Method for replacing rack and rack of pinion drive and clamp assembly

Abstract

A method of replacing a rack of a rack and pinion drive device, the device comprising a first rack (10) and a gearbox (20) comprising a plurality of pinions arranged to mesh with the first rack (10), the pinions being connected to respective main gears by rotary compliance means. The method includes: providing a rack and pinion drive having a first rack (10) mounted in meshing engagement with the pinion of the gearbox (20); providing a clamp assembly comprising a second rack (31) and coupling means (40, 50, 60); arranging the second rack (31) in longitudinal coaxial alignment with the first rack (10); connecting the first end (32a) of the second rack (31) to the proximal end (11b) of the first rack (10) by means of the coupling means (40, 50, 60); through the linear displacement of the first rack (10) and the second rack (31), the second rack (31) is engaged with the pinion of the gearbox (20), and the first rack (10) is disconnected from the second rack (31). When either the first rack (10) or the second rack (31) is engaged with the pinion of the gearbox (20), the nominal rotational position between the respective pinion and the main gear (23) can be calibrated. A clamp assembly (30) for use in performing the method is also disclosed.

Description

Technical Field Background Art

[0001] Rack and pinion drives are often used to convert a rotary motion into a linear motion and / or vice versa. Such rack and pinion drives can be used, for example, in linear actuators and lifting devices, where the rotary motion of a motor is converted into a linear actuating or lifting motion. Another exemplary application area is energy harvesting, such as wave energy harvesting, where the reciprocating linear motion of a buoy or the like is converted into a rotary motion of an output shaft by a rack and pinion drive.

[0002] In applications where large forces and / or torques are to be converted, a rack and pinion drive preferably comprises a plurality of pinions meshing with the same rack. In this way, the torque to be transmitted can be distributed between the plurality of pinions and between a corresponding number of gears fixed to the respective pinions, so that the load on each torque transmitting tooth flank can be reduced. Such a rack and pinion drive comprising a plurality of pinions is overdetermined. Such overdetermination may lead to problems associated with the tooth flanks of different pinions and gears that are simultaneously in load transmitting engagement being subjected to different loads. In order to overcome these problems, it has been proposed to introduce a certain rotational flexibility or compliance between each pinion and its corresponding gear.

[0003] EP2921694B1 discloses a rack and pinion drive device, which includes a rack and a gearbox, the gearbox containing a plurality of pinions meshing with the rack. Each pinion is fixed to a corresponding main gear, which is mechanically connected to a common input shaft or output shaft of the gearbox. In order to enhance the load distribution of all tooth surfaces engaged simultaneously, each pinion is fixed to the corresponding main gear by a corresponding elastically deformable fixing device, which allows limited relative rotation between the corresponding pinion and the main gear.

[0004] In such rack and multi-pinion drives provided with means for rotational compliance between a pinion gear and a corresponding main gear, it is important to accurately adjust or calibrate the relative nominal rotational position between each pinion gear and the main gear. In addition, any pre-tensioning of the elastically deformable means providing rotational compliance needs to be accurately adjusted or calibrated for each pair of pinion gears and main gears and relative to each other pair of pinion gears and main gears.

[0005] Such adjustment or calibration needs to be performed before or during commissioning of the device and with the rack mounted in engagement with the pinion. However, in many applications, the rack has a considerable length relative to the gearbox. In addition, the rack generally needs to be strong and durable, which results in a heavy rack. In high-precision applications, the straightness of the rack as well as the geometry and surface finish of the teeth need to be maintained within narrow tolerances. Therefore, the assembly and adjustment or calibration and other handling of such rack and pinion drives including a long and heavy rack are generally cumbersome and there is generally a considerable risk that the rack may be damaged.

[0006] Another problem arises from the fact that the rack needs to remain in meshing contact with the pinion after adjustment or calibration until commissioning in order not to lose calibration. Especially in applications where a long and heavy rack is required, this makes the transport of the device with the mounted rack from the assembly site to the site of use difficult and cumbersome. Summary of the invention

[0007] An object of the present disclosure is to provide a method for replacing a rack of a rack and pinion drive, and a fixture assembly that facilitates assembly, calibration, testing, transportation, installation and / or commissioning of the rack and pinion drive, which includes a device for rotational compliance between a pair of pinion gears and a main gear.

[0008] Another object of the present invention is to provide a method which is easy to implement.

[0009] Another object is to provide a clamp assembly that is simple in design.

[0010] In general, unless otherwise explicitly defined herein, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field. Unless otherwise explicitly stated, all references to "a / an / the element, device, component, means, step, etc." are to be openly interpreted as referring to at least one instance of an element, device, component, means, step, etc. Unless explicitly stated otherwise, the steps of any method disclosed herein do not have to be performed in the exact order disclosed.

[0011] According to a first aspect, the present disclosure provides a method of replacing a rack of a rack and pinion drive, the rack and pinion drive comprising a first rack and a gearbox, the gearbox comprising a plurality of pinions arranged to mesh with the first rack, the pinions being connected to respective main gears via rotationally compliant means. The method is defined in the accompanying claim 1 and comprises:

[0012] - providing a rack and pinion drive having a first rack mounted in meshing engagement with said pinion of said gearbox,

[0013] - providing a clamp assembly comprising a second rack and a coupling device,

[0014] - arranging the second rack to be longitudinally coaxially aligned with the first rack,

[0015] - connecting the first end of the second toothed rack to the proximal end of the first toothed rack by means of the coupling means,

[0016] - meshing engagement of the second rack with the pinion of the gearbox by linear displacement of the first rack and the second rack, and

[0017] - disconnecting the first rack from the second rack, the method further comprising:

[0018] - When the first rack or the second rack is in meshing engagement with a pinion of the gearbox, calibrating the nominal rotational position between each pinion and the main gear.

[0019] Thus, the first rack may constitute a "universal rack", which is hereinafter named as a rack intended to be installed in a gearbox and to engage with the pinion during normal operation of the rack and pinion drive. The second rack may constitute an "auxiliary rack", which is hereinafter named as a rack intended to be used temporarily as a replacement for the universal rack, e.g. during assembly, calibration, test transport and / or commissioning of the rack and pinion drive.

[0020] The term "clamp assembly" is used herein to name the collection of components arranged to locate, guide and / or maintain one of the components in alignment with another component that does not form part of the clamp assembly. More specifically, the "clamp assembly" described herein comprises a second or auxiliary rack and a coupling arrangement arranged to releasably connect the second or auxiliary rack to and align it with a first or universal rack that does not form part of the clamp assembly.

[0021] The method allows the auxiliary rack to be easily fixed as a longitudinal extension to the universal rack of the rack and pinion drive. In this way, the universal rack can be used during assembly and calibration of the rack and pinion drive. The use of the universal rack in toothed engagement with the pinion during calibration determines the nominal relative rotational position between each pinion and the main gear and the pretensioning of any elastically compliant member is precisely adjusted relative to the actual tooth geometry of the universal rack. Once the calibration has been completed, the universal rack and the auxiliary rack fixed to the end of the universal rack can be linearly displaced until the pinion of the gearbox forms a toothed engagement with the auxiliary rack. Thereafter, the universal rack can be disconnected from the auxiliary rack. As long as the auxiliary rack presents substantially the same tooth geometry as the universal rack, the nominal relative rotational position and the pretensioning performed during calibration will be maintained after replacing the universal rack with the auxiliary rack in the gearbox.

[0022] Thereafter, the rack and pinion drive can be transported with the universal rack separated from the gearbox with the auxiliary rack. This provides an important advantage since the universal rack can be very long relative to the length of the gearbox in many applications. Due to the slender construction of such a long and heavy universal rack, transportation and other handling of the rack and pinion drive with the universal rack mounted amounts to a considerable risk of damaging the universal rack and / or the gearbox. This problem is effectively eliminated or reduced by the method, which allows the long and heavy universal rack to be transported and handled separately from the gearbox until the rack and pinion drive is finally commissioned at the site of use. During such transport and handling, the auxiliary rack, which remains in toothed engagement with the pinion, ensures that the calibration of the gearbox is maintained during transport and handling.

[0023] After transport to the place of use, this method allows the universal rack to be easily fixed to the auxiliary rack as an extension. Thereafter, the universal rack can be engaged with the pinion in the gearbox, again without the risk of previously completed calibration being lost. Once the universal rack has finally been mounted, the auxiliary rack can be disconnected and removed from the universal rack. Thereafter, the auxiliary rack can be used in a similar manner for other rack and pinion drives.

[0024] The auxiliary rack in engagement with the pinion can also be used during calibration and during testing of the gearbox if the auxiliary rack has the same tooth geometry as the universal rack. In this case, the auxiliary rack can remain in engagement with the pinion until final assembly or commissioning of the rack and pinion drive, where the auxiliary rack is replaced by the universal rack by fixing the universal rack as an extension of the universal rack and linearly displacing the rack so connected until the universal rack engages with the pinion.

[0025] The method can also be used for maintenance and repair of rack and pinion drives where temporary removal or replacement of the universal rack is required. In this case, the auxiliary rack is fixed to the existing universal rack and then linearly moved until the pinion engages with the auxiliary rack. Thereafter, the existing universal rack is disconnected from the auxiliary rack for maintenance and thereafter connected again to the auxiliary rack to re-engage with the pinion by linear displacement. Alternatively, after disconnecting the existing universal rack, a replacement universal rack can be connected to the auxiliary rack and engaged with the pinion.

[0026] Thus, the method provides a simple and effective means for calibrating and / or maintaining alignment of the pinion and main gear of a rack and pinion drive during assembly, testing, shipping, commissioning, repair and maintenance.

[0027] According to one embodiment, the method comprises arranging at least one toothed surface of the second rack in coplanar alignment with a corresponding toothed surface of the first rack.

[0028] The method may include inserting at least one spacing member between the first end of the second rack and the proximal end of the first rack for adjusting a spacing between an outermost tooth at the first end and an outermost tooth at the proximal end.

[0029] The coupling means may include a rod extending longitudinally in a hole through the second rack, and the method may then include connecting the rod to the proximal end and longitudinally tensioning the rod to press the first end toward the proximal end.

[0030] The step of meshingly engaging the second rack with the pinion of the gearbox by linear displacement of the first rack and the second rack may be achieved by rotating the input / output shaft of the gearbox.

[0031] According to a second aspect, there is provided a clamp assembly as claimed in claim 6. The clamp assembly is intended for use when replacing a rack of a rack and pinion drive device, the device comprising a first rack and a gearbox, the gearbox comprising a plurality of pinions arranged to mesh with the first rack. The clamp assembly comprises: a second rack extending from a first end to a second end; and a coupling arrangement for releasably connecting the first end of the second rack to the proximal end of the first rack. The coupling arrangement comprises: a guide arrangement arranged to maintain the second rack in longitudinal coaxial alignment with the first rack, a rod extending through a longitudinal hole in the second rack and having a first rod end connectable to the proximal end of the first rack, and a tensioning arrangement connectable to the rod and arranged to engage the second rack for tensioning the rod to press the first end towards the proximal end.

[0032] The clamp assembly provides an efficient means for carrying out the method according to the first aspect.

[0033] The clamp assembly may include at least one spacing member arranged to be interposed between said first end of the second rack and the proximal end of the first rack when the second rack is connected to the first rack. The spacing member may include a shim or similar device. Such a single spacing member or multiple spacing members may be interposed between the second rack and the first rack for maintaining the correct tooth geometry at the transition between the universal rack and the auxiliary rack. In particular, such a single or multiple spacing members may be used to adjust the pitch between the outermost teeth at the first end and the outermost teeth at the proximal end.

[0034] The guiding means may comprise a bushing which is received radially guidingly in said bore at a first end and is arranged to connect the rod to the proximal end.

[0035] The bushing may include a first portion received in the bore by a transition fit, a clearance fit, or an interference fit.

[0036] The bushing may comprise an external or internal thread arranged to form a threaded engagement with a corresponding thread arranged at the proximal end of the first rack. This allows a simple and reliable design of the clamp assembly and allows the first rack and the second rack to be connected to each other by a simple operation.

[0037] The bushing may include an externally threaded portion that protrudes longitudinally from the first end of the second rack.

[0038] The tensioning device may include a first screw joint.

[0039] The first threaded joint may comprise an external thread arranged at the second rod end of the rod and a stop member having a corresponding internal thread and a stop surface arranged to be supported by an end surface arranged at the second end of the second rack.

[0040] The clamp assembly may further include at least one annular support member arranged to be received in the aperture and supportingly receive the rod.

[0041] The rod may be secured to the bushing by a second threaded joint.

[0042] The clamp assembly provides the same advantages as described above.

[0043] Further objects and advantages will appear from the following description of exemplary embodiments and from the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Various aspects and embodiments will now be described by way of example with reference to the accompanying drawings, in which:

[0045] Figure 1is a partial perspective exploded view showing a rack and pinion drive provided with a clamp assembly according to one embodiment when secured to a universal rack of the rack and pinion drive.

[0046] Figure 2 It is shown Figure 1 A partial perspective exploded view of a portion of the clamp assembly and universal rack shown in

[0047] Figure 3 is a longitudinal section on an enlarged scale showing Figure 1 A portion of the rack and pinion drive of the clamp assembly shown in FIG.

[0048] Figure 4 yes Figure 3 A longitudinal section of a portion of the device shown in FIG. DETAILED DESCRIPTION

[0049] Aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown.

[0050] However, these aspects can be embodied in many different forms and should not be interpreted as limiting; on the contrary, these embodiments are provided by way of example so that this disclosure will be thorough and complete and fully convey the scope of all aspects of the invention to those skilled in the art. Throughout the specification, the same reference numerals represent the same elements.

[0051] Figure 1-4 A rack and pinion drive according to a first embodiment is shown provided with a clamp assembly 30. The rack and pinion drive comprises a first rack in the form of a universal rack 10 and a gearbox 20.

[0052] The universal rack 10 extends longitudinally from a first end 11a to a second end 11b. As will be explained in more detail below, when the clamp assembly is used, the second end 11b forms the proximal end. The universal rack 10 presents a first planar toothed surface 12a and a second planar toothed surface 12b arranged opposite to the first toothed surface. The first toothed surface 12a and the second toothed surface 12b extend substantially over the entire length of the universal rack 10, in particular, the two toothed surfaces 12a, 12b extend all the way to the second proximal end 11b. The toothed surfaces 12a, 12b are connected by a curved circumferential surface of the rack 10, so that the universal rack presents an elliptical cross section.

[0053] For reasons of visibility, the universal rack 10 shown in the figure is shorter than the universal racks in many applications where it is usually used. Typically, universal racks can be up to 10m long. Universal racks can be formed from different materials, and one example is machined cast steel. For reasons of strength and durability, universal racks are usually formed solid without internal cavities, holes, etc. Typically, a 10m long universal rack can weigh up to 1000kg.

[0054] The gearbox 20 comprises a housing 21 having a longitudinal passage 22 for receiving a portion of the universal rack 10. In the example shown, the gearbox comprises eight pinions (not shown) arranged in the housing 21 so that each pinion can mesh with one of the toothed surfaces 12a, 12b of the universal rack 10. Here, four pinions mesh with each of the toothed surfaces 12a, 12b. Each pinion is connected to a corresponding main gear 23 via a shaft 24 and a rotationally compliant device 25. The main gears 23 are arranged so that two main gears 23 connected to the corresponding pinions meshing with the first toothed side 12a and two main gears 23 connected to the corresponding pinions meshing with the second toothed side 12b mesh together with the same auxiliary gear (not shown). The gearbox 20 thus comprises two secondary gears. Each secondary gear is also connected to a tertiary gear 26 via a corresponding shaft 27. The two tertiary gears 26 mesh with a common tertiary gear (not shown), which in turn is connected to a single output shaft or input shaft (not shown) of a rack and pinion drive. In the example shown, where the device can be used as a linear actuator or a lifting device, the tertiary gear is connected to an input shaft (not shown) which in turn is connected to an electric motor (not shown).

[0055] In order to enhance the load distribution between the cog flanks of the pinion and gear that are simultaneously engaged during torque transmission, the gearbox 20 includes means for providing rotational compliance. In the example shown, this is achieved by connecting each pinion with the corresponding main gear 23 by means of a rotationally compliant device 25. Each rotationally compliant device is fixed to a corresponding shaft 24 and the main gear 23. Each rotationally compliant device 25 also includes an elastically deformable fixing device (not shown) that allows limited relative rotation between the main gear 23 and the pinion.

[0056] A known rack and pinion drive comprising a plurality of compliance devices as described above is disclosed in EP 2 2 921 694 B1 and will not be described in further detail here.

[0057] The clamp assembly 30 comprises a second rack forming an auxiliary rack 31. The auxiliary rack 31 extends longitudinally from a first end 32a to a second end 32b. When the clamp assembly 30 is in use, the first end 32b will face the proximal end 11b of the universal rack 10. The auxiliary rack 31 presents a first planar toothed surface 33a and a second planar toothed surface 33b arranged opposite to the first toothed surface 33a. The first toothed surface 33a and the second toothed surface 33b extend substantially over the entire length of the universal rack 10, in particular, both toothed surfaces 33a, 33b extend all the way to the first end 32a. The toothed surfaces 33a, 33b are connected by a curved circumferential surface of the auxiliary rack 31, so that the universal rack 31 presents an elliptical cross-section similar to the cross-sectional geometry of the universal rack 10.

[0058] The tooth geometry of the first toothed surface 33a and the second toothed surface 33b is similar to the tooth geometry of the universal rack 10. In applications where the clamp assembly 30 will mesh with a pinion in the gearbox 20 during calibration of the rack and pinion arrangement, it is important that the tooth geometry of the auxiliary rack is nearly identical to the tooth geometry of the universal rack used under normal operation. In cases where the universal rack used in normal operation is also used for calibration, and where the auxiliary rack is used, for example, in transportation of the rack and pinion arrangement, it may be sufficient that the tooth geometry of the auxiliary rack is substantially similar to the tooth geometry of the universal rack. Also in this case, the auxiliary rack meshing with the pinion during transportation will be able to maintain the nominal relative rotation between the pinion and the main gear and the pretensioning of the elastically deformable compliant member achieved by calibration.

[0059] Typically, the auxiliary rack 31 can be much shorter than the universal rack 10. Typically, it is sufficient that the auxiliary rack 31 is slightly longer than the longitudinal length of the gearbox 20. In addition, since the auxiliary rack is not intended to be exposed to any significant loads that may occur during normal operation, the auxiliary rack can be formed from a lighter and cheaper material that is weaker, less sustainable and therefore has lower performance than a universal rack.

[0060] The auxiliary rack 31 has a central hole 34 extending from a first end 32a to a second end 32b of the auxiliary rack 31. The central hole 34 presents a central portion 34a having a first diameter and two end portions 34b arranged at respective ends 32a, 32b of the auxiliary rack 31. The diameter of the end portions 34b is slightly larger than the diameter of the central portion 34b, so that an outwardly facing annular stop surface 34c is formed near each end portion 32a, 32b of the auxiliary rack 31.

[0061] The clamp assembly 30 also comprises coupling means for connecting the auxiliary rack 31 to the universal rack 10. The coupling means comprises guide means which, in the example shown, comprise bushings 40. The coupling means also comprises a rod 50 and a tensioning device 60.

[0062] The bushing 40 has a first cylindrical portion 41 which is received in a close-fitting state in that end portion 34b of the hole arranged at the first end 32a of the auxiliary rack 31. The first cylindrical portion 41 has a central internally threaded recess 41a facing the second end 32b of the auxiliary rack 31. A second cylindrical portion 42 having a smaller diameter extends axially from the first cylindrical portion 41 and is received in a close-fitting state in a cylindrical recess 13 arranged in the proximal end 11b of the universal rack 10. A third cylindrical portion 43 having an external thread extends axially from the free end of the second cylindrical portion 42 and is threadedly engaged in an internally threaded recess 14 extending axially from the bottom of the cylindrical recess 13 in the universal rack 10.

[0063] The rod 50 is received in the hole 34 and has a first rod end 51a arranged near the first end 32a of the auxiliary rack 31 and a second rod end 51b extending through the second end 32b of the auxiliary rack 31. The first rod end 51a has an axial internal threaded recess 52, and the second rod end 51b has an external thread. The rod 50 is connected to the bushing 40 by means of a threaded joint. More precisely, in the example shown, the first rod end 51a is connected to the bushing 40 by an external threaded fixing member 55, which is threadedly engaged in the recess 41a of the bushing and is threadedly engaged with the recess 52 in the first rod end 51a.

[0064] The tensioning device 60 also includes a threaded joint. In the example shown, the tensioning device 60 includes a stop member 61 in the form of an internally threaded nut, which is threadedly engaged with the external thread on the second rod end 51b. The stop member 61 is axially supported by the end surface of the second end 32b of the auxiliary rack 30. In the example shown, a washer 62 is arranged between the stop member 61 and the end surface. Two additional nuts 63, 64 are threaded onto the threaded second rod end 51 and interlock with each other to allow the rod 50 to be rotated by a wrench or similar tool engaging either or both of the additional nuts 63, 64.

[0065] In the example shown, the clamp assembly also includes an alignment collar 70, which can be used to align the planar toothed surfaces 33a, 33b of the auxiliary rack 31 with the planar toothed surfaces 12a, 12b of the universal rack during the fixing of the auxiliary rack 31 to the universal rack 10. The alignment collar includes an upper half 71 and a lower half 72, each half presenting a corresponding inner planar toothed surface 71a, 72a. The upper half 71 and the lower half 72 can be fixed to each other by fastening means (such as screws, etc.) not shown.

[0066] When the universal rack 10 mounted to engage with the pinion of the rack and pinion drive arrangement is replaced by the auxiliary rack, the universal rack 10 is first linearly displaced so that the proximal end 11b protrudes accessible from the gear box 20. The second cylindrical portion 43 of the bushing 40 is then screwed into the threaded recess 14 at the proximal end 11b of the universal rack 10. Thereby, the bushing 40 is fixed to the universal rack 10 in such a manner that its first cylindrical portion 41 extends axially from the proximal end 11b. Thereafter, the first end 32a of the auxiliary rack 31 is positioned face to face with the proximal end 11b of the auxiliary rack 10 so that they are longitudinally aligned and rotationally oriented so that each planar toothed surface 33a, 33b of the auxiliary rack 31 is coplanar with the corresponding toothed surface 12a, 12b of the universal rack 10. To facilitate this operation, the inner planar toothed surfaces 71a, 72a of the alignment collar 70 may engage the first and second toothed surfaces 12a, 33a, 12b, 33b of the universal and auxiliary racks, respectively, and then the two alignment collar halves 71, 72 may be fastened together.

[0067] When the auxiliary rack 31 has been thus positioned relative to the universal rack 10 , the first cylindrical portion 41 of the bushing 40 is received in the end 34 b of the hole 34 .

[0068] Thereafter or before, the rod 50 can be prepared by screwing the fixing member 55 into the recess 52 at the first rod end 51a. The rod 50 can then be inserted into the hole 34 from the second end 32b of the auxiliary rack and linearly displaced until the first rod end 51a reaches the bushing 40. To facilitate this insertion, an annular spacing member 57 for receiving the rod 50 can first be inserted into the hole 34. In the example shown, two such spacing members 57 have been inserted into the hole 34 in a close-fitting state, one at each transition from the central hole portion 34a of the hole 34 to the corresponding end 34b. In this way, each spacing member 57 is supported radially and in the corresponding axial direction.

[0069] Thereafter, the rod 50 can be fixed to the bushing 40 by rotating the rod so that the free end of the fixing member 55 is screwed into the threaded recess 41a of the first cylindrical portion 41 of the bushing 40. When the rod 50 has been firmly fixed to the bushing 40, the rod 50 can be axially tensioned by tightening the stop member 61 so that the washer 62 is clamped between the stop member 61 and the end surface of the second end 32b of the auxiliary rod 31. This tensioning of the rod 50 causes the first end 32a of the auxiliary rack to be forced into contact with the end surface of the proximal end of the universal rack 10. At the same time, the auxiliary rack 31 is radially fixed relative to the universal rack 10 by means of the bushing 40, which is threadedly fixed to the universal rack and received in the hole 34 of the auxiliary rack in a close-fitting state. In this way, the auxiliary rack 31 has been rigidly and firmly fixed to the universal rack 10, and the alignment ring 70 can then be removed.

[0070] After such fixing, the universal rack 10 and the auxiliary rack 31 can be jointly linearly displaced until the universal rack is removed from the gearbox housing 21 and the auxiliary rack 31 is meshedly engaged with the pinion of the gearbox 20 .

[0071] The universal rack 10 can then be disconnected from the auxiliary rack by rotating the rod 50 so that the fixing member 55 disengages the bushing 40, which allows the universal rack 10 to be removed. Thereafter, the bushing 40 can be unscrewed from the proximal end 11b of the universal rack 10.

[0072] like Figure 4 As shown, the clamp assembly may also include one or more shims 58 that may be inserted between the end surface of the proximal end 11b of the universal rack 10 and the end surface of the first end 32a of the auxiliary rack 31. Such shims 58 may be used to determine the correct tooth geometry, in particular the correct tooth pitch, at the junction between the universal rack 10 and the auxiliary rack 31. Depending on the tolerances of the machined surfaces of the universal rack and the auxiliary rack and the bushing 40, any suitable number of shims may be inserted to achieve the correct distance between adjacent teeth at the junction between the two racks 10, 31.

[0073] Various aspects of the present disclosure are described above mainly with reference to several embodiments and examples thereof. However, as will be readily appreciated by those skilled in the art, other embodiments than those disclosed above are equally possible within the scope of the present disclosure as defined by the attached patent claims. For example, the threaded joints described above may be reversed so that the internal threads are replaced by external threads, and vice versa. In addition, where applicable, other fastening devices other than threaded joints may be used, such as bayonet couplings and the like. Naturally, the rack and pinion drive may be constructed in many other ways than those shown in the figures and disclosed above. The gearbox may, for example, be provided with any suitable number of pinions, such as 2, 4, 6, 10 or 12, and a corresponding number of main gears. The methods and fixture assemblies disclosed herein may find advantageous application in many different such rack and pinion drives, particularly if they are overdetermined and include means for achieving rotational compliance between the pinions and the corresponding main gears.

Claims

1. A method of replacing a rack of a rack and pinion drive device, the device comprising a first rack (10) and a gearbox (20), the gearbox (20) comprising a plurality of pinions arranged to mesh with the first rack (10), the pinions being connected to respective main gears (23) via rotationally compliant means (25), the method comprising: - providing a rack and pinion drive having a first rack (10) mounted in meshing engagement with a pinion of the gearbox (20), - providing a clamp assembly (30), said clamp assembly (30) comprising a second rack (31) and a coupling device (40, 50, 60), - arranging the second rack (31) to be longitudinally coaxially aligned with the first rack (10), - connecting the first end (32a) of the second rack (31) to the proximal end (11b) of the first rack (10) by means of the coupling means (40, 50, 60), - meshing engagement of the second rack (31) with the pinion of the gearbox (20) by linear displacement of the first rack (10) and the second rack (31), and - disconnecting the first rack (10) from the second rack (31), the method further comprising: - When the first rack (10) or the second rack (31) is in meshing engagement with a pinion of the gearbox (20), the nominal rotational position between each pinion and the main gear (23) is calibrated.

2. A method according to claim 1, comprising arranging at least one toothed surface (33a, 33b) of the second rack (31) in coplanar alignment with a corresponding toothed surface (12a, 12b) of the first rack (10).

3. The method according to claim 1 or 2 includes inserting at least one spacing member (58) between the first end (32a) of the second rack (31) and the proximal end (11b) of the first rack (10) for adjusting the spacing between the outermost teeth at the first end (32a) and the outermost teeth at the proximal end (11b).

4. The method according to any one of claims 1 to 3, wherein: The coupling means comprises a rod (50) extending longitudinally through the second rack (31) in a hole (34), and wherein the method comprises connecting the rod (50) to the proximal end (11b) and longitudinally tensioning the rod (50) to press the first end (32a) towards the proximal end (11b).

5. The method according to any one of claims 1 to 4, wherein: By rotating the input shaft or the output shaft of the gear box (20), the second rack (31) is meshed with the pinion of the gear box (20) through linear displacement of the first rack (10) and the second rack (31).

6. A fixture assembly (30) for replacing a rack of a rack and pinion drive device, the device comprising a first rack (10) and a gear box (20), the gear box (20) comprising a plurality of pinions arranged to mesh with the first rack (10), the pinions being connected to respective main gears (23) via rotationally compliant means (25), the fixture assembly (30) comprising: - a second rack (31) arranged to mesh with the pinion of the gearbox and extending from a first end (32a) to a second end (32b); and - coupling means (40, 50, 60) for releasably connecting the first end (32a) of the second rack (31) to the proximal end (11b) of the first rack (10), the coupling means (40, 50, 60) comprising: a guide device arranged to keep the second rack (31) longitudinally coaxially aligned with the first rack (10), a rod (50) extending through a longitudinal hole (34) in the second rack (31) and having a first rod end (51a) connectable to the proximal end (11b) of the first rack (10), A tensioning device (60) connectable to the rod (50) and arranged to engage the second rack (31) for tensioning the rod (50) thereby pressing the first end (32a) towards the proximal end (11b).

7. The clamp assembly according to claim 6 further includes at least one spacing member (58), and the at least one spacing member (58) is arranged to be between the first end (32a) of the second rack (31) and the proximal end (11b) of the first rack (10) when the second rack (10) is connected to the first rack (31).

8. The clamp assembly according to claim 6, wherein: The guide means comprises a bushing (40) which is radially and guidingly received in the hole (34) at the first end (32a) and is arranged to connect the rod (50) to the proximal end (11b).

9. The clamp assembly according to claim 6, wherein: The bushing (40) includes a first portion (41) received in the bore (34) by a transition fit, a clearance fit, or an interference fit.

10. The clamp assembly according to claim 8 or 9, wherein: The bushing (40) comprises an external thread or an internal thread arranged to form a threaded engagement with a corresponding thread arranged at the proximal end (11b) of the first rack (10).

11. The clamp assembly according to claim 10, wherein: The bushing (40) includes an externally threaded portion (43) that protrudes longitudinally from the first end (32a) of the second rack (31).

12. The clamp assembly according to any one of claims 6 to 11, wherein: The tensioning device (60) includes a first threaded joint.

13. The clamp assembly according to claim 12, wherein: The first threaded joint comprises an external thread arranged at the second rod end (51b) of the rod (50) and a stop member (61), the stop member having a corresponding internal thread and a stop surface, the stop surface being arranged to be supported by an end surface arranged at the second end (32b) of the second rack (31).

14. The clamp assembly according to any one of claims 1 to 13, further comprising at least one annular support member (57) arranged to be received in the aperture (34) and supportingly receive the rod (50).

15. The clamp assembly according to any one of claims 1 to 14, wherein: The rod (50) can be fixed to the bushing (40) by a second threaded joint.

16. A rack and pinion drive device, comprising a first rack (10) and a gear box (20), wherein the gear box (20) comprises a plurality of pinions, wherein the plurality of pinions are arranged to mesh with the first rack (10), and the pinions are connected to corresponding main gears (23) via rotationally compliant devices (25), and the rack and pinion drive device also comprises a clamp assembly according to any one of claims 6-15.

Images