Abstract:
Apparatus shears foreign matter that might entangle propellers and related structures on a moving vessel by action of a blade rotating with the propeller that cooperates with a non-rotating blade held close to the rotating blade. The mechanisms for holding the blades close and parallel include a lubricant packed passage for a supporting cylinder portion of the non-rotating blade, enclosed clamping elastic bias elements for controlled movement of the cylinder, and adjustments for holding the blade parallel.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to marine devices that cut lines, weeds, nets, and the like, and more particularly to shearing cutters that employ a blade rotating with the propeller of a vessel that cooperates with a non-rotating blade mounted on a non-rotating portion of a vessel adjacent the propeller shaft to engage and shear items that appear between the two cutters. Lines, nets, weeds and the like are commonly encountered by vessels. They may be swept by the propeller blades into the propeller shaft apparatus i.e. into the space where the propeller shaft extends from its housing where they can cause great harm. There they may cut through the oil seals causing loss of lubricant. The current trend toward long line fishing wherein heavy monofilament nylon many miles long is lying in the water has exacerbated the problem. 
   DESCRIPTION OF RELATED ART 
   U.S. Pat. No. 6,004,174 issued Dec. 21, 1999 to applicant discloses a rotating blade that rotates with the propeller of a vessel that cooperates with a non-rotating blade on a non-rotating portion of a vessel adjacent the propeller shaft to shear foreign items that appear between the blades. The position of the propeller will change relative to the hull, advancing axially when under way in forward due to the forward thrust of the propeller. Heating and cooling of the shaft will also change propeller axial position. Means are provided for maintaining a close distance between the pair of radially extending shearing cutters. A mechanism senses propeller location and a moving mechanism moves the non-rotating blade to accommodate these changes in relative propeller location to maintain a fixed, very close spacing between the two blades for effective shearing action. The non-rotating blade moves axially within its support. A slot follower connected to the non-rotating blade engages a slot carried by the rotating blade to adjust the axial position of the non-rotating blade to compensate for axial movement of the rotating blade. A wedge and valley mechanism holds the two blades together when a foreign item is engaged to enhance shearing action. An adjustable clamping force restrains free axial movement of the non-rotating blade. This clamping force is applied by screw adjustments that include polyurethane elastomeric segments. Over time, these elastomeric segments deform so that the preset clamping force is reduced to unacceptable levels. It has been found that over time, the support for axial movement of the non-rotating blade becomes bound by its exposure to sea water. When the vessel is in dry dock, the rope guard onto which the support for the non-rotating blade is welded must be cut away for maintenance access to the propeller shaft bearings and/or seals. When the rope guard is welded back in place, it is difficult to reposition the non-rotating blade support so that the non-rotating blade is parallel to the rotating blade. If the non-rotating blade and support are broken away during operation, it would be useful to be able to replace them underwater. This is not feasible with the prior art apparatus because parallel relationship of the blades cannot be adjusted. 
   BRIEF SUMMARY OF THE INVENTION 
   It is accordingly an object of the invention to provide improvements to the prior art rotary weed and line cutter to overcome the problems encountered in long term use of the device. It is an object of the invention to overcome the deformation of the elastomeric segment. It is an object of the invention to overcome the binding action on the axial motion support by lubricant enclosure. It is a further object of the invention to provide means for enabling enhanced adjustment of positioning of the non-rotating blade support assembly even under water so that the non-rotating blade will be parallel to the rotating blade. 
   The system includes a non-rotating blade that has a shearing plane perpendicular to the axis of rotation of the shaft. This blade rides in a blade holder that permits limited axial movement of the blade. The blade holder generally mounts on a strut or the rope guard that surrounds the rotary shaft and its bearing. One or more rotating blades are mounted on the propeller hub or shaft with a shearing plane parallel to the non-rotating blade. The shearing planes of the two blades must be very close together for effective cutting. To ensure optimal axial positioning of the two blades, the rotating blade carries along with it a positioning groove or slot. The non-rotating blade carries a slot follower with tapered leading and following edges. As the slot encounters a tapered edge of the slot follower during its rotation, the slot follower and its blade are moved axially until the slot follower fits into the slot, thereby moving the two blades into the blade spacing necessary to begin the shearing action. Adjustable damping means are provided to slow the axial movement to avoid excessive axial movement between revolutions from the thrust of the moving water that includes means for maintaining a preset tension of the damping adjustment over time. A wedge and valley mechanism is also provided to bring the blades together for shearing when an item appears between them. These and other objects, features and advantages of the invention will become more apparent when the detailed description is studied in conjunction with the drawings, in which like reference characters indicate like elements in the various drawing figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view, partially cut away, of a cutter apparatus of the prior art. 
       FIG. 2A  is a sectional detail view through line  2 A- 2 A of  FIG. 1 . 
       FIG. 2B  is a sectional detail view through line  2 B- 2 B of  FIG. 1 . 
       FIG. 3  is a sectional isometric view of the cutter of the invention. 
       FIG. 4  is a perspective view, partially broken away, of the apparatus of the invention installed on a vessel. 
       FIG. 5  is a front elevation view of the non rotating portion of the cutter of the invention. 
       FIG. 6  is a sectional view through line  6 - 6  of  FIG. 4 . 
       FIG. 7  is a top view of the non rotating portion of the cutter of the invention. 
       FIG. 8  is a sectional view through line  8 - 8  of  FIG. 7 . 
       FIG. 9  is a sectional view through line  9 - 9  of  FIG. 7 . 
       FIG. 10  is an exploded view of the no-rotating portion of the cutter of the invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring now first to description of the prior art in  FIGS. 1 ,  2 A and  2 B, a vessel  81  has a propeller shaft  82  journalled within a propeller shaft housing  83  with a propeller hub  84  carrying propeller  85  affixed to the shaft. A rotating blade assembly  93  is affixed to the shaft or propeller hub. A rope guard  86  surrounds the shaft and is fixed to the vessel. A support block  87  for supporting the non-rotating blade  92  is bolted to the rope guard  86  in correct position for cooperating with the rotating blade assembly  93 . The support block  87  is bolted by bolts to support member  88  that is welded to the rope guard. The support member is held to correct non-rotating blade position relative to the rotating blade assembly  93  and then welded to the rope guard  86 . During dry dock maintenance operations, the rope guard may be cut off in order to access the shaft bearing and/or seal. To weld it back in correct position is a difficult task. The rotary blade assembly  93  is bolted to the propeller hub  84  so that the rotary blade  95  extends radially beyond the hub  84 , with its shear plane perpendicular to the axis of shaft  82 . This positions the blade  95  so that it catches foreign matter as it turns and twists it inward where it will be caught and sheared against the non-rotating blade  92 . Blade  92  is held radially extended with its shearing plane parallel to the shearing plane of the rotary blade by the support block  87 . During operation of the vessel, various forces are at work that tend to move the propeller axially relative to the supporting structures holding the non-rotating blade  92 . These forces include thrust of the propeller blades against the water and expansion and contraction from heating and cooling. In order to maintain optimum spacing of the two blades when the rotating blade is moved axially by these forces, the non-rotating blade supported by the fixed support block must move axially by a corresponding amount. A slot  90  on the rotating blade assembly  93  cooperates with slot follower  91  on blade  92  to maintain the relative positions of the two blades. The axial movement of blade  92  within support block  87  is provided by cylinder  99  extending from blade  92  which slides axially within lubricous sleeve bearing  100  fixed in axial hole  104  in support block  87 . Adjustment screws  105  force elastomeric segments  103  against plates  106  to clamp the cylinder  99  in the sleeve. A wedge  101  affixed to blade  92  fits into valley  102  in support block  87 . When foreign material is caught between the blades, the wedge is forced against the valley. This causes the blade  92  to move against the rotating blade  93  compressing the segments  103  as the cylinder twists in the sleeve. After prolonged operation, it has been found that the cylinder  99  no longer slides freely within the sleeve bearing  11 , interfering with operation. Also, the elastomeric clamping segments  103  become deformed, losing their adjustment. 
   Referring now to the drawing  FIGS. 3-10 , the instant invention is shown with improvements to overcome the problems encountered with the prior art apparatus. A vessel hull  54  has a propeller shaft  52  journalled within a propeller shaft housing  53  with a propeller hub  58  carrying propeller  51  affixed to the propeller shaft  52 . At least one first support rotating blade assembly  3  carrying a first blade  1  having a first shearing plane  2  is affixed to the shaft or propeller hub and arranged to rotate in conjunction with the propeller. The first support positions the first blade extending radially beyond the first support to engage foreign matter that may be encountered. At least one second blade  4  having a second shearing plane  5  is arranged with the second shearing plane substantially parallel to the first shearing plane. A second support  6  is adapted to support the second blade in a position extending radially parallel to the first blade to engage foreign matter for shearing foreign matter between the first and second blades, the second support  6  includes attaching means  7  for fixedly attaching support  6  to a non-rotating member of the hull; the first blade and the second blade each have radially extending shearing edges  8  on at least one margin of the shearing planes for cutting foreign matter when the propeller rotates. The second support is arranged to provide limited axial movement of the second blade with adjustable clamping means  9  for engaging the second blade with adjustable tension, the clamping means including elastic bias members  10  for maintaining adjustable tension. A combination of a slot  11  and a slot follower  12  regulate the axial position of the second blade. One of the combination of the slot and slot follower is connected to the first blade and the other is connected to the second blade. Each blade is arranged in a plane perpendicular to the axis  55  of the propeller shaft and extends through an arc so that the slot follower fits within the slot during a fraction of each rotation of the shaft to regulate the axial position of the second blade for close approximation of the first and second shearing planes for enhanced shearing action between the blades. The second support provides limited pivotal movement of the second blade. A combination of a wedge  13  and a valley  14  interact to apply axial force to move the second blade toward the first blade when the second blade pivots in the second support. One of the combination of the wedge and the valley is connected to the second blade and the other is connected to the second support, and the limited pivotal movement is generated by foreign matter the may be interposed between the first and second blades during propeller rotation. 
   The second support has an elongate, axially disposed cylindrical passage  15  that holds a cylindrical member  16  that is affixed to the second blade. It is adapted for limited movement of the blade as the cylindrical member reciprocates within the passage. The passage is provided with a lubricant seal such as, but not limited to, the plate  17  at a forward end thereof and a lubricant seal, such as but not limited to, the O-ring  18  at an aft end thereof for retention of lubricant  19  within the passage. The clamping mechanism  9  includes elastic bias members  10  that apply tension between the cylindrical member and the passage to limit motion therebetween. The elastic bias members  10  are enclosed within rigid elements including a piston  23  sliding within a rigid enclosing sleeve  22  that encloses the elastic bias member  10  to prevent deformation of the elastic bias members over time. Sleeve  22  is part of adjustment bolt  21  that is threadedly engaged in support  6  for providing adjustable clamping force on plate  59  that is forced against the cylindrical member  16 . 
   Attaching means  7  fixedly attach the second support  6  to a non-rotating member of the hull  54 . Attaching means  7  comprise a rigid metal member  26  for affixing to the hull by such well known affixing means as welding, the rigid metal member  26  having a first surface  27  adapted for receiving thereon at least one alignment screw member  28  threadedly engaged by the second support  6 . The first surface is provided with at least two threaded apertures  29  for receiving threaded fasteners  30  from the second support for removably affixing the metal member to the second support after the at least one alignment screw member has been adjusted to maintain the second shearing plane parallel to the first shearing plane. A fixed rod  31  extends upwardly from the first surface  27 . The rod  31  is received loosely in aperture  32  in support  6  while manipulating the alignment screw(s)  28  before securing the alignment with fasteners  30 . 
   The above disclosed invention has a number of particular features which should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While I have shown and described the preferred embodiments of my invention, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention.