JP3158126B2 - Manual brake device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base which is fixed to a vehicle body and pivotally supports a base of a brake lever, extends a tip end thereof near an operator, and applies a force to the tip end. The present invention relates to a manual brake device that applies a brake by pushing and pulling a brake cable in accordance with swing of a brake lever.

[0002]

2. Description of the Related Art When an elastic coil is wound around an outer periphery of a drum so that a fixed end at one end is locked and the other end is set to a play side without being locked, one direction depends on the direction in which the drum is rotated. In one direction, the elastic coil cannot be rotated due to the tightening of the elastic coil, and in the other direction, the elastic coil is loosened when the drum rotates, and it rotates easily, and this phenomenon is used to brake the brake lever. A manual brake device has been proposed in which the brake is released by pressing the play side from outside and loosening the elastic coil after braking.

A general structure proposed in such a case is shown in FIG. 6, for example. That is, the elastic coil member 1 is wound so as to elastically contact the outer periphery of the drum 2, the fixed end 1a at one end of the elastic coil member 1 is locked to the base side, and the other end is not locked.
The end is slightly extended in the radial direction of
There is. When the drum 2 is rotated in the direction A, the coil portion 1c of the elastic coil member 1 cannot wind around the drum 2 to rotate, and in the opposite direction B, the drum 2 moves relative to the coil portion 1c of the elastic coil member 1. When relatively rotating, the coil portion 1c is loosened and easily rotates.

In the case of a manual brake device, the drum 2 and the brake lever are linked to each other, and if the rotation direction of the drum 2 when the brake lever is operated during braking is set to the direction in which the coil portion 1c is loosened, the braking direction Can easily rotate the drum 2 and, after braking, the drum 2
Cannot rotate even if it rotates in the reverse direction, and the braking state is maintained. Then, if the free end 1b is pushed so as to loosen the coil portion 1c, the coil portion 1c cannot wind the outer periphery of the drum 2 and can release the braking.

[0005]

However, such a conventional technique has the following various problems to be improved.

(1) Since a lock load (a force for preventing the brake lever from returning in the braking state) concentrates on one end 1a of the elastic coil member 1 and a portion 1d connected thereto, a method of fixing the one end 1a ( Careful management of caulking, bolt tightening, and friction) was required, and considerable design and manufacturing time was required.

(2) Further, in order to make the tension concentratedly applied to a part of the elastic coil member 1 by the lock load to be within the range of the tensile strength of the wire, the entire elastic coil member 1 is formed. There was a problem that the coil diameter or the wire diameter had to be increased, resulting in an increase in size. In particular, in the direct operation system in which the coil is arranged at the center of rotation of the pedal without using a gear, the load applied to the strand cannot be reduced due to the gear ratio, and this problem is remarkable.

(3) Since one end of the elastic coil member is locked to the base side, once the free end 1b of the elastic coil member is pushed once by the release lever, regardless of the swing of the brake lever, the elastic coil member is driven. The member is maintained in a relaxed state, and the brake lever is instantly returned to the non-braking position by the tension of the brake cable. For this reason, it is necessary to provide a shock absorber for alleviating the impact force at the time of releasing the lock, which is a problem in reducing the number of parts, and in reducing the manufacturing cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is not necessary to manage and fix one end of an elastic coil member by a predetermined method, and the load applied to the elastic coil member is dispersed. It is an object of the present invention to provide a manual brake device that can reduce the diameter of a coil or a wire as a whole and does not need to provide a shock absorber that reduces an impact force at the time of release.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the present invention is as follows. 1. The base (31) of the brake lever (30) is swingable on a base (11) fixed to a vehicle body. It pivots, extends its tip to the vicinity of the operator, applies a force to this tip, and applies a brake cable (2
8) In a manual brake device in which a brake is applied by pushing and pulling, a drum (34) pivotally supported by the base side and rotated in response to swing of the brake lever.
And a plurality of shoes (51) arranged at predetermined intervals along the inner circumference of the drum, and a plurality of shoes (51) interposed between the respective shoes. A plurality of claws (26) extending from the base into the drum so as to prevent rotational movement of each shoe; and a plurality of claws (26) elastically contacting the inner peripheral surface of the shoe, one end of which is locked to the drum. An elastic coil member (52) in which the other end side is a free end side without being locked, and the winding direction is arranged such that the direction in which the brake lever returns from the braking state is the radially enlarged direction;
A manual brake device characterized in that a locking mechanism (50) is constituted by a release member (53) for reducing the diameter by pushing the free end side of the elastic coil member.

2. A base of a brake lever is pivotally supported on a base fixed to the vehicle body so as to be swingable, a tip of the base is extended near an operator, a force is applied to the tip, and a brake is applied according to the swing of the brake lever. In a manual brake device which applies a brake by pushing and pulling a cable, a drum pivotally supported by the base side and rotated in accordance with swinging of the brake lever, and a shaft slidingly contacting the outer peripheral surface of the drum A plurality of shoes, each having a right-angle cross section formed in an arc shape and arranged at predetermined intervals along the outer periphery of the drum, and the base being interposed between the shoes to prevent the rotational movement of each shoe from the base. A plurality of claws extending to the periphery and arranged so as to be in elastic contact with the outer peripheral surface of the shoe, one end is locked to the drum, the other end is a free end without being locked, and the brake lever is A locking mechanism is constituted by an elastic coil member arranged in a winding direction so that the direction of returning from the braking state is the diameter reducing direction, and a release member that presses the free end side of the elastic coil member to increase the diameter. And manual brake device.

3 A cylindrical support spring (54) elastically pressed against the peripheral surface of the elastic coil member and pressing the elastic coil member against the shoe is provided to provide a noise preventing structure. Item 1 or 2 characterized by the above-mentioned.
Manual brake device as described.

4. The manual brake device according to claim 1, wherein a liner member (55) is interposed between the elastic coil member and the shoe to prevent squeal and noise.

5 has one end locked to the release member,
A return spring (56) is provided so that the other end is locked to the drum and the restoring force is applied in a direction to return the release member to the non-operation position and return the brake lever from the braking state. Item 1, characterized by
The manual brake device according to 2, 3, or 4.

[0015]

When the brake lever (30) is in the released state, no braking reaction is applied to the base of the brake lever, and the brake cable (28) is relaxed. When the brake lever is rotated about the base from this state, the brake cable is pulled.

At this time, the drum (34) and the elastic coil member (52) rotate in response to the swing of the brake lever. Rotate relative to. This direction of rotation is a direction in which the elastic coil member moves away from the shoe by reducing or expanding the diameter, so that it easily rotates, and when the brake lever is sufficiently swung, the brake cable is contracted to generate a sufficient braking force. .

When the application of force to the brake lever is stopped, the brake lever attempts to return due to the braking reaction force from the brake cable. However, the direction of returning from the braking state is such that the elastic coil member expands in diameter due to the relative rotation of the elastic coil member with respect to the shoe. Alternatively, the diameter is reduced and the shoe is pressed against the drum,
A strong resistance is generated and the brake lever cannot return, and the braking state is maintained.

At this time, the force for preventing the rotation of the drum, that is, the brake lever (the above-described lock load) is a frictional force between the shoe and the drum, and this force is applied to the base side via a plurality of shoes. Burden on the formed nails.
For this reason, this locking load does not concentrate on a part of the elastic coil member, and the load applied to the elastic coil member is such that the shoe is pressed against the drum, and is distributed over the whole.

Then, when the release member (53) of the locking mechanism (50) is operated to push the free end (52b) side of the elastic coil member to release the restraint of the brake lever, the shoe is moved by the elastic coil member. The pressing state against the drum is temporarily released, and the drum and the brake lever swing toward the non-braking position. However, at this time, the elastic coil member also swings integrally with the brake lever or the like, so that the shoe and the elastic coil member rotate relative to each other, and the shoe is pressed against the drum again to be in a locked state.

In this way, each time the release member is operated or as the operation is continued, such swinging and stopping are intermittently or continuously repeated, and the brake lever is gradually released according to the operation speed of the release member. It returns to the operating position and the brake cable is completely relaxed.

When the support spring (54) is provided, when the shoe and the elastic coil member rotate relative to each other, the entire elastic coil member slides on the shoe with a substantially constant elastic force, and partially contacts the shoe. There is no sliding contact, and the occurrence of squeaking noise is suppressed due to the fact that the stick phenomenon hardly occurs.

Further, when the liner member (55) is provided, the shoe slides on the liner member but does not directly slide on the elastic coil member, so that the stick phenomenon of the elastic coil member hardly occurs. Again, the generation of unusual noises is suppressed.

Further, one end is locked to the release member, and the other end is locked to the drum, so that the restoring force is exerted in a direction of returning the release member to the non-operation position and returning the brake lever from the braking state. When the return spring (56) is provided, the return member is returned to the non-operation position and the return force of the brake lever is supported by the single return spring.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The manual brake device 10 is a foot-operated type, and a brake lever 3 is provided on a base 11 fixed to a vehicle body.
The base mechanism 31 is pivotally supported by a pivot shaft 32, and a locking mechanism 5 for restraining the brake lever 30 around the pivot shaft 32.
0 is provided.

As shown in FIG. 5, the base 11 is
Attachment portions 13a, 13b, 13c, 13d on which 2a, 12b, 12c, 12d are respectively formed, boss portions 14a, 14b at which both ends of pivot shaft 32 are respectively supported, and these attachment portions and the boss portions are connected. Multiple beams 15a, 15
b,... 21a, 21b, and has a rigid frame structure in which the joint between the beam and the mounting portion or the boss portion is a fixed node, and is manufactured by die casting, for example.

The base 11 is composed of two base components 11a and 11b, and is divided into two parts on the left and right sides in the axial direction of the pivot axis of the brake lever 30. That is, the mounting portion 13 is attached to the base constituent member 11a.
a, 13d, a boss portion 14a, and beams 15a,... 21a are formed, and the mounting portions 13b,
13c, a boss 14b, and beams 15b,..., 21b are formed, and the base constituent member 11a and the base constituent member 11b are formed.
25a, 25b are fixed by bolts at small boss portions 22a, 22b,... 25a, 25b formed at appropriate intervals at the ends of the beams.

The boss 14b of the base 11 is formed with three claws 26 extending from the equally-spaced position on the outer periphery toward the boss 14a. This claw 26
Is a component of the locking mechanism 50, and has a circular cross section perpendicular to the axis. Further, an arc-shaped slit 27 is formed in the boss 14b along the periphery of the center hole. The small boss portion 24b of the base component 11b
In the vicinity, a guide hole 12e through which a release cable for operating a release lever 53 described later is inserted and guided.
Are formed.

Here, the mounting holes 12a, 12
b, 12c, 12d, among the mounting holes 12a, 12b, 1
2c is for fixing the base 11 to the vehicle body with bolts, and the mounting hole 12d is for mounting the outer tube 29 of the brake cable 28 for transmitting the braking force as shown in FIG.

The brake lever 30 is pivotally supported with its base 31 sandwiched between the bosses 14a and 14b of the base 11. That is, the base 3 of the brake lever 30
1, a pivot boss 33 is formed as shown in FIG.
When the pivot boss 33 is fitted to the pivot shaft 32 via a bearing 34, the brake lever 30 is pivotably supported. As shown in FIG. 4, the pivot boss 33 has engaging portions 33 a, 3 to which one end of an elastic coil member 52 or a return spring 56 described later is locked.
3b is formed.

Outside the pivot boss 33 at the base 31 of the brake lever 30, a drum 34 having the same central axis as the pivot boss 33 is formed. This drum 34
Is sized so that the claw 26 is disposed inside, and a circumferential groove 35 is formed on the outer periphery on the base end side. The brake cable 28 is provided in the groove 3
5 is wound around the base end side of the drum 34 in a state of being fitted into the adjustment lever 5, and the end thereof is attached to an adjustment nut mechanism 35 provided on the base 31 side of the brake lever 30 so that the initial tension can be adjusted. .

The distal end of the brake lever 30 extends to the foot near the operator, and a pedal 36 having a tread surface 36a directed in the direction of the leg of the operator is fixed at the most distal end.
A pad 37 is attached to the tread surface 36a of No. 6. The pad 37 has an outer shape that does not protrude beyond the peripheral edge of the pedal 36, and is attached by inserting a projection 37a formed on the back surface thereof into a hole 36b formed in the center of the pedal 36.

As shown in FIGS. 3 and 4, the locking mechanism 50 includes the drum 34, the shoe 51, the claw 26,
Elastic coil member 52, release lever 53 (release member), support spring 54, liner member 5
5 and a return spring 56.

The shoes 51 are formed in an arc-shaped cross section perpendicular to the axis so as to be in sliding contact with the inner peripheral surface of the drum 34, and a plurality of the shoes 51 are arranged at predetermined intervals along the inner periphery of the drum 34 with the claws 26 interposed therebetween. In this case, three)
6 prevents the rotational movement.

The elastic coil member 52 is disposed so as to elastically contact the inner peripheral surface of the shoe 51, and is engaged with the drum 34 (brake lever 30) by fitting one end 52a into the engaging portion 33a. The end 52b is a free end side without being locked. The elastic coil member 52 expands in diameter due to friction generated by the relative rotation of the shoe 51 and the elastic coil member 52 when the brake lever 30 rotates in a direction returning from the braking state (counterclockwise direction in FIG. 1). , Its winding direction is set.

The release lever 53 is rotatably attached at its base end to the boss portion 14b of the base 11, and
b swings along the outer side surface thereof, a hook portion 53a is formed at the tip thereof, and the slit 2a is formed on the inner side surface.
7 extending through the inside of the drum 34
3b is formed.

The release lever 53 has a hook 53
a of which is pulled by a release cable guided in the guide hole 12e and swings counterclockwise in FIGS. 1 and 4 to move the elastic coil member 52 when the brake lever 30 is in the braking position. The tip of the projection 53b abuts on the free end 52b and pushes the free end 52b,
The diameter of the elastic coil member 52 is reduced.

The support spring 54 is attached to the inner peripheral surface of the elastic coil member 52 by elastic contact, has a C-shaped cross section, and has a cylindrical shape for elastically pressing the elastic coil member 52 against the shoe 51. Thus, a squealing noise prevention structure is configured.

The liner member 55 includes the elastic coil member 52
And one end 55a bent in the radial direction has a C-shaped cross section.
The rotation is prevented by being inserted between the hook 1 and the claw 26. The liner member 55 also constitutes a squeal and abnormal noise prevention structure.

The return spring 56 is a coil spring disposed inside the elastic coil member 52 along the outer circumference of the pivot boss 33, and one end 56a is provided at one end 56a.
The other end 56b is engaged with the projection 53b of the release lever 53. The return spring 56 has a restoring force of the release lever 5.
3 is pushed in the direction toward the non-operation position (clockwise direction in FIGS. 1 and 4), and the brake lever 30 is turned in the direction toward the non-braking position (counterclockwise direction in FIGS. 1 and 4). The direction and the mounting direction are set.

Next, the operation will be described. Brake lever 30
Is in the released state (the state shown in FIG. 1), no braking reaction force is applied to the base 31 of the brake lever 30, and the brake cable 28 is relaxed. When the brake lever 30 is swung clockwise in FIG. 1 by depressing the pedal 36 with a foot from this state, the brake cable 28 is pulled.

At this time, the drum 34 and the elastic coil member 52 rotate according to the swing of the brake lever 30,
Since the shoe 51 is prevented from rotating by the pawl 26 and does not move, the elastic coil member 52 rotates relative to the shoe 51. This rotation direction is a direction in which the elastic coil member 52 contracts in diameter and moves away from the shoe 51, so that it easily rotates, and when the brake lever 30 is sufficiently swung, the brake cable 28 is contracted to generate a sufficient braking force. I do.

When the stepping on the pedal 36 is stopped, the braking reaction force from the brake cable 28 and the return spring 56
Of the elastic coil member 52 due to the relative rotation of the elastic coil member 52 with respect to the shoe 51 (liner member 55).
2, the shoe 51 is pressed in a direction to press the drum 34 against the drum 34, and a strong resistance is generated, so that the brake lever 30 cannot return and the braking state is maintained.

At this time, the force (lock load) for preventing the rotation of the drum 34, that is, the brake lever 30, is a frictional force between the shoe 51 (liner member 55) and the drum 34, and this is a plurality of shoes. A plurality of claws 26 formed on the base 11 are borne via the base 51. For this reason,
This lock load does not concentrate on a part (for example, one end 52a) of the elastic coil member 52, and the load applied to the elastic coil member 52 is only a reaction force for pressing the shoe 51 against the drum 34. This load is spread throughout.

When the free end 52b of the elastic coil member 52 is pushed by operating the release lever 53 of the locking mechanism 50 to release the restraint of the brake lever 30, the elastic coil member 52 moves the shoe 51 to the drum 34. Is released once, the drum 34 and the brake lever 30 are released.
Rotates toward the non-braking position (counterclockwise in FIG. 1) by the braking reaction force from the brake cable 28 and the restoring force of the return spring 56. However, at this time, since the elastic coil member 52 also rotates integrally with the brake lever 30 and the like, the shoe 51 (liner member 55) and the elastic coil member rotate relative to each other, and the shoe 51 is pressed against the drum again, and the locked state is established. Becomes

In this way, each time the release lever 53 is operated or as the operation is continued, such rotation and stop are intermittently or continuously repeated, and the brake lever 30 is operated in accordance with the operation speed of the release lever 53. The brake cable 28 is returned to the non-operation position slowly, and the brake cable 28 is completely relaxed.

When the release cable is loosened, the release lever 53 returns to the non-operating position by the urging force of the return spring 56. In the above operation, when the shoe 51 and the elastic coil member 52 rotate relatively, the entire elastic coil member 52 slides on the shoe 51 with a substantially constant elastic force by the action of the support spring 54 and partially slides. Since the shoe 51 does not touch the elastic coil member 52 directly due to the interposition of the liner member 55, the stick phenomenon of the elastic coil member 52 is less likely to occur, and the generation of noise and noise is suppressed.

As described above, in the manual brake device, since the load does not act intensively on one end of the elastic coil member 52, it is not necessary to manage and fix the one end in a predetermined manner. It is possible to reduce the diameter of the coil or the diameter of the wire 52. When the brake is released, the brake lever 30 gradually returns to the non-operation position in accordance with the operation speed of the release lever 53, so that it is not necessary to provide a shock absorber for reducing the impact force.
Further, the dual action of the support spring 54 and the liner member 55 reliably prevents generation of unpleasant squeal and noise.

The above embodiment is an example in which a shoe and an elastic coil member are disposed inside the drum, which is an optimal mode from the viewpoint of miniaturization of the apparatus. The locking mechanism may be a sequentially arranged locking mechanism.

That is, the shoes are formed so as to be in sliding contact with the outer peripheral surface of the drum, the claws are provided between the shoes so as to extend around the drum so as to prevent the rotational movement of the shoes, and the elastic coil member is provided. The elastic coil member is arranged so as to be in elastic contact with the outer peripheral surface of the shoe via a liner member. The winding direction of the elastic coil member is set so that the direction in which the brake lever returns from the braking state is reduced in diameter. It is also possible to adopt a configuration in which the support ring is fitted outside the elastic coil member.

Further, the present invention is not limited to the one in which the brake lever and the drum are integrally provided as in the above-described embodiment, but may be applied to a structure in which these are separately provided and interlocked by a gear. The same operation and effect can be achieved such that it is not necessary to fix one end of the light emitting element. However,
By applying the present invention, it is not necessary to adopt such a configuration that has a disadvantage that the size is slightly increased and an extra configuration of a gear is required in order to obtain the load reduction effect by the gear ratio.

[0051]

According to the manual brake device of the present invention, since the load does not act intensively on one end of the elastic coil member, it is not necessary to manage and fix the one end in a predetermined manner. It is possible to reduce the coil diameter or the wire diameter of the member. Further, when the brake is released, the brake lever returns to the non-operation position slowly according to the operation speed of the release lever, so that it is not necessary to provide a shock absorber for reducing the impact force. Therefore, the design and manufacture of the manual brake device are facilitated, and the cost or the size of the device can be reduced.

Further, when the support spring is provided, when the shoe and the elastic coil member rotate relative to each other, the entire elastic coil member slides on the shoe with a substantially constant elastic force and partially slides. There is no contact, and the occurrence of squeak and noise is suppressed because the stick phenomenon caused by this does not easily occur.

When the liner member is provided, the shoe is in sliding contact with the liner member but not in direct contact with the elastic coil member, so that the stick phenomenon of the elastic coil member due to this is unlikely to occur. As a result, the generation of unusual noises is suppressed, so that the user is not discomforted and the practicality is improved.

Further, one end is locked to the release member, and the other end is locked to the drum, so that the release member returns to the non-operation position and the restoring force acts in the direction of returning the brake lever from the braking state. If a return spring is provided, the return member returns to the non-operation position and the return force of the brake lever is supported by the single return spring. The number of parts can be further reduced and cost can be reduced as compared with the conventional case where a spring is provided.

[Brief description of the drawings]

FIG. 1 is a side view of a manual brake device showing one embodiment of the present invention.

FIG. 2 is a view taken in the direction of the arrow II in FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV of FIG.

FIG. 5 is an exploded perspective view of a manual brake device showing one embodiment of the present invention.

FIG. 6 is a diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Manual brake device 11 ... Base 26 ... Claw 28 ... Brake cable 30 ... Brake lever 31 ... Base 34 ... Drum 50 ... Locking mechanism 51 ... Shoe 52 ... Elastic coil member 52b ... Free end 53 ... Release member (release lever) 54 ... Support spring 55 ... Liner member 56 ... Return spring

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60T 7/06 G05G 1/14 F16D 13/08

Claims (5)

(57) [Claims] A base portion of a brake lever is pivotally supported on a base fixed to a vehicle body so as to be swingable, a front end portion thereof is extended near an operator, and a force is applied to the front end portion. In a manual brake device in which a brake cable is pushed and pulled to apply a brake, a drum pivotally supported by the base side and rotated according to the swing of the brake lever, and slidably contacts an inner peripheral surface of the drum A plurality of shoes are formed at a predetermined interval along the inner periphery of the drum, and the base is interposed between the shoes to prevent rotational movement of each shoe. And a plurality of claws extending into the drum, and arranged so as to elastically contact the inner peripheral surface of the shoe, one end of which is locked to the drum, and the other end of which is a free end without being locked, and the brake lever is System The locking mechanism is constituted by an elastic coil member arranged in a winding direction so that the direction returning from the moving state is the radially expanding direction, and a release member that presses the free end side of the elastic coil member to reduce the diameter. And manual brake device. 2. A base of a brake lever is pivotally supported on a base fixed to a vehicle body so as to be swingable, a tip end thereof is extended near an operator, a force is applied to the tip end, and a swing is applied to the brake lever. In a manual brake device for applying a brake by pushing and pulling a brake cable, a drum pivotally supported by the base side and rotated in accordance with swinging of the brake lever, and slidably contacts an outer peripheral surface of the drum. A cross section perpendicular to the axis is formed in an arc shape, and a plurality of shoes are provided at predetermined intervals along the outer periphery of the drum. The base is interposed between the shoes to prevent the rotational movement of each shoe. A plurality of claws extending around the drum, arranged so as to be in elastic contact with the outer peripheral surface of the shoe, one end of which is locked to the drum, and the other end of which is free to lock without being locked, and the brake lever is A locking mechanism is constituted by an elastic coil member arranged in a winding direction so that a direction returning from the braking state is a diameter reducing direction, and a release member for pushing the free end side of the elastic coil member to increase the diameter. And manual brake device. 3. A squeak and noise control structure comprising a tubular support spring which is elastically attached to a peripheral surface of said elastic coil member and presses said elastic coil member elastically against said shoe. The manual brake device according to claim 1 or 2, wherein: 4. The manual brake device according to claim 1, wherein a liner member is interposed between said elastic coil member and said shoe to prevent squeal and noise. 5. One end is locked to the release member, and the other end is locked to the drum. The restoring force is applied in a direction to return the release member to the non-operation position and return the brake lever from the braking state. 5. The manual brake device according to claim 1, further comprising a return spring operatively mounted.