Patent Searching with a Patent Classification SystemThe USPTO SystemPatent classification systems. Ask most professional patent searchers and they will probably tell you that any serious search will have include a through search of one or more of the classification systems. What does that mean? Most (maybe all) of the major patent offices around the world have patent classification systems. They are all different but use similar ideas in how they are organized. The bad news is that you couldn't possibly learn all of them. The good news is that you don't have to. Unless you plan to spend more money on your patent search than on your patent you will probably constrain your search to the USPTO patent classification system or the IPC system. As we discussed earlier you can do a quick and dirty search by using a patent search engine and make skilled use of boolean search terms. That , in fact, is where I often start. But quite frankly, if that is all you do, you may miss some key patents because search engines are inherently dumb - they search only with the terms you give them. And if you hire someone to do a search for you you should insist they do a through search using a patent classification system. Skilled searchers (and examiners) often know their patent classification system well enough to zero in on the correct class or sub-class quickly. If you don't do this regularly then finding the correct patent classification system may be the most problematic part of your search. You will see why below. I will suggest later a step-by step process for zeroing in on your class or sub-class. Let's first try to understand a patent classification system. For the remainder of this article I will use the USPTO patent classification system as the example. In another article I will get into the IPC (International Patent Classification) System. Also I will assume in this article that you are using the search capability of the USPTO website. For starters - all patents are classified by subject matter. There are hundreds of categories. Each with many sub-categories and sub-sub-categories. To get a taste of this just look at category 475 - PLANETARY GEAR TRANSMISSION SYSTEMS OR COMPONENTS. It can be found here: http://www.uspto.gov/go/classification/uspc475/sched475.htm CLASS 475 PLANETARY GEAR TRANSMISSION SYSTEMS OR COMPONENTS 475 PLANETARY GEAR TRANSMISSION SYSTEMS OR COMPONENTS 1 INPUT FROM INDEPENDENT POWER SOURCES 2 .Condition responsive motor control 3 .Including manual input 4 ..And electric motor input 5 .Including electric motor input 6 .Plural outputs 7 .Worm gear in drive train 8 .One-way clutch or brake in drive train 9 .Bevel planet pinion in drive train 10 .Intermeshing planet pinions in drive train 11 ROTARY PLANETATING OUTPUT 12 REVERSAL OF DIRECTION OF POWER FLOW CHANGES POWER TRANSMISSION TO ALTERNATE PATH 13 .Input and output exchange functions 14 CYCLICAL OR INTERMITTENT DRIVE 15 .Plural outputs 16 .With means to adjust cycle or drive during operation 17 .Multilated or noncircular gear in drive train 18 STEERING BY DRIVING 19 .With condition responsive steer control 20 .With cooling or lubrication 21 .With infinitely variable drive 22 ..Variable drive is fluid drive 23 ...Hydrostatic type24 ....Plural pump-motor sets25 ..Belt type 26 ..Variable drive is friction drive 27 .Fluid steer control 28 .With plural power paths to a planetary transmission at each output 29 .With planetary reaction brake steering 30 ..And carrier input to planetary gearing 31 FLUID DRIVE OR CONTROL OF PLANETARY GEARING 32 .Diverse fluid drives 33 .Plural impeller-turbine type fluid circuits 34 ..Fill and empty type 35 .Single impeller-turbine type fluid circuit divides or combines plural power paths 36 ..Planetary gearing divides paths 37 ..Three fluid outputs 38 ...And stator 39 ..Two fluid outputs and stator 40 ...With variable fluid drive control 41 ...And mechanical drive path 42 ..Control of or by fluid drive 43 ..With speed or torque responsive clutch or brake control 44 ..Stator rotatable in reverse direction to provide drive 45 ...Turbine braked, stator provides reverse drive 46 ....And adds torque in forward drive 47 .Impeller-turbine type fluid circuit and mechanical path in parallel 48 ..With control of or by the fluid circuit 49 ...Gearing controlled by fluid circuit condition 50 ...Fill and empty type fluid circuit 51 ..With speed responsive control 52 ..And nonplanetary gearing 53 ..Planetary gearing divides paths 54 ..Sun, orbit and carrier braked 55 ..Sun and orbit braked 56 ..Sun and carrier braked 57 ..Orbit and carrier braked 58 ..Orbits braked 59 .Impeller-turbine type fluid circuit in series with planetary gearing 60 ..And condition responsive control 61 ...Control of or by fluid circuit 62 ....Control responsive to relative impeller and turbine speeds 63 .....System or servo fluid pressure controlled 64 ....Fluid circuit controlled 65 .....By lock-up clutch actuation 66 ..And nonplanetary gearing 67 ..With synchronizing of positive clutch or brake 68 ..With nonratio brake 69 ..Fluid circuit controlled 70 ...Pressure controlled 71 ..And differential in series 72 .Fluid pump and motor in one of plural paths to or from planetary gearing 73 ..Plural fluid power paths to planetary gearing 74 ..Plural outputs 75 ..Three pumps or motors 76 ..Speed responsive control 77 ...Constant speed output 78 ..Interrelated fluid unit and gear control 79 ...With constant speed ratio between input and one fluid unit 80 ..Plural speed ranges 81 ...With constant speed ratio between input and one fluid unit 82 ....Having single planet carrier 83 .Pump and motor in series with planetary gearing 84 .Control of differential planetary gearing 85 ..Special fluid 86 ..By fluid operated mechanical clutch 87 ...Operated by viscous drag 88 ...Operated by a pump responsive to differential action 89 ..Fluid resistance controls relative rotation of outputs 90 ...Fluid pumped by differential gears 91 .Fluid resistance inhibits relative rotation 92 ..Fluid damper for reaction element 93 ..Valve inhibits fluid flow 94 ...Speed or torque responsive valve control 95 ....Centrifugally actuated valve controls fluid clutch 96 .....Clutch connects planet pinion and carrier 97 .....With fluid brake control 98 ....Centrifugally actuated valve controls fluid brake 99 ...Interrelated valve control and mechanical clutch or brake 100 ....Valve control and mechanical clutch 101 .....Pump pressure engages mechanical clutch 102 ...Fluid brake(s) for plural planetary elements 103 ...Plural fluid clutches 104 ...Fluid brake for planetary element 105 ....And fluid clutch 106 ....Bevel gearing 107 ....Sun or orbit braked 108 ...Fluid clutch includes gear type pump 109 ...Planet clutched to carrier 110 ....With reversing means 111 ..Planet clutched to fluid flywheel 112 ..Fluid container connected to planet pinion 113 ..Impeller-turbine type fluid unit used as brake114 .Fluid control of friction planetary gearing 115 ..Stepless ratio change controlled 116 .Fluid controlled mechanical clutch or brake 117 ..Temperature responsive control 118 ..Speed responsive control 119 ...Safety device 120 ...Pressure control 121 ...Ratio change 122 ....Speed responsive valve control 123 .....Electrical control 124 .....Centrifugal control 125 ..Torque responsive control 126 ...Responsive to torque reversal 127 ..Pressure regulation 128 ...Valving controls shift timing 129 ....With fluid accumulator 130 ...Manual regulator 131 ..Manually actuated ratio selector 132 ...Electrical 133 ...With safety valve 134 ...Plural selector valves 135 ...Rotary valve 136 ..With ancillary pump or governor drive 137 ...Plural pumps 138 ..With positive clutch or brake 139 ...And friction synchronizer 140 ..Spring engaged, fluid released clutch or brake device 141 ...Plural devices simultaneously spring engaged 142 ...Single fluid motor engages one device and releases other 143 ..Expanding fluid motor chamber mechanically contracts second motor 144 ..Fluid controlled one-way devices 145 ..Fluid motor controls device through cam or lever 146 ..Fluid motor structure 147 ...Radially expanding motor 148 ...With one-way device 149 ELECTRIC OR MAGNETIC DRIVE OR CONTROL 150 .Differential drive or control 151 .Plural power paths 152 ..With nonplanetary drive to electric or magnetic path 153 .With condition responsive control 154 .With electric or magnetic controlled brake155 ..And manual speed selector 156 ..Electric or magnetic device disengages brake 157 ..Electric or magnetic engaged brake and spring engaged lockup clutch 158 WITH INDICATOR OR ALARM 159 WITH LUBRICATON 160 .For differential planetary gearing 161 WITH TRANSMISSION COOLING OR HEATING MEANS 162 PLANET PERIPHERY SURROUNDS AXIS OF INTERACTING GEAR (E.G., ECCENTRICALLY DRIVEN TRANSMISSON) 163 .Wabbler transmission 164 ..Single member has oppositely axially facing tooth sets 165 .Friction gearing 166 ..Variable speed 167 .Link chain gearing 168 .Gear teeth comprise rolling bodies 169 .Means to change speed ratio between input and output 170 ..Variable eccentricity 171 ..Plural power paths to planetary gearing 172 ..Condition responsive control 173 ..Plural planetary elements braked 174 .Plural outputs 175 .With releasable clutch or brake 176 .Gear has plural circumferential tooth sets 177 ..Internal and external tooth sets 178 .Circumferentially spaced connector pins 179 ..Roller bearing surrounds pin 180 .Particular gear tooth 181 .Particular counterweight 182 PLANET PINION ENGAGES FLEXIBLE BELT OR CHAIN 183 PLANET PINION IS FRICTION GEAR 184 .Plural outputs (e.g., differential) 185 .Variable speed ratio (without slippage) 186 ..Condition responsive ratio change 187 ..Releasably braked element 188 ...Plural elements releasably braked 189 ..Planet pinion is a ball 190 ..Planet pinion rotatable about axis at angle to axis of input or output gear 191 ...Planet pinion is member having axis fixed or adjustable to position perpendicular to axis of input or output gear 192 ....Pinion engages facing concave surfaces (e.g., mounted in torus) 193 ...Conical or frusto-conical planet pinion194 ....Torque responsive means to increase contact pressure 195 .Torque responsive means to increase contact pressure 196 .Planet pinion is ball 197 .Planet pinion rotatable about axis at angle to axis of input or output gear 198 VARIABLE SPEED OR DIRECTION TRANSMISSION COMBINED WITH DIFFERENTIAL 199 .Condition responsive 200 .Differential is beneath prime mover or transmission 201 .Differential is between prime mover and tranmission in the path of power flow 202 .With universal joint in drive train 203 .Plural selectively driveable gears surround differential 204 .Variable speed or direction is planetary transmission 205 ..Plural planetary units combined with differential 206 .Transmission output shaft parallel to differential output shafts 207 NONPLANETARY VARIABLE SPEED OR DIRECTION TRANSMISSION COMBINED WITH PLANETARY TRANSMISSION 208 .Condition repsonsive 209 .Interrelated control of in series transmissions 210 .Nonplanetary transmission is belt or chain gearing 211 ..Plural power paths to planetary gearing 212 ...Nonplanetary transmission is chain gearing 213 ..Nonplanetary transmission is chain gearing 214 .Nonplanetary transmission is friction gearing 215 ..Plural power paths to planetary gearing 216 ...Friction gear engages facing concave surfaces 217 ...Nonplanetary transmission is disc and wheel 218 .Plural power paths to planetary gearing 219 .Plural planetary units 220 DIFFERENTIAL PLANETARY GEARING 221 .Differential or nondifferential planetary combined with differential (e.g., two differentials) 222 .With universal joint in drive train 223 .Including means to selectively apply rotational power to only one output 224 ..By braking other output 225 .With additional gearset between differential output and load 226 .Planet pinion is worm gear 227 ..And spur gear on pinion 228 .Worm drive on input shaft 229 ..And roller bearing supporting worm from casing 230 .Bevel gear differential 231 ..With means to limit overspeed of one output (e.g., lock-up clutch) 232 ...Centrifugal actuator 233 ...Lock-up clutch between pinion and pinion carrier 234 ...By axial movement of output gear 235 ....With spring bias on gear or clutch 236 ...Particular gear shape or tooth interaction limits overspeed 237 ...Manual actuator 238 ....Friction clutch 239 .....Plate clutch 240 ...Spring bias on overspeed limiting means 241 ....Helically coiled spring 242 ..Separate planet pinions or separate tooth set on same pinion for each output 243 ..Output gear rotatable relative to axial support shaft 244 ...Support shaft coupled to other output gear 245 ...With roller bearing between output gear and shaft 246 ..With roller bearing between gear and its support 247 ...Ball bearing 248 .Spur gear differential 249 ..With means to limit overspeed of one output 250 ...Manual actuator 251 ..Pinion axis at angle intersecting axis of output 252 ..Intermeshing planet pinions 253 ..With roller bearing between gear and its support 254 CONDITION RESPONSIVE CONTROL 255 .Eccentrically weighted planet 256 .Downshift responsive to high speed limit 257 .Speed responsive control adjusted or opposed by torque 258 .Centrifugally controlled clutch or brake 259 ..One-way clutch or brake 260 ..Centrifugal brake control 261 ..Positive clutc 262 ..Axially engaged friction clutch 263 .Overload release 264 ..Spring applied friction drive establishing means 265 ...Drive establishing means is friction brake 266 .Stepped, torque responsive ratio change 267 .With flywheel or centrifugal weight control 268 ..With planet pinion axis at angle to axis of mating gear (e.g., bevel gears) 269 WITH MEANS TO VARY DRIVE RATIO OR DISCONNECT DRIVE (E.G., BRAKE OR CLUTCH) 270 .Manual force provides reaction during drive 271 .Plural elements selectively braked 272 ..With preselection 273 ..Axis of planet pinion at angle to axis of mating gear (e.g., bevel gears) 274 ...And additional planetary gearset having axis of pinion parallel to axis of mating gear 275 ..Transmission includes three relatively rotatable sun gears 276 ...With brake for sun, carrier and orbit 277 ...With brake for plural sun gears 278 ....And brake for carrier 279 ...With brake for plural orbits 280 ..Brake for sun, carrier and orbit 281 ...Including one-way clutch or brake282 ..Brake for sun and orbit 283 ...Including one-way clutch or brake 284 ..Brake for sun and carrier 285 ...Including one-way clutch or brake 286 ..Brake for orbit and carrier 287 ...Including one-way clutch or brake 288 ..Plural suns braked 289 ...Including one-way clutch or brake 290 ..Plural orbits braked 291 ...Including one-way clutch or brake 292 ..Including one-way clutch or brake 293 .Speed responsive clutch or brake 294 .Ratio shift initiated by reverse rotation of input shaft 295 .Plural outputs 296 .Plural drive ratios other than unity 297 ..Including one-way clutch or brake 298 .Gear shiftable axially to disconnect or vary ratio 299 ..Orbit shiftable relative to sun and carrier 300 ..Sun shiftable relative to orbit and carrier 301 .Brake or clutch on surface of helically coiled member 302 .Nonplanetary gearing combined with planetary 303 .With synchronizing clutch or brake 304 .Planet pinion is worm gear 305 .Including releasable clutch directly between planet pinion and carrier 306 .Brake for planetary transmission having axis of planet pinion at angle to axis of mating gear (e.g., bevel gears) 307 ..Including one-way clutch or brake 308 ..And lock-up clutch 309 ...Friction clutch 310 ....Plate clutch 311 .Sun braked 312 ..Including one-way clutch or brake 313 ..Intermeshing planet pinions on single carrier 314 ..And lock-up clutch 315 ...Friction clutch 316 ....Plate clutch 317 .Orbit braked 318 ..Including one-way clutch or brake 319 ..Intermeshing planet pinions on single carrier 320 ..And lock-up clutch 321 ...Friction clutch 322 ....Plate clutch 323 .Carrier braked 324 ..Including one-way clutch or brake 325 ..Intermeshing planet pinions on single carrier 326 ..And lock-up clutch 327 ...Friction clutch 328 ....Plate clutch 329 PLURAL POWER PATHS TO PLANETARY GEARING 330 .Plural planetary units 331 PLANETARY GEARING OR ELEMENT 332 .Plural outputs 333 .Planet pinion is worm gear 334 .Floating support annulus in rolling contact with planet pinion 335 .Toothed planet pinion has smooth bearing surface engaging raceway on sun or orbit gear 336 .Axis of planet pinion at angle intersecting rotational axis of mating gear (e.g., bevel gears) 337 .Plural planet carriers in series move at different speeds 338 .Coaxial teeth around planet pinion engage axially spaced relatively rotatable gears 339 ..Engage plural relatively rotatable sun gears 340 ...And orbit gear 341 ..Engage plural relatively rotatable orbit gears 342 ...And sun gear 343 .Nonplanetary gearing combined with planetary 344 .Particular gear tooth feature 345 ..Nonmetallic or resilient 346 .Floating or flexible coupling or support 347 ..Resilient member 348 .Planet pinion supported by roller bearings 349 .With manual input This class - one of many in the US patent classification system, is clearly focused on planetary gear transmissions systems. But broken up into many classes, sub classes, and yes sub-sub classes. You may have noticed the dots in front of the definitions for the various classes and sub-classes. These dots indicate additional hierarchy levels in the class/subclass structure of the patent classification system. In this example, the class (475) is at the highest level; everything else falls under class 475. But only some of the subclasses are directly under class 475. All of the all-cap definitions with no dot in front of them are directly in 475. You know this because they have no dots in front of their definitions which would indicate additional steps down in the hierarchy structure. So class 331 (written as CCL/475/331 is directly in 475. Subclass 338 on the other hand, is not directly under class 475. It is actually under subclass 331. Note that 339 has two dots and is thus a subclass of 338 and 340 is a subclass of 339. Calling all of these as subs and sub-subs, etc would get quickly confusing, so they distinguish the different levels with dots - the more dots, the lower it is in the hierarchy. If you are trying to figure out what class or subclass a given category falls under, go up the listing from the category of interest to the first class or subclass with one less dot. It works just like an outline, but dots are used in place of Roman numerals, and other traditional outline level designations. It is extremely important to understand this hierarchical system. If you do not understand the patent classification system, it is absolutely impossible to know if you are looking in right places when you do a search. As you look through that example you will quickly see that depending on the details of your invention it becomes difficult to see it in just one category. And in fact there is no way to know under which class/subclass the USPTO examiners decided to file an invention. And, a single invention can be filed under more than one class/subclass (in fact, most inventions are filed in several classes/subclasses). You may now have an Excedrin headache. The patent classification system can have that effect. This is one of the most important challenges of patent searching: Thoroughly understanding the patent classification system, and wisely choosing which classes/subclasses appear to be most relevant to the search you are performing. If you choose poorly, there may be another class/subclass filled with dozens of patents relevant to your search, and you may miss them. Frankly - unless you do this fairly often using the patent classification system will be very tedious for you. But it can be a very comprehensive way of doing a search. Let's assume that you have done this though and zoomed in on a few classes and sub-classes that correspond well to the invention you are searching. Then from the USPTO website you can quickly move into lists of patents in your chosen subclasses. Let's assume that you are convinced that your invention is a planetary gear transmission system steered by driving with an infinitely variable fluid drive of the hydrostatic type. Setting Class 475 to display all indent levels revels CCL/475/23, which fits your criteria, and is a 3 dot sub-level. You can then click on "A" to see the published applications in that sub-class , which will show about 3 applications. Clicking on "P" to see patents will reveal about 78 patents. Now comes the hard part - you have to read them. Although the first level of effort is to read the abstracts. This will usually enable you to eliminate many of the patents and applications as to relevance. All of this may sound complicated - because it is. I have suggested that searching the patent classification categories is the way the pros do it. But frankly good patent searching is more of an art than a science. In other articles I will suggest what I consider practical approaches to doing good searches that will eventually lead you to probable patent classification categories to search. In other words I view patent classification searching as one of the tools to use but not the final answer. LinksPatent Classification Getting a US Patent Search The Business of Patents Home Page Mike Ervin Contact Me
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