Adjustable elliptical trainer

1. An adjustable elliptical trainer comprising:

a base having

two supporting bars protruding up from the base; and

a transmission wheel mounted rotatably between the supporting bars;

two driving brackets connected respectively to the transmission wheel;

two handles located respectively at opposite sides of the transmission wheel, mounted pivotally on one of the supporting bars and connected pivotally and respectively to the driving brackets;

two pedal assemblies located at the opposite sides of the transmission wheels and each pedal assembly having

a lever being curved and connected pivotally to one of the driving brackets; and

a pedal mounted on a rear end of the lever; and

an adjustment assembly mounted on a front end of the base and having

two guiding rods mounted on the base;

a guiding bracket connected to the transmission wheel and mounted slidably on the guiding rods;

wherein the transmission wheel has a shaft mounted through the transmission wheel and two cranks mounted respectively and securely on two ends of the shaft and extending along opposite directions;

wherein the driving brackets are connected respectively to the cranks; and

whereby the adjustment assembly allows the pedal assemblies to move along two different elliptical motion paths by moving the guiding bracket along the guiding rods to a lower position or an upper position.

2. The adjustable elliptical trainer as claimed in claim 1 , wherein the adjustment assembly further has

a motor mounted securely on the base;

a bolt mounted on and rotated by the motor and having an outer thread formed on the bolt; and

a movable nut mounted securely on the guiding bracket, mounted movably around the bolt and having an inner threaded hole defined through the movable nut and engaging the outer thread of the bolt.

3. The adjustable elliptical trainer as claimed in claim 2 , wherein

the base further has

a front bar mounted uprightly on the front end of the base;

an upper bracket mounted on a top end of the front bar and having two through holes defined through the upper bracket;

a lower bracket mounted on the base behind the front bar and having two mounting holes defined through the lower bracket;

the guiding rods are mounted respectively through the through holes of the upper bracket, are mounted respectively through the mounting holes of the lower bracket, and the guiding bracket has two ends and two sleeves formed on the guiding bracket and mounted slidably and respectively around the guiding rods, and each sleeve has a sleeve hole defined therethrough; and

the motor is mounted securely on the upper bracket.

4. The adjustable elliptical trainer as claimed in claim 3 , wherein

the base further has two rail bars mounted obliquely on a rear end of the base; and

each pedal assembly further has a roller slide mounted securely on the lever and mounted slidably around one of the rail bars of the base.

5. The adjustable elliptical trainer as claimed in claim 4 , wherein each roller slide has multiple rollers mounted rotatably on the roller slide and rolling on the rail bar.

6. The adjustable elliptical trainer as claimed in claim 5 , wherein each handle has a handlebar being longitudinal and having

an intermediation section mounted pivotally on one of the supporting bars;

a top end; and

a bottom end connected pivotally to a linking bar that is connected pivotally to one of the driving brackets.