Patent Publication Number: US-2009223191-A1

Title: Mechanical Interlock for a Control Member

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an interlock for a control member, and more particularly to a mechanical interlock allowing selective actuation of an implement control member. 
     A variety of implements, such as lawnmowers, snow-throwers, string trimmers, augers, blowers, and the like, incorporate some type of control member (e.g., paddle, lever, bar, trigger, etc.) to actuate the working device of the implement. For example, a snow-thrower may include a pair of control paddles, one to activate the horizontal auger and vertical impeller to direct snow, and the other to activate the drive wheels to propel the snow-thrower in the desired direction. 
     Several systems and devices have been developed to reduce the frequency and ease with which the control member of an implement can be unintentionally actuated. Many of the current developments use electrical components to monitor the position of the control member and/or a secondary safety member in an attempt to ensure that the operator intends to activate the implement. 
     Electronic interlock systems suffer from several drawbacks. For instance, environmental contaminants (e.g., dirt, dust, water, etc.) can degrade or prevent the consistent operation of the electrical interlock system. Additionally, use of electrical contacts, position sensors, wire harnesses, and the like, may be both expensive and unnecessarily complex. 
     Many of the electrically based systems also incorporate an assortment of mechanical components. Mechanical designs often present additional drawbacks, such as requiring alignment or adjustment by a skilled technician in order to ensure proper operation of the interlock and control member. Moreover, many of the current mechanical interlocks are difficult to operate as they require the operator to perform a series of steps or are not ergonomically engaged. 
     Therefore, a need exists for a mechanical interlock for a control member that is robust, efficient to manufacture, easy to install and maintain, and reduces inadvertent actuation of the associated control member. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides a mechanical interlock reducing inadvertent engagement of a control member. In one aspect, the present invention provides an implement including a handle extending from the implement and a control member pivotally coupled to the handle about a control axis. A mechanical interlock includes an interlock bracket that is pivotally coupled to the control member about an interlock axis. A guide path is formed in the interlock bracket and has a locking segment and an actuating segment that intersect at an acute angle. And, a guide member is coupled to the handle and configured to engage the guide path. The mechanical interlock is positionable at a locked position where the guide member is proximate the locking segment, an engaged position where the guide member is proximate the intersection of the locking segment and the actuating segment, and an actuated position where the guide member is proximate the actuating segment. The control member is prevented from pivoting about the control axis when the mechanical interlock is in the locked position. 
     In another aspect, the present invention provides a mechanical interlock that is coupleable to a control member pivotally coupled to a handle about a control axis. The mechanical interlock includes an interlock bracket that defines a guide path having a locking segment and an actuating segment that form an intersection at an acute angle. A guide member is configured to engage the guide path. One of the interlock bracket or the guide member is pivotally coupled to the control member about an interlock axis and the other is coupled to the handle. The guide path and the guide member are selectively positionable between a locked position where the guide member is proximate the locking segment, an engaged position where the guide member is proximate the intersection, and an actuated position where the guide member is proximate the actuating segment. The control member is prevented from pivoting about the control axis when the guide path and the guide member are positioned at the locked position. 
     In yet a further aspect, the invention provides a method of activating a control member that is pivotally coupled to a control handle about a control axis and that incorporates a mechanical interlock. The method includes the steps of providing an interlock bracket defining a guide path having a locking segment and an actuating segment that form an intersection at an acute angle, and providing a guide member configured to selectively engage the guide path. Then, pivoting one of the interlock bracket or the guide member about an interlock axis from a locked position at which the guide member is proximate the locking segment to an engaged position at which the guide member is proximate the intersection, and pivoting the control member about the control axis to move the interlock bracket and the guide member from the engaged position to an actuated position at which the guide member is proximate the actuating segment. 
     These and still other aspects of the present invention will be apparent from the description that follows. In the detailed description, a preferred example embodiment of the invention will be described with reference to the accompanying drawings. This embodiment does not represent the full scope of the invention; rather the invention may be employed in other embodiments. Reference should therefore be made to the claims herein for interpreting the breadth of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an implement incorporating a mechanical interlock in accordance with the present invention; 
         FIG. 2  is a perspective view of the mechanical interlock; 
         FIG. 3  is an isometric exploded view of the mechanical interlock; 
         FIG. 4A  is a side elevation view of the mechanical interlock in the locked position; 
         FIG. 4B  is a side elevation view of the mechanical interlock in the engaged position; and 
         FIG. 4C  is a side elevation view of the mechanical interlock in the actuated position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EXAMPLE EMBODIMENT 
     The preferred example embodiment of the mechanical interlock will be described in relation to a lawnmower having a control paddle; however, the present invention is equally applicable to other types and styles of implements (such as snow-throwers, string trimmers, augers, blowers, and the like) having a variety of control members (such as levers, bars, triggers, and the like). Additionally, while the example embodiment will describe a mechanical interlock that selectively locks the control member in the deactivated position, the invention contemplates a mechanical interlock adapted to selectively lock a control member in the activated position or any desired intermediate position. 
     A mechanical interlock  10 , in accordance with an example embodiment, is shown in  FIG. 1 . The mechanical interlock  10  is coupled to a lawnmower implement  12  generally used for mowing grass in a residential or commercial environment. The lawnmower implement  12  includes an engine  14  mounted to a deck  16 . The engine  14  powers a pair of drive wheels  18  via a first clutch attached to a power take off (PTO) (not shown). A pair of swivelable steering wheels  20  extend forward of the deck  16 . A pair of blades (not shown) are rotatably mounted under the deck  16  and are driven by a second clutch coupled to the PTO (not shown). 
     A handle assembly  22  extends rearward and upward from the deck  16  terminating in a pair of handles  24  that allow an operator to control the movement of the lawnmower implement  12 . The example lawnmower implement  12  includes a pair of control paddles  26 , one for engaging or actuating the first clutch coupled to the drive wheels  18 , and another for activating the second clutch coupled to the blades. The general design and construction of the basic lawnmower implement  12 , clutches, and PTO are known to those having ordinary skill in the art. 
     Each control paddle  26  incorporates a mechanical interlock  10  to prevent unintended engagement of the PTO; however, only one of the control paddles  26  will be used to describe the preferred construction and operation of the mechanical interlock  10 , as the other operates and is constructed in substantially the same manner. It is further contemplated by the present invention that any number of control paddles  26  may be incorporated with the implement as desired. For example, a string trimmer may only require a single control paddle to activate the rotation of a spindle head from which the string extends to shear grass, shrubs, and the like. 
     With additional reference to  FIGS. 2 and 3 , the control paddle  26  is pivotally coupled to the handle  24  to rotate with respect to the handle  24  about a control axis  28 . In the example embodiment, the handle  24  has a pair of handle holes  30  formed essentially perpendicular to the central axis of the handle  24 , thus defining the control axis  28 . A pair of collar bushings  32  have an interior surface  33  contoured to match the radius of the handle  24  and are assembled to capture the handle  24  by aligning a collar hole  34  formed in each with the handle hole  30  formed in the handle  24 . Alternatively, the control paddle  26  may be rotatably attached to the handle in a variety of other ways, such as by a blind rivet. Furthermore, the handle  24  need not be circular in cross-section but may be rectangular, octagonal, oval, or any other suitable form factor. Accordingly, the collar bushings  32  will be configured to ensure sufficient engagement between the collar bushings  32  and the handle  24 . 
     In the example embodiment, the control paddle  26  includes a pair of flanges  38 , each having a coaxial control paddle hole  40 . The flanges  38  are slid over a bearing portion  37  of the collar bushings  32  to align the control paddle holes  40  with the collar holes  34  and the handle holes  30  (best shown in  FIG. 3 ). A pair of stepped, cylindrical bushings  42  are adjacent to the outer surface  44  of the flanges  38  and extend partially inwards through the control paddle holes  40 . A biasing member, such as a control paddle torsion spring  48 , is included between one of the flanges  38  and one of the collar bushings  32  to bias the control paddle  26  toward the open, deactivated position (shown in  FIG. 2  and  FIG. 4A ). The torsion spring  48  includes a first index tab  50  seated between forks  36  extending from the collar bushing  32  and a second index tab  52  seated in a notch  78  formed in a flange  38  (note that the first index tab  50  and the second index tab  52  of the torsion spring  48  are shown in the unengaged state). Each collar bushing  32  includes a pair of opposing forks  36  to allow the collar bushings  32  to be interchangeable. 
     A fastener  46 , such as a partially threaded cap screw and nut, is inserted along the control axis  28  through the bushings  42 , control paddle holes  40 , collar holes  34 , handle holes  30 , and torsion spring  48  to rotatably couple the control paddle  26  to the handle  24 . As a result, the control paddle  26 , while biased open (i.e., away from the handle  24 ), can rotate about the control axis  28  to activate and deactivate the PTO for the coupled working device (e.g., drive wheels  18 , blades, auger, impeller, fan, and the like). The control paddle  26  further includes a tab  106  having a hole  108  formed therein. The hole  108  is sized to receive and secure a cable mount  109 , such as a pin, that is linked to a cable (not shown) to energize and de-energize the corresponding PTO as is know to one of ordinary skill in the art. However, in order for the control paddle  26  to be activated or depressed, the mechanical interlock  10  must be unlocked, as discussed below. 
     The mechanical interlock  10  includes an interlock bracket  54  that is pivotally coupled to the control paddle  26  so as to be selectively rotatable about an interlock axis  56 . The interlock bracket  54  rotates relative to the control paddle  26  and also moves with the control paddle  26  because it is coupled thereto. In the preferred embodiment described, the control axis  28  and the interlock axis  56  are not coaxial, however, the mechanical interlock  10  may be configured such that the control axis  28  and interlock axis  56  are the same axis. 
     The interlock bracket  54  is mounted to the control paddle  26  via a mounting rod  58  having a curved portion  60  secured, for example by welding, to the top surface  62  of the control paddle  26 . A straight portion  64  of the mounting rod  58  is seated in a support plate  66  that is fixed (by any standard technique, such as welding) to a flange  38  of the control paddle  26 . A spacer  68  and a torsion spring  70  (i.e., biasing member) are slid over the straight portion  64  of the mounting rod  58  and sandwiched between the interlock bracket  54  and the support plate  66 . A first index tab  72  of the torsion spring  70  is seated in a slot  74  formed in the interlock bracket  54  and a second index tab  76  engages a bearing surface  77  of the support plate  66 , resulting in the interlock bracket  54  being biased clockwise as viewed in  FIG. 4A  (again, it is of note that the first index tab  72  and the second index tab  76  of the torsion spring  70  are shown in  FIG. 3  in the unengaged state). The interlock bracket  54  includes a mounting hole  80  that receives the straight portion  64  of the mounting rod  58 . A stepped bearing  82  abuts the exterior surface  84  of the interlock bracket  54  and extends partially into the mounting hole  80 . An end cap  86  is secured to the mounting rod  58  by internal barbs (not shown) to capture the interlock bracket  54  while allowing it to rotate about the interlock axis  56 . 
     To initiate rotation of the mechanical interlock  10  about the interlock axis  56  and against the bias of the torsion spring  70 , the interlock bracket  54  includes a bent over activation tab  88  covered by a grip  90 . The rotation of the interlock bracket  54  is further constrained by a guide path  92  formed in the interlock bracket  54 . In the example embodiment, the guide path  92  rides along a guide member  94  during activation of the interlock bracket  54  and the control paddle  26 . The guide member  94  may extend from the handle  24  after passing through a pair of holes  96  formed through the handle  24 , and may be secured via welding or any conventional technique. An end cap  98  is secured, again preferably by internal barbs (not shown), to an end  100  of the guide member  94  to bear against the exterior surface  84  of the interlock bracket  54 . In the example embodiment, the guide member  94  is in the form of a pin that extends from the handle  24 , however, the guide member  94  may be any suitable structure capable of engaging and riding along or within the adjacent guide path  92 . 
     The guide path  92  is preferably a generally L-shaped path having an actuating segment  102  and a locking segment  104  forming an intersection  103 . The relative alignment between the actuating segment  102  and the locking segment  104  at the intersection  103  defines a preferably acute angle θ (best shown in  FIG. 4C ). The acute angle θ helps ensure that the mechanical interlock  10  will prevent unwanted activation of the control paddle  26  and help ensure that the interlock bracket  54  is biased toward the locked position when the control paddle  26  is attempted to be actuated without first actuating the mechanical interlock  10 . Additionally, the guide path  92  is preferably slightly wider than the guide member  94  to prevent binding and the need for the guide path  92  to be arcuate to accommodate the pivoting of the interlock bracket  54  about the interlock axis  56  and the control axis  28 . 
     The guide path  92  is preferably sized to allow full actuation of the control paddle  26 , however, the actuating segment  102  may be sized to prohibit full actuation of the control paddle  26  to prevent, for example, an operator&#39;s fingers from being pinched between the control paddle  26  and the handle  24 . Additionally, the guide path  92  may include multiple intersections  103  to establish a series of actuating segments  102  and locking segments  104 , forming a stepped guide path  92  defining intermediate locked positions. 
     In the example embodiment, the guide path  92  is machined from the interlock bracket  54  to create the profile shown most clearly in  FIGS. 4A-4C . Alternatively, the guide path  92  may take the form of a recess, channel, cavity, and the like, that is capable of capturing and directing the guide member  94 . For example, while the cutout guide path  92  shown may be preferable, a three-sided guide path  92  defined by a channel formed into the interlock bracket  54  may have use in applications where it is desirable to prevent foreign objects (e.g., grass, twigs, etc.) from entering the guide path  92  and obstructing the engagement between the guide path  92  and the guide member  94 . Many other variations are contemplated and are within the scope of the present invention. 
     One skilled in the art will appreciate the numerous variations for constructing and mounting the mechanical interlock  10 . For example, in coupling the interlock bracket  54  to the control paddle  26 , the mounting rod  58  may comprise a post welded to the control paddle  26 , thereby eliminating the use of the support plate  66 . 
     The components of the mechanical interlock  10 , are preferably made of typical metallic, plastic, and composite materials. For example, the interlock bracket  54  may be easily produced from low carbon steel; alternatively, the interlock bracket  54  may be produced from acrylonitrile butadiene styrene (commonly referred to as ABS), fiberglass, and the like. Many variations and alterations will be appreciated by one skilled in the art. 
     The mechanical interlock  10  is generally moveable between three positions, namely a locked position, an engaged position, and an actuated position. With initial reference to  FIG. 4A , the mechanical interlock is shown in the locked position. In this position, force applied to pivot the control paddle  26  toward the handle  24  will drive the distal end  110  of the locking segment  104  of the interlock bracket  54  into the guide member  94 . The slightly acute intersection  103  ensures that the guide member  94  is directed toward the distal end  110  of the locking segment  104  and prevents actuation of the control paddle  26 . 
     In order to pivot the control paddle  26 , an operator must first apply force to the activation tab  88  to pivot the interlock bracket  54  about the interlock axis  56  to the engaged position shown in  FIG. 4B . With the guide member  94  located at the intersection  103 , the interlock bracket  54 , and thus the control paddle  26 , can be pivoted substantially in unison about the control axis  28 . Continuing to depress the control paddle  26  toward the handle  24  results in the actuated position shown in  FIG. 4C  with the guide member  94  adjacent the actuation stop surface  112  of the actuating segment  102 . 
     Releasing or deactivating the control paddle  26  results in the torsion spring  48  acting on the control paddle  26  to bias the control paddle  26  upwards to the de-energized position shown best in  FIG. 4B . At the same time, the torsion spring  70  acting on the interlock bracket  54  biases the guide path  92  clockwise against the guide member  94  such that once the guide member  94  is positioned proximate the intersection  103 , the interlock bracket  54  pivots to the locked position shown best in  FIG. 4A . The mechanical interlock  10  is thus automatically reset to the locked position after the control paddle  26  is released. 
     The mechanical interlock  10  requires that the operator engage both the mechanical interlock  10  and the control paddle  26  to engage the PTO and the coupled working device. As a result, the mechanical interlock  10  reduces the operator&#39;s ability to involuntarily engage the PTO, and therefore creates an elegant, efficient system that minimizes inadvertent operation of the associated implement, while also reducing the occurrence of damage to the implement and working device. 
     While there has been shown and described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention defined by the following claims. For example, where relative movement takes place between a moveable component and a stationary component, such as between the moveable guide path  92  and the stationary guide member  94 , the dynamic characteristics of the components may be switched (i.e., the guide member  94  may be configured as moveable and the guide path  92  as stationary) and yet remain within the scope of the present invention.