WO1996000022A2

WO1996000022A2 - Manual work station with indirect observation

Info

Publication number: WO1996000022A2
Application number: PCT/CA1995/000367
Authority: WO
Inventors: Valeri F. Venda
Original assignee: University Of Manitoba
Priority date: 1994-06-23
Filing date: 1995-06-22
Publication date: 1996-01-04
Also published as: WO1996000022A3; GB9412610D0; AU2709795A

Abstract

A work station at which an operator can perform manual tasks using the hands is modified by the addition of an indirect viewing system which includes an image generating system looking downwardly onto a work surface at which the hands of the operator are placed and the screen placed behind the work surface and viewed by the operator looking above the work surface. The work surface is preferably tilted to provide a negative tilt away from the operator at an angle of the order of 7°. The screen is preferably positioned so that it is at or slightly below horizontal from the eyes of the operator. The image generating system is preferably a television camera which cooperates with a monitor, both of which are mounted on a stand movable to the work station and adjustable relative thereto.

Description

MANUAL WORK STATION WITH INDIRECT OBSERVATION

BACKGROUND OF THE INVENTION

This invention relates to a work station at which an operator can be located to effect a manual task.

The conventional work station of the type at which manual tasks are effected, for example small assembly, traditionally requires that a worker bends over the horizontal work surface looking down onto the work surface thus bending the neck, back and wrists of the operator. Another approach is to locate the hands at a location which is suitable for the eyes but again this is uncomfortable for the operator. Such tasks are generally of a repetitive nature with the risk of injury due to the repetition. The present invention is, however, not limited to tasks which are strictly repetitive.

Almost every day new data on repetitive strain (stress) injuries (RSI), or cumulative trauma disorders (CTD), epidemic expansion is published. On December 28, 1994 Investors Business Daily published a report of US Labor Department stating a 10% increase of RSI during 1994 with 302,000 workers claiming injuries versus 34,700 workers claimed RSI's in 1984.

There are several detailed surveys on RSI and ergonomic studies of their prevention (Marek, Wos, Karwowski, Hamiga, 1992, Fisher, Andres, Airth, Smith, 1993). Experience has been studied on RSI at the assembly plants of Northern Telecom and other electronics, communication, computer, watch and other companies, and in material handling (diamond processing, etc.). It was found that neck and shoulder RSI are the most widely spread traumas among the workers of the slidelines where printed circuit boards (PCB) are assembled and in manual material handling. The RSI's are caused by bending a worker's neck along with lifting arms during a work shift at assembly slideline and material handling: (Fisher, D.L., Andres, R. O., Airth, D., and Smith, S. S. (1993); Marek, T., Wos, H., Karwowski, W., and Hamiga, K. (1992); Schuldt, K., Ekholm, J., Harms-Ringdahl, K., Nemeth, G., and Arborelius U. P. (1986).)

It was found that all current designs of the assembly workstations leading to massive RSI's were based on the assumption that it is possible to find solution optimal both, for the worker's arms and eyes.

Statistics Canada reported in 1991 that repetitive strain injuries (RSI) or cumulative trauma disorders (CTD) of back, wrists, hands and fingers made 48% of all occupational diseases. US Bureau of Labor Statistics stated in November 1990 that RSI increased from 18% in 1981 to 52% in 1989. Aetna Insurance Company Safety Engineering Department estimated in November 1991 , that RSI cost nation about $20 billion in a year. There are several detailed surveys on RSI and ergonomic studies of their prevention (Marek, Wos, Karwowski, Hamiga, 1992, Fisher, Andres, Airth, Smith, 1993).

Carpal tunnel syndrome and neck RSI are of the most widely spread traumas in the electronic assembly industry. They are caused by positive or neutral tilt of the printed circuit board and bending a worker's neck and body during a work shift at assembly plants.

None of the existing assembly workstations allows a negative tilt of the object (work surface) where assembling is being done. SUMMARY OF THE INVENTION

It is one object of the present invention, therefore, to provide an improved work station which reduces or overcomes the problems with RSI.

According to one aspect of the invention there is provided a work station at which an operator can be located to effect a repetitive task comprising a work surface supported at a position for receiving the hands of the operator in effecting the task, and an indirect viewing system including

SUBSTITUTE SHEET display means displaying an image of the work surface and hands by which the operator can view the work surface.

Preferably the display means displaying an image of the work surface and hands is positioned so that the operator views the display means while looking forwardly. Preferably the display means comprises a screen positioned rearwardly of the work surface.

Preferably the work station is arranged such that the operator is seated and includes an arm rest positioned forwardly of the work surface.

According to a second aspect of the invention there is provided a viewing apparatus for use with a work station at which an operator can be located to effect a repetitive task including a work surface arranged to be supported at a position for receiving the hands of the operator in effecting the task, the apparatus comprising a support means, image generating means mounted on the support means so as to be directed generally downwardly for observing the work surface and display means mounted on the stand for displaying an image from the image generating means of the work surface and hands by which the operator can view the work surface, the display means being arranged for viewing by the operator in a direction which is approximately horizontal.

The present invention provides a new type of the assembly and material handling workstations where the work surfaces for the arms and eyes are separated and optimized.

The above defined new assembly and material handling workstation allows the workers to be seated in a straight neutral work position thus lowering fatigue, risk of RSI's of the neck, shoulders and back. The workstation allows also a negative tilt of work surface thus lowering a

SUBSTITUTE SHEET risk of carpal tunnel syndrome. Lowering the fatigue may lead to essentially increased work productivity and quality.

One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic illustration of a first embodiment of the invention.

Figure 2 is a schematic illustration of a second embodiment of the invention.

Figure 3 is a graph showing optimal angles of work surface for arms ( Fa) and for eyes (Fe). DETAILED DESCRIPTION

In Figure 1 the work station comprises three separate elements including a chair 9, a separate desk 8 which has height and tilt control 7 and a TV monitor 1 with support 6. These separate elements can be relatively moved. On the desk 8 is provided the work surface 3 which includes the work piece for example a PCB (printed circuit board). The work surface is mounted on the desk at a negative tilt angle that is the work surface is inclined to the horizontal and tilted away from the operator.

In view of the fact that the negative tilt prevents the operator from directly viewing the work piece without severe bending of the neck and back, a TV camera 2 is provided which views the work piece in a substantially perpendicular direction and transmits the image so obtained to the TV monitor 1.

The device further includes an arm support 4 which is positioned forwardly of the work piece and engages the operator's arms in the area beyond the elbow and in front of the wrist so as to provide vertical support

SUBSTITUTE SHEET for the arms. The arm support is inclined slightly upwardly and rearwardly to support the wrist at a position above the front of the work surface.

In addition a lighting array is indicated at 5 with a handle 5A by which the lighting array can be tilted.

The TV camera 2 and the monitor 1 are mounted on the support 6 so as to be separate from the work station itself. In this way the viewing apparatus defined by the support 6, the monitor 1 and the TV camera 2 can be supplied as a separate element for use with an existing work station.

The support 6 comprises a base 6A with wheels 6B allowing the apparatus to be moved into position adjacent the work station. The wheels 6B are mounted on a suitable spider arrangement which carries a hub 6C upstanding from the spider. On the hub is mounted a mast 6D which extends vertically upwardly to a height above the work station and the person seated at the work station. The mast 6D includes a horizontal portion 6E which extends outwardly from the mast toward the work station. The TV camera 2 is mounted on a suitable support bracket 6F at the end of the horizontal section 6E allowing the TV camera to be adjusted in horizontal position and in orientation about a horizontal axis at right angles to the horizontal section 6E. Thus the angle of viewing along the line 2A of the TV camera can be adjusted from a directly vertical orientation to an orientation slightly to each side of the vertical. In the position shown, the line 2A is directed downwardly and forwardly toward the work surface so the line 2A is substantially at right angles to the work surface. Thus the angle between the line 2A and the vertical is equal to the angle between the work surface and horizontal.

SUBSTITUTE SHEET The mast 6D includes one or more adjustment sections allowing the height of the mast to be adjusted to adjust the height of the TV camera 2 relative to the work surface.

The hub 6C carries an arm 6G which is pivotal about a horizontal axis relative to the hub 6C and carries a support bracket 6H supporting the monitor 1. The bracket 6H is pivotal relative to the arm 6G about a horizontal axis parallel to the axis at the hub 6C thus allowing the monitor to be pivoted to adjust a line of viewing 1A of the monitor and can be raised and lowered to adjust the line of viewing relative to the height of the operator seated in the chair 9.

It will be noted in the example as shown in Figure 1 that the line 2A is generally downwardly onto the work surface either in a vertical direction or as shown pivoted slightly forwardly in view of the negative tilt of the work surface. Furthermore the line 1A which represents the viewing line from the eyes of the operator to the center of the screen of the monitor is substantially horizontal in that it is generally at right angles to the line 2A and across the work surface at a height above the work surface. This therefore raises the line 1 A significantly above the work surface to avoid the operator bending over the work surface to observe the work in progress.

Unlike existing assembly and material handling workstations the present workstation allows to separate worker's eyes from direct viewing operations and the assembly or handling object. In addition to the usual direct viewing operations, the separation allows the worker to be seated at the workstation invented in a straight position viewing the assembly or handling operations and object (material, PCB) at the TV, computer or optical screen. The workstation allows the worker to change work position, use direct and indirect viewing of the operations. This lowers fatigue and risk of

SUBSTITUTE SHEET the neck, shoulder, back RSI at electronic, watch, mechanic, electric, toy and many other assembly and material handling operations.

Unlike existing assembly and material handling workstations the present workstation allows a negative tilt of work surface (object, material, PCB) where assembling is being done. This lowers risk of the carpal tunnel syndrome prevention. The workstation allows the negative tilt of the object (work surface) where assembling is being done, as well as zero and positive tilt.

Unlike existing assembly and material handling workstations the present workstation allows to present at the screen the current operations along with shop aid, manuals and instructions including those displayed by the computer that could be connected with the screen.

Existing workstations could be easily converted into this one with simply attachment of the autonomous module made as a trolley or stand 6 with adjustable height and angle of the surface for TV monitor and the adjustable telescopic or other support for TV camera. The Optical projector and screen can be also made as a separate module then attached to the existing traditional workstation and therefore transforming a traditional workstation into the workstation of the present invention for higher productivity and lower risk of occupational injuries. This additional module includes major standard components (TV camera and monitor), it is very cheap and does not require any complicated assembling. Many injured workers stay at home on the disability compensation several years. Compensation paid for one such worker may be more expensive than modules of the present workstation for many workers. Figure 2 shows a similar arrangement which is modified to utilize in place of the TV camera and monitor an optical projector 21 for projecting onto a screen 22.

Other arrangements for indirect viewing of the work piece can be provided in which an image is taken from the work piece by a detector system positioned above the work piece and viewing it substantially perpendicular to the work piece. The screen as shown is positioned behind the work piece and at an angle so that the operator can view the screen in a forward direction while seated upright. The viewing is therefore mainly horizontal with a slightly downward component which is approximately parallel to the upper surface of the work piece.

At the workstations proposed the worker's wrists are relaxed because the negative tilt of the work surface. Of course the tilt may be also adjusted or manufactured at a fixed position so that the tilt is positive or zero. The worker is seated in straight, neutral position, watching the assembly operations at the TV screen, projected on the screen with optical projector Figure 3. The workstation based on using TV camera and monitor allows to use a negative tilt of the printed circuit board (PCB) and some other objects to be assembled. For the workers who already had got a carpal tunnel syndrome or neck RSI these types of the workstations could be the only chance to return to the assembly plant. The workstations allow also positive and zero angle tilts.

The workstation proposed allows the workers to seat at straight position and relax wrists, neck, back watching the operations are being made indirectly, at the screen.

Indirect watching of the projected assembly operations at the screen, allows negative tilt of the object to be assembled.

SUBSTITUTE SHEET Straight work posture decreases neck, wrist, back muscle strain and risk of the repetitive strain injuries (cumulative trauma disorders).

This invention can help to fight a massive repetitive strain injury in assembly industry around the glove.

For the assembly workers who already had got neck, wrist, back repetitive strain injuries and cannot work any more at traditional work stations with bent neck, wrists, back. After some training all assembly workers can work at the workstations are being proposed with high productivity, quality, low risk of RSI.

Tests have been carried out on the present invention and have revealed the following results.

In Figure 1 the angle of the eye line is indicated at Fe and the angle of the work surface is indicated at Fa. In Figure 3 is shown a graph of the angles Fe and Fa in relation to a measured convenience of operation indicated at Q. It will be noted that the convenience of operation for the eyes provides a maximum at a position significantly offset from that for the arms. The angle Fa is indicated as being negative for negative tilt of the work surface as shown.

It will be appreciated that the preferred angle of negative tilt is of the order of 7°. However operation of the work surface at 0 tilt or positive tilt is also possible.

Twelve workers of participated in the experiments. Each of them worked first one-two days at the Traditional workstation or Cut-out workstation (advanced traditional). After that each worker worked seven days at the present workstation based at Traditional one (coded as VT) or at Cut-out one (coded as VC).

SUBSTITUTE SHEET Hereinafter in the following table are data on comparison workstations T vs. VT and C vs. VC on tempo and productivity of work in relative units (data on workstations T and C are coded as 1.00); data obtained with PHY-400 (EMG-Right trapesius, EMG-Left trapesius, Neck Flexion, Neck Side motions, Back Flexion and Back Side Motions) are shown as relative positive change from T (or C) to VT (or VC).

SUBSTITUTE SHEET Parameter Workst. T Workst. WWoorrkksstt.. CC WWoorrkk!st VC Workst. T and C Workst. VT and VC VT

Productivity 34 46 53 57 44 52

(number of

PCB assembled in a shift)

EMG-Right 0.04 0.04 0.22

EMG-Left 0.24 0.41 0.32

Neck 0.59 0.48 0.53

Flexion

Neck Side 0.25 0.20 0.23 motions

Back 0.12 0 0.06

Flexion

Back Side 0.20 0.08 0.14 motions

Conclusions:

1. Industrial testing of the invention have proved its advantages in comparison with existing traditional workstations (including advanced ones). All assembly operations including inserting electronic components, bending, cutting and soldering their leads were successfully done by all participating workers. Training period was very short and effective, it took 4-6 shifts. Training was done at the work processes with minimal initial losses of productivity.

2. Productivity of work (as a number of PCB assembled during the shift) was higher when the Present workstations were used: 46 for VT vs. 34 for T and 57 for VC vs. 53 for C.

3. All parameters registered using PHY-400, including muscle strain, neck and back flexion and side motions are better when the present workstations were used. Improvement is especially significant for the neck flexion (important factor causing neck injuries) - 0.53, and for EMG of left. 4. Experiment has shown that the new type of the workstations significantly increases work productivity and decreases muscle strain and consequently risk of RSI injuries.

This invention helps to fight repetitive strain injuries (or CTD) at the assembly and material handling plants and productions. The Present- workstations allow the worker to be seated in a straight, neutral position. Therefore the workstations lower muscle strain of the upper trapesius, neck, shoulders, back. The present workstations allow also to use negative tilt of the work surface lowering wrists flexion and therefore risk of carpal tunnel syndrome.

The present workstations allow also to use a large magnification of the product assembled or handled decreasing visual strain and increasing work productivity.

The present workstations allow return to the active work those workers who already had got neck, wrist, back repetitive strain injuries and cannot work any more at traditional workstations with bent neck, wrists, back.

Potential users: companies producing assembly and material handling workstations; telecommunication, computer, electronic, audio-visual assembly companies; insurance companies; Workers' Compensation Boards (to return injured workers instead of paying them compensation for long time); manual material handling productions and plants.

The indirect viewing system using the TV camera and monitor allows also the possibility of expansion of the viewed image to view further detail. In place of the mast of Figure 1 , the camera can be mounted on a horizontal rail suspended from the ceiling for adjustment longitudinally of the rail. In this case the monitor may be mounted on a rear part of the work

SUBSTITUTE SHEET surface support again for adjustment relative thereto in vertical and horizontal directions.

Since various modifications can be made in our invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

SUBSTITUTE SHEET

Claims

CLAIMS:

1 . A work station at which an operator can be located to effect a manual task comprising a work surface supported at a position for receiving the hands of the operator in effecting the task, and an indirect viewing system including display means displaying an image of the work surface and hands by which the operator can view the work surface.

2. The work station according to Claim 1 wherein the work surface is arranged such that it can be oriented at a negative tilt angle, that is at an incline to the horizontal facing away from the operator.

3. The work station according to Claim 1 wherein the work surface is arranged forwardly and downwardly of the shoulders of the operator for engagement with the hands of the operator when extended forwardly and wherein the display means is positioned so that the operator views the display means while looking forwardly at a height above the work surface.

4. The work station according to Claim 1 wherein the work station is arranged such that the operator is seated.

5. The work station according to Claim 1 wherein the display means is positioned rearwardly of the work surface.

6. The work station according to Claim 1 including an arm rest positioned forwardly of the work surface.

7. The work station according to Claim 1 wherein he work station is arranged for the assembly of components on a work piece carried on the work surface.

8. A viewing apparatus for use with a work station at which an operator can be located to effect a manual task including a work surface arranged to be supported at a position for receiving the hands of the operator

SUBSTITUTE SHEET in effecting the task, the apparatus comprising a support means, image generating means mounted on the support means so as to be directed generally downwardly for observing the work surface and display means mounted on the stand for displaying an image from the image generating means of the work surface and hands by which the operator can view the work surface, the display means being arranged for viewing by the operator in a direction which is approximately horizontal.

9. The viewing apparatus according to claim 8 wherein the image generating means and the display means are mounted for adjustment on the support means to accommodate different work surfaces.

10. The viewing apparatus according to claim 8 wherein the display means is mounted on the support means for viewing in a direction which is between horizontal and an angle of the order of 30 degrees below horizontal.

SUBSTITUTE SHEET