Patent Description:
It is known that the axles for trailers of agricultural type traditionally have drum brakes for reasons of economy and simplicity in which the pair of shoes provided with friction material is articulated on a single common fulcrum point.

As is known, the machining and the assemblies of the various components of the axle and the brake may have even significantly different tolerances.

The mechanical machining and coupling of the ends of the axles with the roller bearings and the wheel hub, like the coupling of the brake drum with the wheel drum can have tolerances of the order of a hundredth of a millimetre, within which the longitudinal axis of the axle coincides with the axis of the wheel hub and of the brake drum.

The so-called "brake mass", consisting of the whole of the pair of shoes pivoted on a single pin fixed to a "brake plate", is coupled differently with the axle, for reasons of constructional simplicity and economy, with a process for welding the brake plate to the axle: the greater tolerances and the different thermal shrinkages of the components can result in coupling between the brake plate, and thus brake mass, and the axle in which the respective axes are misaligned also by an order of magnitude by a few millimetres.

It is also known that this misalignment accordingly involves an eccentricity of the shoes and of the respective friction materials with respect to the inner surface of the drum on which the braking action develops: this eccentricity causes a limitation of the braking power, differing wear to the friction materials, braking vibrations, and even breakage of the friction materials with locking of the brake or elimination of braking, with devastating consequences for the safety of operators and of the trailer.

A need is thus felt to improve the structure of a brake for trailer axles of agricultural type of known type.

The technical task which is proposed for the present invention is, therefore, to create a brake for trailer axles of agricultural type which makes it possible to eliminate the technical drawbacks complained of in the prior art.

Within the context of this technical task an object of the invention is to create a brake for trailer axles of agricultural type that ensures a coincidence between the technical axis, i.e. the ideal axis of the braking shoes and the longitudinal axis of the axle, of the wheel hub and of the brake drum.

Another object of the invention is to create a brake for trailer axles of agricultural type that maintains the ideal axis of the braking shoes coinciding with the longitudinal axis of the axle, of the wheel hub and of the brake drum fixed over time.

Another object of the invention is to create a brake for trailer axles of agricultural type that maintains the ideal axis of the braking shoes coinciding with the longitudinal axis of the axle, of the wheel hub and of the brake drum with simple means that is easy to activate and is cheap fixed over time.

The technical task, together with these and other objects according to the present invention are achieved by creating a brake for trailer axles of agricultural type comprising at least one axle, a wheel hub, a brake drum and a brake mass rigidly connected to said axle and comprising at least one brake plate, at least two shoes equipped with friction material and an articulating pin of said two shoes that has a head and a stem, said stem of said pin being removably housed axially in a hole provided on said brake plate, and a tightening nut for tightening said pin in said hole being further provided, characterised in that said stem of said pin is housed with radial clearance in said hole and in that locking means is provided with a distance set between the axis of said pin and the axis of said hole, said locking means comprising at least two reciprocally engaged conjugate surfaces, at least one of which has a rippled finish.

According to the invention, the surface with a rippled engagement finish is in the form of a radial or diamond-shaped rippling.

According to the invention, said at least one engagement surface can coincide with the surface of the circular crown defined by the outer diameter of said head and by the outer diameter of said stem of said pin.

According to an embodiment of the invention, said brake comprises a bush fixed to said plate, in which said bush surrounds said hole and has an axial cavity having cylindrical generatrices arranged on the prolongation of the cylindrical generatrices of said hole, in which said at least two conjugate surfaces comprise a surface of said head of said pin engaged with a conjugate surface of said bush, at least one of said engagement surface of said pin and said conjugate surface of said bush having said rippled finish.

According to another embodiment of the invention, each shoe has a first and a second shoe rib that are opposed and positioned symmetrically on opposite sides of said plate and engage respective rotation guides supported by said pin.

In one embodiment of the invention, said first shoe rib engages a first rotation guide present on said head of said pin and said second rib engages a second rotation guide present on a ring supported by said pin.

According to this further embodiment of the invention, said at least two conjugate surfaces comprise a first pair of surfaces of reciprocal engagement between said head of said pin and a first side of said hole and a second pair of surfaces of reciprocal engagement between said ring and a second side of said hole opposite said first side, at least one of the surfaces of said first pair and at least one of the surfaces of said second couple having a rippled finish.

The invention also discloses a method for making the brake for trailer axles of agricultural type, comprising the steps of:.

Further characteristics and advantages of the invention will more fully emerge from the description of a preferred but not exclusive embodiment of the brake for trailer axles of agricultural type according to the invention, illustrated by way of non-limiting example in the accompanying drawings, in which:.

The following detailed description refers to the appended drawings, which form a part thereof. In the drawings, similar reference numbers typically identify similar components, unless the context indicates otherwise.

The embodiments described in the detailed description and in the drawings are not intended to be limiting.

The aspects of the present description, as generally described in the present context and illustrated in the figures, may be arranged, replaced, combined and designed in a wide range of different configurations, which are all contemplated explicitly and are part of this description.

With reference to the cited figures, a brake for trailer axles of agricultural type is denoted in its entirety by reference number <NUM>.

The brake for trailer axles of agricultural type <NUM> comprises at least one axle <NUM> fixed to the trailer with fixing means not indicated in figures and connected axially to the end <NUM> thereof with rotational fixing means, typically rolling bearings, to the wheel hub <NUM>.

The brake drum <NUM> is fixed rigidly to the wheel hub <NUM>, the brake drum <NUM> being dragged by the wheel hub <NUM> in the rolling of the wheel on the terrain rotating around the longitudinal axis Y of the axle <NUM>.

The brake mass <NUM> comprises at least one brake plate <NUM> and at least one pair of shoes <NUM> A and <NUM> B, which are substantially opposite and symmetrical with respect to an axis that is perpendicular to the axis Y.

The brake mass <NUM> is solidly constrained to the fixed axle <NUM> through the rigid connection of the brake plate <NUM> with the axle <NUM>, typically by welding along the edges of a seat <NUM>.

The shoes <NUM> A and <NUM> B are equipped with friction material respectively <NUM> A and <NUM> B; the two shoes <NUM> A and <NUM> B are elastically connected together by springs <NUM> A and <NUM> B.

The spring <NUM> A retains and engages symmetrically the two ends <NUM> A and <NUM> B against a braking activation cam <NUM>.

The springs <NUM> B (a single spring in the first embodiment illustrated in <FIG>, two springs in the second embodiment illustrated in <FIG>) retain and engage symmetrically the two ends <NUM> A and <NUM> B that rotate freely around a rotation fulcrum coinciding with an axis Y1 substantially parallel to the axis Y and coinciding with the axis of a pin <NUM> removably housed in an axial direction in a hole <NUM> of the brake plate <NUM>.

The articulating pin <NUM> of the two shoes <NUM> A, 50B having a head <NUM> and a stem <NUM> that is removably housed axially in the hole <NUM> of the brake plate <NUM>.

The pin <NUM> has a head <NUM> of a greater diameter and a stem <NUM> of a lesser diameter than that of the head <NUM>.

The pin <NUM> is fixed to the hole <NUM> by a suitable tightening nut <NUM>.

Advantageously, the stem <NUM> of the pin <NUM> is housed with radial clearance in the hole <NUM> and locking means is provided with a distance set between the axis Y1 of the pin <NUM> and the axis Y2 of the hole <NUM>.

The radial clearance of the stem <NUM> of the pin <NUM> housed in the hole <NUM> is equal to the difference in diameter DB of the hole <NUM> and the outer diameter DS of the stem <NUM>.

Advantageously, the locking means comprises at least two reciprocally engaged conjugate surfaces <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> at least one of which has a rippled finish.

The surface <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> preferably has a rippled finish in the form of a radial or diamond-shaped rippling.

At least one of these conjugate surfaces coincides with the surface of the circular crown defined by the outer diameter of the head <NUM> and by the outer diameter of the stem <NUM> of the pin <NUM>.

Reference is now made to the embodiment illustrated in <FIG>.

The brake comprises a bush <NUM> fixed to the plate <NUM>.

The bush <NUM> surrounds the hole <NUM> and has an axial cavity having cylindrical generatrices arranged on the prolongation of the cylindrical generatrices of the hole <NUM>.

In this case, a pair of conjugate surfaces is provided that engage reciprocally and comprise a surface <NUM> of the head <NUM> of the pin <NUM> and a surface <NUM> of the bush <NUM>.

Typically, the pin <NUM> and the bush <NUM> are made of steel.

The stem <NUM> has a length that is greater than that of the bush <NUM> and the end opposite the suitably threaded head <NUM> on which the nut <NUM> acts.

Suitably, the head <NUM> has a seat <NUM> in which the freely rotating conjugate surfaces of the two ends <NUM> A and <NUM> B of the shoes <NUM> A and <NUM> B are housed.

The head <NUM> of the pin <NUM> thus acts as an articulation fulcrum of the shoes <NUM> A and <NUM> B.

The stem <NUM> has the outer diameter DS significantly less than the diameter DB of the bush <NUM>, which in turn has a longitudinal axis coaxial with the axis Y2 of the hole <NUM>.

The stem <NUM> is then housed in the bush <NUM> with radial clearance, because of the difference of DB with DS, and the axis Y1 of the pin <NUM> can but does not necessarily coincide with the axis Y2 of the bush <NUM>.

In this case, as said, the engagement surface <NUM>, coinciding with the surface of the circular crown defined by the outer diameter of the head <NUM> and by the outer diameter of the stem <NUM>, engages during the locking step against the conjugate engagement surface <NUM> of the bush <NUM>; further, as said, at least one of the engagement surface <NUM> of the pin <NUM> and the conjugate engagement surface <NUM> of the bush <NUM> has a rippled finish, for example, as shown, only the engagement surface <NUM> of the pin <NUM>.

In a further embodiment, shown in a <FIG>, the pin <NUM> is made of two pieces: a first piece corresponds to the stem <NUM> with which a first head <NUM> A is associated that has a solidly constrained abutment <NUM> B against which a second piece is assembled by forcing that has a second head <NUM> C comprising the seat <NUM> and the engagement surface <NUM>.

Advantageously, in this embodiment the material of the first piece and the material of the second piece can be different, with physical characteristics that are more closely attuned to the required performance, in particular the hardness of the rippled finish of the engagement surface <NUM>. Reference is made to the embodiment illustrated in <FIG>.

Each shoe 50A, 50B in this case has a first shoe rib 50A' , 50B' and a second shoe rib 50A", 50B" that are opposed and positioned symmetrically on opposite sides of the plate <NUM>.

The first shoe rib 50A', 50B' engages a first rotation guide <NUM> present in particular on the head <NUM> of the pin <NUM> and the second rib 50A", 50B" engages a second rotation guide <NUM> present in particular on a ring <NUM> supported by the pin <NUM>.

In particular, the ring <NUM> is fitted to the stem <NUM> of the pin <NUM>.

The first rotation guide <NUM> and the second rotation guide <NUM> are formed by circular grooves <NUM>', <NUM>' that are coaxial with the axis of the pin <NUM>.

In this case, the conjugate surfaces comprise a first pair of surfaces <NUM>, <NUM> of reciprocal engagement between the head <NUM> of the pin <NUM> and a first side of the hole <NUM> and a second pair of surfaces <NUM>, <NUM> of reciprocal engagement between the ring <NUM> and a second side of the hole <NUM> opposite the first side of the hole <NUM>.

At least one of the surfaces of the first pair <NUM>, <NUM> and at least one of the surfaces of the second couple <NUM>, <NUM> has a rippled finish.

This solution offers the advantage that the two shoe ribs 50A', 50B', 50A", 50B" transmit to the brake plate <NUM> via the pin <NUM> a system of balanced force, as the brake plate <NUM> is symmetrically interposed between the two shoe ribs 50A' , 50B', 50A", 50B".

Thus, torsional and bending moments are not created on the brake plate <NUM> that, if present, could modify the configuration of the brake plate <NUM> and consequently the orientation of the pin <NUM> with a negative impact on the braking efficiency of the brake <NUM>.

The brake plate <NUM> is welded or otherwise fixed below to the axle <NUM> by the shaped surface <NUM> thereof.

In this case, the brake <NUM> comprises a second support brake plate <NUM> of the activation cam <NUM>. The second brake plate <NUM> is welded or otherwise fixed above to the axle <NUM> in a position that is staggered from the first brake plate <NUM> with respect to the axis of the axle <NUM>.

The operation of the brake for trailer axles of agricultural type according to the invention is clear from what is disclosed and illustrated and, in particular, is as follows.

The brake for trailer axles of agricultural type <NUM> is substantially assembled by connecting by welding the brake plate <NUM> and the second brake plate <NUM> to the axle <NUM> in the case of the embodiment illustrated in <FIG>, then by fitting the preassembled brake mass <NUM>.

Owing to the type and tolerances of the welding task, the geometric axis Y3 of the brake mass <NUM>, and thus of the entirety of the shoes <NUM> A and <NUM> B pivoted on the pin <NUM> does not coincide necessarily with the geometric axis Y of the axle <NUM>.

The axle <NUM> - brake mass <NUM> assembly is assembled with the wheel hub <NUM> to which the drum <NUM> is fixed that is free to rotate around the geometric axis Y of the axle <NUM>.

When the activation cam <NUM> is controlled, by control means that is not shown in the figure, the activation cam <NUM> moves away reciprocally the ends <NUM> A and <NUM> B of the shoes <NUM> A and <NUM> B, and the friction material respectively <NUM> A and <NUM> B engages with the surface of the inner wall of the drum <NUM>, slowing rotation thereof and thus activating braking.

In a first step, the pin <NUM> is coupled with the hole <NUM>, but not locked by the nut <NUM>; an initial braking is performed, and the free shoes <NUM> A and <NUM> B of a radial movement of the geometric axis Y1 of the pin <NUM> with respect to the geometric axis Y2 of the hole <NUM> within the limits of the difference in diameter DS of the stem <NUM> and in diameter DB of the hole <NUM>, adhere with the friction material respectively <NUM> A and <NUM> B to the surface of the inner wall of the drum <NUM> and self-centre dragging the braking activation axis Y3 - within the above limits - to coincide with the longitudinal axis Y of the brake drum, of the wheel hub and of the axle.

In this movement, the shoes <NUM> A and <NUM> B drag the head <NUM> of the pin <NUM> to which they are pivoted in the seat <NUM>, and then the stem <NUM> in the hole <NUM>, in a new thus defined position of the axis Y1 with respect to the axis Y2.

This new position ensures centring of the shoes <NUM> A and <NUM> B with respect to the inner wall of the drum <NUM>, thus ensuring braking that is effective, balanced and reliable over time.

In this new position the pin <NUM>, with the axis Y1 is rigidly and solidly locked with respect to the hole <NUM> with an axis Y2 by the engagement of the nut <NUM>.

Tightening the nut <NUM> -locked by the washer <NUM> A- on the end of the stem <NUM> thus results in the engagement between the pair of surfaces <NUM>, <NUM> in the embodiment illustrated in <FIG>, between the first pair of surfaces <NUM>, <NUM> and between the second pair of surfaces <NUM>, <NUM> in the embodiment illustrated in <FIG>.

With reference to the first embodiment of the invention, in <FIG> and <FIG> the reciprocal positions are shown schematically of the components of the brake mass <NUM>, and in particular of the axes Y1 and Y2, before and after self-centring of the shoes <NUM> A and <NUM> B against the inner surface of the drum <NUM>: in <FIG> the example is illustrated of a maximum axial movement of the axis Y1 of the pin <NUM> with respect to the axis Y2 of the hole <NUM>, at the limit of the difference of the diameters DB of the hole <NUM> and DS of the stem <NUM>.

In the condition illustrated in <FIG>, the engagement of the nut <NUM> and the reciprocal engagement of the engagement surface <NUM> of the pin <NUM> with the engagement surface <NUM> of the bush <NUM> are activated.

With reference to the second embodiment of the invention, in <FIG> and <FIG> the reciprocal positions are shown schematically of the components of the brake mass <NUM>, and in particular of the axes Y1 and Y2, before and after self-centring of the shoes <NUM> A and <NUM> B against the inner surface of the drum <NUM>: in <FIG> the example is illustrated of a maximum axial movement of the axis Y1 of the pin <NUM> with respect to the axis Y2 of the hole <NUM>, at the limit of the difference of the diameters DB of the hole <NUM> and DS of the stem <NUM>.

In the condition illustrated in <FIG> the engagement of the nut <NUM> and the reciprocal engagement between the first pair of surfaces <NUM>, <NUM> and between the second pair of surfaces <NUM>, <NUM> are activated.

It clearly emerges that the safe operation, efficiency and reliability over time of the brake <NUM> depend, amongst other things, but significantly, on the maintenance over time and use of the pin <NUM> in this defined new position.

Advantageously, under the engagement pull of the nut <NUM>, the cusps of the rippled finishes provided between the pair of surfaces <NUM>, <NUM> in the embodiment illustrated in <FIG>, between the first pair of surfaces <NUM>, <NUM> and between the second pair of surfaces <NUM>, <NUM> in the embodiment illustrated in <FIG>, indent the corresponding engagement surface, also fixing radially the reciprocal position of the two engagement surfaces, and thus of the respective axis Y1 of the pin <NUM> and axis Y2 of the hole <NUM>.

As said, it is possible that both surfaces <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of reciprocal engagement have a rippled finish: in this case favourably, the cusps and the cavities of the respective rippled finishes couple reciprocally, ensuring reciprocal fixing over time of the reciprocal position of the axes Y1 and Y2.

Advantageously, according to the present invention, in order to maintain the new defined position of the pin <NUM> with respect to the hole <NUM>, and thus of the axis Y1 with respect to the axis Y2, a torque setting is applied to the nut <NUM> within the limits of the torque available with normal workshop tools, in which the rippled finish of the respective engagement surface(s) ensures an increase in friction necessary and sufficient for maintaining the reciprocal positions, also over time and in the operating conditions of the brake.

In practice, it has been established that a brake for trailer axles of agricultural type according to the invention is particularly advantageous for ensuring the fixed position over time of the ideal axis of the braking shoes coinciding with the longitudinal axis of the brake drum, of the wheel hub and of the axis, with simple means that is easy to activate and cheap.

A brake for trailer axles of agricultural type as conceived herein is susceptible to many modifications and variants, all falling within the scope of the inventive concept as defined by the claims; further, all the details are replaceable by technically equivalent elements.

Claim 1:
A brake for trailer axles of agricultural type (<NUM>) comprising at least one axle (<NUM>), a wheel hub (<NUM>), a brake drum (<NUM>) and a brake mass (<NUM>) rigidly connected to said axle (<NUM>) and comprising at least one brake plate (<NUM>), at least two shoes (<NUM> A, <NUM> B) equipped with friction material (<NUM> A, <NUM> B) and an articulating pin (<NUM>) of said two shoes (<NUM> A, 50B) having a head (<NUM>) and a stem (<NUM>), said stem (<NUM>) of said pin (<NUM>) being removably housed in an axial direction in a hole (<NUM>) provided on said brake plate (<NUM>), and a tightening nut (<NUM>) for tightening said pin (<NUM>) to said hole (<NUM>) being provided, characterised in that said stem (<NUM>) of said pin (<NUM>) is housed with radial clearance in said hole (<NUM>) and in that locking means is provided to lock rigidly and firmly a distance set between an axis (Y1) of said pin (<NUM>) and an axis (Y2) of said hole (<NUM>), said locking means comprising at least two reciprocally engaged conjugate surfaces (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), at least one of which has a rippled finish.