You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a lifting mechanism for removing and replacing the cover of a spa. The use of spas has become widespread, and most spas are equipped with covers which when closed prevents debris, rain and the like from contaminating the tub water. The cover further serves to retain heat within the tub. As a consequence, spa covers tend to be relatively heavy and difficult to remove and replace. 
     Lifting devices have been developed to aid in the removal and replacement of these relatively heavy spa covers which can be operated with varying amounts of difficulty. Some problems exist with past lifting mechanism designs. A unit with one bar can produce excessive wear on the edge of spa and the bottom of the spa cover when the cover is slid and pushed to the “off” position. 
     With only one lift bar rigidity suffers and spa covers tends to become angularity offset when the operator pulls or pushes on one side only. 
     Many lifters require the user to fold the cover at the half-way seam. If the wind is blowing at a stiff breeze this can be a difficult struggle for a young athletic person, an impossible task for the elderly or disabled person. However, many spa owners do not have adequate space to rotate a large cover. Thus owners could request a folding cover on a rotating lifter; this choice is illustrated in these embodiments. 
     2. Description of Related Art 
     I have found a number of spa cover lifter patents using an “over end” motion. Such as; Wall U.S. Pat. No. 5,048,153A, Oyelette U.S. Pat. No. 5,548,081A, Perry U.S. Pat. No. 5,819,332A, Pucci U.S. Pat. No. 5,974,600A, Tedrick U.S. Pat. No. 6,032,305A, Tedrick U.S. Pat. No. 6,393,630B1, there in on conflict. I do have one patent, U.S. Pat. No. 6,550,077B1, which uses the lift, and rotate method to remove and store the cover. There are three major differences between 077 and this invention. 1. All the lifting is done at the bottom of the push tube instead of under the swash plate. 2. The swash plate, roller and guide tube are not used, new mount bocks are used to hold and guide the push tube. 3. Shelves are not required to hold the various lifting apparatus. 
     Refer to 077, in all the drawings I show a solid spa cover, a folding cover could be used in those instances where desired. In this invention I have shown folded covers in all drawings. These covers are interchangeable. 
    
    
     DESCRIPTION OF THE INVENTION 
     This invention is designed to lift a spa cover ( 42 - 43 ) and allow the cover to be rotated to clear the spa tub ( 44 ). Means for raising and lowering is accomplished by using one of several power devices, namely a crank and screw ( 50 ) and ( 51 ), a hydraulic jack ( 57 ), a foot ratchet ( 54 ), a linear actuator ( 58 ) and a cam jack ( 59 ). A fabric hinge is shown as ( 53 ). 
     A selected device applies an upward force on push tube ( 46 ). Crane arm ( 44 ) is attached to the push tube ( 46 ). Attachment ( 45 ) holds the cover ( 43 ) to the crane arm ( 44 ). An upper ported mount block ( 47 ) and a lower ported mount block ( 48 ) maintain alignment for push tube ( 46 ) operation. A post ( 55 ) may be installed near the spa ( 41 ) to provide lifting without attachment to the spa ( 41 ). Emplacement ( 56 ) keeps post ( 55 ) in place. 
     DESCRIPTION OF THE DRAWINGS 
     The foregoing objects and many of the attendant advantages of this invention will become more readily apparent as the same becomes better understood by reference to the following drawings. The crane arm with cover attached is common to all drawings. 
     FIG. ( 1 ) is a side view of the spa with mount blocks attached, push tube is aligned thru the blocks, and the crank and screw provides the lifting power. 
     FIG. ( 2 ) is a side view of the spa with mount blocks attached to a post near the spa, push tube is aligned thru the blocks, and the crank and screw provides the lifting power. The post is set in its emplacement. 
     FIG. ( 3 ) is a side view of the spa with mount blocks attached, push tube is aligned thru the blocks, and the hydraulic jack provides the lifting power. 
     FIG. ( 4 ) is a side view of the spa with mount blocks attached to a post near the spa, push tube is aligned thru the blocks, and the hydraulic jack provides the lifting power. The post is set in its emplacement. 
     FIG. ( 5 ) is a side view of the spa with mount blocks attached, push tube is aligned thru the blocks, and the foot ratchet provides the lifting power. 
     FIG. ( 6 ) is a side view of the spa with mount blocks attached to a post near the spa, push tube is aligned thru the blocks, and the foot ratchet provides the lifting power. The post is set in its emplacement. 
     FIG. ( 7 ) is a side view of the spa with mount blocks attached, push tube is aligned thru the blocks, and the linear actuator provides the lifting power. 
     FIG. ( 8 ) is a side view of the spa with mount blocks attached to a post near the spa, push tube is aligned thru the blocks, and the linear actuator provides the lifting power. The post is set in its emplacement. 
     FIG. ( 9 ) is a side view of the spa with mount blocks attached, push tube is aligned thru the blocks, and the rotating cam provides the lifting power. 
     FIG. ( 10 ) is a side view of the spa with mount blocks attached to a post near the spa, push tube is aligned thru the blocks, and the rotating cam provides the lifting power. The post is set in its emplacement.

Summary:
A device for removing spa covers and putting them aside while the spa is in use, and returning them to cover the spa after use. This invention lifts the cover in the flat position, then the cover may be rotated clockwise or counter clockwise to uncover the spa for use.