TECHNICAL FIELD

[001] The invention relates to tire retreading and refers to a tire buffing machine. BACKGROUND OF THE INVENTION

[002] A buffing machine is used in a tire retreading process to scrape the worn tread of a used tire in order to prepare the tire to receive a new tread.

[003] Among the conventional models, there is the buffing machine that has a tire support comprising a horizontal axis rotating mandrel. The mandrel supports an expandable rim on which the tire to be retreaded is mounted. A rasp head is supported on a pedestal capable of moving in relation to the expandable rim. The rasp head scrapes the tread while the tire is kept in rotation. An example of this type of buffing machine can be observed in EP0531953.

[004] Another example of buffing machine is revealed in US2015047453, In this model, the rasp head is supported on a robotized arm. In one of the disclosed embodiments, the robotized arm attends three tire supports, each supporting a rotating mandrel with an expandable rim for mounting a respective tire to be retreaded.

SUMMARY OF THE INVENTION

[005] It is an object of the invention to provide a tire buffing machine with increased productivity compared to state-of-the-art machines. It is a further object of the invention to provide a tire buffing machine with ergonomic benefits for a machine operator in relation to state-of-the-art machines.

[006] The tire buffing machine comprises a scraping assembly including a rasp head having a rasping tool, a tire support assembly, and means to selectively move the rasp head in relation to the tire support assembly. According to the invention, the tire support assembly comprises a tower supporting a first horizontal axis rotating mandrel that supports a first expandable rim and supporting a second horizontal axis rotating mandrel that supports a second expandable rim. Further, the tire support assembly comprises means to rotate the tower in relation to a vertical axis to selectively position the first and second expandable rim in a loading and unloading position and in a scraping position.

[007] In operation, first an operator assembles a first tire on the first expandable rim located in loading and unloading position. Then, the tower is rotated in order to move the first expandable rim together with the first tire to the scraping position. Consequently, from the tower rotating, the second expandable rim that was in scraping position is moved to the loading and unloading position. When the first tire is in scraping position, the scraping assembly performs a scraping operation to remove the tread. Meanwhile, the operator assembles a second tire on the second expandable rim located in loading and unloading position. When the scraping operation on the first tire is completed, the tower is rotated to move the first expandable rim together with the first tire to the loading and unloading position, so as to move the second expandable rim together with the second tire to scraping position. When the second tire is in scraping position, the scraping assembly performs a scraping operation to remove the tread. Meanwhile, the operator removes the first tire from the first expandable rim and assembles a next tire on the first expandable rim located in the loading and unloading position. And so on.

[008] Advantageously, from the proposed solution, a tire buffing machine is obtained in which the scraping operation of a tire is performed simultaneously in relation to the unloading and loading operation of other tires, thus increasing the productivity of the machine, as compared to a conventional buffing machine, such as disclosed in EP0531953.

[009] Advantageously, in the buffing machine according to the invention, the physical space in which the operator performs loading and unloading operations remains unchanged, so as that the operator needs not to move to suit different tire supports, such as occurs in the machine embodiment having three tire supports disclosed in US2015047453, which contributes to reduce operator fatigue during a working day.

BRIEF DESCRIPTION OF THE DRAWINGS

[010] The invention will be better understood with the following detailed description, which will be better understood with the aid of the figures, as follows:

[011] Figure 1 shows a first view in perspective of the tire buffing machine.

[012] Figure 2 shows a second view in perspective of the tire buffing machine.

[013] Figure 3 shows a third view in perspective of the tire buffing machine.

[014] Figure 4 shows a front view of the tire buffing machine.

[015] Figure 5 shows a first view in perspective of the tire support assembly.

[016] Figure 6 shows a second view in perspective of the tire support assembly.

[017] Figure 7 shows a view according to sectional plane "A-A" shown in Figure 4, with a locking element in the locked position.

[018] Figure 8 shows a view according to the sectional plane "A-A" shown in Figure 4, with the locking element in the unlocked position.

[019] Figure 9 shows a top view of the buffing machine with a first tire in loading and unloading position.

[020] Figure 10 shows a top view of the buffing machine in an intermediate position during a tower rotating movement to switch the first tire to the scraping position.

[021] Figure 11 shows a top view of the buffing machine with the first tire in scraping position and a second tire in the loading and unioading position.

[022] Figure 12 shows a top view of the buffing machine in an intermediate position during a tower rotating movement to switch the first tire to the loading and unloading position and the second tire to the scraping position.

[023] Figure 13 shows a top view of the buffing machine with the first tire in loading and unloading position and the second tire in the scraping position.

[024] Figure 14 shows a top view of the buffing machine after unloading the first tire and with the second tire in the scraping position.

DETAILED DESCRIPTION

[025] The invention proposes a tire buffing machine (10) comprising a scraping assembly (20) including a rasp head (22) having a rasping tool (221), a tire support assembly (30), and means to selectively move the rasp head (22) in relation to the tire support assembly (30). According to the invention, the tire support assembly (30) comprises a tower (31) supporting a first rotating mandrel (32) of horizontal axis that supports a first expandable rim (33) and supporting a second rotating mandrel (34) of horizontal axis that supports a second expandable rim (35). Further, the tire support assembly (30) comprises means to rotate the tower (31) in relation to a vertical axis to selectively position the first (33) and the second expandable rim (35) in a loading and unloading position and in a scraping position. In Figures 1 to 4, the first expandable rim (33) is in a scraping position and the second expandable rim (35) is in a loading and unloading position.

[026] The means to rotate the tower (31) comprise a fixed base (42) from which protrudes a vertical rod (43), wherein the tower (31) is bearing mounted on the vertical rod (43) with freedom of rotation. The means to rotate the tower (31) further comprise a motor element having a driving gear (46) coupled to a driven gear (47) fastened to the tower (31). In the represented embodiment, as can be better viewed in Figures 2, 4 and 5, the motor element corresponds to an electric motor (44) associated with a gearbox (45). The rotation of the driving gear (46) produces rotation of the driven gear (47) and consequently the rotation of the tower (31). Thus, from the driving of the motor element, the first expandable rim (33) can be switched from the scraping position to the loading and unloading position, and vice versa, while the second expandable rim (35) is rotated from the loading and unloading position to the scraping position, and vice versa.

[027] Preferably, the tire support assembly (30) comprises a position indexing device configured to correctly position the tower (31) so that the expandable rims (33, 35) are correctly aligned in the scraping position and the loading and unloading position. In the represented embodiment, the position indexing device comprises an end stop portion (52) which interacts with a pair of stops (54, 54') fastened on one side of the driven gear (47). For example, in Figure 6 it is possible to see the end stop portion (52) in contact with a stop (54). From this position, as can also be seen in Figure 5, and upon activating the rotation of the tower (31), said tower (31) will rotate until the other stop (54') contacts the end stop portion (52).

[028] Preferably, the tire support assembly (30) comprises a locking device configured to selectively lock the tower (31) in a desired position, preventing its rotating movement, in the represented embodiment, the locking device comprises a casing (56) that houses a locking element (57) linearly sliding in relation to the casing (56), the locking element (57) having gear teeth adapted to fit with gear teeth of the driven gear (47) and the locking element (57) being fastened to a rod (59) of a pneumatic actuator (58) that moves the locking element (57) between a locked position and an unlocked position. [029] Figure 7 shows the locking element (57) in a locked position, i.e. with the teeth of the locking element (57) engaged between the teeth of the driven gear (47). In this position, the tower (31) is unable to rotate. Locking the tower (31) is important to maintain the expandable rims (33, 35) stabilized in the loading and unloading position and in the scraping position while the loading and unloading and scraping operations are performed. For example, considering the first expandable rim (33) in the scraping position, as can be seen in Figures 1 to 4, and equipped with a tire to be scraped, it is important that the tower (31) is properly locked while the rasping tool (221) of the rasp head (22) is contacting the tire surface, thereby preventing unwanted rotation of the tower (31).

[030] Figure 8 shows the locking element (57) in an unlocked position, i.e. with the teeth of the lock element (57) disengaged from the teeth of the driven gear (47). In this position, the tower (31) has its rotation movement released, which can be executed from the rotation of the driving gear (46). Leaving from the locking element (57) in the locked position, as can be seen in Figure 7, the unlocking is done by means of a drive to retract the rod (59) of the pneumatic actuator (58), causing the locking element (57) to slide to the unlocked position shown in Figure 8. The locking is performed in a reverse manner, from a drive to extend the rod (59) of the pneumatic actuator (58).

[031] The first rotating mandrel (32) has its rotation driven by a first gear motor (36) and the second rotating mandrel (34) has its rotation driven by a second gear motor (37).

[032] In the represented incorporation, as can be seen in Figures 1 to 4, the means to selectively move the rasp head (22) comprise a fixed platform (25) having a pair of rails (252) oriented in a Ύ" direction and a mobile platform (26) having a pair of guides (262) assembled on the pair of rails (252) of the fixed platform (25). Thus, the mobile platform (26) slides over the fixed platform (25) in the Ύ" direction. The movement of the mobile platform (26) is driven by a first rotary threaded shaft (263).

[033] The mobile platform (26) has a pair of rails (264) oriented in a "X" direction. The means to selectively move the rasp head (22) comprise a base (27) having a pair of guides (272) assembled on the pair of rails (264) of the mobile platform (26). Thus, the base (27) slides on the movable platform (26) in the "X" direction. The movement of the base (27) is driven by a second rotary threaded shaft (273).

[034] The base (27) receives a pedestal (24) that supports the rasp head (22). The pedestal (24) is conventionally configured to rotate in relation to the base (27). The combination of movements of the mobile platform (26), the base (27) and the pedestal (24) enables the rasp head (22) to advance and retreat in relation to the expandable rim (33, 35) positioned in scraping position. This combination of movement also allows the rasp head (22) to contour and scrape the surface of a tire assembled on the expandable rim (33, 35) positioned in scraping position.

[035] The rasping too! (221) rotates according to a horizontal axis conventionally driven by a drive motor (28) and a transmission assembly (29). The scraping operation is performed by the rasping tool (221) in rotation, while the tire in scraping position is kept in rotation due to rotation of the corresponding expandable rim (33, 35) caused by the rotation of the corresponding rotating mandrel (32, 34).

[036] The tire buffing machine (10) may further include a measuring head (60) conventionally equipped with measurement sensors such as ultrasound or laser sensor, inductive sensor, and/or a linear position transducer, with the function of monitoring scraping operations in order to reach a scraping result compatible with the programmed dimensions. [037] The tire buffing machine (10) may be configured to work in an automated way. In this case, there is a control unit (70) equipped with a programmable logic controller (PLC) and a control panel (72). The programmable logic controller (PLC) is connected in a conventional manner with the means to move the rasp head (22), with the drive motor (28) of the rasping tool (221) and with the sensors of the measurement head (60).

[038] in particular, according to the invention, the means to rotate the tower (31) and the means to lock the tower (31), including position sensors, they may also be connected with the programmable logic controller (PLC) so that the rotation of the tower (31) and the locking of the tower (31) are performed in an automated manner. This level of automation is at the reach of a person skilled in the art.

[039] The tire buffing machine (10) may be equipped With a finishing device (32). In the represented embodiment, as can be better viewed in Figures 5 and 6, the finishing device (82) comprises an articulated arm (84) bearing mounted on the fixed base (42) of the tower (31). The articulated arm (84) supports a rotary cutting tool (86) according to a horizontal axis conventionally driven by a drive motor (87) and a transmission assembly (88). The finishing device (82) further comprises a pair of handles (89). The finishing device (82) serves for an operator to perform a finishing operation on a tire already scraped by the rasp head (22), such tire positioned in the loading and unloading position.

[040] The following describes an example of operation of the tire buffing machine (10) based on Figures 9-14.

[041] First, as can be seen in Figure 9, an operator (80) assembles a first tire (92) on the first expandable rim (33) located in loading and unloading position. After assembling the first tire (92), the operator (80) can select on the control panel (72) a scraping recipe suitable to the dimensions of the first tire (92). Then the tower (31) is rotated so as to move the first expandable rim (33) together with the first tire (92) to the scraping position. Figure 10 illustrates the tire buffing machine (10) in an intermediate position while the tower (31) rotates.

[042] Accordingly, from rotating the tower (31), the second expandable rim (35), which was in scraping position, is moved to the loading and unloading position. When the first tire (92) is in scraping position, as can be seen in Figure 11 , the rasp head (22) scrapes the tire in order to remove the tread, while the first tire (92) is kept rotating due the rotation of the first rotating mandrel (32). Meanwhile, the operator (80) assembles a second tire (94) on the second expandable rim (35) located in the loading and unloading position, and selects a scraping recipe suitable to the dimensions of the second tire (94).

[043] Once the scraping operation on the first tire (92) are terminated, the tower (31) is rotated so as to move the first expandable rim (33) together with the first tire (92) to the loading and unloading position, so as to move the second expandable rim (35) together with the second tire (94) to the scraping position. Figure 12 illustrates the tire buffing machine (10) in an intermediate position while rotating the tower (31).

[044] When the second tire (94) is in scraping position, as can be seen in Figure 13, the rasp head (22) scrapes the tire to remove the tread, while the second tire (94) is maintained rotating due to the rotation of the second rotating mandrel (34). Meanwhile, if necessary, the operator (80) can perform a finishing operation on the first tire (92) located in loading and unloading position with aid of the finishing device (82).

[045] Also during the scraping operation of the second tire (94), the operator (80) removes the first tire (92) from the first expandable rim (33) in loading and unloading position, leaving such first expandable rim (33) available to assembly a next tire to be processed by the buffing machine (10), as shown in Figure 14. And so on.

[046] Alternatively, according to a not represented embodiment, the means to selectively move the rasp head (22) comprise a robotized arm.