GB2190716A

GB2190716A - Spring applied force actuator

Info

Publication number: GB2190716A
Application number: GB08624235A
Authority: GB
Inventors: David John Wickham
Original assignee: Westinghouse Brake and Signal Co Ltd
Current assignee: Siemens Mobility Ltd
Priority date: 1986-05-17
Filing date: 1986-10-09
Publication date: 1987-11-25
Also published as: ZA872894B; KR870010993A; KR870010984A; JPS62274152A; ZA872852B; GB8629765D0; GB2190441B; GB8612061D0; GB8624235D0; GB2190441A; JPS6323526A

Abstract

A spring applied force actuator for a brake comprises an output member 1 movable from a first retracted position to a second, output (brake engaged) position by rotation of a sleeve 17 which is threadedly engaged with the output member a first, compression spring 4 by which can be generated on the output member an output force when the member is in its second position, first power means by which the first spring can be compressed and held until it is released to apply its stored force as an output force on the output member, a second spiral spring 10 on unwinding, rotates the sleeve 17 to move the output member from its first position to or towards its second output position, and second power means including motor 30 for rotating sleeve 17 by which the output member can be moved back from its second output position to its first position thereby, at the same time, winding-up the second spring. Subsequently the output member is moved back to its second output position upon release and unwinding of that second spring, and, if slack exists in the brake system when the spring 10 has unwound, by operation of the motor 30. The first and second power means include electric motors 5,30 and associated electro-magnetic brakes 42,31 and the energy stored in the springs is released by releasing the electromagnetic brakes. Means (15, 16, Fig. 3) is provided whereby the output member 1 will be moved back the same (brake clearance) distance on each operation of the actuator. <IMAGE>

Description

1 GB2190716A 1 SPECIFICATION spring and in this case and when said part

mentioned above is a cylindrical housing, the Electric actuators second spring may be housed in the end of the cylindrical housing remote from the end These inventions all relate to electric actuators 70 through which the first spring extends into the and, more particularly although not exclusively, - housing. The second spring may be connected to such actuators for railway braking systems. by one end to a rotatable threaded member This invention relates specifically, to electri- threadedly engaged with the output member.

cal actuators of the type in which a spring is With such a construction a so-called -slack- the source of the output force of the actuator, 75 adjusting- facility can readily be incorporated this spring having its potential energy gener- into the actuator. This can readily be done by ated by an electric motor operable to vary the including in the drive path between the second length of the spring and held stored in the spring and the output member a one-way spring until the spring is subsequently released clutch such that in the event of the second to allow the stored energy of the spring to be 80 spring having completed its normal variation of released as the output force. In such actuators length corresponding to movement of the out it is commonly required that the output force put member to its second output position and be exerted by the spring on the output mem- it being indicated that the output member has ber of the actuator only after the output mem- not, in fact, reached that position, the second ber has been moved into a predetermined 85 electric motor can be operated to continue force-exerting position-in the case of a brake movement of the output member until it is actuator, only after the brakes have been en- detected as being in its second output posi gaged. This requirement is because, if the tion.

spring which is to exert the output force is One embodiment of the invention will now used also to move the output member into 90 be described in greater detail, by way of the predetermined force-exerting position, the example only with reference to the accom necessary variation of the length of the spring panying drawings of which:

to effect this movement will detract from the Fig. 1 shows a general arrangement drawing maximum value of the output force which the of the actuator, spring could subsequently exert in the force- 95 Fig. 2 shows a cross- section on the line exerting position of the output member. 'A'-'A' of Fig. 1, and To obviate this problem, this invention pro- Fig. 3 shows a cross-section on the line W vides an electric actuator having an output 'B' of Fig. 1.

member movable from a first position to a The accompanying drawings show an elec- second output position, a first power spring 100 tric actuator which is a railway brake actuator by which can be generated on the output although the invention is equally applicable to member an output force when the member is other electric actuators.

in its second output position, a first Power Referring to the drawings, the actuator com means by which potential energy can be gen- prises an output member 1 movable from its erated in the first spring therein to be held 105 first position as shown in Fig. 1 in the direc until the spring is released to apply its stored tion of arrow -A- to its second output posi force as an output force on the output mem- tion in which the brake blocks (not shown) ber, a second spring release of the potential engage the railway-vehicle wheel (also not energy stored in which moves the output shown).

member from its first position to its second 110 Within the annular chamber 2 of a hollow output position, and second power means by walled cylindrical housing 3 is a first power which the output member can be moved back spring 4 arranged to be compressed to gener from its second output position to its first ate potential energy in the spring 4 by an position thereby, at the same time, generating electric motor 5 through gearing 6, a screw- in the second spring the potential energy suband-nut combination 7, lever 8 and pin 9 se- sequently to move the output member back to cured to the housing 3.

its second output position upon the subse- A second clock-type spring 10 is located in quent release of that second spring. the left-hand end (as viewed in the drawing) The first power means may be an electric of the housing 3. The clock spring 10 is se motor as may also the second power means. 120 cured at 11 by one end of the spring to the The first spring may extend between---land-housing 3 and at 12 by its other end to the and a part movable to generate the potential central boss 13 of a spring housing 14. The energy in the first spring by the first power housing 14 has a radial protrusion 15 (Fig. 3) means which operates on the part. In such an from the boss 13 engageable by a pin 16 arrangement, the first power means may be 125 fixed in the housing 3. By this protrusion-and connected to said part via a lever fulcrumed pin 15/16 arrangement, the spring housing 14 to---land-and pivotally connected to said can rotate relative to the housing 3 through part. Said part may be a cylindrical housing only a limited angular distance-say, 300 de into which extends the first spring. grees.

The second spring may be a clock-type 130 The spring housing14 is drivingly-engaged 2 GB2190716A 2 with tube 17 through a one-way clutch 18. site direction in which it rotates to---windup The tube 17 is provided with a flange 19 by the spring 10. Such operation of the motor which the tube 17 is located axially within the 30, through gear chain 25, chain-gear wheel housing 3 between a shoulder 20 in the hous- 24, tube 17 and thread 22 will drive the out ing 3 and a washer 21. The tube 17 is 70 put member 1 still further to the left (the one threaded at its right-hand end portion (as way clutch 18 -freewheeling-) until further viewed in Fig. 1) threadedly to engage the leftward moement of the output member 1 is threaded portion 22 on the output member 1. finally halted by its reaching its second At its left-hand extremity (as viewed in Fig. 1) -brakes-engaged- position.

the tube 17 has keyed to it at 23 chain-gear 75 When the output member 1 is detected as wheel 24 arranged to be driven by chain 25 being in its second force- exerting position-- by a second electric motor 30 fitted with an i.e. its -brakes-engaged- position-the elec electromagnetic brake 31. tromagnetic clutch 42 of the first electric mo It can thus be seen that the clock-spring 10 tor 5 will be released. This will free the power can be---wound-up- to generate in it potential 80 spring 4 to expand exerting an output force force, by operation of the second electric mo- on the output member 1. Bxpansion of the tor 30 through chain 25, chain-gear wheel 24, power spring 4 will also rotate the motor 5 tube 17, one-way clutch 18 and the spring backwards by virtue of the expansion of the housing 14. spring 4 acting through the pivot 9, lever 8, In the -releaseposition of the above de- 85 nut-and-screw combination 7 and gearing 6.

scribed actuator, the first power spring 4 will Such rotation of the motor 5 can be measured have been compressed by the motor 5. Previ- by an encoder 50 and this measurement will ous operation of this motor 5 will have, be indicative of the output force being gener through gearing 6, screw-and-nut combination ated on the output member 1 by the spring 4.

7 and lever 8 have moved the housing 3 to 90 This measurement can be compared with the the right (as viewed in Fig. 1) thus compress- degree of rotation of the motor 5 equating ing the power spring 4 between the end wall with the required value of the output force and land 41. In this compressed condition and when rotation of the motor 5 indicates of the power spring 4 in which potential en- that this required value has been reached, the ergy will have been stored in the spring 4, the 95 motor 5 can be locked against further rotation motor 4 will have been locked to hold the by its electromagnetic brake 42 holding the spring 4 compressed by energisation of the output force at the required value.

electromagnetic brake 42 of the motor 4. The brakes are subsequently released by se Also, the second clock-spring 10 will have quential reenergisation of motors 5 and 30 been -wound up- by the motor 30. Previous 100 firstly to re-compress and hold re-compressed operation of the motor 30 will have, through the power spring 4 and thereafter to re-wind chain 25, chain-gear wheel 24, and one-way and hold re-wound the clock- spring 10.

clutch 23 and will have rotated the spring It will be seen that the protrusion-and-pin housing 14 to---windup- the spring 10. In construction 15/16 limiting as it does the ex this condition of the spring 10 in which poten- 105 tent of wind-back of the output member 1 will tial energy will have been stored in the spring ensure a predetermined degree of movement 10, the motor 30 will have been locked to back of the output member 1 to its first posi hold the spring 10 -wound up- by energisa- tion and, therefore, a predetermined degree of tion of the electromagnetic brake 42 of the 11 clearance- of the brakes. Thus, this con motor 30. 110 struction provides a -slack adjustment- func The brakes are -applied- by the following tion.

operations: Firstly, the electromagnetic brake

Claims

31 is released. This allows the -wound up- CLAIMS clock spring 10 to

unwind rotating the output 1. A spring applied force actuator having an member 1 through the one-way clutch 23. By 115 output member movable from a first position virtue of the threaded connection of the right- to a second output position, a first power hand end (as viewed in Fig. 1) of tube 17 spring by which can be generated on the out with the screw threaded portion 22 of the put member an output force when the mem output member 1, the output member 1 will ber is in its second position, first power be driven to the left (as viewed in Fig. 1). 120 means by which potential energy can be gen Such moement of the output member 1 will erated in the first spring therein to be held normally be terminated when the brakes are until the spring is released to apply its stored engaged-Le. force as an output force on the output mem when the output member is in its second ber, a second spring release of potential en force-exerting position. However, should there 125 ergy stored in which moves the output mem be excessive slack in the brakes, the output ber from its first position to its second output member 1 will not have reached its second position, and second power means by which position when the spring 10 has fully un- the output member can be moved back from wound. When this condition is detected, the its second output position to its first position motor 30 is energised to rotate in the oppo- 130thereby, at the same time, generating in the 3 GB2190716A 3 second spring the potential energy subsequently to move the output member back to its second output position upon the subsequent release of that second spring.
2. An actuator as claimed in Claim 1, wherein the first power means is an electric motor.
3. An actuator as claimed in Claim 2, wherein the second power means is an elec- tric motor.
4. An actuator as claimed in any one of Claims 1 to 3, wherein the first spring extends between---land-and a part movable to generate the potential energy in the first spring by the first power means which operates on the part.
5. An actuator as claimed in Claim 4, wherein the first power means is connected to said part via a lever fulcrumed to---land- and pivotally connected to said part.
6. An actuator as claimed in Claim 4 or Claim 5, wherein said part is a cylindrical housing into which extends the first spring.
7. An actuator as claimed in any one of the preceding Claims, wherein the second spring is a clock-type spring.
8. An actuator as claimed in Claim 7 when dependent on Claim 6, wherein the second spring is housed in the end of the cylindrical housing remote from the end through which the first spring extends into the housing.
9. An actuator as claimed in either Claim 7 or Claim 8, wherein one end of the second spring is connected to a rotatable threaded member threadedly engaged with the output member.
10. An actuator as claimed in any one of the preceding Claims, wherein there is included in the drive path between the second spring and the output member a one-way clutch such that such that in the event of the second spring having completed its normal variation of length corresponding to movement of the output member to its second output position and it being indicated that the output member has not, in fact, reached that position, the second electric motor can be operated to continue movement of the output member until it is detected as being in its second output position.
11. An actuator substantially as herein described with reference to and as illustrated in Figs. 1 to 3 of the accompanying drawings.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987. Published at The Patent Office, 25 Southampton Buildings, London, WC2A l AY, from which copies may be obtained.