Safety device for torque limiter

Abstract: A safety device for a torque limiter composed of an external body (2), which is rigidly coupled to the driving shaft (6) for transmitting motion to a working implement and inside which there is a seat (4) for accommodating an internal body (5) which is rigidly coupled to the driven motion transmission shaft (3) and is provided with a series of radial sliding seats (7) for corresponding tabs (8) which can move, in contrast with elastic elements (8a), alternatively between a centrifugal position providing engagement and transmission in corresponding slots (9) formed in the external body (2) and a centripetal position for disengagement from the slots (9) and for stopping the transmission; the movement is activated by means of a corresponding centered plate (10) which forms a protruding ring (10a) for wedging and centrifugally pushing the tabs (8) and provides for the in-line interposition, between the internal body (5) and the plate (10), of pushers (11) for axially pushing the plate (10) into the configuration for forced disengagement from the tabs (8).

Description: The present invention relates to a safety device for a torque limiter. The demand to render absolutely safe every machine used in production work is becoming increasingly widespread. This trend is also increasingly followed in the field of agricultural machines, also in order to comply with international standards. Operators handling or using agricultural implements for tilling fields and tending to the cultivations that derive from them are in fact often involved in accidents. Specifically, it has been found that it is increasingly necessary to provide a way to mutually disconnect the agricultural implements used by tractors and the like from the power take-offs with which these tractors are equipped. The first and immediate form of operator protection in fact consists, in case of accident, in stopping the machines being used as quickly as possible, using devices which are activated automatically but require manual resetting in order to restore the operating conditions, consequently removing the dangerous conditions. The prior art provides many devices for protecting the elements that potentially constitute sources of possible accidents. However, these devices consist, in most cases, of static protections which prevent access to dangerous parts, but they do not allow dynamic intervention if these devices turn out to be ineffective and a dangerous condition arises. The aim of the present invention is to solve the above-mentioned problems of the prior art shown in figures 5 and 6 of the present application and corresponding to the preamble of claim 1 in order to provide a safety device for torque limiter which allows to interrupt, in a controlled way, the transmission of motion between the power take-off and the implement, stopping its operation, when abnormal and dangerous conditions occur during work, by acting on the limiter assembly, and can be reset in an absolutely manual way when the dangerous condition ends. This aim, this object and others are achieved by a safety device for a torque limiter as defined by claim 1. Further advantages will become apparent from the following detailed description of a preferred embodiment of a safety device for torque limiter, illustrated only by way of non-limitative example in the accompanying drawings, wherein: Figure 1 is a top view of a mechanical coupling between a torque limiter and a gear casing of a power take-off of an agricultural machine; Figure 2 is an enlarged-scale transverse sectional view, taken along the plane II-II of Figure 7; Figures 3 and 4 are sectional views, taken along a longitudinal plane, of a torque limiter provided with the safety device according to the invention, respectively during normal motion transmission and during intervention of the safety device; Figures 5 and 6 are two sectional views, taken along longitudinal and transverse planes, of a conventional type of torque limiter without the safety device, shown in the motion transmission configuration and in the transmission limiting configuration, respectively; Figures 7 and 8 are longitudinal sectional views of a possible further second, embodiment of the safety device, shown in the normal motion transmission condition and in the intervention condition, respectively. With reference to the above figures, 1 designates a torque limiter, for power take-offs of agricultural machines in the specific case, which is composed of an external body 2 which is rigidly coupled to the driving shaft 6 for transmitting motion to a working implement (not shown for the sake of simplicity). Inside the body 2 there is a seat for accommodating an internal body 5 which is rigidly coupled to the driven shaft 3 for motion transmission and is provided with a series of seats 7 in which corresponding tabs 8 are inserted and can slide radially; these tabs can move, in contrast with elastic means 8a shown schematically, for the sake of simplicity, alternatively between a centrifugal position for engagement and transmission in corresponding slots 9 formed in the external body 2 and a centripetal position for disengagement from the slots 9 and consequently for interrupting transmission. The centrifugal movement of the tabs 8 is activated by means of a corresponding centered plate 10 which peripherally forms, on one face, a protruding ring 10a which is adapted to wedge itself and push the tabs 8 in a centrifugal direction. Means 11 for axially pushing the plate 10 in the configuration for forced disengagement from the tabs 8 are interposed in-line between the internal body 5 and the plate 10. The axial pusher means 11 are constituted, in a first possible embodiment of the safety device according to the invention, by at least one pin 12 which is actuated so that it can slide axially in a corresponding seat 13 which is formed coaxially in the driven shaft 3, with corresponding actuation means 14 which are arranged in contact with one end of the pin; the opposite end of the pin 12 is coaxial and is connected by contact with the centered plate 10. In a second possible embodiment, the axial pusher means 11 are constituted by at least one pair of pins 112 which lie parallel and diametrically opposite to the rotation axis A of said driving shaft 6 and the driven shaft 3; the pins 112 can be actuated so as to simultaneously move axially and slide in corresponding seats 113 formed in the internal body 5 of the limiter 1 through actuation means 114 which act on the corresponding ends thereof; the opposite ends of the pins 112 are kept in contact with the centered plate 10. In the first embodiment of the invention, the means 14 for actuating the pin 12 are constituted by a secondary pin 15 which is fitted so as to rest transversely at the end of the pin 12 that lies opposite the one in contact with the plate 10; the secondary pin 15 can slide axially in a transverse seat 16 which is formed in the driven shaft 3, and is kept in contact with means 17 which can be separated axially and are provided with elements 17a for locking the separated configuration. The axially separable means 17 are constituted by two facing coaxial disks 18 and 19 which can be coupled by means of twin sets of teeth 20 which mutually interpenetrate; the sets of teeth 20 can be disengaged by contrast after turning at least one of the disks 18 or 19 with respect to the other; the first disk 18 is fitted on the driven shaft 3 so as to rotate independently of it and to freely move axially, while the second disk is rigidly coupled to the end of the conventional casing 21 that accommodates the gears constituting the power take-off 22. The elements 17a for locking the separated configuration are constituted by at least one pin 23 which is supported by one of the coaxial disks, the second one 19 in the specific case, in a perpendicular seat 24 and with elastic pusher means 25, in practice a pre-compressed spring, interposed; the opposite disk 18 in turn has a hollow seat 26 which is normally rotationally offset with respect to the seat 24 and in which the pin 23 engages automatically when the first disk 18 is moved to the configuration in which it is rotated and accordingly spaced with respect to the second coaxial disk 19. In the second possible embodiment of the invention, the actuation means 114 are constituted by a first disk 118 which is keyed on a male hub 5a which protrudes from the internal body 5 of the limiter 1 with centering elements 27 interposed. The first disk 118 centrally forms a female hub 118a which is fitted on the male hub 5a and whose front surface 5a is kept in constant contact with the corresponding ends of the pins 112. Moreover, the female hub 118a is rotationally coupled to the male hub 5a with corresponding means 28 having one degree of freedom and the first disk 118 can be moved axially together with a second disk 119 which faces it: friction means 29 are interposed between the first and second disks. The second disk 119 is supported and centered on the driven shaft 3 and engages, by means of a twin set of teeth which is identical to the set of teeth 20, a flange 120 which is rigidly coupled at the end of the conventional casing 21 that accommodates the gears constituting the power take-off 22. The means 28 for coupling with one degree of freedom between the male hub 5a and the female hub 118a are constituted by two teeth 30 which protrude towards the center from the female hub 118a and by a corresponding pair of longitudinal grooves 31 formed radially in the male hub 5a; the teeth 30 can slide parallel to the axis of the hubs in the grooves 31 for a preset extent. The centering elements 27 are constituted by a ring 32 which is rigidly fitted at the end of the male hub 5a and is provided with a front resting surface 32a which has a concave conical profile for coupling to an opposite convex profile 118b that protrudes from the first disk 118. The elements 17a for locking the disengaged configuration of the twin set of teeth 20, which can be deactivated manually, are fitted between the first disk 118 and the second disk 119. The operation of the invention is described hereinafter separately for both embodiments of the invention. In the first embodiment, shown in Figures 3 and 4, the disengagement of the plate 10 is provided by moving axially the pin 12 which can slide in the seat 13 formed centrally and coaxially in the driven shaft 3. The head of the pin 12 is in contact with the base of the stem 33, to which the pack of Belleville washers 34 is keyed and whose head is in turn in contact with the plate 10. When the pin 12 moves to the left according to the orientation of the figures, the ring 10a of the plate 10 disengages from the tabs 8, which move towards the center in the seats 7, leaving the slots and thus rendering rotationally independent the external body 2, which is rigidly coupled to the driving shaft 6, and the internal body 5, which is rigidly coupled to the driven shaft 3. In this condition, torque transmission is interrupted. The axial actuation of the pin 12 is achieved by way of the rotation of the disk 18 with respect to the disk 19, which is rigidly coupled to the casing 21 that accommodates the gears that compose the power take-off 22. This rotation can be activated with a conventional type of actuator 35 which can be actuated by the operator and mutually disconnects the teeth of the twin set of teeth 20, causing the disk 18 to move away from the disk 19. In particular, the disk 18 moves towards the limiter 1, producing an equal movement in the seat 16 of the pin 15 which is fitted transversely in contact with the pin 12; this pin slides, as above-mentioned, and disengages the plate 10 from the tabs 8. The rotation of the disk 18 with respect to the disk 19 also causes the angular alignment of the pin 24 and the seat 26; the pin 24, actuated by the pre-compressed spring 25, spontaneously engages in the seat 26 and prevents return rotations of the disk 18, keeping it spaced from the disk 19. Only the manual intervention of an operator allows to disengage the pin 24 from the seat 26 and thus allows the disk 18 to turn in order to reengage the teeth of the twin set of teeth 20 and move to the right, with respect to the orientation of the drawings, the disk 18 and therefore the pin 12. The second possible embodiment of the invention, shown in Figures 7 and 8, works substantially like the preceding one; the pair of pins 112 that can slide in the respective seats 113 are in fact actuated axially, and by being in contact with the ring 10a of the plate 10, when they move to the left with respect to the orientation of the drawings they lift it from engagement with the tabs 8, which can thus move towards the center by sliding in the seats 7 and can disengage from the slots 9, interrupting the transmission of torque in the limiter 1. The movement of the pins 112 is activated by the female hub 118a of the disk 118, which moves axially on the male hub 5a, which is pushed by the mutual disengagement of the teeth of the twin set of teeth 20, interposed between the second disk 119 and the flange 120. A gasket of friction material, for example brake lining, can optionally be inserted between the two disks 118 and 119 and brakes the rotation of the driven shaft 3 with respect to the driving shaft 6 when it is disengaged therefrom. As in the previously described embodiment, the rotation of the disks 118 and 119 with respect to the flange 120, which is rigidly fitted at the end of the casing 21, causes the angular alignment of the seat 26, which in this case is formed in the second disk 119, with the pin 23, which engages in it automatically, actuated by the spring 25, thus keeping fixed the torque transmission interruption configuration. In this second embodiment of the invention also, in order to restore the normal transmission conditions it is necessary for an operator to manually act by disengaging the pin 23 from the seat 26. In this manner, the disk 118 can retract together with the disk 119, moving to the right with respect to the drawings, and the pins 112 stop pushing against the plate 10, which can thus reengage between the tabs 8 and restore the torque transmission condition. In practice it has been observed that the above-described invention achieved the intended aim. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept. All the details may further be replaced with other technically equivalent ones. In practice, the materials employed, as well as the shapes and the dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the appended claims. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: A safety device for a torque limiter composed of an external body (2), which is rigidly coupled to the driving shaft (6) for transmitting motion to a working implement and inside which there is a seat (4) for accommodating an internal body (5) which is rigidly coupled to the driven motion transmission shaft (3) and is provided with a series of radial sliding seats (7) for corresponding tabs (8) which can move alternatively between a centrifugal position, against the force of elastic means (8a), providing engagement and transmission in corresponding slots (9) formed in said external body (2) and a centripetal position for disengagement from said slots (9) and for stopping the transmission, said movement being activated by way of a corresponding centered plate (10) which forms a protruding ring (10a) for wedging and centrifugally pushing said tabs (8), characterized in that pusher means (11) for axially pushing the plate (10) into the configuration for forced disengagement from said tabs (8) are interposed between said plate (10) and actuation means (14). The safety device according to claim 1, characterized in that said axial pusher means (11) are constituted by at least one pin (12) which is actuated so as to slide axially in a corresponding seat (13) and is actuated by said actuation means (14) which are in contact with one end of said pin, the opposite end thereof being connected coaxially in contact with said centered plate (10). The safety device according to claim 2, characterized in that said seat (13) for the sliding of the pin (12) is formed coaxially in the driven transmission shaft (3). The safety device according to claim 1, characterized in that said axial pusher means (11) are constituted by at least one pair of pins (112) which are arranged parallel to the rotation axis (A) of said driving (6) and driven shaft (3), are diametrically opposite, and can be actuated simultaneously with an axial sliding motion in corresponding seats (113) formed in said internal body (5) of the limiter through actuation means (114) which act on corresponding ends thereof, their opposite ends being kept in contact with said centered plate (10). The safety device according to claims 2 and 3, characterized in that said means (14) for actuating said pin (12) are constituted by a secondary pin (15) which is fitted transversely so as to rest on the end of said pin (12) that lies opposite the one for contact with said plate (10), said secondary pin (15) being able to slide axially in a transverse seat (16) formed in driven shaft (3) and being kept in contact with axially separable means (17) which are provided with elements (17a) for locking the separated configuration. The safety device according to claim 5, characterized in that said axially separable means (17) are constituted by two coaxial disks (18, 19) which face each other and rotatably coupled to each other by twin sets of teeth (20) and rotatably decoupled by disengagement of the teeth (20) after moving at least one of said disks (18, 19) with respect to the other one, a first disk (18) being fitted on said driven shaft (3) so as to be able to rotate independently and move axially, a second disk (19) being rigidly coupled to the end of the conventional casing (21) that accommodates the gears that constitute the power take-off (22). The safety device according to claims 5 and 6, characterized in that said elements (17a) for locking the separated configuration are constituted by at least one pin (23) which is supported by one of said coaxial disks (19) in a perpendicular seat (24) with elastic pusher means (25) interposed, the opposite disk (18) being provided with a rotationally offset hollow seat (26) for the automatic engagement of said pin (23) in a rotated and separated configuration of said coaxial disks (18, 19). The safety device according to claim 7, characterized in that said pin (23) can be disengaged from said seat (24) manually in order to restore the torque transmission conditions. The safety device according to claims 4 and 5, characterized in that said actuation means (114) are constituted by a first disk (118) which is keyed on a male hub (5a) which protrudes from said internal body (5) of the limiter (1), with interposed centering elements (27), said first disk (118) centrally forming a female hub (118a) which is fitted onto said male hub (5a) and whose front surface (5a) is kept in constant contact with said corresponding ends of the pins (112) and is rotationally coupled to said male hub (5a) by way of corresponding coupling means (28) which have one degree of freedom, said first disk (118) being able to move axially by contact with a second disk (119) which faces it, with friction means (29) interposed, is supported on said driven shaft (3) so as to be centered thereon, and is provided with engagement means (20) for engaging a fixed flange (120) which is mounted at the end of the casing (21) that accommodates the gears that compose the power take-off (22). The safety device according to claim 9, characterized in that said coupling means (28) with one degree of freedom between said male (5a) and female (118a) hubs are constituted by two teeth (30) which protrude towards the center from said female hub (118a) and by a corresponding pair of longitudinal grooves (31) which are formed radially in said male hub (5a), said teeth (30) being able to slide parallel to the axis of the hubs (118a, 5a) in said grooves (31) by a preset extent. The safety device according to claim 9, characterized in that said engagement means are constituted by a twin set of teeth (20) with interpenetrating front teeth. The safety device according to claim 9, characterized in that said centering elements (27) are constituted by a ring (32) which is fitted in a fixed configuration to the end of said male hub (5a) and is provided with a front resting surface (32a) which has a concave-conical profile for coupling to an opposite convex profile which protrudes from said first disk (118). The safety device according to claims 5, 9 and 11, characterized in that said locking elements (17a) for locking the disengaged configuration of said twin sets of front teeth (20) are fitted between said second disk (118) and said flange (120).

Inventors: BRUNAZZI ACHILLE, PROSPERO ROBERTO, BRUNAZZI, ACHILLE, PROSPERO, ROBERTO
Applicants: COMER IND S P A, COMER INDUSTRIES S.P.A.
Application year: 2000
Main classification: F16P3
IPC codes: F16P3