Chipper feed mechanism and throat opening sensor for use therewith

A wood chipper includes a cutting assembly and a feed wheel for feeding material through an adjustable throat opening adjacent the feed wheel and toward the cutting assembly. A throat sensor measures the size of the throat opening and an electronic control unit (ECU) controls operation of the wood chipper in accordance with the size of the throat opening. The ECU controls forward, reverse and non-rotation of the feed wheel as well as down pressure applied by the feed wheel on feed material moving through the throat opening. The feed wheel down pressure may be constant or vary in any number of ways. One option includes applying down pressure in a pulsating manner.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates generally to wood chippers. More particularly, the invention relates to a control system for controlling the feed wheel of a wood chipper wherein the feed wheel moves up and down to alter the size of a throat opening through which feed material is moved by the feed wheel. Specifically, the invention relates to such a control system having a throat sensor for determining the throat size and an electronic control unit for controlling rotation and down pressure of the feed wheel in accordance with the throat size.

2. Background Information

Typically, wood chippers include a feed chute, a rotating feed wheel and a cutting assembly whereby feed material is fed through the feed chute and drawn in by the feed wheel to the cutting assembly where the feed material such as branches and the like are cut by the cutting assembly. Some wood chippers utilize a single feed wheel while others utilize a pair of feed wheels which rotate in opposite directions to draw the feed material into the cutting assembly. Due to the various sizes of branches and logs that may be fed into a wood chipper, often the feed wheel or one of the feed wheels is movable in order to increase the size of the throat through which the feed material is drawn by the feed wheel. As disclosed in U.S. Patent Application Publication No. US2003/0111566 of Seaman et al., at least one wood chipper is known to have a feed control system which is hydraulically operated in order to provide additional pressure to the upper feed drum which corresponds to the pressure within the hydraulic motor which rotatingly drives the feed drum. Seaman et al. disclose a control system which when in automatic mode constantly urges the upper feed drum downwardly to apply a constant load to the feed material regardless of the position of the upper feed drum relative to the lower feed drum and thus regardless of the size of the gap between the two drums. The control mechanism of this wood chipper is entirely hydraulic in nature. More particularly, an increase in the load on the hydraulic motor which controls the upper feed drum causes an increase in the pressure of hydraulic fluid associated with the motor and this increased pressure of hydraulic fluid is directly applied to a hydraulic actuator to increase the down pressure on the feed drum. While this system has its advantages, it has also limited by the fact that the increased load on the feed wheel motor and thus the increased pressure on the hydraulic fluid can only be responded to by the increased down pressure of the feed drum. This control system is also operable in a manual mode in order to move the upper feed drum away from the lower feed drum to increase the gap to accommodate larger feed material or to provide additional down pressure on the feed drum when desired. Thus, while Seaman et al. provides certain advantages, there is still room for an improved feed mechanism for wood chippers.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a method comprising the steps of moving feed material toward a cutting assembly of a wood chipper having a rotatable feed wheel via a gap which is adjacent the feed wheel, which is disposed between a first member and a gap-bounding member and which is adjustable by changing a distance from the first member to the gap-bounding member; determining the distance; and controlling at least one of the feed wheel and a structural member in light of the distance wherein the feed material passes between the feed wheel and the structural member.

Similar numbers refer to similar parts throughout the specification.

DETAILED DESCRIPTION OF THE INVENTION

The wood chipper of the present invention is indicated generally at10inFIG. 1. Wood chipper10is configured to control the rotation of the feed wheel thereof and the down pressure typically applied by the feed wheel in accordance with the size of the throat opening adjacent the feed wheel. In one preferred embodiment, wood chipper10is configured to apply increased force or pressure in a pulsating manner to feed material being fed into the wood chipper in order to improve the feeding characteristics thereof.

Wood chipper10is a wheeled vehicle having a frame12with an engine14mounted thereon. A cutting assembly16is mounted on frame12and is operatively connected to and powered by engine14. A feed wheel assembly18is mounted on frame12adjacent cutting assembly16and opposite engine14. Feed wheel assembly18includes a feed wheel20rotatably mounted within a feed wheel housing22. A feed chute24is mounted adjacent feed wheel housing22whereby feed material may be fed through feed chute24into housing22and be drawn by feed wheel20into cutting assembly16. Feed chute24includes a substantially flat bottom wall27, a pair of spaced side walls25extending upwardly from bottom wall27and a top wall29extending between and connected to each of side walls25. Side walls25and bottom wall27extend rearwardly to form respective portions of feed wheel housing22. Feed wheel20is rotatably mounted on a carriage26about a first axis A which passes through an axle28of feed wheel20. More particularly, carriage26includes a pair of carriage members30(only one shown) which are spaced from one another and disposed generally on either side of housing22. Carriage26is pivotally mounted about an axis B which is substantially parallel to axis A. The pivotal mounting of carriage26allows for the pivotal movement of feed wheel20in a generally up and down direction. It is noted that while feed wheel20is oriented to rotate about a substantially horizontal axis and carriage26is also pivotal about a substantially horizontal axis, feed wheel20, carriage26and the corresponding structure may be arranged so that the feed wheel and carriage respectively rotate and pivot about axes in different orientations. In addition, it is contemplated that a carriage may be movably mounted other than pivotally, such as along a linear path. Housing22includes a stationary portion32and a movable portion34which is rigidly mounted on carriage26and disposed between the spaced carriage members30. Moveable portion34is thus moveable along with carriage26as it pivots about axis B.

With reference toFIGS. 1 and 2, and in accordance with a feature of the invention, a throat opening or throat gap sensor35A is mounted on feed wheel housing22and a reference strip37is mounted adjacent sensor35A on carriage member30whereby strip37is moveable with respect to sensor35A. With reference toFIG. 2, strip37is an elongated arc having first and second opposed ends39and41. InFIG. 2, sensor35A is adjacent first end39of strip37. Strip37is thus moveable along with carriage26and consequently corresponds to the position of feed wheel20. Sensor35A may be of a variety of types known in the art, including mechanical and electronic sensors which are able to determine the relative position of strip37. Wood chipper10further includes an actuator36in the form of a hydraulic piston-cylinder combination having a cylinder38and piston40. Cylinder38is pivotally connected adjacent a first end42of actuator36to frame12and cylinder38is pivotally mounted adjacent a second end44of actuator36to carriage26. Actuator36is extendable and retractable between a retracted position shown inFIG. 2and a fully extended position shown inFIG. 5. Actuator36thus moves carriage26and feed wheel20via axle28with respect to frame12of wood chipper10. An alternate throat gap sensor35B may be disposed within actuator36in the form of a proximity sensor which determines the position of piston40with respect to cylinder38whereby sensor35B is able to determine the position of feed wheel20and the throat opening or gap discussed below. An alternate sensor may use trigonometry to determine the size of the throat opening.

With reference toFIG. 2A, walls25,27and29of feed chute24define an input46which narrows toward cutting assembly16to a throat48disposed below feed wheel20. Throat48is bounded by and defined by feed wheel20and portions of side walls25and bottom wall27of feed chute24, which are more particularly portions of feed wheel housing22. More particularly, bottom wall27includes a structural member in the form of a gap-bounding portion or member50and feed wheel20includes a point or line52on the outer perimeter thereof wherein gap-bounding member50and point52on feed wheel20define therebetween a distance or gap G1which varies (FIGS. 3A,4A and5A) with the movement of feed wheel20in response to the extension and retraction of actuator36. Gap G1ofFIG. 2Ais zero or substantially zero and represents the narrowest or nearly the narrowest gap in accordance with a full or nearly full retraction of actuator36. Increasingly larger gaps are shown at G2inFIG. 3A, G3inFIG. 4Aand G4inFIG. 5A, the latter representing the widest or nearly widest gap in accordance with a full or nearly full extension of actuator36. For certain purposes of the present application, G2represents a three inch gap, G3represents a six inch gap and G4represents a fifteen inch gap, although the gap sizes may vary.

With reference toFIGS. 3-3Aand in accordance with a feature of the invention, the feeding of material via feed wheel20is partially described. With feed wheel20rotating in the forward direction as indicated by Arrows C, a first amount of feed material54A is fed (Arrow D) via input46of feed chute24into throat48, adjacent which feed wheel20contacts a portion of feed material54A and draws it through throat48toward cutting assembly16. While feed material54A is shown schematically as tree branches which may be large or small, various materials may be fed into wood chipper10. As will be detailed further below, actuator36is operated to apply a downward force or down pressure via feed wheel20. When feed material54A is fed into wood chipper10, material54A engages feed wheel20and gap-bounding member50and overcomes this downward force on feed wheel20to a certain degree, thereby moving feed wheel20upwardly as indicated by Arrow F inFIG. 3A. As feed material54A moves feed wheel20upwardly as indicated by Arrow F inFIG. 3A, measuring strip37A is moved with carriage26in the direction indicated by Arrow G inFIG. 3so that a length of strip37adjacent first end39moves past sensor35A. Sensor35A thus senses this movement which is associated with the movement of feed wheel20and by which gap G2may be determined.

This upward movement of feed wheel20thus establishes gap G2, which as noted earlier is approximately three inches for the present purposes. Gap G2thus represents a first threshold such that movement of feed wheel20is controlled in a first manner if the gap is less than the first threshold and in a second manner if the gap is greater than the first threshold. The various manners of controlling feed wheel20will be discussed in further detail subsequently. In general, if gap G2is below the first threshold, feed wheel20will be rotated in a forward direction in a continuous manner and down pressure applied by feed wheel20on feed material54A will be continuous and typically substantially constant.

With reference toFIGS. 4 and 4A, a second amount of feed material54B is fed into feed chute24as indicated by letter D inFIG. 4A. Second amount of feed material54B is generally larger than first amount54A shown inFIGS. 3 and 3A. As a result, a portion of feed material54B engages feed wheel20and gap-bounding member50and moves feed wheel20further upwardly as indicated by Arrow J inFIG. 3Ato establish gap G3. As feed wheel20is moved upwardly, carriage26and measuring strip37are moved in the direction indicated by Arrow K inFIG. 4so that an additional length of strip37moves past sensor35A whereby sensor35A detects this movement and the distance of gap G3may be determined as discussed further below. Gap G3generally represents a second threshold which is greater than the first threshold of gap G2shown inFIG. 3A. Thus, when the feed wheel is in a position which is greater than gap G2or the first threshold and less than gap G3or the second threshold, the movement of feed wheel20is controlled in the second manner previously mentioned. One preferred second manner of controlling feed wheel20involves applying a continuous force which is substantially constant as was the case when the gap was less than the first threshold and also to rotate feed wheel20in a forward direction for a predetermined period of time and then reverse and/or stop rotation of feed wheel20for a second period of time which primarily serves either to prevent the operational speed of engine14and cutting assembly16from dropping below a desired value or allows the operational speed of engine14and cutting assembly16to recover to a desired value.

When the distance between feed wheel20and gap-bounding member50exceeds gap G3or the second threshold, feed wheel20is controlled in a third manner which is different from each of the first and second manners described above. One preferred third manner includes rotating feed wheel20in a similar fashion as described with regard to the second manner such that feed wheel20is rotated in the forward direction for a first period of time and reversed and/or stopped for a second period of time. In addition, the preferred third manner includes applying pressure via feed wheel20toward gap-bounding member50and feed material54B at a first force for a first predetermined amount of time and at a second force which is greater than the first force for a second predetermined amount of time whereby the first and second pressures are applied in an alternating or pulsating manner. Typically, the first period of time is substantially longer than the second period of time, as will be detailed further below.

With continued reference toFIG. 4A, and in accordance with a feature of the invention, actuator36may be operated to retract and extend in a pulsating manner at predetermined time intervals whereby feed wheel20is respectively lowered and raised at said time intervals. Actuator36is thus part of a pulsating mechanism for moving feed wheel20in a pulsating manner up and down as indicated by Arrow J and the reverse thereof in order to alternate the size of the gap of throat48between, for example, gap G2and gap G3. It is noted that with respect to the up and down movement of feed wheel20, gaps G2and G3are merely representative of two different gap sizes or distances which will vary in accordance with a particular scenario and depends upon the amount of force applied by actuator36as well as the type of feed material54being fed into wood chipper10. Obviously, the more that feed material54gives in response to the pressure or force applied by actuator36via feed wheel20, the more the gap will change. Thus, in some cases the gap will narrow and widen in an alternating fashion to different degrees whereas when the feed material is sufficiently sturdy and thus does not give, the gap may not change at all, at least not noticeably, in response to the amount of force applied. Whether or not the gap between feed wheel20and gap-bounding member50changes in response to the force applied via actuator36, the downward force or pressure will allow feed wheel22to better grip or grasp feed material54in order to facilitate pulling feed material54toward cutting assembly16. In most cases, the force applied by actuator36will move feed wheel20up and down and this is particularly useful for feed material in the form of branches because the downward movement of feed wheel20is sufficient to break or crush Y-branches or crotches as they are known in the art, and the upward movement prevents the stalling of engine14and allows it, if necessary, to recover to a suitable operational speed. This facilitates the feeding of the feed material into wood chipper10.

As previously noted, the pulsating motion of feed wheel20occurs at predetermined time intervals. Thus, the intermittent time periods that feed wheel20remains in a relatively lowered position are predetermined as well as the intermittent time periods that feed wheel20remains in a relatively raised position. Most commonly, actuator36is controlled to apply a first relatively lesser or normal force or pressure via feed wheel20toward feed material54and then at regular time intervals actuator36is retracted at a predetermined amount of force to apply a relatively greater force to feed wheel20and feed material54for relatively short time periods in comparison with the time periods that the normal pressure is applied.

With reference toFIGS. 5 and 5A, a third amount of feed material54C is fed into feed chute24as indicated by Arrow D inFIG. 5A. Third amount of feed material54C is larger than second amount54B shown inFIGS. 4 and 4Aand thus further moves feed wheel20upwardly as indicated by Arrow L inFIG. 5Ato form a gap G4between feed wheel20and gap-bounding member50. As feed wheel20moves upwardly, carriage26and strip37move as indicated by letter M inFIG. 5so that an additional length of strip37moves past sensor35A and second end41of strip37is disposed adjacent sensor35A. Sensor35A senses this movement so that the distance of gap G4may be determined. Gap G4represents a maximum gap which can be achieved with wood chipper10.

The exemplary embodiment in the figures includes a single feed wheel although it is common within the art to have a pair of feed wheels. Thus, it is noted that the gap-bounding member represented at50may also be a lower feed wheel so that the gap is defined between the upper and lower feed wheels. In addition, it is noted that the exemplary embodiment shows the feed wheel being movable in order to change the size of the gap during the pulsating movement of the feed wheel. However, it is within the scope of the invention that a gap-bounding member like member50or a second feed wheel acting as the gap-bounding member may be movable instead of the feed wheel shown or in addition to movement of the feed wheel as shown in the figures. Thus, while it may be preferred and easier to move the feed wheel to change the gap or to move the upper feed wheel in a wood chipper having a pair of feed wheels, at least one of the gap-bounding member and the feed wheel will be movable toward one another in order to effect the pulsating movement required for the invention.

With reference toFIG. 6and in accordance with another feature of the invention, wood chipper10further includes a hydraulic system56and an electronic control unit (ECU)58as shown as a microprocessor which controls the various hydraulic and related elements in order to produce the desired movement of feed wheel20. Hydraulic system56includes a hydraulic pump60which is powered by engine14. Hydraulic system56further includes a reservoir or tank62, a valve block64and one or more hydraulic feed motors66. Valve block64includes a relief valve68, a flow regulator or flow control valve70, a directional control valve assembly72and a counterbalance valve74. These various elements of the hydraulic system56are interconnected by hydraulic lines as generally indicated at76. Directional control valve assembly72includes a first or forward directional control valve78and a second or reverse directional control valve80. A first or forward solenoid82is operatively connected to forward directional control valve78and a second or reverse solenoid84is operatively connected to a reverse directional control valve80. First solenoid82is in electrical communication with microprocessor58via a first electrical circuit86. Likewise, second solenoid84is in electrical communication with microprocessor58via a second electrical circuit88. Hydraulic system56further includes a flow regulator90in fluid communication with valve block64via hydraulic line92, a proportional down pressure relief valve94in fluid communication with regulator90via hydraulic line96, an actuator control valve98in fluid communication with relief valve94via hydraulic lines100and actuator36, which is in fluid communication with control valve98via hydraulic lines102. Microprocessor58is in electrical communication with flow regulator90via a regulator electric circuit91, with relief valve94via a relief valve electric circuit95and with control valve98via a control valve electric circuit99via a solenoid.

With continued reference toFIG. 6, the control system of wood chipper10includes sensor35for sensing the distance or gap (G1-G4) between feed wheel20and gap-bounding member50. Sensor35is in electrical communication via a sensor electrical circuit110with ECU58. The control system further includes a timing device in the form of a clock114which is in electrical communication with ECU58. ECU58may be in communication with the various components other than by electrical circuits, for example, radio frequency or other suitable mechanisms.

With continued reference toFIG. 6, the operation of hydraulic system56is described. Pump60is powered by engine14to pump hydraulic fluid through a feed line104to valve block64. Hydraulic fluid is returned from valve block64via a return line106to tank46. When first and second directional control valves78and80are properly configured, hydraulic fluid flows via hydraulic lines116and118in order to rotate feed motor66in either a forward direction as indicated at Arrow N or a reverse direction as indicated at Arrow P to respectively rotate feed wheel20in the forward direction (Arrows C inFIGS. 3A,4A and5A) or the reverse direction.

With continued reference toFIG. 6, microprocessor58controls activation and inactivation of valves78and80in order to control feed motor66to rotate in the forward direction, rotate in the reverse direction or to stop and remained stopped as long as desired. More particularly, microprocessor58sends an electrical signal to activate solenoid82, which in turn activates valve78to allow the flow of hydraulic fluid from feed line104into hydraulic line116in order to rotate feed motor66in the forward direction indicated by Arrow N. Similarly, microprocessor58sends an electrical signal via circuit88to activate solenoid84, which in turn activates second directional control valve80. Activation of valve80allows hydraulic fluid to flow from feed line104into hydraulic line118in order to rotate feed wheel66in a reverse direction indicated by Arrow P. It is noted that first and second control valves78and80are operated in the alternative. That is, in order to rotate feed motor66in a forward direction, microprocessor58activates first solenoid78while second solenoid84and second valve80remain in or are moved to their respective inactivated positions. To rotate feed motor66in the reverse direction, the reverse is true so that microprocessor58activates solenoid84while solenoid82is inactivated. In order to stop the rotation of feed motor66in either direction, microprocessor58opens circuits86and88so that solenoids82and84are each inactivated and valves78and80are likewise inactivated. In this inactivated state, no hydraulic fluid flows through lines116and118and therefore feed motor66stops rotating.

With continued reference toFIG. 6and in accordance with a feature of the invention, microprocessor58controls the flow of hydraulic fluid through flow regulator90, proportional relief valve94, control valve98and actuator36in order to control the pulsating or other force applied by actuator36in either an extended or retracted direction thereof in order to control the pulsating or other force applied to and movement of feed wheel20as previously discussed. More particularly, microprocessor58controls relief valve94via circuit95in order to alter the amount of hydraulic fluid flowing from regulator90through control valve98to actuator36in order to control the amount of force upon feed wheel20via actuator36. Thus, flow regulator90maintains a given amount of flow of hydraulic fluid and relief valve94dumps hydraulic fluid in a proportional manner controlled by microprocessor58in order to control the amount of fluid going to actuator36and thus the amount of force applied to feed material54via feed wheel20. Directional control valve98controls the direction of flow of hydraulic fluid through lines102and thus determines whether piston40of actuator36will be extended or retracted. Alternately, microprocessor58may control a flow regulator such as regulator90in order to control the amount of fluid going to actuator36without the use of a relief valve like valve94. A variety of other configurations and methods may be used to control the down pressure applied by actuator36, to include the use of potentiometers, in-line resistors, a modulated signal from the microprocessor or any other suitable mechanisms known in the art. Microprocessor58is configured with a logic circuit which controls hydraulic system56generally, to include information from clock114in order to control the predetermined time intervals for the movement or application of pulsating or other force to feed wheel20via actuator36.

Thus, ECU58and hydraulic system56are configured to control the movement of feed wheel20in virtually any manner desired. For example, feed wheel20may be rotated in a forward direction in a continuous manner or for a given period of time. In addition, the rotation of feed wheel20may either be stopped or reversed for any desired period of time. In addition, actuator36may be operated in order to apply a down pressure via feed wheel20in any manner desired. As previously noted, one preferred embodiment involves the application of force via feed wheel20in a pulsating manner. In addition, feed wheel20may apply a continuous and substantially constant down pressure if desired. However, feed wheel20may also be operated to provide varying pressures which are not applied in a pulsating or alternating manner. For instance, feed wheel20may be operated to apply a first force or pressure for a first period of time and subsequently a second force for a second period of time wherein the second force is different from the first force. Likewise, a third force may be subsequently applied which is different from each of the first and second forces. The time periods for which these various forces may be applied are infinitely variable. Thus, for example, the second force may be greater than the first force and the third force may be greater than the second force, or to the contrary, the second force may be less than the first force and the third force less than the second force. In addition, the various forces may be substantially constant during the time they are applied or they may gradually increase or decrease.

With reference toFIG. 7and in accordance with a feature of the invention, a preferred manner of controlling feed wheel20with ECU58is described. More particularly, the table ofFIG. 7shows a preferred feed wheel operating plan which is based on the size of the throat opening or gap defined between the feed wheel and the gap-bounding member as previously discussed. The table ofFIG. 7includes a column120which indicates the throat opening sensor feedback or the size of the gap. Second column122indicates the forward feed cycle time or forward rotation time of feed wheel20. Third column124indicates the reverse feed cycle time or reverse rotation cycle time of feed wheel20. Fourth column126indicates a pause or dwell cycle time of feed wheel20. Fifth column128indicates the amount of time that feed wheel20is operated at a normal or first down pressure. A sixth column130indicates the amount of time that feed wheel20is operated at a high down pressure. The operational parameters within columns122,124,126,128and130are dependent upon the size of the gap or throat opening indicated in column120.

With reference to column120, when the throat opening or gap is one to three inches, feed wheel20is operated in the forward direction in a continuous manner as indicated in column122and at a continuous and substantially constant normal down pressure as indicated at column128. In this preferred manner of operation, three inches is the first threshold, as discussed previously with regard to gap G3inFIG. 4A.FIG. 7more broadly represents that when the gap is anywhere from nearly zero to three inches, feed wheel20will operate in a forward direction continuously at a normal down pressure which is continuous. This is in keeping with the relatively small amount of feed material represented at54A inFIG. 3Aor54B inFIG. 4Awhich can generally be handled by wood chipper10with a continuous forward rotation of feed wheel20and a continuous normal down pressure thereof. However, when the throat opening or gap increases above this first threshold, it is preferred to operate feed wheel20in a different manner. As previously discussed and as shown inFIG. 7, once the throat opening or gap is greater than the first threshold or three inches, feed wheel20is operated in a forward direction for a certain period of time as indicated in column122and then reversed and/or stopped for a certain period of time, as indicated in columns124and126.

As previously discussed, there is a second threshold of the gap or throat opening at which the movement of feed wheel20generally changes. In the present example, the second threshold is at six inches. Thus, the table ofFIG. 7indicates that when a throat opening is four inches or five inches, which corresponds to a gap which is between the first and second threshold, feed wheel20will be rotated in a forward direction for ten seconds, reversed for 0.5 seconds and stopped for four seconds while operating at a continuous and normal down pressure. Once the throat opening reaches or exceeds the second threshold, which is six inches in the present illustration, ECU58controls feed wheel20to apply the normal down pressure for a first period of time and a higher down pressure for a second period of time which is typically less than the first period.

As shown inFIG. 7, this is true for all throat opening sizes which are six inches or greater. As column122inFIG. 7shows, the amount of forward feed cycle time of feed wheel20generally decreases as the throat opening increases. In addition, column126shows that at the largest throat openings of 14 and 15 inches, the dwell time of feed wheel20is increased from four seconds to five seconds. At those same largest throat opening sizes, column128shows that the amount of time that the normal down pressure is applied is reduced from six seconds to four seconds and column130shows that the amount of time that the high down pressure is applied is increased from 1 second to 1.5 seconds. While these time periods may vary, these time ranges provide an example of the type of cycle which will allow for an increased down pressure which will not stall the engine due to the increased load translated from feed wheel20during this increased down pressure. Typically, the increased down pressure is maintained for no more than 2-second time periods and the normal down pressure for no more than 10-second time periods when in a pulsating mode. In addition, the normal down pressure time periods are typically from two to ten times as long as the increased down pressure time periods and preferably two to six times as long when in the pulsating mode.

Various patterns of controlling feed wheel20with ECU58in accordance with the size of the throat opening or gap are described with reference toFIGS. 8-11. Certain portions of the process shown inFIGS. 8-11are repeated and are thus numbered accordingly. With reference toFIG. 8, ECU58determines via sensor35and circuit110(FIG. 6) whether the throat opening or gap is greater than three inches or the first threshold as indicated at132. If not, feed wheel20continues operating as shown at134with continuous forward rotation and continuous normal down pressure. If the throat opening is greater than three inches, ECU158controls feed wheel20to rotate forward for a predetermined period of time as indicated at block136and then to dwell or stop rotating as indicated at block138.

Alternately and with reference toFIG. 9, feed wheel20may be operated in a slightly different manner. The same steps occur in blocks132,134and136ofFIG. 9as discussed with reference toFIG. 8. However, block140ofFIG. 9shows that feed wheel20may be operated in reverse rotation for a predetermined period of time instead of dwelling or stopping the rotation as indicated at block138ofFIG. 8. As previously noted with reference toFIG. 7, ECU58may control feed wheel120to reverse and stop rotating if desired.

With reference toFIG. 10, the procedure shows additional control of feed wheel20with regard to the pressure applied thereby to the feed material. More particularly,FIG. 10also shows the same first three blocks132,134and136as discussed with regard to the process ofFIGS. 8 and 9. The process ofFIG. 10further adds that during the forward rotation of feed wheel20for the predetermined period of time as indicated at block136, feed wheel20is operated at a normal down pressure for a predetermined period of time as indicated at142and subsequently at a high or higher down pressure for a predetermined period of time as indicated at block144. Typically, the normal down pressure and higher down pressure are applied in an alternating fashion. Once the periods of normal and higher down pressure are completed, ECU58stops the rotation of feed wheel20as indicated at146.FIG. 11shows the same process as discussed with regard toFIG. 10except that instead of stopping rotation as indicated at146inFIG. 10, the feed wheel is reversed for a predetermined period of time as indicated at block148inFIG. 11. As previously noted, ECU58may control feed wheel20to both reverse and stop rotation of feed wheel20if desired.

Thus, wood chipper10provides a control system which controls the movement of feed wheel20in light of the gap between feed wheel20and the gap-bounding member50, the gap typically being set in a variable manner by the size of the feed material which is fed into and cut by wood chipper10. ECU58is thus programmed to control the rotation and down pressure of feed wheel20in response to a signal from the throat opening sensor indicating the size of the gap which of course correlates to the size of the feed material being fed therethrough. Thus, ECU58may be programmed to control the movement of feed wheel20in a first manner associated with a first relatively small range of throat opening sizes, and a second manner related to a second range of throat opening sizes which is larger than the first, and so forth. ECU58is thus pre-programmed to optimize the rotation of feed wheel20and down pressure applied thereby in accordance with the size of the feed material.

While the exemplary embodiment shows the gap being defined between feed wheel20and gap-bounding member50, the variable gap or distance which is measured by a sensor such as sensor35A or35B may involve the use of members which may be separate from feed wheel20and gap-bounding member50. For example, a first member and a gap-bounding member may be disposed upstream of feed wheel20and gap-bounding member50so as to define therebetween the gap at issue. Thus, at least one of these upstream members is movable with respect to the other so as to define a variable gap therebetween which may be measured by the sensor. In such a case, at least one of feed wheel20and gap-bounding member50would be controlled in light of the distance measured between this alternate first member and alternate gap-bounding member. In such a scenario, gap-bounding member50may be thought of in terms of being a structural member whereby feed material is fed between feed wheel20and the structural member while the gap or distance sensed by sensor35would be the distance between the first member and the alternate gap-bounding member. A similar option is to use a first member other than feed wheel20and to define the gap between the first member and gap-bounding member50. Alternately, the gap may be measured between feed wheel20and an alternate gap-bounding member. Thus, the invention contemplates a variable-size throat opening or gap which may be defined between the feed wheel20and gap-bounding member50; between a pair of members that are separate therefrom; or between one of feed wheels20and gap-bounding member50and another member. With this in mind, it will be understood that the feed material54may be fed into feed chute24to engage and move at least one of these alternate members to establish the distance of the gap therebetween, and the control system of the wood chipper may be configured to control feed wheel20and gap-bounding member50in light of this distance.