Abstract:
An oscillating variable displacement ring pump provides both positive and variable displacement. A housing circumscribes a pump chamber. The pump chamber encases an oscillating ring driven by a crankshaft. The crankshaft&#39;s offset shaft is located inside the pump chamber. The ring encircles the offset shaft. A bearing rotatably attached to the offset shaft rolls inside the ring. When the pump chamber is sealed, rotation of the offset shaft causes ring oscillation in the chamber. Ring oscillation creates vacuum pressure, which draws substances into pump chamber via an inlet port while pumping out substances of the pump chamber via an outlet port. A valve within the pump chamber contacts the ring and follows ring oscillation to help separate incoming substances from outgoing substances. The pump can include an adjustable internal by-pass means to control the volume and pressure of substances delivered by the pump.

Description:
TECHNICAL FIELD  
       [0001]     This application claims the benefit of pending U.S. provisional patent application No. 60/813,810 filed 15 Jun. 2006 on behalf of the applicant hereof. 
     
    
       [0002]     The invention relates to the field of variable displacement pumps. In particular, the invention relates to an oscillating variable displacement ring pump that draws and delivers substances, such as liquids, into and out of a pump chamber by movement of a displacement ring.  
       BACKGROUND  
       [0003]     Displacement pumps can take the form of gear pumps, vane-type pumps and oscillating slide pumps. With these forms of pumps, the volume of substances displaced or delivered is typically fixed due to the physical dimensions of the pumps and cannot be easily varied. It is, therefore, desirable to provide a pump that can be easily changed to vary the amount of substances displaced or delivered.  
       SUMMARY  
       [0004]     An oscillating variable displacement ring pump is provided. In one embodiment, the pump can have a housing circumscribing a pump chamber. The pump chamber includes an inlet port and an outlet port. The pump chamber encases an oscillating variable displacement ring. A valve within the pump chamber contacts the ring to help isolate the outlet port from the inlet port and to separate incoming substances from outgoing substances. The pump draws and delivers substances by movement of the displacement ring within the pump chamber. When the pump chamber is sealed, ring oscillation creates a vacuum on the inlet port and pressure on the outlet port. The vacuum draws substances into the pump chamber through the inlet port while driving substances out of pump chamber through the outlet port.  
         [0005]     In one embodiment, a crankshaft rotatably disposed within the pump housing drives ring oscillation. In this embodiment, the crankshaft comprises an input shaft and an offset shaft whereby rotation of input shaft rotates the offset shaft. The offset shaft is located inside the pump chamber and is encircled by the ring. A spacer, such as a bearing, is set on the offset shaft and rolls inside the ring as the crankshaft rotates. The diameter of the spacer and the width of the ring sidewall is chosen such that there is minimal clearance between the ring and the spacer and between the ring and the chamber sidewall.  
         [0006]     In another embodiment, the housing can form a pump face, which opens into the pump chamber. A cover plate can attach to the housing to cover the pump face and to form an airtight seal with the pump chamber. The cover plate can attach to the housing, by attaching means including, but not limited to, bolts and screws.  
         [0007]     In one embodiment, the pump can comprise a valve that has an anchored end and a free end. The anchored end can be pivotally attached to the pump chamber&#39;s inside wall at a position between the inlet port and the outlet port. The free end extends toward the pump chamber&#39;s centre. The valve can pivot into a recess in the pump chamber&#39;s inside wall in order to make the valve flush with the inside wall surface. During pumping, the valve free end contacts the ring and follows the ring&#39;s oscillating movement. In response to ring contact, the free end is cyclically pushed into the recess until the pushing force from the oscillating ring has passed. The ring and the valve separate the inlet port from the outlet port. The valve can be of various types or styles, including but not limited to a flapper valve, a sliding valve, a wedge valve, a reed valve and a rocking valve.  
         [0008]     In another embodiment, the pump can include adjustable internal by-pass protection means to prevent over-pressuring and to control the output pressure of substances being pumped. The by-pass protection means can comprise, but is not limited to: (a) a check valve, a needle valve or a poppet valve located in a passageway connecting the outlet port to the inlet port, or (b) a spring mounted directly on the offset shaft to limit the pressure applied to ring against the internal wall of the pump chamber allowing substances to by-pass internally in the pump chamber past the ring. In another embodiment, the passageway valve can be controlled by a spring-loaded mechanism, such as a thumbscrew or other suitable means, to adjust and set the pressure at which the valve will open.  
         [0009]     The pump on/off means can include, but is not limited to, an electric clutch or a mechanically engaging a gear or shaft operatively coupled to the crankshaft.  
         [0010]     In one embodiment, the pump can provide both positive and variable displacement, wherein the volume of substances displaced by the pump can be varied, by increasing or decreasing ring diameter without affecting ring thickness or any other pump dimensions. The volume displaced by the pump is calculable and, therefore, the ring dimensions required for delivering an exact volume per revolution can also be calculated. The volume of substances displaced by the pump per crankshaft revolution is inversely proportional to the ring diameter. As the ring diameter is increased, the volume available for substances in the chamber decreases.  
         [0011]     In another embodiment, the pump can be used with a ring of a customized size. Furthermore, the pump can be used with a kit, wherein the kit contains rings of differing diameters, allowing user to change the volume of substances displaced by the pump in order to provide the desired pumping rate.  
         [0012]     In representative embodiments, the pump can have few moving parts to promote ease of repair. The pump can be designed with little friction loss in order to lengthen the duration of time the pump stays in calibration and to help ensure long, dependable substance delivery. To reduce wear and to help prevent unwanted or accidental adjustment, the pump can be internally adjustable and can have no exposed parts.  
         [0013]     In a representative embodiment, the pump can have a simple design, which allows the pump: (a) to be manufactured at low cost, compared to other pumps in the field; (b) to be used for a variety of applications; and (c) to be made small and light relative to the substance it can inject. In other embodiments, the pump can be made mostly out of plastic for use in small, every day public applications such as soap injectors or agricultural chemical injectors. In further embodiments, the pump can be made with extreme precision with materials to be used in applications including but not limited to medicine, aerospace, or military applications. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a front elevational cross-section view depicting a housing of one embodiment of an oscillating ring pump.  
         [0015]      FIG. 2  is a front elevational cross-section view depicting one embodiment of an oscillating ring pump.  
         [0016]      FIG. 3  is a side elevational cross-section exploded view depicting the pump of  FIG. 2 .  
         [0017]      FIG. 4  is a front elevational cross-section view depicting a first alternate embodiment of an oscillating ring pump.  
         [0018]      FIG. 5  is a front elevational cross-section view depicting a second alternate embodiment of an oscillating ring pump.  
         [0019]      FIG. 6  is a front elevational cross-section view depicting a third alternate embodiment of an oscillating ring pump.  
         [0020]      FIG. 7 a  front elevational cross-section view depicting a fourth alternate embodiment of an oscillating ring pump.  
         [0021]      FIG. 8  is a front elevational cross-section view depicting a fifth alternate embodiment of an oscillating ring pump.  
         [0022]      FIG. 9  is a top cross-sectional plan view depicting a pressure relief/bypass valve on the ring pump of  FIG. 2 .  
         [0023]      FIG. 10  is a front elevational view depicting the oscillating ring pump of  FIG. 2  with the ring located near top dead centre (“TDC”).  
         [0024]      FIG. 11  is a front elevational view depicting the oscillating ring pump of  FIG. 2  with the ring rotated about 80° from TDC.  
         [0025]      FIG. 12  is a front elevational view depicting the oscillating ring pump of  FIG. 2  with the ring rotated about 175° from TDC.  
         [0026]      FIG. 13  is a front elevational view depicting the oscillating ring pump of  FIG. 2  with the ring rotated about 240° from TDC.  
         [0027]      FIG. 14  is a front elevational view depicting the oscillating ring pump of  FIG. 2  with the ring rotated about 270° from TDC.  
         [0028]      FIG. 15  is a front elevational cross-section view depicting a sixth alternate embodiment of an oscillating ring pump.  
     
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
       [0029]     Shown in  FIG. 1  is a representative embodiment of housing  12  of pump  10 . Housing  12  comprises pump chamber  14  having sidewall  13 . In this embodiment, chamber  14  can be substantially circular in cross-section. Pump  10  comprises inlet and outlet ports  14  and  16  that provide communication between exterior side  11  of pump  10  and chamber  14 . Inlet port  16  terminates in chamber inlet  17  in chamber  14 . Outlet port  18  terminates in chamber outlet  19  in chamber  14 . In the illustrated embodiment, pump  10  can comprise flapper valve  22  that comprises fixed end  32  and free end  30 . Valve  22  can be pivotally attached to housing  12  at pivot point  34  between inlet port  16  and outlet port  18  thereby allowing valve free end  30  swing towards and away from the center of chamber  14 . Housing  12  can further comprise recess  15  whereby valve  22  can swing into recess  15  and be substantially flush with chamber sidewall  13 .  
         [0030]     Referring to  FIG. 2 , an embodiment of pump  10  is shown with crankshaft  24  disposed at the center of chamber  14 . Crankshaft  24  has a longitudinal axis that is substantially perpendicular to chamber wall  7  and is coaxially aligned with the center of chamber  14 . Disposed on crankshaft  24  is offset shaft  26 . Offset shaft  26  has an axis that is offset and substantially parallel to the longitudinal axis of crankshaft  24  such that offset shaft  26  moves in a circular path within chamber  14  as crankshaft  24  rotates. Annular spacer  28  is placed on offset shaft  26  and can freely rotate about offset shaft  26 . In one embodiment, spacer  28  can comprise a roller bearing. In other embodiments, spacer  28  can comprise a needle bearing, a bushing or any other suitable bearing member that can rotate about offset shaft  26  as would be obvious to those skilled in the art. Disposed within chamber  14  is annular pump ring  20  such that it is placed about spacer  26 . Ring  20  comprises sidewall  21  that has a thickness that can be equal to or less than the minimum distance separating the outer edge of spacer  28  and chamber sidewall  13  whereby there is minimal clearance between spacer  28  and ring  20  and between ring  20  and sidewall  13 . In this manner, ring  20  can freely rotate or oscillate within chamber  14  as crankshaft  24  rotates yet maintain contact between spacer  28  and sidewall  13 . In another embodiment, ring sidewall  21  can have a rectangular cross-section to maximize the contact with spacer  28  and sidewall  13 .  
         [0031]     Pump  10  can further comprise inlet check valve  42  and outlet check valve  44 . Check valve  42  can include ball  46  and spring  50 . Spring  50  urges ball  46  to rest on valve seat  48  thereby sealing off inlet port  16 . Check valve  42  acts to prevent substances from prematurely entering chamber  14 . The spring constant of spring  50  determines the required pressure to lift ball  46  off of valve seat  48  and allow substances to enter chamber  14 . Similarly, check valve  44  acts to prevent substances from prematurely exiting chamber  14 . The spring constant of spring  56  determines the required pressure to lift ball  52  off of valve seat  54  and allow substances to exit chamber  14 . In representative embodiment, check valve  42  can be configured with a release pressure of approximately 2 p.s.i. whereas check valve  44  can be configured with a release pressure of approximately 10 p.s.i.  
         [0032]     In further embodiments, housing  12  can comprise o-ring groove  8  and boltholes  6 . An o-ring seal can be placed in groove  8  to provide a seal between housing  12  and a cover (not shown) that can be bolted to housing  12  using bolts engaging boltholes  6 .  
         [0033]     In operation, ring  20  can be an oscillating variable displacement ring. The movement of ring  20  pumps substances in and out of chamber  14  via inlet port  16  and outlet port  18 , respectively. Crankshaft  24  rotates to move offset shaft  26  in a circular path. Rotation of offset shaft  26  causes ring  20  to oscillate within chamber  14 . Oscillation of ring  20  creates vacuum pressure on inlet port  16  to draw substances into pump chamber  14 . The vacuum pressure is greater than the release pressure of check valve  42  thereby allowing substances to enter chamber  14  via chamber inlet  17 . As ring  20  moves within chamber  14 , substances are pushed towards chamber outlet  19  and check valve  44 . The pressure on the substances being pumped will exceed the release pressure of check valve  44  and allow substances to then exit via outlet port  18 . All the while, the pressure of the substances in chamber  14  will urge free end  30  of flapper valve  22  to maintain contact with ring  20  so as to provide a barrier that prevents substances from moving towards chamber inlet  17 .  
         [0034]     By maintaining contact with ring  20 , free end  30  can be pushed into recess  15  by the movement of ring  20  until ring  20  has cyclically moved past recess  15 . Fixed end  32  is positioned on sidewall  13  such that flapper valve  22  covers chamber outlet  19  when pushed into recess  15  by ring  20  thereby closing off chamber outlet  19 .  
         [0035]     Referring to  FIG. 3 , an exploded side view of pump  10  is shown. In this embodiment, crankshaft  24  can be operatively coupled to input shaft  29  that passes through opening  27  in housing  12  and can be supported by a pair of bearings  31 . Bearings  31  can be of the tapered roller variety or any other suitable replacement such as ball bearing, needle bearing, bushing or any other bearing as well known to those skilled in the art. Pump  10  can further include seal  25  disposed around crankshaft  24  to seal off chamber  14 . When assembled, spacer  28  is set upon offset shaft  26  and ring  20  is set upon spacer  28 . O-ring  7  can be placed in groove  8 . Cover  33  is placed against o-ring  7  on housing  12  to enclose and seal chamber  14 . Cover  33  can be secured into position with retainer ring  35  fastened to housing  12  by bolts  5  threaded into boltholes  6 . Cover  33  can be made of any suitable material that can withstand the pressure of substances being delivered by pump  10 . In a representative embodiment, cover  33  can be made of transparent plexiglas of suitable thickness so as to enable visual inspection of pump  10  when in operation.  
         [0036]     Referring to  FIG. 4 , another embodiment of pump  10  is shown. In this embodiment, flapper valve  22  can further include reed valve  36 . Reed valve  36  has fixed end  40  and free end  38 . Reed valve  36  can be positioned between flapper valve  22  and ring  20 . Reed valve  36  can be made of flexible material, such as spring steel or other suitable materials as known to those skilled in the art. The inclusion of reed valve  36  can enhance the seal made by flapper valve  22  when it contacts ring  20 .  
         [0037]     In another embodiment, pump  10  can include biasing means to urge flapper valve  22  to contact ring  20 . In one embodiment, the biasing means can comprise spring  23  or it can be any other suitable mechanism as known to those skilled in the art.  
         [0038]     Referring to  FIG. 5 , another embodiment of pump  10  is shown. In this embodiment, pump  10  can use wedge  58  as a valve as described above. Wedge  58  has fixed end  62  that is pivotally attached to housing  12  at pivot point  64  and free end  60  that contacts ring  20 . In this embodiment, spring  66  urges wedge  58  towards ring  20 . Spring  66  is secured in place by spring sleeve  68  and bolt  70  threaded into opening  74  in housing  12 . Shim  72  can be placed between spring  66  and bolt  70 . Shim  72  can be varied in thickness to vary the pre-load tension on spring  66 , that is, thinner shims will reduce the tension whereas thicker shims will increase the tension.  
         [0039]     Referring to  FIG. 6 , another embodiment of pump  10  is shown. In this embodiment, slider valve  76  can be used to separate or isolate inlet  16  from outlet  18 . Slider valve  76  comprises valve face  77  that contacts ring  20 . Slider valve  76  is slidably disposed in valve guide opening  80  in housing  12  that is configured to receive slider valve  76 . Spring  78  can be disposed within opening  80  and valve  76  as illustrated to provide biasing means to urge slider valve  76  to the center of chamber  14  and to have slider valve face  77  maintain contact with ring  20 . In this embodiment, slider valve  76  can be configured to be substantially perpendicular to exterior surface  11  of housing  12 .  
         [0040]     Referring to  FIG. 7 , another embodiment of pump  10  is shown. In this embodiment, pump  10  can have slider valve  82  slidably disposed in valve guide opening  90  disposed in housing  12  to receive slider valve  82 . Slider valve  82  can further comprise ball end  84  with valve shoe  86  rotatably coupled thereon. Shoe  86  can rotate on ball end  84  to maintain contact with ring  20  as ring  20  oscillates within chamber  14 . Spring  88  can be disposed within opening  90  and valve  82  as illustrated to provide biasing means to urge slider valve  82  to the center of chamber  14  and to have slider valve shoe  86  maintain contact with ring  20 .  
         [0041]     Referring to  FIG. 8 , another embodiment of pump  10  is shown. In this embodiment, slider valve  92  and valve guide opening  94  disposed at an angle with respect to exterior surface  11  of housing  12 . In a representative embodiment, slider valve  94  and opening  94  are canted at an angle of approximately 10° off of vertical. In this embodiment, slider valve  92  can include opening  97  configured to receive valve shoe  98  that maintains contact with ring  20  as it rotates within chamber  14 . In this embodiment, shoe  98  can be semi-circular in cross-section and can have a concave contact surface for contacting ring  20 . Spring  96  can be disposed within opening  94  and valve  92  as illustrated to provide biasing means to urge slider valve  92  to the center of chamber  14  and to have slider valve shoe  98  maintain contact with ring  20 .  
         [0042]     Referring to  FIG. 9 , another embodiment of pump  10  is shown. In this embodiment, pump  10  can comprise passageway  100  disposed in housing  12  to provide means for controlling the output pressure or amount of substances delivered by pump  10 . In the illustrated embodiment, housing  12  can comprise passageway  99  that provides communication between passageway  100  and the passageway that connects chamber outlet  19  to output port  18 . Passageway  99  can further comprise valve seat  108  for receiving ball valve  106 . Biasing means can be provided to urge ball valve  106  against valve seat  108  to close off passageway  99 . In the illustrated embodiment, the biasing means can include thumbscrew  104 , spring  110  and spring sleeve  112 . Spring  110  and spring sleeve  112  can be slidably disposed within opening  114  of thumbscrew  104 . The output pressure of substances delivered by pump  10  is dependent on the pressure required to lift ball valve  106  off of valve seat  108 . The more thumbscrew  104  is threaded into housing  12 , the more spring  110  is compressed to increase the pressure required to open ball valve  106 . The more thumbscrew  104  is threaded out of housing  12 , the less spring  110  is compressed thereby decreasing the pressure to open ball valve  106 . In a further embodiment, passageway  100  can comprise access port  101  and plug  102  to close off port  101  during operation of pump  10 . It should obvious to those skilled in the art that means other than a ball valve can be used to control the output pressure of substances delivered by pump  10  such as a needle valve as well as any other suitable means.  
         [0043]     Referring to FIGS.  10  to  14 , operation of an embodiment of pump  10  is illustrated. In  FIG. 10 , pump  10  is shown with ring  20  at approximately top dead center (“TDC”). For the purpose of these illustrations, substances are contained in pump chamber  14  in this initial condition. Pump  10  begins to operate when input rotational power is applied to crankshaft  24 . The input rotational power is applied to an input shaft (not shown) operatively attached to crankshaft  24 . The input rotational power can be obtained from any suitable source such as a motor or from rotating shafts that are operatively coupled to the input shaft, either by meshed gears, a belt and pulleys, a chain and sprockets or any other suitable means as well known to those skilled in the art. In the illustrated embodiment, crankshaft  24  can rotate clockwise as shown in chamber  14  thereby allowing flapper valve  22  to move away from recess  15 . It should be obvious to one skilled in the art, however, that pump  10  can be assembled in a mirrored configuration whereupon crankshaft  24  can rotate in a counter clockwise direction.  
         [0044]     Referring to  FIG. 11 , ring  20  is at approximately 80° rotated from TDC. In this position, flapper valve  22  has moved away from recess  15  to expose chamber outlet  19 . Substances in pump chamber  14  are forced through chamber outlet  19  and exit through check valve  44  and output port  18 . As ring  20  rotates clockwise, pump chamber inlet side  14   a  is formed and begins to create a vacuum to draw in substances through inlet port  16 , check valve  42  and chamber inlet  17 .  
         [0045]     Referring to  FIG. 12 , pump ring  20  is shown at approximately 175° rotated from TDC. In this position, pump chamber inlet side  14   a  is approximately the same volume as pump chamber outlet side  14   b.  As ring  20  rotates clockwise, the volume of pump chamber outlet side  14   b  decreases thereby forcing substances through chamber outlet  19  to exit through check valve  44  and outlet port  18 . Flapper valve  22  acts as a barrier between pump chamber outlet side  14   b  and pump chamber inlet side  14   a.  As crankshaft  24  continues to rotate clockwise, pump chamber inlet side  14   a  increases in volume thereby drawing in more substances in through chamber inlet  17 .  
         [0046]     Referring to  FIG. 13 , pump ring  20  is shown at approximately 240° rotated from TDC. In this position, the volume of pump chamber outlet side  14   b  has decreased and flapper valve  22  has begun to retreat back into recess  15  to close off chamber outlet  19 . The volume of pump chamber inlet side  14   a  continues to increase to draw in more substances through chamber inlet  17 .  
         [0047]     Referring to  FIG. 14 , pump ring  20  is shown at approximately 270° rotated from TDC whereby the volume of pump chamber outlet side  14   b  has been decreased to nearly zero. Flapper valve  22  is almost fully retracted into recess  15  to close off chamber outlet  19 . As pump ring  20  continues to move clockwise to TDC, the pumping process continues in the manner described whereby substances are drawn into and pumped out of pump chamber  14  simultaneously with each revolution of crankshaft  24 . The volume of substances displaced by pump  10  in each revolution of crankshaft  24  is a function of the diameter of ring  20 . As the diameter of ring  20  is increased, the amounts of substances drawn in and expelled by pump  10  decreases as the available volume for pump chamber inlet and outlet sides  14   a  and  14   b  has decreased. Similarly, as the diameter of ring  20  is decreased, the amounts of substances drawn in and expelled by pump  10  increases as the available volume for pump chamber inlet and outlet sides  14   a  and  14   b  has increased.  
         [0048]     In another embodiment of pump  10 , pump  10  can be provided with a kit having a multiple number of rings  20  in various diameters but all having sidewall  21  of the same thickness. In this fashion, pump  10  can be easily configured to change the amount of substances it can displace or deliver simply by changing ring  20  of one diameter for another ring  20  having a different diameter. In this regard, a pump having variable displacement can be provided.  
         [0049]     Referring to  FIG. 15 , a side view of pump  10  is shown. In this embodiment, crankshaft  24  can be operatively coupled to input shaft  29  that passes through opening  27  in housing  12  and can be supported by a pair of bearings  31 . Disposed on the end of offset shaft  26  is opening  128  that can receive offset shaft  126  disposed on crankshaft  120 . Crankshaft  120  can be rotatably disposed within housing cover  116  that can be, in turn, fastened to housing  12  using bolts, screws or any other suitable means. O-ring  7  can be placed between housing  12  and housing cover  116  to seal off chamber  14 . Crankshaft  12  can be operatively coupled to output shaft  122  which can be supported in shaft opening  118  of housing cover  116  by bearings  124 . Bearings  31  and  124  can be of the tapered roller variety or any other suitable replacement such as ball bearing, needle bearing, bushing or any other bearing as well known to those skilled in the art. Output shaft  122  can be used in any number of ways to provide rotational power to other devices. In one embodiment, one or more pumps  10  can be connected in tandem whereby the input shaft of one pump  10  is operatively coupled to the output shaft of a previous pump  10 . In this fashion, different substances can be pumped simultaneously at the same, one substance per pump in the tandem.  
         [0050]     In another embodiment, two or more pumps can be connected in tandem to pump the same substance thereby increasing the amount of substances that can be delivered per revolution of the pump crankshafts.  
         [0051]     In a further embodiment, an input manifold, as well known to those skilled in the art, can be used to collectively feed the input ports of the tandem-connected pumps from a single source of substances.  
         [0052]     In yet another embodiment, an output manifold can be used to connect the output ports of the tandem-connected pumps to a single output whereby all of the pumped substances are delivered from a single output port.  
         [0053]     In yet a further embodiment, the offset shafts of the tandem-connected pumps can be rotationally spaced apart from one another with respect to the longitudinal axis of the crankshafts. For example, in a two tandem pump configuration, the offset shafts can be spaced approximately 180° apart. For a three tandem pump configuration, the offset shafts can be spaced approximately 120° apart, and so on. By configuring the offset shafts in this manner, especially when using an output manifold, the pulsing of delivered substances that naturally occurs with a single pump can be reduced or smoothed out in the delivery of substances exiting the output manifold.  
         [0054]     Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.