Patent Application
20160091041
This application claims benefit of Canadian patent application number 2,865,386, filed Sep. 26, 2014, which is herein incorporated by reference.
The present invention relates generally to textured material, and more particularly to textured material with pointed structures extending from a surface of the material.
Laminates are used in various applications (e.g. building materials, panels for automotive applications, large scale industrial parts). In making laminated materials, it is common to use adhesive to join the laminae. However, adhesives have many known deficiencies. They are expensive, messy and emit noxious fumes. Many typical adhesives used for laminating heterogeneous materials are also prone to failure or shattering/cracking under various stresses (temperature, bending, cutting). Further, adhesives are undesirable from an environmental point of view as they foul the underlying materials and prevent recycling or reclamation of the laminae. It would be desirable to avoid the use of adhesive without compromising the strength of the laminate.
Vehicles with disc brake pads use friction to stop. Such disc brake pads are a laminate with one lamina being a stiff backing plate, usually of steel, and second lamina being a hard-wearing friction material. Such brake pads fit into a stationary caliper that hydraulically clamps them with enormous force against a rotating disc (“rotor”) whereby the vehicle is slowed by the resulting friction. The high temperatures and pressures wears away (ablates) the friction material over time.
The friction generates a very high shear force between the friction material and the plate. It follows that the means of attachment of the mineral-based friction material to the metal-based plate is extremely important for safe and reliable braking. Similar concerns exist for laminates subject to shear forces generally.
The friction material generally begins as a powder comprising a complex mixture of minerals, fibres and binders that is hot-compressed onto the plate. Adhesives and/or holes, hooks, weldments and other ant-shear features in, on or through the plate, are conventionally used to securely attach the friction material to the plate.
In a first aspect, the present invention provides a differentially textured workpiece comprising a workpiece made of a ductile material with a substantially flat face. Multiple rows of integral raised barbs are on the flat face. A first group of the barbs are at least 10% higher, relative to the substantially flat face, than a second group of barbs. The first group of barbs includes at least 10% of the barbs, and the second group of barbs includes at least 10% of the barbs.
Preferably, the first group of barbs includes at least 25% of the barbs, and the second group of barbs includes at least 25% of the barbs.
Preferably, the barbs are curved. The barbs in the second group of barbs may be bent so that they are not straight and not deformed. Alternatively, the barbs in the second group of barbs may be deformed so that they have a flattened distal end.
Preferably, the height variation of the barbs forms a regular pattern.
The ductile material is preferably steel, and the base workpiece may be a sheet of steel.
The base workpiece may be a disc brake backing plate, and the barbs may be configured to receive and retain friction material.
Each barb in the first group of the barbs may be at least 25% higher than each barb in the second group of barbs. Each barb in the first group of barbs may be at least 50% higher than each barb in the second group of barbs.
The first group of barbs may include at least 40% of the barbs, and the second group of barbs may also include at least 40% of the barbs. Also, each barb in the first group of barbs may be at least 25% higher than each barb in the second group of barbs.
In a second aspect, the invention provides a brake pad including a differentially textured steel workpiece and a friction element. The steel workpiece is configured to be a disc brake backing plate and has a substantially flat face with rows of integral raised barbs. The heights of the barbs above the substantially flat face vary substantially. The friction material is adhered to the textured face of the differentially textured workpiece to form a brake pad. Preferably a first group of barbs are at least 10% higher than a second group of barbs, the first group of barbs includes at least 10% of the barbs, and the second group of barbs includes at least 10% of the barbs.
In a third aspect, the invention provides a method of making a differentially textured workpiece. The method is applied to a base workpiece made of ductile material having a flat face. The flat face of the base workpiece is first textured with rows of integral raised barbs having substantially the same height relative to the flat face. Then, a second group of barbs is reshaped to substantially reduce the height of each barb in the second group of barbs relative to each barb in a first group of barbs.
In this method, the reshaping is preferably done so that the height variation of the barbs forms a regular pattern.
The step of texturing the flat face of the base workpiece may involve gouging or planing the flat face of the base workpiece with a plurality of toothed blades so that each blade creates a row of raised barbs on the flat face of the base workpiece to texture the base workpiece. The toothed blades may have cutting tip geometries configured to cut grooves in the flat face of substantially the same length, thereby creating barbs of substantially the same height.
In this method, the barbs formed by texturing the flat face of the base workpiece are preferably curved. The barbs in the second group of barbs may be bent so that they are not straight and not deformed. Alternatively, the barbs in the second group of barbs may be deformed so that they each have a flattened distal end.
The step of reshaping the second group of barbs may be performed by passing a lobed roller over the textured face, thereby causing the lobes to bend each barb in the second group of barbs substantially more than any barbs in the first group of barbs are bent. It may be the case that none of the barbs in the first group of barbs are bent (or deformed) by the lobed roller.
The step of reshaping the second group of barbs may be performed by pressing the second group of barbs downward using a fluted plate in a stamping press to reduce the height of each barb in the second group of barbs.
In this method, the ductile material may be steel. The base workpiece may be a sheet of steel, and the barbs may be configured to receive and retain friction material.
In this method, the base workpiece may be a disc brake backing plate.
In this method, at least 25% of the barbs may be included in the second group of barbs and those barbs may each be at least 10% lower than each of the barbs in the first plurality of barbs. At least 25% of the barbs may be included in the second group of barbs and those barbs may each be at least 25% lower than each of the barbs in the first plurality of barbs.
In this method, the base workpiece may be configured to be a disc brake backing plate and the barbs may be configured to receive and retain friction material.
In a fourth aspect, the invention provides another method of making a differentially textured workpiece. The method is applied to a base workpiece made of ductile material having a flat face. The flat face of the base workpiece is first gouged or planed with a plurality of toothed blades, each knife cutting the face to create a row of raised barbs thereby texturing the workpiece. The toothed blades have different cutting tip geometries configured to cut grooves in the substantially flat face of varying lengths thereby creating barbs of varying heights. In this method, at least 25% of the barbs may be included in the second group of barbs and those barbs may each be at least 10% lower than each of the barbs in the first plurality of barbs. The blades may be configured to cause the height variation of the barbs to form a regular pattern.
a is perspective of rows of barbs and the grooves from which they are raised.
a is an end view of the roller shown in
b shows another method of changing the height of some of the barbs by the use of a roller, shown in an end view, with variable shape lobes or rolls including a V-shaped roll.
a is a side view showing the plate of
Barbs are generally curved and pointed structures, which may be relatively sharp, that can be added to ductile materials by, for example, using blades with multiple teeth that are made to travel from opposite directions whereby the teeth gouge (or cut or plane or impact) a flat face of the ductile material, cutting to a shallow depth and for a short distance. In this way a short, shallow (non-piercing) tapered groove is ploughed, resulting in an un-severed projection (the barb) being raised at the end of each groove. Such barbs are generally formed on a flat face of a base workpiece, such as on one side of a sheet of steel.
The term “substantially flat face” is intended to describe the face before and after the integral barbs have been raised from a completely flat face since the grooves are relatively shallow and the remainder of the face remains completely flat.
The term “base workpiece” as used herein refers a piece of ductile material, such as sheet of steel, that is used to form a textured workpiece.
The term “barb” as used herein refers to any type of nail-like or pin-like structure, or curved or hooked structure or protrusion, raised from a surface of a workpiece by carving, gouging, planing or scraping its surface, such as is described in Canadian patent numbers 1,330,521, 1,337,622, and 2,127,339, which are incorporated herein by reference. Barbs may be straight and substantially perpendicular to the face from which they are raised, or may be curved or bent to varying degrees. By “bent” it is meant that the barb is not straight (i.e. the bending referred to is not relative to the face the barb was raised from). While curved barbs are preferred for use in making disc brake backing plates to help retain the friction element made of friction material, embodiments with relatively straight barbs extending substantially perpendicularly from the flat surface of the workpiece may be preferable, for example, where a hard solid material is being attached to the textured surface to facilitate the barbs piercing into the hard material. In some embodiments, the barbs may be angled relative to the flat surface of the workpiece while still being straight, although such embodiments are not preferred.
In prior art backing plate manufacture, the “forest” of hook-like barbs on a textured surface are all of equal height. Friction powder is moulded onto the plate by compression and heated until cured to form a friction element. When the resulting disc brake pad is then subjected to sufficient shear force to fracture or cleave the hardened friction material from the plate, a wavy fracture surface results. Some wave “troughs” descend into the barb zone leaving patchy friction remnants and exposed barbs indicating less than desirable attachment strength. For use with friction material it is preferred that the barbs be curved, or hook shaped, so that portions of each barb are above friction material when it hardens, thereby helping to retain the friction material on the backing plate (“above” being in the context of the substantially flat textured face of the plate being horizontal with the textured face facing upward).
In the present invention, raised, curved hook-like barbs are also generally used for friction attachment but the barbs' heights are made to vary substantially across the plate. This unexpectedly creates a more planar fracture surface with an even layer of friction material remaining on the plate over the barbs, a very desirable result.
The “height” of a barb is the perpendicular distance from a substantially flat face of the textured workpiece to the point on the barb furthest from the flat face. For a substantially perpendicular barb, the height of the barb is approximately equal to its length. In contrast, for a curved or hooked barb the height of the barb is less than its length.
By “vary substantially”, it is meant that the tallest barbs are higher than the shortest barbs by more than a substantial height differential percentage, such as 10%, 20%, 30%, 40%, 50% or even 75% to 100% or more. It is further preferred than a substantial total percentage of the barbs exhibit such height differentials, so that, for example, the heights of a certain percentage of the barbs exceed the heights of another certain percentage (or that same percentage) of the barbs by at least a substantial height differential percentage, where a substantial height differential percentage may be, for example, 10%, 20%, 25%, 30%, 40%, 45% or close to 50%. In an ideal case, for example, 50% of the barbs may have a height that is about 50% to 100% greater than the height of the other 50% of the barbs, where the heights of all the barbs in each half are equal.
Of course, there is no need for the substantial height differential percentage to be the same as percentage of barbs exhibiting that height differential. For example, for some embodiments, the substantial height differential percentage may be 10% and it may be the case that 50% of the barbs exhibit this height differential relative to the other 50%. In other embodiments, for example, the substantial height differential percentage may be 20% and it may be the case that 25% of the barbs exhibit this height differential relative to the other 75%, or with respect to only 50% or 25% of the other barbs. Although generally not preferred, the substantial height differential percentage may be less 10%.
A secondary benefit is that the taller barbs protect the shorter barbs from damage during manufacturing, handling, tumble-washing, packaging and shipping. The protected barbs retain their sharp-edged characteristics which further helps to retain the friction material.
One method of making such unequal height barbs is by using toothed blades having different cutting tip geometries. Tooth tips that are higher up on the blade will enter the plate later than lower tips resulting in longer and shorter grooves with longer and shorter barbs. In practice, tips on one blade can be at different heights, or, each blade can have tip heights different from other blades. Tip heights can also vary along the length of each blade.
A second and preferred method is to make all the barbs of one height (or substantially the same heights), for example, using toothed blades with cutting tip geometries configured to cut grooves in a face of a base workpiece of substantially the same lengths thereby creating barbs of substantially the same heights, and then bend or deform some (a subset comprising a plurality) of the barbs (the “reshaped barbs”) to a lower height. It is preferred that the reshaped barbs be bent but still pointed, as shown, for example, in
In
In the top view of
In a preferred embodiment, the top view in
a show a preferred method of reshaping barbs with a roller B having raised lobes C.
In a more preferred embodiment one or more rollers may employ one or more a “V” shaped lobe or roll arranged to travel between the rows of barbs pushing them aside to reform them and create lower height barbs. Multiple lobes/rolls and spacers may be arranged so as to only deform alternate rows or selected rows.
In another embodiment, some of the barbs may be deformed to form a flattened head, similar to the head of a nail.
In
Evidence of the advantage of the present invention can be seen in
Various ductile materials can be used to create such differentially textured workpieces. Although preferred embodiments are made from steel sheeting or stampings, the processes described herein to produce differentially textured workpieces can be made to work on various harder plastics (Shore hardness of approximately D55 and up) and other materials in a range of widths and thicknesses. The workpiece can also be cooled or heated prior to impacting in order to make it more ductile or otherwise amenable to the texturing operation. For example, soft and rubbery materials (including those below the suggested Shore hardness of D55) may be cooled or frozen to apply this process.
It is preferred that heights of the barbs in the differentially textured material form a regular pattern. For example, in a simple example, all the barbs in every other row may be one height, and all the barbs in the other rows a second height (for example 25% lower). The methods of forming the differentially textured material described above will naturally produce such regular height variation patterns.
Preferably, rows of barbs on the face of a workpiece are formed substantially without gaps along the length of the workpiece, such as a sheet of steel. Various patterns, arrangements, densities and dimensions of projections are possible. In one embodiment, each of the higher barbs has a finished height of less than 2.5 mm (0.1 inches). The barb dimensions may be based on a tiered scale of barb grades for different applications, such as 1.8 mm (0.07 inches), 1.5 mm (0.06 inches), 1.15 mm (0.045 inches) and 0.75 mm (0.03 inches). Preferably, in this embodiment, each barb has a finished thickness at its base of less than 0.050″, and more preferably, less than 0.040″. In this embodiment where the workpiece is a sheet of steel, each of the higher barbs preferably has a finished height between about 150% to about 300% of the thickness of the sheeting. Preferably, in this embodiment, the density of barbs on the sheeting is between approximately 30-200 barbs per square inch, such as approximately 6 barbs per square cm (40 barbs per square inch) for workpieces where the taller barbs are at least 1.5 mm (0.06 inches) high, 12 barbs per square cm (80 barbs per square inch) for workpieces where the taller barbs are at least 1.15 mm (0.045 inches) high, or 30 barbs per square cm (190 barbs per square inch) for workpieces where the taller barbs are at least 0.75 mm (0.03 inches) high. Nonetheless, a great variety of dimensions and geometries of barbs are possible. Further, the barbs need not be provided in precisely matching rows over the entire material, but may be formed in zones or patterns to suit a particular application.
The abbreviation mm as used herein refers to millimetres (or in the US, “millimeters”). The abbreviation cm as used herein refers to centimetres (or in the US, “centimeters”).
It should be understood that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are only examples of implementations, and merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention as will be evident to those skilled in the art.
Where, in this document, a list of one or more items is prefaced by the expression “such as” or “including”, is followed by the abbreviation “etc.”, or is prefaced or followed by the expression “for example”, or “e.g.”, this is done to expressly convey and emphasize that the list is not exhaustive, irrespective of the length of the list. The absence of such an expression, or another similar expression, is in no way intended to imply that a list is exhaustive. Unless otherwise expressly stated or clearly implied, such lists shall be read to include all comparable or equivalent variations of the listed item(s), and alternatives to the item(s), in the list that a skilled person would understand would be suitable for the purpose that the one or more items are listed.
The words “comprises” and “comprising”, when used in this specification and the claims, are to used to specify the presence of stated features, elements, integers, steps or components, and do not preclude, nor imply the necessity for, the presence or addition of one or more other features, elements, integers, steps, components or groups thereof.
The scope of the claims that follow is not limited by the embodiments set forth in the description. The claims should be given the broadest purposive construction consistent with the description and figures as a whole.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2865386 | Sep 2014 | CA | national |
