Two-masted lifting apparatus
The present invention generally relates to a two-masted lifting apparatus for lifting a weighty object such as a vehicle or the like to a certain height, and more particularly relates to a two-masted lifting apparatus of the kind in which it is possible to incline at a desired angle a vehicle or the like which has been lifted up to a certain height; whereby the inspecting, repairing or cleaning works upon the underside of the vehicle or the like can be carried out easily and safely. 
     Although there have heretofore been proposed various types of two-masted lifting apparatus, most of them are not provided with such a mechanism that is capable of inclining a vehicle or the like which has been horizontally supported at a certain height. This is primarily because great risks such as slipping accidents are very likely to occur when inclining the weighty objects lifted up above the ground. 
     It is therefore a prime object of the present invention to provide a two-masted lifting apparatus which is capable of not only lifting a vehicle or the like horizontally but also inclining it at a desired angle in safety. 
     According to one aspect of this invention, a carriage having at least two supporting means for supporting a vehicle or the like is slidably mounted on each of two opposing upright masts and an independent driving means is disposed within each of the two masts. Both of the carriages are associatively connected to each other by a chain so that when one of the two driving means is actuated both carriages can move up or down along the respective masts in synchronism with each other. On the other hand, the other driving means is adapted to administer only the sliding movement of one of the two carriages along the mast. 
     Hence, it will readily be understood that one of the two driving means serves to horizontally lift a vehicle or the like to a certain height while the other driving means serves to incline it at a desired angle. 
     According to another aspect of the invention, each of the supporting means for supporting a vehicle or the like is horizontally movable toward or away from each mast. In accordance with one embodiment of the invention, each supporting means comprises a sleeve mounted on the carriage, an arm slidably inserted within the sleeve and a step rotatably mounted on the arm. The two opposing steps are connected with each other by a chain so that, when the driving means for inclining the vehicle is actuated, the arms slidably inserted within sleeves are dragged out of the sleeves by the chain; thereby keeping the distance constant between the two opposing steps on which the vehicle is supported. Thus, it becomes possible to incline in much safety the vehicle which has been supported horizontally by the steps. 
    
    
     One of preferred embodiments of a two-masted lifting apparatus in accordance with the present invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a front view showing one embodiment of a two-masted lifting apparatus according to the invention, 
     FIG. 2 is a sectional view of the same, when taken along the line A--A in FIG. 1, and 
     FIG. 3 is a sectional view of the same, when taken along the line B--B in FIG. 1. 
    
    
     With particular reference to FIGS. 1 and 2, there is shown a base 1 on which two masts 2a and 2b of channel section are vertically mounted such that the connected portions of the channel-shaped masts 2a and 2b oppose each other. A carriage 3a or 3b of channel section is slidably mounted on each of the masts 2a and 2b. 
     Respectively secured to the front and the rear faces of the left-hand carriage 3a are two brackets 4a and 4a&#39; to the outer ends of which bearing members 5 and 5&#39; are secured. These two bearing members 5 and 5&#39;, as shown in FIG. 3, are of channel section and in parallel with each other. Each bearing member 5 or 5&#39; has a vertical pin 7 adapted to pivotally support an end portion of a hollow sleeve 6a or 6a&#39; of square section, into which an arm 8a or 8a&#39; is slidably inserted to constitute a telescopic structure. 
     Each of these two arms 5 and 5&#39; has a pin-block 9a on the upper surface of its free end portion so as to secure a step 10a or 10&#39; thereon, whereby each step 10a or 10a&#39; is rotatable with respect to the arm 5 or 5&#39;. 
     Similarly, a bracket 4b or 4b&#39; is firmly secured to the front or the rear face of the carriage 3b slidably mounted on the right-hand mast 2b. Each bracket 4b or 4b&#39; has at its outer end a hollow sleeve 6b or 6b&#39; of square section into which an arm 8b or 8b&#39; is slidably inserted. Both arms 8b and 8b&#39; inserted within the sleeves 6b and 6b&#39; are in parallel with each other and have on the upper surfaces of their free end portions pin-blocks 9b and 9b&#39; respectively for securing steps 10b and 10b&#39; thereon. Between the two opposing steps 10a(10a&#39;) and 10b(10b&#39;), there is removably installed a chain 11 or 11&#39; as shown in FIG. 2. 
     In order to move up or down the carriage 3a along the mast 2a, a lifting means 12a which utilizes, for example, fluid pressure such as oil pressure is vertically disposed within the mast 2a of channel section. A piston rod 13a of the lifting means 12a has a sprocket wheel 14a on its upper end. A chain 15, one end of which is secured to an appropriate portion 15a of the mast 2a and other end of which is also secured to a horizontal pin 16 anchored to the carriage 3a, extends around the sprocket wheel 14a of the piston rod 13a. 
     Similarly, within the right-hand mast 2b of channel section, a lifting means 12b of the fluid pressure type is vertically disposed; its piston rod 13b having a sprocket wheel 14b on the top thereof around which a chain 18 extends. This chain 18, one end of which is secured to a pin 17a mounted on the left-hand mast 2a and the other end of which is also secured to a horizontal pin 17b mounted on the right-hand carriage 2b, goes around a sprocket wheel 19a rotatably mounted on the bottom portion of the mast 2a and passes through the base 1. It further extends around another sprocket wheel 19b rotatably mounted on the bottom portion of the right-hand mast 2b and the sprocket wheel 14b mounted on the top of the piston rod 13b and reaches the horizontal pin 17b on the carriage 3b. 
     Both of the above described lifting means 12a and 12b of the fluid pressure type, being connected to a fluid pressure source 20 mounted on the top of the left-hand mast 2a, are actuated independently from each other. 
     When the foregoing descriptions in mind, attention will now be directed to the operation of the lifting apparatus of the present invention. 
     To begin with, both lifting means 12a and 12b are actuated to lower the carriages 3a and 3b along the masts 2a and 2b down to their ultimate bottom portions. A vehicle or the like to be inspected is then driven between the two masts 2a and 2b. Thereafter, sleeves 6a or 6a&#39; pivotally mounted on the left-hand carriage 3a are suitably swung, and the length of arms 8a, 8a&#39;, 8b and 8b&#39; slidably inserted within the sleeves is also suitably adjusted until all of the steps 10a, 10a&#39;, 10b and 10b&#39; are brought into positive engagement with the most appropriate portions of the underside of the vehicle. Chains 11 and 11&#39; are installed without any slack between 10a and 10b or between 10a&#39; and 10b&#39; respectively. 
     Next, only the left-hand lifting means 12a is actuated to raise its piston rod 13a so that the left-hand carriage 3a moves upward along the mast 2a. At the same moment, the right-hand carriage 3b associatively connected with the left-hand carriage 3a through a chain 18 moves up synchronously along the mast 2b. Thus, the vehicle supported by the four steps moves upward maintaining its original posture. 
     As soon as the vehicle has reached an appropriate position, the actuation of the left-hand lifting means 12a is stopped. Then, the right-hand lifting means 12b is actuated. At this moment, since the left-hand lifting means 12a is not working, only the right-hand lifting means 12b moves upward. The actuation of the right-hand lifting means 12b is continued until a desired inclination angle of the vehicle is obtained. 
     In this case, the distance between the two opposing steps 10a(10a&#39;) and 10b(10b&#39;) tends to expand, because only the right-hand carriage 3b moves upward. Each pair of the steps, however, are connected to each other by a chain 11 or 11&#39; so that arms 8b or 8b&#39; slidably inserted within the right-hand sleeves 6b or 6b&#39; are dragged out of the sleeves toward the left-hand mast 2a; whereby the distance between the steps is kept constant. 
     Thus, according to the two-masted lifting apparatus of the invention, it becomes possible to incline a vehicle or the like at a desired angle without any fear of slippage of the vehicle.