Abstract:
A double gear reduction drive mechanism for powering movement of a boat lifting cable for moving of a watercraft upwardly from the water to an elevated position and downwardly from the elevated position of storage to a position in the water therebelow. The device includes two gear reduction mechanisms within the same housing or within separate adjacent housings which can be connected to a drive means for powering rotational movement of a cable spool with at least one boat lift cable attached thereto. This gear drive is a direct drive system since it does not include any belts, chains or pulleys but utilizes direct engagement between two immediately adjacently positioned pairs of gears each of which reduces rotational speed to effect an increase in power, torque and accurate control of movement of boat lifting cable.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention deals with the field of devices for controlling boat lift apparatus. Boat lift apparatus is used normally adjacent large bodies of water for removing a boat or other watercraft from the water to an elevated position for storage. This is normally controlled by a cable mechanism attached to the boat lift apparatus. 
     This boat lift cable must be accurately controlled for movement and the present invention provides a double reduction gear drive for powering movement of such boat lifting cables which is significantly improved since it utilizes direct engagement of gearing rather than chains or pulleys or other remote means for connecting rotating shafts. Also the mutual orientation of the axis of the input shaft, the internal shaft, the output shaft and the winding spool provide a distinct improvement over the prior art since lubrication is significantly enhanced and smaller sized designs can be utilized. The maintenance requirements for chain and belt drive systems is problematic in the relatively harsh environments that are normally experienced at the locations where such boat lifts are utilized. For this reason the use of a direct drive double reduction gear mechanism is a significant enhancement over the prior art. 
     2. Description of the Prior Art 
     Various prior art devices have been utilized for the purposes of controlling movement of boat lifting mechanisms such as shown in U.S. Pat. No. 3,191,389 patented Jun. 29, 1965 to J. B. Poe on a “Boat Lift”; and U.S. Pat. No. 3,265,024 patented Aug. 9, 1966 to C. W. Kramlich on a “Boat Lift”; and U.S. Pat. No. 3,504,502 patented Apr. 7, 1970 to L. H. Blount on a “Lift Dock For A Water Borne Vessel”; and U.S. Pat. No. 3,675,258 patented Jul. 11, 1972 to Bradley M. Osmundson on a “Boat Hoist”; and U.S. Pat. No. 3,778,855 patented Dec. 18, 1973 to Nikolai Kariagin et al and assigned to Whittaker Corporation on a “Telescopic Gravity Davit”; and U.S. Pat. No. 3,791,229 patented Feb. 12, 1974 to Heinz Litezki and assigned to Schiess Aktiengesellschaft on a “Lifting Device For Lifting And Lowering Heavy Loads”; and U.S. Pat. No. 4,337,868 patented Jul. 6, 1982 to Narahari Gattu and assigned to Harnischfeger Corporation on a “Telescopic Crane Boom Having Rotatable Extend/Retract Screws”; and U.S. Pat. No. 4,589,800 patented May 20, 1986 to Charles L. Nasby, Jr. on a “Dock Structure And Method And Apparatus For Raising And Lowering Same”; and U.S. Pat. No. 4,641,996 patented Feb. 10, 1987 to Morton Seal on a “Side Loading Boat Lifts”; and U.S. Pat. No. 4,686,920 patented Aug. 18, 1987 to James L. Thomas on a “Cradle Type Boat Lifts”; and U.S. Pat. No. 4,954,011 patented Sep. 4, 1990 to Samuel H. Stenson on a “Powered Method And Apparatus For Lifting A Boat”; and U.S. Pat. No. 4,983,067 patented Jan. 8, 1991 to David M. Montgomery on a “Boat Lift Apparatus”; and U.S. Pat. No. 5,020,463 patented Jun. 4, 1991 to Robert E. Franklin et al on an “Arrangement For Raising Or Lowering Boats Or The Like”; and U.S. Pat. No. 5,051,027 patented Sep. 24, 1991 to George F. Horton on a “Boat Lift”; and U.S. Pat. No. 5,090,842 patented Feb. 25, 1992 to David M. Montgomery on a “Boat Lift Apparatus And System”; and U.S. Pat. No. 5,140,923 patented Aug. 25, 1992 to Kevin L. Wood on a “Raising And Lowering Device”; and U.S. Pat. No. 5,211,124 patented May 18, 1993 to John N. Reiser and assigned to Triton Corporation on a “Winch Construction For Boat Lift”; and U.S. Pat. No. 5,261,347 patented Nov. 16, 1993 to Peter W. Mansfield on a “Sailboat Davit”; and U.S. Pat. No. 5,287,821 patented Feb. 22, 1994 to Byron L. Godbersen on an “Electric Drive Mechanism For Boat Hoist Winch”; and U.S. Pat. No. 5,390,616 patented Feb. 21, 1995 to Henry Roth on a “Dock Mounted Small Boat Lifting System”; and U.S. Pat. No. 5,593,247 patented Jan. 14, 1997 to James A. Endres et al and assigned to Endcor Inc. on a “Programmable Boat Lift Control System”; and U.S. Pat. No. 5,687,663 patented Nov. 18, 1997 to Noel D. Wahlstrand on a “Boat Lift Transport Apparatus”; and U.S. Pat. No. 5,701,834 patented to Richard A. Lyons on Dec. 30, 1997 on a “Lift For Watercraft”; and U.S. Pat. No. 5,755,529 patented May 26, 1998 to R. R. Brad Follett on a “Boat Lift”; and U.S. Pat. No. 5,769,568 patented Jun. 23, 1998 to David G. Parkins et al and assigned to ABL Boat Lifts on an “Adaptable Boat Lift”; and U.S. Pat. No. 5,772,360 patented Jun. 30, 1998 to Donald M. Wood, II on a “Topless Watercraft Lifting Apparatus With A Differential Gearing System”; and U.S. Pat. No. 5,803,003 patented Sep. 8, 1998 to Robert V. Vickers and assigned to The Louis Berkman Company on a “Rotary Boat Lift”; and U.S. Pat. No. 5,915,877 patented to Charles L. Sargent et al on Jun. 29, 1999 and assigned to Quality Boat Lift, Inc. on a “Positive Drive Boat Lift”; and U.S. Pat. No. 5,934,826 patented Aug. 10, 1999 to Peter W. Mansfield on a “Boat Lift Apparatus”; and U.S. Pat. No. 5,947,639 patented Sep. 7, 1999 to Richard B. Bishop et al on a “Boat Lift Apparatus”; and U.S. Pat. No. 5,957,623 patented to Charles L. Sargent et al on Sep. 28, 1999 and assigned to Quality Boat Lifts Inc. on an “Electrically Insulated Positive Drive Boat Lift”; and U.S. Pat. No. 5,988,941 patented Nov. 23, 1999 to Charles L. Sargent et al and assigned to Quality Boat Lifts, Inc. on a “Boat Lift Cable Lock Apparatus”; and U.S. Pat. No. 6,006,687 patented Dec. 28, 1999 to Jeffrey M. Hillman et al and assigned to Marine Floats, Inc. on a “Modular Floating Boat Lift”; and U.S. Pat. No. 6,033,148 patented Mar. 7, 2000 to Lynn P. Norfolk et al and assigned to Norfolk Fabrication, Inc. on a “Housing For A Boat Lift Motor, Pulley And Gear Drive”; and U.S. Pat. No. 6,122,692 patented Feb. 8, 2000 to Lynn P. Norfolk et al and assigned to Norfolk Fabrication, Inc. on a “Housing For A Boat Lift Motor Pulley And Gear Drive” and U.S. Pat. No. 6,122,994 patented Sep. 26, 2000 to Lynn P. Norfolk et al and assigned to Norfolk Fabrication, Inc. on a “Housing For A Boat Lift Motor, Pulley And Gear Drive”; and United States Design Patent No. Des. 390,188 patented Feb. 3, 1998 to Lynn P. Norfolk et al and assigned to Norfolk Fabrication, Inc. on a “Boat Lift Motor And Gear Housing”. 
     SUMMARY OF THE INVENTION 
     The present invention provides a double reduction gear drive device for powering movement of a boat lifting cable which includes a main housing defining a main housing chamber therein. The main housing also preferably defines an input aperture and an output aperture therein both in fluid flow communication with respect to the main housing chamber. 
     An input shaft is also included rotatably mounted with_respect to the main housing and extending through the input aperture into the main housing chamber. A primary input shaft bearing is also included mounted in the main housing immediately adjacent the input aperture. This primary input shaft bearing is adapted to receive the input shaft extending therethrough to facilitate rotational movement thereof relative to the main housing. 
     A secondary input shaft bearing may also be included mounted in the housing spatially disposed from the primary input shaft bearing and adapted to receive the input shaft therethrough in order_to facilitate rotational movement thereof relative to the main housing. 
     An input gear is also preferably included secured to the input shaft at a position within the main housing chamber. An internal shaft is rotatably movably mounted within the main housing chamber of the main housing in a position extending approximately parallel to the input shaft and slightly displaced laterally therefrom. This input shaft and the internal shaft are both oriented in a generally vertically plane parallel with respect to one another. 
     A main internal gear may be also included secured on the internal shaft to be rotatable therewith. This main internal gear is preferably in engagement with respect to the input gear in such a manner as to be rotatably driven responsive to rotation of the input gear. The main internal gear is preferably larger than the input gear in order to cause the internal shaft to rotate at a rotational speed less than the rotational speed of the input shaft. A first internal shaft bearing may also be mounted within the main housing in such a manner as to receive the internal shaft extending therethrough to facilitate rotational movement thereof relative to the main housing. Similarly a second internal shaft bearing may be mounted within the main housing spatially disposed from the first internal shaft bearing. It is adapted to receive the internal shaft extending therethrough to facilitate rotation thereof relative to the main housing. 
     A worm gear is also preferably included secured on the internal shaft for rotation therewith. This worm gear is positioned at an intermediate position on the internal shaft spatially disposed from the main internal gear. 
     A main bearing journal is also preferably fixedly mounted within the main housing chamber. Preferably the second input shaft bearing and the first internal shaft bearing are both mounted in the main bearing journal and maintained thereby spatially disposed from one another to maintain fixed positioning thereof relative to the main housing. 
     An output shaft is also movably mounted within the main housing chamber of the main housing to be rotatable with respect thereto. The output shaft is positioned to also extend outwardly through the output aperture. The output shaft and the internal shaft are preferably oriented in a generally vertically extending plane and are oriented approximately perpendicular with respect to one another. The output shaft is partially positioned within the main housing and extends outwardly therefrom through the output aperture. A first output shaft bearing and a second output shaft bearing are also mounted within the main housing spatially disposed from one another and adapted to receive the output shaft extending therethrough to facilitate rotational movement thereof relative to the main housing. 
     An output gear is secured to the output shaft to be rotatable therewith and is positioned in engagement with respect to the worm gear to move therewith. The output gear is preferably larger than the worm gear to cause the output shaft to rotate at a rotational speed less than the rotational speed of the internal shaft. 
     A boat lifting cable spool is attached to the output shaft outside of the main housing chamber and is rotatable therewith to control winding of one or more boat lifting cables thereon. The boat lifting cable spool extends generally horizontally preferably and approximately perpendicular with respect to the internal shaft and the input shaft. 
     A drive means is operatively coupled with respect to the input shaft to selectively drive it. In this manner it will cause rotation of the boat lifting cable spool with enhanced torque and lower rotational velocity than the drive means itself in order to control movement of the boat lifting cable. The drive means preferably includes a drive shaft extending outwardly therefrom and being rotationally driven therewith. The drive shaft is coupled to the input shaft for selectively causing rotation thereof. 
     A boat lifting cable can also be included in a position secured to the boat lifting cable spool for controlling winding thereof on the spool. Two such boat lifting cables are normally utilized spaced apart on the spool. 
     A coupling means may also be attached to the drive shaft and the input shaft in order to cause simultaneous and similar movement therebetween. The coupling means preferably includes a key means positioned between the first drive shaft and the coupling means for securing them to one another. Another keying means is included positioned between the input shaft and the coupling for selectively securing them with respect to one another. 
     A coupling housing may also be included extending around the coupling itself. This coupling housing will preferably define a coupling chamber therein and a coupling input aperture and outlet aperture. The coupling housing is preferably securable with respect to the drive with the drive shaft thereof extending into the coupling through the coupling input aperture. The coupling also is preferably securable with respect to the main housing with the coupling aperture positioned in registration with respect to the main housing input aperture and with the input shaft extending through the coupling output aperture into the coupling chamber to a position adjacent the drive shaft. The coupling is preferably rotatably movable with respect to the coupling chamber and is secured to the drive shaft and input shaft to cause similar rotational movement. The coupling housing also includes a coupling bearing mounted therein immediately adjacent the coupling output aperture which is adapted to receive the input shaft therethrough to facilitate rotation thereof relative to the coupling housing. 
     The main housing of the present invention may include an enlarged wall section adjacent the first output shaft bearing in order to facilitate placement and lubrication thereof. Also the output gear may actually be configured as a helical flange gear as shown best in FIGS. 1 and 2 to facilitate engagement thereof with respect to the worm gear. Also the worm gear itself is preferably constructed with the teeth thereof having a lead angle of less than 7 degrees and 30 minutes in order to avoid backdriving thereof and enhance self-locking characteristics. 
     It is important to appreciate that the present invention is positionable with the two gear reduction mechanisms within a single housing. However, it is also contemplated within the scope of the present invention that the gear reduction mechanisms can each be positioned within their own housing. In this case the main overall housing can be defined as the composite of the two housings wherein the first step of gear reduction occurs in the first housing member and the second step of gear reduction occurs in the second housing member. This could be easily achieved merely by defining two separate housing members which comprise the overall housing itself with one set of reduction gears located in one housing and the second set of reduction gears located in a second immediately adjacent housing. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein two steps of gear reduction are achieved with two sets of reducing gears in direct engagement with respect to one another thereby eliminating the need for any chain or belt operatively interconnecting the rotating shafts of the reduction means. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein controlled operation of a boat lift is achieved. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein a horizontally extending boat cable spool is operatively controlled for achieving full functionality of a boat lift. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein lubrication is significantly enhanced. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein two pairs of reduction gears are included which may be positioned within the same housing or may be separated and positioned within adjacent housings. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein all reduction gearing is achieved by direct interconnection of gear teeth rather than use of any indirect connection such as chains and sprockets or V-belts and pulleys. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein maintenance requirements are minimized. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein parts replacement is greatly facilitated. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein a drive means is connected through a direct drive to the boat lifting cable winding spool. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein self-locking and anti backdriving is achieved by utilizing a worm gear with a lead angle of less than 7 degrees and 30 minutes. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein no exposed mechanical parts extend outside of the housing means. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein a one-piece gear housing can be utilized. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein a compact low profile design provides an aesthetically pleasing external appearance. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein capacities from 4500 lbs. to 120,000 lbs. are achievable. 
     It is object of the present invention to provide a double reduction gear drive mechanism for powering movement of boat lifting cables wherein the housing can be sealed to provide a totally maintenance free environment under certain conditions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     While the invention is particularly pointed out and distinctly claimed in the concluding portions herein, a preferred embodiment is set forth in the following detailed description which may be best understood when read in connection with the accompanying drawings, in which: 
     FIG. 1 is a front cross-sectional view of an embodiment of the double reduction gear drive means of the present invention; 
     FIG. 2 is a top cross-sectional view of the embodiment shown in FIG. 1; and 
     FIG. 3 is a front perspective illustration of an embodiment of the double gear reduction drive means of the present invention showing the complete external housing thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides a means for controlling operation of a boat lift by accurately controlling the powering and operation of one more boat lifting cables  10  and  11 . The apparatus of the present invention preferably includes a main housing  12  which defines a main housing chamber  14  therein. Main housing chamber  14  is in fluid flow communication with respect to an input aperture  16  and an output aperture  18  both defined in the external surface of the main housing means  12 . The input aperture  16  is adapted to receive power thereinto and the output aperture  18  is designed to provide power outwardly therefrom. Preferably the output aperture  18  is spatially positioned away from the input aperture  16 . 
     The double reduction gear drive of the present invention preferably includes an input shaft  20  which extends through the input aperture  16  of main housing  12  and is rotatable with respect thereto. Preferably this rotation is achieved by having the input shaft  20  extend through a primary input shaft bearing  22  positioned immediately adjacent the input aperture  16  in the main housing  12 . A secondary input shaft bearing  24  is preferably positioned within the main housing chamber  14 . A main bearing journal  38  may be included in the main housing  12  within the main housing chamber  14  thereof and may be adapted to receive the secondary input shaft bearing  24  mounted therein. In this manner input shaft  20  will extend through the primary input shaft bearing  22  and through the secondary input shaft bearing  24  as well as through the input aperture  16 . Thus the input shaft  20  will be rotatably movable with respect to the housing and will extend from a position within the main housing chamber  14  through the input aperture  16  to a position external of the main housing chamber  14 . 
     An input gear  26  is preferably secured fixedly to the input shaft  20  at a position within the main housing chamber  14 . 
     An internal shaft  28  will preferably be contained entirely within the main housing  12  and will be positioned to be freely rotatable with respect to the main housing  12  by being mounted within a first internal shaft bearing  32  and a second internal shaft bearing  34 . Both shaft bearings  32  and  34  will be positioned within the main housing  12  with one preferably and optionally being positioned within the main bearing journal  38  at a position spatially disposed from the secondary input shaft bearing  24  mounted therein. 
     With the above-described configuration a main internal gear  30  is preferably fixedly mounted on the internal shaft  28  at a position immediately adjacent to the input gear  26  mounted on the input shaft  20 . As such, gear  30  and gear  26  are directly meshed with one another to provide direct gear powering therebetween. Thus, rotational movement of the input gear  26  will cause similar rotational movement of the main internal gear  30 . Preferably main internal gear  30  will be larger than the input gear  26  thereby achieving the first level of gear reduction desired by the apparatus of the present invention. 
     A worm gear  36  is mounted preferably at an intermediate location on the internal shaft  28 . Preferably the internal shaft  28  will include the first internal shaft bearing  32  mounted in the main bearing journal  38  and the second internal shaft bearing  34  mounted in the wall of the main housing  12 . Thus, rotation of the internal shaft  30  will cause similar rotation of the worm gear  36 . 
     An output shaft  40  is also preferably included in the apparatus of the present invention which will preferably extend through the output aperture  18  and be rotatably movable with respect thereto. Output shaft  40  will preferably be positioned within a first output shaft bearing  42  and a second output shaft bearing  44  both positioned within the main housing  12  and preferably within the wall area thereof. In a preferred configuration as shown in FIG. 2 the first output shaft bearing  42  will require the inclusion of an enlarged wall section  68  in the main housing  12  to allow sufficient clearance on both sides of an output gear  46 . Output gear  46  is a large preferably helical flange gear which requires significant clearance therearound for lubrication and effective operation thereof. The enlarged section  68  in the external wall of the main housing  12  helps achieve this purpose. 
     Helical flange output gear  46  is preferably in engagement with worm gear  36 . Since gear  46  is significantly larger than worm gear  36  the second stage of gear reduction is achieved by this direct drive gear connection. These two gears are intermeshed with respect to one another to achieve this solid reliable element of gear reduction. Preferably the second output shaft bearing  44  will be positioned immediately adjacent to and in registration with respect to the output aperture  18  of main housing  12 . 
     The output shaft  40  preferably will include a boat lifting cable spool  48  secured thereto at a location outside of the main housing  12 , external of the main housing chamber  14 . This spool will allow the boat lifting cables  10  and  11  to be wound therearound such that rotation of the output shaft  40  will cause similar rotation of the boat lifting cable spool  48  and allow operative control of positioning of the boat lifting cable  10 . In the preferred configuration the boat lifting cable spool  48  is shown with two boat lifting cables  10  and  11  mounted thereon, however the actual number of boat lifting cables can be one or more. 
     A drive means  50  may also be included in the present invention to provide powering for rotation of the input shaft  20 . This drive means  50  preferably includes a drive shaft  52  rotatably driven thereby and extending outwardly therefrom. A coupling  54  is preferably positioned adjacent the drive shaft  52  and preferably is fixedly secured thereto. Similarly the coupling  54  is preferably secured fixedly with respect to the input shaft  20  such that rotation of the drive shaft  52  will cause similar rotation of the input shaft  20 . The coupling between the drive shaft  52  and the coupling means  54  is achieved by a first keying means  56 . As shown in FIG. 1 this keying means can comprise a single keying stud. Similarly direct connection between the coupling  54  and the input shaft  20  can be achieved by a second keying means  58  which can comprise a plurality of splines. The specific configuration of the first keying means  56  and the second keying means  58  can be of any conventionally available keying means for achieving simultaneous rotation of a shaft and a collar, coupling or other member extending thereabout. 
     To protect the coupling  54  from the external environment a coupling housing  60  may extend therearound. Preferably coupling housing  60  defines a coupling chamber  62  therein in which the coupling  54  is located. Coupling housing  60  defines a coupling input aperture  64  through which the drive shaft  52  extends such that it can be keyed to the coupling  54  within the coupling chamber  62 . The coupling outlet aperture  70  defined in the coupling housing  60  is designed to receive the input shaft  20  extending therethrough such that it can reach to a position immediately adjacent the coupling  54  for engagement therewith. A coupling housing bearing  66  is preferably positioned within the coupling housing  60  at a position immediately adjacent to the coupling outlet aperture  70  thereof and preferably in registration therewith for the purpose of receiving the input shaft  20  extending therethrough for maintaining alignment between the coupling housing  60  and the main housing  12 . In order to achieve proper operation of the apparatus of the present invention the coupling output aperture  70  should be positioned in registration with respect to the input aperture  16  of the main housing  12 . 
     It should be appreciated that in the configuration of the present invention it is contemplated that various embodiments can include the positioning of the gear reduction elements in a single housing or in two separate housings. As shown best in FIG. 1 the main housing  12  can be divided by an interior housing wall  72  into a first housing member  74  containing the gear reduction resulting from engagement of input gear  26  and main internal gear  30 . A second housing member  76  can be defined also within the main housing member  12  which contains the gear reduction achieved by the engagement between the worm gear  36  and the output gear  46 . These two different pairs of gears can both be positioned within the same housing or in separate housings and, if they are positioned in separate housings, the construction which achieves the separate housing can be of many different varieties of possible configurations. One such configuration is shown by the dotted lining in FIG. 1 which shows the main bearing journal  38  extended outwardly to such an extent that it provides an internal wall or panel within the main housing chamber  14  which divides first housing member  74  from second housing member  76 . Thus, in this specific configuration, the main bearing journal  38  would not only contain bearings  24  and  32  but will also provide an interior housing wall  72  which minimizes fluid flow communication between the first housing member  74  and the second housing member  76 . This is one particular manner in which the gear reduction can occur in separate non-communicating chambers. The separation of each direct drive gear reduction mechanism is not necessary but is possible under various operating and application conditions. In a preferred configuration as shown in the solid line portions of FIGS. 1 and 2 both gearing reductions will occur within a single housing. Applicant has defined that housing as a main housing means such that it can comprise a single housing or multiple independent housings all of which come within the definition of a main housing means. 
     While particular embodiments of this invention have been shown in the drawings and described above, it will be apparent, that many changes may be made in the form, arrangement and positioning of the various elements of the combination. In consideration thereof it should be understood that preferred embodiments of this invention disclosed herein are intended to be illustrative only and not intended to limit the scope of the invention.