GB2325655A - Bicycle seat post with spring shock absorber - Google Patents

Abstract

The seat post comprises an outer tube 11, for sliding into a bicycle frame tube, and an inner seat support 19 that is slidingly carried in the outer tube on a spring 20. The outer tube has an annular flange (Figure 2) in which four screw threaded cavities that communicate with the interior of the outer tube are formed. The four cavities are positioned at 90 degree increments around the tube in a cross formation. Each cavity receives a grub screw, for example, 28 and 30 that abuts against the support 19 to minimise lateral and twisting movement of the support whilst still allowing it to slide vertically. Locking grub screws, for example, 32 and 34 are also provided to lock the grub screws 28, 30 in position. To further prevent rotation, the support 19 may comprise a non - circular section that slides in a correspondingly shaped part of the outer tube or it may comprise a longitudinal slot which receives a projection from the outer tube. The inner surface of the outer tube may be tapered to accommodate the lateral expansion of the spring under axial compression. A tie rod 23 extends through an axial cavity in the support and the outer tube and is held in place by circlips, for example, 25 that locate in annular grooves. The spring 20 may be replaced with a spring of different rating to accommodate for users of different weight.

Description

SEAT SUPPORT The invention relates to a seat support especially for a bicycle.

Conventionally, cycle seats have been mounted on the upper end of a post which is adjustably carried in the rear down-tube of the cycle frame. Unless the rear wheel is connected to the frame via a resilient linkage, the only damping effect for the comfort of the rider depended on the inherent softness or springiness of the saddle itself. More recently, resilient seat supports have been proposed but they typically rely on hydraulic dampers, gas struts and the like and are consequently relatively expensive. In any event, known resilient seat supports do not generally make provision for adjustment to the weight of the user or the required hardness or softness of the ride, having regard to the nature of the terrain or other surface to be ridden on.

It is an object of the invention to provide a resilient seat support which meets the requirements of most cyclists, having regard to those proposed in the at hitherto.

According to one aspect of the present invention, a resilient seat support assembly especially for a bicycle frame comprises an outer tube adapted for receipt in the frame and an inner seat support member slidingly mounted within the outer tube, in which said outer tube and support member are operatively connected together by resilient means which is removable from and replaceable within the assembly.

It will be appreciated that the assembly is usable with resilient means, preferably compression springs, of different resilience ratings, thus providing the ability of the user to select an appropriate resilience in advance by, if necessary, removing the existing resilient means and replacing it with another having a different rating.

In order to provide the removable resilient means, the assembly may be arranged to be partially dismantled to allow the resilient means to be withdrawn from within the outer tube. Preferably, the seat support member is capable of being withdrawn upwardly from the outer tube, thereby allowing the resilient means also to be withdrawn upwardly. The upper end of the outer tube may comprise releasable bearing means for the seat support member, whereby release of the bearing means permits the seat support member to be withdrawn together with the spring or other resilient means. The releasable bearing means are preferably carried in lateral or radial chambers which are in communication with the interior of the outer tube, and allow sliding movement of the seat support member while minimising lateral movement and exclude moisture and dirt from ingress to the outer tube. The bearing means may be urged into contact with the support member by spring means or may be adjustable, whereby bearing wear may from time to time be taken up by tightening the bearing means.

Advantageously, the support member includes means to prevent it from turning or swivelling within the outer tube. The support member may for example include a longitudinal slot or channel which receives a projection extending inwardly from the outer tube to restrain the support member from swivelling but preferably the support member comprises a non-circular part which slides within a correspondinglyshaped part of the outer tube. For example, the support member may be square in cross section in at least part of its length and the bearing means may act against at least two opposed faces of the support member to prevent the support member from turning. Advantageously, the bearing means comprise four screw-threaded adjusters with bearing faces mounted equi-angularly about the support member, each bearing against a respective longitudinal face of the support member. The bearing faces preferably extend across substantially the entire width of the longitudinal faces of the support member.

The inner surface of the outer tube is preferably provided with a slight flare angle whereby it tapers outwardly towards the upper end, to accommodate the small extent of lateral expansion of the spring on longitudinal or axial compression thereof without it rubbing or squeaking against the inner wall of the tube. The lower inner end of the tube may be provided with an annular shoulder or flange which acts as a seat for locating the lower end of the spring.

The support member preferably includes a central bar or rod element which extends axially through the apparatus from the upper end of the support member to and through the lower end of the outer tube. The rod is provided with end retainer means to retain it within the support member. Such end retainer means may comprise a washer held in place by a screw-threaded nut, a circlip carried in an annular groove, or the like; one end of the rod may be formed as a radiallyenlarged head or flange to bear against the corresponding end of the outer tube. The rod is slidable through the lower end of the outer tube and enhances the strength of the assembly and particularly the resistance thereof to bending or deformation.

The invention also includes a screw-threaded adjuster for applying bearing pressure to a seat support member in an assembly as hereinbefore described, the adjuster comprising a cylindrical body with an external screw thread and an axial faceted cavity extending therethrough to open at each end face, at least one said end face being substantially flat and constituting a bearing surface for sliding engagement in use with a longitudinal face of a seat support member.

Preferably, each end face constitutes a bearing surface, whereby the adjuster may be inserted either way round in the chamber which communicates with the interior of the outer tube.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a longitudinal section of a bicycle seat support in the fullyextended position; Figure 2 is a section along the line II-II of Figure 1; Figure 3 is similar to Figure 1, the support carrying a bicycle seat and being shown in a partiallycompressed condition; and Figure 4 is a side elevation of a screw-threaded adjuster for use in the support of Figures 1 to 3.

With reference firstly to Figure 1, the support consists essentially of an outer tube member 11 formed with an annular outwardly-extending flange 12 at its upper end in which are formed four radially-disposed cavities 13-16 positioned at respective 90" increments, as shown in Figure 2. The cavities are formed with screw threads.

The lower end of the tube member is formed as a thickened wall portion 17 defining an inner annular shoulder or seating 18. The outer diameter of the tube member is 25.4mm, sized to be a sliding fit in a cycle frame tube, and the inner wall tapers from an inner diameter of 20mm at the upper end to 19mm at the lower end, immediately above the shoulder 18.

An inner seat support member 19 of square-section tubing with chamfered edges and a cylindrical axial cavity therethrough is slidingly carried in the tube member 11; the lower end of the support member 19 engages the upper end of a helical compression spring 20 via a bush 21. The lower end of the spring 20 is received against the shoulder 18 via another bush 22. A tie-rod 23 extends through the outer tube member 11 and the support member 19; the tie-rod is formed with upper and lower annular grooves which carry circlips 24, 25 which retain the tie-rod within the support member. The upper end 26 of the support member 19 is formed as a plain cylinder, to engage the mounting bracket of a bicycle seat 27 (see Figure 3).

Grub screws 28-31 are carried in respective cavities 13-16 and each abuts a respective face of the support member 19, to take up any lateral play and to prevent the support member 19 from axial twisting movement. The grub screws may be adjusted to a desired pressure against the support member 19, for which purpose they (RfM) may be provided with axial cavities to receive an Allen key or a slot to receive a screwdriver, and locked in position by locking grub screws 32-35, also provided with axial cavities or end slots for tightening and release purposes. An optional cover member such as bellows element 36, made for example from polyurethane, is disposed about the support member 19 and over the flange 12.

In Figure 3, the support member 19 is shown partially depressed with the spring 20 under compression. The lower end of the tie-rod 23 extends from and below the bottom of the outer tube member 11.

The screw adjuster shown in Figure 4, suitable for use as the grub screws 2835, consists of a cylindrical body 41 having an external screw thread 42 terminating in flat end faces 43, 44 having the same diameter as the outside diameter of the helical ridge which defines the screw thread. The body has a hexagonal-section axial cavity 45 extending therethrough and opening in each end face 43,44 for receiving a hexagon key for rotational driving thereof. The adjuster is preferably formed from a plastics material, especially an engineering plastics material with self-lubricating properties.

In use, the interior of the seat support assembly is packed with grease. The axial cavities through the screw adjusters, which are in mutual registration as between each grub screw 28-31 and the respective locking grub screw 32-35, allow grease to move in each direction therethrough, under internally-generated positive or negative pressure, as the seat support moves up and down within the outer tube. Furthermore, the axial cavities can be used for the purpose of re-charging the interior with more grease.

In order to change the spring 20 for one having a different rating, it is necessary only to remove the upper circlip or the lower circlip 25 and to slacken the grub screws 28-35 to allow the support member 19 to be withdrawn upwardly, following which the spring may be withdrawn and replaced with a higher or lower rated spring to compensate for more or less body weight.

Claims (14)

1. A sprung loaded seat support for a bicycle comprising of eight adjusters equily-spaced surrounding the centre shaft to eliminate movement laterally, but still allow vertical movement.Also the ability to exchange the torsional springs No.20 to compensate for varying body weights to maximise spring efficiency, and a centre shaft to increase rigidity and strength.

2. A sprung loaded seat support as claimed in claim 1 contains 8 adjustable screw adjusters equily spaced surrounding the centre square member No.19 Fig.3 from horizontal movement but still allowing vertical movement.

3.A sprung loaded seat support as claimed in claim 2 & 3 has means of removing the spring unit to replace with a more or less torsional springing motion to compensate for varying body weight differences.

4. A sprung loaded seat support as claimed in claim 2 carries a square centre shaft to reduce lateral movement two thirds of its length and a cylindrical top section that allows different types of saddle brackets to be secured to the top fixing.

5. A sprung loaded seat support as claimed, containing a plastic bush located in the end section of the body tube Fig.2 to reduce friction and wear occuring in this area.

6. A sprung loaded seat support as claimed in claim 1,2,3,4 & 5 containing a longitudinal shaft running the full length of the unit, collectively holding the unit together by two circlips positioned either end of the centre shaft and alike.

7. A sprung loaded seat support as described here in with reference to figures 1-6 of the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. A support post for a cycle seat, comprising a tubular outer member, a spring-loaded support member mounted within the outer member and projecting from an upper end thereof to support a seat in use, and said outer member being provided with a plurality of bearing members mutually spaced at intervals around the support member to slidably guide said support member therein and being adjustably engaged with said outer member to permit adjustment of their bearing contact with the support member.

2. A support post according to Claim 1 in which said bearing members act against substantially flat areas of said support member.

3. A support post according to Claim 2, in which there are four such bearing members acting against two mutually orthogonal pairs of mutually opposed faces of said support member.

4. A support post according to any preceding claim, in which said bearing members have substantially flat bearing surfaces for contact with said support member.

5. A support post according to any preceding claim, in which said bearing members are adjustably engaged in passages in said outer member.

6. A support post according to Claim 5, in which said bearing members are adjustably engaged in said passages by means of screw threads.

7. A support post according to Claim 6, in which said bearing members contain axial cavities to receive a turning tool.

8. A support post according to any preceding claim, in which said bearing members are formed of plastics.

9. A support post according to Claim 6 or 7, in which each of said bearing members is held in its adjusted position by a respective locking screw received in an outer portion of the respective passage.

10. A support post according to Claim 9, in which said bearing members have substantially flat bearing surfaces for contact with said locking screws.

11. A support post according to Claim 9 or 10, in which said locking screws have substantially flat bearing surfaces for contact with said bearing members.

12. A support post according to any of Claims 9 to 11, in which said locking screws contain axial cavities to receive a turning tool.

13. A support post according to any of Claims 9 to 12, in which said locking screws are formed of plastics.

14. A support post for a cycle seat, substantially as described with reference to the accompanying drawings.