WO2008037067A1

WO2008037067A1 - Ergonomic armrest

Info

Publication number: WO2008037067A1
Application number: PCT/CA2007/001704
Authority: WO
Inventors: Michele Oliver; Taylor Murphy
Original assignee: University Of Guelph
Priority date: 2006-09-27
Filing date: 2007-09-27
Publication date: 2008-04-03

Abstract

An ergonomic armrest provides support while allowing a natural movement pattern tor a person's arm, the ergonomic armrest comprising a support structure having trajectory tracks, and an arm support connected to the trajectory tracks, the arm suppoπ operable to move linearly and rotationally along a movement path. The movement path allows a person to move his/her forearm along naτural motion trajectories and provides support throughout the range of motion, thereby reducing the myoelectric activity in the person's shoulder complex.

Description

ERGONOMIC ARMREST

Field of the Invention

The present invention relates to dynamic and ergonomic armrests. The present invention further relates to armrests for use in repetitive movement applications. The present invention particularly relates to armrests for controllers operating heavy machinery, e.g., forestry, construction, excavation and mining heavy equipment.

Background of the Invention

The interaction of potential nsk factors associated with the manipulation of controllers (e.g , joysticks) in heavy machinery is a complex problem, involving postural affects resulting from controller design, external and internal forces, workplace requirements, and repetition o I^" movements, as well as psychosocial concerns.

Past research has indicated that during joystick manipulation, muscle activation in die shoulder (upper trapezius, or '"UT") is at a constant static load of 2% Maximum Isometric Voluntary Contraction ("MVC") According to some experts, static loads exceeding 2% MVC are considered inappropriate and can lead to long term damage of muscles and the development of repetitive strain injuries. Others feel that a more acceptable upper limit is 1% MVC unless adequate rest periods are given. It is known from prior research work that the UT is almost entirely dedicated to stabilizing the shoulder complex during joystick manipulation

Qualitatively, the muscle activation during die joystick operations is mainly due to the operator being obliged to keep his/her anus raised above the machines' armrest while operating the machine in order to affect long lever strokes or to activate manually operable controls in the cabtn which requires the operator to lift and possibly maintain his arms above the armrests. Machines are often controlled using one of two rypes of controllers/joysticks, one type is a pronated or semi-pronaied hand-lever and the other is a mmi-Iever. These controllers are used typically in conjunction with armrests. Although studies have shown that mini-levers slightly decrease shoulder muscle activation (and pain prevalence), these small controls have not been shown to reduce the prevalence of pain in the neck. As the armrests support as much as 35% of arm's weight they have generally been considered to reduce muscle activation further to that achievable with the mini-levers.

Previously known armrests offer some mechanical features such as the ability lo adjust at front and rear ends, the ability to incline where needed and to be able to adjust the position of manual controls so that hand and arm are in a comfortabje position on an armrest pad. These features are usually sturdy, fast and easy to adjust and relatively inexpensive.

For example, U.S. Patent No. 6,341,821 to Rousseau teaches an ergonomtc armrest and joystick assembly that allows an operator to adjust the position of an armrest.

However, known armrests have failed to provide adequate support across the entire aim movement range. During forward lever motion the amplitude of sagittal plane arm movement requires the forearm to be raised from the armrest, requiring the UT to provide the majority of the stabilization. During backward joystick motion, the armrest resists natural arm pendulation, necessitating shoulder elevation or arm abduction, requiring excess UT activation through increased stabilization.

What is therefore needed is an armrest that provides for a natural motion path of a person's arm when performing repetitive movements (e.g., in the sagittal plane), for example, manipulating a controller What is further needed is an armrest that implements this motion path into an ergonomically correct arm support.

Summary of the Invention

The present invention is an crgoπomic armrest for operating a controller comprising a support structure having trajectory members, and an arm support connected to the trajectory members The arm support may be operable to move along the trajectory members so that the trajectory members define a movement path. The movement path may allow for the linear and rotational movement of the arm support in a plane of^" direction. The ergonomie armrest provides Support while allowing a natural movement pattern for a person's ann when performing repetitive movements, for example, while operating a controller. The ergonomic amrest obviates the disadvantages of the previously known armrest designs, In particular, the ergonomic armrest follows the natural movement of a person's forearm and provides support throughout a range of motion, therefore requiring less stabilization from the shoulder, and more specifically, lower UT activation. The result is a reduction in myoelectric activity in the shoulder complex and a decrease in risk of the person developing musculoskeletal disorders.

In a particular embodiment, the ergonomic armrest includes a pair of front trajectory supports, a pair of trajectory rear supports, and an arm support having two axels. Each trajectory support includes a track or nice defining a movement path, and the axels are operable to move along ;he track, e.g., by means of bearings. The rear tracks trace an upward path as ihe arm support moves forward, and the front tracks trace a slightly downward path as the arm support moves forward, such that the ergonomic armrest moves linearly and rotationally in the sagittal plane, thereby replicating the natural or unencumbered motion of a person's forearm while performing a task involving repetitive movements.

Brief Description of the Drawings

Λ detailed description of the preferred embodiments is provided herein below by way of example only and with reference to the following drawings, in which:

Figure 1 illustrates a perspective view of an ergonomic armrest in accordance with a preferred embodiment of the present invention;

Figure 2 illustrates paths of motion for the ergonomic armrest;

Figure 3 illustrates an exploded view of the ergonomic armrest;

Figure 4 illustrates a further exploded view of ihe ergonomic armrest;

Figure 5 is the ergonomic armrest in use with a hydraulic actuation joystick in a laboratory Setting, illustrating the position of the arm support when the operator pulls the joystick backward; Figure 6 is the ergonomic armrest in use with a hydraulic actuation joystick in laboratory setting, illustrating the position of the arm support when the operator has the joystick in the neutral position;

Figure 7 is the ergonomic armrest in use with a hydraulic actuation joystick in laboratory setting, illustrating the position of the arm support when the operator pushes the joystick forward; and

Figure 8 illustrates an ergonomic armrest seen fitted to a laboratory mock-up of a typical North American excavator cab and right handed hydraulic actuation joystick.

Figure 9 illustrates a perspective view of an ergonomic armrest in accordance with a second preferred embodiment of the present invention;

Figure 10 illustrates a perspective view of an ergonomic armrest;

Figure 11 illustrates an exploded view of the ergonomic armrest; Figure 12 illustrates a further exploded view of the ergonomic armrest;

In the drawings, one embodiment of the invention is illustrated by way of example. Tt is to be expressly understood that the description and drawings are only for the purpose of illustration and as an aid to understanding, and are not intended as a definition of the limits of the invention.

Detailed Description of the Invention

The ergonomic armrest, in one embodiment as illustrated in Figure 1 and the other drawings, provides support for an operator's forearm when the operator uses a controller. It should be understood that a controller is any device that provides inputs to machinery, equipment or another device, wherein the controller is operable to at least move forwards and backwards along the sagittal plane (the sagittal plane as defined by the operator). For example, a controller is a joystick used to control the movements of a iraclor loader. However, it should be expressly understood that the present invention encompasses any situation or application where a person is called upon to perform repetitive movements in the sagittal plane. For example, the ergonomic armrest could be implemented in manufacturing environments where a worker is involved in changing fixtures on a machine, whether lhe worker is standing or in a sitting position. The present invention is even extendable to wheelchair applications, or even automotive applications, as would be readily appreciated by a person of skill in the art.

The ergonomic armrest provides paths of motion for an" operator's forearm as shown in Figure 2.

As shown in Figure 3, the ergonomic armrest is attached to the ground or a seating assembly by means of support structure 1. The support structure 1 provides a means of securing the ergonomic armrest to die ground or the seating structure, secured by means of bolts placed through the anchor holes A (shown in Figure 4). The ergonomic armrest could also be fixed directly to the backrest of a chair or to an adjacent part of a cabin or workspace, for example, where applicable.

Although the drawings illustrate an ergonomic armrest attached to the ground, the ergonomic armrest could be alternatively provided to the person from above. In other words, the support structure could be attached or affixed from the ceiling of a workspace, for example.

Further, although the ergonomic armrest is generally implemented in conjunction with a seating structure, this is not essential. The ergonomic armrest is also capable of providing support throughout the range of motion when an operator is using a controller standing up. In that case, the support structure 1 would have Io have to be taller to account for the height difference, and the height would be preferably adjustable to accommodate operators' different heights.

Connected to the support structure 1 are four trajectory supports 2 (two forward and two rear) that include trajectory tracks D which convey and define a predetermined path in which an arm support 6 will travel to replicate the natural Or unencumbered motion of the forearm during a given task. The rear trajectory supports 2 trace an upward path as the arm Support 6 moves forward. The front trajectory supports 2 trace a slightly downward path as the arm support 6 moves forward. Tn other words, the ergonomic armrest translates and rotates in the sagittal plane, thereby replicating the natural or unencumbered motion of a person's forearm while performing a task.

Figures 5 to 7 depict the positions of die arm support when the operator pulls the joystick backward, when the operator has the joystick in the neutral position, and when the operator pushes the joystick forward, respectively.

The trajectory supports 2 are attached to the support structure 1 by a bolt running through vertical height adjustment holes B in the support structure 1 and vertical height adjustment slots C of the trajectory supports 2. When the bolt is loose, the trajectory supports 2 are free to move in the vertical directions to accommodate varying sizes of operators and/or environments. Once the correct height is found, the bolt is tightened and the trajectory 2 supports are firmly positioned until no further adjustment is required.

Referring to Figures 9 to 12 the trajectory supports 2 may also be positioned so as to provide a compact ergonomic armrest. Specifically the arm support 1 may be positioned above the trajectory supports namely the two rear trajectory supports and the two forward trajectory, which are integral with One another. Furthermore the two Front trajectory supports with their respective trajectory tracks are positioned below the two rear trajectory supports with their respective trajectory tracks. In this combination vertical adjustment of the arm rest occurs at the support structure 1 and allows for a complete compact armrest that can be easily retrofitted into already existing seating systems Such as a wheelchair.

Another feature of each trajectory supports 2 is a cut-out section which allows the trajectory support to be mounted on the support structure while reducing rotational movement ihat might be created by moments created as a result of the weight of the user's arm.

The motion of the arm support 6 of the ergonomic armrest can be accomplished through a conveying means 7 such as bearings 7 that travel in the trajectory tracks D of the trajectory supports 2, one bearing per track. In this case, the trajectory tracks D serve as races for the bearings 7. The bearings 7 arc connected in front and back pairs via axels 3 that are substantially perpendicular the principal direction of motion. It should be understood that the specific construction and assembly of the trajectory tracks D, as well as the type of bearing 7 and configuration of the other components of ihe ergonomic armrest discussed herein is by way of example only; what is important is that the device is operable to convey a person's forearm along a natural trajectory. In this regard, the movement of the arm support 6 could also be accomplished by other methods including, for example, using sliders, bushings, or any means that would provide a smooth and near fπctionless movement.

The axels 3 are preferably secured transverse to an attachment bracket 4, with each axel 3 welded or otherwise affixed near either end of the auachmenl bracket 4. The attachment bracket 4 is attached to the arm support 6. The attachment bracket 4 also has arm support anchor holes E which are used to fasten the ami support 6 to the attachment bracket 4. The arrangement of the arm support anchor holes E in the attachment bracket 4 is determined according to the Specific needs of the arm support 6. Optionally, as shown in FlG. 3 and FIG. 4, the assembly of the ergonomic armrest requires a spacer 5 between the attachment bracket 4 and the arm support 6 to allow for clearance. Again, ihe aπn support anchor holes E used for securing ihe spacer 5 are arranged according the specifics of the arm support 6.

The trajectory tracks D are preferably mirror images of one another in the sagittal plane, and provide a surface or track in which the bearings 7 can travel, creating a near friciionless translation of the ergonomic armrest when using a controller.

The trajectory supports 2 housing the trajectory tracks D can be constructed of 6061 aluminum, and machined with a CNC mill, for example. The support structure 1 to which the trajectory supports 2 are attached can be constructed of a mild steel (1018) and milled manually. The bearings 7 oan be four 19 mm deep groove ball bearings (NSK. Ltd., Tokyo, Japan), and used to create near friciionless translation in the trajectoiy tracks D of the trajectory supports 2. In addition, the ergonomic armrest is adjustable in the vertical direction to allow for various heights with an objective of customizing for an individual, as mentioned above.

Preferably, the natural motion path of the forearm can be determined by capturing the kinematic data on a person during unrestricted forward and backward joystick manipulation using a camera-based motion capture system. Data collected from this analysis can then be used to produce trajectories that represent the "natural motion" of the person's wrist and elbow. The captured trajectories can then be incorporated into the design of the ergonomic armrest such thai it replicates the "natural motion" to reduce muscle activation in Hie shoulder of a 50th percentile male while operating a hydraulic- actuation joystick, for example, in a manner thai is known.

The ability of the dynamic design of the present invention to reduce a person's muscular activation in comparison io lhe other available designs can be validated by recording and analyzing electromyographic signals from neck and shoulder muscles during the forward and backward motion of the arm, in a manner that is known.

In a further embodiment (not shown), the ergonomic armrest would allow for movements of the device associated with lateral morions of a person's arms. For example, lhe ergonomic armrest could allow for the movements associated with lateral movements of a joystick by allowing the entire assembly to pivot. For example, the pivot can be incorporated into the support structure by means of a bushing or bearing. The purpose of this would be to farther reduce muscular load of the shoulder by increasing arm support through replication of the natural motion path of an operator's arm during fore-afi as well as side-to-side joystick manipulation,

As well, the ergonomic armrest could be readily fitted with a lockout mechanism. The lockout mechanism would fix the arm support relative to the trajectory tracks if the operator is taking a break or in order to reduce movement during heavy vibration conditions, for example, when nding over rough ground while operating a forestry machine. In thai case, die lockout mechanism would prevent an unintentional motion of the operator's arm as a result of inertia.

Although the present invention is well-suited for forestry, construction, excavation and/or mining machinery controlled by a joystick device, it should be understood that the ergonomic armrest is can be implemented in any application wherein a controller is movable by an operator in multiple directions, as discussed herein.

It will be appreciated by those skilled in the art that other variations of the preferred embodiment may also be practised without departing from the scope of the invention.

Claims

What is claimed is:

1. An ergonomic armrest comprising:

a support structure having trajectory members; and

an arm support connected to the trajectory members, the arm support operable to move along the trajectory members; wherein the trajectory members define a movement path, the movement path allowing for the linear and rotational movement of ihe arm support in a plane of direction.

2. The ergonomic armrest of claim 1 wherein the trajectory members are trajectory supports each having trajectory tracks.

3. The ergonomic armrest of claim 2 wherein the trajectory supports arc two forward trajectory supports and two rear trajectory supports.

4. The ergonomic armrest of claim 3 wherein the arm support is positioned above the two rear trajectory supports and the two forward trajectory supports are positioned below the two rear trajectory supports.

5. The ergonomic armrest of claim 3 wherein the arm support moves along the from and rear trajectory supports and respective trajectory tracks by a conveying means.

6. The ergonomic armrest of claim 4 wherein the arm support moves along the front and rear trajectory supports and respective trajectory tracks by a conveying means.

7 The ergonomic armrest of claims 5 and 6 wherein conveying means are sliders, bearings or bushings.

8. The ergonomic armrest of claim 4 wherein the from and rear trajectory supports are integral with One anodier.

9. The ergonomic armrest of claim 1 for use with the operation of a controller.

10. The ergooomic armrest of claim 9 wherein the controller is a joystick.

1 1. The ergonomic armrest of claim 1 wherein the plane of direction is a sagittal plane defined by a position of a user.

12. The ergonomic armrest of claim 1 wherein die movement path substantially replicates natural or untmcumbered motion of a forearm of a user.

13. The ergonomic armrest of claim 3 wherein the trajectory supports further comprise vertical height adjustment means.

14. The ergonomic armrest of claim 1 connected to a seating structure.

15. The ergonomic armrest of claim 14 wheroin the seating structure is a wheelchair.

16. The ergonomic armrest of claim 1 for operation in a standing position.