`
`PCT
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Office
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`WO 99/41513
`(51) International Patent Classification6:
`(11) International Publication Number:
`F16D 1/033, 1/076
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`(43) International Publication Date: 19 August 1999 (19.08.99)
`
`A1
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`(81) Designated Contracting States: CZ, European Patent
`(AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU,
`MC, NL, PT, SE).
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`Published:
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`With the International Search Report.
`for
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`Before expiration of
`the period allowed
`amendments to the claims; publication to be
`repeated if amendments are submitted.
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`(21) International Application No.: PCT/EP99/00893
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`(22) International Filing Date: 11 Feb 1999 (11.02.99)
`
`(31) Priority Data:
`198 05 676.1 12 February 1998 (12.02.98) DE
`298 02 374.1 12 February 1998 (12.02.98) DE
`
`(71) Applicant: VOITH TURBO GMBH & CO. KG
`(DE/DE);
`Alexanderstrasse
`2,
`D-89522
`Heidenheim (DE)
`
`(72) Inventor: BETZLER, Hans; Ludwig-Richter-Strasse
`10, D89520 Heidenheim (DE), LINDENTHAL,
`Hans; Kistelbergstasse 81, D-89522 Heidenheim
`(DE)
`
`(74) Representative: DR. WEITZEL & PARTNER;
`Friedenstrasse 10, D-89522 Heidenheim (DE)
`
`
`(54) Title: MACHINE ELEMENT WITH HIRTH-TYPE SERRATIONS
`(57) Abstract:
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`The invention relates to a machine element
`with Hirth-type serrations, characterized
`in that
`individual
`serration
`elements
`are
`configured
`asymmetrically.
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`SONY Exhibit 1013
`SONY v. FUJI
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`FOR INFORMATION PURPOSES ONLY
`Codes used to define PCT countries added to page 1 of the pamphlet of Unexamined International Patent
`applications according to the PCT.
`ES - Spain
`LS - Lesotho
`FI - Finland
`LT - Lithuania
`FR - France
`LU - Luxembourg
`GA - Gabon
`LV - Latvia
`GB - United Kingdom
`MC - Monaco
`GE - Georgia
`MD - Republic of Moldova
`GH - Ghana
`MG - Madagascar
`GN - Guinea
`MK - Macedonia, the
`GR - Greece
` former Yugoslavian
`HU - Hungary
` Republic
`IE - Ireland
`ML - Mali
`IL - Israel
`MN - Mongolia
`IS - Iceland
`MR - Mauretania
`IT - Italy
`MW - Malawi
`JP - Japan
`MX - Mexico
`KE - Kenya
`NE - Niger
`KG - Kyrgyzstan
`NL - Netherlands
`KP - Democratic People's
`NO - Norway
` Republic of North
`NZ - New Zealand
` Korea
`PL - Poland
`KR - Korea Republic
`PT - Portugal
`KZ - Kazakhstan
`RO - Romania
`LC - St. Lucia
`RU - Russian Federation
`LI - Liechtenstein
`SD - Sudan
`LK - Sri Lanka
`SE - Sweden
`LR – Liberia
`SG - Singapore
`
`AL – Albania
`AM - Armenia
`AT - Austria
`AU - Australia
`AZ - Azerbaijan
`BA - Bosnia and Herzegovina
`BB - Barbados
`BE - Belgium
`BF - Burkina Faso
`BG - Bulgaria
`BJ - Benin
`BR - Brazil
`BY - Belarus
`CA - Canada
`CF - Central African Republic
`CG - Congo
`CH - Switzerland
`CI - Ivory Coast
`CM - Cameroon
`CN - China
`CU - Cuba
`CZ - Czech Republic
`DE - Germany
`DK - Denmark
`EE - Estonia
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`SI - Slovenia
`SK - Slovakia
`SN - Senegal
`SZ - Swaziland
`TD - Chad
`TG - Togo
`TJ - Tajikistan
`TM - Turkmenistan
`TR - Turkey
`TT - Trinidad and Tobago
`UA – Ukraine
`UG -- Uganda
`US - United States of
` America
`UZ - Uzbekistan
`VN - Vietnam
`YU - Yugoslavia
`ZW – Zimbabwe
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`WO 99/41513
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`Machine Element with Hirth Toothing
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`The invention relates to a machine element with Hirth toothing for a positive-locking
`connection to a second machine element having complementary toothing.
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`Hirth toothing designs have been known for a long time as construction elements for a wide
`variety of different purposes. Reference is made to the Voith company brochures G 749 9.92
`1500 as a representative example. Thus, for the purpose of transfer of torque on a machine
`element, the basic idea of Hirth toothing designs is to design all the geometric lines of a spur
`gearing in a wedge shape and to have them merge centrally at one point. The result is thus a
`gear rim running in the circumferential direction with teeth extending in the radial direction,
`relative to the central axis. The design of two machine elements to be coupled together, having
`mutually complementary Hirth toothing designs, making it possible to create a form-fitting,
`self-centering connection between the two, wherein the Hirth toothing designs as such are
`used as a space-saving part element with a high precision of parts or as a fixation element with
`a high repeat precision. The possible uses of such connecting elements are quite varied and are
`not limited to specific examples of use. Use in general mechanical engineering is conceivable,
`for example, for connecting high-speed compressors and turbine rotors to the rotor shaft, gear
`wheel sets or crankshafts. An increase in power can be achieved here with the same volume in
`cases where traditional screw connections, for example, flanges, hubs and shafts have reached
`or even exceeded the limit of transfer capacity. With such a connection, it is also possible to
`achieve an increase in volume and weight in cases where the space is already greatly limited.
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`Assembly is very simple because of the centering effect and components designed in this way
`are also very easy to replace.
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`For implementation of a torque transfer and compensation of the axial forces occurring
`because of the resulting circumferential force, the connection between two machine elements
`having mutually complementary Hirth toothing designs is usually prestressed axially. To this
`end, means for enabling axially tension on the two machine elements to be coupled to one
`another are additionally used for the positive-locking and self-centering connection. Axial stress
`is understood to refer to the creation of a stress with at least one component in the direction
`parallel to the axis of rotation of the machine elements. Means that may be considered include
`mainly screw connections as well as tension anchors. In addition to causing an additional
`increase in weight, these also cause an increased need for installation space, which must
`already be calculated into the design of the connection in advance in accordance with the
`intended purpose.
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`Therefore, the object of the invention is to improve upon a positive-locking connection by
`means of Hirth toothing, such that the aforementioned disadvantages are avoided, in particular
`due to the fact that the increased requirements with respect to a minimum design space and
`weight can be met. The structural complexity is to be minimized as much as possible.
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`The approach according to the invention is characterized by the features of claim 1.
`Advantageous embodiments are defined in the dependent claims.
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`Thus, a Hirth toothing design and/or a machine element provided with a Hirth toothing design
`for transfer of torque to another second machine element, which is provided with a
`complementary Hirth toothing design is designed by implementing a positive-locking
`connection between the two in such a way that at least one or at least individual ones of the
`toothing elements are designed to be asymmetrical, i.e., to have an asymmetrical geometry
`with regard to the tooth profile.
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`Hirth toothing is understood to refer to teeth, which are preferably used on rotating
`components and are designed so that the geometric lines of the spur gearing are designed with
`a wedge shape and are merged centrally at a point located on the axis of symmetry and/or the
`axis of rotation of the machine element. The teeth per se form a splined gearing, in which the
`individual flanks can be described essentially by means of a plane. The teeth per se are
`arranged in the circumferential direction of the rotating component. The individual toothing
`elements extend in the radial direction, based on the axis of rotation, and the flanks are each
`aligned in the circumferential direction. The height of each tooth is different with respect to the
`height and dimensions of the individual gearing elements and the dimensions of the teeth, as
`seen in the radial direction from the axis of rotation. The teeth are designed to be inclined
`relative to the central midpoint and/or to the axis of rotation.
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`The embodiment of the individual gearing elements with an asymmetrical geometry offers the
`advantage that, depending on the choice of the direction of rotation, either
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`a part, which can be compensated by the positive-locking and self-centering connection
`of the Hirth toothing in a part of the axial force occurring in the transfer of torque due
`to the circumferential force can be compensated by the positive-locking and self-
`centering connection of the Hirth toothing, wherein this part is a function of the number
`of compensation points, i.e., the suitably designed tooth elements and/or the geometry
`of the individual tooth elements;
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`use as a safety coupling in the form of an overrunning clutch, in which the flanks of the
`two mutually engaging Hirth toothing designs of the two machine elements to be
`coupled slide over one another when a predefined axial force is exceeded in accordance
`with the geometry.
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`The asymmetrical structure is achieved by the fact that a first flank of the individual gearing
`elements is designed to be steeper than the other, the second flank. The positions of the flanks
`can be described on the basis of the flank angle, which can be described by the plane, which
`can itself be described by the single flank and a plane perpendicular to the head height line of
`the gearing and/or of the gearing element, said plane described by a line running perpendicular
`to the axis of rotation and through the head height line and makes it possible to describe the
`axis of rotation. The first flank, as seen in one direction of rotation and/or in the circumferential
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`direction, and which is preferably steeper, preferably forms an angle between 0° and < 29°. The
`second, shallower flank of a gearing element forms an angle of 29° < 80°, preferably <80°.
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`However a negative flank angle is also conceivable, so that in the operating condition, the
`machine elements become engaged. The angle of the flanks is understood to be the angle
`formed between the plane described by the flank and another plane running perpendicular to
`the axis of rotation and passing through the flank. This plane can also be described by the
`central axis and/or the axis of rotation and a flank angle of the individual gearing element. The
`angle can additionally be described as follows:
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`90° - (cid:258)(cid:374)(cid:336)(cid:367)(cid:286)(cid:3)(cid:626)1 or 90° - (cid:258)(cid:374)(cid:336)(cid:367)(cid:286)(cid:3)(cid:626)2,
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`(cid:449)(cid:346)(cid:286)(cid:396)(cid:286)(cid:3)(cid:626)1 (cid:258)(cid:374)(cid:282)(cid:3)(cid:626)2 represent the inclination of the flank with respect to the head height line.
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`In the first case, i.e., to compensate for the resulting axial forces, the direction of rotation is
`such that the surface of the gearing flank with the steeper flank is facing and/or is directed in
`the circumferential direction, opposite the direction of rotation. In a preferred embodiment,
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`the steeper flank is embodied as a straight flank, i.e., with an angle of 90° to the head line, so
`that a flank angle of 0° is achieved. This embodiment is characterized by a little effort in terms
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`of the manufacturing technology in addition to the implementation of the function of self-
`centering of the individual machine elements with Hirth spur gearing to be coupled to one
`another.
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`In the second case, i.e., when using the Hirth toothing for connections that function as a safety
`clutch or as an overrunning clutch, the embodiment of the individual gearing elements is such
`that the steeper flank, as seen in the circumferential direction, faces in the direction of the axis
`of rotation. In this case, the flanks of the toothing designs of the two machine parts engaged
`with one another slide against one another when a certain predefined axial force is exceeded in
`accordance with the design of the geometry of the individual gearing, in particular the
`shallower flank.
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`Between the individual tooth designs gearings next to one another in the circumferential
`direction, a tooth base, preferably in rounded form, is incorporated into the gearing. The tooth
`head of the Hirth toothing is preferably embodied as a planar surface.
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`There are multiple possible uses for the arrangement and embodiment of the individual gearing
`elements, including:
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`Arranging the individual gearing elements in the circumferential direction, based on the
`axis of rotation of the machine element over the entire circumference;
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`Arrangement of individual gearing elements in partial regions, based on the
`circumferential direction.
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`In the first case, there is preferably the option of designing the individual gearing elements to
`be similar with regard to their geometry, so that a tooth rim is formed. This possibility is a
`preferred embodiment which is characterized by ease of production and permits optimum
`compensation of the axial force through a corresponding number of available flanks.
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`In the second case, individual tooth elements may either be combined into a single tooth
`element and/or a positive-locking connecting element, or partial regions may be embodied to
`be entirely free of teeth, as seen over the circumference. In addition to that, the tooth
`elements may have a uniform geometry or a differing geometry. However, when gap regions or
`tooth elements comprised of multiple individual elements are provided, one factor to be taken
`into account is that the mating element must be designed accordingly. This yields various
`possibilities. A first possibility consists of a complementary design of the gap region and the
`tooth segment, so that the two machine elements essentially also abut against one another
`over large areas in these regions. In addition, the tooth elements combined from multiple tooth
`elements may be designed with a smaller head height than the tooth elements adjacent to
`them on the same machine elements, so that surface contact of the two machine elements to
`be coupled to one another is achieved in this region, such that this region can be utilized
`optimally for the accommodation and/or arrangement of connecting elements, or large clear
`areas remain between two machine elements.
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`The design, geometry and/or determination of dimensions of the individual tooth elements
`may take place similarly to that of other toothing elements with the different embodiment
`elements, with the tooth elements preferably being produced with a uniform geometry and
`uniform dimensions. However, another possibility is to design individual elements to be
`different from one another with regard to their geometry and/or dimensions.
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`The teeth that are designed to be asymmetrical are preferably designed with regard to their
`geometry in such a way that flanks directed in the same direction, wherein the direction can be
`described by the course of the flank plane, each point in a direction based on the
`circumferential direction. With the same alignment of the flanks, the function is defined in
`accordance with the direction of rotation. Steeper flanks than the first flanks, as seen in the
`circumferential direction during rotation, cause tension. Steeper flanks than the second flank of
`a gearing element in the circumferential direction during rotation serve to implement the
`second function as an overrunning clutch. However, there is also the theoretical possibility,
`which will now be considered in detail, of designing the individual gearing elements with regard
`to their geometry and/or dimensions, so that support of axial force components in one
`direction of rotation as well as the direction of rotation of the machine element are both
`possible. This is preferably achieved by creating individual segments, as seen in the
`circumferential direction of the machine element, which are provided with teeth of different
`tooth geometries, in particular their flank planes, as considered in the circumferential direction
`being aligned opposite from one another. However, such an embodiment presupposes an
`increased effort in terms of manufacturing technology, but this is compensated again by the
`universal usability, regardless of the direction of rotation.
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`The asymmetrically designed gearing can be produced by means of milling or by grinding disks.
`In addition, it is also possible to produce the individual gears by drop forging, by ramming, by
`sintering methods and by rolling methods. In this case, there may also be an additional impact
`strengthening. The functions of the torque transfer/rotational speed transfer and the increase
`in precision and repeatability are also optimally fulfilled. Stresses can be minimized through
`suitably designed surface pressure. The application cases per se may be embodied in a great
`variety of ways. The installation situation of the machine elements and thus the orientation of
`the Hirth spur gearing are irrelevant. Possible representative examples of use include use in
`articulated shaft lines, as the connecting element and power transfer element for use in nuclear
`reactors, rotary machines, e.g., compressors, fans and machine tools.
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`The specific choice of the geometry of the individual gearing elements, the entire gearing in the
`circumferential direction, in particular the use of the possibility of combining individual gearing
`elements to form one gearing element and/or the possibility of embodying gearing
`arrangements with gap regions depends on the specific application case and the stresses
`occurring there and is therefore up to the judgment of the responsible person skilled in the art.
`The advantages of Hirth spur gearing are also optimally utilized by means of the approach
`according to the invention, wherein there is additionally the option of greatly reducing the axial
`forces required for prestressing the two machine elements to be coupled to one another and
`thus also reducing the number of required means for applying this prestressing force for a
`certain direction of rotation, and furthermore, addition with the same alignment of the flanks
`of the successive gearing elements in the other second direction of rotation, the same
`connecting element may also be used as a safety coupling.
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`The inventive approach will be explained below on the basis of the figures, in which the
`following are shown in detail:
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`Figure 1a
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`shows a possible embodiment of an Hirth spur gearing according to the
`invention for implementation of a positive-locking and self-centering connection
`between two machine parts to be coupled to one another on the basis of a detail
`of the two;
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`Figure 1b
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`illustrates the inclination of the flank of the angle describing the individual
`gearing element in an unwound representation of individual successive gearing
`elements according to Figure 1a;
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`Figure 2
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`illustrates an embodiment with asymmetrical gearing elements designed
`according to the invention, wherein the gearing has partial regions, which are
`characterized by the fact that individual adjacent gearing elements are combined
`into a single gearing element;
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`Figure 3
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`illustrates another possible embodiment of a machine element with Hirth spur
`gearing designed according to the invention, wherein the gearing running in the
`circumferential direction has gap regions that are free of gearing elements;
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`illustrates an embodiment of a machine element suitable for any direction of
`rotation by using individual segments of different geometries and orientations;
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`Figure 5
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`illustrates an embodiment with a negative flank angle.
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`Figure 1a illustrates the basic principle of the Hirth spur gearing 1 designed according to the
`invention in a simplified diagram on the basis of one exemplary embodiment. Two machine
`elements that are to be coupled for the purposes of transfer of torque, a first machine element
`2, which can be coupled at least indirectly to a drive machine (not shown in detail here) and a
`second machine element 2' which can be coupled at least indirectly to an output (not shown in
`detail here) are each designed with complementary Hirth spur gearing 1 and 1', respectively.
`The Hirth spur gearing designs 1 and/or 1', respectively, are based on the fundamental idea that
`all the geometric lines of a spur gearing are designed in a wedge shape and converge centrally
`at a point, namely point G here. These individual geometric lines are shown in Figure 1a for
`three gearing elements as an example. The three gearing elements are labeled here as 3, 4 and
`5. The corresponding geometric lines are each labeled as 3', 4', 5' and/or 3", 4" and 5" and/or
`3''', 4''' and 5'''. These geometric lines can be described by the points of intersection of the
`imaginary lines theoretically describing and lengthening the flanks on the individual gearing
`element as well as the points of intersection of the theoretical lines lengthening the flanks with
`a base line GL running parallel to the tooth height ZH in the circumferential direction. In the
`case illustrated here, the individual flanks of the individual gearing element – a first flank and a
`second flank – are each labeled as 3a, 4a and/or 5a and 3b, 4b and/or 5b for the gearing
`elements 3, 4, and/or 5, for example. The theoretical lines describing the flanks 3a, 4a and/or
`5a and 3b, 4b and/or 5b, respectively, when the cross section is projected onto a plane are
`themselves labeled as 6, 6' and/or 6" and 7, 7' and/or 7", respectively. The theoretical lines
`labeled as 6 are assigned to the flanks 3a, 4a and/or 5a, and the theoretical lines labeled as 7
`describe the flanks 3b, 4b and/or 5b, respectively.
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`The Hirth spur gearing 1 and/or 1', which is designed according to the invention, is
`characterized in that the individual gearing element is designed to be asymmetrical. This means
`that the individual flanks, namely the flanks 3a and/or 3b, 4a and/or 4b and 5a and/or 5b,
`respectively, are representative of the individual gearing elements here, namely 3, 4 and/or 5,
`and converge at different angles to one another. As illustrated in Figure 1a, the individual
`gearing elements, which are arranged over the circumference U of the first and/or second
`machine element(s) 2 and/or 2' respectively, as illustrated in Figure 1a, are preferably arranged
`at uniform distances from one another, and/or constructed with the same geometry.
`Specifically, this means that there is a constant distance between any two points on two
`neighboring gearing elements, which are selected at random and are situated on a common
`diameter, based on the axis of rotation and/or the central axis. Figure 1a illustrates this for the
`individual gearing elements 9 and/or 10 on the basis of points 11 and 12 as an example, where
`the distance is labeled as a. This is also true by analogy for the distances between the individual
`flanks directed in the same direction, for example, 3a, 4a, 9a, 10a, 5a and/or 3b, 4b, 9b, 10b,
`5b, for example, of the individual elements neighboring and/or following one another in the
`circumferential direction.
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`For the purposes of transfer of torque between the first machine part 2 and the second
`machine part 2', the Hirth spur gear designs 1 and/or 1', which are designed to be
`complementary to one another, are brought to engagement with one another. The Hirth spur
`gear designs 1 and/or 1' on the individual machine elements 2 and/or 2' permit a positive-
`locking connection between them. The asymmetrical design according to the invention has the
`effect of creating a force component corresponding at least partially to the axial prestressing
`force for prestressing the two machine elements 2 and/or 2. To do so, however, it is necessary
`to design the geometry of the gearing in accordance with the direction of rotation.
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`This geometry is determined essentially by the angles of the flanks. The flanks 3a, 4a and/or 5a
`each describe a plane E13a, E14a and/or E15a and/or E23b, E24b and E25b over their extent b in
`the radial direction to the central midpoint G, which is simultaneously on the axis of symmetry
`and/or the axis of the rotation of the machine element 2 and/or 2', respectively. The angle of
`the flanks can then be represented as the angle of these planes E1 and/or E2 with respect to
`the line describing the head height ZH of the individual gearing element.
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`Figure 1b shows for this purpose a detail of the Hirth spur gearing 1 of the machine element 2
`in the circumferential direction in an unwound form. The two gearing elements 4 and 9
`adjacent to one another in the circumferential direction are illustrated here as representative.
`The line describing the head height ZH always runs in a plane perpendicular to a plane drawn
`through the plane of symmetry of the machine element 2 and/or 2', said plane being
`describable by the axis of symmetry S and a line running perpendicular to the latter. The angle
`of the planes E1 and/or E2 described by the flanks with the line describing the head height ZH
`serves to describe the geometry of the gearings. In the case illustrated here, the angle of the
`flank 4a and/or 9a with the plane and/or head line ZH (cid:349)(cid:400)(cid:3)(cid:367)(cid:258)(cid:271)(cid:286)(cid:367)(cid:286)(cid:282)(cid:3)(cid:258)(cid:400)(cid:3)(cid:626)(cid:1005), and the angle of the
`flank 4b and/or 9b with the plane and/or head line is lab(cid:286)(cid:367)(cid:286)(cid:282)(cid:3)(cid:258)(cid:400)(cid:3)(cid:626)(cid:1006)(cid:856)
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`The flank angle is obtained by subtracting 90° – (cid:626)1 and/or 90° – (cid:626)2. The individual gearing
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`elements, which follow one another in the circumferential direction of the machine element 2,
`are preferably embodied with the same geometry as that illustrated in Figure 1a. The size of the
`axial prestressing forces applied by the geometry of the gearing and required for transfer of
`torque between the two machine elements 2 and/or 2' is a function of the number of gearing
`elements and the geometry, in particular the angle of the individual flanks.
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`WO 99/41513
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`13
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`PCT/EP99/00893
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`5
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`The steeper flank of the two flanks is preferably designed with the flank angle between 0° and
`29°, and the angle of the shallower flank is designed with an angle between 30° and 80°. The
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`choice of the size of the angles is preferably such that the angles are below the limit of self-
`inhibition. However, it is also conceivable for a negative angle to be used for the steeper flank.
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`Theoretically, there is also the option, which is not illustrated separately here, of designing the
`individual gearing elements, which are next to one another in the circumferential direction of
`the machine element 2 and/or 2', so that they have different geometries, wherein the first
`and/or second flanks of two neighboring gearing elements, following one another in the
`circumferential direction, are oriented in the same direction.
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`The asymmetrical design of the gearing elements according to the invention, which follow one
`another in the circumferential direction of the machine elements and cause a reduction in the
`mutually required axial forces for prestressing the two machine elements in the axial direction
`to one another, makes it possible to eliminate the use of additional means for generating the
`axial prestressing force between the two machine elements 2 and/or 2'. The direction of the
`axial prestressing forces is described by a line parallel to the axis of symmetry and/or during
`operation of the axis of rotation of the machine elements 2 and/or 2'. Since it is possible to
`largely reduce the use of the means required to generate the axial prestressing force, this
`eliminates additional structural measures on the individual machine elements 2 and/or 2' to
`accommodate these means, for example, in the form of bores, which may be arranged in the
`area of the gearing of the machine elements. This offers the advantage that the gearing can be
`used completely for a transfer of power, in particular for a transfer of torque.
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`WO 99/41513
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`14
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`PCT/EP99/00893
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`5
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`The advantages of the conventionally designed Hirth spur gearing can also be achieved with the
`approach according to the present invention because there has not been any change in the
`basic idea that all the geometric lines of a spur gearing are to be designed in a wedge shape and
`are to be merged at a central point, and the end faces have been turned to a conical shape to
`achieve a tooth head surface that is limited by the parallel line, i.e., to design the tooth head
`surfaces with parallel side lines. The inventive geometric design also makes it possible to
`establish a positive-locking, self-centering connection. The Hirth spur gearing as a positive-
`locking, soft-centering connecting element, can be used as a space-saving subelement with a
`high precision of parts or as a fixation element with a high repeat precision. The assembly itself
`is of a relative simple design and individual machine elements are easily replaceable.
`
`Figure 2 illustrates another design option for the Hirth spur gearing with the design according to
`the invention. The basic principle and the basic design of the Hirth spur gearing, in particular
`the individual gearing elements, correspond essentially to those described in Figure 1, which
`why the same reference numerals are used for the same elements. The crucial difference is that
`the individual gearing elements are not designed with the same geometry in the circumferential
`direction of the machine elements 2. The approach according to Figure 2 is characterized in that
`individual gearing elements are combined according to Figure 1a to form a single gearing
`element. In the case illustrated here, these are the two gearing elements 14 and 15, which
`preferably have the same angles as those of the other adjacent gearing elements with respect
`to their flanks 14a and/or 15a and 14b and/or 15b, but these each form a stop surface, namely
`labeled as 16 here for the gearing element 14 and 17 for the gearing element 15 for a
`corresponding stop surface on the machine element 2' that is to be coupled to the machine
`element 2. This stop surface 16 and/or 17 is formed by the head surface of this gearing element
`14 and/or 15, which is widened in the circumferential direction. These regions are preferably
`utilized in the rotation of symmetrically designed elements to receive the boreholes and/or
`threads to be provided in the means required to hold together the individual machine elements
`2 and/or 2'.
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`WO 99/41513
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`The embodiment of the individual gearing elements combined to form one gearing element
`with different dimensions in comparison with the remaining other gearing elements, as
`illustrated in Figure 2, represents only one possible option of many possibilities. According to
`the individual use case, the individual elements may be combined with regard to the number of
`gearing elements to be combined as well as the number of combinations to be made. In
`addition, there is the possibility of designing the individual gearing elements, also those formed
`with different geometries, by combining the elements. In particular the individual gearings may
`be different with regard to the angles of the flanks.
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`The designs of the embodiments of Hirth spur gears according to the invention, as illustrated in
`and described with reference to Figures 1 and 2, is preferably used for the positive-locking
`coupling of two machin