Directly acting hydraulic tappet body having an outer oil reservoir

Abstract

 A hydraulic tappet body comprising an element substantially in the shape of a sleeve and an upper disc which is secured to it, wherein the sleeve element (2) comprises essentially a comparatively thin tubular outer wall which extends inwardly at its upper end along a horizontal portion (5) providing a fairly wide shoulder on to which said upper disc is soldered and, somewhat downwardly, in a conical portion (6). The latter continues downwards in a tubular cylindrical part (8) which acts as a guide for the moving elements of the tappet, the conical portion (6) thus providing an outer oil reservoir (7) of relatively small dimensions. An oil supply duct (20) opens out into the upper end part of the outer reservoir (7). In the upper part of the wall of the sleeve element (2) there is provided a thickening (18) in which said oil supply duct (20) is formed. A depression or groove (22) in which the oil collects is provided, by rolling, on the outer surface of said tubular wall, and an annular hump (24) is formed adjacent to this groove (22), but on the inner surface of such wall.

Description

[0001] The present invention concerns a direct-acting hydraulic tappet body providing an outer oil reservoir of reduced dimensions.

[0002] Directly insertable, direct-acting hydraulic tappets comprise, as a rule, a body having a flat upper surface which receives the action of a cam exerting a downwards thrust, which the tappet transfers downwards on to a valve stem urged in its turn upwards by a spring. The valve is thus opened and allowed to close with minimum lost motion, and without necessity for manual adjustments thereof.

[0003] Inside the tappet body which provides an outer oil reservoir, there is housed a small inverted bowl whose base presents the upper surface upon which the mentioned cam acts. This small bowl houses in its turn a hollow plunger acting as an inner reservoir. The lower end of said hollow plunger .has an opening enabling the oil to flow through, which opening can be closed from underneath by means of a spherical element biased to the closing position by a spring whose lower end rests against a small hat-shaped retaining member and also by the upward pressure of the oil surrounding the spherical element.

[0004] The aim of the present invention is the provision of a tappet body as light as possible in order that the friction is minimised under working conditions as a result of the body being light. This is achieved by making the walls of the body lighter.
However, as the tappet body necessarily comprises a sleeve which must be suitably shaped internally and to which is attached a strong upper disc to withstand the repeated thrusts of the control cam, provision must be made, on the upper circular edge of the sleeve, for sufficient soldering area for the upper disc, while maintaining the sleeve walls as thin and therefore as light as possible. According to the invention, on the upper edge of the sleeve of the tappet body, there is provided a wide flat area enabling the upper disc to be securely soldered. Thus, the soldering is strong even when the sleeve walls are thin. Moreover, the upper disc receiving the thrust from the cam can be made of a much stronger material than the ones normally used, thus enabling a weight reduction of up to 24% as a result of the provision of a wider soldering area. By way of example, whereas a conventional element weight 75 grams (35mm diameter), the one according to the present invention weighs 57 grams.

[0005] According to the present invention, the provision of an increased and oversize soldering area enables soldering to be carried out on an outer annular area only, if so required.

[0006] Furthermore, according to the present invention, the oil supply duct opens out directly on to the upper edge of the sleeve forming the periphery of the tappet body by flowing through a thickening of the sleeve wall. By this solution, the oil is fed directly to the upper part of the main reservoir, hence the level of the oil tends to be better retained under non working conditions. The thickening provided in order to obtain the oil supply duct, together with the possibility of rolling the depression wherein the oil collects, causes the lateral wall of the sleeve to be stronger in its upper part.

[0007] A more detailed description of the present invention will now be given, according to a preferred form of embodiment, and, with reference to the only drawing, wherein the body of the hydraulic tappet is shown is longitudinal section, the other component parts of the tappet being indicated by broken lines.

[0008] According to the present invention, the tappet body comprises two parts which are to be joined together by soldering, namely a part shaped substantially as a sleeve 2 and an upper disc 4 made of a material highly resistant to wear and tear, which may be different from the material of which the sleeve is made. The sleeve part 2 comprises essentially a tubular outer wall which extends inwardly at its upper end along a wide horizontal portion 5 and, downwardly, in a conical portion 6 which ends in a tubular cylindrical part 8. Part 8 acts as a guide for an axially sliding bowl shaped element 10, which surrounds and can slide on a plunger element 12. The conical portion 6 provides an outer oil reservoir 7 of reduced dimensions, hence the total bulk of the tappet is correspondingly reduced by the reduction in the weight of the oil inside the outer reservoir 7. Correspondingly also, such outer reservoir 7 can be recharged with oil more quickly after the vehicle equipped with the tappet has been parked non-operationally for a long time.

[0009] Between the end of the plunger 12 and the base of the bowl shaped element 10 there is provided a conventional compression spring 14 acting on the plunger element 12; the lower end of the plunger element is fitted with a valve element consisting, as usual, of a spherical element 16 biased to a closing position by another spring (not clearly visible in the drawing) and by a retaining member 15.
The upper part of the outer peripheral tubular wall of the sleeve 2 has a thickening 18, inside which there is provided an oil supply duct 20 opening out into the upper end part of the outer reservoir 7. A depression or groove 22 wherein the oil collects, is made, by rolling, over the outer surface of the tubular wall of sleeve 2, and the ridge or hump 24 resulting from the depression, together with the thickening 18, contribute to increase the rigidity of the sleeve element 2. When the upper disc 4 is soldered on the shoulder portion 5 of the sleeve element 2, a large support area for the disc 4 is available, and consequently an increased soldering area too. If required, this area being so great, soldering can be limited to only an annular outer part of the shoulder portion 5, and not soldering the disc 4 to the shoulder portion 5 all the way inwards to its inner edge. Whether the area is partially or completely soldered, this increased soldering area provided by the wide shoulder portion 5 will make it easier for the upper disc 4 to be effectively joined to the remaining part of the body, even if the disc 4 is made of a special alloy difficult to solder.

[0010] The object of the present invention has been herein described by way of a non-limiting example only in a preferred form of embodiment, but modifications can be made within the scope of the invention as claimed.

Claims

1. A hydraulic tappet body comprising an element substantially in the shape of a sleeve and an upper disc which is secured to it, characterised in that the sleeve element (2) substantially comprises a comparatively thin tubular outer wall which has an inward extension at its upper end to form a horizontal portion (5) providing a fairly wide shoulder and, then the horizontal portion (5) has a slantingly downward extension to form a conical portion (6), and this has a further downward and axial extension to form a tubular cylindrical part (8) which acts as a guide to receive the moving elements of the tappet, the conical portion (6) thus providing an outer oil reservoir (7) of only limited or reduced dimensions, and there being an oil supply duct (20) opening out into the upper end part of the outer reservoir (7).

2. A hydraulic tappet body according to Claim 1, characterised in that in the upper part of the tubular outer tubular wall of the sleeve element (2) there is provided a thickening (18) wherein said duct (20) for carrying the oil to the outer oil reservoir (7) is formed.

3. A hydraulic tappet body according to one or more of Claims 1 and 2, characterised in that a depression or groove (22), wherein the oil collects, is provided by rolling, on the outer surface of the tubular wall of the sleeve element (2), and on the inner surface of said wall of the sleeve element (2) there is a ridge or annular hump (24) projecting inwardly, eg produced also by the rolling.

4. A hydraulic tappet body according to one or more of Claims 1 to 3, characterised in that the upper disc (4) is soldered on the shoulder portion (5) of the sleeve element (2) by means of a soldered joint; either over the whole of the shoulder portion (5) or over an outer region thereof only.

5. A hydraulic tappet body according to one or more of Claims 1 to 4, characterised in that the upper disc (4) is made of material highly resistant to wear and tear.

6. A hydraulic tappet body according to Claim 3, characterised in that the annular hump (24) resulting from rolling the depression or groove (22) on the inside of the wall of the sleeve element (2), and the thickening (18) provided in the upper part of the wall of the sleeve element (2) also act as reinforcing members for the annular wall of the sleeve element (2).

Drawing