Minimum grip sprocket drive system

A minimum grip drive sprocket. A sprocket having a knurled chain engagement surface rotably engages a drive chain typically in an environment exposed to a slick or lubricating medium allowing an acceptable degree of drive chain slip while maintaining rotation of the minimum grip drive socket.

TECHNICAL FIELD

This description relates generally to drive mechanisms and more specifically to drive mechanisms used in slippery environments.

BACKGROUND

Exemplary, parts washers are often used in machine shops, manufacturing, automotive transmission, and engine repair shops. Also used in cleaning are soak tanks. Soak tanks are vessels containing a solvent, such as a mixture of water and detergent, which may take hours to “soften” the built-up road grime, fluids, tars, and oils enough to be manually rinsed off prior to disassembly and repair. Heating the solution and brushing can aid in loosening dirt and grime.

Gasoline, diesel fuel, and kerosene were commonly used to clean and degrease parts. Later, chlorinated solvents used in vapor degreasers were common. Environmental concerns led to the banning of chlorinated solvents for parts cleaning, which lead back to aqueous-based cleaning systems, but with improvements. Hydraulic sprays may be used to improve the cleaning of parts by directing a pressurized solvent stream at a part from nozzles typically placed in fixed locations, as is the case in manufacturing, so that spray may be applied where needed to effectuate cleaning. Typically a parts washer may require a drive system to move various mechanical components like conveyors, pumps and the like.

Typically, such machinery through the use of such solvents, greases and oils on parts being cleansed tends to broadcast, spray, or deposit slippery substances on the machine and over nearby surfaces. This may cause problems with mechanical linkages that may be used to drive various components by friction. Also, it may be advantageous to have a drive system that has a limited amount of slip built in, so that if a device being driven jams that the device attempting to turn it does not burn out.

A common low cost drive mechanism with built in slip may be a drive belt and pulley system. However, in a slick environment the lubricating substances can foul the belt causing it to completely loose friction, and hence drive capability. A typical solution could be to use gears that engage each other directly. However, gears tend to be expensive to produce and require more precise alignment for proper engagement. Also, direct gears are unforgiving as there is no slip between the driving gear and the gear being driven. Typically a clutch might be included to provide some slippage.

Another solution might be to use a drive chain and a toothed sprocket. However while low cost, no built in slip is allowed with a sprocket. Typically a clutch might be included to provide some slippage.

It would be advantageous to have a drive system with limited slip that works in a slippery environment that contains fluids and other slippery substances, is inexpensive and has some built in slippage when driven.

SUMMARY

The present example provides a minimum grip drive sprocket having a knurled chain engagement surface that rotably engages a drive chain typically in an environment exposed to a slick or lubricating medium allowing an acceptable degree of drive chain slip while maintaining rotation of the minimum grip drive socket.

DETAILED DESCRIPTION

The examples below describe a minimum grip sprocket and a drive system utilizing the minimum grip sprocket. Although the present examples are described and illustrated herein as being implemented in a parts cleaning system, the system described is provided as an example and not a limitation. As those skilled in the art will appreciate, the present examples are suitable for application in a variety of different types of systems in which the drive may be subjected to fouling by wet and/or slippery substances.

The minimum grip drive sprocket is useful in applications where slippery substances are present that might foul, or cause complete loss of traction. The minimum grip drive sprocket may slip somewhat, but in general it continues to engage with a coupled drive chain—even when coated with slick and slippery substances. To help maintain the proper slippage the somewhat deep knurling tends to push out excess grease and oil to maintain sufficient engagement.

The minimum grip drive sprocket is particularly useful as a cost effective drive system in low torque applications, and those where some slippage may be tolerated or desired, as opposed to directly engaging gears. A conventional toothed drive sprocket when used in such an environment tends to lock up, as it does not allow slippage. Accordingly a clutch is not needed to allow for slippage as would be needed in a toothed gear sprocket system. It is also worth noting that a rubber belt tends to foul and completely loose traction in a slippery environment. The minimum grip sprocket tends to maintain traction with an acceptable amount of slippage in an oily environment and eliminate the need for a clutch.

FIG.1is a top view of a minimum grip drive sprocket (or as used herein “sprocket”)101engaged with a chain link12and having exaggerated features for descriptive purposes. The minimum grip drive sprocket body1is generally round and ring shaped, with a knurled minimum grip drive sprocket outer edge3, and a minimum grip drive sprocket inner edge2as shown. The body may also include a top bevel4adjacent to the minimum grip drive sprocket outer edge3. The minimum grip drive sprocket101turns about a center axis of rotation8.

The minimum grip drive sprocket outer edge3may include a knurled103pattern that can include various patterns of ridges6and groves7. The knurling103may be provided to aid in engaging the rollers13of a chain to turn the chain. One chain link12of an exemplary drive chain is shown in engagement with the minimum grip drive sprocket101. The chain link shown is a conventional drive chain including links14for retaining rollers13, and coupling to adjacent links (not shown) that make up the drive chain. The minimum grip drive sprocket101may also include a bevel4that thins the body1material so that the rollers13of the chain may contact the knurled103outer edge3.

The exemplary minimum grip drive sprocket101may be constructed from ferrous metal, although in equivalent examples, aluminum, brass, plastic, nylon or the like may be used.

FIG.2is a side view of a minimum grip drive sprocket101and having exaggerated features for descriptive purposes. The minimum grip drive sprocket101includes a circular aperture10, centered about a centerline, or axis of rotation9. The edge of the minimum grip drive sprocket101may be beveled on one, or both sides4,5. The bevels4,5are formed so that the edge3of the minimum grip drive sprocket fits between the links of a conventional metal, or the like, drive chain (14ofFIG.1). The thickness of the minimum grip drive sprocket at the beveled edge must not be so thick as to prevent the knurled outer edge from contacting, and subsequently driving, rollers (113ofFIG.1) of a drive chain (12ofFIG.1).

Adjacent to the outer edge of the minimum grip drive sprocket3there are typically a bevels4,5, reducing the thickness11of the minimum grip drive sprocket101. A reduction in thickness may be desired to provide clearance of the space between the links of an engaged drive chain (not shown) so that the knurled103outer edge may engage the chain roller links (not shown). Various types of reductions in thickness may be provided. Here a linear reduction from overall thickness11to minimum grip drive sprocket outer edge thickness3is a linear taper. However in equivalent examples reductions of thickness may be made by one or more steps or the like.

The ring shape facilitates coupling to a hub (ofFIG.7) inserted through the aperture10. However, in alternative examples (not shown) the minimum grip drive sprocket101may be disk shaped rather than ring shaped, or equivalent, to attach to a shaft passing through the center of the minimum grip drive sprocket rather than a hub.

The surface of the outer minimum grip drive sprocket edge3is typically parallel to an axis of rotation9of an installed minimum grip drive sprocket101.

The knurl103may be in a pattern of parallel lines as shown, or other equivalent pattern (cross hatched, dimpled or the like) disposed around the outer edge of the minimum grip drive sprocket101. Alternatively other irregular or rough surfaces may be utilized that are sufficient to contact the rollers of a drive chain, to the extent needed to turn the minimum grip drive sprocket101, while allowing some slippage. The knurl103in the example shown is a series of parallel groves7and ridges. In practice the knurled pattern may be considerably finer than as shown here.

FIGS.1-2show the minimum grip drive sprocket101from the top and side. The sprocket has a body1formed from a flat work piece (typically metal, or the like) of uniform thickness11. It has a top side and a bottom side of defined thickness11. It is circular with an outer sprocket edge3, and a concentric aperture10disposed therein. The sprocket101is beveled on the top4and bottom5around the outer edge3to reduce its thickness on the outer edge. The sprocket101includes a top bevel4around the top outer edge, and a matching bottom bevel5around the bottom edge. The bevels4,5reduce the thickness of sprocket body1to that of a sprocket outer edge3.

The sprocket outer edge3may be knurled or textured. The top and bottom bevels are calculated to reduce the sprocket thickness so that parallel chain links clear the sprocket in the beveled area and allow the sprocket outer edge to engage rollers of the chain with its knurled outer edge.

FIG.3is a magnified side view of a minimum grip drive sprocket101engaged with a chain link12and having exaggerated features for descriptive purposes. The thickness11of the minimum grip drive sprocket101may be made thin enough so that no bevel is needed to clear the chain links14, or in the case of thicker minimum grip drive sprockets101beveled on the top4, and or bottom5so that the minimum grip drive sprocket outer edge3, with knurled103groves7and ridges6, may extend to the rollers13. The knurls tend to provide traction against the rollers13in a slippery environment. Alternatively, if something happens to prevent the chain from turning the minimum grip drive sprocket may continue to turn by slipping over the knurled103surface of the minimum grip drive sprocket101. If not beveled the links14would contact the minimum grip drive sprocket101first preventing the knurled surface103from contacting the rollers13. When sized so that the rollers13contact the outer edge3the bevel may be sized so that the links14contact the minimum grip drive sprocket101, or sized so that there is clearance15between the minimum grip drive sprocket101and links14. The bevels4,5also tend to center the chain12on the minimum grip drive sprocket101.

FIG.4is a side view of a first example of a minimum grip drive sprocket101engaged with a chain link12. This drawing is of truer proportion to a fabricated minimum grip drive sprocket101. The knurling103contacting the roller13is quite fine. Top and bottom bevels4,5provide a clearance15on both sides of the minimum grip drive sprocket101so that links14do not interfere with the knurl103contacting the chain rollers13.

FIG.5is an inclined edge view of the first example of the minimum grip drive sprocket101. The minimum grip drive sprocket101thins down to a reduced thickness beveled edge105having groves7and ridges6on the outer circumference16.

FIG.6is a top view of the first example of the minimum grip drive sprocket101. In this example the top bevel extends over about a third of the width of the ring body1. The thickness of the minimum grip drive sprocket between the minimum grip drive sprocket outer3and inner edge2is somewhat narrow as this exemplary minimum grip drive sprocket is made to fit over a hub (not shown). The outer edge3includes a knurled pattern103.

FIG.7shows an inclined view of the first example of a minimum grip drive sprocket101attached to a hub303. Here the minimum grip drive sprocket101is welded in spots to the hub303. This allows a flexible positioning of the minimum grip drive sprocket101, as it may be attached at various positions along the hub303surface. Alternatively the hub and minimum grip drive sprocket may be formed as one piece. Also the minimum grip drive sprocket may be attached to the hub by any equivalent method known to those skilled in the art in the various positions along the hub or continuously.

FIG.8shows the first example of a minimum grip drive sprocket in use in a machine such as an exemplary parts washer507. Here two minimum grip drive sprockets and hubs301are coupled via a drive chain501. A chain tensioner503is provided to take out slack that may be present in the chain, typically through mechanical bias such as a spring or the like. It will be noted that a clutch is not present in the drive train as it is not needed since the slippage in the minimum grip drive sprocket and hub301, make a clutch unnecessary should a jam occur in the drive train301501where one component stops rotating or “locks”. The chain will continue to move as it loses traction on the hub that has ceased turning.

Here the two minimum grip drive sprockets are shown as identical. However, this need not be the case as different diameters or sizes may be used as well as more minimum grip drive sprockets as called for in a given application. Also a single minimum grip drive sprocket may be used in conjunction with other types of minimum grip drive sprockets if desired. In use a slick environment may be present due to a solvent sprayed by sprayer505within the machine507. If a belt and pulley were used, even with a tensioning device503excessive belt slippage is more likely to occur than the arrangement using a minimum grip drive sprocket301.

FIG.9shows a close up view of a chain and the first example of a minimum grip drive sprocket101used in the machine ofFIG.8. The fitting of the minimum grip drive sprocket101between drive chain links603tends to keep the drive chain501from jumping off of the minimum grip drive sprocket101, especially when traction against the knurled surface103may be lost. If a typical exemplary bicycle sprocket (not shown) were used the chain would be kept in place by teeth extending through gaps between chain rollers, but the chain would be locked in place by the sprocket teeth engaging gaps between chain rollers.

The bevel105allows the knurled surface103to extend between the links and contact the chain rollers605. The chain501has an overlap601allowed by the bevel105. In alternative examples a minimum grip drive sprocket may be made of a uniform thickness sufficient to fit between the links603. In further alternative examples the bevel105, instead of being a uniform slope may be a step or other suitable shape so that the knurl103may reach and engage rollers605.

FIG.10is a top view of a second example of the minimum grip drive sprocket1001. The second example of a minimum grip drive sprocket, may be constructed as previously described. However, instead of a knurled pattern about the minimum grip drive sprocket perimeter, a dimpled pattern1002may be utilized to provide a rough surface and to clear fouling by dirt and grease.

Those skilled in the art will realize that the process sequences described above may be equivalently performed in any order to achieve a desired result. Also, sub-processes may typically be omitted as desired without taking away from the overall functionality of the processes described above.