Locking cam stop

Abstract

A locking cam stop conducts rotation from a driving part, such as a tire ring, to a driven part, such as a rotary dryer or kiln. The device utilizes clamping cams with logarithmic profiles to secure the tire ring without welding or direct attachment, only frictional force. The cams provide immediate, powerful holding force in the desired direction, while allowing free counter-rotation when necessary. The device utilizes a tension link to maintain sufficient contact with the tire ring, ensuring that the cams will engage and hold the tire ring when necessary.

Claims

1. A locking cam stop for conducting rotation from a driving part to a driven part, the locking cam stop comprising: a pair of riser blocks securable to the driven part; a pair of rotatable cams, one each secured to each of the pair of riser blocks; and a tension link connected between the pair of rotatable cams, wherein the rotatable cams include a logarithmic spiral cam profile, and wherein the rotatable cams are displaceable in an axial direction into engagement with the driving part by rotation according to the logarithmic spiral cam profile, wherein when the rotatable cams are engaged with the driving part, the driven part is rotated by the driving part.

2. A locking cam stop according to claim 1, wherein the pair of rotatable cams are positioned on axial opposite sides of the driving part.

3. A locking cam stop according to claim 2, wherein the tension link urges the locking cams toward each other.

4. A locking cam stop according to claim 1, wherein the tension link urges the locking cams toward each other.

5. A locking cam stop according to claim 1, wherein the tension link comprises a spring.

6. A locking cam stop according to claim 1, wherein the locking cams are rotatable on posts respectively secured in the pair of riser blocks.

7. A locking cam stop according to claim 1, wherein functional surfaces of the rotatable cams are roughened.

8. A rotary drum assembly comprising: a rotary drum supported for rotation about a longitudinal axis; a tire ring disposed surrounding the rotary drum; and a locking cam stop that conducts rotation from the tire ring to the rotary drum, the locking cam stop including: a pair of riser blocks securable to the rotary drum, a pair of rotatable cams, one each secured to each of the pair of riser blocks, and a tension link connected between the pair of rotatable cams, wherein the rotatable cams include a logarithmic spiral cam profile, and wherein the rotatable cams are displaceable in an axial direction into engagement with the tire ring by rotation according to the logarithmic spiral cam profile, wherein when the rotatable cams are engaged with the tire ring, the rotary drum is rotated by the tire ring.

9. A rotary drum assembly according to claim 8, wherein the pair of rotatable cams are positioned on axial opposite sides of the driving part.

10. A rotary drum assembly according to claim 9, wherein the tension link urges the locking cams toward each other.

11. A rotary drum assembly according to claim 8, wherein the tension link urges the locking cams toward each other.

12. A rotary drum assembly according to claim 8, wherein the tension link comprises a spring.

13. A rotary drum assembly according to claim 8, wherein the locking cams are rotatable on posts respectively secured in the pair of riser blocks.

14. A rotary drum according to claim 8, wherein functional surfaces of the rotatable cams are roughened.

15. A locking cam stop for conducting rotation from a tire ring to a rotary drum, the locking cam stop comprising: a pair of rotatable cams disposed on opposite sides of the tire ring, wherein the rotatable cams include a logarithmic spiral cam profile; and a tension link connected between the pair of rotatable cams, the tension link including a spring that urges the rotatable cams toward each other, wherein the rotatable cams are displaceable in an axial direction into engagement with a driving part by rotation according to the logarithmic spiral cam profile.

16. A locking cam stop according to claim 15, wherein the tension link is disposed offset from a plane defined by cam surfaces of the rotatable cams.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects and advantages will be described in detail with reference to the accompanying drawings, in which:

(2) FIG. 1 is a plan view of the locking cam stop according to the described embodiments;

(3) FIG. 2 is a perspective view of the locking cam stop; and

(4) FIG. 3 is a plan view of a locking cam stop conducting rotation from a tire ring to a rotary dryer.

DETAILED DESCRIPTION OF THE INVENTION

(5) With reference to the drawings, a locking cam stop 10 includes a pair of riser blocks 12 that may be secured to a driven part, such as a rotary dryer, in one or more locations. One each of a pair of rotatable cams 14 is secured to each of the riser blocks 12. As shown in FIG. 3, the cams 14 are positioned on axial opposite sides of a driving part or tire ring 20. The cams 14 are rotatable on a post 16 cooperable with the riser blocks 12. The rotatable cams are provided with a logarithmic spiral cam profile.

(6) A tension link 18 is connected between the pair of rotatable cams 14. The tension link 18 preferably includes a spring or other elastic member and acts to pull the rotatable cams 14 toward each other. The rotatable cams 14 are displaceable in an axial direction (A in FIG. 1) into engagement with the driving part by rotation according to the logarithmic spiral cam profile.

(7) A roughening process such as linear knurling or the like may be added to the functional services of the cams 14 to ensure that a sufficient frictional surface is present. The assembly is designed so that it may be installed on existing dryers or retrofit to older designs.

(8) In operation, rotational force is applied to the tire ring 20 in a direction perpendicular to the assembly. Friction between the tire ring 20 and the cams 14 translates the tire ring 20 applied force into a normal force, resulting in a clamping action on the sides of the tire ring 20. The cams 14 provide sufficient frictional force to hold the tire ring 20 relative to the assembly and ensure that the rotary drum 22 rotates with the tire ring 20. This may be accomplished by designing the assembly so that each cam 14 contacts the tire ring 20 at a calculated angle, based on the coefficient of friction between the respective materials (e.g., steel-on-steel). Per Amontons's First Law of Friction, the force of friction is directly proportional to the applied load. Utilizing the equation for frictional force and calculations determined by a free body diagram of the system, a direct relationship between coefficient of friction and maximum cam angle can be determined. The final cam angle is determined with safety factor considerations, maximum resultant load calculations, and experimentation.

(9) The logarithmic spiral cam profile guarantees that the desired cam angle is always met. A logarithmic spiral is a spiral such that the angle between the tangent and the radius vector is the same for all points of the spiral. In polar coordinates (r, ), the logarithmic curve can be written as: r=ae.sup.b, where r is the distance from the origin, is the angle from the x-axis, and a and b are arbitrary constants. At any chosen point along the spiral, the tangent and radial vectors create the same angle between them (, alpha). This establishes that at any point along the logarithmic surface, a mechanism translating force through tangential contact will be exerting that force at the same angle, relative to the center of the spiral; and therefore, the magnitude of the force will be same, regardless of contact location.

(10) In the designed cam 14, the post 16 is placed at the center of the logarithmic spiral, so that as the cam 14 rotates, the cam face follows the logarithmic curvature. This ensures that the cam 14 will always contact the tangent surface of the tire ring 20 at the same angle, regardless of radial distance (within the designed range of the cam). In other words, the distance between the cam post 16 and the tire 20 is noncritical and can be adjusted, and the results will not be affected. This profile will allow for installation error, tire defects, cam wear, etc., and still provide the same required holding force.

(11) As shown in FIG. 2, the tension link 18 is disposed offset from a plane defined by the cam surfaces of the rotatable cams 14. Preferably, the tension link 18 is positioned on an underside of the cams 14 so that the driving part or tire ring 20 is positioned in the space between the cam surfaces.

(12) The locking cam stop thus secures a driven part, such as a rotary drum, to a driving part, such as a tire ring, in the direction of rotation. In the rotary dryer example, the assembly is attached to the drum, and when force is applied to the tire ring, the assembly will hold the tire ring, pulling the drum around with it. The device can provide release of the tire ring and allow it to slip, relative to the drum if counter-rotational motion occurs. The device thus allows a slow and dampened stop, rather than abrupt, reducing the possibility for added stress and damage. Installation direction is dependent on the direction of drum rotation.

(13) The device secures the rotary drum to its tire ring using frictional force. In the exemplary embodiment, the assembly makes contact by steel pressed against steel with no welding or other direct attachment to the tire ring. The friction between the two objects will hold the tire ring with a force proportional to the rotational force of the tire ring.

(14) While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.