Patent Publication Number: US-2018031456-A1

Title: Lift table for a load frame

Description:
FIELD 
     The present disclosure relates to a lift table. More specifically, the present disclosure relates to a lift table for a load frame. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     In various industries, load frames are employed to evaluate the tensile/compressive properties of certain components. These load frames require the use of heavy fixtures and load cells that are difficult to install and remove. For example, heavy tensile test fixtures are difficult to attach to the load frame crosshead because the operator typically uses one hand for holding the fixture and maintaining alignment and the other hand for turning the fixture to thread its threaded end into the crosshead. Moreover, removing heavy fixtures from the load frame produce additional issues. For example, as the fixture is being removed from the crosshead, the operator may not be able to identify when the threads are about to run out. Consequently, the fixture may fall which requires the operator to quickly catch the fixture and might pose safety hazards/injuries. 
     Accordingly, there is a need in the art for an apparatus that enables easy and safe installation and removal of heavy fixtures and load cells from a load frame. 
     SUMMARY 
     The present invention provides a lift table for a load frame. 
     Accordingly pursuant to one aspect, a lift table includes a first adjuster having a base with a bore and a collet that is threaded into the bore of the base, the first adjuster being configured to selectively secure the lift table to the load frame, and a plate that sits atop the collet, the plate being configured to hold a fixture that is attached to the load frame. Rotation of the collet in a first direction relative to the base raises the plate and rotation of the collet in a second direction relative to the base lowers the plate. 
     This aspect may be further characterized by one or any combination of the features described herein, such as :the first adjuster includes a locking feature to prevent over-rotation and separation of the collet from the base; the lift table includes a second adjuster, the first adjuster being a coarse adjuster and the second adjuster being a fine adjuster; the second adjuster enables rotation of the plate relative to the collet in the first direction to raise the plate and rotation of the plate relative to the collet in the second direction to lower the plate; the second adjuster includes a locking feature to prevent over-rotation and separation of the plate from the collet; the table includes centering marks to aid in aligning the fixture; the lift table further includes a centering tool secured to the top of the plate to aid in aligning the fixture on top of the plate; the fixture is provided with a thread end indicator to warn of thread disengagement of the fixture from the load frame; the collet includes one or more notches that engage with a wrench to provide leverage for rotating the collet; the lift table may further includes a spring-load mechanism that prevents binding during rotation and secures the plate to the collet. 
     Accordingly, pursuant to another aspect, a lift table for a load frame includes a coarse adjuster having a base with a bore and a collet that is threaded into the bore of the base, the coarse adjuster being configured to selectively secure the lift table to the load frame, a plate that sits atop the collet, the plate being configured to hold a fixture that is attached to the load frame, rotation of the collet in a first direction relative to the base raising the plate and rotation of the collet in a second direction relative to the base lowering the plate, and a fine adjuster that enables rotation of the plate relative to the collet in the first direction to raise the plate and rotation of the plate relative to the collet in the second direction to lower the plate. 
     This aspect may be further characterized by one or any combination of the features described herein, such as: the coarse adjuster includes a locking feature to prevent over-rotation and separation of the collet from the base; the fine adjuster includes a second locking feature to prevent over-rotation and separation of the plate from the collet; the lift table further includes a centering tool secured to the top of the plate to aid in aligning the fixture on top of the plate. 
     Accordingly, pursuant to another aspect, a lift table for a load frame includes an adjuster having a base with a bore and a collet that is threaded into the bore of the base, the adjuster being configured to selectively secure the lift table to the load frame; a plate that sits atop the collet, the plate being configured to hold a fixture that is attached to the load frame, rotation of the collet in a first direction relative to the base raising the plate and rotation of the collet in a second direction relative to the base lowering the plate, and a spring-load mechanism that prevents thread binding during rotation, and secures the plate to the collet, the spring-load mechanism including a plurality of springs positioned to float the plate on top of the collet. The plurality of springs may be rated for about 50 Newtons in excess to the total weight of the fixture. 
     Further features, advantages, and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the drawings: 
         FIG. 1  illustrates a spring-less lift table for a load frame in accordance with the principles of the present invention; 
         FIG. 2  illustrates various fixtures for use in the load frame; 
         FIG. 3  illustrates the lift table with a fixture; 
         FIG. 4  is a cross-sectional view of the spring-less lift table; 
         FIG. 5  is a close-up view of thread-end indicator in accordance with the principles of the present invention; 
         FIGS. 6A and 6B  illustrate the thread-end indicator in use; 
         FIG. 7  illustrates various centering tools for use with the lift table; 
         FIG. 8  illustrates a centering tool in use with a fixture; 
         FIG. 9  illustrates the spring-loaded lift table in accordance with the principles of the present invention; and 
         FIG. 9A  is a close-up view of the region  9 A in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     Referring now to  FIG. 1 , a lift table embodying the principles of the present invention is illustrated therein and designated at  10 . The lift table  10  is selectively secured to a T-slotted table  14  of a load frame  12  with a nut  15 . The lift table  10  is employed for attaching various types of fixtures  22 ,  24 ,  26 ,  28 , and  30  shown in  FIG. 2 , as well as accessory load cells, to the main load cell  18 . The adaptor  20  is attached to a load cell  18  which, in turn, is attached to a crosshead  16 . Specifically, any one of the fixtures  22 ,  24 ,  26 ,  28  and  30  are initially placed on top of the lift table  10 , which is employed to raise the selected fixture  22 ,  24 ,  26 ,  28  or  30  up to the adaptor  20  to enable threading a threaded end  32 ,  34 ,  36 ,  38  or  40  into the adaptor  20 . After, the fixture  22 ,  24 ,  26 ,  28  or  30  is attached to the adaptor, the lift table  10  is lowered and removed from the load frame&#39;s T-slotted table  14 . 
     Referring now to  FIG. 3 , there is shown a particular fixture  42  placed on the lift table  10  prior to attaching threaded end  44  of the fixture  42  to the adaptor  20 . Referring also to  FIG. 4 , the lift table  10  includes a base  52  with a threaded end  58  that is configured to be threaded into load frame&#39;s T-slotted table  14  and secured with a nut  15 . The lift table  10  also includes a collet  54  threaded into the base  52  and a plate  56  threaded into the collet  54 . More specifically, the collet  54  includes a threaded end  66  that threads into an enlarged bore region  60  of the base  52 . Hence, rotating the collet  54  in one direction, for example, counter-clockwise, raises the collet  54  relative to the base  52 , while rotating the collet  54  in the opposite direction, for example, clockwise, lowers the collet  54 . 
     The plate  56  is generally circular in various arrangements and is attached to the collet  54  with a hollow threaded stud or shaft  74 , and a centering tool  50  is threaded onto the shaft  74  to secure the plate  56  to the collet  54 . As such, as the plate  56  is rotated in one direction, for example, counter-clockwise, the shaft  74  threads out of a bore  75  of the collet  54  to raise the plate  56  relative to the collet  54 . And when the plate  56  is rotated in the opposite direction, for example, clockwise, the shaft  74  threads into the bore  75  to lower the plate  56  relative to the collet  54 . In the particular arrangement shown in  FIG. 4 , the shaft  74  has a 1″-14 thread and the threaded end  66  has a 2″-12 thread. Accordingly, rotation of the collet  54  relative to the base  52  provides a coarse adjuster to raise and lower the plate  56  while rotation of the plate  56  relative to the collet  54  provides a fine adjuster to raise and lower the plate  56 . 
     Each of the aforementioned adjusters includes a locking feature to prevent separation of the collet  54  from the base  52  and separation of the plate  56  from the collet  54  during the operation of the lift table  10 . Specifically, the collet  54  includes a shaft  68  that extends from its threaded end  66 . The shaft  68  extends through the enlarged bore  60 , through a reduced bore region  62  into an end bore region  64 . The shaft  68  has a threaded end  70  onto which a nut  72  is attached. The nut  72  allows the shaft  68  to reciprocate in the bore regions  60 ,  62  and  64 . The flange of nut  72 , however, is large enough to prevent the nut  72  and hence the thread end  70  from entering into the reduced bore region  62 . Accordingly, as the collet  54  is rotated counter-clockwise to raise the plate  56 , the nut  72  ultimately prevents the shaft  68  and consequently the collet  54  from rising further relative to the base  52 . Thus, this locking feature prevents the over-rotation and separation of the collet  54  from the base  52 . 
     As for the locking feature of the fine adjuster, a bolt  80  has a threaded end  84  that threads into a region  86  of the collet  54 . The bolt  80  extends through an enlarged bore  76  and a reduced bore  78  of the threaded shaft  74 . The bolt  80  includes an enlarged end  82  that is sized to prevent it from entering into the reduced bore  78 . Hence, when the lift table is in use, the bolt  80  remains stationary relative to the collet  54 , while the threaded shaft  74  and the plate  56  rises and lowers relative to the collet  54  and the enlarged end  82  is able to reciprocate in the enlarged bore  76 . As the plate  56  is rotated to raise the plate  56 , the enlarged end  82  ultimately is prevented from entering into the reduced bore  78  to prevent the threaded shaft  74  and the plate  56  from rising further relative to the collet  54 , which prevent the over-rotation and separation of the plate  56  from the collet  54 . 
     In various arrangements the threaded ends  32 ,  34 ,  36 ,  38 ,  40  and  44  of the fixtures  22 ,  24 ,  26 ,  28 ,  30  and  42  include a thread end indicator and a dog-point  90  that facilitates alignment of the threaded end  44  with respect to the adaptor  20  ( FIGS. 6A and 6B ). For example, as shown in  FIG. 5 , the threaded end  44  of the fixture  42  includes a milled slot  92  that is aligned with milled slot  94  on a surface of fixture  42 . The milled slot  92  can be positioned on, for example, the last two threads of the threaded end  44 . Accordingly, after the threaded end  44  is threaded and engaged with the adaptor  20 , an operator can rotate the fixture  42  to disengage the fixture  42  from the adaptor  20 . As the operator continues to rotate the fixture  42 , the milled slot  94  ( FIG. 6A ) alerts the operator where to look for the milled slot  92 . When the milled slot  92  ultimately appears ( FIG. 6B ), the operator knows that the thread disengagement is imminent. 
     Referring now to  FIG. 7 , there is shown a centering tool  100  along with the centering tool  50 . The centering tool  50  is shaped and sized, for example, cone frustum shape, to fit within a region  48  ( FIG. 3 ) of the fixture  42  to facilitate centering the fixture  42  relative to the plate  56 . Note that the surface of the plate  56  may include inscribed concentric rings  57  to also aid in centering a fixture onto the plate  56 . Hence, after the fixture  42  is centered onto the plate  56 , the operator rotates the coarse and fine adjuster to raise the threaded end  44  to the adaptor  20 . The dog point  90  helps guide the threaded end  44  into the adaptor  20  so that further rotation of the fixture  42  secures the fixture to the adaptor  20 . The reverse process is employed to remove the fixture  42  from the adaptor  20 . 
     The centering tool  100  has a rectangular cross-section and is configured to center a fixture with an opening that corresponds to the shape of the tool  100 . For example, as shown in  FIG. 8 , the fixture  26  includes a pair of arms  102  that are spaced apart to define a region  104 . The tool  100  is threaded onto the shaft  74  to secure the tool  100  to the plate  56 . The tool  100  is sized and shaped to fit within the region  104  of the fixture  26 . Hence, an operator is able to place and center the fixture  26  on the plate  56  with the aid of the centering tool  100  to facilitate threading the threaded end  36  into the adaptor  20 . Other sized and shaped centering tools are contemplated depending on the interior region of the fixture being attached to the adaptor  20 . 
     Referring now to  FIG. 9 , there is shown an alternative lift table  200  with a spring load mechanism in accordance with the principles of the present invention. The lift table  200  includes a collet  252  with a threaded end  253  that threads into the base  52 . The centering tool  50  or the centering tool  100  is attached to plate  256  via a threaded bolt  274 . The enlarged end  275  of the bolt  274  is sized to be slightly smaller than a bore  264  of the collet  252  so that the enlarged end  275  can fit within the bore  264 . The plate  256  includes a set of counter-bore regions  257  and  258 . A set of respective allen head shoulder bolts  254  include shaft portions  258  that thread into threaded regions  260  in the collet  252 . The allen head shoulder bolts  254  include enlarged ends  262  that fit within the bore regions  257  but are larger than the bore regions  258 . A set of springs  262  are placed about the shoulder regions of allen head shoulder bolts  254  and between the plate  256  and the collet  252 . Hence, in this arrangement, the springs  262  provide an upward biasing force so that the plate  256  floats on top of the collet  252 , while the allen head shoulder bolts  254  prevent the separation of the plate  256  from the collet  252 . The number of springs  262  and corresponding allen head shoulder bolts  254  can be as few as six to eight. In various arrangements, the combined set of springs is rated for about 50 Newtons in excess to the total fixture weight. As such, when a fixture is placed on the table  256 , rotation of the plate  256  along with the collet  252 , for example, counter-clockwise, relative to the base  52  raises the plate and the fixture up to the adaptor  20 . Since the plate  256  floats on the springs  262 , the plate  256  is able to tilt off axis from a longitudinal axis extending along the threaded bolt  274 . Such movement helps in aligning the threaded end of any of the aforementioned fixtures with the adaptor  20  so that the threaded end can be threaded into the adaptor  20 . The process is reversed to remove the fixture from the adaptor  20 . Accordingly, the spring-loaded lift table  200  can be used with all load frames. The springs will support the fixture weight and give approximately 50 Newtons of usable end force for assembling the fixture to the load frame  12 . 
     Although the above arrangements employs four springs and generates approximately 205 Newtons of lifting force, other arrangements employ six to eight springs and generate the same force. By placing the springs under the plate on, for example, a five inch bolt circle, the fixture weight is evenly supported around the table, which eliminates any uneven tipping forces on the table. After supporting all the fixtures&#39; weight, a small spring force of approximately 50 Newtons remains for fixture assembly. This small end load is enough to allow the threads to smoothly engage and allow the fixtures to be threaded together without binding during the installation process. 
     In another configuration, a lift table without any springs can be used with load frames that have an electronic circuit such as, for example, the Specimen Protect feature available from Instron Corporation. The electronic circuit in these load frames will allow the lift table to work correctly without the springs. For example, the Specimen Protect circuit works by adjusting the crosshead  16  position up or down to maintain the required usable end load of approximately 50 Newtons. This is the same process as the spring-loaded option 
     In sum, the lift tables  10  and  200  hold and support the weight of heavy fixtures and load cells, while allowing for the installation and removal of the threaded ends of the fixtures and load cells from the crosshead of the load frame. This eliminates the dependence on the operator&#39;s physical strength, improves efficiency, and prevents safety/ergonomic issues associated with lifting heavy items. 
     The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.