CN113062936B - Safety rope brake and braking method based on shear thickening fluid - Google Patents

Abstract

The invention relates to a safety rope brake based on shear thickening fluid and a braking method, belonging to the technical field of passive braking; comprises a base, a cavity wall, a piston, a bolt, an inner wall, shear thickening fluid, a central shaft disc, a spring, a sealing ring and a cover; the cavity formed by fixedly mounting the cavity wall and the base is filled with shear thickening liquid, a blind hole is formed in the end face of the piston head of the piston and sleeved on the central shaft of the base, and the spring is sleeved on the piston rod; and a plurality of through holes are arranged on the central shaft disc of the central shaft and the inner wall of the base. The base is fixed on the safety rope connector or the shaft core of the rope tying bobbin, and the end of the piston rod penetrates through the cavity wall to be fixedly connected with the root of the safety rope. The invention has passive braking function, firstly, the damping force generated by the piston compression spring is used for preliminary buffering, and then the shear thickening fluid can realize braking according to the change of the moving speed of the piston; the damping force of the spring is combined with the solidification and braking of the shear thickening fluid, so that the reliability of the safety rope is enhanced.

Description

Safety rope brake and braking method based on shear thickening fluid

technical field

The invention belongs to the technical field of passive braking, and in particular relates to a safety rope brake and a braking method based on shear thickening fluid.

Background technique

The safety rope is a protective product to prevent workers from falling at heights. In terms of strength, safety ropes usually assess two strength indicators, namely tensile strength and impact strength. The national standard requires that the tensile strength (ultimate tensile force) of the safety belt and its strings must be greater than the longitudinal tensile force caused by the weight of the human body in the direction of falling. Because the greater the height of the fall, the greater the impact force received, therefore, the safety rope must meet the following two basic conditions: (1) must have sufficient strength to withstand the impact force when the human body falls. (2) It can prevent the human body from falling to a certain limit that can cause injury; this condition needs to be explained again. If the impact force is too large, the internal organs of the human body will be damaged and death will be caused.

Traditional safety ropes are braided with synthetic fibers and are used to protect people and objects that may fall, mainly relying on the tensile strength of the rope itself and the connection strength between the safety rope and the connector or tether spool core; The falling object or human body at the end of the rope is affected by gravity very quickly, so when the safety rope is fully deployed, the pulling force generated on the connector or the tether spool shaft core is also very large, and an instantaneous impact force will be generated. The safety of falling objects or persons cannot be fully guaranteed.

Shear thickening fluid is a kind of intelligent material, its viscosity will change with the shear rate, after the liquid bears a certain shear rate, the viscosity of the liquid will suddenly increase greatly, and it will change from liquid phase to solid phase in a short time. Phase, that is, the shear thickening behavior occurs, and this change is reversible. When the shear rate is withdrawn, the liquid can return from the solid phase to the liquid phase. Applying this material to the buffer of the safety rope can provide the safety rope with new characteristics of passive braking and phase change energy absorption, further improving safety.

Contents of the invention

Technical problem to be solved:

In order to avoid the deficiencies of the prior art, the present invention proposes a safety rope brake and braking method based on shear thickening fluid. Characterized by a sharp increase in viscosity, it acts as a brake protector.

The technical solution of the present invention is: a safety rope brake based on shear thickening fluid, which is characterized in that it includes a base, a cavity wall, a piston, a bolt, an inner wall, a shear thickening fluid, a central axis, and a central axis disc , a spring, a sealing ring, and a cover; the cavity wall is a sleeve structure with one end closed, flanges are provided on the outer peripheral surfaces of the closed end and the open end, and a through hole is opened in the center of the closed end;

The base is coaxially fixedly connected with the flange plate at the opening end of the cavity wall through bolts, and the cavity composed of the cavity wall and the base is filled with shear thickening liquid; There is an inner wall with a ring structure and a central axis; the outer diameter of the inner wall is smaller than the inner diameter of the cavity wall, the axial height is smaller than the axial height in the cavity wall, and a plurality of through holes are opened on the inner wall close to the peripheral surface of the base; An annular boss is arranged on the outer peripheral surface of the end of the central axis close to the base, as a central axis disk, and a plurality of holes are opened on the end surface of the central axis disk along the circumferential direction; the outer end surface of the base is connected with the safety rope connector or tether The shaft core of the spool is fixed;

The piston head of the piston is a disc structure, and the piston rod is an optical axis vertically arranged at the center of the disc end face; the disc is coaxially installed in the inner wall of the base, and a blind hole is opened at the center of the outer end face. The blind hole is coaxially set on the central axis of the base, and is a clearance fit; the end of the piston rod passes through the through hole at the closed end of the cavity wall, and is fixedly connected with the root of the safety rope;

The spring is coaxially sleeved on the piston rod and located between the disc and the inner bottom surface of the cavity wall;

The cover is a circular plate with a central hole, which is fixed to the flange at the closed end of the cavity wall by bolts. The central hole is located on one side of the cavity wall and has an annular groove for placing the sealing ring to realize the movement of the piston rod. seal.

A further technical solution of the present invention is: the bearing force of the brake is calculated using the Newtonian viscous flow experimental formula:

Among them, μ is the viscosity of the fluid, A is the area of the two interfaces that produce the flow velocity difference, and v/h is the velocity gradient, that is, the shear rate.

A further technical scheme of the present invention is: the diameter of the central shaft is 6 mm, the outer diameter of the piston rod of the piston is 12 mm, and the length of the central shaft is 130 mm; the inner diameter of the inner wall is 60 mm, the outer diameter of the inner wall is 66 mm, the outer diameter of the piston head is 56 mm, and the cavity wall The inner diameter is 80mm; the viscosity of the shear thickening fluid μ=300Pa·s, the shear rate=10s ^-1 ; the calculated side area of the central axis of the piston A ₁ =0.0049m ³ , and the side area of the inner wall A ₂ =0.0245m ³ , the bearing force of the brake is 88N.

A further technical solution of the present invention is: the base is connected to the safety rope connector through a lock hook.

A further technical solution of the present invention is: a pair of lugs are provided on the outer end surface of the base, and are hinged to the core of the tether spool through a shaft.

A further technical solution of the present invention is: the end of the piston rod is provided with a through hole, and the root of the safety rope passes through the hole and then fastened with a rope clip.

A braking method for a safety rope brake based on a shear thickening fluid, characterized in that the specific steps are as follows:

Step 1: when the safety rope is fully deployed, the root is subjected to an impact force, and the impact force pulls the piston rod;

Step 2: the piston rod drives the piston to move axially and compresses the spring, and the spring generates a damping force on the piston;

Step 3: As the piston moves in the axial direction, the shear thickening liquid flows in the cavity under the push of the piston, and the shear thickening liquid pushed by the piston is sheared between the central axis and the inner wall At the same time, the liquid flowing between the inner wall and the cavity is also subject to shearing; finally, it is also subject to shearing when it flows through the hole of the inner wall and the central axis disc; the shear thickening liquid in each part is subject to shearing, and the viscosity gradually increases. Increase until solidified, creating resistance to complete the braking process.

Beneficial effect

The beneficial effects of the present invention are:

1. The structure of the present invention is simple and reliable, and the main functional components of the safety rope brake are only the cavity wall, base, cover and piston. The piston can be directly sleeved on the central axis of the base, which greatly reduces the difficulty of assembly.

2. The present invention has a passive braking effect, and adopts a brake with a damping effect to replace the rigid connection between the safety rope and the connector or tether spool shaft core in the prior art, which relieves the impact force when the safety rope is deployed and protects the The safety of objects or human bodies falling from the end of the rope. The brake first performs preliminary buffering through the damping force generated by the piston compression spring, and then the shear thickening fluid can exert a corresponding braking effect according to the change of the moving speed of the piston; the damping force of the spring and the solidification of the shear thickening fluid are controlled The combined use of motion enhances the safety and reliability of the safety rope.

3. The damping force of the present invention is not only large but also rapid. The output mode of the shear thickening brake is through the shear thickening and solidification of the solution between the walls of the device. When the piston pushes the liquid to move, the liquid between the inner wall and the cavity wall And the liquid at the small hole on the inner wall will also be sheared, providing different thickening effects at different piston speeds, which is different from traditional safety ropes that rely purely on fibers to bear energy and force. The relaxation reaction time between the brake and the end of the brake is short in the invention, the phase change of the liquid absorbs energy and bears the pulling force brought by the rope, and the situation that the safety rope breaks or is separated from the connector is reduced.

Description of drawings

Fig. 1 is a structural diagram of the present invention;

Description of reference signs: 1. Base, 2. Cavity wall, 3. Piston, 4. Bolt, 5. Inner wall, 6. Shear thickening fluid, 7. Central shaft, 8. Central shaft disk, 9. Hole , 10. Spring, 11. Seal ring, 12. Cover.

Detailed ways

The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

As shown in Figure 1, the present invention includes a base 1, a cavity wall 2, a piston 3, a bolt 4, an inner wall 5, a shear thickening liquid 6, a central shaft 7, a central shaft disc 8, a small hole 9, a spring 10, The sealing ring 11 and the cover 12; the cavity wall 2 is a sleeve structure with one end closed, flanges are provided on the outer peripheral surfaces of the closed end and the open end, and a through hole is opened at the center of the closed end;

The base 1 is coaxially fixedly connected with the flange at the opening end of the cavity wall 2 through bolts, and the cavity composed of the cavity wall 2 and the base 1 is filled with a shear thickening liquid 6; An inner wall 5 and a central axis 7 of a ring structure are coaxially arranged on one end surface; the outer diameter of the inner wall 5 is smaller than the inner diameter of the cavity wall 2, and the axial height is smaller than the axial height in the cavity wall 2, and the inner wall 5 is close to A plurality of through holes 9 are provided on the peripheral surface of the base 1; an annular boss is arranged on the outer peripheral surface of the central axis 7 near one end of the base 1, as the central axis disk 8, and the end surface of the central axis disk 8 is circumferentially opened with multiple holes. A hole 9; the outer end surface of the base 1 is fixed with the safety rope connector or the tether spool shaft core;

The piston head of the piston 3 is a disc structure, and the piston rod is an optical axis vertically arranged at the center of the end face of the disc; The blind hole is coaxially sleeved on the central axis 7 of the base 1, and is a clearance fit; the end of the piston rod passes through the through hole at the closed end of the cavity wall 2, and a radial through hole is provided at the end to securely The root of the rope passes through the through hole, and is fixedly connected by a rope clip; the spring 10 is coaxially sleeved on the piston rod, and is located between the disc and the inner bottom surface of the cavity wall 2; the cover 12 is opened with a The circular plate in the center hole is fixed to the flange at the closed end of the cavity wall 2 through the bolt 4, and the center hole is located on the side of the cavity wall 2 with an annular groove for placing the sealing ring 11 to realize the movement sealing of the piston rod.

When the safety rope drives the piston to move relative to the entire cavity, the shear thickening liquid will be subjected to the flow velocity brought by the piston movement, so that the liquid will be sheared at three places in the cavity, namely (1) between the piston and the central shaft, (2) between the inner wall and the cavity wall, (3) the small holes on the inner wall and the central axis disc. The three places will correspond to three different critical thickening piston speeds. When the piston speed gradually increases, the liquid at the small hole will be the first to thicken. As the piston speed increases, the liquid in the other two places will gradually increase. In the whole process, the damping force exerted by the liquid on the piston gradually increases until the liquid is completely solidified, completely preventing further movement of the piston.

The device is designed as the following dimensions: central shaft diameter 6mm, piston rod outer diameter 12mm, piston inner diameter 6mm, set on the central shaft, inner wall inner diameter 60mm, inner wall outer diameter 66mm, central shaft length 130mm, piston piston head diameter 56mm , The inner diameter of the cavity wall is 80mm. Calculate the viscous resistance of the liquid at maximum viscosity as the withstand force of the device. Using the formula obtained in the Newtonian viscous flow experiment:

Among them, μ is the fluid viscosity, A is the area of the two interfaces that produce the flow velocity difference, and v/h is the velocity gradient (also the shear rate). The viscous resistance is obtained by using the viscosity of the liquid in the best braking state and the corresponding shear rate. Use viscosity μ=300Pa·s, shear rate=10s-1. The calculated side area of the central axis of the piston is A1=0.0049m3, and the side area of the inner wall is A2=0.0245m3, so that the bearing force of the device is 88N. This patent only provides a braking solution. In practice, devices with different calibers can be designed according to the needs, and shear thickening fluids with different viscosities and shear rates of the liquid at the maximum viscosity can be configured to meet the needs.

Working principle of the present invention:

When the external force pulls the piston to move relative to the cavity, the piston drives the shear thickening fluid to flow. The viscosity of the shear thickening liquid changes under the shear action between the central axis and the inner wall, between the inner wall and the cavity wall, and in the small hole, and solidifies rapidly when the critical shear rate exceeds the critical shear rate. As the speed increases, the resistance of the safety rope pulling the piston is small when it is pulled slowly, and the resistance increases rapidly when it is pulled quickly, achieving the effect of intelligent braking. When the braking demand disappears, the spring can slowly push the piston to move and reset for the next braking.

In order to achieve different critical braking speeds, the concentration of the starch solution can be adjusted to change the viscosity of the liquid as a function of the shear rate, corresponding to the change in the resistance of the brake at different moving speeds of the piston. When the moving speed of the piston is small, the viscosity of the shear thickening fluid is at a small position, and it is easy to move the piston; when the piston is pulled by the outside at a high speed, that is, when the critical shear rate is exceeded, the viscosity of the shear thickening fluid will decrease. Surge, appear obvious solidification, and play a braking effect. In addition, by adjusting the liquid concentration, the critical thickening rate can be set to a desired value within a certain range to realize the adjustment of the speed limit to meet various needs.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limitations to the present invention. Variations, modifications, substitutions, and modifications to the above-described embodiments are possible within the scope of the present invention.

Claims (6)

1. A safety rope brake based on shear thickening fluid, its characterized in that: comprises a base, a cavity wall, a piston, a bolt, an inner wall, shear thickening liquid, a central shaft disc, a spring, a sealing ring and a cover; the cavity wall is of a sleeve structure with one closed end, the peripheral surfaces of the closed end and the open end of the cavity wall are provided with flange plates, and the center of the closed end is provided with a through hole;

the base is coaxially and fixedly connected with a flange plate at the opening end of the cavity wall through a bolt, and a cavity formed by the cavity wall and the base is filled with shear thickening liquid; the end surface of one side of the base facing the cavity wall is coaxially provided with an inner wall and a central shaft of a circular ring structure; the outer diameter of the inner wall is smaller than the inner diameter of the cavity wall, the axial height of the inner wall is smaller than the axial height of the cavity wall, and a plurality of through holes are formed in the circumferential surface, close to the base, of the inner wall; an annular boss is arranged on the outer peripheral surface of one end of the central shaft close to the base and serves as a central shaft disc, and a plurality of holes are formed in the end face of the central shaft disc along the circumferential direction; the outer end face of the base is fixed with the safety rope connector or the tying rope bobbin core;

the piston head of the piston is of a disc structure, and the piston rod is an optical axis vertically arranged at the center of the end face of the disc; the disc is coaxially arranged in the inner wall of the base, a blind hole is formed in the center of the outer end face of the disc, and the blind hole is coaxially sleeved on a central shaft of the base and is in clearance fit with the central shaft; the end of the piston rod penetrates through the through hole at the closed end of the cavity wall and is fixedly connected with the root of the safety rope;

the spring is coaxially sleeved on the piston rod and is positioned between the disc and the inner bottom surface of the cavity wall;

the cover is a circular plate provided with a central hole, and is fixed with the flange plate at the closed end of the cavity wall through a bolt, and the central hole of the cover is provided with an annular groove at one side of the cavity wall for placing a sealing ring to realize the motion sealing of the piston rod;

the diameter of the central shaft is 6mm, the outer diameter of a piston rod of the piston is 12mm, and the length of the central shaft is 130mm; the inner diameter of the inner wall is 60mm, the outer diameter of the inner wall is 66mm, the outer diameter of the piston head is 56mm, and the inner diameter of the cavity wall is 80mm; the shear thickening fluid has a viscosity μ =300Pa · s and a shear rate =10s ^-1 (ii) a Calculating the side area A of the central axis of the piston ₁ ＝0.0049m ³ Inner wall side area A ₂ ＝0.0245m ³ And the bearing force of the brake is 88N.

2. The shear-thickening fluid-based safety line brake of claim 1, wherein: the bearing capacity of the brake is calculated by utilizing a Newton viscous flow experimental formula to obtain:

where μ is the fluid viscosity, A is the area of the two interfaces that produce the flow velocity difference, and v/h is the velocity gradient, i.e., shear rate.

3. The shear-thickening fluid-based safety line brake of claim 1, wherein: the base is connected with the safety rope connector through a locking hook.

4. The shear-thickening fluid-based safety line brake of claim 1, wherein: a pair of lugs is arranged on the outer end face of the base and hinged with the shaft core of the tether line shaft through a shaft.

5. The shear-thickening fluid-based safety line brake of claim 1, wherein: the end of the piston rod is provided with a through hole, and the root of the safety rope passes through and is fastened by a rope clamp.

6. The braking method of the safety rope brake based on the shear thickening fluid, which is characterized by comprising the following specific steps of:

the method comprises the following steps: when the safety rope is completely unfolded, the root part is subjected to impact force, and the piston rod is pulled by the impact force;

step two: the piston rod drives the piston to move along the axial direction and compress the spring, and the spring generates damping force on the piston at the moment;

step three: along with the axial movement of the piston, the shear thickening liquid flows in the cavity under the pushing of the piston, the shear thickening liquid pushed by the piston is subjected to a shearing action between the central shaft and the inner wall, and meanwhile, the liquid flowing between the inner wall and the cavity is also subjected to the shearing action; finally, the water flows through the inner wall and the hole of the central shaft disc and is also subjected to shearing action; the shear thickening liquid of each part is sheared, the viscosity is gradually increased until solidification, and resistance is generated to finish the braking process.

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