Patent Publication Number: US-8534732-B2

Title: Combination cot loading and fastening system for loading and unloading a cot

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 11/630,549 filed Nov. 13, 2009 which is a U.S. National Phase Entry of PCT US 05/023064 filed Jun. 30, 2005 which claims priority to U.S. Provisional 60/584,012 filed Jun. 30, 2004. 
    
    
     The present invention relates to the safe loading and secure transportation in an emergency rescue vehicle of a patient transport device, e.g., an ambulance cot, a stretcher, a cart, an incubator transporter, and other similar patient transport devices. More particularly, the present invention relates to a combination cot loading and fastening system, and an emergency rescue vehicle having the combination cot loading and fastening system of the present invention, wherein easy and safe loading and unloading of the patient transport device into the emergency rescue vehicle having a transport deck in excess of 78 centimeters (about 31 inches) is provided. 
     Emergency rescue personnel (e.g., paramedics) are required to do considerable kneeling, bending, and heavy lifting, and therefore have an increased risk to back injuries. For example, two emergency rescue personnel are required to take up the full weight of a conventional, fully-manual, wheeled patient transport device, such as an ambulance cot, during loading and unloading into an emergency rescue vehicle (e.g., an ambulance), which is an extreme manual lifting operation. Often, the combined weight of such an ambulance cot and the patient exceeds 136 kilograms (about 300 lbs). 
     The above problem is exacerbated by the fact that in an effort to utilize more cost effective procedures and parts, emergency rescue vehicle manufactures are basing new emergency rescue vehicle (i.e., ambulance) designs on commercially available truck chassis. However, such conventional truck chassis provide a loading bay/transport deck height in excess of 86 centimeters (about 34 inches), approximately 10 centimeters (about 4 inches) increase above the conventional loading height of about 76 centimeters (about 30 inches). In addition to such a loading bay/transport deck height increasing the risk of injury to both patient and emergency rescue personnel, such a loading bay transport height stretches the limit of ambulance cot designs which permit easy and safe loading into the emergency rescue vehicle. For example, emergency rescue personnel (usually two people) may experience increased ergonomic problems lifting an ambulance cot to such an increased loading height. A redesigned ambulance cot will need to provide a higher patient transport surface, approximately 10 centimeters (about 4 inches) in order for the loading wheels of the ambulance cot to reach the higher loading bay of the conventional truck chassis based vehicles. This increase in the ambulance cot&#39;s height in order to have a higher loading range, however, will have a smaller size range of emergency rescue personnel that can safely lift and load the ambulance cot into the emergency rescue vehicle. Emergency rescue personnel outside this reduced range may be disadvantaged in that they face greater risks of musculoskeletal injury from having to lift to a higher height. This may be further exacerbated where emergency rescue personnel pairs are of very different heights. 
     Consequently, while there have been available cot fastener systems utilized in the industry, there has heretofore not been available a combination cot loading and fastening system, and an emergency rescue vehicle having the combination cot loading and fastening system of the present invention, where a range of “average” persons can easily and safely load and unload a conventional ambulance cot into an emergency rescue vehicle having a transport deck in excess of 78 centimeters (about 31 inches), and where redesign of the ambulance cot to be able to reach up and load onto such an exceedingly high transport deck is unnecessary. 
     The above mentioned problems are met by the present invention, wherein provided are a combination cot loading and fastening system, and an emergency rescue vehicle incorporating the combination cot loading and fastening system which permit a range of “average” persons to easily and safely load and unload an ambulance cot having a normal loading height of about 76 centimeters (about 30 inches) into an emergency rescue vehicle having a transport deck in excess of 78 centimeters (about 31 inches). Additionally, the present invention prevents unnecessary cot movement during transport. 
     In accordance with the present invention, provided is a combination cot loading and fastening system for loading and unloading an ambulance cot having a normal loading height of about 76 centimeters (about 30 inches) into an emergency rescue vehicle having a transport deck in excess of 78 centimeters (about 31 inches), the vehicle having an opening providing access to the transport deck. The system comprises a pair of tracks mountable to the transport deck of the emergency vehicle and having a first and second ends, and a longitudinal length extending from the first end to second end, the second end being located adjacent but inward of the opening of the vehicle, the tracks having opposing channels. A shuttle assembly engaged for movement in the opposing channels of the pair of tracks and configured to securely pull the ambulance cot along the pair of tracks is provided. The shuttle assembly comprises a frame having a first end, a second end, and a longitudinal body extending from the first end to the second end. The system also provides a locking mechanism mounted on the shuttle assembly and configured to releasably hold the ambulance cot, wherein the shuttle assembly is configured to position the locking mechanism a distance away from the second end of the pair of tracks and at an angle below the transport deck of the emergency rescue vehicle, the angle ranging from about 10° to 25°, and the distance ranging about 22.8 centimeters (about 9 inches) to about 50 centimeters (about 20 inches). 
    
    
     
       A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings. 
         FIG. 1  is an isometric view, partially broken away, of an emergency rescue vehicle provided with one embodiment of a combination cot loading and fastening system according to the present invention; 
         FIG. 2  is a top perspective view of a shuttle assembly according to the present invention; 
         FIG. 3  is a side perspective view of the shuttle assembly of  FIG. 2  situated to receive a frame member of an ambulance cot; 
         FIG. 4  is a side perspective view of the ambulance cot of  FIG. 3  held by the locking mechanism of the shuttle assembly of the combination loading and fastening system according to the present invention; 
         FIG. 5  is a perspective view of the loading end of the ambulance cot identified in  FIG. 3 , and being held by the locking mechanism of the shuttle assembly while being loading onto the transport deck of the emergency rescue vehicle according to the present invention; 
         FIG. 6  is an isometric view, partially broken away, of the combination cot loading and fastening system holding an ambulance cot secure in its locking mechanism and with the ambulance cot partially loaded in the emergency rescue vehicle; 
         FIG. 7  is a perspective view of the trailing end of the ambulance cot identified in  FIG. 3 , and showing the ambulance cot fully loaded and held in place by a pair of crash rated restrains according to the present invention; 
         FIG. 8  is an isometric view of the emergency rescue vehicle provided with one embodiment of the combination cot loading and fastening system having an extendable ramp according to the present invention; 
         FIG. 9  is a perspective view of another embodiment of a combination cot loading and fastening system having a carriage frame assembly according to the present invention and with the present invention installed in a vehicle shown partially sectioned; 
         FIG. 10  is a side view of the carriage frame assembly of  FIG. 9  securing an ambulance cot with a three point connection in accordance with the present invention; 
         FIG. 11  is a side view of the carriage frame assembly of  FIG. 10  securing the ambulance cot with the three point connection in accordance with the present invention, and with the undercarriage frame of the ambulance cot raised; 
         FIG. 12  is a side elevational view of the combination cot loading and fastening system of  FIG. 11 ; and 
         FIG. 13  is a side view of the combination cot loading and fastening system of  FIG. 12  with the ambulance cot fully loaded in the vehicle according to the present invention. 
     
    
    
     The present invention is described in detail herein with reference to the illustrative embodiments of  FIGS. 1-13 , where like reference numerals are indicative of like structural elements. 
     With reference to  FIG. 1 , there is shown an ambulance cot  20  situated on a transport deck  22  of an emergency rescue vehicle  24 , and loaded and secured thereon with the assistance of a combination cot loading and fastening system  26  according to a first embodiment of the present invention. It is to be appreciated that the transport deck  22  of the vehicle  26  has a vertical height A ranging from about 78 centimeters (about 31 inches) to about 92 centimeters (about 36 inches) above the ground  25 . Additionally, an upper portion or step of a bumper  27  of the vehicle  24  has a vertical height B ranging from about 50 centimeters (about 20 inches) to about 60 centimeters (about 24 inches) above the ground  27 . As a typical bumper  27  has a width BW greater than 22.8 centimeters (about 9 inches) and the vehicle  24  a door frame width DFW of about 5 centimeters (about 2 inches), the combination cot loading and fastening device  26  is capable of reaching downwardly at least 10 centimeters (about 6 inches) and outwardly at least 22.8 centimeters (about 9 inches) in order to latch onto the ambulance cot  20 . 
     A surface mounted outer track  28  of the system  26  extends from a first end  30  of the emergency rescue vehicle  24  to a second end  31  of the emergency rescue vehicle  24  which is adjacent a door opening  32 . It is to be appreciated that the second end  31  of the track  28  is located at least the width DFW, such that a door(s) of the vehicle can seal door opening  32 . As is shown best in  FIG. 7 , outer track  28  has two inwardly facing slotted guide tracks  34  and  36 , one being the minor image of the other, extending in parallel and perpendicular to the transport deck  22 . The second end  31  of outer track  28  has downwardly sloping curvilinear slotted guide track portions  38  and  40  as best shown in  FIG. 3 . 
     It is to be appreciated that the outer track  28  is provided with the same bolt pattern as conventional fastening devices, such as disclosed by U.S. Pat. No. 5,913,559, commonly assigned to Ferno-Washington, Inc., and which the disclosure is fully incorporated by reference herein, to make it convenient to retrofit emergency rescue vehicles with the system of the present invention. 
     With reference to  FIGS. 2 and 3 , the combination cot loading and fastening system  26  includes a shuttle assembly  42  which engages the outer track  28  for movement along the slotted guide tracks  34  and  36  from one end to the other, and for securely guiding an attached ambulance cot along the outer track  28 . The shuttle assembly  42  comprises a second frame  44  defining a shuttle first end  46 , a shuttle second end  48 , and a longitudinal body  50  extending from the shuttle first end  46  to the shuttle second end  48 . As shown in  FIG. 3 , rollers  51 ,  53  are rotatably mounted to the exterior side of the longitudinal body  50  and are accommodated within guide tracks  34 ,  36 . The rollers  51 ,  53  may be adjustable along the length of the longitudinal body  50 . The longitudinal body  50  of the second frame defines upper and lower surfaces of an inner track  52 . A crash rated locking mechanism  54  engages the inner track  52  for movement along the inner track and for releasably holding the ambulance cot  20  ( FIG. 1 ). 
     The shuttle assembly  42  is adapted to have a portion of the inner track  52  and locking mechanism  54  there along extend a distance away from the outer track  28 , reaching beyond and below the transport deck  22  upon which the outer track  28  is mounted. The shuttle assembly  42  also includes first and second safety catches  56  and  58 . The first safety catch  56  releasably locks the rollable locking mechanism  54  adjacent the first end  46 , and the second safety catch  58  releasably locks the locking mechanism  54  a relative distance therefrom. It is to be appreciated that the second safety catch  58  is adjustable along the length of the second frame  44  such that the locking mechanism  54  may reach down and hold cots having various full extension heights. Additionally, it is to be appreciated that the locking mechanism  54  is also height adjustable up or down. 
     In one embodiment, the second frame  44  extends down from a horizontal plane defined by the transport deck  22  due to the curvilinear portions  38 ,  40  of the outer track  28 , in a range from about 10° to 25°, and in one specific embodiment, in a range from about 16° to about 20°. In one embodiment, the shuttle second end  48  of the second frame  44  extends beyond the second end  31  of the outer track  28  in a range of about 22.8 centimeters (about 9 inches) to about 50 centimeters (about 20 inches). With the locking mechanism  54  provided at the end of the second frame  44 , such extension and downward deflection ranges permit the combination cot loading and fastening system  26  to safely and securely load the ambulance cot  20  onto the transport deck  22  having a deck height in the range about 78 centimeters (about 31 inches) to about 92 centimeters (about 36 inches) above the ground  25 . Accordingly, it is to be appreciated that cot loading wheels or an ambulance cot with an upwardly angled loading end is no longer a requirement for loading into such emergency rescue vehicle with extremely high transport decks. 
     To load the ambulance cot  20 , the shuttle assembly  42  is extended and the locking mechanism  54  is positioned adjacent the second end  48  of the second frame  44 , secured in place by the second safety catch  58  as best seen in  FIG. 3 . The ambulance cot  20  is then rolled towards the system  20 , and a handle of the locking mechanism  54  is pulled back in order to place jaws  60  of the locking mechanism  54  between shoulders  62  provided at the loading end  57  of the ambulance cot  20 . Next, while the trailing end  59  ( FIG. 7 ) of the ambulance cot  20  is supported by and operated by at least one operator, the undercarriage frame  61  of the ambulance cot  20  is raised (indicated by arrow  63 ), placing the ambulance cot  20  into lowered position, as is illustrated by  FIG. 4 . 
     With reference also made to  FIGS. 5 and 6 , once the undercarriage frame  61  of the ambulance cot  20  has been securely raised, a release handle  64  for the second safety catch  58  is then pulled (indicated by arrow  59  in  FIG. 5 ), such that locking mechanism  54  guides the ambulance cot  20  along the inner track  52 , until locked in place adjacent the shuttle first end  46  via the first safety catch  56 . It is to be appreciated that this initial movement of the locking mechanism  54  provides the mechanical advantage need to easily lift and guide the ambulance cot  20  on to the transport deck  22  using only one emergency rescue personnel to push the trailing end  59  of the ambulance cot  20  into the vehicle  24 . The shuttle assembly  42  thereafter rolls forwards along the outer track  28  (as indicated by arrow  63  in  FIG. 6 ) until the ambulance cot  20  is fully loaded as illustrated by  FIGS. 1 and 7 . Once the ambulance cot  20  is loaded, it is to be appreciated that crash rated restrains or securing devices  66  and  68  secure the trailing end  59  of the ambulance cot  20 , and lock the ambulance cot  20  in the place on the transport  22  as illustrated by  FIG. 7 . The steps are reversed for unloading. 
     If desired, in another embodiment illustrated by  FIG. 8 , an extendable ramp  70  is provided to help guide the ambulance cot  20  into and out of the emergency rescue vehicle  24 . In still other embodiments, the shuttle assembly  52  may be transitioned under power from a suitable drive unit  71 . Control and powering of the drive unit  71  may be provided in a conventional manner, using a controller  73 , such as discussed hereafter in a later section. 
     In still other embodiments, the combination cot loading and fastening system  26  is configured to lift an attached ambulance cot under power. Such an embodiment, as well as being suitable for non-powered ambulance cots, is particularly suitable for use with ambulance cots having an undercarriage frame that also lifts under power. Such ambulance cots are disclosed, for example, by commonly assigned U.S. patent application Ser. No. 10/982483, entitled “PNEUMATICALLY POWERED LIFT AMBULANCE COT,” and commonly assigned PCT Application Serial No. US05/19547, entitled “ELECTRO-HYDRAULICALLY POWERED LIFT AMBULANCE COT,” the disclosures of which are herein fully incorporated by reference. As will be explained, this embodiment takes advantage of ambulance cot designs that are also provided with side extension arms or pulls, such as disclosed by commonly assigned U.S. Pat. No. 6,701,545, entitled “IMPROVED MULTILEVEL ROLLIN COT,” the disclosure of which is herein fully incorporated by reference. 
     With reference made first to  FIG. 9 , in this alternative embodiment of the combination cot loading and fastening system  26 , the guide tracks  34  and  36  of the track  28  are mounted a greater distance apart in order to slidably accommodate an alternative shuttle assembly  72  which attaches at the front and sides of an ambulance cot as explained hereafter, instead on just at the front of the ambulance cot  20  as with the previously discussed shuttle assembly  42  in reference to  FIGS. 1-8 . Rollers  74 ,  76 , in addition to rollers  51  and  53 , are rotatably mounted to the exterior side of a respective one of a pair of longitudinal frame members  78 ,  79  of a carriage frame  80  and are accommodated within guide tracks  34  and  36 . The rolls  51 ,  53 ,  74 ,  76  are also sized and shaped so that there is only a small gap between the surface of the rollers and the interior of the tracks  34  and  36 . Of course, other track  24  cross-sections may be effective in securing the wheels  36  and the present invention is not limited to the shape as shown in  FIGS. 9-13 . 
     The shuttle assembly  72  in this alternative embodiment includes the carriage frame  80 , two pairs of stabilizer bars  82 ,  84 , and  86 ,  88 , a pair of lifting cylinders  90 ,  92 , and a three point attachment yoke assembly  94 . The carriage frame  80  slides along the length of the tracks  34 ,  36  on the rollers  51 ,  53 ,  74 , and  76 . It is to be appreciated that the carriage frame  80  itself may be formed from a wide variety of members made from a variety of materials, but in the illustrated embodiment, the carriage frame  80  is formed by the pair of longitudinal members  78 ,  79  joined by traverse frame members  96 ,  98 . Adjacent a front end of each longitudinal member  78 ,  79  is an upright support  100 ,  102 , respectively, which each pivotably mount a respective ones of the pairs of stabilizer bars  82 ,  84 , and  86 ,  88 , respectively. 
     The lifting cylinders  90 ,  92  are fluid-operated linear actuators such as hydraulic cylinders or pneumatic cylinders, or electrically operated linear actuators. A first end of each lifting cylinders  90 ,  92  is pivotably mounted, between the respective pair of stabilizer bars  82 ,  84 , and  86 ,  88 , to a respective one of the upright supports  100 ,  102 . The other end of each lifting cylinders  90 ,  92  is pivotably connected to the respective lower stabilizer bar  86 ,  88 . A second end of each stabilizer bars  82 ,  84 ,  86 , and  88  is pivotably mounted to the yoke assembly  94 . It is to be appreciated that the upright supports  100 ,  102  and their associated stabilizer bars  82 ,  84 , and  86 ,  88  pivotably connect the yoke assembly  94  to the carriage frame  80  and define pivot points  104   a - d.    
     As illustrated that the upright supports  100 ,  102  and carrier  80  remain inside the loading bay of the vehicle, and do not extend outwardly therefrom. Accordingly, the associated stabilizer bars  82 ,  84 , and  86 ,  88  are dimensioned to position the pivot points  104   a - d  sufficiently distant from the floor  22  of the vehicle  24  such that the yoke assembly  94  can adequately raise the attached ambulance cot  20  ( FIG. 10 ) over the bumper  27  or other structure on the vehicle  24 . In one embodiment, the stabilizer bars  82 ,  84 , and  86 ,  88  are sized to position the pivot points  104   a - d  about the same extension and downward deflection ranges mentioned above in the previous embodiment having the shuttle assembly  42  ( FIG. 2 ). 
     The yoke assembly  94  may be formed from metal segments arranged in a variety of manners. Of course, other materials having sufficient strength and rigidity may also be used. The yoke assembly  94  includes two substantially parallel arms  106 ,  108  separated and mounted to a head frame  110 . The head  110  is formed from an upper frame member  112  and a lower frame member  114 . Many other arrangements of segments may be used to form the yoke assembly  94  including the use of a single unitary assembly (not shown). 
     The yoke assembly  94  acts as a first class lever to raise the ambulance cot  20 . As mentioned above the yoke assembly  94  provides a three point attachment to releaseably secure the ambulance cot  20  thereto. The first point of attachment of the yoke assembly  94  that engages the ambulance cot  20  is a crash rated locking mechanism  116  provided on the lower frame member  114 . A skid plate  118  is provided to guide the loading end of the ambulance cot  20  into engagement with the ambulance cot locking mechanism  116 . When the loading end  57  of the ambulance cot  20  is contacted with the cot lock mechanism  116 , a latching mechanism  120  automatically springs forward to firmly hold the loading end frame member  128  in the ambulance cot lock. A manual release (not shown) is provided to unlock the ambulance cot lock and simultaneously reset the latching mechanism  120  for operation. 
     The second and third attachment points are holds  122 ,  124  on the ends of each arm  106 ,  108 , respectively which engage the side extension arms or pulls  126  on the ambulance cot  20 , which is best illustrated by  FIG. 10 . As shown by  FIG. 10 , which is the same on the other side, the holds  122 ,  124  are formed in the ends of the arms  106 ,  108  or the yoke assembly  94  and are dimensioned to receive and support the pulls  126  on the ambulance cot  20 . 
     As mentioned previously above, the pivotable engagement between the carriage frame  80  and the yoke assembly  94  defines the pivot points  104   a - d , and the place where the lifting cylinders  90 ,  92  connects to the end of the lower stabilization bars  86 ,  88  is the effort point. As illustrated, the location of the ambulance cot locking mechanism  116  is towards the surface  22  of the vehicle ahead a distance from the pivot points  104   a - d . Such a positioning takes advantage of the fact that the loading end  57  of the ambulance cot  20  is high enough to clear any obstruction on the vehicle, such as the bumper  27 . In this manner, although the pulls  126  on the ambulance cot  20  are located forward of an approximate center of gravity of the ambulance cot  20 , the counter balancing of the moments at the ambulance cot locking mechanism  116  and the holds  122  allow easy rotation of the yoke assembly  94  about the pivot points  104   a - d,  thereby raising the ambulance cot  28 . This allows for optimal positioning of the ambulance cot  20  for loading into the vehicle  24  for transporting. It is to be appreciated that other locations of the effort point and pivots points are possible, such as connecting the ends of the lifting cylinders  90 ,  92  directly to the yoke assembly  94 . 
     A controller  132  ( FIGS. 10-11 ) is used to control the extension of the lifting cylinders  90 ,  92 . The lifting cylinders  90 ,  92  are capable of providing sufficient force to the yoke assembly  94  to raise the ambulance cot  20 . The exact capabilities required of the lifting cylinders  90 ,  92  depend on the dimensions of the yoke assembly  50  and the weight of the ambulance cot  20  being lifted. However, it has been found that the lifting cylinders  90 ,  92  should have a 25.4 centimeter (about 10.0 inch) actuator stroke and a 544 kilograms (about 1200 lb) lift rating. In one embodiment, the lifting cylinders  90 ,  92  are electrically operated and are supplied with electricity from the battery of the vehicle  24 . 
     Referring now to  FIGS. 10-13 , in use the door of the vehicle  24  is opened to allow the carriage frame  80  to slide in the tracks  36  toward the open door to extend the yoke assembly  94  out through the open door. The carriage frame  80  may be locked into place by a locking device  134  to prevent the carriage frame from sliding while the ambulance cot  24  is lifted. Similar locking pins may also be provided at other locations along the tracks  36 . The yoke assembly  94  is lowered by extending the lifting cylinders  90 ,  92  which causes the yoke assembly  94  to pivot about the pivot points  104   a - d  and to be lowered. Then, the ambulance cot is guiding into locking engagement with the ambulance cot locking mechanism  116  which also seats the pulls  126  of the ambulance cot  20  in the holds  122 , thereby securing the ambulance cot  20  to the yoke assembly  94  with three points of connection. 
     It is to be appreciated that the three points of connection provided by the yoke assembly  94  to the ambulance cot  20  eliminates any concern of tilting the ambulance cot on a side due to a side imbalance. Additionally, the undercarriage frame  136  of the ambulance cot  20  may be raised (arrow  138 ) as illustrated in  FIG. 11  also without concern of the ambulance cot tipping or unseating from the yoke assembly  94  due to the front and side connections which securely balance the ambulance cot  20  in the yoke assembly  94 . 
     After the undercarriage frame  136  of the ambulance cot  20  has been raised, the yoke assembly  94  is then raised by retracting the lifting cylinders  90 ,  92  which causes the yoke assembly  94  to pivot about the pivot points  104 , lifting the ambulance cot  20  further above the ground such that the wheels  140  of the ambulance cot  20  are above the surface  22  of the vehicle  24 , as illustrated by  FIG. 12 . Once the ambulance cot  20  is fully raised from the ground, the locking device  134  is released and the ambulance cot  20  is transitioned into the vehicle  22  (indicated by the arrow  140 ) such that the carriage frame  80  slides along the tracks  34 ,  36 . 
     In one embodiment, the horizontal transitioning of the ambulance cot  20  into the fully loaded position illustrated by  13  may be manual, and in another embodiment the horizontal transitioning may by powered by a suitable drive unit  142  configured to move the carriage frame  80  about the tracks  34 ,  36 . In such embodiment, the drive unit  142  is controlled by controller  132  and draws the necessary power from the vehicle  24 . Such a drive unit embodiment, is also suitable for all other embodiments previously discussed herein. When the carriage frame  80  has been fully pushed into the vehicle  22  as illustrated by  FIG. 13 , the yoke assembly  94  may again be lowered (indicated by arrow  144 ) such that the ambulance cot  20  rests on the floor  22  of the vehicle  24  for transport. Securing devices  66 ,  68  are again used to secure the trailing end  59  of the cot  20  as previously discussed above in reference to  FIG. 7 . The steps are reversed for unloading. 
     As will be understood by those familiar with the art, the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. For example, the invention is not limited to the type and dimensions of the emergency rescue vehicle specifically disclosed. Accordingly, the disclosures and descriptions herein are intended to be illustrative, but not limiting and, therefore, the invention is to be taken as including all reasonable equivalents to the subject matter of the appended claims.