WO2014076683A1 - Safety coupling for power mechanical transmissions - Google Patents

Safety coupling for power mechanical transmissions Download PDF

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Publication number
WO2014076683A1
WO2014076683A1 PCT/IB2013/060244 IB2013060244W WO2014076683A1 WO 2014076683 A1 WO2014076683 A1 WO 2014076683A1 IB 2013060244 W IB2013060244 W IB 2013060244W WO 2014076683 A1 WO2014076683 A1 WO 2014076683A1
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WO
WIPO (PCT)
Prior art keywords
coupling
plunger
pressure
torque
coupling part
Prior art date
Application number
PCT/IB2013/060244
Other languages
French (fr)
Inventor
Cesare Padovan
Original Assignee
Maina Organi Di Trasmissione S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Maina Organi Di Trasmissione S.P.A. filed Critical Maina Organi Di Trasmissione S.P.A.
Publication of WO2014076683A1 publication Critical patent/WO2014076683A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D7/00—Slip couplings, e.g. slipping on overload, for absorbing shock
    • F16D7/04—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type
    • F16D7/042—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type with at least one part moving axially between engagement and disengagement
    • F16D7/044—Slip couplings, e.g. slipping on overload, for absorbing shock of the ratchet type with at least one part moving axially between engagement and disengagement the axially moving part being coaxial with the rotation, e.g. a gear with face teeth
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D43/00—Automatic clutches
    • F16D43/28—Automatic clutches actuated by fluid pressure
    • F16D43/286—Automatic clutches actuated by fluid pressure controlled by torque

Definitions

  • the present invention relates to a safety coupling configured to couple rotationally together a first and a second transmission member rotatable about a same axis of rotation, the cou- pling being able to uncouple the two transmission members when the torque transmitted exceeds a given maximum torque threshold value.
  • Safety couplings of the abovementioned type are commonly used in industry for mechanical transmission of power from a power source, for example a motor, having a rotatable output transmission member (typically in the form of a rotating shaft), to a machine having a rotatable input transmission member (also typically in the form of a rotating shaft).
  • the safety coupling is arranged between the two transmission members and is normally kept in a first working condition (closed condition) in which it rotationally couples together these members.
  • the safety coupling is designed to switch automatically, in the event of exces- sive loads or accidental jamming of the machine to which the power is transmitted, to a second working condition (open condition), in which it uncouples the two transmission members in order to prevent malfunctioning or damage to the entire power train.
  • the safety coupling comprises a first coupling part and a second coupling part - i.e. a driving part and driven part, respectively - which are arranged coaxi- ally with each other so as to rotate about a same axis of rotation and are provided with respective front teeth normally each meshing with respective front teeth of a plunger ar- ranged coaxially with the two coupling parts and is mounted slidably inside a pressure chamber provided in one of the two coupling parts.
  • the pressure chamber is filled with incompressible fluid, the charge pressure of which applies on the plunger an axial force tending to keep the front teeth of the said plunger meshed with the respective front teeth of the two coupling parts so as to ensure transmission of the torque between the two coupling parts.
  • the torque transmitted between the two coupling parts produces, as a result of the forces exchanged between the front teeth of the two coupling parts and the front teeth of the plunger, a fluid pressure inside the pressure chamber, the value of which is proportional to the torque transmitted.
  • the safety coupling furthermore comprises a torque-sensitive release system designed to disengage the front teeth of the two coupling parts from the respective front teeth of the plunger, thus interrupting the transmission of the torque, when the torque transmitted between the two coupling parts exceeds a given maximum value.
  • the release system comprises a valve arrangement configured to cause discharging of the fluid from the pressure chamber when a given maximum pressure value of the fluid inside the pressure chamber is exceeded.
  • the invention is based on the idea of providing a safety coupling of the type mentioned initially, in which the plunger has front teeth which, in the closed condition of the coupling, mesh with corresponding front teeth of one of the two coupling parts and which is furthermore permanently connected for rotation with the other coupling part by means of meshing between outer radial teeth provided on the plunger and inner radial teeth provided on the second coupling part.
  • the coupling according to the present invention has a smaller number of components and a smaller radial size than the prior art discussed above, and a very rigid structure, with a high torque transmission capacity.
  • Figure 1 is a partial axial section view of a safety coupling for power mechanical transmissions according to an embodiment of the present invention, in the closed condition (normal working condition).
  • Figure 2 is a diagram which shows a breakdown of the forces exchanged between the front teeth respectively provided on one of the two coupling parts and on the plunger of the safety coupling according to Figure 1 ;
  • Figure 3 is an axial section view, along a cross-sectional plane different from that of Figure 1 , of the safety coupling according to Figure 1 in the open condition resulting from the maximum admissible value of the transmitted torque (releasing torque) being exceeded.
  • a safety coupling for power mechanical transmissions is generally indicated 10 and includes essentially a first coupling part 12 and a second coupling part 14.
  • the first coupling part 12 acts as a driving part of the safety coupling 10 and is therefore intended to be drivingly connected for rotation with a driving part of a transmission, such as a transmission shaft connected to the output of a motor
  • the second coupling part 14 acts as a driven part of the safety coupling 10 and is therefore intended to be drivingly connected for rotation with a driven part of the transmission, such as a transmission shaft connected to the input of an industrial machine.
  • the function of the two coupling parts 12 and 14 could however be reversed, in that the first coupling part 12 and the second coupling part 14 could function as driven part and driving part, respectively.
  • the two coupling parts 12 and 14 are arranged coaxial with each other so as to rotate about a same axis of rotation x.
  • the first coupling part 12 comprises a first element 16 and a second element 18 which are rigidly connected for rotation with each other by means of a splined coupling.
  • the first element 16 has, at its end axially directed towards the inside of the safety coupling 10, front teeth 20.
  • the second element 18 comprises a tubular portion 22, which extends co- axially with the first element 16 inside the latter, and a flanged portion 24 (preferably formed as one piece with the tubular portion 22) which extends perpendicularly to the tu- bular portion 22 and has a plurality of holes 26 for inserting screw-type connecting members (not shown) for rigidly connecting the first coupling part 12 for rotation with the upstream part (driving part) of the transmission.
  • the splined coupling between the two elements 16 and 18 of the first coupling part 12 is obtained by means of meshing between outer radial teeth 28 provided on the outer cylindrical surface of the tubular portion 22 of the second element 18 and inner radial teeth 30 provided on the inner cylindrical surface of the first element 16.
  • the two elements 16 and 18 of the first coupling part 12 are also axially locked together by means of a sleeve 32 which is mounted around the second element 18 and is pressed against the first element 16 so as to keep this element in axial abutment against the flanged portion 24 of the second element 18.
  • the second coupling part 14 comprises a tubular portion 34 which extends coaxially with the first element 16 of the first coupling part 12 and the tubular portion 22 of the second element 18 of the first coupling part 12 and radially outwardly both of the first element 16 and of the tubular portion 22, and a flanged portion 36 (preferably formed as one piece with the tubular portion 34) which extends perpendicularly to the tubular portion 34 and has a plurality of holes 38 for insertion of screw-type connecting members (not shown) for rigidly rotationally the second coupling part 14 for rotation with the downstream part (driven part) of the transmission.
  • the two coupling parts 12 and 14 are supported rotationally with respect to each other around the axis of rotation x by means of rolling bearings arranged between these parts.
  • a first ball bearing 40 radially arranged between the first element 16 of the first coupling part 12 and the tubular portion 34 of the second coupling part 14 and a second ball bearing 42 radially arranged between the tubular portion 22 of the second element 18 of the first coupling part 12 and the tubular portion 34 of the second coupling part 14 are provided.
  • a plunger 44 is arranged between the first coupling part 12 and the second coupling part 14 and, as will emerge more clearly from the following description, is axially movable between a first position ( Figure 1), corresponding to the closed normal working condition of the safety coupling 10, in which it ensures rotational coupling between the two coupling parts 12 and 14 and therefore transmission of the torque between the two - driving and driven - parts of the transmission, and a second position ( Figure 3), corresponding to the open condition of the safety coupling 10, in which it uncouples the two coupling parts 12 and 14, thus preventing transmission of the torque between the two - driving and driven - parts of the transmission.
  • the plunger 44 comprises, on the side directed downstream, i.e.
  • the plunger 44 also comprises, on the side directed upstream, i.e. towards the driving part of the transmission, a head portion 50 which is formed as an annular portion.
  • the plunger 44 also comprises, between the stem portion 46 and the head portion 50, an intermediate portion 52 which is formed as an annular portion and is axially guided inside a cylindrical cavity 54, with a diameter greater than that of the cylindrical cavity 48, provided in the tubular portion 34 of the second coupling part 14.
  • the stem portion 46, the head portion 50 and the intermediate portion 52 of the plunger 44 are preferably formed as one piece.
  • the plunger 44 is rigidly connected for rotation with the second coupling part 14 by means of a splined coupling, obtained by means of meshing between outer radial teeth 56 provided on the outer cylindrical surface of the head portion 50 of the plunger 44 and inner radial teeth 58 provided on the inner surface of a cylindrical cavity 60, with a diameter greater than that of the cylindrical cavity 54, of the tubular portion 34 of the second coupling part 14.
  • the head portion 50 of the plunger 44 has, on its front face axially directed towards the first element 16 of the first coupling part 12, front teeth 62 which in the closed condition of the safety coupling (Figure 1) mesh with the front teeth 20 of the first element 16 of the first coupling part 12.
  • a chamber 64 radially comprised between the stem portion 46 of the plunger 44 and the inner surface of the cylindrical cavity 54 and axially comprised between the intermediate portion 52 and the tubular portion 34 of the second coupling part 14 is filled with incompressible fluid for operating as a pressure chamber.
  • a seal 66 radially arranged between the intermediate portion 52 of the plunger 44 and the inner surface of the cylindrical cavity 54 and a seal 68 radially arranged between the stem portion 46 of the plunger 44 and the inner surface of the cylindrical cavity 48 ensure the hermetic seal of the pressure chamber 64.
  • the pressure of the fluid inside the pressure chamber 64 pushes the plunger 44 axially towards the first element 16 of the first coupling part 12, thus ensuring meshing between the front teeth 62 of the plunger 44 and the front teeth 20 of the first element 16.
  • FIG. 2 shows, on a larger scale, the front teeth 20 of the first element 16 of the first coupling part 12 and the front teeth 62 of the plunger 44, the front teeth 20 and 62 meshing with each other in the closed condition of the safety coupling 10.
  • the front teeth 20 and 62 are axially pushed against each other by an axial force originating from the charge pressure of the fluid present inside the pressure chamber 64. For as long as there is no relative movement between the front teeth 20 and 62, i.e.
  • the pressure inside the pressure chamber 64 is kept constant at the value of the charge pressure also when there is an increase in torque in the first coupling part 12 (driving part).
  • the increase in torque in the first coupling part 12 is such as to overcome the frictional resistance between the flanks of the front teeth 20 and 62
  • the front teeth 20 transfer onto the front teeth 62 the axial component F a of the tangential force F t produced by the torque transmitted.
  • the axial component F a produces a reduction in the volume of the pressure chamber 64 and therefore an increase in the pressure inside this chamber which is proportional to the torque transmitted.
  • the safety coupling 10 further comprises valve means designed to perform automatically discharging of the pressure chamber 64, and therefore uncoupling between the front teeth 20 and 62 of the first element 16 of the first coupling part 12 and of the plunger 44, respectively, with consequent opening of the coupling, when the pressure inside the pressure chamber 64 reaches a given maximum pressure value corresponding to a given maximum value of torque transmitted which may be adjusted by the user.
  • These valve means comprise a relief valve 70 and a pilot valve 72 which, in the example of embodiment shown, are housed inside respective seats provided both in the tubular portion 34 of the second coupling part 14.
  • the relief valve 70 controls opening of a relief conduit 74 which connects the pressure chamber 64 to the outside environment.
  • the relief valve 70 keeps the relief conduit 74 closed (safety coupling 10 in the closed condition).
  • the relief valve 70 opens the re- lief conduit 74, the fluid under pressure contained inside the pressure chamber 64 is discharged outwards, with consequent disengagement between the front teeth 20 and 62, i.e. with consequent opening of the safety coupling 10.
  • the pilot valve 72 is in fluid communication with the pressure chamber 64 so as to sense the pressure present inside this chamber and is set to a given set pressure so as to cause opening of the relief valve 70, thus allowing discharging of the fluid from the pressure chamber 64, when the pressure inside this chamber exceeds the set pressure and therefore when the torque transmitted by the safety coupling 10 exceeds a given maximum value.
  • the relief valve 70 switches from the condition for closing the relief conduit 74 to the open condition, thus allowing discharging of the fluid contained inside the pressure cham- ber 64 and therefore disengagement between the front teeth 20 and 62.
  • the pressure of the fluid inside the pressure chamber 64 varies upon variation of the temperature of the safety coupling 10.
  • the maximum value of the torque transmitted at which opening of the coupling occurs is advantageously adjusted to a pressure value which is significantly higher than that corresponding to the maximum operating temperature. In this way, pressure variations resulting from temperature variations do not influence opening of the coupling, since the maximum pressure produced by the maximum operating temperature will be always less than the pressure corresponding to opening of the coupling.
  • the safety coupling may be provided with a device for detecting the torque transmitted including a pressure transducer able to detect the pressure inside the pressure chamber (which, as explained above, is proportional to the torque transmitted between the two - driving and driven - parts of the coupling) and a transmitter able to send to a fixed or movable receiver the signals supplied by the pressure transducer.
  • the user may thus verify, at each instant or as required, the value of the torque transmitted by the safety coupling.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Hydraulic Clutches, Magnetic Clutches, Fluid Clutches, And Fluid Joints (AREA)
  • One-Way And Automatic Clutches, And Combinations Of Different Clutches (AREA)
  • Mechanical Operated Clutches (AREA)

Abstract

The safety coupling (10) comprises: a first coupling part (12) and a second coupling part (14) which are arranged coaxially with each other so as to rotate about a same axis of rotation (x) and are provided with respective front teeth (20, 62); and torque- sensitive releasing means (44, 64, 70, 72) designed to uncouple the first coupling part and second coupling part, thus interrupting the transmission of the torque, when the torque transmitted between the two coupling parts exceeds a given maximum torque value. The torque-sensitive releasing means include: a plunger (44) which is permanently connected for rotation with the second coupling part and is slidable along the axis of rotation between a normal working position, in which it ensures that the two coupling parts are coupled for rotation with each other, and a safety position, in which it uncouples the two coupling parts; a pressure chamber (64) filled with incompressible fluid such as to apply on the plunger a force tending to keep the plunger in the normal working position; and valve means (70, 72) adapted to allow the fluid to be discharged from the pressure chamber, and hence the plunger to be moved from the normal working position to the safety position when the pressure of the fluid in the pressure chamber exceeds a given maximum pressure value, the maximum torque value being linked to the maximum pressure value. The front teeth are first front teeth (20) provided on the first coupling part and second front teeth (62) provided on the plunger, which teeth directly mesh with each other when the plunger (44) is in the normal working position.

Description

Safety coupling for power mechanical transmissions
The present invention relates to a safety coupling configured to couple rotationally together a first and a second transmission member rotatable about a same axis of rotation, the cou- pling being able to uncouple the two transmission members when the torque transmitted exceeds a given maximum torque threshold value.
Safety couplings of the abovementioned type are commonly used in industry for mechanical transmission of power from a power source, for example a motor, having a rotatable output transmission member (typically in the form of a rotating shaft), to a machine having a rotatable input transmission member (also typically in the form of a rotating shaft). The safety coupling is arranged between the two transmission members and is normally kept in a first working condition (closed condition) in which it rotationally couples together these members. The safety coupling is designed to switch automatically, in the event of exces- sive loads or accidental jamming of the machine to which the power is transmitted, to a second working condition (open condition), in which it uncouples the two transmission members in order to prevent malfunctioning or damage to the entire power train.
A safety coupling having the characteristic features specified in the preamble of independ- ent Claim 1 is known from International Patent Application WO2009/ 144686. According to this known solution, the safety coupling comprises a first coupling part and a second coupling part - i.e. a driving part and driven part, respectively - which are arranged coaxi- ally with each other so as to rotate about a same axis of rotation and are provided with respective front teeth normally each meshing with respective front teeth of a plunger ar- ranged coaxially with the two coupling parts and is mounted slidably inside a pressure chamber provided in one of the two coupling parts. The pressure chamber is filled with incompressible fluid, the charge pressure of which applies on the plunger an axial force tending to keep the front teeth of the said plunger meshed with the respective front teeth of the two coupling parts so as to ensure transmission of the torque between the two coupling parts. The torque transmitted between the two coupling parts produces, as a result of the forces exchanged between the front teeth of the two coupling parts and the front teeth of the plunger, a fluid pressure inside the pressure chamber, the value of which is proportional to the torque transmitted. The safety coupling furthermore comprises a torque-sensitive release system designed to disengage the front teeth of the two coupling parts from the respective front teeth of the plunger, thus interrupting the transmission of the torque, when the torque transmitted between the two coupling parts exceeds a given maximum value. The release system comprises a valve arrangement configured to cause discharging of the fluid from the pressure chamber when a given maximum pressure value of the fluid inside the pressure chamber is exceeded. By suitably choosing this maximum pressure value it is thus possible to set the release torque value, i.e. the maximum torque value at which opening of the coupling occurs.
It is an object of the present invention to provide a safety coupling for power mechanical transmissions which has a simpler and more compact structure compared to the safety coupling known from the prior document discussed above. This and other objects are fully achieved according to the present invention by means of a safety coupling having the characteristic features defined in the characterising part of independent Claim 1.
Advantageous embodiments of the safety coupling according to the invention form the subject matter of the dependent claims, the contents of which are to be understood as forming an integral and complementary part of the description which follows.
In short, the invention is based on the idea of providing a safety coupling of the type mentioned initially, in which the plunger has front teeth which, in the closed condition of the coupling, mesh with corresponding front teeth of one of the two coupling parts and which is furthermore permanently connected for rotation with the other coupling part by means of meshing between outer radial teeth provided on the plunger and inner radial teeth provided on the second coupling part. Owing to the fact that the rotational connection between the two coupling parts is obtained by means of meshing between a pair of front teeth, respec- tively provided on one of the two coupling parts and on the plunger, and by means of meshing between inner radial teeth provided on the other coupling part and outer radial teeth provided on the plunger, instead of between a pair of front teeth, respectively pro- vided on one of the two coupling parts and on the plunger, and between a second pair of front teeth, respectively provided on the other coupling part and on the plunger, as instead occurs in the prior art discussed above, the coupling according to the present invention has a smaller number of components and a smaller radial size than the prior art discussed above, and a very rigid structure, with a high torque transmission capacity.
Further characteristic features and advantages of the present invention will emerge clearly from the following detailed description, provided purely by way of a non-limiting example with reference to the accompanying drawings in which:
Figure 1 is a partial axial section view of a safety coupling for power mechanical transmissions according to an embodiment of the present invention, in the closed condition (normal working condition).
Figure 2 is a diagram which shows a breakdown of the forces exchanged between the front teeth respectively provided on one of the two coupling parts and on the plunger of the safety coupling according to Figure 1 ; and
Figure 3 is an axial section view, along a cross-sectional plane different from that of Figure 1 , of the safety coupling according to Figure 1 in the open condition resulting from the maximum admissible value of the transmitted torque (releasing torque) being exceeded.
In the description and in the claims which follow, terms such as "axial" and "longitudinal" are understood as referring to the direction of the axis of the safety coupling, namely the axis of rotation of the two coupling parts (driving part and driven part), while terms such as "transverse" and "radial" are understood as referring to directions perpendicular to the axis of the safety coupling.
With reference to Figures 1 and 3, a safety coupling for power mechanical transmissions according to an embodiment of the present invention is generally indicated 10 and includes essentially a first coupling part 12 and a second coupling part 14. According to an em- bodiment, the first coupling part 12 acts as a driving part of the safety coupling 10 and is therefore intended to be drivingly connected for rotation with a driving part of a transmission, such as a transmission shaft connected to the output of a motor, while the second coupling part 14 acts as a driven part of the safety coupling 10 and is therefore intended to be drivingly connected for rotation with a driven part of the transmission, such as a transmission shaft connected to the input of an industrial machine. The function of the two coupling parts 12 and 14 could however be reversed, in that the first coupling part 12 and the second coupling part 14 could function as driven part and driving part, respectively. The two coupling parts 12 and 14 are arranged coaxial with each other so as to rotate about a same axis of rotation x.
The first coupling part 12 comprises a first element 16 and a second element 18 which are rigidly connected for rotation with each other by means of a splined coupling. The first element 16 has, at its end axially directed towards the inside of the safety coupling 10, front teeth 20. The second element 18 comprises a tubular portion 22, which extends co- axially with the first element 16 inside the latter, and a flanged portion 24 (preferably formed as one piece with the tubular portion 22) which extends perpendicularly to the tu- bular portion 22 and has a plurality of holes 26 for inserting screw-type connecting members (not shown) for rigidly connecting the first coupling part 12 for rotation with the upstream part (driving part) of the transmission. The splined coupling between the two elements 16 and 18 of the first coupling part 12 is obtained by means of meshing between outer radial teeth 28 provided on the outer cylindrical surface of the tubular portion 22 of the second element 18 and inner radial teeth 30 provided on the inner cylindrical surface of the first element 16. The two elements 16 and 18 of the first coupling part 12 are also axially locked together by means of a sleeve 32 which is mounted around the second element 18 and is pressed against the first element 16 so as to keep this element in axial abutment against the flanged portion 24 of the second element 18.
The second coupling part 14 comprises a tubular portion 34 which extends coaxially with the first element 16 of the first coupling part 12 and the tubular portion 22 of the second element 18 of the first coupling part 12 and radially outwardly both of the first element 16 and of the tubular portion 22, and a flanged portion 36 (preferably formed as one piece with the tubular portion 34) which extends perpendicularly to the tubular portion 34 and has a plurality of holes 38 for insertion of screw-type connecting members (not shown) for rigidly rotationally the second coupling part 14 for rotation with the downstream part (driven part) of the transmission.
The two coupling parts 12 and 14 are supported rotationally with respect to each other around the axis of rotation x by means of rolling bearings arranged between these parts. In the embodiment shown, for example a first ball bearing 40 radially arranged between the first element 16 of the first coupling part 12 and the tubular portion 34 of the second coupling part 14 and a second ball bearing 42 radially arranged between the tubular portion 22 of the second element 18 of the first coupling part 12 and the tubular portion 34 of the second coupling part 14 are provided.
A plunger 44 is arranged between the first coupling part 12 and the second coupling part 14 and, as will emerge more clearly from the following description, is axially movable between a first position (Figure 1), corresponding to the closed normal working condition of the safety coupling 10, in which it ensures rotational coupling between the two coupling parts 12 and 14 and therefore transmission of the torque between the two - driving and driven - parts of the transmission, and a second position (Figure 3), corresponding to the open condition of the safety coupling 10, in which it uncouples the two coupling parts 12 and 14, thus preventing transmission of the torque between the two - driving and driven - parts of the transmission. The plunger 44 comprises, on the side directed downstream, i.e. towards the driven part of the transmission, a stem portion 46 which is formed as an annular portion and is axially guided inside a cylindrical cavity 48 provided in the tubular portion 34 of the second coupling part 14. The plunger 44 also comprises, on the side directed upstream, i.e. towards the driving part of the transmission, a head portion 50 which is formed as an annular portion. The plunger 44 also comprises, between the stem portion 46 and the head portion 50, an intermediate portion 52 which is formed as an annular portion and is axially guided inside a cylindrical cavity 54, with a diameter greater than that of the cylindrical cavity 48, provided in the tubular portion 34 of the second coupling part 14. The stem portion 46, the head portion 50 and the intermediate portion 52 of the plunger 44 are preferably formed as one piece. The plunger 44 is rigidly connected for rotation with the second coupling part 14 by means of a splined coupling, obtained by means of meshing between outer radial teeth 56 provided on the outer cylindrical surface of the head portion 50 of the plunger 44 and inner radial teeth 58 provided on the inner surface of a cylindrical cavity 60, with a diameter greater than that of the cylindrical cavity 54, of the tubular portion 34 of the second coupling part 14. The head portion 50 of the plunger 44 has, on its front face axially directed towards the first element 16 of the first coupling part 12, front teeth 62 which in the closed condition of the safety coupling (Figure 1) mesh with the front teeth 20 of the first element 16 of the first coupling part 12. In this condition, therefore, the torque is transmitted from the first coupling part 12 to the plunger 44 by means of meshing between the front teeth 20 and 62 and from the plunger 44 to the second coupling part 14 by means of the splined coupling formed by the radial teeth 56 and 58. As shown in Figure 1, a chamber 64 radially comprised between the stem portion 46 of the plunger 44 and the inner surface of the cylindrical cavity 54 and axially comprised between the intermediate portion 52 and the tubular portion 34 of the second coupling part 14 is filled with incompressible fluid for operating as a pressure chamber. A seal 66 radially arranged between the intermediate portion 52 of the plunger 44 and the inner surface of the cylindrical cavity 54 and a seal 68 radially arranged between the stem portion 46 of the plunger 44 and the inner surface of the cylindrical cavity 48 ensure the hermetic seal of the pressure chamber 64. In the normal working condition of the safety coupling 10 (closed condition), shown in Figures 1 and 2, the pressure of the fluid inside the pressure chamber 64 pushes the plunger 44 axially towards the first element 16 of the first coupling part 12, thus ensuring meshing between the front teeth 62 of the plunger 44 and the front teeth 20 of the first element 16. In this condition, therefore, the torque can be transmitted from the first coupling part 12 (driving part) to the second coupling part 14 (driven part) passing in order through the second element 18 of the first coupling part 12, the first element 16 of the first coupling part 12, the plunger 44 and the second coupling part 14. Figure 2 shows, on a larger scale, the front teeth 20 of the first element 16 of the first coupling part 12 and the front teeth 62 of the plunger 44, the front teeth 20 and 62 meshing with each other in the closed condition of the safety coupling 10. The front teeth 20 and 62 are axially pushed against each other by an axial force originating from the charge pressure of the fluid present inside the pressure chamber 64. For as long as there is no relative movement between the front teeth 20 and 62, i.e. the front teeth 20 and 62 are in a static condition with respect to each other, the pressure inside the pressure chamber 64 is kept constant at the value of the charge pressure also when there is an increase in torque in the first coupling part 12 (driving part). However, when the increase in torque in the first coupling part 12 is such as to overcome the frictional resistance between the flanks of the front teeth 20 and 62, the front teeth 20 transfer onto the front teeth 62 the axial component Fa of the tangential force Ft produced by the torque transmitted. The axial component Fa produces a reduction in the volume of the pressure chamber 64 and therefore an increase in the pressure inside this chamber which is proportional to the torque transmitted.
With reference in particular to Figure 3, the safety coupling 10 further comprises valve means designed to perform automatically discharging of the pressure chamber 64, and therefore uncoupling between the front teeth 20 and 62 of the first element 16 of the first coupling part 12 and of the plunger 44, respectively, with consequent opening of the coupling, when the pressure inside the pressure chamber 64 reaches a given maximum pressure value corresponding to a given maximum value of torque transmitted which may be adjusted by the user. These valve means comprise a relief valve 70 and a pilot valve 72 which, in the example of embodiment shown, are housed inside respective seats provided both in the tubular portion 34 of the second coupling part 14. The relief valve 70 controls opening of a relief conduit 74 which connects the pressure chamber 64 to the outside environment. Under normal working conditions, the relief valve 70 keeps the relief conduit 74 closed (safety coupling 10 in the closed condition). When the relief valve 70 opens the re- lief conduit 74, the fluid under pressure contained inside the pressure chamber 64 is discharged outwards, with consequent disengagement between the front teeth 20 and 62, i.e. with consequent opening of the safety coupling 10. The pilot valve 72 is in fluid communication with the pressure chamber 64 so as to sense the pressure present inside this chamber and is set to a given set pressure so as to cause opening of the relief valve 70, thus allowing discharging of the fluid from the pressure chamber 64, when the pressure inside this chamber exceeds the set pressure and therefore when the torque transmitted by the safety coupling 10 exceeds a given maximum value.
Therefore, when the torque transmitted by the safety coupling 10 is such that the pressure of the fluid inside the pressure chamber 64 is greater than the set pressure of the pilot valve 72, the relief valve 70 switches from the condition for closing the relief conduit 74 to the open condition, thus allowing discharging of the fluid contained inside the pressure cham- ber 64 and therefore disengagement between the front teeth 20 and 62.
The pressure of the fluid inside the pressure chamber 64 varies upon variation of the temperature of the safety coupling 10. After defining the temperature operating range of the coupling and defining the charge pressure range of the fluid inside the pressure chamber 64, the maximum value of the torque transmitted at which opening of the coupling occurs is advantageously adjusted to a pressure value which is significantly higher than that corresponding to the maximum operating temperature. In this way, pressure variations resulting from temperature variations do not influence opening of the coupling, since the maximum pressure produced by the maximum operating temperature will be always less than the pressure corresponding to opening of the coupling.
According to an embodiment of the present invention, the safety coupling may be provided with a device for detecting the torque transmitted including a pressure transducer able to detect the pressure inside the pressure chamber (which, as explained above, is proportional to the torque transmitted between the two - driving and driven - parts of the coupling) and a transmitter able to send to a fixed or movable receiver the signals supplied by the pressure transducer. The user may thus verify, at each instant or as required, the value of the torque transmitted by the safety coupling.
Naturally, the principle of the invention remaining unchanged, the embodiments and the constructional details may be greatly varied with respect to those described and illustrated purely by way of a non-limiting example, without thereby departing from the scope of the invention as defined in the accompanying claims.

Claims

1. Safety coupling (10) for power mechanical transmissions, comprising
a first coupling part (12) and a second coupling part (14) which are arranged coaxi- ally with each other so as to rotate about a same axis of rotation (x) and are provided with respective front teeth (20, 62) by means of which said first and second coupling parts (12, 14) can be coupled for rotation with each other, and
torque-sensitive releasing means (44, 64, 70, 72) designed to uncouple said first and second coupling parts (12, 14), thus interrupting the transmission of the torque, when the torque transmitted between said first and second coupling parts (12, 14) exceeds a given maximum torque value,
wherein said torque-sensitive releasing means (44, 64, 70, 72) include
a plunger (44) slidable along the axis of rotation (x) between a normal working position, in which it ensures that said first and second coupling parts (12, 14) are coupled for rotation with each other, and a safety position, in which it uncouples said first and second coupling parts (12, 14),
a pressure chamber (64) filled with incompressible fluid at a charge pressure such as to apply on the plunger (44) a force directed along the axis of rotation (x) and tending to keep the plunger (44) in the normal working position, the torque transmitted between said first and second coupling parts (12, 14) producing an increase in the pressure of the fluid in the pressure chamber (64) proportional to the transmitted torque, and
valve means (70, 72) adapted to allow the fluid to be discharged from the pressure chamber (64), and hence the plunger (44) to be moved from the normal working position to the safety position, when the pressure of the fluid in the pressure chamber (64) exceeds a given maximum pressure value, said maximum torque value being linked to said maximum pressure value,
characterized in that
said front teeth (20, 62) are first front teeth (20) provided on said first coupling part (12) and second front teeth (62) provided on the plunger (44), which teeth (20, 62) directly mesh with each other when the plunger (44) is in the normal working position, and in that the plunger (44) is permanently connected for rotation with said second coupling part (14) by means of meshing between outer radial teeth (56) provided on the plunger (44) and inner radial teeth (58) provided on the second coupling part (14).
2. Safety coupling according to Claim 1, wherein said first coupling part (12) comprises a first element (16) and a second element (18) rigidly connected for rotation with each other and wherein said first front teeth (20) are provided on said first element (16).
3. Safety coupling according to Claim 1 or Claim 2, wherein said valve means (70, 72) include a relief valve (70) and a pilot valve (72), the relief valve (70) controlling opening of a relief conduit (74) which connects the pressure chamber (64) to the external envi- ronment, and the pilot valve (72) being in fluid communication with the pressure chamber (64) so as to sense the pressure in that chamber and being set to a given set pressure so as to cause the relief valve (70) to open and thus allow the fluid to be discharged from the pressure chamber (64) when the pressure in that chamber exceeds the set pressure and hence when the torque transmitted by the safety coupling (10) exceeds said maximum value.
4. Safety coupling according to any one of the preceding claims, wherein said first coupling part (12) and said second coupling part (14) are the driving part and the driven part of the safety coupling (10), respectively.
PCT/IB2013/060244 2012-11-19 2013-11-19 Safety coupling for power mechanical transmissions WO2014076683A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITTO2012A001004 2012-11-19
IT001004A ITTO20121004A1 (en) 2012-11-19 2012-11-19 SAFETY JOINT FOR MECHANICAL POWER TRANSMISSIONS.

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WO2014076683A1 true WO2014076683A1 (en) 2014-05-22

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WO (1) WO2014076683A1 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2389797A1 (en) * 1977-05-07 1978-12-01 Vulkan Kupplung Getriebe
JPS55159335A (en) * 1979-05-28 1980-12-11 Sanyo Kogyo Kk Torque limiter
DE3017092A1 (en) * 1980-05-03 1981-11-05 Volkswagenwerk Ag, 3180 Wolfsburg DEVICE FOR SWITCHABLE COUPLING OF TWO SHAFT PARTS WITH PRESET TURNING ANGLE ASSIGNMENT
WO2009144686A1 (en) 2008-05-30 2009-12-03 Maina Organi Di Trasmissione S.P.A. Safety coupling for the transmission of rotary motion

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2389797A1 (en) * 1977-05-07 1978-12-01 Vulkan Kupplung Getriebe
JPS55159335A (en) * 1979-05-28 1980-12-11 Sanyo Kogyo Kk Torque limiter
DE3017092A1 (en) * 1980-05-03 1981-11-05 Volkswagenwerk Ag, 3180 Wolfsburg DEVICE FOR SWITCHABLE COUPLING OF TWO SHAFT PARTS WITH PRESET TURNING ANGLE ASSIGNMENT
WO2009144686A1 (en) 2008-05-30 2009-12-03 Maina Organi Di Trasmissione S.P.A. Safety coupling for the transmission of rotary motion

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