GB2196075A

GB2196075A - Braking system

Info

Publication number: GB2196075A
Application number: GB08721191A
Authority: GB
Inventors: Engineer Valerian Kremer; Dr Engineer Bernd Obertrifter
Original assignee: Mannesmann Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 1986-09-09
Filing date: 1987-09-09
Publication date: 1988-04-20
Anticipated expiration: 2007-09-09
Also published as: PL156173B1; DE3630681A1; GB8721191D0; GB2196075B; PL267323A1; DE3630681C2

Abstract

The invention relates to a safety braking system for the transport means in a mine which has a brake released by venting a space 8. A safety brake control 39 has a valve means 40 providing control of the brake pressure release in a controlled reproducible manner. In particular, a directly actuated pressure relief valve 43 has its opening controlled via cam control means 49 which in turn is moved by a hydraulic cylinder 53. The speed of operation of the cylinder 63 is controlled by an energy source charging apparatus 57 which has an adjustable throttle means 65.

Description

SPECIFICATION Braking system The invention relates to a braking system and specifically to a safety braking system. More specifically the invention relates to the safety braking system for a conveying or winding eqipment for a mine. More generally the invention relates to valve means which can be adjusted by valve adjustment means such that a predetermined pressure characteristic is obtained for the valve means, particularly, when venting a venting space.

The present invention relates particularly to a braking system as set forth in the preamble of claim 1. In a known braking system of the this type different throttle means or nozzles are arranged between a venting space and the tank; this can also be done in a parallel arrangement and also with a pressure relief valve in series. Regarding the brake pressure characteristics obtained for such arrangements it is noted that they are not reproducible curves. Moreover, the fine adjustment of the throttles is difficult because of the small amounts of oil involved; this is one particular reason which leads to the non-reproducible kind of operation. Even though an apparently small adjustment of the throttle is present, the same characteristic for the brake pressure is not obtained.

It is an object of the present invention to overcome the disadvantages of the prior art. It is a particular object of the invention to design a brake system set forth in the preamble of claim 1 in such a manner that a reproducible brake pressure characteristic is obtained.

Moreover, a low cost as well as compact design shouid be obtained.

To attain the above object the invention provides the features set forth in the characterizing clause of claim 1. preferred embodiments of the invention are disclosed in the dependent claims.

Additional advantages, objects and details of the invention may be gathered from the description of embodiments shown in the drawing; in the drawing: Fig. 1 is a brake system of the prior art; Fig. 2 shows the brake pressure characteristic for the system of claim 1; Fig. 3a is a schematic representation of a first embodiment of the invention; Fig. 3b shows an essential part of Fig. 3a; Fig. 4 is an actually realized embodiment of Fig. 3; Fig. 5 is a sectional view taken along line 55 in Fig. 4; Fig. 6 is another practical realization of a brake system of the invention, similar to the system shown in Fig. 3.

Fig. 1 shows a known brake system 1 which can be used for conveying or winding equipment in the mining industries. Conveying means in the mining industry use, as is wellknown, a drive or winding wheel which is embraced by a transportation cable. The angle of embracement is generally about 1800. If brake operations occur, care has to be taken that no dangerous slip of the cable on the drive wheel occurs. Moreover, predetermined force values for the acceleration and deceleration must not be exceeded. Commonly, the speeds achieved by the cable in said conveying means are between 8 and 18 m/s.

The conveying means are provided with brakes which are used during operating phases of non-movement of said conveying means. Said brakes are nowadays frequently designed in the form of disc brakes. In such disc brakes the maximum brake force is generated by built-in packets of cup springs, so as to transmit the brake force onto the brake shoes having a brake shoe lining. In contrast to the known disc brake for a motor vehicle, the braking units of the brakes of said conveying means are in their active, i. e. braked condition, due to the force excerted by the cup springs, unless the release of the brakes is carried out by a so-called venting operation which is actually a built-up of hydraulic pressure in the brake system 1.

The brake system 1 of the prior art comprises a brake unit 2 and a brake control means 3 conntected therewith. The brake unit 2 comprises a brake cylinder 4 having a housing within which a piston 6 is reciprocally mounted and is subjected to a cup spring package 7. The piston 6 defines a vent space or chamber 8 and is used for actuating a disc brake which is schematically shown at 9.

The brake unit 2 is shown in its condition of release, is, however, right at the beginning of moving into the brake condition. The condition of release shown in Fig. 1 was achieved by suppiying the vent space 8 with a pressure medium, preferably a hydraulic medium supplied by a pump 19 yet to be described. This hydraulic pressure medium has pressed the cup spring package 7 into the position shown in Fig. 1. The movement of the piston 6 from the brake condition to the release condition occurs along the so-called venting path which is referred to by "L" in Fig. 1 The venting path is generally only about 1 mm. This leads to extremely short response times for the brake. It is also possible to make the venting path adjustable.

The braking unit is connected via conduits 11 and 14 with a braking apparatus 15. The braking unit 2 is further connected via conduits 11 and 16 with a safety brake control 17.

The braking apparatus 15 comprises the hydro-pump 19 connected to a tank 21. The hydro-pump 19 is connected via an electrically direct operated 2/2 directional control valve 22 with conduit 14. A pressure relief valve 20 is provided parallel to the pump 19.

The 2/2 directional control valve 22 is bi assed by means of a spring 23 into the shown closing position if a magnet 24 is not energized. In case the magnet 24 is energized, the valve 22 will switch into its opening position to connect the pump via conduits 14 and 11 with the vent space 8.

The pressure relief valve 20 serves for the adjustment of the "vent pressure", i. e. the pressure which provides the vent space 8 with a pressure so high that the brake is released. This release is carried out by moving the piston 6 along the vent path L towards the right in Fig. 1. Just to provide some information about the orders of magnitude involved, it should be noted that the venting pressure can be for instance 140 bar.

So as to adjust the braking moments to the load which is present, a controlled or regulated braking is provided by means of the hydraulic venting pressure which is supplied.

The pressure relief valve 20 can be designed as an electrically operated pressure relief valve and can be used for regulating the brake force which is supplied. The actuation of the pressure relief valve 20 occurs continuously, without steps, by means of a proportional magnet. The current received by the proportional magnet is proportional to the operating pressure of the hydraulic pump 19 and thus provides an increase.

In this context it should be noted that with regard to a brake operation a distinction has to be made between an normal operating braking condition and a safety braking condition. The braking control 17 shown in Fig. 1 and also the braking control of the invention yet to be described relates to a safety braking condition.

Such a safety braking operation will be initiated in an emergency situation, for instance, if the power supply breaks down, if a position end switch in the pit is overrun, or if an excess operating speed occurs. In such a situation the control valves are separated from the power supply, so that automatically the spring-loaded brake units 2 will be actuated inasmuch as the hydraulic pressure in the vent space 8 is decreased. For such a safety braking operation it is important that the actual braking characteristic is in accordance with deceleration values which are predetermined for the brake system used.

So as to provide for a controlled reduction of pressure in the venting space 8 in case of a safety braking operation, the safety braking control 17 is provided. The safety braking control 17 is connected with vent space 8 by means of conduit 16 and conduit 11. Conduit 16, in turn, is connected with an electrically direct operated 2/2 directional valve 27. The output of said valve 27 is connected via a conduit 30 to a throttling means 31. The output of the throttling means 31 is connected via a pressure relief valve 32 with tank 21.

An adjustable throttle means 33 is arranged in parallel to the pressure relief valve 32. The pressure relief valve 32 is adapted to reduce the brake pressure to the drain pressure (which will cause the application of the brake shoes).

The operation of the brake system 1 can be summarized as follows: At the beginning of the operation of the system the pump 19 is switched on by a switching means not shown, and by means of magnets 24 and 29 the control valves 22 and 27 are moved from their rest positions as shown into their operating positions. As a consequence, the vent space 8 can be supplied with pressure medium. As soon as the vent pressure of, for instance 120 bar as defined by the pressure relief valve 20 is reached, the piston 6 will move into the shown position and the brake will be released. The safety brake control 17 is for all practical purposes separated due to the valve 27 being in its operating position. In this operating position regular braking operatings can be carried out by electrically controlling the valve 20.

In an emergency situation it is necessary to automatically initiate, as mentioned above, a safety braking operation. In such a situation automatically all control valves which normally are supplied with electrical energy, are cut off from the energy supply, i. e. in the brake system 1 of Fig. 1 the electromagnets 28 and 29 are de-energized, so that the pump 19 is separated from the vent space 8, while the safety brake control 17 is now connected with the vent space 8. Consequently, the pressure medium exits from the vent space 8 and a pressure characteristic (the pressure in the vent space 5 depending on the time t) is obtained as is shown for example by the parabolic characteristic of Fig. 2.Due to the use of the throttle means 31, 33 only parabolic characteristics are obtained, which, moreover, are not reprocucible, i. e. the characteristics obtained change from one safety braking operation to the next safety braking operation.

Indeed, the fine adjustment of the throttle means 33 is difficult because of the small amount of oil which is present in the vent space 8. This leads to the non-reproducible results. This means that even if the same adjustment of the throttle means is present, it will not be possible to achieve the same pressure characteristic.

Fig. 2 shows the relationship between the pressure in the vent space 8 depending on the time t. At the time t = 0 the safety brake operation is initiated, i. e. the valve 27 is opened. Up to the time t = .2 the pressure medium will flow via the fixed throttle means 31 and the pressure relief valve 32. After the pre-adjusted pressure at the pressure relief valve 32 of, for example 100 bar, is reached, the pressure medium will only flow via the fixed throttle means 31 and the adjustable throttle means 33. The result is the character istic described so far. After about 0.4 seconds at the time t = .6 a pressure of 30 bar will be reached. This so-called remaining pressure will be maintained for a time of about 10 to 15 seconds.

Figs. 3a and 3b disclose the brake system 10 of the invention. The brake system 10 comprises, as does the brake system 1 of Fig. 1, a brake unit 2 which is identical to the brake unit 2 of Fig. 1. The brake system 10 of the invention comprises further a brake control 38 which is connected with the brake unit 2 by means of conduit 11.

The brake control 38 of the invention comprises a brake apparatus 15 which is identical to the brake apparatus 15 of Fig. 1. Brake apparatus 15 is again connected by means of a conduit 14 with conduct 11. The brake control 38 comprises the safety brake control 39 which becomes active in an emergency situation and causes the brake operation. The safety brake control 39 is connected via a conduit 16 with the conduit 11.

The safety brake control 39 comprises in a manner identical to the system of Fig. 1 a 2/2 control valve 27. The output conduit 30 of said control valve 27 is connected to tank 21 by means of valve means (brake valve means) 40 which defines the brake characteristic and a conduit 42. The brake valve means 40 replaces the different throttle means known from Fig. 1 and avoids the disadvantages thereof. The valve means 40 provide for a control of the brake pressure in a reproducible manner, so that a desired predetermined characteristic is achieved.

The brake valve means 40 of the invention comprise adjustable valve means (adjustment valve means) 78 and means for the adjustment of the adjustable valve means (valve adjustment means) 79.

The valve adjustment means 79, in turn, comprise control cam means 80 and adjustment/return means for the control cam means 80.

In the embodiment shown in Fig. 3, the adjustment valve means 78 are provided in the form of a directly actuated pressure relief valve 43. Due to the direct actuation of the pressure relief valve 43 the loss of oil is avoided or at least held at a small level which is important in view of the small volumes of oil or pressure medium present. Alternatively, a piiot-controlled pressure relief valve may be used instead of the pressure relief valve 43.

The pressure relief valve 43 can be adjusted with regard to its opening pressure by transmitting a force by means of a pin 48 onto the valve poppet 70, a force which is smaller or larger, depending on the requirement. It should be noted that the valve poppet 40 as Well as the pin 48 are not shown in Fig. 3, but are clearly shown in Fig. 4 yet to be described in detail. This transfer of force occurs by means of a sensing apparatus 46 which abuts at the control cam means provided in the form of an elongate element 49.

The elongate element 49 forms a control cam 50 which is in engagement with roller means 47. As pointed out above, the design of said roller means 47 as well as other details are explained below in connection with Fig. 4.

The cam means 50 of the cam control means 49 cause the adjustment of the opening pressure of the pressure relief valve 43, i.

e. the pressure F in the venting space or chamber 8 depending on the time for the opened valve 27 when the cam means 50 moves past the sensing apparatus 46. This movement past the cam means 50 is caused by the adjustment/return means 81. Said means 81 move the cam means 50 from the initial position shown in Fig. 3 into an end position not shown effecting thereby the pressure adjustment of the valve 43. In addition said means 81 cause a return of the control means 50 into the initial position after the safety braking operation has occured.

In the embodiment shown the adjustment/return means 81 comprise a hydraulic cylinder 53, an energy source 52 and an energy source charging apparatus 57. The hydraulic cylinder 53 comprises a piston 54 and a piston rod 55 which is connected via a support 51 with the elongate element 59. At the bottom end of the piston rod 55 a weight 59 is provided which causes the movement of the control cam 50 past the sensing apparatus 46.

The energy source 52 shown in Fig. 3 is charged, i. e. the weight 59 is lifted and the elongate element 49 is located in its initial position together with its control means 50.

For charging the energy source 52 the energy source charging apparatus 57 is provided. Apparatus 57 is connected via a hydraulic conduit 56 with the cylinder space of the hydraulic cylinder 53 and is further connected via a conduit 58 with the conduit 16.

A direct electrically operated 4/2 directional valve 61 is connected with its input to conduit 58 and tank 21. The output side of the valve 61 is connected via conduit 64 with an adjustable throttle means 65 and with conduit 56. A check valve 66 is arranged in parallel to the throttle means 56. Valve 61 is biassed by means of a spring 62 into the rest position shown. When energizing magnet 63 the valve 61 can be moved into its operating position where conduit 58 is connected to conduit 64.

This is the case at the beginning of the operation of the brake system. At the beginning of the operation, the magnets 24 and 29 already mentioned, and also the magnet 63 are energized. As a consequence, pressure medium is supplied by pump 19 via conduits 14 and 16 to valve 61 and from there the pressure medium flows via conduit 64 and check valve 66 to the cylinder space of the cylinder 53, as a consequence of which the weight 59 is lifted, i. e. the energy source 52 is charged. This energy is then available for actuating the elongate element 49 if a safety braking operation has to be carried out.

It should be noted that the invention is not restricted to the shown embodiment. The elongate element 49, generally the control cam means 49, can also be moved from their initial position to their end position in a different manner, and it is also possible to return said means to their initial position from the end position in a different manner.

In the embodiment shown a weight 59 is used for moving the control cam means 49 from the initial position to the end position.

Alternatives for this purpose are: 1. a spring load 2. a gas storage means 3. a hydro storage means.

Also, the return, i. e. the movement of the control cam means 49 from the (not shown) end position back into the (shown) initial position could be carried out in a different manner, for instance, by means of a mechanical drive.

Prior to discussing additional modifications of the invention a concrete embodiment of the adjustment valve means 78 and the control cam means 49 together with their drive means will be described in connection with Figs. 4 and 5.

Figs. 4 and 5 disclose a preferred design of a portion of the brake valve means 40 of Fig.

3. Reference numeral 43 refers to the pressure relief valve, 59 refers to the weight and 49 refers to the control cam means. The brake system is shown in its initial position, i.

e. it is ready for a safety braking operation.

At the end of the safety braking operation the braking system will be in its end position. Accordingly, in Fig. 4 the elongate element 49 is shown in its initial position. The elongate element 49 will reach its end position if the sensing apparatus 46 has pivoted in the direction of the arrow 88 by an angle alpha into the position marked by reference numeral 89.

It can be recognized that the pressure relief valve 43 forms together with the elongate element 49 and the actuating means thereof for all practical purposes a unit. Parallel to the cylinder 53 extend three actuating rods 84 which are mounted on the one hand side to a support 51 and on the other hand side to a elongate element support 83. At the opposite end of the elongate element support 83 a switch actuating rod 87 is mounted and serves for the actuation of a switch 77.

Switch 77 supplies to the brake system information with regard to the position of the elongate element and therefore information with regard to the pressure relief valve 43.

An angular support 67 is pivotally mounted by means of a pin 74 in a housing of the pressure relief valve 43. Angular support 69 carries at its two additional end points a roller 71 and a roller 72, respectively. Roller 71 is in contact with the control cam 50 and roller 72 abuts at a pin 48 which, in turn, is in abutment with a spring 44.

Elongate element adjustment means 90 are provided in the form of elongate holes 85 in the elongate element itself, and balls 86 are provided, so as to provide for a brake charac teristic in accordance with the requirements.

By loosening or tightening the balls 86 an ad justment of the control cam means 49 can be carried out.

With regard to the operation of the brake system of the invention reference is made to what was said with regard to the initiating operation of the brake system of Fig. 1. Also, the charging of the energy storage means 52 was already described above. If an emergency situation occurs and the safety braking oper ation is to be initiated automatically, then all magnets 24, 29 and 63 become separated from the electric power. Valve 22, therefore, separates the pump from the vent space 8 and the valve 27 connects the vent space with the tank 21 via the brake valve means 41 of the invention.

In accordance with the invention, the brake valve means 40 are opening in accordance with a predetermined brake pressure charac teristic. The desired brake pressure character istic is practically stored in the cam shape of the control cam 50. Inasmuch as at the begin ning of the safety brake operation the valve 61 separates the piston space of the hydraulic cylinder from the conduit 58 and connects it via the adjustable throttle means 65 with the tank 21, the weight 59 can move the elon gate element 49 from its shown initial position to its downward end position. During the downward movement the adjustable throttle means 65 acts as follows: Due to the differ ent volume flow via the throttle means an ajdustable speed for the elongate element is achieved Thereby, the time for the safety brake operation is changeable.

In connection with Fig. 6 another embodi ment of the invention will be described. This embodiment discloses an alternative possibility particularly with regard to the valve adjust ment means 79 of Fig. 3. In Fig. 6 the valve adjustment means are referred to by reference numeral 179. Moreover, the adjustment/re turn-means 81 of Fig. 1 for the valve adjust ment means are designed in a different man ner than is shown in Fig. 3. In the embodi ment of Fig. 6 a spring 159 is used instead of the weight 159 so as to move the valve ad justment means 179 from its initial position to its end position. Generally, the energy source 152 of Fig. 6 is modified with respect to the energy source 52 of Fig. 3. The energy sto rage charging apparatus 57 of Fig. 3 is in substance also used in the embodiment of Fig. 6 as is pointed out by the use of the same reference numerals as in Fig. 3.

Generally, in the embodiment of Fig. 3 the valve means defining the brake characteristic, i. e. the so-called brake valve means, are referred to by reference numeral 140. Said brake valve means 140 are located essentially in a plane above the roller means 47 of a directly operated pressure relief valve 43 which is provided in the same manner in Fig.

6 as in Fig. 3.

The brake valve means 140 comprise housing means 112 which are provided to the left in Fig. 6 with a energy source charging apparatus 157 of a similar design as shown in Fig.

3. Adjacent thereto an energy source 152 is located in the housing means 112; energy source 152 comprises a hydraulic cylinder 153 and at the opposite end of the housing 112 the actual energy source in the form a spring 159.

In said housing means 112 a cylinder space 160 is formed; the cylinder space 160 is closed at one side by the energy storage charging apparatus 157 and is bordered on the other side by a piston 154 which comprises a piston rod 155. Valve adjustment means 179 are fixedly mounted to the piston rod 155. The valve adjustment means 179 are fixedly mounted to a support 183 for the elongate element. The support 183, in turn, is fixedly mounted to the piston rod 155. The elongate element support 183 supports an elongate element 149 which comprises a parabolic control cam means 150 adapted for cooperation with roller means 47. In the position of Fig. 6 the elongate element is located in its initial position. It can be moved along the distance referred to as stroke 400 according to the movement of the piston 154.During said movement the adjustment pressure or preset pressure of the valve 43 can for instance be lowered from 120 bar to 30 bar. The movement of the elongate element 149 in the direction of the arrow is caused by the spring 59 already mentioned, a spring which surrounds an abutment rod 111. The abutment rod 111 forms an abutment for the piston rod 155 in the position as shown where the movement along the length defined by the stroke 400 has occured. Guide means 113 are provided for the elongate element support 183. Summarizing it can be said with respect to the shown embodiments that the adjustable throttle means 65 can be used for the adjustment of the speed with which the elongate element 49 and 149, respectively moves from the initial position to the end position.Correspondingly, the pressure relieve valve 43 is increasingly opened, i.e. the opening pressure of the valve 43 is changed between the initial maximum value of for instance 140 bar to a minimum value of for instance 30 bar. The braking time which can be adjusted by means of the throttle valve 65 is commonly between a minimum of one second and a maximum of two seconds up until stand still is achieved.

The adjustability of this time is desirable and is generally carried out depending on the depth of the pit, the load, and the transportation speed. Generally, the braking time should not be longer than two seconds in as much as this corresponds, for commonly used transportation speeds, for instance to a braking distance of four meters which is already possibly too much.

In the embodiment disclosed, the adjustment valve means 78 are provided in the form of a direct operated pressure relieve valve. It is also possible to provide the adjustment valve means 78 in a different manner as long as the desired braking force characteristic is obtained. For instance, the adjustment valve means 78 can be in the form of flow control valve. In the embodiments shown a longitudinal cylinder 53 and 153, respectively, is used.

Instead of the longitudinal cylinder also a rotary cylinder may be used. The control cam means 49 are, as already mentioned, adjustable. Instead of the linear cam or curve shape shown in Fig. 4 a variable cam or curve shape may be used. This is examplified in Fig. 6 where a parabolic control curve 150 is shown.

The brake or control speed is determined by the adjustable throttle means 65 (adjustable flow resistance). It should be noted that also constant flow resistances can be used.

The throttle means 65 determine for all purposes the brake or control speed and therefore the braking time while the shape of the control curve 50 and 150, respectively, determines the reduction of the pressure in the vent space 6 depending on the time in a reproducible manner.

Claims

1. A brake system comprising a braking unit (2) and a braking control means (38), said braking unit (2) including one or more brake cylinders (4) defining venting space means (8) and said braking control means (38) comprising a safty braking control (39) for carrying out a safty braking operation, said safty braking control being adapted to connect the venting space means to a tank (21) by means (43) which determine the said venting space means, i.e. the degrees of pressure (P) in said venting space means (8), characterized in that said venting space means for determing the brake characteristic comprise valve means (43) which are actuable by control cam means (50, 150) determining the brake characteristic.

2. The brake system of claim 1, characterized in that the valve means are spring-loaded valve means independent of the volume.

3. The brake system of one or more of the preceding claims characterized in that the valve means is a pressure valve.

4. The brake system of one or more of the preceding claims, characterized in that the valve means are a direct controlled pressure relief valve.

5. The brake system of one or more of the preceding claims, characterized in that the control cam means (49) comprise a control cam (50) corresponding to the desired brake pressure characteristic.

6. The brake system of one or more of the preceding claims, characterized in that the control cam means are movable between an initial and an end position, wherein the movement between the initial position and the end position is determined by either adjustable or by constant flow resistances.

7. The brake system of one or more of the preceding claims, characterized in that the movement of the control cam means from the end position to the initial position, i. e. the return movement, is effected pneumatically or hydraulically.

8. The brake system of one or more of the preceding claims, characterized in that the return is carried out by a longitudinal cylinder or by a rotary cylinder.

9. The brake system of one or more of the preceding claims, characterized in that the movement of the cam means from the initial position to the end position is effected by means of a weight.

10. The brake system of one or more of the preceding claims, characterized in that the return of the cam means is carried out by means of a hydraulic cylinder, the movement of the cam means from the initial position to the end position is carried out by a weight mounted to the hydraulic cylinder, and the braking speed is adjustable by means of throttle means which are connected to the hydraulic cylinder.

11. The brake system of one or more of the preceding claims, characterized in that adjustment means (90) for the control cam means (49) are provided so as to change the brake pressure, (i. e. the pressure in the vent space) and the brake force characteristic.