Abstract:
An internal combustion engine having a vacuum release mechanism that includes a centrifugally actuated member movably attached to the camshaft and having a vacuum release cam extending therefrom. The vacuum release cam is in lifting engagement with the exhaust valve assembly at crankshaft cranking speeds during a portion of the power stroke to relieve vacuum forces opposing motion of the piston. The vacuum release cam centrifugally pivots out of engagement with the exhaust valve assembly in response to the crankshaft attaining running speeds.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Serial No. 60/231,818, entitled “MECHANICAL COMPRESSION AND VACUUM RELEASE”, filed on Sep. 11, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention.  
           [0003]    This invention generally relates to internal combustion engines, and more particularly to a compression release and vacuum release mechanism for four-stoke cycle engines.  
           [0004]    2. Description of the Related Art.  
           [0005]    Compression release mechanisms for four-stroke cycle engines are well known in the art. Generally, means are provided to hold one of the valves in the combustion chamber of the cylinder head slightly open during the compression stroke while cranking the engine during starting. This action partially relieves the force of compression in the cylinder during starting, so that starting torque requirements of the engine are greatly reduced. When the engine starts and reaches running speeds, the compression release mechanism is rendered inoperable so that the engine may achieve full performance. It is normally advantageous for the compression release mechanism to be associated with the exhaust valve so that the normal flow of the fuel/air mixture into the chamber through the intake valve, and the elimination of spent gases through the exhaust valve is not interrupted, and the normal direction of flow through the chamber is not reversed. Examples of compression release mechanisms for four-stroke engines are shown in U.S. Pat. Nos. 3,381,676; 3,496,922; 3,897,768; 4,453,507; 4,977,868; 5,150,674 and 5,184,586, the disclosures of which are incorporated herein by reference. Although known compression release mechanisms are generally effective for relieving compression in the cylinder during cranking the engine, these mechanisms are typically designed to provide compression relief and do not remedy the significant torque established by vacuum in the combustion chamber during the power stroke.  
           [0006]    Presently, conventional four-stoke engines require a significant amount of torque to turn the engine over during the power stroke when combustion is not taking place, because the piston is moving downwardly against a pressure difference due to increasing suction or vacuum in the combustion chamber resulting from the partial discharge of gas from the combustion chamber during the immediately preceding compression stroke. The increase of torque required corresponds to a substantial operator or starter force required to drive the piston downwardly against such pressure difference.  
           [0007]    In response to the suction torque, one known combustion engine suggests using a contoured cam lobe which acts to hold the valve open longer between the compression and power strokes. Starting torque was decreased by this mechanism, however compression and accordingly engine power would significantly decrease compared to conventional engines which employ the traditional “pear-shaped” cam lobes. Yet another known mechanism employs a light spring placed on the stem side of the exhaust valve to hold the valve open during start up. However, in such an arrangement, significant intake and exhaust manifold pressures are required to close the exhaust valve and thus longer times and increased user effort is required to start the engine.  
           [0008]    It may be seen that torque, due to compression during start-up, is related to the torque due to vacuum during start-up. Specifically, the release of a significant amount of trapped air during the compression stroke, through the mechanical compression release, causes higher vacuum pressure to form in the cylinder. Very little user effort is required to turn the engine over during the compression stroke, however a substantial starting effort is required during the power stroke. Conversely, though, if very little air is released by the mechanical compression release then beneficially the pressure due to vacuum will be less. However, the pressure caused by compression will be high.  
           [0009]    Accordingly, it is desired to provide a release mechanism that addresses the significant torque developed by both the compression and power strokes, is effective in operation, and is relatively simple in construction.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention overcomes the disadvantages of prior internal combustion engines by providing a mechanical compression and vacuum release mechanism which is of simple construction and which significantly reduces the effort required to start the engine. The present compression and vacuum release mechanism includes a centrifugally responsive compression and vacuum release member pivotally mounted to the camshaft, the compression and vacuum release member including compression and vacuum release cams which are in lifting engagement with one of the intake or exhaust valve assemblies of the engine during engine starting to relieve compression and vacuum forces within the combustion chamber and thereby facilitate easier engine starting. After the engine is started and reaches a running speed, the compression and vacuum release member pivots about the camshaft such that the compression and vacuum release cams are disengaged from the lifting engagement with the intake or exhaust valve assemblies for normal engine operation.  
           [0011]    In one form thereof, the present invention provides an internal combustion engine, including a cylinder block including a cylinder therein and having a piston reciprocally disposed within the cylinder, the piston operably engaged with a crankshaft; a camshaft in timed driven relationship with the crankshaft; at least one intake valve reciprocally driven by the camshaft; at least one exhaust valve assembly reciprocally driven by the camshaft; and a vacuum release mechanism, including a vacuum release member attached to the camshaft and centrifugally moveable between first and second positions, the vacuum release member including a vacuum release cam extending therefrom, the vacuum release cam in lifting engagement with one of the valve assemblies in the first position during a portion of a power stroke of the piston to relieve vacuum forces opposing the power stroke, the vacuum release cam disposed out of engagement with the one of the valve assemblies in the second position.  
           [0012]    In another form thereof, the present invention provides an internal combustion engine, including a cylinder block including a cylinder therein and having a piston reciprocally disposed within the cylinder, the piston operably engaged with a crankshaft; a camshaft in timed driven relationship with the crankshaft; at least one intake valve assembly reciprocally driven by the camshaft; at least one exhaust valve assembly reciprocally driven by the camshaft; and a compression and vacuum release mechanism, including a compression and vacuum release member attached to the camshaft and centrifugally moveable between first and second positions, the compression and vacuum release member including a compression release cam and a vacuum release cam extending therefrom, the compression and vacuum release cams respectively in lifting engagement with one of the valve assemblies in said first position during a portion of a compression and a portion of a power stroke of the piston to relieve compression and vacuum forces respectively opposing the compression and the power strokes, the compression and vacuum release cams disposed out of engagement with the one of said valve assemblies in the second position.  
           [0013]    In a further form thereof, an internal combustion engine, including a cylinder block including a cylinder therein and having a piston reciprocally disposed within the cylinder, the piston operably engaged with a crankshaft; a camshaft in timed driven relationship with the crankshaft; at least one intake valve assembly reciprocally driven by the camshaft; at least one exhaust valve assembly reciprocally driven by the camshaft; and a compression and vacuum release mechanism, including a centrifugally actuated common yoke member moveably attached to the camshaft between a first position corresponding to a cranking speed of the engine and a second position corresponding to a running speed of the engine; a compression release cam extending from the yoke member and in lifting engagement with one of the valve assemblies in the second position during a portion of a compression stroke of the piston to relieve compressive forces opposing the compression stroke; and a vacuum release cam extending from the yoke member and in lifting engagement with the one of the valve assemblies in the first position during a portion of a power stroke of the piston to relieve vacuum forces opposing the power stroke; the compression and vacuum release cams disposed out of lifting engagement with the one of the valve assemblies in the second position. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The above mentioned and other features and objects of this invention will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0015]    [0015]FIG. 1 is a partial vertical sectional view of a single cylinder four-stroke internal combustion engine that incorporates a mechanical compression and vacuum release device in accordance with the principles of the present invention;  
         [0016]    [0016]FIG. 2 is a sectional view of the engine of FIG. 1 showing the compression and vacuum release in the start position;  
         [0017]    [0017]FIG. 3 is a perspective view of a first embodiment compression and vacuum release assembly engaged with a camshaft;  
         [0018]    [0018]FIG. 4A is a side view of the compression and vacuum release assembly of FIG. 3, showing the assembly in the start position and showing the run position in phantom;  
         [0019]    [0019]FIG. 4B is a side view of the compression and vacuum release assembly of FIG. 3, showing the assembly in the run position;  
         [0020]    [0020]FIG. 5 is a sectional view of the view compression and vacuum release assembly of FIG. 4A taken along line  5 - 5  of FIG. 4A;  
         [0021]    [0021]FIG. 6 is a perspective view of a second embodiment compression and vacuum assembly of the present invention engaged with a camshaft;  
         [0022]    [0022]FIG. 7A is a side view of the compression and vacuum release assembly of FIG. 6, showing the assembly in the start position and showing the run position in phantom;  
         [0023]    [0023]FIG. 7B is a side view of the compression and vacuum release assembly of FIG. 6, showing the assembly in the run position; and  
         [0024]    [0024]FIG. 8 is a sectional view of the view compression and vacuum release assembly of FIG. 6A taken along  8 - 8  of FIG. 6A. 
     
    
       [0025]    Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent several embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention.  
       DETAILED DESCRIPTION  
       [0026]    Referring now the drawings and particularly to FIG. 1, there is shown a vertical crankshaft, single cylinder, four-stroke internal combustion engine  10  including a compression and vacuum release mechanism according to one embodiment of the present invention. As is customary, engine  10  includes cylinder block  11 , crankshaft  12  and piston  14 , the piston being operatively connected to crankshaft  12  through connecting rod  16 . Piston  14  coacts with cylinder block  11  and cylinder head  18  to define combustion chamber  20 . Spark plug  22  secured in cylinder head  18  ignites the fuel/air mixture after it has been drawn into combustion chamber  20  through intake valve  21  (FIG. 2) during the intake stroke and has been compressed during the compression stroke of piston  14 . The spark is normally timed to ignite the fuel/air mixture just before piston  14  completes its ascent on the compression stroke. The fuel/air mixture is drawn into combustion chamber  20  from the carburetor of the engine through an intake passage controlled by a conventional intake valve (not shown), and the products of combustion are expelled from the cylinder during the exhaust stroke through exhaust port  24  controlled by poppet-type exhaust valve  26 . Although either valve  21 ,  26  may be opened to vent compression and vacuum during start-up, it is recognized that preferably exhaust valve  26  functions as the compression and vacuum release valve in a manner to be discussed hereinafter.  
         [0027]    Other conventional parts of the valve operating mechanism, or valve assembly, include timing gear  27  mounted on crankshaft  12  for rotation therewith, and camshaft gear  28  mounted on camshaft  30  and rotatably driven by timing gear  27  to thereby rotate camshaft  30  at one-half crankshaft speed. Camshaft  30  comprises conventional pear-shaped intake and exhaust camshaft lobes  32  and  34 , respectively, (FIGS. 1 and 2) which rotate with camshaft  30  to impart reciprocating motion to the intake and exhaust valves  21 ,  26  via tappets or cam followers  36  and  38 , respectively. Although FIGS. 1 and 2 illustrate the compression and vacuum release mechanism in a side valve engine, this is but one engine type, and it is envisioned that the compression and vacuum release mechanism is amenable to other engine types, such as OHV and OHC engines of a vertical or horizontal crankshaft type, for example.  
         [0028]    Referring to FIG. 2, intake lobe  32  is the outboard lobe furthest removed relative to camshaft gear  28 , and exhaust lobe  34  is inboard from camshaft gear  28  and lobe  32 . The exhaust valve train is shown in FIG. 1 and includes cam follower  38  having face  42  adapted to bear tangentially against, and remain in a continuous abutting relationship with, peripheral surface  44  of exhaust camshaft lobe  34 . Referring to FIG. 1, cam follower  38  slides in guide boss  48  of crankcase  50 , and its upper end pushes against tip  46  of valve  26 . In operation, cam follower  38  lifts stem  52  of exhaust valve  26  which lifts face  53  from valve seat  55 . Valve spring  54  encircles stem  52  between valve guide  56  and spring retainer  58 . Spring  54  biases valve  26  closed and also biases cam follower  38  into tracking contact with exhaust lobe  34 . Although the valve train or valve assembly shown in FIGS. 1 and 2 includes a camshaft having lobes which directly actuate the intake and exhaust valves, other engines in which the present invention may be used may include different valve trains or valve assemblies, such as, for example, an overhead camshaft driven from the crankshaft via linkage and including lobes for opening and closing the intake and exhaust valves; a camshaft driven from the crankshaft and including lobes for actuating push rods connected to rocker arms which in turn open and close the intake and exhaust valves; or a camshaft having a single cam lobe actuating rocker arms which in turn open and close the intake or exhaust valves. Other valve train or valve assemblies are also possible in engines in which the present invention may be used.  
         [0029]    To aid in starting engine  10 , mechanical compression and vacuum release  70  is provided and will be described below. While device  70  is in its inoperative position (FIG. 4B), which is designated as the “run” position of the engine, the rotation of outboard lobe  34  with camshaft  30  at “running speed” causes normal operation of valve  26 , so that valve  26  opens and closes in timed and periodic relation with the travel of piston  14  according to conventional engine timing practice. Thus, exhaust lobe  34  is adapted to open valve  26  near the end of the power stroke and to hold the same open during ascent of the piston on the exhaust stroke until the piston has moved slightly past top dead center. As camshaft lobe  34  continues to rotate, spring  58  forces cam follower  38  downwardly and valve  26  is reseated. Valve  26  is held closed during the ensuing intake, compression and power strokes. Intake camshaft lobe  32  is likewise of conventional fixed configuration to control the intake valve such that it completely closes shortly after the piston begins its compression stroke and remains closed throughout the subsequent power and exhaust strokes, and reopening to admit the fuel mixture on the intake stroke.  
         [0030]    Since in a conventional engine the intake and exhaust valves are normally closed for the major portion of the power stroke, cranking of the engine is impeded because the piston must pull against a vacuum in the combustion chamber. Such vacuum may be created in the combustion chamber by the operation of a conventional compression release mechanism during engine starting. However, by incorporating the compression and vacuum release mechanism of the present invention, compression and vacuum relief is automatically obtained at cranking speeds to greatly reduce cranking effort and thereby facilitate starting. Moreover, a conventional engine need not be physically altered to effect compression and vacuum release with the mechanism of the present invention incorporated therein. The compression and vacuum release mechanism is responsive to engine speed such that it is automatically rendered inoperative at engine running speeds to prevent compression loss or loss of efficiency of the engine when it is running under its own power.  
         [0031]    Referring to FIGS.  3 - 5 , a first embodiment of a compression and vacuum release mechanism  70  of the present invention is shown. Compression and vacuum release mechanism  70  includes pivotable yoke member  72 , having a pair of legs  74 ,  76  that straddle camshaft  30 . Legs  74 ,  76  are pivotally connected to the camshaft by means of pin  78  and connected together by arcuate saddle portion  80  of yoke member  72 . Saddle portion  80  carries a pair of outwardly curved projections serving as first and second auxiliary cam members or mechanical compression release and vacuum release cams  82 ,  84 . At the ends of legs  74 ,  76  are respective counterweights  86 ,  88  which are shown extending along a line generally oblique to the axis of rotation of camshaft  30 . Counterweights  86 ,  88  serve to bias the yoke member  72  by gravity, to the position shown in FIG. 4A, in which auxiliary cam members  82 ,  84  are in a valve unseating or “start” position corresponding to crankshaft  12  rotating at cranking speed.  
         [0032]    Referring to FIG. 5, a pair of projections serving as stop members  90 ,  92  extend from inner portion  94  of saddle  80  and are radially and inwardly directed toward camshaft  30 . At cranking speed, incidently concomitant with the start position illustrated in FIG. 4A, yoke member  72  pivots counterclockwise shown by arrow  96 , coming to a rest when stop members  90 ,  92  contact peripheral surface  98  of camshaft  30 . In this condition, during cranking of the engine, auxiliary cam members  82 ,  84  will engage the cam follower  38 , first, during an early portion of the compression stroke, and second, during the latter portion of the power stroke to respectively release compression and vacuum formed in combustion chamber  20 . Auxiliary cam members  82 ,  84  may be radially spaced apart corresponding to an angle of 90°, for example (FIG. 5).  
         [0033]    It may be seen, with reference to FIG. 4A, that relatively flat underface  42  of cam follower  38  is displaced from its abutting relationship with surface  44  of cam lobe  34  due to first auxiliary cam or mechanical compression release cam  82  displacing cam follower  38  to correspondingly raise valve face  53  off seat  55  and vent combustion chamber  20 . Thus, at low crankshaft speeds, auxiliary cam members  82 ,  84  assume their FIG. 4A position where they engage cam follower  38  to successively unseat valve  26  which releases compression during the compression stroke and vacuum during the power stroke.  
         [0034]    Referring to FIG. 4B, illustrating camshaft  30  in the run position, centrifugal force acting through the center of mass of yoke member  72  causes yoke member  72  to pivot from its position of FIG. 4A to the position shown in FIG. 4B, in which arms  74 ,  76  are shown extending substantially perpendicularly to camshaft  30 . Yoke member  72 , pivoting about pin  78 , and auxiliary cam members  82 ,  84  projecting from yoke member  72  swing away from cam follower  38  such that underface  42  of cam follower  38  and peripheral surface  44  of cam lobe  34  are in continuous abutting engagement with one another.  
         [0035]    Compression and vacuum release mechanism  70  affects the lift of exhaust valve  26  relative to rotation of crankshaft  12  as hereinafter described. Referring to FIG. 1, a four-stroke cycle internal combustion engine  10  is shown and provides four strokes of piston  14  to complete a cycle of operation of the engine, coinciding with 720° of rotation of crankshaft  12 . On the intake stroke, piston  14  moves downwardly from the top of its travel (referred to as top dead center or TDC) to the bottom of its travel (referred to as bottom dead center or BDC). Intake valve  21  (FIG. 2) is opened and exhaust valve  26  is closed during the intake stroke. During the intake stroke, and at crankshaft running speed, a charge of air/fuel mixture is drawn into cylinder  20  above the head of piston  14  and through intake valve  21 . Following the intake stroke both intake and exhaust valves  21 ,  26  close and the compression stroke is started. Toward the middle of the compression stroke, approximately 110° of crankshaft rotation before TDC, for example, mechanical compression release cam  82  lifts exhaust valve  26  to relieve cylinder pressure and then closes at about 60° before TDC. Following the compression stroke, piston  14  is urged toward BDC in the power stroke, which coincides with both intake and exhaust valves  21 ,  26  substantially closed. At approximately 60° of crankshaft rotation following TDC during the power stroke, vacuum release cam  84  lifts exhaust valve  26  off of its seat and suction forces due to vacuum formed in cylinder  20  are relieved.  
         [0036]    For instance, in an exemplary embodiment of the compression and vacuum release  70 , intake valve  21  may have a lift of 0.2 inches during the intake stroke and exhaust valve  26  may be lifted 0.03 inches, and held open for 50° of camshaft rotation, by mechanical compression release cam  82  during the compression stroke. Specifically, the mechanical compression release opens the exhaust valve  26  at a crankshaft rotation of 110° prior to TDC and holds open exhaust valve  26  until crankshaft  12  is approximately 60° before TDC. The vacuum release activated by vacuum release cam  84  opens exhaust valve  26  a distance of 0.02 inches at a crankshaft rotation of 60° after TDC to vent suction caused by cylinder vacuum during the power stroke. Thus, the energy of the compressed air/fuel mixture is used to assist moving the piston during the power stroke. Cam  84  holds open exhaust valve  26  at 60° after TDC for a duration of 50° of crankshaft rotation.  
         [0037]    Due to the balanced relationship provided to yoke member  38  through counterweights  86 ,  88  the counterweights may be seen to extend radially outwardly and reach an equilibrium position. When rotation of crankshaft  12  is slowed or stopped, the gravitational force will once again become dominant and yoke member  72  will pivot to its start position shown in FIG. 4A. While the drawings show the compression and vacuum release member  70  being biased to its start position solely by gravity, it is contemplated that in certain installations, the compression release member may be biased to its run position by a spring or other resilient member.  
         [0038]    Referring to FIGS.  6 - 8 , shown is a second embodiment of a mechanical compression and vacuum release  70 ′ of the present invention. Mechanical compression and vacuum release  70 ′ differs from mechanical compression and vacuum release  70  in that release  70 ′ includes auxiliary cams  82 ′,  84 ′ which pivot inwardly into recesses  100 ,  102  respectively provided in axial end  104  of exhaust cam lobe  34 ′.  
         [0039]    Referring to FIG. 6, compression and vacuum release mechanism  70 ′ includes pivotable yoke member  72 ′, having a pair of legs  74 ′,  76 ′ that straddle camshaft  30 ′. Legs  74 ′,  76 ′ are pivotally connected to the camshaft by means of pin  78 ′ and connected together by arcuate saddle portion  80 ′ of yoke member  72 ′. Saddle portion  80 ′ carries a pair of outwardly curved projections serving as first and second auxiliary cam members  82 ′,  84 ′. Auxiliary cams  82 ′,  84 ′ may be radially spaced 90° apart, for example (FIG. 8). At the ends of legs  74 ′,  76 ′ are respective counterweights  86 ,  88  that extend along a line substantially parallel to the axis of rotation of camshaft  30 ′. Counterweights  86 ′,  88 ′ serve to bias the yoke member  72 ′ by gravity, to the position shown in FIG. 7A, in which auxiliary cam members  82 ′,  84 ′ are in a valve unseating or “start” position.  
         [0040]    Referring to FIG. 7A, yoke member  72 ′ is urged into position by counterweights  86 ′,  88 ′ tending to pull respective legs  74 ′,  76 ′ inwardly toward and substantially parallel with axis of rotation  89  of cam  30 ′. Auxiliary cams  82 ′,  84 ′ are outwardly extended and correspondingly unseat underface  42  of cam follower  38  from cam lobe  34 ′. In this condition, during cranking of the engine, mechanical compression release and vacuum release cams  82 ′,  84 ′ will successively engage cam follower  38 ′, first, during the compression stroke, and second, during the power stroke to respectively release compression and vacuum formed in combustion chamber  20 . It may be seen, with reference to FIG. 7A, that cam follower underface  42  of cam follower  38  is displaced from its abutting relationship with surface  44 ′ of cam lobe  34 ′ due to mechanical compression release cam  82 ′ displacing cam follower  38 ′ to correspondingly raise valve face  53  off seat  55  and vent compression chamber  20 . Thus, at low crankshaft speeds, cam members  82 ′,  84 ′ assume their FIG. 7A position where they engage cam follower  38  to unseat valve  26  which releases compression during the compression stroke and vacuum during the power stroke.  
         [0041]    Referring to FIG. 7B, illustrating camshaft  30 ′ the run position, centrifugal force acting through the center of mass causes yoke member  72 ′ to pivot from its position of FIG. 7A to the yoke member position shown in FIG. 7B. Yoke member  72 ′, pivoting about pin  78 ′, and auxiliary cam members  82 ′,  84 ′ projecting from yoke member  72 ′ swing away from cam follower  38  such that underface  42  of cam follower  38  and peripheral surface  44 ′ of cam lobe  34 ′ are in continuous abutting engagement with one another.  
         [0042]    Referring again to FIG. 7B, recesses  100 ,  102  formed in axial end  104  of camshaft lobe  34 ′ provide respective stops for auxiliary cams  82 ′,  84 ′ in the run position. Specifically, auxiliary cams  82 ′,  84 ′ are urged to recede under the peripheral surface  44 ′ of cam lobe  34 ′ and auxiliary cams  82 ′,  84 ′ are in abutment with respective recesses  100 ,  102 . When rotation of crankshaft  12  is slowed or stopped, the gravitational force will once again become dominant and yoke member  72 ′ will pivot to its start position shown in FIG. 7A. While the drawings show the compression and vacuum release member  70 ′ being biased to its start position solely by gravity, it is contemplated that in certain installations, the compression release member may be biased to its run position by a spring or other resilient member.  
         [0043]    Further, it is envisioned that the mechanical compression release, provided by mechanical compression release cams  82 ,  82 ′, and the vacuum release, provided by vacuum release cams  84 ,  84 ′ may be structured and arranged to engage the respective exhaust and intake valves independently of one another. This may be accomplished by providing two yokes, each yoke possessing only a single auxiliary cam, rather than a pair of auxiliary cams. Each yoke is pivotably and independently supported by the camshaft, one having mechanical compression release cam  82  or  82 ′ to relieve compression in the cylinder and the other yoke including vacuum release cam  84  or  84 ′ to relieve vacuum in the cylinder.  
         [0044]    The disclosed embodiments are not intended to be exhaustive or limit the invention to the precise forms disclosed in the detailed description. While the present invention has been described as having exemplary designs, the present invention can be further modified within the spirit and scope of this disclosure. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.