Abstract: A folding treadmill includes a tread base supported by a foot structure which has guide plates formed with elongated slots on two sides of the tread base. The tread base is connected pivotally on the base support through pivot members which are mounted movably within the respective slots so that the tread base is turnable between a folded position and an unfolded position and movable rearward when the tread base turns to the folded position or forward when the tread base turns to the unfolded position. The foot structure further includes a guide rail structure on two sides of the tread base to support movably a first roller which is attached to the tread base and a lifting device for lifting the tread base.

Abstract: A folding treadmill includes a tread base supported by a foot structure which has guide plates formed with elongated slots on two sides of the tread base. The tread base is connected pivotally on the base support through pivot members which are mounted movably within the respective slots so that the tread base is turnable between a folded position and an unfolded position and movable rearward when the tread base turns to the folded position or forward when the tread base turns to the unfolded position. The foot structure further includes a guide rail structure on two sides of the tread base to support movably a first roller which is attached to the tread base and a lifting device for lifting the tread base.

Abstract: A method for purifying hydrofluoric acid, comprising the steps of filtering the hydrofluoric acid to remove particulates, passing the filtered acid through a cation exchange material and an anion exchange material to remove ions therefrom, at least periodically automatically monitoring the acid that has passed through at least a predetermined portion of the cation exchange material for a predetermined level of cationic impurity representative of actual or impending ionic breakthrough in the cation exchange material, at least periodically automatically monitoring the acid that has passed through at least a predetermined portion of the anion exchange material for a predetermined level of anionic impurity representative of ionic breakthrough in the anion exchange material, automatically interrupting flow of acid through the anionic or cationic exchange material at or prior to the time the breakthrough in such material occurs, while the flow is interrupted, regenerating the anionic or cationic exchange material,