Patent Description:
The background description provided here is for the purpose of generally presenting the context of the disclosure.

Early engine oil filters had a permanent housing containing a replaceable filter. In the mid-<NUM>, a spin-on filter design was introduced that included a self-contained housing and filter assembly that could be unscrewed from an engine block, discarded, and replaced with a new one. Typically, the spin-on filter must be rotated through several turns to assemble or disassemble the spin-on filter to or from the engine block.

More recently, automotive companies have developed filter head assemblies that attach an oil filter to an engine via a bayonet connection and that transport oil between the oil filter and the engine. In contrast to a spin-on filter connection, the bayonet connection enables assembling or disassembling an oil filter to or from an engine with a partial turn. Thus, such filter head assemblies reduce the time and effort required to replace an oil filter.

A filter device comprising a connection head and a replaceable filter unit which are connected by means of a bayonet-type connection device, additionally having a pretensioning element, is described in <CIT>. A similar device having guiding means in order to facilitate the connection between connection head and filter unit is disclosed in <CIT>.

An example of a filter head assembly according to the present disclosure includes a filter head and threaded bayonet connection adapter having a rotational position tolerance improving retainer ring. In one aspect of the invention the filter head is configured to be attached, for example, to an engine block and to enable fluid flow (for example, oil, fuel or other fluids) between, for example, an engine block and a filter connected to the filter head.

The filter head includes a base and a tubular body protruding from the base, the tubular body defining threads. The threaded bayonet connection adapter is configured to connect the filter to the filter head via a bayonet connection. The threaded bayonet connection adapter includes an annular body defining threads configured to engage the threads on the tubular body of the filter head to attach the threaded bayonet connection adapter to the filter head.

The rotational position tolerance improving retainer ring is annular. The rotational position tolerance improving retainer ring is arranged on the tubular body and compressed, preferably elastically compressed, between the filter head and the threaded bayonet connection adapter. Generally, the rotational position tolerance improving retainer ring is deformable, i.e. compressible, in axial direction. Compressing the rotational position tolerance improving retainer ring between the filter head and the threaded bayonet adapter allows (first) tightening the threaded bayonet adapter to a predetermined final assembly torque and (second) further tightening the threaded bayonet adapter until a required final rotational position of the threaded bayonet adapter relative to the filter head is achieved. Thereto, the predetermined final assembly torque may be exceeded to some extent. The compressibility of the rotational position tolerance improving retainer ring allows reaching this final rotational position without overloading the other components (such as the filter head and the bayonet adapter). Further, the compressibility of the rotational position tolerance improving retainer ring limits the amount by which the predetermined final assembly torque is exceeded upon reaching the final rotational position.

In one aspect, the base of the filter head includes a disc-shaped body, and the tubular body protrudes from disc-shaped body along a central axis thereof.

In one aspect, the threads on the filter head are external threads on an outer radial surface of the tubular body, and the threads on the threaded bayonet connection adapter are internal threads on an inner radial surface of the annular body.

In one aspect, the threaded bayonet connection adapter further includes tabs protruding radially outward from the annular body thereof. The tabs are configured to be inserted into corresponding slots in an axial end wall of the oil filter.

In one aspect, the annular body of the threaded bayonet connection adapter includes a first portion having a straight sidewall and a second portion having a curved sidewall. The first portion of the annular body defines the threads on the annular body. The tabs protrude radially outward from an axial end of the second portion of the annular body.

In one aspect, the filter head assembly further includes a spring. Generally, the spring is arranged on the filter head. The spring is configured to bias the oil filter away from the filter head and thereby inhibit rotation of the tabs on the threaded bayonet connection adapter out of the slots in the oil filter.

The spring may be arranged between the threaded bayonet connection adapter and the filter head. The threaded bayonet connection adapter may hold the spring in place relative to the filter head.

In one aspect, the rotational position tolerance improving retainer ring is configured to be assembled between the bayonet connector and the filter head and to hold the spring in place relative to the filter head.

In one aspect, the spring includes straight segments disposed in a common plane and U-shaped segments joining the straight segments to one another and protruding out of the plane. The straight segments of the spring are configured to be clamped between the retainer ring and the filter head, and the U-shaped segments of the spring are configured to apply a biasing force to the axial end wall of the oil filter urging the oil filter away from the filter head. Preferably, the straight segments are held clamped between the rotational position tolerance improving retainer ring and the filter head.

In one aspect, the rotational position tolerance improving retainer ring is made of aluminum, brass, copper, or combinations thereof.

In one aspect, the rotational position tolerance improving retainer ring is configured to deform under a compression load applied to the threaded bayonet connection adapter when the threaded bayonet connection adapter is rotated on the tubular body and tightened onto the filter head to a predetermined final assembly torque. In other words, the rotational position tolerance improving retainer ring is configured to advantageously deform under a load applied by the threaded bayonet connection adapter when the threaded bayonet connection adapter is tightened onto the filter head to at least a predetermined final assembly torque. Preferably, upon reaching the predetermined final assembly torque, the rotational position tolerance improving retainer ring is configured to permit further rotation by further deformation at an applied torque in a region near the predetermined final assembly torque so as to permit further rotation to provide rotational alignment of the threaded bayonet connection adapter to a required rotational position on the filter head. In other words, the rotational position tolerance improving retainer ring is configured to be further deformable to permit required further rotation beyond the predetermined final assembly torque to align the threaded bayonet connection adapter to a required rotational position on the filter head, in particular such that open and locked position indications on the filter head agree with the actual open and locked positions of the filter element (the oil filter) on the filter head. This enhances correct operation of the open and locked position indicators on the filter head.

In one aspect, the rotational position tolerance improving retainer ring includes an axial top end face and an axial bottom end face. A plurality of deformable radially extending axial projections are formed on the axial top end face, the axial bottom end face; or on both of the axial top end face the axial bottom end face. The axial projections project axially outwardly away from the rotational position tolerance improving retainer ring.

In one aspect, the rotational position tolerance improving retainer ring has a substantially U-shaped cross-section and the rotational position tolerance improving retainer ring has an annular center end face, an annular radially outer slanted leg, and an annular radially inner slanted leg. The slanted legs together with the annular center end face form the substantially U-shaped cross-section. The U-shaped cross-section provides the further rotation of the rotational position tolerance improving retainer ring beyond the predetermined final assembly torque to achieve the required rotational position on the filter head by the further deformation and deflection of the slanted legs.

In one aspect, at least the annular center end face includes a plurality of concentrically arranged and radially spaced projecting rings formed on the annular center end face and projecting axially outwardly therefrom. The further rotation of the rotational position tolerance improving retainer ring is further provided by further deformation of the plurality of concentrically arranged and radially spaced projecting rings.

In one aspect, the tabs have V-shaped lower surfaces. The V-shaped lower surfaces are configured to engage corresponding V-shaped upper surfaces of the axial end wall of the oil filter adjacent to the slots to inhibit rotation of the tabs out of the slots.

In one aspect, the filter head assembly is configured to hold the oil filter in place relative to the engine block when the axial end wall of the oil filter is pressed toward the filter head to overcome a biasing force of the spring and the oil filter is rotated relative to the filter head until the tabs on the bayonet connector are received in the slots on the axial end wall of the oil filter and the V-shaped lower surfaces on the tabs engage the V-shaped upper surfaces of the axial end wall.

In one aspect, the filter head is made of aluminum, and the bayonet connector is made of steel.

In one aspect, the threads on the filter head are external threads on an outer radial surface of the tubular body of the filter head, the threads on the threaded bayonet connection adapter are internal threads on an inner radial surface of the annular body of the threaded bayonet connection adapter, and the threaded bayonet connection adapter further includes tabs protruding radially outward from the annular body of the bayonet connector. The tabs are configured to be inserted into corresponding slots in an axial end wall of the oil filter.

An example of a threaded bayonet connection adapter according to the present disclosure is for connecting an oil filter to a filter head via a bayonet connection. The threaded bayonet connection adapter includes an annular body and tabs. The annular body defines threads configured to engage threads on the filter head to attach the threaded bayonet connection adapter to the filter head. The tabs protrude from the annular body and are configured to be inserted into corresponding slots in an axial end wall of the oil filter to attach the oil filter to the threaded bayonet connection adapter.

In one aspect, the threads on the threaded bayonet connection adapter are internal threads on an inner radial surface of the annular body, and the tabs protrude radially outward from the annular body.

In one aspect, the annular body includes a first portion having a straight sidewall and a second portion having a curved sidewall. The first portion of the annular body defines the threads on the annular body. The tabs protrude radially outward from an axial end of the second portion of the annular body.

In one aspect, the tabs have V-shaped lower surfaces configured to engage corresponding V-shaped upper surfaces of the axial end wall of the oil filter adjacent to the slots to inhibit rotation of the tabs out of the slots.

An example of a method of forming a threaded bayonet connection adapter for connecting an oil filter to a filter head via a bayonet connection according to the present disclosure includes drawing a blank in a first direction to form at least a portion of an annular body, and drawing the blank in a second direction to form tabs protruding radially outward from the annular body. The annular body and the tabs collectively make up the threaded bayonet connection adapter. The tabs are configured to be inserted into corresponding slots in an axial end wall of the oil filter to attach the oil filter to the threaded bayonet connection adapter and thereby to the filter head.

In one aspect, the method further includes drawing the blank in the first direction to form a first portion of the annular body, and drawing the blank in the second direction to form a second portion of the annular body and the tabs. The tabs protrude radially outward from an axial end of the second portion of the annular body.

In one aspect, the method further includes forming internal threads on an inner radial surface of the annular body. The internal threads on the annular body are configured to engage external threads on the filter head to attach the threaded bayonet connection adapter to the filter head.

In one aspect, the second direction in which the blank is drawn is opposite of the first direction in which the blank is drawn.

The invention further relates to a filter device comprising the filter head assembly and an oil filter.

Furthermore, the invention relates to an engine assembly comprising an engine block and the filter head assembly. Preferably, the engine assembly further comprises an oil filter.

Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

Referring now to <FIG>, a filter head assembly <NUM> includes a filter head <NUM>, a threaded bayonet connection adapter <NUM>, a spring <NUM>, and a rotational position tolerance improving retainer ring <NUM> (<FIG> and <FIG>). The filter head <NUM> is attachable to an engine block (not shown) using, for example, fasteners. When the filter head <NUM> is attached to the engine block, the filter head <NUM> enables oil flow between the engine block and an oil filter <NUM> connected to the filter head <NUM>. The filter head <NUM> may be made of aluminum.

The oil filter <NUM> filters engine oil that flows through the oil filter <NUM>. The oil filter <NUM> is rotatable relative to the filter head <NUM> between an unlocked position shown in <FIG> and a locked position shown in <FIG>. When the oil filter <NUM> is in its locked position, the filter head <NUM> secures the oil filter <NUM> to the engine block. When the oil filter <NUM> is in its unlocked position, the oil filter <NUM> can be removed from the filter head <NUM>. In the example shown, the oil filter <NUM> is rotated through an angle A1 degrees to adjust the oil filter <NUM> between its unlocked and locked positions.

The oil filter <NUM> includes a cylindrical sidewall <NUM> and an axial end wall <NUM>. The cylindrical sidewall <NUM> of the oil filter <NUM> has a lock indicator <NUM>, and the filter head <NUM> has an unlock indicator <NUM> and a locked indicator <NUM>. Alignment of the lock indicator <NUM> on the oil filter <NUM> with the unlock indicator <NUM> on the filter head <NUM> as shown in <FIG> indicates that the oil filter <NUM> is not locked to the filter head <NUM>. Alignment of the lock indicator <NUM> on the oil filter <NUM> with the lock indicator <NUM> on the filter head <NUM> as shown in <FIG> indicates that the oil filter is locked to the filter head <NUM>. The rotational position tolerance improving retainer ring <NUM> is critical to achieving the correct alignment of the threaded bayonet connection adapter <NUM> on the filter head <NUM> so the locked and unlocked positions correctly correspond to the locked and unlocked indications on the filter head.

With additional reference to <FIG> and <FIG>, the filter head <NUM> includes an engine attachment portion <NUM> and a filter support portion <NUM>. The engine attachment portion <NUM> of the filter head <NUM> includes a base <NUM> having a disk-shaped body <NUM> and tabs <NUM> protruding from an outer radial surface <NUM> of the disk-shaped body <NUM>. The disk-shaped body <NUM> of the engine attachment portion <NUM> has an engine mounting surface <NUM> that abuts the engine block when the filter head <NUM> is attached thereto.

The tabs <NUM> of the engine attachment portion <NUM> can be used to locate the filter head <NUM> relative to the engine block when attaching the filter head <NUM> thereto. As best shown in <FIG>, the base <NUM> of the engine attachment portion <NUM> defines an inlet port <NUM> that receives oil from the engine block and an outlet port <NUM> that returns filtered oil to the engine block.

The filter support portion <NUM> of the filter head <NUM> includes a base <NUM> having a disk-shaped body <NUM>, a tubular body <NUM> protruding from the base <NUM> along a central axis <NUM> thereof, and a lock indicator tab <NUM> protruding from an outer radial surface <NUM> of the base <NUM>. The base <NUM> of the filter support portion <NUM> further includes a spring retention boss <NUM> (<FIG>) protruding from a top surface <NUM> of the disk-shaped body <NUM> and defining grooves <NUM> that receive the spring <NUM>. The tubular body <NUM> of the filter support portion <NUM> defines external threads <NUM> on an outer radial surface <NUM> thereof. The unlock and lock indicators <NUM> and <NUM> are disposed on the lock indicator tab <NUM>.

The threaded bayonet connection adapter <NUM> connects the oil filter <NUM> to the filter head <NUM> via a bayonet connection. The threaded bayonet connection adapter <NUM> may be made of steel. As best shown in <FIG>, the threaded bayonet connection adapter <NUM> includes an annular body <NUM> and tabs <NUM> protruding radially outward from the annular body <NUM>. The annular body <NUM> of the threaded bayonet connection adapter <NUM> includes a first portion <NUM> having a straight sidewall and a second portion <NUM> having a curved sidewall. An inner radial surface <NUM> of the annular body <NUM> defines internal threads <NUM> that engage the external threads <NUM> on the tubular body <NUM> of the filter head <NUM> as shown in <FIG> and <FIG>.

The tabs <NUM> of the threaded bayonet connection adapter <NUM> protrude radially outward from an axial end <NUM> of the second portion <NUM> of the annular body <NUM>. As best shown in <FIG> and <FIG>, to secure the oil filter <NUM> to the filter head <NUM>, the oil filter <NUM> is placed onto the threaded bayonet connection adapter <NUM> so that the tabs <NUM> of the threaded bayonet connection adapter <NUM> project through slots <NUM> in the axial end wall <NUM> of the oil filter <NUM> adjacent to first ends <NUM> thereof. The oil filter <NUM> is then rotated until the tabs <NUM> of the threaded bayonet connection adapter <NUM> are adjacent to second ends <NUM> of the slots <NUM> in the axial end wall <NUM> of the oil filter <NUM>. Rotating the oil filter <NUM> so that the tabs <NUM> on the bayonet connector <NUM> move through the slots <NUM> in the axial end wall <NUM> of the oil filter <NUM> from the first ends <NUM> thereof to the second ends <NUM> thereof adjusts the oil filter <NUM> from its unlocked position to its locked position.

The tabs <NUM> of the threaded bayonet connection adapter <NUM> have V-shaped lower surfaces <NUM> that engage corresponding V-shaped upper surfaces <NUM> of the axial end wall <NUM> of the oil filter <NUM> adjacent to the slots <NUM> in the axial end wall <NUM>. The V-shaped lower surfaces <NUM> of the threaded bayonet connection adapter <NUM> engage the V-shaped upper surfaces <NUM> of the oil filter <NUM> when the tabs <NUM> of the threaded bayonet connection adapter <NUM> are adjacent to the second ends <NUM> of the slots <NUM>. The engagement between the V-shaped lower surfaces <NUM> of the threaded bayonet connection adapter <NUM> and the V-shaped upper surfaces <NUM> of the oil filter <NUM> inhibits rotation of the tabs <NUM> out of the slots <NUM> and thereby maintain the oil filter <NUM> in its locked position.

Referring now to <FIG>, the spring <NUM> biases the oil filter <NUM> away from the filter head <NUM> and thereby further inhibits rotation of the tabs <NUM> on the threaded bayonet connection adapter <NUM> out of the slots <NUM> in the oil filter <NUM>. The spring <NUM> may be made of steel. The spring <NUM> includes straight segments <NUM> disposed in a common plane and u-shaped segments <NUM> joining the straight segments <NUM> to one another and protruding out of the plane. The straight segments <NUM> of the spring <NUM> are inserted into the grooves <NUM> in the filter head <NUM> and clamped between the tolerance improving retainer ring <NUM> (<FIG> and <FIG>) and the filter head <NUM>. The u-shaped segments <NUM> of the spring <NUM> apply a biasing force to the axial end wall <NUM> of the oil filter <NUM> urging the oil filter <NUM> away from the filter head <NUM>.

To secure the oil filter <NUM> to the filter head assembly <NUM>, the oil filter <NUM> is oriented in its unlocked position with respect to the filter head <NUM>, and the axial end wall <NUM> of the oil filter <NUM> is pressed toward the filter head <NUM> to overcome a biasing force of the spring <NUM>. The oil filter <NUM> is then rotated relative to the filter head <NUM> until the tabs <NUM> on the threaded bayonet connection adapter <NUM> are received in the slots <NUM> on the axial end wall <NUM> and the V-shaped lower surfaces <NUM> on the tabs <NUM> engage the V-shaped upper surfaces <NUM> of the axial end wall <NUM>. When this occurs, the oil filter <NUM> is in its locked position with respect to the filter head <NUM>, and the filter head assembly <NUM> holds the oil filter <NUM> in place relative to the engine block.

As best shown in <FIG> and <FIG>, the rotational position tolerance improving retainer ring <NUM> according to any of <FIG> or <FIG> is assembled between the bayonet connection adapter <NUM> and the filter head <NUM>. The rotational position tolerance improving retainer ring <NUM> holds the spring <NUM> in place relative to the filter head <NUM>. To assemble the filter head assembly <NUM>, the straight segments <NUM> of the spring <NUM> are inserted into the grooves <NUM> in the filter head <NUM>, and the retainer ring <NUM> is placed over the straight segments <NUM> of the spring <NUM>. The threaded bayonet connection adapter <NUM> is then threaded onto the filter head <NUM> by engaging the internal threads <NUM> on the threaded bayonet connection adapter <NUM> with the external threads <NUM> on the filter head <NUM> and rotating the threaded bayonet connection adapter <NUM> bayonet connector <NUM> until the retainer ring <NUM> is clamped between the bayonet connector <NUM> and the filter head <NUM>.

The threaded bayonet connection adapter <NUM> is threaded onto the filter head <NUM> until the torque applied to the threaded bayonet connection adapter <NUM> is within a predetermined torque range. The threaded bayonet connection adapter <NUM> is then rotated, if needed, a further rotational distance until a critical predetermined angular orientation of the threaded bayonet connection adapter <NUM> with respect to the filter head <NUM> is correctly achieved. <FIG> illustrates an example of such a predetermined angular orientation of the threaded bayonet connection adapter <NUM>. In <FIG>, one of the tabs <NUM> on the threaded bayonet connection adapter <NUM> is oriented at an angle A2 of <NUM> degrees with respect to a visual alignment nub <NUM> on the filter head <NUM>. In various implementations, the predetermined angular orientation of the threaded bayonet connection adapter <NUM> may be defined using other features of the filter head <NUM>, for example the lock indicator tab <NUM>.

Since the threaded bayonet connection adapter <NUM> is threaded onto the filter head <NUM>, there are multiple factors that affect the final assembly orientation of the bayonet connector <NUM>. These factors include the starting location of the internal threads <NUM> of the bayonet connector <NUM>, the starting location of the external threads <NUM> on the filter head <NUM>, and the thickness of the retainer ring <NUM>, and the specific rotational position tolerance improving retainer ring <NUM> configuration selected, as shown on <FIG>. Due to the stack up of tolerances associated with these factors, without certain measures, the threaded bayonet connection adapter <NUM> may not be positioned at the predetermined angular orientation with respect to the filter head <NUM> when the filter head assembly <NUM> is fully assembled at the required torque. In turn, the lock indicator <NUM> on the oil filter <NUM> may not be correctly aligned with a lock indicator <NUM> on the filter head <NUM> when the oil filter <NUM> is secured to the filter head <NUM>.

Due to the stack up of tolerances of these components, there could be too much variation in the final orientation of the threaded bayonet connection adapter <NUM> relative to the filter head <NUM>. The threaded bayonet connection adapter <NUM> could end up being out of position potentially for some assemblies, such that the rotational locked/unlocked positions of the filter <NUM> on the bayonet connector <NUM> do not properly correspond to the locked/unlocked positions on the lock indicator tab <NUM>. For proper and reliable mounting of the filter <NUM>, it is critical that the rotational locked/unlocked positions of the filter <NUM> on the bayonet connector <NUM> properly correspond to the locked/unlocked positions indicated on the lock indicator tab <NUM> of the filter head <NUM>. This is accomplished with the rotational position tolerance improving retainer rings <NUM> as disclosed in <FIG>.

This critical requirement drives the need for an inventive scheme that will allow for a large window of assembly torque in order to be able to overcome these stack up tolerances, and enables and provides the threaded bayonet connection adapter <NUM> to be fixedly mounted with required frictional restraint onto the filter head <NUM> in the required correct position.

In order to achieve this relatively flat "torque vs rotational angle" behavior, it has been found preferable to choose a material with a comparatively low Young's modulus for the rotational position tolerance improving retainer ring <NUM>. A low Young's Modulus indicates a low amount of force required for a set amount of deformation. In our development testing, we have found that <NUM> H14 aluminum provided the desired relatively flat "torque vs rotational angle". In our tests, for example, flat stainless steel and aluminum rotational position tolerance improving retainer rings were assembled at a <NUM> torque. Between the two flat retainer rings, the bayonet connector's final position can be rotated <NUM>% further with the aluminum ring, providing flatter "torque vs angle" behavior with the aluminum rings, thereby allowing the rotational locked/unlocked positions of the filter <NUM> on the bayonet connector <NUM> to properly correspond to the locked/unlocked indicator <NUM> of the filter head <NUM>. However, as the proper rotational alignment of the alignment of the threaded bayonet connection adapter <NUM> relative to the filter head <NUM> is important for the correct open/closed indicator operation, an even wider range of the flatter "torque vs angle" behavior is desired.

To address the issue noted above, the retainer ring <NUM> is designed to yield a large window of assembly torque in order to be able to overcome the stack up of tolerances. For example, the retainer ring <NUM> may be made of a material (e.g., a metal) with a low modulus of elasticity (e.g., less than or equal to <NUM> gigapascals (GPa) such as aluminum, brass, copper, or combinations thereof. In a specific example, the rotational position tolerance improving retainer ring <NUM> is preferably made of <NUM> aluminum with a modulus of elasticity of <NUM> GPa. Such a material would require applying only a low amount of tightening torque to the bayonet connector <NUM> in order to deform the retainer ring <NUM> by a predetermined amount. Thus, the retainer ring <NUM> may be designed to deform under low load and thereby enable both tightening the bayonet connector <NUM> to within the predetermined torque range and adjusting the bayonet connector <NUM> to the predetermined angular orientation.

<FIG> shows a rotational position tolerance improving retainer ring <NUM> of the threaded bayonet connection adapter of <FIG>, having an axial top end face 18A and opposite bottom end face 18B. The rotational position tolerance improving retainer ring <NUM> is provided with a plurality of deformable radially arranged axial projections 18C formed onto on or both of the end faces 18A, 18B. Preferably, the deformable radially arranged axial projections have a rectangular cross-section. The deformable radially arranged axial projections 18C provide for a larger flattened torque range after the threaded bayonet connection adapter <NUM> is tightened onto the filter head <NUM> to at least a predetermined final assembly torque, providing additional rotation of the threaded bayonet connection adapter <NUM> on the filter head <NUM> to the required rotational position on the filter head <NUM> such the open and locked position indications on the filter head agree with the actual open and locked positions of the filter element (oil filter <NUM>) on the filter head <NUM>. This is important for a correct operation of the open and locked position indicators <NUM>, <NUM> on the filter head <NUM>.

<FIG> show another aspect of a rotational position tolerance improving retainer ring <NUM> of the threaded bayonet connection adapter <NUM> of <FIG>, having a deformable generally U-shaped cross section (<FIG>), the rotational position tolerance improving retainer ring <NUM>, according to <FIG>, <FIG>, <FIG> and <FIG>, thereby providing for the further deformation of the rotational position tolerance improving retainer ring <NUM> (<FIG>) beyond the predetermined final assembly torque to achieve the critical final rotational position for the correct operation of the open (unlocked) and locked position indicators <NUM>, <NUM> on the filter head <NUM>. This is critical to a correct operation of the open and locked position indicators <NUM>, <NUM> on the filter head <NUM>. As shown in <FIG>, the rotational position tolerance improving retainer ring <NUM> of <FIG> is substantially U-shaped, having a center end face <NUM>, a radially outer slanted leg 18E and a radially inner slanted leg 18D. The substantial U-shape of the rotational position tolerance improving retainer ring <NUM> provides for further deformation of the rotational position tolerance improving retainer ring <NUM> beyond the predetermined final assembly torque to achieve the critical final rotational position for the correct operation of the open and locked position indicators <NUM>, <NUM> on the filter head <NUM>, the deformation occurring by the deflection of the slanted legs 18D and 18E during compression of the rotational position tolerance improving retainer ring <NUM> between the threaded bayonet connection adapter <NUM> and the filter head <NUM>. This is important for a correct operation of the open and locked position indicators <NUM>, <NUM> on the filter head <NUM>.

<FIG> is a schematic top perspective view of another aspect of the rotational position tolerance improving retainer ring <NUM> of the threaded bayonet connection adapter of <FIG>. Similar to <FIG> and including a plurality of concentrically arranged and radially spaced projecting rings 18F formed on the axial face of the rotational position tolerance improving retainer ring <NUM>, thereby providing for further deformation of the rotational position tolerance improving retainer ring <NUM> beyond the predetermined final assembly torque to achieve the critical final rotational position for the correct operation of the open and locked position indicators <NUM>, <NUM> on the filter head <NUM>. As shown in <FIG>, the rotational position tolerance improving retainer ring <NUM> of <FIG> is substantially U-shaped, having a center end face <NUM>, a radially outer slanted leg 18E and a radially inner slanted leg 18D. The plurality of concentrically arranged and radially spaced projecting rings 18F are arranged on at least the center end face <NUM> and may be arranged on one or both of the slanted legs 18D, 18E.

Referring now to <FIG>, an example method of forming the bayonet connector <NUM> will now be described. The method includes drawing a blank in a first direction <NUM> to form the first portion <NUM> of the annular body <NUM> and drawing the blank in a second direction <NUM> to form the second portion <NUM> of the annular body <NUM> and the tabs <NUM>. The second direction <NUM> is opposite of the first direction <NUM>. The method further includes forming the internal threads <NUM> on the inner radial surface <NUM> of the annular body <NUM> using, for example, a tap and die.

The example method of forming the bayonet connector <NUM> described above is enabled at least in part by the threaded connection between the bayonet connector <NUM> and the filter head <NUM>. Without this threaded connection, a bayonet connector (not shown) may need to include fastener tabs through which fasteners may be inserted to attach the bayonet connector to the filter head <NUM>. The fastener tabs may need to be disposed within a common plane, and therefore the remainder of the bayonet connector may be formed by deep drawing a blank in a single direction away from that plane. As a result, the wall thickness of the bayonet connector may be limited, and the bayonet connector may experience a thinning effect during the drawing operation that may lead to microcracks in the bayonet connector. The fatigue life of the bayonet connector may be improved by subjecting the bayonet connector to shot peening after the drawing process and placing a stabilizing ring (not shown) on top of the bayonet connector. However, such measures increase the cost and complexity of the overall assembly.

In contrast the such a single-direction drawing process, the above-described two-directional drawing process of forming the bayonet connector <NUM> enables the bayonet connector <NUM> to have a thicker wall thickness. In turn, the bayonet connection adapter <NUM> may achieve better robustness and a longer fatigue life without taking measures such as subjecting the bayonet connection adapter <NUM> to shot peening after the drawing process or placing a stabilizing ring on top of the bayonet connection adapter <NUM>. As a result, the cost of the filter head assembly <NUM> may be minimized relative to other filter head assemblies.

Claim 1:
A filter head assembly (<NUM>) comprising:
a filter head (<NUM>) configured to be attached to an engine block and to enable oil flow between the engine block and an oil filter (<NUM>) connected to the filter head (<NUM>), the filter head (<NUM>) including a base (<NUM>),
characterized in that the filter head (<NUM>) further includes
a tubular body (<NUM>) protruding from the base (<NUM>), the tubular body (<NUM>) defining threads (<NUM>); and
a threaded bayonet connection adapter (<NUM>) configured to connect the oil filter (<NUM>) to the filter head (<NUM>) via a bayonet connection, the bayonet connection adapter (<NUM>) including
an annular body (<NUM>) defining threads (<NUM>) configured to engage the threads (<NUM>) on the tubular body (<NUM>) of the filter head (<NUM>) to attach the bayonet connection adapter (<NUM>) to the filter head (<NUM>);
an axially deformable rotational position tolerance improving retainer ring (<NUM>), which is annular and is arranged on the tubular body (<NUM>) and compressed, preferably elastically compressed, between the filter head (<NUM>) and the threaded bayonet connection adapter (<NUM>).