Surgical instrument with discrete articulation

The invention generally relates to surgical instruments, and more specifically to the articulation of surgical instruments.

Minimally invasive surgery is performed through small incisions in the body, into which trocar ports may or may not be placed. One or more surgical instruments are inserted through each incision in order to perform the surgical procedure. In order to effectuate one of the objectives of minimally invasive surgery, which is the minimization of incisions to the body to reduce healing time and scarring, it is desirable to minimize the number of incisions made in the body. The number of incisions and their placement are determined by the particular surgical procedure to be performed and the configuration of the instruments used to carry out that procedure.

One problem encountering during the performance of a minimally invasive surgical procedure is access to the tissue to be treated. Depending on the specific anatomy of the patient, it may be difficult to reach an area to be treated with a specific surgical instrument. As a result, one or more additional incisions may need to be made in the patient in order to access that tissue. The surgeon may need to obtain a different surgical instrument, adding to the time and expense of the procedure. Additionally, where more incisions may be made or additional instruments may be utilized, it can be difficult and/or time-consuming for the surgeon to find the surgical site again.

FIG. 1 is a schematic view of a surgical tool.

FIG. 2 is a perspective view of an exemplary surgical tool.

FIG. 3 is a perspective view of the end effector of the exemplary surgical tool of FIG. 2 .

FIG. 4 is a perspective cutaway view of an articulation assembly located in the handle of the exemplary surgical tool of FIG. 2 , in a neutral configuration.

FIG. 5 is a perspective view of an articulation button of the articulation assembly of FIG. 4 .

FIG. 6 is an end view of the articulation button of FIG. 5 .

FIG. 7 is a perspective view of an articulation gear of the articulation assembly of FIG. 4 .

FIG. 8 is a side view of the articulation gear of FIG. 7 .

FIG. 9 is a perspective cutaway view of the articulation assembly of FIG. 4 .

FIG. 10 is a perspective cutaway view of the articulation assembly of FIG. 4 .

FIG. 11 is a perspective cutaway view of the articulation buttons and articulation gear during articulation through a first discrete angle.

FIG. 12 is a perspective cutaway view of the articulation buttons and articulation gear at completion of articulation through a first discrete angle

FIG. 13 is a perspective cutaway view of the articulation assembly at the limit of articulation.

FIG. 14 is a perspective view of a feeder belt to which staples are frangibly connected.

The use of the same reference symbols in different figures indicates similar or identical items.

U.S. Patent Application Publication No. 2009/0065552, published on Mar. 12, 2009 (the “Endocutter Document”), is hereby incorporated by reference herein in its entirety.

Referring to FIGS. 1-2 , an exemplary end effector 4 of a surgical tool 2 may include a staple holder 8 and an anvil 6 , where at least one of the staple holder 8 and the anvil 6 are rotatable and/or otherwise movable relative to one another. The staple holder 8 and anvil 6 need not be directly connected together in order to move relative to one another, as set forth in greater detail below. However, the staple holder 8 and the anvil 6 may be directly connected to one another in any suitable manner, if desired. The staple holder 8 and anvil 6 may be configured substantially as set forth in the Endocutter Document, as modified by the contents of this document. The staple holder 8 and anvil 6 may be fabricated from any suitable material or materials. As one example, both the staple holder 8 and anvil 6 may be fabricated from stainless steel. As another example, at least one of the staple holder 8 and anvil 6 may be fabricated at least in part from a ceramic material, to provide enhanced stiffness. As another example, the end effector 4 may be any other suitable item for treating or visualizing tissue, such as but not limited to at least one electrode (bipolar or otherwise), adhesive applicator, camera, ultrasound emitter, forceps, or other items. The end effector 4 may be connected to the distal end of a shaft 10 . The shaft 10 may be rigid along part or all of its length, and/or may include an articulating region 12 , such as described in U.S. patent application Ser. No. 12/400,760, filed on Mar. 9, 2009 (the “Articulation Document”), which is hereby incorporated by reference in its entirety. As another example, the shaft 10 may be proximally spaced apart from the end effector 4 , such that the articulating region 14 is connected to the end effector 4 and thereby spaces the shaft 10 apart from the end effector 4 .

The handle 12 may be attached to the proximal end of the shaft 10 , or any other suitable portion of the shaft 10 . The shaft 10 may be fabricated integrally with the handle 12 . Alternately, the shaft 10 and the handle 12 may be two separate items that are connected together in any suitable manner. The handle 12 may include any mechanism, mechanisms, structure or structures that are suitably configured to actuate the end effector 4 . The handle 12 may be actuated purely by hand, meaning that the handle 12 mechanically converts force applied thereto by hand to force utilized to actuate the end effector 4 . As another example, the handle 12 may include a source of stored energy for actuating the end effector 4 . The source of stored energy may be mechanical (such as a spring), electrical (such as a battery), pneumatic (such as a cylinder of pressurized gas) or any other suitable source of stored energy. The source of stored energy, its regulation, and its use in actuating the end effector 4 may be as described in the U.S. patent application Ser. No. 11/054,265, filed on Feb. 9, 2005, which is herein incorporated by reference in its entirety. The handle 12 may instead, or also, include a connector or connectors suitable for receiving stored energy from an external source, such as a hose connected to a hospital utility source of pressurized gas or of vacuum, or an electrical cord connectable to a power source.

Referring to FIGS. 3-4 , one or more articulation bands 16 extend proximally from the end effector 4 through the articulation region 14 and the shaft 10 to the handle 12 . The articulation bands 16 may be generally rectangular in cross section, where the bands 16 may be significantly greater in the height dimension than in the lateral dimension. In this way, the articulation bands 16 have a suitably low moment of inertia to allow lateral flexing of the articulation region 14 . Alternately, the articulation bands 16 may have any other suitable cross-section, and such cross-section need not be constant along the length of either articulation band 16 . Further, the articulation bands 16 may be composed of a material such as spring steel that allows the articulation bands 16 to provide resistance to compressive force. Each articulation band 16 may be fixed at or near its distal end to the end effector 4 by welding, adhesive, or any other suitable connection. Each articulation band 16 may extend to a different lateral side of the end effector 4 . Alternately, at least one articulation band 16 may be oriented relative to the end effector 4 .

A central core 18 may be located proximal to the end effector 4 . The central core 18 may be fixed to the end effector 4 , such as at or near the proximal end of the end effector 4 . As another example, the central core 18 may be compressed between the end effector 4 and the shaft 6 or a fitting in the shaft 6 proximal to the articulation region 14 . The central core 18 may extend into and/or completely through the articulation region 14 . Consequently, at least the portion of the central core 18 that is located in the articulation region 14 is flexible and/or bendable. As one example, at least the portion of the central core 18 located in the articulation region 14 may be composed of a flexible material, such as but not limited to silicone or elastomer. This flexible material may be resilient, meaning that it tends to return to a neutral state after deflection, or nonresilient, meaning that it tends to remain in a deflected state after deflection. As another example, at least the portion of the central core 18 located in the articulation region 14 may include a plurality of segments. As another example, the central core 18 may be the articulation insert described in U.S. patent application Ser. No. 12/436,087, filed on May 5, 2009 or U.S. patent application Ser. No. 12/477,065, filed on Jun. 2, 2009 (collectively referred to as the “Insert Documents”), both of which are herein incorporated by reference in their entirety. The central core 18 may include passages 20 defined generally longitudinally therein along which the articulation bands 16 are slidable. In this way, the passages 20 guide the articulation bands 16 , particularly as articulation begins.

Referring to FIGS. 2 and 4 , at least one articulation button 22 may be connected to the handle 12 . Each articulation button 22 may be held within a knob 24 . Optionally, the knob 24 may be fixed to the shaft 10 , and the shaft 10 may be rotatable relative to the handle 12 such that rotation of the knob 24 causes the shaft 10 , or at least the portion of the shaft 10 rigid and proximal to the articulation region 12 , to rotate about its longitudinal axis relative to the handle 12 . However, the knob 24 may be fixed relative to the handle 12 such that it does not rotate or move relative to the handle 12 . As another example, the knob 24 may be omitted altogether.

Referring also to FIGS. 5-6 , each articulation button 22 may include a depression surface 26 that a user may press, as described in greater detail below. The depression surface 26 may be the most proximal surface of the articulation button 22 , or may be any other suitable surface of the articulation button 22 . A compression spring 28 may extend from the distal end of the articulation button 22 , or from any other suitable portion of the articulation button 22 . At least one pushing arm 30 may extend from the articulation button 22 . Each pushing arm 30 may extend generally longitudinally, and flare inward near its distal end. As another example, at least one pushing arm 30 may be oriented or configured differently. At least one holding arm 32 may extend from the articulation button 22 . As one example, each holding arm 32 may extending generally transversely, and flare vertically near its distal end. As another example, at least one holding arm 32 may be oriented or configured differently. Two articulation buttons 22 may be utilized: a left articulation button 22 a and a right articulation button 22 b , where “left” and “right” are defined relative to the longitudinal centerline of the shaft 10 viewed from the proximal end toward the distal end. Alternately, only a single articulation button 22 may be utilized. Where two pushing arms 30 and two holding arms 32 extend from each articulation button 22 , optionally only one of each arm 30 , 32 may be used by each articulation button 20 to actually control articulation. By providing two arms 30 , 32 on each articulation button 20 , the same articulation button 20 can be flipped such that the same configuration of articulation button 20

Referring to FIGS. 4 and 7-8 , an articulation gear 40 is shown. The gear 40 may be generally circular in shape. The articulation gear 40 may include outer teeth 42 defined along at least a portion of its outer perimeter 44 . The gear 40 may include an upper surface 46 and a lower surface 48 . At least one upper tooth 50 may extend upward from the upper surface 46 . The upper teeth 50 may be organized into two separate arcs on the upper surface 46 . The outer arc may include the outer, upper teeth 50 a , and the inner arc may include the inner, upper teeth 50 b . As another example, the upper teeth 50 b may be omitted, and the upper teeth 50 a may be organized into a single arc on the upper surface 46 . The outer, upper teeth 50 a may be organized into an arc, where a neutral tooth 50 c occupies the center of the arc. The neutral tooth 50 c may have two substantially vertical lateral walls 52 . The upper surface 53 of the neutral tooth 50 c may be substantially horizontal. On each side of the neutral tooth 50 c , each outer, upper tooth 50 a may include a ramp surface 54 sloping upward and away from the neutral tooth 50 c . Each upper tooth 50 a may include a vertical wall 56 opposite the ramp surface 54 . The upper surface 58 of each upper tooth 50 a may be substantially horizontal. As another example, each upper tooth 50 a may be shaped in a different manner. The vertical wall 56 of each upper tooth 50 a , and an arbitrary line parallel to the upper surface 46 of the gear 40 lying on the ramp surface 54 of each upper tooth 50 a , may be substantially aligned with a radius of the gear 40 . Alternately, at least one upper tooth 50 a may be oriented differently on the upper surface 46 of the gear. The inner, upper teeth 50 b may be organized into an arc as well, where the neutral tooth 50 c is positioned further from the center of the gear 40 than the inner, upper teeth 50 b . On each side of the neutral tooth 50 c , each inner, upper tooth 50 b may include a ramp surface 60 sloping upward and away from the neutral tooth 50 c . Each inner, upper tooth 50 b may include a vertical wall 62 opposite the ramp surface 60 . The upper surface 64 of each upper tooth 50 a may be substantially horizontal. As another example, each inner, upper tooth 50 b may be shaped in a different manner. The vertical wall 56 of each upper tooth 50 a , and an arbitrary line parallel to the upper surface 46 of the gear 40 lying on the ramp surface 54 of each upper tooth 50 a , may be substantially angled relative to a radius of the gear 40 , and thus out of alignment with a radius of the gear 40 . Alternately, at least one upper tooth 50 a may be oriented differently on the upper surface 46 of the gear 40 .

A spindle 70 may extend substantially perpendicular to the gear 40 . The longitudinal centerline of the spindle 70 may extend through the center of the gear 40 . Alternately, the longitudinal centerline of the spindle 70 may be offset from the center of the gear 40 . The spindle 70 may include an upper spindle 72 that extends upward from the upper surface 46 of the gear 40 and a lower spindle 74 that extends downward from the lower surface 48 of the gear 40 . Referring also to FIG. 9 , the spindle 70 is received in at least one receiver 76 defined in the knob 24 . Advantageously, the upper spindle 72 and lower spindle 74 are each received in a separate receiver 76 in the knob 24 . The gear 40 may be passive, and may be biased to a neutral position by a torsion spring 78 . An anchor 80 may extend downward from the lower surface 48 of the gear 40 , spaced radially apart from the lower spindle 74 . The torsion spring 78 wraps around the spindle 70 and the anchor 80 , which are spaced apart from one another, such that the torsion spring 78 biases the gear 40 to a neutral position.

Spindle teeth 82 may extend radially outward from the spindle 70 . As one example, the spindle teeth 82 extend radially outward from the upper spindle 72 . As another example, the spindle teeth 82 may extend radially outward from any other portion of the spindle 70 . The spindle teeth 82 may be generally rectangular, or may have any other suitable shape. For example, the spindle teeth 82 may be spiral or cylindrical. The spindle teeth 82 may be oriented such that their longer dimension is substantially vertical and their shorter dimension is horizontal. However, the spindle teeth 82 may be oriented in any other suitable direction or directions. Referring also to FIG. 10 , apertures 84 may be defined through the articulation bands 16 , near the proximal ends thereof. The apertures 84 may be sized and shaped to receive the spindle teeth 82 therein. As described in greater detail, rotation of the gear 40 about the spindle 70 causes the spindle teeth 82 to rotate and thereby cause differential motion of the articulation bands 16 , urging one articulation band 16 proximally and the other articulation band 16 distally.

Referring also to FIG. 14 , a portion of at least one feeder belt 90 may extend from the shaft 10 into, or be positioned within, the end effector 4 . The feeder belt 90 and its associated hardware may be as set forth in U.S. patent application Ser. No. 11/851,379, filed Sep. 6, 2007; U.S. patent application Ser. No. 11/956,988, filed Dec. 14, 2007; and U.S. patent application Ser. No. 12/263,171, filed Oct. 31, 2008 (the “Endocutter Documents”), which are herein incorporated by reference in their entirety. In the interest of brevity, the feeder belt 90 will not be described in detail herein. Each feeder belt 90 may be a long, narrow, thin strip of material from which one or more staples 92 extend. At least one staple 90 may be integral with the feeder belt 90 , and frangibly connected to the feeder belt 90 at one end, with the other end of the staple being free. One row 94 of staples 92 may be located along each side of the feeder belt 90 . Each feeder belt 90 may be movable relative to the end effector 4 , as set forth in the Endocutter Applications, such that the end effector 4 can be actuated multiple times without the need to exchange cartridges or remove the end effector 4 from the patient between actuations. The end effector 4 may be configured generally as set forth in the Endocutter Documents, as one example, or may be configured differently.

Operation

The user possesses the surgical tool 2 . The end effector 4 is placed in the body in proximity to its desired location relative to tissue. Advantageously, the end effector 4 is advanced through a trocar port or other minimally-invasive opening into the body. Where the end effector 4 includes a staple holder 8 and anvil 6 , the end effector 4 may be opened such that at least the distal end of the anvil 6 is spaced apart from the staple holder 8 to allow tissue to be placed therebetween. However, the end effector 4 may be any other implement for treating tissue.

Referring also to FIG. 4 , in order to articulate the end effector 4 relative to the shaft 10 , the user actuates one of the articulation buttons 22 . For clarity, the articulation of the end effector 4 leftward is described here. Articulation “leftward” refers to motion of the end effector 4 generally to the left as viewed by the user from the proximal toward the distal direction. In order to articulate the end effector 4 leftward, the user actuates the right articulation button 22 b . The “right” articulation button 22 b is the one on the right as viewed by the user from the proximal toward the distal direction. Actuation of the right articulation button 22 b may be performed by pressing the right articulation button 22 b generally distally. This exertion of force on the right articulation button 22 b overcomes the bias exerted by the compression spring 28 against the right articulation button 22 b in the proximal direction.

Referring also to FIGS. 4-5, 7-8 and 10 , as the right articulation button 22 b advances distally relative to the knob 24 or other structure on the handle 12 , the pushing arms 30 and holding arms 32 fixed to the right articulation button 22 b advance distally as well. Referring also to FIG. 11 , as the lower pushing arm 30 advances, it encounters and engages an outer tooth 42 of the articulation gear 40 . Because the outer tooth 42 is laterally spaced from the spindle 70 , the force exerted by the lower pushing arm 30 on the outer tooth 42 in the distal direction creates a moment about the spindle 70 , causing the articulation gear 40 to rotate. As viewed from the underside of the articulation gear 40 in FIG. 11 , the articulation gear 40 rotates in a clockwise direction. Consequently, as viewed from above, the articulation gear 40 rotates in a counterclockwise direction. As the right articulation button 22 b continues its motion distally and the articulation gear 40 rotates, the outer, upper teeth 50 a of the articulation gear 40 rotate with the articulation gear 40 . Referring also to FIG. 12 , during this rotation, the lower holding arm 32 of the left articulation button 22 a slides up the ramp surface 54 of the outer, upper tooth 50 a that is immediately to the left of the neutral tooth 50 c , as viewed from the top. The lower holding arm 32 may flex as its distal end slides up the ramp surface 54 , such that it snaps downward toward and/or against the upper surface 46 of the articulation gear 40 after it slides past the ramp surface 54 and the upper surface 58 of the outer, upper tooth 50 a.

At such time, the right articulation button 22 b has been depressed distally a sufficient amount, and may be released. The right articulation button 22 b is urged proximally to its original position by the compression spring 28 . As the right articulation button 22 b moves proximally, the lower pushing arm 30 retracts out of engagement with the outer tooth 42 it had previously urged distally. However, the lower holding arm 32 of the left articulation button 22 a holds the articulation gear 40 in place. The torsion spring 78 biases the articulation gear 40 in a direction opposite to the direction in which the articulation gear 40 had been rotated, such that the vertical wall 56 of the outer, upper tooth 50 a adjacent to the tip of the lower holding arm 32 is biased against the lower holding arm 32 . In this way, the lower holding arm 32 of the left articulation button 22 a holds the articulation gear 40 in position.

During rotation of the articulation gear 40 as described above, the upper spindle 72 rotates with the articulation gear 40 , as do the spindle teeth 82 . The spindle teeth 82 engage apertures 84 of each articulation band 40 . Rotation of the articulation gear 40 and upper spindle 72 in the direction described above—counterclockwise as viewed from the top—thus causes the right articulation band 16 to advance distally, and the left articulation band 16 to retract proximally. The left articulation band 16 may be fixed to the left side of the end effector 4 , and the right articulation band 16 may be fixed to the right side of the end effector 4 . As a result, that distal force exerted on the right side of the end effector 4 by the right articulation band 16 , and the proximal force exerted on the left side of the end effector 4 by the left articulation band 16 , cause a moment that bends the articulation region 12 laterally leftward. Bending of the articulation region 10 relative to the shaft 6 to change the orientation of the end effector 4 is referred to as “articulating” the end effector 4 . In response to a complete depression and release of the right articulation button 22 b , the end effector 4 has thus articulated leftward in a discrete increment. That is, the angular spacing between the outer, upper teeth 50 a along the circumference of the articulation gear 40 defines increments in which the articulation gear 40 rotates, and in turn those increments of rotation are converted to increments of articulation of the end effector 4 . Put another way, each actuation of an articulation button 22 causes the end effector 4 to articulate a discrete and known amount.

If further articulation of the end effector 4 is desired, the user may actuate the right articulation button 22 b again. If so, the articulation gear 40 rotates as described above, and the end effector 4 articulates by another discrete amount, which may be the same as or different then the previous discrete amount. The end effector 4 may step through several discrete steps of articulation as a result of several depressions of the right articulation button 22 b . Referring also to FIG. 13 , the end effector 4 may continue to be articulated further leftward until the lower holding arm 32 of the left articulation button 22 a is holding the last outer, upper tooth 50 a . As one example, an additional actuation of the right articulation button 22 a simply results in no further articulation of the end effector 4 , because there is not another outer, upper tooth 50 a for the lower holding arm 32 to engage. As another example, depression of the left articulation button 22 a at this point (or at an earlier point in the articulation of the end effector 4 ) moves the lower holding arm 32 out of engagement with the outer, upper tooth 50 a that it had previously engaged, and places the distal end of the lower holding arm 32 at a location inward toward the spindle 70 such that the distal end of the lower holding arm 32 is located radially inward from each of the outer, upper teeth 50 a . As a result, the torsion spring 78 urges the articulation gear 40 back to its neutral position, and consequently the end effector 4 returns to its original, non-articulated position in which it is substantially longitudinally aligned with the shaft 10 .

As another example, where the articulation gear 40 includes a set of inner, upper teeth 50 b , the articulation gear 40 steps in reverse toward the neutral position upon depression of the left articulation button 22 a . Referring also to FIGS. 4, 7 and 10 , as the left articulation button 22 a is depressed, the distal end of the lower holding arm 32 moves inward toward the spindle 70 , out of engagement with the outer, upper tooth 50 a it had previously engaged and held. As a result, the torsion spring 78 urges the articulation gear 40 back toward its neutral position. However, the distal end of the lower holding arm 32 encounters an inner, upper tooth 50 b as the articulation gear 40 moves toward that neutral position. The angular force exerted by the torsion spring 78 may then hold the inner, upper tooth 50 b against the lower holding arm 32 , such that the articulation gear 40 rotates a discrete increment less than the discrete increments that it rotated during the previous articulation of the end effector 4 leftward. Consequently, the end effector 4 articulates rightward by a discrete angle that is less than the discrete angles through which it had articulated leftward. Alternately, the inner, upper tooth 50 b simply arrests the motion of the articulation gear 40 , and the lower holding arm 32 then slides proximally into engagement with the next outer, upper tooth 50 a . In this way, the articulation gear 40 rotates a discrete increment the same as the discrete increments in which it had rotated previously, and the end effector 4 articulates rightward by a discrete angle substantially the same as the discrete angles through which it had rotated during the previous articulation of the end effector 4 leftward.

For conciseness and clarity, articulation of the end effector 4 in the left direction using the right articulation button 22 b has been described above. Articulation of the end effector 4 in the right direction, using the left articulation button 22 a , is performed substantially as set forth above, in a reversed, mirror-image manner. Optionally, the shaft 10 may be rotatable relative to the handle 12 , as set forth in commonly-assigned U.S. Pat. No. 7,918,376, which is herein incorporated by reference in its entirety. In this manner, the end effector 4 can be rotated as well as articulated left and right, in order to place the end effector 4 in a desired position within a patient.

As another example, a single articulation button 22 may be provided, rather than the two articulation buttons 22 a , 22 b described above. If so, the neutral position of the articulation gear 40 is a rotation all the way to one side, such that the end effector 4 is fully articulated laterally in the neutral position. The end effector 4 then may be articulated in discrete increments from that neutral position, utilizing only a single articulation button 22 .

Once the end effector 4 is in the desired position, the end effector 4 may be manipulated in any manner. As one example, the end effector 4 may be closed if it is open, such as by moving the anvil 32 toward the staple holder 30 to clamp tissue. The end effector 4 then may be actuated to treat tissue. As one example, where the surgical tool 2 includes one or more feeder belts 90 , staples 92 may be deployed into tissue from the staple holder 6 against the anvil 4 . The feeder belt or belts 90 then may be advanced, placing a fresh set of staples 92 in position for deployment within the staple holder 6 . Such deployment and advancement may be accomplished as set forth in the Endocutter Documents. Afterwards, the end effector 4 may be reoriented in the manner described above, articulating the end effector 4 in a different direction, so the end effector 4 may treat tissue again. Alternately, the end effector 4 is simply withdrawn from the patient after the first tissue treatment.

The operation of the surgical tool 2 may be carried out in the course of testing at a factory or other location. If so, the user that possesses the surgical tool 2 may be a technician, machine or text fixture that exercises the surgical tool 2 in the course of testing. The term “tissue,” in the context of testing the surgical tool 2 only, includes any substance or material used as a substitute for tissue in the course of testing.

While the invention has been described in detail, it will be apparent to one skilled in the art that various changes and modifications can be made and equivalents employed, without departing from the present invention. It is to be understood that the invention is not limited to the details of construction, the arrangements of components, and/or the method set forth in the above description or illustrated in the drawings. The use of terms such as “upward” and “downward” in this document refers to the orientation of parts on the page for descriptive clarity, and in no way limits the orientation of the device in use. Statements in the abstract of this document, and any summary statements in this document, are merely exemplary; they are not, and cannot be interpreted as, limiting the scope of the claims. Further, the figures are merely exemplary and not limiting. Topical headings and subheadings are for the convenience of the reader only. They should not and cannot be construed to have any substantive significance, meaning or interpretation, and should not and cannot be deemed to indicate that all of the information relating to any particular topic is to be found under or limited to any particular heading or subheading. Therefore, the invention is not to be restricted or limited except in accordance with the following claims and their legal equivalents.