Continuous rotation transmission part 1: Couplings

1. Continuous rotation transmission

1.1. Coupling animations ( see descriptions bellow this video)

Chain drive 1C  

Coil spring coupling 1

Due to revolution joints of the spring supports (in pink) this coupling can compensate a large offset of the shaft axes.

For this simulation:

Coupling outer dia. = 20 mm

Offset = 1 mm

Velocity variation is considerable.

Coil spring coupling 2

Due to spherical joints of the spring supports (in pink) this coupling can compensate a large offset of the shaft axes and a large angular misalignment between them.

For this simulation:

Coupling outer dia. = 20 mm

Offset = 1 mm

Angular misalignment = 4 deg. Velocity variation is considerable.

Oldham coupling 1

 

Oldham coupling 2    

An embodiment of Oldham coupling 1

Axial dimension is reduced in comparison with “Oldham coupling 1”.

Oldham coupling 3      

An embodiment of Oldham coupling.

Axial dimension is reduced. Cylindrical joints are used instead of prismatic ones. It looks like Cardano coupling but it is totally different.

Parallel link coupling 

The absence of backlash makes this parallel coupling a precision, low- cost replacement for gear or chain drives that can also rotate parallel shafts. Any number of shafts greater than two can be driven from any one of the shafts, provided two conditions are fulfilled:

1. All cranks must have the same length.

2.  The  two  polygons  formed  by  shafts  centers  on  the  moving  and grounded frames must be identical.

The main disadvantage of this mechanism is its dynamic unbalance.

The moving frame should be made as light as possible. The mechanism cannot be used for high speed.

Application of parallelogram mechanism 1  

Application of parallelogram mechanism 1 

Transmission of rotation movement between parallel shafts.

Application of parallelogram mechanism 2  

Transmission of rotation movement between parallel shafts

Application of parallelogram mechanism 3 

Transmission of rotation movement between parallel shafts.
The red disk rotates without fixed bearing.

Schmidt coupling 

Transmission of rotation movement between parallel shafts. The pink link rotates without fixed bearing.

Both shafts can move during transmission.

Pin coupling 1  

The pins are arranged on circles of equal radius on the two shafts

A = R1 + R2

A: Axis distance of the two shafts (eccentricity) R1: Rose pin's radius

R2: Green pin's radius

Thus the coupling meets conditions of a parallelogram mechanism. It is a constant velocity coupling.

Numbers of pins on the two shafts must be equal.

Pin coupling 2
 

The pins and the holes are arranged on circles of equal radius on the two shafts

A = R2 - R1

A: Axis distance of the two shafts (eccentricity) R2: Rose hole radius

R1: Green pin's radius

Thus the coupling meets conditions of a parallelogram mechanism. It is a constant velocity coupling.

This type of mechanism can be installed in epicyclical reduction gear boxes. See:

Pin coupling 3 

An embodiment of Pin Coupling 1

When R1 is different from R2 and pin’s radius is larger than shaft’s radius. Transmission ratio is 1.

The mechanism now looks like a gear drive but the two shafts rotate the same direction.

It has a high sensitivity to error in distance between the shaft axes.

Pin coupling 4 

An embodiment of Pin Coupling 1

When R1 is different from R2, number of pins on each disks is 22. Pins on the pink disk is of lens shape because their radius is too large. Transmission ratio is 1.

Pin coupling 5 

An embodiment of Pin Coupling 3

When:

- R1 is different from R2

- Pins radius are larger than shafts radius

- Number of pins is infinite so screw surfaces are created.

The working surface of the blue shaft is created when a circle of radius 10 (in the plane perpendicular to the shaft axis, its center is 5 from the shaft axis) moves along a helix of pitch 20. The working surface of the pink shaft is created similarly by a circle of radius 15 (in the plane perpendicular to the shaft axis, its center is 5 from the shaft axis) moving along a helix of pitch 20. Distance between the shafts is 25.

Transmission ratio is 1. The mechanism now looks like a gear drive but the two shafts rotate the same direction.

Pin coupling 7 

An embodiment of Pin Coupling1.
When number of pins is infinite so screw surfaces are created.

The working surface of each shaft is created when a circle of radius 5 (in the plane perpendicular to the shaft axis, its center is 20 from the shaft axis) moves along a helix of pitch 40. Distance between the shafts is 10. Transmission ratio is 1. The two shafts rotate the same direction. The mechanism is purely imaginary product, perhaps no practice application.

Pin coupling 8 

An embodiment of Pin Coupling 7 when the number of working surfaces is 3. Transmission ratio is 1. The two shafts rotate the same direction. The mechanism is purely imaginary product, perhaps no practice application.