Guide unit for bicycle or motorcycle fork tubes

Abstract

Guide unit for bicycle or motorcycle fork tubes Guide unit (40) for bicycle or motorcycle fork tubes (10), the fork tube (10) having a longitudinal axis (A) and having two coaxial tubes (20)(30), jointly defining a cylindrical space (17), one of which slides telescopically inside the other along the longitudinal axis (A) by virtue of the interposed guide unit (40), which is itself having a pair of sliding bushings (41)(42)(42') interposed radially between the two coaxial tubes (20)(30) and axially spaced from each other inside the cylindrical space (17); each socket (41)(42)(42') having a respective rigid cylindrical body (43)(44) and a respective sliding coating (45)(46) made of a material with a low coefficient of friction and arranged in contact with a respective coaxial tube (20)(30);a plurality of lubricant reservoirs (50) being formed in the sliding coating (45)(46) and distributed uniformly over the respective bushings (41)(42)(42'). [Figure 1];

Description

Title of the invention: Guide unit for bicycle or motorcycle fork tubes Technical field of the invention

[0001] The present invention relates to a guide unit for bicycle or motorcycle fork tubes. Prior art

[0002] Fork tubes for bicycle or motorcycle forks have a longitudinal axis and comprise an outer sleeve and an internal hollow plunger, which are coaxial with each other and with the longitudinal axis, the plunger being able to move inside the sleeve. This movement is made possible by a guide unit comprising, in its most common form, two sliding bushings, which are interposed between the plunger and the sleeve, and are arranged at a given axial distance from each other.

[0003] Each bushing of the guide unit comprises a cylindrical steel body, which gives the bushing high mechanical strength, and a sliding layer, which is usually made of a heat-resistant polymer arranged in contact with the cylindrical body, defining a cylindrical sliding surface to allow better movement of the plunger relative to the sleeve.

[0004] The bushings, in particular the respective sliding layers, are further lubricated with oil which completely fills the cavity of the plunger and the sleeve in which the plunger slides. Summary of the invention

[0005] The present invention aims to provide a fork tube guide unit that is lighter than conventional guide units, which contributes both to environmental sustainability by reducing the amount of oil used in the fork and to optimizing the lubrication of the bushings, and also to reducing friction between the bushings, the fork leg and the plunger in order to improve the performance of the fork tubes themselves.

[0006] These objectives and advantages, as well as others, are achieved according to the invention by a fork tube guide unit having the characteristics set out below. Brief description of the figures

[0007] The invention is described below with reference to the accompanying drawings representing a non-limiting illustrative embodiment thereof, in which:

[0008] - [Fig. 1] is a perspective view, parts of which have been removed for reasons clarity, of a preferred embodiment of a guiding unit for bicycle or motorcycle fork tubes according to the present invention;

[0009] - Figures 2 and 3 are enlarged views, parts having been removed for reasons of clarity, from a first detail of the guidance unit of the [Fig.l];

[0010] - Figures 4 and 5 are enlarged views, parts having been removed for for reasons of clarity, a second detail of the guidance unit of [Fig. 1]; and

[0011] - [Fig.6] illustrates another preferred embodiment of the detail of figures 4 and 5. Detailed description of the invention

[0012] With reference to [Fig.1], the reference sign 10 designates, as a whole, a fork tube for a bicycle or motorcycle fork (known and not illustrated).

[0013] In common use, the fork tube 10 is intended to form part of a bicycle or motorcycle fork comprising two parallel fork tubes that can be connected to the steerer tube of the bicycle or motorcycle by means of respective plates. The fork tube 10 has a longitudinal axis A and comprises:

[0014] - two coaxial tubes 20 and 30, one of them sliding telescopically inside the other, called sheath 20 and plunger 30 in the remainder of this description; and

[0015] - a guidance unit 40 placed between the sleeve 20 and the plunger 30 to guide the diver 30 inside sheath 20, allowing it to move along axis A.

[0016] The sleeve 20 is defined by a cylindrical tubular body 21, which has a circular opening 22, and is delimited internally by a cylindrical surface 21a; while the plunger 30 is defined by a cylindrical tubular body 31 inserted inside the body 21 through the circular opening 22, and delimited externally by a cylindrical surface 31a facing the surface 21a. The surfaces 21a and 31a of the sleeve 20 and the plunger 30 are respectively faced towards each other and together define a cylindrical space or chamber 17, which normally contains a quantity of oil used to minimize friction between the plunger 11 and the sleeve 12 when they slide relative to each other.

[0017] The guide unit 40 comprises a pair of guide bushings 41 and 42, which are radially interposed between the sleeve 20 and the plunger 30 with lower tolerances than the sleeve 20 and the plunger 30 themselves, and are axially spaced from each other within the cylindrical space 17.

[0018] Each bushing 41 and 42 comprises a cylindrical body 43 and 44 made of steel, which gives high mechanical resistance to the bushing 41 and 42 concerned, and a sliding coating 45 and 46, which is made of a material with a low coefficient of friction, such as polytetrafluoroethylene, or a heat-resistant polymer, and is arranged in contact with the respective cylindrical body 20 and 30 to define a respective cylindrical sliding surface 45a and 46a.

[0019] In the example embodiment of the present invention illustrated in [Fig. 1], the sleeve 41 is arranged near the circular opening 22 and axially immobilized in a seat 23 formed in the sleeve 20, is internally and slidably engaged by the plunger 30 and, as better illustrated in Figures 2 and 3, is such that the coating 45 is arranged internally, that is to say, in such a way that the surface 45a is oriented radially in the direction of, and in sliding contact with, the surface 31a of the plunger 30.

[0020] On the other hand, the sleeve 42 is placed near a distal portion 32 of the tubular cylindrical body 31, is axially immobilized on the body 31 itself, and is externally and slidably engaged with the sleeve 20. As illustrated more clearly in figures 4 and 5, the coating 46 is arranged on the outside of the sleeve 42, that is to say such that the surface 46a is oriented radially in the direction of, and in slidable contact with, the cylindrical surface 21a of the sleeve 20.

[0021] The bushings 41 and 42 have different respective axial heights H1 and H2, of which height H1 is greater than height H2, the two bushings 41 and 42 performing similar but not identical tasks precisely by virtue of their axial positioning along axis A within cylindrical space 17. The bushings 41 and 42, in particular the respective sliding liners 45 and 46, are further lubricated by oil within cylindrical space 17. However, both to reduce the amount of oil used in the fork tube 10 and to optimize the lubrication of the bushings 41 and 42 themselves, they are provided with a plurality of lubricant reservoirs 50 formed in the relevant sliding liner 45 and 46 and distributed uniformly over the respective sliding surfaces 45a and 46a.

[0022] The lubricant reservoirs 50, as illustrated in Figures 2 to 5, are formed through the sliding liners 45 and 46, and are defined by blind-bottomed cavities, preferably, but not necessarily, circular, distributed in a staggered arrangement. This arrangement, as well as the shape of the blind-bottomed cavities, can vary according to application requirements, i.e., according to the size of the fork tube 10.

[0023] By way of non-limiting example, [Fig. 6] represents a bushing 42' which is completely identical to the bushing 42 described above, the bushing 42' differing from it in that the lubricant reservoirs 50 are defined by elongated blind-bottom cavities along respective rows of the cylindrical body 44 and are also distributed circumferentially in columns, wherein the lubricant reservoirs 50 of each column are arranged at the same axial distance from the lubricant reservoirs 50 in the same column. The same distribution can also be applied to the bushing 41 and its inner lining 45, and the guide unit 40 itself can have bushings with staggered reservoirs coupled to the bushings, the reservoirs being arranged in columns, and the circular reservoirs 50 can be arranged in rows and columns.

[0024] The distinctive features of these lubricant reservoirs 50 are that they accumulate lubricant which can be released when there is insufficient lubricant in the cylindrical space 17, and that they reduce friction between the sliding surfaces 45a and 46a and the surfaces 21a and 31a due to the increased amount of lubricant available, and that they prevent potential seizing between the surfaces 45a and 46a and the surfaces 21a and 31a, again precisely because of the increased amount of lubricant available. Furthermore, the reservoirs 50, since they are formed through the coating layer 45 and 46, have, firstly, another beneficial effect on friction reduction since they effectively reduce the size of the sliding surface 45a and 46a, i.e., the area of ​​contact between the surfaces.

[0025] It is understood that the invention is not limited to the embodiments described and illustrated herein, which are to be considered as examples of embodiments of the guide unit for fork tubes for bicycle or motorcycle forks, and are subject to changes in the shape and arrangement of parts, structural and functional details, and materials used. For example, the invention can be applied to both inverted fork tubes (USD, i.e., reverse plunger) and conventional fork tubes. It will also be evident that the invention can also be used in single-sided telescopic hydraulic forks. The invention can also be implemented with sliding and / or rotating forks. It is understood that the invention encompasses all variants within its scope of application, as defined by the following claims.

Claims

Demands

1. A guide unit (40) for fork tubes (10) of bicycle or motorcycle forks, the fork tube (10) having a longitudinal axis (A) and comprising two coaxial tubes (20)(30), defining a cylindrical space (17) between them and sliding telescopically into one another along the longitudinal axis (A) by virtue of the interposed guide unit (40), which for its part comprises a pair of sliding bushings (41)(42)(421) interposed radially between the two coaxial tubes (20)(30) and axially spaced from one another inside the cylindrical space (17); each socket (41)(42)(421) comprising a respective rigid cylindrical body (43)(44), and a respective sliding coating (45)(46) made of a material with a low coefficient of friction and is arranged in contact with a relative coaxial tube (20)(30);the guide unit (40) being characterized in that it also comprises a plurality of lubricant reservoirs (50), which are formed in the sliding coating (45)(46), and are distributed uniformly over the relative bushings (41)(42)(42').

2. Unit according to claim 1, characterized in that lubricant reservoirs (50) are made through the sliding coating (45)(46), and are defined by blind-bottom cavities.

3. Unit according to claim 2, characterized in that the lubricant reservoirs (50) are circular in shape.

4. Unit according to claim 3, characterized in that the lubricant reservoirs (50) are elongated in shape.

5. Unit according to claim 3 or 4, characterized in that lubricant reservoirs (50) are distributed in a staggered arrangement.

6. Unit according to claim 3 or 4, characterized in that the lubricant reservoirs (50) are distributed along respective rows of the sleeve (41)(42)(421) and are also distributed along columns equidistant circumferentially spaced, the lubricant reservoirs (50) of each column being equidistant axially from the lubricant reservoirs (50) of the same column.

7. Unit according to any one of the preceding claims, characterized in that each bushing (41)(42)(421) comprises a cylindrical body (43)(44) made of steel to give the bushing (41)(42)(421) itself high mechanical strength, and a sliding coating (45)(46) made of a material with a low coefficient of friction, which is a heat-resistant polymer.

8. Bicycle or motorcycle fork tube comprising a guide unit according to any one of the preceding claims.

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