Abstract:
An electronic game includes a housing supporting a pair of handles and a pivotable turn table. A model bulldozer is supported upon the turntable while each handle supports a moveable squeeze activated control lever. A liquid crystal display is positioned upon the housing and includes a miniature bulldozer image element together with a scrolling background image set. A microprocessor control circuit within the game unit responds to the actuation of the control levers to scroll the image display appropriately. A mechanical linkage mechanism coupled to the turntable is operated by the control levers to appropriately pivot the turntable and model bulldozer thereon to further simulate steering of the bulldozer.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to stand-alone or handheld games and particularly to those utilizing a display screen. 
     BACKGROUND OF THE INVENTION 
     Game apparatus which provide a stand-alone or handheld capability are well known in the art. Such games are known for their capability of performing without additional apparatus such as a computer or television display. In such games, a housing supports a plurality of controls which provide user inputs to the game. In addition, a display screen often formed of a liquid crystal display (LCD) provides a series of images or a moving or scrolling image. Such games have been provided in a virtually endless variety with many games replicating activities such as racing, skiing, motor boating and other vehicle or movement type games. The advent of low-cost powerful microprocessors has facilitated the inclusion of sufficient software within the game. to provide a display movement and image capability which approaches that of video games in its game play potential. 
     Not surprisingly, the extended popularity of handheld game type apparatus has prompted practitioner&#39;s in the art to provide a virtually endless variety of such games having display capabilities. For example, U.S. Pat. No. 5,106,102 issued to Mitsumoto sets forth a PROJECTED IMAGE DRIVE GAME DEVICE having a housing supporting a dashboard-like environment including a steering wheel, a gear shift and a plurality of different controls typical of a motor vehicle. The housing further supports side view mirrors and a display. In front of the display a small model vehicle is pivotally mounted. A transparent running sheet is moveably mounted above a screen supported in proximity to the model. A light source is mounted above the transparent running screen for projecting an image on the screen corresponding to a portion of a pattern such as a road or the like. An electric motor is operative to move the transparent screen in response to the amount of steering wheel manipulation. 
     U.S. Pat. No. 4,602,790 issued to Furukawa sets forth a TOY ARCADE TARGET GAME having a housing with a hollow drum mounted therein. A transparent indicia strip is mounted upon the drum. A spring is located in front of the drum and a light is positioned within the interior of the drum such that the light illuminates the indicia strip of the image of the strip upon the screen. The light is connected to a handle which is controlled by the operator whereby the image of the indicia is moved across the screen depending upon operator movement of the handle. 
     U.S. Pat. No. 4,536,164 issued to Klawitter sets forth a TOY COMPUTER BUSY BOX ASSEMBLY having a housing resembling a computer. A plurality of hand manipulated actuating members within the normal keyboard location of a computer are connected to image producing members through systems of gears and levers. A screen section produces an image having the moveable screen members displayed thereon. 
     U.S. Pat. No. 5,213,327 issued to Kitue set forth a GAME APPARATUS for use with a hand holdable video game device of the type having a video display screen. One or more control buttons and at least one multi-position operating game control for playing the game are provided. The game apparatus also includes a magnifying lens overlying the display screen. 
     U.S. Pat. No. 3,993,309 issued to Morris et al. sets forth a GAME APPARATUS UTILIZING A DISPLAY SCREEN for simulating the game of table tennis. The display screen is arranged such that a game may be simulated thereon in which two players appear to hit a ball back and forth on the screen. The game includes a serve button for initiating a serve at the beginning of the game. The players continue to volley the simulated ball back and forth by timely actuation of two volleying buttons until a miss is detected. 
     U.S. Pat. No. 5,794,936 issued to Kakizaki sets forth a GAME APPARATUS having a housing upon which a play surface supports a scrolling endless belt upon which a roadway or pathway is depicted. The housing further supports a model toy vehicle which is operatively coupled to a steering wheel control. As the endless belt moves the pathway beneath the vehicle, the user moves the toy vehicle laterally attempting to follow the pathway by skillful manipulation of the steering wheel. 
     U.S. Pat. Des. No. 355,446 issued to Sahler and U.S. Pat. Des. No. 399,886 issued to Brase et al. set forth designs for handheld games supporting an image screen. 
     In related arts, a number of control devices for use in electronic games have also been provided. For example, U.S. Pat. Des No. 316,879 issued to Shulman et al. sets forth a design for a joystick to be used in electronic games. 
     U.S. Pat. No. 5,919,092 issued to Yokoi et al. sets forth a MANIPULATOR FOR GAME MACHINE having a housing supporting left and right handles each having grips formed thereon. Direction instructing switches are provided for instructing movement direction of characters. The switches are disposed in the thumb position areas of the hand grips. 
     U.S. Pat. No. 4,976,429 issued to Nagel set forth a HAND-HELD VIDEO GAME IMAGE-PROJECTING AND CONTROL APPARATUS for operatively receiving an interactive electronic video game module. A housing formed of a central body and a pair of side mounted, outwardly extending arms are grasped by a user. Illuminating elements within the housing project images from a substantially transparent screen of the video game module on to a remote viewing and display surface. 
     U.S. Pat. No. 4,856,777 issued to Hirose et al. sets forth a SIMULATOR TOY having a projection light source and plate supporting projectable images thereon. When the plate is rotated, the image simulates a moving street. A projectable car is moveable under the rotation plate by moving a knob. The player uses the turning knob to manipulate the car around the projected objects. 
     U.S. Pat. No. 4,659,313 issued to Kuster et al. sets forth a CONTROL YOKE APPARATUS FOR COMPUTERIZED AIRCRAFT SIMULATION having a housing supporting an aircraft type steering wheel control which is operatively coupled to a video display unit. 
     U.S. Pat. Des. No. 261,787 issued to Breneman and U.S. Pat. No. 3,849,931 issued to Gulley, Jr. each set forth toy vehicles having caterpillar-like treads similar to a tractor or bulldozer. 
     While the foregoing described prior art devices have to some extent improved the art, and in some instances enjoyed commercial success, there remains nonetheless a continuing need in the art for evermore improved, interesting and entertaining stand-alone or handheld electronic game apparatus. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a general object of the present invention to provide an improved electronic game apparatus. It is a more particular object of the present invention to provide an improved electronic game apparatus suitable for playing a bulldozer game. It is a still more particular object of the present invention to provide an improved electronic bulldozer game apparatus having a moveable toy bulldozer model and scrolling travel image both of which are manipulated by the user in a driving style activity. 
     In accordance with the present invention there is provided an electronic game comprising: a housing having a pair of handles and a pivotable turntable and a model toy vehicle supported thereon; a pair of control levers supported by the handles, each control lever having a handle rod extending into the housing; a display supported by the housing having means for displaying a plurality of moveable images thereon including a toy vehicle image; a pair of switches activated by the pair of control levers; a control circuit coupled to the display and the pair of switches operative to scroll images on the display rearwardly relative to the model toy vehicle image when both of the control levers are simultaneously squeezed and to scroll images on the display to one side relative to the model toy vehicle image; and pivot means, coupled to the turntable and to the handle rods, for pivoting the turntable toward the left or right in response to squeezing of one or the other of the control levers while not pivoting the turntable when both of the control levers are squeezed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify like elements and in which: 
     FIG. 1 sets forth a top perspective view of an electronic bulldozer game constructed in accordance with the present invention; 
     FIG. 2 sets forth a partially section bottom view of the present invention electronic bulldozer game; 
     FIG. 3 sets forth a partial section view of the steering apparatus of the present invention electronic bulldozer game executing a left turn movement; 
     FIG. 4 sets forth a partial section view of the steering apparatus of FIG. 3 executing a right turn; 
     FIG. 5 sets forth a section view of the present invention electronic bulldozer game taken along section lines  5 — 5  in FIG. 1; 
     FIG. 6 sets forth a partial section view of the present invention electronic bulldozer game taken along section lines  6 — 6  in FIG. 2; and 
     FIG. 7 sets forth a block diagram of the microprocessor based control circuit utilized in the present invention electronic bulldozer game. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 sets forth a top perspective view of an electronic bulldozer game constructed in accordance with the present invention and generally referenced by numeral  10 . Game  10  includes a housing  11  preferably formed of a molded plastic material or the like. Housing  11  supports an upward and forwardly display housing  12  which defines an aperture  13 . A liquid crystal display  14  is supported within display housing  12  against aperture  13  so as to be viewable therethrough. Display housing  12  further supports a flashing light  35 . 
     Housing  11  further defines a generally horizontal play surface  30  which in turn supports a pivotable turntable  31 . A miniature replica or model of a bulldozer  32  is secured to turntable  31 . Housing  11  further supports a horizontally extending post  50  which in turn supports a control handle  51 . Control handle  51  further supports a moveable control lever  53  and a reverse button  52 . Housing  11  further includes a horizontally extending post  60  generally aligned with post  50  which supports a control handle  61  having a moveable control lever  63  supported therein. Control handles  51  and  61  are sized and configured to form hand grips of the type characteristic of the control apparatus of a conventional bulldozer. Similarly, control levers  53  and  63  are configured for response to the user holding control handles  51  and  61  for simultaneous grasp of control levers  53  and  63 . For purposes of illustration, control lever  53  is shown in its fully extended position while control lever  63  is shown in its inwardly pivoted having been squeezed by a user gripping handle  61  so as to move control lever  63  inwardly in the direction indicated by arrow  62 . 
     Housing  11  further supports a plurality of user operated buttons  40 ,  41  and  42 . In the preferred fabrication of the present invention electronic bulldozer game button  40  provides selection of sound mode while button  41  provides selection of a desired game play. Button  42  provides a pause button which temporarily stops game play. Housing  11  further supports an engine on/off and engine start button  43 . Button  43  is rotatable in the manner indicated by arrows  44 . 
     Display  14  is preferably fabricated of a liquid crystal (LCD) apparatus and shows a number of image objects thereon. In accordance with the preferred fabrication of the present invention, display  14  displays an image  15  which corresponds to the appearance of model bulldozer  32 . In addition, display  14  shows a plurality of image objects utilized in game play such as a landscape object  16 , a tree  18  and a roadway  17 . 
     In operation, the user initially performs and engine start by rotating engine on/off and engine start button  43  to trigger the generation of engine sound within game  10 . In accordance with the preferred fabrication of the present invention a vibrating mechanism (seen in FIG. 6) is operated in combination with the generation of engine noise to vibrate turntable  31  and model bulldozer  32 . This vibration is intended to provide a tactile feel and image to accompany the engine sound. 
     At the initiation of game play, bulldozer image  15  is shown in display  14  together with a plurality of image objects. The user manipulates bulldozer image  15  by gripping control handles  51  and  61  with each hand and thereafter initiating movement or turning or reverse direction travel by appropriate manipulation of control levers  53  and  63  as well as reverse button  52 . The intended play pattern of game  10  is directed toward simulating the operation of a bulldozer. Accordingly, as the user squeezes control lever  63  alone in the direction indicated by arrow  62 , a move in which a typical bulldozer would execute a left turn, apparatus within housing  11  set forth below in FIGS. 3 and 4 causes turntable  31  to be pivoted to the left in the direction indicated by arrow  23 . Additionally, image object  15  corresponding to bulldozer  32  also undergoes an left turn movement upon display screen  14  in the manner indicated by arrow  20 . In this combination of events, the user simultaneously sees the movement of bulldozer  32  and the response of bulldozer image object  15  executing the left turn. It will be apparent to those skilled in the art that should the user release control lever  63  and instead grip control lever  53  a right turn operation is executed in which turntable  31  and bulldozer  32  are pivoted in the direction indicated by arrow  24  while bulldozer image  15  is similarly pivoted in the direction indicated by arrow  28 . In the absence of inward movement of either of control levers  53  or  63 , bulldozer  32  and bulldozer image  15  face forwardly in a straight line relationship. In addition, when neither of control levers  53  or  63  are squeezed into control handles  51  or  61 , no forward movement is depicted upon display  14 . 
     When the user desires to drive bulldozer  32  forwardly, the user grips both control levers  53  and  63  simultaneously. This simultaneous squeezing of control levers  53  and  63  causes bulldozer  32  to remain pointed straight ahead while bulldozer image  15  upon display  14  is depicted as moving by scrolling the remaining objects within display  14  in the appropriate direction. 
     FIG. 2 sets forth a partially sectioned bottom view of electronic game  10 . As described above, electronic game  10  includes a housing  11  supporting a display housing  12  which in turn supports a display  14  (seen in FIG. 1) together with a speaker  45 . Display housing  12  further supports a printed circuit board  100  having a digital electronic control circuit supported thereon. The digital electronic control circuit of game  10  is set forth below in FIG. 6 in greater detail. However, suffice it to note here that circuit board  100  supports a microprocessor  101  having an associated memory  103 . Additional circuit components such as component  102  are further supported upon circuit board  100 . Housing  11  further supports a battery power source comprised of a plurality of batteries such as batteries  46  and  47 . 
     Housing  11  further defines a pair of apertures  54  and  64  on opposite sides of housing  11  in substantial alignment. 
     Housing  11  further defines a pair of apertures  54  and  64  on opposite sides of housing  11  in substantial alignment. Housing  54  receives post  50  having a flange  55  at one end and supporting a handle  51  at the outer end. Flange  55  is engaged by a clamp  56  which secures post  50  in a fixed attachment within aperture  54 . A handle rod  57  extends inwardly from post  50  and, as is better seen in FIG. 5, is operatively coupled to control lever  53  (seen in FIG.  1 ). 
     Aperture  64  receives a post  60  having an internal flange  65  secured by a clamp  66 . The outer end of post  60  supports a handle  61 . As is better seen in FIG. 1, handle  6 i further supports a control lever  63 . A handle rod  67  extends inwardly through post  60  into interior cavity  19  of housing  11 . Handle rods  57  and  67  are moveable forwardly in the directions indicated by arrows  92  and  93  when control levers  53  and  63  (seen in FIG. 1) are respectively squeezed. 
     A vibrator unit  70  includes a housing  71  secured within interior cavity  19  of housing  11 . Vibrator  70  includes a motor  73  supported within housing  71  having an output pulley  74 . Vibrator unit  70  further includes a pulley  76  and a plate  77  rotatably supported by housing  71 . Plate  77  includes a tab  78  extending therefrom. A flexible belt  75  is received upon pulleys  74  and  76 . Housing  71  further defines a tab  72 . 
     A slider  80  having a generally triangular shape and supporting a cross bar  81  and a center plate  84  is received within interior cavity  19 , Cross bar  81  defines end portions  82  and  83  positioned against handle rods  67  and  57  respectively. Center plate  84  of slider  80  defines a slot  85  which receives a post  86  therein. Slider  80  further supports a post  87  which receives one end of a coil spring  88 . The remaining end of spring  88  is secured to tab  72  of vibrator unit housing  71 . Center plate  84  is secured rigidly to cross bar  81  such that the force of spring  88  draws the entire structure of slider  80  such that ends  82  and  83  of cross bar  81  are forced against handle rods  67  and  57  respectively. Housing  11  further supports the above described plurality of controls including engine on/off and engine start switch  43 . A circuit board  95  is supported upon housing  11  and provides coupling to a plurality of connecting wires  58 . Connecting wires  58  make appropriate connections to batteries  46  and  47  as well as speaker  45  and circuit board  100 . 
     As is better seen in FIG. 6, turntable  31  is coupled to a wheel  90  which in turn supports a peg  91 . The function of wheel  90  and peg  91  in cooperation with slider  80  is set forth below in FIGS. 3 and 4. However, suffice it to note here that center plate  84  defines a slot  110  (seen in FIG. 3) which receives peg  91  to provide an eccentric coupling between center plate  84  and wheel  90  and ultimately turntable  31 . 
     In operation, each time the user squeezes either or both of control levers  53  and  63  (seen in FIG.  1 ), handle rods  57  and  67  are moved forwardly in the direction indicated by arrows  92  and  93 . The movement of handle rods  57  and  67  forwardly displaces end portions  83  and  82  of cross bar  81 . This forward movement is accommodated by slots  85  and  110  (seen in FIG. 3) and is resisted by spring  88 . The cooperation of slider  80  and control levers  53  and  63  (seen in FIG. 1) together with wheel  90  and peg  91  provides pivotal movement of wheel  90  when either control lever is squeezed without the other. However, in the event both control levers are squeezed simultaneously, the result is a straight line forward movement of slider  80  without imparting any pivotal force to wheel  90 . The operation of slider  80  in combination of wheel  90  and control levers  53  and  63  (seen in FIG. 1) is set forth below in FIGS. 3 and 4 in greater detail. Suffice it to note here that wheel  90  is moved to the left or to the right in response to movement of control levers  53  or  63  (seen in FIG.  1 ). 
     FIGS. 3 and 4 set forth simplified partial section views of the cooperation of handles  51  and  61  together with slider  80  to affect pivotal movement of turntable  31 . 
     More specifically, housing  11  finds a pair of apertures  54  and  64  supporting respective posts  50  and  60 . Post  50  supports a handle  51  having a control lever  53  while post  60  supports a handle  61  having a control lever  63  supported therein. Turntable  31  (better seen in FIG. 1) is supported by a wheel  90  having a peg  91  extending therefrom. A slider  80  includes a center plate  84  and a cross bar  81 . Cross bar  81  defines ends  82  and  83  while center plate  84  defines slots  85  and  110 . A post  86  is received within slot  85  to guide the movement of slider  80  while peg  91  of wheel  90  is received within slot  110 . Center plate  84  further supports a post  84  which receives one end of a spring  88 . Control levers  53  and  63  are operatively coupled to inwardly extending handle rods  57  and  67  respectively. 
     In the position shown in FIG. 3, slider  80  is pivoted in the direction indicated by arrow  34  as the user squeezes control lever  63  of handle  61  in the direction indicated by arrow  62 . In the manner seen in FIG. 5, the squeezing of control lever  63  moves handle rod  67  forwardly in the direction indicated by arrow  93 . The force thereby exerted upon end  82  of cross bar  81  pivots slider  80  about post  86  against the force of spring  88 . The pivoting movement of slider. 80  and the coupling between slot  110 , and peg  91  causes pivotal movement of wheel  90  and thereby turntable  31  in the direction indicated by arrow  36 . When the force against control lever  63  is removed or released, the force of spring  88  returns slider  80  to the position shown in FIG.  2 . 
     FIG. 4 sets forth the position of slider  80  and turntable  31  together with wheel  90  in response to the user squeezing control lever  53 . 
     More specifically, housing  11  finds a pair of apertures  54  and  64  supporting respective posts  50  and  60 . Post  50  supports a handle  51  having a control lever  53  while post  60  supports a handle  61  having a control lever  63  supported therein. Turntable  31  (better seen in FIG. 1) is supported by a wheel  90  having a peg  91  extending therefrom. A slider  80  includes a center plate  84  and a cross bar  81 . Cross bar  81  defines ends  82  and  83  while center plate  84  defines slots  85  and  110 . A post  86  is received within slot  85  to guide the movement of slider  80  while peg  91  of wheel  90  is received within slot  110 . Center plate  84  further supports a post  84  which receives one end of a spring  88 . Control levers  53  and  63  are operatively coupled to inwardly extending handle rods  57  and  67  respectively. 
     In response to the movement of control lever  53  in the direction of arrow  59 , handle rod  57  is moved in the direction indicated by arrow  92 . This movement in turn pivots slider  80  in the direction indicated by arrow  37 . The pivotal movement of slider  80  in turn pivots wheel  90  and turntable  31  in the direction indicated by arrow  38 . Upon release of handle  53 , spring  88  restores slider  80  to the straight line relationship shown in FIG. 2 returning turntable  31  to the straight line position shown in FIG.  1 . 
     FIG. 5 sets forth a section view of control handle  51  taken along section lines  5 — 5  in FIG.  1 . It will be noted that control handle  51  supports a reverse button  52  which is not repeated on control handle  61 . It should be understood, that but for the use of reverse button  52  upon control handle  51 , the structure set forth in FIG. 5 is identical to the structure of control handle  61 . Accordingly. the structure shown in FIG. 5, (but for button  52 ) as well as the descriptions which accompany FIG. 5 will be understood to apply equally well and be equally by descriptive of control handle  61 . 
     Control handle  51  defines an aperture  23 , a pivot  120  and an aperture  127 . A control lever  53  is pivotally secured at pivot  120  and includes an upper end extending outwardly through aperture  123  and a lower end supporting a handle rod  57 . Handle rod  57  extends through  127  to contact cross bar  81  of slider  80  (seen in FIG.  4 ). Control lever  53  further includes a tab  121  having one end of a spring  124  coupled thereto. A flange  122  supports a switch  126  positioned within the travel path of tab  121  when control lever  53  is pivoted in the direction indicated by arrow  130 . Handle  51  further supports a button  52  and a switch mechanism  125  supported in communication therewith. A plurality of connecting wires  129  and  128  operatively couple switch  125  and switch  126  to the remainder of the operational circuitry (not shown) of the present invention game. 
     In operation. in the relaxed position shown spring  124  pivots control handle  53  outwardly about pivot  120 . When control lever  53  is squeezed inwardly however in the direction indicated by arrow  130 , pivot rod  57  is forced against cross bar  81  of slider  80  in the direction indicated by arrow  131 . Concurrently, the pivotal movement of control lever  53  causes tab  121  to close switch  126 . Thus, each time control lever  53  is squeezed inwardly in the direction indicated by arrow  130 , cross bar  81  is moved forwardly while simultaneously switch  126  is closed. Switch  126  provides an electrical signal condition for the control circuit shown in FIG. 7 to respond to the squeezing of control lever  53 . Similarly, pressing button  52  provides actuation of switch mechanism  125  producing an additional signal input for the circuit of FIG.  7 . 
     FIG. 6 sets forth a partial section view of the vibrating unit of the present invention electronic game taken along section lines  6 — 6  in FIG.  2 . As described above, a pulley  76  is coupled by a belt  75  to pulley  74  of vibrator unit  70  (seen in FIG.  2 ). A plate  77  is joined to and rotatable with pulley  76  and includes an outwardly extending tab  78 . Housing  11  defines an aperture  99  which receives a post  33  in a relatively loose fit. Post  33  is joined to wheel  90  beneath the surface of housing  11  while the upper end of post  33  is joined to turntable  31 . Turntable  31  supports bulldozer  32  in the manner shown in FIG.  1 . 
     In operation, when vibrator unit  70  (seen in FIG. 1) is energized, pulley  76  is rotated in the direction indicated by arrow  98 . This rotation in turn rotates plate  77  causing tab  78  to repeatedly impact one side of wheel  90 . The off-center impacts of tab  78  against wheel  90  cause the combined structure of wheel  90 , post  33 , turntable  31  and bulldozer  32  to be repeatedly vibrated in the directions indicated by arrows  48  and  49 . In the preferred fabrication of the present invention, vibrator unit  70  (seen in FIG. 2) is operated concurrently with the generation of engine sound. 
     FIG. 7 sets forth a block diagram of the operative control circuit within game  10 . In the preferred fabrication of the present invention, the control circuit utilized is a microprocessor based digital electronic circuit having a microprocessor  101  and a memory  103 . Microprocessor  101  is coupled to inputs received from switches  126  and  136  operated by control levers  53  and  63  of handles  51  and  61  respectively (seen in FIG.  1 ). Microprocessor  101  further responds to a plurality of switches  40 ,  41 ,  42  and  43  together with a reverse switch  125 . 
     Microprocessor  101  operates under a stored instruction set within memory  103  to perform the functional operation of the present invention game. Microprocessor  101  includes a plurality of outputs coupled to a vibrator unit  70 , a sound circuit  115 , and a display driver  116 . Vibrator unit  170  is described above, while sound circuit  115  may be entirely conventional in fabrication. Sound circuit  115  operates in response to signals provided by microprocessor  101  to produce audio signals suitable for driving speaker  45 . 
     Display driver  116  receives digitally encoded display signals from microprocessor  101  which are constructed in response to the various switch inputs to microprocessor  101  under the direction of stored instruction game set within memory  103 . Display driver  116  is conventional in fabrication and provides appropriate matrixed display signals for liquid crystal display  14 . 
     The electronic bulldozer game set forth herein provides a novel and amusing game which simultaneously responds to control inputs by the user via a pair of control handles and control levers to move a turntable supported model bulldozer and to move a bulldozer image element upon a display in a scrolling movement. 
     While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.