WO2002004266A2

WO2002004266A2 - Beam blade wiper assembly having varying cross-section

Info

Publication number: WO2002004266A2
Application number: PCT/US2001/021495
Authority: WO
Inventors: Jeffrey Stewart; William Young, Iii
Original assignee: Trico Products Corporation
Priority date: 2000-07-06
Filing date: 2001-07-06
Publication date: 2002-01-17
Also published as: AU2001271900A1; WO2002004266A3

Abstract

A beam blade windshield wiper assembly including an elongated backbone (12) having a longitudinal beam length extending between first (20) and second (22) longitudinal ends of the backbone (12) with a longitudinal center therebetween. The backbone (12) also has an upper surface (26) and an opposed mounting surface (28) with first (30) and second (32) sides extending between the upper surface (26) and the mounting surface (28). A wiper element (14) is mounted to the mounting surface (28) of the backbone (12) and extends for a substantial portion of the longitudinal beam length. The distance between the upper surface (26) and the mounting surface (28) on said backbone (12) defines a thickness thereof and the distance between the first (30) and second (32) sides defines the width of the backbone. The thickness and width of the backbone (12) is constant along the longitudinal length of the backbone (12). At the same time, however, the backbone (12) defines a cross-sectional area which varies along the length of said backbone (12) to selectively determine the force distribution of the beam blade windshield wiper assembly.

Description

BEAM BLADE WIPER ASSEMBLY HAVING VARYING CROSS-SECTION

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, generally, to windshield wiper assemblies and, more specifically, to a beam blade windshield wiper assembly having an elongated, curved backbone with constant thickness and constant width but which has a varying transverse cross-section to determine the force distribution along its length.

2. Description of the Related Art

Conventional windshield wiper assemblies known in the related art include some type of blade assembly mounted to an arm which, in turn, is mounted adjacent to the windshield and pivotally driven to impart reciprocating motion to the wiper blade assembly across the windshield. A rubber wiping element is supported by the blade assembly and contacts the windshield across the surface to be wiped. The wiper element often incorporates one or more metal strips which act to reinforce the wiper element and facilitate wiping contact by the element across what is typically a curved glass surface. One type of blade assembly commonly employed in the related art includes a

"tournament" style superstructure including a primary lever carried by the arm, two or more secondary levers and a series of two or more tertiary levers. The secondary levers are articulated to the primary lever at pivot points located at the opposed, lateral ends of the primary lever. Similarly, the tertiary levers are each articulated to a secondary lever at pivot points located at the opposed lateral ends of the secondary levers. Tournament style windshield wiper assemblies often utilize steel vertebra which are mounted relative to the wiper element to provide a force distribution of the wiper element against the glass. The steel vertebra typically have a uniform cross-sectional area throughout the length of the wiper element. Optimization of the force distribution is accomplished by forming the vertebra to a desired range of free form radii. Based on the range of curvature desired, an offset distance can also be calculated to characterize the vertebra curvature. Traditionally, the curvature of the vertebra has been symmetrical about the horizontal centerline of the windshield wiper assembly. The maximum offset distance is usually located at the lengthwise center of the vertebra. However, the vertebra material, vertebra cross- sectional area and the ability to form a uniform and symmetrical radius of curvature have limited the complete optimization of the force distribution of the wiping element against the windshield. As noted above, the blade assembly is located on the end of the wiper arm and represents a significant portion of the inertia generated by the wiping system when in operation. Furthermore, the profile of the blade assembly as it is reciprocated across the windshield is an important design consideration with respect to avoiding wind lift at higher vehicle speeds. In addition, since components of the windshield wiping system are often visible, even when not in operation, the aesthetic appearance of the components of the system is an important design consideration.

Beam blade type windshield wiper assemblies are also known in the art. The beam blade type windshield wiper includes a single elongated, homogeneous strip forming a spring backbone. The backbone has a connecting formation at a central position for connection to a reciprocally driven arm which applies a downward force and moves the blade assembly across the windshield. The backbone is curved along a single plane which is the same plane of curvature as that defined by the windshield. A wiper element is secured to the backbone. Examples of beam blade type windshield wipers can be found in United States Patent No. 5,325,564 issued July 5, 1994, and 5,485,650 issued January 23, 1996, both in the name of Swanepoel.

The beam blade backbone disclosed in the Swanepoel '650 and '564 patents is made from spring steel and preferably tapers in width from its center towards its free ends or tips. 5 Swanepoel teaches that the thickness and width of the backbone and its radius of curvature should be matched along the length of the backbone so that the backbone will provide a force per unit length distribution in a longitudinal direction which increases towards both tips of the windshield wiper when the windshield wiper is in use, pressed downward intermediate its ends onto a flat surface. Beam blade wiper assemblies have the advantages of a lower profile as l o compared with tournament style wiper assemblies, consist of fewer parts and are considered to be aesthetically pleasing.

However, while beam blade windshield wiper assemblies have gained in popularity, they are difficult to manufacture. More specifically, the Swanepoel '564 and '650 type beam blade windshield wiper assemblies teach the use of backbones that may have both varying thickness

15 and varying width. The manufacture of a beam blade backbone having a free-form radius of curvature along its longitudinal axis as well as both varying thickness and varying width presents certain challenges. Special metal forming machinery must be developed for this purpose which ultimately increases the cost of the beam blade windshield wiper assembly.

Accordingly, there continues to be a need in the art for windshield wiper systems having a 0 low profile with improved wind-lift characteristics and improved performance while maintaining simplicity of parts and a desired aesthetically pleasing appearance. At the same time, there is a need for a beam blade type wiper assembly having improved force distribution characteristics of the backbone against the windshield while maintaining a constant width and thickness of the backbone and at the same time reducing manufacturing costs of the assembly. SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages in the related art by providing a beam blade windshield wiper assembly including an elongated backbone having a longitudinal beam length extending between first and second longitudinal ends of the backbone with a longitudinal center therebetween. The backbone also has an upper surface and an opposed mounting surface with first and second sides extending between the upper surface and the mounting surface. A wiper element is mounted to the mounting surface of the backbone and extends for a substantial portion of the longitudinal beam length. The distance between the upper surface and the mounting surface on said backbone defines a thickness thereof and the distance between the first and second sides defines the width of the backbone. The envelope profile thus defined by such thickness and width of the backbone is substantially constant along the entire longitudinal length of the backbone. At the same time, however, the backbone configuration is characterized by a cross-sectional area of backbone material which varies along the length of said backbone to selectively vary the force distribution of the beam blade windshield wiper assembly.

One advantage of the present invention is that it provides a beam blade windshield wiper assembly having optimum force distribution characteristics. More specifically, the beam blade windshield wiper assembly of the present invention provides an increasing force distribution from the center of the backbone to its longitudinal ends which increases the ability of the wiper element to conform to the windshield. On the other hand, the backbone enjoys increased stiffness near the longitudinal center as compared to the ends of the backbone.

Another advantage of the windshield wiper assembly of the present invention is that it has a low profile and thus enjoys improved wind-lift characteristics when compared to conventional "tournament" style windshield wiper assemblies known in the related art. Still another advantage of the present invention is that it has a limited number of parts, is aesthetically pleasing in appearance while at the same time providing improved performance. Still another advantage of the present invention is that the backbone of the beam blade has a constant envelope thickness and width which reduces the cost to manufacture the windshield wiper assembly of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: Figure 1 is a partial plan view of the front of an automotive vehicle illustrating the beam blade wiper assembly of the present invention;

Figure 2 is a perspective view of a first embodiment of the present invention; Figure 3 is a cross-sectional view taken along lines 3-3 of Figure 2; Figure 4 is a cross-sectional view taken along lines 4-4 of Figure 2; Figure 5 is a plan view of the first embodiment.

Figure 6 is a plan view of a second embodiment of the present invention; Figure 7 is a plan view of a third embodiment of the present invention; and Figure 8 is a plan view of a fourth embodiment of the present invention.

DETAILED DESCRDPTION OF THE PREFERRED EMBODLMENT(S)

Referring now to Figures 1-4, a beam blade wiper assembly of the present invention is generally indicated at 10 where like numbers are used to designate like structure throughout the drawings. The beam blade wiper assembly 10 includes a backbone 12 and a wiper element 14. As illustrated in Figure 1, the beam blade wiper assembly 10 is controlled and driven by a spring loaded arm 16 (shown in phantom) mounted adjacent the windshield 11 of a vehicle and pivotally driven to impart reciprocating motion to the beam blade wiper assembly 10 across the windshield 11, as commonly known in the art. The backbone 12 has a centrally located connector schematically indicated at 18 for releasably connecting the wiper assembly 10 to the spring loaded wiper arm 16. The connector 18 can be of any suitable design. However, those having ordinary skill in the art will appreciate that the connection may be located off center and brazed toward either first or second ends 20, 22, respectively.

The elongated backbone 12 has a longitudinal beam length extending between first and second ends 20, 22. The beam length defines a median line 24 extending along the beam length. The connector portion 18 is located at an intermediate position, commonly at the longitudinal center, between the first and second longitudinal ends 20,22. The backbone 12 is of resiliently flexible material which applies a force from the spring loaded wiper arm 16 through the connecting portion 18 along the backbone's length to the first and second longitudinal ends 20, 22. The backbone 12 is typically made of a single, integral piece of material such that it defines a consolidated cross-section. Alternatively, the backbone 12 may be formed into a single piece by laminates.

The backbone 12 includes an upper surface 26 and an opposing mounting surface 28 with first and second sides 30, 32 extending therebetween. In the preferred embodiment, the cross- section of the backbone 12 has a generally rectangular outer profile making the first and second sides 30, 32 generally perpendicular to both the upper surface 26 and mounting surface 28. However, those having ordinary skill in the art will appreciate that the cross-section may have any suitable geometric shape. The backbone 12 has a width defined as the linear distance along a width line W drawn between the first and second sides 30, 32 and perpendicular to the median line 24. In the preferred embodiment, the width W of the backbone 12 is constant from the longitudinal center to the longitudinal ends 20, 22. Therefore, the width W is constant for substantially the entire longitudinal extent of the backbone between the first and second ends 20, 22. The thickness of the backbone 12 is defined by the linear distance of a line t extending perpendicular to the width between the upper surface 26 and mounting surface 28 (Figure 3). As with its width, the thickness t of the backbone 12 of the beam blade windshield wiper assembly 10 of the present invention is substantially constant along the longitudinal beam length extending between the first and second ends 20, 22 of the backbone 12. Because the width W and thickness t of the backbone 12 is constant, the backbone 12 is easier to manufacture. More specifically, the tools and roll forming machinery used to manufacture the backbone 12 are less complicated than that required to manufacture backbones having varying widths and/or thicknesses.

As best shown in FIGS. 3 and 4, the preferred wiper element 14 has a spine 34, a tip portion 36 and a hinge 38 interconnecting the spine 34 and the tip 36. The tip portion 36 has a "delta" shape in cross-section and is the working end of the wiper element 14 which is operable for wiping action against a glass windshield surface. The hinge 38 allows the tip portion 36 to pivot slightly with respect to the glass surface of the windshield 11 thereby improving wipe quality. The arm 16 includes a biasing mechanism (not shown) such as a spring that creates a force which is distributed to the wiper element 14 through the superstructure to clean the windshield. The wiper element 14 is mounted to the lower surface 28 of the backbone 12 and this may be accomplished in a number of different ways such as by mechanical mounting mechanisms, chemical mounting mechanisms, such as adhesives, or any other suitable mechanism known in the related art. Furthermore, while the wiper element 14 illustrated in the figures has a spine 34, a delta shaped tip portion 36 and a hinge 38, those having ordinary skill in the art will appreciate these components of the wiper element 14 may differ from that disclosed in the figures without departing from the scope of the invention. The backbone 12 is curved longitudinally with a predetermined radius of curvature parallel to the plane of curvature of the windshield 11 and is sometimes referred to in the related art as a "free form" radius of curvature (hereinafter "windshield curvature"). An x-y plane is defined by a cross section taken longitudinally along the median line 24 and through the backbone 12 and wiper elementl4, with the x-axis extending tangentially to the median line 24 at the center of the backbone 12 at connector point 18 and the y-axis extending through the cross- section of the backbone 12 and wiper element 14. The z-axis extends perpendicular to the x-y plane in the direction of the width line drawn at the center or connecting portion 18. The curvature of the backbone 12 in the x-y plane may be symmetrical or asymmetrical depending on the force requirements and the contour of the windshield 11. The flexible, free form, pre-curved backbone 12 straightens out when the wiper arm 16 applies a force thereto to flatten the backbone 12 on a windshield 11. Thus, the backbone 12 must have adequate free-form curvature to ensure a good force distribution on windshields having various curvatures and to effect proper wrapping about the windshield 11. To this end, the disclosure of United States Patent Nos. 5,325,564 and 5,485,650, issued to Swanepoel are incorporated herein by reference. The backbone 12 must also have high lateral stiffness to avoid chatter caused when a backbone's lateral deflection causes stick/slip behavior of the rubber wiper element 14 on the windshield 11. Lateral stiffness is provided mainly by the width of the backbone 12. Furthermore, the backbone 12 must have high torsional stiffness to avoid chatter due to torsional deflection. The torsional stiffness is provided mainly by the thickness of the backbone 12.

The thickness and width of the backbone 12 define a cross-sectional area which is determined by the equation:

A = W* t. The bending moment of a beam blade along its longitudinal length may be determined using the following equations:

M = C I E and I = V5> w t? where: M is the bending moment or force;

C is the curvature of the longitudinal axis (x); I is the moment of inertia for the cross-section; E is the modulus of the material; w is the width; and t is the thickness.

The present invention achieves a targeted force distribution by selective adjustment of the bending moment through altering the Section Moment of Inertia I of the backbone 12. More specifically, the present invention provides for selective reductions in the cross sectional area by removing material internal to a given width profile progressively along the length of the backbone. Therefore, the effective width "W" in the previous equation is varied by changing the material cross-sectional area such that the equation for the moment of inertia I for a given cross- section becomes:

where W, represents the material which has been removed from the cross-section (see Figure 4). Force distribution of the beam blade windshield wiper system of the present invention is optimized by targeting a reduction of the cross-section of the backbone 12 along its length thereby reducing the stiffness of the backbone 12 to achieve a non-symmetrical or localized distribution of the downwardly directed wiper arm force. The reductions in the backbone's cross- section may be symmetrical or asymmetrical along the longitudinal length of the backbone 12 about the longitudinal center. Typically, the reductions are in the form of opening in the backbone 12 which are caused by a removal of material from the backbone 12 thereby altering the backbone cross-sectional area "A" without altering the envelope profile, i.e., the predetermined linear distances of the width W and thickness t of the backbone. As best shown in Figure 4, the reductions 40 may define openings through the backbone 12 having straight sides 42, 44 extending from the upper surface 26 to the mounting surface 28. In this way, the designer may form multiple or non symmetrical radii along the longitudinal length of the backbone 12. Furthermore, by targeting the reduction in the cross-sectional area A of the backbone 12 in combination with a predetermined free form radius of curvature of the backbone, a localized or asymmetrical force distribution may be achieved. Moreover, a backbone 12 having sections of reduced material may be employed with minimal free form radius of curvature for the backbone 12 while still achieving the desired force distribution. In either event, the beam blade windshield wiper assembly 10 of the present invention results in an increase in the ability to match the curvature of the windshield thereby improving wiper blade performance.

Figures 5-8 illustrate the various geometric embodiments of the reductions 40, 140, 240, 340, in the cross-section of representative backbones 12, 112, 212 and 312, respectively. The exact shape of the cross-section reductions 40, 140, 240, 340 are representative only, and it is to be understood that other geometries are possible under the teachings of the invention.

The first embodiment illustrated in Figures 1-5 show rectangular openings 40 of increasing length and increasing width from the center to the longitudinal ends 20, 22. The openings are symmetrical about the longitudinal center of the backbone 12. A larger percentage of the cross-section is taken out by the openings 40 near the longitudinal ends 20, 22 than near the longitudinal center such that the reduction in cross-sectional area is approaching 78% at the longitudinal ends 20, 22. This x-section area reduction allows for an incrementally decreasing stiffness along the longitudinal axis from the center to end 20, 22. This ability to reduce stiffness allows for optimization of curvature as compared to a beam with uniform W and t and also increases the ability of the wiper element 14 to conform to the windshield. On the other hand, the backbone 12 enjoys increased stiffness near the longitudinal center as compared to the ends 20, 22.

A second embodiment is illustrated in Figure 6. The backbone 112 includes oval openings 140 which are symmetrical about the longitudinal center. The third embodiment illustrated in Figure 7 shows a backbone 212 having rectangular openings 240 which are symmetrical about the longitudinal center. In both embodiments of Figures 6 and 7, the center of the openings 140, 240 generally increase along the longitudinal length of the backbonel 12, 212. At the same time, the width varies in an increasing manner along the length of the backbone 112, 212 toward the longitudinal ends 20, 22.

Figure 8 illustrates a fourth embodiment utilizing a backbone 312 which includes asymmetrical openings 340 about the longitudinal center. However, like the embodiments discussed above, the openings 340 increase in length and width along the longitudinal length of the backbone 312 from the center to its ends 20, 22. As illustrated in this figure, the openings 340 are formed in only one side of the backbone 312 from the center toward the end 22. These different embodiments illustrate that the shape, location and size of the reductions in cross- section may be altered depending on the performance or aesthetic characteristics desired. The reductions 40, 140, 240, and 340 may be effected using a stamping process or any other suitable method of manufacture commonly known in the art. Thus, the present invention provides a beam blade windshield wiper assembly having optimum force distribution characteristics. More specifically, the beam blade windshield wiper assembly of the present invention has an increased force distribution from the center of the backbone 12 to its longitudinal ends 20, 22 which increases the ability of the wiper element 14 to conform to the windshield. On the other hand, the backbone 12 enjoys increased stiffness near the longitudinal center as compared to the ends 20, 22 of the backbone 12.

The beam blade windshield wiper assembly 10 of the present invention has a low profile and thus enjoys improved wind-lift characteristics when compared to conventional "tournament" style windshield wiper assemblies known in the related art. Furthermore, it has a limited number of parts, is aesthetically pleasing in appearance while at the same time providing improved performance. Finally, because the backbone 12 of the beam blade has an envelope profile which is of constant thickness and width, the cost to manufacture the windshield wiper assembly of the present invention is less than other beam blade style windshield wiper assemblies known in the related art.

The invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.

Claims

I CLAIM

1. A beam blade windshield wiper assembly comprising: an elongated backbone having a longitudinal beam length extending between first and second longitudinal ends of said backbone, an upper surface and an opposed mounting surface with first and second sides extending between said upper surface and said mounting surface and a wiper element mounted to said mounting surface of said backbone and extending for a substantial portion of said longitudinal beam length; the distance between said upper surface and said mounting surface on said backbone defining a thickness thereof and the distance between said first and second sides defining a width of said backbone, said thickness and said width of said backbone being substantially constant along the longitudinal length of said backbone but wherein said backbone defines a cross- sectional area which varies along the length of said backbone.

2. A beam blade windshield wiper assembly as set forth in claim 1 wherein said backbone includes predetermined reductions in said cross-sectional area which are selectively located at predetermined positions along said longitudinal length to vary the force distribution of said beam blade windshield wiper assembly against the windshield.

3. A beam blade windshield wiper assembly as set forth in claim2 wherein said reductions in said cross-sectional area of said backbone are symmetrical along said longitudinal length of said backbone about the longitudinal center.

4. A beam blade windshield wiper assembly as set forth in claim 2 wherein said reductions in said cross-sectional area of said backbone are asymmetrical along said longitudinal length of said backbone about the longitudinal center.

5. A beam blade windshield wiper assembly as set forth in claim 2 wherein said reductions in said cross-sectional area of said backbone define openings in said backbone.

6. A beam blade windshield wiper assembly as set forth in claim 1 wherein said backbone defines an X-axis extending in the direction of said longitudinal beam length, a Y- axis extending transverse to said X-axis and through said upper surface and said mounting surface so as to define an X-Y plane and a Z-axis extending perpendicular to said X-Y plane; and said backbone being curved in said X-Y plane.

7. A beam blade windshield wiper assembly as set forth in claim 1 wherein said backbone includes a connecting portion disposed intermediate said first and second ends for receiving a wiper arm.

8. A beam blade windshield wiper assembly as set forth in claim 7 wherein said connecting portion is located at said longitudinal center of said backbone.

9. A beam blade wiper assembly as set forth in claim 1 wherein said backbone is a unibody member.

10. A beam blade wiper assembly as set forth in claim 1 wherein said backbone is substantially coextensive with said wiper element.