Cart

1. A cart, comprising:

an upper frame extending outwards toward a first direction;

a lower frame extending outwards toward a second direction;

a rear wheel frame extending outwards toward a third direction;

at least one folding joint mechanism disposed among the upper frame, the bottom frame and the rear wheel frame, and comprising:

a bottom frame joint connected to an end of the bottom frame, and the bottom frame joint including a first opening, and a first arc-rack formed on a portion of an edge of the first opening;

an upper frame joint connected to an end of the upper frame, and the upper frame joint including a second opening, and a second arc-rack formed on a portion of an edge of the second opening;

a rear wheel frame joint connected to an end of the rear wheel frame; and

a linkage gear unit disposed between the bottom frame joint and the upper frame joint, and the linkage gear unit having a first gear and a second gear, and the first gear and the second gear rotating coaxially, and wherein the first gear being engaged with the first arc-rack and the second gear being engaged with the second arc-rack, and the first gear having a number N 1 of gear teeth and the second gear having a number N 2 of gear teeth, and the first arc-rack having a first axle center, a first tooth and a second tooth, and the second tooth being adjacent to the first tooth, and the first tooth having a first end point connected to the first axle center to form a first virtual line and the second tooth having a second end point connected to the first axle center to form a second virtual line, and the second virtual line and the first virtual line defining a first included angle θ 1 , and the second arc-rack having a second axle center, a third tooth, and a fourth tooth, and the fourth tooth being adjacent to the third tooth, the third tooth having a third end point being adjacent to the second axle center to form a third virtual line and the fourth tooth having a fourth end point being adjacent to the second axle center to form a fourth virtual line, and the third virtual line and the fourth virtual line defining a second included angle θ 2 , and the first and second arc-racks having the numbers N 3 and N 4 of gear teeth, and the upper frame extending outwards toward a first direction, the bottom frame extending outwards toward a second direction and the rear wheel frame extending outwards toward a third direction, and the second direction and the third direction defining a third included angle θ 3 and the third direction and the first direction defining a fourth included angle θ 4 , and wherein N 1 , N 2 , θ 1 , and θ 2 meeting the following relations:

360/θ1= N 3, θ1>0;

360/θ2= N 4, θ2>0; and

( N 2/ N 4)*( N 3/ N 1)=θ4/θ3, and both θ3 and θ4 fall within a range of 30°˜150′; and

at least one of N 3 and N 4 is not a positive integer, and both N 1 and N 2 are positive integers.

2. The cart of claim 1 , wherein the cart is particularly a baby stroller or a golf trolley having three or more wheels.

3. The cart of claim 1 , wherein both of the numbers N 1 and N 2 of gear teeth of the first and second gears are greater than or equal to 6.

4. The cart of claim 1 , wherein the first direction, the second direction and the third direction are different directions.

5. The cart of claim 1 , wherein the sum of the third included angle and the fourth included angle falls within a range of 120°˜240°.

6. The cart of claim 1 , wherein the first gear and the second gear are independently separate parts.

7. The cart of claim 1 , wherein the first gear and the second gear are fixedly attached together.

8. The cart of claim 1 , wherein the linkage gear unit further comprises a base disposed between the first gear and the second gear, and the diameter of the base is greater than the diameter of the first gear.

9. The cart of claim 8 , wherein the base includes a notch.