Abstract:
The heater sling according to this invention is capable of lifting, moving and positioning a workpiece. In particular, it relates to a device and method for lifting a circumferential heater used in the manufacture of silicon ingots by the Czochralski method. The invention operates by mechanically extending a plurality of slings under a workpiece, lifting the workpiece, and placing it in a desired location.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus and method for lifting, moving and positioning a workpiece. In particular, it relates to a device and method for lifting a circumferential heater used in the manufacture of silicon ingots by the Czochralski method. 
     2. Description of the Prior Art 
     Traditionally, devices used to lift circumferential heaters used in the manufacture of silicon ingots are lowered around the outside edge of the heater. Slider bars are then inserted under the heater, and secured to the lifter. In some instances, a cage is then placed around the heater. Prior devices required an operator to manually place support plates under the heater, attach a cage to the supports, and then attach this apparatus to a lifting device. The heater could then be lifted from the bottom chamber of a Czochralski-type crystal puller machine for machine cleaning or heater replacement. These same devices are also used to place a new heater in the puller machine. 
     The above device, and similar devices, are appropriate for silicon manufacturing operations. However, they have a number of parts that must be assembled prior to and during the lifting, thereby consuming operator and machine time. This assembly and disassembly results in metal-to-metal contact among the device&#39;s parts, within the assembly, potentially damaging the device. Additionally, heat transfer from the heater the lifter, resulting from contact between the heater and the lifter, can cause the lifter to warp, leading to the added cost and time of replacement parts; it also increases the temperature of the lifter, thereby requiring a cooling period before the lifter can be handled. 
     SUMMARY OF THE INVENTION 
     In view of the above problems, an object of the present invention is to provide an apparatus and method for lifting and positioning a device, such as a circumferential heater, with reduced operator “hands-on” activity. The present device can be lowered into the center of a circumferential heater, the sling foot pads positioned under the heater, and the heater and lifter combination lifted by a single operator, using a remote control box. The present invention improves on past devices due to an operator&#39;s ability to operate it from a distance, reduced metal-to-metal contact, and ease of use. 
     The present invention also has relatively few parts. This reduces the amount of time an operator must spend setting up and taking down the apparatus, thereby enabling a more efficient process. Additionally, the present invention is, essentially, a one-piece construction after assembly. This helps to control warpage and commensurate part misfits. 
     Another improvement over the prior art is the present invention&#39;s elimination of an exterior cage. As opposed to prior heater-lifting devices, which enclosed the heater within a cage or similar means, the present invention lifts a circumferential heater from within its center void. This interior placement eliminates the need for an exterior cage, thereby reducing operator time, warpage, and heat transfer, as described above. 
     The present invention also reduces metal-to-metal contact by using polymer-based, ceramic, graphite, carbon composite or equivalent bushings and pads. These pads protect both the lifter and the heater from damage, and keep the lifter cooler than the previous lifter devices. The pads have the additional benefit of not contributing metal contamination to the Czochralski process. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is described by reference to the examples and the drawings, in which: 
     FIG. 1 is a side view of a preferred embodiment of the present invention, with slings extended and support rod in the up position. 
     FIG. 2 is a top view of a preferred embodiment of the present invention. 
     FIG. 3 is a side view of the support rod. 
     FIG. 4 is a top view of the top support. 
     FIG. 5 is a top view of the bottom support. 
     FIG. 6 is a front side view of an outer sling. 
     FIG. 7 is a front side view of a middle sling. 
     FIG. 8 is a side view of a representative sling. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As delineated in the drawings, and shown in FIG. 1, the present invention comprises a support rod  10 , a top support  20 , a bottom support  30 , and a plurality of slings  40 . 
     As shown in FIG. 3, a support rod  10  comprises a support rod shaft  12 , a bottom pad  14  removably attached to a distal end of the shaft  12 , a top pad  16  removably attached to the end of the shaft  12  opposite the bottom pad  14 , and a hoist mechanism  18  attached to the surface of the top pad  16  opposite the shaft  12 . 
     The top support  20 , as shown in FIG. 4, comprises a hoist mechanism  22  attached to the top surface of the top support  20 , a center void  24  running vertically through the center of the top support  20 , and a plurality of removably attached pivot shafts  26 . In a preferred embodiment, the pivot shafts  26  as shown in FIG. 4 are seated in three-sided notches  28  spaced about the outer edge of the top support  20 . The shafts  26  and notches  28  are distributed reasonably equally about the circumference of the top support  20 , and are sized such that a sling  40  fits into a notch  28 . The notch  28  is wide and deep enough so that the sling  40  can swing freely, but narrow enough so that the sling  40  has limited horizontal play within the notch  28 . 
     The bottom support  30 , shown in FIG. 5, comprises a center void  32  and a plurality of circumferential slots  34 . The slots  34  are arranged substantially similar to the upper support pivot shafts  26  and notches  28 , but are located a greater distance from the bottom support center void  32  than the pivot shafts  26  are from the top support center void  24 . 
     A representative sling  40  is shown in FIG.  1 . The sling  40  has a rigid body  42  and foot plate  44  as shown in FIG.  8 . Fixed stoppers  46  are located approximately medially on the rigid body  42  of the slings. A cylindrical void  48  at one end of the rigid body  42  attaches to the top support pivot shafts  26 . The foot plate  44  attaches to the other end of the rigid body  42 . In a preferred embodiment of the invention, the slings comprise middle slings  50  (FIG. 7) and outer slings  52  (FIG.  6 ). In such an embodiment, the middle slings  50  are wider than the outer slings  52 . The differing widths are necessary in this embodiment because of the configuration of the workpiece supports. If required, all of the slings could be of varying or equal widths, depending on the workpiece. 
     As shown in FIGS. 1,  4 , and  5 , the invention is configured such that the support rod shaft  12  runs through both the top support center void  24  and the bottom support center void  32 . The bottom pad  14  is disposed below the bottom support  30  such that when the invention is in a substantially upright position, the bottom support  30  is supported by the bottom pad  14 . The support rod top pad  16  is disposed above the top support  20  such that the top support  20  is at all times between the top pad  16  and the bottom support  30 . 
     In a preferred embodiment of the invention, though it would not be so limited, a washer (not shown), composed of a polymer-based, heat-resistant material such as Teflon®, covers the inside surface of the top and bottom support center voids  24  and  32  so as to minimize metal-to-metal contact between the support rod  10  and the top support  20  and bottom support  30 . 
     The slings  40  are swingably connected by pivot shafts  26  to the top support  20  such that the cylindrical void  48  of the slings  40  fits into the notches  28  of the top support  20 . In a particular embodiment of the invention, though it would not be so limited, a bushing (not shown), composed of a polymer-based, heat-resistant material such as Teflon®, or another non-metallic, heat resistant material such as a ceramic, is utilized in combination with the pivot shaft  26  such that minimal metal-to-metal contact occurs between the sling  40  and the top plate  20 . 
     In a preferred embodiment, a polymer-based, heat-resistant material such as Teflon® can be used to form pads  45 . The pads  45  are fixably attached to the upper surface of the foot plate  44  of the sling  40 . In addition to a polymer-based material, other heat-resistant, non-metallic materials, such as ceramic, could be utilized in the bushings, washers, pads, and other heat protective elements included in the invention. 
     The slings  40  pass through the slots  34  of the bottom support  30 . The bottom support  30  has a range of motion slidably along the slings with upper and lower limits at the medially positioned stoppers  46  and the sling foot plate  44 . In a preferred embodiment of the invention, though it would not be so limited, the interior of the slots  34  are lined with a polymer-based, heat-resistant material such as Teflon® or equivalent. The heat resistant material would extend outwardly along the upper and lower surface of the bottom support  30  such that when in the open position there is minimal metal-to-metal contact between the bottom support  30  and the sling stoppers  46 . 
     In a preferred method, the apparatus would be used to raise, lower, and position a circumferential heater into the lower portion of a Czochralski-type puller machine utilized in the semiconductor industry. One skilled in the art, however, could utilize both the apparatus and the method in any situation where the workpiece has an interior void suitable for insertion of a circumferential lifter as disclosed herein. 
     In a preferred method, beginning with the step where the apparatus is outside the heater, and the heater is to be lifted out of the puller machine for cleaning, replacement, or other suitable reason, an operator attaches a support line or similar device to the top support hoist mechanism  22 . The support line could be secured to the hoist mechanism by means of a hook, or quick release securing device or equivalent. The operator then raises the apparatus, and lowers the apparatus into the pulling machine such that the apparatus is positioned in the interior of the circumferential heater. The operator then repositions the support line from the top support hoist mechanism  22  to the support rod hoist mechanism  18 . The operator then places tension on the support line, thereby causing the support rod  10  to rise. The rising support rod causes the slings  40  to extend outward and under the circumferential heater. The heater-lifter combination is then ready for lifting or repositioning. The operator can then raise the heater-lifter combination out of the puller machine, and position it on the shop floor or other desired location. After the heater-lifter combination is placed at the desired position, the support line is slacked, causing the support rod  10  to lower. The lowering support rod causes the slings  40  to retract, thereby disengaging the heater from the lifter. The lifter can then be extracted from the interior of the heater by repositioning the support line from the support rod hoist mechanism  18  to the top support hoist mechanism  22 , and lifting the lifter.