Abstract:
In a preferred embodiment, an apparatus, comprising: a rotary motor having an external shaft with an axial slot defined therethrough; a linear motor having a threaded external shaft with a translating nut disposed thereon; and the threaded external shaft being disposed in the slotted external shaft, with a tab on the translating nut extending through the axial slot, the tab preventing the translating nut from rotational motion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     The present application claims the benefit of the filing date of U.S. Provisional Application No. 60/575,356, filed May 28, 2004, and titled COMPACT LINEAR/ROTARY ACTUATOR FOR OFFSET ACTUATION. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to actuators generally, and more particularly, but not by way of limitation, to a novel compact linear/rotary actuator for offset actuation.  
         [0004]     2. Background Art  
         [0005]     There are times when it is desirable to have a single actuator provide both linear and rotary motion. Applications for such an actuator are pick-and-place or sampling.  
         [0006]     There are many existing methods to accomplish this type of motion; however, many are mechanically complicated or require a length which is often more than two times the actual stroke required.  
         [0007]     Many designs also cannot properly handle offset axial loads without excessive deflections. Several of these designs also include an intermediate coupling that is often complicated to manufacture. The coupling can often add hysterisis to the system as well.  
         [0008]     Accordingly, it is a principal object of the present invention to provide a compact linear/rotary actuator that has a linear stroke that is approximately one-half of the overall package size, compared with conventional linear/rotary actuators.  
         [0009]     It is a further object of the invention to provide such a compact linear/rotary actuator that is mechanically simple.  
         [0010]     It is an additional object of the invention to provide such a compact linear/rotary actuator that can effectively support offset axial loads.  
         [0011]     It is another object of the invention to provide such a compact linear/rotary actuator that can be economically manufactured.  
         [0012]     Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.  
       SUMMARY OF THE INVENTION  
       [0013]     The present invention achieves that above objects, among others, by providing in a preferred embodiment, an apparatus, comprising: a rotary motor having an external shaft with an axial slot defined therethrough; a linear motor having a threaded external shaft with a translating nut disposed thereon; and said threaded external shaft being disposed in said slotted external shaft, with a tab on said translating nut extending through said axial slot, said tab preventing said translating nut from rotational motion.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0014]     Understanding of the present invention and the various aspects thereof will be facilitated by reference to the accompanying drawing figures, provided for purposes of illustration only and not intended to define the scope of the invention, on which:  
         [0015]      FIG. 1  is a side elevational view of the linear portion of the linear/rotary actuator of the present invention.  
         [0016]      FIG. 2  is a side elevational view of the rotary portion of the linear/rotary actuator of the present invention.  
         [0017]      FIG. 3  is a side elevational view of a combined linear/rotary actuator of the present invention.  
         [0018]      FIG. 4  is a fragmentary, side elevational view of a bearing support at the distal end of the leadscrew of the present invention.  
         [0019]      FIG. 5  is a side elevational view showing a common housing for the linear and rotary motors of the present invention.  
         [0020]      FIG. 6  is a top plan view showing how samples can be arranged radially around the linear/rotary actuator of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Reference should now be made to the drawing figures on which similar or identical elements are given consistent identifying numerals throughout the various figures thereof, and on which parenthetical references to figure numbers, when used, direct the reader to the view(s) on which the element(s) being described is (are) best seen, although the element(s) may be seen on other figures also.  
         [0022]     The linear/rotary actuator comprises two motors: one to provide the linear motion and one to provide the rotary motion.  
         [0023]     Referring first to  FIG. 1 , which illustrates the linear motor portion  20  of the present invention, constructed according to the present invention and generally indicated by the reference numeral  20 . Linear motor portion  20  of the linear/rotary actuator is of the “external linear” design in that a threaded screw  30  is fixed to a rotor  32  (reference the double headed arrow shown on  FIG. 1 ) in motor  34  and a translating nut  36  is installed on the threaded screw. As in conventional external linear actuators, nut  36  must be prevented from turning on the threaded screw  30  to provide linear motion as the threaded screw selectively turns in the directions indicated by the double headed arrow on  FIG. 1 .  
         [0024]     Referring now to  FIG. 2 , there is illustrated the rotary motor portion of the linear/rotary actuator, constructed according to the present invention, and generally indicated by the reference numeral  50 . Rotary motor portion  50  includes a hollow shaft  60  attached to a rotor  62  (reference the double headed arrow shown on  FIG. 2 ) in motor  64 . Shaft  60  must extend through motor  64  and has an axially slot  70  defined along the external portion of the shaft.  
         [0025]      FIG. 3  illustrates the combined actuator, generally indicated by the reference numeral  80 , and illustrates that threaded screw  30  ( FIG. 1 ) is inserted in slotted shaft  60 . Translating nut  36  extends through slot  70 , which keeps the translating nut from turning. The distal end of translating nut  36  is shown as having two vertically aligned holes  90  for attachment thereof of other apparatus, but any type of means of attachment to other apparatus may be provided as well.  
         [0026]      FIG. 4  illustrates that the distal end of threaded screw  30  is journaled in a bearing  100  fixed in the distal end of slotted shaft  60 , but such may not be required depending on the degree of travel.  
         [0027]      FIG. 5  illustrates that the design may be further simplified by providing a common interface (housing)  110  between motors  34  and  64 . This can lower cost and provide better alignment.  
         [0028]     The operation of linear/rotary actuator  80  ( FIG. 3 ) is as follows:  
         [0029]     For linear motion: motor  64  is locked and motor  34  is run, causing translating nut to  36  to traverse axially. Translating nut  36  is prevented from rotating by a tab extending axially through slot  70 . Radial support and resistance to moments caused by the offset loading are provided by the fit of the outside of translating nut inside slotted shaft  60 .  
         [0030]     For rotary motion: both motors  64  and  34  are rotated simultaneously. Since both motors are rotating together, there is no relative motion between the translating nut  36  and threaded screw  30  and pure rotary motion results.  
         [0031]     Helical motion can be accomplished by rotating motors  64  and  34  at different speeds or by rotating rotary motor  64  and locking linear motor  34 .  
         [0032]     Linear/rotary actuator  80  ( FIG. 3 ) is especially suited for laboratory automation where samples must be withdrawn and dispensed from many locations. This is illustrated on  FIG. 6  where samples, as at  120 , are arranged radially around linear/rotary actuator. In this case, an arm carrying a sampling device is attached to translating nut  36  and samples  120  can be added to or dispensed by the up-and-down and rotary motion of linear/rotary actuator  80 .  
         [0033]     In the embodiments of the present invention described above, it will be recognized that individual elements and/or features thereof are not necessarily limited to a particular embodiment but, where applicable, are interchangeable and can be used in any selected embodiment even though such may not be specifically shown.  
         [0034]     Spatially orienting terms such as “above”, “below”, “upper”, “lower”, “inner”, “outer”, “inwardly”, “outwardly”, “vertical”, “horizontal”, and the like, when used herein, refer to the positions of the respective elements shown on the accompanying drawing figures and the present invention is not necessarily limited to such positions.  
         [0035]     It will thus be seen that the objects set forth above, among those elucidated in, or made apparent from, the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown on the accompanying drawing figures shall be interpreted as illustrative only and not in a limiting sense.  
         [0036]     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.