Patent Application
20070144421
1. Field
This invention relates to the methods and systems for a chain driven positioning device and more generally to the field of providing a chain driven positioning device for use in a vacuum environment.
2. Background
A positioning device may be a device used for repetitive operations, working in hostile environments, working in environments that people are not able to work, or for high volume work. The positioning devices typically have at least one moveable positioning arm to allow the positioning device to move objects from one location to another. The construction of the positioning arms used by the positioning devices typically includes at least one rotating shaft, at least one pulley, and at least one belt. The belt may be of a polymer type with reinforcing materials, similar to the belts used on an automobile engine. The belts may be used with pulleys, with the pulleys attached to the driving rotating shafts.
Belts can become worn and stretched over time, requiring maintenance to replace the belts. In some environments, the replacement of the belts may require the shut down of a system to allow access to the belts, adding to the cost of operating the positioning device and the system it supports. The belts may also become an issue in some environments, such as a vacuum system, where the belts may out gas during the vacuum pump down process.
Accordingly, a need exists for a positioning device that uses alternate materials for the belt to provide long life with minimal service requirements and can be used in many different environments.
Provided herein are methods and systems for providing a positioning arm; and driving the positioning arm with a chain. The chain may be a bicycle type chain. There may be at least one chain in the positioning arm. The chain material may be at least one of stainless steel, nickel plated steel, aluminum, and titanium. The positioning arm may contain at least two sprockets. The sprocket teeth may engage the chain. The sprockets may be the same size or the sprockets may be a different size. The sprocket material may be at least one of stainless steel, nickel plated steel, aluminum, and titanium. A chain drive position arm may contain the chain, at least two sprockets, and the positioning arm. At least one sprocket may be a drive sprocket mounted on a rotating shaft.
A positioning device may contain at least one chain drive position arm. The chain drive position arm may be in a vacuum. The chain drive position arm may have a lubrication material. The lubrication material may be at least one of a vacuum compatible grease and perfluorinated hydrocarbons. A sealed lubrication enclosure may contain a flexible container, the lubrication material, at least one chain, and at least one sprocket. The flexible container may be a polymer material. The sealed lubrication enclosure may have a fixed seal on a rotating shaft. The fixed seal may partially twist the flexible container during the chain drive position arm movement. The chain drive position arm may rotate less than 360 degrees on the rotating shaft. The sealed lubrication enclosure may be evacuated of gases. A self-sealing spring may provide the fixed seal on the rotating shaft when the gases are evacuated.
A self-adjusting tensioner may maintain the chain tension during operation. There may be at least one self-adjusting tensioner for the chain. The self-adjusting tensioner may contain a spring, the chain, and a ratchet. There may be at least one ratchet. The spring may push the chain into the self-adjusting tensioner. The spring may push the chain toward the ratchet when the chain is not in tension. The ratchet may engage a chain link. The spring may push the chain link onto the ratchet. The chain may be in tension when the ratchet locks on the chain link.
The chain drive positioning device may be understood by reference to the following figures:
Referring to
The positioning arm 100 may contain a chain 110, sprockets 104108, and rotating shaft 114118. The chain 110 may be driven by a drive sprocket 104 that may be mounted on a rotating shaft 114. The chain 110 may engage at least one additional sprocket 108 on a shaft 118, this sprocket 108 and shaft 118 may be used to drive an additional positioning arms that may be connected to the shaft 118. The sprockets 104108 of the positioning arm 100 may be the same diameter or of differing diameters. Sprockets 104108 that are the same size may provide a one to one positioning ratio for the positioning arm 100, sprockets 104108 of a different size may provide a gearing ratio that may allow the positioning arm 100 to move faster or slower than the rotating shaft 114 of the drive sprocket 104. It would be obvious to a person knowledgeable in the art that a robotic device may have a plurality of rotating drive shafts 112114 for the positioning of a plurality of positioning arms or providing multiple axis motion to the robotic device.
The use of a chain 100 to drive the positioning arm 100 may be superior to other types of drive devices, such as a belt, that may slip as it becomes worn or loose in time. A belt that allows slippage between the belt and the rotating shafts may provide reduced positioning precision than a chain that is locked on the teeth of a sprocket. The chain 110 engagement to the sprockets 104108 may provide a not slip configuration by the chain 110 interlocking with the teeth of the sprockets 104108.
It should be understood that the chain 110 may be made of different materials and sizes (e.g. thickness of material, height, width, or length) to provide the tension strength required by positioning arm 100. The chain 110 and sprocket 104108 material may be at least one of stainless steel, nickel plated steel, aluminum, and titanium. It should also be understood that there may be more than one chain 110 and sprocket 104108 assembly in a positioning arm. For example, a second chain and sprocket may be used for additional strength on the same rotating shaft or may be used to drive more than one additional positioning arm on a second rotating shaft. The additional chain and sprocket assembly may use a different sprocket diameter and may be driven by a different rotating shaft.
Referring to
A sealed lubrication enclosure 200 may be used to enclose the chain 110 and sprockets 104108 as described in
When the rotating shaft rotates, the sealed lubrication enclosure 200 may twist at the fixed seal 204 without tearing. There may be an interface 202 between the fixed seal 204 and the sealed lubrication enclosure 200 to aid in the twisting of the sealed lubrication enclosure. The interface 202 may have extra material or may have an accordion type design to allow the twisting required by the positioning arm motion.
In an embodiment, with the fixed seal 204 in place for at least one rotating shaft, the positioning arm 100 may be limited in the rotational travel. Instead of rotating a full 360 degrees, the positioning arm 100 with a sealed lubrication enclosure 200 may oscillate back and forth to reach all of the required positions for the positioning device. There may be a limiting device (e.g. mechanical, electrical, or programmed) to limit the rotation motion of the positioning arm 100.
Referring to
Referring to
The detail of the self-adjusting tensioner 400 shows one embodiment of a self-adjusting tensioner 400 design. One end of the chain 410 may be connected to one side of a housing 418. The other end of the chain 402 may pass into the housing 418 and connect to a plate 414. The plate 414 may not be anchored to the housing 418 and may be free moving within the housing 418 or the plate 414 may be attached to the housing 418 using a slide to allow freedom of motion within the housing 418. The chain 402 may also pass through a spring 404, the spring 404 may be positioned between housing 418 and the plate 414. The spring 404 may be of a large enough diameter to allow the chain 402 to pass inside the spring 404 diameter and connect to the plate 414. The spring 404 may be compressed between the housing 418 and the plate 414 when the chain 402 is extended to its max length. With the spring 404 in compression, a force in a direction 408 is applied to the chain 402 exerting a force on the chain 402 to “push” the chain 402 into the housing 418. The spring 404 push on the chain 414 into the housing 418 may remove slack from the chain 110.
To maintain rigidity in the chain 110 when the chain 110 is in tension, the self-adjusting tensioner 400 may have a ratchet 412 that may engage and lock the chain 402. It would be obvious to a person knowledgeable in the art that the location, design, and number of ratchets may vary based on the selected chain 110, spring 404, and housing 418 design. During a move sequence of the chain 110, when the self-adjusting tensioner 400 is on the less tension side of the chain 110, the spring may push the slack chain 402 into the housing 418. The ratchet 412 may automatically lock onto the closest chain 402 link when the spring 404 pushes the chain 402 into the housing. Once the ratchet 412 has locked onto a chain 402 link the chain will be constrained for the next move that has the chain 402 in tension. It should be understood that the self-adjusting tensioner 400 may have at least one ratchet 412. With every chain 110 move the self-adjusting tensioner 400 may attempt to adjust the chain link that the ratchet 412 is locked on. It should be understood that the ratchet 412 may only lock onto an different chain link when the chain 110 has stretched enough to permit locking onto a different chain link.
While the invention has been described in connection with certain preferred embodiments, other embodiments would be understood by one of ordinary skill in the art and are encompassed herein.
