Abstract:
A control for enhanced range shifting in a computer ( 48 ) assisted vehicular compound transmission having a main section ( 16 A) shifted by a manually operated shift lever ( 31 ) and a range section ( 16 B) shifted in response to operation of a range shift selector, such as sensing shift lever ( 31 ) passing through a predetermined actuation point (AR) in the shift pattern. During a compound up-shift, if the vehicle reaches a speed greater than a predetermined value during a coasting condition and the shift lever is in a low range neutral position, then the range section up-shift is automatically completed without undue wear or damage to the range section synchronized clutch ( 130 ). It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a control system/method for controlling range shifting in a compound transmission having a lever-shifted main section and a range section shifted by a range section actuator for selectively positioning a synchronized double-acting positive clutch. The transmission may also have a splitter section. In particular, the present invention relates to controlling range shifting in a lever-shifted, partially automated vehicular transmission system having a microprocessor-based controller for controlling the operation of a range shift actuator and/or an engine fuel control. 
   2. Description of the Related Art 
   Controller-assisted, manually shifted transmission systems are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,582,558; 5,755,639; 5,766,111; 5,791,189; 5,974,906; 5,989,155 and 6,015,366, the disclosures of which are incorporated herein by reference. 
   Compound transmissions having a range and/or combined range- and splitter-type auxiliary transmission section are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,754,665 and 5,390,561, the disclosures of which are incorporated herein by reference. 
   Transmissions having manually shifted main sections and automatically shifted splitter sections are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,435,212; 5,938,711; 6,007,455 and 6,044,721, the disclosures of which are incorporated herein by reference. 
   Compound transmissions having automatically implemented range shifting are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,911,787 and 5,974,906, the disclosures of which are incorporated herein by reference. 
   Drivers have been known to operate their vehicles with a main section of the transmission in neutral on downhill grades for an extended period of time. 
   In an exemplary range section, the high speed range to low speed range step is approximately 3½ to one. That is, when a range shift is executed from low to high, the speed of the high speed gear must be decreased by a factor of 3½ to enable synchronization. At relatively low speeds, this is achieved without significant difficult. However, at relatively high speeds, as might be experienced on highways, the energy needed to decelerate the high speed gear and the rotatably connected auxiliary unit countershafts and gears rotating therewith to synchronous speed is quite considerable. Attempting to synchronize the speeds at elevated road speeds has been identified as a source of damage to the high speed range synchronizers. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, the drawbacks of the prior art are minimized or overcome by the provision of a range shift control for a computer-assisted mechanical transmission system that will sense vehicle operating conditions and will avoid unacceptable range up-shifts to prevent and/or minimize undue wear and/or damage to the high speed range synchronizer during a range up-shift. This is accomplished by causing range up-shifts to occur before the vehicle speed becomes unacceptably high. A range up-shift to a high range is automatically made if (i) a range up-shift has not been already initiated, (ii) a position of a shift lever is in a low range neutral position, and (iii) a vehicle speed is greater than a predetermined value, thereby preventing and/or minimizing undue wear and/or damage to the range synchronizer during a range up-shift. If a range upshift has already been initiated, then established shift protocols are invoked to complete the up-shift. Otherwise, the system continues to monitor the specified conditions to determine the need for an up-shift. 
   These and other aspects of the present invention will become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  is a schematic illustration of an ECU-assisted compound mechanical transmission system advantageously utilizing the range shifting control of the present invention. 
       FIG. 2  is a chart illustrating the shift pattern and representative numerical ratios for the transmission of FIG.  1 . 
       FIG. 3  is a schematic illustration of the structure of the compound mechanical transmission of FIG.  1 . 
       FIGS. 4A and 4B  are schematic illustrations of a shift shaft position sensor mechanism for use in the system of FIG.  1 . 
       FIG. 5  is a schematic illustration, in flow chart format, of the range shift control of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A computer-assisted (i.e., microprocessor-based, controller-assisted) vehicular compound mechanical transmission system  10 , particularly well suited to utilize the range shift control of the present invention, may be seen by reference to  FIGS. 1-4B . 
   System  10  is of the type commonly utilized in heavy-duty vehicles, such as the conventional tractors of tractor/semi-trailer vehicles, and includes an engine, typically a diesel engine  12 , a master friction clutch  14  contained within a clutch housing, a multiple-speed compound transmission  16 , and a drive axle assembly (not shown). The transmission  16  includes an output shaft  20  drivingly coupled to a vehicle drive shaft  22  by a universal joint  24  for driving the drive axle assembly. The transmission  16  is housed within a transmission housing to which is directly mounted the shift tower of the shift lever assembly  30 . The present system is equally applicable to remotely mounted shift levers, as are used in cab-over-engine types of vehicles. 
     FIG. 2  illustrates a shift pattern for assisted manual shifting of a combined range-and-splitter-type compound transmission shifted by a manually operated shift lever. Briefly, the shift lever  31  is movable in the side-to-side or X-X direction to select a particular ratio or ratios to be engaged and is movable in the fore and aft or Y-Y direction to selectively engage and disengage the various ratios. The shift pattern may include an automatic range shifting feature and automatically selected and/or implemented splitter shifting, as is known in the prior art. Manual transmissions utilizing shift mechanisms and shift patterns of this type are well known in the prior art and may be appreciated in greater detail by reference to aforementioned U.S. Pat. Nos. 5,000,060 and 5,390,561. 
   Typically, the shift lever assembly  30  will include a shift finger or the like (not shown) extending downwardly into a shifting mechanism  32 , such as a multiple-rail shift bar housing assembly or a single shift shaft assembly, as is well known in the prior art and as is illustrated in aforementioned U.S. Pat. Nos. 4,455,883; 4,550,627; 4,920,815 and 5,272,931. 
   In the automatic range shifting feature, as the shift lever moves in the transition area between the middle leg (¾-⅚) and the righthand leg (⅞-{fraction (9/10)}) of the shift pattern, it will cross a point, AR, which will actuate a mechanical or electrical range switch, or will be sensed by a position sensor, to cause automatic implementation of a range shift. 
   The present invention also is applicable to transmission systems of the type utilizing range shift selector switches which are manually operated independent of shift lever position, as illustrated in aforementioned U.S. Pat. No. 5,222,404. 
   Shifting of transmission  16 , comprising main section  16 A coupled in series to auxiliary section  16 B, is semi-automatically implemented/assisted by the vehicular transmission system  10 , illustrated in  FIGS. 1-4B . Main section  16 A includes an input shaft  26 , which is operatively coupled to the drive or crank shaft  28  of the vehicle engine  12  by master clutch  14 , and output shaft  20  of auxiliary section  16 B is operatively coupled, commonly by means of a drive shaft  24 , to the drive wheels of the vehicle. The auxiliary section  16 B is a combined range-and-splitter type, as illustrated in U.S. Pat. Nos. 4,754,665 and 5,390,561. 
   The change-gear ratios available from main transmission section  16  are manually selectable by manually positioning the shift lever  31  according to the shift pattern prescribed to engage the particular desired change gear ratio of main section  16 A. 
   The system includes sensors  30  (for sensing engine rotational speed (ES)),  32  (for sensing input shaft rotational speed (IS)), and  34  (for sensing output shaft rotational speed (OS)), and providing signals indicative thereof. As is known, with the clutch  14  engaged (i.e., no slip) and the transmission engaged in a known gear ratio, ES=IS=OS*GR (see U.S. Pat. No. 4,361,060). Accordingly, if clutch  14  is engaged, engine speed and input shaft speed may be considered as equal. Input shaft speed sensor  32  may be eliminated and engine speed (ES), as sensed by a sensor or over a data link (DL), substituted therefor. 
   Engine  12  is electronically controlled, including an engine electronic controller, alternatively known as an engine electronic control unit, or an engine ECU  36  communicating over an electronic data link (DL) operating under an industry standard protocol such as SAE J-1922, SAE J-1939, ISO 11898 or the like. Throttle position (operator demand) is a desirable parameter for selecting shifting points and in other control logic. A separate throttle position sensor  38  may be provided or throttle position (THL) may be sensed from the data link. Gross engine torque (T EG ) and base engine friction torque (T BEF ) also are available on the data link. 
   A manual clutch pedal  40  controls the master clutch  14 , and a sensor  42  provides a signal (CL) indicative of clutch-engaged or -disengaged condition. The condition of the clutch also may be determined by comparing engine speed to input shaft speed if both signals are available. An auxiliary section actuator  44  including a range shift actuator and a splitter actuator  46  is provided for operating the range clutch and the splitter section clutch in accordance with command output signals from a transmission controller or ECU  48 . The shift lever  31  has a knob  50  which contains splitter selector switch  52  by which a driver&#39;s intent to initiate a splitter shift may be sensed. 
   Transmission ECU  48  is preferably a microprocessor-based control unit of the type illustrated in U.S. Pat. Nos. 4,595,986; 4,361,065 and 5,335,566, the disclosures of which are incorporated herein by reference, for receiving input signals  68  and processing same according to predetermined logic rules to issue command output signals  70  to system actuators, such as the splitter section actuator  46 , the engine ECU  36 , the range shift actuator and/or a display unit  54 . A separate system controller may be utilized, or the engine ECU  36  communicating over an electronic data link may be utilized. A single integrated ECU might also be employed. 
   System  10  may include a driver&#39;s display unit  54  including a graphic representation of the six-position shift pattern with individually lightable display elements  56 ,  58 ,  60 ,  62 ,  64  and  66 , representing each of the selectable engagement positions. Preferably, each half of the shift pattern display elements (i.e.,  58 A and  58 B) will be individually lightable, allowing the display to inform the driver of the lever and splitter position for the engaged ratio. 
   As shown in U.S. Pat. Nos. 5,651,292 and 5,661,998 (the disclosures of which are incorporated herein by reference), the splitter actuator  46  is, preferably, a three-position device, allowing a selectable and maintainable splitter section neutral. Alternatively, a “pseudo” splitter-neutral may be provided by deenergizing the splitter actuator when the splitter clutch is in an intermediate, non-engaged position. 
   The structure of the 10-forward-speed combined range-and-splitter-type transmission  16  is schematically illustrated in FIG.  3 . Transmissions of this general type are disclosed in aforementioned U.S. Pat. Nos. 5,000,060; 5,370,013 and 5,390,561. 
   Transmission  16  includes a main section  16 A and an auxiliary section  16 B, both contained within a housing including a forward end wall  16 C, which may be defined by the clutch housing, and a rearward end wall  16 D. In this particular embodiment an intermediate wall separating main section  16 A and auxiliary section  16 B is not employed, but one could be without effect on the present invention. 
   Input shaft  26  carries input gear  76  fixed for rotation therewith and defines a rearwardly opening pocket wherein a reduced diameter extension of output shaft  20  is piloted. A non-friction bushing or the like may be provided in the pocket or blind bore. The rearward end of input shaft  26  is supported by bearing  78  in front end wall  16 C, while the rearward end of output shaft  20  is supported by bearing assembly  80  in rear end wall  16 D. 
   The mainshaft  82 , which carries mainshaft clutches  84  and  86 , and the mainshaft splitter clutch  88  is in the form of a generally tubular body having an externally splined outer surface and an axially extending through bore for passage of output shaft  20 . Shift forks  90  and  92  are provided for shifting clutches  84  and  86 , respectively (see FIG.  4 A). Mainshaft  82  is independently rotatable relative to input shaft  26  and output shaft  20  and preferably is free for limited radial movement relative thereto. 
   The main section  16 A includes two substantially identical main section countershaft assemblies  94 , each comprising a main section countershaft  96  carrying countershaft gear pairs  98 ,  102 ,  104  and  106  fixed thereto. Gear pairs  98 ,  102 ,  104  and  106  are constantly meshed with input gear  76 , mainshaft gears  108  and  110  and an idler gear (not shown), which is meshed with reverse mainshaft gear  112 , respectively. One of the countershaft assemblies  94  may include a gear  100 , commonly known as a power take-off gear. 
   Main section countershaft  96  extends rearwardly into the auxiliary section, where its rearward end is supported directly or indirectly in rear housing end wall  16 D. 
   The auxiliary section  16 B of transmission  16  includes two substantially identical auxiliary countershaft assemblies  114 , each including an auxiliary countershaft  116  carrying auxiliary countershaft gears  118 ,  120  and  122  for rotation therewith. Auxiliary countershaft gear pairs  118 ,  120  and  122  are constantly meshed with splitter gear  124 , splitter/range gear  126  and range gear  128 , respectively. Splitter clutch  88  is fixed to mainshaft  82  for selectively clutching either gear  124  or  126  thereto, while synchronized range clutch  130  is fixed to output shaft  20  for selectively clutching either gear  126  or gear  128  thereto. 
   Auxiliary countershafts  116  are generally tubular in shape, defining a through bore for receipt of the rearward extensions of the main section countershafts  96 . Bearings or bushings are provided to rotatably support auxiliary countershaft  116  on main section countershaft  96 . 
   The splitter jaw clutch  88  is a double-sided, non-synchronized clutch assembly which may be selectively positioned in the rightwardmost or leftwardmost positions for engaging either gear  126  or gear  124 , respectively, to the mainshaft  82  or to an intermediate position wherein neither gear  124  or  126  is clutched to the main shaft. Splitter jaw clutch  88  is axially positioned by means of a shift fork  98  controlled by a three-position actuator, such as a piston actuator, which is responsive to a driver selection switch such as a button or the like on the shift knob, as is known in the prior art and to control signals from ECU  48  (see U.S. Pat. No. 5,661,998). 
   Two-position synchronized range clutch assembly  130  is a two-position clutch which may be selectively positioned in either the rightwardmost or leftwardmost positions thereof for selectively clutching either gear  128  or  126 , respectively, to output shaft  20 . Clutch assembly  130  is positioned by means of a shift fork (not shown) operated by means of a two-position piston device. Either of the range and splitter piston actuators may be replaced by a functionally equivalent actuator, such as a ball screw mechanism, ball ramp mechanism or the like. 
   By selectively axially positioning both the splitter clutch  88  and the range clutch  130  in the forward and rearward axial positions thereof, four distinct ratios of mainshaft rotation to output shaft rotation may be provided. Accordingly, auxiliary transmission section  16 B is a three-layer auxiliary section of the combined range and splitter type providing four selectable speeds or drive ratios between the input (mainshaft  82 ) and output (output shaft  20 ) thereof. The main section  16 A provides a reverse and three potentially selectable forward speeds. However, one of the selectable main section forward gear ratios, the low-speed gear ratios associated with mainshaft gear  110 , is not utilized in the high range. Thus, transmission  16  is properly designated as a “(2+1)×(2×2)” type transmission providing nine or ten selectable forward speeds, depending upon the desirability and practicality of splitting the low gear ratio. 
   Splitter shifting of transmission  16  is accomplished responsive to initiation by a vehicle operator-actuated splitter button  52  or the like, usually a button located at the shift lever knob, while operation of the range clutch shifting assembly is an automatic response to movement of the gear shift lever between the central and rightwardmost legs of the shift pattern, as illustrated in FIG.  2 . Alternatively, splitter shifting may be automated (see U.S. Pat. No. 5,435,212). Range shift devices of this general type are known in the prior art and may be seen by reference to aforementioned U.S. Pat. Nos. 3,429,202; 4,455,883; 4,561,325 and 4,663,725. Alternatively, a driver operator switch could be employed to initiate range shifting. Such shifting may only be initiated with the main section  16 A in neutral. 
   To protect the range synchronizers, a properly executed range shift should occur in the sequence of (i) disengaging the main section by shifting to main section neutral, (ii) then initiating and completing the range section shift, and (iii) then, after the range section shift is completed, engaging the main section in the appropriate ratio. 
   As is known in the prior art, range clutch damage, also called “range synchronizer burnout,” is most likely to occur in three situations: (i) if the main section is engaged prior to completion of a range up-shift, (ii) if the main section is engaged prior to completion of a range downshift, or (iii) if a range downshift is attempted at too high a vehicle speed. The reason for synchronizer damage in situations (i) and (ii) is that with the transmission in gear, the synchronizer simply lacks the capacity to achieve synchronization. Similarly, but less obviously, the high speed range synchronizer lacks the capacity to decelerate high speed gear  126 , and the associated elements including countershaft assemblies  114 , gears  124  and  128 , and shaft  82 . Under normal operating conditions, the shift form low range to high range occurs at a relatively low speed, well within the torsional energy/capacity of synchronizer  130 . However, if an extended downhill coast is initiated with the transmission in neutral and synchronizer  130  in the low range position, the high range side of synchronizer  130  may be damaged in an attempt to shift into range high. Under normal circumstances associated with driving the vehicle under engine torque, an upshift would generally be initiated at the very least at the maximum engine speed. If the maximum engine speed were 2600 RPM, and the range high to range low speed ratio is 3.5:1, then the synchronizer, in an extreme situation, might need to bring the high range gear down from about 1100 RPM to about 300 RPM, a 700 RPM differential. However, in a coasting condition, at freeway speeds, the synchronizer might be forced to attempt decelerating the high range gear from about 3000 RPM down to 900 RPM, a 2100 RPM differential. As will be discussed below, the range shift control of the present invention is effective to minimize or eliminate damage under such occurrences and to allow rapid and dependable completion of permissible range shifts. 
   The position of the shift lever  31  or of the shifting mechanism  32  controlled thereby may be sensed by a position sensor device. Various positioning sensing assemblies are known in the prior art, with a preferred type illustrated in allowed U.S. Pat. No. 5,743,143, assigned to the assignee of this application, the disclosure of which is incorporated herein by reference. 
   Referring to  FIGS. 4A and 4B , shifting mechanism  32  is illustrated as a single shift shaft device  160  having a shaft  162  which is rotatable in response to X-X movements of shift lever  31  and axially movable in response to Y-Y movements of shift lever  31 . Mechanisms of this type are described in detail in aforementioned U.S. Pat. No. 4,920,815. 
   Shift shaft  162  carries the main section shift forks  90  and  92  for selective axial movement therewith and a shift block member  164  for receiving a shift finger or the like. A pair of coils  166  and  168  provides a pair of signals (collectively GR) indicative of the axial and rotational position of shaft  162  and, thus, of shift lever  31  relative to the shift pattern illustrated in FIG.  2 . The rate of change of position (dGR/dt) also may be determined and utilized to enhance shifting of the system  10 . 
   By way of example, referring to  FIG. 2 , if shift lever position can be sensed, the need for a fixed switch or the like at point AR to sense a required initiation of a shift between low range and high range is eliminated. Further, as physical switches are no longer required, the shift pattern position at which a range shift will be commanded can be varied, such as to points  180 ,  182  or  184 , to enhance system performance under various operating conditions. It should be appreciated that, for the purposes of the presentation, a position indicator switch or switches may be employed in place of position sensor devices. 
   If in first (1st) through fourth (4th), a shift into high range is considered unlikely, and the auto range shift initiation point may be moved to position  184  (away from the expected shift lever path) to prevent inadvertent actuation of a range shift. If in sixth (6th) with a high engine speed, a shift into high range is likely. Accordingly, moving the auto range initiation point to position  180  when in sixth gear will allow for a quicker initiation of a range shift. 
   The state of engagement (i.e., engaged or neutral) of the main transmission section  16 A is an important control parameter for system  10 . By way of example, if main section neutral is incorrectly sensed, the range clutch may be commanded to an inappropriate up-shift, potentially damaging the range synchronizer. It is therefore important to prevent or minimize false determinations of main section neutral and/or engaged conditions. 
   Referring to  FIG. 2 , a first narrow band  202  and a second wider band  204  of vertical displacements from the neutral gate portion  200  are utilized to determine if the main section is or is not in neutral. If the transmission main section is not confirmed as being in main section neutral, the neutral confirmation band will be the narrower band  202 . This will assure that the main section  16 A is truly in neutral before declaring a main section neutral condition. If the transmission main section  16 A is confirmed as being in neutral, the neutral confirmation band will be the wider band  204 . This assures that mere overshooting of neutral or raking of main section jaw clutches will not be incorrectly interpreted as a main section engaged condition. 
   Sensing the shift lever at point  206  will always be interpreted as main section neutral, and sensing the shift lever at point  208  will always be interpreted as main section engaged. However, if the shift lever is sensed at point  210 , this will not cause a previous determination of a neutral or engaged condition to change. Alternate means of sensing neutral, such as position switches, may be employed for the purposes of the present invention. However, it should be appreciated that position sensors beneficially are capable of providing information which enable more precise control of shifting. 
   Vehicle operating conditions other than or in addition to currently engaged or neutral condition of the main section  16 A may be used to vary the width of the neutral sensing bands. 
   According to one aspect of the invention, as shown in  FIG. 5 , a protocol for range shift control in the controller-assisted manually shifted vehicular transmission system  10  is described. The protocol begins at step  600 . Vehicle operating conditions are sensed, such as engine speed (“ES”), input shaft speed (“IS”), output shaft speed (“OS”), range selector and shift lever position in step  610 . Then, a determination is made in step  620  as to whether a range up-shift has been selected, typically by either an evaluation of the position of shift lever  31 , or alternatively an evaluation of the state of a range shift switch. If an up-shift has been selected, then the system reverts to or maintains the standard shift protocols already installed within the transmission system  10  in step  670 , the up-shift is completed in step  660 , and the protocol exits at step  680 . If in step  620  a range up-shift has not been selected, then the protocol proceeds to step  630  and a determination is made whether the shift lever is in a low range neutral position. If the shift lever is not in low range neutral position, then the protocol returns to step  610 , updates the sensed parameters, and recycles through the inquires and commands of the protocol. 
   If in step  630  the shift lever is in low range neutral position, thereby indicating that the vehicle is in a coasting condition, then the protocol proceeds to step  640  and a determination is made whether the vehicle speed is high enough to warrant a range up-shift. If for example, the road speed of the vehicle is greater than a predetermined value, then a command is issued to automatically up-shift the range synchronizer from the low range to high range. A coasting condition is defined as a condition in which the engine and the vehicle are drivingly disconnected, as when the transmission is in neutral, and yet the vehicle is moving. The predetermined value is defined as the road speed of the vehicle at which the range synchronizer  130  would be rotating at least at the rotational speed corresponding to the maximum engine speed (determined by manufacturer&#39;s specifications) for a given main section gear ratio plus approximately five hundred (500) RPM. The main section gear ratio chosen is for 3rd gear if the splitter low gear is chosen, and for 4th gear if the splitter high gear is chosen. If the predetermined value is determined to be exceeded, then the protocol proceeds to step  650  and the range synchronizer automatically up-shifts from low range to high range, the up-shift is completed in step  660  and the protocol exits in step  680 . Alternatively, step  640  of the protocol can be satisfied using a calculated engine speed, rather than road speed of the vehicle as the target. Specifically, step  640  is satisfied if the calculated synchronous engine speed corresponding to the measured output shaft speed is greater than or equal to the maximum engine speed plus approximately five hundred (500) RPM for the existing gear ratio. The calculated synchronous engine speed is determined based on the output shaft speed (“OS”) and the 3 rd  gear ratio for splitter low, and the 4 th  gear ratio for the splitter high. It is appreciated that using a factor other than vehicle speed which varies with vehicle speed, such as output shaft speed, or calculated engine speed, or countershaft speed, or the like are equivalent to vehicle speed for the purpose of establishing when to execute a range up-shift. 
   On the other hand, if the vehicle speed is less than the predetermined value in step  640 , for example, if the vehicle speed is too low, i.e., the vehicle speed is less than a predetermined value during a coasting condition, an automatic range up-shift to complete the up-shift is not permissible and the protocol returns to step  610  and continues on through the protocol. It should be appreciated that the system is able to loop through the above described protocol at a relatively high frequency, at a rate of about once every 10 milliseconds. 
   Accordingly, it may be seen that a new and improved range shift control for a computer-assisted, lever-shifted transmission system is provided, which provides protection against undue wear and/or damage to the range synchronized clutch assembly. 
   While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.