Abstract:
The present invention is a handle grip comprising a twist throttle with an integrated hydraulic master cylinder directed to vehicle throttle and brake or clutch controls and suitable for mounting and use on motorcycle handle bar wherein the operator selectively twists the handle grip in one direction to retract a throttle cable and in the opposite direction to release the throttle cable and activate a hydraulic master cylinder capable of providing hydraulic fluid to a hydraulically activated mechanism on the vehicle. A helical cam surface within the twist grip mechanism guides centrally positioned throttle and hydraulic cam followers within an inner stem cylinder bore forcing the followers longitudinally within the bore to activate the hydraulics or throttle. The pitch of the helical cam surface defines the distance of grip rotation and the twisting torque required to move the followers predetermined distances within the stem bore to provide sufficient activation force.

Description:
FIELD OF INVENTION 
     The present invention relates to vehicle throttle and hydraulic activators. More particularly, this invention is directed to an operator twist activated vehicle throttle control with an integral hydraulic master cylinder. The invention is principally directed to motorcycle handlebar mounted throttle and hydraulic activator applications. 
     BACKGROUND OF THE INVENTION 
     Vehicles having steering control by means of a handlebar, such as a motorcycle or scooter, typically have lever mechanisms pivotally mounted to the handlebar adjacent to the handlebar grips with a lever extending over and adjacent to the grip. These levers are typically used to pull cables or to activate hydraulic mechanisms that, in turn, activate the vehicle brake, throttle, or clutch. To utilize the lever mechanisms, the operator must loosen the grasp of the handlebar grip so as to extend the fingers outwardly and over the lever mechanism to grasp the lever portion with the thumb extended around the grip such that a squeezing motion may be used to activate the vehicle brake or clutch mechanism. The motion necessitates the operator to relinquish some control of the steering mechanism to accomplish the braking or clutch motion. 
     The majority of prior art handle controls, including thumb throttles, require activation by relinquishing some steering control to grip and squeeze an adjacent lever mechanism. 
     Various forms of twist grip mechanisms integrated into a handlebar operator grip have been proposed for activation of cable linked throttles wherein a twisting action of the handlebar grip draws a cable onto a rotatable pulley mechanism thereby pulling the cable to activate the throttle located at the remote end of the cable. These forms of twist throttle controls fix and route the control cable to the outside surface of the handlebar. These twist throttle mechanisms have a singular purpose of activating cable linked throttles; however, additional control functions such as clutch and brake control, in particular hydraulic systems, remain relegated to lever activation mechanisms. 
     Braking and clutch mechanisms, particularly on motorcycles, are often hydraulic thereby necessitating a hydraulic master cylinder to be mounted in close proximity to the operator&#39;s hand to accomplish the required activation leverage and hence are positioned on the outside of the handlebar near the operator grip. Hydraulic master cylinders incorporating a lever mechanism activation typically include the hydraulic lines that are lashed to outside surface of the handle bar resulting in exposure of the hydraulic system to damage and road debris as well as being unsightly from a design point of view. 
     What is needed is an improved handlebar mounted vehicle control grip device incorporating hydraulic brake or clutch control with a cable linked throttle control selectively activated by a twisting action of the grip, and having control cables and hydraulic lines positioned within the handlebar for protection and improved aesthetic appearance. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a vehicle control mechanism, and, more specifically, to a twist throttle with an integrated hydraulic master cylinder also activated by a twist motion mountable to the end of a tubular bar such as a handlebar, thereby substantially obviating one or more of the problems due to the limitations and disadvantages of the related art. 
     The present invention is a combination cable type throttle and hydraulic master cylinder mountable to the open end of a tubular handlebar such as a motorcycle handlebar forming an operator grip wherein the grip is rotatable around the axis of the handlebar to activate a variable throttle mechanism when twisted in one direction past a neutral position and to selectively activate a variable hydraulic master cylinder when twisted in the opposing direction past the neutral position. The twist throttle portion draws a throttle cable into the device in proportion to the degrees of rotation past the neutral position of the grip. Similarly, a hydraulic master cylinder transports hydraulic fluid out a hydraulic fluid output port in increasing volume and pressure in direct proportion to the degrees of rotation past the neutral position of the grip in the opposing direction. 
     The twist throttle with integrated hydraulic master cylinder essentially comprises a helically shaped cam formed in a cylindrical sleeve wherein the sleeve is rotatable around the circumference of an inner stem. A pliable grip covers the helical cam sleeve to provide a convenient operator grip. A hydraulic follower, being cylindrically shaped is slidable within an inner longitudinal bore of the inner stem. The hydraulic follower has a cam follower bearing set mounted on a shaft fixed perpendicularly at a point on the circumference of the follower so as to position a top bearing in the helical cam and a lower bearing in a longitudinal guide cam. The guide cam is a slot cut in the inner steam running linearly and longitudinally along the inner stem. The mechanisms provide for the follower to slide back and forth with the bore of the inner sleeve in response to the rotational position of the helical cam sleeve and hence the helical cam relative to the longitudinal guide cam as the helical cam and the longitudinal guide cam openings must coincide as provided by the cam bearings. 
     The helical cam has at least one cam portion having a profile as represented by differing pitches of the helix. As the amount of linear displacement of the hydraulic follower within the inner stem cylinder bore is in direct proportion to the rotation of the helical cam sleeve, the pitch of the profile determines the number of degrees of rotation required for a selected linear displacement. When two cam portions are incorporated, a central neutral position defines the transition between two helical cam portions, one being for throttle activation and the other for hydraulic master cylinder activation. When the hydraulic follower is at the neutral position, neither the hydraulic master cylinder nor the throttle are activated. 
     The inner stem, having a proximate and distal end, has an outside diameter commensurate with the inside diameter of a tubular handlebar with the proximate end inserted into the end of a handlebar thereby forming a handlebar grip and extension. The hydraulic fluid output port and throttle cable routing is through the proximate end of the inner stem thereby permitting the cable and hydraulic lines to be routed internally in a tubular handlebar. The device is fixed to the handlebar by means of the reservoir and clamp comprising a hydraulic fluid reservoir with a curved bottom and a semicircular clamp when bolted to each other on and around the outside diameter of a handlebar fashioned with a hole to accommodate a hydraulic fluid communicator tube extending between the reservoir and the proximate end of inner stem thereby securely fastening the device to the handlebar. 
     The inner stem bore further provides the cylinder for the hydraulic master cylinder portion formed in the proximate end of the apparatus wherein the hydraulic follower presses against the hydraulic piston located in front of the hydraulic follower being within the same bore to activate the master cylinder. A throttle piston, also being a cylindrically shaped element and located behind the hydraulic follower within the inner stem bore, has a throttle cable centrally fixed. When the hydraulic follower moves to the rear of the bore, the throttle piston is forced to the distal end of the device thereby pulling the throttle cable towards the end of the handlebar and activating a connected throttle. The throttle cable is routed from the centrally located cable ferrule formed in the throttle piston through a cable way slot in the hydraulic follower onwards through an opening in the inner stem into a cable guide cut longitudinally along the outer surface of the inner stem through to the front of the apparatus. The throttle cable guide slot therein conceals the throttle cable from the exterior and routes the cable within the handlebar. 
     A thrust bearing is mounted to the distal end of the inner stem providing a bearing surface for the helical cam sleeve to accommodate the longitudinal thrust resulting from the twisting motion of the sleeve. 
     The hydraulic master cylinder is typically used for activating braking or clutch systems; however, any hydraulic system requiring a master cylinder may use this device. As the hydraulic cylinder piston requires less linear displacement by more force to activate than the throttle mechanism, the pitch of the helical cam is higher than that of the throttle portion thereby requiring more rotation of the grip to achieve the required mechanical advantage. Conversely, throttle portion of the helical cam has a lower pitch as less force is required but more linear displacement is required for a cable linked. 
     A twist activated hydraulic master cylinder integrated with a twist activated throttle have numerous advantages over the prior art. The fact that no additional externally mounted mechanical levers are required on the handlebars alone provides numerous advantages related to practicality including improved styling with a clean design, reduction of damage to exposed components, improved reliability, and reduced debris intrusion. More importantly, the constant grip of the steering mechanism is maintained no release of the grip is required to activate the device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate embodiments of the invention and, together with the description, serve to explain the features, advantages, and principles of the invention. 
       In the drawings: 
         FIG. 1  is a perspective view according to the present invention integrated in a motorcycle handle bar, showing the grip, the hydraulic fluid reservoir and a portion of a motorcycle handle bar with the hydraulic line and the throttle cable emerging from the handle bar. 
         FIG. 2  is a top elevation view of the present invention as in  FIG. 1 . 
         FIG. 3  is a cross section view, taken on Line  3 - 3  of  FIG. 2 , showing the hydraulic and throttle mechanism in the neutral position. 
         FIG. 4  is a sectional view taken on Line  4 - 4  of  FIG. 3 , showing the location wherein the reservoir of the present invention is mounted to a handle bar end exposing the hydraulic fluid communicator tube in position in the handle bar mounting slot and above the inner stem hydraulic fluid supply port. 
         FIG. 5  is the cross section view, taken on Line  5 - 5  of  FIG. 3 , showing the reservoir clamped to the handle bar bound with the reservoir clamp, further showing the offset cylinder bore of the inner stem with the throttle cable guide slot longitudinally positioned along the stem and along the outer circumference of the inner stem having the throttle cable in position. 
         FIG. 6  is the cross section view, taken on Line  6 - 6  of  FIG. 3 , showing the reservoir secured to the reservoir clamp by means of screw fasteners and the front end of the hydraulic cylinder positioned in the offset cylinder bore of the inner stem mounted within the handle bar, hydraulic piston return spring in hydraulic piston seal receiver cup and the front seal in direct contact with the outer circumference of the brake piston and the inner circumference of the inner stem bore. 
         FIG. 7  is a cross section view, taken on Line  7 - 7  of  FIG. 3 , showing the grip surrounding the cam sleeve recessed into the helical cam with the upper helical cam follower bearing in the helical cam chase, the lower cam follower bearing in the longitudinally positioned guide cam of the inner stem with the bearings mounted to the brake follower centrally located in the offset bore of the inner stem and throttle cable positioned in the brake piston follower cable way. 
         FIG. 8  is a cross section view, taken on Line  8 - 8  of  FIG. 3 , showing the throttle piston centrally located in the offset bore of the inner stem having a ferrule screw binding the throttle cable in a centrally positioned hole in the throttle piston. 
         FIG. 9  is a top plan view of a portion of the helical cam of the present invention with the grip and cam sleeve removed for clarity of the helical nature of the throttle and brake cam surfaces showing the helical cam follower bearing positioned in the throttle portion of the helical cam surface. 
         FIG. 10  is a cross section view, taken on Line  3 - 3  of  FIG. 2 , wherein the grip has been twisted into the full braking position showing the helical cam follower bearing forward along the helical cam brake surface portion, the brake follower forcing the brake piston forward compressing the brake piston return spring with the forward brake piston seal confining the hydraulic fluid with the inner stem cylinder and out the hydraulic fluid output port to the vehicle braking system hydraulic fluid pipe. 
         FIG. 11  is a cross section view, taken on Line  3 - 3  of  FIG. 2 , similar to  FIG. 10  wherein the grip has been twisted into the neutral position showing the brake piston rear surface relief resting on the set screw being forced back by the brake piston return spring now permitting flow of hydraulic fluid from the reservoir; and, the throttle piston in contact with the brake follower push element. 
         FIG. 12  is a cross section view similar to  FIG. 11  showing an alternate embodiment of the present invention without a throttle piston and throttle cable for applications requiring only a twist activated hydraulic cylinder. 
         FIG. 13  is a top plan view similar to  FIG. 9  showing an alternate embodiment of the helical cam without the throttle cam surface for applications requiring only a twist activated hydraulic cylinder. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. Referring now in greater detail to the various figures of the drawings wherein like reference characters refer to like parts, there is shown in a perspective view at  10  in  FIG. 1 , a new type of twist activated vehicle control for throttle activation and an integral twist activated hydraulic cylinder particularly suitable for mounting and use on a motorcycle hand bar; however, the apparatus is also suitable for other applications requiring similar control activation. 
     The perspective view of the present invention shown at  10  in  FIG. 1 , provides an exterior view of the invention essentially comprising a hydraulic master cylinder and a cable retraction apparatus operator activated by means of a twist mechanism as shown surrounded by an optional cushioned hand grip. The apparatus is preferably mounted to the end of a tubular handle bar of a vehicle such as a motorcycle for purposes of controlling a hydraulic brake or clutch and a cable driven throttle mechanism. When mounted to a handle bar, the apparatus acts as an extension to the handle bar as a handle grip. Twisting the grip around the axis of the handle bar activates the operator twist mechanism of the present invention. Twisting the grip clockwise past a central neutral position proportionally activates the hydraulic master cylinder portion whilst a counter clockwise rotation proportionally activates the throttle mechanism. The operator twist mechanism further comprises a helically formed cam surface rotatable around the central axis of the apparatus followed by a cam follower bearing mounted on a centrally positioned follower piston wherein the piston slides longitudinally within a longitudinally located cylinder responsive to the rotational position of the handle grip. 
     Referring now to  FIG. 2 , the apparatus is inserted into the open end of a tubular handle bar with the threaded hydraulic pipe fitting  152 , being in direct hydraulic communication with the output port of the master cylinder, protruding into the central opening of the handle bar. The threaded hydraulic pipe fitting  152  is further connected to the hydraulic clutch or brake system of the vehicle by means of hydraulic piping routed through the center of the handle bar. The outside diameter of the inner stem  20  is constructed so as to snuggly fit into the central opening of a typical motorcycle tubular handle bar. Convenient wrench flats  42  formed into the end of the inner stem  20  provide a means to grasp the inner stem  20  whilst fixing a hydraulic pipe to the threaded hydraulic pipe fitting  152 . 
     Referring now to  FIG. 3  showing a cross section view, the invention is constructed around a centrally located inner stem  20  forming the structural frame of the device being machined and formed to accommodate the various elements of the assembly. Note that the inner stem assembly further comprises a cylinder bore  30  machined into the inner stem  20  and having a cylinder bore bottom  28  in combination with the cylinder bore forming a brake cylinder wherein hydraulic piston  52  is slidably and first inserted into the bore. Hydraulic follower  68  is a cylindrically shaped piston with a front relief  70  positioned behind the hydraulic piston  52  with an outside diameter so selected as to be free to slide within the inner stem bore  30 . Throttle piston  80  is also a cylindrically shaped and dimensioned to slide within the bore  30  of the inner stem  20 . The throttle piston  80  is positioned behind the hydraulic follower  68 . A hydraulic piston spring  110 , retained by hydraulic piston spring containment cup  54  in the front end of the hydraulic piston  52 , returns the hydraulic piston  52  to a non-activated position, as illustrated in  FIG. 3 , by forcing the hydraulic piston  52  away from the cylinder bore bottom  28  and against the inner stem hydraulic piston set screw  50 . Note that the hydraulic piston set screw  50  is received by the inner stem hydraulic piston set screw threaded receiver  48 . 
     Referring further to  FIG. 3 , the hydraulic follower  68  is a driven element of the apparatus wherein the follower  68  slides longitudinally within the inner stem bore  30  as the longitudinal position is determined by the rotational position of a helically shaped cam surface  132  machined in cam sleeve  126 . The cam sleeve  126  is tubular in shape with an internal diameter selected to slide over the outside diameter of the inner stem  20 . A helical cam follower bearing  138  is mounted to hydraulic follower  68  by means of the follower bearing mount  142 , being a pin shaped shaft, perpendicularly fixed into the outer diameter of the hydraulic follower  68  and retained in the hydraulic follower  68  by being press fitted into the follower bearing receiving recess  130 . The helical cam follower bearing  138  is a roller bearing pressed on to the top end of the bearing mount  142  and so positioned such that the outer bearing surface is adjacent to the helical cam  132  surface in the cam sleeve  126 . Note that the helical cam  132  surface is a spiral shaped slot cut in the cam sleeve  126  having a constant width approximately equivalent to the outside diameter of the helical cam follower bearing  138 . A longitudinal guide cam  38  is machined into the inner stem  20  running along the length of the inner stem  20  for a length selected to limit the longitudinal sliding motion of the hydraulic follower  68 . A guide cam follower bearing  140  is positioned between the helical cam follower bearing  132  and the hydraulic follower  68  being pressed onto the brake follower bearing mount  142 . The longitudinal guide cam  38  has adjacent guide cam surfaces  40  fashioned parallel to each other at a distance approximately the outer diameter of the longitudinal guide cam bearing  140 . The hydraulic follower  68  is therefore selectively positioned longitudinally within the inner stem bore  30  by a rotational movement of the helical cam sleeve  126  wherein the helical cam bearing  138  tracks with the helical cam  132  surfaces forcing the longitudinal guide cam bearing to move longitudinally along the inner stem longitudinal guide cam  38  resulting in the hydraulic follower  68  to respectively be positioned in the corresponding position with the inner stem bore  30 . The helical cam  132  and the longitudinal guide cam  38  interaction thereby determines the location of the hydraulic follower  68  within the inner stem bore  30 . 
     The hydraulic follower  68  may therefore be selectively positioned by a twisting motion of the helical cam sleeve to force the follower  68  forward towards the hydraulic piston  52 . The hydraulic follower  68 , having a hydraulic piston activation surface  72 , not be fixed to the hydraulic piston rear face  58 , pushes the hydraulic piston  52  forward within the inner stem bore  30 . The resulting forward motion of the hydraulic piston  52  forces hydraulic fluid out through the inner stem output port  24  and onwards to devices in direct hydraulic communications with the hydraulic pipe  154  being fixed to the inner stem output port  24  by the threaded hydraulic pipe fitting  152  fitted into the inner stem output port  24 . 
     Still referring to  FIG. 3 , the throttle piston  80 , being cylindrically shaped has a centrally located bore in the face of the piston. This forms a throttle piston cable way  82  having a diameter selected to accommodate a flexible throttle cable  88  being secured within the throttle piston cable way by ferrule screw  86 . A threaded ferrule screw receiver bore  84  is drilled and tapped perpendicular to the outside diameter of the throttle piston  80  such that the ferrule screw  82  may be tightened against a throttle cable  88  within the cable way  82 . The length of the ferrule screw  82  is selected to avoid interference with the inner stem bore  30  surface. 
     The throttle piston  80  is forced longitudinally within the inner stem bore  30  by the adjacently positioned hydraulic follower  68  wherein the follower rear surface  74 , not being fixed to the throttle piston, forces the throttle piston rearward within the inner stem bore  30  when the helical cam sleeve  126  is rotationally positioned to force the hydraulic follower  68  longitudinally rearward through the inner stem bore  30 . It should be emphasized that the throttle piston  80  is not fixed to the follower  68  thereby being free to slide within the bore  30 , being an important feature such that the follower  68  separates from contact with the throttle piston when the hydraulic follower  68  moves forward from a neutral position to activate the hydraulic piston. Conversely, when the hydraulic follower moves rearward, the hydraulic follower surface  72  separates from the hydraulic piston  52 , being restrained by the inner stem hydraulic piston set screw, and the rear surface  74  of the follower  68  contacts the throttle piston  80  forcing the throttle piston  80  rearward through the inner stem bore  30 . Tension on the throttle cable  88 , being in direct mechanical connection with a throttle device to be activated, maintains the contact between the throttle piston  80  and the hydraulic follower  68  whilst the helical cam sleeve is twisted away from the neutral position to activate the throttle mechanism. 
     As illustrated in  FIGS. 3 and 4 , the apparatus is mounted to a tubular bar, such as a motorcycle handle bar, by means of a clamping action formed by a hydraulic reservoir element  90  clamped to a reservoir clamp  98 . During the operation of mounting the apparatus to a tubular handle bar, a circular hole is fashioned perpendicularly into the surface of the tubular handle bar  156  for purposes of retaining a cylindrically shaped hydraulic fluid communicator tube  104 . The front end of the inner stem  20  has an outside diameter engineered to slide snuggly into the bore of the tubular handlebar and positioned such that the hydraulic fluid communication tube receiver  22  being a cylindrically shaped recess fashioned in the outer diameter of the inner stem and having a flat bottom  28 , and a forward and a rear hydraulic fluid supply port,  44  and  46 . The inner stem  20  is slid into the tubular handlebar  156  and positioned such that the communicator tube receiver  22  is aligned with the circular hole in the handlebar  156 . The communicator tube  104  is pressed into the receiver  22  and has sufficient height to accommodate the thickness of the handlebar and to be retained by the communications tube receiver  22  similarly bored into the bottom of the hydraulic fluid reservoir  90 . It will be appreciated that the communicator tube  104  is preferably sealed to the reservoir  90  by hydraulic fluid communicator tube reservoir seal  106  and sealed to the inner stem by inner stem seal  108 , both typically being an o-ring. The assembly provides for hydraulic fluid residing in the hydraulic fluid reservoir  90  to be supplied to the inner stem  20  and further to the hydraulic cylinder of the apparatus. 
     Details of the reservoir clamping action are more clearly illustrated in  FIG. 5 , a cross section taken along line  5 - 5  of  FIG. 3  and  FIG. 6 , a cross section taken along line  6 - 6  of  FIG. 3 . The hydraulic reservoir hydraulic fluid reservoir  90 , forming the top portion of the apparatus mounting mechanism comprises a central reservoir vessel sealed to by means of a removable reservoir screw cap  92  fitted to the top edge of the reservoir permitting the user to adjust the hydraulic fluid level of the apparatus. The bottom surface  96  of the reservoir is curved to match the top half of the circumference of a typical handlebar  156 . The bottom curved surface  96  extends substantially half the circumference of the handlebar  156 , but not the full half circumference so as to allow the reservoir bottom clamp  98 , being similarly formed with a curved surface, to match the opposing half circumference of the handlebar  156  thereby providing a gap between the two pieces when mounted to the handlebar  156  providing clearance to securely clamp the two pieces together, firmly grasping the handlebar  156 . Reservoir screw fasteners  148  are received by threaded receivers  100  in the reservoir  90  portion and inserted through holes in the reservoir clamp  98 . Tightening the fasteners  148  secures the apparatus to the handlebar  156  with the hydraulic fluid communicator tube  104 , being fixed in recesses in the inner stem  20  and the reservoir  90  preventing the apparatus from rotating within the handlebar  156  or from sliding out of the handlebar  156  interior. 
     Note also in  FIGS. 5 and 6 , the throttle cable guide  36  milled longitudinally into the outer surface of the inner stem  20  forming a channel for the throttle cable  88  to be routed from the throttle piston  80 , the end being retained by the ferrule, guiding the cable  88  through to the front of the inner stem  20 , as in  FIG. 1 , and into the annular opening of the handlebar  156  for further routing to a throttle control device. The throttle cable  88  is free to move back and forth within the guide  36  being responsive to the longitudinal position of the throttle piston  80  within the inner stem bore  30  and the tension exerted by a throttle control device. Note also the offset centering of the inner stem bore  30  within the inner stem  20 . This offset permits the wall of the inner stem  20  to provide additional strength and thickness for the longitudinal guide cam, located and centered within the thickest stem portion, while also providing additional surface area for the guide cam bearing  38 . The output port  24  is also offset in the stem and in the cylinder bore bottom  28 , substantially opposing in position the location of the throttle cable guide  36 , for purposes of providing clearance for the throttle cable guide  36  to conveniently stand clear of hydraulic fittings while also avoiding interference with the internal diameter of the handlebar  156 , such as illustrated in  FIG. 3  at  152 . 
     Returning briefly to  FIG. 3 , the hydraulic follower  68  has a throttle cable groove  76  running from the center of the rear face of the follower  68  such that the throttle cable  88  is free to slide and align with the ferrule of the throttle piston  80 . This groove also allows the rear face  74  of the hydraulic follower  68  to press flat against the front face of the throttle piston  80  and eliminates binding of the throttle cable  88  and follower  68 . Note further that the throttle cable  80  is routed through a hole through the inner stem bore  30  aligned with the inner stem throttle cable guide  36  for subsequent routing out the proximate end of the inner stem  20  and into the annulus of a handlebar. 
     Further in  FIG. 6 , showing a cross section view of an embodiment of the present invention taken along line  6 - 6  of  FIG. 3 , the throttle cable guide  36  still visible with the throttle cable  88 , the front portion of the hydraulic piston  52  is shown with hydraulic piston spring  110  seated in a piston spring containment cup  54  feature in the front portion of the hydraulic piston  52 , surrounded by the piston seal  62  sealing the hydraulic piston  52  against the bore of the inner stem  20 . 
     Next in  FIG. 7 , a cross sectional view taken along line  7 - 7  of  FIG. 3 , shows a cross section of the hydraulic follower  68  with the guide cam and helical cam follower bearings  140  and  138  positioned within the respective guide and helical cams  38  and  132 . The cam shell  144  fits into a recess  130  in the helical cam sleeve  126  is optional for securing and protecting the helical cam  132  surfaces from debris. The cam shell  144  is formed from a flat rectangular metal sheet rolled into a tube with a gap  128  between the opposing ends of the metal sheet. The gapped tubular shape of the shell provides for easy of assembly wherein the shell may be temporarily expanded in diameter to slide over the cam sleeve  126  for insertion into the cam sleeve recess  130  in the cam sleeve  126 , as illustrated in  FIG. 3 . The grip  146  encircling the cam shell  144  and cam sleeve  126  is preferably constructed of a polymer or elastomeric material so as to provide characteristics suitable for gripping by and comfort for an operator. In  FIG. 7 , note that the cam sleeve  126  is free to rotate concentrically around the inner stem  20  outer circumference responsive to the rotation of the grip  146  as the helical cam follower bearing  138  is selectably positioned within the helical cam  132 . 
     Details of the relative positioning of the throttle elements are shown in  FIG. 8  being a cross sectional view taken along line  8 - 8  of  FIG. 3 . Note that the throttle piston  80  is free to slide within the offset bore of the inner stem  20 . The cable ferrel mechanism comprises, in part, the ferrel screw  86  tightly seated against the throttle cable  88  in the centrally located cable way  82 . 
     An essential element according to the present invention is illustrated in  FIG. 9  showing details of the helical cam  132  in the cam sleeve  126 , and its relative positioning to the longitudinal guide cam  38  in the inner stem  20 . It will be appreciated that as cam sleeve  126  is rotated in either direction around the inner stem  20 , follower  68  is forced either forward or backward within the bore of the inner stem  20  as the cam follower bearings track the helical cam  132  and longitudinal guide cam  38 . The helical cam  132  is a varying spiral shaped cut in the helical cam sleeve  126  along the longitudinal axis of the sleeve. As configured in  FIG. 9 , the helical cam has a right hand twist shape wherein a right hand rotation of the helical cam sleeve positioned the cam follower bearing  138  closer to the front of the sleeve while a left hand rotation positioned the bearing towards the rear of the helical cam. Note that in the illustrated embodiment the helical cam  132  has two cam portions exhibiting differing profiles  136  and  134 . The pitch of the profile of the cams is selected to determine the degrees of rotation of the cam sleeve required to accomplish a selected respective longitudinal displacement of the follower  68 . The selected pitch to displacement ratio is also directly related to the torque selected and required to twist the grip of the device activate the hydraulic or throttle mechanisms. Therefore the profile of the cams may be fashioned to provide a desired twisting torque force requirement at any point within the range of the apparatus. For example, a linear pitch for a first cam portion associated with the hydraulic cylinder will likely yield an increasing torque requirement as the cylinder is activated depending upon the specifics of the hydraulic requirements of the activated system. The lower the pitch of the profile the greater the longitudinal displacement per degree of rotation. Consequently, the pitch may be varied, if required for a specific application, along the length of the profile to provide a constant or varying predetermined twist force throughout the full range of activation. 
     When force is applied to twist grip  146 , to activate the hydraulic piston  52 , a reactive force is experienced by the cam sleeve  126  tending to force the sleeve towards the back of the inner stem  20  therefore a means of longitudinally securing the helical cam sleeve to the inner stem whilst allowing rotation. Consequently, thrust bearing  120  is provided to resist the force. Any suitable thrust bearing may be utilized. In the illustrated embodiment, the thrust bearing comprises a thrust bearing end cap  112 , a thrust bearing  120  with an inner washer  122  below and an outer washer  124  above slid over the threaded shaft  116  portion of the thrust bearing end cap  112 . Because the cam sleeve  126  rotates around the outer circumference of the inner stem  20 , the thrust bearing assembly also is arranged such that the bearing assembly rotates around the central axis of the inner stem  20 . Accordingly, the rear end of the inner stem  20  is centrally bored and tapped to accommodate the threaded base  118  of the thrust bearing end cap  112 . The thrust bearing thereby is positioned between the rear end of the cam sleeve  126  and the bearing end cap  112  thus providing a thrust surface for the cam sleeve  126  to transfer rearward directed force from the cam sleeve  126  to the inner stem  20  hence retaining the cam sleeve  126  in the apparatus and from sliding off the distal end. The thrust bearing end cap screw slot  114  is provided for convenience of assembly by providing a surface to thread the cap into the inner stem. 
     The hydraulic follower  62  longitudinal position within the central bore  30  determines the mode of operation of the apparatus. Referring to  FIG. 10  wherein the apparatus is shown activating the hydraulic piston  52 , hydraulic fluid is pressurized and forced out the output port  24 . The hydraulic piston  52  has an activator push element  56  being a cylindrically shaped expansion of the rear of the hydraulic piston  52 . The push element  56  provides the hydraulic follower  62  a surface to contact the hydraulic piston while also providing convenient spatial alignment. 
     The hydraulic portion of the apparatus defines a typical hydraulic master cylinder, having functionality well known in the prior art, with the hydraulic piston  52  slidable in a cylindrically shaped bore having a bottom  28  with the output port  24  in fluid communication with the cylinder bore  30 . The apparatus in a hydraulic neutral mode, as shown in  FIG. 11 , comprises a return spring  110  fitted between the front end of the piston  52  and the cylinder bottom  28  providing a return of the hydraulic piston  52  to the hydraulic neutral location in the bore  30 . A forward hydraulic seal  62 , preferably a lip type seal, is positioned such that the lip faces towards the cylinder bottom  28 . The seal is retained by a circumferentially positioned retainer groove  60  proximate to the front end of the hydraulic piston  52 . In the neutral position, the lip seal  62  presses against the cylinder wall at a location behind and proximate to a forward fluid supply port  44  providing fluid communication between reservoir  90  and the cylinder bore  30 . When the hydraulic piston  52  moves forward during activation, the lip seal  62  moves past the forward fluid supply port  44  thereby sealing the cylinder from the reservoir  90  allowing the piston  52  to compress the fluid captured in the cylinder. There is also a hydraulic piston o-ring seal  66  positioned in a retainer groove  64  milled in the hydraulic piston circumference towards the rear of the piston and so engineered to seal against the cylinder bore. The o-ring seal  66  is positioned behind a rear fluid supply port  46  providing fluid communication between the reservoir and the vent chamber defined by the lip seal  62 , the circumference of the hydraulic piston  52 , the rearwardly positioned o-ring seal  66  and the inside surface of the inner stem bore  30 . The o-ring seal  66  is further positioned at a location on the hydraulic piston  52  such that the seal is always longitudinally located behind the rear fluid supply port  46  regardless of the stroke position of the piston  52 . During activation of the hydraulic piston  52 , the rear fluid supply port  46  permits fluid flow back into the reservoir to provide for the volume reduction of the vent chamber as the lip seal  62  expands rearward as hydraulic fluid pressure increases on the forward side of the seal when the hydraulic fluid is compressed. In this manner the lip seal  62  is permitted to press with an increasing hydraulic fluid pressure, during a compressive stroke, against the cylinder wall as the fluid behind the lip seal  62  is vented to the reservoir  90 . 
     It will be appreciated that the elimination of the throttle piston and associated throttle portion of the helical cam, as shown in the alternate embodiment of  FIGS. 12 and 13 , provides a twist activated hydraulic master cylinder for applications where a cable linked throttle are not required. This alternate embodiment may be used, for example, as a clutch activator in application where another embodiment is mounted as the opposing handlebar grip. In the alternate embodiment, the throttle portion of the helical cam is not milled, the throttle piston is absent, and the cable ways are optionally not cut so as to reduce the manufacturing cost of the device.