NO337929B1

NO337929B1 - Shaft clamping assembly

Info

Publication number: NO337929B1
Application number: NO20150820A
Authority: NO
Inventors: Arne Aarre
Original assignee: Arne Aarre As
Priority date: 2015-06-22
Filing date: 2015-06-22
Publication date: 2016-07-11
Also published as: NO20150820A1

Description

Shaft clamping assembly

The present invention relates to a shaft clamping assembly, used to damp a first body to a shaft member.

Background

Clamping assemblies of the kind discussed herein are well known. For instance, US patent application publication US2009120234 describes a clamping assembly where a first body (32) is attached to a second body (34) by means of a shaft (2) which extends through a bore of the second body. To achieve the clamping function, a clamping sleeve (4) is forced into a receiving slot which has a tapered shape. Due to the tapering, the clamping sleeve contacts an outer and inner surface with such a force, that a secure fixation is obtained between the first and second body.

A similar assembly is shown in Norwegian patent publication NO307902 B1. A bearing shaft (12) is supported in a bearing bore in a rotating manner. The bearing shaft extends out from the bearing bore on respective ends with a coned surface. Between these two coned surfaces and respective bores of a first machine part, a clamping sleeve (22) is inserted, and forced into engagement with a clamping disk (28).

When assembling the arrangements of this kind, the clamping disk is typically forced against the clamping sleeves by rotation of tightening bolts. Before the clamping sleeve has been set in a tight and engaged position, the shaft may rotate. To prevent the shaft from rotating, it is common for a second person to retain the shaft in place, while a first person tightens the tightening bolts. Hence, two persons are commonly required in order to assembly such arrangements.

Moreover, particularly after heavy use, the metal of the components of such assemblies may have yielded, so that their shape may deviate from their original shape. Particularly in such cases, it may be difficult to insert the clamping sleeve into the bores against which they shall engage. This problem even exists for assemblies which have not yet been used.

The object of the present invention is to provide a shaft clamping assembly that reduces or eliminates the problems met with the shaft clamping assemblies of the prior art.

The invention

A shaft clamping assembly is provided, comprising a shaft håving a coned portion and a first body håving a cylindrical first bore. The first bore is axially aligned with the coned portion when the shaft clamping assembly is in an assembled mode. The assembly further comprises a coned clamping sleeve which has a radially outer engagement surface that engages the first bore and an inner engagement surface that engages the coned portion, when in the assembled mode. A clamping sleeve clamping element is also part of the assembly. The outer engagement surface is coned. The coned portion (of the shaft) has an engagement distance, wherein the axially inner engagement position of the engagement distance is the axially inner contact line between the inner engagement surface and the coned portion, when in the assembled mode. Moreover, the inner engagement surface of the clamping sleeve has an axially inner end. The diameter of the axially inner end of the inner engagement surface is smaller than the diameter of the inner engagement position, when in an unassembled mode.

The term inner contact line is used to identify the position of a line extending circumferentially about the coned portion of the shaft, at which line the axially inner part of the inner engagement surface contacts the coned portion when in the assembled mode.

Moreover, the inner engagement position is the position on the coned portion where the inner contact line is positioned.

A consequence of the features of the invention (the diameter of the axially inner end of the inner engagement surface being smaller than the diameter of the inner engagement position, when in an unassembled mode), is that the axially inner portion of the clamping sleeve will abut the coned portion before reaching the assembled position (axially inserted end position). Thus, in order to reach the end position, namely the position in which the clamping sleeve has been moved axially all the way into the assembled mode, the clamping sleeve needs to twist or bend, possibly a combination of twisting and bending.

The first bore being axially aligned with the coned portion, means that at least a portion of the first bore has the same axial position as at least a portion of the coned portion. When positioned in this fashion, the clamping sleeve can be inserted in the void or slot existing between the first bore and the coned portion.

The assembled mode is the mode of the assembly where the clamping sleeve has been forced into the said slot, until its end position, to secure the shaft to the first body. Contrary to this, the unassembled mode is the mode where the clamping sleeve is not engaged with the first bore or the coned portion, and exhibits its original shape (where it is not deformed by any forces acting on the clamping sleeve). When moving from the unassembled mode to the assembled mode, the shape of the clamping sleeve will change, as it abuts against the coned portion of the shaft with its inner engagement surface. Such change of shape may occur with plastic deformation, in addition to elastic deformation.

The outer engagement surface of the clamping sleeve is the portion of the outer surface which abuts the surface of the first bore when in the assembled mode. In some embodiments, the clamping sleeve may exhibit an additional outer surface, which however, does not engage the first bore when assembled.

The outer engagement surface has an axially inner end. In a preferred embodiment, the diameter of the first bore is larger than the diameter at the axially inner end, when in an unassembled mode.

When in the unassembled mode, an axially outer engagement portion of the outer engagement surface can advantageously have a larger diameter than the diameter of the first bore.

As a consequence, the axially outer engagement portion of the outer engagement surface will abut against the first bore before the clamping sleeve has reached its end position, i.e. its assembled mode. Furthermore, an axially outer engagement portion of the clamping sleeve will then become compressed by the engagement with the first bore. Thus, in a preferred embodiment, an axially inner portion of the clamping sleeve may expand by engagement with the coned portion of the shaft, while a rear portion of the clamping sleeve may become compressed by the engagement with the first bore.

A further consequence of an engagement between the clamping sleeve and the first bore before reaching the assembled position (inner position of the clamping sleeve), is that such engagement will reduce possible rotation of the clamping sleeve clamping element when the tightening bolts are tightened. In many cases, this feature will make it possible or at least easier for one person to assembly the shaft clamping assembly alone, without the aid of a second person to counteract the possible unwanted rotation during assembling.

The shaft may in some embodiments extend through two first bores of respective first bodies, wherein respective coned portions are aligned with the first bores. The shaft may then exhibit an intermediate cylindrical portion which is aligned with a second bore of a second body. In such an embodiment, respective clamping sleeves can engage respective coned portions and first bores from opposite axial sides. Such an embodiment is illustrated in the example of Fig. 1, which will be described below.

Example of embodiment

Håving described the present invention in general terms above, a more detailed and non-limiting example of embodiment will be given in the following with reference to the drawings, in which

Fig. 1 is a cross section side view of a shaft clamping assembly according to the

present invention;

Fig. 2 is a side view of a clamping plate and associated tightening bolts; Fig. 3 is a cross section side view of the assembly when the clamping sleeve is partially inserted into a slot between the coned portion and the first bore; Fig. 4 is a cross section side view corresponding to Fig. 3, however in a position where the clamping sleeve has been inserted into engagement with the coned portion and the first bore; Fig. 5 is an enlarged cross section view of the situation shown in Fig. 3; Fig. 6 is an enlarged cross section view of the situation shown in Fig. 4; Fig. 7 is an enlarged principle view of a portion of the clamping sleeve, the coned

portion and the first bore; and

Fig. 8 is an enlarged cross section view, corresponding to the situation shown in

Fig. 1.

Fig. 1 shows an embodiment of a shaft clamping assembly 1 according to the present invention. The assembly 1 has a shaft 3 which at respective ends is provided with a coned portion 5. The shaft 3 is inserted through a first bore 7 of respective first bodies 9. In other embodiments, there shaft 3 could be provided with only one coned portion 5 extending through only one first bore 7 of a first body 9.

The coned portion(s) 5 of the shaft 3 is adjacent a cylindrical portion 11. In this embodiment the cylindrical portion 11 is arranged between the two coned portions 5. Inserted between the coned portion 5 and the first bore 7, there is a clamping sleeve 13. In Fig. 1, the shaft clamping assembly 1 is shown in an assembled mode, in which the clamping sleeve 13 has been forced axially inwards along the coned portion 5, until its end position. In this end position, the clamping sleeve 13 abuts radially outwards against the first bore 5, and radially inwards against the coned portion 5. This abutment is of significant force, and secures the shaft 3 to the first body 9.

In order to obtain a clamping force, moving the clamping sleeve 13 axially inwards, a clamping sleeve clamping element, here in the form of a clamping plate 15, is arranged. The clamping plate 15 is bolted to the end face of the shaft 3 with six tightening bolts 17. The tightening bolts 17 engage threaded bores 27 of the end of the shaft. As the clamping sleeve 13 is interposed between the clamping plate 15 and the slot 16 (cf. Fig. 3) appearing between the coned portion 5 and the first bore 7, it will be forced into the slot by tightening of the tightening bolts 17.

In this embodiment, as discussed above, the cylindrical portion 11 of the shaft is arranged between two coned portions 5 (Fig. 1). Moreover, the cylindrical portion 11 is arranged within a second bore 19 of a second body 21. Between the cylindrical portion 11 and the second bore 19, there is a sleeve bearing. The sleeve bearing has a first bearing body 23 attached to the cylindrical portion 11 of the shaft 3, and a second bearing body 25 attached to the second body 21. The first and second bearing bodies 23, 25 are adapted to rotate with respect to each other. Hence, the shaft 3 may rotate with respect to the second body 21. Fig. 2 is a side view illustrating the clamping plate 15 with the heads of the six tightening bolts 17. Fig. 3 is a cross section view of the assembly 1. In this position, the clamping sleeve 13 has been partially inserted into the slot 16. The tightening bolts 17 are inserted through apertures in the clamping plate 15, however not inserted into the threaded bores 27 at the end face of the shaft 3.

The view of Fig. 4 corresponds to the view of Fig. 3, however in this situation the clamping sleeve 13 has been moved into the slot 16 and is abutting the coned portion 5 of the shaft 3. The tightening bolts 17 are in engagement with the threads of the threaded bores 27 of the shaft 3.

Fig. 5 and Fig. 6, respectively, depict the situations shown in Fig. 3 and Fig. 4 in better detail.

Reference is now made to Fig. 7, which is a schematic view of the end portion of the clamping sleeve 13, partially inserted into the slot 16 between the coned portion 5 and the first bore 7. The clamping sleeve 13 has an outer engagement surface 29, which faces radially outwards, toward the first bore 7. Further, the clamping sleeve 13 has an inner engagement surface 31 which faces radially inwards, towards the coned portion 5 of the shaft 3.

The outer engagement surface 29 is a coned surface. Thus, there is an angle a between the cylindrical shape of the first bore 7 and the outer engagement surface 29. A typical size of the angle a may be within the range of 0,5 to 10 degrees. More preferably, however, an appropriate angle a may be within the range of 0,5 to 5 degrees.

As appears from Fig. 7, the angle a is of such orientation that the outer engagement surface 29 is inclined or coned radially inwards, when moving from an axial outer towards an axial inner position.

The outer engagement surface 29, which when in the assembled mode (cf. Fig. 1) is abutting the face of the first bore 7, has an axially inner end 33. As appears from Fig. 7, which shows the clamping sleeve 13 in the unassembled mode, the diameter of the clamping sleeve 13 at the position of the inner end 33 of the engagement surface 29, is less than the diameter of the first bore 7. The inner engagement surface 31 also has an axially inner end 35. In the embodiment shown in Fig. 7, the inner end 35 of the inner engagement surface 31 coincides with the inner end 33 of the outer engagement surface 29. The coned portion 5 has an engagement distance which is the part of the coned portion 5 which abuts the inner engagement surface 31 of the clamping sleeve 13, when in the assembled mode. An axially inner engagement position 37 of the engagement distance is the axially inner contact line between the inner engagement surface 31 and the coned portion 5, when in the assembled mode. Thus, as appears from Fig. 7, the inner end 35 of the inner engagement surface 31 has a diameter which is less than the inner engagement position 37 of the coned portion, when in the unassembled mode. Thus, when the clamping sleeve 13 is forced axially inwards, towards the assembled mode, the inner end 35 of the engagement surface 31 will be stretched to a larger diameter.

Hence, when forcing the clamping sleeve 13 into the assembled mode, it will undergo a twisting movement, about an axis which is parallel to its circumference.

As mentioned above, in the shown embodiment the axially inner end 33 of the outer engagement surface 29 coincides with the axially inner end 35 of the inner engagement surface 31. However, in other embodiments, this may not be the case. For instance, there may be a step arranged at the axially inner end 33 of the outer engagement surface 29, so that the clamping sleeve 13 extends axially beyond the inner end 33 of the outer engagement surface 29. A corresponding step may be arranged at the inner end 35 of the inner engagement surface 31. In such alternative embodiments, there may be an annular void present at the axially inner portion of the slot 16, when in the assembled mode.

Reference is again made to Fig. 5 and Fig. 6. In the situation shown in Fig. 5, the clamping sleeve 13 has entered into the slot 16, however is not in contact with the coned portion 5 or the first bore 7. In the situation shown in Fig. 6, however, the axially inner end 35 of the inner engagement surface 31 abuts the coned portion 5 of the shaft 3.

Moreover, the outer engagement surface 29 of the clamping sleeve 13 abuts against an axially outer edge 39 of the first bore 7. This engagement, between the first body 9 and the clamping sleeve 13, reduces possible rotation of the clamping sleeve 13 and the abutting clamping plate 15 when the tightening bolts 17 are rotated. To move the clamping sleeve 13 further axially inwards, an increasing amount of clamping force is needed. Consequently, an increasing torque of the tightening bolts 17 is needed. This torque is transferred to the clamping sleeve 13. Without the engagement between the clamping sleeve 13 and the first body 9 in this phase of the assembly process, the user could have problems in rotating the tightening bolts 17 with respect to the clamping plate 15, without rotating the clamping plate 15 itself.

Still referring to Fig. 6, an axially outer engagement portion 41 of the outer engagement surface 29 has, in the shown situation, a larger diameter than the axially outer edge 39 of the first bore 7 (and the first bore 7 itself). Thus, when the clamping sleeve 13 is moved from the shown intermediate position shown in Fig. 6, to the assembled position shown in Fig. 8, the outer engagement portion 41 becomes compressed. That is, the diameter of the clamping sleeve 13 at the location of the outer engagement portion 41 is reduced.

Thus, by comparing Fig. 8 (assembled mode) with Fig. 6 (intermediate mode), one will appreciate that the diameter of the axially inner portion (the tip) of the clamping sleeve 13 will increase, while the diameter of the axially outer engagement portion 41 of the clamping sleeve 13 will become compressed. In the prior art solutions, the contact force between the clamping sleeve 13 against the first bore 7 and the coned portion 5 is provided merely by the axially directed force on the clamping sleeve. In contrast to this, additional contact force is provided, since the clamping sleeve 13 has twisted about its own axis (being parallel to its circumference). Hence, an improved coupling between the shaft 3 and the first body 9 has been established.

As will be appreciated by the skilled person, the deformation of the clamping sleeve 13 may in some embodiments occur by plastic deformation in addition to elastic deformation.

Since the inner axially end 33 of the engagement surface 29 has a diameter which is less than the diameter of the first bore 5, the insertion of the clamping sleeve 13 into the first bore 5 is made easier.

Claims

1. A shaft clamping assembly (1) comprising - a shaft (3) håving a coned portion (5); - a first body (9) håving a cylindrical first bore (7), the first bore (7) being axially aligned with the coned portion (5) when the shaft clamping assembly (1) is in an assembled mode; - a coned clamping sleeve (13), håving a radially outer engagement surface (29) engaging the first bore (7) and an inner engagement surface (31) engaging the coned portion (5), when in the assembled mode; and - a clamping sleeve clamping element (15); characterized in that- the outer engagement surface (29) is coned - the coned portion (5) has an engagement distance, the axially inner engagement position (37) of the engagement distance being the axially inner contact line between the inner engagement surface (31) and the coned portion (5), when in the assembled mode; - the inner engagement surface (31) of the clamping sleeve (13) has an axially inner end (35); wherein the diameter of the axially inner end (35) of the inner engagement surface (31) is smaller than the diameter of the inner engagement position (37), when in an unassembled mode.

2. A shaft clamping assembly (1) according to claim 1,characterized in thatwhen in the unassembled mode, an axially outer engagement portion (41) of the outer engagement surface (29) has a larger diameter than the diameter of the first bore (7).

3. A shaft clamping assembly (1) according to claim 1 or 2,characterized in thatthe outer engagement surface (29) has an axially inner end (33), and that the diameter of the first bore (7) is larger than the diameter at the axially inner end (33), when in an unassembled mode.

4. A shaft clamping assembly (1) according to any one of the preceding claims,characterized in thatthe shaft (3) extends through two first bores (7) of respective first bodies (9), håving respective coned portions (5) aligned with the first bores (7), and that the shaft (3) exhibits an intermediate cylindrical portion (11) which is aligned with a second bore (19) of a second body (21), wherein respective clamping sleeves (13) engage respective coned portions (5) and first bores (7) from opposite axial sides.