Patent Publication Number: US-2023132968-A1

Title: Isolator Adapter Insert For Retention In A Modular Saddle Mount Or An Isolator Mounting Plate For Reducing Vibration In Heavy Equipment Cabs

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to heavy equipment and more specifically to an isolator adapter insert for retention in a modular saddle mount or an isolator mounting plate for reducing vibration in heavy equipment cabs, which allows different size vibration isolators to be used in a single modular saddle mount or isolator mounting plate. 
     2. Discussion of the Prior Art 
     The prior art discloses a number of mounting methods for reducing vibration to heavy equipment cabs. U.S. Pat. No. 7,364,223 to Mori et al discloses a cab supporting structure. U.S. Pat. No. 8,517,457 to Yamamoto et al. discloses a construction machine provided with cab. However, it appears that the prior art does not teach or suggest using a detachable saddle mount, which is selectively detachable from a modified frame cross member. The detachable saddle mount is also used for retaining at least one vibration isolator. It also appears that adding mass to a frame cross member to increase the mass thereof and reduce the natural frequency of the frame is also not disclosed in the prior art. 
     Accordingly, there is clearly felt need in the art for an isolator adapter insert for retention in a modular saddle mount or an isolator mounting plate for reducing vibration in heavy equipment cabs, which allows different size vibration isolators to be used in a single modular saddle mount or isolator mounting plate. 
     SUMMARY OF THE INVENTION 
     The present invention provides a modular saddle mount retained in a frame cross member for reducing vibration in heavy equipment cabs, which includes adding mass to a retention frame for reducing the natural frequency of the base frame of the heavy equipment to mitigate the occurrence of resonance. The heavy equipment base frame for in part retaining a cab preferably includes a modified frame cross member, a second frame cross member, a lengthwise frame rail, a corner frame and a cab mounting plate. The modified frame cross member extends inward from the lengthwise frame rail. The second frame cross member extends inward from the lengthwise frame rail. The corner frame extends inward from an end of the lengthwise frame rail and is secured to the second frame cross member. The isolator mounting plate is secured to the lengthwise frame rail and the corner frame. An isolator opening is formed in each end of the isolator mounting plate. 
     The modular saddle mount and modified frame cross member for reducing vibration in heavy equipment cabs (modular saddle mount system) preferably includes the modified frame cross member, a modular saddle mount and at least one vibration isolator. The modified frame cross member preferably includes a frame cross member, two sets of opposed mounting blocks and two cutout filler inserts. The modified cross member preferably includes a first cutout and a second cutout. The first and second cutouts are created to receive two modular saddle mounts. The first and second cutouts allow an overall height of the heavy equipment to be adjusted. Each opposed mounting block is secured to an outside surface of a side of the frame cross member with any suitable attachment method, such as welding. Each mounting block preferably includes at least one tapped hole. The first and second cutout inserts are attached to perimeters of the first and second cutouts. The two cutout filler plates restore rigidity to the frame cross member. 
     The modular saddle mount preferably includes a saddle base member and a pair of fastening inserts. The saddle base member preferably includes a top saddle member, a first side member and a second side member. The saddle base member is preferably fabricated from a single piece of material. The saddle base member and the pair of fastening inserts have a preferable thickness of about 12 mm. However, other thicknesses may also be used to boost vibrational performance of the modular saddle mount. The first and second side members are created by bending over the first and second sides of the top saddle member, respectively. A fastening cutout is formed in each end of the saddle base member to provide clearance for the pair of fastening inserts. Each fastening insert preferably includes a securement flange and an upright flange. The pair of fastening inserts are retained on an inside surface of the saddle base member at opposing ends thereof. At least one isolator opening is formed through the top saddle member to receive a vibration isolator. A plurality of threaded taps are formed through the top saddle member and around a perimeter of the isolator opening, if the vibration isolator includes an attachment flange. Vibration isolators with flanges are referred to as flange mounted isolators. 
     An isolator adapter insert may be secured to a top of the top saddle member, under the vibration isolator. Top and bottom roll over protection plates may be placed above and below the attachment flange of a vibration isolator. At least one roll over protection (ROPS) secondary retention hole may be formed through the top saddle member to receive a ROPS secondary retention bolt. A location of the ROPS secondary retention hole is located to the side of a single vibration isolator or between two vibration isolators. A non-flanged or a through-bolt type vibration isolator also may be used with the modular saddle mount. A modular saddle mount may be created to accommodate a flange mounted vibration isolator or a through-bolt vibration isolator. Use of two flange mounted, through-bolt, or a combination of the flange and through-bolt vibration isolators may be used to increase effective frequency range or shift effective frequency range. 
     Secondary retention devices prevent a heavy equipment cab from separating from a frame during a roll-over event. The second retention device includes a bolt inserted through a cab floor of a heavy equipment cab and a modular saddle mount. A nut is threaded on to the bolt to retain the heavy equipment cab and the modular saddle mount together. A first alternative of a secondary retention device includes a yoke extending upward from a modular saddle mount, an extension plate extending downward from a bottom of a cab floor and a lock pin. The lock pin is inserted through the yoke and extension plate and retained in place with a lock clip. A second alternative of a secondary retention device includes a bent over edge of a cab floor, a bent-up edge of a modular saddle mount and a lock pin. The lock pin is inserted through the bent edge of the cab floor and the bent-up edge of the modular saddle mount. The lock pin is held in place with a lock clip. 
     A third alternative of a secondary retention device includes a retention plate extending downward from a cab floor, a slot opening formed through a top of a modular saddle mount to receive the retention plate and a fastener inserted through the retention plate and a side wall of the modular saddle mount. A nut is threaded on to the bolt to retain the bolt in place. A fourth alternative of a secondary retention device includes a curved tab extending upward from a modular saddle mount and a slot opening formed through a cab floor to receive the curved tab. The curved tab is inserted through the slot opening. An isolator bolt is secured to a vibration isolator in the modular saddle mount. 
     Accordingly, it is an object of the present invention to provide a modular saddle mount system, which reduces the natural frequency of the base frame of the heavy equipment. 
     It is a further object of the present invention to provide a modular saddle mount system, which uses a saddle mount which is selectively detachable from a modified frame cross member. 
     It is yet a further object of the present invention to provide a modular saddle mount of a modular saddle mount system, which is capable of retaining at least one vibration isolator. 
     It is yet a further object of the present invention to provide an isolator adapter insert for retention in a modular saddle mount or an isolator mounting plate for reducing vibration in heavy equipment cabs, which allows different size vibration isolators to be used a single modular saddle mount or isolator mounting plate. 
     Finally, it is another object of the present invention to provide secondary retention devices for retaining a heavy equipment cab on a frame, which prevents a heavy equipment cab from being separated from a frame during a roll over event. 
     These and additional objects, advantages, features and benefits of the present invention will become apparent from the following specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a portion of a heavy equipment base frame and a cab, which illustrate the installation of the modular saddle mount system in accordance with the present invention. 
         FIG.  2    is a perspective view of a modular saddle mount system with a modified frame cross member and a single isolator retained in two modular saddle mounts in accordance with the present invention. 
         FIG.  3    is an exploded perspective view of a modified frame cross member of a modular saddle mount system in accordance with the present invention. 
         FIG.  4    is a perspective view of a modified frame cross member of a modular saddle mount system in accordance with the present invention. 
         FIG.  4   a    is a perspective view of a modified frame cross member with opposed mounting blocks attached to the modified frame cross member with fasteners of a modular saddle mount system in accordance with the present invention. 
         FIG.  4   b    is a perspective view of an alternative embodiment of a modified frame cross member with a strengthening plate attached to a bottom thereof to increase rigidity in accordance with the present invention. 
         FIG.  4   c    is a perspective view of a second alternative embodiment of a modified frame cross member, which does not include a first cutout and a second cutout in accordance with the present invention. 
         FIG.  5    is an exploded perspective view of a modular saddle mount with a single isolator opening of a modular saddle mount system in accordance with the present invention. 
         FIG.  6    is a perspective view of a modular saddle mount with a single isolator opening of a modular saddle mount system in accordance with the present invention. 
         FIG.  6   a    is an exploded perspective view of a modular saddle mount with a support block and a bolt hole formed through the support block of a modular saddle mount system in accordance with the present invention. 
         FIG.  7    is an exploded perspective view of a modular saddle mount and a single vibration isolator with an attachment flange before attachment to the modular saddle mount of a modular saddle mount system in accordance with the present invention. 
         FIG.  8    is an exploded perspective view of a modular saddle mount with an isolator adapter insert and a single vibration isolator with an attachment flange before attachment to the modular saddle mount of a modular saddle mount system in accordance with the present invention. 
         FIG.  8   a    is a bottom perspective view of an isolator adapter insert of a modular saddle mount system in accordance with the present invention. 
         FIG.  9    is an exploded perspective view of a modular saddle mount with an isolator adapter insert and a single vibration isolator with an attachment flange retained between top and bottom roll over protection plates before attachment to the modular saddle mount of a modular saddle mount system in accordance with the present invention. 
         FIG.  10    is a perspective view of a modular saddle mount with a single vibration isolator with an attachment flange and a roll over protection secondary retention bolt retained in the modular saddle mount in accordance with the present invention. 
         FIG.  10   a    is a perspective view of two modular saddle mounts with standoffs or spacers extending from a bottom thereof and tops of opposed mounting blocks located below a bottom of the first and second cutouts of a modified frame cross member in accordance with the present invention. 
         FIG.  11    is an exploded perspective view of a modular saddle mount and two vibration isolators with attachment flanges before attachment to the modular saddle mount of a modular saddle mount system in accordance with the present invention. 
         FIG.  12    is a partially exploded perspective view of a modular saddle mount with two isolator adapter inserts and two vibration isolators with attachment flanges before attachment to the modular saddle mount of a modular saddle mount system and a roll over protection secondary retention bolt retained in the modular saddle mount in accordance with the present invention. 
         FIG.  13    is an exploded perspective view of a modular saddle mount and a single through-bolt vibration isolator before attachment to the modular saddle mount of a modular saddle mount system in accordance with the present invention. 
         FIG.  14    is an exploded perspective view of a modular saddle mount and two through-bolt vibration isolators before attachment to the modular saddle mount of a modular saddle mount system in accordance with the present invention. 
         FIG.  15    is an exploded perspective view of a modular saddle mount, a vibration isolator with an attachment flange and a second vibration isolator, before attachment to the modular saddle mount of a modular saddle mount system in accordance with the present invention. 
         FIG.  16    is an exploded perspective view of a portion of a heavy equipment frame, which illustrates flanged isolators before installation into an isolator adapter plate of a modular saddle mount system in accordance with the present invention. 
         FIG.  17    is an exploded perspective view of a portion of a heavy equipment frame, which illustrates non-flanged through-bolt isolators before installation into a cab mounting plate of the modular saddle mount system in accordance with the present invention. 
         FIG.  18    is a cross sectional view of a secondary retention device as a bolt inserted through a cab floor and a modular saddle mount and retained with a nut threaded on to the bolt in accordance with the present invention. 
         FIG.  19    is a perspective view of a secondary retention device as a bolt inserted through a cab floor and a modular saddle mount and retained with a nut threaded on to the bolt in accordance with the present invention. 
         FIG.  20    is a cross sectional view of a first alternative of a secondary retention device utilizing a yoke extending upward from a modular saddle mount, an extension plate extending downward from a bottom of a cab floor and a lock pin inserted through the yoke and extension plate in accordance with the present invention. 
         FIG.  21    is a perspective view of a first alternative of a secondary retention device utilizing a yoke extending upward from a modular saddle mount, an extension plate extending downward from a bottom of a cab floor and a lock pin inserted through the yoke and extension plate in accordance with the present invention. 
         FIG.  22    is a cross sectional view of a second alternative of a secondary retention device utilizing a bent over edge of a cab floor, a bent-up edge of a modular saddle mount and a lock pin inserted through the bent over cab floor and the bent-up modular saddle mount in accordance with the present invention. 
         FIG.  23    is a perspective view of a second alternative of a secondary retention device utilizing a bent over edge of a cab floor, a bent-up edge of a modular saddle mount and a lock pin inserted through the bent over cab floor and the bent-up edge of the modular saddle mount in accordance with the present invention. 
         FIG.  24    is a cross sectional view of a third alternative of a secondary retention device utilizing a retention plate extending downward from a cab floor, a slot opening formed through a modular saddle mount to receive the retention plate and a fastener inserted through the retention plate and a side wall of the modular saddle mount in accordance with the present invention. 
         FIG.  25    is a perspective view of a third alternative of a secondary retention device utilizing a retention plate extending downward from an edge of cab floor, a slot opening formed through a modular saddle mount to receive the retention plate and a fastener inserted through the retention plate and a side wall of the modular saddle mount in accordance with the present invention. 
         FIG.  26    is a cross sectional view of a fourth alternative of a secondary retention device utilizing a curved tab extending upward from a modular saddle mount and a slot opening formed through a cab floor to receive the curved tab in accordance with the present invention. 
         FIG.  27    is a perspective view of a fourth alternative of a secondary retention device utilizing a curved tab extending upward from a modular saddle mount and a slot opening formed through a cab floor to receive the curved tab in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference now to the drawings, and particularly to  FIG.  1   , there is shown a perspective view of a portion of a heavy equipment base frame  100  for retaining a cab  102 . The heavy equipment frame base  100  preferably includes a modified frame cross member  10 , a second frame cross member  104 , a lengthwise frame rail  106 , a corner frame  108  and a cab mounting plate  110 . The modified frame cross member  10  extends inward from the lengthwise frame rail  106 . The second frame cross member  104  extends inward from the lengthwise frame rail  106 . The corner frame  108  extends inward from an end of the lengthwise frame rail  106  and is secured to the second frame cross member  104  with welding or any other suitable attachment process. The cab mounting plate  110  is secured to the lengthwise frame rail  106  and the corner frame  108 . An isolator opening  112  is formed in each end of the cab mounting plate  110 . 
     With reference to  FIGS.  2 - 4   , the modular saddle mount and modified frame cross member for reducing vibration in heavy equipment cabs (modular saddle mount system)  1  preferably includes the modified frame cross member  10 , two modular saddle mounts  12  and at least two vibration isolator  14 ,  16 . The modified frame cross member  10  preferably includes a frame cross member  18 , two sets of opposed mounting blocks  20  and two cutout filler plates  32 . The frame cross member  18  preferably includes a first cutout  24  and a second cutout  26 . The first and second cutouts  24 ,  26  are created to receive the two modular saddle mounts  12 . The first and second cutouts  24 ,  26  allow an overall height of the heavy equipment to be modified. The frame cross member  18  includes a base member  25  and two side walls  28  that extend downward from opposing sides of the base member  25 . Each opposed mounting block  20  is secured to an outside surface of the side walls  28  of the frame cross member  18  with any suitable attachment method, such as welding. With reference to  FIG.  4     a,  the opposed mounting blocks  20  are attached to frame cross member  18  with fasteners  27 . With reference to  FIG.  4     b,  the frame cross member  18  includes a strengthening plate  21  attached to a bottom of the frame cross member  18  to increase rigidity of the frame cross member  18 . With reference to  FIG.  4     c,  a modified frame cross member  10 ′ does not include the first cutout  24  and the second cutout  26 . 
     Each mounting block  20  preferably includes at least one tapped hole  30 . A top of each mounting block  20  is preferably located above a bottom of the first and second cutouts  24 ,  26 . However, a top of each mounting block  20  could be located at a bottom of the first and second cutouts  24 ,  26  or below the bottom of the first and second cutouts  24 . With reference to  FIG.  10     a,  locating the top of each mounting block  20  below the bottom of the first and second cutouts  24 ,  26 , would require spacers or standoffs  25  extending from a bottom of the modular saddle mounts  12 . The modular saddle mount  12  is preferably a sacrificial component. The first and second cutouts  24 ,  26  are preferably filled with the two cutout filler plates  32 . The two cutout filler plates restore rigidity to the frame cross member  18 . 
     With reference to  FIGS.  5 - 6   , the modular saddle mount  12  preferably includes a saddle base member  34  and a pair of fastening inserts  36 . However, the saddle base member  34  and the pair of fastening inserts  36  could made from a single piece of material. The saddle base member  34  preferably includes a top saddle member  38 , a first side member  40  and a second side member  42 . The saddle base member  34  is preferably fabricated from a single piece of material. The saddle base member  34  and the pair of fastening inserts  36  have a preferable thickness of about 12 mm. However, other thicknesses may be used to boost vibrational performance of the modular saddle mount  34 . The first and second side members  40 ,  42  are created by bending over the first and second sides of the top saddle member  38 , respectively. A fastening cutout  44  is formed in each end of the saddle base member  34  to provide clearance for the pair of fastening inserts  36 . Each fastening insert  36  preferably includes a securement flange  46  and an upright flange  48 . The pair of fastening inserts  36  are retained on an inside surface of the saddle base member  34  at opposing ends thereof. At least one saddle fastening hole  50  is formed through each fastening insert  36  to allow attachment of the modular saddle mount  12  to the pair of mounting blocks  20  with at least two fasteners (not shown). 
     With reference to  FIG.  6     a,  a modular saddle member  12 ′ preferably includes a support block  57  and at least one bolt hole  55  formed through the modular saddle member  12 ′ for receiving a cable bolt  58  or the like. An isolator opening  52  and a plurality of threaded taps  54  are replaced with the at least one bolt hole  55  and the support block  57 . The modular saddle mount  12  is preferred to experience non-linear deformation instead of the modified frame cross member  10 . It is easier to unbolt a deformed modified frame cross member instead of repairing a damaged modified frame cross member  10 . The modular saddle mount  12  is preferably a sacrificial component. 
     With reference to  FIGS.  7  and  11   , at least one isolator opening  52  is formed through the top saddle member  38  to receive a vibration isolator  14 . A plurality of threaded taps  54  are formed through the top saddle member  38  and around a perimeter of the isolator opening  52 , if the vibration isolator  14  includes an attachment flange  15 . Vibration isolators  14  with flanges  15  are referred to as flange mounted isolators. A plurality of threaded fasteners  56  are inserted through a plurality of fastening holes  17  in the attachment flange and threaded into the plurality of threaded taps  54 . A cab fastener  58  with a washer  60  are used to secure the cab  102  to the vibration isolator  14 . 
     With reference to  FIGS.  8 - 8     a,  an isolator adapter insert  62  may be secured to the top of the top saddle member  38 , under the vibration isolator  14 . A location boss  65  preferably extends from a bottom of the isolator adapter insert  62 . The location boss  65  is sized to be received by an isolator opening [not shown]. An isolator opening  64  and a plurality of threaded taps  66  are also formed through the isolator adapter insert  62 . The isolator adapter insert  62  is designed in a way that it allows either flange mounted or through-bolt vibrational isolators to be utilized in a saddle or on an equipment frame with no necessary modifications. Isolator adapter inserts  62  with the same location boss size  65 , but with different size isolator openings  64  would allow the isolator adapter insert  62  to be replaced without having the need for multiple modular saddle mounts  12  with different size insert openings  52 . With reference to  FIG.  9   , a top roll over protection plate  68  is placed on top of the flange  15  of the vibration isolation  14  and a bottom roll over protection plate  70  is placed under the flange  15 . The top and bottom roll over protection plates  68 ,  70  include isolator openings  72  and fastener clearance holes  74 . 
     With reference to  FIG.  10   , at least one roll over protection (ROPS) secondary retention hole may be formed through the top saddle member  38  to receive a retention bolt  76 . The ROPS secondary retention hole is located to the side of a single vibration isolator  14 . With reference to  FIG.  12   , at least one roll over protection (ROPS) hole may be formed through the top saddle member  38  to receive the retention bolt  76 . A location of the ROPS hole  78  is located between first and second vibration isolators  14 . With reference to  FIGS.  13 - 14   , a through-bolt vibration isolator  16  may also be used with the modular saddle mount  12 . The plurality of fasteners  56  are eliminated, because a cab retention bolt  80  is used to retain the vibration isolator  16  in the top saddle member  38 . With reference to  FIG.  15   , a modular saddle mount  12  may be created to accommodate a flange mounted vibration isolator  14  and a through-bolt type vibration isolator  16 . Two isolator holes  52  are formed through the top saddle member  38 . The plurality of plurality of threaded taps  54  are formed around the isolator hole  52  for the vibration isolator  14 . Use of two flange mounted, through-bolt, or a combination of flange mounted and through-bolt vibration isolators may be used to increase effective frequency range or shift effective frequency range. 
     With reference to  FIG.  16   , a plurality of threaded taps  114  are formed around each insert opening  112 . A vibration isolator  14  is inserted into each insert opening  112  and secured to the isolator mounting plate  110  through the isolator adapter insert  62  with a plurality of threaded fasteners  56 . One end of the cab  102  is secured to the two vibration isolators  14  with two cab fasteners  58 . With reference to  FIG.  17   , a vibration isolator  16  is inserted into each insert opening  112  and through the isolator adapter insert  62 . The two vibration isolators  16  and the cab  102  are secured to the isolator mounting plate  110  with two cab retention bolts  80 . Isolator adapter inserts  62  with the same location boss size  65 , but with different size isolator openings  64  would allow the isolator adapter insert  62  to be replaced without having the need for multiple isolator mounting plates  110  with different size isolator openings  112 . However, four modular saddle mounts  12  could be used to support each corner of the cab  102 . 
     Secondary retention devices prevent a heavy equipment cab from separating from a frame during a roll-over event. With reference to  FIGS.  18 - 19   , a secondary retention device Preferably includes the retention bolt  76  inserted through a bolt hole  82  in a cab floor  116  and a bolt hole  19  in the top saddle member  38  of the modular saddle mount  12 . The vibration isolator  14  is retained in the modular saddle mount  12 . The cab floor  116  is secured to the vibration isolator with the bolt  58 . A retention nut  84  is threaded on to the retention bolt  76  to prevent the cab floor  116  from separating from the modular saddle mount  12  during a roll-over event. 
     With reference to  FIGS.  20 - 21   , a first alternative of a secondary retention device includes a yoke  86  extending upward from the top saddle member  38  of the modular saddle mount  12 , an extension plate  88  extending downward from a bottom of the cab floor  116  and a lock pin  90 . The vibration isolator  14  is retained in the modular saddle mount  12 . The cab floor  116  is secured to the vibration isolator with the bolt  58 . The lock pin  90  is inserted through the yoke  86  and the extension plate  88  and the lock pin  90  retained in place with a lock clip  92 . However, the lock pin  90  and the lock clip  92  could be replaced with a threaded fastener and a nut or any other suitable retention device. 
     With reference to  FIGS.  22 - 23   , a second alternative of a secondary retention device includes a bent over edge  118  of the cab floor  16 , a bent-up edge  39  of the top saddle member  38  of the modular saddle mount  12  and a lock pin  94 . The vibration isolator  14  is retained in the modular saddle mount  12 . The cab floor  116  is secured to the vibration isolator with the bolt  58 . The lock pin  94  is inserted through the bent over cab floor  118  and the bent-up edge  39  of the top saddle member  38  of the modular saddle mount  12 . An end of the bent-up  39  includes a vertical orientation. An end of the bent over edge  118  includes a vertical orientation. The lock pin  94  is held in place with a lock clip  96 . However, the lock pin  94  and the lock clip  96  could be replaced with a threaded fastener and a nut or any other suitable retention device. 
     With reference to  FIGS.  24 - 25   , a third alternative of a secondary retention device includes a retention plate  120  extending downward from an edge of the cab floor  116 , a slot opening  98  formed through the top saddle member  38  of the modular saddle mount  12  to receive the retention plate  120  and a fastener  130  inserted through the retention plate  120  and a side of the top saddle member  38  of the modular saddle mount  12 . The vibration isolator  14  is retained in the modular saddle mount  12 . The cab floor  116  is secured to the vibration isolator with the bolt  58 . A nut (not shown) is preferably threaded on to the fastener  130  to retain the fastener  130  in place. However, the fastener  130  and the nut may be replaced with a lock pin and a lock clip or any other suitable retention device. 
     With reference to  FIGS.  26 - 27   , a fourth alternative of a secondary retention device includes a curved tab  132  extending upward from the top saddle member  38  of the modular saddle mount  12  and a slot opening  122  formed through the cab floor  116  to receive the curved tab  132 . The vibration isolator  14  is retained in the modular saddle mount  12 . An end of the curved tab  132  has a horizontal orientation. The curved tab  132  is inserted through the slot opening  122  and the isolator bolt  58  secured to the vibration isolator  14  in the modular saddle mount  12 . 
     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, and 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.