GB2169364A - Improvements relating to wrap spring clutch - Google Patents
Improvements relating to wrap spring clutch Download PDFInfo
- Publication number
- GB2169364A GB2169364A GB08500054A GB8500054A GB2169364A GB 2169364 A GB2169364 A GB 2169364A GB 08500054 A GB08500054 A GB 08500054A GB 8500054 A GB8500054 A GB 8500054A GB 2169364 A GB2169364 A GB 2169364A
- Authority
- GB
- United Kingdom
- Prior art keywords
- wrap spring
- output member
- drive
- clutch unit
- unit according
- Prior art date
- Legal status (The legal status 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 status listed.)
- Withdrawn
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J9/00—Programme-controlled manipulators
- B25J9/10—Programme-controlled manipulators characterised by positioning means for manipulator elements
-
- 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
- F16D27/00—Magnetically- or electrically- actuated clutches; Control or electric circuits therefor
- F16D27/10—Magnetically- or electrically- actuated clutches; Control or electric circuits therefor with an electromagnet not rotating with a clutching member, i.e. without collecting rings
- F16D27/105—Magnetically- or electrically- actuated clutches; Control or electric circuits therefor with an electromagnet not rotating with a clutching member, i.e. without collecting rings with a helical band or equivalent member co-operating with a cylindrical coupling surface
-
- 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
- F16D71/00—Mechanisms for bringing members to rest in a predetermined position
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Robotics (AREA)
- Mechanical Operated Clutches (AREA)
Abstract
A wrap spring clutch unit includes, on the output member 3b, a plurality of right angled notches 13 each of which can be engaged by a roller 12 carried by a spring-biased link 9 whereby if the output member 3b does not stop in precisely the desired position, the action of the roller 12 entering a notch 13 will tend to centre the output member in the desired position, the final part of the motion of the output member being driven independently by the action of the spring-biased roller 12. The spring is controlled by a sleeve having rachet teeth engaged by a latch operated by a solenoid. <IMAGE>
Description
SPECIFICATION
Improvements relating to wrap spring clutch
The present invention relates to a wrap spring clutch and provides for more positive action of the clutch.
A wrap spring clutch employs a helical spring closely wrapping around the cylindrical exterior of a drive member and having one end secured to an output member and the other end able to be displaced rotationally so as to induce either wrapping or unwrapping of the spring with respect to the cylindrical surface of the drive member. When engagement is required, the second-mentioned end of the spring is released to allow it to wrap on the rotating drive member whereupon that rotation will in turn tighten the wrapping effect and, as a result, the output member anchored to the said one end of the spring rotates along with the drive member.When release of the spring is required, the said other end of the spring is moved rotationally in the opposite direction, causing the spring to unwrap from the surface of the drive member and releasing drive engagement between the drive member and the output member. Advantageously, the unwrapping rotation may be confined to simply arresting rotation of a control collar which has the said other end of the spring fastened within it and which otherwise surrounds the spring exterior and is free to rotate with the drive member, when the clutch is engaged.
It is a problem with such a wrap spring clutch that whether or not the spring fully disengages from the drive member depends not only upon the positive action of stopping the control collar with the said other end of the spring carried by it, but also whether the output member has such a low inertia and low resistance to movement that the natural coiling tendency of the spring draws the output member in the same direction of rotation as the input member for a small distance, with the result that the spring is constantly rubbing on the exterior of the drive member. Such sustained rubbing will rapidly lead to wear of the clutch and deterioration of its performance, and in any case results in an imprecise positioning of the output member in its position of rest.
Hitherto it has been known to provide a brake in association with the output member, in order to arrest the load and hence to resist this tendency for the output member to follow the wrapping tendency of the spring. However, such a brake constitutes added frictional drag to be overcome by the clutch and the drive source in the drive-engaged position, and also the braking effect may vary as the brake wears and becomes less effective. More importantly, the position which the output member adopts upon stopping may vary from cycle to cycle.
The present invention aims to provide for more positive operation of the clutch and accurate positioning of the load without relying on high inertia of the driven components or on the presence of a brake in the drive train from the output member.
Accordingly the present invention provides a wrap spring clutch unit comprising a drive member, an output member, a wrap spring positioned for drivingly connecting the drive and output members in a clutchengaged position, and means for controlling wrapping and unwrapping of the wrap spring to effect operation of the clutch, and means in the drive train from the output member effective to drive the output member positively into a desired finishing position independently of the drive transmitted to the output member by virtue of the wrap spring.
In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to the accompanying drawings in which:
FIGURE 1 is an end elevational view of a wrap spring clutch unit in accordance with the present invention;
FIGURE 2 is an end elevation of the opposite end from that viewed in Figure 1; and
FIGURE 3 is a side elevation viewed from the lefthand side of Figure 2.
The wrap spring clutch unit 1 has a drive member 2 freely rotatably surrounding a slotted drive dog 3a for drive output from the clutch. Figure 2 shows a driven hub 3b positioned at the opposite end of the clutch unit; this hub 3b is connected to the output drive dog 3a. Drive between the drive member 2 and the output member 3a, 3b is by means of a wrap spring having one end secured to a control collar 4 which normally rotates with the drive member 2, in the drive-engaged configuration of the clutch unit, but is able to be restrained by a latch 5 (Figure 1) biased by a compression spring 8 towards the control collar 4 and driven away from it by means of a solenoid 6 acting on the latch 5.
The control collar 4 is in this case provided with two diametrically opposed ratchet teeth 7 either of which can be engaged by the latch 5 when they reach the position of the tooth 7 contacting the latch 5 in Figure 1. However, any integral number of such ratchet teeth 7 may be provided and their mutual spacing need not be regular. For example, it is possible to have the interval between two successive teeth greater than or less than the next successive interval between two such teeth where there are at least three ratchet teeth.
As shown in Figure 1, the drive member 4 rotates in the clockwise direction and thus when drive is engaged the output hub 3b will rotate in the anti-clockwise direction as viewed in Figure 2.
Figure 2 illustrates a positive drive mechanism for ensuring that when the clutch is disengaged with the driven hub 3b near, but not exactly at, one of its desired positions of rest the driven hub 3b (and hence the output drive dog 3a) will be driven positively to that position of rest.
The drive mechanism in this case comprises a link 9 spring-biased by means of a helical tension spring 10 for rotation in the clockwise direction about its pivot 11, so as to drive a roller 12 into one of two right angle notches 13 in the periphery of the driven hub 3b. In this particular case the angle subtended by the shoulders 13a at the edges of each notch 13, at the centre of the driven hub 3b is substantially 400 and thus when the output member 3 stops within 20 of its desired finishing position the roller 12 will ride over the shoulder 13a which is rounded for this purpose, and will then positively drive the driven hub 3b for rotation into the final desired position, under the influence of the tension spring 10.
The wrap spring clutch unit also includes sensing switches 14 to detect when the output member 3a, 3b has reached the desired positions.
If, as indicated above, the control collar 4 has a different configuration of ratchet teeth 7, then the same different configuration will apply for the right angled notches 13 of the driven hub 3b although naturally the configuration of notches 13 shown in Figure 2 will be the mirror image of the configuration of the teeth 7 shown in Figure 1.
The wrap spring clutch unit shown in side elevation in Figure 3 operates in the following manner.
Normally, there will be no current energising the solenoid 6 and thus the compression spring 8 will hold the latch 5 in the Figure 1 position. In this configuration the one end of the wrap spring (not shown) which is connected to the control collar 4 will be held in a configuration which keeps the spring unwound and clear of the cylindrical clutch surface of the drive member 2 which will be positioned radially inwardly of the control collar 4. The only part of the drive member 2 which is shown in Figure 3 is the flange which serves to provide a rotational support for the control collar 4.
In this position the output member 3a, 3b will be held in the Figure 2 position by engagement of the roller 12 in the associated notch 13.
When rotation of the output member is required, the solenoid 6 is energised and the pin 6a at the end of its armature draws the latch 5 back for clockwise rotation, to release the ratchet tooth 7 of the control collar 4 and thus to allow the control collar 4 to rotate in the clockwise direction under the influence of the wrapping tendency of the spring of the clutch. As the control collar 4 rotates in this way, the wrap spring of the clutch is free to tighten its hold on the cylindrical clutch surface of the drive member 2 and this frictional hold on the drive member 2 in turn increases the wrapping tendency and ultimately provides sufficient torque to rotate the output member 3a, 3b despite the presence of the springbiased roller 12 in one of the notches 13.
As soon as rotation of the output member 3a, 3b and of the control collar 4 has proceeded far enough, a signal is provided for de-energising the solenoid 6, thus allowing the compression spring 8 to push the latch 5 back into its latching position to engage the next successive ratchet tooth 7 during rotation of the control collar 4. If the output member 3a,3b does not quite reach the desired finishing position, the final part of its motion will be driven not by the clutch engaging action of the wrap spring on the drive member 2, but instead by the driving action of the springbiased roller 12 shown in Figure 2.
The wrap spring clutch unit in accordance with the present invention is particularly useful in applications where the output member is connected to a lever mechanism where the load on the mechanism may vary at different parts of the lever movement and may even drop off to a very low value at the end of the desired movement. In that case, the output member 3a,3b may slightly overshoot its desired position and leave the clutch spring too tightly wrapped on the external cylindrical clutch surface of the drive member 2 with constant drag.
Equally, if the speeds of movement of the clutching members are very low, then it may happen that the driven member stops before it reaches itsdesired finishing position and the operation of the programming switches 14 may be upset in that the correct signal is not attained. This is overcome by the positive driving action of the roller 12 which is able to bring the output member into its desired position either from an overshot position or from an undershot position, by virtue of the symmetry of the notches 13 of hub 3b.
Preferably the wrap spring clutch unit already incorporates the positioning mechanism comprising the lever 9, spring 10 and roller 12 for engagement with notches 13 in thedriven hub 3b,but alternatively it is conceivable for the present invention to employ a separate positioning mechanism connected in the drive train from the output member 3a, 3b. As indicated above, any number of ratchet teeth 7 and of notches 13 may be provided, but equally any number of programming switches 14 may be provided, as desired.
Figure 2 shows a grub screw 15 for allowing fine tuning of the position of the output member 3a, 3b, in relation to the output drive dog to which it is connected.
Any other configuration of recess, other than a right angled notch 13, is possible.
The particular application for the wrap spring clutch unit in accordance with the present invention is in the context of automation of machinery where a control linkage is expected to move at a particular time and to stop its movement at some subsequent time depicted by a programmer. For example, the automated apparatus may comprise a robot for doffing full packages in an open-end spinning installation.
Claims (12)
1. A wrap spring clutch unit comprising a drive member, an output member, a wrap spring positioned for drivingly connecting the drive and output members in a clutch-engaged position, and means for controlling wrapping and unwrapping of the wrap spring to effect operation of the clutch, and means in the drive train from the output member effective to drive the output member positively into a desired finishing position independently of the drive transmitted to the output member by virtue of the wrap spring.
2. A wrap spring clutch unit according to claim 1, wherein said control member comprises a control collar surrounding the wrap spring and including means for controlling the position of the control collar for effecting the desired engagement and disengagement of the wrap spring clutch unit.
3. A wrap spring clutch unit according to claim 2, wherein said means for controlling wrapping and unwrapping of the wrap spring comprise a solenoid-operated mechanism for arresting the rotation of the control collar when separation of drive from the drive member to the output member is desired, and for releasing the control collar for rotation by allowing self-induced wrapping of the spring onto the drive member when the control collar is free to rotate.
4. A wrap spring clutch unit according to claim 3, wherein said solenoid-operated means for releasing and arresting the control collar comprises a latch spring-biased into a position in which it arrests the control collar, the solenoid being effective to overcome the biasing of said spring to move the latch for releasing the control collar.
5. A wrap spring clutch unit according to any one of the preceding claims wherein the means for positively driving the output member into its desired position, independently of drive transmitted by way of the wrap spring, is effective to drive the output member into said desired position from adjacent positions rotationally displaced therefrom to either side.
6. A wrap spring clutch unit according to any one of claims 3 to 5, wherein said control collar includes at least one ratchet tooth and wherein the means for positively driving the output member independently of the drive imparted by the wrap spring comprises at least one recess in the surface of the output member, and a resiliently biased control member movable to be engaged in said at least one recess.
7. A wrap spring clutch unit according to claim 6, wherein said control member comprises a roller carried by a spring-biased support.
8. A wrap spring clutch unit according to claim 7, wherein said spring-biased support comprises a lever carrying the roller at one end.
9. A wrap spring clutch unit according to any one of claims 6 to 8, wherein the recesses in the output member are symmetrically arranged about a central radius corresponding to the median of the desired position.
10. A wrap spring clutch unit according to any one of claims 6 to 9 wherein there are at least three of said ratchet teeth and an equal number and arrangement of said recesses and wherein the rotational displacement intervals between adjacent ones of the ratchet teeth are different.
11. A wrap spring clutch unit according to any one of the preceding claims, including programming switches to detect desired rotational positions of the output member.
12. A wrap spring clutch unit constructed and adapted to operate substantially as herein before described with reference to, and as illustrated in, the accompanying drawings.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08500054A GB2169364A (en) | 1985-01-03 | 1985-01-03 | Improvements relating to wrap spring clutch |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB08500054A GB2169364A (en) | 1985-01-03 | 1985-01-03 | Improvements relating to wrap spring clutch |
Publications (2)
Publication Number | Publication Date |
---|---|
GB8500054D0 GB8500054D0 (en) | 1985-02-13 |
GB2169364A true GB2169364A (en) | 1986-07-09 |
Family
ID=10572336
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08500054A Withdrawn GB2169364A (en) | 1985-01-03 | 1985-01-03 | Improvements relating to wrap spring clutch |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2169364A (en) |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB656016A (en) * | 1947-12-30 | 1951-08-08 | Kodak Ltd | An improved winding mechanism |
GB1099710A (en) * | 1965-09-17 | 1968-01-17 | Ibm | Drive connection |
GB1168923A (en) * | 1966-04-22 | 1969-10-29 | Ibm | Drive Apparatus and Typewriter Incorporating such Apparatus |
GB1481962A (en) * | 1974-06-29 | 1977-08-03 | Metal Box Co Ltd | Pack-forming apparatus |
GB1495494A (en) * | 1975-09-02 | 1977-12-21 | Marquette Metal Products Co | Support for an actuating arm of a control element of a spring clutch |
GB2028456A (en) * | 1978-08-24 | 1980-03-05 | Warner Electric Brake & Clutch | Helical spring coupling with control collar |
-
1985
- 1985-01-03 GB GB08500054A patent/GB2169364A/en not_active Withdrawn
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB656016A (en) * | 1947-12-30 | 1951-08-08 | Kodak Ltd | An improved winding mechanism |
GB1099710A (en) * | 1965-09-17 | 1968-01-17 | Ibm | Drive connection |
GB1168923A (en) * | 1966-04-22 | 1969-10-29 | Ibm | Drive Apparatus and Typewriter Incorporating such Apparatus |
GB1481962A (en) * | 1974-06-29 | 1977-08-03 | Metal Box Co Ltd | Pack-forming apparatus |
GB1495494A (en) * | 1975-09-02 | 1977-12-21 | Marquette Metal Products Co | Support for an actuating arm of a control element of a spring clutch |
GB2028456A (en) * | 1978-08-24 | 1980-03-05 | Warner Electric Brake & Clutch | Helical spring coupling with control collar |
Also Published As
Publication number | Publication date |
---|---|
GB8500054D0 (en) | 1985-02-13 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |