Abstract:
A hydraulically balanced assembly is provided. The assembly includes: a valve body defining a tapered axial passageway; and a rotor having a tapered outer diameter such that the rotor has a first portion having a wider diameter and a second portion having a smaller diameter, the rotor being dimensioned to fit within the axial passageway of the valve body, the rotor further defining a rotor axial passageway having a first passageway portion and second passageway portion, the rotor further defining a first and second port, where each of the first and second ports provide fluid communication between the tapered outer diameter and the rotor axial passageway, wherein the first and second portions define openings having different cross-sectional areas where the first passageway portion is located in a first portion of the rotor and a second passageway portion is located in the second portion of the rotor and the difference in cross-sectional areas between the first passageway portion and second passageway portion and the amount of taper of the outer diameter of the rotor are related according to the Landrum relation.

Description:
FIELD OF THE INVENTION 
       [0001]    This application claims the benefit of two provisional U.S. patent applications entitled Hydraulic Connection Having a Flexible Port Mouth and Method for Connecting Same, having Ser. Nos. 62/387,137 and 62/387,138 and both filed Dec. 23, 2015. The disclosure of these applications is hereby incorporated by reference in its entirety. 
     
    
       [0002]    The present invention relates generally to a hydraulic valve. More particularly, the present invention relates to a hydraulic valve having a modular construction and flexible attaching port. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hydraulic systems use valves to have the hydraulic fluid flow to a desired location. Furthermore, it may be desirable to turn on and off the hydraulic flow. As a result, hydraulic valves are desired. It may also be desirable to balance hydraulic forces placed on hydraulic valves. 
         [0004]    Accordingly, it is desirable to provide hydraulic valve that has balanced hydraulic forces and is useful in valving hydraulic fluid. 
       SUMMARY OF THE INVENTION 
       [0005]    The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments a hydraulic valve system or assembly and method is used to valve hydraulic fluid and to balance the forces placed on the hydraulic valve or valve assembly. 
         [0006]    In accordance with one embodiment of the present invention, a hydraulically balanced assembly is provided. The assembly includes: a valve body defining a tapered axial passageway; and a rotor having a tapered outer diameter such that the rotor has a first portion having a wider diameter and a second portion having a smaller diameter, the rotor being dimensioned to fit within the axial passageway of the valve body, the rotor further defining a rotor axial passageway having a first passageway portion and second passageway portion, the rotor further defining a first and second port, where each of the first and second ports provide fluid communication between the tapered outer diameter and the rotor axial passageway, wherein the first and second portions define openings having different cross-sectional areas where the first passageway portion is located in a first portion of the rotor and a second passageway portion is located in the second portion of the rotor and the difference in cross-sectional areas between the first passageway portion and second passageway portion and the amount of taper of the outer diameter of the rotor are related according to the Landrum relation. 
         [0007]    In accordance with another embodiment of the present invention, a method of hydraulically balancing a valve is provided. The method includes: fitting a tapered rotor into a valve body having a tapered axial passageway; providing a two-part passageway into the rotor the first part having a larger diameter than the second part; and dimensioning an outer tapered surface of the rotor to a difference in diameter between the first and second parts of the passageway according to the Landrum relation. 
         [0008]    In accordance with yet another embodiment of the present invention, an attaching mechanism is provided. The attaching mechanism includes: a first body to finding a tapered dovetail slot; a second body having a tapered dovetail; and a spring loaded projection located in the dovetail slot and the projection is configured to move between an extended position where it extends into the dovetail slot and a retracted position where it does riot extend into the dovetail slot, wherein the dovetail and the dovetail slot are both dimensioned and tapered so that the fitting slides into the dovetail slot and then fits snugly into the valve body and can no longer slide further into the dovetail slot and the spring loaded projection is located in the dovetail slot in a position where it can move to the extended position when the fitting is snugly fit into the valve body and the projection can extend into the dovetail slot trapping the fitting into the dovetail slot. 
         [0009]    There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
         [0010]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
         [0011]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a perspective view of a modular valve in accordance with an embodiment in accordance with the disclosure. 
           [0013]      FIG. 2  is an exploded, perspective view of the valve illustrated in  FIG. 1 . 
           [0014]      FIG. 3  is a side, cross-sectional view of the valve shown in  FIG. 1 . 
           [0015]      FIG. 4  is a perspective view of a flow path through a modular port housing in accordance with an embodiment. 
           [0016]      FIG. 5  is an exploded, perspective view of a modular port housing and the valve body showing a flow path through the modular port housing and the valve body where the valve body and the modular port housing are not shown in the same scale. 
           [0017]      FIG. 6  is a perspective view of the valve body and the manifold showing a flow path through the valve body and manifold where the valve body and the manifold are not shown in the same scale. 
           [0018]      FIG. 7  is a perspective view of the manifold and the valve rotor and a flow path through the manifold and a valve rotor where the manifold and valve rotor are not shown in the same scale. 
           [0019]      FIG. 8  is a perspective view of the valve body and rotor. 
           [0020]      FIG. 9  is a partial side, see-through view of the valve shown in  FIG. 1 . 
           [0021]      FIG. 10  is a partial, disassembled, view of a modular valve in accordance with an embodiment. 
           [0022]      FIG. 11  a cross-sectional view of the valve rotor. 
           [0023]      FIG. 12  is a side view of the valve rotor. 
           [0024]      FIG. 13  partial, cross-sectional view of a portion of the valve rotor shown in  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. An embodiment in accordance with the present invention provides a hydraulic valve utilizing tapered dovetail elements for allowing the valve to be assembled and disassembled in a modular fashion. The dovetail elements reduce the need for threaded fasteners. In some aspects, this disclosure describes a valve that utilizes a tapered valve rotor and element that is pressure balanced or pressure biased to reduce a leakage within the valve and to reduce the effort required to turn the handle. In other embodiments, this disclosure is directed to a valve that utilizes a unique metal seal geometry that reduces a leakage when the seal is under hydraulic pressure. Some embodiments also incorporate a tapered press fit manifold having external grooves to reduce internal communication of flow paths and to reduce the size the manifold and machining required on the manifold. This also allows flow paths to cross. 
         [0026]    A hydraulic valve  10  is shown in  FIG. 1 . The hydraulic valve  10  includes a valve body  12 . The valve body  12  is mounted to a mounting base  14 . In some embodiments, the mounting base  14  may be part of a larger structure to which the hydraulic valve  10  is mounted. The valve body  12  may include a dovetail slot  16  for mounting the hydraulic valve  10  to the mounting base  14 . As shown in  FIG. 2 , the mounting base  14  has a tapered dovetail  18  which may be referred to as the mounting dovetail  18 . The mounting dovetail  18  is configured to slide within the mounting dovetail slot  16  located on the valve body  12 . In this manner, the hydraulic valve  10  is mounted to the mounting base  14 . 
         [0027]    Returning to  FIG. 1 , the hydraulic valve  10  has a center stud  20  that extends through the valve body  12 . The center stud  20  may include attaching structure  22  located on the center stud  20 . The attaching structure  22  may be in the form of a hex shaped hole as shown. In other embodiments, the attaching structure  22  may be structure configured to allow a tool used for turning. For example, the attaching structure  22  may include other attaching structure such as external flats, a slot for a flat screwdriver to fit in, a Phillips slot, or any other suitable mounting structure  22 . 
         [0028]    A selector plate  24  may be located adjacent to the center stud  20 . The center stud  20  extends through the selector plate  24 . A selector rod  26  is mounted to the selector plate  24  and may be equipped with a selector knob  28 . A user may grab the selector knob  28  which is attached to the selector rod  26  and rotate the selector rod  26  to thereby cause the selector plate  24  to reach a desired angular position. For example, indicia such as the letters A and B appearing in  FIG. 1  may be located on the valve body  12  to assist in allowing a user to move the selector rod  26  to a desired angular position. 
         [0029]    A manifold  30  may be located between the valve body  12  and the selector plate  24 . Additional discussion and description of the center stud  20  the selector plate  24  and the manifold  30  will occur further below with respect to  FIG. 2 . 
         [0030]    In some embodiments and as shown in  FIG. 1 , the hydraulic valve  10  may be modularly constructed. Various accessories to the hydraulic valve  10  may be attached or removed from the hydraulic valve  10 . For example, a modular valve port housing  32  may be attached to the valve body  12 . In some embodiments, two or more, (but only two are shown in the FIGS.) such modular valve port housings  32  may be attached to the valve body  12 . Multiple tapered modular port dovetail slots  38  may allow multiple accessories such as modular valve port housings  32  to be attached to the valve  10 . One example modular valve port housing  32  will be described below even though more than one is shown in the FIGS. The multiple modular valve port housings  32  have the same or similar parts and therefore only one will be described. One of ordinary skill the art after reviewing this disclosure will understand that the various features described will be relevant to all of the modular valve port housings  32  and corresponding modular port dovetail slots  38 . 
         [0031]    The modular valve port housing  32  may include a modular valve ports  34  which appear as an opening in the modular valve port housing  32 . In some embodiments, as shown in  FIG. 1 , the modular port valve port  34  may be oriented parallel to the modular valve port dovetail  36 . The modular port dovetail  36  may be a tapered dovetail  36  configured to fit in the modular port tapered dovetail slot  38  located in the valve body  12 . In some embodiments, the front  40  of the dovetail  36  may be wider than the rear  42  of the dovetail  36  such that as the modular valve port housing  32  and moves through the modular tapered dovetail slot  38 , the modular port dovetail  36  will start to have an interference fit with the modular port dovetail slot  38  and at some point will no longer be able to slide in the modular port dovetail slot  38  in the direction of the rear  42  of the dovetail  36 . 
         [0032]    To secure the modular valve port housing  32  in the modular port tapered dovetail slot  38 , a detent pin  44  is located in the modular port tapered dovetail slot  38 . The detent pin  44  is spring-loaded and can move between an extended and retracted position. The position shown in  FIG. 1  is the extended position. When the detent pin  44  is in the extended position, the detent pin  44  prevents the modular valve port housing  32  from sliding out of the modular port tapered dovetail slot  38  in the direction of the front  40  of the dovetail  36 . When it is desired to either attach or remove the modular valve port housing  32  the detent pin  44  can be depressed to overcome the spring bias and be moved out of the way to allow the modular valve port housing  32  to be moved within the modular port tapered dovetail slot  38 . 
         [0033]      FIG. 2  is an exploded view of the hydraulic valve. The center stud  20  is shown with the attaching structure  22  located on the top of the center stud  20 . The center stud  20  also has a first seal  45 , a second seal  46  and a third seal seal  48 . The seals  45 ,  46  and  48  may be in the form of O-rings residing in respective grooves  47 . A stud port  50  is located in the center stud  20  which can be a through hole. The stud ports  50  and  51  provides fluid access to center bores  111  and  113 , through an annulus which will be described additionally below with respect to  FIGS. 3, 4 and 5 . A biased spring  52  is located around the center stud  20 . The selector plate  24  with the selector rod  26  and selector knob  28  are shown. Attaching pins  54  fit within pin holes  56  located in the valve rotor  58 . The pins  54  also fit within pin holes (not shown) in the selector plate  24 . The selector plate  24  is rotationally locked to the valve rotor  58  via the pins  54  angular movement of the selector rod  26  via the selector knob  28  will cause the valve rotor  58  to rotate to various angular positions. 
         [0034]    The valve rotor  58  may be equipped with grooves  60  which provide a fluid pathway along the outer portion of the valve rotor  58 . The valve rotor  58  may also include one or more ports  62 . The exterior of the valve rotor  58  may have a tapered surface  64 . The valve rotor  58  fits within a hole  66  in the manifold  30 . The hole  66  may have a tapered inner surface  68  that is configured to correspond to the taper  64  of the valve rotor  58 . In some embodiments, when the valve rotor  58  is located in the manifold  30  the valve rotor  58  can be axially moved to a position so that the exterior taper  64  of the valve rotor  58  is fit to the tapered inner surface  68  in such a manner as to form a fluid tight connection. In this manner, hydraulic fluid at pressure located in the groove  60  may travel along the grooves  60  without leaking along the interface between the tapered inner surface  68  and the outer tapered surface  64  of the valve rotor  58 . Fluid flowing through the grooves  60  or port  62  may also flow through the port  71  and groove  72  located in the manifold  30 . 
         [0035]    The manifold  30  fits within the hole  74  is located in the valve body  12 . In some instances, the outer surface of the manifold  30  may also be tapered and a corresponding taper may be found in the hole  74  so that the manifold  30  can be pressed into the hole  74  to a location where the connection between the manifold  30  and the body  12  is a fluid tight connection. The body  12  may also define a hole  76  for the detent pin  44 . The detent pin  44  may include a spring  78 . The spring  78  biases the pin  44  to an outward position. When the detent pin  44  is depressed the spring  30  is compressed and when the detent pin  44  is released the spring  78  moves the detent pin  44  back to extended position. 
         [0036]    The body  12  may also define one or more ports  80 . The ports  80  may be associated with various accessories such as the modular port housing  32 . The port  80  may also have a face seal  82  surrounding the port  80  to provide a fluid tight connection with the port hole  98  in the modular valve port  34 . The port hole  98  provides fluid communication between the port  80  in the body  12  and the modular valve port  34  located within the modular valve port housing  32 . 
         [0037]    The modular valve port housing  32  shows the narrow rear portion  90  the wide front portion  86  and the taper  88  located on the modular valve port dovetail  36 . As discussed above, the tapered slot  92  has a narrow rear portion  94  and a wide front portion  96 . The narrow rear portion  94  and the wide front portion  96  are dimensioned so that as the modular valve port dovetail  36  tits into the modular port dovetail slot  38  the modular valve port dovetail  36  will slide part way through the slot  38  and then the taper will cause the modular valve port dovetail  36  to interfere with the modular valve port dovetail slot  38 . One of ordinary skill in the art after reviewing this disclosure will appreciate that the dimensions of the taper, the modular valve part dovetail  36  and the modular part dovetail slot  38  will be selected so that the modular valve port housing  32  will slide into the modular part port dovetail slot  38  and past the detent pin  44  allowing the detent dent pin  44  to extend outwardly thereby securing the modular valve port housing  32  within the modular valve port slot  38  with the constricting taper at one end and the detent pin  44  at the other end of the modular valve port housing  32 . 
         [0038]    The mounting base  14  is also shown with the mounting dovetail  18  having a taper  88 . The dovetail  18  has a wide front portion  86  and a narrow rear portion  90 . The mounting base  14  also contains holes  99  surrounded by face seals  84 . The holes  99  are configured to align with corresponding holes (not shown in  FIG. 2 ) in the valve body  12  or features located in the valve body  12 . In some embodiments, the taper  88  located on the mounting dovetail  18  corresponds with a taper in the mounting dovetail slot  16 . Optionally detent pins  44  may be provided on the dovetail slot  16 . The securing of the mounting dovetail  18  into the mounting dovetail slot  16  is done in a similar manner as discussed with respect to the modular valve port dovetail  36  and modular valve port dovetail slot  38  and detent pins  44 . 
         [0039]      FIG. 3  is a cross-sectional view of the hydraulic valve  10 . The center stud  20  with the attaching structure  22  are shown. The biased spring  52  is illustrated in a compressed condition. The seal  102  is located in the seal groove  100  and the seals  45 ,  46  and  48  are illustrated in their respective grooves  47 . The center stud  20  defines an interior center bore  113 . The interior center bore  113  is part of an interior fluid passageway  112  which includes the fluid passageways  109  in the rotor  58  and the passageway  130  in the mounting base  14 . The passageway  112  may include ports  50  and  62  passageways  109 , center bore  113  and passageway  130 . The connection between the mounting base  114  and the valve  110  may include a seal  84  around holes  99 . The selector plate  24  are shown connected to the selector rod  26 . Movement of the selector rod  26  can cause the rotor  58  to rotate in place and thereby misalign the fluid passageway  109  from passageway  112 . 
         [0040]    The modular valve port housing  32  is shown on the left-hand portion of  FIG. 3 . However it should be understood that a modular port housing  32  would may be present also on the right-hand side of the drawings  FIG. 3  however it has been removed in order to better show the port  110  in the body  12 . When the manifold  30  is suitably aligned, fluid can flow from the modular valve port housing  32  through the port  110  in the body  12  through the port  62  and passageway  112  into the valve rotor  58  into the interior bore  113  through hole  99  into the interior passageway  130 . 
         [0041]      FIGS. 4-9  illustrate how fluid flows through the hydraulic valve  10 . As seen in  FIG. 4 , fluid flows in the direction of arrow A through the modular valve port housing  32  via the modular valve port  34 . The fluid flows out of the modular valve port housing  32  in the direction of arrow B through ports hole  98  in the dovetail  36  of the modular valve port housing  32 . 
         [0042]      FIG. 5  is an exploded view of the modular valve port housing  32  and the valve body  12 . As fluid flows out of the port hole  98  in the modular valve port housing  32  in the direction of arrow B, it flows into the port  80  in the dovetail slot  38  in the valve body  12  into the axial hole  74  in the valve body  12  as illustrated by arrows C as shown in  FIG. 5 . 
         [0043]      FIG. 6  is an exploded view of the valve body  12  and the manifold  30 . The valve body  12  and the manifold  30  are not shown to scale with respect to each other but they do show the flow path along arrows C as the fluid flows through the axial hole  74  out of the valve body  12  and into the groove  72  of the manifold  30  and into the port  71  as shown by arrows C. Once the fluid flows through the port  71  and extends through the manifold  30  as shown by arrow D the fluid flows into the axial hole  66  in the manifold  30 . The port  71  will line up to a part of the valve rotor  58  (see  FIG. 7 ) when the valve is shifted to a position because these two lineup. The outer face  31  of the manifold  30  is tapered and fits into a corresponding tapered  75  axial hole  74  and the valve body  12  these two tapered surfaces  31  and  75  may be press fit together to form a seal and therefore is the valve body  12  and the manifold  30  do not rotate with respect to each other. 
         [0044]      FIG. 7  is an exploded view showing the valve rotor  58  and the manifold  30 . The manifold  30  is not shown in the same scale as the rotor  58  but are shown together to illustrates the flow path as illustrated by arrows D from the manifold  30  to the valve rotor  58 . The fluid flows out of the axial hole  66  in the manifold  30  and into the groove  60  in the valve rotor  58 . The fluid flows along the groove  60  in the direction of arrow E. The groove  60  may be lined up with the hole or port  71  in the manifold  30  due to the position of the valve rotor  58  as selected by an operator. As a result, depending upon the position of the valve rotor  58  as controlled by an operator the fluid may or may not flow along the flow path indicated by arrows D and E. For example, when the port  71  is not aligned with the groove  60  the fluid will not flow. 
         [0045]      FIG. 8  is an exploded view of the valve rotor  58  and the valve body  12 . The valve rotor  58  in the valve body  12  are not shown to scale with respect to each other but are both merely a list shown to illustrate the flow path of fluid from the valve rotor  58  to the valve body  12 . As the fluid flows along the groove  60  along the direction of arrows E, the fluid will flow into the valve body  12  and through a bottom port  114  in the valve body  12 . The fluid will then flow into the mounting base  14  and out of the base port  114  in the mounting base  14  shown in  FIG. 9 . 
         [0046]      FIG. 9  is an assembled view of the hydraulic valve  10 . Arrows G illustrate a flow path through the valve body  12  through the modular valve port  34  and ultimately through the base port  116  in the mounting base  14 . Arrows H show fluid flowing up through the base port  118  and into the valve body  12  via bottom body port  115  and ultimately out of the modular valve port  34 . While the exploded view of figures for through  7  illustrate the general flow path illustrated by arrows G in FIG. It will be apparent to one of ordinary skill the art after reviewing this disclosure that the general flow path shown in  FIG. 9  illustrated by arrows H is very similar (and may the same or a mirror image) to the flow path illustrated by arrows G in  FIG. 9 . As a result,  FIG. 9  will not be explained in full detail as it is merely an assembled view showing flow paths G and H as already explained above. The elements of  FIG. 9  have already been explained above and will not be repeated here. 
         [0047]      FIG. 10  is a partially disassembled view of the hydraulic valve  10  the modular valve port housing  32  shown to be aligned with but not yet inserted into the modular port dovetail slot  38  located on the valve body  12 . The modular valve port  34  can be seen to extend axially into the modular valve port housing  32 . The modular port dovetail  36  is seen along with the wide front portion  86  and the narrow rear portion  90 . The difference in the dimensions between the wide front portion  86  and the narrow rear portion  90  of the dovetail  36  illustrates the taper  88  in the dovetail  36 . The tapered slot  92  in the valve body  12  has a wide front portion  96  and a narrow rear portion  94 . The tapered slot  92  is dimensioned to correspond to the dovetail  36  and allow the modular valve housing  32  to move within the tapered slot  92  to a predetermined location. In some embodiments, it is preferred that the port hole  98  (best seen in  FIG. 2 ) in the modular valve port housing  32  aligns with the port  80  in the tapered slot  92 . The face seal  82  can be seen surrounding the port  80 . A second modular valve port housing  32  is shown to be located and mounted on the valve body  12 . 
         [0048]    The mounting dovetail slot  16  is shown which also has a wide front portion  96  the narrow rear portion  94  forming, a taper  92 . The bottom body ports  114  and  115  are seen. The face seals  84  are also shown. 
         [0049]    Both detent pins  44  are shown in the extended position but can be depressed to allow dovetail to move into the various dovetail slots and then moved to an extended position to lock whatever features located in the slot in position. 
         [0050]      FIG. 11  is a cross-sectional view of the valve rotor  58 .  FIG. 12  is a side view of the valve rotor  58  and  FIG. 13  is a an enlarged partial cross-sectional view of the valve rotor  58 . These three figures will be discussed together. The valve rotor  58  is generally conical in shape and includes a seal groove  100  near its top end. The valve rotor  58  includes a interior passage  123  which includes a larger diameter portion  124  and a second more narrow diameter bore  113 . Sizing the larger diameter bore  124  and the more narrow diameter bore  113  helps to cause the valve rotor  58  to be axially balanced when the high-pressure hydraulic fluid is flowing through, the valve rotor  58 . For example, the tapered outer surface  70  of the valve rotor  58  will tend to urge the valve rotor  58  in an upward direction as shown by arrows J in  FIG. 11 . To counteract this tendency, the larger diameter passage  124  and more narrow down or passage  113  are sized to create a hydraulically balanced valve rotor  58 . Hydraulic fluid flowing from the larger diameter  124  to the smaller diameter  113  passageways will cause a force the direction of arrows I. This sizing of the valve rotor  58  to relate difference in diameter of the larger diameter passage  124  and the more narrow passage  113  with the degree of taper of the outer surface  70  of the valve rotor  58  to cause the value rotor  58  to be neutrally balanced when there is pressured hydraulic fluid flowing the valve rotor  58  is referred to in this document as the Landrum relation. 
         [0051]    The ports  62  to provide entry to passageways  112  and into the interior passage  123 . The ports  62  are surrounded by a seal groove  104 . A port ridge  128  is located between the seal groove  104  and the port  62 . The seal groove  128  is content figured to flex outwardly toward the seal groove  104  when hydraulic fluid is flowing through the valve rotor  58 . 
         [0052]    The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.