Rotary Damper

Abstract: A rotary damper with a housing (10), with a rotor rotatably mounted in a closed chamber of the housing and with a viscous medium filled into the chamber, wherein the rotor is so formed and so cooperates with the wall of the chamber (14) that with a relative rotation of the housing and the rotor, a braking effect is produced by the medium, wherein at least two rotor elements (18,20) are provided which are arranged coaxially, preferably commonly in the chamber, and the neighbouring rotor elements are coupled such that they are freely rotatable relative to one another over a limited rotational angle.

Description: The invention relates to a rotary damper according to the preamble of patent claim 1. Rotary dampers are known in the most varied of formations and fields of application. There are commonly applied with automobiles in which certain parts, such as lids for glove compartments, ash trays, holding grips or likewise are damped in their movement. In most cases it is a case of preventing a heavy knocking of the parts against an abutment. By way of this knocking, specifically undesirable noises are produced and the lifetime of the function is compromised. In many cases a damping is only desirable in one direction, so that the damper is applied with a free running. However these are more complicated with respect to the simple rotary dampers and require more space, which commonly is not available for the installation. A typical rotary damper comprises a housing, mostly of plastic, in which a chamber for the rotor is formed. The rotor is rotatably mounted in the housing and extends via a shaft to one or both sides out of the housing. On the end of the shaft protruding out of the housing, mostly a pinion is seated which can be brought into engagement with a counter-pinion or a rack. Often the damper is stationarily applied so that an arcuate rack on the part to be damped rotates the pinion when the part is moved. In the chamber of the damper housing there is filled a viscous medium which acts between the rotor and the chamber wall when the relative movement between the rotor and the housing takes place. For the formation of a rotor there are the most varied of embodiment forms. A typical formation consists in providing the rotor with at least one vane which radially projects into the chamber and may be observed as a type of rotating piston. With the movement of the vane in the chamber, medium is displaced which is forced through a gap between the vane and the chamber wall or reaches the other side of the vane in another way. In this context it is also known to flexibly design vanes of a rotor for rotary dampers in order to form a differently large gap between the vane and the chamber wall, according to the rotational direction, in order to achieve an effect similar to free running in the one rotational direction. All known rotary dampers described above have in common that on operation they produce a more or less constant braking moment. In some cases of application however the torque on the part to be damped is not constant but changes with the rotational position. If e.g. the flap of a glove compartment is opened the flap is located approximately in the dead centre position, i.e. exerts a very small torque in the direction of the opening position. If the rotary damper has a relatively high braking moment the initial torque of the flap is not sufficient to set this flap in motion. If on the other hand the damper is given a slight braking moment then the opening speed at the end of the adjustment is too large. From DE 196 15 433 A1 a rotary damper has become known wherein the rotor within a chamber comprises at least two rotor elements coaxially disposed within the housing chamber and being adapted to be cooperatively coupled together. This coupling is achieved by threads cooperating between one rotary member and a thread in the part of the chamber adjacent to the thread of the rotary member. A rotation of this rotary member results in an axial displacement thereof so that clutch elements of this rotary member and the second rotary member may interengage so that upon further rotation both rotary members rotate and provide a braking effect. It is the object of the present invention to provide an effective and simply structured rotary damper wherein in rotational direction differing braking moments are produced. This object is achieved by the features of patent claim 1. Common with the prior art above the rotary damper according to the invention has at least two rotor elements which are arranged coaxially, preferably commonly in a chamber. The rotor elements are coupled to each other such that a relative free rotation over a limited rotational angle is possible. It is to be understood that two or more rotor elements produce a higher braking moment than only one rotor element. If therefore at the beginning of an actuation of a part to be braked only the one rotor element is made effective, firstly only a correspondingly low braking moment is produced, which then increases in a stepped manner if also the second rotor element is co-rotated. It is to be understood that in this manner a multitude of coaxial rotor elements may be coupled. It is conceivable that two or more housings of rotary dampers are coaxially arranged with a rotor element in each case, so that their shaft sections guided outwardly may be coupled to one another in the described way and manner. It is however less complicated and requires less constructional space when a common chamber is provided for the rotor elements and the rotor elements within the chamber are connected to one another via a special coupling. The interengagement of the rotor elements allow a simple structure of the rotary damper. The rotary elements need only to rotate and require no axial diplacement within the chamber If the rotor elements are arranged within the common chamber, according to one embodiment of the invention it is advantageous when the ends facing one another form a rotary bearing. This may be effected according to one embodiment of the invention in that a rotor element at one end comprises a central pinion circular in cross section which approximately is fitting in a central, preferably cylindrical bore of the other rotor element. According to which location the coupling is mounted, the pinion and bore are provided with a relatively large diameter approximating the outer diameter of the rotors. For the coupling of adjacent rotor elements in the invention a type of claw coupling is provided, wherein the claw sections are formed or mounted such that a relative rotation between the rotor elements is possible with which a force transmission of one rotor element onto the other does not take place. Two coupling claws lying opposite one another to be provided in an end-side recess of one rotor element, and for the other rotor element with a plate-like coupling section to engage into the recess and selectively to be able to be brought into engagement with a coupling surface of the coupling claws. This engagement is preferably in the manner such that the plate-like section completely engages with the coupling surfaces so that no too high surface loadings occur. The extent of the free rotation between the coupling elements is dependent on which braking behaviour is desirable. If a small braking moment is required over a small rotational angle, then a free rotation may be correspondingly limited and vice-versa. In the extreme case the maximum free rotation is approximately 360° when the one coupling section only extends to approximately the rotational axis and the other rotor element merely comprises an abutment. With such a formation the cooperating coupling sections are however designed relatively weak. Normally however such a large free rotational angle is not required. The invention is hereinafter described in more detail by way of one embodiment example. Fig. 1 schematically shows in section a rotary damper according to the invention. Fig. 2 shows a section through the representation according to Fig. 1 along the line 2-2. Fig. 3 shows the application of a rotary damper according to Figs. 1 and 2 with a flap, wherein the flap is shown in a closed position. Fig. 4 shows a similar representation to Fig. 3 with an opened flap. The rotary damper shown in the Figs. 1 and 2 comprises a cylindrical housing 10 which is opened at one end and at the other end is closed by a floor 12. The housing 10 forms a cylindrical inner space 14 or a chamber which accommodates two rotor elements 18, 20. In the case shown the rotor elements 18, 20 are shown with a cylindrical outer surface. This is however not of importance. Instead of this the rotor elements 18, 20 may comprise at least one radial vane or likewise. Between the rotor elements 18, 20 and the wall of the chamber 14 there is formed an annular gap 22 which is filled with a viscous medium. The rotor element 20 comprises a cylindrical section lying on the outside which may be formed as a pinion. Alternatively the section 24 may be formed with a rectangular deepening 26 for the purpose of engagement with a peg which has a rectangular section for the purpose of transmitting the torque from the peg to the rotor element 20. The rotor element 20 comprises at the inner end a central peg 28 which is circular in cross section and which sits in a corresponding bore 30 at the facing end of the rotor element 18. In this manner a rotational bearing is created between the rotor elements 18, 20. The rotor element 18 is formed with a recess 32 at the end facing the peg 28. On the wall of the recess 32 opposite there are formed coupling sections 34, 36 which are triangular in cross section with coupling surfaces 38 which are approximately at right angles to one another. The coupling sections 34, 36 project radially inwards in the direction of the common axis of the rotor elements 18, 20. The rotor element 20 comprises between the peg 28 and the upper section a plate-like section 40 which is centrally arranged and which engages into the recess 32. One recognises from a common observation of Figs. 1 and 2 that the described coupling permits a relative rotation between the rotor elements 18, 20 of about 90°. In the position shown in Fig. 2 a 45° rotation may take place before the rotor elements 18, 20 are coupled in the one or the other direction. With a free rotation of the rotor element 20, by nature a much lower braking moment is developed than with a rotation of both rotor elements 18, 20. In this manner it is possible to achieve a progressive damping. If a multitude of rotor elements are coupled in the described way and manner, a desired course of torque may be achieved in order to approximate the torque characteristic curve of a part to be damped. In the Figs. 3 and 4 an example for the application of a rotary damper according to Figs. 1 and 2 is shown very schematically. In the Figs. 3 and 4 the rotary damper is indicated at 50. It serves for damping a flap 52 which closes a glove compartment 54. One recognises from Fig. 3 that the opening moment of the flap 52 is very low on account of the flap 52 lying approximately in the dead centre. A large braking moment would consequently prevent an opening of the flap 52 by way of gravity. If a rotary damper corresponding to Figs. 1 and 2 is applied, this with a first rotation produces a relatively low braking moment, in that only the rotor element 20 acts in a braking manner. Only when the second rotor element 18 is coupled is a much larger braking moment achieved, in order to effectively damp the flap with an adjustment into the horizontal position (Fig. 4).

Claims: A rotary damper comprising a housing (10) defining a chamber (14) having an interior peripheral wall, a rotor rotatably disposed within said housing chamber (14) about a rotary axis and a viscous medium disposed within said housing chamber (14), the rotor operatively cooperates with the interior peripheral wall of the housing chamber (14) such that a damping effect is achieved upon rotation of the rotor with respect to the housing (10), the rotor comprising at least two rotor elements (18, 20) coaxially disposed within the housing chamber (14) and adapted to be operatively coupled together such that at least two rotor elements can freely rotate relative to each other through a limited angle of rotation about said rotary axis whereby when a first one of the at least two rotor elements (18, 20) is rotated relative to the housing (10), a first damping effect having a first damping value is achieved, whereas when a second one of the at least two rotor elements (18, 20) is also rotated relative to the housing (10) along with the first one of the at least two rotor elements (18, 20), a second damping effect having a second damping value is achieved, claw clutch means being provided between the ends of the rotor elements (18, 20) facing each other, characterised in that the clutch claw means comprises a recess (32) defined with one end of the second one of said at least two rotor elements (18, 20), a pair of diametrically opposed clutch claws (34, 36) disposed within the recess, wherein each one of the clutch claws (34, 36) has a clutch engagement surface and a plate-like clutch member (40) mounted upon the first one of the at least two rotor elements (28) and disposed within the recess for selectively engaging one of the clutch engagement surfaces of said pair of clutch claws (34, 36). The rotary damper of claim 1, characterised in that the at least two rotor elements (18, 20) have first adjacent ends which define a rotary bearing for permitting at least two rotor elements (18, 20) to rotary with respect to each other about the rotary axis. The rotary damper of claim 2, characterised in that the rotary bearing comprises an axial bore defined within a first end of a first one of the at least two rotor elements (18, 20) and an axial pinion (28) provided upon a first end of a second one of the at least two rotor elements (18, 20) and disposed within the axial bore of the first one of the at least two rotor elements (28). The rotary damper of claim 1, wherein each one of the pair of clutch claws has a geometrical configuration in cross-section with clutch engagement surfaces of each one of the pair of clutch claws being arranged such that the plate-like clutch member can engage one of the clutch engagement surfaces of one of the pair of clutch claws depending upon the direction of rotation of the first one of the rotor elements with respect to the housing. The rotary damper of claim 4, characterised in that each of the pair of clutch claws (34, 36) has a substantially triangular configuration in cross section. The rotary damper of claim 5, characterised in that the clutch engagement surfaces (38) comprises sides of a triangle disposed upon opposite sides of an apex of the triangle wherein the apex of said triangle is disposed radially inwardly towards the rotor axis of said rotor.

Inventors: WONN MARCUS, WONN, MARCUS
Applicants: ITW ATECO GMBH, ITW-ATECO GMBH
Application year: 1998
Main classification: F16F9
IPC codes: F16F9, E05F5