AU2017276156B2 - Vehicle Fire Wall Section and Method of Mounting - Google Patents

Abstract

The present invention relates to the field of automotive engineering, more particularly vehicle construction, such as for the conversion of vehicles from left-hand drive to right hand drive and vice versa. The present invention optimises the firewall and replicates as closely as possible the design intention of the original equipment manufacturer (OEM) while altering the position of the steering assembly and brake assembly of a drive conversion vehicle, despite space limitations and inherent asymmetry of the vehicle. 1/8 105 FIG. la 2a 22 21 23 2b 19 x y FIG. lb

Description

1/8

105

FIG. la

2a

22 21

23 2b 19 x

y FIG. lb

P/00/011 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL COMPLETE SPECIFICATION STANDARDPATENT

Application No. 2017276156 Lodged: 11 December 2017

Invention Title: VEHICLE FIRE WALL SECTION AND METHOD OF MOUNTING

The following statement is a full description of this invention, including the best method of performing it known to:

VEHICLE FIRE WALL SECTION AND METHOD OF MOUNTING FIELD OF INVENTION

[0001] The present invention relates to the field of automotive engineering, more particularly vehicle construction.

[0002] In one form, the invention relates to a device and method suitable for the conversion of vehicles from left-hand drive to right-hand drive and vice versa.

[0003] It will be convenient to hereinafter describe the invention in relation to utility trucks, however it should be appreciated that the present invention is not limited to that use only and has a much wider range of applications in the automotive industry.

BACKGROUND ART

[0004] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor's knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein.

Drive Conversion

[0005] Vehicles are manufactured in either left-hand drive or right-hand configurations, the terms 'left' and 'right' referring to the placement of the driving seat and controls within the vehicle. Most countries have legislation that dictates whether cars in the relevant jurisdiction are left-hand or right-hand drive, and it is common for imported cars to have drive conversion to comply with local law. Typically, countries in which cars drive on the left side of the road use right-hand drive vehicles, and countries in which cars drive on the right side of the road countries use left-hand drive vehicles.

[0006] The overall exterior appearance of most vehicles, particularly the chassis, is symmetrical about the longitudinal axis. However, this is not true of most of the interior mechanical fittings due to the placement of driving controls on the left or the right-hand side of the vehicle. The lack of symmetry is particularly inconvenient when a vehicle is changed from left-hand to right-hand drive or vice versa because it is not necessarily possible to simply rotate components and re-fit them. Often, they must be extensively re engineered and re-positioned.

[0007] For example, large numbers of left-hand drive utility trucks are manufactured in the United States of America. The market for right-hand versions of these utility trucks is too small to justify manufacturing any as right-hand drive vehicles. Accordingly, when the left-hand drive utility trucks are exported to countries such as Australia and New Zealand, they must be converted to right-hand drive to comply with local law. During the drive conversion, left-hand parts have to be replaced with right-hand parts made from scratch because they are not available from the manufacturer. The need to manufacture parts tends to make the drive conversion very expensive.

Steering and Brake Assemblies

[0008] The change from left-hand to right-hand drive raises particular problems with respect to refitting various systems and assemblies including the steering assembly and foot braking systems.

[0009] The steering assembly allows the driver to control the direction in which the vehicle travels. The steering assembly includes:

(iii) a steering column, principally including a shaft having an upper end that supports a steering wheel for manual control by the driver,

(ii) a steering box located at a lower end of the steering column and in or adjacent to the engine bay of the vehicle to change rotary movement of the steering wheel in the hands of the drive into linear motion of the vehicle wheels, and

(iii) steering gear consisting of a system of rods and levers connected between the steering box and the vehicle wheels; the steering gear pushes left or right to swivels the wheels, causing the vehicle to turn.

[0010] Safety is a key consideration when changing a vehicle's steering assembly from one side to the other. Government regulatory requirements for steering conversions from left hand drive to right hand drive typically require that in right hand drive configuration:

(a) The mounting strength and geometry of the OEM's left hand drive steering column is replicated in right hand drive configuration.

(b) The features of the left-hand drive steering column designed by the vehicle OEM which allow a controlled collapse if the vehicle is involved in a frontal collision must not be affected.

(c) The telescopic sections of the steering column must not be extended or contracted from the OEM left hand drive manufactured specification.

[0011] The foot brake system comprises a foot pedal, which moves a lever that forces a piston into a long, narrow cylinder filled with hydraulic fluid. As the piston plunges into the cylinder, it squirts hydraulic fluid out through a long and narrow pipe that feeds into separate hydraulic lines connecting to much wider cylinders positioned next to the vehicle wheels. This in turn pushes the piston in the wider cylinder which forces a pad onto a brake disc or drum. The friction of the brake pad on the disk or drum slows the vehicle wheel.

[0012] The majority of road vehicles operate a disc brake system, which also typically includes a brake booster to provide power assist because the force imparted by the driver's foot may not provide sufficient braking force. The brake booster uses vacuum from the engine to multiply the force that the foot applies to the cylinder. The driver's foot on the brake pedal operates a push-rod which passes through the vehicle firewall and contacts the diaphragm of the brake booster located in the engine compartment.

[0013] The steering assembly and brake system is of asymmetric shape and must fit within the confines of the chassis and engine bay. This presents particular problems during drive conversion because there are a number of structural and safety elements of the steering assembly and brake system that cannot be moved or changed in ways that would compromise the safety of the vehicle.

Vehicle Structure

[0014] In particular, many vehicles such as trucks have a frame comprising two boxed or C-cross section rails (known as 'chassis rails'), held together by cross beams (which together resemble a ladder). Typically, a vehicle will have two straight portions of chassis rails on either side of the passenger compartment, adjacent the rocker panels located under each door. The longitudinal axes of these straight sections are necessarily parallel as deviations from parallel compromise safety and integrity of the vehicle if it is involved in an accident. At either end, the chassis rails are no longer straight, but conform to the curve of the wheel arches. At the front end the frame defines a compartment in which the engine is located.

[0015] The driver is separated from the engine compartment by a metal plate called a 'firewall'. The plate is designed as a bulkhead not only to restrain a fire from passing from the engine compartment to the passenger compartment, but to resist the engine being from forced into the passenger compartment in the event of a front-end collision. By necessity, some systems such as elements of the braking system, steering assembly and usually some cabling have to pass through openings in the firewall.

[0016] In particular the steering shaft and brake pedal bracket must pass through the firewall so the driver can control the critical steering and braking functions of the vehicle.

[0017] A new model of a particular vehicle often has relatively small changes when compared to previous models. Thus, the conversion process is more complicated, in that new components need to be made for each model of vehicle to accommodate the new model changes. This increases the complexity of vehicle drive change over and increases manufacturing time and costs.

[0018] Vehicle safety legislation typically prohibits any changes to the frame or firewall that would be detrimental to its performance, particularly in the event of an accident. This severely limits any modifications that may be performed. Furthermore, the engine of most modern vehicles takes up most of the space in the engine compartment, leaving very little room for manoeuvring or repositioning vehicle components. This raises problems for refitting steering assemblies and brake systems when the vehicle is converted to right hand drive or vice versa.

[0019] Accordingly, there is a need to address the problem of vehicle drive side change over.

SUMMARY OF INVENTION

[0020] It would be desirable to provide a device or method to assist in the changeover of the drive side of a vehicle. In particular, it would be desirable to provide a method of changeover from left-hand to right-hand drive.

[0021] It is an object of the embodiments described herein to substantially overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems.

[0022] In a first aspect of embodiments described herein, there is provided a method for converting a left hand drive vehicle into a right hand drive vehicle including the steps of

(1) providing a section of firewall comprising:

(i) a first opening adapted to receive a brake pedal push-rod, the first opening having a periphery located in a first plane, a first focal point and a second focal point; and

(ii) a second opening adapted to receive a steering shaft, the second opening having a periphery located in a second plane, a third focal point and a fourth focal point,

(2) mounting the section of firewall adjacent a chassis rail and a leading edge of a cross beam, such that the second opening is at an angle in a range of 11 to 13 degrees relative to a xy-coordinate plane defined by a y-axis corresponding to the leading edge of the cross beam and an x-axis corresponding to a longitudinal axis of a straight portion of a chassis rail, and at an angle in a range of 21 to 23 degrees relative to an yz-coordinate plane perpendicular to the xy-coordinate plane

[0023] Specifically, the straight portions of the chassis rails have longitudinal axes that are parallel, in the direction of an x-axis. The chassis rails are separated from each other by a cross beam oriented in the direction of a y-axis. The leading edge of the cross beam is coaxial with the y-axis. It will be appreciated by the person skilled in the art that it is fundamental to the construction of a motor vehicle that the straight sections of the chassis rails are parallel. Thus, the straight sections of the two chassis rails lie in an xy-coordinate plane, which plane will be hereinafter referred to as the 'horizontal' plane. It will be appreciated as a fundamental matter of geometry that a z-axis is perpendicular to the x and y axes. Where used herein the reference to a 'vertical plane' is the yz-coordinate plane.

[0024] In use, the section of firewall would be mounted adjacent the chassis rail and the leading edge of the cross beam. Where referred to herein, the firewall mounting point on the chassis rail is used as the reference or'zero' point at which x, y and z axes intersect. Specifically, this reference point is derived from an x-axis in the direction of the upper surface of the chassis rail and a y-axis co-axial with the leading edge of the cross beam.

[0025] In a preferred embodiment the distances between the focal points of the openings and the x, y and z axes, and the angle of the second plane relative to the horizontal and vertical planes are as set out in Table 1:

Table 1

Preferred Preferred Preferred Preferred Preferred Distance to Distance to Distance to Angle with Angle with X-axis Y-axis (mm) Z-axis (mm) XY YZ axis (mm) (horizontal) (vertical plane) plane) First opening 169-198 490-542 344-380 - first/second focal point Second 61-71 508-568 280-317 opening third/fourth focal point Second plane 110-130 21°-23°

Brake Booster (First) Opening

[0026] In a preferred embodiment, the first opening has both focal points in the same location, such as a centroid when the periphery defines a circle.

[0027] Typically, the first opening is a circle of 57 to 64 mm diameter, preferably 60 to 62 mm diameter.

[0028] The location of the first opening is important because if it is mounted too high it may interfere with the cowl - the front part of the vehicle frame that supports the rear of the hood, windshield, dashboard, pedals and instrument panel. If it is positioned too far to one side, it may interfere with the steering shaft. If it is positioned too far to the other side, it may result in insufficient distance between the brake pedal and the accelerator pedal. If positioned too low, it will reduce pedal length which increases actuator force, and deviate from the manufacturer's design and performance specifications.

Steering Shaft (Second) Opening

[0029] In a preferred embodiment, the second opening is an ellipse and the sum of the distances to the two focal points is constant for every point on the periphery. This shape is important for positioning of the steering shaft. For example, it may be important for maintaining adequate steering shaft clearances to the vehicle front suspension shock absorber mounts and the engine to allow mounting of the steering rack or steering box. The shape is also typically important to allow proper deflection of the steering shaft away from the driver in the event of a front end collision.

[0030] Typically, the second opening is an ellipse having a minor axis of 65 to 71 mm diameter, preferably 65 to 702 mm.

Cable (Third) Opening

[0031] Optionally, the firewall section according to the present invention may include a third opening through which cabling or a cable harness may pass. Typically the opening is circular, having a centroid at a distance of 460 to 510 mm (preferably 480 to 490 mm) from the y-axis, 303 to 333 mm (preferably 315 to 320 mm) from the x-axis, and 344 to 380 mm (preferably 360 to 365 mm) from the z-axis.

[0032] The third opening is typically circular and of 60 to 120 mm in diameter, preferably to 110 mm diameter.

[0033] Typically, the firewall section includes multiple mounting means, such as holes in the flanges, so that it can be located in front of the driver's seat and attached to the remainder of the firewall located in front of the front passenger seat.

[0034] In another aspect of embodiments described herein, there is provided a steering assembly modified according to a method as disclosed herein.

[0035] Other aspects and preferred forms are disclosed in the specification and/or are defined in the appended claims, forming a part of the description of the invention.

[0036] In essence, embodiments of the present invention stem from the realization that it is possible to optimise the firewall and replicate as closely as possible the design intention of the original equipment manufacturer (OEM) while altering the position of the steering assembly and brake assembly of a drive conversion vehicle, despite space limitations and inherent asymmetry of the vehicle.

[0037] Advantages provided by the present invention comprise the following:

a. the major part of the OEM firewall may be reused, thus avoiding the expense of custom making a new firewall;

b. the modified steering assembly can work with the existing, manufacturer installed OEM systems that control the vehicle;

c. the modified firewall section maintains adequate steering shaft clearances so that there is proper deflection of the steering shaft in the event of a front end collision;

d. the distances and pedal lengths between the brake and accelerator pedals can be maintained at their OEM values which is critical for maintaining the same actuation force (pedal length of brake pedal is shortened);

e. the firewall of the present application may be used in more than one model of vehicle - thus streamlining components and costs associated with new components.

[0038] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein.

[0040] For purposes of description herein, the terms "upper," "lower," "right," "left," "rear," "front," "vertical," "horizontal," "interior," "exterior," and derivatives thereof shall relate to the invention as oriented in FIG. 5. However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawing, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. Additionally, unless otherwise specified, it is to be understood that discussion of a particular feature of component extending in or along a given direction or the like does not mean that the feature or component follows a straight line or axis in such a direction or that it only extends in such direction or on such a plane without other directional components or deviations, unless otherwise specified.

FIG. 1 is a side plan view of a typical vehicle chassis of the type used in utility trucks such as, but not limited to, a Ford F-250 illustrating the position of the section of firewall according to the present invention;

FIG. 2 is a top plan view of the vehicle of FIG. 1 illustrating the horizontal orientation of the section of firewall according to the present invention;

FIG. 3 is a front perspective plan view of the vehicle of FIG. 1 illustrating the angle and position of the section of firewall according to the present invention;

FIG. 4 is the section of firewall of FIGS. 1 to 4 shown in isolation in front perspective view;

FIG. 5 illustrates a perspective vies of the orientation of a chassis rail relative to the cross beam and the section of firewall depicted in FIG. 4;

FIG. 6 is a top view of the structural elements shown in perspective view in FIG. 5;

FIG. 7 is a front view of the structural elements shown in perspective view in FIG. 5.

FIG. 8 is a side view of the structural elements shown in perspective view in FIG. 5.

[0041] List of parts referred to the illustrations:

1 vehicle 2 chassis rail (2a right chassis rail; 2b left chassis rail) 3 firewall 4 wheel front bumper 6 front windscreen 7 rear bumper 8 wing mirror 9 front wheel arch 10 rear wheel arch 11 passenger/driver compartment 16 first opening (brake booster opening) 13 engine compartment 14 second opening (drive shaft opening) 15 tray 12 third opining (wiring harness opening) 17 engine 18 passenger end of firewall 3 19 cross beam 21 front cross beam 22 right suspension bracket 23 left suspension bracket

DETAILED DESCRIPTION

[0042] FIG. la is a side plan view of vehicle 1, more specifically a truck such as, but not limited to, a Ford T M F150 or SuperDuty that has been converted from left hand drive to right hand drive. The vehicle 1 includes a frame comprising two parallel boxed rails known as chassis rails of which one chassis rail 2 can be seen in this view. FIG. lb depicts the both chassis rails 2a, 2b which are located on either side of the vehicle and the front cross beam 21 and cross beam 191 that separate them. Typically a vehicle will have two straight portions of chassis rail 2 on either side of the passenger compartment 11, adjacent the rocker panels. At either end, the chassis rails are no longer straight, but conform to the curve of the wheel arches. The chassis rails terminate inside the front bumper 5 and rear bumper 7 respectively. Vehicle safety legislation typically prohibits any changes to the frame that would be detrimental to its performance, particularly in an accident.

[0043] In this view the longitudinal axis of the straight section of the chassis rails are parallel to the x-axis and are parallel and separated in the direction of the y-axis. Thus, the two chassis rails lie in the xy-coordinate plane, which plane will be hereinafter referred to as the 'horizontal' plane. The perpendicular yz-coordinate plane is referred to as the 'vertical' plane.

[0044] In this view it can be seen that the section of firewall according to the present invention is oriented at an acute angle relative to the vertical plane.

[0045] FIG. 2 is a top plan view of the vehicle of FIG. 1 illustrating the position of the section of firewall 3 on the driver's side of the vehicle.

[0046] FIG. 3 is a front perspective plan view of the vehicle of FIG. 1 illustrating the angle and position of the steering box. In this view it is also possible to see the position of the steering box 9 relative to the engine 17 and the vehicle chassis. The steering box may be supported by a bracket of plate that is attached to the chassis.

[0047] FIGS. 4a and 4b depict the section of firewall 3 according to the present invention as shown in FIGS. 1 to 3. In this view can be seen a first opening (brake booster opening) 16 adapted to receive a brake pedal push-rod located between a brake pedal inside the passenger/driver compartment and a brake booster inside the engine compartment. In this embodiment the opening is circular, having a centroid 16a (or a first focal point and second focal point at the centroid position) and the periphery of the opening lies on a first plane.

[0048] In this view there can also be seen a second opening (steering shaft opening) 14 adapted to receive steering shaft. In this embodiment the second opening is elliptical in shape, having a third focal point 14a and a fourth focal point 14b, with its periphery lying in a second plane.

[0049] In this embodiment the section of firewall 3 includes a third opening (cable opening) 12, having a centroid 12a. The third opening typically receives communications and control wiring including a wiring harness for cables.

[0050] In this embodiment, the first plane is provided at an angle of 90deg relative to XY and 0 deg relative to YZ planes.

[0051] FIG. 5 illustrates the orientation of a chassis rail 2 relative to the cross beam 1 and the section of firewall 3. The section of firewall 3 is not attached in this view, but is merely shown separately in the preferred orientation relative to the chassis rail 2 and cross beam 1.

[0052] In use, the section of firewall 3 would be mounted adjacent the chassis rail 2 and the leading edge of the cross beam 19a. Where referred to herein, the mounting point is used as the reference or'zero' point at which x, y and z axes intersect. Specifically, this reference point is derived from an x-axis in the direction of the upper surface of the chassis rail 2 and a y-axis in the direction of the leading edge 19a of the cross beam 19.

[0053] As shown in the drawings, for reference, a vertical plane is defined by the y and z axes and a horizontal plane is defined by the y and x axes.

[0054] FIG. 6 is a top view of the structural elements shown in perspective view in FIG. 5. Intended to illustrate typical distances and orientation of the firewall 3 relative to the chassis rail 2 and the cross beam 18 when the firewall is mounted. Specifically, the distances (typically +/- 5%) are preferably as follows:

• the distance (a) from focal point 14a to the y-axis is 535 mm

* the distance (b) from focal point 14b to the y-axis is 541 mm

• the distance (d) from centroid 16a to the y-axis is 485 mm

[0055] While the position of the third opening for cables is not an essential feature, in this embodiment the distance (c) from centroid 12a of the third opening to the y-axis is 516 mm.

[0056] FIG. 7 is a front view of the structural elements shown in perspective view in FIG. 5, intended to illustrate typical distances and orientation of the firewall 3 relative to the chassis rail 2 and the cross beam 18 when the firewall is mounted. Specifically, the distances (+/- 5%) are preferably as follows:

• the distance (e) from focal point 14a to the x-axis is 68 mm

* the distance (f) from focal point 14b to the x-axis is 64 mm

• the distance (g) from centroid 12a to the x-axis is 318 mm

• the angle between the plane of the second opening and the z-axis is 120.

[0057] While the position of the third opening for cables is not an essential feature, in this embodiment the distance (h) from centroid 16a of the third opening to the x-axis is 178 mm.

[0058] FIG. 8 is a side view of the structural elements shown in perspective view in Fig. , intended to illustrate typical distances and orientation of the firewall 3 relative to the chassis rail 2 and the cross beam 18 when the firewall is mounted. Specifically, the distances and angles (+/- 5%) are preferably as follows:

• the distance (i) from focal point 14a to the z-axis is 362 mm

* the distance (j) from focal point 14b to the z-axis is 337 mm

* the distance (k) from centroid 12a to the z-axis is 302 mm the angle between the plane of the first opening and the z-axis is 220.

[0059] While the position of the third opening for cables is not an essential feature, in this embodiment the distance (I) from centroid 16a of the third opening to the z-axis is 285 mm.

[0060] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

[0061] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive.

[0062] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures.

[0063] Each of the words "comprises" and "comprising" and "includes" and "including" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and claims of this specification, the words "comprise", "comprising", "includes", "including", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Claims (5)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for converting a left-hand drive vehicle into a right-hand drive vehicle, including the steps of:

(1) providing a section of firewall comprising:

(i) a first opening adapted to receive a brake pedal push-rod, the first opening having a periphery located in a first plane, a first focal point, and a second focal point, and

(ii) a second opening adapted to receive a steering shaft, the second opening having a periphery located in a second plane, a third focal point, and a fourth focal point, and

(2) mounting the section of firewall adjacent a chassis rail and a leading edge of a cross beam, such that the second opening is at an angle in a range of 11 to 13 degrees relative to a xy-coordinate plane defined by a y-axis corresponding to the leading edge of the cross beam and an x-axis corresponding to a longitudinal axis of a straight portion of the chassis rail, and at an angle in a range of 21 to 23 degrees relative to an yz-coordinate plane perpendicular to the xy-coordinate plane

2. A method according to claim 1, wherein the first focal point and/or the second focal point of the first opening is located at a distance in a range of 169 to 198 mm from the x axis, 490 to 542 mm from the y-axis, and 344 to 380 mm from the z-axis.

3. A method according to claim 1 wherein the third focal point and/or the fourth focal point of the second opening is located at a distance in a range of 61 to 71 mm from the x axis, 508 to 568 mm from the y-axis, and 280 to 317 mm from the z-axis.

4. A steering assembly modified according to a method as claimed in any one of claims 1 to 3.

5. A portion of vehicle firewall when used according to the method of claim 1.