FIELD OF THE INVENTION

[0001] The present invention relates to master cylinders and, more particularly, to master cylinders capable of being controlled by way of handlebars of a vehicle.

BACKGROUND OF THE INVENTION

[0002] Master cylinders are typically employed with brakes and/or clutches of a motor vehicle with handlebars, such as, a motorcycle. A conventional handlebar master cylinder typically includes a master cylinder body that defines a chamber for housing a piston therewithin. Also associated with the handlebar master cylinder is a reservoir. The reservoir stores a working fluid that is in fluid communication with the chamber, typically, via one or more ducts and/or channels such that, upon operation, the piston acts upon the working fluid to facilitate a braking or clutching action. Additionally, the master cylinder and, particularly, the piston of the master cylinder is operatively connected to an operating lever, such that the piston can be operated by actuating the operating lever.

[0003] Currently available handlebar master cylinders often possess one or more shortcomings including, for example, having a large space claim (also referred to as "footprint") and a large dead stroke such that movement of the operating lever is required before inception of system pressure/vehicle deceleration. The assembly of components is also often difficult and typically requires manipulation of multiple small clips, o-rings, fasteners and/or springs to hold the assembly in position. In addition, in conventional handlebar master cylinders, the lever (e.g., operating lever) reach, typically defined by the distance an operator must extend his or her hand to grip the lever, is excessive. Further, a non-integrated reservoir or switch packs (e.g., a group of switches mounted in a single housing or housing portion) require redundant additional components that limit styling opportunity for improved aesthetics. In addition to the aforementioned problems, conventional handlebar master cylinders do not provide for indication of minimum and/or maximum reservoir brake fluid level without removal of the reservoir cap. Typically, conventional handlebar master cylinders provide only indication of minimum fluid level, without provision for a user to detect maximum fluid level without removal of a reservoir cap. [0004] It would therefore be advantageous if an improved handlebar master cylinder addressing at least some of the problems described above is developed.

SUMMARY OF THE INVENTION

[0005] In one aspect, the present invention relates to a master cylinder assembly for use with a handlebar of a vehicle, the master cylinder assembly comprising a master cylinder body, a chamber defined by the master cylinder body and a piston slidably received within the chamber, the piston connected at least indirectly to an operating lever of the vehicle. A link member operatively engages the piston to the operating lever, the link member having a first portion engaged at least indirectly with the piston through a first magnetic member and a second portion at least indirectly engaged with the operating lever through a second magnetic member, wherein the piston, the link member and the first magnetic member are biased in position at least partially against a first out stop member. Additionally, an axis of the chamber is offset with respect to a handlebar axis of rotation.

[0006] Li at least some other aspects, the present invention relates to a master cylinder assembly for mounting on a handlebar of a vehicle, the master cylinder assembly comprising a master cylinder body, a master cylinder chamber defined at least partially by the master cylinder body and a piston slidably received within the master cylinder chamber and biased in position by a piston return spring. The master cylinder assembly additionally includes a link member housed within the master cylinder chamber and having a first link portion and a second link portion, the first link portion engaged with the piston via a first magnetic member and the second link portion engaged at least indirectly with an operating lever via a second magnetic portion, and a sight glass integrated with respect to the master cylinder body, the sight glass for indicating both high and low levels of a working fluid within a reservoir, such that upon mounting, the master cylinder chamber is positioned at least substantially under the handlebar and offset therefrom.

[0007] In yet other aspects, the present invention relates to a method of assembling a master cylinder assembly, the method comprising providing (i) a master cylinder body; (ii) a chamber defined by the master cylinder body; (iii) a piston capable of being slidably received within the chamber, the piston connected at least indirectly to an operating lever of a vehicle; and (iv) a link member for operatively engaging the piston to the operating lever through first and second link portions and first and second magnetic members. The method additionally comprises magnetically retaining the piston with the first magnetic member and inserting the magnetically retained piston into the chamber through the first portion of the link member. The method further comprises operatively connecting the second portion of the link member to the operating lever.

[0008] Other aspects and embodiments are contemplated and considered within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments of the invention are disclosed with reference to the accompanying drawings and these embodiments are provided for illustrative purposes only. The invention is not limited in its application to the details of construction or the arrangement of the components illustrated in the drawings. Rather, the invention is capable of other embodiments and/or of being practiced or carried out in other various ways. The drawings illustrate a best mode presently contemplated for carrying out the invention.

Like reference numerals are used to indicate like components. In the drawings:

[0010] FIGS. 1 A-IC show various views of an exemplary embodiment of a master cylinder assembly that includes a mating housing portion secured thereto, and is assembled with respect to a handlebar of a motorcycle and employing a first embodiment of a sight glass, in accordance with one aspect of the invention;

[0011] FIG. 2A shows a perspective view of the master cylinder assembly of FIG. IA, with the mating housing portion removed, in accordance with at least some embodiments of the present invention;

[0012] FIG. 2B shows an alternate perspective view of the master cylinder assembly of

FIG. 2A;

[0013] FIG. 3A is a top view of the master cylinder assembly of FIG. 2A;

[0014] FIG. 3B is a cross-sectional view of the master cylinder assembly of FIG. 2A taken along line 3B-3B of FIG. 3 A;

[0015] FIG. 4A is a right side view of the master cylinder assembly shown in FIG. 2A;

[0016] FIG. 4B is a cross-sectional view of the master cylinder assembly taken along line

4B-4B of FIG. 4A;

[0017] FIG. 4C is a partial cross-sectional view of the master cylinder assembly of FIG.

4B;

[0018] FIG. 5 is a cross-sectional view of the master cylinder assembly taken along line [0019] FIGS. 6A-6C show portions of the master cylinder assembly of FIG. 3B illustrating take-up during over run conditions of an operating lever of the master cylinder assembly, in accordance with at least some embodiments of the present invention;

[0020] FIG. 7 is an alternate view of a portion of the master cylinder assembly of FIG. 3B illustrating a point of zero radial piston load of the master cylinder assembly;

[0021] FIG. 8 A is another right side view of the master cylinder assembly of FIG. 2B; and

[0022] FIG. 8B is a cross-sectional view of a portion of the master cylinder assembly taken along line 8B-8B of FIG. 8 A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] Referring to FIGS. 1A-1C and FIGS. 2A-2B, an exemplary master cylinder assembly (also referred herein as handlebar master cylinder or HBMC) 2 is shown, in accordance with at least some embodiments of the present invention. In particular, FIGS. IA- 1C show various views of the master cylinder assembly 2 assembled with respect to a handlebar 4 of a vehicle (not shown), while FIGS. 2A and 2B show a perspective view of the master cylinder assembly detached from the handlebar 4. In at least some embodiments, the vehicle onto which the master cylinder assembly 2 has been mounted can be a motorcycle, although in other embodiments, the vehicle can be representative of various other motor vehicles having handlebars. As shown, the master cylinder assembly 2 includes a master cylinder body 6 to which an operating lever 8 (also referred herein as lever) is pivotally connected. In addition, a mating housing portion 5 is provided that secures in a mating fashion, to the master cylinder body 6, where the mating housing portion 5 can include various items, such as a switch pack 11. As will be explained in greater detail below, operation of the master cylinder assembly 2 can be facilitated by way of operating the operating lever 8. The handlebar 4 can additionally have mounted thereto a light 7 (e.g., a turn signal light), a side view mirror 9 and various hand controls, such as throttle controls of the vehicle. Other conventional components that are commonly associated with handlebars of vehicles of the kind described above are contemplated and considered within the scope of the present invention. [0024] Referring now to FIGS. 3A-3B and 4A-4C in conjunction with FIG. 2 A, the master cylinder assembly 2 is mounted to the handlebar 4 (See FIGS. 1 A-IC) by way of a clamp 10 which, as shown, can be integrally connected to the master cylinder body 6. In at least some embodiments, the clamp 10 can be a strap clamp, which securely connects the master cylinder assembly 2 to the handlebar 4 by receiving the handlebar within a loop 12 formed at least partially by the strap clamp and at least partially by the cylinder body 6 and affixing the master cylinder assembly to the handlebar 4 by way of top and bottom screws 14 and 16, respectively. Notwithstanding the fact that, in the present embodiment, the clamp 10 is secured to the master cylinder body 6, in at least some embodiments, the clamp can be integrally formed or otherwise integrated with respect to the master cylinder body as well.

[0025] The clamp 10 is designed such that upon mounting the master cylinder assembly 2 onto the handlebar 4, the clamp is hidden or substantially hidden from view of at least the operator. In other words, the clamp 10 is mounted onto the handlebar 4 in a manner such that the clamp is practically not visible without un-mounting the master cylinder assembly 2 from the handlebar. By virtue of concealing the clamp 10 from view, the clamp (or at least the surface of the clamp) can be constructed of significantly less expensive material (as compared to conventional clamps in which the clamp is visible and is therefore often expensively constructed to maintain a cosmetically aesthetic look). [0026] Furthermore, the clamp 10 is positioned such that upon mounting the master cylinder assembly 2 onto the handlebar 4, a bore 20 (also referred to herein as a chamber 20) (described below) of the master cylinder assembly is disposed at least substantially below the handlebar and offset therefrom as shown in FIG. 3B. In at least some embodiments, the term "offset" with respect to the handlebar 4 can be defined such that an axis 44 of the bore is not coplanar with a handlebar axis of rotation 43 (e.g. the axis of rotation of the throttle 3, as shown in FIG. IA). Further, the axis of rotation 43 is coincident with axes 43', 43" of the handlebar and the handlebar clamp 10 (shown in FIG. 3B), respectively. In some embodiments, the aforementioned axes 44, 43, 43', 43" are centrally disposed or substantially centered, with respect to the structures to which they serve as a reference. In at least some other embodiments, the bore 20 need not only be non-coplanar with respect to the handlebar 4 to be "offset", but it can also be positioned oblique (e.g., at an angle) with respect thereto or to a plane of operation of the operating lever 8, as well as positioned oblique with respect to a plane 45, which in at least some embodiments, and as shown, is a horizontal plane substantially consistent with the orientation and position of the chamber 20 in its intended use. For example, in at least some embodiments, and as shown, the bore 20 and, particularly, the axis 44 of the bore, can be positioned at or substantially at about 90 degrees to the axis of rotation 43 of the handlebar 4, with an angle between the horizontal plane 45 and the angle of the bore 20 being about 15 degrees. In alternate embodiments, the angle between the horizontal plane 45 and the axis 44 of the bore can be up to about 25-30 degrees. By virtue of positioning the bore 20 offset from the handlebar 4, a reduced footprint or space claim for the master cylinder assembly 2 can be achieved.

[0027] In at least some embodiments, the clamp 10 can be constructed of stamped steel with additional plating on its surface. In other embodiments, other durable and non- expensive components for constructing the clamp 10 can be utilized. Notwithstanding the fact that in the present embodiment, the clamp 10 is employed for securely mounting the master cylinder assembly 2 with respect to the handlebar 4, in other embodiments, other mechanisms that are at least substantially not visible from view upon mounting can be employed as well. Furthermore, the clamp 10 need not always employ screws (e.g., the top and bottom screws 14 and 16, respectively) for mounting the master cylinder assembly 2 to the handlebar 4. Rather, in other embodiments, other fastening and/or engaging mechanisms including, nuts, bolts, as well as a variety of adhesives and welding procedures can be employed as well.

[0028] Also integrated into the master cylinder body 6 is a reservoir 18. The reservoir 18 is in fluid communication with the bore 20 (also referred herein as chamber) via ducts 22. A working fluid (not shown) stored within the reservoir can pass from the reservoir to the bore 20 via the ducts 22 for compression and for providing a hydraulic pressure for the operation of the master cylinder assembly 2. In at least some embodiments, the reservoir 18 is secured to (or integrally formed with) the master cylinder body 6 to be situated in a vertical orientation. In one embodiment, the reservoir 18 is substantially perpendicular to the axis 44 of the bore 20, although in other embodiments the reservoir 18 need not be substantially perpendicular to the axis 44. Further, the reservoir 18 is equipped with a reservoir opening 25 for filling the working fluid therein. The reservoir opening 25 can be covered by a reservoir cap 24 having threads on an inner surface thereof, which threadingly engage threads on an outer surface of the reservoir opening. The threadingly engaged reservoir cap 24 is in contrast to conventional reservoir caps, which are typically machined and/or screwed into the reservoir 18, and therefore can add to the overall cost of the master cylinder assembly 2.

[0029] Notwithstanding the fact that, in the present embodiment, the reservoir cap 24 is threadingly engaged with the reservoir opening 25 of the reservoir 18, in other embodiments, other mechanisms (e.g., snap/friction fit, hinged connection, etc.) may be employed for securely closing the reservoir opening with the reservoir cap. Further, in some embodiments, the reservoir cap 24 can be constructed out of a cast/painted injection molded plastic, although other durable and inexpensive materials can be employed as well. Further, to prevent, or substantially prevent, leakage and/or spillage of the working fluid from the reservoir 18, particularly during changes in the outside temperature or changes in the operating conditions of the master cylinder assembly 2, the reservoir and particularly the reservoir opening 25 of the reservoir is equipped with a plastic gasket locator 26 and a gasket 28. The gasket 28 is typically constructed out of a flexible material, such as rubber, and is seated around or substantially around the gasket locator 26 to provide a tight fitting seal by flexing between the reservoir cap 24 and the reservoir opening 25 of the reservoir 18. In other embodiments, the gasket locator 26 and/or the gasket 28 can be constructed out of other materials that are commonly employed for such conventional components in master cylinder assemblies.

[0030] Additionally, to facilitate viewing of the working fluid level within the reservoir 18 (which is typically constructed out of an opaque material) from outside, the present invention provides an inner port 30 (FIG. 3B) in the wall of the reservoir 18 that has a sight glass 32 (FIG. 4A) situated thereover along the outside of the reservoir wall. In particular, the sight inner port 30 and the sight glass 32 are formed or provided as a window through the reservoir wall. The sight glass 32 provides information regarding the level of working fluid in the reservoir. In at least one embodiment, demarcations are provided on the sight glass 32 that indicate both a low-level (e.g., minimum level) of the working fluid, and a high-level (e.g., maximum level) of the working fluid. By virtue of providing the sight glass 32, the level of the working fluid within the reservoir 18 can be checked without removing the reservoir cap 24. In addition, the sight glass 32 can include various measuring aids and rulers for measuring the quantity of working fluid within the reservoir 18. To further facilitate accurate working fluid levels, in at least some embodiments, a fluid reservoir having a high aspect ratio (e.g., height/width or diameter) such that a change in the volume of the reservoir fluid within the reservoir 18 effects a comparatively large change in the reservoir fluid height is provided by the use of the offset bore 20.

[0031] Referring still to FIGS. 3A-4C in conjunction with FIG. 2A, the bore 20 houses a piston 34, a piston return spring 36, a primary cup 38, first and second magnetic links 40 and 42, respectively, a link 46 and various sealing mechanisms assembled together in operational association. In particular, the piston 34 is a floating piston capable of moving along the axis 44 and biased in position by way of the piston return spring 36. More particularly, the piston 34 is capable of moving between a first initial position, shown in FIG. 3B and a second final position (shown in FIG. 7). In the initial position, the piston 34 is urged to a maximum distance from the handlebar 4 by the return spring 36, while in the final position the piston overcomes the force of the return spring and compresses the working fluid within the chamber 20 to advance towards the handlebar 4 to accomplish a braking action.

[0032] Typically, the movement of the piston 34 between the first and the second positions is facilitated by operation of the operating lever 8, which is connected to the piston via the rod or link 46. In particular, the link 46 includes a first link portion 48, which interacts with the piston 34 via the first magnetic link 40 and the primary cup 38 and a second link portion 50 that bears spherically, as described further below, against a socket 52 via the second magnetic link 42. The socket 52 in turn is fixedly and threadingly engaged to the operating lever 8. The threaded engagement between the socket 52 and the operating lever 8 is illustrated at 54 in FIG. 4C. The second magnetic link 42 between the second link portion 50 and the socket 52 prevents, or substantially prevents, rattle between the link 46 and the socket. Relatedly, the first magnetic link 40 prevents, or substantially prevents, rattle between the piston 34 and the first link portion 48. To maintain a connection between the piston 34 and the link 46 via the first magnetic link 40, and the link and the socket 52 via the second magnetic link 42, the piston and the link are constructed out of ferrous materials. Thus, by virtue of connecting the link 46 to the piston 34 at one end and to the operating lever 8 at the other end, pivotal motion of the operating lever can be transferred via the link to move the piston between the first and second positions. In at least some embodiments, the first and the second magnetic links 40 and 42, respectively, can be Neodymium (NdFeB) magnets available from the A-L-L Magnetics Inc. Company of Anaheim, CA. In other embodiments, other types of magnets, available as off-the-shelf components for the magnetic links 40, 42 can be utilized as well. Further, in some embodiments, the magnets 40 and 42 can be replaced with a spring mechanism such as a bias spring (not shown) to eliminate or substantially eliminate rattle, where the bias spring acts between the body 6 and the lever 8, such that with the piston 34 against a primary out stop 60 (discussed below), the second link portion 50 and the piston 34 remain in contact.

[0033] In at least some embodiments, the second link portion 50 can be (or a portion thereof can be) a ball joint (not visible) capable of providing a two degree freedom of motion between the link 46 and the socket 52. As previously noted, the link 46 and, particularly, the second link portion 50 of the link bears spherically against the socket 52 by way of the ball joint. The ball joint advantageously does not require a specific orientation of the link 46 and/or the socket 52, thereby making the assembly of those parts convenient and self-disassembly difficult. Additionally, the ball joint provides a provision for magnetic retention (via the second magnetic link 42) between the link 46 and the socket 52 in order to eliminate fasteners that would otherwise hold those components together. The ball joint also allows re-take up (e.g., re-assembly of disassembled parts) of the link 46 and the socket 52 in over run circumstances when the operating lever 8 returns to its home or out stop position while the piston 34 is still at the bottom (e.g., in the second position) of the bore 20, as explained in greater detail below. Notwithstanding the fact that, in the present embodiment, the second link portion 50 is a ball joint, in at least some other embodiments, other mechanisms and features capable of providing the advantages described above can be employed as well. Furthermore, although the link 46 bears spherically against the socket 52 (e.g., by way of the ball joint) in the present embodiment, in at least some other embodiments, multiple joints are arranged such that two degrees of freedom between the link and the operating lever 8 (e.g., through the socket) or the link and the piston 34 is maintained, can be provided. Alternate arrangements can also include various joints, such as a universal joint having a pair of pins with axes perpendicularly arranged, or a Rzeppa joint having an arrangement of ball bearings and receptacles. Other joints and mechanisms capable of providing two degrees of freedom of motion can be employed as well in alternate embodiments. [0034] Further, to ensure the proper positioning of the piston 34 and the link 46 with respect to the operating lever 8 and to maintain a proper pressure differential of the working fluid within the chamber 20, the present invention provides the primary cup 38 and a plurality of other stop and seal mechanisms. For example, the piston 34 contains a pilot 56 that locates the return spring 36 and additionally acts like a down stop for preventing, or substantially preventing, coil-on-coil compression of the return spring. Similarly, the piston 34 and the return spring 36 are located within the chamber 20 by way of the primary cup 38. The primary cup 38 in particular is a seal or seal-like mechanism that on one side carries the pressurized hydraulic fluid (e.g., the working fluid) for passing to a caliper (not shown) or an ABS system (not shown) of the vehicle (not shown), and on the other side carries near atmospheric pressure to maintain a pressure differential across the piston 34. Generally, the primary cup 38 commences pressure generation of the working fluid within the bore 20 after the primary cup closes or crosses across a timing cup or timing hole 35 (also referred herein as primary port or port time hole) due to motion of the piston 34 for facilitating a braking action. [0035] In addition to the primary cup 38, the bore 20 houses a seal 58 and the primary out stop 60. Li at least some embodiments, the primary out stop 60 can be in the form of a snap ring securely positioned within the chamber 20, although in other embodiments, other mechanisms, such as, 0-rings, for holding the piston 34, the return spring 36, and the primary cup 38 in position can be employed. The primary out stop 60 is typically positioned between the walls of the bore 20 and the piston 34 such that a tolerance stack between the closing of the port time hole 35 and the primary out stop is small enough to reduce sensitivity to machining and component variation. By virtue of the positioning of the primary out stop 60, a reduction in free motion of the piston 34 during traversing the bore 20, before producing any pressure for facilitating a braking action, is achieved. In addition to the primary cup 38 and the primary out stop 60 engaging and biasing the piston 34 and the link 46, the link is additionally sealed by way of a seal member, such as a dust boot 62 or other similar structure. Other sealing and positioning mechanisms that are commonly employed with conventional master cylinder assemblies are additionally contemplated and considered within the scope of the present invention. [0036] Referring specifically now to FIGS. 4A-4C and 5, FIG. 4B is a cross-sectional view taken along lines 4B-4B of FIG. 4A, while FIG. 4C is an enlarged portion of FIG. 4B. FIG. 5 is a cross-sectional view taken along lines 3A-3A of FIG. 3 A. In particular, FIGS. 4B and 4C illustrate the location of a pivot pin 64 of the operating lever 8 where the operating lever is pivotally connected to the master cylinder body 6. Typically, the pivot pin 64 threadingly engages the master cylinder body 6 and locks in position by way of a tapered fit, as illustrated in FIG. 5. Notwithstanding the fact that, in the present embodiment, the operating lever 8 is pivotally held in position about the master cylinder body 6 via the pivot pin 64, in other embodiments, other mechanisms of pivotally securing the operating lever with respect to the master cylinder body can be employed. [0037] The master cylinder assembly 2 additionally includes a secondary out stop 66 (as shown in FIG. 4B), which prevents, or substantially prevents, over-extension of the operating lever 8. The secondary out stop 66 in particular augments the reduction in free motion of the piston 34 provided by the primary out stop 60 and additionally allows the operating lever 8 to be retained and/or constrained such that, in an event when the operating lever returns to its home or out stop position before the piston returns to its home position, the assembly of the components within the bore 20 does not self- disassemble or fall apart, as explained further below. Self-disassembly of the various components with respect to one another is generally avoided by providing the primary and secondary out-stops 60 and 66, respectively.

[0038] A nominal clearance between the operating lever 8 and the master cylinder body 6 at the secondary out stop 66 ensures that the piston 34 engages the primary out stop 60 under most, if not all, significant cases. In at least some embodiments, significant cases can include circumstances in which as the piston 34 returns to its home position, the movement of the piston is arrested not by the primary out stop 60, but rather because the movement of the operating lever 8 is arrested by the secondary out stop 66. Generally, the contact between the secondary out stop 66 and the master cylinder body 6 with the piston 34 at the home position does not result in any additional dead stroke. Any rattle occurring due to the nominal clearance between the operating lever 8 and the master cylinder body 6 and/or between the various components within the chamber 20 is prevented, or substantially prevented, by way of the first and the second magnetic links 40 and 42, respectively. The nominal clearance between the operating lever 8 and the master cylinder body 6 at the secondary out stop 66 is shown in FIG. 5 by way of a side elevation offset section of the secondary out stop. The secondary out-stop 66 additionally locates the piston 34 such that the piston is retained with the necessary degrees of freedom while preventing, or substantially preventing, the working fluid in the reservoir 18 from exiting the bore 20. To the extent that the secondary out stop 66 is capable of locating and retaining the piston 34 in substantially the same manner as the primary out stop 60, in at least some embodiments, the secondary out stop behaves and functions as the primary out stop.

[0039] Referring now to FIGS. 6A-6C, take-up of the piston 34 and the link 46 to the socket 52 in the event of overrun of the operating lever 8 is shown, in accordance with at least some embodiments of the present invention. Generally, overrun of the operating lever 8 occurs when the operating lever is manually or inertially returned to its out stop position (e.g., in an initial or home position away from the handlebar 4 when no input force is being applied to the operating lever) while the piston 34 remains at or near the bottom of the bore 20 (e.g., in the final position) due to low brake fluid (e.g., working fluid) temperature induced viscous resistance. To accommodate such conditions, the geometries of the piston 34, the link 46 and the socket 52 are such that the link is properly re-engaged with the piston and socket via the return force of the return spring 36 and the primary and the secondary out stops 60 and 66, respectively. The position of the ball joint on the end of the second portion 50 of the link 46 is typically designed to be within the envelope provided by the socket 52 such that when the two components (e.g., the link and the socket) are re-joined, those components are returned to proper relative positions. FIG. 6A in particular shows a "worst case" scenario of overrun of the operating lever 8 in which, upon return of the operating lever to its out stop position, the link 46 is initially disengaged with the socket 50, while FIG. 6B shows a worst case position of the link 46 upon re-engagement. FIG. 6C in turn shows the re-engaged assembly returned to the out stop position.

[0040] Turning now to FIG. 7, a displaced position of the master cylinder assembly 2 at which all loads from the operating lever 8 through the link 46 and into the piston 34 are coaxial (as evidenced by the 180 degrees between the piston and the link) with a centerline of the piston is shown, in accordance with at least some embodiments of the present invention. Typically, the displaced position is selected such that the position conforms with a desired certain level of brake-induced vehicular deceleration at which zero radial load (e.g., side load) is invoked between the piston 34 and the master cylinder body 6 or to correspond with the largest load typically induced by the operator on the operating lever 8.

[0041] Referring now to FIGS. 8A and 8B, FIG. 8A illustrates a schematic view of the master cylinder assembly 2 employing the sight glass 32, while FIG. 8B is a cross- sectional view taken, in cut-away, along lines 8B-8B of FIG. 8 A, in accordance with at least some embodiments of the present invention. In particular, and as shown particularly in FIG. 8B, the sight glass 32 is constructed out of a suitably transparent material, sealed against the master cylinder body 6 by way of one or more seals 70, stretched to an oblong shape and compressed against the master cylinder body by way of a fastener, such as self- tapping screws 72. The seal(s) 70 can take a variety of forms including for example, snap rings, 0-rings and the like. Other forms of sealing mechanisms can be employed as well. Relatedly, mechanisms other than the tapping screws 72 for compressing and holding the sight glass 32 against the master cylinder body 6 can be employed. [0042] Thus, by virtue of the master cylinder assembly components described above, assembly of those components within the master cylinder assembly is made more economical and expedient. Elimination of the retention fasteners normally found in conventional master cylinder assemblies additionally adds to the convenience of assembling the master cylinder assembly. As described above, fasteners employed in conventional master cylinder assemblies have been replaced by the inclusion of the primary and the secondary out stops 60 and 66, respectively.

[0043] The assembly of the various components of the master cylinder assembly typically begins by placing the piston return spring 36 on the pilot 56 of the piston 34. The primary cup 38 and the seal 58 are then retained in glands provided on the piston 34. Generally, the seals (e.g., the seal 58) have appropriately designed glands into which they can be seated within the master cylinder body 6. The first magnetic link 40 is then placed and magnetically retained to a hole provided on the piston 34, which as indicated above, is typically constructed out of a ferrous material. The link 46 then assists in the insertion of the above described sub-assembly (e.g., the piston return spring 36, the piston 34 and the primary cup 38, the seal 58 and the first magnetic link 40 assembled together) to the bore 20 in the master cylinder body 6. Subsequently, the link 46 is retained via the assembly of the primary out stop 60 (e.g., an internal snap ring) to an appropriate bore groove in the master cylinder body. The rubber dust boot 62 is snapped into the grooves of the master cylinder body 6 and the link 46 to seal the link in position. The socket 52 then receives the second magnetic link 42 and is then threaded to the operating lever 4. The operating lever 4 with the socket 52 is subsequently fixedly attached to the link 46 until concentricity is achieved at the lever pivot. The pivot pin 64 is torqued into the master cylinder body 6, in a tapered fit as described above to retain all the aforementioned components of the master cylinder assembly 2. Advantageously, unlike conventional master cylinder assemblies, the assembly of the master cylinder assembly 2 described above need not overcome the spring force of the piston return spring 36 during the insertion of the pivot pin 64, thereby easing assembly of the various components in a manner described above.

[0044] Further, during operation of the master cylinder assembly 2, users of the level range indicating sight glass 32 can visually discern the level of working fluid in the integrated reservoir 18 without removal of the reservoir cap 24. Various markings are provided on the sight glass 32 to indicate a working fluid level that is too low for safe vehicle operation. For example, in some embodiments, this can be shown by a fluid level marker below the minimum or the low level marking. In some alternate embodiments, the sight glass 32 can be designed such that if no working fluid is visible through the sight glass, the working fluid level is too low for safe vehicle operation. Likewise, a second mark can be provided for indicating a working fluid level that is too high to accommodate thermal expansion of the fluid and therefore also unsafe for vehicle operation. IQ some embodiments, the too high level marker can be shown with a fluid level marker above the maximum or high level marking. In alternate embodiments, the sight glass 32 can be designed such that when the entire field of view for the sight glass shows the working fluid therein, the vehicle is unsafe for operation due to inability to accommodate thermal expansion.

[0045] The master cylinder assembly 2 of the present invention provides a reduced space claim, which as described below, can be attributed to one or more features described above. For example, by virtue of the placement of the bore axis 44 under the handlebar 4, an overall reduction in the space claim or footprint of the master cylinder assembly is achieved. The reduction in the space claim is accomplished at least in part by providing a joint having two degrees of freedom (DOF) at both ends of the link 46 by way of the first and the second magnetic links 40 and 42, respectively. Positioning the operating lever 8 and fixedly attaching the socket 52 to the operating lever at an orientation such that all force transfer is in line with the centerline of the piston 34 when a Gross Vehicle Weight Restriction (GVWR) vehicle experiences 75% front system lockup deceleration also provides a reduced space claim. Additionally, the integrated nature of the various components, and particularly, the design of the clamp 10 further reduces overall space claim when compared to a separate handlebar master cylinder and switch pack arrangement. Space claim reduction provides a value for motorcycles requiring one inch handlebars and increased piston stroke required for heavy bikes and anti-braking systems (ABS). Generally, the required stroke (displacement) of the piston 34 increases for a heavy vehicle. As a result, the resulting additional axial space claim when in a plane shared with the radius of the handlebar 4 requires the pivot pin 64 of the operating lever 8 to be positioned further from the handlebar. The related structures housing the pivot pin 64 are also moved further afield from the handlebar 4, thereby increasing the space claim of the master cylinder assembly 2. Thus, vehicles with a larger handlebar diameter require moving the components of the piston 34 and the bore 20 that are coplanar with the handlebar axis of rotation radially further from the handlebar centerline, thereby increasing the space claim. However, by virtue of employing the master cylinder assembly 2 of the present invention, the space claim of a heavy vehicle can be reduced in comparison with the space claim of a heavy vehicle employing a conventional master cylinder assembly. This can typically be achieved by positioning the bore 20 below the handlebar 4 and offset therefrom, and stacking the various components (e.g., the piston 34, the link 46 and the various seals and out stops) in a manner described above. [0046] In addition to reducing the space claim, the master cylinder assembly 2 additionally provides a reduced dead stroke. Dead stroke reductions of 40% or more are typically achieved because the out stop (e.g., the secondary out stop 66) acts directly between the piston 34 and the master cylinder body 6, thereby greatly reducing the number of dimensions in the out stop tolerance stack, where the out stop tolerance stack is a calculation whose output represents the dead stroke of the assembly. As such, by reducing the number of components on whose dimensions the dead stroke is dependent, the dead stroke of the assembly is reduced.

[0047] Further, an assembly that does not require fasteners of the HBMC 2 components saves time and cost. Typically, in conventional master cylinder assemblies, placing the out stop (e.g., the secondary out stop 66) between the piston 34 and the master cylinder body 6 requires fastening the piston to the link 46 and the operating lever 8 to prevent, or substantially prevent over-extension of the lever, thereby adding to the overall cost of the master cylinder assembly. Incorporation of a standard dust boot for sealing the link is additionally difficult in such conventional master cylinder assemblies. To alleviate these problems, the present design replaces previously employed piston-link-lever fasteners with the secondary out stop 66 engaging at a point that does not change or otherwise affect the dead stroke of the assembly, and take up magnets (e.g., the first and second magnetic links 40 and 42, respectively) at the piston 34 to the link 46 connection and the link to the socket 52 connection. Further, geometry of the piston 34, the link 46 and the socket 50 is such that even if the operating lever 8 returns before the piston (in the case of cold fluid viscous lock-up), the piston-link-socket alignment is maintained and inadvertent disassembly can be eliminated, or substantially eliminated, as described above with regard to HGS. 6A-6C.

[0048] In addition to the above advantages, the orientation and positioning of the various components of the master cylinder assembly 2 of the present invention reduces operating lever reach (as defined in SAE J 108) of .22" over current master cylinder assemblies. Generally speaking, the offset bore allows reduction in the handlebar centerline to lever pivot centerline distance, thereby allowing both a reduction in lever reach for a given vehicle and improved lever ergonomics supporting finger braking. [0049] Further, in the present embodiment, a cost reduction is obtained due to various integrated hand controls, reservoir eliminated switch pack cast housings, cosmetic clamp (e.g., the clamp 10), cast reservoir cover (e.g., the reservoir cap 24), reservoir screws and related machining. Integration of the components additionally provides a potential for improved aesthetics. Further, the hand control switches (e.g., the switch packs) are placed in an injection molded non-structural housing that clips and screws to the master cylinder body 6. Also, as described above, the clamp 10, which holds the master cylinder assembly 2 to the handlebar 4 is not visible without disassembly of the unit and therefore offers a cost reduction over conventional clamps.

[0050] In addition, conventional master cylinder assemblies that have opaque reservoirs only provide a provision for indicating a minimum working fluid level. Typically, in conventional master cylinder assemblies, a high reservoir aspect ratio dictating a large change in the reservoir fluid volume is required to affect indicatable change in working fluid level. Alternatively, a separate reservoir (remote reservoir) molded from translucent material (PP) provides a level range indication (high and low level). Such an arrangement is typically visually unappealing. To alleviate the problems associated with the level indicators of conventional master cylinder assemblies, the present invention provides a provision for inspection of minimum and maximum reservoir fluid level via the sight glass 32 integrated with respect to the reservoir 18.

[0051] Generally speaking, a low aspect ratio (narrow and tall) design of the sight glass 32 allows appreciable change in reservoir fluid level for a given change in fluid volume, while the oblong shape of the sight glass with provision for using a stretched standard o- ring allows an indication of both maximum and minimum reservoir fluid levels. In addition, use of a face seal housed in the molded sight glass and use of self-tapping retention screws allows the level range indicating sight glass to be incorporated without any machining operations required, thereby reducing cost and providing a more reliable and robust design.

[0052] In addition to the aforementioned, a lever pivot pin (e.g., the pivot pin 64) that fits directly within the master cylinder body 6 by employing a tapering fit between the pivot pin and the body, prevents or substantially prevents the pivot pin from loosening due to vibration and repeated lever activation. Further, by virtue of utilizing the pivot pin 64, a pivot pin snap ring or nut and any associated installation labor involved with conventional master cylinder assemblies can be eliminated. Given that the master cylinder assembly 2 of the present invention does not require fasteners, the possibility of misplacing a snap ring at the point of assembly or after service can be eliminated. [0053] Notwithstanding the embodiments of the master cylinder assembly 2 described above with respect to FIGS. 1A-8B, various additional features including refinements to the features above are contemplated and encompassed within the invention. The shape, size, orientation and material of construction can vary in other embodiments from that described above, without deviating from the primary objective of the invention. Other conventional components not described above including various sealing mechanisms, ducts and connectors that are present in master cylinder assemblies can also be present. [0054] Inclusion of an adjustable lever that replaces the socket 50 described above with a socket equipped with a secondary out stop is contemplated in other embodiments. In some embodiments, the socket need not thread directly into the lever, but rather into a secondary lever pin fixed in the lever except for rotation about its axis and threaded radially to accept the threads of the socket. Provision for an adjustable lever ratio ("power") is additionally contemplated and considered within the scope of the present invention by augmenting the mechanism described above with respect to the adjustable lever with a slot and jackscrew along which the secondary lever pin can travel. The slot is oriented along a line connecting the lever pivot to an SAE point such that lever ratio remains constant throughout the stroke. The slot can also be shaped to provide a tailored lever displacement versus a ratio curve to suit the specific demands of vehicle dynamics. [0055] It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.