GB2397050A

GB2397050A - Adjustable seat system

Info

Publication number: GB2397050A
Application number: GB0300694A
Authority: GB
Inventors: Jon Frank Ross Whyte
Original assignee: ATB Sales Ltd
Current assignee: ATB Sales Ltd
Priority date: 2003-01-13
Filing date: 2003-01-13
Publication date: 2004-07-14
Anticipated expiration: 2023-01-13
Also published as: GB2397050B; GB0300694D0

Abstract

The system, particularly for a bicycle, comprises a socket member (12) with a wall defining a receiving passage, a seat having a support post (15) slidably inserted in the passage and fixable in the passage in a selectable position, and a clamp (16) for fixing the post (15) by frictional couple without distortion of the socket member (12) or application of fracture-inducing stress to the post. The socket member (12) has an opening (20), which communicates with the passage, in its wall and the clamp (16) has a pressure-exerting element (3) for exerting pressure on the post by way of the opening to urge the post against the boundary surface of the passage thereby to clamp the post to the socket member. The element (30) acts on the post by way of a face (30a) providing area contact with the circumferential surface of the post, e.g. with a curvature matching that of the post circumference, which can be circular, oval or ovoid. The opening (20) has a seal and the member top end also has a seal providing resistance to post movement.

Description

ADJUSTABLE SEAT SYSTEM

The present invention relates to an adjustable seat system, for example a seat system suitable for incorporation in a vehicle such as a bicycle.

Adjustable seat systems are employed in many fields, including two-wheel vehicles such as bicycles, exercise machines with bicycle-type format and furniture such as secretarial chairs. In the case of bicycles it is conventional practice for the seat to be carried by a tubular support post, generally of circular cross-section, telescopically engaged in socket member of the bicycle frame. The socket member, which usually has the form of an integral element - known as a seat tube - of the frame, has an axial slot at the top and the support post of the seat is fixed in a selected axial position in the seat tube by a split clamping ring applying stress to close the slot and thus cause the tube wall to grip the post.

Such a method of fixing Is satisfactory when the clamping ring is tightened by use of a threaded fastener allowing generation of a high closing force sufficient to, in effect, distort the seat tube. However, problems arise in the case of use of manually operated quick- action clamping rings, which are increasingly popular, where the clamping force must be lower to allow easy manual operation without use of tools. Much of the available clamping force is absorbed in distorting the seat tube and after the clamping ring has been released the distorted seat tube may prevent easy sliding of the seat support post, as a consequence of which quick and easy adjustment of the seat is compromised. In addition, much of the applied force is lost in closing the clamping ring itself, unless use is made of a hinged two-part ring, which then introduces the possibility of creating a fracture-promoting stress point on the seat tube in the vicinity of the hinge.

A further problem that arises with existing systems regardless of whether a single split clamping ring or a hinged two-part ring is used is susceptibility to ingress of dirt and moisture into the seat tube by way of the top of the tube and the axial slot, which are difficult or impossible to effectively seal. This problem is particularly significant in the case of off-road bicycles ridden in wet and dirty environments. Ingress of dirt and water between the seat support post and the seat tube can cause fretting and corrosion of the contacting surfaces, which can make adjustment even more difficult.

Moreover, the only tube and post cross-sechon satisfactory for existing systems is circular, since other shapes, such as square, oblong, oval, etc., do not allow even distribution of clamping force throughout the section. Nevertheless, repeated seat adjustment with a system of the kind currently in use can lead to fatigue failure or cracking of the seat tube in the region of the axial slot due to the distortion occurring on each occasion the clamp is operated.

It is accordingly the principal object of the present invention to provide an adjustable seat system that may overcome or lessen the effect of some of the constraints of existing systems, particularly by avoidance of positional fixing by component distortion.

A supplementary object of the invention is to provide an adjustable seat system amenable to use of a quick-action clamp to provide secure fixing without the need for tools or the exercise of undue physical effort.

Yet another supplementary object of the Invention is to m,nimise or eliminate the susceptibility of adjustable seat systems to the penetration of moisture and contaminants.

According to the present',nvention there is provided an adjustable seat system comprising a socket member with a wall defining a receiving passage, a seat provided with a support post slidably engaged in the passage and fixable therein in a selectable axial relationship to the member, and a clamp for fixing the post in the selected relationship by friction couple without distortion of the member, the member being provided in the wall thereof with an opening communicating with the passage and the clamp comprising a pressure- exerting element for exerting pressure on the post by way of the opening to urge the post into pressurable engagement with part of the boundary surface of the receiving passage thereby to clamp the post to the member, the element acting on the post by way of a face providing area contact with the circumferential surface of the post in a region opposite the engaged part of the boundary surface of the passage.

Such an adjustable seat system provides positional fixing of the seat support post - which can be a solid bar but for reasons of weight and cost will normally be tubular - by frictional couple resulting from pressurable surface-to-surface engagement primarily between the post and the boundary surface of the passage and secondarily between the post and the pressure-exertng element. The load applied by the pressure-exerting element, although relatively concentrated, is nevertheless distributed over an area so that a stress-induc,ng force liable to cause fracture of the post Is avoided. The direct action on the seat post by a pressureexerting element via an opening in the wall of the socket member eliminates the need to distort any component in order to generate clamping force.

Preferably, the face of the element and at least the region of the circumferential surface of the post contacted by the face have substantially complementary profiles in cross-section of the post. Such a configuration has the result that the face of the pressure-exerting element is in contact over the whole area thereof with the associated region of the circumferential surface of the post, so as to maximise the contact achievable with the element. The complementary profiles can be curved, for example substantially circularly arcuate or parabolic, or substantially straight or can be defined by regular or irregular shapes. If the profiles are curved, the circumferential surface of the post can be cylindrical and the face of the element can be concave with substantially the same curvature as the circumferential surface of the post. Alternatively, the circumferential surface can be substantially oval or ovoid, for example elliptical, egg-shaped or teardrop-shaped, in crosssection and the face of the element can be concave with substantially the same curvature as the narrower end of the post cross-secton. Various profiles are possible depending on the specific requirements.

The face of the element can, in projection, be any desired shape, but for preference is substantially oblong or square so as to maxmise the area in contact with the post in the circumferential direction thereof. T he opening in the wall of the socket member is preferably an aperture with a closed perimeter, that is to say without communication with the entry end of the socket member in the manner of the open-ended slot of the previously described prior art system. The pressure-exerting element can be a sliding fit in the aperture, so that the scope for ingress of moisture or dirt into the passage in the member via the aperture is minimal.

The clamp is preferably a quick-action clamp so that release of the support post for positional adjustment of the seat and reapplication of clamping pressure to fix the post in a newly selected position can be carried out quickly and, in particular, without requiring a tool such as a spanner. The quick-action facility is preferably achieved by providing lever actuation.

In basic construction, the clamp can comprise at least one grip member embracing the socket member in the region of the opening and tightenable around the socket member to cause movement of the pressure-exerting element towards and away from the post. In that case, the pressureexerting element can be formed by a part of the grip member or one of the members, for example by an integral or separately constructed protrusion fitting into the opening in the wall of the socket member. In one construction of the clamp, two such grip members are present and can be entirely separate from one another, but, for convenience, are pivotably connected together and movable relative to one another about the pivot connection to be tightenable around the socket member. In another construction of the clamp, a single grip membems present and is tightenable about the socket member against an intrinsic resilience of the grip member. For the purpose of operation, the clamp may comprise a rotary eccentric acting on the grip member or one of the grip members for the tightening thereof around the socket member. The eccentric can be, for example, an Integral part of a manually operable lever in the case of a lever-actuated clamp.

The possibility of ingress of moisture or dirt Into the socket member by way of the opening provided in its wall can be effectively excluded if sealing means are present to sealngly close the opening. The sealing means can comprise a sealing ring acting between the clamp and the outer circumferential surface of the socket member. The ring can be arranged to bear on the outer circumferential surface of the socket member adjacent to and around the perimeter of the opening and can, for convenience, be mounted on the pressure-exerting element.

In addition, the system can include resilient means arranged to provide a seal between the boundary surface of the passage and the circumferential surface of the post in the region of an upper entry end of the passage and to generate resistance to relative movement of the post and socket member. Such resilient means can conveniently take the form of a resilient ring seated in a recess in the boundary surface of the passage and pressurably bearing against the circumferential surface of the post. The resilient ring is located at or near the top of the socket member and assists sealing the interior of the member. In addition, it offers resistance to the tendency of the seat support post to drop down in the socket member when the clamp is released and thus is able to retain the post and the seat In a selected new position until the clamp is retightened.

For preference, the seat is formed to have front, back and side orientations with respect to a predetermined intended position of a user supported thereon and the opening In the post is disposed at the back of the seat. Other dispositions of the opening are possible, however, including at the front or either side of the seat, the preferred disposition to some extent being dependent on the construction of the clamp and ease of access to the clamp for the purpose of fixing and releasing the post.

The adjustable seat system is particularly suitable as part of a vehicle, especially a bicycle, but is usable In other contexts such as seating furniture.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view of part of a bicycle incorporating an adjustable seat system embodying the invention; Fig. 2 is a side view, partly in section on the line lull in Fig. 3 and in exploded form, of part of a first adjustable seat system embodying the invention; Fig. 3 is a back view and plan view, respectively, of components of the system shown in Fig. 2; Fig. 4 Is a side view, partly in section on the line IV-IV of Fig. 5 and in exploded form, of part of a second adjustable seat system embodying the invention; and Fig 5 is an exploded front view and plan view, respectively, of components of the system shown in Fig. 4.

Referring now to the drawings there is shown in Fig. 1 part of a bicycle incorporating an adjustable seat system 10, the bicycle comprising a frame of which only a down tube 11 and a seat tube 12 are designated. The two tubes carry a rear suspension schematically represented by a swing arm 13. A seat 14 for the rider of the bicycle Is adjustably mounted on the frame by way of a support post 15 which is slidably engaged in the seat tube 12 and secured therein by way of a clamp 16. The seat 14, seat post 15, clamp 16 and the seat tube 12, or at least a part of the seat tube, form the adjustable seat system 10.

The significant parts of the seat system are shown in more detail in Figs. 2 and 3 to enlarged scale. The seat tube 12 represents a socket member of the system 10 and, in the illustrated embodiment, consists of a thinwalled tube defining an axial passage 17 with a circularly cylindrical boundary surface 18. The seat tube 12 is open at its upper end and has, at that end, a wall enlargement with an internal encircling groove receiving a resilient ring 19 of elastomeric material. In addition, the tube is provided in its wall and just below the ring 19 with an opening 20 in the form of a closed-perimeter aperture of oblong shape, but with radiused corners. The opening 20, which communicates with the axial passage 17, is disposed at the back of the seat tube 12 with respect to the forward direction of travel of the bicycle and enables clamping of the seat post 15 by the clamp 16 as described in more detail further below.

The seat post 15 similarly consists of a tube of circular cross-section, thus with a cylindrical circumferential surface, and is a sliding fit In the passage 17 of the seat tube 12.

The post 15 carries the seat 14 at its upper end, for example by way of a pivotable and lockable coupling (not shown), and is fixed in a selectable axial position in the passage 17, thus in a selectable axial relationship to the seat tube 12, by the clamp 16.

The clamp 16 Is shown, for the sake of clarity, separately from the seat tube 12 in Figs. 2 and 3, but also schematically depicted - by dashed lines - in position on the seat tube 12 in Fig. 2. The clamp 16 consists of two grip members 21 and 22 which are pivotably connected together by an axle pin 23 to define an enclosure of variable diameter for the seat tube 12 and which terminate, remote from the point of pivotal interconnection, in two generally parallel lugs 21a and 22a formed with mutually aligned bores. A tightening bolt 24 is captively retained in the bores by a threadedly adjustable stop element 25 at one end and a pivotable eccentric 26 at the other end, the eccentric 26 being rotationally coupled to an eye of the bolt 24 and bearing on a concave support surface of a thrust pad 27 between the eye and the adjacent one of the lugs of the grip members. Rotation of the eccentric 26 can be effected by way of an integrally formed lever 28 which tightens or relaxes the enclosure of the seat tube 12 by the grip members 21 and 22. The lever-actuated eccentric 26 and associated tightening bolt 24 thus provide a quick-action operation and also self- locking of the eccentric 26 in the tightened state of the clamp 16.

One of the grip members, in particular the member 21, has a concave surface 29 with substantially the same radius of curvature as that of the outer circumferential surface of the seat tube 12 so as to closely embrace the seat tube and the other grip member 22 defines a pressure- exerting element 30 which is partly in the form of a protrusion and is a sliding fit In the opening 20 In the wall of the seat tube, the element 30 extending into the opening in both the tightened and the relaxed state of the clamp. The element 30 has a concave face 30a with substantially the same radius of curvature as that of the circumferential surface of the seat post 15 and the cylindrical boundary surface 18 of the axial passage 17 of the seat tube 12. The orientation of the concave face 30a is such that, in the tightened state of the clamp 16 as shown in Fig. 3, the face lies on a notional cylinder generally concentric with that of the boundary surface 18 of the passage 17. In this tightened state, the concave face 30a of the element 30 bears on a portion of the circumferential surface of the seat post 15 and urges the post pressurably against an opposite portion of the boundary surface 18 of the passage 17 in the seat tube 12, so as to generate a frictional couple sufficient to fix the seat post in the seat tube in a selected position even under a load significantly exceeding the weight of a rider supported on the seat The area contact of the concave face 30a of the element 30 with the circumferential surface of the seat post 15 enables a high level of frictional clamping to be achieved without distortion of either the seat tube or the tubular seat post and, in particular, without exertion of fracture-promoting stress on the wall of the seat post. This clamping is achieved by the lever action of the clamp 16 and is quickly and easily released by reverse operation of the lever 28.

The sealing ring 19 located in the groove in the boundary surface 18 of the passage 17 produces a constant friction couple with the circumferential surface of the seat post 15 sufficient to hold the post against displacement under its own weight into the seat tube 12 when the clamp 16 is released. The couple is, however, such that it can be readily overcome by the user in order to select a new post position. The frictional engagement of the ring 19 with the seat post 15 additionally provides sealing of the top of the seat tube 12 against ingress of moisture, which can otherwise be readily carried into the interior of the tube when the post Is slid downwardly in the passage.

The opening 20 in the wall of the seat tube 12, through which the element 30 extends and which - in open-ended slot form in prior art systems - has represented a sealing problem in the past, is sealed by an O-ring 31 of elastomeric material extending around the element and pressurably beanng, in the tightened state of the clamp 16, against the outer circumferential surface of the seat tube 12 adjacent to the perimeter of the opening 20.

The closed perimeter permits sealing action entirely around the opening so that moisture and dirt are effectively excluded from entry into the passage 17.

In the further embodiment of the adjustable seat system illustrated in Figs. 4 and 5, the same reference numerals have been adopted for corresponding components, but distinguished by indices. The principal distinction in relation to the embodiment of Figs. 2 and 3 resides In the substitution of the circular-section seat tube and seat post by a seat tube 12' and seat post 15' each of egg-shaped cross-secton offering enhanced aerodynamics and strength. The opening 20' in the wall of the seat tube 12' is located at the narrower end of the cross-section, but otherwise has the same form as in the first embodiment. The clamp 16' again comprises two grip members 21' and 22'. However, these are connected together not by an axle pin, but by a coupling bolt 32 with sufficient tolerance to allow relative movement of the grip members when the clamp is released.

Tightening and relaxation of the clamp 16' is similarly by way of a leveractuated eccentric 26', thrust pad 27', tightening bolt 24' and stop element 25', which co- operate to draw the grip members 21' and 22' together when the eccentric 26' is rotated to exert thrust on the pad 27'. In cross-section, the grip members 21' and 22', respectively define a curved surface 29' conforming with part of the outer circumference of the seat tube 12' at its wider end and a pressure-exerting element 30' having a curved face 30a' conforming with part of the circumference of the seat post 15' at its narrower end. The principle of clamping the seat post 15' in place in the seat tube 12' is the same as in the case of the first embodiment and sealing rings 19' and ring 31' are provided for the same purposes as in the first embodiment.

The two different cross-sectonai shapes of seat tube and seat post shown in the drawings are merely by way of example and a feature of the adjustable seat system according to the invention is that it operates effectively with a variety of different cross-sections, including polygonal. Equally, the clamp can take different forms, subject only to the requirement for area contact with the seat post via the opening in the seat tube. In a particularly economic alternative construction the clamp consists of a single split ring tightenable, against the intrinsic resilience of the ring, by a tightening bolt and eccentric system operating in the same manner as in the case of the illustrated embodiments. In addition, the pressure- exerting element, insofar as it is formed wholly or in part by a protrusion, can be provided by a separate part secured to, rather than integral with, the grip member or split ring of the clamp. This measure, too, may reduce production cost of the clamp.

The system can be incorporated in a wide range of products in which adjustable seats are employed and is particularly suitable for folding bicycles and other such applications where seat adjustment is regularly repeated and consequently seat clamping by component distortion is undesirable. lo

Claims

1. An adjustable seat system comprising a socket member with a wall defining a receiving passage, a seat provided with a support post slidably engaged in the passage and fixable therein in a selectable axial relationship to the member, and a clamp for fixing the post In the selected relationship by friction couple without distortion of the member, the member being provided in the wall thereof with an opening communicating with the passage and the clamp comprising a pressureexerting element for exerting pressure on the post by way of the opening to urge the post Into pressurable engagement with part of the boundary surface of the receiving passage thereby to clamp the post to the member, the element acting on the post by way of a face providing area contact with the circumferential surface of the post in a region opposite the engaged part of the boundary surface of the passage.

2. A system as claimed in claim 1, wherein the face of the element and at least the region of the circumferential surface of the post contacted by the face have substantially complementary profiles in cross-section of the post.

3. A system as claimed in claim 2, wherein the profiles are curved.

4. A system as claimed in claim 3, wherein the profiles are substantially circularly arcuate or parabolic.

5. A system as claimed in claim 4, wherein the circumferential surface of the post is cylindrical and the face of the element is concave with substantially the same curvature as the circumferential surface of the post.

6. A system as claimed in claim 4, wherein the post is substantially oval or ovoid in cross-section and the face of the element is concave with substantially the same curvature as the narrower end of the post crosssection.

7. A system as claimed in claim 2, wherein the profiles are substantially straight.

8. A system as claimed In claim 2, wherein the profiles are defined by regular or Irregular shapes.

9. A system as claimed in any one of the preceding claims, wherein the face of the element is a substantially oblong or square in projection.

10. A system as claimed in any one of the preceding claims, wherein the opening is an aperture with a closed perimeter.

11. A system as claimed in claim 10, wherein the element is a sliding fit in the aperture.

12. A system as claimed in any one of the preceding claims, wherein the clamp is a quick-action clamp.

13. A system as claimed in claim 12, wherein the clamp is a leveractuated clamp.

14. A system as claimed in any one of the preceding claims, wherein the clamp comprises at least one grip member embracing the socket member in the region of the opening and tightenable around the socket member to cause movement of the pressure- exerting element towards the post.

15. A system as claimed in claim 14, wherein the element is formed by a part of the grip member or one of the grip members.

16. A system as claimed in claim 14 or claim 15, wherein the clamp comprises a rotary eccentric acting on the grip member or one of the grip members for tightening thereof around the socket member.

17 A system as claimed in any one of claims 14 to 16, wherein the clamp comprises two such grip members pivotably connected together and movable relative to one another about the pivot connection to be tightenable around the socket member.

18. A system as claimed in any one of claims 14 to 16, wherein the clamp comprises a single grip member tightenable around the socket member against an intrinsic resilience of the grip member.

19 A system as claimed in any one of the preceding claims, comprising sealing means to seemingly close the opening.

20. A system as claimed in claim 17, wherein the sealing means comprises a sealing ring acting between the clamp and the outer circumferential surface of the socket member.

21. A system as claimed in claim 20, wherein the sealing ring is arranged to bear on the outer circumferential surface of the socket member adjacent to and around the perimeter of the opening.

22. A system as claimed in claim 20 or claim 21, wherein the sealing ring is mounted on a circumferential portion of the element.

23. A system as claimed in any one of the preceding claims, comprising resilient means arranged to provide a seal between the boundary surface of the passage and the circumferential surface of the post in the region of an upper entry end of the passage and to generate resistance to relative movement of the post and socket member.

24. A system as claimed in claim 23, wherein the resilient means comprises a resilient ring seated in a recess in the boundary surface of the passage in the socket member and pressurably bearing against the circumferential surface of the post.

25. A system as claimed in any one of the preceding claims, wherein the seat is formed to have front, back and side orientations with respect to a predetermined intended position of a user supported thereon and the opening in the post is disposed at the back of the seat.

26. A vehicle comprising a system as claimed in any one of the preceding claims.

27. A vehicle as claimed in claim 26, wherein the vehicle is a bicycle.

28. An item of seating furniture comprising a system as claimed in any one of the preceding claims.