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International patent classification


The International Patent Classification (IPC), established by the Strasbourg Agreement 1971, provides for a hierarchical system of language independent symbols for the classification of patents and utility models according to the different areas of technology to which they pertain.

The IPC divides technology into eight sections with approximately 70,000 subdivisions. Each subdivision has a symbol consisting of Arabic numerals and letters of the Latin alphabet.

The appropriate IPC symbols are indicated on each patent document, of which more than 1,000,000 were issued each year in the last 10 years. The IPC symbols are allotted by the national or regional industrial property office that publishes the patent document.

Main eight groups :




  • The following notes are meant to assist in the use of this part of the classification scheme; they must not be read as modifying in any way the elaborations.
    • In this sub-section, the separation of different materials, e.g. of different matter, size, or state, is predominantly found in the following subclasses:
      • B01D
      • B03B, B03C, B03D
      • B04B, B04C
      • B07B, B07C.
    • The classifying characteristics of these subclasses are:
      • the physical state of the matter to be separated;
      • the principle of the process used;
      • particular kinds of apparatus.

      The first of these characteristics involves six different aspects, assembled in three groups:

      • liquid/liquid or liquid/gas and gas/gas;
      • solid/liquid or solid/gas;
      • solid/solid.
    • These subclasses are to be used according to the following general rules:
      • B01D is the most general class as far as separation other than solids from solids is concerned.
      • Apparatus for separating solids from solids are covered by B03B when the process concerned is regarded as the equivalent of “washing” in the sense of the mining art, even if such apparatus is a pneumatic one, especially pneumatic tables or jigs. Screens per se are not covered by this subclass but are classified in B07B, even if they are being used in a wet process. All other apparatus for the separation of solids from solids according to dry methods are classified in B07B.
      • If the separation takes place as a result of the detection or measurement of some feature of the material or articles to be sorted it is classified in B07C.
      • It should also be noted that the separation of isotopes of the same chemical element is covered by B01D 59/00, whatever process or apparatus is employed.

Note(s) [2009.01]

  • In section C, the definitions of groups of chemical elements are as follows:
    • Alkali metals: Li, Na, K, Rb, Cs, Fr
    • Alkaline earth metals: Ca, Sr, Ba, Ra
    • Lanthanides: elements with atomic numbers 57 to 71 inclusive
    • Rare earths: Sc, Y, Lanthanides
    • Actinides: elements with atomic numbers 89 to 103 inclusive
    • Refractory metals: Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W
    • Halogens: F, Cl, Br, I, At
    • Noble gases: He, Ne, Ar, Kr, Xe, Rn
    • Platinum group: Os, Ir, Pt, Ru, Rh, Pd
    • Noble metals: Ag, Au, Platinum group
    • Light metals: alkali metals, alkaline earth metals, Be, Al, Mg
    • Heavy metals: metals other than light metals
    • Iron group: Fe, Co, Ni
    • Non-metals: H, B, C, Si, N, P, O, S, Se, Te, noble gases, halogens
    • Metals: elements other than non-metals
    • Transition elements: elements with atomic numbers 21 to 30 inclusive, 39 to 48 inclusive, 57 to 80 inclusive, 89 upwards
  • Section C covers :
    • pure chemistry, which covers inorganic compounds, organic compounds, macromolecular compounds, and their methods of preparation;
    • applied chemistry, which covers compositions containing the above compounds, such as: glass, ceramics, fertilisers, plasticscompositions, paints, products of the petroleum industry. It also covers certain compositions on account of their having particular properties rendering them suitable for certain purposes, as in the case of explosives, dyestuffs, adhesives, lubricants, and detergents;
    • certain marginal industries, such as the manufacture of coke and of solid or gaseous fuels, the production and refining of oils, fats and waxes, the fermentation industry (e.g., brewing and wine-making), the sugar industry;
    • certain operations or treatments, which are either purely mechanical, e.g., the mechanical treatment of leather and skins, or partly mechanical, e.g., the treatment of water or the prevention of corrosion in general;
    • metallurgy, ferrous or non-ferrous alloys.
  • In all sections of the IPC, in the absence of an indication to the contrary, the Periodic System of chemical elements referred to is the one with 18 groups as represented in the table below.
    • fig401
    • In the case of operations, treatments, products or articles having both a chemical and a non-chemical part or aspect, the general rule is that the chemical part or aspect is covered by section C.
    • In some of these cases, the chemical part or aspect brings with it a non-chemical one, even though purely mechanical, because this latter aspect either is essential to the operation or treatment or constitutes an important element thereof. It has seemed, in fact, more logical not to dissociate the different parts or aspects of a coherent whole. This is the case for applied chemistry and for the industries, operations and treatments mentioned in Notes (1)(c), (d) and (e). For example, furnaces peculiar to the manufacture of glass are covered by class C03 and not by class F27.
    • There are, however, some exceptions in which the mechanical (or non-chemical) aspect carries with it the chemical aspect, for example:
      • Certain extractive processes, in subclass A61K;
      • The chemical purification of air, in subclass A61L;
      • Chemical methods of fire-fighting, in subclass A62D;
      • Chemical processes and apparatus, in class B01;
      • Impregnation of wood, in subclass B27K;
      • Chemical methods of analysis or testing, in subclass G01N;
      • Photographic materials and processes, in class G03, and, generally, the chemical treatment of textiles and the production of cellulose or paper, in section D.
    • In still other cases, the pure chemical aspect is covered by section C and the applied chemical aspect by another section, such as A, B or F, e.g., the use of a substance or composition for:
      • treatment of plants or animals, covered by subclass A01N;
      • foodstuffs, covered by class A23;
      • ammunition or explosives, covered by class F42.
    • When the chemical and mechanical aspects are so closely interlocked that a neat and simple division is not possible, or when certain mechanical processes follow as a natural or logical continuation of a chemical treatment, section C may cover, in addition to the chemical aspect, a part only of the mechanical aspect, e.g., after-treatment of artificial stone, covered by class C04. In this latter case, a note or a reference is usually given to make the position clear, even if sometimes the division is rather arbitrary.

Note(s) [2014.01]

  • In this section, the following terms are used with the meanings indicated:
    • “fibre” means a relatively-short, elongated member of natural or man-made material;
    • “filament” means an endless or quasi-endless, elongated member of natural or man-made material;
    • “yarn” means a unitary assembly of fibres, usually produced by spinning;
    • “thread” means an assembly of yarns or filaments, usually produced by twisting;
    • “synthetic” fibres or filaments means fibres or filaments or the like manufactured from synthesising polymers or small molecules. Examples are polyamide, acrylic, polyester or carbon fibres;
    • “artificial” fibres or filaments means fibres or filaments or the like manufactured by man from natural polymers or their derivatives. Examples are regenerated cellulosic fibres or semi-synthetic fibres;
    • “man-made” fibres or filaments means fibres or filaments which are manufactured by man including “synthetic” or “artificial” fibres.


  • Guide to the use of this subsection (classes F01-F04)
  • The following notes are meant to assist in the use of this part of the classification scheme.
    • In this subsection, subclasses or groups designating “engines” or “pumps” cover methods of operating the same, unless otherwise specifically provided for.
    • In this subsection, the following terms or expressions are used with the meanings indicated:
      • “engine” means a device for continuously converting fluid energy into mechanical power. Thus, this term includes, for example, steam piston engines or steam turbines, per se, or internal-combustion piston engines, but it excludes single-stroke devices. “Engine” also includes the fluid-motive portion of a meter unless such portion is particularly adapted for use in a meter;
      • “pump” means a device for continuously raising, forcing, compressing, or exhausting fluid by mechanical or other means. Thus, this term includes fans or blowers;
      • “machine” means a device which could equally be an engine and a pump, and not a device which is restricted to an engineor one which is restricted to a pump;
      • “positive displacement” means the way the energy of a working fluid is transformed into mechanical energy, in which variations of volume created by the working fluid in a working chamber produce equivalent displacements of the mechanical member transmitting the energy, the dynamic effect of the fluid being of minor importance, and vice versa ;
      • “non-positive displacement” means the way the energy of a working fluid is transformed into mechanical energy, by transformation of the energy of the working fluid into kinetic energy, and vice versa ;
      • “oscillating-piston machine” means a positive-displacement machine in which a fluid-engaging work-transmitting member oscillates. This definition applies also to engines and pumps;
      • “rotary-piston machine” means a positive-displacement machine in which a fluid-engaging work-transmitting member rotates about a fixed axis or about an axis moving along a circular or similar orbit. This definition applies also to engines and pumps;
      • “rotary piston” means the work-transmitting member of a rotary-piston machine and may be of any suitable form, e.g., like a toothed gear;
      • “cooperating members” means the “oscillating piston” or “rotary piston” and another member, e.g., the working-chamber wall, which assists in the driving or pumping action;
      • “movement of the co-operating members” is to be interpreted as relative, so that one of the “co-operating members” may be stationary, even though reference may be made to its rotational axis, or both may move;
      • “teeth or tooth equivalents” include lobes, projections or abutments;
      • “internal-axis type” means that the rotational axes of the inner and outer co-operating members remain at all times within the outer member, e.g., in a similar manner to that of a pinion meshing with the internal teeth of a ring gear;
      • “free piston” means a piston of which the length of stroke is not defined by any member driven thereby;
      • “cylinders” means positive-displacement working chambers in general. Thus, this term is not restricted to cylinders of circular cross-section;
      • “main shaft” means the shaft which converts reciprocating piston motion into rotary motion or vice versa ;
      • “plant” means an engine together with such additional apparatus as is necessary to run the engine. For example, a steam engine plant includes a steam engine and means for generating the steam;
      • “working fluid” means the driven fluid in a pump or the driving fluid in an engine. The working fluid can be in a compressible, gaseous state, called elastic fluid, e.g. steam; in a liquid state; or in a state where there is coexistence of an elastic fluid and liquid phase.
      • “steam” includes condensable vapours in general, and “special vapour” is used when steam is excluded;
      • “reaction type” as applied to non-positive-displacement machines or engines means machines or engines in which pressure/velocity transformation takes place wholly or partly in the rotor. Machines or engines with no, or only slight, pressure/velocity transformation in the rotor are called “impulse type”.
    • In this subsection:
      • cyclically operating valves, lubricating, gas-flow silencers or exhaust apparatus, or cooling are classified in subclasses F01L, F01M, F01N, F01Pirrespective of their stated application, unless their classifying features are peculiar to their application, in which case they are classified only in the relevant subclass of classes F01-F04;
      • lubricating, gas-flow silencers or exhaust apparatus, or cooling of machines or engines are classified in subclasses F01M, F01N, F01P except for those peculiar to steam engines which are classified in subclass F01B.
    • For use of this subsection with a good understanding, it is essential to remember, so far as subclasses F01B, F01C, F01D, F03B, and F04B, F04C, F04D, which form its skeleton, are concerned:
      • the principle which resides in their elaboration,
      • the classifying characteristics which they call for, and
      • their complementarity.
        • Principle
          • This concerns essentially the subclasses listed above. Other subclasses, notably those of class F02, which cover better-defined matter, are not considered here.
          • Each subclass covers fundamentally a genus of apparatus (engine or pump) and by extension covers equally “machines” of the same kind. Two different subjects, one having a more general character than the other, are thus covered by the same subclass.
          • Subclasses F01B, F03B, F04B, beyond the two subjects which they cover, have further a character of generality in relation to other subclasses concerning the different species of apparatus in the genus concerned.
          • This generality applies as well for the two subjects dealt with, without these always being in relation to the same subclasses.
          • Thus, subclass F03B, in its part dealing with “machines”, should be considered as being the general class relating to subclasses F04B, F04C, and in its part dealing with “engines” as being general in relation to subclass F03C.
        • Characteristics
          • The principal classifying characteristic of the subclass is that of genera of apparatus, of which there are three possible:
            • Machines; engines; pumps.
          • As stated above, “machines” are always associated with one of the other two genera. These main genera are subdivided according to the general principles of operation of the apparatus:
            • Positive displacement; non-positive displacement.
          • The positive displacement apparatus are further subdivided according to the ways of putting into effect the principle of operation, that is, to the kind of apparatus:
            • Simple reciprocating piston; rotary or oscillating piston; other kind.
          • Another classifying characteristic is that of the working fluid, in respect of which three kinds of apparatus are possible, namely:
            • Liquid and elastic fluid; elastic fluid; liquid.
        • Complementarity
          • This resides in association of pairs of the subclasses listed above, according to the characteristics under consideration in respect of kind of apparatus or working fluid.
          • The subclasses concerned with the various principles, characteristics and complementarity are shown in the subsection index below.
  • It is seen from this index that:
    • For the same kind of apparatus in a given genus, the characteristics of “working fluid” associates:
      • F01B and F04B to Machines
      • F01C and F04C to Machines
      • F01D and F03B to Machines
      • F01B and F03C to Engines
      • F01C and F03C to Engines
      • F01D and F03B to Engines
    • For the same kind of working fluid, the “apparatus” characteristic relates subclasses in the same way as considerations of relative generality.


  • In this section, the following term is used with the meaning indicated:
    • “variable” (as a noun) means a feature or property (e.g., a dimension, a physical condition such as temperature, a quality such as density or colour) which, in respect of a particular entity (e.g., an object, a quantity of a substance, a beam of light) and at a particular instant, is capable of being measured; the variable may change, so that its numerical expression may assume different values at different times, in different conditions or in individual cases, but may be constant in respect of a particular entity in certain conditions or for practical purposes (e.g., the length of a bar may be regarded as constant for many purposes).
  • Attention is drawn to the definitions of terms or expressions used. Some appear in the notes of several of the classes in this section, see in particular the definition of “measuring” in class G01. Others appear in paragaph 187 of the Guide to the IPC, see in particular the definitions of “control” and “regulation”.
  • Classification in this section may present more difficulty than in other sections, because the distinction between different fields of use rests to a considerable extent on differences in the intention of the user rather than on any constructional differences or differences in the manner of use, and because the subjects dealt with are often in effect systems or combinations, which have features or parts in common, rather than “things”, which are readily distinguishable as a whole. For example, information (e.g., a set of figures) may be displayed for the purpose of education or advertising (G09), for enabling the result of a measurement to be known (G01), for signalling the information to a distant point or for giving information which has been signalled from a distant point (G08). The words used to describe the purpose depend on features that may be irrelevant to the form of the apparatus concerned, for example, such features as the desired effect on the person who sees the display, or whether the display is controlled from a remote point. Again, a device which responds to some change in a condition, e.g., in the pressure of a fluid, may be used, without modification of the device itself, to give information about the pressure (G01L) or about some other condition linked to the pressure (another subclass of class G01, e.g., G01K for temperature), to make a record of the pressure or of its occurrence (G07C), to give an alarm (G08B), or to control another apparatus (G05).
    • The classification scheme is intended to enable things of a similar nature (as indicated above) to be classified together. It is therefore particularly necessary for the real nature of any technical subject to be decided before it can be properly classified.


  • These Notes cover the basic principles and general instructions for use of section H.
    • Section H covers :
      • basic electric elements, which cover all electric units and the general mechanical structure of apparatus and circuits, including the assembly of various basic elements into what are called printed circuits and also cover to a certain extent the manufacture of these elements (when not covered elsewhere);
      • generation of electricity, which covers the generation, conversion and distribution of electricity together with the controlling of the corresponding gear;
      • applied electricity, which covers :
        • general utilisation techniques, viz. those of electric heating and electric lighting circuits;
        • some special utilisation techniques, either electric or electronic in the strict sense, which are not covered by other sections of the Classification, including:
          • electric light sources, including lasers;
          • electric X-ray technique;
          • electric plasma technique and the generation and acceleration of electrically charged particles or neutrons;
      • basic electronic circuits and their control;
      • radio or electric communication technique;
      • the use of a specified material for the manufacture of the article or element described. In this connection, paragraphs 88 to 90 of the Guide should be referred to.
    • In this section, the following general rules apply:
      • Subject to the exceptions stated in I(c), above, any electric aspect or part peculiar to a particular operation, process, apparatus, object or article, classified in one of the sections of the Classification other than section H, is always classified in the subclass for that operation, process, apparatus, object or article. Where common characteristics concerning technical subjects of similar nature have been brought out at class level, the electric aspect or part is classified, in conjunction with the operation, process, apparatus, object or article, in a subclass which covers entirely the general electrical applications for the technical subject in question;
      • The electrical applications referred to under (a), above, either general or particular, include:
        • the therapeutic processes and apparatus, in class A61;
        • the electric processes and apparatus used in various laboratory or industrial operations, in classes B01 and B03 and in subclass B23K;
        • the electricity supply, electric propulsion and electric lighting of vehicles in general and of particular vehicles, in the subsection “Transporting” of section B;
        • the electric ignition systems of internal-combustion engines, in subclass F02P, and of combustion apparatus in general, in subclass F23Q;
        • the whole electrical part of section G, i.e. measuring devices including apparatus for measuring electric variables, checking, signalling and calculating. Electricity in that section is generally dealt with as a means and not as an end in itself;
      • All electrical applications, both general and particular, presuppose that the “basic electricity” aspect appears in section H (see I(a) above) as regards the electric “basic elements” which they comprise. This rule is also valid for applied electricity, referred to in I(c), above, which appears in section H itself.
    • In this section, the following special cases occur:
      • Among the general applications covered by sections other than section H, it is worth noting that electric heating in general is covered by subclasses F24D or F24H or class F27, and that electric lighting in general is partly covered by class F21, since in section H (see I(c), above) there are places in H05B which cover the same technical subjects;
      • In the two cases referred to under (a), above, the subclasses of section F, which deal with the respective subjects, essentially cover in the first place the whole mechanical aspect of the apparatus or devices, whereas the electrical aspect, as such, is covered by subclass H05B;
      • In the case of lighting, this mechanical aspect should be taken to cover the material arrangement of the various electric elements, i.e., their geometrical or physical position in relation to one another; this aspect is covered by subclasses of class F21, the elements themselves and the primary circuits remaining in section H. The same applies to electric light sources, when combined with light sources of a different kind. These are covered by subclass H05B, whereas the physical arrangement which their combination constitutes is covered by subclasses of class F21;
      • As regards heating, not only the electric elements and circuitry designs, as such, are covered by subclass H05B, but also the electric aspects of their arrangement, where these concern cases of general application; electric furnaces being considered as such. The physical disposition of the electric elements in furnaces is covered by section F. If a comparison is made with electric welding circuits, which are covered by subclass B23K in connection with welding, it can be seen that electric heating is not covered by the general rule stated in II, above.

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