LAMP ASSEMBLY

FIELD OF INVENTION The present invention relates to a lamp assembly for a vehicle, a method of installing such a lamp assembly, a method of manufacturing sets of such lamp assemblies, and to a vehicle comprising such a lamp assembly.

The invention has been developed primarily for use with car headlamp assemblies, and will be described with reference to that application. It will be appreciated, however, that the invention may have application with lamp assemblies for other applications such as trucks, buses and motorbikes, and for other types of lamp assemblies such as tail light clusters.

BACKGROUND

In the automotive field, it is desirable to maintain consistent gaps between, for example, lamp assemblies and surrounding bodywork. This has become increasing difficult as bodywork and lamp assembly contours have become more complex.

During initial manufacture of a vehicle such as a car, jigs, templates and alignment tools may be employed to ensure good relative alignment between bodywork and lamp assemblies when the lamp assemblies are installed. A difficulty arises when a lamp assembly subsequently needs to be removed by an owner or mechanic, for example to replace a failed component of the lamp assembly. The owner or mechanic may not have the tools and/or skills to ensure that the lamp assembly is reinstalled with the correct alignment relative to the bodywork. As well as being an aesthetic consideration, a misaligned headlamp may be unsafe or potentially even illegal depending on the resultant direction and spread of light from the re-installed lamp assembly. Further complicating matters, it may be a regulatory requirement that certain components of a vehicle, such as a headlamp assembly or sub-component thereof, be repairable at the roadside. In such cases, it may not be possible to move the vehicle to a fully equipped workshop to make the required repair. This further limits the ability of the user or mechanic to ensure that the headlamp is reinstalled in the correct position relative to the surrounding bodywork. l SUMMARY

In accordance with a first aspect of the invention, there is provided a lamp assembly for installation in or on a vehicle, the lamp assembly comprising:

a housing for at least one lamp;

a first bracket on the housing; and

a second bracket releasably attached to the first bracket;

wherein the first and second brackets are configured such that:

a final position of the lamp assembly relative to the bodywork can be fixed using the second bracket; and

subsequently detaching the second bracket from the first bracket allows removal of the lamp assembly from the bodywork.

The lamp assembly may comprise a first locating feature on the housing for locating a first portion of the housing relative to bodywork of a vehicle and wherein during manufacture of the vehicle, an initial position of the lamp assembly relative to the bodywork can be established using the first locating feature, and then a final position of the lamp assembly relative to the bodywork can be fixed using the second bracket.

In accordance with a second aspect of the invention, there is provided a lamp assembly for installation in or on a vehicle, the lamp assembly comprising:

a housing for at least one lamp;

a first locating feature on the housing for locating a first portion of the housing relative to bodywork of a vehicle; a first bracket on the housing; and

a second bracket releasably attached to the first bracket;

wherein the first and second brackets are configured such that:

during manufacture of the vehicle, an initial position of the lamp assembly relative to the bodywork can be established using the first locating feature, and then a final position of the lamp assembly relative to the bodywork can be fixed using the second bracket; and

subsequently detaching the second bracket from the first bracket allows removal of the lamp assembly from the bodywork.

The first locating feature may be configured to cooperate with a complementary locating feature on the bodywork. The first locating feature may be a pin and the complementary locating feature may be a recess or aperture for receiving the pin. The first locating feature may be configured to locate the lamp assembly relative to the bodywork of the vehicle at a first point such that the lamp assembly remains moveable in at least one axis relative to the bodywork until fixed using the second bracket.

The lamp assembly may comprise a second locating feature on the housing for locating a second portion of the lamp assembly relative to the bodywork.

The second locating feature may be releasably attached to an intermediate bracket, the intermediate bracket being configured to be attached to the bodywork of the vehicle during installation of the lamp assembly on or in the vehicle.

The first locating feature and the second locating feature may be configured to locate the lamp assembly relative to the bodywork of the vehicle during installation, such that the lamp assembly remains moveable in at least one axis relative to the bodywork until fixed using the second bracket.

A position of the second bracket relative to the first bracket may be fixed by way of complementary bracket-locating features on the first and second brackets respectively. The complementary bracket-locating features may comprise a bracket-locating pin and a complementary bracket-locating aperture or recess for receiving the locating pin.

In accordance with a further aspect of the invention, there is provided a method of installing a lamp assembly according to the second aspect onto or into a vehicle, the method comprising:

positioning the lamp assembly such that the first locating feature locates a first portion of the lamp assembly relative to bodywork of the vehicle;

adjusting a position of the lamp assembly until the lamp assembly is in a final position while the first portion remains located relative to the bodywork by the first locating feature; and

fixing the second bracket to the bodywork, thereby to lock the lamp assembly in the final position.

In accordance with another aspect of the invention, there is provided a method of manufacturing sets of lamp assemblies, comprising: manufacturing a first set of the lamp assemblies in which relative positions of complementary bracket-locating features are selected based on an estimated installation position of each lamp assembly relative to the bodywork;

for at least a plurality of the first set of lamp assemblies, measuring actual installation positions of each lamp assembly relative to the bodywork;

determining a variance between the estimated installation position and the measured actual installation positions; and

using the determined variance to adjust the relative positions of the complementary bracket-locating features for manufacturing a second set of the lamp assemblies, such that the average actual installation positions of the lamp assemblies relative to the bodywork for the second set is improved relative to the first set.

In accordance with a fourth aspect of the invention, there is provided a vehicle comprising a lamp assembly according to the first or second aspect.

Fewer disassembly steps may be required to allow access to the first bracket for removal of the lamp assembly from the vehicle compared with the number of steps required to allow access to the second bracket. BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a lamp assembly according to the invention;

Fig. 2 is a plan view of the lamp assembly of Fig. 1 ; Fig. 3 is a detailed front elevation of a vehicle in the form of a car, showing a lamp assembly receptacle in the bodywork of the car for receiving the lamp assembly of Fig. 1 ;

Fig. 4 is a detailed front elevation of the car of Fig. 3, showing installation of the lamp assembly of Fig. 1 in the lamp assembly receptacle;

Figs 5A to 5C are sectional and underside views of portions of first and second brackets for use with a lamp assembly according to the invention; Fig. 6 is a perspective view of an alternative lamp assembly according to the invention;

Fig. 7 is a front elevation of the lamp assembly of Fig. 6; Fig. 8 is a plan view of the lamp assembly of Fig. 6; Fig. 9 is a detailed perspective view of the lamp assembly of Fig. 6;

Fig. 10 is a detailed side/rear perspective view of a portion of the lamp assembly of

Fig. 6;

Fig. 1 1 is a detailed underside perspective view of a portion of a vehicle in the form of a car showing an installation position of the lamp assembly of Fig. 6; Fig. 12 is a front perspective view of the portion of the car shown in Fig. 1 1 showing an installation position of the lamp assembly of Fig. 6.

Fig. 13 is a plan view of the portion of the car shown in Fig. 12;

Fig. 1 is a section taken through an intermediate bracket and a second ball pin;

Fig. 15 is a flowchart showing a method of installing a lamp assembly, such as the lamp assembly of Fig. 1 or Fig. 6, according to the invention;

Fig. 16 is a flowchart showing a method of manufacturing sets of lamp assemblies, according to the invention; and

Fig. 17 is a side elevation of a vehicle in the form of a car, comprising lamp assemblies according to the invention. DETAILED DESCRIPTION

Referring to Figs 1 and 2, a lamp assembly 100 includes a housing 102. The lamp assembly 100 is a composite component that is installed as a single unit in a car as described in detail below. The housing 102 comprises, in this case, a high beam lamp 104, a low beam lamp 106 and an indicator lamp 108. Other combinations of one or more lamps may be provided in other embodiments. As best shown in Fig. 2, a first locating feature in the form of a first ball pin 1 10 is provided on a first portion 1 12 of the lamp assembly 100. The first ball pin 1 10 extends, when installed, rearwardly from the first portion 1 12. The first ball pin 1 10 is tapered to assist in the installation process described below. A first bracket 1 14 is provided on the housing 102. The first bracket 1 14 extends, when installed, from the housing 102 towards an axial centre line of the car.

A second bracket 1 16 includes a bracket aperture 1 17. The second bracket 1 16 is releasably attached to the first bracket 1 14 by way of a bolt 1 18 that passes through an aperture (not shown) in the first bracket and screws into a threaded aperture (not shown) in the second bracket 1 16.

The skilled person will appreciate that wherever bolts and threaded apertures are mentioned, any other suitable fixture can be used instead (or as well). For example, a bolt may be used with a corresponding nut instead of relying on a threaded aperture. A self tapping screw or bolt may be used. Clamps or other mechanical fixtures may be used. In the case of mounting the second bracket 1 16 to the bodywork, a more permanent fixing method may be employed if it is deemed unnecessary for the second bracket to be removed after installation. The more permanent fixing method can include, for example, bonding or welding.

The skilled person will also appreciate that shims, washers, packers, spacers, locknuts or other additional components may be used with any bolt, nut, screw or other fixture. This can be for the purpose of adjusting an installation position of the lamp assembly and/or to prevent loosening or movement of the fixtures over time.

Installation of the lamp assembly 100 of Figs 1 and 2 during manufacture of a vehicle in the form of a car 120 will now be described with reference to Fig. 3, which shows a receptacle 122 formed in bodywork 124 of the car 120. The receptacle 122 is sized and shaped to receive the housing 102 of the lamp assembly 100. A complementary locating feature in the form of a first aperture 126 for receiving the first ball pin 1 10 is positioned within the receptacle 122 as shown in Fig. 3. A first mounting point in the form of a first threaded aperture 128 is provided within the receptacle 122, as also shown in Fig. 3. During manufacture of the car 120, an initial position of the assembly 100 relative to the bodywork 124 is established using the first ball pin 1 10. This is achieved by pushing the first portion 1 12 of the lamp assembly 100 into the receptacle 122 until the first ball pin 1 10 initially engages and is then seated within the first aperture 126. As shown in Fig. 4, this holds the first portion 1 12 in approximately the correct position. The end of the assembly 100 adjacent the first bracket 1 14 can then be moved slightly in at least one axis to allow the final position of the lamp assembly 100 as a whole to be adjusted before being fixed in place. As shown in Fig. 4, the adjustment may be vertical as indicated by double-headed arrow 129, that is, about a lateral (relative to the car) horizontal axis through the first aperture 126. Once the lamp assembly 100 is in the final position, that position is fixed by bolting the second bracket 1 16 to the first threaded aperture 128 with a bolt 131 . The adjustment can be enabled by, for example, making the bracket aperture 1 17 larger than the diameter of the bolt 131 in the direction(s) in which adjustment is desired. If two- dimensional adjustment is required the bracket aperture may be round and larger than the diameter of the bolt 131 . If one-dimensional adjustment is required the bracket aperture may be a slot only slightly wider than the diameter of the bolt 131 . Other aperture shapes may be used. In other embodiments, the cross-sectional shape of the pin can be adjusted to achieve similar outcomes.

The final position of the lamp assembly 100 can be determined in any suitable way, such as by measurement and/or with a suitable jig or template. In one embodiment, further components, such as a grill 130 (dotted line) as shown in Fig. 4, are added until assembly of the car 120 is complete.

If the lamp assembly 100 must be removed to allow inspection, service or repair of any of its components, a technician or other user can loosen the bolt 1 18 holding the first bracket 1 14 to the second bracket 1 16. The second bracket 1 16 stays bolted to the first threaded aperture 128, while the first bracket 1 14 remains with the housing 102. The lamp assembly 100 can then be pulled forward to disengage the first ball pin 1 10 from the first aperture 126, enabling the lamp assembly 100 to be removed from the car 120.

A potential advantage of at least the illustrated embodiment is that it is not necessary to remove the grill 130 to access bolt 131 to remove the lamp assembly 100, because the bolt 1 18 holding the first bracket 1 14 to the second bracket 1 16 is accessible from behind the grill 130 when the car's bonnet/hood (not shown) is open. More generally, in other embodiments, accessing the bolt 1 18 (or any other releasable fixture used) may require removal of fewer components to access it than must be removed to access the bolt 131 . Reinstalling the lamp assembly 100 is the reverse of the original installation process described above, except that instead of bolting the second bracket 1 16 to the first threaded aperture 128, the first bracket 1 14 is reattached to the second bracket 1 16. Because the second bracket 1 16 remains fixed in place throughout the removal and re-installation process, the lamp assembly 100 is automatically re-installed with the correct alignment.

The method of installing the lamp assembly 100 of Figs 1 and 2 into a vehicle such as a car will now be described with reference to Fig. 15. The method includes positioning 144 the lamp assembly 100 such that the first locating feature (such as the ball pin 1 10) locates a first portion of the lamp assembly 100 relative to the bodywork 124 of the vehicle. A position of the lamp assembly 100 is adjusted 146 until the lamp assembly 100 is in a final position while the first portion remains located relative to the bodywork 124 by the first ball pin 1 10. The second bracket 1 16 is then fixed to the bodywork 124, thereby to lock 148 the lamp assembly 100 in the final position.

To further improve alignment of the lamp assembly 100, a position of the second bracket 1 16 relative to the first bracket 1 14 may optionally be fixed by way of complementary bracket-locating features on the first and second brackets respectively. For example, one of the first and second brackets may include a bracket-locating pin, and the other of the first and second brackets may include a complementary bracket-locating aperture or recess for receiving the bracket-locating pin 132. Fig 5A, for example, shows a detailed cross section of the first bracket 1 14 and the second bracket 1 16 prior to them being joined. The first bracket 1 14 includes a bracket-locating pin 132. In this embodiment, the bracket-locating pin 132 is tapered to assist in bringing together the first and second brackets during assembly, but the taper is optional. The second bracket 1 16 includes a bracket-locating aperture 134 that is sized and shaped to be an interference fit with the bracket-locating pin 132.

As shown in Fig. 5B, when the first bracket 1 14 is assembled with the second bracket 1 16, the bracket-locating pin 132 engages the bracket-locating aperture 134. The bolt 1 18 is then used to hold the first and second brackets together.

It will be appreciated that the bracket-locating features may take a different form to the bracket-locating pin 132 and bracket-locating aperture 134 of Figs 5A to 5C. For example, the pin and/or aperture may be of different shapes in plan as compared with the examples shown in Figs 5A to 5C. Instead of a bracket-locating aperture 134, there may be provided a blind recess for the bracket-locating pin 132 to engage. Instead of a pin and aperture, complementary formations may be formed on the first and second brackets, such as on one or more bosses on one bracket that engage with spaces between bosses on the other bracket. Further aspects are described below in relation to the method of Fig. 16. In other embodiments, one or more additional locating features, first and second brackets pairs, and/or ordinary brackets may be employed. Referring to Figs 6 to 14, in which reference numerals from Figs 1 to 4 are used to indicate like features, there is shown an embodiment in which a second locating feature in the form of a second ball pin 136 is provided on the housing 102. As best shown in Fig. 10, the second ball pin 136 extends, when installed, rearwardly from the housing 102 at point lower than, and forward from, the first ball pin 1 10.

As shown in Fig. 14, the lamp assembly 100 in this embodiment includes an intermediate bracket 150 that includes a second aperture 138 for receiving the second ball pin 136. In this embodiment, the second aperture 138 includes a resilient insert 156 that is sized and configured to maintain an interference fit with the second ball pin 136. The intermediate bracket 150 also includes a mounting aperture 152, enabling it to be mounted to the car 120 during installation of the lamp assembly 100, as described below. Typically, the intermediate bracket 150 is preinstalled on the second ball pin 136 prior to installation of the lamp assembly 100 in a car, but this is optional.

The first aperture 126 may also include a resilient insert (not shown) similar to the resilient insert 156.

The process for installing the lamp assembly of Figs 6 to 10 during manufacture of the car is similar to that described in relation to the embodiment of Figs 1 to 4. The first portion 1 12 of the lamp assembly 100 is pushed into the receptacle 122 until the first ball pin 1 10 initially engages and is then seated within the first aperture 126 (or within a resilient insert if provided). This accurately locates the first portion 1 12 of the lamp assembly 100 relative to the adjacent bodywork 124. A position of the lamp assembly 100 can still, however, be adjusted by pivoting or rotating the lamp assembly 100 relative to the first ball pin 1 10This allows final positioning of the lamp assembly 100 as a whole before the lamp assembly 100 is fixed in place. The final position of the lamp assembly 100 can be determined, and that position fixed, as described above in relation to the embodiment of Figs 1 to 4. The main difference is that in the Figs 6 to 10 embodiment, the intermediate bracket 150 needs to be attached to the bodywork 124. There may be some scope for aligning the lamp assembly 100 prior to fixing the intermediate bracket 150 in place. For example, the rotational position of the lamp assembly 100 relative to the first ball pin 1 10 may be established and then locked in by attaching the intermediate bracket 150 to the bodywork 124 by using a bolt 154 through the mounting aperture 152. Typically, this is done prior to attachment of the second bracket 1 16 to the bodywork 124.

Removal and reinstallation similarly follow the method described above in relation to the embodiment of Figs 1 to 4, except that both the first and second ball pins are removed from their respective apertures. This means that it is not necessary to detach the intermediate bracket 150 from the bodywork 124 to remove the lamp assembly 100. Upon reinstallation, once both the first and second balls pins are seated in their respective apertures and the first bracket 1 14 is reattached to the second bracket 1 16 by the bolt 1 18, the lamp assembly 100 is positioned exactly as it was when the car left the factory, without the need for special alignment tools, templates or jigs.

It will be appreciated that the first locating feature (and the second and any additional locating feature(s), where provided) need not be a ball pin, and can instead take any other suitable form. The main requirement for this feature is that it accurately positions an adjacent portion of the lamp assembly 100 relative to the bodywork 124, while allowing subsequent adjustment of the lamp assembly 100 to a final position. To this end, the (or each, where more than one is provided) locating feature may comprise a bracket, tongue, rib, boss, bolt, pin, recess, aperture or any other formation, designed to engage a corresponding feature or features on the bodywork 124 of the car to which the lamp assembly is to be installed. The (or each) locating feature may initially locate an adjacent portion of the lamp assembly such that it constrains the position of the adjacent portion of the lamp assembly 100 in one or more dimensions. For example, a first locating feature (and corresponding feature on the car) may constrain the adjacent portion of the lamp assembly in a horizontal direction relative to the car, while a second locating feature (and corresponding feature on the car) may constrain the adjacent portion of the lamp assembly so as to constrain a rotational position of the lamp assembly 100 relative to the car. Where several locating features are provided, they may constrain adjacent portions of the lamp assembly 100 in the same manner or a different manner. Depending on the embodiment and desired installation process, the locating feature(s) may locate the adjacent portion(s) of the lamp assembly in translation and/or rotation. Further advantages may be achieved by using a method of manufacturing sets of the lamp assemblies. Referring to Fig. 16, the method comprises manufacturing 138 a first set of lamp assemblies in which relative positions of the complementary bracket-locating features are selected based on an estimated installation position of the lamp assembly 100 relative to the bodywork 124. The relative positions of the complementary bracket-locating features, such as the bracket-locating pin 132 and the bracket-locating aperture 134 described in relation to Figs 5A to 5C, define the precise position of the second bracket 1 16 relative to the first bracket 1 14 when the two brackets are fastened together. The installation position may be estimated by modelling the first and second brackets, and the bodywork 124 and fixing points to which they will be fitted, and/or by prototyping.

As well as establishing the relative position of the first and second brackets, the bracket- locating features may also effectively position the lamp assembly 100 relative to the car along or around an axis. For example, in the embodiment of Figs 5A to 5C, the position of the pin 132 on the first bracket 1 14 effectively only defines a position of the lamp assembly 100 relative to the car along the longitudinal (ie, front to back) axis of the car. This is because, in use, the position at which the second bracket 1 16 is fixed to the bodywork 124 is adjustable vertically and laterally. The exact positions of the bracket-locating pin 132 and bracket-locating aperture 134 therefore have limited impact on the vertical and lateral installation positions of the lamp assembly 100 relative to the bodywork 124, because these positions can be adjusted by changing where the second bracket 1 16 is attached to the bodywork. In contrast, unless some form of shim or spacer is used, the longitudinal positionof the second bracket 1 16 (and therefore the lamp assembly 100) relative to the car cannot easily be adjusted.

At least some of the first set of lamp assemblies are installed during the manufacture of a series of cars. After installation, actual installation positions of each lamp assembly 100 relative to the bodywork 124 are measured 140. The measurements may, for example, relate to one or more degrees of freedom that do not correspond with a degree of freedom (such as an axis or plane) along or about which the lamp assembly 100 can be adjusted prior to fixing it in place via the second bracket 1 16. For example, the measurements may be in relation to the longitudinal position of the lamp assembly 100 relative to the car, which cannot easily or repeatably be adjusted by altering an installation position of the second bracket 1 16 relative to the car (other than by using shims or spacers, or physically modifying the brackets themselves). The measurements may be taken by, for example, measuring gaps and/or angles of each installed lamp assembly relative to the adjacent bodywork. This may be done immediately after installation, or later. As with the initial installation, jigs or templates can be used to assist in this process.

Next, a variance between the estimated installation position and the measured actual installation positions is determined 142. This may be done in any suitable way, such as by averaging, or more sophisticated statistical analysis as will be understood by the skilled person.

The determined variance may then be used 143 to adjust the relative positions of the complementary bracket-locating features for manufacturing a second set of the lamp assemblies, such that the average actual installation positions of the lamp assembly 100 relative to the bodywork 124 for the second set is improved relative to the first set.

In the context of the embodiment of Figs 5A to 5C, for example, the determined variance may relate to a longitudinal position of the lamp assembly 100 relative to the bodywork. A position of the bracket-locating pin 132 relative to the first bracket 1 14 may be adjusted based on the determined variance, in one of the directions indicated by arrows 151 . The result of this adjustment is to change the relative position of the first bracket 1 14 and second bracket 1 16 in the longitudinal (when installed in the car) direction when they are assembled together. Alternatively, or in addition, a position of the aperture 134 in the second bracket 1 15 may be moved as required. Of course, if different locating features, such as ribs or bosses are used, their relative locations on the first and second brackets may be changed as required.

The process may be iterated to further improve tolerances, or to ensure that tolerances remain acceptable over a series of production runs.

By feeding back measured installation parameters into the manufacturing process in this manner, closer tolerances can be achieved over a series of production runs. In at least some embodiments, the use of first and second brackets may allow easier removal of the lamp assembly 100 for maintenance or repair. For example, the initial installation of the lamp assembly 100 may take place while certain components of the car 120 have not yet been installed. For example, in Fig. 4 it can be seen that the lamp assembly 100 is installed in that embodiment before the grill 130 (dotted line) is installed. Once the grill 130 is installed, yet other components may be installed that make subsequent removal of the grill 130 more difficult or time-consuming. In that embodiment, it is possible to remove the lamp assembly 100 from the car by accessing the bolt 1 18 vertically from behind the grill 130. This makes removal faster and simpler than having to remove the bolt 131 that attaches the second bracket 1 16 to the car. It will be understood that in other embodiments, the various components of the invention may be designed and configured such that fewer (or easier/shorter) disassembly steps are required to allow access to the first bracket 1 14 compared to the second bracket 1 16. This means that the lamp assembly 100 can be removed more easily than would be the case if it were necessary to access the second bracket 1 16.

The skilled person will appreciate that although the first bracket 1 14 has been described in the specific embodiments as being an element that extends from the housing 102, it can in practice take any form capable of allowing the second bracket 1 16 to be releasably attached to it. The first bracket 1 14 may, for example, take the form of a hole or aperture on or in the housing 102 to which the second bracket 1 16 is fixed with a bolt or screw. The first bracket 1 14 may alternatively take the form of a threaded stud or boss to which the second bracket 1 16 may be attached with a nut. The first bracket may alternatively take the form of a shape or formation to which the second bracket 1 16 may be clamped or otherwise releasably attached. The first bracket 1 14 may be formed integrally with the housing 102 by machining, moulding, additive manufacture, or any combination thereof. The first bracket 1 14 may be formed separately and attached to the housing 102 by an adhesive, clamping, or a physical fixture such as a screw or bolt.

Although the invention has been described with reference to a headlamp assembly, the skilled person will appreciate that the invention also has application in other lamp assemblies, such as, for example, tail light clusters. Similarly, although the invention has been described with reference to cars, the skilled person will appreciate that the invention has application in other vehicles/automobiles, including trucks, buses and motorcycles.

For the avoidance of any doubt, the word "bodywork" is used to denote any aspect of a vehicle's frame, chassis or panels, or intermediate/subsidiary components attached to any of those features, whether or not the features or components form an outwardly visible or aesthetic element of the vehicle. The invention has been described with reference to a number of specific embodiments and implementations. The skilled person will appreciate that the claimed invention may be embodied in many other embodiments and implementations.