Cassette valve assembly

Abstract: To simplify assembly of components on a valve stem (10), the components, namely a seal (18), bias spring (22), washer (26) and cotters (32), are mounted in a container (40) and presented to the valve stem (10) as a pre­ formed cassette. From the position shown, compression of the cassette causes engagement of the cotters (32) with the groove (34) on the valve stem (10) whereafter the container (40) may be discarded.

Description: This invention is concerned with the stem seal and bias spring assembly mounted at the outer end of the stem of a valve in an internal combustion engine. As seen in Fig. 1 of the accompanying drawings the stem 10 of the valve 12 of an internal combustion engine extends through a bushing 14 in the engine casing 16. At the top of the bushing 14 is mounted a seal 18 having an external flange 20 seated on the outer surface of the casing. A bias spring 22 (in this case a pair of concentric springs) extends between the flange 20 and the external flange 26 of the washer 28 which is secured in place by means of a tapered internal skirt 30 engaged by the tapered external surface of normally a pair of cotters 32 which are clipped into a groove 34 at the top of the valve stem. The assembly as shown in Fig. 1 is entirely conventional, and the method of assembly involves normal selection of the component parts from storage bins in a particular sequence followed by the actual assembly of the individual parts. This however is a time consuming operation which requires considerable operator skill and logistical problems in providing multiple storage bins on the assembly line and keeping the bins appropriately stocked. It has been proposed in DE-C-3711436 and EP-A-341480 (a document relevant under Article 54(3) and (4) of the E.P.C.) to provide a valve stem seal assembly in which prior to mounting on the valve stem, the seal, spring and washer are secured together by a tubular member to form a unitary assembly. It is an object of the present invention to provide an improved valve stem seal assembly. The present invention is a valve stem seal assembly comprising a valve stem seal 18 having an external flange 20, a washer 28, a spring 22 extending between the flange 20 on the seal and the washer 28 and a member 50 engaging the seal and the washer and holding the seal, spring and washer together, characterised in that the member 50 has a lower tubular portion 52, an intermediate conical portion 54 engaged by the sealing lip of the seal, and flexible fingers 56 at its upper end in engagement with a tapered axial bore 60 in the washer 22. The present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a view showing showing the components assembled on the valve stem. Fig. 2 is a front sectional elevation of the present invention; and Fig. 3 is a side view of part of Fig. 4. Figs. 2 and 3 illustrate the invention utilising a central sleeve member 50 made in this embodiment of a plastics material. The sleeve 50 consists of a lower tubular portion 52, an intermediate conical portion 54 and an upper flat portion 55 terminating in a plurality of, in this embodiment two, flexible fingers 56 each provided with an external knuckle 58. To mount the seal 18, spring 22 and washer 28 on the sleeve 50, the seal 18 is first placed over the sleeve 50 so that the seal lip is located on the conical portion 54. The spring 22 is then placed in position on the outer flange 20 of the seal and the washer 28 is placed at the top of the spring and pressed down until the knuckles 58 on the fingers engage the inner tapered bore 60 of the washer 28, the fingers flexing inwardly to allow the knuckles to enter the bore. The seal, spring and washer are now held together by the sleeve 50. On assembly on the valve stem 10, the tubular portion 52 of the sleeve is first located over the valve stem and the cotter groove pressure is applied by the mounting tool to the washer, this pressure causing the seal to move down until its external flange is properly seated on the engine casing, the seal lip then having passed down beyond the tubular portion and being engaged with the valve stem. The central sleeve 50 is then withdrawn upwardly, the cotters are placed in the tapered bore of the washer 20 and as the pressure on the washer is released, the washer moves up until the cotters snap into the cotter grooves. The invention has the advantage that the sealing lip is protected by the tubular portion 52 from damage by the cotter grooves as it passed down over the valve stem, the assembly operation on the engine production line being quick and simple. Seal assemblies as described above may be secured together on a suitable jig to facilitate the loading of automatic machinery on an assembly line. Ideally the number of seal assemblies so secured would correspond to the number of valves in a cylinder head.

Claims: A valve stem seal assembly comprising a valve stem seal (18) having an external flange (20), a washer (28), a spring (22) extending between the flange (20) on the seal (18) and the washer (28), and a member (50) engaging the seal (18) and the washer and holding the seal (18), spring (22) and washer (28) together, characterised in that the member (50) has a lower tubular portion (52), an intermediate conical portion (54) engaged by the sealing lip of the seal (18), and flexible fingers (56) at its upper end in engagement with a tapered axial bore (60) in the washer (22). A valve stem seal assembly as claimed in claim 1, in which each finger (56) is provided with an outwardly projecting knuckle (58) which engages the axial bore (60).

Inventors: HILL DAVID, LITTLEPROUD ANTONY, HILL, DAVID, LITTLEPROUD, ANTONY
Applicants: SEAL TECHNOLOGY SYSTEMS
Application year: 1990
Main classification: F01L3
IPC codes: F01L3, B25B27, B23P19