Abstract:
A wiper apparatus for a vehicle window has a wiper arm pivot rotatably mounted in a pivot holder fixedly securable to vehicle structure. An end portion of the wiper arm pivot normally extends exteriorly of an impact line defined by vehicle structure. The wiper arm pivot includes an inner pivot shaft telescopingly displacable with respect to an outer pivot shaft upon the imposition of an impact load on the exterior end of the wiper arm pivot. A first pin separably holds the inner pivot shaft to the outer pivot shaft at a first position. An energy absorption material mass is disposed between the inner pivot shaft and the outer pivot shaft to control the telescoping movement of the inner pivot shaft in the outer pivot shaft and to absorb impact forces acting on the inner pivot shaft. A second fixed pin is carried by the outer pivot shaft and limits movement of the inner pivot shaft to a second position adapted for temporary operation of the wiper apparatus.

Description:
BACKGROUND 
   The present invention relates, in general, to vehicle windshield wiper assemblies and, more specifically, to vehicle windshield wiper assemblies having pedestrian collision safety features. 
   In vehicle windshield wiper assemblies, wiper blades are mounted on wiper arms. The wiper arms, in turn, carry a mount which is attached to a rotatable pivot shaft. The pivot shaft is rotatably mounted in a pivot shaft housing or holder fixedly mounted on vehicle structure, such as on the vehicle plenum or cowl panel immediately below the lower edge of the vehicle windshield. Although two wiper blades and wiper arms are normally provided on a single windshield, only one of the wiper pivot shafts is typically coupled by a drive lever to a drive source, such as an electric motor. Linkages connect the pivot shaft of one wiper arm to the pivot shaft of the other wiper arm to impart reciprocal motion to both pivot shafts when the motor reciprocally drives the drive lever. 
   Recent studies have shown that pedestrians have a high likelihood of injury when struck by a vehicle traveling at above certain speeds. Such injuries occur when the pedestrian is thrown by impact with the front bumper or front fenders of the vehicle hood onto the hood where the pedestrian&#39;s head and/or torso then contacts the windshield with considerable force. 
   Although windshield wiper assemblies are provided in a large number of different configurations, typical wiper assemblies have the upper end of the pivot shaft and the wiper arm attached thereto protruding above an impact line usually defined by the exterior surface of the vehicle hood. As the pivot shaft, although rotatable in the pivot holder, is nevertheless axially fixed relative to the vehicle structure, the protruding portions of the wiper assembly act as a fixed object or projection which increases the likelihood of serious injury to a pedestrian during a collision. 
   Certain countries or regional groups have initiated legislation to protect pedestrians and other road users in the event of a collision with a vehicle. Under such legislation, manufacturers will have to insure that the pivot shafts of windshield wiper assemblies do not act as an external projection during a pedestrian collision with a vehicle. 
   As a result, windshield wiper manufacturers have provided a number of different pivot shaft mounting arrangements which are capable of pivoting below the hood impact line or breaking away from the fixed mount to the vehicle structure and dropping below the vehicle hood so as to lower the protruding portion of the pivot shaft and the wiper arm below the impact line during a pedestrian collision. 
   However, providing a pivot shaft mounting design which is capable of pivotal movement under impact is directly opposed to the wiper system requirements of a solid mount for torsional loading and radial force management. In current pivot housing assemblies, the pivot shaft is solidly mounted in the axial direction in the pivot shaft housing. The pivot shaft is constrained within the pivot housing by various methods. One example utilizes a solid ring with full contact to the pivot shaft so as to exert a retaining force on the pivot assembly. Another example is an E-clip retaining ring that fits into a slot on the pivot shaft and mechanically retains the pivot shaft in the pivot shaft housing. On the other end of the pivot shaft, the pivot assembly is constrained by the interference caused by embedded knurling in the pivot shaft and the interference hole in the mating drive plate when the two pieces are mechanically riveted together. 
   While this current pivot shaft housing design has sufficient strength in both the axial and radial directions to meet current federal and customer requirements, the design is ineffective in minimizing injury from the impact load of a pedestrian. 
   Prior pivot shaft mounting designs which provide break-away or pivot functions do not remain in a workable wiper operating position after movement thereby rendering the entire wiper system inoperative. This prevents the vehicle from being safely used after a collision to at least enable the driver to proceed home or to a repair location with reduced wiper operability. 
   A wiper apparatus has been designed with a pedestrian safety feature. This design uses an axially displacable, spring biased pivot shaft. A spring acts on a wiper arm pivot mounting to maintain the wiper pivot shaft in a normal wiper operating position. Impact forces acting on the wiper pivot shaft overcome the biasing force of the spring and enable the pivot shaft to axially displace under the impact forces below the vehicle hood impact line to prevent substantial contact between a pedestrian and the exposed portions of the pivot shaft during a pedestrian/vehicle collision. Once the impact forces are removed from the pivot shaft, the spring biases the pivot shaft back to the normal wiper operating position, assuming that minimal damage has been inflicted on the wiper arm and the pivot shaft. 
   What is still needed is a vehicle windshield wiper apparatus having a rotatable wiper pivot shaft which meets wiper system requirements for torsional and radial force loading while being capable of controlled axial displacement below the vehicle hood impact line to prevent substantial contact between a pedestrian and the exposed portions of the pivot shaft and/or wiper arm during a pedestrian/vehicle collision. It would also be desirable to provide a vehicle windshield wiper apparatus which provides energy absorption during pedestrian impact with the wiper arm and/or pivot shaft to minimize impact forces on the pedestrian and to provide a controlled collapse of the pivot shaft below the vehicle hood impact line. It would also be desirable to provide a vehicle windshield wiper apparatus having an axially displacable pivot shaft which is displacable below the vehicle hood impact line to a lowered position which still provides a reduced amount of wiper operability assuming minimal damage to the wiper arm and/or pivot shaft during a pedestrian/vehicle collision. 
   SUMMARY 
   The present invention is a vehicle wiper pivot housing with an energy absorbing, axially displacable pivot shaft which uniquely meets the requirements of solid wiper system mounting for torsional loading and radial force and an impact load pivot shaft displacement and energy absorption capability for pedestrian safety during a pedestrian/vehicle collision. This pedestrian safety feature is provided in a manner which enables the wiper pivot to be lowered under impact forces in a controlled, energy absorbing manner to a lowered position which minimizes the exposure of the pivot shaft and the wiper arm above the vehicle hood impact line while still positioning the pivot shaft and the wiper arm in an operable position providing at least a minimal amount of wiper operability for wiper operation during movement of the vehicle from the collision site. 
   In one aspect, the wiper apparatus includes a pivot holder which is adapted to be fixedly mounted to a vehicle. A wiper arm pivot is rotatably mounted in the pivot holder. The wiper arm pivot is adapted for carrying a wiper arm at one end. One end of the wiper pivot nominally extends exteriorly of vehicle structure for receiving the wiper arm when the wiper pivot is in a normal wiping operation position. The wiper pivot is axially displacable under a predetermined impact force exerted on the exposed end of the wiper pivot in an amount to lower the exposed end of the wiper pivot below the surrounding vehicle structure with energy absorption for a controlled low impact collapse. 
   In another aspect, means are provided for axially fixing the inner pivot shaft to the outer pivot shaft in the first position. The fixing means is separable at a predetermined impact force to allow movement of the inner pivot shaft with respect to the outer pivot shaft from the first position. The fixing means is, by example, a pin extending through the inner pivot shaft to the outer pivot shaft. 
   The holding means also includes means carried in the outer pivot shaft and engaged by the inner pivot shaft for limiting movement of the inner pivot shaft at the second position. The limiting means is, by example, in the form of another pin extending through the outer pivot shaft. 
   In one aspect, the energy absorption means is a deformable mass carried in the outer pivot shaft. Preferably, the deformable mass includes voids or interstices. The interstices may be holes which decrease in one of average diameter or average number from one end of the mass to the other or increase in number or diameter from one end to the other end of the mass. 
   In another aspect, means are provided for guiding the telescoping movement of the inner pivot shaft relative to the outer pivot shaft. The guide means may comprise at least one or more complimentary projections and mating recess formed in the inner pivot shaft and the outer pivot shaft. 
   In another aspect of the invention, the guide means includes means for varying the resistance to movement of the inner pivot shaft in the outer pivot shaft as the inner pivot shaft moves from the first position toward the second position. 
   In another aspect of the invention, a method for manufacturing a wiper pivot apparatus capable of lowering a vehicle wiper arm attached to the pivot apparatus from a first normal wiping position to a second lower position under an impact force is disclosed. The method includes the steps of: A method for manufacturing a wiper pivot apparatus capable of lowering a vehicle wiper arm attached to the pivot apparatus from a first normal wiping position to a second lower position under a predetermined impact force, the method comprising the steps of: 
   mounting a wiper arm pivot adapted to carry a wiper arm at a first end and a pivot holder adapted to be fixed to a vehicle; 
   forming the wiper arm pivot of an inner pivot shaft telescopingly movable from a first position placing the wiper arm in a normal wipe position on the vehicle to a second position telescoped within the outer pivot shaft and axially fixed with respect to the pivot holder; releasably fixing the inner pivot shaft at the first position to the outer pivot shaft, the inner pivot shaft released from the fixed first position at a predetermined force acting on the inner pivot shaft; and 
   placing energy absorption material between the inner pivot shaft and the outer pivot shaft to control the telescoping movement of the inner pivot shaft between the first and seconds positions. 
   The wiper apparatus of the present invention provides a unique axially displacable wiper arm pivot which is capable of axial displacement relative to the surrounding fixed pivot holder upon the imposition of a predetermined impact force on an end of the wiper arm pivot normally exposed above a hood impact line with energy absorption. The axial displacement is controlled to allow the external end of the wiper arm pivot to retract below the surrounding vehicle structure to minimize fixed contact between the wiper arm pivot and a pedestrian impacting with the vehicle structure during a collision. At the same time, the axial displacable wiper arm pivot retains sufficient strength in the axial and radial directions to provide a solid mount for torsional loading and radial force management for wiper arm movement. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The various features, advantages and other uses of the present invention will become more apparent by referring to the following detailed description and drawing in which: 
       FIG. 1  is a partially cross-sectioned, side elevational view of a vehicle wiper pivot apparatus in accordance with one aspect of the present invention shown in a normal wiping position; 
       FIG. 2  is a cross-sectional view, generally taken along line  2 — 2  in  FIG. 1 ; 
       FIG. 3  is a partial, perspective view showing the normal mounting position of the inner pivot shaft and a first connector; 
       FIG. 4  is a cross-sectional view, similar to  FIG. 1 , but showing the position of the wiper pivot shaft after an impact on the exterior end of the pivot shaft;  and 
       FIG. 5  is a partial, perspective view showing another aspect of the guide means of the present invention. 
   

   DETAILED DESCRIPTION 
   Referring now to  FIGS. 1–3 , there is depicted various aspects of a vehicle windshield wiper apparatus  10 , which is only partially shown, as the present wiper apparatus  10  may be employed with many different wiper arm configurations. 
   As a large number of the components in a vehicle windshield wiper apparatus are conventional, such are not shown in order that the features of the present invention may be more clearly identified. However, it will be understood that the wiper apparatus  10  utilizes a drive motor connected by a drive lever  13  to a pivot shaft  12  rotatably mounted in a pivot shaft holder or housing  14 . 
   As shown in  FIG. 1 , at least an upper, portion  30  of the pivot shaft  12  is disposed exteriorly of an impact line  32  which is generally formed by a major plane or edge of a vehicle hood, not shown. The exposed end  30  of the pivot shaft  12 , which receives a not shown wiper arm, is disposed adjacent to a bottom edge of a vehicle windshield, also not shown. 
   The wiper pivot assembly  10  shown in  FIG. 1  is a so-called “top drive” wiper system in that the drive lever  13  is mounted on top of one end of the pivot housing  14 . The drive lever  13  is axially and rotatably fixed to the pivot shaft  12  by a press-fit joint or a clip  36 , by example only. Movement of the drive plate  13  is generated by rotation of the output shaft of the wiper drive motor, not shown, which imparts bi-directional rotation to the pivot shaft  12  in a conventional manner. However, the clip  36  restrains the pivot shaft  12  in an upward direction with respect to the pivot housing  14 . 
   Also mounted in the through bore  40  are first and second bushings  46  and  48  which are disposed between the inner surface of the bore  40  and the pivot shaft  12 . Another retainer or C-clip  50  is disposed on the second end  44  of the pivot housing  14  and engages a slot formed at a second end  52  of the pivot shaft  12  to axially restrain the pivot shaft  12  relative to the pivot housing  14 . 
   As shown in  FIGS. 1–4 , the pivot shaft  12  is formed of an inner pivot shaft  60  and a concentric, outer pivot shaft  62 . The inner pivot shaft  60  may be is in the form of a tubular member which can be solid or hollow. An upper, outer end  64  of the inner pivot shaft  60  is formed with a suitable mount, such as knurlings, for a press-fit connection of a wiper arm head  66  thereon. 
   The inner pivot shaft  60  is axially displacable relative to the outer pivot shaft  62 . However, the inner pivot shaft  60  is non-rotatably connected to the outer pivot shaft  62  by a first connector, such as a pin  66 . The pin  66  is in the form of a tubular member having opposed first and second ends  68  and  70 . The first and second ends  68  and  70  extend through aligned, diametrically opposed apertures  72  and  74  spaced from a lower end  76  of the inner pivot shaft  60  as shown in  FIGS. 1 and 3 . By way of example, the apertures  72  and  74  may be in the form of open ended slots extending from an open end at the second end  76  of the inner pivot shaft  60  to a closed inner end. The pin  66  extends through aligned apertures  80  and  82  in the outer pivot shaft  62  which apertures  80  and  82  are spaced from a first or upper end  84  of the outer pivot shaft  62 . The location of the apertures  72  and  74  in the inner pivot shaft  60  and the apertures  80  and  82  in the outer pivot shaft  62  are positioned to dispose the upper end  64  of the inner pivot shaft  60  in a normal wiper arm position shown in  FIG. 1 . 
   A second connector or pin  84  extends through a second pair of aligned, diametrically opposed apertures  86  and  88  spaced from a second or lower end  90  of the outer pivot shaft  62 . The connector or pin  84  is located approximately one quarter of the length of the outer pivot shaft  62  from the second end  90 , by example only. This position of the second connector or pin  84  defines the fixed lowered position or limit of the inner pivot shaft  60  which places the upper end  64  of the inner pivot shaft  60  and the attached wiper arm  66  in a temporary use wiping position to provide at least a minimal amount of wiping capability to the vehicle after a collision. 
   The inner and outer pivot shafts  60  and  62  are fixed for simultaneous, unitary rotation by means of guide means shown more clearly in  FIG. 2 . By way of example only, the guide means includes at least one projection or lobe  92 , with three equi-circumferentially spaced projection or lobes  92 ,  94  and  96  being depicted by way of example only. The lobe  92  extends radially inward from an inner surface of the outer pivot shaft  62 . The inner pivot shaft  60  is formed with one or more complimentary recesses, with three equi-circumferentially spaced recesses  98 ,  100  and  102  being depicted by way of example only. The projections or lobes  92 ,  94  and  96  and the recesses  98 ,  100  and  102 , respectively, are complementarity shaped and positioned for rotative interlocking as shown in  FIG. 2  to enable equal and simultaneous rotation of the inner pivot shaft  60  and the outer pivot shaft  62  during pivotal movement of the drive lever  13 ; while still enabling axial displacement or sliding movement of the inner pivot shaft  60  relative to the outer pivot shaft  62 . The position of the mating lobes and recesses may be reversed such that the projections or lobes may be formed in a radially outward extending manner on the inner pivot shaft  60  to seat within complimentary formed recesses carried in the inner surface of the outer pivot shaft  62 . 
   The mating lobes  92 ,  94  and  96  and projections  98 ,  100  and  102  minimize backlash between the inner pivot shaft  60  and the outer pivot shaft  62  during the rotation of the entire pivot shaft  12 . 
   The present invention uniquely includes an energy absorption means  110  which is carried between the outer pivot shaft  62  and the movable portions of the inner pivot shaft  60 . Suitable plugs or caps may be provided in the outer pivot shaft  62  and the inner pivot shaft  60  to retain the energy absorption means  110  in the position shown in  FIG. 1 . 
   By way of example only, the energy absorption means is in the form of a collapsible matrix, such as a honeycomb nylon matrix in which a blow holes or cavities are formed within a nylon material mass. The blow holes form a means for controlling the deformation of the mass  110   
   The blow holes pictorially depicted by reference number  112  may be provided in a substantially constant distribution and a substantially constant diameter or size throughout the entire axial length of the energy absorption means or matrix  110 . Alternately, the blow holes  112  may be provided in a varying diameter or size from a first or upper end to a second or lower end of the energy absorption matrix  110  to provide any desired energy absorption profile, such as an increasing force or energy absorption profile during axial displacement of the second end  76  of the inner pivot shaft  60  within the outer pivot shaft  62  or a decreasing force or energy absorption profile during axial displacement of the inner pivot shaft relative to the outer pivot shaft  62 . 
   The collapsing energy absorption feature controls the axial displacement of the inner pivot shaft  60  relative to the outer pivot shaft  62  and absorbs a substantial portion of the impact forces exerted on the inner pivot shaft  60  which cause such axial displacement. 
   As soon as the impact force is exerted on the upper end  64  of the inner pivot shaft  60  exceeds the rigid structural force provided by the energy absorption means or matrix  110  in the normal mounting position shown in  FIG. 1 , the inner pivot shaft  60  will axial displace within the outer pivot shaft  62  thereby lowering the upper end  64  of the inner pivot shaft  60  below the vehicle hood impact line  32 . The second end  76  of the inner pivot shaft  60  as well as the central portion of the connecting pin  66  will deform or crush the energy absorption matrix  110  during such axial displacement by collapsing the blow holes  112 . 
   According to a unique feature of the present apparatus, the connector or pin  66  is provided with a breakaway feature such that the first and second ends  68  and  70  of the connector or pin  66  will break away or de-couple from a central portion of the pin  66  when the impact force exerted on the inner pivot shaft  60  exceeds a predetermined force equal to the shear strength of the connector  66 . Prior to reaching this impact force level, the pin  66  holds the inner pivot shaft  60  in the normal wiper arm operating position shown in  FIGS. 1 and 3 . However, once the first and second ends  68  and  70  of the pin  66  de-couple from the central portion of the pin  66 , the inner pivot shaft  60  is capable of axial displacement within the outer pivot shaft  62 . 
   The energy absorption means or matrix  110  then comes into play to control the axial displacement or telescoping movement of the inner pivot shaft  60  within the outer pivot shaft  62 . The guide means in the form of the mating lobes  92 ,  94  and  96  and the recesses  98 ,  100  and  102  maintain the inner pivot shaft  60  in a rotatably fixed position relative to the outer pivot shaft  62  during such axial displacement. This enables the apertures or slots  72  and  74  to engage the fixed pin  84  extending through a lower portion of the outer pivot shaft  62 . The fixed pin  84  has a high shear strength so as not to shear or break away during any nominal magnitude of impact forces which may be exerted on the inner pivot shaft  60 . The slots  72  and  74  in the inner pivot shaft  60  slide over the fixed pin  84  until the fixed pin  84  reaches the closed inner end of each slot  72  and  74 . 
   When the fixed pin  84  engages the inner end of the slots  72  and  74 , further axial displacement or telescoping movement of the inner pivot shaft  60  relative to the outer pivot shaft  62  ceases as shown in  FIG. 4 . This second or lowered position of the inner pivot shaft  60  defines a position for the upper end  64  of the inner pivot shaft  60  and the attached wiper arm  66  which affords at least a minimal amount of wiping capability assuming no substantial damage to the wiper apparatus during the collision. Thus, pivotal movement of the drive lever  13  by activation of the wiper motor will cause the inner and outer pivot shafts  60  and  62  to rotate in a normal manner to effect pivotal movement of the wiper arm  66  over the vehicle window. This affords a temporary capability to enable the vehicle to be moved from the collision site with at least a minimal amount of wiping capability. 
   As shown in  FIG. 5 , the guide means may also include means for varying the resistance to axial translation of the inner pivot shaft  60  with respect to the outer pivot shaft  62 . As shown in  FIG. 5 , the varying means may include means for varying the depth or width of one or more of the recesses  98 ,  100  and  102  so as to cause a change in the depth or width of the mating projection  92 ,  94  or  96  on the outer pivot shaft  62  as the inner pivot shaft  60  axially translates within the outer pivot shaft  62 . The varying means may provide an increasing or decreasing resistance, with an increasing resistance being shown in  FIG. 5  by varying the width of the recess  102  from a first constant width  110  to a gradually narrowing second width  112 . The varying means may be gradual as in the form of the tapered recess width  112  shown in  FIG. 5  or provided as a step function formed of a series of gradually decreasing or increasing widths or thicknesses of the recess  102 . 
   The reverse is also true in that the varying means may be formed of a varying depth or thickness projection  96  in the outer pivot shaft  62  which is engaged by a constant diameter and depth recess  102  in the inner pivot shaft  60 . 
   In summary, there has been disclosed a unique vehicle wiper apparatus which has a unique energy absorption capability to control and absorb impact forces exerted on an exposed end of an axially displacable inner pivot shaft so as to absorb such impact forces during lowering of the inner pivot shaft during a pedestrian/vehicle collision. This controlled energy absorption feature reduces the force exerted by the exposed portions of the wiper pivot shaft and the wiper arm on a pedestrian impacting with the vehicle in a safe, controlled manner. According to another feature of the present invention, the controlled telescoping displacement of the inner pivot shaft with respect to an outer pivot shaft is limited at a lowered position which affords a minimum amount of wiper operability.