5 and the limiting block 7; S4. Forklift frame welding: After spot welding is completed, the forklift frame is fully welded along the splicing edges of the upper crossbeam 1, lower crossbeam 4, 2 connecting plates 3, 2 vertical plates 5, 2 uprights 2, 4 stiffening plates 8, 2 chain hanging plates 6, and one limiting block 7 to form the forklift frame welding 12. Figure 2 (The part with double dots and dashes in the middle). S5. Forklift frame welding correction: (e.g.) Figure 3As shown, the upper crossbeam 1 and lower crossbeam 4 of the fork frame welded 12 are pressed and leveled using a press 13 until the two surfaces are horizontal and flush. Figure 4 As shown, the two vertical plates 5 of the fork frame welded 12 are then corrected by the hydraulic straightening clamp 16 until the vertical plane 17 of the two vertical plates 5 is parallel, and the width distance L of the outer side of the vertical plane 17 of the two vertical plates 5 meets the requirements. The vertical plane 17 of the two vertical plates 5 is perpendicular to the plane 18 where the upper crossbeam 1 and the lower crossbeam 4 are located. S6, 2 longitudinal roller shafts, 9, 4 composite roller shafts, 10 welded together: (e.g.) Figure 5 As shown, the fork frame body welding assembly 12, two longitudinal roller shafts 9, and four composite roller shafts 10 are spliced ​​and positioned on the fork splicing roller shaft welding fixture 19. Multiple spot welds are made to the splicing edges of the two vertical plates 5 and the two longitudinal roller shafts and four composite roller shafts 10. The two longitudinal roller shafts 9 are spot welded to be coaxial and meet the positional dimension requirements. The line connecting the axes of the two longitudinal roller shafts 9 is parallel to the horizontal plane of the upper crossbeam 1 and the lower crossbeam 4 and perpendicular to the vertical plane of the two vertical plates. The four composite roller shafts 10 are distributed as shown in the figure so that the two pairs of composite roller shafts 10 correspond one-to-one and are coaxial, and meet the positional dimension requirements. The line connecting the axes is parallel to the horizontal plane of the upper crossbeam 1 and the lower crossbeam 4 and perpendicular to the vertical plane of the two vertical plates.

[0016] S7. Welding of the two longitudinal roller shafts 9 and four composite roller shafts 10 of the fork carriage: After spot welding is completed, full welding is performed along the splicing edge of the two longitudinal roller shafts 9, four composite roller shafts 10 and vertical plate 5 to form a welded fork carriage body; If the width distance L of the outer side of the vertical surface 17 of the two vertical plates 5 is not in line with the measurement, the two vertical plates 5 are corrected again by hydraulic straightening clamp 16 until the vertical surface 17 of the two vertical plates 5 is parallel and the width distance L of the outer side of the vertical surface 17 of the two vertical plates 5 meets the requirements.

[0017] S8. Painting process for welded forklift frames: Welding – Straightening – Installation of protective coating devices – Shot blasting – Pre-degreasing – Degreasing – Secondary water washing – Silane – Secondary water washing – Drying – Powder coating – Leveling and curing – Strong cooling – Coating and warehousing. This process is existing technology, and specific details and parameters are not required.

[0018] By adopting the above technical solutions, such as Figure 3 After the fork carriage body is welded in the fork carriage body welding 12, the upper crossbeam 1 and lower crossbeam 4 are straightened using a press 13 to ensure that the upper crossbeam 1 and lower crossbeam 4 of the fork carriage body welding 12 are horizontal and aligned. Figure 5 The hydraulic straightening clamp 16 is used to straighten the two vertical plates 5 to make the vertical surfaces 17 of the two vertical plates 5 parallel, and the width distance L of the outer side of the vertical surfaces 17 of the two vertical plates 5 meets the requirements; the vertical surfaces 17 of the two vertical plates 5 are perpendicular to the plane 18 where the upper crossbeam 1 and the lower crossbeam 4 are located.

[0019] Optional, such as Figure 3 The press 13 is used to level the horizontal surfaces of the upper crossbeam 1 and lower crossbeam 4 of the fork frame welded 12. An arc-shaped anti-deformation support device is added between the upper crossbeam 2 and the lower crossbeam 4 so that the press 13 presses down the upper crossbeam 1 and the lower crossbeam 4 to the limit stroke and then retracts. After elastic deformation, the horizontal surfaces of the upper crossbeam 1 and the lower crossbeam 4 can reach a horizontal and flat state. like Figure 4 The hydraulic straightening clamp 16 straightens the vertical surfaces 17 of the two vertical plates 5 welded to the fork frame body 12 until the vertical surfaces 17 of the two vertical plates 5 are parallel and the outer width distance L of the vertical surfaces 17 of the two vertical plates 5 meets the requirements. The vertical surfaces 17 of the two vertical plates 5 are perpendicular to the plane 18 where the upper crossbeam 1 and the lower crossbeam 4 are located. The length and width of the vertical surfaces 17 of the two vertical plates 5 must meet the requirements of the outer width distance L.

[0020] By adopting the above technical solution and utilizing the correction after welding the fork frame, the subsequent welding of the longitudinal roller shaft 9 and the composite roller shaft 10 can effectively avoid the error caused by the deformation of the vertical surface 17 of the upper crossbeam 1, lower crossbeam 4 and the two vertical plates 5 due to the welding between the two vertical plates 5 and the upper crossbeam 1 and lower crossbeam 4. This ensures the geometric accuracy of the longitudinal rollers and composite rollers after they are installed on the longitudinal roller shaft 9 and the composite roller shaft 10.

[0021] By adopting the above technical solution, after being transferred to the painting production line, the welded fork frame assembly is shot blasted to remove its surface oxide scale and eliminate the welding stress of the fork frame assembly.

[0022] By adopting the above technical solution, the welded fork frame assembly is treated with silane (including cleaning) and then powder coated. The silane treatment increases the adhesion of the cured powder coating and meets the requirements for harmless and environmentally friendly treatment. Optional, such as Figure 6 As shown, before the welded fork frame assembly enters the painting line, the outer circle and end face of the longitudinal roller shaft 8 and the composite roller shaft 9, as well as the screw holes of the column 2, the vertical plate 5, the chain plate 6, and the screw holes, must be protected (i.e., protective workpieces are installed on the inner hole and screw hole of the chain plate assembly, the column screw hole, the outer circle and end face of the longitudinal roller assembly, the vertical plate screw hole, the outer circle and inner hole and end face of the composite roller assembly, the inner hole and screw hole of the chain plate assembly, the column screw hole, and the outer circle and end face of the longitudinal roller assembly) to prevent damage to the assembly outer circle, assembly inner hole, and assembly screw hole by shot blasting and powder spraying.

Claims

1. A welding process for forklift fork carriages, characterized in that, Includes the following steps: Step 1): Fork frame assembly welding: On the fork frame assembly welding fixture (11), assemble the positioning upper crossbeam (1), lower crossbeam (4), 2 connecting plates (3), 2 uprights (2), 2 vertical plates (5), 4 stiffening plates (8), 2 chain hanging plates (6), and limit block (7); weld multiple spot welds to the edges of the upper crossbeam (1), lower crossbeam (4), connecting plates (3), and vertical plates (5) for assembly; weld multiple spot welds to the edges of the upper crossbeam (1), lower crossbeam (4), and uprights (2) for assembly; weld multiple spot welds to the edges of the upper crossbeam (1), lower crossbeam (4), and stiffening plates (8) for assembly; weld multiple spot welds to the edges of the vertical plates (5) and chain hanging plates (6) for assembly; weld multiple spot welds to the edges of the vertical plates (5) and limit block (7) for assembly. Step 2): Fork frame welding: Weld the upper crossbeam (1), lower crossbeam (4), connecting plate (3), vertical plate (5), column (2), stiffening plate (8), hanging chain plate (6), and limit block (7) to form a fork frame weld (12); Step 3): Fork frame welding and straightening: Use a press (13) to press and straighten the upper crossbeam (1) and lower crossbeam (4) of the fork frame welding (12) to be level and flush. Use a hydraulic straightening fixture (16) to straighten the two vertical plates (5) of the fork frame welding (12) to be parallel to the vertical surface (17) of the vertical plate (5) and the width distance between the outer sides of the vertical surface (17) of the two vertical plates (5) meets the requirements. The vertical surface (17) of the two vertical plates (5) is perpendicular to the plane (18) where the upper crossbeam (1) and lower crossbeam (4) are located. Step 4): Welding of longitudinal roller shaft (9) and composite roller shaft (10): On the fork frame welding roller shaft welding fixture (19), the positioning fork frame welding fixture (12), longitudinal roller shaft (9), and composite roller shaft (10) are spliced ​​together; multiple spot welds are made to the vertical plate (5) and the splicing edge of the longitudinal roller shaft (9) and composite roller shaft (10), and spot welds are made to ensure that the two longitudinal roller shafts (9) are coaxial and meet the position and size requirements, so that the two longitudinal rollers are aligned. The axis of shaft (9) is on the same straight line and is parallel to the plane (18) where the upper crossbeam (1) and lower crossbeam (4) are located, and perpendicular to the vertical plane (17) of the vertical plate (5). The corresponding composite roller shafts (10) are coaxially distributed and meet the position and size requirements. The axis of the corresponding composite roller shaft (10) is on the same straight line and is parallel to the plane (18) where the upper crossbeam (1) and lower crossbeam (4) are located, and perpendicular to the vertical plane (17) of the vertical plate (5). Step 5): Welding of longitudinal roller shaft (9) and composite roller shaft (10): Weld along the splicing edge of longitudinal roller shaft (9), composite roller shaft (10) and vertical plate (5) to form a fork frame welded product; Measure the distance on the outside of the vertical surface (17) of the vertical plate (5). If there is a discrepancy, use hydraulic straightening clamp (16) to straighten the two vertical plates (5) again until the vertical surface (17) of the vertical plate (5) is parallel and the width distance on the outside of the vertical surface (17) of the two vertical plates (5) meets the requirements. Step 6): The welded forklift frame can then be painted.

2. The forklift fork frame welding process as described in claim 1, characterized in that, In step 6), a painting protection device is installed on the welded assembly of the fork frame before painting.

3. The forklift fork frame welding process as described in claim 2, characterized in that, The coating protection device is used to prevent the coating spray from damaging the outer circle, inner hole and screw hole of the component. The specific installation positions are: the outer circle and end face of the longitudinal roller shaft (8) and the composite roller shaft (9), the screw hole of the column (2), the screw hole of the vertical plate (5), and the inner hole and screw hole of the hanging chain plate (6).

4. The forklift fork frame welding process as described in claim 1, characterized in that, In step 6), post-treatment is required after coating, including: shot peening, pre-degreasing, degreasing, secondary water washing, silane treatment, secondary water washing, drying, powder spraying, leveling and curing, and strong cooling.

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