A torsion multiplier fixture for liquid rocket engines

Abstract

The application discloses a torsion multiplier fixing device for a liquid rocket engine, which comprises a base, a gland and a counterforce bearing bolt. The base is fixed to the flange surface of an internally threaded part, the inner cavity of the main body part of the base is adapted to the outer wall of the output end of the torsion multiplier and forms an axial bearing; the gland is fastened above the base and applies axial, radial and inclined constraints to the shell together with the base; the counterforce bearing bolt is screwed into the threaded hole of the base through the gland and serves as a connecting piece and a force bearing piece, and bears the counter torque generated by the original counterforce handle bearing. The shell counter torque is transmitted to the flange surface of the internally threaded part through the counterforce handle, the counterforce bearing bolt and the base in sequence, forming a closed force transmission path irrelevant to the external environment; an axial gap is reserved between the end surface of the output end and the end surface of the tightening adapter tool, and the torque is only transmitted through the interface of the four-square joint. The application eliminates the dependence on external fulcrums, does not need manual support, has high torque accuracy and is suitable for large torque precision fastening in narrow spaces such as valves and turbine pumps.

Description

Technical Field

[0001] This invention relates to the field of aerospace engine assembly process equipment technology, specifically a torque multiplier fixing device for liquid rocket engines. Background Technology

[0002] A torque multiplier is a manual force-increasing fastening tool that uses planetary gear transmission as its torque-increasing principle. A reaction arm is a cantilevered member commonly used in existing technology to balance the reaction torque of the torque multiplier housing. This solution has been widely used in the routine maintenance of large fixed equipment and has proven to be largely effective. However, it suffers from systemic defects such as strong fulcrum dependence, uncertain fulcrum position, safety risks associated with manual support, operational accuracy affected by fulcrum conditions, and poor adaptability.

[0003] The assembly of valve components and turbopump components in liquid rocket engines places far more stringent requirements on the use of torque multipliers than in ordinary industrial scenarios, and its special characteristics are mainly reflected in the following four aspects.

[0004] (1) Extreme Cryogenic Conditions. Liquid rocket engines use cryogenic propellants as working fluids. The operating temperature of liquid oxygen is approximately -183°C, and that of liquid hydrogen is approximately -253°C. In this temperature range, the elastic modulus, yield strength, and elongation of metallic materials change significantly. Furthermore, due to differences in the coefficient of linear expansion of different materials, the fit clearance and contact stiffness of threaded pairs change when transitioning from room temperature assembly to cryogenic operation. There must be a precise margin between the preload torque applied during assembly and the actual preload force maintained under cryogenic conditions. This requires that the torque applied during room temperature assembly must be highly accurate and reproducible. Any torque deviation introduced by unstable tool fixing or uncertain force path will be further amplified after cryogenic contraction, directly jeopardizing the reliability of valve seals.

[0005] (2) High-pressure sealing reliability requirements. The working pressure of the propellant delivery pipeline system of a liquid rocket engine is usually 5-25 MPa. The preload of the threaded connection on the valve seat sealing surface directly determines the establishment of the sealing specific pressure, and thus the sealing reliability and valve operation sensitivity. If the preload torque exceeds the process tolerance zone: if it is too small, it will lead to insufficient specific pressure on the sealing surface and propellant leakage, which is very likely to cause combustion and explosion accidents in low temperature, high pressure and strong oxidation environment; if it is too large, it may cause plastic crushing of the sealing surface or yielding of the threaded connection, which will also result in loss of sealing function.

[0006] (3) Extremely high assembly precision requirements for turbopump assemblies. The turbopump rotor assembly (including rotor shaft, impeller locking nut, bearing clamping parts, etc.) of liquid rocket engines operates at speeds in the tens of thousands or even hundreds of thousands of revolutions per minute. The tightening torque precision of its threaded connections directly determines the bearing preload, rotor dynamic balance characteristics, critical shaft speed, and bearing clearance. Excessive torque deviation will lead to abnormal shaft stiffness and dynamic balance failure, and in severe cases, it will cause rotor jamming or high-cycle resonance fatigue fracture, endangering the safety of the entire machine.

[0007] (4) Limitations of narrow and enclosed assembly space. The components inside the engine compartment are densely packed, with propellant lines, sensors, cables and supports intertwined, leaving extremely limited free space for tools. The external support space required by traditional reaction arm solutions is difficult to guarantee in such situations, and operators cannot safely extend their arms to support the reaction arm, severely restricting the effective implementation of high-torque fastening operations.

[0008] In summary, the liquid rocket engine assembly field has placed comprehensive demands on the fixing scheme of torque multipliers, including "strong spatial adaptability, safe and reliable operation, and high torque accuracy." Existing reaction arm schemes, with their open force transmission paths, rely on the external environmental conditions of the work site and cannot simultaneously meet the above three requirements. Therefore, a novel fixing device design is urgently needed to address this issue. Summary of the Invention

[0009] To address the shortcomings of the existing technology, the present invention aims to provide a torque multiplier fixing device for liquid rocket engines, which completely overcomes the dependence of traditional reaction arm schemes on external fulcrums, and simultaneously solves the safety and torque output accuracy problems of high torque fastening operations. This enables the torque multiplier to reliably, safely, and with high precision perform high torque fastening operations in the narrow and enclosed assembly parts of liquid rocket engine compartments where there are no available support structures.

[0010] This invention is based on the concept of self-closing force transmission path. The self-closing force transmission path, as referred to in this invention, means that the reaction torque generated by the torque multiplier during operation is directly transmitted back to the flange surface of the tightened part through a structured force transmission path defined within the fixing device. This ensures that the starting and ending points of the force path fall on the same part, and the entire force system achieves complete self-balancing locally within the tightened part, thereby forming an independent closed force transmission loop independent of the external environment.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a torque multiplier fixing device for a liquid rocket engine, comprising a base, a pressure cap, and a reaction force abutment bolt. The base is fixed to the flange face of an internally threaded part, and the inner cavity of the base body is adapted to the shape of the outer wall of the output end of the torque multiplier to form axial support; the pressure cap is fastened to the top of the base, and the inner cavity of the pressure cap body is adapted to the outer wall of the input end of the torque multiplier, and together with the base, applies axial, radial, and tilt constraints to its shell; the reaction force abutment bolt passes through the pressure cap and is screwed into the threaded hole of the base to fix the two together, and bears the reaction torque generated by the original reaction force handle of the torque multiplier; the reaction torque of the torque multiplier shell is transmitted sequentially through the original reaction force handle, the reaction force abutment bolt, and the base to the flange face of the internally threaded part, forming a closed force transmission path independent of the external environment.

[0012] Furthermore, the base is an integral metal component, comprising a first flange, a base body, and a second flange in sequence; the first flange has a plurality of first mounting holes, and the base is fixed to the flange face of the internally threaded part by clamping bolts passing through the first mounting holes; the second flange has a plurality of threaded holes for screwing in reaction force abutment bolts and bearing the shear force and bending moment transmitted therefrom.

[0013] Furthermore, the pressure cap is an integral metal component, including a third flange and a pressure cap body; the third flange has several second mounting holes, the positions of which correspond one-to-one with the positions of the threaded holes on the base, for inserting the reaction force abutment bolts; the inner cavity shape of the pressure cap body is adapted to the outer wall shape of the torque multiplier input end, and the pressing surface of the pressure cap body is in contact with the end face of the torque multiplier input end.

[0014] Furthermore, the inner cavity of the base body and the outer wall of the output end of the torque multiplier, and the inner cavity of the pressure cap body and the outer wall of the input end of the torque multiplier, maintain a radial clearance fit, so that the input and output ends of the torque multiplier can rotate freely within the base and the pressure cap during tightening operations without contacting or rubbing against the base or the pressure cap.

[0015] Furthermore, the number of reaction force abutment bolts is three, and the three reaction force abutment bolts are evenly distributed along the circumference of the pressure cap. The three reaction force abutment bolts jointly bear the total reaction torque on the torque multiplier housing, and the reaction torque borne by a single reaction force abutment bolt is about one-third of the total value.

[0016] Furthermore, the first flange portion has six first mounting holes, which are evenly distributed around the circumference of the base to provide sufficient flange fastening contact area and uniform clamping force distribution.

[0017] Furthermore, it also includes a tightening adapter, one end of which has a square hole that mates with the square connector of the torque multiplier output end, and the other end has a drive groove that mates with the head of the external threaded part. The tightening adapter transmits the torque amplified by the planetary gear mechanism from the torque multiplier output end to the external threaded part. An axial clearance is reserved between the end face of the torque multiplier output end and the end face of the tightening adapter.

[0018] Furthermore, after the base is installed on the flange face of the internal threaded part, its installation orientation allows the cantilever end of the original reaction handle of the torque multiplier to naturally abut against the side of the reaction force abutment bolt during tightening operations. No structural modifications to the torque multiplier body are required, and the reaction torque of the housing is directly transmitted to the reaction force abutment bolt by reusing the original reaction handle.

[0019] Furthermore, the base and the pressure cap are made of alloy structural steel or titanium alloy.

[0020] Furthermore, the axial clearance between the output end face of the torque multiplier and the end face of the tightening adapter prevents axial contact between the two end faces, and the actual preload torque acting on the external threaded part is uniquely determined only by the four-way connector interface.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] (1) Completely eliminates dependence on external support points. Through the self-closed design of the force transmission path, the fixing device can independently bear and transmit the reaction torque at any assembly position, without relying on any external environmental conditions. It is particularly suitable for complex assembly occasions where the space inside the liquid rocket engine compartment is closed and there are no suitable supports around.

[0023] (2) Significantly improves the safety of high torque operation. The operator does not need to hold or support the reaction arm during the entire operation, which fundamentally eliminates the risk of mechanical injury caused by sudden slippage of the reaction arm, while reducing labor intensity and improving the safety level of the operation.

[0024] (3) Significantly improves torque application accuracy. The axial clearance isolation design at the output end eliminates the additional torque error caused by end face friction, and the single-channel torque transmission of the four-way joint ensures the uniqueness of the torque transmission path; the three-dimensional constraint of the base and the pressure cap on the shell eliminates the additional bending moment caused by tool tilting, so that the preload torque actually applied to the threaded connection has good accuracy and reproducibility, meeting the stringent process requirements of the assembly of valve sealing surfaces of liquid rocket engines and turbine pump rotor shaft system.

[0025] (4) The structure is simple and compact, and highly adaptable. The main parts are only three types: base, cover and reaction bolt. The small outline can be used effectively in narrow spaces such as engine compartment. By replacing the base and cover with different internal cavity sizes, different specifications of torque multipliers can be adapted to form a series of products.

[0026] (5) No modification required to the tool body. This invention reuses the original reaction handle of the torque multiplier as the torque transmission bridge, without requiring any processing or modification of the commercially available torque multiplier, making it highly versatile and economical.

[0027] (6) Easy installation and disassembly, and standardized operation. The installation and disassembly steps of the fixing device are fixed, and the operation process is highly repeatable, avoiding inconsistent torque application caused by operator differences and improving the repeatability accuracy of batch assembly. Attached Figure Description

[0028] Figure 1 This is a top view of one embodiment of the torque multiplier fixing device of the present invention;

[0029] Figure 2 for Figure 1 Sectional view of section AA;

[0030] Figure 3 This is a functional module diagram of the torque multiplier fixing device of the present invention;

[0031] Figure 4 This is a schematic diagram of the force transmission path of the torque multiplier fixing device of the present invention.

[0032] In the diagram: 1. Base; 2. Pressure cap; 3. Reaction bolt; 4. Internal threaded part; 5. Clamping bolt; 6. Torque multiplier; 7. Tightening adapter; 8. External threaded part. Detailed Implementation

[0033] The following is in conjunction with the appendix Figure 1 To be continued Figure 4 The technical solution of the present invention will be further described in detail below. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. Equivalent substitutions and improvements made by those skilled in the art without departing from the concept of the present invention all fall within the scope of protection of the present invention.

[0034] In the following description, "axial" refers to the direction parallel to the axis of the externally threaded part 8 being tightened, i.e., the direction of the line connecting the input and output ends of the torque multiplier 6; "radial" refers to the direction perpendicular to and passing through the axis; and "circumferential" refers to the circumferential direction around the axis. The internally threaded part 4 is an assembly with an internally threaded hole and a mounting flange surface on a liquid rocket engine, such as a valve body, pump housing, or bearing clamping seat; the externally threaded part 8 is a threaded connection that requires a large preload torque, such as a valve seat fastening bolt or an impeller lock nut.

[0035] like Figure 1 As shown, the torque multiplier fixing device in this embodiment has a rotating body shape when fully assembled. Figure 1 This is a top view taken from the input end of the torque multiplier 6: the center of the view shows the outline of the square connector at the output end of the torque multiplier 6, and its outer periphery shows the inner cavity outline of the main body of the pressure cover 2, the outer circle outline of the third flange of the pressure cover 2, and the outer circle outline of the first flange of the base 1; among the multiple circular holes evenly distributed circumferentially, the one on the outer ring is the first mounting hole through which the clamping bolt 5 passes, and the one on the inner ring is the second mounting hole through which the reaction force abutment bolt 3 passes. Figure 1 The rod-shaped component extending outward from the outer circle of the device is the original reaction handle of the torque multiplier 6. Its cantilever end abuts against the side of the reaction bolt 3 during tightening. Figure 1 The AA line and arrow in the text indicate Figure 2 The cutting position and projection direction of the sectional view.

[0036] like Figure 2 As shown, by cutting along AA and projecting in the direction of the arrow, the stacked assembly relationship of this device can be clearly seen. Figure 2 In the middle, the leftmost part is the internally threaded part 4 to be assembled, which has a flange face on its upper part for mounting the fixing device, and an internally threaded hole machined inside to mate with the externally threaded part 8; the base 1 is fitted with the flange face of the internally threaded part 4 with its first flange part, and is fastened by the clamping bolt 5 passing through the first mounting hole; the base body of the base 1 extends to the right and forms an inner cavity to accommodate the output end of the torque multiplier 6; the torque multiplier 6 is placed into the inner cavity from right to left, and its output end face is supported on the support surface of the base body; the tightening adapter 7 is located between the output end of the torque multiplier 6 and the head of the externally threaded part 8, and transmits the amplified torque to the externally threaded part 8; the pressure cap 2 is located at Figure 2 On the far right, the torque multiplier 6 is fastened to the input end and fixed by the reaction force abutting bolt 3 to the threaded hole of the second flange of the base 1.

[0037] The base 1 is a one-piece metal component, which consists of three functional sections along the axial direction. The use of a one-piece structure instead of a welded or assembled structure is to avoid micro-movement and relaxation at the connection interface under large torque and alternating loads, and to ensure the rigidity determination of the reaction torque transmission path.

[0038] The first flange section is the connection section between the base 1 and the assembled component. Six first mounting holes are evenly spaced along the circumference of this section. The base 1 is fixedly connected to the flange face of the internally threaded part 4 by six clamping bolts 5 passing through these first mounting holes. The reason for choosing six bolts and their even circumferential distribution is twofold: firstly, to provide sufficient flange tightening contact area, allowing the reaction torque to be evenly introduced to the flange face of the internally threaded part 4 in the combined form of frictional torque and bolt shear; secondly, to obtain a uniform distribution of clamping force, avoiding localized plastic deformation on the thin-walled valve body or pump casing flange of the liquid rocket engine due to excessive local clamping force, thereby protecting the dimensional accuracy and sealing surface flatness of the assembled component.

[0039] The main body of the base serves as the support and radial positioning section. Its inner cavity shape precisely matches and maintains a clearance fit with the outer wall shape of the torque multiplier 6's output end. This provides full-circumferential radial positioning for the torque multiplier 6, preventing radial displacement during tightening. Furthermore, the fitted inner cavity shape constrains the torque multiplier 6's tilting freedom relative to the base 1, ensuring the coaxiality of the torque multiplier 6's output axis with the axis of the external threaded part 8, and preventing the introduction of additional bending moments on the threaded pair due to eccentricity. The stepped end face of the main body of the base facing the internal threaded part 4 forms a support surface, fitting against the output end face of the torque multiplier 6 to provide axial support.

[0040] The second flange section is the load-bearing and connection section. Three threaded holes are evenly distributed along the circumference of this section for screwing in the reaction bolts 3. The second flange section is the final structural node where the reaction torque is transmitted from the fixing device to the flange face of the internally threaded part 4: the shear force and bending moment borne by the reaction bolts 3 are converted into torsional and bending internal forces within the body of the base 1 and transmitted along the main body of the base to the first flange section.

[0041] The gland 2 is also an integral metal component, consisting of two functional areas: the third flange and the main body of the gland.

[0042] The third flange has three second mounting holes, which correspond one-to-one with the three threaded holes on the second flange of the base 1, for inserting the reaction bolts 3. The inner cavity shape of the gland body is adapted to the outer wall shape of the input end of the torque multiplier 6, and its clamping surface fits against the end face of the input end of the torque multiplier 6. When the reaction bolts 3 are tightened, their preload is applied to the end face of the input end of the torque multiplier 6 through the clamping surface of the gland body, forming a pair of axial clamping forces in opposite directions with the supporting force of the base body on the output end face, thereby firmly clamping the housing of the torque multiplier 6 axially between the base 1 and the gland 2.

[0043] In this embodiment, three reaction bolts 3 are provided, evenly distributed around the circumference of the pressure cap 2. They pass through the second mounting hole of the pressure cap 2 and are screwed into the corresponding threaded hole of the second flange of the base 1. The reaction bolts 3 have a dual function of connection and load-bearing in this device: firstly, as a connecting component, they detachably fix the base 1 and the pressure cap 2 and provide axial clamping preload; secondly, as a load-bearing component, they directly bear the shear force and bending moment generated by the original reaction handle of the torque multiplier 6 during the tightening operation, and are a key load-bearing node on the reaction torque transmission path. The three reaction bolts 3 are evenly distributed around the circumference and jointly bear the total reaction torque on the housing of the torque multiplier 6. The reaction torque borne by a single bolt is about one-third of the total value, which reduces the load level of a single bolt and keeps the force on the device circumferentially symmetrical under high torque conditions, preventing the device from tilting or loosening.

[0044] The tightening adapter 7 has a square hole at one end that mates with the square connector at the output end of the torque multiplier 6, and a drive groove (e.g., internal hexagonal groove, external hexagonal hole, or slotted / cross drive groove, depending on the head shape of the part being tightened) at the other end that mates with the head of the external threaded part 8. Its function is to transmit the torque amplified by the planetary gear mechanism from the output end of the torque multiplier 6 directly to the external threaded part 8. The square connector (square drive) refers to a metric / imperial universal square drive interface with four planes for torque transmission. It features a standard contact form, stable transmission efficiency, and no axial force component, forming the structural basis for achieving a single torque transmission channel in this invention.

[0045] The inner cavity of the base body and the outer wall of the output end of the torque multiplier 6, as well as the inner cavity of the gland body and the outer wall of the input end of the torque multiplier 6, maintain a radial clearance fit. This fit serves two purposes: it limits the radial offset and tilt of the housing through shape adaptation, and it allows the input and output ends of the torque multiplier 6, which rotate relative to the housing, to rotate freely within the base 1 and gland 2 during tightening operations without contacting or rubbing against them. If an interference or zero-clearance fit were used here, an additional frictional torque would be generated between the rotating and stationary components. This torque would be directly deducted from the input torque, resulting in an actual output torque lower than the tool's rated value, thus compromising the certainty of torque transmission.

[0046] Another key design feature of this invention is that an axial gap is reserved between the output end face of the torque multiplier 6 and the end face of the tightening adapter 7, so that there is no axial contact between the two end faces, and the torque is transmitted only through the four-way connector interface.

[0047] The technical significance lies in the fact that, in high-precision, high-torque fastening operations, the contact friction between the tool end face and the driven workpiece end face is a major source of error causing the actual applied torque to deviate from the target value. If there is axial contact between the two end faces, let the axial contact force between the end faces be F. axial If the equivalent friction radius of the end-face contact area is r and the end-face friction coefficient is μ, then the additional torque error caused by end-face friction is ΔT = μ·F axial The additional torque ΔT, combined with the torque transmitted at the four-way connector interface, acts on the external threaded part 8, causing the actual preload torque obtained by the external threaded part 8 to deviate from the calibrated output value of the torque multiplier 6. Simultaneously, the end-face friction coefficient μ is affected by surface roughness, lubrication status, assembly frequency, and contamination level, exhibiting large numerical dispersion and being uncalibrable. The resulting torque error is neither predictable nor compensable in the manufacturing process. This invention explicitly designs the axial clearance at this interface, ensuring that the axial contact force F between the end faces... axial =0, substituting into the above formula, we get the additional torque error ΔT = μ·F axial When r = 0, the additional torque error caused by end-face friction is completely eliminated. The actual preload torque acting on the external threaded part 8 is uniquely determined only by the four-way joint interface, thus ensuring the uniqueness of the torque transmission channel and the reproducibility of the torque value at the principle level. This is particularly critical for the assembly of valve sealing surfaces in liquid rocket engines and turbine pump rotor shaft systems—the preload torque tolerance zones in these parts are often extremely narrow, and any uncalibrated error sources must be structurally eliminated during the tooling design phase, rather than relying on operator experience for correction.

[0048] Based on the above-described cooperation, it can be seen that the base 1 and the pressure cap 2 exert coordinated constraints on the torque multiplier 6 housing in three directions: axial constraint is achieved by the clamping of the base body's supporting surface and the pressure cap's pressing surface on both ends of the housing, preventing axial movement of the housing under high torque conditions; radial constraint is achieved by the shape adaptation of the inner cavities of the base body and the pressure cap body, preventing radial displacement of the housing; and tilt constraint is also achieved by the shape adaptation of the inner cavities, ensuring the coaxiality of the output axis and the axis of the tightened threaded connector. The coordinated action of these three factors ensures that the torque multiplier 6 maintains precise positioning throughout the high torque operation, providing structural assurance for high-precision fastening.

[0049] like Figure 3 As shown, the torque multiplier fixing device of the present invention can be divided into three modules in terms of function. The three modules work together on the torque multiplier 6, and the flange face of the internal thread part 4 serves as the self-balancing basis of the entire force system.

[0050] The fixed support module consists of a base 1 and clamping bolts 5. This module is responsible for fixing the entire device to the flange face of the internally threaded part 4. It serves as both the installation base of the device and the end point, i.e., the closing point, of the reaction torque transmission path. At the same time, the inner cavity of the base body provides support and radial positioning for the output end of the torque multiplier 6.

[0051] The housing constraint module consists of a pressure cap 2 and a reaction force abutment bolt 3. This module provides axial clamping constraint to the housing of the torque multiplier 6, and directly bears the reaction torque transmitted from the original reaction force handle through the reaction force abutment bolt 3, and then transmits it to the fixed bearing module.

[0052] The torque transmission module consists of a tightening adapter 7. This module transmits the torque amplified by the torque multiplier 6 to the external threaded part 8 through a four-way connector interface, and uses an axial clearance isolation design on the end face to ensure the accuracy of torque transmission.

[0053] The above module division shows that the present invention completely separates the two force flows of "bearing the reaction torque" and "transmitting the working torque" in terms of structure. The reaction torque is borne by the fixed bearing module and the shell constraint module, and the working torque is borne by the torque transmission module. The two force flows do not interfere with each other. This is the structural reason why the device can achieve reliable fixation and high-precision torque transmission at the same time.

[0054] Figure 4 The fundamental difference between the prior art and the present invention in terms of force transmission path is shown by comparison.

[0055] like Figure 4As shown in (a), the force transmission path of the existing reaction arm scheme is as follows: the operator applies input torque → the torque multiplier housing generates a reverse torque → reaction arm (cantilever) → external support (tooling fixture, adjacent bolts, or ground structure) → the external environment bears the reaction torque. The endpoint of this path falls on the external environment other than the tightened part, which is an open path. Whether it is valid depends entirely on whether there is a suitable, sufficiently rigid, and stable external support at the work site.

[0056] like Figure 4 As shown in (b), the force transmission path of the present invention is divided into two branches: forward torque transmission and reverse torque transmission. The forward torque transmission path is as follows: the operator applies input torque at the input end of the torque multiplier 6 → the planetary gear mechanism amplifies the torque according to the transmission ratio → the four-way connector at the output end → tightening the adapter 7 → the external threaded part 8 obtains the precise preload torque. The reverse torque transmission path, i.e., the closed loop of the force transmission path, is as follows: the housing of the torque multiplier 6 generates a counter-torque equal to and opposite to the output torque → the counter-torque is transmitted through the housing to the original counter-torque handle → the cantilever end of the counter-torque handle abuts against the side of the counter-torque abutment bolt 3, converting the torque into shear force and bending moment acting on the bolt → the counter-torque abutment bolt 3 transmits the load to the base 1 through its connection with the threaded hole of the second flange → the base 1 transmits the counter-torque to the flange face of the internal threaded part 4 through the first flange and the clamping bolt 5 → the force system is completely self-balanced here, and the path is closed.

[0057] Since the final point of application of the reaction torque (the flange face of the internally threaded part 4) and the object being tightened (the externally threaded part 8 screwed into the internally threaded part 4) are located on the same assembly of parts, the entire force path forms a complete self-closed loop, completely decoupled from the external environment. This means that as long as the internally threaded part 4 being assembled has a flange face for mounting the base 1, this device can establish reliable reaction force support in any working position and under any spatial conditions, without needing to find any external support points in the surrounding area.

[0058] When performing high-torque fastening operations using the fixing device of the present invention, the following steps shall be performed:

[0059] Step 1: Align base 1 with the flange face of internal thread part 4, and adjust the installation position of base 1 so that the predetermined installation position of reaction force abutment bolt 3 corresponds to the natural abutment position of the original reaction force handle of torque multiplier 6.

[0060] Step 2: Insert the clamping bolts 5, fix the base 1 to the flange face of the internal threaded part 4, and tighten each clamping bolt 5 evenly to the specified torque in a diagonal alternating sequence;

[0061] Step 3: Place the output end of the torque multiplier 6 into the inner cavity of the base body, so that the end face of its output end fits against the supporting surface, and complete the bottom positioning;

[0062] Step 4: Insert the square hole end of the tightening adapter 7 into the square connector of the output end of the torque multiplier 6, align the drive groove end with the head of the external thread part 8, and confirm that there is an axial gap between the end face of the output end of the torque multiplier 6 and the end face of the tightening adapter 7.

[0063] Step 5: Fasten the pressure cap 2 to the torque multiplier 6 from the input end side, so that the end face of the input end is in contact with the pressing surface of the pressure cap body;

[0064] Step 6: Insert the three reaction bolts 3 and tighten them diagonally alternately to the specified torque to complete the installation of the fixing device;

[0065] Step 7: The operator applies input torque through the handle at the input end of the torque multiplier 6. At this time, the original reaction handle naturally abuts against the side of the reaction bolt 3, and the device automatically establishes reaction support to complete the high torque fastening operation of the external threaded part 8.

[0066] Step 8: After the work is completed, remove the fixing device in the reverse order of the above steps.

[0067] It should be noted that the adjustment of the installation position of the base 1 in step one is the key to the device's ability to "reuse the original reaction handle without modification": since there are six first mounting holes evenly distributed around the circumference, the base 1 can be installed around the axis in increments of 60°, so that the reaction force abutment bolt 3 falls exactly on the natural placement position of the original reaction handle, without the need for any structural modification to the torque multiplier 6 body, nor any additional adapter tooling.

[0068] The above-mentioned structural design of the present invention corresponds one by one to the four special operating conditions required for the assembly of liquid rocket engines.

[0069] Firstly, in response to the high requirements for the accuracy and reproducibility of assembly torque under ultra-low temperature conditions, this invention eliminates the parasitic frictional torque between fixed and rotating parts through radial clearance fit, eliminates the additional torque error caused by end face friction through axial clearance isolation, and eliminates the additional bending moment caused by tool tilting through three-dimensional constraints. This makes the preload torque applied during the normal temperature assembly stage have clear certainty, providing a prerequisite for the accurate maintenance of preload under low temperature conditions.

[0070] Secondly, in response to the high-pressure sealing reliability requirements, this invention ensures the accuracy of the pre-tightening torque of the threaded connection of the valve seat sealing surface, so that the sealing specific pressure is stably within the process tolerance zone, avoiding low-temperature propellant leakage due to insufficient pre-tightening or sealing surface crushing due to excessive pre-tightening.

[0071] Thirdly, in response to the extremely high assembly precision requirements of the turbine pump rotor assembly, the single torque transmission channel and three-dimensional constraints of this invention jointly ensure the tightening torque accuracy and consistency of the impeller locking nut, bearing clamping parts, etc., which is beneficial to stabilizing the bearing preload and rotor dynamic balance characteristics.

[0072] Fourth, in response to the limitations of narrow and enclosed assembly spaces, the self-closing force transmission path of the present invention eliminates the need for the device to occupy any space other than the tightened part to construct a fulcrum. The overall outline of the device is only slightly larger than the torque multiplier 6 body, allowing it to be used in engine compartments with dense pipes and cables. At the same time, no manual support is required throughout the operation, and operators do not need to extend their arms into narrow spaces for extended periods, significantly improving operational safety.

[0073] The base 1 and pressure cap 2 in this invention are preferably made of alloy structural steel (e.g., 42CrMo, 40Cr, etc., which are heat-treated to achieve a balance between high strength and good toughness) or titanium alloy (e.g., TC4) to meet the comprehensive requirements of strength and lightweight of the fixing device in the liquid rocket engine assembly environment. In cases where weight reduction is extremely important, such as for tooling that needs to be transported with the product, the base 1 and pressure cap 2 can also be made of high-strength aluminum alloy (e.g., 7075-T6) to further reduce the weight of the device while ensuring strength. The reaction bolt 3 should be a high-strength bolt (e.g., grade 12.9) because it bears a combined load of shear force and bending moment during operation, and its strength should be checked based on one-third of the total reaction moment and a safety factor of not less than 1.5.

[0074] In cases where the assembled parts do not have flange bolt holes, the fixing method between the base 1 and the internal threaded part 4 can be replaced by a high-strength permanent magnet adsorption structure or a quick-release snap-fit ​​connection structure to adapt to the structural form of different workpieces; in this case, the adsorption force or the torsional resistance of the snap-fit ​​should be checked according to the maximum reaction torque.

[0075] In this embodiment, three reaction bolts 3 are evenly distributed circumferentially. Depending on the actual reaction moment magnitude and spatial constraints, the number can be adjusted to two (symmetrically arranged) or four (circumferentially distributed), and the number and position of the threaded holes on the second flange of the base 1 can be adjusted accordingly. Increasing the number of bolts can reduce the load level of a single bolt, but it will occupy more circumferential space; this should be weighed during implementation.

[0076] By replacing the base 1 and the pressure cap 2 with different internal cavity sizes and shapes, torque multipliers 6 of different brands and specifications (different torque amplification factors and external dimensions) on the market can be adapted to form a series of tooling products. Since the core of this invention lies in the self-closing configuration of the force transmission path rather than the specific internal cavity size, the above-mentioned series of modifications are all equivalent embodiments of this invention.

[0077] The type of drive groove for tightening adapter 7 can be selected according to the actual type of the head of the external threaded part 8, such as external hexagon, internal hexagon, dodecagon or special spline type; when the type of the head of the tightened part can be directly matched with the square connector of the output end of torque multiplier 6, tightening adapter 7 can also be omitted. In this case, it should be ensured that the axial clearance is reserved between the end face of the output end of torque multiplier 6 and the tightened part to maintain a single torque transmission channel.

[0078] The technical features of this invention make it applicable not only to the assembly of valves and turbopumps in liquid rocket engines, but also to the following applications: assembly of high-precision threaded connections such as turbine disks and compressor rotors in aero-engines; precision tightening of flange bolts on reactor pressure vessels in nuclear power plants; high-torque operations on underwater sealing flanges in deep-sea oil and gas development; and high-strength bolt tightening in confined spaces of various large and heavy machinery. Wherever the parts to be tightened have flange faces suitable for base mounting, and the working space is insufficient to accommodate a traditional reaction arm, the universal, high-precision, and highly safe high-torque tightening tool solution provided by this invention can be used.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A torque multiplier fixing device for a liquid rocket engine, characterized in that: The device includes a base (1), a pressure cap (2), and a reaction bolt (3). The base (1) is fixed to the flange face of the internal threaded part (4). The inner cavity of the main body of the base is adapted to the shape of the outer wall of the output end of the torque multiplier (6) and forms an axial support. The pressure cap (2) is fastened to the top of the base (1). The inner cavity of the main body of the pressure cap is adapted to the outer wall of the input end of the torque multiplier (6) and together with the base (1) applies axial, radial, and tilt constraints to its housing. The reaction bolt (3) passes through the pressure cap (2) and is screwed into the threaded hole of the base (1) to fix the two together and bear the reaction torque generated by the original reaction handle of the torque multiplier (6). The reaction torque of the housing of the torque multiplier (6) is transmitted to the flange face of the internal threaded part (4) in sequence through the original reaction handle, the reaction bolt (3), and the base (1).

2. The torque multiplier fixing device according to claim 1, characterized in that: The base (1) is an integral metal component, comprising a first flange, a base body, and a second flange in sequence; the first flange has a plurality of first mounting holes, and the base (1) is fixed to the flange face of the internal threaded part (4) by clamping bolts (5) passing through the first mounting holes; the second flange has a plurality of threaded holes for screwing in the reaction force abutment bolt (3) and bearing the shear force and bending moment transmitted therefrom.

3. The torque multiplier fixing device according to claim 1, characterized in that: The pressure cap (2) is an integral metal component, including a third flange and a pressure cap body; the third flange has several second mounting holes, the positions of which correspond one-to-one with the positions of the threaded holes on the base (1), for inserting the reaction force abutment bolts (3); the inner cavity shape of the pressure cap body is adapted to the outer wall shape of the input end of the torque multiplier (6), and the pressing surface of the pressure cap body is in contact with the end face of the input end of the torque multiplier (6).

4. The torque multiplier fixing device according to claim 1, characterized in that: The inner cavity of the base body and the outer wall of the output end of the torque multiplier (6), and the inner cavity of the pressure cap body and the outer wall of the input end of the torque multiplier (6) are both kept in radial clearance fit, so that the input end and the output end of the torque multiplier (6) can rotate freely in the base (1) and the pressure cap (2) during the tightening operation, without contacting or rubbing against the base (1) or the pressure cap (2).

5. The torque multiplier fixing device according to claim 1, characterized in that: The number of reaction force abutment bolts (3) is three. The three reaction force abutment bolts (3) are evenly distributed along the circumference of the cover (2). The three reaction force abutment bolts (3) jointly bear the total reaction torque on the torque multiplier (6) housing. The reaction torque borne by a single reaction force abutment bolt (3) is about one-third of the total value.

6. The torque multiplier fixing device according to claim 2, characterized in that: The first flange has six first mounting holes, which are evenly distributed around the base (1) to provide sufficient flange fastening contact area and uniform clamping force distribution.

7. The torque multiplier fixing device according to claim 1, characterized in that: It also includes a tightening adapter (7), one end of which is provided with a square hole that matches the square connector of the output end of the torque multiplier (6), and the other end is provided with a drive groove that matches the head of the external threaded part (8). The tightening adapter (7) transmits the torque amplified by the planetary gear mechanism from the output end of the torque multiplier (6) to the external threaded part (8). An axial gap is reserved between the end face of the output end of the torque multiplier (6) and the end face of the tightening adapter (7).

8. The torque multiplier fixing device according to claim 1, characterized in that: After the base (1) is installed on the flange face of the internal threaded part (4), its installation position allows the cantilever end of the original reaction handle of the torque multiplier (6) to naturally abut against the side of the reaction force abutment bolt (3) during the tightening operation. No structural modification is required to the body of the torque multiplier (6). The reaction torque of the shell is directly transmitted to the reaction force abutment bolt (3) by reusing the original reaction handle.

9. The torque multiplier fixing device according to claim 1, characterized in that: The base (1) and the cover (2) are made of alloy structural steel or titanium alloy.

10. The torque multiplier fixing device according to claim 7, characterized in that: The axial gap between the output end face of the torque multiplier (6) and the end face of the tightening adapter (7) prevents the two end faces from making axial contact, and the actual preload torque acting on the external threaded part (8) is uniquely determined only by the quad joint interface.

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