Patent Application
20110173786
1. Field of the Invention
This invention relates, in general, to cutting analytical instrument tubing and more particularly to cutting apparatus and methods for their use.
2. Description of Related Art
There exist a number of different types of analytical instruments that utilize tubing for transporting, filtering, and separating analytes. Some of these instruments include and are not limited to ion chromatographs, mass spectrometry systems, gas chromatography systems, high performance liquid chromatography (HPLC) systems, and others. The types of tubing employed with each of these systems can differ slightly based on composition, internal diameter, thickness and flexibility. The tubing used for these instruments needs to be periodically replaced and is typically cut from a longer stand of tubing to provide an appropriate length. A difficulty is that the operation of these instruments can be affected by the quality of the cut.
Over time and with use, most tubing materials break down and need to be repaired. After the tubing breaks, begins to leak or wear, it can often take some time for a technician to replace or repair. This loss of production time can be costly to scientists who need to run large sample lots quickly or conduct drug screening tests that require high throughput. Therefore, various tubing has been developed that can be cut at differing lengths or sizes as appropriate for the application. Common methods and techniques for cutting tubing include manual and automated devices such a cutting device with a spinning blade to score or make a partial cut into the tubing. The extra portion or segment of tubing is then snapped-off at the score or partial cut.
A problem with this technique is that it can result in defects on the cut end, which is the cross-sectional surface formed at the end of the tube when the tube is cut and the extra segment of tubing is snapped-off. Defects include structural and physical changes in the tubing on the cross-sectional surface of the cut end, lumen surface adjacent to the cut end, or outer tubular surface adjacent to the cut end. Such defects can be observed with the naked eye or with the use of an instrument. Examples of defects include, but are not limited to, flaws, burrs, cuts, frays, cracks, chips, nicks, blemishes, gauges, artifacts, extra tubing material, stretch marks or lines, compromised materials, peaks or valleys, and varying levels of surface area height or width, whether such defects are visible to the naked eye or only with the aid of instrumentation. Defects also can include snap lines, which are lines, ridges, or other defects running across at least a portion of the surface of the cut end. Although snap lines commonly result from snapping off the extra segment of tubing at the site of a partial cut, they also can result from other processes and techniques.
A related problem is that such defects in analytical instrument tubes can cause zero void volumes, which are empty volumes at the point where the tube is connected to the instrument with ferrules or other structures. Zero void volumes can negatively impact the performance of instrumentation such as chromatography equipment by affecting fluid flow and the retention time of fluids. For chromatography, the defects can affect the position, shape, width, and height of chromatography peaks. Defects also can negatively affect the performance of other instrumentation in addition to chromatography.
In addition, imperfectly cut or finished tubing under high pressure will quickly magnify leaks, loss of sample, or even cause instrument failure. Yet another problem with existing cutting tools is that they can be quite large, unwieldy, or difficult to use.
In general terms, this patent document relates to an apparatus and method for cutting tubing used with analytical instruments.
One aspect is an apparatus for cutting analytical instrument tubing. The apparatus comprises a blade for cutting a tube. A clamp assembly is configured to securely hold at least a portion of the tube. The clamp assembly is movable between a first position to hold the tube in a first cutting location relative to the blade and a second position to hold the tube in a second cutting position relative to the blade. A tube advancement mechanism is operably connected to the clamp assembly.
Another aspect is a method for cutting an analytical instrument tube having a first cross section and a second cross section proximal to the first cross section. The method comprises positioning the tube in a first cutting position relative to a cutting edge of a blade; at least partially cutting the tube across the first cross section to form a first cut surface; advancing the tube to a second cutting position relative to the cutting edge of the blade; and cutting the tube across the second cross section of the tube to form a second cut surface, the second cut surface having fewer imperfections than the first cut surface.
Various embodiments will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the appended claims.
Within this patent document, the conjunction “or” connotes “and/or” unless stated otherwise or the use of the conjunction “and/or” is clearly inappropriate. The indefinite articles “a” and “an” connotes “one or more” unless stated otherwise or where the use of “one or more” is clearly inappropriate. Additionally, qualifiers such as “about” and “substantially” connotes physical structures, physical relationships, and values for given measurements, parameters, ranges, and the like, can vary due to differences in manufacture tolerances and conditions of use.
A collar 134 defines a collar hole 136 and is connected to the bottom surface 114 of the support structure 104 so it does not rotate relative to the support structure 104. The collar hole 136 is centered on the centerline 126 and is axially aligned with the sleeve hole 124 in support structure 104. A stop 138 projects from a bottom surface 140 of the collar 134. The diameter of the collar hole 136 is smaller than the diameter of the lower portion 130 of the sleeve hole 124. As explained in more detail herein, the lip 132, sleeve hole 124, and collar 134 support the clamp assembly 108.
A first mounting flange 142 extends from the first side portion 120 of the support structure 104 and a second mounting flange 144 extends from the second side portion 122 of the support structure 104. The first and second mounting flanges 142 and 144 each define a hole 146 and 148, respectively, for receiving bolts, pins, or other mounting fasteners. The first and second mounting flanges 142 and 144 face and are proximal to the rear portion 118 of the support structure 104 and can be used to selectively mount the cutting tool 100 to a bench top, fixture, or any other suitable structure for holding the cutting tool 100. The cutting tool 100 can include any other mounting structure suitable for mounting the support structure 104 in a secure portion. Alternatively, the cutting tool 100 can not include any mounting structure. A user can use the cutting tool 100 by either mounting the cutting tool 100 on another structure such as a bench top or by holding the support structure 104 in their hand.
First and second support flanges 150 and 152 extend from the rear portion 118 of the support structure 104. The first support flange 150 is proximal to the first side portion 120 and defines a bar hole 154 and a slot 156 that extends from the bar hole 154 to a rear surface 158 of the first support flange 150. The slot 156 defines top and bottom portions 160 and 162 of the first support flange 150. A non-threaded hole 164 is defined in the top portion 160 of the first support flange 150 and extends from a top surface of the first support flange 150 to an upper surface 164 of the slot 156. A threaded bolt hole (not shown) is defined through a bottom surface 168 of the slot 156 and into the bottom portion 162 of the first support flange 152 and is axially aligned with the non-threaded hole 164. The second support flange 152 is proximal to the second side 122 and also defines a bar hole 170 and a slot 172 that extends from the bar hole 170 to a rear surface 174 of the second support flange 152. The slot 172 defines top and bottom portions 176 and 178 of the second support flange 152. A non-threaded hole 180 is defined in the top portion 176 of the second support flange 152 and extends from a top surface 182 of the second support flange 152 to an upper surface 184 of the slot 172. An axially-aligned threaded bolt hole (not shown) is defined through a bottom surface 188 of the slot 172 and into the bottom portion 178 of the second support flange 152 and is axially aligned with the non-threaded hole 180.
A bar 190 extends through the bar hole 154 in the first support flange 150, across the gap between the first and second support flanges 150 and 152, and into the bar hole 154 in the second support flange 152. A bolt 194 passes through the non-threaded hole 164, across the slot 156 in the first support flange 150, and is threaded into the threaded bolt hole of the first support flange 150. The bolt 194 urges the top and bottom portions 160 and 162 of the first support flange 150 together to secure the bar 190 in the bar hole 154 with a frictional fit. A second bolt 196 is similarly passes through the non-threaded hole 180, passes across the slot 172, and is threaded into the threaded bolt hole of the second support flange 152.
Referring now to
The clamp assembly 108 includes a clamp member 218 having a base 220 and a rod 222 projecting from the base 220 and toward the sleeve 106. The rod 222 is centered on the centerline 126 and defines threads 224 sized and arranged to mate with the threads 207 on the inner surface 206 of the sleeve 106. The threads 222 are left-handed threads. The threads 224 on the rod 222 and the mating threads 207 on the inner surface 206 of the sleeve 106 form a tube advancement mechanism, which is discussed in more detail herein.
The threads 224 on the rod 222 have a major diameter that is smaller then the collar hole 136 so the rod 222 will fit freely through the collar hole 136 and into the clamp assembly hole 208 of sleeve 106. The base 220 defines a notch 226 in its sidewall 228 that extends radially toward the centerline 126. A tab 230 is attached to the base 220 and extends radially from the notch 226. The notch 226 and tab 230 provide a location for a person to grip or otherwise engage and rotate the clamp assembly 108 with a thumb or finger.
The clamp member 218 has an inner surface 232 with threads 234 that defines a bolt hole 236. The bolt hole 236 is centered on the centerline 126 and has an open end 238 at the base 220 and a closed end 240 positioned along the centerline 126. The clamp member 218 also defines a second tube passage 242 that is centered on the centerline 126 and that extends between the closed end 240 of the bolt hole 236 and the end 238 of the threaded rod 222. The diameter of the bolt hole 236 is larger than the diameter of the second tube passage 242. The closed end 240 of the bolt hole 236 has a tapered portion 244 that tapers toward the second tube passage 242 and has a circular conic shape. The closed end 240 of the bolt hole 236 forms a first ferrule seat.
The clamp assembly 108 also includes a clamp bolt 246 and a ferrule 248. The clamp member 218 forms a first clamp member and the clamp bolt 246 forms a second clamp member. The ferrule 248 forms a compression fitting. The clamp bolt 246 has a bolt head 250 and a threaded shaft 252. The threads 254 on the threaded shaft 252 are sized and arranged to mate with the threads 234 on the inner surface 232 of the bolt hole 236. The clamp bolt 246 defines a third tube passage 254 that is centered on the centerline 126 and extends all the way through the bolt head 250 and the threaded shaft 252. The end of the third tube passage 254 has a tapered portion 256 that tapers toward the centerline 126 from the end 258 of the threaded shaft 252 toward the bolt head 250 to provide a circular conic shape and form a second ferrule seat. The ferrule 248 has an inner surface 260 defining a fourth tube passage 262. The ferrule 248 also has a first outer surface 264 having a circular conic section that sits in the first ferrule seat and a second outer surface 266 having a circular conic section that sits in the second ferrule seat. The first, second, third, and fourth tube passages 214, 242, 254, 262 have substantially the same diameter and form a tube passage.
When the sleeve 106 and the clamp assembly 108 is assembled, the sleeve 106 is positioned in the support structure 104 hole so that the bottom of the rim 198 is resting against the lip 132 and the cutting surface lies substantially in the same plane as the top surface of the support structure 104. Additionally, the outer circumference of the rim 198 is slightly smaller than the upper diameter of the sleeve hole 124 so there is minimal gap between the rim 198 and the support structure 104. The rod 222 from the clamp member 218 is inserted through the collar hole 136 and is threaded to the threads 207 on the inner surface 206 of the sleeve 106. The clamp bolt 246 is threaded into the third tube passage 254. The ferrule 248 is positioned so the first outer surface 264 is positioned against the first ferrule seat and the second outer surface 266 is positioned against the second ferrule seat.
Referring to
After a sufficient length of tubing is inserted through the tube passage 214, 242, 254, 262, the clamp bolt 246 is sufficiently tightened so that the first outer surface 264 of the ferrule 248 is urged against the first ferrule seat and the first ferrule seat compresses a portion of the inner surface 260 of the ferrule 248 against the tube 102. This compression holds the tube 102 in a secure position relative to the ferrule 248 and prevents the tube 102 from slipping along the centerline 126. The second outer surface 266 of the ferrule 248 is urged against the second ferrule seat to similarly compress a portion of the inner surface 260 of the ferrule 248 against the tubing 102.
Referring to
In an exemplary embodiment, the angle of rotation between the first and second rotational positions 352a and 352b translates to a linear advancement distance of the tube 102 from the first cutting position to the second cutting position in a range from about 0.0001 mm to about 10 mm. Other possible embodiments have a different distance between the first and second cutting positions. Examples of other possible ranges, include but are not limited to, about 0.001 mm to about 0.009 mm (about 0.001 to about 0.009 inch), about 0.001 to about 0.01 mm, and about 0.001 mm to about 1 mm. A linear advancement distance for the tube 102 that provides a substantially defect free surface after the second cut can very depending on a variety of factors such as the cross-sectional area of the tube 102, the material used to form the tube 102, other physical characteristics of the tube, the sharpness of the cutting edge for the blade, the angle of the blade relative to the cutting surface, the speed at which the blade travels when cutting the tube 102, and the like. Additionally, the distance of linear advancement for the tube 102 per degree of rotation for the clamp member 218 will depend on the thread angle for the threads 224 on the rod 222.
Many other alternative embodiments of the tube advancement mechanism are possible. For example, the threads on the rod 222 could mate with threads defined on an inner surface of the support structure 104 thereby negating the need for the sleeve 106. In this alternative embodiment, the cutting surface would be formed on the top portion of the sleeve 106 assembly. Other alternative tube advancement mechanisms could include other thread configurations, gearing mechanisms, lever arrangements, or any other structure that can move the clamp assembly 108 between first and second positions, and the tube between first and second cutting positions, as described in more detail herein.
Referring to
In this configuration, the cutting assembly 110 slides along the linear path of travel 192 and between a retracted position 294 (as shown in
In possible alternative embodiments, the tube hole 216 is located between the first side surface 274 of the blade mounting structure 268 and the first side portion 120 of the support structure 104 when the cutting assembly 110 is in the retracted position 294. In these alternative embodiments, the tube hole 216 is not obstructed when the cutting assembly 110 is in the retracted position 294 and the cutting assembly 110 does not need to be rotated into the loading position to move or advance the tube 102 though the tube hole 216.
Referring to
An elongated slot 318 is defined in a lower portion 320 of the blade mounting structure 268 and is positioned between the bar hole 284 and the bottom surface 279 of the blade mounting structure 268. The elongated slot 318 is open on a surface of the lower portion 320 of the blade mounting structure 268 and extends to an inner surface 322. An elongated pressure member 324 is inserted lengthwise into the slot. One or more springs 326 are positioned in the elongated slot 318 between the elongated pressure member 324 and the inner surface 322. The springs 326 urge the cutting assembly 110 around the bar 190 and into the cutting position.
The blade 272 is substantially flat has a cutting edge 300 and a flat surface of the blade 272 is positioned against the beveled surface 280 of the blade mounting structure 268. The cutting blade 300 can be designed in various shapes and sizes. For example, the thickness of the blade in some possible embodiments is in a range about 0.004 to about 0.012 mm. Other possible embodiments of the blade might have a thickness outside of this range. The blade can be formed with any material suitable for cutting analytical instrument tubing. Examples of such materials include, but are not limited to, glass, ceramic, steel, stainless steel and carbon.
Alternative embodiments can include more than one blade. For example, one blade can be used to make the first cut and another blade can be used to make a second cut. In these embodiments, the blades used for each cut can have different structures and positioning relative to the tube hole 216. For example, one blade might have one angle relative to the cutting surface 200 and the other blade might have a different angle relative to the cutting surface. In yet other possible embodiments, the blade has two cutting edges orientated at an angle, with the apex of the angle pointing toward the front portion 116 of the support structure 104. In these later embodiments, the first cut is made as the cutting assembly moves from the retracted position to the advanced position, and the second cute is made as the cutting assembly 110 returns from the advanced position to the retracted position.
The blade 272 defines holes 328 that are aligned with bolt holes 330 defined through the beveled surface 280. The blade clamp 270 defines holes 334 and is positioned over the blade 272 so the clamp plate holes 334 are aligned with the blade holes 328 and the bolt holes 330. Bolts 336 extend through the holes 334, 328, 330 and securely fasten the blade 272 between the blade clamp 270 and the beveled surface 280 of the blade mounting structure 268. The blade clamp 270 distributes the force exerted by bolts 336 across the surface of the blade 272. The blade clamp 270 can be formed with any suitable material. Examples of materials include, but are not limited to, TEFLON® brand fluoropolymers such as polytetrafluoroethylene (PTFE), metal materials, plastic materials, glass materials, and ceramic materials.
Referring to
Referring back to
In use, the cutting assembly 110 is placed in the retracted position 294 along the bar 190 and is rotated around the bar 190 into the loading position. As illustrated in
As illustrated in
After the first cut is complete, the cutting assembly 110 is returned to the retracted position 294 and rotated around the bar into the loading position. While the cutting assembly 110 is in the loading position, the clamp assembly 108 is rotated to the second rotational position 352b, which causes the tube 102 to advance through the tube hole 216 into the second cutting position. The cutting process is then repeated and the tube 102 is cut a second time. This repeated process again includes the acts of rotating the cutting assembly 110 around the bar 190 and into the cutting position and then moving the cutting assembly 110 to the advanced position 296 to make a second cut across the cross section of the tubing 102.
After the second cut, the cut end of the tube 102 has a substantially flat cross-sectional area that is substantially defect free. Examples of a substantially flat surface include cross-sectional areas that deviate from a plane orthogonal to the centerline 196 of the tube 102 by an amount of about 1 micrometer or less, by an amount of about 10 micrometers or less, by an amount of about 100 micrometers or less, or by an amount of about 1000 micrometers or less. Examples of substantially defect free surface at the cut end include a cross-sectional surface that has about 10 or fewer defects per square micrometer, about 20 or fewer defects per square micrometer, about 100 or fewer defects per square micrometer, or about 1000 or fewer defects per square micrometer. Analytical instrument tubes having a cut end with a substantially flat cross-sectional area that is substantially defect free can be connected to analytical instruments with minimal zero-void volumes.
Referring now to
In possible embodiments of the automated cutting tool 382, the tube hole 216 is located between the first side surface 274 of the blade mounting structure 268 and the first side portion 120 of the support structure 104 when the cutting assembly 110 is in the retracted position 294. This embodiment eliminates the need to rotate the cutting assembly 110, which is connected to the piston rod 370, to load or advance the tube 102 between first and second cutting positions. Additionally, the mechanical components of the cutting tool 100 can be reinforced or modified to withstand the force that the first and second actuators 358 and 366 apply to the clamp member 218 and the cutting assembly 110.
The controller 380 can have any type of configuration for controlling the first and second actuators 358 and 366 and can be formed with valves, pumps, filters, fluid reservoirs, and electronics as required. The controller 380 also can include programmable and non-programmable electronics for controlling actions of the mechanical components including computers, solid-state electronics, and mechanical control elements such as relays, timers, latches, switches, and other components. Additionally, alternative embodiments can include any other type of suitable actuators such as hydraulic cylinders, solenoids, motors, and the like.
In use, the tube 102 is mounted on the cutting tool 100 as described herein. The controller 380 actuates the second actuator 366 so the piston rod 370 extends from the pneumatic cylinder 368, which slides the cutting assembly 110 from the retracted position 294 to the extended position 296 and so the blade 272 will make the first cut. The controller 380 then controls the second actuator 366 to retract the piston rod 370 to return the cutting assembly 110 to the retracted position 294. After the cutting assembly 110 is returned to the retracted position 294, the controller 380 controls pneumatic cylinder 360 of the first actuator 358 to extend the piston rod 362 to rotate the clamp member 218 from the first rotational position 358a to the second rotation position 358b. After the clamp member 218 is in the second rotational position 358b, the controller 380 again controls the second pneumatic cylinder to move the cutting assembly 110 from the retracted position 294 to the extend position 296 to make the second cut.
After the second cut, the controller 380 controls the first actuator 358 to return the clamp member to the first rotational position 358a and the second actuator to return the cutting assembly 110 to the retracted position 294. The tube 102 can then be adjusted and the process can be repeated to cut an end on another segment of tubing.
For convenience in explanation and accurate definition in the appended claims, the terms “upper” and “lower”, etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
