JP2011247422A - Brake pad for disk brake - Google Patents

Abstract

The present invention reduces brake noise without significant changes in the disc brake structure.
In a brake for a pad for a disc brake having a plate for supporting a friction lining that can come into contact with a disc in a braking process, the vibration of the pad may cause disc brake noise during braking. Providing a pad characterized in that it comprises means 115a, 115b firmly coupled to the plate for changing the mass of at least one portion 121a, 121b of the plate so as to fulfill the inertia of the pad substantially preventing .
[Selection] Figure 1

Description

  The present invention relates to a pad for a disc brake and a disc brake using the pad.

Conventional technology

  In general, in a disc brake, the brake activity is caused by means such as a cylinder / piston unit acting on the opposite surface of the disc rotated by a pad.

  As is known, noise is often generated during the operation of this brake. This noise is a particularly unpleasant whistle form that reduces driving comfort.

  The occurrence of this type of noise is thought to be the result of a vibration phenomenon involving the various components of the brake including the pad.

A lot of research has been done to suggest techniques for reducing or eliminating braking noise.
One such technique proposes connecting a weight by means of an elastic body to a member of a disc brake that can start vibration. According to this technique, the predetermined vibration of this member of the brake is transmitted to a weight that vibrates in synchronism with the member to which it is connected at low frequencies. As the vibration frequency increases, the vibration between the weight and the brake member will gradually become out of synchronization until the opposite phase situation is fulfilled, and the vibration of the member will be reduced or eliminated. Further, with this technique, the weight can be secured to the caliper body or pad instead of the piston.

This technique requires that the overall structure of the brake be specifically designed.
Such a design also forms an intermediate elastic member suitable for being positioned between the brake member to be vibration-removed and a suitable weight, and the weight is vibrated in the middle to deform the elastic body. It is necessary to provide a seat that can be

  A major drawback is that the brake structure must be significantly changed to reduce the whistling phenomenon. In fact, given the complexity of this phenomenon that occurs during braking and the fact that these depend on the particular application, ie the type of vehicle in which the disc brake is used, the theoretical simulation It can happen that the particular solution that is optimized on the basis is not sufficient as a result of experimentation or use in other applications not given.

  Thus, structures that do not significantly affect the overall structure of the disc brake are of particular interest.

  The problem on which the present invention is based is to propose a disc brake having structural and functional features that overcome the above-mentioned drawbacks described with reference to the prior art.

  The problem is that in the brake process, in a pad for a disc brake with a plate for supporting a friction lining that can be brought into contact with the disc associated with the disc brake, this pad causes disc brake noise during braking. Solved by a pad, characterized in that it comprises means rigidly coupled to the plate to change the mass of at least one portion of the plate so as to exert a pad inertia that substantially prevents possible pad vibration The

  Further features and advantages of the invention will become apparent from the following description of preferred embodiments, given by way of non-limiting example, with reference to the accompanying drawings.

FIG. 1 shows a perspective view of a brake unit having two pads with different parts according to a first embodiment of the present invention. FIG. 2 shows a plan view of the disc brake of FIG. 1 partially shown in section along line II-II. FIG. 3 shows a side view, partly in section, of the disc brake of FIG. FIG. 4 shows a schematic plan view of a prior art disk and pad. FIG. 5 shows a schematic front view of a second embodiment of a pad according to the invention. FIG. 6 shows a schematic front view of a third embodiment of a pad according to the invention. FIG. 7 shows successive steps A to F for the manufacture of the pad plate of FIG. FIG. 8 shows a plan view of a fourth embodiment of a pad according to the present invention. FIG. 9 shows a perspective view of a fixed caliper disc brake according to the present invention.

  Referring to FIGS. 1, 2 and 3 together, these show a disc brake 1 for a motor vehicle, not shown, which can act on the braking band 2 of the disc 3 forming the braking unit 4.

  In the special embodiment shown in FIGS. 1, 2 and 3, the disc brake 1 is a floating caliper type. However, the invention is also applicable to different types of disc brakes, such as fixed caliper disc brakes.

  The disc brake 1 is attached to the stub axle of the automobile suspension, and the disc 3 can be provided in connection with the wheels of the automobile. Referring to FIG. 2, with respect to the rotation of the disk 3 in the direction indicated by the arrow F1, the portions of the disk located on the left side and the right side of the line III-III are respectively relative to the disk 3. It is defined as an input area and an output area.

  The disc brake 1 has a caliper holder body 5 which has two bridge members or yokes 5a, 5b which are U-shaped and lie on a plane spaced apart from each other. Each yoke 5a (5b) has a substantially shaft-shaped end 6a (6b) and two side portions 7a, 8a (7b, 8b). The two yokes 5a (5b) are firmly connected to each other by respective cross-members 7c and 8c in the region of the end portions of the side portions 7a and 7b and the side portions 8a and 8b. .

  Respective seats 9, 10 are formed in the side parts 7, 8 to accommodate the respective pads 11, 12.

  The caliper holder main body 5 has holes 14a and 14b arranged at both ends of the cross member 7c in order to attach the caliper holder main body 5 to a stub axle of an automobile suspension.

  A spring 15 is provided for fastening the pads 11, 12. The spring 15 extends between the pads 11 and 12 and the main body 5 of the caliper holder. In particular, the spring 15 is formed as a plate spring in which one end is supported using a pin 15b by a lug 15a protruding from the end 6a and the other end is attached under the end 6b. . The spring 15 has two arm portions 16 and 17 acting on the pads 11 and 12 in an intermediate region.

  The disc brake 1 has a substantially rectangular solid frame 18 extending through the caliper holder body 5 with the disc brake assembled. The rigid frame 18 can surround the caliper holder body 5 as a frame.

  In particular, the strong frame 18 is formed by long side portions 19 and 20 facing each other and short side portions 21a and 21b facing each other.

  The long side 19 extends along and near the side 7 at the height of the seat 9 and has a seat 22 for the fluid pressure piston 23 acting on the pad 11.

  Further, the long side portion 20 extends near the side portion 8 at the height of the seat portion 10 of the pad 12, and faces the seat portion 10, and includes a protrusion 24 having a flat surface 25 that can act on the pad 12. Have

  In the region of the long side 19, the frame 18 has two cylindrical seats 26 a, 26 b, which are respectively located on both sides of the seat 22 of the piston 23, these seats comprising the side 7 a, In the region 7b, two cylindrical guides 27a and 27b fixed to the caliper holder main body 5 are engaged with each other so as to be guided and slid.

  The pads 11 and 12 have plates 111 and 112 for supporting the corresponding friction linings 113 and 114, respectively.

  Means are coupled to both ends of each plate 111 (112) to change the mass of these ends. In the particular example shown, these mass changing means have two weights 115a, 115b attached to the plate 111 and two weights 116a, 116b attached to the plate 112.

  The pad 11 and plate 111 are described in detail below, but as will be apparent to those skilled in the art, the description is exactly the same as the pad 11 and plate 111. Can also be easily applied.

  The plate 111 effectively includes a portion 121a and a portion 121b each having a round shape. These two parts 121a, 121b are arranged at both ends of the plate, thus these parts are located in the input area and the output area of the disc 3 when the plate is provided in the disc brake 1. Face each one. These two parts 121a, 121b of the plate 111 have an initial mass mi.

  According to the particular embodiment of the invention shown in FIGS. 1 to 3, the two parts 121 a, 121 b are cylindrical in the embodiment shown and are suitable for receiving screws 122. A screw 122 is appropriately provided for fixing the weights 115a and 115b each having a hole. These weights 115a, 115b can be made of the same material as the plate or a material having a unique weight different from the material of the plate.

  The weights 115a, 115b are arranged on the plate 11 in a suitable manner so that they are positioned beyond the outer edge of the disc when the plate is provided in the disc brake 1. Thus, contact between the weights 115a, 115b and the disk 3 is avoided even after the friction lining 113 is worn.

  In order to prevent the weights 115a, 115b from contacting the corresponding symmetrical weights 116a, 116b of the plate 112 as a result of wear of the friction lining 113, these weights 115a, 115b, 116a, 116b are preferably disc 3 Projecting inward relative to the disc brake 1 by a distance equal to less than half of the thickness of the disc brake 1.

  Also, note that other means such as rivets, nails, caulking, welding, adhesives, etc. can be used in place of the screws 122 to secure the weights 115a, 115b to the plate 111. must not.

  The securing means used for the pad 11 is such that the weights 115a, 115b are substantially rigidly structurally to the plate 111, i.e. the plate 111 substantially forms a single rigid body with the weight. Allows to be coupled to.

  The portions 121a, 121b provided with the weights 115a, 115b have a total mass mc changed in a particular case, which is larger compared to the initial mass mi with the weight not fixed, It is shown.

  In particular, it has been shown that the overall inertia of a pad provided with weights 115a, 115b is altered in light of the inertia of the pad alone.

  Cylindrical weights 115a, 115b are a special example of mass changing means that can be secured to an appropriate portion of plate 111.

  Also, additional means for changing the mass of the portion of the plate 111 can be formed “in one piece” with the plate during manufacture of the plate. For example, if the plate 111 is manufactured by casting, a portion of the plate having a large material content and thus a large mass is formed. Alternatively, these parts with a large mass can be produced, for example, by folding the appropriate end of the plate over the plate. In this case, the plate 111 is formed by blanking of the plate gold resulting from the pressing process provided with the necessary additional members in the shape of the end suitable for bending. This additional member can be bent by deformation to give the desired shape to the portion of the plate. FIG. 6 shows a schematic front view of this type of pad 200. The pad 200 has a plate 201 which supports the friction lining 113 and has two ends 221a, 221b in the region of the parts 121a, 121b that can be deformed and bent on themselves. In the embodiment shown in FIG. 6, the ends 221a, 221b shown in broken lines are strip-shaped.

  FIG. 7 shows six side views AF of the plate 201 corresponding to six successive stages of bending of the portions 221a, 221b. In stage A, the portions 221a, 221b of the plate 201 are in an unfolded state until they are formed in the final structure F in subsequent stages as they are manufactured by blanking. , These will be folded over themselves.

  Also, the weights 115a and 115b can be manufactured using the same material as the friction lining 113. In this context, according to the prior art, the friction lining is fixed to the plate by adhering the material comprising this friction lining to the surface of the plate by a suitable half-open molding that gives the desired shape. You must be careful. Adhesion of the lining to the plate is accomplished by pressing the mold and thus the material held therein against the plate at the appropriate temperature in addition to the possible adhesive.

  To produce weights 115a, 115b of the same material as the lining, use a mold that has been modified to provide suitable cavities for positioning additional members corresponding to these weights, for mounting the lining. The method described above can be used.

  The physics and geometric properties and the arrangement on the plate 111 of the means for changing the mass of one or more parts of the plate are the vibrations of the pad that can occur during braking and cause disc brake noise. In this case, the inertia of the pad 11 is substantially prevented.

  In particular, the mass changing means employs a natural vibration frequency that the pad 11 cannot substantially generate during operation of the disc brake 1.

  For purposes of explanation, the operation of the disc brake 1 will be described below.

  At the time of braking, as a result of the thrust of the piston 23 against the pad 11, both the pad 11 acting on the piston 23 and the pad 12 acting against this and the flat surface 25 are in contact with the braking band 2. Moves or floats along the guide until it is pushed into and acts on it by equal and opposite forces.

  The advantages relating to the noise of the disc brake according to the present invention will become apparent from the following description of an analysis based on experiments performed on a conventional disc brake.

  FIG. 4 shows a plan view of the disk 40 rotating in the direction indicated by the arrow F2. This disc 40 is in contact with a lining 43 of a pad 41 having a plate 42 for supporting a friction lining 43.

  As a result of the test, and as schematically shown in FIG. 4, it has been found that during braking, the braking band of the disk 40 takes a substantially sinusoidal shape as indicated by curve 45 and vibrates. It was.

  The vibration of the braking band of the disk 40 excites the pad 41, which causes the disk to vibrate. The pad 41 can be vibrated by a pivoting movement about an axis indicated by a cross in FIG. 4 that is substantially transverse to the pad and parallel to the radial axis of the disk 40. understood. This vibration motion is observed as a result of measurements made by a vibration accelerometer located on the pad 41, which is in each area of the pad facing the input area and the output area of the disc 40, respectively. Different acceleration values were detected.

  In FIG. 4, the difference between the measured accelerations is indicated by arrows F3 and F4 having different sizes. It is shown that a greater acceleration is measured in the output area than in the input area of the disc 40. Furthermore, when the whistling phenomenon occurs, it should be noted that not only the vibration of the brake band and the pad occurs, but also the various members of the brake resonate and vibrate and affect each other. That is, a chain of member vibrations transmitted to the pad and caliper body due to the disk is established until this causes a temporary stop of the vehicle and the vehicle body. All members constituting the disc brake vibrate at its own natural frequency.

  In the disc brake 1 according to the present invention, the moment of inertia of the pad 11 when the means for changing most of one or more parts of the pad 11 is evaluated with respect to the axis on which the pad vibrates during braking is evaluated. Allows to be changed.

  As is known, the natural vibration frequency of any body at which this body resonates is inversely proportional to the moment of inertia of the body.

  The change in the moment of inertia of the pad performed by the mass changing means described above adopts a value at which the natural frequency of the pad cannot be substantially generated by other members of the disc brake or the disc itself during braking. enable. That is, in the disc brake formed according to the present invention, the chain of vibration members established during the whistle generation is broken. The pad according to the present invention is shown as a vibration braking member because it does not generate or transmit vibration.

  Tests made with a disc brake formed in accordance with the present invention and similar to disc brake 1 showed a reduction in whistle during braking.

  In particular, the pad 11 formed in accordance with the present invention has a natural vibration frequency that is not generated by braking activity or is outside the range of frequencies that normally cause a whistle phenomenon.

  The characteristics of the mass changing means coupled to the plate can be determined based on specific applications, i.e. experiments related to specific disc brakes and special vehicles.

The following is an example of a method for determining characteristics.
A conventional disc brake with two pads having an initial structure determined in relation to a conventional design method and suitable for mounting on a particular vehicle is conceivable. For example, mention may be made of a disc brake of the type shown in FIGS. 1 to 3, in which the plates 111, 112 do not have weights 115a, 115b or 116a, 116b. In this case, the plates 111 and 112 are substantially plate-shaped.

  In a first step, the movement of the operating disc brake is analyzed, for example, by adapting it to a vehicle designed for it and evaluating its performance during braking.

  The performance of this can be evaluated by conventional equipment by determining the spectrum of noise revealed by the whistle generated during braking or by listening directly to the noise. The brake performance is also measured by a vibration accelerometer known to those skilled in the art, preferably by measuring the magnitude of the pad vibration at the portion of the plate facing the input and output areas of the disc. Can be evaluated.

  Those skilled in the art can easily establish a reference noise level corresponding to sufficient performance for a range of frequencies.

  If the performance is not sufficient, i.e. the level of noise is greater than the reference level, a subsequent step of changing the mass of one or more portions of the plate is performed.

  As described above, such a change in mass is accomplished, for example, by firmly securing a weight to each plate.

  Each plate effectively has one or more securing means that allow the weight to be secured, similar to the securing means described above.

  Alternatively, the pad for the described method may be of the type schematically shown in FIG. In FIG. 5 and the subsequent drawings, the same reference numerals as in the previous drawings are used to indicate the same or equal members.

  The pad 150 of FIG. 5 has a plate 151 with a removable portion 152. Each portion 152 can be removed or replaced without being replaced so that it can be replaced with a portion having a different mass, eg, the same capacity but a different inherent weight.

  Removal of one or more portions 152 of plate 151 causes a decrease in the moment of inertia of pad 150. This reduction in moment of inertia can change the natural vibration frequency of the pad 150 to a value that is higher, but outside the range of frequencies that are specifically generated during braking. Also, parts of the members of the plate can be removed by drilling parts of the plate to the extent that the structural performance of these parts allows.

  The weights secured to the plates 111, 112 are effectively positioned in such a way that they do not contact the friction lining, as do other means that may be used to change the mass.

  These weights are preferably located in the areas facing the input and output areas of the disc 3, respectively, at the opposite ends of the plate. Thus, the overall plate and pad moment of inertia increase is maximized to reduce its natural frequency.

The weights effectively have a mass proportional to the acceleration of the area of the plate to which they are fixed.
Based on the measured value of the test, the mass of the weight 115b fixed to the area of the plate corresponding to the output area of the disk 3 is typically the weight fixed to the area of the plate corresponding to the input area of the disk 3. It is larger than the mass of 115a.

  Thus, the modified disc brake movement is analyzed again to assess whether the level of noise is below or above the reference level.

  The change of mass is repeated until the disc brake has the desired performance in relation to the noise, i.e. until a level of noise is obtained which is preferably approximately equal to a value below the reference level.

  Further changes can be made by exchanging pre-fixed weights with other weights with a larger or smaller mass, or by adding other weights and / or changing their position. Is done. Fixing means adapted to the plate, such as screws 122, effectively allows for subsequent removal after a pre-fixed weight. Furthermore, the other mass changing means described above or other means suitable for this purpose are also applicable to this method.

  If the analyzed disc brake performed satisfactorily, the corresponding plate had adopted an optimal final structure as a result of changes.

  These plates represent plates suitable for a particular disc brake or can be considered as a prototype for the final plate design. For example, the final plate may be made of a mass changing means that is integrally formed in the manufacturing process, as described above, but does not have characteristics similar to those produced by the tests performed. In this regard, FIG. 8 shows a side surface of a pad 160 having a plate 162.

  The plate 162 has a main body 163 that is substantially plate-shaped and two portions 164 that are secured to the main body 163 at the ends thereof. The two portions 164 are cast and have a function similar to the weight used in the above-described method according to the present invention. As shown in FIG. 8, the two portions 164 appear as protrusions extending from the main body 163 to the lining 113, leaving the plate 162 generally out of the shape of a plate. In the embodiment of FIG. 8, the mass of the two portions 164 are different, depending on the position where the two portions 164 are fitted in the disc brake with respect to the input and output areas of the disc.

  The above-described method according to the present invention is such that changes made to the structure of the plate to determine the optimal structure do not involve substantial changes in other parts of the disc brake (eg, caliper body or piston). Therefore, it is particularly effective. This means that the pads formed by the method according to the invention can be used to be replaced with conventional pads provided in current disc brakes of the same type.

FIG. 9 shows a fixed caliper disc brake 100.
This unit has a caliper, generally designated 102, that extends across the area of the brake disc 109. The caliper 102 includes a first half 103, a second half 104, and two connection members 105, 105 ′ between the first half 103 and the second half 104. .

  The caliper 102 may be secured to the stub axle of the automobile suspension. The disc 109 is suitable for being associated with a vehicle wheel. The first half 103 and the second half 104 are positioned on opposite sides of the disk 109, respectively, and have the shape of an asymmetric long shell so as to reflect.

  In particular, the first half 103 is arranged to face the first braking surface 191 of the disc. The second half 104 is positioned to face the second braking surface 104 of the disc.

  Each of the first half 103 and the second half 104 has surfaces 130 and 141 facing the disk and surfaces 131 and 140 facing the surfaces. Each of the surface 130 of the first half 103 facing the disk and the surface 141 of the second half 104 facing the disk is a seat formed near the corresponding central portion 132, 142. 133, 143 (FIG. 9 shows only the lateral seat 143).

  Each of the lateral seats 133, 143 has through holes 134, 144 for receiving corresponding screws 135, 145 for attachment to the connecting members 105, 105 ′, respectively.

  On the other hand, at each center 132, 142, two fluid pressure braking cylinders are integrally formed in the first half 103, the second half 104, and each surface 130 facing the disk, It is arranged to face 141 and to open on top of it. Only the cylinder 140 of the second half 104 is shown in FIG.

  In addition, each of the first half 103 and the second half 104 has a pair of pistons that are guided to slide within a fluid pressure cylinder.

  The first half 103 and the second half 104 have ducts for supplying a braking fluid to a cylinder which is formed in the half and is accommodated in a conventional manner.

  Each center part 132, 142 is provided with two through holes 136, 146 for engaging with the two guide pins 106.

  The guide pin 106 has a function of guiding two pads 107 provided between the pistons of the first half 103 and the second half 104 and the braking surfaces 191 and 192 of the disc.

  In particular, the two pads 107 that are typically equal and opposite each have a plate 171 for supporting a corresponding friction lining 172, respectively. The friction linings 172 are each attached to the support surface 173 of the plate that faces the braking surface of the disk in a conventional manner. Further, each plate 171 has two through holes 174 corresponding to the through holes 136 and 146 formed in the first half 103 and the second half 104, respectively.

  Plate 171 has weights 115a, 115b in portions 122a, 122b that are similar to the weights described with reference to FIGS. These weights 115a and 115b can be fixed to the plate 171 in the manner described above.

  A fixed caliper disc brake unit 100 is completely conventional elastic means 108 for supporting the pads 107 on the guide pins 106 and for keeping them away from the disc when the disc brake unit is not in operation. It has further.

  The connecting members 105, 105 ′ are located between the first half 103 and the second half 104 of the caliper 102. In the embodiment shown, member 105 'is located in the area that rises from the caliper during rotation of the disk (as indicated by arrow "i" in FIG. 9), and member 105 away from this member 105' For example, the disk is arranged in an area that enters the caliper during rotation.

  The operation of the fixed caliper disc brake of FIG. 9 is well known and thus will not be described in detail. The advantages relating to the performance of the disc brake of FIG. 9 are evident from the above description with reference to the disc brake of FIG.

  Inevitably, specialists in the field can apply the above pads and disc brakes to many variations to meet accidental and specific needs, all of which are attached. Within the protection scope of the present invention as defined by the claims.

3 ... disk, 11 ... pad, 111 ... plate, 113 ... friction lining, 115a ... weight, 115b ... weight, 121a ... part, 121b ... part, 122a ... part, 122b ... part, 164 ... weight

Claims (19)

  In a pad (11) for a disc brake with a plate (111) for supporting a friction lining (113) that can be brought into contact with the disc (3) associated with the disc brake in the braking process, this pad is Strong to the plate to change the mass of at least one part (121a, 121b, 122a, 122b) of the plate so as to exert pad inertia that substantially prevents pad vibration that may cause disc brake noise therein A pad comprising means (115a, 115b, 164) coupled to the pad.   The pad has a moment of inertia evaluated relative to a central axis on which the pad vibrates during braking, corresponding to a natural frequency of pad vibration that is not substantially generated during the braking process. Pads for disc brakes.   The pad of claim 1, wherein the mass modifying means comprises at least one weight (115a) that can be rigidly connected to a portion of the plate.   4. The pad of claim 3, wherein the plate has means (122) for securing at least one weight.   5. The pad of claim 4, wherein the means for securing the at least one weight allows the weight to be removed and / or replaced.   The pad (160) of claim 3, wherein the at least one weight (164) and plate (162) are manufactured by casting to form a single rigid body.   The mass changing means includes first mass changing means and second mass changing means which are located at both ends of the plate and are respectively provided in areas which can face the input area and the output area of the disc. The pad of claim 1.   The first means has a first weight, the second means has a second weight, and the first weight has a mass smaller than the mass of the second weight. Or 7 pads.   Pad according to claim 1, wherein the mass changing means comprises at least one part (221a, 221b) of a plate having a shape that can be changed by deformation.   The pad of claim 1, wherein the mass modifying means comprises at least one portion (152) of the plate that is removable from the plate.   The pad of claim 1, wherein the mass changing means comprises at least one member that can be rigidly connected to the plate and has a unique weight that is different from the unique weight of the plate member.   A plate (111) for supporting a friction lining for a disc brake pad (11) according to any one of the preceding claims. A pad (11) that can be positioned to contact a disc (3) associated with a brake to perform braking activities;
A caliper holder body (5) that is aligned across the disc and can accommodate the pads;
12. A disc brake (1) comprising means operatively connected to a pad for driving a braking force, characterized in that the pad is according to any one of claims 1 to 11. Disc brake.   Having inertia to substantially prevent vibrations of the pad that may cause disc brake noise during braking, comprising the step of tightly coupling the plate and means for changing the mass of at least one portion of the plate A method for manufacturing a pad for a disc brake with a plate for supporting a friction lining.   The method of claim 14, wherein the step of coupling the mass changing means comprises the step of securing at least one weight to a portion of the plate.   15. The method of claim 14, wherein combining the mass modifying means comprises providing a plate with at least one portion removable from the plate. A method for manufacturing a low noise disc brake having a pad with a plate for supporting a friction lining comprising:
Subjecting the disc brake to a first braking action such that the lining is positioned to contact the disc associated with the brake;
Evaluating a first level of noise associated with the first braking action;
Changing the mass of at least one portion of the plate to provide pad inertia corresponding to a second level of noise during braking that is less than the first level of noise.   18. The method of claim 17, wherein changing the mass comprises securing at least one weight to the plate so as to increase the mass of a portion of the plate.   The method of claim 17, wherein changing the mass comprises removing at least one portion of the plate to reduce the mass of the plate.

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