Wiper system including an adjustable arm load mechanism

An adjustable arm load mechanism for an automotive windshield wiper is provided in which a load-adjusting linkage assembly is provided between the pivot shaft of the windshield wiper assembly and the wiper arm. The linkage assembly includes a cam member operative with a lever to effect variation of the spring load imposed upon the wiper arm in response to reversing reciprocal rotative movement of the pivot shaft so that wiper arm load is reduced at its extreme positions and increased in its intermediate positions.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The present invention relates generally to devices for controlling the load 
imposed by a windshield wiper to the windshield of an automotive vehicle, 
and more specifically to a mechanism for adjusting such load responsive to 
reciprocal rotative movement of the windshield wiper driving shaft. 
2. Description of the Prior Art 
The problems and technical considerations considered in the setting of the 
forced to be imposed by the wiper arm and a windshield wiper mechanism of 
an automobile to urge the wiper against the windshield are well 
appreciated in the prior art. On the one hand, sufficient loading of the 
wiper is needed to overcome the lifting of the wipers from the windshield 
surface at high vehicle speeds, while on the other hand providing 
sufficient load to overcome the tendency of blades to lift the high speed 
may result in sticking and shattering of the blades under load speed 
operation where the lift is not present to counterbalance the loading 
force imposed at assembly. 
A variety of approaches have been used in the automotive industry to effect 
loading of the wiper arm and hence the wiper blade in the direction of the 
windshield. One of the most common schemes involves the use of an 
extension spring grounded at one end on the wiper arm and at the other end 
on wiper structure through which the wiper arm is rotated. To make the 
force of this spring adjustable in response to the diverse loading 
requirements referred to above, the industry has made a number of attempts 
at devising suitable mechanisms exemplary of such attempts as that shown 
in U.S. Pat. No. 4,698,872 to Watanabe. Such devices have been found to be 
unsuitably heavy and expensive to manufacture, and the Watanabe device in 
particular requires subjected evaluation of the load by the operator of 
the vehicle and actuation of the switch mechanism to effect change in 
load. 
SUMMARY OF THE INVENTION 
The aforementioned deficiencies and others are overcome by the adjustable 
arm load mechanism according to the present invention, which automatically 
and without outside agency of the operator of the vehicle provides 
adjustments of the load of the wiper arm in response to movement of the 
wiper arms so that at the extreme ends of the wiping action when the wiper 
blade must reverse to reciprocate across the windshield load is reduced 
while at the center of the wiping stroke the arm load and hence the load 
of the wiper blade against the windshield may be maximized. 
This is accomplished in a mechanism that includes a longitudinally 
extending pivot shaft that is rotatably reversibly driven with respect to 
the windshield, a wiper arm head drivingly engaging the pivot shaft for 
rotation with it, a wiper arm pivotally mounted on the wiper arm head to 
engage the wiper blade against the windshield, a spring member operatively 
disposed between the wiper head and the wiper arm, and a load adjusting 
linkage assembly interposed between the pivot shaft and the spring member 
to vary the load imposed on the wiper arm between the extreme positions of 
wipe at which the load is minimum and the position intermediate the 
extreme positions in which the load is maximum.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to FIG. 1, an automotive vehicle 10 is illustrated as including 
a body, indicated generally at 12, in which is mounted a windshield 14. A 
windshield wiper system, indicated generally at 16, is provided mounted on 
a portion of the body 12 for cleaning the windshield 14. As is 
conventional, the windshield wiper system includes a wiper blade assembly, 
indicated at 18, that is driven through an arm assembly 20 that is driven 
for reciprocal rotated movement between extreme positions, one being the 
park position shown in FIG. 1, the other being a position moved clockwise 
with respect to a position approximately located as indicated by the 
numeral 22 in FIG. 1. According to the present invention, the arm assembly 
20 is mounted to provide minimum loading of the wiper 18 against the 
windshield 14 at the two extreme positions while providing a maximum 
loading at a point intermediate those two positions. 
Turning next to FIGS. 2 through 5, a preferred embodiment of an adjustable 
arm load mechanism 24 according to the present invention is illustrated. 
The adjustable arm load mechanism 24 is illustrated as including a pivot 
shaft 26 carried in a pivot housing 28 and having a drive end 30 at its 
end. The drive end 30 is illustrated in FIG. 2 as comprising a spline 
connection, but those skilled in the art will appreciate that other drive 
connections may be substituted. Complementary structure to the drive end 
30 is provided in a wiper arm head 32 so that reciprocal rotative movement 
of the pivot shaft 26 effects following movement of the wiper arm head 32. 
At an end of the wiper arm head 32, indicated at 34, displaced from the 
longitudinal axis of the pivot shaft 26, a pivotal connection 36 is 
effected to the longitudinally extending wiper arm 38. A spring member 40, 
preferably an extension spring, is carried within the wiper arm 38 and is 
grounded in a portion of the wiper arm 38 remote from the pivotal 
connection 36 through conventional mechanism (not shown). The inner end 42 
of the spring member 40 is operatively connected to a load-adjusting 
linkage assembly, indicated generally at 44, which is operatively disposed 
between the spring member 40 and the pivot shaft 26. The load-adjusting 
linkage assembly 44 is illustrated as including a cam member 46 carried in 
surrounding relationship with respect to pivot shaft 26, as may best seen 
in FIGS. 3 and 5, and a lever assembly 48. 
The lever assembly 48 includes a lever 50 being mounted for pivotal 
movement to the wiper arm head 32 as by the bolt indicated at 52. The 
lever 50, in the configuration shown in FIG. 2, is mounted for movement 
about an axis generally parallel to the axis of the pivot shaft 26 and 
includes a depending follower member, indicated at 54, which may be 
rotatably mounted at one end 56 of the lever 50. A hook receiving pin 58 
is illustrated as standing upwardly from the lever 50 at the end 60 
opposite the end 56, and a connecting wire 62 extends between the pin 58 
and the end 42 of the spring member 40. 
During operation, as the pivot shaft 26 is rotatably reciprocally driven, 
the load adjusting linkage assembly 48 is carried for movement with the 
wiper arm head 32 so that the follower 54 abuttingly engages the outer 
surface 64 of the cam member 46 continually urged against it by the 
tension load of the spring member 40. As the follower 54 continues along 
the surface 64, its position with respect to the center of the pivot shaft 
26 varies between two extreme positions indicated at 66, 68 closest to the 
pivot shaft 26 center and the position indicated generally at 70 most 
remote therefrom. Movement between the positions 66, 68 and the position 
70 effects pivotal movement of the link 50 and extension of the spring 
member 40 increasing the load imposed by the spring. Since, as is 
illustrated in FIG. 2, the spring effects loading on the arm assembly 20 
below the pivotal connection 36, this effects greater loading of the wiper 
blade 18 against the windshield 14 of the automotive vehicle 10. The 
positions 66, 68 on the cam member 46 are configured to correspond to the 
park position shown in FIG. 1 and the extreme position 22 shown in FIG. 1, 
since at these points the attitude of blade 18, with respect to the 
windshield 14, must reverse for reversing movements of the blade 18. The 
cam configuration shown reduces loading in a desirable fashion. This tends 
to effect reduction in the noise of the wiper blade during reversal. The 
maximization of loading corresponding to the cam position 70 effects an 
increase in loading desirable during the major portion of the sweep of the 
wiper arm assembly 20 to effect sufficient loading to counteract high 
speed lift and to ensure good quality wiping of the windshield by the 
blade 18. 
Turning next to FIG. 6, an alternative embodiment is illustrated in which 
like numbers preceded by the numeral 6 are used to signify parts like 
those described with respect to FIGS. 2-5 configuration. The embodiments 
essentially differ in two respects. One is in the way mounting of the 
load-adjusting linkage assembly is mounted to the wiper arm heads, and the 
way in which driving connection is effected between the wiper arm heads 
and the pivot shaft. 
As to the latter, a drive connection 530 is illustrated as including a nut 
and bolt connection 72 that may include conventional drive connections 
(not shown) for effecting driving connection between the pivot shaft 526 
and the arm head housing 532. The load-adjusting linkage assembly 544 is 
illustrated as including a depending follower 554 rotatable about an axis 
74 parallel to the pivot axis while the adjusting link member 550 is 
pivotally mounted by pin 76 for movement about an axis generally 
perpendicular to the axis of the pivot shaft 526. In the configuration of 
the first described embodiment, it is clearly more vertically compact as 
shown in these views. However, it is appreciated that in certain 
applications, the packaging and mechanical loading requirements of an 
application may make the FIG. 6 configuration more optimal. 
While only two embodiments of the present invention have been shown and 
described, others may occur to those skilled in the automotive windshield 
wiper arts without departing from the scope of the following claims.