Abstract:
An improved one-way valve for use in breathing apparatus comprising a valve housing, a one-way valve disposed in the valve housing that is in sealing contact to the valve housing, and a flexible retainer ring. The flexible retainer ring allows the one-way valve to unseat a greater distance within the valve housing thereby allowing an increase in the amount of expiratory gas through an exhaust port of the valve housing and the flexible retainer ring also prevents the deformation and inversion of the one-way valve thereby maintaining the proper flow of both respiratory and expiratory gases.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates in general to valve devices and, more particularly, to a valve adapted for use in breathing apparatus such as respiration assistance apparatus or anesthesia administration equipment. 
     FIELD OF THE INVENTION 
     Non-rebreathing valves, or NRVs, are commonly used in an assortment of anesthesia administration equipment and respiration assistance apparatus including, inter alia, ventilators, resuscitators and sleep apnea treatment devices. The NRV is typically situated in the breathing apparatus gas flow circuit between a source of respiratory gas (e.g., ambient or pressurized air, pressurized oxygen and/or anesthetic gas) and a patient interface means such as a nasal or oral/nasal mask, an endotracheal (intubation) tube or nasal prongs. The function of the NRV is to act essentially as a two-way check valve. More particularly, when it is desired to deliver respiratory gas to the patient, the NRV permits such flow. When the patient exhales, however, the NRV vents the patient&#39;s expiratory gases while temporarily stopping the flow of respiratory gas responsive to back pressure created by the patient&#39;s expiratory efforts. In this manner, the NRV effectively prevents mixing of the patient&#39;s expiratory gases with the delivered respiratory gas whereby the patient does not “rebreathe” his expiratory gases. 
     Although their functions are essentially the same, NRVs assume a broad variety of structural configurations and levels of functional sophistication. Because of its relative simplicity in construction and low resistance to administered respiratory gas flow, a commercially popular NRV is the type commonly known as a “duck-bill” valve. A duck-bill valve derives its name from the peculiar shape of its valve element. That is to say, a duck-bill valve element typically comprises a thin, resilient diaphragm that is secured at its periphery to a valve housing and from which projects, in the direction of administered respiratory gas flow, a hollow, wedge-like extension that terminates in a small slot and generally resembles the shape of a duck bill. 
     The duck-bill valve element is constructed such that its slot is normally closed. However, in response to a flow of respiratory gas, which may arise from negative pressure associated with a patient&#39;s inspiration and/or delivery of respiratory gas under positive pressure, the slot opens to permit the respiratory gas to flow to the patient&#39;s airway. When the patient thereafter exhales, the back pressure exerted by the patient&#39;s expiratory gases closes the slot and displaces the valve element from the valve housing seat whereupon the expiratory gases are diverted to and discharged from suitable exhaust port means provided in the valve housing. 
     Examples of presently known duck-bill valves are provided in U.S. Pat. Nos. 3,363,833, 3,556,122, 4,774,941, 5,109,840 and 5,279,289. Ironically, the primary feature which renders duck-bill valves particularly desirable for use in breathing apparatus, namely, a thin, flexible valve element that offers minimal resistance to respiratory gas flow, is a source of potentially serious malfunctions in such valves. Specifically, should the exhalation efforts of the patient be extremely forceful, such as, for example, when the patient coughs, the sudden imposition of high-level impulses of back pressure on the valve element may cause the duck-bill portion of the valve element diaphragm to invert. Under these circumstances, the duck-bill would point in the direction of the administered respiratory gas flow and the slot thereof would be caused to close under the influence of the applied respiratory gas. As a consequence, the supply of respiratory gas to the patient would become effectively occluded whereby the patient may experience harmful or even fatal respiratory distress, particularly if the patient is unconscious or is not being closely monitored by medical personnel. 
     Perhaps recognizing, although not specifically identifying, the need to prevent inversion of the duck-bill portions of their valve elements, the valves disclosed in U.S. Pat. Nos. 3,363,833, 3,556,122 and 5,109,840 disclose valve housings which incorporate various and sometimes elaborate structures upstream of the duck-bill which permit respiratory gas to flow through the duck-bill but, by virtue of their location, would appear to prevent the duck-bill from inverting. U.S. Pat. No. 5,279,289, on the other hand, expressly provides for a retainer ring upstream of the duck-bill valve element to “support” the valve element. 
     The retainer ring disclosed in U.S. Pat. No. 5,279,289 is designed to stay in a fixed position. Whereas, the present invention provides a flexible retainer ring having a center portion that can deflect in response to the duck-bill valve being moved by the flow of the expiratory gas. This movement of the flexible retainer ring of the present invention allows the duck-bill valve to unseat further from the valve housing seat thereby increasing the flow of the expiratory gas through the exhaust port of the valve housing. This increase in flow of expiratory gas to the exhaust port of the valve housing allows the valve housing to be made smaller than a conventional valve housing while maintaining the necessary flow rate for expiratory gas through the exhaust port of the valve housing. This smaller housing can be extremely useful in the care of infants and neonatal patients. 
     In addition, the flexible retainer ring of the present invention is able to provide better protection against inversion and distortion of the duck-bill valve. Since the flexible retainer ring is able to deflect in response to movement of the duck-bill valve, the flexible retainer ring is able to act as a shock absorber. This shock absorbing capability helps to prevent inversion and deformation of the duck-bill valve. 
     The flexible retainer ring of the present invention can also be employed in any industry needing to control the flow of two fluids in opposing directions. 
     An advantage exists, therefore, for a flexible retainer ring which is simple in design, economical to manufacture, and increases the flow of expiratory gas while preventing the inversion and distortion of the duck-bill valve element. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided an improved duck-bill non-rebreathing valve (NRV) adapted for use in breathing apparatus such as anesthesia administration equipment and respiratory assistance apparatus. The duck-bill NRV may be situated in the breathing circuit between a source of respiratory gas (e.g., ambient or pressurized air, pressurized oxygen and/or anesthesia gas) and a patient interface means such as a nasal or oral/nasal mask, an endotracheal tube or nasal prongs. 
     The duck-bill NRV of the present invention comprises a thin, resilient valve element in the form of a diaphragm adapted to be secured at its periphery to a valve housing and from which projects, in the direction of administered respiratory gas flow, a hollow, wedge-shaped formation that terminates in a small slot and generally resembles the shape of a duck bill. The improvement in the NRV is the inclusion of a flexible retainer ring which has a center portion that that can deflect in response to the duck-bill valve being moved by the flow of the expiratory gas. This movement of the flexible retainer ring of the present invention allows the duck-bill valve to unseat further from the valve housing seat thereby increasing the flow of the expiratory gas through the exhaust port of the valve housing. This increase in flow of expiratory gas to the exhaust port of the valve housing allows the valve housing to be made smaller than a conventional valve housing while maintaining the necessary flow rate for expiratory gas through the exhaust port of the valve housing. This smaller housing can be extremely useful in the care of infants and neonatal patients. 
     In addition, the flexible retainer ring of the present invention is able to provide better protection against inversion and distortion of the duck-bill valve. Since the flexible retainer ring is able to deflect in response to movement of the duck-bill valve, the flexible retainer ring is able to act as a shock absorber. This shock absorbing capability helps to prevent inversion and deformation of the duck-bill valve. 
     According to a preferred embodiment, the improved non-rebreathing valve comprises a valve housing that has a first opening at one end, a second opening at an opposite end, an exhaust port in between the first opening and the second opening, and an internal valve housing seat. A one-way valve element is disposed in the valve housing between the first opening and the exhaust port. The one-way valve element is in sealing contact with the internal valve housing seat of the valve housing. A respiratory gas flows through the first opening, through the one-way valve element, continuing through the valve housing, and only out of the second opening and eventually reaching the patient. The patient expels an expiratory gas back through the second opening, into the valve housing to the one-way valve element. The one-way valve element blocks the flow of the expiratory gas and, as a result, is unseated from the internal valve housing seat. Once the one-way valve element is unseated, the expiratory gas can then flow to the exhaust port and out of the valve housing. The flexible retainer ring of the present invention allows the one-way valve element to unseat a greater distance from the internal valve housing seat thereby increasing the flow of the expiratory gas to the exhaust port of the valve housing. 
     In addition, the above preferred embodiment of the present invention provides for shock absorption through the flexible retainer ring in the event the patient expels with great force against the one-way valve element. The flexible retainer ring, constructed according to the present invention, prevents the deformation and inversion of the one-way valve element while allowing the continuous flow of the respiratory gas in an opposite direction. 
     According to an alternative embodiment, the improved one-way valve comprises a valve housing that has a first opening at one end, a second opening at an opposite end, an exhaust port in between the first opening and the second opening, and an internal valve housing seat. A one-way valve element is disposed in the valve housing between the first opening and the exhaust port. The one-way valve element is in sealing contact with the internal valve housing seat of the valve housing. A first fluid flows through the first opening, through the one-way valve element, continuing through the valve housing, and only out of the second opening. A second fluid or back flush of the first fluid returns back through the second opening into the valve housing to the one-way valve element. The one-way valve element blocks the flow of the second fluid or back flush of the first fluid and, as a result, is unseated from the internal valve housing seat. Once the one-way valve element is unseated, the second fluid or back flush of the first fluid can then flow to the exhaust port and out of the valve housing. The flexible retainer ring of the present invention allows the one-way valve element to unseat a greater distance from the internal valve housing seat thereby increasing the flow of the second fluid or back flush of the first fluid to the exhaust port of the valve housing. 
     With an NRV or one-way valve so constructed, the flexible retainer ring of the present invention allows the valve housing to be made smaller than a conventional valve housing while maintaining the necessary flow rate for the expiratory gas or second fluid through the exhaust port of the valve housing. This smaller housing can be extremely useful in the care of infants and neonatal patients or in industrial applications requiring smaller instruments. Further, the flexible retainer ring offers increased protection against inversion and effectively maintains the integrity of the one-way valve element while producing an assembly of uncomplicated yet rugged design, comparatively low cost to manufacture and reliable operation. 
     Other details, objects and advantages of the present invention will become apparent as the following description of the presently preferred embodiments and presently preferred methods of practicing the invention proceeds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become more readily apparent from the following description of preferred embodiments thereof shown, by way of example only, in the accompanying drawings wherein: 
     FIG. 1 is an exploded view of a conventional duck-bill NRV attached to a breathing assistance apparatus; 
     FIG. 1A is a blown up cross-sectional view of the duck-bill valve element within the valve housing of the NRV; 
     FIG. 2 is an exploded view of a conventional duck-bill NRV attached to a breathing assistance apparatus with a retainer ring; 
     FIG. 3 is a cross-sectional view of the prior art wherein the duck-bill portion of the NRV valve element is shown in a non-use position in conjunction with a conventional retainer ring; 
     FIG. 4A is an exploded cross-sectional view of the prior art wherein the duck-bill portion of the NRV valve element is shown in normal operation during the flow of a respiratory gas in conjunction with a conventional retainer ring; 
     FIG. 4B is an exploded cross-sectional view of the prior art wherein the duck-bill portion of the NRV valve element is shown in normal operation during the flow of an expiratory gas in conjunction with a conventional retainer ring; 
     FIG. 5A is an exploded cross-sectional view of the present invention wherein the duck-bill portion of the NRV valve element is shown in normal operation during the flow of a respiratory gas in conjunction with a retainer ring of the present invention; 
     FIG. 5B is an exploded cross-sectional view of the present invention wherein the duck-bill portion of the NRV valve element is shown in normal operation during the flow of an expiratory gas in conjunction with a retainer ring of the present invention; 
     FIG. 6A is a blown up view of the flexible retainer ring showing the flexible supports; and 
     FIG. 6B is a blown up view of the flexible retainer ring showing the flexible supports being made from springs. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, there is depicted a conventional non-rebreathing valve (NRV)  10  attached to a breathing assistance apparatus. It is noted that for purpose of illustration, but not limitation, the breathing assistance apparatus is shown as a resuscitator apparatus commonly known as a “squeeze bag” or “bag-valve-mask” type resuscitator, the general operation of which is well known to those skilled in the subject art. 
     As best shown in FIG. 1, the NRV  10  includes a valve housing  12  having a first opening  14  at one end, a second opening  16  at an opposite end, and exhaust port  18  in between the first opening  14  and the second opening  16 . The first opening  14  fits within the exit port  72  of the resuscitator bag  70 . 
     A one-way valve element  20  is disposed within the valve housing  12  for directing the flow of a fluid. Resuscitator bag  70  delivers respiratory gas (e.g., ambient or pressurized air, pressurized oxygen or a combination of such gases) to a patient&#39;s airway through the one-way valve element  20  and a suitable patient interface means  44  such as a nasal or oral/nasal mask, intubation tube or nasal prongs. It will thus be appreciated that resuscitator bag  70  may also be, inter alia, a ventilator, a sleep apnea treatment apparatus or an anesthesia administration device. 
     Typically, the one-way valve element  20  is made in the shape of a duck&#39;s bill. As best shown in FIG. 1A, there is a blown up cross-sectional view of a duck-bill valve  22  within the valve housing  12 . The duck-bill valve  22  shown comprises an outer peripheral portion  24  which is continuously and sealingly affixed to the valve housing  12  internally at a point between the first opening  14  and the exhaust port  18 . In addition, the duck-bill valve  22  has an inner portion  26  that projects towards the second opening  16  of the valve housing  12 . This inner portion  26  is hollow and wedge-shaped which generally resembles the shape of a duck&#39;s bill. At the distal end of the inner portion  26  is a small slot  36 . 
     Typically, the duck-bill valve  22  is a unitary diaphragm member formed of thin, flexible, resilient material such as silicone rubber or the like. The outermost peripheral portion  24  of the duck-bill valve  22  is normally continuously and sealingly affixed by suitable adhesives and/or clamping means to the valve housing  12 . 
     Extending radially inwardly of and contiguous with the outer peripheral portion  24  is a sealing portion  30  which may include a generally semi-toroidal region  32  for rendering the duck-bill valve  22  less resistant to the pressure generated by the patient&#39;s expiratory efforts. As is known, except when the patient is exhaling, the sealing portion  30  typically contacts an internal valve housing seat  34  and operates to effect a gas tight seal between the interior of the valve housing  12  and the exhaust port  18  provided in the valve housing  12  which communicates with the ambient atmosphere. This seal is further enhanced when the NRV  10  is delivering a respiratory gas  38  through the duck-bill valve  22  to the airway of the patient. Respiratory gas  38  is represented by arrow  38 . 
     Regardless of the specific breathing apparatus within which it is deployed, the NRV  10 , as is the NRV  10  of the present invention to be described hereinafter, is installed in the breathing circuit between a source of selected respiratory gas  38  and the patient interface means  44  such that the inner portion  26  of the duck-bill valve  22  points in the direction of the flow of the administered respiratory gas  38 . 
     Whereas, should the patient exhale an expiratory gas  40 , represented by arrow  40 , or the respiratory gas  38  flow be stopped, the small slot  36  closes. Once the small slot  36  is closed, the patient&#39;s expiratory gases  40  flow in a direction opposite to the flow of the respiratory gas  38 . 
     So long as the patient&#39;s respiration proceeds according to substantially uneventful phases of inspiration and expiration, the NRV  10  functions quite satisfactorily for its intended purposes. If, however, the patient&#39;s exhalation efforts become exceptionally forceful such as, for example, when the patient coughs, the sudden impingement of high-level impulses of back pressure on the inner portion  26  may cause the inner portion  26  to invert. Should this occur, the inner portion  26  would point in the direction of the administered respiratory gas  38  flow and the small slot  36  thereof would be urged to close under the influence of the applied respiratory gas  38 . Such a scenario represents more than a simple inconvenience in that it temporarily disables the NRV  10 . Indeed, under these conditions, the supply of respiratory gas  38  to the patient becomes effectively occluded, whereby the patient may experience harmful or possibly fatal respiratory distress, particularly if the patient is unconscious or is not being closely monitored by medical personnel. 
     To avoid potential inversion of the inner portion  26 , it has been suggested to provide means upstream of the duck-bill valve  22  to support the duck-bill valve  22  when it is subjected to extreme back pressures that may be exerted by the patient. An example of such an arrangement is shown in FIG.  2 . The NRV of that figure is identified by reference numeral  10 ′ and is constructed and functions substantially similarly to the NRV  10  discussed hereinabove. Hence, the components of NRV  10 ′ which have the same reference numerals as components identified in FIGS. 1 and 1A, but which are distinguished by prime symbols, may be considered to be the substantial equivalents in structure and function to their counterparts in FIGS. 1 and 1A and thus will not be described in detail. For brevity, therefore, only that structure in FIG. 2 which materially departs in structure and/or function from that disclosed in FIGS. 1 and 1A will be addressed here below. 
     In this regard, the primary distinction between NRV  10  and NRV  10 ′ is the provision of a retainer ring  50  which is positioned adjacent to duck-bill valve  22 . The retainer ring  50  has been previously disclosed in the prior art. It typically assumes the form of a cage-like retainer ring or a grate which resists inversion of the inner portion  26 , but which includes one or more openings to permit the passage of respiratory gas  38 . 
     It is important to note that the retainer ring  50  of the prior art only functions to prevent the duck-bill valve  22  from inverting. In the prior art, retainer ring  50  is made of a hard plastic material and is designed not to flex in response to the duck-bill valve  22 . 
     As is best shown in FIG. 3, the retainer ring  50  of the prior art is positioned between the first opening of the valve housing  12  and the duck-bill valve  22 . In FIG. 3, the duck-bill valve  22  is in the seated position, meaning that the sealing portion  30  is in sealing contact with the internal valve housing seat  34 . When the duck-bill valve  22  is in the seated position, a first fluid or respiratory gas that flows into the first opening  14  can only flow out of the second opening  16 . As is shown in FIG. 3, the center portion  52  of the retainer ring  50  of the prior art is in close proximity to the inner portion  26  of the duck-bill valve  22 . This feature of the retainer ring  50  is important because the duck-bill valve  22  could invert if the retainer ring  50  was not present when a second fluid or expiratory gas flowed into the second opening  16  and impinged on the duck-bill valve  22 . When the second fluid or expiratory gas strikes the duck-bill valve  22 , the sealing portion  30  unseats from the internal valve housing seat  34 . This unseated position allows the second fluid or expiratory gas to flow only out of the exhaust port  18 . However, it is important to note, that the retainer ring  50  of the prior art only allows the sealing portion  30  to unseat from the internal valve housing seat  34  a small distance. This small distance only allows a small amount of the second fluid or expiratory gas to be exhausted through exhaust port  18 . 
     FIG. 4A is an exploded cross-sectional view of the valve housing  12  showing the retainer ring  50  of the prior art and the duck-bill valve  22  in positions adjacent to their actual respective positions. In FIG. 4A, the first fluid or respiratory gas  38  is flowing through the retainer ring  50  and impinges upon the inside surface of the inner portion  26  of the duck-bill valve  22 . The first fluid or respiratory gas  38  forces open the small slot  36  of the duck-bill valve  22  and forces the sealing portion  30  to remain in sealing contact with the internal valve housing seat  34 . Accordingly, the first fluid or respiratory gas  38  is then forced to travel through the duck-bill valve  22  and only out of the second opening  16  of the valve housing  12 . Note, the retainer ring  50  of the prior art serves no purpose when only the first fluid or respiratory gas  38  is flowing. 
     FIG. 4B is an exploded cross-sectional view of the valve housing  12  showing the retainer ring  50  of the prior art and the duck-bill valve  22  in positions adjacent to their actual respective positions. In FIG. 4B, the second fluid or expiratory gas  40  is flowing through the second opening  16  and impinges upon the outside surface of the inner portion  26  of the duck-bill valve  22 . The second fluid or expiratory gas  40  forces closed the small slot  36  of the duck-bill valve  22  and forces the sealing portion  30  to unseat a small distance from the internal valve housing seat  34 . Accordingly, the second fluid or expiratory gas  40  is then forced to travel through the small space created by the unseating of the sealing portion  30  from the internal valve housing  34  and only out of the exhaust port  18  of the valve housing  12 . Note, the retainer ring  50  of the prior art only functions to prevent inversion of the duck-bill valve in response to a forceful flow of the second fluid or expiratory gas  40 . 
     FIG. 5A is an exploded cross-sectional view of the valve housing  12  showing the flexible retainer ring  60  of the present invention and the duck-bill valve  22  in positions adjacent to their actual respective positions. In FIG. 5A, the first fluid or respiratory gas  38  is flowing through the flexible retainer ring  60  and impinges upon the inside surface of the inner portion  26  of the duck-bill valve  22 . The first fluid or respiratory gas  38  forces open the small slot  36  of the duck-bill valve  22  and forces the sealing portion  30  to remain in sealing contact with the internal valve housing seat  34 . Accordingly, the first fluid or respiratory gas  38  is then forced to travel through the duck-bill valve  22  and only out of the second opening  16  of the valve housing  12 . Note, the flexible retainer ring  60  of the present invention assists in the opening of the small slot  36  of the duck-bill valve  22  by pushing against the inside surface of inner portion  26  in response to the flow of first fluid or respiratory gas  38 . The flexible retainer ring  60  of the present invention is able to assist in the opening of the small slot  36  of the duck-bill valve  22  because of the flexible supports  64  that are connected to the center portion  66 , allowing the center portion  66  to deflect towards the small slot  36  in response to the flow of the first fluid or respiratory gas  38 . Further, the center portion  66  of the flexible retainer ring  60  is of a substantial width and depth to seat within the inner portion  26  of the duck-bill valve  22 . 
     FIG. 5B is an exploded cross-sectional view of the valve housing  12  showing the flexible retainer ring  60  of the present invention and the duck-bill valve  22  in positions adjacent to their actual respective positions. In FIG. 5B the second fluid or expiratory gas  40  is flowing through the second opening  16  and impinges upon the outside surface of the inner portion  26  of the duck-bill valve  22 . The second fluid or expiratory gas  40  forces closed the small slot  36  of the duck-bill valve  22  and forces the sealing portion  30  to unseat from the internal valve housing seat  34 . Accordingly, the second fluid or expiratory gas  40  is then forced to travel through the space created by the unseating of the sealing portion  30  from the internal valve housing seat  34  and only out of the exhaust port  18  of the valve housing  12 . Note, the flexible retainer ring  60  of the present invention also prevents inversion of the duck-bill valve  22  in response to a forceful flow of the second fluid or expiratory gas  40 . In addition, the flexible retainer ring  60  of the present invention is able to prevent distortion and act as a shock absorber for the inner portion  26  of the duck-bill valve  22  because of the flexible supports  64  that are connected to the center portion  66  allowing the center portion  66  to deflect with the inner portion  26  in response to the flow of the first fluid or respiratory gas  38 . 
     Most importantly, the flexible retainer ring  60  of the present invention allows the sealing portion  30  to unseat a greater distance from the internal valve housing seat  34 . Accordingly, a greater amount of the second fluid or expiratory gas  40  can travel through the larger space created by the unseating of the sealing portion  30  from the internal valve housing  34  and only out of the exhaust port  18  of the valve housing  12 . The flexible retainer ring  60  of the present invention is able to allow the sealing portion  30  to unseat a greater distance from the internal valve housing  34  while still preventing inversion of the duck-bill valve  22 . The flexible retainer ring  60  of the present invention is able to allow the sealing portion  30  to unseat a greater distance from the internal valve housing  34  because of the flexible supports  64  that are connected to the center portion  66 , allowing the center portion  66  to deflect with the inner portion  26  of the duck-bill valve  22  in response to the flow of the second fluid or expiratory gas  40 . 
     As is best shown in FIG. 6A, the flexible retainer ring  60  of the present invention comprises a thin substantially circular portion  62  for attaching to the valve housing  12 ; a plurality of flexible supports  64  extending radially inward from the circular portion  62 ; and a center portion  66 . In one embodiment, the plurality of flexible supports  64  can be made from silicone rubber. In an alternative embodiment, as best shown in FIG. 6B, the plurality of flexible supports  64  of the flexible ring  60  can be made of springs. 
     The flexible retainer ring of the present invention thus provides a novel NRV or one-way valve. The flexible retainer ring of the present invention allows the valve housing to be made smaller than a conventional valve housing while maintaining the necessary flow rate for expiratory gas through the exhaust port of the valve housing. This smaller housing can be extremely useful in the care of infants and neonatal patients or in industrial applications requiring smaller instruments. Further, the flexible retainer ring offers increased protection against inversion and effectively maintains the integrity of the one-way valve element while producing an assembly of uncomplicated yet rugged design, comparatively low cost to manufacture and reliable operation. 
     Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.