Patent Publication Number: US-6659816-B2

Title: Water jet propeller

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-284064 filed on Sep. 18, 2001 the entire contents thereof is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a water jet propeller used in ships and, more particularly, to a structure of a water intake port thereof. 
     2. Description of Background Art 
     Japanese Patent Laid-open No. Hei 10-119883 discloses a conventional water jet propeller. 
     FIGS.  6 ( a ) to  6 ( c ) illustrate the water jet propeller, with FIG.  6 ( a ) being a cross-sectional view, FIG.  6 ( b ) being an enlarged cross-sectional view taken along line b—b in FIG.  6 ( a ), and FIG.  6 ( c ) being a cross-sectional view taken along line c—c in FIG.  6 ( a ). 
     The water jet propeller is mounted to a rear portion of a ship body  1 . There is provided a water intake port  5  provided with a filter  4  in a side wall of a stator  3 , in which an impeller  2  is rotatably disposed. 
     The impeller  2  is coupled to a drive shaft  6 , a front portion of which is coupled to an output shaft of an engine not shown. When the impeller  2  is rotatably driven by the engine and spurts of a stream of water are sent through a nozzle  3   a  of the stator  3  to propel the ship body  1 . 
     As shown in FIG.  6 ( b ), the water intake port  5  is opened in a substantially rectangular shape. A substantially rectangular filter  4  is then mounted in this opening which, in turn, is covered with a lid member  7  which also is of a substantially rectangular shape. 
     The lid member  7  is provided integrally with a pipe section  7   a  that communicates with the water intake port  5 . A flexible hose  9  is connected by way of a connection pipe  8  to the pipe section  7   a . An end portion not shown of the flexible hose  9  is, in turn, connected to the engine. 
     When the impeller  2  is rotatably driven, therefore, part of a water stream on a downstream side thereof is supplied from the water intake port  5  to the engine by way of the filter  4  and further through the pipe section  7   a  of the lid member  7 , the connection pipe  8 , and the flexible hose  9 , thus being used as engine coolant. 
     Referring to FIGS.  6 ( b ) and  6 ( c ), the filter  4  is provided with a flange  4   b,  while the lid member  7  is also provided with a flange  7   b . The filter  4  and the lid member  7  are jointly fastened together using four bolts  7   c  with the flanges  4   b ,  7   b  mated to each other. Thus, the filter  4  and the lid member  7  are removably mounted with respect to the side portion of the stator  3 . 
     According to the conventional water jet propeller described in the foregoing paragraphs, the filter  4  and the lid member  7  of the water intake port  5  are shaped into a substantially rectangle, and they are mounted to the stator  3  by jointly fastening them together using four bolts  7   c  with the flanges  4   b ,  7   b  mated to each other. This makes the mounting job extremely laborious. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     It is therefore an object of the present invention to solve this problem and to provide a water jet propeller that allows a filter and a lid to be mounted with ease. 
     To achieve the foregoing object, according to the present invention, there is provided a water jet propeller wherein a water intake port includes a filter that is provided in a side wall of a stator containing a rotatable impeller, wherein the side wall of the stator is provided with a tubular filter accommodation chamber that forms the water intake port. A tubular filter is housed in the filter accommodation chamber and an opening is formed in a circular shape in the filter accommodation chamber and is closed by a circular lid through tightening screws or press-fitting. 
     According to the present invention, a flow path is integrally formed with respect to a peripheral wall of the filter accommodation chamber and a bottom portion of the tubular filter is formed by an inclined surface that is inclined with respect to an axial direction of the tubular filter. In addition, an inclined step portion is formed in the filter accommodation chamber so as to abut against and receive an edge portion of the inclined surface of the tubular filter. An opening, which communicates with the flow path when the inclined surface edge portion abuts against the inclined step portion so that the two portions are brought into coincidence with each other, is formed in the tubular filter. 
     According to the present invention, a flow path is integrally formed with respect to a peripheral wall of the filter accommodation chamber. An inner peripheral surface of the filter accommodation chamber and an outer peripheral surface of the tubular filter are partially formed into a flat surface. An opening, which communicates with the flow path when the flat surface portion of the tubular filter coincides with the flat surface portion of the filter accommodation chamber, is formed in the tubular filter. 
     In the water jet propeller according to the present invention, the water intake port that includes the filter is provided in the side wall of the stator containing the rotatable impeller. The tubular filter accommodation chamber forming the water intake port is provided in the side wall of the stator. The tubular filter is housed in the filter accommodation chamber with the circular opening formed in the filter accommodation chamber. The circular lid is either screwed or press-fitted in position to close the circular opening. According to the water jet propeller having this arrangement, the filter and the lid can be mounted to the side wall of the stator by simply closing the opening in the filter accommodation chamber through either screwing or press-fitting, after the tubular filter has been placed in the tubular filter accommodation chamber. 
     Namely, in the water jet propeller according to the present invention, it is remarkably easier to mount the filter and the lid than in the conventional arrangement. 
     According to the water jet propeller of the present invention, the flow path is integrally formed with respect to the peripheral wall of the filter accommodation chamber and the bottom portion of the tubular filter is formed by the inclined surface that is inclined with respect to the axial direction of the tubular filter, the inclined step portion is formed in the filter accommodation chamber so as to abut against and receive the edge portion of the inclined surface of the tubular filter. The opening, which communicates with the flow path when the inclined surface edge portion abuts against the inclined step portion so that the two portions are brought into coincidence with each other, is formed in the tubular filter. All this offers the following function. 
     Namely, in the conventional water jet propeller described earlier, the flow path from the filter accommodation chamber is formed by the pipe section  7   a  that is integrated with the lid member  7 . Therefore, if the lid member  7  is mounted in a reverse direction with respect to a fore-and-aft direction, the flow path  7   a  is also mounted in a reverse direction with respect to the fore-and-aft direction. More attention should therefore be paid to the mounting of the lid member  7 , thus making the mounting job even more laborious. 
     According to the water jet propeller of the present invention, on the other hand, the problems inherent in the conventional technology will not occur, since the flow path is formed integrally with respect to the peripheral wall of the filter accommodation chamber. 
     In addition, the bottom portion of the tubular filter is formed by the inclined surface that is inclined with respect to the axial direction of the tubular filter, the inclined step portion is formed in the filter accommodation chamber so as to abut against and receive the edge portion of the inclined surface of the tubular filter. In view of the opening, which communicates with the flow path when the inclined surface edge portion abuts against the inclined step portion so that the two portions are brought into coincidence with each other, formed in the tubular filter, the flow path in the filter accommodation chamber and the opening in the filter are automatically brought into communication with each other when the tubular filter is inserted in the filter accommodation chamber and the edge portion of the inclined surface of the tubular filter abuts against (or fit into) the inclined step portion of the filter accommodation chamber. 
     This helps make the mounting job of the filter and the lid even easier. 
     According to the water jet propeller of the present invention, the flow path is integrally formed with respect to the peripheral wall of the filter accommodation chamber. The inner peripheral surface of the filter accommodation chamber and the outer peripheral surface of the tubular filter are partially formed into the flat surface and the opening, which communicates with the flow path when the flat surface portion of the tubular filter coincides with the flat surface portion of the filter accommodation chamber, is formed in the tubular filter. This offers the following additional function. 
     Namely, as described earlier, in the conventional water jet propeller, the flow path from the filter accommodation chamber is formed by the pipe section  7   a  that is integrated with the lid member  7  and, therefore, if the lid member  7  is mounted in a reverse direction with respect to the fore-and-aft direction, the flow path  7   a  is also mounted in a reverse direction with respect to the fore-and-aft direction. More attention should therefore be paid to the mounting of the lid member  7 , thus making the mounting job even more laborious. 
     According to the present invention, on the other hand, the problems inherent in the conventional technology will not occur, since the flow path is formed integrally with respect to the peripheral wall of the filter accommodation chamber. 
     Since the inner peripheral surface of the filter accommodation chamber and the outer peripheral surface of the tubular filter are partially formed into the flat surface, and the opening, which communicates with the flow path when the flat surface portion of the tubular filter coincides with the flat surface portion of the filter accommodation chamber, is formed in the tubular filter, the flow path in the filter accommodation chamber and the opening in the filter are automatically brought into communication with each other when the tubular filter is inserted in the filter accommodation chamber so that both of the above-mentioned flat surface portions coincide with each other. 
     Therefore, the job of mounting the filter and the lid becomes even easier. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a partly cutaway schematic side elevational view showing a typical small planing boat employing one embodiment of a water jet propeller according to the present invention; 
     FIG. 2 is a schematic plan view showing the same; 
     FIGS.  3 ( a )- 3 ( b ) illustrate the jet pump  30 , FIG.  3 ( a ) being a fragmentary side sectional view and FIG.  3 ( b ) being a cross-sectional view taken along line b—b in FIG.  3 ( a ); 
     FIGS.  4 ( a )- 4 ( d ) illustrate a stator  31  of the jet pump  30 , FIG.  4 ( a ) being a front elevational view (looking the ship body from the front), FIG.  4 ( b ) being a side elevational view, FIG.  4 ( c ) being a plan view of FIG.  4 ( b ), and FIG.  4 ( d ) being a cross-sectional view taken along line d—d in FIG.  4 ( c ); 
     FIGS.  5 ( a )- 5 ( d ) illustrate a filter, FIG.  5 ( a ) being a side elevational view (as viewed from the side of the ship body from a side), FIG.  5 ( b ) being a plan view of FIG.  5 ( a ), FIG.  5 ( c ) being a side elevational view of FIG.  5 ( a ), and FIG.  5 ( d ) being a cross-sectional view taken along d—d in FIG.  5 ( a ); and 
     FIGS.  6 ( a ),  6 ( b ) and  6 ( c ) are explanatory drawings of the conventional technology. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the present invention will be described with reference to the accompanying drawings. 
     FIG. 1 is a partly cutaway schematic side elevational view showing a typical small planing boat employing one embodiment of a water jet propeller according to the present invention. FIG. 2 is a schematic plan view showing the same. 
     As shown in FIGS. 1 and 2, a small planing boat  10  is a riding type small watercraft, in which a passenger sits on a seat  12  on a ship body  11  and grips a handlebar  13  provided with a throttle lever to steer the boat. 
     The ship body  11  is of a floating body structure that forms a space  16  internally between a hull  14  and a deck  15  joined to each other. An engine  20  is installed on the hull  14  inside the space  16 . In addition, a water jet propeller (hereinafter referred to also as a jet pump)  30  is provided as a propulsion means driven by the engine  20  that is installed in a rear portion of the hull  14 . 
     The jet pump  30  is provided with an impeller  32  disposed inside a flow path  18  that extends from a water inlet port  17  opened in a bottom of the boat to a jet port  31   c   2  opened in a trailing edge of the ship body. A deflector  38  is provided adjacent to the jet port  31   c   2 . A shaft (drive shaft)  22  for driving the impeller  32  is coupled to an output shaft  21  of the engine  20  by way of a coupler  23 . When the impeller  32  is rotatably driven by the engine  20  through the coupler  23  and the shaft  22  spurts of water taken in through the water inlet port  17  are sent from the jet port  31   c   2  through the deflector  38 , thus propelling the ship body  11 . A driving speed of the engine  20 , or a propulsion force provided by the jet pump  30 , is controlled by circularly moving a throttle lever  13   a  (see FIG. 2) of the handlebar  13  either forward or backward. The deflector  38  is connected to the handlebar  13  through a control cable not shown. It is operated as the handlebar  13  is turned either forward or backward as necessary to change a direction of travel of the ship body  11 . 
     Referring to FIGS.  3 ( a ) and  3 ( b ), the jet pump  30  is provided with a stator (duct)  31  that forms the flow path  18  communicating with the water inlet port  17  (see FIG. 1) provided in the bottom portion of the ship body  11 , with the impeller  32  disposed inside the stator  31 . A bearing portion  33  of the impeller is provided inside the stator  31 . A cap  34  plugs up a trailing edge of the bearing portion  33 . 
     The jet pump  30  is mounted removably to the hull  14  when a flange portion  31   d  (see FIGS.  4 ( a )- 4 ( d )) formed at a front portion of the stator  31  is secured to the hull  14  using bolts not shown. 
     The stator  31  is provided with an impeller accommodation portion  31   a , inside which the impeller  32  is disposed, a bearing accommodation portion  31   b , and a nozzle portion  31   c  (see FIG.  1 ). The impeller accommodation portion  31   a  and the bearing accommodation portion  31   b  are formed integrally with each other. The bearing portion  33  is formed integrally within the bearing accommodation portion  31   b  through a stator blade  31   b    1 . 
     A front portion of a boss portion  32   a  of the impeller  32  is engaged with splines  22   b  formed on a rear end of the drive shaft  22  and the impeller  32  turns with the drive shaft  22 . As noted earlier, the leading edge of the drive shaft  22  is coupled to the output shaft  21  of the engine  20  mounted in the ship body  11  through the coupler  23  (FIG.  1 ). 
     An impeller shaft  35 , which supports a rear portion  32   b  of the boss portion  32   a  of the impeller  32 , is rotatably supported on the bearing portion  33  through ball bearings  33   a ,  33   b . External threads  35   a  are formed on a leading edge of the impeller shaft  35 . The external threads  35   a  engage internal threads formed on the rear portion  32   b  of the boss portion of the impeller  32 , which provides a connection between the impeller  32  and the impeller shaft  35 . 
     In summary, the front portion of the boss portion  32   a  of the impeller  32  is coupled to the shaft  22 , while the rear portion  32   b  of the boss portion is coupled to the impeller shaft  35 , which allows the impeller  32  to turn with the shaft  22  and the impeller shaft  35 . 
     There are formed, at a front portion of the cap  34 , an insertion portion (a cylindrical portion)  34   b  to be inserted into a rear portion of the bearing portion  33  and three (only one is shown) insertion holes  34   c  for a screw  36  (see FIG.  3 ( a )). A groove, into which an O-ring  34   e  is mounted, is formed at the cylindrical insertion portion  34   b.    
     The cap  34  is therefore mounted to the rear portion of the bearing portion  33  as follows. Namely, the insertion portion  34   b  is inserted (press-fitted) into the rear portion of the bearing portion  33  with the O-ring  34   e  mounted to the insertion portion  34   b  as shown in FIG.  3 ( a ) and the screw  36  is finally tightened. 
     A partial cutout  34   d  is formed on an abutting surface between the cap  34  and the bearing portion  33 . During maintenance service procedures, the cap  34  can be easily removed by inserting a tip of a tool (for example, a screwdriver) into this cutout  34   d  with the screw  36  removed. 
     Referring to FIGS. 3 and 4, a filter accommodation chamber  31   g  of a tubular shape (a cylindrical shape according to the embodiment) is formed integrally on a side wall  31   e  of the stator  31 , serving to form a water intake port  31   f  in a portion downstream of the impeller  32 . A filter  40  of a tubular shape (a cylindrical shape according to the embodiment) is housed in the filter accommodation chamber  31   g  as shown in FIG.  3 ( b ). An opening  31   h  in the filter accommodation chamber  31   g  is closed by a circular lid  50  that is screwed into position. The opening  31   h  may instead be closed by press-fitting the lid  50 . 
     Referring to FIGS.  4 ( a )- 4 ( d ), a flow path  31   j , through which water from the water intake port  31   f  flows in, is integrally formed in a peripheral wall  31   i  of the filter accommodation chamber  31   g . A coolant hose is connected to an end portion  31   k  of the flow path  31   j  by way of a joint pipe not shown, through which coolant is supplied to the engine  20 . 
     Referring to FIGS.  5 ( a )- 5 ( d ), the filter  40  is provided with a cylindrical portion  41  and a bottom portion  42  formed integrally therewith. A number of holes  43  are made in the bottom portion  42 . The diameter of each of the holes  43  should be about 3 mm. 
     In addition, there is formed an opening  44  of a U-shaped cutout in the cylindrical portion  41 . 
     Referring to FIG.  4 ( b ), part of an inner peripheral surface of the filter accommodation chamber  31   g  is formed into a flat surface (the flat surface portion is indicated by a reference numeral  31   m ). Referring further to FIGS.  5 ( a ) and  5 ( c ), part of an outer peripheral surface of the tubular filter  40  is also shaped into a flat surface (the flat surface portion is indicated by a reference numeral  45 ). 
     When the filter  40  is inserted into the filter accommodation chamber  31   g , therefore, unless these flat surface portions  31   m  and  45  are properly aligned with each other, the filter  40  cannot be inserted. When the filter  40  is inserted into the filter accommodation chamber  31   g  with the flat surface portions  31   m  and  45  aligned, the opening  44  in the filter  40  opposes the flow path  31   j  in the filter accommodation chamber  31   g  brings the two into communication with each other [see FIG.  3 ( b )]. 
     Furthermore, according to the embodiment, the bottom portion  42  of the tubular filter  40  is formed by an inclined surface  46  that is inclined with respect to an axial direction [a right-and-left direction in FIGS.  5 ( c ) and  5 ( d )] of the tubular filter  40 , as shown in FIGS.  5 ( a )- 5 ( d ). As shown further in FIG.  3 ( b ) and FIG.  4 ( d ), an inclined step portion  31   n , which abuts against and receives an edge portion  47  of the inclined surface  46  of the tubular filter  40 , is formed in the filter accommodation chamber  31   g.    
     When the filter  40  is inserted into the filter accommodation chamber  31   g , therefore, the inclined surface  46  at the bottom portion  42  of the filter must be brought into coincidence with the inclined step portion  31   n  of the filter accommodation chamber  31   g , otherwise, a head portion  48  of the filter  40  protrudes from the filter accommodation chamber  31   g , thus preventing the filter  40  from being completely housed in the filter accommodation chamber  31   g , which hampers the lid  50  from being mounted in position. If the inclined surface  46  of the filter bottom portion  42  is brought into coincidence with the inclined step portion  31   n  of the filter accommodation chamber  31   g  as the filter is inserted into the filter accommodation chamber  31   g , the opening  44  in the filter  40  opposes the flow path  31   j  in the filter accommodation chamber  31   g,  bringing the two into communication with each other [see FIG.  3 ( b )]. 
     According to this embodiment, the following two arrangements are employed; namely: 
     an arrangement, in which partial flat surface portions  31   m  and  45  are formed on the inner peripheral surface of the filter accommodation chamber  31   g  and the outer peripheral surface of the filter  40 ; and, 
     ii. an arrangement, in which the bottom portion  42  of the tubular filter  40  is made into the inclined surface  46  and the inclined step portion  31   n  is formed in the filter accommodation chamber  31   g.    
     It is nonetheless possible to employ either one of these two arrangements i and ii. 
     Referring to FIGS.  3 ( a )- 3 ( b ), a hexagon recessed portion  51  is formed in the lid  50  at a head portion thereof and, in addition, external threads  52  are formed on an outer periphery thereof. Internal threads  31   p  are formed, on the other hand, on an inner peripheral surface on an upper portion of the filter accommodation chamber  31   g.    
     The opening  31   h  in the filter accommodation chamber  31   g  can be easily plugged with the lid  50  by a manner that when, after the filter  40  has been housed in the filter accommodation chamber  31   g  as described above, the two types of threads  52 ,  31   p  are brought into threaded engagement with each other by a tool engaged in the hexagon recessed portion  51  in the lid. 
     According to the embodiment, referring to FIG.  3 ( a ) and FIG.  4 ( b ), there is provided a partial recessed portion  31   q  on an inner peripheral surface in the opening  31   h  of the filter accommodation chamber  31   g . After the lid  50  has been mounted in the opening  31   h  of the filter accommodation chamber  31   g , a tool is inserted into the recessed portion  31   q  for collapsing the threads  52  in the lid  50 , thereby preventing the lid  50  from thereafter turning and thus preventing the lid  50  from coming off the filter accommodation chamber  31   g.    
     According to the water jet propeller having arrangements as described above, the following operational effects can be achieved. 
     The tubular filter accommodation chamber  31   g  that forms the water intake port  31   f  is provided on the side wall  31   e  of the stator  31 , inside which the impeller  32  is rotatably disposed. The tubular filter  40  is housed in the filter accommodation chamber  31   g . The opening  31   h  is formed circularly in the filter accommodation chamber  31   g  and is closed by the circular lid  50  through screwing or press-fitting. Thanks to this arrangement, the filter  40  and the lid  50  can be mounted to the side wall  31   e  of the stator  31  by placing the tubular filter  40  in the tubular filter accommodation chamber  31   g  and closing the opening  31   h  in the filter accommodation chamber  31   g  with the circular lid  50  through screwing or press-fitting. 
     Namely, according to this water jet propeller, the mounting job of the filter  40  and the lid  50  is made remarkably simpler as compared with the conventional type. 
     (b) The flow path  31   j  is integrally formed with respect to the peripheral wall of the filter accommodation chamber  31   g . The bottom portion of the tubular filter  40  is formed by the inclined surface  46  that is inclined with respect to the axial direction of the tubular filter. The inclined step portion  31   n , which abuts against and receives the edge portion  47  of the inclined surface  46  of the tubular filter  40 , is formed in the filter accommodation chamber  31   g . In addition, the opening  44 , formed in the tubular filter  40 , communicates with the flow path  31   j  when the inclined surface edge portion  47  and the inclined step portion  31   n  abut against each other so as to bring the two into coincidence with each other. These arrangements offer the following additional operational effects. 
     Namely, in the conventional water jet propeller described earlier, the flow path from the filter accommodation chamber is formed by the pipe section  7   a  formed integrally with the lid member  7 . As a result, if the lid member  7  is mounted in a reverse direction with respect to a fore-and-aft direction, the flow path  7   a  is also mounted in a reverse direction with respect to the fore-and-aft direction. More attention should therefore be paid to the mounting of the lid member  7 , thus making the mounting job even more laborious. 
     According to the water jet propeller according to the embodiment of the present invention, on the other hand, such a problem inherent in the conventional technology will not occur, since the flow path  31   j  is formed integrally with respect to the peripheral wall of the filter accommodation chamber  31   g.    
     Furthermore, the bottom portion of the tubular filter  40  is formed by the inclined surface  46  that is inclined with respect to the axial direction of the tubular filter. The inclined step portion  31   n , which abuts against and receives the edge portion  47  of the inclined surface  46  of the tubular filter  40 , is formed in the filter accommodation chamber  31   g . In addition, the opening  44 , formed in the tubular filter  40 , communicates with the flow path  31   j  when the inclined surface edge portion  47  and the inclined step portion  31   n  abut against each other so as to bring the two into coincidence with each other. The flow path  31   j  in the filter accommodation chamber  31   g  and the opening  44  in the filter  40  are automatically brought into communication with each other. Therefore, when the tubular filter  40  is inserted in the filter accommodation chamber  31   g  the edge portion  47  of the inclined surface  46  of the tubular filter  40  abuts against (or fit into) the inclined step portion  31   n  of the filter accommodation chamber  31   g.    
     This helps make the mounting job of the filter  40  and the lid  50  even easier. 
     (c) Part of the inner peripheral surface of the filter accommodation chamber  31   g  and part of the outer peripheral surface of the tubular filter  40  are formed into a flat surface ( 31   m ,  45 ). In addition, there is formed in the tubular filter  40  the opening  44  that communicates with the flow path  31   j  when the flat surface portion  45  of the tubular filter  40  and the flat surface portion  31   m  of the filter accommodation chamber  31   g  are brought into coincidence with each other. When the tubular filter  40  is inserted into the filter accommodation chamber  31   g  so as to bring the two flat surface portions  31   m  and  45  into coincidence with each other, it automatically causes the flow path  31   j  in the filter accommodation chamber  31   g  to communicate with the opening  44  in the filter  40 . 
     The mounting job for the filter  40  and the lid  50  will therefore become even easier. 
     While the invention has been described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the preferred embodiments or structures. Rather, the invention is intended to cover various modifications within the spirit and scope of the invention. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.