Abstract:
A motor vehicle wiper comprising a driving head designed to be fixed to a free upper end of a wiper driving shaft at a bore includes a wiper arm, which is articulated on the driving head by a rear longitudinal end around a transverse axis which is substantially perpendicular to the general longitudinal direction of the wiper and perpendicular to the driving shaft axis, between a raised position and an operative position toward which it is returned by a helical compression spring inserted between the driving head and a support surface of the arm, the helical compression spring extends around the bore.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a motor vehicle windshield wiper comprising a spring for generating wiper pressure. The invention concerns more particularly a motor vehicle wiper comprising a driving head designed to be fixed to a free upper end of the wiper shaft at a bore, and containing a wiper arm which is articulated onto the driving head by a rear longitudinal end, around a transverse axis which is substantially perpendicular to the general longitudinal axis of the wiper and perpendicular to the driving shaft axis, between a raised position and an operative position towards which it is returned by a helical compression spring inserted between the driving head and a support surface of the arm. 
     In such a wiper, the wiper arm has at its front longitudinal end, a wiper blade equipped with a wiping scraper designed to come into contact with the window to be wiped. The wiping scraper is produced from a supple material and it is, for example, carried by a structure articulated to the blade in a manner that it can hug the curve, as long as it is convex. 
     In addition, so that the wiping scraper closely hugs the curve of the window, it is necessary that the wiper arm exerts a wiping pressure on the blade in order to press the scraper against the window, the pressure being assured by a wiping pressure spring which pulls the wiper arm towards its operative position. 
     According to a traditional idea of a wiping pressure spring, this spring is created in a helical tension spring form which is hung by the first end on the arm and by the other end on the driving head along a longitudinal movement line such that, when the arm is near its operative position, the spring pulls the arm in such a manner that the spring presses the scraper against the window, and, in opposition, when the arm is close to its raised position, the spring acts on the arm in order to support it in a means of propping up which defines this raised position. 
     According to such a conception of a wiper, it is thus necessary to plan that the rear part of the wiper arm be sufficiently large in the transverse direction to be able accommodate the helical tension spring which, in addition, is generally of a relatively long length. 
     In addition, it had already been proposed in document DE-A-35.08.542, for example, a wiper of which the arm contains a rear part covering the driving head articulated around a transverse axis constructed to the front of the driving head in relation to the driving shaft onto which is mounted the head, and in which a compression screw is constructed to the rear of the driving head in order to cooperate with a supporting surface of the arm which extends above the screw in order to move the arm into rotation around its articulated axis on the driving head towards the operative position. 
     Such an arrangement notably presents the inconvenience of extending, in an significant manner, the driving head towards the rear, that is to say, to the opposite of the really useful part of the wiper. This is so much more cumbersome that it is necessary to take into account the fact that this longitudinal offshoot towards the rear possesses an angular clearance in rotation around the axis of the driving shaft equal to that of the wiper, which makes it necessary to plan a corresponding clearance space. 
     The object of the invention is to propose a new conception or means of imposing a wiping pressure to the wiper blade, these means allowing the conception of the most compact wiper possible. 
     In addition, the object of this invention is to propose, in the frame of a wiper containing a wiping pressure spring which works by compression, means which allow keeping the wiper arm in a raised position, especially in order to facilitate the act of replacing the wiper blade. 
     SUMMARY OF THE INVENTION 
     In this goal, the invention proposes a wiper of the type previously described characterized by a helical compression spring extending around the bore. 
     According to the characteristics of the invention: 
     the spring extends at least in part around a cylindrical block from the head in which is constructed a bore designed to receive the upper end of the driving shaft; 
     the wiping surface of the arm is an annular surface which is laid out above the driving shaft, which is turned towards the back end against which presses the upper end of the spring; 
     the lower end of the spring is supported against a support surface of the driving head; 
     the support surface of the head is formed at the bottom of an annular groove; 
     the wiper includes means of locking the arm in a raised position; 
     the wiper includes a locking lever which is mobile in relation to the head, and which is attracted by elastic means in a cooperative manner, while the arm is in a raised position, with a surface complimentary to the arm in order to keep the arm in a raised position; 
     the elastic means comprise the compression spring which is supported by a lower end on a surface by action of the lever which is placed between the lower end of the spring and the support surface of the head; 
     the surface of the locking lever&#39;s action is formed on an annular ring which rests against a support surface of the driving head and which has an axis considerably parallel to that of the driving shaft while the lever is in a resting position, and the lever contains a locking tab which reaches towards the top from the ring from the rear side in relation to the driving head, and is of such a type that a free end of the tab, forming an indentation, is susceptible to be engaged in a housing complimentary to the arm while the arm is in a raised position; and 
     while the arm is led from its operative position towards its raised position, the free end of the lever tab slides along the length of an inclined section of the arm which provokes the swinging of the lever in such a way to compress the compression spring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Other characteristics and advantages of the invention will appear in the reading of the detailed description which follows and for the comprehension of which one will refer to the attached drawings in which: 
     FIGS. 1 and 2 are partial views cut longitudinally of a rear part of a first method of production of a wiper conforming to the description of the invention, the arm being represented, respectively, in an operative position and a raised position; and 
     FIGS. 3 and 4 are similar views to those of FIGS. 1 and 2 and illustrate a wiper comprising an advanced means of locking in the raised position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Represented in FIGS. 1 and 2, the rear longitudinal end  10  of a wiper arm  12  of which the front longitudinal end (not represented) is, for example, designed to carry a wiper blade. 
     In a known manner, the rear end  10  of the arm  12  is shown articulated around a transverse axis A 1  on a driving head  14 . The driving head  14  is mounted in a fixed manner on the upper end  16  of a driving shaft  18  of the axis A 2  which is represented in a vertical position in FIGS. 1 and 2, and which is notably perpendicular to a window to be wiped (not represented.) 
     The upper end  16  of the shaft  18  has a section shaped like a truncated cone  20  of the axis A 2  which narrows towards the top and into which a cylindrical section  22  is threaded lengthwise. 
     The driving head  14  consists of a bore  26  into which is engaged the upper end  16  of the shaft  18 . The bore  26  extending along the axis A 2  unblocks the two axial ends and is of a complimentary form to that of the upper end of the shaft  18  in such a way that the threaded section  22  of the shaft  18  reaches above an upper side  24  of the driving head  14 . In a known manner, a nut  27  is screwed onto the threaded section  22  pressing against the upper face  24  in order to move the driving head  14  towards the bottom in relation to the shaft  18  and to lead while supporting a bore part  26  shaped like a truncated cone  29  identical with the section shaped like a truncated cone  20  of the shaft  18  to immobilize the driving head  14  in relation to the shaft  18 . 
     In addition, the section shaped like a truncated cone  20  of the shaft  18  can be fluted in a manner to immobilize the driving head  14  in rotation around the axis A 2  in relation to the shaft  18 . 
     The shaft  18  is driven into rotation around its axis A 2  by a driving mechanism of the wiper (not represented) which imposes a rotating sweeping motion alternating around the axis A 2  to a group of elements comprising the shaft  18 , the driving head  14  and the arm  12 . 
     In a known manner, thanks to its articulation onto the driving head  14 , the blade  12  can be moved from an operative position, illustrated in FIG.  1  and into which it reaches notably and longitudinally perpendicular to the axis A 2  in order to press the wiper blade against the window to be wiped, to a raised position illustrated in FIG.  2  and into which the front part of the arm  12  is lifted towards the top, in order to move the front longitudinal end of the arm  12  away from the window. 
     As one can see in the drawing, the transverse axis of articulation of the arm  12  is constructed longitudinally towards the front of the driving head  14  in relation to the axis A 2  from the driving shaft  18  and from the bore  26 . In addition, while the arm  12  is lifted towards its raised position, the rear longitudinal end  10  of the arm  12 , which entirely covers the driving head  14 , tends to descend, that is to say, to near the driving head  14 . 
     In accordance with the details of the invention, the wiping pressure, that is to say, the force exerted by the arm  12  onto the blade, in order to efficiently clean the window, is exerted by a helical compression spring  28  which is constructed in order to be, at least while the arm  12  is in the operative position, notably coaxial to the shaft  18  around the upper end  16  of the shaft  18 . 
     As one can see in the drawing, the spring  28  reaches, on a majority of its length, around a cylindrical block  30  of the axis A 2  of the head  14  in which is constructed the bore  26  and which is limited towards the top by the upper surface  24  of the head. The spring  28  is pressed by its lower end  32  against a support surface  34  of the driving head  14  and, by its upper end  36 , against a support surface  40  constructed onto the arm  12  above the upper end  16  of the shaft  18 . 
     The support surface  34  of the driving head  14  is an annular surface perpendicular to the axis A 2  which stretches around the base of the cylindrical block  30 . In the illustrated example of production of the wiper arm  12 , the annular support surface  34  of the head  14  forms the bottom of an annular groove  42  of the head  14  which surrounds the block  30 . The groove  42  is open towards the top. 
     Thus, the compression spring  28 , by its action, tends to make the arm  12  pivot around the axis A 1 , in a clockwise direction in the drawing, which allows the arm  12  to impose the necessary force to wipe the window. 
     When the arm  12  is brought towards its raised position, its rear end  10  nears the driving head  14 , which augments the compression of the spring  28 , such that the spring  28  exerts enough pressure to return the arm  12  from its raised position to its operative position. 
     As one can see more clearly in FIG. 1, the support surface  40  of the arm  12 , against which the upper end  36  of the spring  28  rests, is constructed in an annular flange  38  which is attached to the arm  12  and which keeps the upper end  36  of the spring  28  radially fixed in relation to the axis A 2 . The flange  38  can be created as part of the arm  12  or, as it is illustrated in FIG. 1, as an attached piece. 
     Thus, even though the spring  28  is subjected to a certain radial deflection while the arm  12  is moved towards the raised position, the upper end  36  can not slip and escape the support surface  40 . Of course, the lower end  32  of the spring  28  is radially immobilized by the cylindrical block  30 . 
     Thanks to the arrangement of the spring  28  according to the invention, the spring  28  finds itself strongly limited in movement between the driving head  14 , such that the rear end  10  of the arm  12  can be of reduced dimensions, notably in the longitudinal direction, and, more specifically, to the rear of the axis A 2  of the driving shaft  18  and the bore  26 . In addition, this arrangement of the spring  28  allows obtaining an angular course of the arm  12  to be relatively significant between the operative and raised positions. 
     In addition, the cylindrical block  30  forms a perfect means of guiding the spring  30  which notably avoids all buckling problems of the spring  28 . 
     Another objective of the invention is to propose a means to keep the arm  12  in a raised position in order to facilitate replacing the wiper blade. An example of a wiper containing such means is illustrated in FIGS. 3 and 4 in which the elements are identical or similar to those is FIGS. 1 and 2 are designated by the same reference numbers. 
     As one can see in this production example, it is planned that a locking lever  44  is equipped with a locking tab  46  of which a free end  48  is designed to cooperate with a housing  50  in a complimentary form created in the arm  12  in order to keep the arm in a raised position. 
     The arm  12 , the driving head  14 , and the shaft  18  are identical to those described in the first production method in FIGS. 1 and 2. 
     The lever  44  contains an annular ring  52  which is supported at the bottom of the groove  42 , against the support surface  34 , and which is constructed such that the lower end  32  of the spring  28  is supported against an upper side of the annular ring  52 . When the arm  12  is in an operative position, the ring  52  is pressed against the support surface  34  and its axis is merged with that of the shaft  18 . 
     The tab  46  extends towards the top from the ring  52  from the rear side of the driving head  14  and is slightly inclined towards the rear. The end  48  of the tab  46  forms an offshoot which is radially steered towards the axis A 2  of the shaft  18  and towards the front of the driving head  14 . 
     The flange  38  of the arm  12 , in which the support surface  40  for the upper end  36  of the spring  28  is formed, is equipped to correspond with the tab  46 . A mouthpiece  54  which presents an inclined section  56  is turned towards the bottom and the rear of the arm and is constructed in the form of a recess. The housing  50  into which the free end  48  of the tab  46  is designed to be received is open towards the rear. 
     While the arm  12  is moved towards its raised position, the inclined section  56  is designed to come into contact with the free end  48  of the tab  46  and, as it is effectively turned towards the rear, the arm  12  tends to provoke a lowering of the lever  44  around a transversal axis passing by a junction zone linking the tab  46  to the ring  52 . 
     The lowering of the lever  44  in an anticlockwise direction in the drawing, tends to provoke a supplementary compression of the spring  28 . Thus, the compression spring  28  not only assures the wiping pressure of the wiper, but also the return of the lever  44  towards its resting position illustrated in FIG.  1 . 
     The lowering angle of the lever  44  increases such that the free end  48  of the tab  46  does not pass the upper end of the inclined section  56 . Once the free end  48  passes the mouthpiece  54 , the compression spring  28 , by its action on the ring  52 , tends to force the free end  48  to the interior recess  50  constructed above the mouthpiece  54 . 
     Thus, as one can see in FIG. 4, the complimentary forms of the free end  48  and the housing  50  assure, in an automatic manner, blocking of the arm  12  in a raised position. Preferably, these complimentary forms are planned to allow the free end  48  to free itself from the housing  50  when the user applies sufficient pressure to the arm  12  in the direction of returning it to its operative position. 
     The conception of the means of locking the arm in a raised position presented here is advantageous because it is of reduced bulk and it uses, as a means of returning the lever  44  to a resting position, the compression spring  28  used to supply the pressure force to the blade  12 .