Abstract:
The invention concerns a clutch ( 10 ), comprising a clutch disk ( 22 ) connected with a first shaft (A) and a brake device ( 17 ) connected with a second shaft (B). By means of the brake cylinder ( 19 ) of the brake device ( 17 ), the brake pad ( 18 ) can be coupled into engagement with the clutch disk ( 22 ), in which case a movement of rotation between the shafts (A and B) is prevented. In the solution of equipment, between the shaft (A) and the shaft (B), there is a support bearing ( 21 ), which supports the movement of rotation between the shafts (A and B) when the clutch is supposed to slip. According to the invention, in the pressure line ( 59 ), there is a holding pressure maintained by means of accumulators ( 100 ), which holding pressure determines the torque at which the clutch slips.

Description:
FIELD OF THE INVENTION 
     The invention concerns a clutch. 
     BACKGROUND OF THE INVENTION 
     In the operation of, for example, soil milling machines, an important problem has become the rapid wear of the clutches. The occurrence of torques of different magnitudes in milling work is a highly important problem. In the present patent application, an improvement is suggested for the problem stated above. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is suggested in the present patent application that, when an overload acts upon a brake disk by the intermediate of a cardan shaft, the clutch slips at the friction joint between the brake disk and the brake pads and cuts off the excessively high torque peak. When the torque is lowered to a level lower than the corresponding torque that is held by the friction force, the clutch starts holding again. Thus, the clutch just cuts off the peaks, but holds directly after the torque has become lower. The normal force is supplied to the brake pads that form the friction joint, for example, by means of a fluid pressure supplied from a tractor. In such a case, the brake pads are pressed with a force against the clutch flange. The brake pads and their brake calipers are coupled with the shaft B, and the clutch disk is coupled with the shaft A, respectively. Rotation is permitted between the shafts A and B. Further, the shafts A and B are favourably supported on each other revolvingly by means of a support bearing. The device in accordance with the invention can be used either as a normal clutch or as an overload clutch or as both. When the pressure is discharged from the brake, the clutch slips immediately, i.e. the connection of rotation drive from the drive shaft A to the driven shaft B is cut off. 
     In the commonest embodiment of the present invention, the pressure circuit passing to the brake cylinders is filled to a certain pressure level, which is maintained by pressure accumulators. Said pressure level in said circuit determines the torque at which the clutch starts slipping. In said embodiment, the clutch is employed exclusively as an overload clutch in order to protect the power transmission from excessive torques. 
     In a second embodiment of the invention, in connection with the hub part of the shaft B, additionally a connector piece  50  is used, which is coupled with the hub part  11  of the shaft B. In the solution in accordance with the invention, a pressure fluid is passed, for example, from a tractor first into the connector piece and after that into the revolving hub part  11 . From the hub part the fluid is passed through a bore further to the cylinders of the brake device, placed in the brake caliper/calipers at the brake disks. By means of the fluid pressure, the brake cylinders press the brake pads into contact with the clutch disk. 
     In the connector part in accordance with the invention, there is/are a bearing or bearings between the hub part and the connector part. Favourably, pressure seals are also employed in order that the pressurized fluid could be passed without leakages from the bore in the connector piece further into the bore provided in the hub part  11  of the shaft B. 
     The overload clutch in accordance with the invention comprises a hub part, whose central bore is connected with the shaft of the device that is driven, for example a milling drum. The tool is attached from its shaft to the centre hole in the hub part, and rotation of the tool and the hub part in relation to one another is prevented by means of a groove joint. To the hub part, a connector part in accordance with the invention has been attached, through which the fluid pressure is passed first into the hub part and after that to the cylinders in the brake caliper at the brake disks. 
     Further, from a bore in the outer face of the hub part, pipes pass to the brake cylinders of the brake device. The output shaft of the driving machine, for example a tractor, is coupled with the clutch disk of the clutch. When the preset maximal torque is exceeded, the overload clutch cuts off said torque portions in excess of the maximal torque mentioned above, and the clutch slips. In such a case, between the brake pads connected with the hub part and the clutch disk, rotation is permitted. When the maximal torque is not exceeded, the rotation drive is transferred from the shaft A to the shaft B. 
     In accordance with the invention, from the fluid system of, for example, a tractor, the pressurized fluid is passed through the connector in accordance with the invention into the bore provided in the hub part and further, through the hub part, to the brake cylinders, in which connection the brake pads can be pressed with the desired force into contact with the clutch flange of the driving shaft. The overload clutch in accordance with the present invention operates as an overload protection and/or as a clutch device and/or as a brake device. 
     The clutch in accordance with the invention is characterized in what is stated in the patent claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in the following with reference to some preferred embodiments of the invention illustrated in the figures in the accompanying drawings, the invention being, yet, not supposed to be confined to said embodiments alone. 
     FIG. 1A is a cross-sectional view of an overload clutch in accordance with the invention. 
     FIG. 1B is a sectional view taken along the line I—I in FIG.  1 A. 
     FIG. 2 illustrates the passing of pressure to the brake cylinder. 
     FIG. 3 shows an embodiment in which the connector comprises two bearings. 
     FIG. 4 shows a hydraulic diagram in which, in the circuit after the connector to the brake cylinders, there are a resistor-check valve and a pressure accumulator. 
     FIG. 5 shows an embodiment of the invention in which the hub part comprises a flange connected with the hub part and revolving along with the hub part and pressure accumulators connected with the flange. The illustration is a sectional side view of a clutch in accordance with the invention. 
     FIG. 6A shows the pressure control of a check valve in an enlarged scale. 
     FIG. 6B illustrates a hydraulic diagram of the control of the check valve connected with the construction as shown in FIG.  6 A. 
     FIGS. 7A,  7 B and  7 C illustrate a pressure cartridge at different pressure levels. 
     FIG. 8 shows an embodiment of the invention in which a separate connector  50  is not employed at all and in which the circuit  59  of the clutch can be charged through a filling connector, i.e. through a what is called filling cartridge. 
     FIG. 9 illustrates the time T in the horizontal system of coordinates and the torque in the vertical system of coordinates, and the graph f 1  illustrates the limit torque line that has been regulated by means of the pressure set in the pressure circuit  59 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As is shown in FIG. 1A, the overload clutch  10  in accordance with the invention comprises a hub part  11 , to whose central bore  11   a  the shaft  12   a  of the device to be rotated, such as the milling drum  12  of the milling device, has been connected. 
     As is shown in FIG. 1A, the end shaft  12   a  of the milling drum  12  has been connected to the hub part  11  by means of a groove coupling  13  so that the end screw  14  presses the flange  15  against the inner shoulder  11   c  in the central hole  11   a  in the hub part  11 . 
     The hub part  11  comprises a flange  11   b  in its central area. To the flange  11   b,  further, a caliper  17   a  of the brake device  17  has been connected by means of screws  16 , and said brake device  17  further comprises a brake pad/pads  18  and brake cylinders  19  (in FIG. 2) in the interior of the brake caliper  17   a . The brake clutch device  17  favourably consists of three brake device assemblies  17 ′,  17 ″,  17 ″′, each of which comprises two brake pads at both sides of the clutch disk. The number of brake cylinders  19  in one assembly can be, for example, two or, for example, four. 
     Between the shafts A and B, there is a bearing  21 , a so-called support bearing. The bearing supports the movement of rotation between the shafts A and B when the clutch is open or slips. The bearing  21  is fitted inside the bearing housing  20  between the outer face of the end part lid of the hub part  11  and the inner face of the sleeve-like portion  20   a  of the bearing housing  20 . The bearing housing  20  comprises an annular disk  20   b  connected with the sleeve-like portion  20   a,  to which disk, further, the clutch disk  22  or clutch flange, which operates as the backup face of the brake pads  18  of the brake device  17 , is attached by means of screws R 1 . The clutch disk  22  is attached from its fastening ring  22   a  between a separate flange D 1  and the part  20   b  by means of the screws R 1 . The flange D 1  is connected to the flange D 2 , which is connected with the power output shaft, for example, of the tractor. The joint between the flanges D 1  and D 2  is preferably a screw joint. 
     In the embodiment shown in FIG. 1A, the solution of equipment comprises a connector  50  in accordance with the invention. The connector comprises flange-like frame parts  50   a  and  50   b,  which have been interconnected by screw means R 10 . Into the annular part  50   b,  a duct, favourably a bore  51 , has been made, which passes from the outer circumferential face  50 ′ of the connector to its inner face  50 ″. Between the parts  50   a  and  50   b,  there is a bearing  52 . The bearing  52  is connected from its outer race both with the part  50   a  and with the part  50   b,  and from its inner race with the hub part  11 . At the side of the bearing  52  that is connected to the part  50   a,  there is a pressure seal  53 , and on the face connected to the part  50   b  and to the bore  51 , there is a pressure seal  54 . The bearing  52  has been mounted on the outer face of the hub part  11  of the shaft B. The front face of the part  50   a  is placed against the shoulder  55  of the hub part  11 . Inside the annular parts  50   a  and  50   b,  there are sleeve parts  55   a,    55   b.  The sleeve parts are placed between the hub part  11  and the parts  50   a  and  50   b.  The connector  50  has been attached to the hub part  11  by the intermediate of the end ring  56 . Against the end ring  56 , a lock ring  57  is placed, which has been fitted onto the shaft  12   a  of the milling drum into its ring groove U. 
     Thus, when the rotation drive is passed from the shaft A to the clutch flange  22 , the rotation drive is transferred further through the brake device to the hub part  11  and further through it to the shaft  12   a  and further to the milling drum  12 . Even though, during operation, the shafts A and B and the connected parts  11 ,  12   a,  etc. revolve, the connector part  50  remains non-revolving. The bearing  52  has been fitted between the connector part  50  and the connected hub part  11 , and it permits rotation of the hub part  11  in relation to the non-revolving connector  50 . 
     In the solution of equipment in accordance with the invention, the apparatus can be used as an overload protection alone or as a brake device or as a clutch device or both as an overload protection and as a clutch device. The fluid pressure intake opening C at the medium connection of the connector  50  can have been connected, for example, to a pressure accumulator, in which case the pressure of the medium, for example oil, determined by the pressure accumulator determines the limit torque at which the clutch slips. The clutch slips when the torque arising from loading exceeds a predetermined value determined by the pressure accumulator. Further, the equipment can be connected with a fluid pressure regulation circuit, which can be controlled, for example, from the cabin of the tractor. Thus, for example, exactly in the case of a milling drum  12 , the solution of equipment in accordance with the invention permits the use of the solution of equipment both as an overload clutch and as an active clutch device. 
     When the clutch is in engagement, the brake pads  18  of the brake device  17  are kept in contact with the clutch flange  22  by the pressure in spite of possible wear of the brake shoes or brake pads  18 . In such a case, the operation of the device is reliable, and the preset torque at which slipping occurs remains at its preset, invariable value. The duct  58  placed in the hub part  11  of the shaft B communicates, at the side face of the hub part  11 , with the duct or pipe  59  that passes to the brake cylinder  19 . 
     FIG. 1B is a sectional view taken along the line I—I in FIG.  1 A. The figure illustrates the brake device assemblies  17 ′, 17 ″,  17 ″′. 
     FIG. 2 illustrates the passing of pressure to the brake cylinder  19  placed in the brake space  17   a  of the brake device  17 , which brake cylinder has been fitted to press the brake pad or friction pad  18  with a force. 
     FIG. 3 shows the connector  50 , which comprises two bearings: the bearings  52   a   1  and  52   a   2 , by means of which bearings a movement of rotation between the connector  50  and the rotatable hub part  11  placed in the central hole in said connector is permitted. Through the duct  51 , a pressure medium is passed into the duct  58  in the hub part  11  and from the duct  58  through the line, such as a hose  59  or equivalent, further to the cylinders  19  or equivalent of the brake/clutch device. 
     FIG. 4 is a schematic illustration of an embodiment of the invention which is in the other respects similar to the embodiment shown in FIG. 2, but in which a resistor-check valve  101  has been fitted in the duct  59 , and additionally, between the resistor-check valve  101  and the brake device  17 , a pressure accumulator  100  has been fitted. By means of this arrangement, an invariable pressure is maintained in the brake cylinders  19  in the brake device assemblies  17 ′, 17 ″, 17 ″′ of the brake/clutch device  17 . Said brake cylinders press the brake pads  18  constantly against the clutch disk  22  with an invariable force, and in said arrangement of equipment the force remains invariable irrespective of wear of the brake pads. In such a case, the connector  50  can also be kept non-pressurized. The connector  50  is used as a pressure supply arrangement when it is desirable to increase the pressure at the outlet side of the resistor-check valve  101  in the duct  59  or when it is desirable to check the pressure in said duct  59 . Through the valve V 1 , the pressure is passed from a source of pressure P 1 , for example a pump, to the brake cylinders  19 . 
     FIG. 5 shows an embodiment of the invention in which the hub part  11  comprises a flange connected with the hub part and revolving along with the hub part and pressure accumulators  100  connected with the flange  11   b.  Favourably, there are three pressure accumulators with uniform angular spacing, in which case they are placed at an equilibrium in the hub part  11 . Thus, pressure accumulators  100  or pressure cartridges are fitted on the flange  11   b  in such a way as uniformly spaced that the hub  11  is balanced as a whole. 
     The flange  11   b  connected with the hub  11  has been sealed at the edges of the annular fluid space D by means of sealing means  105 , 106 . The fluid space D communicates through ducts  107  passing through the flange  11   b  with the pressure accumulators  100 , favourably vessel constructions which comprise a piston  100   a  and a spring  100   b , in which connection the fluid space D can be filled, at the opposite side of the piston  100   a , against the spring force of the spring  100   b,  to the desired pressure in order to obtain the desired clutch holding torque for the clutch. Into the space D, a line  59  is opened through the connector  11   b,  which line passes the pressure to the cylinders  19  so as to press the brake pads  18  against the flange  22 . 
     Further, as is shown in the figure, the fluid space D communicates through the check valve  109   a  with a filling connection  109 . In the embodiment shown in FIG. 5, a duct  58  is opened from the connector  50  to the fluid space D between the flange  11   b  and the hub part  11 . As is shown in the figure, the duct  58  includes a check valve  101 , which can be pre-controlled by means of the rod  110 . The rod  110  is placed in the duct  58 . When the pressure is passed into the duct  58 , the rod  110  is controlled when the pressure acts upon the piston part  110   a   1  of the rod, for example a shoulder, whereby the check valve  101  is opened. The valve operation related to FIG. 5 is illustrated in FIGS. 6A and 6B. 
     FIG. 6A illustrates the operation of the rod  110  placed in the duct  58  for controlling the check valve  101  in an enlarged scale. FIG. 6B is a block diagram illustration of the hydraulic system of control of the check valve  101  related to the construction shown in FIG.  6 A. The rod  110  comprises a shoulder  110   a   1 , which operates as a piston part, in which connection, when the pressure enters into connection with the shoulder  101   a   1  out of the ducts  58   b   1 , 58   b   1 , the rod  110  is displaced in the direction of the arrow T 1  so that it opens the check valve  101 , in which case the pressure can be discharged through the set of ducts  58   a   2 , 58   a   1  opening into the duct  58  further to the valve V 1  and further out when the block E 1  in the valve V 1  communicates with the ducts  58   a   1 , 58   b   1 . 
     Similarly, when the block E 3  in the valve V 1  is switched on, the pressure can be charged through the connector  50  into the line  59 , which is placed at the other side of the check valve  101  and which includes the pressure accumulator  100 . 
     When the middle block E 2  in the valve V 1  has been switched on, i.e. when it communicates with the lines  58   a   1 , 58   b   1 , the lines  58   a   1  and  58   b   1  are closed. In such a case, the pressure is not passed to the check valve  101 , nor is the control pressure passed to said check valve  101 . 
     Thus, the solution of equipment in accordance with the invention is suitable for use either exclusively as a torque protection, in which case a certain holding pressure is maintained in the pressure circuit by means of the pressure accumulator  100 , while said holding pressure can be charged into the pressure circuit  59  and while it can be maintained by means of the pressure accumulator  100 /accumulators  100 . The charging of the pressure circuit with pressure can be carried out through a filling connector  109 , i.e. through a so-called filling cartridge. The filling connector  109  is preferably a so-called instant connector, which comprises a check valve  109   a  in its connection. One embodiment of the device is its use both as a disconnecting clutch and as a torque protection. In such a case, the connector  50  is used, which has been mounted in relation to the hub  11  by means of bearing means, in the way illustrated in the embodiments shown in the earlier figures. 
     FIGS. 7A,  7 B and  7 C illustrate the construction of the pressure cartridge, i.e. of the pressure accumulator  100 , and its operation at different pressure levels. As is shown in FIG. 7A, the pressure cartridge comprises a rod  100   c  connected with the piston  100   a,  around which rod a spring  100   b  has been fitted. In accordance with the pressure, the piston moves towards the bottom e 1  of the cartridge and shifts the rod  100   c  connected with the piston  100   a  out of the cartridge through the hole e 2  in the bottom of the cartridge, in which case the pressure that has been reached in the space D can be observed from outside. The cartridges  100  may be provided with springs  100   b  different from one another, said spring having different spring coefficients. In such a case, the rod of each cartridge projects from the cartridge at a different pressure. In this way it is possible to observe the generation of the pressure in the space D. When a pressure accumulator with spring construction is used as the pressure accumulator  100 , by means of suitable selection of the springs a compensation for temperature is made possible as the clutch is heated in operation. The more intensively the spring force is increased when the piston of the pressure cartridge is pressed against the spring, the higher is the pressure that is generated in the space D, which pressure is needed to compensate for the changes of thermal expansion that are produced in the clutch construction and that arise from heating of the clutch. 
     FIG. 7A shows a degree of filling of the pressure accumulator in which the end of the rod  100   c  of the pressure accumulator has projected through the hole e 2  in the bottom of the pressure accumulator, and FIG. 7C shows a stage in which the pressure has increased further in the piston space J 1  of the pressure accumulator, placed in connection with the piston  100   a.  The increased pressure can be read further from the fact that the rod  100   c  projects further out of the cartridge. 
     The clutch in accordance with the invention can be used exclusively as an overload clutch (embodiment shown in FIG. 8) or, when a separate connector  50  and a pressure control related to it are employed, both as an overload clutch and as a disconnecting clutch. 
     The commonest embodiment of the invention is illustrated in FIG.  8 . The clutch shown in FIG. 8 operates as an overload clutch only. By means of the use of pressure accumulators  100 , a suitable holding pressure is maintained in the circuit  59  of the brake cylinders, which pressure determines the desired torque of slipping. 
     In accordance with the invention, the pressure in the brake cylinders can be charged into the circuit  59  through the filling connection  109 . Through the filling connection, the pressure can be charged, for example, by means of a grease gun which is provided with a pressure gauge. From the pressure gauge, the filling pressure can be read that is desired for the brake cylinders in order to maintain the desired pressure and, thus, the torque protection. The embodiment shown in FIG. 8 is in the other respects similar to the embodiment shown in FIG. 5, except that there is no connector  50  in the embodiment of FIG.  8 . Thus, the flange  11   b  comprises an annular space D between the flange  11   b  and the hub part  11 . The flange  11   b  revolves along with the hub part  11 . The space D is pressurized by means of a grease gun through the filling connection  109 , and the pressurized grease/oil or any other pressure medium applies the pressure through the line  59  to the brake cylinder/cylinders  19 . The pressure accumulators  100  have been fixed to the outer face of the flange  11   b  with uniform angular spacing. Their pressure medium space J 1  communicates through the line  107  with the space D. Favourably, oil or grease is used as the pressure medium. 
     FIG. 9 illustrates the conduct of a clutch in accordance with the invention in an overload situation. The clutch slips when a certain holding torque that has been regulated by means of the charged pressure is exceeded. 
     In FIG. 9, the horizontal system of coordinates represents the time T, and the vertical system of coordinates represents the torque. The limit torque line f 2  is the torque limit at which the clutch starts slipping. Said torque limit can be adjusted so that the equipment is charged with a certain pressure, which pressure is maintained by the pressure accumulator/accumulators  100 . The graph f 1  illustrates the conduct of the clutch. At the point H 1  the clutch starts slipping, and at the point H 2  the clutch starts holding. In FIG. 9, the shaded area is the area of cut-off torque.