Patent ID: 12196279

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, a brake apparatus for a vehicle will be described with reference to the accompanying drawings through various embodiments.

Here, thicknesses of lines, sizes of constituent elements, or the like illustrated in the drawings, may be exaggerated for clarity and convenience of description. In addition, the terms used below are defined in consideration of the functions thereof in the present disclosure and may vary depending on the intention of a user or an operator or a usual practice. Therefore, such terms should be defined based on the entire contents of the present specification.

In addition, in the present specification, when one constituent element is referred to as being “connected to (or coupled to)” another constituent element, the constituent elements can be “directly connected to (coupled to)” each other, and can also be “indirectly connected to (coupled to)” each other with other elements interposed therebetween. In addition, unless explicitly described to the contrary, the word “comprise (or include)” and variations such as “comprises (or includes)” or “comprising (or including)” will be understood to imply the further inclusion of stated elements, not the exclusion of the stated elements.

In addition, throughout the specification, the same reference numerals denote the same constituent elements. Even though the same or similar reference numerals are not mentioned or described with reference to specific drawings, the same or similar reference numerals may be described with reference to the other drawings. In addition, even though there are parts denoted by no reference numeral in specific drawings, the parts may be described with reference to the other drawings. In addition, the numbers, shapes, sizes, relative differences in sizes, and the like of the detailed constituent elements illustrated in the drawings of the present application are set for convenience of understanding, do not limit the embodiments, and may be variously implemented.

FIG.1is a perspective view schematically illustrating a configuration of a brake apparatus for a vehicle according to an embodiment of the present disclosure,FIG.2is a perspective view illustrating the configuration of the brake apparatus for a vehicle according to the embodiment of the present disclosure at a point in time different from a point in time illustrated inFIG.1,FIG.3is an exploded perspective view schematically illustrating the configuration of the brake apparatus for a vehicle according to the embodiment of the present disclosure,FIG.4is a cross-sectional view taken along line A-A′ and illustrating the configuration of the configuration of the brake apparatus for a vehicle according to the embodiment of the present disclosure, andFIG.5is a cross-sectional view taken along line B-B′ and illustrating the configuration of the brake apparatus for a vehicle according to the embodiment of the present disclosure.

Referring toFIGS.1to6, a brake apparatus1for a vehicle according to an embodiment of the present disclosure includes a pad unit100, a first caliper body unit200, a first pressing unit300, a second caliper body unit400, a second pressing unit500, and a restoration unit600.

The pad unit100is disposed to face a disc unit10that rotates together with a wheel of a vehicle. The pad unit100according to the embodiment of the present disclosure includes a first pad part110and a second pad part120.

The first and second pad parts110and120are symmetrically disposed with the disc unit10interposed therebetween. That is, the first and second pad parts110and120are spaced apart from each other at a predetermined interval in an axial direction of the disc unit10and have inner surfaces that face two opposite surfaces of the disc unit10. The first and second pad parts110and120are supported on the first caliper body unit200to be described below so as to be slidable in a direction parallel to the axial direction of the disc unit10. The first and second pad parts110and120come into contact with the disc unit10or separate from the disc unit10. A friction pad made of a material, such as rubber, with a high frictional coefficient may be attached to each of the inner surfaces of the first and second pad parts110and120that face the disc unit10.

The first and second pad parts110and120come into contact with or separate from the disc unit10while reciprocating in the direction parallel to the axial direction of the disc unit10in conjunction with a pressing force applied by the first pressing unit300or the second pressing unit500which will be described below. When the first and second pad parts110and120come into contact with the disc unit10, the first and second pad parts110and120apply a braking force to the vehicle while interfering with the rotation of the disc unit10. When the first and second pad parts110and120separate from the disc unit10, the first and second pad parts110and120permit the rotation of the disc unit10, thereby releasing the braking force applied to the vehicle. The specific shapes of the first and second pad parts110and120are not limited to the shapes illustrated inFIG.3and may be variously changed in design within the technical spirit of a brake pad that comes into contact with the disc unit10.

The first caliper body unit200is fixed to a vehicle body and supports the pad unit100so that the pad unit100is movable in the direction parallel to the axial direction of the disc unit10. The first caliper body unit200defines a space in which the first pressing unit300, the second caliper body unit400, the second pressing unit500, and the restoration unit600may be installed.

The first caliper body unit200according to the embodiment of the present disclosure includes a first housing210, a second housing220, support parts230, seating parts240, and a sleeve part250.

The first and second housings210and220define external appearances of two opposite sides of the first caliper body unit200. The first and second housings210and220are symmetrically disposed with respect to the disc unit10. That is, the first and second housings210and220face each other and are spaced apart from each other at a predetermined interval in the axial direction of the disc unit10with the disc unit10and the pad unit100interposed therebetween.

FIG.6is a front view schematically illustrating a configuration of the first housing according to the embodiment of the present disclosure.

Referring toFIGS.3and6, a longitudinal direction of the first housing210according to the embodiment of the present disclosure extends in a circumferential direction of the disc unit10. Therefore, the first housing210may have an approximately arc shape. An inner surface of the first housing210faces an outer surface of the first pad part110.

The first housing210has a first cylinder part211that supports a first piston part310of the first pressing unit300, which will be described below, so that the first piston part310is movable. The first cylinder part211according to the embodiment of the present disclosure may be provided in the form of a chamber concavely recessed into the first housing210from the inner surface of the first housing210that faces the first pad part110. A longitudinal direction of the first cylinder part211is parallel to the axial direction of the disc unit10. The first cylinder part211is provided in plural, and the plurality of first cylinder parts211may be disposed to be spaced apart from one another at predetermined intervals in the longitudinal direction of the first housing210. The interior of the first cylinder part211is filled with a braking liquid. The first cylinder part211may form a hydraulic pressure therein by means of the braking liquid.

FIG.7is a front view schematically illustrating a configuration of the second housing according to the embodiment of the present disclosure.

Referring toFIGS.3and7, a longitudinal direction of the second housing220according to the embodiment of the present disclosure extends in the circumferential direction of the disc unit10. Therefore, the second housing220may have an approximately arc shape. An inner surface of the second housing220faces an outer surface of the second pad part120.

The second housing220has a second cylinder part221that supports a second piston part320of the first pressing unit300so that the second piston part320is movable. The second cylinder part221according to the embodiment of the present disclosure may be provided in the form of a chamber concavely recessed into the second housing220from the inner surface of the second housing220that faces the second pad part120. A longitudinal direction of the second cylinder part221is parallel to the axial direction of the disc unit10. The second cylinder part221is provided in plural, and the plurality of second cylinder parts221may be disposed to be spaced apart from one another at predetermined intervals in the longitudinal direction of the second housing220. The interior of the second cylinder part221is filled with a braking liquid. The second cylinder part221may form a hydraulic pressure therein by means of the braking liquid.

Any one of the first cylinder part211and the second cylinder part221may have a hydraulic port (not illustrated) through which the braking liquid is received from the outside or the braking liquid is discharged to the outside. In this case, the first cylinder part211and the second cylinder part221may communicate with each other through a separate transmission flow path (not illustrated). Therefore, the hydraulic pressure formed in the first cylinder part211and the hydraulic pressure formed in the second cylinder part221may be synchronized with each other.

The second housing220has a third cylinder part222that supports a third piston part510of the second pressing unit500so that the third piston part510is movable. The third cylinder part222according to the embodiment of the present disclosure may be provided in the form of a chamber concavely recessed into the second housing220from the inner surface of the second housing220that faces the second pad part120. A longitudinal direction of the third cylinder part222is parallel to the axial direction of the disc unit10. When a pair of second cylinder parts221is provided, the third cylinder part222may be disposed between the pair of second cylinder parts221.

The third cylinder part222may be disposed at a relatively higher position than the second cylinder part221. That is, a distance at which the third cylinder part222is spaced apart from a central axis of the disc unit10may be longer than a distance at which the second cylinder part221is spaced apart from the central axis of the disc unit10. Therefore, when the pad unit100and the disc unit10are brought into contact with each other by the second pressing unit500to be described below, the third cylinder part222increases a magnitude of an effective radius by which the braking force is applied, which makes it possible to improve parking braking efficiency.

The second housing220has fixing parts223fixed to the vehicle body and configured to support the entire first caliper body unit200. The fixing part223according to the embodiment of the present disclosure may be provided in the form of a bracket perpendicularly extending from a lower end of the second housing220. The fixing part223may be detachably fixed to the vehicle body by a bolt or the like. A pair of fixing parts223may be provided, and the pair of fixing parts223may be disposed at two opposite sides of the second housing220and spaced apart from each other at a predetermined interval.

The support part230is installed between the first and second housings210and220and supports the pad unit100so that the pad unit100is movable. The support part230according to the embodiment of the present disclosure may be provided in the form of a rod having two opposite ends respectively fixed to the inner surfaces of the first and second housings210and220. The support part230is disposed in the direction parallel to the axial direction of the disc unit10. A pair of support parts230may be provided, and the pair of support parts230is spaced apart from each other at a predetermined interval in the longitudinal direction of the first and second housings210and220. The two opposite sides of each of the first and second pad parts110and120are slidably connected to the pair of support parts230, respectively, by a hook, a ring, or the like.

The seating part240is disposed between the first and second housings210and220and defines an upper external appearance of the first caliper body unit200. The seating part240according to the embodiment of the present disclosure extends in the axial direction of the disc unit10and is disposed to cover an upper side of the disc unit10. Two opposite ends of the seating part240are respectively and integrally connected to upper ends of the first and second housings210and220.

The seating parts240define a seating groove241in which a bridge part410of the second caliper body unit400, which will be described below, is seated. The seating groove241according to the embodiment of the present disclosure may be provided in the form of a hole that perpendicularly penetrates a central portion between the seating parts240in a radial direction of the disc unit10. A longitudinal direction of the seating groove241extends in the axial direction of the disc unit10. An inner surface of the seating groove241faces an outer surface of the bridge part410.

The sleeve part250extends from the second housing220and supports the second caliper body unit400to be described below so that the second caliper body unit400is slidable. The sleeve part250according to the embodiment of the present disclosure extends from an outer surface of the second housing220in a direction parallel to the axial direction of the disc unit10. The sleeve part250has a vacant inner space and communicates with the second cylinder part221. A central axis of the sleeve part250is disposed coaxially with a central axis of the second cylinder part221. A cross-sectional shape of the sleeve part250may be changed in design to have various shapes such as a polygonal or elliptical shape in addition to a circular shape.

The first pressing unit300is installed on the first caliper body unit200so as to be movable forward or rearward. When moving forward, the first pressing unit300presses the pad unit100to apply a main braking force. In this case, for example, the main braking force may be a braking force generated when the pad unit100comes into contact with the disc unit10as a driver manipulates a brake pedal while the vehicle travels.

The first pressing unit300according to the embodiment of the present disclosure may include the first piston part310and the second piston part320.

The first piston part310is slidably inserted into the first cylinder part211. The first piston part310according to the embodiment of the present disclosure has an approximately cylindrical shape and is inserted into the first cylinder part211. A front end of the first piston part310faces the outer surface of the first pad part110. The first piston part310moves forward or rearward in the longitudinal direction of the first cylinder part211, i.e., the direction parallel to the axial direction of the disc unit10in conjunction with the hydraulic pressure formed in the first cylinder part211. When the first piston part310moves forward, a front surface portion of the first piston part310presses the outer surface of the first pad part110and brings the first pad part110into contact with the disc unit10, thereby generating the braking force. The first piston part310may be provided in plural. In this case, the plurality of first piston parts310may be slidably inserted into the plurality of first cylinder parts211, respectively. A sealing member may be installed between an outer peripheral surface of the first piston part310and an inner peripheral surface of the first cylinder part211and prevent the braking liquid which fills the interior of the first cylinder part211, from leaking to the outside.

The second piston part320is slidably inserted into the second cylinder part221. The second piston part320according to the embodiment of the present disclosure has an approximately cylindrical shape and is inserted into the second cylinder part221. A front end of the second piston part320faces the outer surface of the second pad part120. The second piston part320moves forward or rearward in the longitudinal direction of the second cylinder part221, i.e., the direction parallel to the axial direction of the disc unit10in conjunction with the hydraulic pressure formed in the second cylinder part221. When the second piston part320moves forward, a front surface portion of the second piston part320presses the outer surface of the second pad part120and brings the second pad part120into contact with the disc unit10, thereby generating the braking force. The second piston part320may be provided in plural. In this case, the plurality of second piston parts320may be slidably inserted into the plurality of second cylinder parts221, respectively. A sealing member may be installed between an outer peripheral surface of the second piston part320and an inner peripheral surface of the second cylinder part221and prevent the braking liquid, which fills the interior of the second cylinder part221, from leaking to the outside.

The second caliper body unit400is slidably installed on the first caliper body unit200. The second caliper body unit400moves relative to the first caliper body unit200in conjunction with the forward or rearward movement of the second pressing unit500to be described below. The second caliper body unit400moves toward one side and presses the pad unit100to apply a parking braking force together with the second pressing unit500. In this case, for example, the parking braking force may be a braking force generated when the pad unit100comes into contact with the disc unit10as a driver manipulates a parking brake button when the driver parks or stops the vehicle.

FIG.8is a perspective view schematically illustrating a configuration of the second caliper body unit according to the embodiment of the present disclosure.

Referring toFIGS.1to8, the second caliper body unit400according to the embodiment of the present disclosure includes the bridge part410, a guide part420, a finger part430, and a flange part440.

The bridge part410defines an external appearance of a central portion of the second caliper body unit400and overall supports the guide part420, the finger part430, and the flange part440, which will be described below. The bridge part410according to the embodiment of the present disclosure may have an approximately rod. A longitudinal direction of the bridge part410is disposed in the direction parallel to the axial direction of the disc unit10. The bridge part410is seated in the seating groove241formed at the central portion between the seating parts240. Two opposite surfaces of the bridge part410face the inner surface of the seating groove241.

The guide part420extends from one side of the bridge part410and defines a rear external appearance of the second caliper body unit400. The guide part420is slidably inserted into the sleeve part250and guides the sliding of the second caliper body unit400. The guide part420according to the embodiment of the present disclosure may have a cylindrical shape opened at one side thereof. An upper end of the guide part420is integrally connected to a lower surface of a rear end of the bridge part410. An inner diameter of the guide part420has a size corresponding to an outer diameter of the sleeve part250. The sleeve part250is inserted into the guide part420through an open side of the guide part420. An inner peripheral surface of the guide part420is in slidable contact with an outer peripheral surface of the sleeve part250.

The guide part420slides in the direction parallel to the axial direction of the disc unit10by a reaction force applied in a direction opposite to the pressing force applied to the pad unit100by the second pressing unit500. A central axis of the guide part420is disposed coaxially with a central axis of the sleeve part250and a central axis of the third piston part510of the second pressing unit500to be described below. Therefore, the central axis of the sliding of the guide part420may be coincident with the central axis of the reaction force transmitted from the second pressing unit500, which makes it possible to prevent the second caliper body unit400from being twisted or damaged by rotational moment of force.

The finger part430extends from the other side of the bridge part410and defines a front external appearance of the second caliper body unit400. The finger part430presses or releases the pad unit100in conjunction with the sliding of the guide part420. The finger part430according to the embodiment of the present disclosure may be provided in the form of a rod perpendicularly extending downward from a front end of the bridge part410. The finger part430may be integrated with the bridge part410by welding, pressing, bending, or the like. The finger part430penetrates the seating groove241, and an inner surface of the finger part430faces the outer surface of the first pad part110. When the guide part420slides, the finger part430slides together with the guide part420by means of the bridge part410.

The flange part440extends from the guide part420and defines a space in which a drive part520to be described below may be supported. The flange part440according to the embodiment of the present disclosure may be provided in the form of a circular plate extending in a radial direction of the guide part420from an outer peripheral surface of a rear end of the guide part420. The flange part440may have a plurality of coupling holes that penetrates the flange part440in a direction perpendicular to the axial direction of the disc unit10. The plurality of coupling holes is spaced apart from one another at predetermined intervals in a circumferential direction of the flange part440.

The second pressing unit500is installed on the first caliper body unit200so as to be movable forward or rearward. The second pressing unit500moves forward and presses the pad unit100to guide the sliding of the second caliper body unit400and apply the parking braking force together with the second caliper body unit400.

The second pressing unit500according to the embodiment of the present disclosure includes the third piston part510and the drive part520.

The third piston part510is slidably inserted into the third cylinder part222. The third piston part510according to the embodiment of the present disclosure has a cylindrical shape having a vacant space and is inserted into the second cylinder part221. A front end of the third piston part510faces the outer surface of the second pad part120. A rear end of the third piston part510is opened so that a power transmission part522to be described below is inserted into the third piston part510. A screw thread is formed on an inner peripheral surface of the third piston part510, and the screw thread extends in a spiral shape in a longitudinal direction of the third piston part510. The third piston part510moves forward or rearward in the longitudinal direction of the third cylinder part222, i.e., the direction parallel to the axial direction of the disc unit10in conjunction with an operation of the drive part520to be described below. When the third piston part510moves forward, a front surface portion of the third piston part510presses the outer surface of the second pad part120and brings the second pad part120into contact with the disc unit10, thereby generating the braking force. The third piston part510is installed so as not to rotate about a central axis thereof. Therefore, the third piston part510may be stably moved forward or rearward by a rotational force transmitted from the drive part520to be described below.

The third piston part510may be disposed at a relatively higher position than the first piston part310and the second piston part320. That is, a distance at which the third piston part510is spaced apart from the central axis of the disc unit10may be longer than a distance at which the first and second piston parts310and320are spaced apart from the central axis of the disc unit10. Therefore, when the pad unit100and the disc unit10come into contact with each other, the third piston part510increases an effective radius by which the braking force is applied, thereby improving the parking braking efficiency.

The drive part520is connected to the third piston part510, generates driving power during parking and braking of the vehicle, and moves the third piston part510forward or rearward.

The drive part according to the embodiment of the present disclosure includes a power generating part521, the power transmission part522, and a bearing part523.

The power generating part521is fixed to the second caliper body unit400and generates the rotational force by electric power applied from the outside. The power generating part521according to the embodiment of the present disclosure faces a rear surface of the flange part440and is fixed to the flange part440by a bolt or the like. The power generating part521may include a speed reducer and an electric motor configured to generate the rotational force by electric power applied from a battery or the like in the vehicle.

Two opposite sides of the power transmission part522are respectively connected to the power generating part521and the third piston part510. The power transmission part522converts a rotational motion of the power generating part521into a rectilinear motion of the third piston part510. The power transmission part522according to the embodiment of the present disclosure may be provided in the form of a rod having a screw thread formed on an outer peripheral surface thereof. The power transmission part522is disposed in the direction parallel to the axial direction of the disc unit10. A central axis of the power transmission part522is disposed coaxially with the central axis of the third cylinder part222, the central axis of the guide part420, and the central axis of the third piston part510. One side of the power transmission part522is connected to an output shaft of the power generating part521, and the power transmission part522is rotated about the central axis thereof by the rotational force generated by the power generating part521. The other side of the power transmission part522penetrates the guide part420and is disposed in the third cylinder part222and thread-coupled to the inner peripheral surface of the third piston part510. Therefore, the power transmission part522may rotate relative to the third piston part510and move the third piston part510forward or rearward in the direction parallel to the axial direction of the disc unit10.

The bearing part523is installed between the guide part420and the power transmission part522and supports the power transmission part522so that the power transmission part522is rotatable relative to the guide part420. For example, the bearing part523according to the embodiment of the present disclosure may be a thrust bearing having one side rotatably connected to the power transmission part522so that the bearing part523rotates together with the power transmission part522, and the other side fixed to an inner surface of the guide part420. Therefore, the bearing part523may prevent the reaction force from separating the power transmission part522from the third cylinder part222, the reaction force being generated by the contact between the third piston part510and the second pad part120. In addition, the bearing part523may guide the transmission of the reaction force to the guide part420, the reaction force being generated by the contact between the third piston part510and the second pad part120.

The restoration unit600is provided between the sleeve part250and the guide part420and uses an elastic restoring force thereof to perform sealing, damping, and a reduction in drag. More specifically, the restoration unit600moves the guide part420to an initial position thereof when the second pressing unit500releases the pad unit100. In this case, for example, the initial position of the guide part420may indicate a position of the guide part420in a state in which the finger part430is maximally spaced apart from the first pad part110before the second pressing unit500operates. For example, the initial position of the guide part420may be a position of the guide part420illustrated inFIG.4. The restoration unit600absorbs vibration generated when the guide part420slides. The restoration unit600seals a portion between the sleeve part250and the guide part420and prevents the penetration of foreign substances.

FIG.9is an enlarged view schematically illustrating a configuration of the restoration unit according to the embodiment of the present disclosure.

Referring toFIG.9, the restoration unit600according to the embodiment of the present disclosure may be provided in the form of a circular ring. The restoration unit600may be made of an elastically deformable material such as rubber or silicone. An inner peripheral surface and an outer peripheral surface of the restoration unit600are in close contact with and fixed to the outer peripheral surface of the sleeve part250and the inner peripheral surface of the guide part420, respectively. As illustrated inFIG.9, a cross-sectional shape of the restoration unit600may have a corrugated pipe shape or have a circular shape, a polygonal shape, or the like.

A center of gravity C of the second caliper body unit400and a center of gravity C of the second pressing unit500may be disposed on the central axis of the third cylinder part222and the central axis of the guide part420and provided at positions facing the inner peripheral surface of the restoration unit600. In this case, the center of gravity C of the second caliper body unit400and the center of gravity C of the second pressing unit500mean the points at which no net torque is generated by gravity. Therefore, the restoration unit600may support both the sleeve part250and the guide part420on the same plane as the center of gravity C of the second caliper body unit400and the center of gravity C of the second pressing unit500. Therefore, the restoration unit600may maximize the damping performance and prevent the leftward or rightward rolling of the second caliper body unit400caused by the rotational moment of force.

Hereinafter, an operation of the brake apparatus1for a vehicle according to the embodiment of the present disclosure will be described in detail.

FIGS.10and11are operational views schematically illustrating a process in which the brake apparatus for a vehicle according to the embodiment of the present disclosure applies the main braking force.

Referring toFIGS.10and11, when a driver pushes a brake pedal while a vehicle travels, the first and second cylinder parts211and221form the hydraulic pressure by means of the braking liquid introduced thereinto.

The first and second piston parts310and320respectively move forward toward the first and second pad parts110and120in conjunction with the hydraulic pressure formed in the first and second cylinder parts211and221.

The first and second piston parts310and320press the first and second pad parts110and120toward the disc unit10, and the first and second pad parts110and120come into contact with the disc unit10and generate the braking force.

Thereafter, when the driver releases the brake pedal, the braking liquid is discharged from the first and second cylinder parts211and221, and a negative pressure is formed in the first and second cylinder parts211and221.

The first and second piston parts310and320release the braking force while being moved rearward by the negative pressure in the direction away from the first and second pad parts110and120.

FIGS.12and13are operational views schematically illustrating a process in which the brake apparatus for a vehicle according to the embodiment of the present disclosure applies the parking braking force.

Referring toFIGS.12and13, when a driver manipulates a parking brake button to park or stop a vehicle, the power generating part521receives a control signal from an ECU or the like and generates the rotational force.

The power transmission part522is rotated about the central axis thereof by the rotational force generated by the power generating part521.

The third piston part510thread-coupled to the power transmission part522moves forward toward the second pad part120in conjunction with the rotational motion of the power transmission part522.

The third piston part510presses the second pad part120toward the disc unit10while moving forward and brings the second pad part120into contact with the disc unit10.

The reaction force is applied to the third piston part510in the direction opposite to the pressing force applied to the second pad part120by the third piston part510.

The reaction force is transmitted to the guide part420sequentially through the third piston part510, the power transmission part522, and the bearing part523.

The guide part420slides rearward in the longitudinal direction of the sleeve part250from the initial position of the guide part420.

The restoration unit600accumulates the elastic restoring force while being elastically deformed by the sliding of the guide part420.

At the same time, the restoration unit600cancels out the vibration, which is generated when the guide part420slides, while being elastically deformed in the direction opposite to the vibration.

The finger part430slides rearward together with the guide part420and comes into contact with the first pad part110.

The first pad part110is brought into contact with the disc unit10by the pressing force applied by the finger part430and generates the braking force together with the second pad part120.

Thereafter, when the driver manipulates the parking brake button to release the parked or stopped state of the vehicle, the drive part520operates in the reverse order to the above-mentioned operation and moves the third piston part510rearward.

When the third piston part510moves rearward and separates from the second pad part120, the pressing force and the reaction force applied to the second pad part120are eliminated.

The guide part420returns to the initial position thereof while sliding forward in the longitudinal direction of the sleeve part250by the elastic restoring force accumulated by the restoration unit600.

Although exemplary embodiments of the disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as defined in the accompanying claims. Thus, the true technical scope of the disclosure should be defined by the following claims.