Internal Geneva Mechanism

AIM:

simulate the internal geneva mechanism for the given condition and plot the graph for respective condition.

• Contact force (between driving and the driven wheel) as a function of time.
• Angular Displacement of the driven wheel.

INTRODUCTION:

The Geneva drive is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion.

The rotating drive wheel is usually equipped with a pin that reaches into a slot located in the other wheel (driven wheel) that advances it by one step at a time. The main wheel also has an elevated circular blocking disc that "locks" the rotating driven wheel in position between steps.

An internal Geneva drive is a variant on the design. The axis of the drive wheel of the internal drive can have a bearing only on one side. The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one, where the switch time is therefore greater than the time the driven wheel stands still.

APPLICATION AND ANIMATION:

• One application of the Geneva drive is in film movie projectors and movie cameras, where the film is pulled through an exposure gate with periodic starts and stops. The film advances frame by frame, each frame standing still in front of the lens for a portion of the frame cycle (typically at a rate of 24 cycles per second), and rapidly accelerating, advancing, and decelerating during the rest of the cycle.
• Other applications of the Geneva drive include the pen change mechanism in plotters, automated sampling devices, banknote counting machines, and many forms of inaxable equipment used in manufacturing (such as the tool changers in CNC machines; the turrets of turret lathe, screw machine, and turret drills; some kinds of indexing hrad and rotary table and so on). The iron ring clock uses a Geneva mechanism to provide intermittent motion to one of its rings.

PROCDUCE:

Create internal geneva mechanism deiven part first

skeching three circle

1120mm dia , 520 mm radius and 120 mm radius

connect middile and outer circle with construction line

create an circle offset for 4 entities and then give 50 mm fillite and the trime unwanted skeched.

then extrude 40 mm and save.

Create internal geneva mechanism driving wheel

According to dimension create 420 mm diameter wheel and extrude up to 20 mm and save it

Assembly

before starting assembly first fid out the distance between both the circle , driven and driver

So creating sketch to fid the gape and result is 226.27 mm

Then create assembly of the parts the the driven part is placed to top plain and both right and front plan co incident with there axis

Then driver part is also coincident with right plan and provide 226.27 mm distance with front plain

Motion analysis

1) Add rotary motor in clockwise direction and set 10 rpm

2) then add solid body contact

3) then go to motion study properties

4) set 60 frame rate and uncheck precise contact

5) creat result for Contact force (between driving and the driven wheel) as a function of time.

6) creat result for Angular Displacement of the driven wheel.

7) then repeat process for Precise contact

8) same process repeat which is describe in point 5,6,7 but in there case rpm is changed 10 to 20 rpm and fps changed for 60 to 160 fps.

9) than again repeat process which is discribe in point 8 for Precise contact

after those proces we obtained 8 plots which is following :

results

plot 1

plot 2

plot 3

plot 4

plot 5

plot 6

plot 7

plot 8

explain
plot 1 = Contact force without Precise contact 10 rpm 60 fps
plot 2 = Angular Displacement without Precise contact 10 rpm 60 fps
plot 3 = Contact force Precise contact 10 rpm 60 fps
plot 4 = Angular Displacement Precise contact 10 rpm 60 fps

plot 5 = Contact force Precise contact 20 rpm 120 fps
plot 6 = Angular Displacement Precise contact 20 rpm 120 fps
plot 7 = Contact force without Precise contact 20 rpm 120 fps
plot 8 = Angular Displacement without Precise contact 20 rpm 120 fps

end thanks