AU1218799A - Ergonomic base and chair providing constrained lateral movement there between - Google Patents

Description

WO 99/25221 PCT/AU98/00952 -1 ERGONOMIC BASE AND CHAIR PROVIDING CONSTRAINED LATERAL MOVEMENT THERE BETWEEN Field of the Invention 5 The invention relates to chair bases and more particularly to a base for reducing back strain in occupational situations where lateral movement from a seated position is an advantage. Background of the Invention 10 Many occupational situations require lateral or side to side movement in a sitting position. Dealers and croupiers in casinos, postal sorters, office workers and receptionists etc. are often required to slide from side to side in the course of their work. In a healthy individual, this kind of repetitive motion may be a source of strain or injury. In a person with an existing back injury, this kind of motion may preclude them from working effectively, or at all. As the 15 lateral motion is accomplished largely by the base of the chair (as opposed to the seat) there exists therefore, a need for a chair or for a chair base adapted to receive a seat which allows the user to move laterally, with the minimum effort. It is an object of the invention to provide a chair or chair base which alleviates the above 20 problem or other problems associated with the prior art. According to the present invention there is provided a base for a chair, the base comprising: a chassis, at least one landing operatively connected to the chassis; a carrier for reduced friction sliding along the landing; the carrier being adapted to support a pedestal. 25 Preferably, the base has a forward end and a rearward end and the carrier is adapted for movement along the or each landing in a direction generally laterally with respect to an axis extending between the forward and rearward ends. 30 In one preferred form, the landing is a rod and the carrier supports one or more friction WO 99/25221 PCT/AU98/00952 -2 reducing bearings for linear motion along the rod. Preferably, the pedestal is affixed to an upper part of the carrier. The base may further include a footrest which may be located forward of that part of the carrier adapted to join the pedestal. In one preferred form, the bearings are linear bearings and the rod is ground. In one preferred form, there are two landings and each 5 landing is a rod. In another preferred form, the landing is a rail and the bearings are carried by rollers which bear on the landing. Preferably, the rollers are used in pairs, one roller in each pair used as a stabilising roller. 10 Preferably, the carrier supports the pedestal for reciprocal vertical movement in a collar, the vertical movement of the pedestal used to deactivate a brake, carried by the base and mechanically linked to the collar, which otherwise would prevent lateral movement along the landing. 15 The landing may be in the form of a channel and the bearings are carried by bogeys which ride in the landing. Preferably, each bogey has at least one wheel with bearings. In another arrangement each bogey has two pairs of wheels connected by a tie. Preferably, the channel is an inverted "U" and the tie supports a suspended shaft which attaches to the carrier. 20 In one form one bogey may include a brake mechanism which impinges on the channel when there is no load on the seat. Preferably, the brake mechanism is activated by a bias which is compressed when there is a load on the seat. Preferably, each chassis further comprises a retractable wheel. Preferably, the 25 clearance between the wheel and the interior top surface of the channel in which it rides prevents excessive motion. Preferred embodiments of the invention will be hereinbefore described with reference to the accompanying drawings. 30 WO 99/25221 PCT/AU98/00952 -3 Figure 1 is a perspective drawing of a chair base adapted to receive a chair for lateral movement. Figure 2 is a plan view of an alternate chair base. 5 Figure 3 is front elevation of a chair base and chair for lateral movement. Figure 4 is a plan views of the device shown in Figure 3. 10 Figure 5 is cross section of the chair base shown in Figure 3. Figure 6 is a side view of a brake. Figure 7 is a perspective drawing of a chair base adapted to receive a chair for lateral 15 movement. Figure 8 is an inverted perspective drawing of a chair base adapted to receive a chair for lateral movement. 20 Figure 9 is a perspective drawing of a bogey on a channel type landing. Figure 10 is a cut away perspective drawing of a bogey on a channel type landing. Figure 11 is a perspective drawing of a retractable wheel on a chassis. 25 Description of the Preferred and Other Embodiments The subject matter of this disclosure pertains to an ergonomic chair. The chair includes a base, a pedestal and a seat. The base includes a friction reducing mechanism. The pedestal 30 extends between the base and the seat. Any number of seats may be suitable for use with the WO 99/25221 PCT/AU98/00952 -4 disclosed base. The invention is therefore not limited to any particular seat. As shown in Figure 1, a base 10 for a chair includes two side chassis 11. Each chassis 11 supports, along a portion of its mid-section, the ends 13 of two parallel rods 12. The rods 5 may be up to several metres long if required. The rods act to support some form of bearing for linear motion along the rod. Similarly, rails may be used in place of rods. Together with other known mechanisms for supporting a weight, for linear motion the terms "rail" and "rod" are used as examples of landings. 10 Each chassis also supports one end of a pivoting, adjustable footrest 14. The position of the footrest 14 is governed by a ratchet and pawl or detent mechanism 15 whereby the elevation of the footrest 14 may be maintained against the weight of the user, until it is adjusted. 15 The parallel rods 12 support a sliding carrier 16. The carrier 16 includes bearings 17 which slide on the rods so that the carrier can traverse, laterally the space between the chassis 11. The carrier extends between the bearings 17. A chair support 18 is affixed to the carrier 16 and is adapted to receive the post or pedestal of a chair. Obviously, any suitable chair on a post or pedestal can in this way be incorporated onto the base. Where circumferential linear bearings 20 17 are used with ground rods 12, lateral motion is accomplished with little frictional resistance. In this example, four bearings 17 are illustrated. As shown in Figure 2, the carrier 16 may be triangular and provided with three bearings 17, one rod 12 and two bearings 17 on the other rod 12. This reduces friction, weight and cost. 25 Another embodiment is depicted in Figures 3-6. As shown in those Figures, the rods 12 have been replaced with rails 20. In this example, rectangular tubes are used as rails 20. This allows the friction reducing bearings to reside within rollers or wheels 21 rather than bear directly on the rails 20. As such, polymeric rollers or wheels 21 (e.g. nylon or urethane) which 30 are supplied with bearings may be supported by a stamped and pressed sheet metal carrier 32.

WO 99/25221 PCT/AU98/00952 -5 Roller blade and skateboard wheels may be suitable with little or no modification. To prevent the rollers 21 from disengaging the rails 20, stabilizing rollers 22 are supported by the carrier. The stabilizing rollers 22 are maintained so that they engage the lower 5 outside edge 23 of the rail. Openings 24 in the carrier through which the rollers 21, 22 extend are punched directly into the sheet metal forming the carrier 32. The metal displaced from the forming of the openings 24 is used to form the ears 25 which support the axles or fasteners 26 which pass through the various rollers 21, 22. 10 In this example, a triangular carrier is used with three pairs of rollers 21, 22. The front and rear edges 27, 28 of the carrier 32 are provided with a radius so that the weight bearing rollers 21 and the stabilizing rollers 22 can be supported by the same stamped and pressed piece of sheet metal. This stamping 33 may be joined to a reinforcement, such as another stamped piece of sheet metal 34. Preferably, this affixed to one end of a rigid opening 35 formed in the 15 centre of the carrier 32. The other extremity 36 of the reinforcement 34 therefore acts like a cantilever against the portion of the carrier that supports the rollers 2 1, 22. The upward facing portion of the opening 35 receives a collar 40. The collar 40 serves several purposes. It's main function is to receive and support the post or pedestal 41 of the seat 20 42. It has an internal bore 43 which may be tapered to receive a tapered pedestal 44. The end 45 of the collar 40 extends beyond the lower edge 46 of the opening 35. This end 45 attaches to a brake 47. The brake 47 comprises a rigid bar 48 that extends between the rails 20 (or rods 12). Each end of the bar 48 has brake pads 49 which engage the rails tightly when there is insufficient weight on the seat 42. When a pre-determined weight is reached (when someone 25 sits down) a compression spring 50 is overcome. The collar slides in the bore 35 against the resistance of the spring 50. This moves the brake 47 away from the rails 20 and allows the carrier to slide freely. An alignment pin 51 extends from the brake bar 48 through a clearance hole 52 formed into the carrier 32. This keeps the brake 47 in alignment with the rails. 30 More direct means may be used to attach the pedestal 44 to the upper surface or part of WO 99/25221 PCT/AU98/00952 -6 the carrier 32. To allow the entire base to slide forward and back, the chassis are mounted on wheel or castors. As shown in Figure 1, wheels or castors 60 may be mounted on or under the chassis 5 11. Figure 6 illustrates a spring biased detent mechanism 61. The mechanism 61 includes a handle 62 which lifts a spindle 63 out of engagement with a wheel 60. The wheel 60 includes radial openings 62. In "down" or "free" position 64, the spindle 63 is free of the wheel openings 62. 10 As shown in Figure 4, the parallel rails 20 are supported at each end by chassis 11. Each chassis 11 may be equipped with wheels 60 so that the entire base may be rolled at least forward and backward. As shown in Figure 5 and 6, the base may include a rigid cover 70 with footrest features 15 formed directly on it. Another embodiment is depicted in Figures 7 - I 1. As shown in Figure 7* the base 100 has chassis 101 formed from rectangular steel tubes and two landings 102 formed from steel channel. Each chassis 101 supports one end of an adjustable footrest 103. A retractable wheel 20 104 is positioned within each chassis, forward of the footrest 103. A cast metal (or other) carrier 105 rides on the landings 102, suspended from bogeys 106 (see Figures 8-10). As shown in Figures 8, 9 and 10, each landing 102 is in the form of an inverted "U" shaped channel. The ends 110 of the channel are bent to form parallel grooves. The grooves 25 serve as a track for wheeled bogeys 111. In this example each of the three legs 112 of the carrier 105 is suspended from a four wheel bogey 111. A single grove landing in the form of a "J" could be employed and would be less expensive but less robust, more vulnerable to dust and dirt build up and less stable. 30 Each bogey 111 has two pairs wheels 113 which are interconnected by a central tie 117.

WO 99/25221 PCT/AU98/00952 -7 A suspended threaded shaft 114 is affixed to the middle of the tie 117 and extends out of the channel 102. The carrier leg 112 is affixed to the threaded shaft 114 by a nut 115. A yoke 116 distributes the load imposed by the tightened nut 115 and bears on the ends of the tie 117. In the case of the single front leg 112 in this example (as shown in Figure 10), a single brake 5 mechanism 120 is clamped between the nut 115 and the yoke 116. The brake mechanism 120 includes an O-ring 122. The nut 115 bears directly on a first flange 123 formed on the end of a sleeve 124 which fits around the shaft 114. A sliding sleeve 125 has a second flange 126. Under load, leg of the carrier acts on the second flange 126 to compress the O-ring 122 until the sliding sleeve 125 bottoms out against the shoulder 127 formed in the sleeve 124. When 10 a person gets off the seat, the O-ring expands to its original shape and urges the carrier mounted circumferential urethane pad 121 into contact with the channel 102. This acts as a safety brake when there is no load and inhibits the carrier from sliding on the landings. Each end of the tie 117 is affixed to a pair of wheels 113. In one embodiment, the 15 wheels have a metal core and a polymeric contact surface. Each wheel is mounted on bearings to a cross shaft 128. The small clearance between the top of the wheels 113 and the interior top 129 of the channel prevents excessive motion of the bogey. Wheeled bogeys of this general type (but not with brakes) are known in the fabrication of large sliding, hanging doors. 20 Figure 11 illustrates a retractable wheel assembly 150 mounted within a forward portion of a chassis 101. The assembly 150 utilises a pair of vertical slots 151 to trap the shaft 153 of a retractable wheel 152. The wheel is normally biased into a retraced position (as shown) and may be deployed with a foot pedal 153. The foot pedal 153 pivots about a shaft 154. A cam surface 155 urges the wheel down and into contact with the ground and maintains it there when 25 the foot pedal 153 is depressed. This allows the entire base 100 to be wheeled forward and back on its four wheels 152, 160 (see Figure 8). When the wheels 152 are retracted, the base 100 rests on its rear wheels 160 and front pads 161. Further, it should be understood that the various embodiments of the invention disclose 30 different components and alternatives which are considered compatible with one another for WO 99/25221 PCT/AU98/00952 -8 the purposes of chair construction. The present invention has been described with reference to particular details of manufacturing. It should be appreciated that these are provided by way of example and not as 5 limitations to the scope or spirit of the invention. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or comprising" , will be understood to imply the inclusion of a stated integer or step or group of integers or steps but 10 not the exclusion of any other integer or step or group of integers or steps.

Claims (20)

1. A base for a chair comprising: at least one landing affixed rigidly to a chassis; 5 a carrier for reduced friction sliding along the landing; the carrier being adapted to support a pedestal.

2. A base according to claim 1 wherein said base has a forward end and a rearward end and the carrier is adapted for movement in a direction generally laterally with respect to an axis 10 extending between the forward and rearward ends.

3 The base of claim 2, wherein: the landing is a rod and the carrier supports one or more friction reducing bearings for linear motion along the rod. 15

4. The base of claim 3, wherein: a pedestal is affixed to an upper part of the carrier.

5. The base of claim 3, further comprising: 20 a footrest, affixed to the base and located forward that part of the carrier adapted to join the pedestal.

6. The base of claim 5, wherein: the bearings are linear bearings and the rod is ground. 25

7. The base of claim 3, wherein: there are only two landings and each landing is a rod.

8. The base of claim 1 or claim 2, wherein: 30 the landing is a rail and the bearings are carried by rollers which bear on the landing. WO 99/25221 PCT/AU98/00952 -10

9. The base of claim 8, wherein: rollers are used in pairs, one roller in each pair used as a stabilising roller.

10. The base of claim 2, wherein: 5 the carrier supports the pedestal for reciprocal vertical movement in a collar, the vertical movement of the pedestal used to deactivate a brake, carried by the base and mechanically linked to the collar, which otherwise would prevent lateral movement along the landing.

11. The base of claim 2, wherein: 10 the landing is a channel and the bearings are carried by bogeys which ride in the landing.

12. The base of claim 11, wherein: each bogey has at least one wheel with bearings. 15

13. The base of claim 12, wherein: each bogey has two pairs of wheels connected by a tie.

14. The base of claim 13, wherein: 20 the channel is an inverted "U" and the tie supports a suspended shaft which attaches to the carrier.

15. The base of claim 14, wherein: one bogey includes a brake mechanism which impinges on the channel when there is 25 no load on the seat.

16. The base of claim 15, wherein: the brake mechanism is activated by a bias which is compressed when there is a load on the seat. 30 WO 99/25221 PCT/AU98/00952 -11

17. The base of claim 11, wherein: each chassis further comprises a retractable wheel.

18. The base of claim 11, wherein: 5 each chassis is affixed to one end of a footrest.

19. The base of claim 12, wherein: the clearance between the wheel and the interior top surface of the channel in which it rides prevents excessive motion. 10

20. A chair comprising a pedestal extending between a seat and a base as claimed in any one of claims 1 - 19.