Abstract:
A torque limiting apparatus is provided having an input shaft, an output shaft, a housing, a spring, and a length adjustable shank and collar assembly. The input shaft communicates with a rotating end segment having a cam surface. The output shaft communicates with a rotating end segment having a complementary cam surface for engaging with the cam surface of the input shaft. The cam surfaces cooperate to generate separation forces between the respective rotating end segments. The housing encases the first end segment and the second end segment. The spring is supported in the housing, and is configured to oppose the separation forces generated by the cam surfaces, and is configured to urge together the first end segment and the second end segment to remain in rotating coupled engagement. The length adjustable shank and collar assembly is provided between the spring and the housing and is configured to adjust compressive force on the spring to change torque output of the apparatus. A method is also provided.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/442,225 filed Feb. 12, 2011, entitled “Torque Tool”, the entirety of which is incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The presently disclosed subject matter pertains to apparatus and methods for limiting loads from a motor to an output shaft. More particularly, the presently disclosed subject matter relates to apparatus and methods for coupling a drive source to an output shaft with a clutch and torque limiting tool. 
       BACKGROUND OF THE INVENTION 
       [0003]    Techniques are known for limiting torque delivery to an output shaft, such as when tightening lug nuts on threaded studs during a wheel mounting operation. Improvements are needed in how torque is accurately set and limited when securing together threaded fasteners when bolting together structures using threaded fasteners. 
       SUMMARY OF THE INVENTION 
       [0004]    A torque limiting apparatus and method are provided with a torque adjustment mechanism that compresses a disengagement spring. 
         [0005]    According to one aspect, a torque limiting apparatus is provided having an input shaft, an output shaft, a housing, a spring, and a length adjustable shank and collar assembly. The input shaft communicates with a rotating end segment having a cam surface. The output shaft communicates with a rotating end segment having a complementary cam surface for engaging with the cam surface of the input shaft. The cam surfaces cooperate to generate separation forces between the respective rotating end segments. The housing encases the first end segment and the second end segment. The spring is supported in the housing, and is configured to oppose the separation forces generated by the cam surfaces, and is configured to urge together the first end segment and the second end segment to remain in rotating coupled engagement. The length adjustable shank and collar assembly is provided between the spring and the housing and is configured to adjust compressive force on the spring to change torque output of the apparatus 
         [0006]    According to another aspect, a torque limiting apparatus is provided having an input shaft, a circumferential array of cam surfaces, a cylindrical collar, a spline shaft, a housing, and a spring. The input shaft communicates with a cylindrical end segment having a circumferential array of cam surfaces. The cylindrical collar has a complementary cylindrical end segment with a complementary circumferential array of co-acting cam surfaces. The cylindrical collar includes a circumferential array of radially inwardly extending drive lugs and a clearance raceway disposed axially from the lugs. The cylinder includes a circumferential array of radially inwardly extending lugs and a clearance raceway disposed axially from the lugs. The spline shaft has a radially outwardly extending array of driven lugs. The housing encases the first end segment and the second end segment. The spring urges together the first end segment and the second end segment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Preferred embodiments of the disclosure are described below with reference to the following accompanying drawings. 
           [0008]      FIG. 1  is an exploded schematic perspective view from an output end of a torque limiting apparatus having features in accordance with one embodiment. 
           [0009]      FIG. 2  is an exploded schematic perspective view of an adjuster plate of  FIG. 1 . 
           [0010]      FIG. 2A  is a further enlarged exploded perspective view from the encircled region  2 A of  FIG. 2 . 
           [0011]      FIG. 2B  is a plan view of the adjuster plate of  FIG. 2 . 
           [0012]      FIG. 2C  side view of the adjuster plate of  FIGS. 2 and 2B . 
           [0013]      FIG. 2D  is a centerline sectional view taken along line  2 D- 2 D of  FIG. 2B . 
           [0014]      FIG. 3  is a perspective view of an end plate of  FIG. 1 . 
           [0015]      FIG. 3A  is a plan view of the end plate of  FIG. 3 . 
           [0016]      FIG. 3B  is a side view of the end plate of  FIGS. 3 and 3A . 
           [0017]      FIG. 3C  is a centerline sectional view taken along line  3 C- 3 C of  FIG. 3A . 
           [0018]      FIG. 4  is a perspective view of an adjuster plate of  FIG. 1 . 
           [0019]      FIG. 4A  is a plan view of the adjuster plate of  FIG. 4 . 
           [0020]      FIG. 4B  is a side view of the adjuster plate of  FIGS. 4A and 4B . 
           [0021]      FIG. 4C  is a bottom view of the adjuster plate of  FIGS. 4 ,  4 A and  4 B. 
           [0022]      FIG. 4D  is a centerline sectional view taken along line  4 D- 4 D of  FIG. 4A . 
           [0023]      FIG. 5  is a perspective view of a sealed bearing assembly of  FIG. 1 . 
           [0024]      FIG. 5A  a centerline sectional view taken along line  5 A- 5 A of  FIG. 5 . 
           [0025]      FIG. 6  a perspective view of a threaded adjuster collar. 
           [0026]      FIG. 6A  is a plan view of the threaded adjuster collar of  FIG. 6 . 
           [0027]      FIG. 6B  is a side view of the threaded adjuster collar of  FIGS. 6 and 6A . 
           [0028]      FIG. 6C  is a centerline sectional view taken along ling  6 C- 6 C of  FIG. 6A . 
           [0029]      FIG. 7  is a perspective view of a coil spring of  FIG. 1 . 
           [0030]      FIG. 8  is a perspective view of a cam body of  FIG. 1 . 
           [0031]      FIG. 8A  is a plan view of the cam body of  FIG. 8 . 
           [0032]      FIG. 8B  is a centerline sectional view taken along line  8 B- 8 B of  FIG. 8A . 
           [0033]      FIG. 8C  is a side view of the cam body of  FIG. 8 . 
           [0034]      FIG. 8D  is a side view of a lug taken from within the encircled region  8 D of  FIG. 8B . 
           [0035]      FIG. 9  is a perspective view of a spline output shaft of  FIG. 1 . 
           [0036]      FIG. 9A  is a view from below of the spline output shaft of  FIG. 9 . 
           [0037]      FIG. 9B  is a centerline sectional view taken along line  9 B- 9 B of  FIG. 9A . 
           [0038]      FIG. 9C  is a side view of the spline output shaft of  FIG. 9 . 
           [0039]      FIG. 9D  is a side view of a lug taken from within the encircled region  9 D of  FIG. 9C . 
           [0040]      FIG. 10  is a perspective view of a housing member of  FIG. 1 . 
           [0041]      FIG. 10A  is a plan view of the housing member of  FIG. 10 . 
           [0042]      FIG. 10B  is a centerline sectional view taken along line  10 B- 10 B of  FIG. 10A . 
           [0043]      FIG. 10C  is a side view of the housing member of  FIG. 10 . 
           [0044]      FIG. 11  is a perspective view of a cam body of  FIG. 1 . 
           [0045]      FIG. 11A  is a side view of the cam body of  FIG. 11 . 
           [0046]      FIG. 11B  is a bottom view of the cam body of  FIGS. 11 and 11A . 
           [0047]      FIG. 11C  is a centerline sectional view taken along line  11 C- 11 C of  FIG. 11B . 
           [0048]      FIG. 12  is a perspective view of a sealed bearing assembly of  FIG. 1 . 
           [0049]      FIG. 12A  is a centerline sectional view of the bearing assembly taken along line  12 A- 12 A of  FIG. 12 . 
           [0050]      FIG. 13  is a perspective view of an end plate of  FIG. 1 . 
           [0051]      FIG. 13A  is a plan view of the end plate of  FIG. 13 . 
           [0052]      FIG. 13B  is a side view of the end plate of  FIGS. 13 and 13A . 
           [0053]      FIG. 14  is an exploded centerline sectional view of the torque limiting apparatus of  FIG. 1 . 
           [0054]      FIG. 15  is a perspective view of the torque limiting apparatus of  FIGS. 1 and 14 , assembled together and with the housing assembly, spring adjustment catch assembly, and adjuster collar and shank removed. 
           [0055]      FIG. 16  is simplified representative view taken in a radial outward direction as shown in  FIG. 15  and depicted unwound in a planar view showing the array of radially outwardly extending driven lugs on the spline output shaft of  FIG. 1 . 
           [0056]      FIG. 17  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and depicted unwound in a planar view showing the array of radially inwardly extending driven lugs and drive collar. 
           [0057]      FIG. 18  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and depicted unwound in a planar view showing the input/drive cam body. 
           [0058]      FIG. 19  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and showing the array of driven lugs on the spline output shaft, the driven cam body, and the drive cam body overlaid in an engaged drive position as held together by the coil spring within the housing assembly while applying torque to a nut at the output end. 
           [0059]      FIG. 20  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and showing the array of driven lugs on the spline output shaft, the driven cam body, and the drive cam body overlaid in an engaged drive position as held together by the coil spring within the housing assembly, but while the spring begins to engage (between the positions shown in  FIGS. 19 and 21 ) while applying torque to a nut at the output end. 
           [0060]      FIG. 21  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and showing the array of driven lugs on the spline output shaft, the driven cam body, and the drive cam body overlaid in a disengaged drive position as the coil spring is compresses within the housing assembly when a set torque limit has been exceeded. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0061]    This disclosure is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8). 
         [0062]      FIG. 1  illustrates a torque limiting apparatus, or device  10  according to one embodiment. Device  10  includes a housing assembly, or frame  12  that includes a cylindrical body  14 , an output end plate  16 , an input end plate  18 , a drive cam body  20 , a driven cam body  22 , a spline output shaft  24 , a coil spring  28 , a spring compression adjustment assembly having a threaded adjuster collar  30  and a complementary threaded adjuster shank  34 , and an adjustment catch assembly  38 . 
         [0063]    As shown in  FIG. 1 , adjuster shank  34  is threaded relative to adjuster collar  30  in order to increase or decrease the compression of coil spring  28  which decreases or increases respectively the force used to push together a circumferential array  42  of cam surfaces  90  on a circumferential array of drive fingers  88  against a complementary circumferential array  52  of cam surfaces  94  on a circumferential array of driven fingers  92 . 
         [0064]    When a preset torque value is exceeded, spring  28  is compressed, and cam surfaces  90  and  94  move apart such that individual lugs  78  within an array  46  radially outwardly extending driven lugs  78  move into cylindrical clearance raceways within an array  54  of radially inwardly extending drive lugs  80  of cam drive body. Hence, cam drive body  20  separates from cam driven body  22 , as shown by the position represented in  FIG. 21 . When operating under the preset torque, spring  28  retains cam drive body  20  and cam driven body  22  together such that lugs  80  and  78  are engaged together to drive a spline output shaft  24  in rotation. In one case, a socket for a lug nut is mounted onto a driven output post  44  of spline output shaft  24 . 
         [0065]    An array of male threads  58  on adjuster shank  34  of  FIG. 1  mate in threaded engagement with complementary female threads  56  on adjuster collar  30 , enabling lengthening and shortening of the resulting assembly, thereby causing compression and relief to spring  28  in the assembly. Adjuster shank  34  is rotated to specific angular positions relative to collar  30  as adjustment catch assembly  38  provides a definitive rotary catch at each 90 degree angle of shank  34  relative to collar  30 . More particularly, adjuster plate  36  is secured with a plurality of threaded fasteners, or machine screws  66  that pass through individual respective bores  64  and into threaded apertures  62  in shank  34 , thereby securing plate  36  onto shank  34 . During rotation of shank  34  in collar  30 , collar  30  is prevented from rotating by a circumferential array of ribs, or tenons  60  that move axially within respective axial slots  61  within an inner wall surface of cylindrical body  14 . 
         [0066]    Adjustment catch assembly  38  comprises a threaded fastener, or screw  68 , a coil spring  70 , a hardened steel ball bearing  74 , and a threaded bore, or aperture  74  in plate  36  that cooperate with a respective one of several semi-spherical recesses  76  provided in a circumferential array atop end plate  16 . Plate  36  and shank  24  can be rotated relative to plate  16 , as spring  70  compresses until ball bearing  72  is received into a next adjacent recess  76  where the rotary position is then held in place by ball bearing  72  seating within the respective recess  76 . 
         [0067]    In assembly, end plate  18  is secured within a bottom of cylindrical body  14  with a plurality of circumferentially spaced-apart threaded fasteners, or machine screws  86 , that pass through apertures  84  and into complementary threaded apertures  82  in end plate  18 , as shown in  FIG. 1 . A sealed cylindrical bearing  26  is received within end plate  18  where it is press fit. A cylindrical drive input post  40  on cam drive body  20  is seated for rotation within bearing  26 . Similarly, a sealed cylindrical bearing  32  is press fit within a recess  67  (see  FIG. 4D ) where a cylindrical portion of driven output post  44  is received for rotation. A circumferential array of threaded fasteners, or machine screws  96  pass through respective apertures  95  in adjuster plate  36  and into respective threaded bores  63  (see  FIG. 10 ) in cylindrical body  14  to secure plate  36  to body  14 . When assembled together, plates  36  and  18  and housing  12  cooperate with collar  30  to compress coil spring  28 . When a desired torque is exceeded between input post  40  and output post  44 , cam surfaces  90  and  94  drive apart cam drive body  20  and cam driven body  22 , causing spring  28  to further compress. 
         [0068]    As shown in  FIG. 1 , array  46  comprises three unique circumferential rows  41 ,  43  and  45  of radially outwardly extending lugs  78  from surface  48  (see  FIG. 9 ). Array  46  of lugs  78  mate in engagement with a complementary array  54  of radially inwardly extending lugs  80  on cylindrical drive collar  50  of cam drive body  22 . As angular surfaces of coacting cam surfaces  90  and  94  engage with increasing torque, axial force is generated against spring  28 , eventually compressing spring  28  and driving apart cam drive body  20  and cam driven body  22  until they lock apart in the configuration shown in  FIG. 21  where individual shelves  93  hold apart bodies  20  and  22  via fingers  92  being seated atop respective shelves  93 . 
         [0069]      FIG. 2  illustrates construction of the adjustment catch assembly including threaded screw  68 , coil spring  70 , ball bearing  72  and threaded aperture  74  of plate  36 .  FIG. 2A  further illustrates threaded screw  68 , spring  70  and ball bearing  72 . An inner cylindrical surface  100  on plate  36  is shown in  FIGS. 2B and 2D  which is received over a complementary cylindrical outer surface  63  on shank  34  (see  FIG. 4 ). Each through bore  34  in plate  36  of  FIGS. 2B-2D  receives a respective threaded fastener  66  (see  FIG. 1 ) for securing plate  36  onto shank  34  (see  FIG. 4 ). Radial slots  98  are provided in plate  36 . Slots  98  provide a visual indicator of rotated position of shank  34  correlated with spring pressure and torque setting. Optionally, a visual scale can be provided on an outer surface of end plate  16  to indicate relative position between shank  34  and plate  16 . 
         [0070]    FIGS.  3  and  3 A- 3 C illustrate the construction of end plate  16 . An inner circumferential surface  102  on plate  16  of  FIG. 3  is received for rotation about cylindrical outer surface  63  on shank  34  (see  FIG. 4 ). A circumferential array of recessed through bores  95  provide for passage of fasteners  96  (see  FIG. 1 ) in assembly. 
         [0071]    FIGS.  4  and  4 A- 4 D depict construction of adjuster shank  34 . More particularly, shank  34  includes cylindrical outer surface  63  and cylindrical inner surface  65 , as shown in  FIG. 4 . A circumferential array of through bores, or apertures  62  are provided for receiving threaded fasteners  66  (see  FIG. 1 ) in assembly. A circumferential recess, or bearing seat  67  shown in  FIGS. 4C and 4D  is configured to receive bearing assembly  32  (see  FIG. 1 ) in assembly.  FIGS. 5 and 5A  illustrate sealed bearing assembly  32  in greater detail. 
         [0072]    FIGS.  6  and  6 A- 6 C illustrate features of threaded adjuster collar  30 . A radial array of outwardly extending ribs, or tenons  60  and female threads  56  are formed in collar  30 , as shown in FIGS.  6  and  6 A- 6 C. 
         [0073]      FIG. 7  shows coil spring  28  which is formed from spring steel. Optionally, other types of springs can be used. Coil spring  28  has open coil windings that allow for compression of spring  28 . 
         [0074]    FIGS.  8  and  8 A- 8 D show construction of cam drive body  22  including cylindrical drive collar  50 , cylindrical shoulder  51 , and circumferential array  52  of fingers  92 , each with a cam surface  94 . As shown in  FIG. 8 , array  54  includes radially inwardly extending lugs, or drive arms  80  provided in three unique circumferential rows  87 ,  89  and  91 , with clearance raceways  81 ,  83  and  85  provided adjacent each row  87 ,  89  and  91 , respectively, as shown in  FIG. 8B . 
         [0075]    FIGS.  9  and  9 A- 9 D illustrate construction of spline output shaft  24 . More particularly, shaft  24  includes array  46  of lugs, or driven arms  78  provided in three distinct circumferential rows  41 ,  43  and  45  and extending from circumferential outer surface  48 , as shown in  FIG. 9 . Each lug  78  has a sloped engagement surface that mates with a complementary sloped engagement surface on each respective lug  80  (of  FIG. 8 ). 
         [0076]    FIGS.  10  and  10 A- 10 C show construction of housing assembly  12 , namely cylindrical body  14 . Four axially extending slots  61  are formed in an inner cylindrical surface  65  of body  14  for receiving ribs  60  (see  FIG. 1 ). Each rib  61  communicates with an expanded inner cylindrical surface  69  within body  14 , as shown in  FIG. 10B . 
         [0077]    FIGS.  11  and  11 A-C shown construction of cam drive body  20 , including a circumferential array  42  of fingers  88 , each having a cam surface  90  with a compound curved and flat shape. Each finger  88  has a horizontal flat surface  93  on cam surface  90  for seating cooperating fingers  92  on cam drive body  22  when spring  28  is compressed under excessive torque, which disengages bodies  20  and  22  (see  FIG. 21 ), thereby placing lugs  78  in clearance raceways  81 ,  83  and  85  (see  FIG. 8B ). As shown in  FIGS. 11A-11C , a square socket recess  77  is provided in post  40  (see  FIG. 11 ) for receiving the drive head of a pneumatic wrench (or other drive tool). 
         [0078]      FIGS. 12 and 12A  further illustrate construction of sealed cylindrical bearing assembly  26 . 
         [0079]      FIG. 13  shows end plate  18  and further depicts a cylindrical bearing recess  97  and a cylindrical seal recess  99 . Bearing  26  is received within recess  97  in assembly. 
         [0080]      FIG. 14  illustrates in exploded centerline sectional view torque limiting apparatus  10 . Insertion of spline output shaft  24  within housing  12  and between cam drive body  20  and cam driven body  22  are clearly illustrated. 
         [0081]      FIG. 15  illustrates a perspective view of the torque limiting apparatus of  FIGS. 1 and 14 , assembled together and with the housing assembly, spring adjustment catch assembly, and adjuster collar and shank removed. Cam drive body  20  and cam driven body  22  are shown in engaged positions for imparting torque from the input post to the output post via the spline output shaft. 
         [0082]      FIG. 16  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and depicted unwound in a planar view showing the array  46  of radially outwardly extending driven lugs  78  on the spline output shaft  24  of  FIG. 1 . 
         [0083]      FIG. 17  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and depicted unwound in a planar view showing the array  54  of radially inwardly extending driven lugs  80  and cam drive collar  22 . 
         [0084]      FIG. 18  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and depicted unwound in a planar view showing the input/drive cam body  20 . 
         [0085]      FIG. 19  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and showing the array  46  of driven lugs  78  on the spline output shaft  24 , the cam driven body  22 , and the drive cam body  20  overlaid in an engaged drive position as held together by the coil spring (not shown) within the housing assembly (not shown) while applying torque to a nut at the output end of spline shaft  24 . 
         [0086]      FIG. 20  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and showing the array  46  of driven lugs  78  on the spline output shaft  24 , the driven cam body  22 , and the drive cam body  20  overlaid in an engaged drive position as held together by the coil spring (not shown) within the housing assembly (not shown), but while the spring begins to engage (between the positions shown in  FIGS. 19 and 21 ) while applying torque to a nut at the output end of spline shaft  24 . 
         [0087]      FIG. 21  is a simplified representative view taken in a radial outward direction as shown in  FIG. 15  and showing the array  46  of driven lugs  78  on the spline output shaft  24 , the driven cam body  22 , and the drive cam body  20  overlaid in a disengaged drive position as the coil spring (not shown) is compressed within the housing assembly (not shown) when a set torque limit has been exceeded at the end of spline output shaft  24 . 
         [0088]    In compliance with the statute, embodiments of the invention have been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the entire invention is not limited to the specific features and/or embodiments shown and/or described, since the disclosed embodiments comprise forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.