Abstract:
A headlamp adjuster which includes an adjuster output shaft which is engageable with a reflector of a headlamp assembly. The adjuster output shaft extends from a housing, and the headlamp adjuster is configured such that in an overload condition, the adjuster output shaft is prevented from translating substantially axially, thereby reducing the risk of damage resulting from over-travel of the adjustor output shaft.

Description:
RELATED APPLICATION 
     this application claims the benefit of U.S. Provisional Application Ser. No. 60/168,865, filed Dec. 3, 1999. 
    
    
     BACKGROUND 
     The present invention relates generally to headlamp adjusters which are used to adjust the position of a reflector of an automobile headlamp assembly, and relates more specifically to a headlamp adjuster which includes an overload clutch mechanism. 
     Modern day headlamps for vehicles are engineered and designed to be aerodynamically efficient. In this regard, the headlamps are designed as sealed assemblies wherein the portion of the headlamp approximate the outer surface of the automobile is relatively stationary, and is aerodynamic. 
     A typical modern day headlamp assembly  12  is illustrated in a plan view seen as FIG. 1, and normally includes: a fixed housing  20 , to which an outer headlamp lens  22  is affixed; a movable reflector  24 , which is mounted within the fixed housing  20 ; and a stationary headlamp bulb (not shown), which is positioned within the movable reflector  24 . Typically, the movable reflector  24  is mounted to the housing  20  by a universal or ball-type pivot  26  which is stationary, or fixed, on the housing  20 . 
     A first pivot point  28  is disposed generally vertical of the fixed pivot  6 , and a second pivot point  30  is disposed generally horizontal of the fixed pivot  26 . As such, the movable reflector  24  may be pivoted about the fixed pivot  26  in the vertical and horizontal planes to aim the headlamp beam. Adjustment mechanisms, or headlamp adjusters,  40  and  42  are typically provided at the first and second pivot points,  28  and  30 , normally termed the vertical pivot and the horizontal pivot, and the headlamp adjusters  40  and  42  can be operated to effect movement of the reflector  24  in the vertical and horizontal planes. 
     The headlamp adjusters  40  and  42  are typically mounted to the housing  20  of the headlamp assembly  12  and have adjuster output shafts  44 ,  46  operatively connected to the movable reflector  24  by ball and socket type pivots, or the like, such that linear movement of the adjuster output shafts  44 ,  46  produces pivoting of the movable reflector in the vertical and horizontal planes. Specifically, each headlamp adjuster  40 ,  42  typically includes drive structure  48 ,  50  for receiving a tool, and typically the drive structure  48 ,  50  is precision geared to the adjuster output shaft  44 ,  46 . The gearing provides that using the tool to rotate the drive structure  48 ,  50  causes linear translation of the adjuster output shaft  44 ,  46  and therefore adjustment of the position of the headlamp reflector  24 . 
     Before an automobile is released to the consumer, the movable reflectors of the headlamp assemblies are adjusted to a desired position so that the headlamp beams are properly aimed in both the vertical and horizontal directions. To this end, headlamp adjusters are normally operated at the automobile assembly plant. Thereafter, if a movable reflector moves from its desired position, due, for example, to vibration, jarring, or the vehicle being in an accident, a mechanic can operate the headlamp adjusters in order to properly re-align the reflectors. 
     Typically, headlamp adjusters are structured such that over-travel of the adjuster shafts (i.e.  44  in FIG. 1) is not prevented. Over-travel of the adjuster shaft can cause breakage of the headlamp adjuster housing and/or the reflector to which the adjuster shaft is connected. Specifically, over-extension of the adjuster screw from the housing can damage the reflector, and over-retraction of the adjuster screw into the housing can cause the end of the adjuster screw to contact an interior wall of the housing and result in damage to the housing, such as cracking. A crack in the housing can permit moisture, dirt, etc. to enter the housing which is undesirable. 
     OBJECTS AND SUMMARY 
     Accordingly, it is an object of an embodiment of the present invention to provide a headlamp adjuster which is structured such that over-travel of the adjuster output shaft is generally prevented. 
     Another object of an embodiment of the present invention is to provide a headlamp adjuster which includes an overload clutch mechanism which generally prevents over-travel of the adjuster output shaft. 
     Briefly, and in accordance with one or more of the foregoing objects, the present invention provides a headlamp adjuster which includes an adjuster output shaft which is engageable with a reflector of a headlamp assembly. The adjuster output shaft extends from a housing, and the headlamp adjuster is configured such that in an overload condition, the adjuster output shaft is prevented from translating substantially axially, thereby reducing the risk of damage resulting from over-travel of the adjustor output shaft. 
     Although a few embodiments and alternatives are discussed herein, it should be understood that modifications may be made thereto while staying within the scope of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The organization and manner of the structure and function of the invention, together with further objects and advantages thereof, may be understood by reference to the following description taken in connection with the accompanying drawings, wherein: 
     FIG. 1 is a plan view of a typical headlamp assembly; 
     FIG. 2 is a side view, in partial cross-section, of a headlamp adjuster which is in accordance with an embodiment of the present invention; 
     FIG. 3 is a front, elevational view of the headlamp adjuster shown in FIG. 2; 
     FIG. 4 is a perspective view of a bushing of the headlamp adjuster shown in FIGS. 2 and 3; 
     FIG. 5 is a top, plan view of the bushing shown in FIG. 4; 
     FIG. 6 is a side, elevational view of the bushing shown in FIG. 4; 
     FIG. 7 is a front, elevational view of the bushing shown in FIGS. 4-6; 
     FIG. 8 is a cross-sectional view of the bushing shown in FIGS. 4-7, taken along line  8 — 8  of FIG. 6; 
     FIG. 9 is a cross-sectional view of the bushing shown in FIGS. 4-8, taken along line  9 — 9  of FIG. 7; 
     FIG. 10 is a side view, in partial cross-section, of a headlamp adjuster which is in accordance with another embodiment of the present invention; 
     FIG. 11 is a front, elevational view of the headlamp adjuster shown in FIG. 10; 
     FIG. 12 is an exploded perspective view of a headlamp adjuster which is in accordance with still yet another embodiment of the present invention; 
     FIG. 13 is a side, elevational view, partially in section, of an output gear, retaining member and clutch bushing configuration which is used in connection with the headlamp adjustor which is shown in FIG. 12; 
     FIG. 14 is a side, elevational view, partially in section, of a rear portion of the headlamp adjuster shown in FIG. 12; and 
     FIG. 15 is a rear, cross-sectional view of the headlamp adjuster shown in FIG. 12, taken along line  15 — 15  of FIG.  14 . 
    
    
     DESCRIPTION OF EMBODIMENTS 
     While the present invention may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, embodiments of the invention with the understanding that the present description is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to that as illustrated and described herein. 
     Shown in the FIGURES are several different headlamp adjusters which are in accordance with the present invention. Specifically, FIGS. 2 and 3 illustrate a headlamp adjuster  100   a  which is in accordance with a first embodiment of the present invention, FIG. 10 and 11 illustrate a headlamp adjuster  100   b  which is in accordance with a second embodiment of the present invention, and FIG. 12 illustrates a headlamp adjuster  100   c  which is in accordance with a third embodiment of the present invention. Each headlamp adjuster  100   a ,  100   b ,  100   c  is configured for engagement with the reflector of a headlamp assembly (see FIG.  1 ). As will be described, each headlamp adjuster  100   a ,  100   b ,  100   c  includes an overload clutch mechanism which generally prevents over-travel of an adjuster output shaft  104   a ,  104   b ,  104   c.    
     The headlamp adjuster  100   a  which is shown in FIGS. 2 and 3 will be described first, and then the other two headlamp adjusters  100   b  and  100   c  will be described. In the following description, like reference numerals are used to identify like parts, and different alphabetic suffixes (i.e., “a”, “b” and “c”) are used for each of the different embodiments. At times, a detailed description of a part is omitted with the understanding that one may review the description relating to like parts of the other embodiments. 
     The headlamp adjuster  100   a  shown in FIGS. 2 and 3 includes an adjuster output shaft  104   a  which is configured for engagement with a reflector  24  of a headlamp assembly  12  (see FIG.  1 ). Specifically, the adjuster output shaft  104   a  provides a threaded shaft portion  106   a  and a ball portion  108   a  at one end for engagement in a corresponding socket in a reflector  24  (see FIG. 1, and above description, for example; see also FIG. 12 which shows an adjuster output shaft  104   c  which is identical to adjuster output shaft  104   a ). 
     The headlamp adjuster  100   a  also includes a housing  110   a , and the adjuster output shaft  104   a  extends from a shaft hole  112   a  in a bushing  150   a  which is disposed in the housing  110   a . The housing  110   a  is preferably mountable to the headlamp assembly or to some other structure (see FIG.  1 ), such as a frame-like structure, which is generally proximate the headlamp assembly. Preferably, the headlamp adjuster  100   a  is “twist lock” mounted, such that the headlamp adjuster  100   a  is mountable to a headlamp assembly  12  by inserting an end  114   a  of the housing  110   a  into an aperture in a housing  20  of the headlamp assembly  12  (see FIG.  1 ), and rotating the housing  110   a  of the headlamp adjuster  100   a  relative to the headlamp assembly  12  through a 120° (one third) rotation. To this end, the housing  110   a  preferably includes tabs  116   a  (shown in FIG. 2, but omitted from FIG. 1) for engaging corresponding structure in the aperture in the housing  20  of the headlamp assembly  12 . 
     Preferably, a sealing member (not shown in connection with the headlamp adjuster  100   a , but shown as part  118   c  in connection with headlamp adjuster  100   c  illustrated in FIG.  12 ), such as an elastomeric sealing ring formed of R7744 Silicone, is disposed generally proximate the end  114   a  of the housing  110   a . Preferably, when the headlamp adjuster  100   a  is installed in the aperture in the housing  20  of the headlamp assembly  12 , the sealing member engages the housing  20  of the headlamp assembly  12  to provide an axial force between the housing  20  of the headlamp assembly  12  and the housing  110   a  of the headlamp adjuster  100   a  and generally reduces the amount of moisture which enters the headlamp assembly  12  through the aperture in the housing  20  of the headlamp assembly  12  and provides axial detent force for rotary lock. As will be described more fully later herein, once the headlamp adjuster  100   a  is properly mounted and engaged with the reflector  24 , the headlamp adjuster  100   a  can be manipulated to cause the adjuster output shaft  104   a  to translate relative to the housing  110   a  and effect an adjustment to the position of the reflector  24 . 
     The housing  110   a  may be formed of, for example, Zytel 70G13HS1L, and the adjuster output shaft  104   a  may be formed of, for example, Delrin 570 or Zamac-3 (die casting) with a finish of Zinc/yellow dichromate. Regardless, preferably the adjuster output shaft  104   a  is easy to mold with plastic or die cast, and is relatively low cost. 
     As shown in FIG. 2, preferably the adjuster output shaft  104   a  has a retaining member  120   a , such as a retaining ring, thereon. Preferably, the retaining member  120   a  is “snapped” onto the adjuster output shaft  104   a . While the end  122   a  of the adjuster output shaft  104   a  opposite the ball portion  108   a  limits retraction of the adjuster output shaft  104   a  into the housing  110   a  by nature of contact between the end  122   a  of the adjuster output shaft  104   a  and a rear internal stop wall  124   a  in the housing  110   a , the retaining member  120   a  disposed on the adjuster output shaft  104   a  limits extension of the adjuster output shaft  104   a  from the housing  110   a  by nature of contact between the retaining member  120   a  and a forward internal stop wall  126   a  in the housing  110   a  (this position is shown in phantom in FIG.  2 ). 
     An output gear  130   a  is seated in the housing  110   a , and the output gear  130   a  generally coaxially receives the adjuster output shaft  104   a  through a central bore  132   a  in the output gear  130   a . Preferably, the central bore  132   a  of the output gear  130   a  is tapped such that it threadably engages the threaded portion  106   a  of the adjuster output shaft  104   a . As a result, rotation of the output gear  130   a  in the housing  110   a  causes the adjuster output shaft  104   a  to translate generally axially in the housing  100   a  when rotation is prevented by the flats  162   a , as seen in FIG. 3, or as will be described more fully later herein, causes the adjuster output shaft  104   a  to rotate relative to the housing  100   a.    
     An input gear  134   a  is driveably engaged with the output gear  130   a  such that rotation of the input gear  134   a  causes the output gear  130   a  to rotate. Specifically, preferably external surfaces  136   a  and  138   a  of the input gear  134   a  and output gear  130   a , respectively, provide gear teeth with engage each other. Preferably, a drive shaft portion  140   a  of the input gear  134   a  extends from an aperture  142   a  in a cover  144   a  of the housing  110   a , and is configured to be engaged by a tool (not shown) to effect rotation of the input gear  134   a , and therefore rotation of the output gear  130   a  in the housing  110   a . As shown, an o-ring may be provided between the cover  144   a  and the input gear  134  to provide a seal therebetween. 
     Preferably the adjuster output shaft  104   a  not only extends through the central bore  132   a  in the output gear  130   a , but also extends through a central bore  148   a  in a bushing  150   a  which is also disposed in the housing  110   a . A flange or tab  152   a  on the cover  144   a  engages a recess  154   a  on the exterior surface of the bushing  150   a . This engagement generally prevents the bushing  150   a  from moving generally axially within the housing  110   a  while allowing the bushing  150   a  to rotate within the housing. 
     As shown in FIGS. 3 and 8, preferably the adjuster output shaft  104   a  extends from an opening  156   a  in the end  158   a  of the bushing  150   a , and the opening  156   a  in the end  158   a  of the bushing  150   a  is shaped such that it generally corresponds to the cross-sectional area of the adjuster output shaft  104   a . Specifically, preferably the opening  156   a  in the end  158   a  of the bushing  150   a  is shaped such that it provides opposing walls  160   a  which are configured to engage flat surfaces  162   a  (i.e., “bi-flats”) on the adjuster output shaft  104   a . The engagement between the opposing walls  160   a  and the flat surfaces  162   a  of the adjuster output shaft  104   a  provides that the adjuster output shaft  104   a  is generally prevented from rotating relative to the bushing  150   a . Therefore, for the adjuster output shaft  104   a  to rotate relative to the housing  110   a , the bushing  150   a  must also be allowed to rotate relative to the housing  110   a.    
     Preferably, the bushing  150   a  is formed of plastic or some other relatively flexible material. As shown in FIGS. 2-9, the bushing  150   a  includes two diametrically-opposed flexible detents  166   a  which are preferably molded as part of the bushing  150   a . As shown in FIGS. 2 and 3, the bushing  150   a  is journalled within the housing  110   a , and the housing  110   a  contains a plurality of static detents  170   a  (see FIG. 3) which are formed around the shaft hole  112   a  in the end  114   a  of the housing  110   a . The flexible detents  166   a  on the bushing  150   a  are engageable with and disengageable from the static detents  170   a  on the housing  110   a . When the flexible detents  166   a  of the bushing  150   a  are engaged with the static detents  170   a  of the housing  110   a , the bushing  150   a  is prevented from rotating relative to the housing  110   a . In contrast, when the flexible detents  166   a  of the bushing are disengaged from the static detents  170   a  of the housing  110   a , the bushing  150   a  can rotate relative to the housing  110   a . Therefore, because of the engagement between the walls  160   a  at the opening  156   a  in the end  158   a  of the bushing  150   a  and the flat surfaces  162   a  on the adjuster output shaft  104   a , the adjuster output shaft  104   a  cannot rotate in the housing  110   a  so long as the flexible detents  166   a  of the bushing  150   a  are engaged with the static detents  170   a  of the housing  110   a . In contrast, the adjuster output shaft  104   a  can rotate, along with the bushing  150   a , in the housing  110   a  when the flexible detents  166   a  of the bushing  110   a  are disengaged from the static detents  170   a  of the housing  110   a.    
     In operation, the input gear  134   a  of the headlamp adjuster  100   a  is rotated (such as by using a tool on the drive shaft portion  140   a ) to change the position of the reflector. As the input gear  134   a  is rotated, the output gear  130   a  rotates and causes the adjuster output shaft  104   a  to translate axially in the housing  110   a , thereby changing the position of the reflector. So long as the end  122   a  of the adjuster output shaft  104   a  does not move into engagement with the rear stop wall  124   a  in the housing  110   a , and the retaining member  120   a  disposed on the adjuster output shaft  104   a  does not move into engagement with the forward stop wall  126   a  in the housing  100   a , the flexible detents  166   a  of the bushing  150   a  remain engaged with the static detents  170   a  on the housing  110   a , and the bushing  150   a  and adjuster output shaft  104   a  are prevented from rotating relative to the housing  110   a . Hence, so long as the end  122   a  of the adjuster output shaft  104   a  does not move into engagement with the rear stop wall  124   a  in the housing  110   a , and the retaining member  120   a  disposed on the adjuster output shaft  104   a  does not move into engagement with the forward stop wall  126   a  in the housing  110   a , rotation of the input gear  134   a  causes the adjuster output shaft  104   a  to translate axially in the housing  110   a , as opposed to rotate in the housing  110   a . 
     Once the input gear  134   a  has been rotated enough such that either the end  122   a  of the adjuster output shaft  104   a  moves into engagement with the rear stop wall  124   a  in the housing  110   a  or the retaining member  120   a  disposed on the adjuster output shaft  104   a  moves into engagement with the forward stop wall  126   a  in the housing  110   a , the flexible detents  166   a  on the bushing  150   a  disengage from the static detents  170   a  on the housing  110   a  and continued rotation of the input gear  134   a  in the same direction causes the adjuster output shaft  104   a  (and bushing  150   a ) to rotate in the housing  110   a , as opposed to continue to translate axially, further moving the reflector. Hence, over-travel of the adjuster output shaft  104   a  in either direction is prevented by a clutch mechanism which is provided by the detents  166   a  on the bushing  150   a  and the static detents  170   a  of the housing  110   a.    
     Preferably, the range of axial travel of the adjuster output shaft  104   a  is limited to six rotations of the input gear  134   a , and during this range of travel, the adjuster output shaft  104   a  travels about 12 mm. When the input gear  134   a  is rotated and the retaining member  120   a  on the adjuster output shaft  104   a  moves into engagement with the forward stop wall  126   a  in the housing  110   a , the tension in the adjuster output shaft  104   a  increases due to the output gear  130   a  being constrained in the housing, bearing on surface  176   a . This axial tension effectively couples the output gear  130   a  to the adjuster output shaft  104   a  by means of friction at the thread interfaces between the output gear  130   a  and the adjuster output shaft  104   a . When this occurs, the adjuster output shaft  104   a  tends to rotate the bushing  150   a , thereby causing the flexible detents  166   a  of the bushing  150   a  to disengage from the static detents  170   a  on the housing  110   a . Thereafter, as the input gear  134   a  continues to be rotated in the same direction, the bushing  150   a  is free to rotate in the housing  110   a , and the adjuster output shaft  104   a , instead of continuing to translate, rotates along with the bushing  150   a . Therefore, the adjuster output shaft  104   a  does not over-travel in the extending direction (i.e., toward the reflector) as the input gear  134   a  continues to be rotated in the same direction. 
     Turning the input gear  134   a  in the opposite direction releases the axial tension between the adjuster output shaft  104   a  and the output gear  130   a . Hence, the friction coupling reduces and the torque on the bushing  150   a  reduces. When this occurs, the flexible detents  166   a  on the bushing  150   a  re-engage the static detents  170   a  on the housing  110   a  and the bushing  150   a  is prevented from continuing to rotate relative to the housing  110   a . When the bushing  150   a  stops rotating, the adjuster output shaft  104   a  also stops rotating, and instead begins to translate axially away from the stop interference. 
     As the input gear  134   a  continues to be rotated in the same direction such that the adjuster output shaft  104   a  sufficiently axially translates causing the end  122   a  of the adjuster output shaft  104   a  to move into contact with the rear stop wall  124   a  in the housing  110   a , the tension in the adjuster output shaft  104   a  increases due to the output gear  130   a  being constrained in the housing  110   a , bearing on surface  178   a . This axial tension effectively couples the output gear  130   a  to the adjuster output shaft  104   a  by means of friction at the thread interfaces between the output gear  130   a  and the adjuster output shaft  104   a . When this occurs, the adjuster output shaft  104   a  tends to rotate the bushing  150   a , thereby causing the flexible detents  166   a  of the bushing  150   a  to disengage from the static detents  170   a  on the housing  110   a . Thereafter, as the input gear  134   a  continues to be rotated in the same direction, the bushing  150   a  is free to rotate in the housing  110   a , and the adjuster output shaft  104   a , instead of continuing to translate, rotates along with the bushing  150   a . Therefore, the adjuster output shaft  104   a  does not over-travel in the retracting direction (i.e., away from the reflector) as the input gear  134   a  continues to be rotated in the same direction. 
     Turning the input gear  134   a  in the opposite direction releases the axial tension between the adjuster output shaft  104   a  and the output gear  130   a . Hence, the friction coupling reduces and the torque on the bushing  150   a  reduces. When this occurs, the flexible detents  166   a  on the bushing  150   a  re-engage the static detents  170   a  on the housing  110   a  and the bushing  150   a  is prevented from continuing to rotate relative to the housing  110   a . When the bushing  150   a  stops rotating, the adjuster output shaft  104   a  also stops rotating, and instead begins to translate axially away from the stop interference. 
     Hence, over-travel of the adjuster output shaft  104   a  in either direction is prevented by a clutch mechanism which is provided by the detents  166   a  on the bushing  150   a  and the static detents  170   a  of the housing  110   a . The detent force is important to the clutch mechanism function. One having ordinary skill in the art would recognize that a higher initial coupling (frictional) between the adjuster output shaft  104   a  and the output gear  130   a  would allow for more margin to meet clutch slip torque which is determined by the detenting. 
     The headlamp adjuster  100   b  shown in FIGS. 10 and 11 is similar to the headlamp adjuster  100   a  shown in FIGS. 2 and 3. Therefore, similar reference numerals are used to identify similar parts, and the alphabetic suffix “b” is used. At times, a detailed description of a part is omitted with the understanding that one may review the description relating to a corresponding part of one of the other embodiments. 
     The headlamp adjuster  100 b shown in FIGS. 10 and 11 includes an adjuster output shaft  104   b  having a ball portion  108   b , a threaded portion  106   b , and flat surface portions  162   b  (i.e., “bi-flats”), and the adjuster output shaft  104   b  has a retaining member  120   b  thereon. The headlamp adjuster  100   b , like headlamp adjuster  100   a , includes a housing  110   b , a cover  144   b  and a sealing member  143   b . As shown in FIG. 11 (but omitted from FIG.  10 ), like the housing of headlamp adjuster  100   a , preferably the housing  110   b  of headlamp adjuster  100   b  has tabs  116   b  thereon which engage corresponding structure in the aperture in the housing  20  of the headlamp assembly  12  (see FIG.  1 ), thereby providing that the headlamp adjuster  100   b  is “twist lock” mountable. The housing  100   b  includes a shaft hole  112   b  from which the adjuster output shaft  104   b  extends. As shown in FIG. 11, the shaft hole  112   b  is shaped such that it generally corresponds to the cross-sectional area of the adjuster output shaft  104   b . Specifically, preferably the shaft hole  112   b  provides opposing walls  160   b  which are configured to engage the flat surfaces  162   b  (i.e., the “bi-flats”) on the adjuster output shaft  104   b . The engagement between the opposing walls  160   b  and the flat surfaces  162   b  of the adjuster output shaft  104   b  provides that the adjuster output shaft  104   b  is generally prevented from rotating relative to the housing  110   b.    
     As shown in FIG. 10, the headlamp adjuster  100   b , like headlamp adjuster  100   a , includes an input gear  134   b  and an output gear  130   b . However, unlike headlamp adjuster  100   a , the output gear  130   b  of headlamp adjuster  100   b  is not threadably engaged with the adjuster output shaft  104   b . Instead, a clutch bushing  150   b  is threadably engaged with the adjuster output shaft  104   b , and the output gear  130   b  has a free running fit on the external surface of the clutch bushing  150   b . The clutch bushing  150   b  includes a shoulder  180   b , and a friction coupling member  182   b , such as an o-ring formed of nitrile, which is compressed between the output gear  130   b  and the shoulder  180   b  of the clutch bushing  150   b . In addition to providing a friction coupling, the elastomeric nature of the o-ring also provides a biasing action. As shown in FIG. 10, the clutch bushing  150   b , elastomeric member  182   b ,and output gear  130   b  are disposed in a seat  184   b  in the housing  110   b . The compressed elastomeric member  182   b  provides a friction coupling between the threaded clutch bushing  150   b  and the output gear  130   b , which can slip under an overload condition. 
     In operation, the input gear  134   b  of the headlamp adjuster  100   b  is rotated (such as by using a tool) to change the position of the reflector. As the input gear  134   b  is rotated, the output gear  130   b  rotates and, because of the friction coupling between the output gear  130   b  and clutch bushing  150   b , provided by the compressed friction coupling member  182   b , the clutch bushing  150   b  also rotates. Rotation of the clutch bushing  150   b  causes the adjuster output shaft  104   b  to translate due to the threadable engagement between the output gear  130   b  and adjuster output shaft  104   b  and the engagement of the adjuster output shaft  104   b  with the opposing walls  160   b  at the shaft hole  112   b  in the housing  110   b  (see FIG.  11 ). As the adjuster output shaft  104   b  translates axially, the position of the reflector changes. So long as the end  112   b  of the adjuster output shaft  104   b  does not move into engagement with a rear stop wall  124   b  in the housing  110   b , and the retaining member  120   b  disposed on the adjuster output shaft  104   b  does not move into engagement with a forward stop wall  126   b  in the housing  110   b , rotation of the input gear  134   b  causes the clutch bushing  150   b  to rotate and the adjuster output shaft  104   b  to translate axially. 
     Once the input gear  134   b  has been rotated enough such that either the end  122   b  of the adjuster output shaft  104   b  moves into engagement with the rear stop wall  124   b  in the housing  110   b  or the retaining member  120   b  disposed on the adjuster output shaft  104   b  moves into engagement with the forward stop wall  126   b  in the housing  110   b , the output gear  130   b  will slip relative to the clutch bushing  150   b  and the clutch bushing  150   b  will not rotate. That is to say, an overload condition will exist, such that continued attempt to rotate the input gear  134   b , will overcome the friction coupling provided by the elastomeric member  182   b  and output gear  130   b  will in effect “slip” relative to the clutch bushing  150   b . Thus, the input gear  134   b  and the output gear  130   b  can rotate without movement of the output shaft  104   b . Hence, the adjuster output shaft  104   b  does not continue to translate axially. The clutch action between the output gear  130   b  and the clutch bushing  150   b  when the end  122   b  of the adjuster output shaft  104   b  moves into engagement with the rear stop wall  124   b  in the housing  110   b  or the retaining member  120   b  disposed on the adjuster output shaft  104   b  moves into engagement with the forward stop wall  126   b  in the housing  110   b  provides that over-travel of the adjuster output shaft  104   b  in either direction is prevented. 
     Preferably, the range of axial travel of the adjuster output shaft  104   b  is limited to six rotations of the input gear  134   b , and during this range of travel, the adjuster output shaft  104   b  travels about 12 mm. When the input gear  134   b  is rotated and the retaining member  120   b  on the adjuster output shaft  104   b  moves into engagement with the forward stop wall  126   b  in the housing  110   b , the tension in the adjuster output shaft  104   b  increases due to the output gear  130   b  being constrained in the housing, bearing on surface  176   b . This axial tension effectively couples the clutch bushing  150   b  to the adjuster output shaft  104   b  by means of friction at the thread interfaces between the clutch bushing  150   b  and the adjuster output shaft  104   b . When this occurs, further rotation of the input gear  134   b  causes the output gear  130   b  to slip relative to the clutch bushing  150   b , and the adjuster output shaft  104   b  no longer translates axially. Therefore, the adjuster output shaft  104   b  does not over-travel in the extending direction (i.e., toward the reflector) as the input gear  134  continues to be rotated in the same direction. 
     Turning the input gear  134   b  in the opposite direction releases the axial tension between the adjuster output shaft  104   b  and the clutch bushing  150   b . Hence, the friction coupling reduces, and the clutch bushing  150   b  begins to move along with the output gear  130   b , and the adjuster output shaft  104   b  begins to translate axially. 
     As the input gear  134   b  continues to be rotated in the same direction such that the adjuster output shaft  104   b  sufficiently axially translates causing the end  122   b  of the adjuster output shaft  104   b  to move into contact with the rear stop wall  124   b  in the housing  110   b , the tension in the adjuster output shaft  104   b  increases due to the clutch bushing  150   b  being constrained in the housing  110   b , bearing on surface  178   b . This axial tension effectively couples the clutch bushing to the adjuster output shaft  104   b  by means of friction at the thread interfaces between the clutch bushing  150   b  and the adjuster output shaft  104   b . When this occurs, further rotation of the input gear  134   b  causes the output gear  130   b  to slip relative to the clutch bushing  150   b , and the adjuster output shaft  104   b  no longer translates axially. Therefore, the adjuster output shaft  104   b  does not over-travel in the retracting direction (i.e., away from the reflector) as the input gear  134   b  continues to be rotated in the same direction. 
     Turning the input gear  134   b  in the opposite direction releases the axial tension between the adjuster output shaft  104   b  and the clutch bushing  150   b . Hence, the friction coupling reduces, and the clutch bushing  150   b  begins to move again along with the output gear  130   b , and the adjuster output shaft  104   b  begins to translate axially. 
     Hence, over-travel of the adjuster output shaft  104   b  in either direction is prevented by a clutch mechanism which is provided by the interaction between the output gear  130   b , the elastomeric member  182   b  and the clutch bushing  150   b.    
     The headlamp adjuster  100   c  shown in FIG. 12 is similar to the headlamp adjusters  100   a  and  100   b  shown in FIGS. 2-3 and  10 - 11 , respectively. Therefore, similar reference numerals are used to identify similar parts, and the alphabetic suffix “c” is used. At times, a detailed description of a part is omitted with the understanding that one may review the description relating to a corresponding part of one of the other embodiments. 
     The headlamp adjuster  100   c  shown in FIG. 12 includes an adjuster output shaft  104   c  having a ball portion  108   c , a threaded portion  106   c , and flat surface portions  162   c  (i.e., “bi-flats”), and the adjuster output shaft  104   c  has a retaining member  120   c  thereon. Preferably, the retaining member  120   c  is crimped onto the adjuster output shaft  104   c  (represented with force arrows “F” in FIG. 15) so that the retaining member  120   c  does not have a tendency to rotate relative to the adjuster output shaft  104   c . The headlamp adjuster  100   c , like headlamp adjusters  100   a  and  100   b , includes a housing  110   c , a cover  144   c  and a sealing member  143   c , and preferably includes a sealing member  118   c  proximate the front  114   c  of the housing  110   c  for sealing against the housing  20  of the headlamp assembly  12  (see FIG.  1 ). As shown, preferably the housing  110   c  of headlamp adjuster  100   c  has tabs  116   c  thereon which engage corresponding structure in the aperture in the housing  20  of the headlamp assembly  12 , thereby providing that the headlamp adjuster  100   c  is “twist lock” mountable. The housing  110   c  includes a shaft hole  112   c  from which the adjuster output shaft  104   c  extends. As shown in FIGS. 12 and 14, a tower  190   c  is attached to the rear of the housing  110   c , and the end  122   c  of the adjuster output shaft  104   c  extends into the tower  190   c.    
     As shown in FIG. 12, the headlamp adjuster  100   c , like headlamp adjuster  100   b , includes an input gear  134   c , an output gear  130   c , a clutch bushing  150   c  and a friction coupling member  182   c , such as an elastomeric washer. However, unlike the headlamp adjuster  100   b  shown in FIGS. 10 and 11, the headlamp adjuster shown in FIG. 12 includes a clutch mechanism which has an additional member in the form of a friction washer  196   c  which is disposed intermediate the output gear  130   c  and the clutch bushing  150   c . The configuration of the output gear  130   c , friction coupling member  182   c , friction washer  196   c  and clutch bushing  150   c  is shown in FIG.  13 . As shown, the output gear  130   c  provides a seat  198   c  for receiving the elastomeric friction coupling member  182   c , and the friction washer  196   c  is provided between the elastomeric member  182   c  and the clutch bushing  150   c . Preferably, the output gear  130   c  has a free running fit on the external surface of the extension on the clutch bushing  150   c , and the compressed friction coupling member  182 c provides a friction coupling between the clutch bushing  150   c  and the output gear  130   c . The biasing action provided by the elastomeric member  182   c , forces the friction washer  196   c  into engagement with clutch bushing  150   c . Preferably, the friction washer  196   c  is formed of a flexible non-asbestos molded material with medium to high friction, good stability and good wear characteristics. 
     Specifically, the friction washer  196 c may be obtained from Great Lakes Friction Products, Inc. 8601 North 43rd Street, Milwaukee, Wis. 53209 pursuant to Engineering Product Data Sheet GL134-142. The friction washer  196   c  effectively acts as a barrier to adhesion between the elastomeric member  182   c  and the clutch bushing  150   c . In other words, the friction washer  196   c  will have a tendency to slip relative to the clutch bushing  150   c  before the elastomeric member  182   c  has a tendency to slip between the friction washer  196   c  and the output gear  130   c . As a result, a more constant breakaway torque (between the clutch bushing  150   c  and output gear  130   c ) is maintained over time compared to the embodiment wherein the friction washer  196   c  is not utilized (i.e., as shown in FIG.  10 ). It should be noted however, that while it is preferred that the clutch action take place between the friction washer  196   c  and clutch bushing  150   c , slippage may also occur between member  182   c  and the friction washer  196   c.    
     As shown in FIG. 12, a nut  200   c  is provided in a seat  202   c  in the housing  110   c . Preferably, unlike with headlamp adjuster  100   b , the clutch bushing  150   c  is not threadably engaged with the adjuster output shaft  104   c . Instead, the adjuster output shaft  104   c  is threadably engaged with the nut  200   c  which is seated in the housing  110   c , as shown in FIG. 14, and the clutch bushing  150   c  provides opposing walls  160   c  (see FIG. 12) which engage the flat portions  162   c  of the adjuster output shaft  104   c . Hence, the adjuster output shaft  104   c  cannot rotate relative to the clutch bushing  150   c , and rotation of the clutch bushing  150   c  causes the adjuster output shaft  104   c  to also rotate, however the shaft  104   c  is free to translate relative to the bushing  150   c . The threadable engagement between the nut  200   c  which is seated in the housing  100   c  (see FIG. 14) and the adjuster output shaft  104   c  causes the adjuster output shaft  104   c  to translate axially when the adjuster output shaft  104   c  rotates. Therefore, rotation of the clutch bushing  150   c  causes the adjuster output shaft  104   c  to translate axially, thereby changing the position of the reflector which is engaged with the adjuster output shaft  104   c  (see FIG.  1 ). 
     In operation, the input gear  134   c  of the headlamp adjuster  100   c  is rotated (such as by using a tool) to change the position of the reflector. As the input gear  134   c  is rotated, the output gear  130   c  rotates and, because of the friction coupling between the output gear  130   c , elastomeric member  182   c , friction washer  196   c  and clutch bushing  150   c , the clutch bushing  150   c  also rotates. Rotation of the overall clutch mechanism, including bushing  150   c  causes the adjuster output shaft  104   c  to translate due to the threadable engagement between the adjuster output shaft  104   c  and the nut  200   c  which is seated in the housing  110   c  (see FIGS.  12  and  14 ). As the adjuster output shaft  104   c  translates axially, the position of the reflector changes. So long as the end  122   c  of the adjuster output shaft  104   c  does not move into engagement with a rear stop wall  124   c  in the tower  190   c , and the retaining member  120   c  disposed on the adjuster output shaft  104   c  (see FIGS. 12 and 14) does not move into engagement with a forward stop wall  126   c  on the housing  110   c , rotation of the input gear  134   c  causes the clutch bushing  150   c  to rotate and the adjuster output shaft  104   c  to translate axially. 
     Once the input gear  134   c  has been rotated enough such that either the end  122   c  of the adjuster output shaft  104   c  moves into engagement with the rear stop wall  124   c  in the tower  190   c  or the retaining member  120   c  disposed on the adjuster output shaft  104   c  moves into engagement with the forward stop wall  126   c  on the housing  110   c , the output gear  130   c , elastomeric member  182   c  and friction washer  196   c  will slip relative to the clutch bushing  150   c  and the clutch bushing  150   c  will not rotate. That is to say, an overload condition will exist, such that continued attempt to rotate the input gear  134   c , will overcome the friction coupling provided by the elastomeric member  182   c  and output gear  130   c  will in effect “slip” relative to the clutch bushing  150   c . Thus, the input gear  134   c  and the output gear  130   c  can rotate without movement of the output shaft  104   c . Hence, the adjuster output shaft  104   c  does not continue to translate axially. The clutch action between the output gear  130   c  and the clutch bushing  150   c  when the end  122   c  of the adjuster output shaft  104   c  moves into engagement with the rear stop wall  124   c  in the tower  190   c  or the retaining member  120   c  disposed on the adjuster output shaft  104   c  moves into engagement with the forward stop wall  126   c  on the housing  110   c  provides that over-travel of the adjuster output shaft  104   c  in either direction is prevented. 
     Preferably, the range of axial travel of the adjuster output shaft  104   c  is limited to six rotations of the input gear  134   c , and during this range of travel, the adjuster output shaft  104   c  travels about 12 mm. When the input gear  134   c  is rotated and the retaining member  120   c  on the adjuster output shaft  104   c  moves into engagement with the forward stop wall  126   c  on the housing  110   c , the tension in the adjuster output shaft  104   c  increases due to the output gear  130   c  being constrained in the housing  110   c . This axial tension effectively couples the clutch bushing  150   c  to the adjuster output shaft  104   c  by means of friction at the interface therebetween. When this occurs, further rotation of the input gear  134   c  causes the output gear  130   c , elastomeric member  182   c  and friction washer  196   c  to slip relative to the clutch bushing  150   c , and the adjuster output shaft  104   c  no longer translates axially. Therefore, the adjuster output shaft  104   c  does not over-travel in the extending direction (i.e., toward the reflector) as the input gear  134   c  continues to be rotated in the same direction. 
     Turning the input gear  134   c  in the opposite direction releases the axial tension between the adjuster output shaft  104   c  and the clutch bushing  150   c . Hence, the friction coupling reduces, and the clutch bushing  150   c  begins to move along with the output gear  130   c , and the adjuster output shaft  104   c  begins to translate axially. 
     As the input gear  134   c  continues to be rotated in the same direction such that the adjuster output shaft  104   c  sufficiently axially translates causing the end  122   c  of the adjuster output shaft  104   c  to move into contact with the rear stop wall  124   c  in the tower  190   c , the tension in the adjuster output shaft  104   c  increases due to the clutch bushing  150   c  being constrained in the housing  110   c . This axial tension effectively couples the clutch bushing  150   c  to the adjuster output shaft  104   c  by means of friction at the interface therebetween. When this occurs, further rotation of the input gear  134   c  causes the output gear  130   c , elastomeric member  182   c  and friction washer  196   c  to slip relative to the clutch bushing  150   c , and the adjuster output shaft  104   c  no longer translates axially. Therefore, the adjuster output shaft  104   c  does not over-travel in the retracting direction (i.e., away from the reflector) as the input gear  134   c  continues to be rotated in the same direction. 
     Turning the input gear  134   c  in the opposite direction releases the axial tension between the adjuster output shaft  104   c  and the clutch bushing  150   c . Hence, the friction coupling reduces, and the clutch bushing  150   c  begins to move again along with the output gear  130   c , and the adjuster output shaft  104   c  begins to translate axially. 
     Hence, over-travel of the adjuster output shaft  104   c  in either direction is prevented by a clutch mechanism which is provided by the interaction between the output gear  130   c , the elastomeric member  182   c , the friction washer  196   c  and the clutch bushing  150   c.    
     By providing that each headlamp adjuster  100   a ,  100   b ,  100   c  includes a clutch mechanism, each headlamp adjuster  100   a ,  100   b ,  100   c  is configured to generally prevent over-travel of the adjuster output shaft  104   a ,  104   b ,  104   c  in both the extending and retracting directions. Hence, the reflector and the headlamp adjusters  100   a ,  100   b ,  100   c  do not tend to become damaged as a result of over-rotation of the input gear  134   a ,  134   b ,  134   c.    
     While embodiments of the present invention are shown and described, it is envisioned that those skilled in the art may devise various modifications without departing from the spirit and scope of the foregoing description.