GB2470068A - Horizontally sliding seat with means to prevent unintentional separation of the sliding seat from a base support - Google Patents

Abstract

A horizontally sliding seat apparatus having a first seat plate 20 detachably and slidably mounted to a second base plate 21 has a specially designed ratchet to prevent unintentional separation of the seat plate from the base plate. In normal use, the position of the first plate relative to the second plate is determined by the engagement of a spring biased latch 36 with a ratchet means 55. The ratchet, which may be in the form of a slot 55, defines a plurality of notches 57 and a plurality of teeth 56, having a first notch 58 of lesser depth than the remaining notches and a first tooth 59 of greater height than the remaining teeth. In normal use, the latch 36 is operable to clear the remaining teeth but not the first tooth 59 thus preventing the latch 36 engaging the first notch 58 at which position the latch can be disengaged from the ratchet and the two plates separated from one another, e.g, to allow reupholstering, repair or maintenance of the apparatus. If separation of the plates is required, a tool may be used to displace the latch 36 sufficiently to clear the first tooth 59, allowing the latch to engage the first notch 58. Also disclosed is a sliding seat apparatus having: a first plate with slots 28,29 and spring biased detents 30,31 displaceable within the slots; apertures 53,54 on a second plate for receiving the detents; and a detent between the plates.

Description

Slidable Seat Apparatus This invention relates to an improved slidable seat apparatus which enables a seat of an office chair to be selectively positioned, in a plurality of positions with respect to the remainder of the chair.

Background of the Invention

Modern office chairs generally comprise a pedestal supported by an array of radially extending feet with castors or sliders to engage the floor. The pedestal carries a seat structure which includes a housing incorporating a variable tilt mechanism, for adjustment of the position of the back of the chair and of the seat portion. The seat portion includes a cushion assembly which is mounted on top of the seat structure, and may be adjustable in position forwards and rearwards, in a plurality of possible positions. These positions may be determined by a ratchet device, comprising one or more sets of ratchet teeth on either the seat portion or the cushion assembly, and a cooperative latch or pawl member on the other thereof. The cushion assembly is usually either not adapted for dismountability, or the mounting is achieved using additional attachments to the ratchet and pawl assembly, due to the fact that the use of the latter alone would entail a risk of accidental detachment, as the ratchet teeth are uniform, and when raised the pawl or latch can be pulled clear of the ratchet if excessive force is used and there are not other limiting means.

Examples of chair seat assemblies with slidable seats incorporating ratchet devices are set out in for example CH 692,716 and US 5,755,488. The Swiss Patent discloses a slidable seat which is not linked to the movements of the back rest, so that fully independent seat retraction and extension is provided. A ratchet is provided on the seat base which co-operates with a counter-toothed member on the moveable seat part.

It is an object of the invention to provide a sliable seat apparatus, in an adjustable chair, which will enable a slidable seat assembly to be mounted on an adjustable chair with the minimum of attachments, and which is adapted to provide a safety feature to prevent unintentional detachment of the seat when adjusting the position of the seat with respect to the rest of the chair.

According to the invention, from a first aspect, a slidable seat apparatus comprises a first plate member for connection to, or connected to, a seat cushion assembly, and a second plate member, for connection to or connected to, a base housing; one of the first or second plate members having a ratchet means defining a plurality of notches and a plurality of teeth, and the other plate having a latch which is biased to engage into one of said notches and against disengagement from said teeth, characterised in that said ratchet defines a first notch of lesser depth than the remaining notches and a first tooth of greater height than the remaining teeth, the latch being operable against said bias to in ordinary use, clear said remaining teeth but not said first tooth, to thereby prevent unintended disengagement of said latch from said ratchet.

The latch may be operated by a handle which can displace the latch against the force of a spring, using an intermediate ann.

According to a second aspect of the invention, a slidable seat apparatus comprises a first plate member for connection to, or connected to a seat cushion assembly, and a second plate member for connection to or connected to a base housing; one of the first or second plate members having a ratchet means defining a plurality of notches and a plurality of teeth and the other plate having a latch which is biased to engaged into one of said notches and against disengagement from said teeth, characterised in that one of said plates has detent means displaceably mounted in respective slit or slots in said one plate and biased towards an end of the plate by spring means, and apertures in said other plate to receive said detent means, whereby the plates can be connected together under tension, a further detent between the plates providing a resistance to said bias.

The further detent may comprise a part which can be mounted in an aperture in one of the plates, and in a slot in the other of the plates.

Said detent means, and the further detent may comprise bosses or studs of the type known as "mushroom headed", with wider heads which can be inserted through widened parts of slots or "keyholes", and narrower shanks which can be slid along slots which are too narrow to allow passage of the heads.

A preferred embodiment of displaceable seat arrangement and of a chair incorporating this arrangement, in accordance with the invention, will now be described by way of example with reference to the accompanying drawings, wherein:-Figure 1 is a diagrammatic side elevation of a chair incorporating a displaceable seat arrangement according to the invention; Figure 2 is a diagrammatic sectional view of the interface between a seat position and a tilting mechanism housing in the chair of Figure 1; Figure 3 is a perspective view from below of a slide assembly plate for the underside of a seat cushion, and a complementary plate forming the upper wall of a tilting mechanism "exploded"; Figure 4 is a perspective view similar to Figure 3 showing the two plates mounted one upon the other, in an initial joining position; Figure 5 is a perspective view similar to Figure 4 showing the two plates mounted one upon the other in a displaced position of the seat; Figure 6 is a perspective view from above of the plates in the Figure 4 position of the plates; and Figure 7 is a view corresponding to Figure 6 wherein the seat plate is advanced into a forward position of the seat.

Referring firstly to Figure 1, which is a general view of a chair, an office chair comprises a back 10, pivoted at 11 to a base 12 enclosing a tilt system of known type.

The base 12 supports a cushion assembly 14 which is mounted to be slidable fore-and-aft and secured in any desired position, using the device according to the invention. The chair is supported by a pedestal 15 resting on a foot 16 with castors or sliders.

Figure 2 shows in more detail the relationship of the cushion assembly 14, and the upper side of the base 12. A seat base plate 20 is attached to the underside of the cushion assembly 14 and this engages slidably in face to face relationship with a base cover plate 21, mounted on the upper side of the base 12. The slidable engagement is by means of projections on the seatbase plate 20 engaging in slots in the base cover plate 21. The seat base plate 20 also has a catch device operable by a handle 22, and cooperating with means to be described later in the base cover plate 21, to permit sliding of the cushion assembly 14 within limits defined by the lengths of slots etc in the base cover plate 21.

Figures 3 to 7 show the seat base plate 20, and the base cover plate 21 in more detail, without the cushion assembly 14, or base 12.

In Figure 3, the undersides of the plates 20 and 21 are shown, the latter fully, the former partially obscured by the plate 21. The seat base plate 20 is generally planar, but is formed with four raised parts 23 with eyes 24 for passage of bolts or other fasteners for securement to the cushion assembly. A depressed area 25 is disposed about a slot 26 in the right hand end of the plate 20 and is disposed along the longitudinal centre line of the plate 20. The slot 26 has a widened end 27 at the left hand end. Two further slots 28, 29 are disposed to the left of the end of slot 26 to either side of the longitudinal centre line, and these act as slideways for two pin members 30, 31 which are biased to the left in Figure 3 by respective tension springs 32, 33 which are each anchored to a housing 34 below the plate 20.

The housing 34 has a slot 35 from which a latch 36 protrudes. This latch is mounted on a lever member which extends through the housing and has a cam surface which is hidden in the housing but which is displaced by a nose member which is displaced by operation of the lever 22, which is pivoted on axis 37. The lever member protrudes from the ends of the housing so as to be engageable by a suitable tool, as at 38 in Figure 3. The member 38 is biased towards the bottom of the Figure, to bias the latch 36 into an engaging or latching position.

The housing 34 has at each side boss members 39, 40 which are undercut to resemble mushroom heads, for engagement in key slots in the base cover plate 21.

The base cover plate 21 is a generally planar member, with sidewalls 41. A pair of aligned apertures 42, 43 provide for engagement with the chair lock tilt axis, and raised parts 44 with fastener holes 45 provides for connection to the base housing.

An aperture 46, having a widened end, receives a separable connector member which has a rectangular head 47 at one end to fit through the aperture 46 in one orientation, but be retained by the aperture in other orientations of the head 47. The connection member 50 has a second circular head 48 which is receivable by the widened end 27 of the slot 26 in the plate 20. It is held in place in the slot 46 by means of a strip member 49 which provides wrings extending to each side of the member 50.

The member 50 and strip 49 may be provided separately, and are the only parts which are separable from the plates 20, 21.

The plate 21 has a transverse recess or saddle 51, with holes therein for fasteners, and a central recess 52, which is provided with a pair of apertures 53, 54 which receive the pin members 30, 31 on the plate 20, and are provided with widened ends which enable the heads of the pins to pass through, and narrower ends which allow thinner shank portions of the pins 30, 31 to be drawn to the left and retained under the action of the springs 32, 33.

A toothed slot 55 is provided in the recess 52 for engagement by the latch 36.

This slot 55 is configured to provide a series of teeth 56 separated by indentations 57, and at the right hand end of the slot 55, with an initial entry detent 58 of lesser depth than the indentations 57, and an initial tooth 59 of greater length than the teeth 56.

The latch 36 is biased by spring means in the housing 34 into the indentations 58 and 57.

To each side of the recess 52, elongate wide slots 60, 61 are provided with their right hand ends widened, at 62, 63. These enable the boss members 39, 40 to enter the slots 60, 61 and then to slide in the slots as the plate 20 is moved relatively to the plate 21.

Operation Firstly, the base cover plate 21 is prepared by slotting the connection member into the aperture 46, with the wrings of the strip 49 extending laterally width wise across the plate 21. The seat base plate 20 is then placed over the base cover plate 21 with the pins 30, 31 directed downwardly towards the base cover plate, and aligned so that the member 50 enters the slot 26, and the pins 30, 31 enter the apertures 53, 54.

The handle 22, which was hitherto in its uppermost position is then lowered to click into place over the edge of the base cover plate 21, which draws the plate 20 a short distance to the left in the drawings.

This pulls the member 50, and the members 39, 40 into the narrow parts of their receiving slots. The latch 36 which initially entered the detent 58, is drawn over the higher tooth 59 by the action of the lever 22, and now enters the first notch 55.

The relative position of the plates may be adjusted by pressing the lever 22 to retract the latch 36 from the notches 55, and clear the teeth 56, so that by then pulling or pushing the lever, the seat may be moved to the right or left so that the latch 36 enters another notch 55. This operation does not raise the latch 36 sufficiently to clear the higher tooth 59, so that accidental disconnection is avoided.

To intentionally disconnect the plates 20 and 21, an appropriate tool may be used to press the end of the member 38 located at the lower end in Figure 3, into the housing against the spring bias exerted thereon. This does displace the latch 36 sufficiently to clear the tooth 59, enabling riglitward pressure on the handle 22 to return the latch 36 to notch 58, and the pins 30, 31 and members 50, 39 and 40 to the wider parts of their respective slots, thus enabling the plates to be disconnected, and thus the cushion part to be removed from the base part e.g. for reupholstering or access to the base part for repair or maintenance.

Claims (7)

1. Claims 1. A slidable seat apparatus comprising a first plate member for connection to, or connected to, a seat cushion assembly, and a second plate member, for connection to or connected to, a base housing; one of the first or second plate members having a ratchet means defining a plurality of notches and a plurality of teeth, and the other plate member having a latch which is biased to engage into one of said notches and against disengagement from said teeth, characterised in that said ratchet defines a first notch of lesser depth than the remaining notches and a first tooth of greater height than the remaining teeth, the latch being operable against said bias to in ordinary use, clear said Lt) remaining teeth but not said first tooth, to thereby prevent unintended disengagement of said latch from said ratchet.N

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2. 2. The slidable seat apparatus according to claim 1, wherein the latch is operated by a handle.
3. 3. The slidable seat apparatus according to claim 2, wherein the handle can displace the latch against the force of a spring, using an intermediate arm.
4. 4. A slidable seat apparatus comprising a first plate member for connection to, or connected to a seat cushion assembly, and a second plate member for connection to or connected to a base housing; one of the first or second plate members having a ratchet means defining a plurality of notches and a plurality of teeth, and the other plate member having a latch which is biased to engaged into one of said notches and against disengagement from said teeth, -10 -characterised in that one of said plate members has detent means displaceably mounted in a respective slit or slots in said one plate member and biased towards an end of the plate member by spring means, and apertures in said other plate member to receive said detent means, whereby the plate members can be connected together under tension, a further detent between the plate members providing a resistance to said bias.
5. 5. The slidable seat apparatus according to claim 4, wherein the further detent comprises a part which can be mounted in an aperture in one of the plate members, and in a slot in the other of the plate members.
6. 6. The slidable seat apparatus according to any one of claims 4 or 5, wherein said detent means, and the further detent comprises bosses or studs of the type known LI) as "mushroom headed", with wider heads which can be inserted through widened parts of slots or "keyholes", and nanower shanks which can be slid along slots Q which are too narrow to allow passage of the heads.
7. 7. A slidable seat apparatus substantially as hereinbefore described, having reference to the accompanying drawings.