Patent Publication Number: US-6210156-B1

Title: Heat treatment material handling unit

Description:
TECHNICAL FIELD 
     This invention relates to heat treatment of small parts and, more particularly, to a material handling unit for sequentially processing individual parts through a heat treatment system. 
     BACKGROUND OF THE INVENTION 
     It is customary in heat treating small parts to treat them in batches by placing a batch of such parts in a heat treatment basket and immersing in a furnace. This method of handling parts often encounters problems of consistency in the heat treatment of all parts, with some being over- or under-heat treated due to the inconsistent distribution of parts throughout the batch and resulting unequal exposure to a constant temperature and process conditions. 
     It would be desirable to provide a material handling unit which enables parts to be individually and consistently heat treated. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a material handling unit which enables parts to be individually and consistently heat treated. 
     In one aspect, this invention features a method for sequentially processing a plurality of parts individually through a heat treatment process at a predetermined rate, whereby each part is heat treated for a predetermined time so that all parts are heat treated equally, comprising the steps of arranging a plurality of parts in a vertical stack in a heat treatment furnace, and sequentially removing and inserting parts at the ends of the stack at predetermined intervals so that each part progresses from one end of the stack to the other. 
     Preferably, the method includes the steps of lifting the stack to facilitate removing and inserting parts, removing a part from one of the top or bottom end of the stack, and inserting a part into the other of the top or bottom of the stack. 
     In another aspect, this invention features a material handling unit for sequentially processing a plurality of parts individually through a heat treatment process at a predetermined rate, whereby each part is heat treated for a predetermined time so that all parts are heat treated equally. A vertical guide holds a plurality of parts in a vertical stack. Slides with movable jaws are provided at the top and bottom of the stack for sequentially removing and inserting parts at the ends of the stack so that each part progresses from one end of the stack to the other, and a blocking bar is inserted to immobilize the stack during removal and insertion of parts. A rod lifts the stack to facilitate removing and inserting parts. 
     Preferably, the material handling unit includes a pallet supporting each part. The slides move between a position aligning the pallet with the stack and a position moving the pallet outside the stack. The vertical guide maintains alignment of the stack of parts and can be a vertical tube or three or more spaced vertical rods. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical sectional view of a portion of a heat treating furnace schematically illustrating the structure of a heat treatment material handling unit for heat treating small parts according to this invention; 
     FIG. 2 is a horizontal sectional view of the material handling unit of FIG. 1; 
     FIGS. 3 through 12 are detail views of a portion of the material handling unit of FIGS. 1 and 2, illustrating the sequencing of the parts through the unit; 
     FIG. 13 is a detail plan view of the lower slide assembly used in the material handling unit of this invention; 
     FIGS. 14 a ,  14   b  and  14   c  are plan, side and end views of the bottom slide member of the upper slide assembly of FIG. 13; 
     FIGS. 15 a ,  15   b  and  15   c  are plan, side and end views of the outer clamping member of the upper slide assembly of FIG. 13; 
     FIGS. 16 a ,  16   b  and  16   c  are plan, side and end views of the inner clamping member of the upper slide assembly of FIG. 1; 
     FIGS. 17 a ,  17   b  and  17   c  are plan, side and end views of the blocking bar used in the material handling unit of this invention; 
     FIG. 18 is detail plan view of the upper slide assembly used in the material handling unit of this invention; 
     FIGS. 19 a ,  19   b  and  19   c  are plan, side and end views of the outer clamping member of the upper slide assembly of FIG. 18; 
     FIGS. 20 a ,  20   b  and  20   c  are plan, side and end views of the inner clamping member of the upper slide assembly of FIG. 18; 
     FIGS. 21 a  and  21   b  are enlarged side and top views of a relatively large part supported on a pallet for handling by the material handling unit of this invention; 
     FIGS. 22 a  and  22   b  are enlarged side and top views of a relatively small part supported on a pallet for handling by the material handling unit of this invention; 
     FIG. 23 is a vertical sectional view of a part contained within a cage assembly for handling by the material handling unit of this invention; 
     FIG. 24 is a plan view of the cage shown in FIG. 23; and 
     FIG. 25 is a sectional view taken along line  25 — 25  of FIG.  24 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2 show a portion of a heat treating system that includes a heat treatment material handling unit  30 , which is utilized to process a plurality of small parts, as will be described in detail later. Unit  30  comprises a cylindrical housing  32  made of an insulating material, and a heating element  34 , forming a toroidal heat treating chamber  36 . A plurality of cylindrical heat treating vertical guides in the form of tubes  38  are annularly spaced within chamber  36  and are mounted on a rotatable cartridge  40 , having a base  42  and a drive spindle  44  that is driven by an electric motor (not shown). A computerized controller (not shown) controls movement of the elements of the heat treatment material handling unit  30  via conventional hydraulic or pneumatic operators. 
     Base  42  mounts a plurality of vertically-slidable lift rods  46 , one for each tube  38 . An actuator rod  48  is located beneath a transfer station  50 , located at one side of furnace  30 , that includes an entry chamber  52 , having a door  54 , and an exit chamber  56 , having a door  58 . Actuator rod  48  reciprocates to engage and lift the lift rod  46  of whichever tube  38  is located at the transfer station  50 . A sensing rod  60  is located at the top of transfer station  50  in alignment with tube  38 . 
     The heat treating material handling units of this invention are designed to handle many small parts, such as two-inch steel transmission gears, individually. As illustrated, unit  30  comprises  15  of the tubes  38 , each of which is shown containing a stack of  10  parts  62 , each carried by a pallet  64 . Details of the parts and pallets will be later described in reference to FIGS. 21-25. Each part is handled separately and is heat treated for the same predetermined time. For example, if heat treating time is 750 seconds, parts must be inserted into and removed from unit  30  every five seconds. Although unit  30  is illustrated as containing 150 parts, more or fewer can be processed simultaneously by varying the number or diameters of tubes  38 , or by varying the height of the stack of parts. 
     The removal and insertion of parts, detailed in FIGS. 3-12, is provided by three slides shown in FIGS. 13-20 c . An unloading clamping slide  70  (FIG. 13) operates in exit chamber  58 , as does a blocking slide  72  (FIGS. 17 a-c ), while a loading clamping slide  74  (FIG. 18) operates in entrance chamber  54 . Both slides  70  and  74  have jaws that close and open to grip and release a part  62  and its pallet  64 , as described in detail later. 
     FIG. 3 illustrates tube  38   a  at transfer station  50  prior to sequential removal and insertion of parts  62 . When it is time to remove a fully heat-treated part, actuator rod  48  is extended to raise lift rod  46 , which engages the bottom pallet  64   a  and lifts the entire column of pallets and parts within tube  38   a , as shown in FIG.  4 . Simultaneously, door  58  opens and unloading slide  70 , with open jaws, is inserted through exit chamber  56  to a position beneath the raised stack, as shown in FIG.  4 . 
     Actuator rod  48  then partially retracts to partially lower the stack, with the lowest part and pallet  62   a ,  64   a  descending from tube  38   a  to a position partially within the open jaws of unloading slide  70 , as depicted in FIG.  5 . Blocking slide  72  is then inserted beneath the pallet  64   b  of the next lower part  62   b , and actuator rod  48  fully retracts to lower pallet  64   a  onto slide  70 , which then closes to grip part and pallet  62   a ,  64   a , as shown in FIG.  6 . The remaining stack of nine parts and pallets is supported on blocking slide  72 . Slide  70 , with part  62   a  on pallet  64   a , is removed through chamber  56 , as shown in FIG.  7 . 
     Next, in FIG. 8, actuator rod  48  extends to raise the stack of parts off blocking slide  72 , which is then removed. Door  58  is closed, actuator rod  48  retracts to lower the stack of parts in tube  38   a , and upper door  54  opens to admit loading slide  74  that carries a new part  62   c  on its pallet  64   c  and locates them above the stack, to begin heat treatment, as illustrated in FIG.  9 . Sensing rod  60  is extended to detect the presence of new part  62   c . This signals actuator rod  48  to extend to engage top part  62   d  with pallet  64   c . When sensing rod  60  detects that part  62   c  and pallet  64   c  are lifted off loading slide  74 , then actuator rod  48  stops lifting and jaws of slide  74  open to release part  62   c , as shown in FIG.  10 . Next, actuator rod  48  retracts to lower the stack of  10  parts fully, FIG. 11, and door  54  is closed after slide  74  is withdrawn from chamber  52 , as in FIG.  12 . 
     Cartridge  40  is then indexed to align another tube  38  of parts with transfer station  50 . The above process is repeated endlessly to sequentially remove heat-treated parts and insert new parts at a predetermined rate, which depends on the capacity of the unit and the time of heat treatment. Parts will gradually work their way down the stacks as cartridge  40  continues to index, removing and inserting parts at a predetermined rate. In this manner, every part is handled individually and receives the identical heat treatment, unlike heat treatment in the conventional batch process. 
     FIG. 13 shows the assembled removal slide  70 , which is in three parts, shown in FIGS. 14 a, b, c ;  15   a, b  and  c ; and  16   a, b  and  c . A slide base  76  has a notch  78  that is wide enough to slide around lift rod  46 , and a pair of guide rails  80 ,  82 . An outer jaw  84  has a pair of grippers  86 ,  88  spaced by a slot  90  that are formed on the ends of rails  92 ,  94 . Slot  90  is wide enough to allow passage around rod  46 . Rails  92 ,  94  fit outside guide rails  80 ,  82  of base member  76 . An inner jaw  96  comprises a gripper  98  formed on the end of a rail  100 , which fits between guide rails  80 ,  82  of base  76 . FIG. 13 illustrates the assembly of parts, with the jaws shown open as in FIG.  4 . To close and clamp a part and pallet, jaws  84  and  96  are slid together on base  76 , as in FIG.  6 . 
     Blocking slide  72  (in FIG. 17) is a plate having a slot  102  that is narrower than a pallet  64 , but wider than a part  62 . This enables insertion around a part beneath a pallet to support the stack, as in FIG.  6 . 
     Loading slide  74  comprises a base  104  having an opening  106  bounded on one side by an outer jaw  108 , and a guide slot  110 . Opening  106  is larger than a pallet to enable pallet  64   c  to descend through it, as illustrated in FIGS. 10 and 11. An inner jaw  112  is mounted on the end of a rail  114 . When inner jaw  112  is slid toward outer jaw  108 , it forces a pallet onto the narrowed ledge  116  bordering opening  106 , and the narrowed ledge  118  on jaw  112 . Both ledges  116  and  118  form an opening larger than a part  62 , but smaller than a pallet  64 . This enables part  62   d  to engage the bottom of pallet  64   c  as in FIG.  10 . 
     Slides  70 ,  72  and  74  can be operated by any conventional hydraulic or pneumatic operators, which themselves form no part of this invention. All movement is controlled by a microprocessor/controller which has been programmed in a well-known manner to operate unit  30 . 
     FIGS. 21 a, b  and  22   a, b  illustrate in detail the range of sizes that may be heat treated with the same equipment, ranging from a small part  62 ″ to a large part  62 ′—both supported on the same size pallet  64 . Variations in the height the part  62  will vary the height of the stack of parts within tubes  38 . Thus, in this illustrative example described above, part height is critical to operation. A change in part height may require adjustment of cycle time, stack height, and rate of part removal and insertion, which could require physical equipment modifications and operation. To enable the processing of a variety of sizes of parts with the same equipment, a modified form of pallet, shown in FIGS. 23-25, may be used. 
     A cage  122  within which a part  124  is confined separates a top and bottom  120 . Cage  122  includes annularly spaced windows  126  to enable the free circulation of heat treating gases. Use of the cage provides a consistent height dimension for the process equipment, regardless of the size of part being heat treated. This also would eliminate the need for the sensing rod  60 . 
     Thus, this invention enables parts to be individually and consistently heat treated in a sequential, timed manner. The apparatus and method of this invention can be utilized for any heat treatment operation, such as preheating, carburizing, equalizing, quenching, tempering and testing, 
     While only a preferred embodiment has been shown and described, many modifications are contemplated within the scope if this invention and the appended claims. For example, the vertical guides could take a form different from tubes  38 , such as three or more annularly spaced rods, which would have the identical function of maintaining the parts on pallets aligned in vertical stack as it moves up and down during part removal and insertion. Also, depending on process requirements, parts could be inserted at the top and removed at the bottom of the stack by using the same equipment.