The present invention refers to a rotary damper, comprising:

- a casing having a substantially tubular shape;

- a rotor, mounted within the casing, and rotatable with respect thereto;

- a spring, a first end of which is fixedly coupled to the casing, and a second end of which is fixedly coupled to the rotor;

in which said casing and rotor cooperate so as to sealingly enclose a braking chamber containing a viscous braking fluid;

in which, at its first end, said casing is closed by a fixedly jointed plug, and at its second end sealingly embraces said rotor; and

in which said spring is a helical spring, the first and second end of which extend in the axial direction of the rotor and are housed in respective seats formed on the plug and on the rotor, respectively.

The purpose of the present invention is that of making a rotary damper the structure of which makes it possible to achieve high length/diameter ratios of the damper, for example in the order of 10, with an outer diameter of the device as small as possible.

Such a purpose is achieved according to the invention by a rotary damper of the type defined at the beginning, in which

- said plug comprises a central portion and a terminal portion having a section which is smaller than that of the central portion, and

said casing at its first end has a terminal portion and an axially inner portion adjacent to the latter, in which the section of the inner bore of the casing at the terminal portion of the casing is smaller than that of the axially inner portion of the casing, and in which the terminal portion and the axially inner portion of the casing house the terminal portion and the central portion of the plug, respectively.

In a device having the characteristics defined above it is possible to build a tube-like casing with an inner diameter slightly greater than the outer diameter of the helical spring. Moreover, the number of components necessary to build the damper is substantially limited. Such aspects consequently make it possible to considerably reduce the overall transversal dimensions of the damper.

Preferred embodiments of the invention are defined in the dependent claims, that should be intended as an integral part of the present description.

Further characteristics and advantages of the device according to the invention shall become clearer from the following detailed description of an embodiment of the finding, provided with reference to the attached drawings, given purely for illustrative and not limiting purposes, in which:

- Figures 1 and 2 are perspective views of a rotary damper according to the invention;

- Figure 3 is a longitudinal section view of the damper of Figures 1 and 2;

- Figure 4 is a cross-section view of the damper of Figure 1, taken along the line IV-IV of Figure 3;

- Figure 5 is an enlarged longitudinal section view of an end of the damper of Figures 1 and 2;

- Figure 6 is an exploded view of the damper of Figures 1 and 2; and

- Figure 7 is an enlarged perspective view of an end of the damper of Figures 1 and 2, shown without the casing of the damper.

The Figures illustrate a rotary damper 10 of the type known in the field as "barrels". Such dampers approximately have the shape of a cylinder, the outer diameter of which is generally smaller than the height (length) of the cylinder itself. In particular, the damper illustrated has an outer diameter which is substantially smaller than its height (or length), and thus takes up a shape that can be compared to that of a cigarette. The damper 10 is suitable for being applied to a mobile member the movement of which is wished to be slowed down with respect to another element, like for example in the case of a lid of a box. In particular, the device is suitable for being mounted at the rotation or hinging axis of the mobile member. The device illustrated can be used for example in a flat box, like a face-powder box. The device 10 comprises a casing 12 having a substantially tubular shape, which has a side wall 13, and is passed through from one end 12a (that hereafter shall be indicated as first end) to the other 12b (that hereafter shall be indicated as second end) by a bore. The side wall 13, at the first axial end 12a, comprises a terminal portion 13a and, adjacent to the terminal portion 13a, an axially inner portion 13b. The section of the inner bore of the casing 12 at the terminal portion 13a is smaller than that of the axially inner portion 13b, and has a non-circular shape, for example rectangular-shaped (as can be seen in Figure 2). Between the axially inner portion 13b and the terminal portion 13a there is thus a shoulder surface 14, at which there is the transition of section of the inner bore from the terminal portion 13a to the axially inner portion 13b.

At the second axial end 12b the side wall 13 comprises a terminal portion 13c, at which the inner diameter of the wall 13 is smaller than the inner diameter of such a wall at the axially inner portion 13b of the first end 12a.

Between the first and the second axial end 12a, 12b the side wall 13 of the casing 12 comprises an intermediate portion 13d, at which the inner diameter of the wall 13 is equal to the inner diameter of such a wall at the axially inner portion 13b of the first end 12a. However, on the radially inner surface of the intermediate portion 13d of the wall 13 a plurality of recesses 13e js formed distributed equidistant from one another in the circumferential direction, and more clearly visible in Figure 4. Such recesses 13e extend along the intermediate portion 13d of the wall 13, in the axial direction of the damper.

At the first end 12a of the casing 12, the damper 10 also comprises a plug 15 fixedly jointed inside the casing, so as to close it. Such a plug 15 comprises a central portion 15a, with an outer diameter which is substantially equal to the inner diameter of the wall of the casing 12 at the axially inner portion 13b of the wall 13 of the casing and, from opposite axial ends, terminal portions 15b and 15c with outer diameter which is smaller than that of the central portion 15a of the plug 15. One of the terminal portions, 15c, has its outer diameter smaller than that of the central portion 15a. The other terminal portion, 15b, has a section complementary with respect to that of the inner bore of the wall 13 at the terminal portion 13a of the latter, in which it is inserted. Although in the Figures such a section is illustrated as rectangular, it can alternatively be triangular, or more in general polygonal. Such a provision prevents the plug 15 from rotating with respect to the casing 12. Alternatively, other provisions are possible, for example by using keys arranged between the plug and the casing, or by welding the plug to the casing. It is necessary for the plug to be rota- tionally locked.

Due to its particular construction, the plug 15 is mounted by inserting it inside the casing from the second end 12b of the latter. On the central portion 15a of the plug 15 a slot 15d is also formed, visible in Figures 5 and 7. Such a slot 15d extends along the central portion 15a of the plug 15 in the axial direction of the damper.

The damper 10 also comprises a rotor 16, which is mounted inside the casing 12, and is rotatable with respect thereto. The rotor 16 comprises a central portion 16a, with an outer diameter which is slightly smaller than the inner diameter of the wall of the cylindrical casing 12 at the intermediate portion 13d of the wall 13 of the casing and, from opposite axial ends, terminal portions 16b and 16c. On the central portion 16a of the rotor 16 a plurality of projections 16d is formed distributed equidistant from one another in the circumferential direction, and visible more clearly in Figure 4. Such projections 16d extend along the central portion 16a of the rotor 16, in the axial direction of the damper, and during the operation of the damper they substantially act as blades.

The casing 12 and the rotor 16 indeed cooperate so as to enclose a braking chamber C (illustrated more clearly in Figure 4) containing a viscous braking fluid, for example silicone oil. The central portion 16a of the rotor 16 and the intermediate portion 13d of the casing 12 face onto the chamber C of the rotary damper.

A terminal portion 16b of the rotor 16 is arranged inside the casing 12, and has an outer diameter which is smaller than the outer diameter of the central portion 16a of the rotor 16. On the central portion 16a of the rotor 16, near to the aforementioned terminal portion 16b, a slot 16e is formed, visible in Figures 5, 6 and 7. Such a slot 16e extends in the axial direction of the damper. The other terminal portion 16c of the rotor 16 is arranged at the terminal portion 13c of the wall 13 at the second end 12b of the cylindrical casing 12. Between the aforementioned terminal portion 16c and the central portion 16a of the rotor 16 a groove 16f is formed, in which an O-ring 16g is housed ensuring a seal between the rotor 16 and the casing 12. The terminal portion 16c of the rotor 16 also comprises a shaft portion 17 coming out from the casing 12. Such a shaft portion 17 is provided with driving formations, which are conventionally used to connect the rotor 16 so that it rotates as a unit with one of the two elements for which it is desired to slow down the reciprocal rotation movement. For such a purpose, the casing 12 is provided with one or more tabs 20, for connecting to the other one of the two elements.

In order to keep the rotor 16 inside the casing 12 it is foreseen for the edge of the terminal portion 13c of the wall 13 at the second end 12b of the casing 12 to be folded inwards, for example through hot or ultrasound caulking.

The rotor 16 indeed has a shoulder surface 16h formed on its radially outer surface, intended to be axially engaged by the folded edge of the terminal portion 13c of the wall 13. Of course, the type of assembly of the rotor 16 onto the casing 12 is not very important for the purpose of the invention, as long as it allows their relative rotation.

The damper 10 finally comprises a spring 25, and in particular a helical spring, one first end 25a of which is fixedly coupled to the casing 12, and a second end 25b of which is fixedly coupled to the rotor 16. More in particular, the first end 25a of the spring 25 extends in the axial direction of the damper 10 (i.e. of the rotor 16), and is housed in a seat made up of the slot 15d formed in the central portion 15a of the plug 15. On the other side, the second end 25b of the spring 25 extends in the axial direction of the rotor 16 and is housed in a seat made up of the slot 16e formed in the central portion 16a of the rotor 16 near to the terminal portion 16b of the rotor 16 inside the casing 12.

The spring 25, from the opposite ends, is mounted around the terminal portion 15c of the plug 15 and around the terminal portion 16b of the rotor 16 inside the casing 12, so as to envelop them. Such terminal portions 15c of the plug 15 and 16b of the rotor 16 therefore, substantially act as a guide for the spring 25.

The aforementioned configuration thus makes it possible to couple the ends of the spring 25 on one side to the casing, and on the other side to the rotor. Such a coupling makes it possible to drive one end of the spring with respect to the other, with a consequent torsion of the spring, when the rotor is made to rotate with respect to the casing. Preferably, the spring 25 is installed inside the casing 12 with a certain pre-compression, so as to bias the rotor 16 against the folded edge of the terminal portion 13c of the wall 13 of the casing. Moreover, the spring 25 possibly makes it possible to elastically compress the rotor 16 inside the casing 12, to allow a snap assembly of the damper in a corresponding seat (not il-lustrated) formed in a hinge intended to receive the damper.

When installed, the aforementioned damper is capable of rotating in one direction against the elastic force of the spring 25, whereas in the other direction, the rotation is promoted by such a force. The braking fluid in the chamber C acts so as to slow down the reciprocal movement of the rotor with respect to the casing.

In a damper thus configured, it is possible to build a tube-like casing with an inner diameter which is slightly greater than the outer diameter of the helical spring. Moreover, the number of components necessary to build the damper is considerably limited. Such aspects consequently make it possible to considerably reduce the overall transversal dimensions of the damper.

The device according to the finding is generally made from plastic material, except for the spring, made from spring steel. The Applicant has for example made a device of the aforementioned type, with an overall diameter of about 0.5 cm and an overall length of about 5-