Rotary Damper

Abstract: Rotary damper, in particular for an actuating member in motor vehicles, comprising a housing (10) having a cylindrical damper chamber, a liquid viscous medium within the chamber, a rotatably supported shaft (22) within the chamber having at least one substantially radially extending vane (40) such that upon rotation of the shaft displaced medium flows between a narrow passage between the cylindrical wall of the chamber and the free end of the vane (40), at least a radially outer portion of the vane being inclined with respect to a diameter extending through the basis of the vane towards the circumferential direction and being bendable such that upon a rotation of the shaft (22) towards the inclination direction the vane is bent towards the cylindrical wall and upon an opposite rotation the vane is bent towards the shaft, wherein at least one locking cam (61) is provided at the cylindrical wall of the chamber which extends radially inwards and is adapted to be engaged by the free end of the vane if it is bent towards the cylindrical wall a certain extent.

Description: The invention relates to a rotary damper, in particular for the actuation part in motor vehicles, according to the preamble of patent claim 1. From DE 42 44 484 there has become known a rotary damper with which in a damping chamber which contains a viscous medium there is arranged a vane which is mounted to a shaft. With a rotation of the shaft the medium is displaced and flows through between the end of the vane and the chamber wall. With the known rotary damper the vane is inclined towards one side in the circumferential direction and is deformable or bendable relative to the shaft in a manner such that it is pivoted with a rotation in the inclination direction towards the cylindrical chamber wall and with an opposite rotation towards the shaft. By way of this a rotary damper is provided which in opposite rotational directions creates a damping of differing strength. With a pivoting of the vane in the direction of the chamber wall, the gap present to the wall is reduced so that a relatively high braking force is developed. If the shaft however is rotated in the opposite direction, the vane pivots in the direction of the shaft so that the distance of the vane to the cylindrical chamber wall is enlarged. By way of this a larger flow cross section is provided, and the rotational force in this direction is braked much less. As a result with such a rotary damper a type of free-running is created. There are cases in which the braked movement of an actuated part is often not sufficient to prevent damage, for example with back rests or likewise. It is therefore the object of the invention to provide a rotary damper in particular for an actuation part in motor vehicles which prevents a braking acceleration from exceeding a predetermined value. This object is achieved by the features of patent claim 1. With the rotational damper according to the invention in the damping chamber there is arranged a locking cam which extends radially inwards and with which the free end of the vane comes into engagement when the vane is pivoted about a certain measure towards the chamber wall. A pivoting of the vane towards the chamber wall is dependent on the torque or the acceleration of the rotor (the shaft plus the vane). If the acceleration reaches a certain value which possibly is critical for the actuation of the part to be actuated, the vane comes into engagement with the locking cam so that any further movement is completely blocked. As soon as the acceleration is zero the vane may retract from the part locking cam and as a result is released again. The movement of the part to be actuated may as a result be continued It is to be understood that with several vanes to each one there may be allocated a locking cam. Also a number of locking cams may be provided which is a multiple of the number of vanes. This is advantageous when a very rapid stop is to be obtained on reaching the predetermined acceleration. In one embodiment of the invention it is provided that on one side of the vane a support rib or likewise is mounted on the shaft in such a manner that the vane bears against the support rib when it is pivoted towards the chamber wall by a certain measure. The support rib has the object of preventing the vane from being bent through and at the same time rattling past the locking cam. The rib thus fulfills the object of preventing a rotation beyond the locking position. Advantageous formations of the invention are specified in the dependent claims. One embodiment example of the invention is hereinafter explained in more detail by way of drawings. Fig. 1 shows a section through a rotary damper according to the invention, in the resting condition. Fig. 2 shows the rotary damper according to Fig. 1 with a rotation of the rotor in the clockwise direction. Fig. 3 shows the rotary damper according to Fig. 1 with a rotation in the anti-clockwise direction. Fig. 4 shows the lateral view of the rotor of the rotary damper according to the Figures 1 to 3, partly in section. The rotary damper represented in the Figures 1 to 3 comprises a pot-like housing 10 which at the open side is closed with a lid (not shown). In the housing there is located a fluid (not shown), e.g. silicon oil. In the housing there is arranged a rotor 16 which comprises a cylindrical section 18 which is connected via a radial section 20 between the ends to a shaft 22. The cylindrical section 18 extends approximately between the floor, not shown, of the pot-like housing 10 and the lid. The shaft 22 extends through a central opening of the lid (not shown). On the outer lying section of the shaft a pinion may be mounted in a rotationally secure manner. On the opposite side of the wall 20 there is formed an accommodating chamber 30 for an axial collar of the housing 10, which is not shown. The construction described up to now is of no particular importance and is otherwise known from DE 42 44 484. On the circumference of the cylindrical section 18 there are arranged a row of vanes 40. The shape of the vanes can be clearly deduced from the Figures 1 to 3. They are slightly curved and inclined to one rotational direction (here anti-clockwise), i.e. opposite to the diameter which goes through the respective base section 42. The free end is curved more heavily but however comprises an oblique surface section 44 on the outer side. Neighbouring vanes 40 are laterally displaced as can be deduced from Fig. 4. On the outer sides the ends comprise inclinations 46 which alternately run on the one or the other side. They favour the meandering course of the flow between the vanes when the rotor 16 is rotated in the housing 18. The vanes 40 which are formed as one part with the rotor 16 from plastic, comprise weakenings 48 near to the base section 42. The weakenings simplify a pivoting of the vanes 40 in the direction of the rotor 16 when this rotor is rotated in the clockwise direction. This is to be recognized in Figure 2. Figure 1 shows the rotor 16 at a standstill. By way of this between the free ends of the vanes 40 and the cylindrical wall of the chamber a more or less large passage is formed, so that the rotor may be rotated relatively easily (free-running). In the reverse direction on the other hand essentially only the described flow path laterally past the vanes 40 is possible, so that a relatively strong braking effect occurs. With an even stronger rotation there is effected a deformation of the vanes in a manner such that the vanes abut against radially running abutment surfaces of cams 61 which are arranged on the inner side of the housing 10. The abutment surface of the cams 61 and the vanes 40 is such that on abutting they bear against one another in a relatively flush manner. On the end which is distant to the abutment surface the cams are formed in a ramp-like manner. By way of this with a rotation of the rotor 16 in the clockwise direction there is formed a sliding surface. In each case a support rib 60 is allocated to a vane 40, this support rib being similarly inclined as the vane 40 and extending approximately up to the circle on which the radially inner lying surfaces of the cams 61 lie. The support ribs 60 are relatively narrow as can be recognized from Fig. 4 and taper in a triangular manner in the clockwise direction. By way of this the support ribs 60 only apply a relatively slight braking moment with the free-running rotation (Fig. 2). With an opposite rotation the ribs serve for supporting the vanes when these abut against the cams 61 (Fig. 3). It is prevented that the rotor 16 continues rotating in spite of the abutment of the vanes 40 on the cams 61, in that the vanes fold. A folding over or bending around of the vanes 40 is prevented by the support ribs 60.

Claims: Rotary damper, in particular for an actuating member in motor vehicles, comprising a housing (10) having a cylindrical damper chamber, a liquid viscous medium within the chamber, a rotatably supported shaft (22) within the chamber having at least one substantially radially extending vane (40) such that upon rotation of the shaft (22) displaced medium flows between a narrow passage between the cylindrical wall of the chamber and the free end of the vane (40), at least a radially outer portion of the vane (40) being inclined with respect to a diameter extending through the basis of the vane (40) towards the circumferential direction and being bendable such that upon a rotation of the shaft (22) towards the inclination direction the vane (40) is bent towards the cylindrical wall and upon an opposite rotation the vane (40) is bent towards the shaft (22), characterized in that at least one locking cam (61) is provided at the cylindrical wall of the chamber which extends radially inwards and is adapted to be engaged by the free end of the vane (40) if it is bent towards the cylindrical wall a certain extent. The rotary damper of claim 1, wherein a plurality of vanes (40) is provided and the same number of locking cams (61) or a multiple thereof, with the locking cams (61) being circumferentially equally spaced. The rotary damper of claim 1 or 2, wherein the locking cam (61) at the inner side is ramp-shaped and ascends towards the abutment surface of the cam (61). The rotary damper of claim 1, wherein a supporting rib (60) or the like is connected with the shaft (22) on one side of the vane (40) such that the vane (40) engages the supporting rib (60) if the vane (40) is bent towards the cylindrical chamber wall a certain extent. The rotary damper of claim 4, wherein the engagement of the vane (40) with the supporting rib (60) takes only place after the free end of the vane has engaged the locking cam (61). The rotary damper of claim 1, wherein the free end of the vane (40) is formed by an oblique surface having an inclination relative to the longitudinal extension of the vane (40) such that the surface completely engages the associated engagement surface of the locking cam (61) upon corresponding deformation of the vane (40). The rotary damper of claim 1, wherein in a rest state the vane (40) extends radially approximately up to the position of the locking cam (61). The rotary damper of claim 1, wherein the shaft and the vane (40) are integrally formed of plastic material. The rotary damper of claim 4, wherein the supporting rib (60) is triangular in cross section with the apex of the triangle facing opposite to the inclination direction of the vane (40). The rotary damper of claim 1, wherein the vane (40) has a weakened cross-sectional portion, preferably near the base portion of the vane (40). The rotary damper of claim 1, wherein the vane (40) is arcuately formed. The rotary damper of claim 1, wherein adjacent vanes (40) in circumferential direction have are offset relative to each other. The rotary damper of claim 1, wherein with a plurality of vanes (40) the ends thereof have beveled surfaces at alternating outer sides. The rotary damper of claim 1, wherein the locking cam (61) is integrally formed with the housing (10).

Inventors: FUSS JUERGEN, KORB HOLGER K, FUSS, JUERGEN, KORB, HOLGER K., Fuss, Jürgen
Applicants: ITW ATECO GMBH, ITW-ATECO GMBH
Application year: 1998
Main classification: F16F9
IPC codes: F16F9