FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See Section 10, and rule 13)
1. TITLE OF INVENTION STRUCTURAL UNIT
2. APPLICANT(S)

a) Name : ZF FRIEDRICHSHAFEN AG
b) Nationality ; GERMAN Company
c) Address : 88038 FRIEDRICHSHAFEN
GERMANY
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

The invention relates to a structural unit according to the pre-characterising clause of patent claim 1.
DE 199 00 264 Al describes, using the example of a tie rod for a motor vehicle, a structural unit having a pipe which is provided at least at one side with an inner thread which extends in a first rotation direction, there being screwed into the pipe at the end side an adjusting sleeve which has a corresponding outer thread. A shaft of a ball-and-socket joint is screwed into this adjusting sleeve. To this end, the shaft has an outer thread which extends in the opposite direction to the first rotation direction and which corresponds to the inner thread of the adjusting sleeve. Owing to a movement of the adjusting sleeve, which has for this purpose a keying face for attaching a tool, the pipe and the shaft can be moved in an axial direction relative to each other. This means that, with the rotation of the adjusting sleeve, the pipe and the shaft move towards each other or away from each other. This is brought about by the opposing thread extents. With this adjustment possibility, the structural unit can undergo an axial length adjustment, with respect to the common longitudinal centre axis of the pipe, the adjusting sleeve and the shaft, which is significant for the adjustment of the tracking of the vehicle, in particular for the example set out in the specification of a tie rod for motor vehicles. Owing to the use of an adjusting sleeve between the pipe and shaft, however, it is necessary to provide two different thread diameters. Consequently, the force which is introduced over the keying face in order to adjust the components relative to each other is transmitted from the ball-and-socket joint to the pipe via the threads of different diameter. Consequently, the thread with a smaller diameter constitutes a weak point which could lead to a failure in a tie rod of this type. Furthermore, another disadvantage has become evident with solutions of this type, in that the shaft is inadvertently unscrewed so far out of the adjusting sleeve which receives it that only a small thread portion is available for force transmission or the shaft even becomes completely detached from the adjusting sleeve. This risk is further increased by damage to the threads.

In order to prevent the shaft from being unscrewed too far out of the adjusting sleeve, DE 77 32 250 Ul sets out a solution which limits the axial adjustment path of the pipe relative to the shaft. The structural unit which is set out in this specification and which is constructed in a similar manner in relation to the tie rod described above also allows adjustment of the adjusting sleeve over a keying face which is provided for this purpose so that the shaft and the pipe can move relative to each other in an axial direction. However, a specific aspect of this construction to be taken into consideration is that the screw connection which is generally provided on tie rods in this instance to fix the structural unit is used to secure a locking member to the tie rod. In the present example, the locking member comprises a sheet metal strip which has an angled end portion. This angled end portion is located on a planar surface which is formed for this purpose on the shaft. When viewed in the extraction direction of the shaft, the shaft further has a groove in which the bent end portion of the metal sheet engages when the shaft is disengaged from the screw connection beyond a permissible axial displacement path. Although the solution described in the specification allows advantageous limitation of the axial path when adjusting the structural unit, the technical complexity involved in the production of the planar surface on the shaft is disadvantageous. In addition, this construction variant involves considerable complexity in terms of assembly. A further disadvantage is that the sheet metal strip is located outside the tie rod and consequently, when the tie rod is used in conventional manner in motor vehicles, it is impossible to prevent damage or deformation of the sheet metal strip with the result that it could possibly become inoperative. Furthermore, this sheet metal portion is subject to increased environmental influences and there is consequently the risk that it will prematurely become corroded or worn.
Furthermore, DE 10211 066 Al discloses for a tie rod of a motor vehicle a structural unit having a pipe which is provided with an inner thread extending in a first rotation direction and into which an adjusting sleeve is screwed at the end side. The adjusting sleeve has an inner thread which extends in an opposite direction to the

first rotation direction and into which there is screwed a shaft whose adjustment path is delimited by a locking member, through which the shaft extends and which is associated with the adjusting sleeve.
The technical problem addressed by the invention is to provide a structural unit which has two structural elements, which can be adjusted relative to each other, and which allows limitation of the axial adjustment path that is simple to produce and reliable.
This technical problem is solved with the features of patent claim 1.
The appended dependent claims relate to other configurations of the invention.
A structural unit having a pipe which is provided at least at one side with an inner thread extending in a first rotation direction and into which an adjusting sleeve is screwed at one end, the adjusting sleeve having an inner thread which extends in an opposite direction to the first rotation direction and into which there is screwed a shaft whose adjustment path is limited by a locking member, the adjusting sleeve having a locking member through which the shaft extends, was further developed according to the invention in that the locking member is received so as to be able to be axially moved in a limited manner in a groove provided in the outer covering face of the shaft.
With the solution according to the invention, it is possible to prevent undesirable disengagement of the individual components of the structural unit set out in a safe and reliable manner. The limited path provided for axial adjustment of the components relative to each other is defined in a simple manner by this configuration. Owing to the fact that the shaft extends through the locking member, the locking member may be arranged within the structural unit. Consequently, in a state protected from mechanical or thermal and chemical influences, it constitutes a

reliable safety device which is ensured over the entire service-life of the structural unit. However, the solution according.to the invention also has other advantages involving, for example, preventing incorrect adjustment movement of the structural unit or the simple structure of the structural unit. The product can be used directly in already-existing mass-produced products without any significant expense.
A first and particularly simple configuration of the invention makes provision for the groove to be formed in a continuous manner along the outer covering face of the shaft. This variant constitutes a particularly simple production possibility. In addition to a continuous groove, there are also solutions within the scope of the notion of the invention in which the groove is formed on only part of the periphery of the outer covering face of the shaft.
The locking member should preferably be inserted in a groove which is formed in the inner covering face of the adjusting sleeve. Consequently, the adjusting sleeve can be produced together with the locking member as a prefabricated structural unit before the final assembly of the structural unit according to the invention is carried out. The assembly as a whole is consequently simplified.
A further development of this solution may involve the locking member being fitted without axial play, but with a free space in a radial direction in the groove in the inner covering face of the adjusting sleeve. The radial play within the groove for receiving the locking member allows the inherent resilience of the locking member to be used, which is significant for the assembly of the structural unit.
This inherent resilience is advantageous according to the invention since, according to a development of the invention, the locking member has a through-opening whose clear width corresponds to the outer dimensions of the groove of the shaft. Consequently, when the structural unit is assembled, the locking member is in abutment with the surface of the groove of the shaft via the surface of the through-

opening. Consequently, there is axial movability within the groove, in order to define therewith the adjustment path of the structural unit. During the adjustment movement, the locking member consequently slides with the through-opening thereof along the groove of the shaft.
In order to simplify the assembly of the structural unit according to the invention, it is proposed that the shaft has a mushroom-head-like end piece and the outer dimensions of this end piece are larger than the clear width of the through-opening of the locking member. In this context, it will be understood that the locking member is intended to have inherent resilience. When the structural unit is assembled/ the shaft is introduced with the mushroom-head-like end piece thereof into the through-opening of the locking member which, as a result of its inherent resilience, consequently expands inside the groove of the adjusting sleeve in a radial direction and can be guided over the mushroom-head-like end piece of the shaft. After passing the mushroom-head-like end piece of the shaft, the locking member becomes contracted owing to its inherent resilience so that it almost has a through-opening which corresponds to the periphery of the outer covering face of the groove inside the shaft. Consequently, the locking member is now directly in abutment with the surface of the groove in the groove of the shaft. The groove of the shaft has two lateral abutment flanges which limit the axial adjustment path of the structural unit. The abutment flanges act as a stop for the locking member.
The mushroom-head-like configuration of the end piece of the shaft may be such that the end piece of the shaft has a spherical, conical or tapered contour. It is significant in this instance only that the outer dimensions of the shaft widen from the end thereof towards the groove so that the locking member guided over the end piece, owing to its inherent resilience, is subject to an expansion oi the through-opening thereof when the structural unit is assembled. Behind the mushroom-headlike end piece is the groove of the shaft in which the locking member subsequently engages.

In a manner known per se, the adjusting sleeve may further have, at the outer free side thereof that protrudes from the pipe, a keying face for attaching a tool. This keying face consequently serves to adjust the structural unit by a rotational movement being transmitted to the adjusting sleeve which, owing to the opposing threads, causes the pipe and the shaft to move towards each other or away from each other in relative terms.
One application possibility of a structural unit according to the invention involves the structural unit being an integral component of a tie rod for motor vehicles and the shaft consequently being the end of a ball-and-socket joint housing shaft of this tie rod. In such an application, the advantage mentioned in the introduction also becomes evident, according to which the solution according to the invention can be used directly in current mass-produced products without considerable additional expense. In tie rods which are already in use and as explained in conjunction with the specifications of the prior art, the components pipe, adjusting sleeve and shaft are already present. It is simply necessary to provide a groove in the shaft and to construct the mushroom-head-like end piece and to form in the inner sleeve of the structural unit a groove into which the locking member according to the invention can then be inserted. With these few modifications, the structural unit according to the invention can be used directly for numerous applications.
The invention is explained in greater detail below with reference to the appended drawings. The embodiment shown does not constitute a limitation of the variant illustrated but serves only to explain the notion of the invention. In order to be able to illustrate the operating method according to the invention, only heavily simplified schematic illustrations are shown in the Figures in which the components which are not essential to the invention have been dispensed with. However, this does not mean that components of this type are not present in a solution according to the invention.

Figure 1 is an enlarged view of part of a structural unit according to the invention
using the example of a tie rod for motor vehicles,
and
Figure 2 is an end piece of a tie rod having a structural unit according to the
invention.
The enlarged view of part of the structural unit according to the invention in Figure 1 constitutes an integral component of a tie rod for a motor vehicle. Figure 1 corresponds to the detail I in Figure 2.
The structural unit illustrated has a pipe 2 having an inner thread 1. In this inner thread 1 there is screwed an adjusting sleeve 3 having an outer thread 17 which is provided on the adjusting sleeve 3 so as to correspond to the inner thread 1 of the pipe 2. The inner sleeve 3 has, on the inner covering face 8 thereof, an inner thread 4 which serves to screw a shaft 5 into the adjusting sleeve 3. To this end, the shaft 5 has, on the outer covering face thereof, an outer thread 18. It is significant for the configuration of the invention that the inner thread 1 of the pipe 2 and the inner thread 4 of the adjusting sleeve 3 are threads which are constructed so as to extend in mutually opposing directions. For example, if the inner thread 1 of the pipe 2 is a right-hand thread, the inner thread 4 of the adjusting sleeve 3 is constructed as a left-hand thread. Consequently, when the adjusting sleeve 3 is rotatably moved about the common longitudinal centre axis of the components pipe 2, adjusting sleeve 3 and shaft 5 (not illustrated), the shaft 5 can be moved relative to the pipe 2. Consequently, an axial adjustment movement of the tie rod is possible. At the end side, the adjusting sleeve 3 further has a groove 9 into which a locking member 6 with limited resilience is inserted. The locking member 6 can be deflected within the groove 9 in a radial direction. There is no provision for axial movability of the locking member 6 within the groove 9. Consequently, the locking member 6 abuts with both lateral faces thereof the corresponding delimiting faces of the groove 9. There is further formed in the shaft 5 a groove 7 which is located in the region of the

end portion of the shaft 5. This groove 7 is delimited at the two sides by an abutment flange 19 and 20, respectively. The region between the abutment flanges 19 and 20 is the maximum possible adjustment path of the structural unit according to the invention. The locking member 6 further has a through-opening 10 whose inner surface directly abuts the outer surface of the groove 7 of the shaft 5. A sliding movement in the axial direction within the groove 7 is ensured in this instance. For the solution according to the invention, it is further significant that the end piece 11 of the shaft 5 is constructed in a mushroom-head-like manner. In the example in Figure 1, the mushroom-head-like contour of the end piece 11 of the shaft 5 is achieved by means of a plurality of geometries which merge into each other. For instance, beginning at the end of the shaft 5, two conical geometries alternate with different gradients with respect to the longitudinal centre axis. Following the conical geometries of the end piece 11, it has a circular-cylindrical cross-section which merges at the groove side into the abutment flange 20,
The structural unit is assembled in the following manner:
Firstly, the individual components are produced. Subsequently, the locking member 6 is inserted into the groove 9 provided for this purpose in the adjusting sleeve 3. The locking member 6 has inherent resilience which, when the shaft 5 is screwed into the adjusting sleeve 3, allows the mushroom-head-like end piece 11 of the shaft 5 to be guided first through the through-opening 10 of the locking member 6. Owing to the inherent resilience mentioned, the locking member 6 expands in a radial direction within the groove 9. It slides with the through-opening 10 thereof along the conical geometries of the end piece 11. After passing the mushroom-head-like end piece 11, the locking member 6 engages in the groove 7 of the shaft 5 and contracts again owing to its inherent resilience so that it abuts the surface of the groove 7. The part-structural unit produced as a result can now be screwed, via the outer thread 17 of the adjusting sleeve 3, into the inner thread 1 of the pipe 2.

Figure 2 illustrates, for a better understanding of the solution according to the invention, a structural unit using the example of a tie rod 13 for a motor vehicle. The tie rod 13, of which only an end piece is illustrated in this instance, has a pipe 2 into which the adjusting sleeve 3 is screwed. In order to adjust the adjusting sleeve 3, a keying face 12 is provided on the outer covering face thereof. With the shaft 5 which forms a ball-and-socket joint housing shaft, a ball-and-socket joint 14 is connected to the adjusting sleeve 3. In order to fix the components relative to each other, there is used a clamping collar 15 which is attached to the outer covering face of the pipe 2. This clamping collar 15 is contracted by means of a screw connection 16 and consequently tensions the structural unit as a whole. Consequently, an adjustment movement can no longer be carried out after the clamping collar has been tightened, As can be seen from the illustration of Figure 2, the structural unit according to the invention is located in the pipe 2 of the tie rod 13 illustrated, by means of which it is protected from impurities and mechanical damage.

List of reference numerals
1 Inner thread (pipe)
2 Pipe
3 Adjusting sleeve
4 Inner thread (adjusting sleeve)
5 Shaft
6 Locking member
7 Groove (in the shaft)
8 Inner covering face (of the adjusting sleeve)
9 Groove (in the adjusting sleeve)
10 Through-opening (of the locking member)
11 End piece
12 Keying face
13 Tie rod
14 Ball-and-socket joint
15 Clamping collar
16 Screw connection
17 Outer thread (of the adjusting sleeve)
18 Outer thread (of the shaft)
19 Stop flange
20 Stop flange

WE CLAIM:
1. Structural unit having a pipe (2) which is provided at least at one side with an
inner thread (1) extending in a first rotation direction and into which an
adjusting sleeve (3) is screwed at one end, the adjusting sleeve (3) having an
inner thread (4) which extends in an opposite direction to the first rotation
direction and into which there is screwed a shaft (5) whose adjustment path is
limited by a locking member (6), the adjusting sleeve (3) having a locking
member (6) through which the shaft (5) extends,
characterised in that
the locking member (6) is received so as to be able to be axially moved in a limited manner in a groove (7) provided in the outer covering face of the shaft (5).
2. Structural unit according to claim 1,
characterised in that
the groove (7) is formed in a continuous manner along the outer covering face of the shaft (5).
3. Structural unit according to either of the preceding claims,
characterised in that
the locking member (6) is inserted in a groove (9) which is formed in the inner covering face (8) of the adjusting sleeve (3).
4. Structural unit according to claim 3,
characterised in that

the locking member (6) is inserted into the groove (9) without axial play, or with very little play and with radial play with respect to the longitudinal axis of the adjusting sleeve (3).
5. Structural unit according to any one of the preceding claims,
characterised in that
the locking member (6) has limited inherent resilience.
6. Structural unit according to any one of the preceding claims,
characterised in that
the locking member (6) has a through-opening (10) whose clear width corresponds to the outer dimensions of the groove (7) of the shaft (5).
7. Structural unit according to claim 6,
characterised in that
the shaft (5) has a mushroom-head-like end piece (11) and the outer dimensions of this end piece (11) are larger than the clear width of the through-opening (10) of the locking member (6).
8. Structural unit according to any one of the preceding claims,
characterised in that
the end piece (11) of the shaft (5) has a spherical, conical or tapered contour.
9. Structural unit according to any one of the preceding claims,
characterised in that

the adjusting sleeve (3) has, at the outer free side thereof that protrudes from the pipe (2), a keying face (12) for attaching a tool.
10. Structural unit according to any one of the preceding claims, characterised in that
the structural unit is an integral component of a tie rod (13) for motor vehicles and the shaft (5) is the end of a ball-and-socket joint housing shaft of this tie rod (13).