Honing stone and guide assemblies

Abstract

 A honing stone assembly comprises an abrasive honing stone (15) bonded to a plastics shoe (14). The shoe is a snap fit on the platform (10) of a stone holder. A similar plastics snap-on honing guide (21) fits a platform of a guide holder.

Description

[0001] The invention relates to honing assemblies and in particular to the mounting of honing stones and the construction and mounting of honing guides.

[0002] In honing a bore, abrasive honing stones are mounted on a honing mandrel to be radially urged against the wall of the bore as the mandrel is rotated. Usually a pair of honing stones is urged outwardly in opposition. In order to prevent noise and chattering and generally to assist in maintaining bore roundness it is found necessary to provide guides which are disposed between the honing stones and urged resiliently from the mandrel against the wall of the bore. The guides are non-abrasive and should preferably wear at approximately the same rate as the stones.

[0003] The stones and guides must be replaced when they have worn to a certain extent. Existing arrangements for replacing stones and guides have disadvantages. The present invention seeks to provide improvements in the construction and mounting of honing stones and guides which not only facilitates replacement but also reduces the cost of the replacement stones and guides.

[0004] According to one aspect of the invention there is provided a honing stone assembly comprising an abrasive honing stone bonded to a plastics shoe, the shoe being adapted by virtue of its shape and inherent resilience to be a snap fit on a stone holder.

[0005] Honing generates a significant amount of heat and it is to be understood that the plastics material of the shoe should be selected accordingly. As used herein "plastics" means a cross-linked or vulcanised plastics or elastomere material which includes silicones and resins such as phenolic and melamine resins. Cross-linking may be applied to the following groups of material for example: polyamides, polyethylenes, polypropylenes, polyurethanes, and polyvinylacetates. A suitable group of materials are acetals and polyacetals. Glass-filling may be used to enhance the properties of the material.

[0006] The stone may be bonded directly or via a metal shell, perhaps of steel, to the plastics shoe. Bonding may be accomplished by using suitable adhesives or by fusing, welding or moulding the shoe directly onto the stone or shell, perhaps after priming or plating.

[0007] The invention includes the combination of the stone holder and the mounted shoe. The stone holder preferably comprises a platform which is mounted on a pair of legs. The legs have serrations which constitute a rack for co-operation with a pinion in the mandrel, whereby the stone holders may be moved radially with respect to the bore being honed.

[0008] Preferably the shoe has an elongate rebate which accommodates one edge of the platform, and the other edge of the platform constitutes a ledge to retain the opposite side of the shoe. A preferred arrangement is that the shoe on said opposite side has a depending wall with an inwardly projecting rib at its extremity, the wall being flexible enough to allow the rib to be forced over the ledge, whereby it is retained.

[0009] It is necessary to locate the shoe on the holder against longitudinal movement. While it is envisaged that the ends of the shoe and holder may be adapted to provide such location, a preferred arrangement is to provide a rebate in the first-­mentioned edge of the platform and in the co-operating key shape in the shoe.

[0010] The provision of a plastics shoe of the kind described allows simple snap-on, snap-off replacement of worn stones. The time-consuming rivetting or screwing of replacement shoes in conventional arrangements is obviated. Also, the manufacture of replacement shoes is simplified and made significantly less expensive by the use of moulded or extruded plastics rather than cast metal, as hitherto.

[0011] Another aspect of the invention relates to honing guides, and in accordance therewith there is provided a honing guide made of plastics and being adapted, by virtue of its shape and inherent resilience, to be a snap fit on a guide holder. The invention includes the combination of the guide holder and the mounted guide. The guide holder preferably comprises a platform which is mounted on a pair of legs. The platform may be identical with the above-­described platform for the stone holder, and the legs similarly identical. It must be observed, however, that if the stone holders and guide holders are to be used in the same mandrel, the disposition of the legs on the platforms must be respectively different so that the legs of the stone holders do not interfere with the legs of the guide holders.

[0012] Since the platforms of the stone holders and guide holders are preferably identical, the provision of similar rebate, wall, rib and key will be understood to apply to the guide and holder combination. However, the preferred configuration of the guide differs in a significant respect from the configuration of the stone shoe. This is because the guide is to be resiliently urged against the wall of the bore whereas there is no similar resilience for the shoe. Thus, the base of the shoe is flat against the platform. On the other hand, a feature of the present invention provides an inclined base region for the guide whereby a gap is provided beneath the guide and the body of the guide constitutes a leaf spring to provide the necessary resilience. It is to be noted that the leaf spring provided by this arrangement extends over the full length of the guide and not merely locally as in prior arrangements. The plastics material is suitably selected, preferably being an acetal material and may be loaded with other material, for example carbon fibre or glass fibre to give the required strength and resilience.

[0013] The guide may be differentially loaded with selected materials so as to give pre-selected wear characteristics at its wear face while retaining required resilience at the spring region and strength at the rebate, for example.

[0014] The invention will further be described with reference to the accompanying drawings, of which:-

Figure 1 is a schematic plan view of a honing mandrel embodying the invention;

Figure 2 is an end elevation of a stone holder of Figure 1;

Figure 3 is a plan view of the stone holder of Figure 2;

Figure 4 is a side elevation of the stone holder of Figure 2;

Figure 5 is an end elevation of a stone shoe for fitting the holder of Figures 2 to 4;

Figure 6 is a plan view of the shoe of Figure 5;

Figure 7 is an end elevation of a guide of the mandrel of Figure 1;

Figure 8 is a plan view of the guide of Figure 7; and

Figure 9 is an end elevation of another honing stone assembly embodying the invention.

[0015] Referring to Figure 1 the mandrel 1 is inserted into the bore 2 of a cylinder to be honed. A block 3 carries two honing stone units 4 and 5 and two guide units 6 and 7. Each of the units is mounted on a pair of legs 8 which have serrations which constitute racks which mesh with a pinion 9. The stone and guide units are urged outwardly by rotation of the pinion and honing is effected by rotation of the mandrel as a whole with respect to the cylinder and by stroking the mandrel longitudinally with respect to the cylinder.

[0016] Figures 2 to 4 show a stone holder having legs 8 mounted on a platform 10. The platform has an edge 11 which has a central rebate 12 (Figure 3) to constitute a key. The platform has a ledge 13 opposite the edge 11.

[0017] Figures 5 and 6 show a shoe 14 made of moulded acetal material and having bonded to it an abrasive honing stone 15. Bonding is effected by the use of Loctite Prism 757 prime in conjunction with Loctite Prism 406 adhesive. The shoe is shaped to have a rebate 16 which accommodates the edge 11 of the platform. The rebate has a key portion 17 which fits the rebate 12 to key therewith and prevent longitudinal movement of the shoe with respect to the platform.

[0018] The shoe has a depending wall 18 with an inwardly facing curved-section rib 19. A slot 20 aids the flexing of the wall so that the shoe may be snapped on to the platform by forcing the rib beyond the ledge 13. The shoe can thus be snapped on and off the platform.

[0019] Referring now to Figures 7 and 8 there is shown a honing guide in accordance with the invention. The guide 21 is made of plastics and has a rebate, a key shape 17, a depending wall 18, a rib 19 and a slot 20 whereby the guide can be a snap fit on a platform in the same manner as the shoe of Figures 5 and 6. The guide has an upstanding wear block 22 which bears against the wall of the cylinder. The block is shaped with a central neck 23 as shown in Figure 8.

[0020] An important feature of the guide is the shape of its base at 24, where it is angled to provide a gap 25 beneath it. Portion 26 of the guide thus constitutes a leaf spring to give resilience to the action of the wear block on the bore wall. It will be appreciated that the rib is allowed to ride down beyond the ledge 13 of the platform.

[0021] Figure 9 shows an alternative shoe for the honing stone assembly. Instead of being bonded directly to the shoe, the stone 15 is bonded to a reinforcing steel shell 30 which itself is bonded to the shoe. Bonding is effected by adhesives as described above.

[0022] The shape of the shoe differs in some respects from that of the shoe and guide described above. For example, the rib 19 of the above described shoe is replaced by an angled member 31 having a wedge shape. The key 17 has an angle at 32. At each end, the wall 18 has a 10 angle shown at 33. It is to be understood that a corresponding guide also has these characteristics.

[0023] The invention is not restricted to the details of the embodiments described above with reference to the drawings. For example, the guide of Figures 7 and 8 could be modified by the provision of slots of chosen size and spacing (perhaps varied along the length of the guide) to adjust the guide characteristics. Exemplary slots are shown in broken line at 27. Similarly a slot or slots could be provided in wall 18 if required.

[0024] Furthermore, ledge 13 could be provided with a cut-out of a similar nature to cut-out 12 in edge 11. This additional cut-out would co-operate wikth a key portion on the shoe similar to key portion 17 and would give additional support against the effect of longitudinal forces exerted on the shoe.

[0025] The invention is not restricted to the details of the embodiment described above with reference to the drawings. For example other primes and adhesives may be used.

Claims

1. A honing stone assembly comprising an abrasive honing stone bonded to a plastics shoe, the shoe being adapted by virtue of its shape and inherent resilience to be a snap fit on a stone holder.

2. A honing stone assembly as claimed in claim 1 wherein the honing stone is bonded directly to the shoe.

3. A honing stone assembly as claimed in claim 1 wherein the honing stone is held in a metal shell, the metal shell being bonded directly to the shoe.

4. A honing stone assembly as claimed in any of the preceding claims wherein the bonding is effected by the use of Loctite Prism 757 prime in conjunction with Loctite Prism 406 adhesive.

5. A honing guide made of plastics and being adapted by virtue of its shape and inherent resilience to be a snap fit on a guide holder.

6. A honing guide as claimed in claim 5 which has an inclined base region so as to provide a gap beneath the guide when on the guide holder, the body of constituting a leaf spring to provide resilience.

7. The combination of a honing stone assembly as claimed in any of claims 1 to 4 with a stone holder or a honing guide as claimed in claim 5 or claim 6 with a guide holder wherein the stone or guide holder comprises a platform which is mounted on a pair of legs, the shoe or guide has an elongate rebate which accommodates one edge of the platform and the other edge of the platform constitutes a ledge to retain the opposite side of the shoe or guide.

8. The combination claimed in claim 7 wherein the shoe or guide or said opposite side has a depending wall with an inwardly projecting rib at its extremity, the wall being flexible enough to allow the rib to be forced over the ledge whereby it is retained.

9. The combination as claimed in claim 7 or claim 8 wherein the shoe or guide is located against longitudinal movement with respect to the platform by a rebate in the first mentioned edge of the platform and a co-operating key shape in the shoe or guide.

Drawing