Field of the Disclosure

[001] The present disclosure relates to a saw apparatus including an endless cutting chain.

Background of the Disclosure

[002] There are forestry machines that have a forestry head to fell a tree and to buck the tree into one or more logs. The head has a saw to perform such sawing operations.

[003] The endless cutting chain of the saw has broken during sawing causing a portion of the chain to fly away from the saw area. The chain failures result from chain link stretching and direct damage to the chain. Stretching fatigues the metal enabling fragment separation from the chain.

[004] It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

[005] Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Summary of the Disclosure

[006] According to an aspect of the present disclosure, a saw apparatus comprises a mount, a chain support attached movably to the mount for movement relative thereto, a chain driver, an endless cutting chain trained about the chain support and the chain driver, a chain tensioner urging the chain support to move relative to the mount to tension the chain, and a sensor positioned to sense a position of the chain support relative to the mount.

[007] According to another aspect of the present disclosure, the saw apparatus comprises an electronic control system. The sensor is configured to generate a position signal indicative of the position of the chain support relative to the mount. The control system is configured to receive the position signal, and determine if the cutting chain has stretched to a stretch threshold that is dependent on the position of the chain support relative to the mount. The control system may be configured to activate an alert if the cutting chain has stretched to the stretch threshold. The saw apparatus may thus be configured to determine chain stretch during usage of the saw apparatus to determine if there is an increased risk of chain breakage.

[008] The above and other features will become apparent from the following description and the attached drawings.

Brief Description of the Drawings

[009] The detailed description of the drawings refers to the accompanying figures in which:

[010] FIG. 1 is a diagrammatic view showing a saw apparatus including, for example, a forestry head;

[011] FIG. 2 is an elevational view showing the forestry head;

[012] FIG. 3 is a perspective view, with portions broken away, showing a chain saw of the forestry head;

[013] FIG. 4 is a perspective view, with portions of the saw broken away;

[014] FIG. 5 is an exploded perspective view showing a chain support of the saw;

[015] FIG. 6 is an exploded perspective view showing the chain support exploded from a swing of the saw;

[016] FIG. 7 is a perspective view showing the chain support assembled to the swing and a sensor positioned to sense a position of the chain support;

[017] FIG. 8 is a sectional view taken along lines 8-8 of FIG. 7 showing a first groove of an arm of the swing;

[018] FIG. 9 is a sectional view taken along lines 9-9 of FIG. 7 showing a second groove of the swing arm, and a sensor target embedded within a bar holder;

[019] FIG. 10 is a diagrammatic view showing a control system of the saw apparatus; and

[020] FIG. 11 is a flow chart showing a control scheme of the saw apparatus.

Detailed Description of the Drawings

[021] Referring to FIG. 1 , a saw apparatus 10 may be configured as a forestry machine that includes, for example, a self-propelled base machine 12, a forestry head 14, a boom assembly 16 attached pivotally to the base machine 12, and a coupler 17 interconnecting the boom assembly 16 and the head 14. The base machine 12 may be a track-type machine (FIG. 1) or a wheeled machine, either of which may have an operator's station at which a human operator may control the apparatus 10 and its head 14.

[022] Referring to FIG. 2, the forestry head 14 may be any type of forestry head with a saw. In FIG. 2, the forestry head 14 is configured, for example, as a harvester head. In such a case, the coupler 17 may be configured in any suitable manner so as to suspend the head 14 from an end of the boom assembly 16. For example, the coupler 17 may be configured for pivoting of the head 14 between a generally upright, felling position and a generally prone, processing position, and may include a frame 18 attached pivotally to the coupler 17 and a chain saw 20 attached to the frame 18 and configured to fell a tree in the harvesting position of the head 14 and to buck the tree into one or more logs in the processing position of the head 14 (the chain of chain saw 20 not shown in FIG. 2 for simplification of illustration).

[023] The head 14 may include a number of other features, such as, for example, a number of feed wheels 22, a number of delimb arms 24, a front delimb knife 26, a length-measurement wheel 28, and a topping saw 30. Two of the feed wheels 22 are attached respectively to two feed arms 32 attached pivotally to the frame 18, and a number of feed wheels 22 (e.g., one) may be attached to the frame 18 such that its axis of rotation is fixed relative to the frame 18. Each of the delimb arms 24 and the delimb knife 26 has a blade for delimbing the tree when the tree is fed past the arms 24 and knife 26 by the feed wheels 22 during processing. The topping saw 30 may be used to cut off a small-diameter top portion of the tree to maximize the value recovery of the tree (the chain of topping saw 30 not shown for simplification of illustration).

[024] Referring to FIGS. 3 and 4, the saw 20 is mounted to a saw housing 32 of the frame 18. The saw 20 includes an endless cutting chain 34, a chain support 36, a chain driver 38, and an attachment device 40 attaching the chain 34, the chain support 36, and the chain driver 38 to the saw housing 32.

[025] The attachment device 40 includes a saw support ring 42 fastened to the saw housing 32 with threaded fasteners, a driver support ring 44 fastened to the saw support ring 42 with threaded fasteners, a bearing support ring 46 fastened to the driver support ring 44 with threaded fasteners, a bearing 48, and a swing 50. The swing 50 includes an arm 52 and an arm support ring 54 to which the arm 52 is fastened with threaded fasteners. The bearing 48 is positioned between the bearing support ring 46 and the arm support ring 54 for rotation of the swing 50, the chain support 36 attached to the swing 50, and the chain 34 attached to the chain support 36 about an axis of rotation 56 of the chain driver 38.

[026] The chain support 36 includes a guide bar 58 and a bar holder 60 holding the guide bar 58. The chain 34 is trained about the guide bar 58 and the chain driver 38. The bar holder 60 is attached movably to a mount 62 of the saw apparatus 10 for movement of the bar holder 60 and the guide bar 58 relative to the mount 62.

[027] The mount 62 may be any suitable mount to which the bar holder 60 may be attached movably. In the illustrated example, the mount 62 includes the base machine 12, the boom assembly 16, the coupler 17, the frame 18, and the attachment device 40. In such a case, the bar holder 60 is attached movably to the swing 50 for movement of the bar holder 60 and the guide bar 58 relative to the swing 50. Exemplarily, the bar holder 60 is attached movably to the arm 52 for movement of the bar holder 60 and the guide bar 58 relative to the arm 52.

[028] The chain driver 38 includes a hydraulic motor 64 and a sprocket 66. The sprocket 66 is attached to an output shaft of the motor 64 for rotation about the rotation axis 56. The chain 34 is trained about the sprocket 66.

[029] A hydraulic swing cylinder 68 is attached to the arm 52 and the frame 18 therebetween. The cylinder 68 is operable to pivot the swing 50, the chain support 36, and the chain 34 about the rotation axis 56 between a stowage position retracted into the saw housing 32 and a deployed position during a sawing event (e.g., felling, bucking).

[030] Referring to FIGS. 5 and 6, the bar holder 60 includes a first plate 70, a second plate 72, and a connector 73 connecting the first and second plates 70, 72 therebetween. The connector 73 includes a T-shaped body 74 and a support body 76. The T-shaped body 74 and the support body 76 are positioned between the first and second plates 70, 72. The base of the T-shaped body 74 is positioned against the first plate 70, and the support body 76 is positioned against the second plate 72. The cross member of the T-shaped body 74 merges into the support body 76 such that the T-shaped portion and the support body 76 cooperate to form an L-shaped body 77. Exemplarily, the plates 70, 72, T-shaped body 74, and support body 76 cooperate to form a monolithic body cut out of a block of material.

[031] An end portion of the guide bar 58 has two tongues 78 with a slot 80 open at one end defined between the tongues 78. The guide bar 58 is fitted to the bar holder 60 such that the base of the T-shaped body 74 is positioned in the slot 80 with the tongues 78 positioned on either side of the base of the T-shaped body 74 and between the L-shaped body 77 and the first plate 70, in particular, between the first plate 70 and the cross member of the T-shaped body 74 and the support body 76. Two threaded fasteners 82 fasten respectively the tongues 78 to the first plate 70, thereby attaching the guide bar 58 to the bar holder 60. Each fastener 82 includes a threaded portion that is proximal to the head of the fastener 82 and threaded to the first plate 70 and an unthreaded portion that is distal from the head, smaller in outside diameter than the threaded portion, and positioned in a respective unthreaded hole of the tongue 78.

[032] Referring to FIGS. 7 and 8, the bar holder 60 is fitted to the swing arm 52. The swing arm 52 has a slot 84 open at a first end thereof. The connector 73, for example its L-shaped body 77, is positioned in the slot 84. The arm 52 includes a first branch 86 and a second branch 88. The slot 84 is defined between the branches 86, 88. When the connector 73, for example its L-shaped body 77, is positioned in the slot 84, the first plate 70 and the tongues 78 are positioned to a first side of the swing arm 52, and the second plate 72 is positioned to a second side of the swing arm 52 opposite to the first side. The first plate 70 overlaps the first and second branches 86, 88 such that the two tongues 78 are positioned respectively between the first and second branches 86, 88. The second plate 72 overlaps the first and second branches 86, 88.

[033] Referring to FIG. 4, the saw 20 includes a chain tensioner 90 urging the bar holder 60 and the guide bar 58 to move relative to the mount 62 to tension the chain 34. The chain tensioner 90 is attached to the swing 50 and its arm 52 and includes, for example, a piston and a spring urging the piston to extend through an opening in an end wall of the slot 84. During operation, the piston is under hydraulic pressure that urges the piston to extend through that opening. During replacement of the chain 34, the hydraulic pressure is relieved, allowing manual retraction of the piston against the spring to facilitate chain removal and subsequent installation of the new chain. Manual pressure on the piston is released so that the spring pre-tensions the chain. Hydraulic pressure is then re-introduced to raise the chain tension to an operational level.

[034] The chain tension 90 contacts the bar holder 60. The piston of the chain tensioner 90 contacts the T-shaped body 74 of the bar holder 60 so as to urge the bar holder 60 and the guide bar 58 away from the swing 50 and its arm 52, thereby tensioning the chain 34.

[035] Referring to FIG. 8, the bar holder 60 is positioned for slidable, linear movement in the slot 84 relative to the swing 50 and its arm 52 and thus relative to the mount 62 in response to pressure from the chain tensioner 90. The swing 50 is configured to guide the bar holder 60 and thus the guide bar 58 so as to move linearly. The connector 73, for example its L-shaped body 77, is positioned laterally between the branches 86, 88 for slidable movement against the branches 86, 88. The branches 86, 88 are positioned transversely between the first and second plates 70, 72 and between the second plate 72 and the tongues 78.

[036] Referring to FIGS. 8 and 9, the arm 52 of the swing 50 includes a linear first groove 92 in the first branch 86 and a linear second groove 94 in the second branch 88. The second plate 72 overlaps the first and second grooves 92, 94. The bar holder 60 includes a first post 96 and a second post 98. Each post 96, 98 includes, for example, a threaded portion that is proximal to the head of the post 96, 98 and threaded to the second plate 72 and an unthreaded portion that is distal from the head and smaller in outside diameter than the threaded portion.

[037] The first post 96 extends through the second plate 72 into the first groove 92 for linear, slidable movement in and against the first groove 92, as shown, for example, in FIG. 8. The threaded portion of the first post 96 is threaded to the second plate 72, and the unthreaded portion is positioned in the first groove 92. The first post 96 can contact the opposite, closed ends of the first groove 92 to limit travel of the bar holder 60 and the guide bar 58 relative to the swing 50 and its arm 52.

[038] Referring to FIG. 9, the second post 98 extends through the second plate 72 into the second groove 94 for linear, slidable movement in and against the second groove 94. The threaded portion of the second post 98 is threaded to the second plate 72, and the unthreaded portion is positioned in the second groove 94.

[039] The bar holder 60 comprises a sensor target 100. The sensor target 100 is embedded within the bar holder 60. For example, the sensor target 100 is embedded within the second plate 72 of the bar holder 60. The second plate 72 includes a hole 109, and the sensor target 100 is positioned and secured within the hole 109 (e.g., press fit into the hole 109). If the hole 109 is a through-hole, filler material (not shown), e.g., epoxy, may fill the hole 109 above the sensor target 100, inhibiting ingress of debris into the hole 109. The sensor target 100 is thus in register with the second groove 94 for linear movement along the second groove 94 with the bar holder 60. The sensor target 100 is configured, for example, as a permanent magnet.

[040] Alternatively, the sensor target 100 may be attached to a tip of the second post 98 so as to be mounted thereto. In such a case, the sensor target 100 is positioned in the second groove 94 for linear movement therein as the bar holder 60 moves linearly.

[041] Referring to FIGS. 7 and 9, the saw 20 has a sensor 102 positioned to sense a position of the chain support 36 relative to the mount 62. The sensor 102 is positioned to sense a position of the bar holder 60 relative to the swing 50 and thus the mount 62 by use of the sensor target 100 of the bar holder 60. The sensor 102 is configured to generate a position signal indicative of the position of the sensor target 100 of the bar holder 60 of the chain support 36 relative to the swing 50 of the mount 62.

[042] The sensor 102 is configured, for example, as a magnetostrictive linear position sensor configured to sense linear position. In such a case, the sensor 102 has an electronics unit 104 and a magnetostrictive sensing element 106 in the form of a longitudinal waveguide. The electronics unit 104 is positioned in a cavity 108 of the arm 52. The cavity 108 is filled with a filler material (not shown), e.g., epoxy, sufficient to secure the unit 104 in the cavity 108. The sensing element 106 is positioned in the second groove 94 so as to extend longitudinally therein and is used to determine the position of the sensor target 100 along the length of the sensing element 106. A dead band 107 is positioned at either end of the sensing element 106. The second groove 94 is filled with a filler material (not shown), e.g., epoxy, sufficient to secure the sensing element 106 in the second groove 94. The filler material may only partially fill the second groove 94, allowing space for the post 98 to extend into and move linearly in the second groove 94. In an example, the sensor 102 is model C-S-0072-V-P1 available from MTS Systems Corporation, Sensors Division, in Cary, North Carolina.

[043] In another example, the sensor target 100 may comprise a series of magnets mounted to the plate 72 of the bar holder 60 (e.g., via a magnet carrier) and arranged linearly relative to one another along the linear path of movement of the bar holder 60. In the case where the sensor 102 is a magnetostrictive linear position sensor, the sensor 102 may be configured to sense the position of those magnets with the sensing element 106 (e.g., in the form of a longitudinal waveguide) and resolve those measurements into a single voltage output from the electronics unit 104 indicative of the position of chain support 36, and its bar holder 60, relative to the mount 62. Use of the series of linearly arranged magnets promotes accuracy and error reduction in the position determination. The electronics unit 104 may be smaller than depicted in the drawings, and the sensing element 106 may be without a deadband at each of its opposite ends. The sensor target 100 and the sensor 102 may be mounted respectively to the bar holder 60 and the arm 52 in any suitable manner.

[044] Referring to FIG. 10, the saw apparatus 10 includes an electronic control system 1 10. The control system 1 10 includes one or more electronic controllers, each controller including a processor and memory having stored therein instructions which, when executed by the processor, causes the processor to perform the various operations of the controller. For example, the control system 1 10 includes a first controller 112 on board the head 14 and a second controller 1 14 on board the base machine 12. The controllers 112, 114 are connected to one another via a communications bus 1 16 (e.g., a CAN bus). The sensor 102 is coupled electrically to the first controller 112. The head 14 has a number of valves 118 arranged, for example, in a valve block and coupled electrically to the first controller 1 12 so as to be under its control. The valves 118 include, for example, a motor valve configured to control operation of the motor 64 and a swing valve configured to control pivotal movement of the swing 50.

[045] Referring to FIG. 11 , the control system 1 10 is configured to perform a control scheme 210. As part of the control scheme 210, the control system 110 is configured to receive the position signal and determine if the cutting chain 34 has stretched to a stretch threshold dependent on the position of the sensor target 100 of the bar holder 60 of the chain support 36 relative to the swing 50 of the mount 62 in order to determine if a risk of chain breakage has increased. In an example, the control system 1 10 may be configured to monitor a stretch trend of the chain 34 and determine if the stretch trend reaches the stretch threshold. In so doing, the control system 1 10 may be configured to determine a predicted stretch indication and an actual stretch indication and to determine if the actual stretch indication exceeds the predicted stretch indication by at least the stretch threshold. The control system 1 10 may activate an alert if the actual stretch indication does exceed the predicted stretch indication by at least the stretch threshold. An example of the control scheme 210 is shown in FIG. 12.

[046] In step 212 of the control scheme 210, a human operator operates an operator input device 122 located at the operator's station of the base machine 12 in response to which the second controller 1 14 receives from the operator input device 122 an operate-saw request signal indicative of a request from the human operator to operate the saw 20. In response to the operate-saw request signal, the second controller 1 14 broadcasts an operate-saw request message on the bus 1 16. The first controller 1 12 receives that message and, in response thereto, outputs control signals to the two valves 1 18 responsible respectively for controlling the motor 64 and the swing cylinder 68 and takes an initial position reading, P ₀ , of the position of the sensor target 100 from the sensor 102. The first controller 1 12 stores this initial position reading in its memory so as to begin a historical watch of the behavior of the chain 34. Before the control scheme 210 advances to step 214, the first controller 1 14 may set a counter variable, n, equal to 1 and a variable S _S UM equal to 0.

[047] Step 214 relates to the next time that a human operator operates the operator input device 122. In step 214, the second controller 1 14 receives from the operator input device 122 the operate-saw request signal indicative of another request from the human operator to operate the saw 20. In response to that operate-saw request signal, the second controller 1 14 broadcasts an operate-saw request message on the bus 1 16. The first controller 1 12 receives that message and, in response thereto, outputs control signals to the two valves 1 18 responsible respectively for controlling the motor 64 and the swing cylinder 68 and takes a position reading, P _n , of the position of the sensor target 100 from the sensor 102. P _n would be Pi if it is the position reading immediately after P ₀ , or P ₂ if it is the position reading immediately after P-i, and so on. As such, P ₀ and Pi are consecutive position readings, and P _n and P _n+ i are consecutive positions readings. The control scheme 210 advances to step 216.

[048] In step 216, the first controller 1 12 determines an actual stretch indication, S _n , indicative of an actual stretch in the length of the chain 34 between P _n and P _n -i. In an example, the first controller 1 12 determines the actual stretch indication according to the following equation:

S _n = ^ - ^ (100)

- ^» v i— 1

In such a case, the actual stretch indication is an actual stretch percentage.

[049] In step 218, the first controller 1 2 determines if n is greater than or equal to 2. If yes, the control scheme 210 advances to step 220. If no, the control scheme 210 advances to step 228 in which the first controller 1 12 adds one to the counter n and then advances back to step 214. Alternatively, in step 218, the first controller 112 may determine if n is equal to 1 , and, if yes, the control scheme 210 advances to step 228, and, if no, the control scheme 210 advances to step 220.

[050] The control scheme 210 advances to step 220 if the counter is two or more, meaning that at least three position readings have been taken from the sensor 102. In step 220, the first controller 112 determines the sum, S _S U , of all prior actual stretch indications, i.e., Si to S _n- i. The sum does not include the current actual stretch indication, S _n . The first controller 1 12 may determine the sum according to the following equation: S _S UM = SSUM + S _n- i. The control scheme 210 advances to step 222.

[051] In step 222, the first controller 1 12 determines a predicted stretch indication, SpR. In an example, the predicted stretch indication is the average of all prior actual stretch indications, and is determined according to the following equation:

SPR = SSUM /(n-1). The control scheme 210 advances to step 224.

[052] In step 224, the first controller 1 12 determines if the chain 34 has stretched to a stretch threshold, S _T H- For example, the first controller 112 determines if the actual stretch indication exceeds the predicted stretch indication by at least the stretch threshold. The first controller 112 does so by determining if the difference between the current actual stretch indication and the predicted stretch indication is greater than or equal to the stretch threshold according to the following equation: S _N - SPR > STH. If no, the control scheme 210 advances to step 228. If yes, the control scheme 210 advances to step 226. To determine the stretch threshold, chain manufacturers may be contacted for an indication of acceptable chain stretch. The stretch threshold may be about 1 .0% to about 1 .5%.

[053] In step 226, the control system 1 10 activates an alert if the cutting chain 34 has stretched to the stretch threshold. The first controller 12 broadcasts an alert message on the bus 1 16, and the second controller 1 14 receives the alert message. The second controller 1 14 outputs a control signal causing an output device 124 to issue the alert. The alert may be in any suitable form, such as, for example, a visual indication, an audible indication, a tactile indication, or any combination thereof, to name but a few possibilities. In an example, the output device 124 is a monitor, and the alert is a visual alert on the screen of the monitor (e.g., a pop-up). Illustratively, the output device 124 is coupled electrically to the second controller 1 14. In other examples, the output device 124 may be coupled electrically directly to the bus 1 16.

[054] The alert may remain active until the human operator acknowledges the alert. For example, in the case where the output device 124 is a monitor and the alert is a visual alert on a screen of the monitor, the visual alert may remain active until the operator presses a button (e.g., escape button on a keyboard coupled electrically to the second controller 1 14 configured as a PC) or other operator input device, acknowledging the alert.

[055] In step 228, the first controller 1 12 adds one to the counter n. Afterwards, the control scheme 210 advances back to step 214.

[056] The first controller 1 12 may store in its memory a number of values. For example, for historical and evaluation purposes, it may store all of the position readings and/or all of the actual stretch percentages, so as to keep a historical log of those values ("and/or" means and-or-or). It may also store the stretch threshold as a constant, and may store all SSUM and/or SPR values so as to keep a historical log of those values or only store them until updated in the next loop of the control scheme 21 0.

[057] In the above example of the control scheme 210, the actual and predicted stretch indications are stretch percentages. In another example of the control scheme 210, the actual stretch indication is an actual change in position from one position reading to the next position reading, and the predicted stretch indication is a predicted change in position. Change in position may be represented by Δ, and the control scheme 210 may be modified as follows:

step 216 is replaced by Δ _Η = P _n - Pn-1,

step 220 is replaced by Δ _δ υινι = &SUM + Δ _η- ι,

step 222 is replaced by A _PR = AsuM (n-1 )

step 224 is replaced by Δ _Η - APR≥ ΔΤΗ- [058] In such an example of the control scheme 210, the first controller 1 12 may store in its memory all of the position readings and/or all of the actual changes in position, so as to keep a historical log of those values. It may also store the stretch threshold as a constant, and may store all Asm and/or APR values so as to keep a historical log of those values or only store them until updated in the next loop of the control scheme 210.

[059] In yet another example, the control scheme 210 may be modified such that no predicted stretch indication is taken into account, and the actual stretch indication is the position reading from the sensor 102. In such a case, the first controller 1 12 compares each position reading to a stretch threshold in the form of a position threshold. Once the position reading reaches the position threshold, the first controller 1 12 signals the second controller 1 14 to activate the alert. In such an example of the control scheme 210, the first controller 1 12 may store in its memory all of the position readings, so as to keep a historical log of those values. It may also store the position threshold as a constant.

[060] In another example of the saw apparatus 10, the saw apparatus may be configured as a hand-held saw apparatus. In that case, the mount may be the frame of the hand-held device to which the saw is attached, without a swing. The chain support may be attached movably to the frame for movement relative thereto. The chain tensioner may urge the chain support to move relative to the frame to tension the chain. The sensor may be positioned (e.g., attached to the frame) to sense a position of the chain support relative to the frame. Since the saw apparatus is a hand-held device, the control system may have a single electronic controller.

[061] The welds, threads, and hydraulic and electrical lines of the forestry head have not been shown for simplification of illustration, it being understood that it would be well within the skill of one of ordinary skill in the art to provide those features without undue experimentation. [062] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that illustrative embodiment(s) have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. It will be noted that alternative embodiments of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the appended claims.