Abstract:
An improved apparatus and method for assembly of a hydrokinetic torque converter which comprises a hydraulic pump, a turbine, a stator, a driven hub, and a housing that is driven by the output element of an engine of a motor vehicle, and which functions to transmit torque to the hydraulic pump is disclosed. In such a torque converter the housing is coaxial with the pump and the turbine, and further defines an interior chamber, which encloses the turbine as well as a bypass or lockup clutch cooperating with a torsion damper having an input member and an output member. The present invention provides a positive interlocking connection between the output member of the torsion damper and the driven hub of the turbine by forming a circumferential array of staked protuberances in the driven hub to compressively engage a mating circumferential serration formed in the output member to prevent axial rotation thereof Thus, the inherently complex manufacturing processes required to form the internal and external splines conventionally utilized to interlock such components are eliminated thereby reducing the manufacturing costs of the torque converter. In addition, other components of the torque converter cooperating with the torsion damper are integrated into a single component to reduce space requirements of the torque converter.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This Application claims foreign priority benefits under 35 U.S.C. §119(a-d) to German patent application 199 00 861.2, filed Jan. 12, 1999 by inventors, Rudolf Hönemann, Thomas Heck, and Steven Olsen for an invention entitled Hydrodynamischer Drehmomentwandler (“Hydrokinetic Torque Converter”). 
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     This invention relates to improvements in apparatus for transmitting torque in power trains by way of a hydrokinetic torque converter which is equipped with a bypass or lockup clutch and, more particularly, to improvements in transmitting torque by way of a hydrokinetic torque converter which can transmit torque by way of a turbine and/or by way of a bypass or lockup clutch constructed and assembled to operate in parallel with such turbine. Still more particularly the present invention relates to an improved apparatus and method utilized in the construction and assembly of such a torque converter, which reduces the complexity, the weight, the space requirements, and manufacturing costs of the torque transmitting apparatus. 
     As a general rule, a hydrokinetic torque converter which can be utilized in accordance with the present apparatus and method comprises an impeller or hydraulic pump, a turbine, a stator, and a housing, which is driven by the rotary output element of a prime mover (such as the engine of a motor vehicle), and serves to transmit torque to the hydraulic pump. The housing is coaxial with the pump and with the turbine and defines an interior chamber, which accommodates the turbine as well as a bypass clutch or lockup clutch cooperating with a torsion damper including an input element and an output element whose torque capacity (i.e. the maximum torque which the damper can transmit) is less than the nominal (i.e. maximum achievable) torque of the prime mover. The damper prevents the transmission of any appreciable oscillations of torque from the output element of the engine of the motor vehicle to the input shaft of the transmission while the motor vehicle is operated within the main driving range. 
     The bypass clutch or lockup clutch serves merely to operate with slip in order to compensate for peaks of oscillations of the torque that is being transmitted by the output element of the engine. When the operation of the motor vehicle is within the main driving range as well as when the bypass clutch is operated with slip, undesirable fluctuations of torque cannot be transmitted to the input element of the transmission by the expedient of reducing the magnitude of the torque which can be transmitted by the clutch. Such pronounced fluctuations of torque are likely to develop, for example, due to resonance, to an abrupt change of the load and/or for certain other reasons. 
     Such a bypass or lockup clutch can include a friction clutch having a first friction surface on a substantially radially extending portion of the housing and a second friction surface provided on an axially displaceable piston which is movable in the direction of the turbine to move its friction surface into or away from frictional engagement with the first friction surface such that the magnitude of torque, which the clutch can transmit, depends on the extent of frictional engagement between the first and second surfaces. The second friction surface is normally provided on a radially outer portion of the piston, and the radially inner portion of such piston can transmit torque directly to the turbine or to the rotary input element of a transmission, which receives torque from the turbine or a driven hub which is separably connected to the turbine. 
     2. Description of Related Art 
     Under the current state of the art, the connection between the output element of the torsion damper and the hub driven by the turbine is either made by mating internal and external splines or as a riveted joint. This has the inherent disadvantages of the rather expensive and time consuming manufacturing processes required to machine the mating splines and/or requires numerous component parts and/or other fasteners and related labor costs to install the damper in the torque converter. 
     Hydrokinetic torque converters of the above-outlined character are disclosed, for example, in U.S. Pat. Nos. 5,029,087 and 4,577,737 recited herein, and also disclosed in U.S. Pat. No. 5,752,894, which is commonly owned and incorporated herein by reference. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides an improved apparatus and method for assembly of a hydrokinetic torque converter comprising a hydraulic pump, a turbine a stator, and a housing which is driven by the output element of an engine of a motor vehicle and serves to transmit torque to the hydraulic pump. The housing is coaxial with the pump and the turbine and defines an interior chamber, which accommodates the turbine as well as a bypass or lockup clutch cooperating with a torsion damper including an input member and an output member. In the conventional practice, the connection between the output member of the torsion damper and the hub driven by the turbine is made by mating internal and external splines and/or as a riveted joint. 
     The present invention provides an improved apparatus and method for interlocking the output member of the torsion damper with the driven hub of the turbine by utilizing a metal staking process in combination with a circumferential serration formed on the output member to form a fixed, non-rotatable connection therebetween. 
     Thus, the inherently expensive and complex manufacturing processes for such splined components and other related components and/or fasteners are significantly reduced or eliminated. In addition, other related components of the torque converter cooperating with the torsion damper have been integrated into single components to reduce the space requirements of the torque transmitting apparatus. 
     In view of the above, it is an object of the present invention to provide useful improvements in a hydrokinetic torque converter and in the assembly methods thereof in which a metal staking process in combination with a circumferential serration formed in such output member are utilized to form a non-rotatable axial connection between the driven hub of the turbine and the output member of the torsion damper. 
     Another object of the present invention is to provide an improved hydrokinetic torque converter in light of the described state of the art, which in contrast to the state of the art, is relatively less complex mechanically, requires fewer manufacturing and machining processes, and as a result is less expensive to manufacture and assemble. 
     Another object of the invention is to create a torque converter, which is more compact as the result of having fewer component parts and/or multiple parts integrated into a single component having reduced space requirements. 
     Other features and technical advantages of the present invention will become apparent from a study of the following description and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of the present invention are set forth in the appended claims. The invention itself, however, as well as other features and advantages thereof will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures, wherein: 
     FIG. 1 is a fragmentary schematic partly elevational and partly axial sectional view of a torque transmitting apparatus labeled PRIOR ART employing a hydrokinetic torque converter and a bypass clutch wherein the present invention is to be utilized; 
     FIG. 2 is a partial exploded elevational view of the input member of the PRIOR ART torsion damper which is shown in FIG. 1; 
     FIG. 3 is an elevational view of the output member of the PRIOR ART torsion damper which is shown in FIG. 1; 
     FIG. 4 is a fragmentary elevational view of a multi-stage torsion damper of the PRIOR ART which can be utilized in combination with a lockup clutch in accordance with the present invention; 
     FIG. 5 is a sectional view taken along the section line  5 — 5  as indicated by directional arrows in FIG.  4  and labeled PRIOR ART; 
     FIG. 6 is a fragmentary axial sectional view of a torsion damper modified in accordance with the present invention; and 
     FIG. 7 is a fragmentary sectional view taken along the section line  7 — 7  as indicated by directional arrows in FIG. 6 showing details of the present staking method. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Prior to describing the improvements of the present invention in detail, it may be beneficial to review the structure and function of a hydrokinetic torque converter with which the apparatus and method of present invention are to be utilized. Referring to FIG. 1 there is shown therein a torque transmitting apparatus, indicated generally at  110  and labeled PRIOR ART, comprising a hydrokinetic torque converter  111 , which is an integral part of the power train of a motor vehicle (not shown) having an engine and a transmission wherein the transmission is preferably a continuously variable transmission (CVT). Such a continuously variable transmission is disclosed in commonly owned U.S. Pat. No. 5,879,253. 
     The torque converter  111  includes a bypass clutch  112  and a damper  135  which is installed between the clutch  112  and the hub  114  of the turbine  118  forming part of the torque converter. The turbine  118  is mechanically attached to the hub  114  at a radially inner portion of the turbine cover  118   a  by rivets  141 . The torque converter  111  further comprises a housing  116  which is driven by the engine (not shown) of a motor vehicle by way of fasteners  116   a  and drives the impeller or hydraulic pump  117  residing therein. Housing  116  is comprised of two interconnected covers  116   b  and  116   c  which are mechanically coupled, for example, by weldment to prevent rotation thereof and are joined together in a fluid-tight attachment. The fasteners  116   a  (only one shown in FIG. 1) function to secure the housing  116  of the torque converter  111  to a disc (not shown) on the rotary output element (e.g. the crankshaft) of the combustion engine. 
     The stator  119  of the torque converter  111  is installed between the pump  117  and the turbine  118  in fluid communication therewith forming a closed toroidal fluid flow circuit driven by the pump  117 , which is attached to the rotary output element of the engine. 
     Still referring to FIG. 1, the bypass clutch  112  comprises an annular piston  136  whose axis coincides with the axis X—X of the torque converter  111  and which is installed between the housing  116  and the turbine  118 . The bypass or lockup clutch  112  can be of the single plate or multiplate type as explained hereinafter in further detail. 
     The piston  136  is preferably constructed of sheet metal and its radially inner portion is non-rotatably but axially movably mounted on the hub  114  of the turbine  118 . The radially outer portion of the piston  136  constitutes a conical frustum and is provided with a friction lining  121  having an exposed friction surface  122  on the adjacent frustoconical portion of the housing  116 . 
     The piston  136  is disposed between a compartment  124  and a compartment  125  forming part of the enclosure of the housing  116 . The compartment  124  is disposed between the piston  136  and the turbine  118 , and the compartment  125  is disposed between the piston  136  and the housing  116 . The means for changing the axial position of the piston  136  includes means for varying the pressure of fluid in the compartment  125 , namely for varying the differential between the pressures of the fluids in the compartments  124  and  125 . The magnitude of the torque, which is being transmitted by the bypass clutch  112 , is a function of such pressure differential. 
     The bypass clutch  112  serves merely to operate with slip in order to compensate for peaks of oscillations of the torque that is being transmitted by the output element of the engine. To this end the operation of the bypass clutch  112  within the main driving range of the motor vehicle is regulated in such a way that the maximum torque which can be transmitted via the bypass clutch  112  is a relatively small fraction of the nominal torque of the engine, but the maximum torque which the bypass clutch  112  can transmit is larger than the torque actually being transmitted by the engine to the housing  116  of the torque converter  111 . 
     The construction and mounting of the damper  135  are such that the torque capacity of the damper is less than the nominal torque of the combustion engine, which drives the housing  116 . In other words, the damper  135  begins to act like a solid body when the magnitude of the torque transmitted by the bypass clutch  112  is still less than the maximum torque which the engine can transmit to the housing  116  of the torque converter  111 . 
     Stated differently, the input member  138  of the damper  135  ceases to move relative to the flange-like output member  139  of the damper before the magnitude of the torque which is being transmitted to the housing  116  by the combustion engine of the vehicle in which the torque transmitting apparatus is installed reaches a maximum value. This can be achieved in a number of different ways. For example, the convolutions of the coil springs  137  forming part of the damper  135  can be caused to fully abut each other so that the springs  137  act like one-piece solid bodies, or the input and output members  138 ,  139  of the damper  135  can be provided with stops which come into abutment with each other before the magnitude of the torque being transmitted to the housing  116  reaches a maximum value. 
     In the torque converter  111  of the prior art, the input member  138  of the damper  135  is non-rotatably secured to the piston  136 , and the output member  139  of the damper  135  is non-rotatably but axially movably coupled to the hub  114  of the turbine  118 . To this end the output member  139  is provided with a set of internal axially parallel teeth mating with complementary axially parallel external teeth of the hub  114 . FIGS. 2 and 3 illustrate the details of damper  135 , which can be utilized in combination with the bypass or lockup clutch  112 . 
     The elements  137  of the damper  135  prevent the transmission of any oscillations of torque from the output element of the engine to the input shaft of the transmission while the motor vehicle is operated within the main driving range. The damper  135  is provided with an input element  138  and an output element  139  wherein such elements can be rotated relative to each other in a given angular range against the restoring force of the springs  137  captured between them. 
     The input member  138  of the damper  135  comprises a plurality of segment-shaped sections  140 , namely a first pair of sections  140  which confront each other at one side of the axis X—X and a second pair of sections  140  confronting each other at the other side of the axis X—X diametrically opposite the sections  140  of the first pair. The sections  140  of each pair of sections are affixed to the piston  136  by means of one or more rivets  141  and/or other suitable fasteners. 
     FIG. 3 shows the flange-like output member  139  of the damper  135 . This output member comprises an annular main portion  139   a  which carries two radially outwardly extending arms  142  disposed diametrically opposite each other. The arms  142  have windows  143  for the energy storing elements or springs  137  of the damper  135 . Each arm  142  is disposed between a pair of sections  140  as most clearly seen in FIG.  1 . 
     To this end the sections  140  of each pair are provided with confronting pockets  145  jointly defining a receptacle or pocket for the respective arm  142  as seen in FIG.  2 . The dimensions of the pockets  145  are selected in such a way that the input and output members  138 ,  139  of the damper  135  have limited freedom of angular movement relative to each other. This is illustrated in FIG. 3 wherein the two end positions of each of the arms  142  relative to the respective pair of sections  140  are indicated by phantom lines as at  146 . 
     The piston  136  is provided with an annulus of circumferentially spaced-apart axial projections  147  as shown in FIG. 1 which extend toward the turbine  118  and abut circumferentially spaced-apart portions  144  as seen in FIG. 2 of the immediately adjacent sections  140  of the input member  138 . The rivets  141  secure the portions  144  of the sections  140  forming part of the input member  138  to the adjacent axial projections  147  of the piston  136 . 
     The median portions of the sections  140  forming part of the input member  138  are provided with windows  148  for the adjacent energy storing elements or springs  137 . The windows  148  are in accurate axial alignment with the windows  143  in the arms  142  of the output member  139  and the dimensions of the windows are selected in such a way that the springs  137  are received therein without play, i.e. each spring  137  begins to store energy as soon as the input and output members  138 ,  139  begin to turn relative to each other, when the arms  142  of the output member  139  begin to leave their central positions in the respective pairs of pockets  145 . 
     Further, it is known to select the dimensions of the springs  137  and/or the dimensions and relative positions of the windows  143  and  148  in such a way that at least one of the energy storing elements or springs  137  is received in the respective windows  143 ,  148  with at least some clearance. Furthermore, at least one of the elements  137  can be installed in the respective windows  143  and  148  in at least slightly pre-stressed condition. Such expedients render it possible to select the manner in which the elements  137  undergo compression and/or additional compression while the input and output members  138 ,  139  of the damper  135  turn relative to each other. 
     The damper  135  can be designed in such a way that the elements  137  can transmit between approximately 40% to 50% of the nominal (maximum) torque of the engine which drives the housing  116  of the torque converter  111 . Further, the angular movability of the input and output members  138 ,  139  of the damper  135  relative to each other can be selected in such a way that it need not exceed a relatively narrow angular range between ±2° to ±8°, preferably between ±3° and ±6°. Thus, the total angular displacement of the input and output members  138 ,  139  relative to each other (in the clockwise and counterclockwise directions) can be between about 4° and 16° preferably between 6° and 12°. 
     Such relatively small angular displacement is particularly desirable and advantageous when the operation of a motor vehicle embodying the torque transmitting apparatus is shifted from coasting to pulling a load or vice versa. Relatively small angular displacements of the input and output members  138 ,  139  of the damper  135  under such circumstances reduces the likelihood of an excessive buildup of resonant vibrations in the power train of the motor vehicle. Any fluctuations of torque beyond the torque capacity of the damper  135  are compensated for in that the friction surfaces of the bypass clutch  112  are caused to slide relative to each other. Thus, the combination of the bypass clutch  112  and the damper  135  is effective within a wide range of operations of a motor vehicle with the torque converter  111  operatively disposed between the engine and the continuously variable transmission. 
     FIGS. 4 and 5 illustrate an example of a prior art multiplate lockup clutch, indicated generally at  212 , wherein the improvements and method of the present invention can also be utilized. The multiplate lockup clutch  212  is installed in a hydrokinetic torque converter having a housing  216  and a turbine  218  with a hub  214 . The lockup clutch  212  comprises a multiple-stage torsional damper  235  having a first set of energy storing elements  237  and a second set of energy storing elements  250 . In the embodiment shown, the illustrated energy storing elements  237  and  250  are coil springs. 
     The illustrated lockup clutch  212  is a multiplate clutch having a radially inner plate carrier  251  and a radially outer plate carrier  252 . The latter is non-rotatably affixed to the housing  216  of the hydrokinetic torque converter. That portion of the plate carrier  252 , which is nearer to the turbine  218  of the torque converter, supports a plate-like stop  253 . The housing  216  of the torque converter and the piston  236  of the lockup clutch  212  define a compartment  254 , which constitutes a plenum chamber and can receive a body of hydraulic fluid. The pressure in the compartment  254  determines the magnitude of the torque which is to be transmitted by the lockup clutch  212 . 
     The plate carrier  251  of the multiple-stage damper  235  constitutes the output member of the lockup clutch  212  and its radially inner portion is provided with an annulus of axially parallel teeth  255  mating with clearance with the external teeth  256  provided on the hub  214  of the turbine  218  (i.e. on the output element of the hydrokinetic torque converter). The external teeth  256  are (or can be) provided on a spur gear which is made of sheet metal and is riveted (as at  262 ) or otherwise non-rotatably affixed to the hub  214 . 
     The multistage damper  235  further comprises an input member  238  which is connected with the aforementioned plate carrier or output member  251  of the lockup clutch  212 . The input member  238  of the multistage damper  235  is an annular component which is provided with radially inwardly extending tongues or prongs  257  received in slit-shaped recesses  258  provided in the output member  251  of the lockup clutch  212 . The tongues  257  are received in the respective recesses in such a way that they establish a practically clearance-free connection between the output member  238  of the damper  235  (i.e. the parts  238  and  251  are coupled to each other for rotation about the axis X—X of the lockup clutch  212  and the hydrokinetic torque converter including the housing  216  and the turbine  218 ). 
     FIG. 4 shows that the input member  238  of the damper  235  is provided with windows  259 ,  260 ′ for the energy storing elements  237  and  250 , respectively. The dimensions of the windows  260 ′ and of the energy storing elements  250  are selected in such a way that the elements  250  are received in the respective windows  260 ′ with clearance in the clockwise and counterclockwise directions. The annular input member  238  is disposed between two discs  260  and  261  of the lockup clutch  212 . The discs  260 ,  261  have confronting cupped portions at the radially outer portion of the input member  238  and are riveted to one another radially outwardly of the member  238  as shown in FIG.  5 . 
     The disc  261  is adjacent the turbine  218  and extends radially inwardly all the way to the hub  214  and is non-rotatably affixed to such hub by the aforementioned rivets  262 . FIG. 5 shows that the rivets  262  serve as a means for non-rotatably affixing the disc  261 , the gear  256 , and the cover  218   a  of the turbine  218  to the hub  214 . 
     Referring to FIGS. 6 and 7 the improved apparatus and method of the present invention will now be described in detail. FIG. 6 shows an enlarged partial view of an improved damper  135 ′ in accordance with the present invention. 
     In the preferred embodiment, it can be seen that the turbine cover  118   a  enclosing the turbine  118  is attached to the radially outer portion  114   a ′ of the modified hub  114 ′ by a circumferential weldment as at  170  in lieu of the riveted connection of the prior art described hereinabove and illustrated in FIGS. 1 and 5. 
     The present damper  135 ′ includes a modified input member, indicated generally at  138 ′, and a modified output member, indicated generally at  139 ′. The input member  138 ′ is comprised of two sheet metal sections or members  151  and  152 , which are arranged in confronting relation and secured at the radially outermost portions thereof as shown in FIG. 6 by a rivet  153  or other suitable fastener. Energy storing elements or springs  137  are disposed between the input member  138 ′ and the output member  139 ′ of the modified damper  135 ′ as shown being aligned in the direction of angular rotation. The output member  139 ′ may also include a diaphragm spring  190  disposed in operative relation to a confronting surface of the section  151  of the input member  138 ′ as seen in FIG.  6 . 
     The modified damper  135 ′ includes structures for providing a positive locking connection between the output member  139 ′ of the damper  135 ′ and the modified hub  114 ′. Such structures form interlocking means including but not limited to those hereinafter described. Still referring to FIG. 6, the modified output member  139 ′ is constructed as a generally disc-shaped component having a central opening (not shown) substantially conforming in size to the diameter of a shoulder as at  162  formed on the hub  114 ′. The output member  139 ′ is installed on this shoulder diameter and abuts a radially outer portion  114   a ′ of the modified hub  114 ′ as shown being axially fixed in this position. 
     Referring now to FIG. 7, a circumferential serration  161  having a plurality of axially projecting teeth  161   a  is formed in the output member  139 ′ adjacent the periphery of the central opening thereof. In the preferred embodiment the serration  161  is fabricated to predetermined dimensions by a metal stamping process using conventional metal stamping dies and a mechanical and/or hydraulic press. 
     Since such metal stamping processes are well known to those skilled in the art, further detailed discussion of the same is not deemed necessary. 
     The output member  139 ′ is secured in non-rotatable engagement with the hub  114 ′ by a metal staking process in accordance with the present invention. In such a metal staking process, the output member  139 ′ is positioned on the mating shoulder diameter of the hub  114 ′ as shown in FIG.  2 . This sub-assembly comprised of the output member  139 ′ and the hub  114 ′ is placed in a hydraulic press including a metal staking tool or die (not shown) constructed for this purpose and the shoulder diameter of the hub  114 ′ is staked as at  162  creating raised metal protuberances or segments  163 , which are compressed axially against the serration  161  securing output member  139 ′ in position and preventing axial rotation thereof 
     In a preferred staking method, the staked segments  163  are discontinuous being formed in discrete, interrupted segments  163  of a short length alternating with non-staked areas  164  as shown in FIG. 7 to secure the output member  139 ′ in position on the hub  114 ′. Such a staked connection between the output member  139 ′ and the hub  114 ′ has proven to be of sufficient strength to transmit the nominal torque generated by the engine. 
     A particular advantage of staking the hub  114 ′ as at  162  in interrupted segments  163  lies in the convenience of interlocking components having large diameters. In such cases a significant amount of pressure is not required as compared to those applications in which such a staking process would be applied to the entire circular diameter. 
     Using the above-described staking method, a costly and labor-intensive construction of a unitary component (not shown) comprised of the hub  114 ′ and the output member  139 ′ can be avoided. To this end the output member  139 ′ may be constructed by a less expensive metal stamping process and attached to the machined hub  114 ′ utilizing the present staking method. Advantageously, present method permits the hub  114 ′ and the output member  139 ′ to be manufactured as separate components and to be constructed of different materials if desired. 
     In the embodiment shown in FIG. 6, the input member  138 ′ of the damper  135 ′ is attached to the bypass or lockup clutch, which can be either a single plate clutch (as in bypass clutch  112 ) or multiplate clutch (as in lockup clutch  212 ) described hereinabove. If the lockup clutch is composed of multiple plates (as in lockup clutch  212 ), then the input member  138 ′ of the present damper  135 ′ is comprised of a multiple plate carrier (such as inner plate carrier  251  or outer plate carrier  252 ) described hereinabove and shown in FIG.  5 . 
     This requires that the plate carriers such as  251 ,  252  of the prior art be mechanically attached to section  151  of the present input member  138 ′ or that the multiple plate carriers and the section  151  of the present input member  138 ′ be constructed as a single component. To this end, the present invention provides a modified multiple plate carrier  252 ′ as shown in FIG. 6, which is integrally formed with the input member  138 ′ and extending in the axial direction. 
     In accordance with the present invention, the input member  138 ′ of the damper  135 ′ may include alternative structures for integrating the input member  138 ′ with such a multiplate clutch. Such structures form integrating means including but not limited to those described hereinabove. 
     Although not specifically illustrated in the drawings, it should be understood that additional equipment and structural components will be provided as necessary and that all of the components above are arranged and supported in an appropriate fashion to form a complete and operative hydrokinetic torque converter incorporating features of the present invention. 
     It is also understood that variations may be made in the present invention without departing from the scope of the invention. Moreover, although illustrative embodiments of the invention have been described, a latitude of modification, change, and substitution is intended in the foregoing disclosure, and in certain instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate the appended claims be construed broadly and in a manner consistent with the scope of invention.