Torque-stabilizing rotary damper

Abstract

Rotary damper (10), comprising: - a casing (12) comprising a chamber (16) containing a viscous braking fluid, - a cover (21), and - a rotor (14), rotationally connected to the casing (12) and mounted thereon, the rotor (14) having a control portion (23c) protruding outside the chamber (16) through a hole (22) formed in the cover (21). The rotor comprises an axially fixed part (23) on which the control portion (23c) is formed, and an axially floating part (25) interposed between the axially fixed part (23) of the rotor (14) and the end wall (19) of the casing (12) and prismatically coupled with the axially fixed part (23) of the rotor (14), the axially floating part (25) being capable of axially translating with respect to the axially fixed part (23) of the rotor (14) and with respect to the casing (12).

Description

[0001] Torque- stabilizing rotary damper

[0002] The present invention relates to a rotary damper of the type comprising: a casing comprising a side wall and an end wall which delimit a chamber containing a viscous braking fluid, a cover mounted on the casing on the opposite side with respect to the end wall so as to close said chamber, and a rotor, rotationally connected to said casing and mounted thereon, said rotor having a control portion protruding outside the chamber through a hole formed in the cover.

[0003] Devices of this type are commonly known, in which the control portion of the rotor and the casing are configured for coupling to respective parts whose relative movement is to be slowed down.

[0004] It is generally observed that the resisting torque applied by the rotary damper varies significantly as a function of the temperature and the rotational speed during operation of the device. Such variability in performance is often undesirable.

[0005] An object of the present invention is therefore to implement a rotary damper capable of operating in a more stable manner than known rotary dampers.

[0006] Said object is achieved according to the invention by a rotary damper of the type defined at the beginning, in which the rotor comprises an axially fixed part on which said control portion is formed, and an axially floating part interposed between the axially fixed part of the rotor and the end wall of the casing and prismatically coupled with the axially fixed part of the rotor, said axially floating part being capable of axially translating with respect to the axially fixed part of the rotor and with respect to the casing, wherein elastic means are interposed between the axially fixed part and the axially floating part of the rotor to urge the axially floating part of the rotor towards the end wall of the casing. It has indeed been found that the presence of the floating part of the rotor allows for a compensating effect, as the operating conditions (temperature, rotational speed) vary, which results in at least partially stabilizing the performance of the device.

[0007] Preferred embodiments of the invention are defined in the dependent claims.

[0008] Further characteristics and advantages of the device according to the invention will become clearer from the following detailed description of one embodiment of the invention, made with reference to the accompanying drawings, provided purely by way of illustrative and non-limiting example, in which:

[0009] - figure 1 is a sectional view of a rotary damper according to the invention,

[0010] - figure 2 is an exploded view of the damper of figure 1 ; and

[0011] - figures 3 and 4 are enlarged views of a detail of figure 2, in two different operating positions.

[0012] In the figures a rotary damper, denoted overall by 10, of the barrel type is illustrated. Such damper may have rather small dimensions, for example of the order of a few centimetres or even smaller. The spatial attributes used below, such as “axial” and “radial”, refer to the axis of rotation of the rotor of the rotary damper 10.

[0013] The damper 10 comprises a casing 12 made of plastic material, on which a rotor 14 made of plastic material is mounted, rotatable about an axis x. The casing 12 is substantially cylindrical and comprises one or more fastening lugs 15, which allow mounting of the device on a support (not illustrated). The shape of the fastening lugs is not essential for the purposes of the invention and depends on the installation conditions of the device. Alternatively, the fastening lugs may be absent and replaced by other fastening means known to the expert in the field.

[0014] The casing 12 is a one-piece element and defines a chamber 16 containing a viscous fluid, for example a silicone oil. The chamber 16 is laterally delimited by a side wall 17, and at one end is closed by an end wall 19. The end of the chamber 16 opposite the end wall 19 is open. At said end an annular groove 17a and a shoulder 17b are arranged, which are formed on a radially inner surface of the side wall 17.

[0015] On an axially inner surface of the end wall a rotation pin 19a is formed, projecting towards the inside of the chamber 16. Coaxially with the rotation pin 19a, a spacer formation 19b is formed, also projecting towards the inside of the chamber 16.

[0016] The side wall 17 comprises an inner surface portion 17c tapered towards the end wall 19 of the casing 12. The inner surface portion 17c is arranged coaxially with the rotation pin 19a. According to a less performing embodiment, the side wall 17 may be without the inner surface portion 17c tapered towards the end wall 19 of the casing 12, and therefore have a radially inner cylindrical surface along the entire height extension of the chamber 16.

[0017] The damper 10 further comprises a cover 21 mounted on the casing 12 on the opposite side with respect to the end wall 19 so as to close the chamber 16. The cover 21 has a through hole 22. In the illustrated example, the edge of the cover snaps into the annular groove 17a formed in the side wall 17. The assembly arrangement of the cover is not essential for the purposes of the invention and may be different from that described above, provided that the same function of closing the chamber 16 is achieved.

[0018] The rotor 14 comprises an axially fixed part 23 and an axially floating part 25 interposed between the axially fixed part 23 of the rotor 14 and the end wall 19 of the casing 12. Each of said parts 23 and 25 is made as a one-piece element, for example in plastic material.

[0019] The axially fixed part 23 of the rotor 14 comprises a main body 23a from which a flange portion 23b extends radially outward, and from which a control portion 23c extends axially outward. The control portion 23c protrudes outside the chamber 16 through the hole 22 formed in the cover 21, and is configured to be coupled to a part (not illustrated) whose movement relative to the support to which the casing 12 of the rotary damper 10 is fixed is to be slowed down. In the illustrated example, the control portion 23c is configured to be prismatically coupled to a toothed wheel 24, which in turn is to be coupled to a further toothed element not illustrated. The type of coupling of the control portion 23c to the elements external to the rotary damper is not essential for the purposes of the invention and may be different from that described above.

[0020] In the main body 23a of the axially fixed part 23 of the rotor 14 a guide hole 23d is formed extending in the axial direction.

[0021] The axially fixed part 23 of the rotor 14 is axially retained between the cover 21 and the shoulder 17b formed on the side wall 17 of the casing 12. In this way, the retention of the axially fixed part 23 of the rotor 14 is achieved in a particularly simple manner. This arrangement is not, however, essential for the purposes of the invention and may be replaced by an equivalent arrangement that still achieves the retention of the axially fixed part 23 of the rotor 14.

[0022] The axially floating part 25 of the rotor 14 has a cup-shaped body arranged around the main part 23a of the axially fixed part 23 of the rotor 14. The axially floating part 25 comprises an outer surface portion 25a tapered towards an axial end of the axially floating part 25 facing the end wall 19 of the casing 12, approximately conforming to the inner surface portion 17c of the side wall 17 of the casing 12. According to a less performing embodiment, the axially floating part 25 may be without the tapered outer surface portion 25a, and therefore have a radially outer cylindrical surface.

[0023] The axially floating part 25 of the rotor 14 is prismatically coupled with the axially fixed part 23 of the rotor 14. The axially floating part 25 is therefore capable of axially translating with respect to the axially fixed part 23 of the rotor 14 and with respect to the casing 12. To this end, on the side of the axially floating part 25 of the rotor 14 facing the axially fixed part 23, a guide pin 25b is formed, prismatically coupled with the guide hole 23d formed in the axially fixed part 23 of the rotor 14. Although preferred for its simplicity of implementation, this arrangement is not essential for the purposes of the invention and may be replaced by an equivalent arrangement that achieves the required prismatic coupling. For example, the pin-hole arrangement may be reversed with respect to that described, having the guide pin on the axially fixed part and the guide hole on the axially floating part of the rotor. Preferably, the guide pin 25b and the guide hole 23d have a substantially triangular cross- sectional shape.

[0024] The axially floating part 25 of the rotor 14 is rotatably coupled with the end wall 19 of the casing 12. To this end, on the side of the axially floating part 25 of the rotor 14 facing the end wall 19, a guide hole 25b is formed, coupled with the rotation pin 19a formed on the end wall. Although preferred for its compactness, this arrangement is not essential for the purposes of the invention and may be replaced by an equivalent arrangement that achieves the required coupling. For example, the pin-hole arrangement may be reversed with respect to that described, having the rotation pin on the axially floating part and the hole on the end wall.

[0025] Figures 3 and 4 show the axially extreme positions that can be reached in operation by the axially floating part 25, respectively in abutment against the end wall 19 of the casing 12 (more precisely, against the spacer formation 19b), and in abutment against an end of the axially fixed part 23 of the rotor 14. The rest position of the axially floating part 25 normally corresponds to the position of figure 3, while due to the operating conditions, for example a high number of revolutions imposed on the damper or a high operating temperature, the axially floating part 25 tends to move towards the position of figure 4. In this way, a greater quantity of viscous fluid tends to flow into the area between the axially floating part 25 of the rotor 14 and the end wall 19 of the casing 12. Generally, a few tenths of a millimetre of travel between the two extreme positions are sufficient to obtain a compensating effect, as the operating conditions (temperature, rotational speed) vary, sufficient to appreciably stabilize the performance of the device in terms of resisting torque. In order for there to always be a sufficient quantity of viscous fluid in the area between the axially floating part 25 of the rotor 14 and the end wall 19 of the casing 12, the spacer formation 19b establishes a given non-zero distance d between a pair of axially opposed surfaces 19s, 25s of the end wall 19 of the casing 12 and of the axially floating part 25 of the rotor 14, respectively. The spacer formation 19b may be arranged differently from what is described above and shown in the figures. Preferably, elastic means are interposed between the axially fixed part 23 and the axially floating part 25 of the rotor 14 to urge the axially floating part 25 of the rotor 14 towards the end wall 19 of the casing 12. Said elastic means may comprise a spring 26, in particular a coil spring, arranged coaxially with the axially fixed part 23 of the rotor 14. The elastic means serve to restore the rest position of the axially floating part 25 when the conditions that caused its movement away from the end wall 19 of the casing 12 are no longer present. According to an alternative embodiment, less preferable, the elastic means may be absent.

[0026] An annular gasket 27 is interposed between a radially outer surface of the axially floating part 25 of the rotor 14 and the side wall 17 of the casing 12. Said annular gasket 27 separates the chamber 16 into a first region between the axially floating part 25 of the rotor 14 and the casing 12, wherein the viscous fluid is present, and into a second region between the axially floating part 25 and the axially fixed part 23 of the rotor 14, where the viscous fluid is substantially absent.

Claims

CLAIMS1. Rotary damper (10), comprising :- a casing (12) comprising a side wall (17) and an end wall (19) which delimit a chamber (16) containing a viscous braking fluid,- a cover (21) mounted on the casing (12) on the opposite side to the end wall (19) so as to close said chamber (16), and- a rotor (14), rotationally connected to said casing (12) and mounted thereon, said rotor (14) having a control portion (23c) protruding outside the chamber (16) through a hole(22) formed in the cover (21), wherein said rotor comprises an axially fixed part (23) on which said control portion (23c) is formed, and an axially floating part (25) interposed between the axially fixed part (23) of the rotor (14) and the end wall (19) of the casing (12), and prismatically coupled with the axially fixed part (23) of the rotor (14), said axially floating part (25) being capable of axially translating with respect to the axially fixed part (23) of the rotor (14) and with respect to the casing (12). characterised in that elastic means (26) are interposed between the axially fixed part(23) and the axially floating part (25) of the rotor (14) to urge the axially floating part (25) of the rotor (14) towards the end wall (19) of the casing (12).

2. Damper according to claim 1, wherein said side wall (17) comprises an inner surface portion (17c) tapered towards the end wall (19) of the casing (12), said inner surface portion (17c) surrounding the axially floating part (25) of the rotor (14).

3. Damper according to claim 1 or 2, wherein said elastic means comprise a spring, in particular a coil spring.

4. Damper according to any one of the preceding claims, wherein one of said end wall (19) of the casing (12) and axially floating part (25) of the rotor (14) is provided with a rotation pin (19a) coupled to a hole (25c) formed in the other of said end wall (19) of the casing (12) and axially floating part (25) of the rotor (14), said rotation pin (19a) defining the axis of rotation (x) of the rotor (14).

5. Damper according to claim 5, wherein a spacer formation (19b) is formed on at least one of said end wall (19) of the casing (12) and axially floating part (25) of the rotor (14) to establish a given non-zero distance (d) between a pair of axially opposed surfaces (19s, 25s) of the end wall (19) of the casing (12) and of the axially floating portion (25) of the rotor (14), respectively.

6. Damper according to any one of the preceding claims, wherein one of said axially floating part (25) and axially fixed part (23) of the rotor (14) is provided with a guide pin (25b) prismatically coupled to a guide hole (23d) formed in the other of said axially floating part (25) and axially fixed part (23) of the rotor (14).

7. Damper according to claim 6, wherein said guide pin (25b) and said guide hole (23d) have a substantially triangular cross-sectional shape.

8. Damper according to any one of the preceding claims, wherein a gasket (27) is radially interposed between said axially floating part (25) of the rotor (14) and said side wall (17) of the casing (12).

9. Damper according to any one of the preceding claims, wherein the axially fixed part (23) of the rotor (14) is axially retained between the cover (21) and the side wall (17) of the casing (12).

10. Damper according to any one of the preceding claims, wherein each of said casing (12), axially fixed part (23) of the rotor (14) and axially floating part (25) of the rotor (14) is a one-piece element.

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