Wiperarmforawindshieldwipermechanism,partic……

1、Wiper arm for a windshield wiper mechanism, particularly for motor vehicles            FIELD OF THE INVENTIONThe invention pertains to a wiper arm for a windshield wiper mechanism, particularly for motor vehicles, wherein the wiper arm is r

2、igidly mounted on the end of a drive shaft that is driven such that it carries out reciprocating pivoting motion. Consequently, the reciprocating pivoting motion of the drive shaft causes a reciprocating wiping movement of the wiper arm and the wiper blade fastened thereon within a corresponding wip

3、ing angle. BACKGROUND OF THE INVENTIONMost wiper arms of this type comprise a mounting part with an opening that is usually realized in the form of an inner cone. This opening extends coaxially with the drive shaft, on the end of which the wiper arm is then mounted. When mounting the wiper arm on th

4、e drive shaft, the opening of the mounting part is attached to the end of the drive shaft. The mounting part of the wiper arm is pressed onto the end of the drive shaft and rigidly fastened by screwing a separate fastening nut or separate fastening screw on or in the end of the drive shaft, with a w

5、asher being arranged between the mounting part and the fastening nut or fastening screw. Wiper arms of this type are already known. DE-GM 71 04 759 discloses a wiper arm with a mounting part that is realized in the form of a die-cast part and provided with an opening in the shape of an inner cone. T

6、he opening of the mounting part is attached to a knurled cone arranged on the end of a solid drive shaft and held by a separate fastening nut, with the fastening nut being screwed on the threaded stem of the drive shaft that extends through the opening in the mounting part in the form of an extensio

7、n of the knurled cone. A covering cap of plastic covers the attached mounting part and the fastening nut. DE 41 40 959 A1 discloses a different wiper arm in which the mounting part is realized in the form of a sheet metal body. A cast metal part that is provided with a conical opening for rigidly mo

8、unting the wiper arm on the conical end of a drive shaft is fastened to the aforementioned sheet metal part. This wiper arm is mounted on the drive shaft by attaching the mounting part onto the end of the drive shaft which is provided with an outer cone and a cylindrical threaded projection. A separ

9、ate fastening nut is then attached. Consequently, the cast metal part of the mounting part is pressed onto the cone arranged on the end of the drive shaft and rigidly held thereon. A wiper arm with a mounting part that is realized in the form of a die-cast part with a conical opening is known from D

10、E 41 17 107 A1 or DE 41 34 980 A1. This wiper arm is fastened to the end of a drive shaft as described previously by utilizing a separate fastening nut. In this case, the drive shaft is realized in the form of a hollow shaft, with the hollow space of the drive shaft being used as a lead-through for

11、the windshield-washing fluid. The mounting part and the fastening nut as well as the hose connection on the end of the drive shaft for conveying the windshield-washing fluid are covered with a covering cap after the wiper arm is mounted on the drive shaft. All these known wiper arms are associated w

12、ith the disadvantages described below. When mounting the wiper arm on the drive shaft, a separate fastening nut must be screwed on the end of the drive shaft after the opening of the mounting part of the wiper arm is attached to the end of the drive shaft. This requires the additional transport and/

13、or storage of fastening nuts as well as an increased mounting expenditure. After a certain time, the wiper arm may require removal or replacement, e.g., if the windshield becomes damaged, the motor vehicle is repainted or the wiper arm is deformed due to excessive stress. However, the removal of the

14、 wiper arm is very complicated in most instances because the mounting part is very firmly seated on the drive shaft since it is pressed onto the end of the drive shaft. Once the fastening nut is unscrewed, the wiper arm can only be removed from the drive shaft with a very high expenditure of force.

15、In this case, intact wiper arms are frequently bent or damaged such that they are rendered unusable and must be replaced. If unsuitable tools are used, the drive shaft or its bearings are frequently damaged, i.e., these components also must be replaced and the repair costs are significantly increase

16、d. Hollow drive shafts with lead-through for the windshield-washing fluid are particularly sensitive in this respect. If such drive shafts are damaged during the removal of the wiper arm, the repair costs are also increased. SUMMARY OF THE INVENTIONAn object of the present invention is to provide a

17、wiper arm less costly to mount on the drive shaft, and uncomplicated to remove from the drive shaft without damaging the drive shaft or the wiper arm. According to the invention, this objective is attained with a wiper arm having a fastening element in the form of a fastening screw or fastening nut

18、which is held on the mounting part of the wiper arm in captive fashion at least approximately in the mounting position. The fastening element is configured to facilitate easy removal of the wiper arm off the drive shaft. The fastening element is held on the mounting part of the wiper arm in such a w

19、ay that the wiper arm can be carefully pulled off the drive shaft with a relatively low expenditure of force by simply loosening or unscrewing the fastening element. This basic solution provides the advantage that the fastening element is already situated in the mounting position on the wiper arm to

20、 be mounted on the drive shaft. Consequently, the fastening element need not be transported and stored separately. In addition, the fastening element need not be handled as a separate component during the mounting process. The complete wiper arm with the fastening element simply must be attached to

21、the end of the drive shaft, with a precise centering of the fastening element taking place during this attachment. The fastening element is then attached. This mounting process is significantly less complicated than solutions known thus far. One additional advantage of the solution according to the

22、invention can be seen in the careful removal of the wiper arm from the drive shaft which requires very little force and no additional tools except the tool used for tightening and loosening the fastening element. According to an embodiment, a fastening nut is arranged on the upper side of the wiper

23、arm mounting part which opposes the windshield to be cleaned in the form of an axial extension of the opening in the mounting part that serves for mounting the wiper arm on the drive shaft, with the fastening nut being aligned at least approximately coaxially with the aforementioned opening in the m

24、ounting part. In this case, the fastening nut can be turned about its axis and held such that it can be moved relative to the mounting part in the axial direction within a limited range. The axial moving range is limited by one or more limit stops that are connected to the mounting part and, in addi

25、tion to a holding function, ensure the pull-off function of the fastening nut. During the axial unscrewing movement, the fastening nut comes in contact or effectively engages with the mounting part at the end of the axially limited moving range and pulls the entire wiper arm with the mounting part o

26、ff the drive shaft on which it is firmly seated. The required pulling force of the fastening nut is relatively low and carefully transferred from the fastening nut to the drive shaft via the fastening thread and onto the mounting part via the limit stops. The drive shaft and the mounting part of the

27、 wiper arm absorb these oppositely directed force components without becoming damaged. Consequently, the wiper arm can be carefully removed from the drive shaft with simple conventional tools and without damaging the wiper arm and/or the drive shaft or its bearings, i.e., the wiper arm can be reused

28、. It is also advantageous to arrange a washer between the wiper arm mounting part and the fastening nut or fastening screw. In light of the relatively high pressing forces that occur during the mounting of the wiper arm on the drive shaft, this washer should be correspondingly stable. The underside

29、of the fastening nut or fastening screw does not move on the mounting part of the wiper arm, but rather on the washer that adjoins the mounting part. Consequently, the surface of the mounting part is protected. This represents a particularly advantageous aspect if a layer of enamel is applied to the

30、 mounting part. If the washer is held on the underside of the fastening nut, the complete arrangement of the wiper arm and the fastening nut can be simplified. The washer can be attached to the mounting part of the wiper arm simultaneously with the fastening nut in one single production step. In a v

31、ery simple and cost-efficient embodiment, the underside of the fastening nut which adjoins the mounting part of the wiper arm is provided with a radially extending, circumferential collar that is preferably cylindrical. One or more limit stops that are connected to the mounting part of the wiper arm

32、 overlap this collar. If only one limit stop is provided, said limit stop should extend over most of the circumferential collar so as to attain a uniform distribution or uniform introduction of the forces for pulling off the wiper arm. If a small structural height is desired, in particular, in a mou

33、nting part that is realized in the form of a cast metal part, the mounting part can be provided with a preferably cylindrical recess on the upper side that faces away from the windshield to be cleaned. The opening for mounting the wiper arm on the drive shaft ends in the base of this recess. The fas

34、tening nut is arranged inside this recess in at-least partially counterbore fashion, with the underside of said fastening nut adjoining the base of the recess or the washer situated at this location. The limit stops arranged above the collar also extend inside this recess. In addition, the recess ca

35、n be covered by means of a relatively small covering cap such that an attractive appearance is attained. A pair of pins can be used to form a quite simple, but rather robust and reliable type of limit stop. These pins form a bridge over the recess and are arranged above the collar in flush bores arr

36、anged in the wall that surrounds the recess. The pins are situated on opposite sides of the fastening nut and extend in a plane perpendicular to the rotational axis of the fastening nut, at least approximately parallel to one another. The pins and the corresponding flush bores can be aligned paralle

37、l or perpendicular to the imaginary central longitudinal axis of the mounting part. Depending on the geometric ratios of the mounting part, the intensity of the forces to be transmitted and the friction between the collar and the limit stop, a person skilled in the art is able to select the correct

38、or optimal cross-sectional shape of the pins from a variety of round, rectangular or differently profiled cross sections. In yet another embodiment, the fastening nut is only held on the mounting part by the limit stops if so required or deemed advantageous, i.e., when mounting the wiper arm on the

39、drive shaft and removing the wiper arm from the drive shaft. The limit stops can be removed while the fastening nut is screwed on the threaded projection of the drive shaft. This particular embodiment is advantageous if the limit stops have an unattractive appearance. The removable limit stops are a

40、dvantageously formed by two parallel pins that are arranged at a distance from one another and rigidly connected to one another at one end by a bridge-like element. This two-prong fork can be inserted into or removed from correspondingly parallel, flush bores from the outside of the mounting part, w

41、ith said bores extending at least through one wall of the mounting part. Additional advantageous variations for mounting a fastening nut in a recess of the mounting part of a wiper arm are disclosed. In one such variation, a shoulder arranged radially adjacent to the collar of the fastening nut is p

42、rovided on the bottom edge of the recess. The shoulder extends continuously in the circumferential direction or in the form of sectors, with the individual sectors being distributed over the circumference. The shoulder is at least slightly higher than the collar of the fastening nut so as to ensure

43、that the fastening nut can be turned. A perforated disk lies on the shoulder and overlaps the collar of the fastening nut with its inner edge. Since the perforated disk is additionally fixed on the mounting part, it acts as a limit stop for the collar of the fastening nut. The upper part of the fast

44、ening nut protrudes through the perforation of the perforated disk. In yet another variation, a perforated disk lies loosely on the collar of the fastening nut, with a lock washer being arranged above the perforated disk such that it radially overlaps this perforated disk. In addition, the lock wash

45、er is held or fixed on the walls of the recess. In this case, the lock washer forms the limit stop for the collar of the fastening nut. A clamping bridge that forms a limit stop is arranged above the collar of the fastening nut with its inner edge, with the outer edge or sections thereof being suppo

46、rted by the walls of the recess. A radially split washer that acts as a limit stop for the collar of the fastening nut is arranged in the wall of the recess such that it is axially supported and can be radially moved within a certain range. The inner edge of the split washer radially protrudes into

47、the recess. The collar of the fastening nut is stepped. The lower part of the collar is conically tapered in such a way that it can be pressed through the inner opening of the split washer while temporarily widening the lock washer. The diameter of the upper part of the stepped collar is slightly sm

48、aller than the inner diameter of the split washer in its normal condition. After the conical part of the collar has been pressed through the split washer, said split washer assumes its original shape and size on the upper part of the collar and consequently acts as a limit stop. The previously descr

49、ibed variations directed to retention of the fastening nut within a recess in the mounting provide the advantage of a small structural height and a counterbore arrangement of the fastening nut. The recess in the mounting part can also be closed by a relatively small covering cap in this case. Also d

50、isclosed is a wiper arm that can be manufactured in particularly simple fashion. The mounting part of this wiper arm consists of a sheet metal part that has an essentially U-shaped cross section and is provided with a cast metal insert, with the opening for mounting the wiper arm on the drive shaft

51、being arranged in the cast metal part. The rear part of the sheet metal part is provided with an aperture. The cast metal part that comprises the opening for mounting the wiper arm on the drive shaft is arranged on the sheet metal part underneath the aperture and fastened thereon by means of bent re

52、gions of the sheet metal part that are especially realized in the form fastening tabs. The cast metal part is provided with a recess that extends concentric to the opening underneath the aperture, with the fastening nut and its collar being arranged in said recess. The edge of the recess in the shee

53、t metal part overlaps the collar of the fastening nut in the form of a limit stop, with the upper part of the fastening nut projecting through the aperture such that it protrudes above the upper side of the sheet metal part. Related variations for attaching the fastening nut on a mounting part of th

54、e wiper arm in which the fastening nut adjoins the upper side of the mounting part, i.e., the rear part of the mounting part are also disclosed. In one such variation, a perforated disk is arranged above the collar of the fastening nut and overlaps said collar and, if so required, a washer, with the

55、 upper part of the fastening nut protruding through the perforation of the perforated disk. In this case, the perforated disk also comprises projecting fastening sections, by means of which it is fastened to the mounting part of the wiper arm. In this case, the perforated disk forms the limit stop f

56、or the collar of the fastening nut. In order to reduce the space requirements as well as the material and the weight of this solid and robust embodiment, another embodiment of the perforated disk is directly attached to the fastening nut without a collar. For this purpose, the underside of the faste

57、ning nut has a correspondingly stable, hollow-cylindrical extension that extends through the perforation of the perforated disk, with the edge of said extension being flanged on the underside of the perforated disk. This flange is realized in such a way that the fastening nut can be turned relative

58、to the perforated disk and the pull-off function of the fastening nut is ensured. This means that the flange must be able to transmit the required pulling forces from the fastening nut to the perforated disk. Such a fastening nut with a flanged perforated disk simplifies the attachment of the fasten

59、ing nut on the mounting part of the wiper arm. The outer circumference of the perforated disk comprises at least two opposing fastening sections or several fastening sections that are distributed over the circumference and project from the perforated disk, with said fastening sections being fastened to the mounting part in preferably positive fashion depending on the design, shape and size of the wiper arm mounting part. The fastening sections can extend axially outward along one side wall of the mounting part, wherein a groove-like recess can also be provided in the sid