Patent Publication Number: US-2013244513-A1

Title: Trim and tilt apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of non-provisional application Ser. No. 12/477,749 filed in the United States Patent and Trademark Office on Jun. 3, 2009 which itself claims the benefit of provisional application 61/058,860 filed in the United States Patent and Trademark Office on Jun. 4, 2008, priority to which are claimed. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a trim and tilt system for use with a propulsion unit mounted on a marine craft. 
     2. Description of the Related Art 
     Conventional trim and tilt systems include a unitary trim and tilt cylinder apparatus, as disclosed in U.S. Pat. No. 5,032,094, issued Jul. 16, 1991 to Sadaji Katogi, hereinafter Katogi. Katogi discloses a trim and tilt system for trimming and tilting an outboard propulsion unit mounted on a marine craft. The trim and tilt system disclosed by Katogi includes a unitary trim and tilt cylinder apparatus having a tilt cylinder unit and a trim cylinder unit; a stern bracket configured to be mounted on the transom of the marine craft; a swivel bracket for supporting the outboard propulsion unit; the swivel bracket being pivotally supported on an upper end of the stern bracket; and a hydraulic fluid circuit for actuating the tilt cylinder unit and the trim cylinder unit. The trim and tilt cylinder apparatus has an upper end pivotally supported on the stern bracket and a lower end pivotally supported on the swivel bracket. 
     In the trim and tilt system disclosed by Katogi undue stress may be applied to the trim cylinder units at points of contact between the trim rods and the swivel bracket. This excessive stress is in part due to the unitary construction of the trim and tilt cylinder apparatus. As the outboard propulsion unit pivots during the trimming phase, the angle of the trim rods changes with respect to the swivel bracket. The weight of the propulsion unit is therefore applied to the trim rods at various angles throughout the trimming phase. This may lead to a considerable amount of transverse stress being applied to the trim rods and their respective trim cylinders which, in turn, may lead to undue wear and fatigue. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved trim and tilt system which reduces the stress experienced by trim cylinder units during the trimming of a marine propulsion unit. 
     There is accordingly provided a trim and tilt system for use with a propulsion unit and a marine craft. The trim and tilt system includes a stern bracket for mounting the trim and tilt system on the marine craft. A swivel bracket is pivotably connected to the stern bracket. The swivel bracket supports the propulsion unit. A tilt cylinder unit is connected to the swivel bracket. The tilt cylinder unit includes a tilt cylinder and a tilt rod reciprocatingly received by the tilt cylinder. A trim cylinder unit is pivotably coupled to the tilt cylinder unit. The trim cylinder unit has a trim rod reciprocatingly received by the tilt cylinder. The trim rod has at least one chamfer at a distal end thereof. A trim receiver is mounted on the swivel bracket. The trim receiver has a curved three dimensional surface for applying a force on the trim rod. 
     The trim receiver may be pivotably or rotatably mounted on the swivel bracket. The curved three dimensional surface may be a hyperboloid or paraboloid surface. The distal end of the trim rod may include a rounded surface which tapers towards the trim cylinder and a pair of spaced apart chamfers. The propulsion unit may be an outboard motor. 
     The trim and tilt system disclosed herein provides the advantage of allowing the curved three dimensional surface of the trim receiver and the distal end of the trim rod to self-align so that a force applied to the trim rod acts substantially along a longitudinal axis thereof. 
    
    
     
       BRIEF DESCRIPTIONS OF DRAWINGS 
       The invention will be more readily understood from the following description of the embodiments thereof given, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of an improved trim and tilt system in an operative arrangement between a marine craft and a propulsion unit; 
         FIG. 2  is a front elevation view of a trim and tilt cylinder apparatus of the trim and tilt system of  FIG. 1 ; 
         FIG. 3  is a side view of the trim and tilt system of  FIG. 1  shown in a lower position; 
         FIG. 4  is a side view of the trim and tilt system of  FIG. 1  shown in an intermediate position; 
         FIG. 5  is a side view of the trim and tilt system of  FIG. 1  in show in an upper position; 
         FIG. 6  is a perspective view of a trim cylinder unit of the trim and tilt cylinder apparatus  FIG. 2 ; 
         FIG. 7  is a top, front perspective view of a distal end of a trim rod of the trim cylinder unit of  FIG. 6 ; 
         FIG. 8  is a top plan view of the distal end of the trim rod of  FIG. 7 ; 
         FIG. 9  is a side elevation view of the distal end of the trim rod of  FIG. 7 ; 
         FIG. 10  is a perspective view of a trim receiver of the trim and tilt cylinder system of  FIG. 1 ; and 
         FIG. 11  is a side elevation view of the trim receiver of  FIG. 10 . 
     
    
    
     DESCRIPTIONS OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, and first to  FIG. 1 , this shows a trim and tilt system indicated generally by reference numeral  10 . The trim and tilt system  10  is for trimming and tilting a propulsion unit  12  mounted on a transom  14  of a marine craft  16 . In particular, the trim and tilt system  10  operates to move the propulsion unit  12  between a lower position and an upper position. The trim and tilt system  10  includes a stern bracket  18 , a swivel bracket  20 , and a trim and tilt cylinder apparatus  22 . The stern bracket  18  is mounted on the transom  14  of the marine craft  16 . A pivotal connection  19 , in the form of a pivot shaft in this example, connects the swivel bracket  20  to the stern bracket  18 . The swivel bracket  20  also supports the propulsion unit  12 . The trim and tilt cylinder apparatus  22  has a bottom end supported by the stern bracket  18  and is pivotally connected at a top end with the swivel bracket  20 . The propulsion unit  12  may be an outboard motor. 
       FIG. 2  shows the trim and tilt cylinder apparatus  22  in greater detail. The trim and tilt cylinder apparatus  22  includes a tilt cylinder unit  24  and at least one trim cylinder unit, of which there are two trim cylinder units  30  and  40  in this example. The trim cylinder units  30  and  40  are on opposite sides of the tilt cylinder unit  24  in this example. 
     The tilt cylinder unit  24  includes a tilt cylinder  26 , a tilt rod  28  reciprocatingly received by the tilt cylinder  26 , and a piston (not shown) disposed within the tilt cylinder  26 . The piston is mounted on the tilt rod  28 . The tilt rod  28  extends from a top  27  of the tilt cylinder  26 . There is a clevis  29 , in the form of an annular ring in this example, at a distal end of the tilt rod  28 . A pivot rod (not shown) extends through the clevis  29  and pivotally connects the trim and tilt cylinder apparatus  22  to the swivel bracket  20 . 
     The trim cylinder units  30  and  40  each include a trim cylinder  32  and  42  respectively. Trim rods  34  and  44  each reciprocatingly received by a corresponding one of the trim cylinders  32  and  42 , and a piston (not shown) disposed within each of the trim cylinders  32  and  42 . The pistons are mounted on the trim rods  34  and  44 . The trim rods  34  and  44  extend from the tops  35  and  45  of the trim cylinders  32  and  42 . As best shown in  FIG. 2 , the trim cylinder units  30  and  40  also have respective pivot pins  36  and  46  extending through bottoms  37  and  47  thereof. The pivot pins  36  and  46  are rotatably received by the tilt cylinder unit  24  and provide a pivotal connection between the tilt cylinder unit  24  and the corresponding trim cylinder units  30  and  40 . In this example, the pivotal connections are independent of each other, allowing the trim cylinder units  30  and  40  to pivot independently. However this is not a requirement. The trim cylinder units  30  and  40  are minor images of one another with like parts which function in a like manner. Accordingly, only one of the trim cylinder units  30  is described in detail herein. 
     The trim cylinder unit  30  is shown in greater detail in  FIG. 6 to 9 . A rounded distal end  39  of the trim rod  34  is defined by a truncated semi-cylindrical body  50 . In particular, there are spaced apart chamfers  52  and  54  at opposite sides  56  and  58  of the truncated semi-cylindrical body  50 . The chamfers  52  and  54  extend along axes which are generally perpendicular to a longitudinal axis  100  of the trim rod  34 . Portions of the sides  56  and  58  of the truncated semi-cylindrical body  50  are also cut away so that a rounded surface  51  of the truncated semi-cylindrical body  50  tapers towards the trim cylinder  32 . 
     In this example, the truncated semi-cylindrical body  50  is machined separately from the trim rod  34 . As best shown in  FIGS. 7 to 9 , the truncated semi-cylindrical body  50  is machined as a protuberance on a substantially annular or cylindrical base  53 . The base  53  is then pressed into a bore (not shown) at an end of the trim rod  34 . In other embodiments however the base and the end of the trim rod may be threadedly inter-engaged or machined as a unitary structure. Preferably the truncated semi-cylindrical body  50  is formed from bronze ore and, as best shown in  FIG. 8 , the chamfers  52  and  54  are off center and not aligned with each other. 
     Referring back to  FIG. 2 , pads  31  and  33  limit pivoting of the first trim cylinder unit  30  relative to the tilt cylinder unit  24 . Similarly, pads  41  and  43  limit pivoting of the second trim cylinder unit  40  relative to the tilt cylinder unit  24 . In this example, the pads are aluminum pads, but in other embodiments the pads may be resilient pads, e.g. non-linear springs, non-linear rubber bumpers, or polyurethane pads. The pads may also be in the form of inserts which can be installed and removed allowing for easy maintenance should the pads become damaged or worn. Preferably, the pads are disposed near the tops  35  and  45  and bottoms  37  and  47  of the trim cylinder units  30  and  40  respectively. 
     The trim and tilt cylinder apparatus  22  also includes a hydraulic reservoir  60  and a pumping unit  62  which together provide hydraulic fluid to the tilt cylinder unit  24  and the trim cylinder units  30  and  40 . The reservoir  60 , the pumping unit  62 , the tilt cylinder unit  24 , and the trim cylinder units  30  and  40  form a hydraulic circuit. During operation of the trim and tilt cylinder apparatus  22  hydraulic fluid is pumped into and out of the tilt cylinder  26  and the trim cylinders  32  and  42  in order to move the propulsion unit  12 , which is shown in  FIG. 1 , between the lower position and the upper position. 
     Referring now to  FIGS. 3 to 5 , the trim and tilt system  10  further includes a pair of trim receivers, each of which is configured to receive the trim rod of a corresponding one of the trim cylinder units. However, only one of the trim receivers  70 , which receives the trim rod  34  of the first trim cylinder unit  30 , is shown in the drawings. The trim receiver  70  is rotatably mounted on the swivel bracket  20 . The other trim receiver (not shown) is also rotatably mounted on the swivel bracket  20  and receives the trim rod  44  of the second trim cylinder unit  40 . The trim receivers are mirror images of one another with like parts which function in a like manner. Accordingly, only the trim receiver  70  shown in the drawings is described in detail herein. 
     The trim receiver  70  is best shown in  FIGS. 10 and 11 . In this example, the trim receiver  70  has bore  72  which allows the trim receiver  70  to be rotatably mounted about a cylindrical projection or shaft  25  on the swivel bracket  20  as shown in  FIGS. 3 to 5 . However, in other embodiments other means may be used to rotatably or pivotally connect the trim receiver to the swivel bracket. Referring back to  FIGS. 10 and 11 , the trim receiver  70  has a concave receptacle  74  for receiving the trim rod  34  of the first trim cylinder unit  30 . The receptacle  74  has a three-dimensional, curved surface  76  which defines a vertex  78  of the receptacle  74 . The curved surface  76  may be a hyperboloid or paraboloid surface, or other such surface. As best shown in  FIGS. 3 to 5 , when the trim receiver  70  is mounted on the swivel bracket  20 , at least a portion  79  of the curved surface  76  faces laterally outward of the swivel bracket  20 . 
     In operation, when the propulsion unit  12  is in the lower position, the tilt rod  28  is substantially disposed within the tilt cylinder  26  as best shown in  FIG. 2 . The trim rods  34  and  44  are also substantially disposed within the trim cylinders  32  and  42  as shown in  FIG. 2 . This is also shown in  FIG. 3  for the first trim cylinder unit  30 . 
     To move the propulsion unit  12  from the lower position to the upper position, the pumping unit  62  is operated to pump hydraulic fluid from the reservoir  60  into the bottoms of the tilt cylinder  26  and both of the trim cylinders  32  and  42 . As shown in  FIG. 4 , this causes the tilt rod  28  to extend from the tilt cylinder  26  and pivot the swivel bracket  20  upwards about the pivotal connection  19  between the swivel bracket  20  and the stern bracket  14 . The trim rods  34  and  44  also extend from the trim cylinders  32  and  42 . As shown in  FIG. 4 , for the first trim cylinder unit  30 , this causes the distal end  39  the trim rod  34  to come into operative engagement with the corresponding trim receiver  70 . The trim cylinder units  30  and  40  thereby also act pivot the swivel bracket  30  upwards. This phase of the operation is considered the trimming phase during which an operator is able to set a running position of the propulsion unit  12 . 
     The trimming phase ends when the trim rods  34  and  44  are fully extended out of the trim cylinders  32  and  42 . After the trim rods  34  and  44  are fully extended, the tilt rod  28  may continue to extend out of the tilt cylinder  26  and pivot the swivel bracket  20  upwards. As shown in  FIG. 5 , for the first trim cylinder unit  30 , this causes the trim receiver  70  to move away from the trim rod  34 . The swivel bracket  20  continues to pivot upwards until the tilt rod  28  is fully extended out of the tilt cylinder  26 . This phase of the operation is considered the tilting phase during which an operator is able to bring the propulsion unit  12  out of the surrounding water. 
     Considering now the opposite motion, to move the propulsion unit  12  from the upper position to the lower position, the pumping unit  62  is operated to pump hydraulic fluid from the reservoir  60  into the top of the tilt cylinder  26 . This causes the tilt rod  28  to retract into the tilt cylinder  26  and pivot the swivel bracket  20  downwards about the pivotal connection  19  between the swivel bracket  20  and the stern bracket  14 . Eventually the trim receivers  70  come into operative engagement with the trim rods  34  and  44 . The weight of the propulsion unit  12  exerts a force on the trim rods  34  and  44 , causing the trim rods to retract into the trim cylinders  32  and  42 . The swivel bracket  20  continues to pivot downwards until the tilt rod  28  and both of the trim rods  34  and  44  are fully retracted into their respective cylinders  32  and  42 . 
     The trim receivers disclosed herein provide the advantage of allowing the trim rods  34  and  44  to self-align therewith. Accordingly, when the propulsion unit  12  is moved between lower and upper positions, the force exerted by the propulsion unit  12  on the trim rods  34  and  44  is substantially along the longitudinal axes of the trim rods  34  and  44 . This minimizes the stress put on the trim cylinder units  30  and  40  as the propulsion unit  12  is moved between the lower and the upper positions. It also allows the trim cylinder units  30  and  40  to handle greater loads. 
     When the rounded distal ends of the trim rods  34  and  44  come in to engagement with the trim receivers  70 , the curved surface  76  of the receptacle  74  guides the rounded distal ends of the trim rods  34  and  44  towards the vertex  78  of the receptacle  74 . This is facilitated, at least in part, by the pivotable and/or rotatable disposition of the trim cylinder units  30  and  40  and the trim receivers  70 . The trim rods  34  and  44  are thereby able to substantially self-align with the trim receivers  70 . Furthermore, once the trim rods  34  and  44  are aligned with the trim receivers  70 , the chamfers on the  52  and  54  on the rounded distal ends of the trim rods  34  and  44  prevent the trim rods  34  and  44  from skewing outwards of the trim receivers  70 , thereby ensuring lateral stability. 
     If the trim rods  34  and  44  are misaligned with the trim receivers, the chamfers  52  and  54  on the rounded distal ends of the trim rods  34  and  44  engage with the portion  79  of the curved surface  76  of the receptacle which faces laterally outward of the swivel bracket  20 . The non-aligned, off center position of the chamfers  52  and  54  allow the trim rods  34  and  44  to twist out and thereby provide a restorative moment which brings the trim rods  34  and  44  into alignment. As shown in the Table 1 below, the present invention allows misaligned trim rods to self-align within approximately two strokes. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Experimental Data Showing the Strokes 
               
               
                 Required for a Trim Rod to Self-Align 
               
            
           
           
               
               
            
               
                 Degree of 
                 Strokes Required for a 
               
               
                 Misalignment 
                 Trim Rod to Self-Align 
               
               
                   
               
               
                  45° 
                 less than half a stroke 
               
               
                  90° 
                 approximately one stroke 
               
               
                 105° 
                 approximately two strokes 
               
               
                 120° 
                 Less than half a stroke 
               
               
                   
               
            
           
         
       
     
     It will be understood by a person skilled in the art that the terms “top”, “bottom”, “upwards”, and “downwards” as used herein, are used in only in relation to positions and directions as shown in the Figures. 
     It will be understood by a person skilled in the art that many of the details provided above are by way of example only, and are not intended to limit the scope of the invention which is to be determined with reference to the following claims.