Parallel arm windshield wiper assembly

An improved parallel arm windshield wiper assembly is disclosed of the type in which a drive spindle projects through an aperture formed in a windshield. The drive spindle is connected at one end to a motor and has a wiper arm attached to its opposite end. The wiper arm supports a wiper blade which is aligned parallel to a control arm which is also pivotally connected near the outer end of the drive spindle. The ends of the control arm and the wiper arm are connected together by a wiper blade support member which supports a wiper blade. The improvement includes a spacer tube and a sleeve coaxially aligned about the drive spindle with the spacer tube being on the outside. A bracket is mateable with the outer end of the spacer tube and is held in place by a nut threaded onto the sleeve. The bracket is angled outward away from the windshield and has a stud secured to its distal end to which the control arm is pivotally attached. The position of the stud is such that a line drawn between the centerline of the drive spindle and the centerline of the stud combines with the wiper arm, the control arm, and the wiper blade support member to form a parallelogram. This parallelogram permits the wiper blade to maintain a constant orientation throughout its oscillatory sweep of the windshield.

FIELD OF THE INVENTION 
This invention relates to an improved parallel arm windshield wiper 
assembly of the type in which a drive spindle projects through a single 
aperture formed in a windshield. 
BACKGROUND OF THE INVENTION 
Various types of windshield wiper assemblies are currently available for 
motor vehicles. Of the type which extend through a windshield, it is 
common to support and position the wiper arm on a through-the-pane drive 
spindle which is attached to a motor fixed to the inside cab of the 
vehicle. In this design, it is necessary to provide a fixed and correctly 
positioned pivot for a control arm which lies parallel to the wiper arm. 
In order to ensure a correct position of the control arm relative to the 
drive spindle, one prior art patent (Switzerland 244,749) has suggested 
that the control arm supporting shaft also extends through the windshield. 
However, this solution is unattractive because two holes have to be formed 
in the windshield and this is both expensive and creates a region of 
weakness in the windshield. 
For those patents which teach the use of a single drive spindle to control 
both the wiper arm and the control arm, see Great Britain Pat. No. 
1,234,040 and U.S. Pat. No. 3,893,204, there is a problem in that torque 
arising during the operation of the wiper blade causes the drive spindle 
to bend and/or vibrate. When the drive spindle has a bushing around it 
which is snug against the outer circumference of the windshield, the 
vibration is directly transmitted to the windshield and this is 
undesirable. Also, the bending of the drive spindle can disrupt the 
oscillatory sweeps of the wiper blade. Still another solution to having 
only one hole formed in the windshield and still avoid the vibration 
problem is to mount the control arm on a bracket located on the outside of 
the windshield and to secure it to the windshield frame. However, with 
this design it is impossible to ensure a precise alignment between the 
position of the drive spindle which is mounted through the windshield from 
the inside and the control arm bracket which is mounted on the outside of 
the windshield. Any variations in the relative positions of the drive 
spindle to the control arm bracket affects the orientation of the wiper 
blade and/or the end positions of its oscillatory sweep of the windshield. 
By misaligning the wiper blade, the desired sweep surface may be 
unattainable. 
Now an improved parallel arm windshield wiper assembly has been invented 
which resolves the drawbacks present in the prior art. 
SUMMARY OF THE INVENTION 
Briefly, this invention relates to a parallel arm windshield wiper assembly 
of the type in which a drive spindle projects through an aperture formed 
in a windshield. The drive spindle is connected at one end to a motor and 
has a wiper arm attached to its opposite end. The wiper arm supports a 
wiper blade which is aligned parallel to a control arm which is also 
pivotally connected near the outer end of the drive spindle. In addition, 
a wiper blade support member pivotally connects the distal end of the 
wiper arm to the distal end of the control arm. The improvement includes a 
spacer tube and a sleeve coaxially aligned about the drive spindle with 
the spacer tube being on the outside. A bracket is mateable to the outer 
end of the spacer tube and is held in place by a nut threaded onto the 
sleeve. The bracket is angled and has a stud secured to its distal end to 
which the control arm is pivotally attached. The position of the stud is 
such that a line drawn between the centers of the drive spindle and the 
stud combines with the wiper arm, the control arm and the wiper blade 
support member to form a parallelogram which permits the wiper blade to 
maintain a constant orientation throughout its oscillatory sweep on the 
windshield. 
The general object of this invention is to provide an improved parallel arm 
windshield wiper assembly of the type in which a drive spindle projects 
through a single aperture formed in a windshield. A more specific object 
of this invention is to provide an improved parallel arm windshield wiper 
assembly of the type which has a drive spindle passing through a single 
aperture formed in the windshield without imparting vibration produced 
from the movement of the wiper blade back into the windshield. 
Another object of this invention is to provide an improved parallel arm 
windshield wiper assembly which maintains the wiper blade in a set 
orientation throughout its oscillatory sweep on the windshield. 
Still another object of this invention is to provide an improved parallel 
arm windshield wiper assembly which is easy to assemble and install onto a 
motor vehicle. 
Other objects and advantages of the present invention will become more 
apparent to those skilled in the art in view of the following description 
and the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1-3, a glass or plastic windshield 10 is shown 
surrounded by a rubber strip 12 and a frame 14. A mounting plate 16 is 
attached to an upper portion of the inside surface of the frame 12 and has 
a motor 18 bolted to it. Projecting out from the motor 18 is a drive 
spindle 20 having a central axis 22. The drive spindle 20 projects through 
an aperture 24 formed in the windshield 10 and has a splined surface 26 
and a threaded end 28 onto which a wiper arm 30 is fitted. The wiper arm 
30 is secured to the drive spindle 20 by a nut 32. 
Coaxially aligned about the drive spindle 20 is a hollow stationary sleeve 
34 fixed to the motor 18 and having a threaded outer end 36 which tapers 
down in a step-like manner to the circumference of the drive spindle 20. 
Surrounding the sleeve 34 is a spacer tube 38 which has a pair of tabs 40 
and 42 formed on its inner and outer ends, respectively, which project 
outward. The tabs 40 mate with a pair of slots formed in the outer surface 
of the mounting plate 16 while the tabs 42 mate with a pair of slots 
formed in a bracket 44. The bracket 44 is preferably angled outward away 
from the windshield 10, and contains an opening 46 at one end which 
permits the bracket 44 to be positioned about the sleeve 34. The bracket 
44 is held in place against the spacer tube 38 by the tabs 42 and by a nut 
48 threaded onto the end 36 of the sleeve 34. The purpose of the spacer 
tube 38 is to position the bracket 44 at a predetermined distance away 
from the windshield 10 while coaxially aligning and holding the bracket 44 
stationary about the drive spindle 20. By so attaching the bracket 44, 
only one hole 24 has to be formed in the windshield 10 thereby reducing 
machining cost and eliminating the possibility of weakening the glass. 
It should be noted that the inner diameter of the aperture 24 formed in the 
windshield 10 is larger than the outer diameter of the spacer tube 38. 
This size difference ensures that any vibration or bending motion imparted 
into the drive spindle 20 will not be transmitted to the windshield 10. In 
order to seal the aperture 24 a resilient skirt 50, preferably constructed 
of a plastic or rubber material, surrounds the spacer tube 38 and is 
sandwiched between the bracket 44 and the outside surface of the 
windshield 10. The resilient skirt 50 is shown as having a conical 
configuration thereby permitting greater tolerance discrepancy in the size 
of the aperture 24. 
Mounted on an opposite end of the bracket 44 is a stud shaft 52 having a 
central axis 54, see FIG. 3. This stud shaft 52 pivotally supports one end 
of a control arm 56 which is aligned parallel to the wiper arm 30. The 
wiper arm 30 and the control arm 56 are pivotally connected at their outer 
ends 58 and 60, respectively, by a wiper blade support member 62 which has 
a wiper blade 64 mounted on it. These members 30, 56, 62 and 64 are shown 
in schematic form in FIG. 1, since their construction is known to those 
skilled in the art. 
The parallelogram configuration made by the position of the wiper arm 30, 
the control arm 56, the wiper blade support arm 62 and a line drawn 
between the two centerlines 22 and 54 maintains the wiper blade 64 in a 
vertical orientation throughout the oscillatory sweep of the windshield 
10. This provides a desirable shape to the cleaned surface of the 
windshield 10, which is defined at the sides by the limit positions 66 and 
68 of the wiper blade 64 and at the top and bottom by the arcs 70 and 72 
swept out by the tips of the wiper blade 64. 
It should be noted that the distance between the two centerlines 22 and 54 
can be changed by altering the length or shape of the bracket 44. This 
permits the bracket 44 to be formed with sufficient precision in relation 
to the desired dimension between the centerlines, 22 and 54, so that the 
wiper arm 30 is always retained parallel to the control arm 56. 
While the invention has been described in conjunction with a specific 
embodiment, it is to be understood that many alternatives, modifications, 
and variations will be apparent to those skilled in the art in light of 
the aforegoing description. Accordingly, this invention is intended to 
embrace all such alternatives, modifications, and variations which fall 
within the spirit and scope of the appended claims.