Patent Publication Number: US-6217400-B1

Title: Control for marine transmission

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a control for a marine transmission and more particularly to an improved actuator assembly for such transmissions. 
     Conventional marine transmissions employ a driveshaft which has a bevel gear that is affixed to its lower end and which is engaged with a pair of diametrically opposed, and hence, counter-rotating-driven beveled gears. This driven bevel gears are journaled on the propeller shaft and are selectively clutched for driving relationship therewith by a dog-clutching mechanism that is positioned between the bevel gears. 
     It is conventional to utilize a shift plunger which extends into one end of the propeller shaft and which operates in conjunction with a pin that carries the dogclutching element for effecting the axial shifting of the dog-clutching element into engagement with selected ones of the driven counter-rotating bevel gears. 
     Various types of mechanisms have been employed for actuating the shift plunger. Some of these utilize a cam mechanism that is operated by a rotating cam formed at the lower end of a shift rod which is actuated by the vessel operator. This cam mechanism requires the cam to be held against rotation about the propeller shaft axis while the shift plunger does rotate along with the pin that couples it to the dog-clutching element. Hence, a number of small pieces must be assembled together in order to complete this mechanism. This adds to the cost and complexity and also gives an area where failures may occur. 
     Another type of mechanism employs a crank pin that operates in a slot in the shift plunger. This eliminates the need for the connecting member to permit relative rotation. However, these types of mechanisms require a fairly large bearing area and generally make it difficult to keep a small size for the lower unit. If the lower unit&#39;s size is increased, particularly at its forward end where this mechanism resides, then hydrodynamic drag can be unacceptably increased. 
     It is, therefore, a principal object of this invention to provide an improved transmission control for a marine transmission reversing-gear shifting mechanism. 
     It is a further object of this invention to provide an improved actuating mechanism for the shift plunger of a marine transmission that can be relatively small in operation and size, can be conveniently assembled, and also will have a relatively large bearing area. 
     SUMMARY OF THE INVENTION 
     This invention is adapted to be embodied in a marine transmission that is comprised of a propeller shaft having a pair of counter-rotating-driven bevel gears journaled on its forward end. A dog-clutching element is disposed in keyed relationship with the propeller shaft between these driven bevel gears. The dog clutching element is axially movable therealong to effect driving engagement between selected ones of the driven bevel gears and the propeller shaft. A shift plunger extends within a bore formed in this end of the propeller shaft and is coupled to the dog-clutching element for effecting its reciprocation into driving engagement with the selected driven bevel gear. 
     An area at the upper portion of the lower unit is formed with a key hole shaped opening through which a shift rod passes. The shift rod has a cylindrical bearing portion that is complementary in diameter to the cylindrical portion of the key hole shaped opening, and thus is rotatably journaled therein. A crank arm depends from this bearing portion and is engaged in a groove formed in the shift plunger for operating the shift plunger upon rotation of the shift rod. The crank arm has an offset dimension which is only slightly less than the long dimension of the key hole shaped slot, so that it can pass through the key hole shaped slot for assembly purposes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of an outboard motor constructed in accordance with an embodiment of the invention. 
     FIG. 2 is an enlarged cross-sectional view taken through the forward end of the lower unit of the outboard motor and shows the transmission and transmission actuating mechanism in cross-section. 
     FIG. 3 is a partially exploded, perspective view showing the mechanism illustrated in FIG. 2 with the slotted opening that receives the shift rod moved forwardly so as to more clearly show its shape. 
     FIG. 4 is an enlarged cross-sectional view taken through the forward end of the propeller shaft and is generally an enlargement of the portion show in cross-section in FIG.  2 . 
     FIG. 5 is a cross-sectional view taken along the line  5 — 5  of FIG.  2 . 
     FIG. 6 is cross-sectional view taken along the line  6 — 6  of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
     Referring now in detail to the drawings and initially to FIG. 1, an outboard motor constructed in accordance with an embodiment of the invention is identified generally by the reference numeral  11 . Although the invention is described in conjunction with an outboard motor, the invention deals primarily with the transmission for transmitting driving forces to a propeller  12 . Therefore, the invention may also be practiced in conjunction with other types of marine outboard drives, such as an inboard/outboard drive that utilizes a similar type of transmission to an outboard motor. 
     The outboard motor  11  is comprised of a power head that consists of a powering internal combustion engine which is not shown and may be of any well-known type. This engine is surrounded by a protective cowling comprised of a lower tray portion  13  and an upper main cowling portion  14  that is detachably connected to the tray portion  13  in any suitable manner. 
     A lower unit, indicated generally by the reference numeral  15 , depends from the power head and is comprised of an upper driveshaft housing casing  16  and a lower unit casing  17 , which are connected to each other in a suitable manner. 
     A steering shaft  18  is journaled for steering rotation within a swivel bracket  19 . The steering shaft  18  is connected by means of a lower connecting member  21  and an upper connecting member, which is not shown, to the driveshaft housing  16 , for steering of the outboard motor  11  about a vertically extending steering axis. A tiller  22  is affixed to the upper end of the steering shaft  18  for effecting this steering movement. 
     The swivel bracket  19  is pivotally connected by means of a pivot pin  23  to a clamping bracket  24 . The pivot pin  23  permits tilt-and-trim adjustment of the outboard motor  11 , in a manner well-known in the art. 
     The clamping bracket  24  has a mechanism by which it may be clamped to the transom of a watercraft hull, which is shown partially and in cross-section in FIG. 1, and identified by the reference numeral  25 . 
     Referring now primarily to the remaining figures, the engine which is mounted in the power head has its output shaft coupled to a vertically extending driveshaft  26  that is journaled in a suitable manner within the driveshaft housing and lower unit  15 . This driveshaft  26  depends into the lower unit outer housing  17 . 
     A bevel driving gear  27  is affixed for rotation with the lower end of the driveshaft  26 . This driving bevel gear  27  forms a portion of a reversing transmission and shift mechanism, indicated generally by the reference character S, that is contained within the lower unit housing  17 . 
     A pair of driven bevel gears  28  and  29  are journaled on the forward end of a propeller shaft  31  to which the propeller  12  is affixed in a known manner. Because these driven bevel gears  28  and  29  are engaged with diametrically opposite sides of the driving bevel gear  27 , these gears will be driven in opposite directions of rotation as the driveshaft  26  rotates. The driven bevel gears  28  and  29  have hub portions that are journalled by bearings  30  in the lower unit  17 . 
     The driven bevel gears  28  and  29  have facing dog-clutching teeth  32  and  33  formed on opposite sides of a dog clutching element  34 . The dog-clutching element  34  has a splined connection to the propeller shaft  31  and oppositely facing dog-clutching teeth  35  and  36 . These teeth  35  and  36  are adapted to be brought into engagement with selective of the teeth  32  and  33  associated with the driven gears  28  and  29 , for establishing a driving relationship between those gears and the propeller shaft  31 . When so engaged, the propeller shaft  31  and propeller  12  will be driven in selected forward or reverse directions. 
     The construction, as thus far described, may be considered to be conventional. The invention deals with the mechanism for shifting the dog-clutching element  34  between the neutral position shown in FIG. 2, and the forward or reverse drive positions. 
     This mechanism includes a shift plunger  37  that is slidably supported within a bore  38  formed in the forward end of the propeller shaft  31 . A drive pin  39  extends through an opening  41  formed in the rear end of this shift plunger  37 . This drive pin  39  also extends through a slotted opening formed in the propeller shaft  31  and into receptive openings formed in the dog-clutching element  34 . A spring encircles the ends of the pin  39  and holds it in place. 
     The shift plunger  37  also includes a detent locking mechanism for releasably retaining the shift plunger  37  in the neutral position, as shown in FIG. 2, and may also cooperate so as to releasably retain the dog-clutching element  34  and shift plunger  37  in either or both of the forward or reverse drive positions. 
     This detent mechanism comprises a plurality of detent balls  42  that are trapped between a pair of collar members  43  and  44 . The collar member  43  is slidable upon a rod  45  which is fixed at one end to a caging member  46 . A coil compression spring  47  acts between the collar member  43  and the end plate  46 . 
     The rod  45  has a threaded connection to another end plate  48  which is engaged with the collar  44 . Hence, the spring  45  tends to urge the detent balls  42  outwardly through openings  49  formed in the plunger  37  so as to engage detent recesses  51  formed in the interior surface of the propeller shaft  31  so as to achieve the releasable locking afore referred to. If sufficient force is exerted, the balls  42  will be cammed inwardly to permit the shift to be effected. 
     The forward end of the plunger  37 , indicated by the reference numeral  52 , is formed with a headed portion  53  that defines a slot  54 . This extends into a cavity  55  formed at the front of the lower unit housing  17 . 
     A shift rod  56 , which is inserted and journaled in a manner to be described, has an offset crank arm end portion  57  that is received in the slot  54 . As a result, the plunger  37  may rotate, but the crank arm  57  can effect reciprocation of the plunger  37  along the axis of the propeller shaft  31  within the bore  38 . 
     As best seen in FIG. 3, the upper end of the shift rod  56  is formed with a splined portion  60  which passes through a guide plate  58  that is received in an opening  59  formed in the upper end of the forward part of the lower unit housing  17 . 
     A shift actuating rod  61  has a female splined portion that is received over the male splines  60  so as to effect rotation of the shift rod  56 . The shift actuating rod  61  extends upwardly through an opening in the steering shaft  18  and is rotated by a shift actuator  62  carried at the forward end of the tiller  22 . 
     The lower portion of the opening through which the shift rod  56  extends is formed with a key hole shaped opening  63  which has at its rear end a generally cylindrical portion  64  that has a diameter which is complementary to the diameter of a bearing portion  66  formed on the lower end of the shift rod  63 . From this cylindrical part, the keyhole-shaped slot  56  has a pair of forwardly extending sides  65  which terminate at a flat edge that is spaced at a distance L+α, that is slightly greater than the dimension L of the crank arm  57 . 
     As a result, by rotating the shift rod  56  ninety degrees ( 90 °) from the position shown in FIG. 3, it may be withdrawn from or inserted into the keyhole-shaped opening  63  and then rotated back into the position shown in FIG. 3 where it can register with the slot  54  upon further insertion. Once further inserted, the bearing portion  66  will be trapped in the cylindrical portion  64  of the slot  63  and the shift rod  56  will be held in position but free to rotate about the axis defined by the cylindrical portion  64  and the bearing portion  66 . Hence, it is possible to provide a very easily assembled arrangement that minimizes the number of parts and which also can be easily assembled and which also permits the lower unit outer housing  17  and particularly the submerged portion thereof, to be kept quite small. As a result, the mechanism is made not only simpler and less expensive that the prior art type constructions, but is more reliable. 
     Of course, the foregoing description is that of a preferred embodiment of the invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.