Rocking Conveyor Mechanism

Contents

TABLE OF CONTENTS

Introduction

1. Dynamic synthesis of lever mechanism by unevenness coefficient

Dynamic Lever Analysis

Design of the kinematic diagram of the planetary reduction gear and construction of the involute engagement pattern

Synthesis of cam mechanism

Conclusion

List of sources used

Task

In the course project (KP), the mechanisms of the swinging conveyor are considered. Initial data are given in Table 1.1 of FP.

The CP includes the following sections.

1. Dynamic synthesis of lever mechanism by unevenness coefficient.

1.1 Build mechanism position plans for 12 equally spaced driving link positions and their corresponding rotated speed plans.

Plot the moment of inertia of the mechanism brought to the driving link depending on the rotation angle of the driving link for the steady-state cycle.

Plot the moments of the resistance forces and driving forces brought to the driving link, depending on the angle of rotation for the steady-state cycle.

1.4 Plot the kinetic energy change of the lever mechanism.

Construct an energy-mass diagram (Wittenbauer diagram).

Determine the value of the moment of inertia of the flywheel, which provides rotation of the drive link with the given coefficient of unevenness of motion.

2. Dynamic analysis of the lever mechanism.

Determine the angular acceleration of the drive link at the specified position of the mechanism.

Construct a mechanism diagram, velocity plan and acceleration plan for this position. Define mass center accelerations and link angular accelerations.

Define the inertial load of the links.

For the specified position of the mechanism, draw structural groups to scale and specify the forces applied to its links.

Using force plans, determine the reactions in all kinematic pairs of the mechanism.

2.6 Find a balancing moment on the link of bringing the mechanism by the method of force plans and by the method of lever N.E. Zhukovsky.

3. Design of the kinematic scheme of the planetary reduction gear and construction of the picture of involute engagement.

3.1 By the gear ratio, module m1 and the number of satellites to, taking into account the conditions of alignment, proximity and equal angles between the satellites, select the number of teeth of all wheels of the planetary mechanism of the given scheme, considering that the zmin≥15 and wheels are zero. When selecting the numbers of teeth, it is allowed to deviate from the given value of the gear ratio up to 5%.

3.2 Calculate initial diameters and draw the diagram of the planetary mechanism in two projections.

Calculate external engagement of a pair of spur gears of involute profiles with fixed axles, cut into standard tool rack of module m. When selecting the rack displacement factors, ensure that there is no undercut of the teeth legs.

Build a picture of involute engagement. Depict three teeth of each wheel, line and arc of engagement, working sections of tooth profiles. Select the hooking scale so that the tooth heights in the drawing are at least 40 mm.

Analytically and based on the hooking pattern, determine the overlap factor.

4. Synthesis of cam mechanism.

4.1 According to the specified law of change of the second derivative from movement of output link along the cam rotation angle, plot the first derivative and movement of output link depending on the cam rotation angle. Define the scope of the construction.

4.2 Determine the main dimensions of the cam mechanism of the smallest dimensions, taking into account the permissible pressure angle or the condition of convexity of the cam profile.

Build the cam profile according to the specified output link law.

For mechanisms with power closure, select the preliminary tension and stiffness of the closing spring, considering that the greatest spring force is 1.52 times higher than the largest inertia force of the output link in the area where the output link can be separated from the cam surface, and the preliminary spring tension is 20-40% of its largest value.

Plot the pressure angle based on the cam rotation angle.

Introduction

Mechanism theory is a science that studies the structure, kinematics and dynamics of mechanisms in connection with their analysis and synthesis.

The problems of mechanism theory can be divided into two groups. The first group of problems is devoted to the study of structural, kinematic and dynamic properties of mechanisms, i.e. the analysis of mechanisms.

The second group of problems is devoted to designing mechanisms with given structural, kinematic and dynamic properties for implementation of required movements, i.e. synthesis of mechanisms.

The problems of the synthesis of mechanisms are conveniently presented by the types of mechanisms, so the task of the synthesis is to design the mechanism of the preselected structure according to given kinematic and dynamic conditions.

The course project involves the synthesis of lever, gear and cam mechanisms.

The synthesis of the lever mechanism according to the given coefficient of unevenness of travel is the largest section in terms of volume of the course project on the theory of machines and mechanisms. The project considers a six-piece mechanism with a degree of mobility equal to one and a rotating input link (crank).

The purpose of the gear mechanism synthesis is to design a planetary mechanism and involute engagement.

The purpose of the cam mechanism synthesis is to determine the basic dimensions of the cam and to construct its profile.

Conclusion

In this course project on the theory of mechanisms and machines, the synthesis of lever, gear and cam mechanisms was carried out.

In the structural analysis, the features of the structure of the mechanism were considered and found - the degree of mobility, the input link, the Assur groups, which are part of the mechanism; determining the sequence of its kinematic and dynamic investigation.

During dynamic synthesis, a dynamic model is formed according to a given coefficient of non-uniformity of travel, its parameters are calculated. According to the Wittenbauer method, the moment of inertia of the flywheel corresponding to the given travel unevenness coefficient is determined.

Dynamic analysis determines the reactions in kinematic pairs and calculates the balancing moment.

When synthesizing the gear mechanism, the number of teeth is calculated, the number of satellites of the planetary mechanism is selected. Geometric dimensions and quality indicators of involute engagement are calculated.

During the synthesis of the cam mechanism, the main dimensions of the cam are determined and its profile is built.