Patent Description:
In accordance with one embodiment of the present disclosure, a spiral conveyor belt system is provided. The system includes: a spiral conveyor belt; and inner and outer drive chains driving the spiral conveyor belt, the inner and outer drive chains each including a plurality of links defined by a plurality of first and second pitches connected by linking pins extending through holes in the pitches, wherein at least a portion of the linking pins of at least one of the inner and outer drive chains are hardened and/or dissimilar linking pins which are harder on an outer surface than other components in the inner and outer drive chains.

According to the invention, a drive chain system for a spiral conveyor belt is provided. The drive chain system includes inner and outer drive chains driving the spiral conveyor belt, the inner and outer drive chains each including a plurality of links defined by a plurality of first and second pitches connected by linking pins extending through holes in the pitches, at least a portion of the linking pins of at least one of the inner and outer drive chains are hardened, wherein the hardened linking pins are made from austenitic stainless steel having outer surfaces which have been hardened by carbon or nitrogen type atoms introduced into the austenitic stainless steel over a predetermined depth, or wherein the hardened linking pins are made from PH martensitic stainless steel.

In any of the embodiments described herein, the outer surfaces of the linking pins may have a hardness greater than <NUM> HV, greater than <NUM> HV, or greater than <NUM> HV.

In any of the embodiments described herein, the predetermined depth may be between <NUM> and <NUM> microns.

In any of the embodiments described herein, the second pitches may include bushings for receiving the linking pins made from austenitic stainless steel and wherein at least a portion of the bushings have surfaces which are hardened and/or dissimilar surfaces which are harder than the other components in the inner and outer drive chains.

In any of the embodiments described herein, the hardened surfaces of the bushings may have a hardness greater than <NUM> HV, greater than <NUM> HV, or greater than <NUM> HV.

In any of the embodiments described herein, the hardened bushings pins may be made from austenitic stainless steel having outer surfaces which have been hardened by carbon or nitrogen type atoms introduced into the austenitic stainless steel over a predetermined depth.

In any of the embodiments described herein, wherein the hardened bushings may be made from PH martensitic stainless steel.

In any of the embodiments described herein, wherein the predetermined depth may be between <NUM> and <NUM> microns.

In any of the embodiments described herein, the inner and outer drive chains may be ball drive chains or roller drive chains.

The foregoing aspects and many of the attendant advantages of this disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:.

The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Similarly, any steps described herein may be interchangeable with other steps, or combinations of steps, in order to achieve the same or substantially similar result.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that many embodiments of the present disclosure may be practiced without some or all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

The present application may include references to "directions," such as "forward," "rearward," "front," "back," "ahead," "behind," "upward," "downward," "above," "below," "top," "bottom," "right hand," "left hand," "in," "out," "extended," "advanced," "retracted," "proximal," and "distal. " These references and other similar references in the present application are only to assist in helping describe and understand the present disclosure and are not intended to limit the present invention to these directions or specific references.

The present application may include modifiers such as the words "generally," "approximately," "about", or "substantially. " These terms are meant to serve as modifiers to indicate that the "dimension," "shape," "temperature," "time," or other physical parameter in question need not be exact, but may vary as long as the function that is required to be performed can be carried out. For example, in the phrase "generally circular in shape," the shape need not be exactly circular as long as the required function of the structure in question can be carried out.

Referring to <FIG>, embodiments of the present disclosure are directed to spiral stacking conveyor belt systems <NUM> driven by inner and outer drive systems <NUM> and <NUM> and components thereof. The inner and outer drive systems <NUM> and <NUM> are generally manufactured from stainless steel components for corrosion resistance. In accordance with embodiments of the present disclosure, the system includes hardened stainless steel components to reduce the elongation of the drive chains over extended periods of use. In accordance with other embodiments of the present disclosure, the system includes hardened and/or dissimilar stainless steel components to reduce galling in the drive chains.

Suitable embodiments of spiral stacking conveyor belts are shown and described in <CIT>, and <CIT>.

However, it should be appreciated that other suitable spiral belt assemblies are also within the scope of the present disclosure.

Referring to <FIG>, when formed as a spiral stack <NUM>, the pervious conveyor belt <NUM> (see close-up perspective view in <FIG>) is configured into a plurality of superimposed tiers <NUM> that are stacked on top of each other (i.e., known in the art as "self-stacking" conveyor belt). In that regard, each tier <NUM> of the stack <NUM> forms a pervious annulus, through which gaseous cooking or cooling medium may travel, whether for cooking or freezing systems. When formed in a spiral stack <NUM>, the plurality of tiers <NUM> creates an inner cylindrical channel <NUM>, through which the gaseous medium may also travel. Workpieces (such as food products) travel on the conveyor belt <NUM> and are affected (either cooked or frozen) by gaseous medium in the cooking or freezing chamber. Exemplary spiral stacks <NUM> may have any number of tiers <NUM>, typically in the range of about <NUM> to about <NUM> tiers.

Referring to <FIG>, as a non-limiting example, the conveyor belt <NUM> may be in the form of a pervious belt mesh <NUM> for conveying workpieces and formed by transverse rods <NUM> interconnected by intermediate links, as well as inner and outer links <NUM> and <NUM> at the ends of the transverse rods <NUM>. The inner and outer links <NUM> and <NUM> are configured to enable spiral stacking for the belt tiers <NUM> and for interaction with the drive system (see <FIG>). When the conveyor belt <NUM> is configured as a spiral stack <NUM>, gaseous medium may travel in a substantially vertical direction through the pervious belt mesh <NUM> of each superimposed tier <NUM>.

Referring to <FIG> and <FIG>, the conveyor belt <NUM> in the illustrated embodiment of <FIG> is driven by a drive system including inner and outer drive systems <NUM> and <NUM>. As seen in <FIG>, the inner drive system <NUM> includes an inner drive station <NUM>, an inner drive chain <NUM>, and an inner chain tensioner take up <NUM>. The outer drive system <NUM> includes an outer drive station <NUM>, an outer drive chain <NUM>, and an outer chain tensioner take up <NUM>.

Referring to <FIG>, the inner drive chain <NUM> is supported by an inner rail <NUM> and the outer drive chain <NUM> is supported by an outer rail <NUM>. The inner and outer rails <NUM> and <NUM> also may include optional drip plates. For example, see the outer rail drip plate <NUM>.

In the illustrated embodiment, the inner and outer drive chains <NUM> and <NUM> are roller chains. Therefore, when driven, rollers <NUM> enable movement of the inner and outer drive chains <NUM> and <NUM> along the inner and outer rails <NUM> and <NUM>. Ball chains are also within the scope of the present disclosure, for example, as described in <CIT>.

As seen in <FIG>, the inner and outer links <NUM> and <NUM> of the conveyor belt <NUM> interact with and are driven by the respective inner and outer drive systems <NUM> and <NUM>.

Referring to <FIG> and <FIG>, the inner drive chain <NUM> will be described in greater detail. The inner drive chain <NUM> is made up of a plurality of links <NUM> including first and second pitches <NUM> and <NUM> at the top side of the links. The first pitch <NUM> includes an upwardly extending flange <NUM> for interaction with the first tier 30a of the conveyor belt (see <FIG>). The first and second pitches <NUM> and <NUM> are coupled to one another so as to enable coupling with adjacent links.

The first pitch <NUM> includes two adjacent holes <NUM> and <NUM> for receiving coupling pins <NUM> and <NUM>. The second pitch <NUM> includes two adjacent holes <NUM> and <NUM> for receiving second and third coupling pins <NUM> and <NUM>. The second pitch <NUM> may include bushings <NUM> for receiving the second and third coupling pins <NUM> and <NUM>.

In the illustrated embodiment, upper and lower plates <NUM> and <NUM> reinforce the coupling between links <NUM>. The first and second pitches <NUM> and <NUM> when assembled define the upper structure of a link <NUM> which can be linked to adjacent links to define the inner drive chain <NUM>.

Referring to <FIG>, the outer drive chain <NUM> is substantially similar to the inner drive chain <NUM> except for differences regarding a glide strip <NUM> and the upward extending flange <NUM> only on the inner drive chain <NUM>.

As mentioned above, elongation wear of the inner and outer drive chains <NUM> and <NUM> is a cause of regular maintenance for the spiral stacking conveyor belt system. In addition, when the outer drive chain wear <NUM> elongates at a faster rate than the inner drive chain <NUM>, increased maintenance is required and potential damage to the system may result.

In chain wear elongation, pitch length increases as pins and bushings apply tension forces to each other and oscillate against each other. Toward the end of a chain service life, the physical elongation from pin-bushing wear can be as much as <NUM>% of assembled chain length. Other wear in the system in addition to wear in the pins and bushings is seen is in rail path, chain, sprocket, and idler wear depths. Over time, to adjust for wear elongation in the chain, pitches of chain are removed in two-pitch links to accommodate chain construction and stoke length.

Differences in inner and outer chain wear is problematic because a <NUM>% elongated chain runs <NUM>% faster in speed compared to a new articulating chain on the same drive sprocket and at the same rotation rate. Some spiral conveyor systems can accommodate small differences in chain elongation and speed, for example, a <NUM>% difference in chain elongation and speed. The greater the differential wear between the inner and outer drives, the greater driving force imbalance on the belt stack by the more heavily wear elongated chain. After a certain amount of elongation of the outer drive chain <NUM> compared to the inner drive chain <NUM>, the system may be driven primarily by the outer drive chain <NUM>, which can result in accelerated elongation and eventual system failure, as described in Example <NUM> with reference to <FIG> below.

Referring to <FIG>, and <FIG>, photographs of work chain links are provided. Referring to <FIG>, a photograph of an outer chain side link fatigue crack is shown as a result of high outer chain tension. Referring to <FIG>, a worn chain sample photograph is provided, as described in greater detail below in Example <NUM>. Referring to <FIG>, a worn pin photograph is provided. In the pin and bushing assembly, pins seem to wear at a faster rate than bushings. As described below in Example <NUM>, pin wear in this non-limiting example accounts for about <NUM>% of total wear elongation from the pin and bushing assembly, and bushing wear accounts for about <NUM>% of the total wear elongation from the pin and bushing assembly.

Observed a problem situation in which <NUM> inches of outer drive chain slip advance under the conveyor belt feed with the inner drive retarded negative (belt was going faster than the inner drive chain). Outer chain wear elongation was <NUM> or <NUM>% while the inner chain elongation was <NUM> or <NUM>% (essentially new chain). When a new (unworn) outer chain was installed, the drive system returned to a normal running condition.

Referring to <FIG>, four pins are identified as <NUM>, <NUM>, <NUM>, and <NUM>, and four bushings are identified as <NUM>, <NUM>, <NUM>, and <NUM>. Data is provided below in Table <NUM> based on wear measured on actual parts for the pins and the corresponding bushings.

Referring to <FIG>, chain wear elongation in chain length (mm) is illustrated over <NUM> days. Elongation is at a substantially linear rate up until day <NUM>. After day <NUM>, elongation is accelerated. It is believed after day <NUM>, there is a greater driving force imbalance on the belt stack by the more heavily wear elongated chain (the outer chain) causing chain wear elongation to accelerate.

To mitigate chain wear elongation, embodiments of the present disclosure includes systems including hardened stainless steel components to reduce the elongation of the drive chains over extended periods of use.

In addition to chain wear elongation, galling, sometimes called cold welding, can also be a problem in drive chains. Galling is a form of severe adhesive wear which can occur when two metal surfaces are in relative motion to each other and under heavy pressure. Stainless steel components are susceptible to galling. When the two surfaces are the same material, these exposed surfaces can easily fuse together. Separation of the two surfaces can result in surface tearing and even complete seizure of metal components.

A galling threshold can be increased by the use of dissimilar materials (bronze against stainless steel), or using different stainless steels (martensitic against austenitic). Lubrication can help reduce the risks of galling. Also, high hardness for certain parts can reduce the risks of galling.

To increase the galling threshold and mitigate the risk of galling, embodiments of the present disclosure includes systems including hardened and/or dissimilar stainless steel components to mitigate the risk of galling.

In food processing applications, corrosion resistant steel is generally used for manufacturing assemblies. Corrosion resistant stainless steel is generally understood to refer to an iron material with at least <NUM>% by weight of chromium added by an alloying process.

Austenitic stainless steel is a group of stainless steel alloys classified by a crystalline structure having austenite as it primary crystalline structure (face centered cubic). An austenite crystalline structure is achieved by sufficient additions of the austenite stabilizing elements nickel, manganese and nitrogen. Due to their crystalline structure, austenitic steels are not hardenable by heat treatment and are essentially nonmagnetic.

There are two subgroups of austenitic stainless steel. <NUM> series stainless steels achieve their austenitic structure primarily by a nickel addition while <NUM> series stainless steels substitute manganese and nitrogen for nickel, though there is still a small nickel content. Type <NUM> is a common austenitic stainless steel, which contains some molybdenum to promote resistance to acids and increase resistance to localized attack (e.g. pitting and crevice corrosion). The higher nitrogen addition in <NUM> series gives them higher mechanical strength than <NUM> series.

Because austenitic steel cannot be hardened by heat treatment, a process for manufacturing hardened components according to one embodiment of the present disclosure includes the acquiring the component (which may be stamped from an austenitic stainless steel strip) and treating the surfaces of the component. Treatment includes diffusing reinforcing atoms of carbon and/or nitrogen into the crystal lattice of the steel over a predetermined depth, preferably between <NUM> and <NUM> microns inclusive.

One suitable treatment may include subjecting the component to molten salt bath treatment, such as a Kolsterisation® treatment, as described in <CIT>.

In the structure of austenitic stainless steel (a cubical face-centered lattice), Non-metal elements such as nitrogen and carbon can be present in a solid solution. If carbon or nitrogen or both elements are successfully diffused into the surface of an austenitic stainless steel and are kept there in a solid saturated or even over-saturated solution, then two effects will occur:.

Other suitable treatments may include a gas treatment, a thermochemical treatment such as a case hardening, a nitridation, a nitrocarburization, an ion implantation, a diffusion heat treatment, etc..

Treatment is selected to obtain a hardening of the treated surfaces to a hardness selected from the group consisting of greater than <NUM> HV, greater than <NUM> HV, and greater than <NUM> HV.

Martensitic stainless steel is another group of stainless steel alloys having a wide range of properties and used as stainless engineering steels, which can be heat treated to provide the adequate level of mechanical properties. The heat treatment typically involves three steps. Austenitizing heats the steel to a temperature in the range <NUM>-<NUM>, depending on the grade. The austenite is a face centered cubic phase. Quenching (a rapid cooling in air, oil or water) transforms the austenite into martensite, a hard a body-centered tetragonal crystal structure. The as-quenched martensite is very hard and too brittle for most applications. Some residual austenite may remain. Tempering (i.e. heating around <NUM>, holding at temperature, then air cooling) increases the tempering temperature decreases the Yield and Ultimate tensile strength but increases the elongation and the impact resistance.

In martensitic types, there is a subgroup of Precipitation Hardening grades: Grade EN <NUM> (a. a <NUM>/4PH), which combines martensitic hardening and precipitation hardening. PH martensitic stainless steel achieves high strength and good toughness, and corrosion resistance similar to that of austenitic stainless steel.

In accordance with embodiments of the present disclosure, the inner and/or outer drive chains <NUM> and <NUM> may include one or more hardened and/or dissimilar components to reduce the wear elongation or galling of the drive chains. In one embodiment, the inner and/or outer drive chains <NUM> and <NUM> may include pins that are either hardened and/or dissimilar from the other components in the drive chains <NUM> and <NUM>. In another embodiment, the inner and/or outer drive chains may include hardened and/or dissimilar bushings in lieu of hardened and/or dissimilar pins or in addition to hardened and/or dissimilar pins. In another embodiment of the present disclosure, the outer drive chain <NUM> may include one or more hardened and/or dissimilar components, which the inner drive chain <NUM> may include no hardened and/or dissimilar components or different hardened and/or dissimilar components to try to accommodate differences in inner and outer drive chain wear.

As a non-limiting example, some components are made from PH martensitic stainless steel having a hardness of <NUM>-<NUM> Rc hardness (<NUM>-<NUM> HV hardness), which is then subjected to a hardening treatment process that takes the particle hardness on the surface up over <NUM> Rc (<NUM> HV).

In some embodiments of the present disclosure, some components of the drive system are made from hardened PH martensitic stainless steel having a hardness of greater than <NUM> HV, greater than <NUM> HV, and greater than <NUM> HV.

While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the scope of the invention as defined in the appended claims.

Claim 1:
A drive chain system for a spiral conveyor belt (<NUM>), the drive chain system having inner (<NUM>) and outer (<NUM>) drive chains driving the spiral conveyor belt, the inner and outer drive chains each having a plurality of links (<NUM>) defined by a plurality of first (<NUM>) and second (<NUM>) pitches connected by linking pins (<NUM>, <NUM>) extending through holes (<NUM>, <NUM>) in the pitches;
characterized by at least a portion of the linking pins of at least one of the inner and outer drive chains are hardened, wherein the hardened linking pins are made from austenitic stainless steel having outer surfaces which have been hardened by carbon or nitrogen type atoms introduced into the austenitic stainless steel over a predetermined depth, or wherein the hardened linking pins are made from PH martensitic stainless steel.