GB2292988A

GB2292988A - Device for assembling the conical parts of a valve spring on four-stroke motor vehicle engines

Info

Publication number: GB2292988A
Application number: GB9518543A
Authority: GB
Inventors: Horst Klann
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-09-12
Filing date: 1995-09-11
Publication date: 1996-03-13
Anticipated expiration: 2015-09-11
Also published as: GB2292988B; DE9414752U1; GB9518543D0; FR2724338B1; FR2724338A1

Abstract

The device, usable for assembly of the conical parts (81, 82 Fig. 4) of a valve spring forming a conical seat for a spring plate on the valve shaft of a valve of a four-stroke motor vehicle engine, is composed of a cylinder (2) with an end wall (4) with a shaped oval opening (5). Radial openings (6, 7) are provided in the cylinder (2) in diametrically opposed relationship. A resilient leaf spring (11) fits in the openings (6,7) and has part cylindrical sections (12, 13) coaxial with the cylinder (2). A clamping element (16) has displaceable parts (17, 18) cooperating with the leaf springs (11) and acted on by springs (20, 21) to adopt a position relative to the wall (4) smaller than the equivalent axial distance of the conical parts. A central adjustment screw (42) locates with a through bolt (35) carrying a plate (31) which is adjustable and the end of the screw (42) forms a pressing surface for forcing the clamping parts away from the wall (4). <IMAGE>

Description

Title: Assembly device for assembling the conical parts of a valve spring on four-stroke motor vehicle engines The present invention relates to an assembly device for assembling a conical seat for conical parts forming a spring plate of a valve spring on the valve shaft of four-stroke motor vehicle engine valve, comprising a hollow cylinder as a compression element for forcing down the upper spring plate of the valve spring.

In order to form a connection between the valve shaft and the spring-loaded spring plate of the valves of a four-stroke motor vehicle engine, usually two conical parts are used forming a conical seat with a through bore which, when fitted on top of one another on their interfaces together form a circumferential conical shell surface. For the axially non-displaceable positive connection with the valve shaft in their bore section, the conical parts have at least one radially inwards directed stop arm, which can be engaged positively in a corresponding radial groove at the upper end region of the valve shaft.

The spring plate has a central through bore which is also conical, by means of which in the assembled state it completely encircles both conical parts biasing the valve spring, and thus a connection is formed between the valve shaft and the spring plate by the conical parts. The spring plate is thus fixed to the end of the valve shaft and cannot slide off the end of the valve shaft.

The assembly of the conical parts is particularly difficult in motor vehicle engines with so-called cup rams arranged above the shaft end, as the upper end of the valve shaft is always recessed in the guide bore of the cylindrical cup ram and thus is only accessible by using special assembly devices for placing the conical parts between the through bore of the spring plate and the valve shaft.

An assembly device of the generic type (DE-PS 2 09 984 C2) for assembling conical parts is known with a stop arm directed inwards on their inner upper edge having a hollow cylinder as a compression element for pressing down the upper valve plate of a valve arranged in the cylinder head of a motor vehicle engine. A replaceable pressing sleeve is screwed onto one end of the hollow cylinder so that the known assembly device can be reset for centring spring plates with different diameters. Furthermore, in the hollow cylinder a pressure bolt axially displaceable against the pressure of a helical spring is arranged coaxially in relation to the hollow cylinder, which pressure bolt in an unloaded initial position extends axially beyond the pressing sleeve. In the pressure bolt a spring-loaded centring pin is also provided which projects out of the pressure bolt.The spring forces acting on the pressure bolt and on the centring pin are adjustable by means of an adjusting screw.

In order to assemble two conical parts to the upper shaft end of a valve shaft, first of all, the conical part halves are inserted into the conical through bore of the spring plate, whereby the spring plate is positioned on the valve spring built into the cylinder head of the motor vehicle engine. The assembly device is fitted onto the valve spring so that the centring shaft engages with the through bore formed by the two conical parts and thus rests centrally on the valve spring. When the assembly device is pressed down, the pressure bolt is positioned on the upper edge of the conical parts. On pressing the assembly device further until the conical parts inserted in the valve plate rest on the upper endwall of the valve shaft, the spring plate moves downwards relative to the valve shaft.If the spring plate is pressed downwards further the conical parts are lifted from the valve shaft end from the conical through bore of the spring plate and can thus move apart radially because of their conical form. The conical parts are now shifted over the valve shaft end by the spring-loaded pressure bolt until they engage with their stop arm in the circumferential stop groove of the valve shaft. On relaxing the valve spring the spring plate moves upwards with its conical through bore and encircles the conical parts engaged with the stop groove so that the desired connection between the spring plate and the valve shaft is formed.

The assembly device cannot be used for conical parts which have to be brought into engagement with more than one stop arm with a corresponding number of stop grooves of a valve shaft, as on sliding the conical parts along the valve shaft the first stop arm at the bottom on reaching the first stop groove of the valve shaft at the top engages therewith and cannot be pressed downwards any further, making it impossible to position the conical parts correctly. The conical parts can be assembled correctly by chance in the known assembly device for conical parts with more than one stop arm, if conical parts do not tilt, e.g. on sliding along the valve shaft, but this is very unlikely with valve shafts that as a rule are not vertical.

An object of the invention is therefore to create an assembly device by means of which conical parts can be assembled correctly securely and easily with more than one stop arm on a valve shaft with a corresponding number of stop grooves.

According to the invention there is provided a device for assembling the conical parts of a valve spring forming a conical seat for a spring plate on the valve shaft of a valve of a four-stroke motor vehicle engine, said device comprising a hollow cylinder usable as a pressing element for forcing down the upper spring plate of the valve spring of the hollow cylinder, an end wall at one end region of the cylinder, a central opening in the end wall behind which in the hollow cylinder there are two diametrically opposed radially resilient spring elements and at least one clamping element arranged in the hollow cylinder axially behind the spring elements wherein the clamping element is held against a spring force directed axially to the endwall at a distance from the endwall which is smaller than the axial length of the conical parts being assembled and a central pressing surface with which the clamping element can be pressed axially inwards against the spring force..

Thus an assembly device is provided which makes it possible to engage conical parts having more than one stop arm to assemble a spring plate onto the shaft end of a valve shaft, securely and easily with the stop grooves of the valve shaft.

The assembly device is firstly equipped with the conical parts to be assembled whereby the conical parts are inserted through the central opening of the endwall clamping and diametrically opposite one another between the clamping element and the endwall. In this position the conical parts press both diametrically opposite spring elements radially outwards.

The spring forces of the spring elements are such that the conical parts cannot press radially inwards against the clamping force with the clamping element. The clamped conical parts are positioned at their interfaces at a distance which is at least large enough for the valve shaft to be pressed between them. The assembly device equipped with the conical parts is now inserted into the cylindrical guide bore of the cup ram in the cylinder head of a four-stroke motor vehicle engine, until it rests with its endwall on the spring plate of the valve spring already positioned in the guide bore. During the subsequent downwards pressing of the assembly device the valve plate is moved downwards relative to the fixed valve shaft against the spring force of the valve spring until the pressing surface rests on the upper endwall of the valve shaft end. Under further downwards pressure the clamping element is prevented by the fixed shaft end or by the fixed endwall of the shaft end by the pressing surface from moving further backwards together with the assembly device. As the conical parts are clamped between the clamping element and the endwall and the endwall moves with the further backwards movement relative to the clamping element the clamping conical parts are released and pressed radially inwards to the valve shaft end by the radially effective spring elements.By selecting the axial distance between the endwall and the pressing surface in relation to the axial distance of the endwall to the clamping element the release of the clamped conical parts can be performed so that they are released precisely at the moment when the stop arms of the conical parts with the assigned stop grooves on the valve shaft end radially cover one another, and thus the conical parts with their stop grooves are pressed against the shaft end by the spring elements into the correct position. Thus in the assembly device according to the invention a precise assembly of the conical parts on the valve shaft end is carried out securely and easily.The assembly is performed in a continuous working process, in which with an appropriate design of the radial spring elements the conical parts are held at the shaft end in the stop grooves until with the backwards movement of the assembly device the spring plate encircles the conical parts with its conical through bore to the extent that with their stop arms they can no longer slide out of the assigned stop grooves of the shaft end and remain continually in engagement therewith until the spring plate with its through bore rests completely on the conical seat formed by the conical parts and the desired connection between the spring plate by the conical parts and the valve shaft end is formed.

The assembly device in accordance with the invention may take the form of a unit for installing in an adapter cylinder the outer dimensions of which are adjusted to the length and the diameter of the guide bore of the cup ram of a valve of a motor vehicle engine. This permits the use of the assembly device in motor vehicle engines with guide cylinders for the cup rams of different geometrical dimensions.

The hollow cylinder may have two diametrically opposite radial openings, axially behind the endwall which are interrupted by two arm sections connecting the endwall with the hollow cylinder. The spring elements can be in the form of leaf springs with part of the leaf springs disposed in the openings and around the connecting arms in the central region of the endwall to form diametrically opposite cylindrical sections curved in an approximately quarter circle shape and coaxial to the longitudinal axis of the hollow cylinder.

Here the leaf spring in the radial openings of the hollow cylinder bent around the connecting arms is extremely easy to assemble in that its can be bent around one of the connecting arms twice so that no further attachment elements are necessary for the leaf spring, i.e. it can be self-supporting.

The cylindrical sections of the spring elements in their initial position may be positioned at a diametrical distance from one another which is smaller than the outer diameter of the conical seat formed by the conical parts and the shape of the cylindrical sections is at least partly adjusted to the conical shape of the conical seat.

This quarter circular design of the cylinder sections of the leaf spring, in the central region of the endwall, ensures a secure guiding and precise diametrically opposite positioning of the conical parts to be clamped between the endwall and the clamping element. Furthermore, with the cylinder sections designed in this way it is impossible for the conical parts to tilt when they are released on the assembly from the clamping element and pressed against the valve shaft by their inwardly directed radial arms into the corresponding radial grooves of the valve shaft.Also the diametrical distance of the cylinder sections in their initial position ensures that the spring elements secure the conical parts on the valve shaft until the spring plate encircles the conical parts with its conical bore on the backwards movement of the assembly device so that the conical parts on the valve shaft for the spring plate fixed form the conical seat.

The clamping element may comprise two approximately semi-cylindrical clamping parts with a gap therebetween which is symmetrical with the common plane of symmetry of the connecting arms. The clamping parts, in their facing dividing surfaces, each have a approximately semi-cylindrical bore half coaxial to the hollow cylinder extending over the whole length of the clamping parts and a radial groove is provided approximately axially symmetrically in the bore halves extending over half the length of the clamping parts.

The conical parts can be thus clamped individually between a clamping part and the endwall of the hollow cylinder, without, on equipping the assembly device, in particular with the second conical part, the first conical part being inadvertently released again by pressing the clamping element down too far.

The clamping parts can be provided with a guide pin for receiving a helical compression spring and directly behind the recesses in the circumferential region of the arm sections there are radially inwardly directed stops against which the clamping parts with their helical compression spring are pressed.

Preferably the clamping parts are pressed independently of one another by a corresponding helical compression spring in the direction of the endwall, so that on equipping the assembly device with the conical parts there can be no interaction between the two clamping parts. The stops provided in the circumferential area of the connecting arms ensure that there is no obstruction to the function of the spring elements as the clamping parts rest on the stops before being equipped with the conical parts. The clamping parts are aligned so that their interface is symmetrical to the joint plane of symmetry of the stops and are positioned on each stop.

A support plate or wall can be provided in the hollow cylinder at the end opposite its endwall which is secured captively by a securing ring in the hollow cylinder and an intermediate plate is provided between the clamping elements or the clamping parts thereof and the support wall on which the or each clamping element is supported axially and in a resilient manner. The intermediate plate can then be supported axially on the support plate by a helical compression spring. Such an arrangement ensures that on assembly, in particular with a very rapid and uncontrolled compression of the assembly device for assembling the conical parts, the conical parts are not inadvertently pressed downwards too far before they are released by pressing back the clamping parts.The low compliability of the intermediate plate ensures that the conical parts are released in a correct position and are pressed by their radial arms into the corresponding radial grooves of the valve shaft.

The support part or wall can be provided with an axially displaceable through bolt coaxial to the hollow cylinder which extends from the outside into the hollow cylinder and on a threaded section of which the intermediate plate is screwed on at a predetermined distance from the support plate, and the distance is selected so that the axial spring deflection of the intermediate plate on the support plate is a maximum of several millimetres. Since the intermediate plate can only perform a minimal axial backwards movement at most of several millimetres, a secure assembly is ensured.

Furthermore, it is possible to adjust the axial hub of the intermediate plate by means of the through bolt so that the assembly device can be adapted to the geometric dimensions of the valve control of different motor vehicles engines.

An axially adjustable screw can be provided in the through bolt extending through the through bolt from the outside inwards and a further adjusting screw is fixed at its clamping part side end region which engages with axial play in the radial grooves of the clamping element or part. The adjusting screw forms the central pressing surface with its end surface.

The assembly device can be adjusted by means of the adjusting screw axially adjustable in the through bolt. An adjusting disc can be attached to the adjusting screw which adjusting disc engages with the radial groove of the clamping parts, so that the conical parts can be released at the moment when they are precisely aligned with their inwardly directed radial arms to the radial grooves of the valve shaft. The distance of the radial grooves of the valve shaft to their endwall is different for each motor vehicle engine so the position of the release of the clamped conical parts must also be adjustable to permit different applications of the assembly device in different motor vehicle engines which is allowed for in embodiments of the invention.The adjusting screw which forms the central pressing surface can be displaced in the pressing direction together with the pressure bolt axially relative to the hollow cylinder, whereby the adjusting disc in this relative movement moves both clamping parts to release the conical parts relative to the hollow cylinder.

The bore halves of the clamping parts can have a bore radius corresponding at least to the radius of the valve shaft. The release of the clamping parts is ensured, in particular when the endwall of the adjusting screw is to be arranged between the clamping elements as a central pressing surface because of the geometric dimensions on the motor vehicle engine, so that the valve shaft can press against the endwall between the bore halves to release the conical parts.

The opening in the end wall is preferably oval and has a length approximately corresponding to twice the diameter of the conical seat formed by the conical parts and its width is greater than the largest diameter of the conical seat.

This feature ensures that after the assembly of the conical parts the assembly device can be moved backward again with the backwards movement past the conical parts with its opening.

The invention is now described in more detail with reference to the drawings.

In the drawings: Fig. 1 is a perspective view of an assembly device constructed in accordance with the invention; Fig. 2 is a perspective view of a second embodiment of an assembly device; Fig. 3 shows the assembly device of fig. 2 in use; Fig. 4 shows an enlarged view of the portion designated IV in fig. 3.

Fig. 1 shows an assembly device 1 comprising a hollow cylinder 2 which has an endwall 4 at its front end 3 provided with a central oval opening 5. The opening 5 extends in its longitudinal extension, as shown, symmetrically with the horizontal longitudinal plane of symmetry of the hollow cylinder 2.

The hollow cylinder has two diametrically opposite radial openings 6, 7 directly behind its endwall 4 which are separated from one another by two arm sections 8, 9 which are also separated from one another and diametrically opposite. The arm sections 8, 9 form a single-piece connection between the hollow cylinder 2 and the endwall 4, whereby they are arranged radially recessed in relation to the sleeve surface 10 of the hollow cylinder 2.

A leaf spring 11 is arranged in radial openings 6, 7 which is bent around the arm sections 8, 9 several times, whereby both its end sections 14, 15 are bent in the region of the arm section 8 around the arm section above one another. In this design, on the one hand, the leaf spring is assembled extremely easily and, on the other hand, no additional fixing elements such as screws or the like are necessary to support the leaf spring 11 in the position shown. Between arm sections 8, 9 the leaf spring 11, symmetrical with the longitudinal axis of symmetry 19 with its upper and low halves has an upper and lower approximately quarter circle shaped cylinder section 12 and 13 in the central part of the endwall 4 which is coaxial to the longitudinal middle axis 24 of the hollow cylinder 2.The width of the leaf spring 11 and the width of the radial openings 6, 7 are aligned with one another so that the leaf spring 11 is almost without play in the radial openings 6, 7.

A clamping element 16 is provided axially behind the radial openings 6, 7 which comprises an upper and lower clamping part 17, 18, the interface of which is symmetrical with the longitudinal axis of symmetry 19 of opening 5 whereby the cylinder sections 12, 13 of the leaf spring 11 are symmetrical with the interface. To position the clamping parts 17, 18 in this way, the latter on their circumferential surface can be provided with radially outwards projecting guide pins, which engage with the corresponding guide grooves of the hollow cylinder (not shown in the drawing). The clamping parts 17, 18 each have a guide pin 29, 30 on their rear side facing away from the endwall 4 for accommodating a helical compression spring 20, 21 by means of which they are pressed against a stop 22, 23 directed radially inwards in the hollow cylinder 2.The stops 22, 23 are thus arranged in the region of arm sections 8, 9 and extend in circumferential direction approximately over the length of arm sections 8, 9 whereby each stop 22, 23 is assigned to both clamping parts 17,18.

The clamping parts 17,18 each have approximately semi-cylindrical bore valves 25 and 26 extending over their total length, coaxial to the longitudinal middle axis 24 of the hollow cylinder 2, which are each provided with a radial groove 27 and 28. The radial grooves 27, 28 are thus arranged to be approximately symmetrical with the common transverse middle plane of the clamping parts 17,18 and extend over approximately half the length of the clamping parts 17,18.

The helical compression springs 20, 21 are each supported in a cylindrical recess 32 and 33 of an intermediate plate 31 in an axial direction. Axially behind the intermediate plate 31 a helical compression spring 34 is arranged coaxially in the hollow cylinder 2 which is supported on a supporting wall 35 sealing the hollow cylinder 2 at the back. The support wall 35 is cylindrical and is secured captively by means of a securing ring 36 in the hollow cylinder 2. The hollow cylinder has a central through bore 37 through which a through bolt 38 extends from the outside to the inside. The through bolt 38 is mounted axially displaceably in the through bore 37 with its shaft section 39 and has a thread section 40 onto which the intermediate plate 31 is screwed using a corresponding thread nut 41.The intermediate plate 31 is screwed to the thread section 41 of the through bolt 38 so far that the intermediate plate 31 is displaceable together with the through bolt 38 in the hollow cylinder 2 against the spring force of the helical compression spring 34 arranged between the intermediate plate 31 and the support wall 35 by a maximum of several millimetres until the helical compression spring 34 is clamped on block. In the initial position of the intermediate plate 31 in relation to the support wall 35 the helical compression spring 34 is biased accordingly.

In the through bolt 38 there is an adjusting screw 42 projecting axially through the helical compression spring 38 which adjusting screw is screwed into a corresponding thread nut 43 of the through bolt 38. The adjusting screw 42 is sufficiently long that it ends with its endwall 44 approximately in the region of the clamping parts 17, 18 and it is axially adjustable in the through bolt 38. At its endwall side an adjusting disc 47 is attached to the adjusting screw 42 by means of two nuts 45, 46 which engage with the two radial grooves 27, 28 of the clamping parts 17, 18. The adjusting disc 47 is approximately half the length of the radial grooves 27, 28 and its diameter is such that the clamping parts 17, 19 are displaceably guided almost without play in the hollow cylinder 2.To adjust the axial position of the adjusting disc 47 in the radial grooves 27, 28 the adjusting screw 42 can be axially adjustable on the through bolt 38 resting with its screw head 49 on the rear endwall of the support wall 35 and can be fixed in this position by means of a counter nut 48. The helical compression springs 20, 21 are thus easily biased in the initial position shown., Fig. 2 shows a second embodiment 1/1 of the assembly device 1. The assembly device 111 is provided with an assembly element 50 the inner and outer design of which corresponds to that of assembly device 1. Thus the assembly element 50, as seen in fig. 2, comprises a hollow cylinder 2/1, an adjusting screw 42/1, an endwall 411, a leaf spring 11/1, an arm section 9/1 and a radial opening 5/1 The other components, such as e.g. the second radial opening, the second arm section and the clamping parts, the helical compression springs, the intermediate plate and the support wall are also present, corresponding to the design of assembly device 1 but are not shown in fig. 2 for reasons of clarity.

The assembly device 1/1 has an adapter cylinder 51 to which the assembly element 50 is firmly attached. On the adapter cylinder 51 on the endwall side there is a circumferential radially inwards directed compression ring arm 52, which is provided with a central opening, the diameter of which corresponds to the maximal extension of oval opening 5/1 of the endwall 4/1. Furthermore, the compression ring arm 52 is provided with a circumferential ring wall 53 on its outer edge, which has the function of accommodating a spring plate almost without play on the assembly of the conical parts of a valve.To attach the assembly element 50 in the adapter cylinder 51 a pressing lid 54 is provided which is screwed into the adapter cylinder at the back and is provided with a pressing wall 55 extending into the adapter cylinder, by means of which pressing wall 55 the assembly element 50 is pressed with its endwalls 4/1 on the inside against the compression ring arm 52. Furthermore, the pressing lid 54 has a central pressing pin 56 which is provided with a semi-spherical head part 57.

The adapter cylinder 51 can be designed with different lengths and diameters and adapts to the assembly device 1/1 with different guide bore designs of the cup rams in a cylinder head of a motor vehicle engine.

Fig. 3 shows the assembly device 1/1 in use. The assembly device 1/1 is inserted into a recess bore 58 of a cylinder head 59 which recess bore 58 during operation of the motor vehicle engine has the function of guiding a socalled cup ram which is normally guided axially displaceably in the upper region in which the assembly device 1/1 is positioned in the guide bore 58 as shown. A valve spring 60 is arranged with a spring plate 61 and valve shaft seal 62 in the guide bore 58. The valve shaft seal 62 has the function of sealing the valve shaft 63 of a valve 64 in the cylinder head 59.

In the embodiment shown in fig. 3 the assembly device 1/1 is fitted onto the spring plate 61 and the valve spring 60 is already partially pressed down. To operate the assembly device 1/1 a lever device is provided which is mounted in a fixed position by means of fixed webs 66 onto the cylinder head 59. A lever arm 67 is provided for pressing down the assembly device 1/1 which at one end has a recess 68 as an abutment with which the lever arm 67 can be inserted on a round bar 69 of the lever device 65. The round bar 69 is mounted by two radial arms 70 (71) on corresponding vertical supports 72 (73) to be adjustable in height. In the drawing only the radial arm 70 and vertical supports 72 are visible, as the radial arm 71 and vertical supports 73 are positioned in this cross-section in front of the plane of the drawing.

Above the assembly device 1/1 the lever arm 67 has a slot-like opening 74 with a stop tooth system 75. A fork-like pressure part 76 is suspended by a transverse bolt 77 in the stop tooth system 75, which transverse bolt 77 on its assembly-device side endwall 78 has an approximately semi-spherical shaped recess 79 adapted to the head part 57 of the pressing pin 56 of the pressing lid 54. The recess 79 of the pressure part 76 forms a pivot bearing to interact with the head part 57 of the pressing lid 54, whereby the pressure element 76 is also pivotably mounted by its transverse bolt 77 in the stop tooth system 75 of the lever arm 67.By these two pivot bearings the movement of the transverse bolt 77 about the round rod 69 along a circular path about the round rod 69 and the straight movement of the head part 57 on pressing down on the longitudinal middle plane 24/1 of the assembly device 1/1 is compensated. The pivot bearing of the head part 57 in the recess 79 provides the advantage that no additional assembly work is necessary to be able to use the lever device 65 with the assembly device 111 for pressing down the assembly device 1/1.

A further means, not illustrated in the drawings, of operating the assembly device is that by using a specially designed pressure element an assembly device designed without the pressing lid 54 is only pressed down by the pressure element by its adapter cylinder 51, so that the valve plate moves downwards. To assemble the conical parts the assembly element 50 axially movable in the adapter cylinder 51, which is equipped with conical parts, can be pressed down separately to assemble said conical parts. With large valve spring forces this may be necessary if the valve spring cannot be pressed down manually.

Fig. 4 shows an enlarged section IV of fig. 3. It can be seen from fig. 4 that the valve spring 60 is pressed together so far, and/or the spring plate 61 is pressed so far into the guide bore 58 of the cylinder head 59, that the assembly device 1/1 is positioned with the end surface 44/1 of its adjusting screw 42/1 on the end surface 80 of the valve shaft 63. The assembly device 1/1 is equipped with two conical parts 81, 82 which are clamped firmly between the associated clamping member 17/1 and 18/1 and the endwall 4/1 of the assembly element 50. Here cylinder sections 12/1 and 13/1 of the leaf spring 11/1 are positioned on the outer conical surfaces of each conical part 81 or 82.The clamping force of both helical compression springs 20, 21 is so great that the conical parts 80 and 81 are held securely clamped and are not moved inwards inadvertently by the radially inwards pressing cylinder sections 12/1 and 13/1 of the leaf spring 1111 in an uncontrolled manner.

In the position shown in fig. 3 the assembly device 1/1 is positioned shortly before the release of conical parts 81 and 82. If the assembly device 1/1 is moved from this position downwards in the direction of arrow 83 the adjusting screw 42/1 stops, resting on the valve shaft 63, and thus moves relative to the assembly element 50 or to the assembly device 1/1 until it rests axially with its adjusting disc 47 in the radial grooves 27/1, 28/1 of clamping parts 17/1 and 18/1 In this position conical parts 81 and 82 are also moved downwards in the direction of arrow 83 so that they are precisely radially opposite the radial grooves 86 of the valve shaft 63 with their radially inwards directed stop arms 84 and 85.With a further downwards movement in the direction of arrow 83 only clamping parts 17/1 and 1811 are held by the adjusting disc 47/1 in their radial grooves 27/1 or 28/1, so that they also perform a relative movement in the assembly element 50 or in relation to the assembly device 1/1. However, as the endwall 411 of the assembly element 50 moves together with the assembly device 1/1 in the direction of arrow 83 the distance between the clamping parts 1711 and 18/1 and the endwall 411, previously determined by conical parts 81 and 82, increases so that conical parts 81 and 82 are pressed inwards by the corresponding outside cylinder sections 1211 and 13/1 of the leaf spring 1111 and are pressed by their stop arms 84 and 85 to fit exactly in the radial grooves 86 of the valve shaft 63.

On returning the assembly device 1/1 in the direction of arrow 87 the spring plate 61 moves upwards along the valve shaft 63, whilst cylinder sections 1211 and 1311 move along the outer shell surface of the conical parts 81, 82 positioned non-displaceably on the valve shaft 63. Cylinder sections 12/1 and 13/1 retain the conical parts 81, 82 in their engaged position on the valve shaft 63 at least until the valve plate 61 encircles the conical parts 81 and 82 with its conical bore 88 so far that they are unable to slide out of the radial grooves 86 with their stop arms 84 or 85. On the further backwards movement in the direction of arrow 87 the conical bore 88 of the spring plate finally encircles the conical parts 81 and 82 completely so that a connection between the spring plate by the conical parts 81 and 82 to the valve shaft 63 is formed.

In order to prevent the conical parts 81 and 82 from being released only with an extremely rapid compression of the assembly device 1/1 in the direction of arrow 83 when they have already been pressed past the radial grooves 86 with their stop arms 84 or 85 the additional helical compression spring 34 is provided with intermediate plate 31/1. The helical compression spring 34/1 is biased so that the intermediate plate 3111 together with the through bolt 3811 is displaceable by about 0.5 mm in the direction of arrow 87 axially in the assembly element 50. The whole arrangement of the clamping parts 1711 18/1 and the intermediate pate 31/1 is compliant as the conical parts 81 and 82 are released securely when with their stop arms 84 and 85 they are positioned precisely opposite to the radial grooves 86 of the valve shaft 63.

Further compression is then no longer possible as the helical compression spring 34/1 is biased on block and thus the further backwards movement of the assembly device 1/1 is prevented by the support wall 35/1, the intermediate plate 31/1, the through bolt 38/1 and the adjusting screw 4211. If an assembler attempted to move the assembly device 1/1 further downwards he would have to press down the valve 64 (Fig. 3) which is held in its closed position by compressed air in the cylinder chamber of the motor vehicle engine. This, however, would reduce excess pressure in the cylinder chamber causing the valve to fail into the cylinder chamber.

In a simplest embodiment not shown, the assembly device 1/1 is provided with a hollow cylinder with an endwall and also has radially effective spring elements. The clamping element can also be constructed in one piece, whereby an axial compression spring can be provided supported on a corresponding support wall in the hollow cylinder pressing the clamping element against a corresponding stop or against the spring elements, in the form of leaf springs. To release the conical parts clamped in this assembly device between the camping element and the endwall a pressing surface can be provided on the clamping element itself by which the clamping element is pressed into the corresponding position of the assembly device in the guide bore of the cup ram from the endwall of the valve shaft thus releasing the conical parts.

The intermediate plate 31 or 3111 need not necessarily be present. However, it has the advantage on interacting with the springs 34 or 34/1 that the conical parts are not unintentionally pressed out with the rapid compression of the assembly device 1 or 1/1 with stop arms by the associated stop grooves of the valve shaft and are not pressed against the valve shaft so late that they tilt on the valve shaft and thus preventing correct assembly.

Claims

1. A device for assembling the conical parts of a valve spring forming a conical seat for a spring plate on the valve shaft of a valve of a four-stroke motor vehicle engine, said device comprising a hollow cylinder (2,2/1) usable as a pressing element for forcing down the upper spring plate of the valve spring of the hollow cylinder (2, 2/1), an end wall (4, 4/1) at one end region (3) of the cylinder, a central opening (5, 5/1) in the end wall (4, 4/1) behind which in the hollow cylinder (2, 2/1) there are two diametrically opposed radially resilient spring elements (11, 12, 13, 11/1, 2/1, and and at least one clamping element (16, 17, 18, 16/1, 17/1, 1811) arranged in the hollow cylinder (2, 2/1) axially behind the spring elements (11, 12, 13, 11/1,12/1,13/1) wherein the clamping element is held against a spring force directed axially to the endwall (4, 4/1) at a distance from the endwall (4, 4/1) which is smaller than the axial length of the conical parts (81, 82) being assembled and a central pressing surface (44, 44/1) with which the clamping element (16,17,18,1611,1711, 18/1) can be pressed axially inwards against the spring force.

2. A device according to claim 1 wherein the hollow cylinder (2, 2/1) has two diametrically opposite radial openings (6, 7, 6/1), axially behind the endwall (4, 4/1) which are interrupted by two arm sections (8, 9, 9/1) connecting the endwall (4, 4/1) with the hollow cylinder (2, 211), and the spring elements (12, 13, 1211, 13/1) are in the form of leaf springs with part of the leaf springs (11,1111) disposed in the openings (6, 7, 6/1) and around the connecting arms (8, 9, 9/1) in the central region of the endwall (4, 4/1) to form diametrically opposite cylindrical sections curved in an approximately quarter circle shape, and coaxial to the longitudinal axis (24, 2411) of the hollow cylinder (2, 211).

3. A device according to claim 2 wherein the cylindrical sections (12, 13, 1211,1311) of the spring elements in their initial position are positioned at a diametrical distance from one another which is smaller than the outer diameter of the conical seat formed by the conical parts (81, 82) and the shape of the cylindrical sections (12, 13, 12/1, 13/1) is at least partly adjusted to the conical shape of the conical seat.

4. A device according to one of claims 2 or 3, wherein the clamping element (16, 16/1) comprises two approximately semi cylindrical clamping parts (17, 18, 17/1, 1811), with a gap there between which is symmetrical with the common plane of symmetry of the connecting arms (8, 9, 911), the clamping parts (17,18,1711,1811) in their facing dividing surfaces each have a approximately semi cylindrical bore half (26, 27) coaxial to the hollow cylinder (2, 2/1), extending over the whole length of the clamping parts (17, 18, 17/1, 1811) and a radial groove (28, 29, 28/1, 2911) is provided approximately axially symmetrically in the bore halves (26, 27) extending over half the length of the clamping parts (17, 18, 17/1, 1811).

5. Assembly device according to claim 4, wherein the clamping parts (17, 18, 17/1, 18/1) on their rear side opposite the endwall (4, 411) are provided with a guide pin (29, 30) for receiving a helical compression spring (20, 21, 20/1, 2111) and directly behind the recesses (6, 7, 7/1 ) in the circumferential region of the arm sections (8, 9, 9/1) there are radially inwardly directed stops (22, 23, 2211) against which the clamping parts (17,18,1711,1811) with their helical compression spring (20, 21, 20/1, 21/1) are pressed.

6. A device according to claim 5, wherein the bore halves (25, 26) of the clamping parts (17, 18, 17/1, 18/1) have a bore radius corresponding at least to the radius of the valve shaft (63).

7. Assembly device according to one of claims 1 to 6, wherein a support plate or wall (35, 3511) is provided in the hollow cylinder (2, 211) at the end opposite its endwall (4, 411) which is secured captively by a securing ring (36) in the hollow cylinder (2, 2/1), an intermediate plate (31, 3111) is provided between the clamping elements (16,1611) or the clamping parts thereof (17,18,1711,1811) and the support wall (35, 35/1) on which the or each clamping element (16, 16/1,17,18, 1711,1811) is supported axially and in a resilient manner, and the intermediate plate (31, 3111) is supported axially on the support plate (35, 3511) by a helical compression spring (34, 34/1).

8. Assembly device according to claim 7, wherein in the support plate (35, 3511) is provided with an axially displaceable through bolt (38, 3811) coaxial to the hollow cylinder (2, 211) which extends from the outside into the hollow cylinder (2, 211) and on a threaded section (40) of which the intermediate plate (31,3111) is screwed on at a predetermined distance from the support plate (35, 35/1), and the distance is selected so that the axial spring deflection of the intermediate plate (31, 3111) on the support plate (35, 3511) is a maximum of several millimetres.

9. Assembly device according to claim 8 wherein an axially adjustable adjusting screw (42, 4211) is provided in the through bolt (38, 3811) extending through the through bolt (38, 3811) from the outside inwards and a further adjusting screw (47, 4711) is fixed at its clamping part side end region which engages with axial play in the radial grooves (27, 28, 27/1, 2811) of the clamping element or part (17,18,1711, 1811) and the adjusting screw (42, 42/1) forms the central pressing surface with its end surfaces (44, 44/1).

10. A device according to one of claims 1 to 9, wherein the opening (5, 5/1) in the endwall is oval and has a length approximately corresponding to twice the diameter of the conical seat formed by the conical parts (81, 82) and its width is greater than the largest diameter of the conical seat.

11. A device according to one of claims 1 to 10, and in the form of a separate assembly unit (50) in an adapter cylinder (51), the outer dimensions of which are adjusted to the length and the diameter of the guide bore of the cup ram of a valve of a motor vehicle engine.

12. Assembly device substantially as described, especially with reference to, and as illustrated in, any one or more of the Figures of the drawings.