Small diameter blast head

Abstract

The invention discloses a small-diameter sand blasting head suitable for sand blasting the inner wall of tubular and cavity workpieces through small holes, which is composed of a main and a secondary boron carbide sand blasting nozzle with a cylindrical shape, a sand blasting nozzle cover, a rigid sand conveying pipe connected with a press-in sand blasting machine sand blasting pipe and a fixing mechanism. The small-diameter sand blasting head eliminates the design defects of the existing inner wall sand blasting head, i.e. the occupied axial position and the forced increase of the radial dimension, and has a more compact overall structure and effectively reduces the radial dimension. These improvements are conducive to the sand blasting head to pass through smaller holes and efficiently process the tubular and cavity workpieces which are difficult to be processed by the existing inner wall sand blasting head.

Description

TECHNICAL FIELD

[0001] The application discloses a small-diameter sand blasting head suitable for sand blasting on the inner wall of a tubular workpiece and a cavity workpiece through a small hole, which is composed of a main part and a sub part of a cylindrical boron carbide sand blasting nozzle, a sand blasting nozzle cover, a rigid sand blasting pipe and a fixing mechanism. BACKGROUND

[0002] The sand blasting technology is widely applied to surface preparation and pretreatment of various workpieces before surface spraying and coating. The main function of sand blasting is to remove the original rust and dirt of the workpiece, expose the material base of the workpiece and produce a rough surface. The surface treated by sand blasting greatly improves the bonding strength and service life of the subsequent coating layer. Therefore, the sand blasting technology has been widely applied in surface engineering.

[0003] The sand blasting head is a device provided with a sand blasting nozzle and capable of generating a high-speed sand blasting jet. The sand blasting nozzle is usually a cylindrical ceramic part provided with a central nozzle, such as boron carbide. The small-hole workpiece usually refers to a tubular and cavity workpiece with a small inlet. It is still a difficulty to perform sand blasting on the inside of such a workpiece in the application of the sand blasting technology. The existing technology for solving such a sand blasting problem includes an inner wall sand blasting head. The inner wall sand blasting head has two types: 1) a bent pipe or a three-pronged pipe sand blasting head, and 2) a scattering sand blasting head.

[0004] The bent pipe or the three-pronged pipe sand blasting head is provided with a sand blasting nozzle at the end of a bent pipe or a three-pronged pipe, and a sand blasting jet with a certain off-axis angle is sprayed out of the nozzle with a bending angle to perform sand blasting on the inner wall surface. The advantages of the sand blasting head are that the high-speed and high-efficiency properties of the sand blasting nozzle are basically maintained. The disadvantages are that the bending head and the three-pronged structure increase the radial dimension, and to a certain extent, affect the passability of the small hole.

[0005] A scattering blasting head consists of a blasting nozzle mounted on the end of a straight pipe. A wear-resistant connecting rod is fixed at a specific position inside the nozzle. The connecting rod extends from the inside along the central nozzle axis, and an axisymmetric conical scattering head is installed at the end of the connecting rod. The blasting jet is ejected from the annular slit nozzle formed between the central nozzle and the connecting rod, creating a free, annular blasting jet. This jet first impacts the conical inclined surface of the scattering head, where it is guided to generate a 360-degree fan-shaped free blasting jet with an off-axis angle, thus achieving the purpose of wall blasting. The disadvantages of scattering sandblasting heads are as follows: 1) The sandblasting jet that reaches the wall is formed after being impacted by the scattering head, resulting in a large energy loss; 2) The sand particles in the fan-shaped sandblasting jet are widely dispersed, the energy is not concentrated and cannot be guaranteed to be uniform, and the surface roughness is low; 3) The connecting rod itself, the fixed support component of the connecting rod, the sandblasting nozzle and the scattering head all have to withstand the high-speed scouring of sand particles, which puts a heavy wear burden on them, involves a lot of wear-resistant materials, and has a complex shape and is difficult to process; 4) The connecting rod itself usually has to be fitted with a thick boron carbide sleeve, and it has to pass through the axis of the central nozzle, which occupies the axis position, resulting in a corresponding increase in the radial dimension of the sandblasting head structure, which also affects the passage of small holes to a certain extent.

[0006] Existing internal wall blasting heads suffer from design flaws, such as occupied axial space and forced increase in radial dimensions, which affect the passage of small holes. In practical applications, the problem of internal wall blasting for holes smaller than 50mm remains unresolved. Summary of the Invention:

[0007] The purpose of this invention is to reduce and eliminate structural factors that lead to an additional increase in radial dimensions, and to provide a small-diameter blasting head suitable for blasting inner walls through smaller orifices.

[0008] The small-diameter blasting head consists of two main and auxiliary boron carbide blasting nozzles with a tightly fitting cylindrical shape as the core functional components, and a blasting nozzle jacket, a rigid sand delivery pipe, and a fixing mechanism as auxiliary installation components.

[0009] The small-diameter blasting head utilizes two core functions—generating a high-speed sandblasting jet and creating an off-axis deflection angle—each performed by two boron carbide nozzles fitted together. The main nozzle generates the high-speed jet, while the secondary nozzle forces it off-axis. This design eliminates the need for a central axial position and avoids obstructing radial space; all components have a cylindrical outer contour, significantly reducing the maximum radial dimension of the blasting head structure.

[0010] Main blasting nozzle: A traditional and effective blasting nozzle with a cylindrical shape and a single center nozzle.

[0011] The secondary blasting nozzle is a solid cylindrical boron carbide part with a slanted groove between its inlet end plane (the surface that mates with the outlet end face of the main blasting nozzle) and the curved surface of the cylinder. The contour line formed by the slanted groove opening on the inlet end plane of the secondary blasting nozzle must be located outside the circular contour line of the main blasting nozzle's central nozzle on the outlet end plane to ensure that the entire blasting jet smoothly enters the slanted groove channel. The blasting outlet of the slanted groove is formed on the curved surface of the cylinder (it cannot extend to the other end plane). The blasting jet, guided by the slanted groove, forms a blasting jet that deviates from the axial direction with a fixed off-axis angle.

[0012] Sandblasting nozzle sleeve: This is a thin-walled tubular part in which two boron carbide sandblasting nozzles are placed in the central cavity. The sleeve has windows on its arc-shaped sidewalls. These windows serve as both the process port for installing the sandblasting nozzles and the injection window for the sandblasting jet. The two ends of the sleeve have threaded connections.

[0013] Rigid sand delivery pipe: This is a rigid pipe that connects to the sandblasting pipe of a pressure-type sandblasting machine at one end and is sealed to the inlet end of the sandblasting nozzle at the other end. The rigid sand delivery pipe serves as a sand flow channel and also allows for real-time sandblasting operations by extending deep into the workpiece.

[0014] Fixing mechanism: Responsible for installing and securing the two sandblasting nozzles in place. The simplest mechanism is the set screw mechanism.

[0015] Two sandblasting nozzles are inserted sequentially into the cavity in the middle of the outer sleeve through the side window of the outer sleeve and secured with set screws. One end of the rigid sand delivery pipe is threadedly sealed to the outer sleeve of the sandblasting nozzle, and the other end is sealed to the sandblasting pipe of the sandblasting machine. During operation, the sandblasting fluid, under air pressure, flows through the sandblasting pipe of the pressure-feed sandblasting machine, through the rigid sand delivery pipe, and reaches the central nozzle of the main sandblasting nozzle. The sandblasting jet, accelerated by the main sandblasting nozzle, is directly injected from the nozzle outlet into the inclined channel in the secondary sandblasting nozzle. Guided by the inclined channel, the sandblasting jet deviates from the axial direction and exits from the inclined channel outlet on the cylindrical curved surface of the secondary sandblasting nozzle, which is also the sand outlet of the small-diameter sandblasting head. The free sandblasting jet with an off-axis angle directly impacts the workpiece wall to complete the sandblasting process.

[0016] Beneficial effects:

[0017] The main improvement of the small-diameter blasting head compared to existing internal wall blasting heads lies in eliminating the design flaws that affect the passage of small holes caused by the occupation of the axial position and the forced increase in radial dimensions. Its advantages also include: 1) It retains the traditional and effective use of a single-center nozzle, maintaining high speed and efficiency; 2) The inlet end plane of the auxiliary nozzle is closely fitted with the outlet end plane of the main nozzle, ensuring unobstructed passage between the main and auxiliary nozzles and minimizing energy loss; 3) The inclined channel, covered by the outlet section of the main nozzle, forms a closed pipe space, still part of the nozzle. The concentrated energy of the blasting jet ejected from the closed inclined channel outlet is consistent, better meeting the requirements of blasting applications than the fan-shaped scattering jet of the internal wall scattering head; 4) The rear of the inclined channel is a large volume of complete boron carbide material, providing high redundancy against erosion and wear, resulting in a long service life; 5) The small-diameter blasting head and its components have a cylindrical shape and are distributed along the axis, eliminating the defects of the occupied central nozzle axial position and increased radial structural dimensions, resulting in a more compact overall structure, especially the radial structure.

[0018] The sand outlet of the secondary sandblasting nozzle is an open, beveled shape. The axis of the cylindrical shape of the secondary sandblasting nozzle coincides with the axis of the main nozzle. The greatest benefit of this design is that the outer contour of this open, beveled secondary sandblasting nozzle is still cylindrical, which allows the radial dimension of the nozzle to be smaller. Attached image description:

[0019] The following is in conjunction with the appendix Figure 1 The working principle of this invention will be further explained below. (Appendix) Figure 1 This is a view and cross-sectional view of a small-diameter sandblasting head, showing its internal structure. It is one embodiment. Detailed implementation method:

[0020] A small-diameter blasting head is characterized by comprising a single-center nozzle boron carbide main blasting nozzle (1), a secondary blasting nozzle (2) with a groove on a solid cylindrical boron carbide body, a blasting nozzle sleeve (3), a rigid sand delivery pipe (4), and a set screw (5); the outlet end plane of the single-center nozzle main blasting nozzle (1) is closely attached to the inlet end plane of the secondary blasting nozzle (2); the secondary blasting nozzle (2) is a cylindrical boron carbide body with a groove extending from the inlet end plane to the cylindrical curved surface; the opening contour lines of the grooves of the secondary blasting nozzle (2) on the inlet end plane are all located outside the circular contour lines formed by the central nozzle of the main blasting nozzle (1) on its outlet end plane, so as to ensure the smooth flow of the blasting jet in the main and secondary blasting nozzles. The channel is unobstructed; the opening formed by the inclined groove on the cylindrical curved surface of the auxiliary sandblasting nozzle (2), i.e. the sandblasting outlet, cannot extend to the end plane of the other end; the sandblasting nozzle sleeve (3) is a thin-walled tubular structure with windows on the side wall, with threads at both ends, and the middle cavity is the position for sequentially installing the main sandblasting nozzle (1) and the auxiliary sandblasting nozzle (2) along the axial direction; the window on the sandblasting nozzle sleeve (3) is both a process hole for assembling the sandblasting nozzle and a window for the sandblasting jet to be sprayed; the rigid sand conveying pipe (4) is a rigid pipe, one end of which is sealed and connected to the sandblasting pipe of the press-type sandblasting machine, and the other end is threaded and sealed and connected to the sandblasting nozzle sleeve (3); the set screw (5) is used to press and fix the main and auxiliary sandblasting nozzles.

[0021] Two sandblasting nozzles (1) and (2) are inserted sequentially into the cavity in the middle of the sandblasting nozzle sleeve (3) through the side window of the sandblasting nozzle sleeve (3) and tightened with set screws (5). One end of the rigid sand delivery pipe (4) is threadedly sealed to the sandblasting nozzle sleeve (3), and the other end is sealed to the sandblasting pipe of the sandblasting machine. During operation, the sandblasting fluid, under the action of air pressure, flows through the sandblasting pipe of the pressure-type sandblasting machine and through the rigid sand conveying pipe (4) to the central nozzle of the main sandblasting nozzle (1). The sandblasting jet accelerated by the main sandblasting nozzle (1) is directly injected from the nozzle outlet into the inclined channel in the auxiliary sandblasting nozzle (2). Under the guidance of the inclined channel, the sandblasting jet deviates from the axial direction and is ejected from the inclined channel outlet on the cylindrical curved surface of the auxiliary sandblasting nozzle (2), which is the sand outlet of the small rod diameter sandblasting head. The free sandblasting jet with an off-axis angle directly impacts the workpiece wall to complete the sandblasting behavior. The sand outlet of the auxiliary sandblasting nozzle (2) is an open inclined surface configuration. The axis of the cylindrical surface of the auxiliary sandblasting nozzle (2) coincides with the axis of the main sandblasting nozzle (1).

Claims

1. A small-diameter sandblasting head, characterized in that: It consists of a single-center-nozzle boron carbide main blasting nozzle (1), a secondary blasting nozzle (2) with a groove on a solid cylindrical boron carbide body, a blasting nozzle sleeve (3), a rigid sand delivery pipe (4), and a set screw (5); the outlet end plane of the main blasting nozzle (1) is in close contact with the inlet end plane of the secondary blasting nozzle (2); the secondary blasting nozzle (2) is a cylindrical boron carbide body with a groove from the inlet end plane to the cylindrical curved surface; the opening contour lines of the grooves of the secondary blasting nozzle (2) on the inlet end plane are all located outside the circular contour lines formed by the central nozzle of the main blasting nozzle (1) on its outlet end plane, so as to ensure that the flow channel of the sandblasting jet in the main and secondary blasting nozzles is unobstructed; the opening formed by the grooves on the cylindrical curved surface of the secondary blasting nozzle (2) is the sandblasting outlet. The sandblasting nozzle sleeve (3) is a thin-walled tubular structure with windows on its sidewalls. It has threads at both ends and the middle cavity is where the main sandblasting nozzle (1) and the auxiliary sandblasting nozzle (2) are installed sequentially along the axial direction. The windows on the sandblasting nozzle sleeve (3) are both process holes for assembling the sandblasting nozzles and windows for the sandblasting jet. The rigid sand conveying pipe (4) is a rigid pipe with one end sealed to the sandblasting pipe of the press-fit sandblasting machine and the other end threaded to the sandblasting nozzle sleeve (3). The set screw (5) is used to press and fix the main and auxiliary sandblasting nozzles. The sand outlet of the auxiliary sandblasting nozzle (2) is an open inclined surface configuration. The axis of the cylindrical surface of the auxiliary sandblasting nozzle (2) coincides with the axis of the main sandblasting nozzle (1).

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