BACKGROUND

The Field of the Invention

[00Θ1] Implementations described herein relate generally to a rotary fluid-displacement assembly, and more particularly to a rotary fluid-displacement assembly having at least one vane that is configured to mount therein a housing and move in relation to a cam slot such that the distal end of the vane can be maintained at a substantially constant distance from a central longitudinal axis of the housing.

Background

[0002] Various vane-type fluid displacement apparatus have been proposed for use in applications such as pumps, compressors, fluid driven motors, and fluid flow meters. Such apparatus have generally performed satisfactorily and have gained acceptance for specific liquid applications. Conventionally, a vane or vane compressor can include a cam ring, a rotor rotatably positioned within the cam ring and having an axial vane slits formed therein; a plurality of vanes slidabiy positioned in the axial vane slit; a drive shaft operatively associated with the rotor; a front side block fixed to a front-side end face of the cam ring; a rear side block fixed to a rear-side end face of the cam ring; a front head secured to a front- side end face of the front side block; and a rear head secured to a rear-side end face of the rear side block. The drive shaft for rotating the rotor can have its opposing ends rotatably supported by radial bearings arranged in the front and rear side blocks, respectively.

Typically, a discharge chamber can be defined by at least a portion of each of an inner wall surface of the front head, the front-side end face of the front side block, and the front-side end face of the cam ring. In operation, the discharge chamber is configured to receive a liquid or gas delivered from at least one compression chamber 102,

[0003J However, prior art vane-type fluid displacement apparatus do present shortcomings that limit their use in other applications. Such shortcomings can include an unsuitability for use with friction-reducing devices limiting their use to applications with moderate power levels; a large fixed-surface to moving-surface contact ratio resulting in high friction; an inability to withstand bending forces applied to the crankshaft; a reliance on discrete cheek valves and similar devices; and an inability to accommodate simultaneous reciprocating flow from a plurality of individual chambers. [0004] The slidable radial vane can also limit performance of the apparatus when it becomes worn. Typically, the slidable radial vane can be fnctionally engaged not only with the cam ring, but also with side surfaces defining the axial vane slit in the rotor. In operation, a spring operably associated with a vane can apply a biasing force and a back pressure can act on the trailing surface of the vane. Thus, the radial inner end of the slidable radial vane can be constantly held in frictional engagement with the cam ring while the opposing side surfaces of the vane can be held in frictional engagement with the corresponding opposing side surfaces of the axial vane slit by a pressure difference existing between the compression and discharge chambers.

[0ΘΘ5] in conventional vane pumps, as speed of the pump increases, the centripetal force acting on the vanes can aggressively urge them against the peripheral surface of the rotor. This can provide a solid sealing force, however, such action can also create high frictional forces between the distal end of the vane and the inner surface of the housing. Thus, relatively high speeds can increase frictional wear as well as reduce the operating efficiency of the compressor.

[0006] Accordingly, a need exists for a rotary fluid-displacement assembly that reduces frictional forces within its articulated rotary assemblies as well as produces less noise and vibration during operation. Additionally, the fluid-displacement assembly should be assembled, operated, and maintained efficiently and cost effectively.

SUMMARY

[0007] it is to be understood that this summary is not an extensive overview of the disclosure. This summary is exemplary and not restrictive, and it is intended to neither identify key or critical elements of the disclosure nor delineate the scope thereof. The sole purpose of this summary is to explain and exemplify certain concepts of the disclosure as an introduction to the following complete and extensive detailed description.

[0008] In various aspects of the present invention, a constrained vane rotary assembly can comprise a housing, a rotor, a fixed cam, and at least one vane, In one aspect, a housing having a longitudinal axis, a first end plate and a second end plate can define an internal cavity. A rotor having a rotor axis of rotation that is eccentric to the housing longitudinal axis, a peripheral surface and at least one axial vane slit formed in the rotor can be positioned within the housing and rotatably supported by the first end plate and the second end plate of the housing. A fixed cam can be positioned within the housing about a cam axis and can be configured to selectively engage portions of the vane to effect axial movement of the vane from a first axial position to a second axial position relative to the peripheral surface of the rotor about a full rotation thereof.

[0009] Additional features and advantages of exemplary implementations of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of such exemplary implementations. The features and advantages of such implementations may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of such exemplary implementations as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[001Θ] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate aspects and together with the description, serve to explain the principles of the methods and systems.

[0011] Figure 1 illustrates an exploded view of a rotary fluid displacement device incorporating constrained vanes.

[0012] Figure 2 illustrates a detailed view of a vane, or vane, with a guide pin,

[0013] Figure 3 illustrates a cross-sectional view showing the rotor and vanes in a first point in their rotation.

[0014] Figure 4 illustrates a cross-sectional view showing the rotor and vanes in a second point in their rotation.

[0015] Figure 5 illustrates a detailed view of the cam carrier and fixed cam operatively coupled to the housing,

[0016] Figure 6 illustrates a detailed view of the cam carrier and fixed cam of Fig. 5, [0017] Figure 7 illustrates alternative cam profile slot geometries 7a, 7b, and 7c. DETAILED DESCRIPTION

[0018] The present invention can be understood more readily by reference to the following detailed description, examples, drawing, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0019] The following description of the invention is provided as an enabling teaching of the invention in its best, currently known aspect. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results described herein. It will also be apparent that some of the desired benefits described herein can be obtained by selecting some of the features described herein without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part described herein. Thus, the following description is provided as illustrative of the principles described herein and not in limitation thereof.

[0020] Reference will be made to the drawings to describe various aspects of one or more implementations of the invention. It is to be understood that the drawings are diagrammatic and schematic representations of one or more implementations, and are not limiting of the present disclosure. Moreover, while various drawings are provided at a scale that is considered functional for one or more implementations, the drawings are not necessarily drawn to scale for all contemplated implementations. The drawings thus represent an exemplary scale, but no inference should be drawn from the drawings as to any required scale.

[0021] In the following description, numerous specific details are set forth in order to provide a thorough understanding described herein. It will be obvious, however, to one skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known aspects of rotary vane devices have not been described in particular detail in order to avoid unnecessarily obscuring aspects of the disclosed implementations. [0022] As used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise, Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0023] "Optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0024] Throughout the description and claims of this specification, the word "comprise" and variations of the word, such as "comprising" and "comprises," means "including but not limited to," and is not intended to exclude, for example, other additives, components, integers or steps, "Exemplary" means "an example of and is not intended to convey an indication of a preferred or ideal aspect. "Such as" is not used in a restrictive sense, but for explanatory purposes.

[0025] As used throughout the description and claims of this specification, the word "fluid" means matter in any state other than solid, for example and without limitation, liquids, gases, slurries, vapors and the like as well as matter comprising a plurality of states.

[ΘΘ26] Disclosed are components that can be used to perform the disclosed methods and systems. These and other components are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these components are disclosed that while specific reference of each various individual and collective combinations and permutation of these may not be explicitly disclosed, each is specifically contemplated and described herein, for all methods and systems. This applies to all aspects of this application including, but not limited to, steps in disclosed methods. Thus, if there are a variety of additional steps that can be perdefined it is understood that each of these additional steps can be perdefmed with any specific aspect or combination of aspects of the disclosed methods.

[0027] Implementations described herein are directed toward rotary fluid-displacement assemblies operable to reduce frictional forces within articulated rotary assemblies, Also, such rotary fluid-displacement assemblies can be configured to produce less noise and vibration during operation. In various aspects, rotary fluid-displacement assemblies can be provided that more efficiently compress a fluid for a given energy input and do so with lighter construction and improved output per cubic inch of overall size relative to conventional rotary fluid-displacement assemblies. In various other aspects, such rotary fluid-displacement assemblies need not rely on fixed cycle phases, friction-inducing eccentric shafts, problematic compression chamber 102 shapes, and need not rely on exotic materials to accomplish its operational goals.

[0028] In one or more aspects, rotary fluid-displacement assembly comprises a housing having a longitudinal axis and a rotor positioned within the internal cavity formed by the housing, The rotor can have an axial vane slits formed therein and can be configured to rotate about a rotor axis of rotation that is eccentric to the housing longitudinal axis. Each vane slit of the rotor can be operatively associated with a vane configured to move radially from a first position, where the distal end of the vane lies a first distance from the surface of the rotor, to a second position, where the distal end of the vane lies a second distance from the surface of the rotor. The distal end of each vane can be constrained to be spaced fractionally from the inner wall surface of the housing as the rotor rotates about its axis of rotation, thereby reducing frictional losses and improving performance.

[0029] Reference will now be made to the drawings to describe various aspects of one or more implementations of the invention. It is to be understood that the drawings are diagrammatic and schematic representations of one or more implementations, and are not limiting of the present disclosure. Moreover, while various drawings are provided at a scale that is considered functional for one or more implementations, the drawings are not necessarily drawn to scale for all contemplated implementations. The drawings thus represent an exemplary scale, but no inference should be drawn from the drawings as to any required scale.

[0030] In the following description, numerous specific details are set forth in order to provide a thorough understanding described herein. It will be obvious, however, to one skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known aspects of rotary vane devices have not been described in particular detail in order to avoid unnecessarily obscuring aspects of the disclosed implementations. [0Θ3Ι] Turning now to Figures 1-7, an implementation of one exemplary aspect of a drill string component storage, handling, and positioning system for drill string components is illustrated.

[0032] It can be contemplated that the rotary fluid-displacement assembly described according to various aspects herein can function as a compressor, a pump, a flow meter, an expander, a hydraulic motor, a fluid motor and/or an engine, in various other aspects, for example and without limitation, the fluid-displacement assembly described herein cam comprise at least a portion of a compressor for pressurized fluid flow, a vacuum pump, a refrigeration assembly, a fluid power assembly, an expander for high pressure fluids, a flow meter, an internal combustion engine and the like. Generally, for clarity, the rotary fluid- displacement assembly can be described herein as a rotary compressor, but it can be of course contemplated, as one skilled in the art will appreciate, that the fluid-displacement assembly can function in a variety of applications such as described above. No limitation can be intended by the discussion of the rotary fluid-displacement assembly as a "rotary

compressor," rather describing the rotary fluid-displacement assembly as a compressor allows for the full appreciation of the fluid-displacement assembly by one skilled in the art.

[0033] According to one aspect, a rotary compressor can be provided that comprises a housing, a rotor, and at least one vane. An exemplary rotary compressor is illustrated in Figure 1. The housing 110, in one aspect, defines an internal cavity having an inner wall surface (both covered by endplate 151 in Figures 1, 3 and 4), The housing 110 further has a longitudinal axis that extends transverse to a housing plane that bisects the inner wall surface. The rotor 150, in one aspect, has a peripheral surface 152 and can be positioned within the internal cavity of the housing. The rotor can be configured to rotate about a rotor axis of rotation. According to a particular aspect, the rotor axis of rotation can be eccentric to the housing longitudinal axis, such as illustrated in Figures 3 and 4. The vane 160a, in one aspect, has a distal end 161 and can be configured to siidably mount with the rotor. The vane 160a can be movable axialiy about and between a first position, in which the distal end 161 of the vane can be positioned at a first distance from the peripheral surface 152 of the rotor, and a second position, in which the distal end of the vane can be positioned at a second distance from the peripheral surface of the rotor. According to a further aspect, the distal end of the vane 160a can be constrained to be spaced proximate from the inner wail surface of the housing as the rotor rotates about the rotor axis of rotation. [0034] According to yet another aspect, at least portions of the peripheral surface 152 of the rotor, portions of the inner wall surface of the housing, and varying portions of the vane 160a proximate the distal end of the vane can define a compression chamber 102 of varying volume as the rotor rotates about the rotor axis of rotation, At least portions of the peripheral surface 152 of the rotor, portions of the inner wall surface of the housing, and varying portions of the vane 160a proximate the distal end of the vane can also define a suction chamber 104. As shown in Figures 3 and 4, as the rotor can be rotated in a counter-clockwise direction, the suction chamber volume behind the vane increases, while the compression chamber volume decreases.

[0035] An exemplary rotor 150 can be illustrated in cross-section in Figures 3 and 4. In one aspect, the rotor has a first side surface 153 and an opposed second side surface 154. The rotor, in certain aspects, can be generally cylindrical in shape; however, other geometries are contemplated, such as can be chosen to alter the volumetric flow of fluid within the rotary compressor. The rotary compressor can comprise a pair of end plates 151a, 151b that are mounted to and rotate therewith the respective first and second side surfaces of the rotor 153 and 154, respectively. The housing 110, in one aspect, has a front surface 111 and an opposed back surface 112. In one aspect, portions of a first end plate 151a of the pair of end plates sealingly and slidabiy contact portions of the front surface of the housing. Similarly, portions of a second end plate 151b of the pair of end plates sealingly and slidabiy contact portions of the back surface of the housing.

[0036] In some aspects of the disclosure the rotary compressor can comprise a fixed cam 35 such as shown in Figures 1 and 3-6. The cam can be positioned in the internal cavity of the housing 110 about a cam axis, and can be configured to selectively engage portions of the vane 160a to effect the axial movement of the vane about and between the first position, in which the distal end 161 of the vane 160 can be positioned at a first distance from the peripheral surface 152 of the rotor 150, and the second position, in which the distal end of the vane can be positioned at a second distance from the peripheral surface of the rotor. The rotor 150 can also be configured to act on select portions of the vane 160 to effect the constrained axial movement of the vane 160 relative to the peripheral surface of the rotor. The cam 35, in some aspects, can be positioned along a shaft. In other aspects, the cam can be fixed to a cam carrier 500 such as shown in Figure 6. [0037] In some aspects, the vane 160 can be provided with a guide pin 161 as shown in Figure 2, said guide pin riding in a fixed cam profile slot 30 shown in Figures 1 and 3-6. in these iterations, fixed cam profile slot 30 serves to position vane 160 as the rotor moves about its axis of rotation, and as the guide pin of the vane follows the profile of fixed cam profile slot 30 and thus the vane 160 can be positioned at a first distance from the peripheral surface 152 of the rotor, and the second position, in which the distal end of the vane can be positioned at a second distance from the peripheral surface 152 of the rotor 150. In this manner, in some aspects, the distal end of the vane 160 can be placed at a chosen distance from the peripheral surface 152 of the rotor at any operational position of the rotor as it rotates about its axis of rotation. In some aspects of the disclosure, the frictional and wear issues typically associated with conventional vane machines ca be advantageously reduced or eliminated through the constraining of the position of the vane with respect to the inner surface of the housing.

[0038] As one skilled in the art will appreciate, in this aspect, the distal end of the vane can be constrained within a desired tolerance of the inner wall surface of the housing as a result of the guide pin riding in the fixed cam profile. In effect, the path the distal end of the van follows as it completes a 360 degree rotation is not constant and will vary directly as a result of the fixed cam profile. This beneficially allows for the use of a compression chamber that does not have a uniform radius, but rather has a shape and size that complementarity fits the governed path profile of the distal end of vane (as governed by the fixed cam profile),

[0039] In some aspects, the aforementioned assembly can be inverted in that the cam profile slot 30 can be provided in a carrier that supports one or more vanes 160a. 160b and the guide pin 161 can be fixed to housing 110.

[0040} An exemplary fixed cam 35 can be shown in Figures 3 and 4. In some aspects, the fixed cam profile slot 30 can be provided in one face of the cam 35 such that it receives a guide pin 161 provided as part of the sub-assembly of vane 160. In other aspects, guide pin 161 can be formed as part of vane 160 rather than as a separate component that can be later assembled to the vane.

[0041] In some aspects of the disclosure, there are guide pins 161 at more than one location in vane 160 to provide the desired level of constraint during operation. It is further contemplated that a second guide pin can be provided on the opposite face of the vane such that the vane can be constrained on both lateral ends, said second guide pin being received by a second fixed cam profile provided in a second fixed cam in the total assembly.

[0Θ42] According to one aspect, it can be contemplated that the cam 35 can be fixed from rotation with respect to the housing 1 10 through a chosen attachment method without the use of a cam carrier 500. In yet another aspect, the guide pin 161 can comprise a bearing such that the frictionai forces between the cam 35 and the vane 160 can be reduced, such as through the use of a bushing, roller bearing, needle bearing, or similar low-friction device known to those skilled in the art, in further aspects, it can be contemplated that the cam 35 can be rotated with respect to the housing 110 to affect the desired positioning of the vane 160 or vanes as they rotate about the rotor axis of rotation. In some aspects the rotation, or phasing, of a moveable cam can be used such that compression or suction performance can be heightened or reduced as chosen, such as can be the case when a refrigerant compressor needs to be unloaded. The positional rotation of the cam 35 can be effected through means known to those skilled in the art, such as belts, gears, chain drives, linkages, and other similar means,

[0043] As described above, in one aspect, the vane 160 can be slidably mounted with the rotor 150 and can be movable axiaiiy about and between the first position, in which the distal end 161 of the vane 160 can be positioned at a first distance from the peripheral surface 152 of the rotor, and the second position, in which the distal end of the vane can be positioned at a second distance from the peripheral surface of the rotor. In one aspect, the first distance can be greater than the second distance. The second distance can be proximal to the peripheral surface 152 of the rotor in one aspect. In another aspect, in the second position, the distal end of the vane can be at or below the peripheral surface of the rotor.

[0044] The distal end 161 of the vane 160 can be constrained to be spaced proximate from the inner wall surface of the housing 110 as the rotor 150 rotates about the rotor axis of rotation. In one aspect, the distal end 161 of the vane can be constrained to be proximate from the inner wall surface of the housing in a constrained range of between about 0.0001 inches to about 0.2000 inches. Optionally, the distal end 161 of the vane can be constrained to be spaced proximate from the inner wall surface of the housing in a constrained range of between about 0.0003 inches to about 0.1500 inches. In yet another aspect, the distal end of the vane can be constrained to be spaced proximate from the inner wall surface of the housing in a constrained range of between about 0.0005 inches to about 0.1000 inches. [0045] In some aspects portions of the peripheral surface 152 of the rotor, portions of the inner wail surface of the housing, and varying portions of the vane 160 proximate the distal end of the vane define the suction chamber 104 and the compression chamber 102, each of varying volume as the rotor rotates about the rotor axis of rotation. It is contemplated that one or more inlet ports in fluid communication with the suction and/or compression chamber can be provided in one or more of the rotor 150, vane 160, housing 0, first end plate ISia and/or second end plate 51b, or other component(s) of the rotary compressor. Similarly, one or more outlet ports can be provided in one or more of the rotor, vane, housing, first and/or second end plates, or other component(s) of the rotary compressor.

[0046] Optionally, in various aspects, the rotary compressor can comprise a rotor 150 having a peripheral surface 152 and a rotor axis, and a housing 110 defining an internal cavity having an inner wail surface. In this aspect, the housing can be configured to rotate about a housing longitudinal axis that is eccentric to the rotor axis. The rotor 150 can be positioned within the internal cavity of the housing, A vane 160, such as described herein, can be siidably mounted therewith the rotor and movable axiaiSy about and between a first position, in which the distal end of the vane can be positioned at a first distance from the peripheral surface 152 of the rotor, and a second position, in which the distal end of the vane can be positioned at a second distance from the peripheral surface of the rotor. In this aspect, first and second end plates can be provided and can be fixedly attached or mounted thereto the rotor. Thus, the rotor and the end plates can be held or maintained in a stationary position as the housing rotates about the housing longitudinal axis. Such a rotary compressor can be used for example, as a compressor, pump, expander, or any combination thereof.

[0047] It can be contemplated, according to various aspects, that the shape of the fixed cam profile slot 30 can be chosen such that the vane 160, which can be constrained within the rotor 150 by the rotor bore, has a radial position defined by the contact points between the guide pin 161 and the fixed cam profile slot 30 and the mating contact points on the at least one bearing surface of the vane 160. As one skilled in the art will appreciate, the rotor rotates about the rotor axis of rotation, the circumferential path of the vane can be defined by the center of rotation of the rotor, and the radial distension of the vane can be fixed by the geometry of the fixed cam profile slot 30. In this way, the distal end 161 of the vane 160 can be constrained to be spaced proximate from the inner wall surface of the housing 110, and can be constrained from pressing with excessive or erratic force against the inner wail surface of the housing. [0048] In one aspect, the fixed cam profile slot 30 can be designed such that the distal end 161 of the vane 160 can be maintained at a spaced distance proximate from the inner wall surface of the housing 110. In one aspect, the distal end of the vane can be constrained to be spaced proximate from the inner wall surface of the housing in a constrained range of between about 0.0001 inches to about 0.2000 inches, in a constrained range of between about 0,0003 inches to about 0.1500 inches, or in a constrained range of between about 0.0005 inches to about 0.1000 inches. In another aspect, the distal end of the vane can be constrained to be spaced proximate from the inner wall surface of the housing in a constrained range of between 0.01% and 15.00/o of the operative diameter of the housing inner surface at any operational position of the rotor as it rotates about its axis of rotation.

[0049] In this manner, wear and contact friction between the vane 60 and the inner wall surface of the housing can be minimized or eliminated. In some aspects of the disclosure, sealing between the distal end of the vane and the inner wail surface of the housing (and/or the inner surfaces of the first and second end plates) can be accomplished by close running clearances achieved through exact machining and assembly tolerances, thereby creating a non-contact sealing function and thus reducing friction and wear.

[0050] In some aspects it is contemplated that the shape of the internal cavity of the housing can be selected to complement the shape of the fixed cam profile slot, and vice versa, such that the distal end of the vane can be constrained to be spaced proximate from the inner wall surface of the housing as the rotor rotates about the rotor axis of rotation. Various alternative cam profile slots are illustrated in Figure 5.

[0051] According to various other aspects, the rotary compressor can comprise vane assemblies incorporating one or more vanes and/or comprising one or more end portions configured to be spaced proximate from the inner wall surface of the housing. For example, as illustrated in Figures 1 and 3, the rotary compressor comprises two vanes 160a and 160b. In certain aspects, each vane can have a distal end and an opposed proximal end. Each vane can be movable axialiy therein the rotor slot about and between a first position in which the distal end of the dual-end vane is positioned at a first distance from the peripheral surface 152 of the rotor 150, and a second position in which the distal end of the dual-end vane is positioned at a second distance from the peripheral surface of the rotor. It is contemplated that, in the first position, the proximal end of the one vane 160 under consideration is positioned at substantially the second distance from the peripheral surface of the rotor, and in the second position, the proximal end of the aforementioned vane is positioned at substantially the first distance from the peripheral surface 152 of the rotor, and concurrently similar positional restraints are imposed on alternate vanes within the assembly. Each of the distal end and proximal end of each vane can be constrained to be spaced proximate from the inner wall surface of the housing as the rotor rotates about the rotor axis of rotation,

[0052] Accordingly, Figures 1-6, and the corresponding text, provide a number of different components and mechanisms for handling, coupling and recovery of drill string components. In addition to the foregoing, implementations described herein can also be described in terms acts and steps in a method for accomplishing a particular result. For example, a method comprising at least one of handling, coupling and recovering a drill string component is described concurrently above with reference to the components and diagrams of Figures 1 through 6.

[0053] The present invention can thus be embodied in other specific forms without departing from its spirit or essential characteristics. The described aspects are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.