1. A pulley structure comprising:
a first rotatable body having a cylindrical shape, over which a belt is stretched;
a second rotatable body that is provided inward of the first rotatable body so as to be rotatable relative to the first rotatable body; and
a torsional coil spring that is accommodated in a space between the first rotatable body and the second rotatable body,
wherein the torsional coil spring has one end region at one end side thereof, the outer circumferential surface of which is in contact with one rotatable body of the first rotatable body and the second rotatable body due to the self elastic restoring force of the torsional coil spring in a diameter increasing direction when the pulley structure is in a stopped state; the other end region at the other end side thereof, the inner circumferential surface of which is in contact with the other rotatable body when the pulley structure is in the stopped state; and a middle region, and
wherein when the torsional coil spring is twisted in the diameter increasing direction due to a relative rotation between the two rotatable bodies, the inner circumferential surface of at least a circumferential portion of the other end region of the torsional coil spring separates from the other rotatable body.
2. The pulley structure according to claim 1,
wherein the other rotatable body has a contact surface that faces an end surface of the other end side of the torsional coil spring in a circumferential direction, and
wherein when the torsional coil spring is twisted in the diameter increasing direction due to a relative rotation between the two rotatable bodies, the end surface of the other end side of the torsional coil spring is brought into contact with the contact surface.
3. The pulley structure according to claim 2, further comprising:
a first gap that is formed between the outer circumferential surface of the other end region of the torsional coil spring and the first rotatable body or the second rotatable body, when the pulley structure is in the stopped state,
wherein when the torsional coil spring is twisted in the diameter increasing direction due to a relative rotation between the two rotatable bodies, the outer circumferential surface of the other end region of the torsional coil spring is not in contact with any one of the two rotatable bodies when the end surface of the other end side of the torsional coil spring is in contact with the contact surface.
4. The pulley structure according to claim 3, further comprising:
a second gap that is formed between an outer circumferential surface of the middle region of the torsional coil spring and the first rotatable body or the second rotatable body, when the pulley structure is in the stopped state.
5. The pulley structure according to claim 4,
wherein the size of the first gap is less than or equal to the size of the second gap.
6. The pulley structure according to claim 2, further comprising
a limiting means for limiting a deformation of the other end region of the torsional coil spring in the diameter increasing direction before the end surface of the other end side of the torsional coil spring is in contact with the contact surface when the torsional coil spring is twisted in the diameter increasing direction due to a relative rotation between the two rotatable bodies.
7. The pulley structure according to claim 6,
wherein the other rotatable body has the limiting means.
8. The pulley structure according to claim 7,
wherein the limiting means is at least one supporting protrusion that protrudes inwards in a radial direction and that faces an outer circumferential surface of a circumferential portion of the other end region of the torsional coil spring, and
wherein when the torsional coil spring is twisted in the diameter increasing direction due to a relative rotation between the two rotatable bodies, at least the one supporting protrusion is in contact with the outer circumferential surface of the other end region of the torsional coil spring and a deformation of the other end region of the torsional coil spring in the diameter increasing direction is limited.
9. The pulley structure according to claim 8,
wherein a region in which the supporting protrusion is formed contains a position distant from the contact surface by 90\xb0 about a rotation axis.
10. The pulley structure according to claim 9,
wherein an angle about the rotation axis formed by the contact surface and a farther end portion of the region in which the supporting protrusion is formed from the contact surface is less than or equal to 315\xb0.
11. The pulley structure according to claim 8, further comprising
a fourth gap that is formed between the outer circumferential surface of the other end region of the torsional coil spring and a portion other than the supporting protrusion of the other rotatable body when the pulley structure is in the stopped state,
wherein the outer circumferential surface of the other end region of the torsional coil spring is in contact with the supporting protrusion, or the pulley structure further comprises a third gap that is formed between the outer circumferential surface of the other end region of the torsional coil spring and the supporting protrusion and is smaller than the fourth gap.
12. The pulley structure according to claim 6,
wherein the torsional coil spring has the limiting means.
13. The pulley structure according to claim 12,
wherein the limiting means is at least one supporting protrusion that protrudes outwards in the radial direction and that is present on the outer circumferential surface of a circumferential portion of the other end region of the torsional coil spring, and
wherein when the torsional coil spring is twisted in the diameter increasing direction due to a relative rotation between the two rotatable bodies, at least the one supporting protrusion is in contact with an inner circumferential surface of the other rotatable body and a deformation of the other end region of the torsional coil spring in the diameter increasing direction is limited.
14. The pulley structure according to claim 6, further comprising
a second gap that is formed between the outer circumferential surface of the middle region of the torsional coil spring and the first rotatable body or the second rotatable body when the pulley structure is in the stopped state.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus for removing a component attached to a printed circuit board (PCB) from said PCB, comprising:
a heating element including a heating element body including a vacuum port in operative communication with a vacuum source;
a plurality of contact plates each comprising a platform extending from a respective one of said plurality of contact plates, wherein said platform of each of said plurality of contact plates comprises a different profile corresponding to different components to be removed from said PCB;
a contact plate selected from said plurality of contact plates in thermal communication with said heating element, wherein said platform of said contact plate has a substantially identical profile as said component; and
a vacuum retention port extending through said contact plate and operative to selectively communicate with said vacuum source, wherein said vacuum port and said vacuum retention port are offset and a channel defined in said contact plate establishes fluid communication between said vacuum port and said vacuum retention port, and wherein said vacuum retention port of each of said plurality of contact plates is in a unique offset location with respect to said vacuum retention ports of others of said plurality of contact plates;
wherein when said platform is in contact with said component attached to said PCB said heating element heats said component and said vacuum retention port is covered by said component and the PCB is not contacted by said contact plate.
2. The apparatus of claim 1, wherein said component is an electro-magnetic shield operative to protect components on said PCB from electro-magnetic interference.
3. The apparatus of claim 2, wherein said component is a radio-frequency (RF) shield operative to protect components on said PCB from radio-frequency (RF) interference.
4. The apparatus of claim 1, wherein said contact plate is removably attachable to said heating element.
5. The apparatus of claim 4, wherein said vacuum retention port terminates at an interface between said platform and said component when said contact plate is in contact with said component.
6. The apparatus of claim 1, wherein said contact plate is clamped to said heating element using at least one clamping mechanism.
7. The apparatus of claim 1, further comprising:
a temperature controller operative to control said heating element to maintain a predetermined temperature of said contact plate.
8. The apparatus of claim 7, further comprising a vacuum controller operative to control a vacuum at said vacuum retention port to selectively establish said vacuum at said vacuum retention port.
9. The apparatus of claim 1, further comprising:
a PCB holder operative to hold said PCB stationary when said contact plate is in contact with said component.
10. An automated system for removing a component attached to a printed circuit board (PCB) from said PCB, comprising:
a PCB having a component attached thereto;
a heating element;
a contact plate assembly comprising:
a contact plate removably attached to said heating element and in thermal communication with said heating element; and
a vacuum retention port extending through said contact plate and in selective communication with a vacuum source such that a vacuum is selectively established at said vacuum retention port;
an actuator engaged with said contact plate assembly and operative to move said contact plate assembly with respect to said PCB between a contacting position and a non-contacting position, wherein when in said contacting position said contact plate contacts said component attached to said PCB and said vacuum retention port is located at an interface between said contact plate and said component and said component covers said vacuum retention port, and wherein when in said contacting position, no portion of said contact plate assembly contacts said PCB; and
a PCB holder operatively engaged with said PCB;
a slide to which said PCB holder is attached, said slide being operative to move with respect to said contact plate from a loading position to a work position, wherein when in said loading position, said PCB holder is accessible by an operator such that a PCB may be loaded onto said PCB holder, and wherein when in said work position, said PCB is aligned with said contact plate such that actuation of said actuator results in placement of said contact plate in said contacting position;
a controller operative to control said heating element to maintain a predetermined temperature at said contact plate, control said vacuum source such that vacuum may be selectively established at said vacuum retention port, and control said actuator to position said contact plate between said non-contacting position and said contacting position, wherein said controller is operative to control said actuator in response to movement of said slide to said work position, to position said contact plate from said non-contraction position to said contacting position, maintain said contact plate in said contacting position for a predetermined amount of time, and after said predetermined amount of time, move said contacting plate to said non-contacting position while controlling the vacuum source to establish a vacuum at said vacuum retention port, wherein when in said contacting position said contact plate heats said component and said vacuum is maintained at said vacuum retention port, such that when said contact plate assembly is moved to said non-contacting position said component is held against said contact plate by said vacuum and removed from said PCB engaged by said PCB holder; and
a component disposal drawer operative to move with respect to said contact plate from a closed position to an open position, wherein when said component disposal drawer is in said open position, upon termination of said vacuum at said vacuum retention port, said component separates from said contact plate and is disposed within said component disposal drawer.
11. The apparatus of claim 1, wherein no portion of said contact plate extends beyond said platform in a direction toward said PCB when said platform is in contact with said component attached to said PCB.
12. The apparatus of claim 1, wherein said unique offset location corresponds to one of said different components to be removed.