Adjustment device and method for automatically adjusting the clearance of a drum brake

Abstract

The present invention relates to an adjustment device and method for automatically adjusting the clearance of a drum brake, the device comprising: an extendable support rod assembly; a first rod assembly, which is associated with the extendable support rod assembly; a second rod assembly, which is hinged to the first shoe and includes a connecting portion at the first end of the second rod assembly; a connecting member, which is connected to the first rod assembly and includes a connecting seat, which is suitable for connecting the second rod assembly, wherein the connecting portion is connected to the connecting seat with a predetermined functional clearance, so that when the shoe moves from a static position to approach a braking surface with a minimum operating clearance under the action of an actuating device, the connecting portion slides in the connecting seat with a free stroke equal to the functional clearance without transmitting the movement to the connecting member and the first rod assembly, and wherein the second rod assembly is configured to at least transmit the movement to the connecting member after the connecting portion has traveled a free stroke equal to the functional clearance.

Description

Technical Field

[0001] The invention relates to a device for automatically adjusting the wear clearance of a parking brake.

[0002] In particular, the invention applies to the field of parking drum brakes, preferably drum brakes associated with disc brakes, in other words of the “drum in disc” (DIH) type. Background Art

[0003] As is known to all, the parking drum brake comprises a drum, a first and a second shoe, and a brake actuator, which is configured to force the shoe from a stationary position to press into contact with a braking surface in the drum.

[0004] In particular, the shoe in the rest position is spaced apart from the braking surface by a minimum functional operating gap, so that in the absence of braking action there is no interference between the shoe and the drum.

[0005] Due to the wear of the friction material connected to the shoe, when the shoe is in a stationary state, the gap between the shoe and the drum increases, and therefore the stroke of the brake actuator required to force the shoe against the drum increases. This increase in actuator stroke affects the performance, safety and size of the brake system.

[0006] In order to keep the actuator stroke substantially constant, some drum parking brakes, in particular those of the DIH type, are provided with means for adjusting the clearance between the shoe and the inner cylindrical surface of the drum.

[0007] Typically, a gap adjustment device of a known type comprises an adjustable strut that is received in a special seat on the shoe and held in place by a retaining spring connected to the shoe. Such an extendable strut comprises a nut-screw mechanism with a rotatable toothed wheel that is configured to extend the strut to adjust the distance between the two shoes when wear occurs.

[0008] In some adjustment devices, the extension adjustment of the strut is of the manual type, requiring the intervention of an operator, while in other adjustment devices it is of the automatic type, with mechanical elements adjusting the clearance, in particular during use of the braking system.

[0009] In particular, known clearance adjustment devices are configured to extend the adjustable strut to restore the wear clearance when the braking action is below a certain predetermined threshold, and not to extend the strut beyond the restoration of the wear clearance.

[0010] For example, document US3216533, US3893548 and US3958674 show a kind of wear adjuster of automatic type, it comprises the actuating rod of the toothed wheel associated with adjustable support rod and the force transmission element connected with this rod and at least one shoe.Actuating rod is hinged to shoe in a rotatable manner, and comprises rod foot, and this rod foot is configured to interact with toothed wheel when actuating rod rotates clockwise.Force transmission element comprises at least one tensioning cable, and this tensioning cable is guided by at least one guiding element integrated with shoe, and is constrained to the fixed plate of drum brake.Actuating rod is maintained in static position, and is biased by the torsion return spring acting on this rod counterclockwise.In addition, torsion spring makes cable remain in predetermined static tension state, and makes rod foot and one of the toothed portion of toothed wheel keep predetermined distance. When the brake actuation is activated by moving the two shoes away from each other, the tension applied to the cable increases, causing the actuating lever to rotate against the force of the torsion return spring and the lever foot to come into contact with one of the teeth of the toothed wheel as soon as the shoe approaches the drum at the minimum working distance. In the event of wear, the shoe is brought closer to the drum as the actuating lever activates the strut and after the shoe contacts the braking surface of the drum, the cable tension is no longer sufficient to transmit a force capable of actuating the toothed wheel.

[0011] However, in the solutions described in these documents, the force transmission element comprises, in addition to the cable, a preloaded spring having a predetermined preload value which is greater than the resistance of the rod return torsion spring, so that when the braking force is so great that the strut can no longer be adjusted, the preloaded spring deforms elastically and possible damage to the wear adjuster is minimized.

[0012] In the described cases known from the prior art, the functional clearance - in other words the distance between the rod foot and the toothing of the toothed wheel before the shoe is pressed into contact with the braking surface of the drum - is designed as a function of: the cable length, the rod positioning tolerance, the cable to rod connection position tolerance, the tolerance of the connection point of the preloaded spring relative to the cable, the number of teeth and the outer diameter of the ring.

[0013] Control of the size of the functional gap is crucial in the braking system, as the creation of a functional gap outside the design tolerance means a high risk of failure of the braking system itself, endangering the safety of the vehicle users and any passengers.

[0014] However, in systems of the above-mentioned known type, controlling the dimensional tolerances of the functional gaps is very expensive due to the large number of components and connections that must be entrusted.

[0015] Furthermore, as the number of mechanical components on which the functional gap dimension depends increases, the risk of assembly errors or of components exceeding the tolerance limits set in the design and therefore of a functional gap dimension to be restored at the end of each braking operation also increases.

[0016] Therefore, there is a strong felt need for a high degree of control over functional clearance tolerances in terms of accuracy and repeatability at a low cost.

[0017] Another strongly felt need is to reduce the probability of errors occurring during assembly steps, which could affect the correct operation of the brake system under high stress conditions.

[0018] In particular, in the field of high-end brake production, where high performance without changes over time must be guaranteed, the need is felt to obtain as close as possible to those detailed determined functional gaps at the lowest possible cost.

[0019] It is also felt that there is a need for a solution that can reduce the likelihood of a lock-up event and reduce residual torque in disc-drum brakes.

[0020] It is also felt that there is a need to provide an automatic wear gap recovery device which is easy to manufacture, replicate and adapt and install in existing drum-in-disc brakes on the market.

[0021] Additionally, a need is felt to provide an automatic wear gap recovery device for drum brakes which device has a small number of parts. Summary of the invention

[0022] The object of the present invention is to overcome the drawbacks of the prior art and to provide a solution to the need for providing an automatic clearance adjustment device for a drum brake as defined in the present invention.

[0023] By means of the automatic clearance adjustment device for a drum brake according to the present invention, the drum brake according to the present invention and the method for adjusting the clearance between the shoes of a drum brake according to the present invention, the above-mentioned needs can be met, and in particular, a minimum operating clearance between the shoe and the drum portion can be obtained, which is maintained within the design tolerance at low cost and high reliability.

[0024] In particular, by providing a first rod assembly suitable for operating a toothed ring of an extendable support rod assembly and a second rod assembly suitable for activating the first rod assembly and being hinged to the first shoe and offset by the rotation of the second shoe, wherein a connecting member is provided to connect the second rod assembly to the first rod assembly, wherein the connecting member allows the second rod assembly to have a free stroke before being able to actuate the first rod assembly to rotate, wherein such free stroke is restored when the two shoes approach the braking surface of the drum with a minimum operating gap, a parking brake wear recovery device is provided, which has a small number of components and is easy to manufacture with strict tolerances so as to obtain a high degree of control in the production of the device and to achieve a functional clearance as close as possible to the designed functional clearance at a low cost.

[0025] Advantageously, compared to the prior art, by reducing the number of components upon which the functional gap dimensions depend, the present invention allows for higher overall tolerances required for manufacturing the various components, thereby reducing production costs, given the same functional gap dimension tolerances. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further features and advantages of the automatic clearance adjustment device for drum brakes according to the invention will become apparent from the description provided below of a preferred embodiment of the invention given by way of non-limiting example, with reference to the accompanying drawings, in which:

[0027] Figure 1 A device for automatic adjustment of the play of a drum brake according to the invention and a partial cross-sectional axonometric view of a drum brake according to the invention are shown, wherein the outer part of the drum or bell of the disc brake is omitted in order to show the inner parts of the drum brake;

[0028] Figure 2 An isometric view of an automatic gap adjustment device according to the present invention is shown, the device comprising an extendable strut assembly, a first rod assembly and a second rod assembly connected by a connecting member;

[0029] Figure 3 Shows Figure 2 An axonometric view of the exploded view of the device components;

[0030] Figure 4 Shows Figure 1 a front view of the device and a drum brake, wherein the shoe of the drum brake is in a rest position, the distance from the braking surface of the drum being at least equal to the minimum operating clearance, and wherein the adjustment device is in a rest position;

[0031] Figure 5 Shows Figure 4 a front view of detail A showing the relative positions of the second rod assembly and the connecting member;

[0032] Figure 6 Shown along Figure 5 A cross-sectional view at a plane taken in the longitudinal direction ll, showing a functional gap existing between the second rod assembly and the connecting member;

[0033] Figure 7 Shown along Figure 4 A cross-sectional view taken along a plane through which the center line aa passes, wherein the connecting pin and the first shoe of the second rod assembly are shown in detail;

[0034] Figure 8 Shows Figure 4 Detail B in which it can be seen that the clearance between the shoe and the braking surface of the drum is at least equal to the minimum operating clearance;

[0035] Fig. 9 Shows Figure 1 a front view of the device and drum brake in which the shoe is in an open position close to the braking surface of the drum with minimum operating clearance, and wherein the automatic wear adjustment device biased by the opening of the shoe is in a functional clearance recovery position;

[0036] Fig.10 Shows Fig. 9 a front view of detail A showing the relative positions of the second rod assembly and the connecting member;

[0037] Fig.11 Shows Fig. 9 Detail B in which the restoration of the minimum operating clearance between the shoe and the braking surface of the drum can be seen;

[0038] Fig.12 Shown along Fig.10 A cross-sectional view at a plane taken along the midline 11, showing a functional gap existing between the second rod assembly and the connecting member;

[0039] Fig.13 Shows Figure 1 a front view of the device and drum brake in which the shoe is in an open position and is close relative to the braking surface of the drum with a minimum operating clearance and clearance due to wear of the friction material relative to the braking surface of the drum, and wherein the adjustment device is in a wear clearance recovery position, wherein the first lever assembly is rotated by activating extension of the extendable strut assembly;

[0040] Fig.14 Shows Figure 1 a front view of the device and drum brake in which the shoe is in an open position in pressing contact with the braking surface of the drum, and wherein the adjustment device is in a braking position in which the connection between the first rod assembly and the second rod assembly is elastically deformed;

[0041] Fig.15 Shows Fig.13 Detail C, in which the elastic element of the connecting member is shown in an extended state;

[0042] Fig.16 and Fig.17 Shows Figure 2 Details of the device, in particular the hot plate according to the first embodiment;

[0043] Fig.18 and Fig.19 Shows Figure 2 Details of the device, in particular the hot plate according to the second embodiment. DETAILED DESCRIPTION

[0044] According to a general embodiment, an adjustment device for automatically adjusting the play of a drum brake is denoted by reference numeral 1 .

[0045] The automatic gap adjustment device 1 comprises an extendable strut assembly 2 having a toothed ring 6 .

[0046] The extendable strut assembly 2 is arranged between a first shoe 38 and a second shoe 39 which cooperate with the braking surface 37 of the drum 36 .

[0047] The shoes 38 , 39 are moved by an actuating device 40 , which biases them from a rest position, in which the shoes 38 , 39 are at least a minimum operating gap 44 away from the braking surface 37 , to a braking position, in which the shoes 38 , 39 abut against the braking surface 37 .

[0048] The extendable strut assembly 2 is subjected to a compression action Fc exerted by the shoes 38 , 39 .

[0049] Such a compression action Fc is directly dependent on and opposite to the braking action Ff transmitted to the shoes 38, 39 by the braking device 40, which, when activated, moves the shoes away from each other to restore the minimum operating clearance until the shoes are pressed against the braking surface of the drum, deforming the friction material of the shoes 38, 39 themselves.

[0050] The adjustment device 1 is configured such that when the braking action Ff and thus the compression action Fc is below a predetermined threshold value Fs, rotation of the toothed ring 6 causes the extendable strut assembly 2 to extend.

[0051] The adjustment device 1 further comprises a first rod assembly 17 associated with the extendable strut assembly 1 .

[0052] The first lever assembly 17 has a ratchet mechanism 19 at its end which is in operative contact with the toothed ring 6 .

[0053] The adjusting device 1 comprises a second rod assembly 20 which is hinged to the first shoe 38 in a rotatable and movably manner and is integrated with the first shoe 38 .

[0054] The second rod assembly 20 includes a second rod assembly first end 26 having a coupling portion 28 thereat.

[0055] When the shoe plates 38 , 39 are biased by the actuating device 40 , the coupling portion 28 is rotationally biased by the shoe plates 38 , 39 .

[0056] The adjustment device 1 comprises a connecting member 29 which is connected to the first rod assembly 17 and the second rod assembly 20 .

[0057] In particular, the connection member 29 includes a connection seat 30, which is suitable for connecting the second rod assembly 20. In other words, the second rod assembly 20 is configured to be connected to the connection member 29 through the connection seat 30.

[0058] The coupling portion 28 is coupled to the connection seat 30 with a predetermined functional gap 45 .

[0059] Such a predetermined functional gap 45 is designed so that when the shoe plates 38, 39 biased by the actuating device 40 move from the static position and approach the braking surface 37 with the minimum operating gap 44, the connecting part 28 slides in the connecting seat 30 with a free travel equal to the functional gap 45 without transmitting the movement to the connecting member 29 and the first rod assembly 17.

[0060] The second rod assembly 20 is configured to transmit the motion at least to the connecting member 29 only after the coupling portion 28 has traveled the free travel equal to the functional gap 45 .

[0061] The connecting member 29 disposed between the first rod assembly 17 and the second rod assembly 20 and mounted with said functional clearance relative to the second rod assembly 20 allows the functional clearance to be easily dimensioned according to the minimum operating clearance.

[0062] According to one embodiment, the connection seat 30 comprises a connection seat first end 31 and a connection seat second end 32 , and extends between the connection seat first end 31 and the connection seat second end 32 .

[0063] According to one embodiment, the connection seat second end 32 is placed in the direction of the first rod assembly 17, while the connection seat first end 31 is placed in the diametrically opposite direction.

[0064] According to one embodiment, the coupling portion 28 comprises a coupling portion first abutment surface 53 and a coupling portion second abutment surface 54 , and extends at least between the coupling portion first abutment surface 53 and the coupling portion second abutment surface 54 .

[0065] According to one embodiment, the coupling portion first abutment surface 53 is placed in the direction of the first rod assembly 17 , while the coupling portion second abutment surface 54 is placed in the diametrically opposite direction.

[0066] According to one embodiment, the coupling part 28 slides inside said connection seat 30 from the coupling part first position to the coupling part second position.

[0067] According to one embodiment, at the first position of the coupling portion, the first coupling portion abutment surface 53 is close to or abuts against the second end portion 32 of the connection seat portion, and the distance of the second coupling portion abutment surface 54 relative to the first end portion 31 of the connection seat portion is equal to the functional gap 45. Alternatively, at the second position of the coupling portion, the second coupling portion abutment surface 54 is in press contact with the first end portion 31 of the connection seat portion.

[0068] According to one embodiment, the connecting seat 30 has a main extension along the longitudinal direction 11 and has a longitudinal seat length L.

[0069] According to one embodiment, the coupling portion 28 has at least one extension along said longitudinal direction 11 and has a coupling portion width W along the longitudinal direction 11.

[0070] According to one embodiment, the coupling portion width W is equal to the distance existing between the coupling portion first abutment surface 53 and the coupling portion second abutment surface 54 .

[0071] According to one embodiment, the functional gap 45 is the difference between the seat length L and at least the coupling portion width W.

[0072] According to one embodiment, the connection seat 30 is a through seat of the connection member 29 .

[0073] According to one embodiment, the coupling portion 28 is positioned through a through-going connection seat 30 .

[0074] According to one embodiment, the through-going connection seat 30 is a closed contour through-going groove.

[0075] According to one embodiment, the closed contour through-groove has: the first end 31 of the connecting seat and the second end 32 of the connecting seat as edges substantially perpendicular to the main extension direction; and the connecting seat edge 55 and an edge opposite in another diameter direction as edges along the main extension direction.

[0076] According to one embodiment, the connection seat 30 has an open contour.

[0077] According to one embodiment, the open profile is C-shaped and has: the first end 31 of the connecting seat and the second end 32 of the connecting seat as edges substantially perpendicular to the main extension direction ll; and a connecting seat edge 55 as an edge along the main extension direction ll.

[0078] According to one embodiment, the second lever assembly 20 is hinged on a second lever assembly pin 21 .

[0079] According to one embodiment, said second lever assembly pin 21 is a pin already present in drum brakes of known type.

[0080] According to one embodiment, the second rod assembly pin 21 is integral with the first shoe 38 and includes a pin head 46 .

[0081] According to one embodiment, the second rod assembly 20 comprises a bushing 23 which is positioned in the rotation fulcrum of the second rod assembly 20 and cooperates with the second rod assembly pin 21 .

[0082] According to one embodiment, the bushing 23 is an articulated connection about which the second rod assembly 20 can rotate.

[0083] According to one embodiment, the second rod assembly 20 comprises an elastic clamping element 22 which is interposed between the pin head 46 and the outer surface of the bushing 23 .

[0084] According to one embodiment, the second rod assembly 20 is held in position on the second rod assembly pin 21 under the bias and correspondence of the elastic clamping element 22 between the plate 24 locked on the pin head 46 and the bushing 23 used as an articulated connection. In other words, the elastic clamping element 22 is compressed between the bushing 23 and the plate 24 locked on the pin head 46 and constrains the second rod assembly to the pin 21.

[0085] According to one embodiment, the elastic clamping element 22 is a compression spring.

[0086] According to one embodiment, the second rod assembly 20 includes a second rod assembly second end 27 .

[0087] According to one embodiment, the adjustment device 1 comprises a tie rod 25 connected to the second end 27 of the second rod assembly and the second shoe 39 .

[0088] According to one embodiment, the tie rod 25 includes a tie rod first connecting end 56 and a tie rod second connecting end 57 .

[0089] According to one embodiment, each tie rod coupling end 56 , 57 may be hook-shaped.

[0090] According to one embodiment, the second end portion 27 of the second rod assembly has a through groove 58 in which the pull rod first coupling end portion 56 is coupled.

[0091] According to one embodiment, the pull rod 25 is connected to the second shoe 39, wherein the second connecting end 57 of the pull rod is connected to the shoe return spring 59, which is connected to the two shoes 38 and 39 of the drum brake and is configured to keep the shoes 38 and 39 integrated with the actuator 40.

[0092] According to one embodiment, the shoe return spring 59 is a traction spring and has a coiled body.

[0093] According to one embodiment, the pull rod 25 is shaped so that it is arranged inside the shoe return spring 59 and so that it and the pull rod second connecting end 57 are connected to the end of the coiled portion of the shoe return spring 59 .

[0094] According to one embodiment, the adjustment device 1 comprises a preloaded torsion spring 47 which continuously acts on the second lever assembly 20 to reset it to the second lever assembly rest position.

[0095] According to one embodiment, the torsion spring 47 is configured to push the coupling portion 28 in the direction of the connecting seat second end 32 and push the second rod assembly second end 27 to keep the pull rod 25 in a tensioned state.

[0096] According to one embodiment, a preloaded torsion spring 47 holds the second lever assembly 20 in its rest position when the brake actuation device is not in operation.

[0097] According to one embodiment, the preloaded torsion spring 47 further comprises the elastic clamping element 22 .

[0098] According to one embodiment, the adjustment device 1 comprises an elastic return element 48 connected to the first rod assembly 17 and the second rod assembly 20 , which elastic return element returns the second rod assembly 20 continuously in the direction of the first rod assembly 17 .

[0099] According to one embodiment, the elastic return element 48 is configured to keep the second rod element 20 in contact with the first rod assembly 17 via the connecting member 29 .

[0100] According to one embodiment, the elastic reset element 48 is configured to pull the connecting portion 28 in the direction of the connecting seat second end 32 and eliminate any gap existing between the connecting portion second abutment surface 54, the connecting seat second end 32 and the second rod assembly 20.

[0101] According to one embodiment, the connection member 29 is configured to allow integral movement of the first rod assembly 17 and the second rod assembly 20 when the compression force Fc applied to the extendable strut assembly 2 is below a predetermined threshold value Fs.

[0102] According to one embodiment, the connection member 29 is configured to allow relative movement between the second rod assembly 20 and the first rod assembly 17 when the compression force Fc acting on the extendable strut assembly 2 is above the predetermined threshold value Fs.

[0103] According to one embodiment, if the compression action Fc blocks and prevents the extension of the extendable strut assembly 2, the first rod assembly 17 together with the ratchet mechanism 19 is directed toward the toothed ring 6, thereby limiting the force dissipated on the toothed ring 6 when the acting tension is released by the elastic extension of the second rod assembly 20.

[0104] According to one embodiment, the connecting member 29 includes a rigid element 34 and an elastic element 33 .

[0105] According to one embodiment, the rigid element 34 comprises at least one connection seat 30 .

[0106] According to one embodiment, the rigid element 34 comprises a rigid element abutment surface 60 which is configured to abut against the corresponding first rod assembly 17 which is biased by the elastic element 33 .

[0107] According to one embodiment, the rigid element 34 comprises a U-shaped end portion having the rigid element abutment surface 60 .

[0108] According to one embodiment, the elastic element 33 is preloaded in an extended state to a preload value Fp corresponding to the predetermined threshold Fs. In other words, when the compression Fc exceeds the predetermined threshold Fs, the elastic element 33 can be elastically stretched under the bias transferred to the second rod assembly 20 by the shoe movement.

[0109] According to one embodiment, the elastic clamping element 33 is a traction spring.

[0110] According to one embodiment, the rigid element 34 is shaped so as to be positioned in the manner of a traction spring within the elastic element 33 .

[0111] According to one embodiment, the elastic element 33 includes an elastic element first end 49 and an elastic element second end 50 .

[0112] According to one embodiment, the elastic element first end 49 is coupled to the first lever assembly second arm 52 .

[0113] According to one embodiment, the elastic element second end 50 is coupled to the rigid element 34 .

[0114] According to one embodiment, the second end portion 50 of the elastic element is located at the second end portion of the connecting seat portion 30 of the rigid element 34 .

[0115] According to one embodiment, the second end portion 50 of the elastic element is made of a metal wire having a diameter D and is attached to the rigid element 34 by passing through the through-connection seat 30 .

[0116] According to one embodiment, the elastic element second end 50 is positioned between the connection seat second end 32 and the coupling portion first abutment surface 53 .

[0117] According to one embodiment, the functional gap results from the difference between the length L of the connection seat, the width W of the coupling portion and the wire diameter D of the elastic element.

[0118] According to one embodiment, at the first position of the coupling portion, the first coupling portion abutting surface 53 abuts against the elastic element 33, and the distance of the second coupling portion abutting surface 54 relative to the first end 31 of the connection seat is equal to the functional gap 45. Alternatively, at the second position of the coupling portion, the second coupling portion abutting surface 54 is in press contact with the first end 31 of the connection seat, and the first coupling portion abutting surface 53 is spaced apart from the elastic element 33.

[0119] According to one embodiment, the first rod assembly 17 is hinged to the extendable strut assembly 2 via a first rod assembly pin 18 .

[0120] According to one embodiment, the first lever assembly 17 includes a first lever assembly first arm 51 having a ratchet mechanism 19 and a first lever assembly second arm 52 .

[0121] According to one embodiment, the first rod assembly 17 is a first-stage rod.

[0122] According to one embodiment, the first lever assembly first arm 51 and the first lever assembly second arm 52 are substantially perpendicular to the fulcrum.

[0123] According to one embodiment, the first lever assembly pin 18 is a spherical pin.

[0124] According to one embodiment, the first lever assembly first arm 51 and the first lever assembly second arm 52 are arranged on staggered action planes. In this way, a torque is generated which is intended to keep the ratchet mechanism 19 against one of the teeth of the toothed ring 6.

[0125] According to one embodiment, in the absence of a braking action Ff, the second rod assembly 20 is maintained in its static position under the bias of the torsion spring 47 and the elastic return element 48, and through the connecting member 29, the second rod assembly 20 transfers the torque to the first rod assembly 17, so that the first arm 51 of the first rod assembly and the ratchet mechanism 19 are kept in contact with the teeth of the toothed ring 6.

[0126] According to one embodiment, the second lever assembly 20 is made in the form of a rocker arm.

[0127] According to one embodiment, the extendable pole assembly 2 comprises a heat plate 15 which is shaped to prevent the action of the ratchet mechanism 19 after thermal deformation.

[0128] According to one embodiment, the heat plate 15 is fixed to the extendable pole by means of fastening elements 16 such as nails.

[0129] According to one embodiment, the heat plate 15 is constrained to the extendable strut assembly 2 and is placed between the toothed ring 6 and the first rod assembly 17 .

[0130] According to one embodiment, when the heat plate 15 is thermally deformed, the first arm 51 of the first rod assembly is blocked by the heat plate 15 and cannot attempt to move.

[0131] According to one embodiment, when the heat plate 15 is thermally deformed, the heat plate 15 pushes the first arm 51 of the first rod assembly in a direction such that the ratchet mechanism 19 loses contact with the ring 6 .

[0132] According to one embodiment, the extendable strut assembly 2 includes a cylinder body 3 and a piston 11 .

[0133] According to one embodiment, the cylinder body 3 has a cylinder body tail 5 and a cavity, which is closed in the direction of the piston body tail 5 and has an opening in the opposite direction.

[0134] According to one embodiment, the cylinder body 3 has a cylinder body abutment surface 4 around the opening.

[0135] According to one embodiment, the piston 11 comprises a piston rod 10 having a piston head 13 having a larger diameter than the diameter of the piston rod 10 and at least one externally threaded piston rod portion 12 .

[0136] According to one embodiment, the toothed ring 6 comprises a ring body 8 having a threaded hole threadedly connected to the externally threaded piston rod portion 12 .

[0137] According to one embodiment, the piston 11 is housed together with its piston rod 10 in the cylinder body 4 , and the toothed ring 6 is interposed between the cylinder body 3 and the piston head 13 .

[0138] According to one embodiment, said toothed ring 6 comprises a ring abutment surface 7 configured to cooperate directly or indirectly with said cylinder body abutment surface 4 .

[0139] According to one embodiment, the compression action Fc generated by the shoes 38 , 39 on the extendable strut assembly 2 acts on the cylinder body tail 5 and the piston head 13 .

[0140] According to one embodiment, the compression action Fc generated by the shoes 38 , 39 on the extendable strut assembly 2 acts between the cylinder body abutment surface 4 and the ring abutment surface 7 .

[0141] According to one embodiment, the ratchet mechanism 19 is a one-way ratchet mechanism that interacts with a toothed ring 6, which includes a ring tooth portion 9, which is formed with: a slide rail-shaped tooth surface that allows the ratchet mechanism 19 to climb over the tooth portion on which the ratchet mechanism 19 acts without rotating the toothed ring 6; and a connecting tooth surface that allows the ratchet mechanism 19 to be connected and the toothed ring 6 to rotate.

[0142] The operation of the device will be described below.

[0143] Stage K

[0144] In the absence of braking action, the adjustment device 1 is in a static position and the shoes 38 , 39 are kept at a distance at least equal to the minimum operating gap 44 from the braking surface 37 of the drum by means of elastic return elements to ensure free rotation of the drum 36 relative to the shoes 38 , 39 .

[0145] In the rest position, the second lever assembly 20 or rocker arm has a coupling portion 28 in press contact with the first lever assembly 17 via a connecting member 29 , and the ratchet mechanism of the first lever assembly 17 is in contact with the toothed ring 6 .

[0146] In more detail, the coupling portion 28 is coupled to the coupling seat 30 of the coupling member 29 and is pressed into contact with the first rod assembly 17 on the coupling member 29, which in turn contacts the first rod assembly 17. The coupling portion 28 is coupled to the coupling seat 30 with a gap equal to the functional gap 45 in the opposite direction to the first rod assembly 17.

[0147] In other words, in the static position, the coupling portion first abutment surface 53 abuts or presses against the connection seat second end 32 , and the coupling portion second abutment surface 54 is at a distance equal to the functional gap from the connection seat first end 31 .

[0148] Phase X

[0149] After the displacement of the shoes 38 and 39 caused by the braking force Fr, which brings the shoes closer to the braking surface 37 of the drum, the distance of which is equal to the minimum operating gap 44, the second rod assembly 20 pulled by the displacement of the second shoe 39 caused by the pull rod 25 rotates relative to the pivot point of the second rod assembly 20 and the first shoe 38.

[0150] As the second rod assembly 20 rotates, the connecting part 28 slides in the connecting seat 30 with a free stroke equal to the functional gap 45 without transmitting movement to the connecting member 29 and the first rod assembly 17. The first rod assembly 17 maintains a ratchet mechanism 19 that contacts the teeth of the toothed ring 6, so that the second abutment surface 54 of the connecting part contacts the first end 31 of the connecting seat.

[0151] If the braking action Ff is released from this position, the adjustment device 1 returns to the initial rest position described in phase K, and the shoes 38, 39 return to a distance from the braking surface 37 of the drum equal to the minimum operating gap 44, returned by the elastic return element.

[0152] After the functional gap 45 is restored by the idling sliding of the coupling portion 28 in the connecting seat 30 and the shoe plates 38, 39 approaching the braking surface 37 with the minimum operating gap 44, two situations may occur:

[0153] Phase Y - Blocked Condition

[0154] Phase Z – Operating in a Recovery State

[0155] Phase Y - operating under blocking conditions - is described below.

[0156] The following situation is described, in which the distance between the shoe and the drum or DIH disc bell is equal to the minimum operating gap 44, so the friction material of the shoe is not worn and there is no need to operate the extendable strut assembly 2 to make the shoe 38, 39 permanently close to the braking surface 37.

[0157] The braking action acts on the shoe by pushing the shoe 38, 39 apart, which applies a compression action Fc to the extendable strut assembly 2. As long as the shoe 38, 39 is not in contact with the braking surface 37, the shoe 38, 39 will be moved away by compressing the extendable strut assembly 2 with the compression action Fc. On the other hand, when the shoe 38, 39 is in contact with the braking surface, the compression action Fc acting on the extendable strut assembly 2 increases rapidly due to the interaction between the friction material and the braking surface 37 of the drum.

[0158] In the absence of wear, after the shoe pieces 38, 39 approach the braking surface 37 with the minimum operating clearance, the second rod assembly 20 rotates and the second abutment surface 54 of the coupling portion is pressed into contact with the first end portion 31 of the connecting seat. The compression action Fc of the support rod prevents any rotation of the toothed ring 6. Therefore, any rotation of the first rod assembly 17 is blocked. Due to the compression of the friction material, the shoe pieces 38, 39 are further pulled apart, so that the second rod assembly 20 rotates relative to the first rod assembly 17 that remains stationary. The relative rotation of the second rod assembly 20 is achieved by extending the elastic element 34 of the connecting member 29.

[0159] When the braking action Ff ceases, the adjustment device 1 returns to its initial configuration by the bias of the elastic return element 48 of the second lever assembly and the shoe return spring 59 .

[0160] Phase Z – Operating in a Recovery State

[0161] The following describes a condition in which the distance between the shoes 38, 39 and the braking surface 37 of the drum, ie the DIH disc bell, is greater than the minimum operating clearance 44 (advanced wear condition).

[0162] In this case, the shoes 38, 39 can be further moved away from stage X; therefore, after the shoes 38, 39 approach the braking surface 37 of the drum with the minimum operating gap 44, the second rod assembly 20 is caused to rotate, causing the connecting part 28 to be pressed into contact with the connecting member 29 in the opposite direction of the first rod assembly 17, and the further approach of the shoes 38, 39 to the braking surface 37 of the drum causes the second rod assembly 20 to rotate further, and the second rod assembly 20 rotates the first rod assembly 17 through the overall movement with the connecting member 29, and the ratchet mechanism 19 of the first rod assembly rotates the extendable support rod assembly 2 by extending the extendable support rod assembly, and thereby removes the shoes 38, 39, thereby permanently restoring the distance between the shoes 38, 39 and the braking surface 37 of the drum due to the wear of the friction material. As long as the compression action Fc on the extendable strut assembly 2 remains almost constant, that is, as long as the shoes 38, 39 are not in pressing contact with the braking surface 37 of the drum and the toothed ring 6 is not blocked, the overall movement of the second rod assembly 20 and the first rod assembly 17 is possible, thereby blocking any rotation of the first rod assembly 17 and activating the extension of the elastic element 33, as in stage Y.

[0163] In the returning step, the adjustment device 1 returns to the rest position and in particular, the first lever assembly 17 is rotated in the opposite direction and, by means of the spherical pivot, the ratchet mechanism 19 slides over the inclined portion of the toothing and enters the next toothing.

[0164] The invention also relates to a drum brake 35 comprising an adjustment device 1 as described above.

[0165] According to one embodiment, the drum brake 35 is of the drum-in-disc type.

[0166] The present invention also relates to a method for adjusting the gap between the shoes 38, 39 of the drum brake 35, the method comprising the following steps:

[0167] - providing an adjustment device 1 according to any of the preceding forms;

[0168] - applying a compression force Fc less than a predetermined threshold value Fs to the extendable strut assembly 2 by rotating the shoes 38, 39;

[0169] - rotating the second rod assembly 20 by sliding the coupling portion 28 in the coupling seat 30 over a free travel equal to the functional gap 45 without transmitting the movement to the coupling member 29 and the first rod assembly 17;

[0170] Alternatively,

[0171] If the compression force Fc continues to remain below the predetermined threshold Fs, the second rod assembly 20 is rotated, thereby transmitting the movement integrally to the connecting member 29 and the first rod assembly 17, engaging the ratchet mechanism 19 in the toothed ring 6, and rotating the toothed ring 6 so as to extend the extendable strut assembly 2.

[0172] or

[0173] If the compression Fc exceeds a predetermined threshold Fs, the second rod assembly 20 is rotated without transmitting movement to the first rod assembly 17 , thus avoiding biasing the toothed ring 6 .

[0174] Reference numerals list

[0175] 1 Adjustment device

[0176] 2 Extendable support rod assembly

[0177] 3 cylinder body

[0178] 4 Cylinder body abutment surface

[0179] 5 cylinder body tail

[0180] 6 Toothed ring

[0181] 7 Ring abutment surface

[0182] 8 ring body

[0183] 9 Ring gear

[0184] 10 Piston rod

[0185] 11 Piston

[0186] 12 External threaded piston rod part

[0187] 13 Piston head

[0188] 15 hot plate

[0189] 16 Hot plate fastening elements

[0190] 17 First rod assembly

[0191] 18 First rod assembly pin

[0192] 19 Ratchet mechanism

[0193] 20 Second rod assembly

[0194] 21 Second rod assembly pin

[0195] 22 Elastic clamping element of the second rod assembly

[0196] 23 Bushing

[0197] 24 Locking plate

[0198] 25 tie rod

[0199] 26 second rod assembly first end

[0200] 27 second end portion of the second rod assembly

[0201] 28 connection part

[0202] 29 Connecting components

[0203] 30 Connecting seat

[0204] 31 Connecting seat first end

[0205] 32 Connecting seat second end

[0206] 33 Elastic element

[0207] 34 Rigid elements

[0208] 35 drum brake

[0209] 36 drum

[0210] 37 Braking surface of drum

[0211] 38 first hoof

[0212] 39 Second hoof

[0213] 40 Brake actuator

[0214] 41 solid blocks

[0215] 42 shoe positioning spring

[0216] 43 shoe return spring

[0217] 44Minimum operating clearance

[0218] 45 Functional Gap

[0219] 46 pin header

[0220] 47 Preloaded torsion spring

[0221] 48 Elastic reset element

[0222] 49 elastic element first end

[0223] 50 elastic element second end

[0224] 51 First rod assembly first arm

[0225] 52 First rod assembly second arm

[0226] 53 coupling portion first abutment surface

[0227] 54 coupling portion second abutment surface

[0228] 55 Connect the seat edge

[0229] 56 pull rod first connection end

[0230] 57 pull rod second connection end

[0231] 58 through slot

[0232] 59 shoe return spring

[0233] 60 Rigid element abuts against surface

[0234] Ff Braking effect

[0235] Fc compression

[0236] Fs predetermined threshold

[0237] Fp preload value

[0238] ll Longitudinal direction

[0239] L Seat length

[0240] W Width of connection part

[0241] D: Wire diameter.

Claims

1. An adjusting device (1) for automatically adjusting the clearance of a drum brake, the adjusting device comprising: - an extendable strut assembly (2), comprising a toothed ring (6), the extendable strut assembly (2) being arranged between a first shoe (38) and a second shoe (39) cooperating with a braking surface (37) of a drum-shaped portion (36), the first shoe (38) and the second shoe (39) being moved by an actuating device (40), the actuating device biasing the first shoe (38) and the second shoe (39) from a rest position to a braking position, in which the first shoe (38) and the second shoe (39) are in a state of being ... 9) at least a predetermined minimum operating gap (44) from the braking surface (37), in the braking position, the first shoe (38) and the second shoe (39) abut against the braking surface (37), and wherein the extendable strut assembly (2) is subjected to a compression (Fc) applied by the first shoe (38) and the second shoe (39), and wherein, when the compression (Fc) is above a predetermined threshold value (Fs), the rotation of the toothed ring (6) is blocked, thereby preventing the extension of the extendable strut assembly (2); The adjusting device (1) further comprises: - a first rod assembly (17) associated with the extendable strut assembly (2) and having a ratchet mechanism (19) at the end of the first rod assembly, The ratchet mechanism is in operative contact with the toothed ring (6), - a second rod assembly (20), the second rod assembly being hinged to the first shoe (38) and comprising a connecting portion (28) at the first end portion (26) of the second rod assembly, wherein when the first shoe (38) and the second shoe (39) are biased by the actuating device (40), the connecting portion (28) is biased by the first shoe (38) and the second shoe (39) to rotate, - a connecting member (29) connected to the first rod assembly (17) and comprises a connecting seat portion (30), wherein the connecting seat portion is suitable for connecting the second rod assembly (20), The connecting portion (28) is connected to the connecting seat (30) with a predetermined functional gap (45), so that when the first shoe (38) and the second shoe (39) When the coupling portion (28) is moved from the rest position to approach the braking surface (37) with the minimum operating gap (44) under the action of the actuating device (40), the coupling portion (28) The second rod assembly (20) slides in the connection seat (30) with a free travel equal to the functional gap (45) without transmitting movement to the connection member (29) and the first rod assembly (17), and wherein the second rod assembly (20) is configured to slide in the connection portion (28) After traveling the free travel equal to the functional gap (45), the movement is at least transmitted to the connecting member (29).

2. The adjustment device (1) for automatically adjusting the clearance of a drum brake according to claim 1, wherein: The connection seat (30) extends between a first end portion (31) of the connection seat and a second end portion (32) of the connection seat, wherein the coupling portion (28) slides in the connection seat (30) from a first coupling portion position to a second coupling portion position, wherein at the first coupling portion position, the coupling portion (28) is close to or in contact with the second end portion (32) of the connection seat, and at the second coupling portion position, the coupling portion (28) is in press contact with the first end portion (31) of the connection seat; and / or among them The coupling portion (28) comprises a first coupling portion abutment surface (53) and a second coupling portion abutment surface (54), wherein the first coupling portion abutment surface (53) faces in the direction of the first rod assembly (17), and the second coupling portion abutment surface (54) faces in the opposite direction in the diameter direction, wherein after the coupling portion (28) travels the free travel equal to the functional gap (45), the second coupling portion abutment surface (54) is pressed into contact with the connecting member (29); and / or among them The connecting seat (30) has a main extension along the longitudinal direction (ll) and has a longitudinal seat length (L), and the coupling portion (28) has at least one extension along the longitudinal direction (ll) and has a coupling portion width (W), wherein the functional gap (45) is the difference between the seat length (L) and at least the coupling portion width (W) in the longitudinal direction, and / or among them The connecting seat (30) is a through seat of the connecting member (29), and the coupling portion (28) is positioned to pass through the through seat.

3. The adjustment device (1) for automatically adjusting the clearance of a drum brake according to claim 2, wherein: The second rod assembly (20) is hinged on a second rod assembly pin (21), and the second rod assembly pin (21) is integrated with the first shoe (38). and / or among them The second rod assembly (20) comprises a second rod assembly second end (27), and the adjustment device (1) comprises a pull rod (25) connected to the second rod assembly second end (27) and the second shoe (39); and / or among them The adjustment device (1) comprises a preloaded torsion spring (47), which is configured to continuously act on the second rod assembly (20) to return the second rod assembly to the second rod assembly static position, thereby returning the coupling part (28) in the direction of the second end (32) of the connecting seat; and / or among them The adjustment device (1) comprises an elastic reset element (48) connected to the first rod assembly (17) and the second rod assembly (20), and the elastic reset element (48) is configured to make the connecting part (28) continuously return in the direction of the second end part (32) of the connecting seat and eliminate any gap between the connecting part (28), the second end part (32) of the connecting seat and the second rod assembly (20).

4. The adjusting device (1) for automatically adjusting the clearance of a drum brake according to claim 2, wherein: The connecting member (29) is configured to allow the first rod assembly (17) and the second rod assembly (20) to move as a whole when the compression force (Fc) acting on the extendable support rod assembly (2) is lower than a predetermined threshold value (Fs), and the connecting member (29) is configured to allow the second rod assembly (20) and the first rod assembly (17) to move relative to each other when the compression force (Fc) acting on the extendable support rod assembly (2) is higher than the predetermined threshold value (Fs), and / or wherein The connecting member (29) comprises a rigid element (34) and an elastic element (33), wherein the rigid element (34) comprises the connecting seat (30), the rigid element (34) contacts the first rod assembly (17) in a manner different from that of the elastic element (33) and under the action of the elastic element (33), the elastic element (33) is preloaded in an extended state to a preload value (Fp) corresponding to the predetermined threshold value (Fs), and the elastic element (33) comprises a first end portion (49) of the elastic element hooked to the first rod assembly (17) and a second end portion (50) of the elastic element hooked to the rigid element (34).

5. The adjustment device (1) for automatically adjusting the clearance of a drum brake according to claim 4, wherein: The first rod assembly (17) comprises a first rod assembly second arm (52), and the first end portion (49) of the elastic element is hooked to the first rod assembly second arm; and / or among them The second end portion (50) of the elastic element hooked with the rigid element (34) is placed between the second end portion (32) of the connection seat and the first abutment surface (53) of the coupling portion, and when the first abutment surface (53) of the coupling portion abuts with the second end portion (50) of the elastic element, the functional gap (45) is obtained by the distance between the first end portion (31) of the connection seat and the second abutment surface (54) of the coupling portion; and / or among them The elastic element (33) is hooked to the rigid element (34) at the second end (32) of the connecting seat of the rigid element and is made in the form of a traction spring made of a wire having a diameter (D), and the functional gap (45) is obtained by the difference between the seat length (L), the connecting part width (W) and the diameter (D).

6. The adjusting device (1) for automatically adjusting the clearance of a drum brake according to any one of claims 1 to 5, wherein: The first rod assembly (17) is hinged to the extendable support rod assembly (2) via a first rod assembly pin (18), and the first rod assembly (17) includes a first rod assembly first arm (51) having the ratchet mechanism (19), and a first rod assembly second arm (52), wherein the first rod assembly first arm (51) and the first rod assembly second arm (52) are arranged on mutually offset action planes.

7. The adjusting device (1) for automatically adjusting the clearance of a drum brake according to claim 6, wherein: The extendable strut assembly (2) includes a heat plate (15) which is shaped to block the action of the ratchet mechanism (19) after thermal deformation.

8. The adjusting device (1) for automatically adjusting the clearance of a drum brake according to claim 7, wherein: The heat plate (15) is constrained to the extendable support rod assembly (2) and is placed between the toothed ring (6) and the first rod assembly (17), and in the event of thermal deformation of the heat plate (15), the first arm (51) of the first rod assembly is blocked by the heat plate (15) and cannot attempt to move. or The hot plate (15) pushes the first arm (51) of the first lever assembly in a direction such that the ratchet mechanism (19) loses contact with the toothed ring (6).

9. A drum brake (35), comprising an adjustment device (1) for automatically adjusting the clearance of a drum brake according to any one of claims 1 to 8.

10. A method for adjusting the gap between a first shoe (38) and a second shoe (39) of a drum brake (35), the method comprising the following steps: - Provide an adjustment device (1) for automatically adjusting the clearance of a drum brake according to any one of claims 1 to 8; - applying a compression (Fc) less than a predetermined threshold value (Fs) to the extendable strut assembly (2) by rotating the first shoe (38) and the second shoe (39); - rotating the second rod assembly (20) by sliding the coupling portion (28) in the connection seat (30) by a free travel equal to the functional gap (45) without transmitting movement to the connection member (29) and the first rod assembly (17); Alternatively, - if the compression (Fc) continues to remain below the predetermined threshold (Fs), rotating the second rod assembly (20) so as to transmit the movement integrally to the connecting member (29) and the first rod assembly (17), engaging the ratchet mechanism (19) in the toothed ring (6), and rotating the toothed ring (6) so as to extend the extendable strut assembly (2); or - If the compression (Fc) exceeds the predetermined threshold (Fs), the second rod assembly (20) is rotated without transmitting movement to the first rod assembly (17), thereby avoiding biasing the toothed ring (6).

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