BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The invention pertains to the field of tensioners. More particularly, the invention pertains to a tensioner with a shipping and an activating mechanism to release the tensioner from a shipping position.

DESCRIPTION OF RELATED ART

Conventional timing system tensioners commonly include a shipping component, usually in the form of a pin or shipping clip, to securely retain the internal components inside the tensioner body during delivery. That shipping component conventionally must be removed in order to activate the tensioner for proper operation after assembly on the engine.

Timing system tensioners with a shipping feature that does not require removal of a component are also known in the art.

U.S. Patent No. 4,772,251, entitled "Novel Chain Tightener Assembly" and issued September 20, 1988 to Goppelt et al., discloses a chain tensioner with a mounting ring that snaps into a groove, which is located at the forward end of the dampening piston and is provided with a beveled surface and an adjacent latch surface. The mounting ring is shiftable onto the latch surface via the beveled surface with a tool insertable in a gap between the housing and the dampening piston. The mounting ring engages a notch of the housing, thereby blocking a movement of the dampening piston relative to the housing to put the tensioner into a shipping condition. The piston is releasable from the shipping position without the use of a tool.

U.S. Patent No. 4,792,322, entitled "Chain Tightener" and issued December 20, 1988 to Goppelt et al., discloses a chain tensioner with a dampening piston guided in a housing and axially acted upon by a spring in the chain tightening direction. A radially- resilient stop ring cooperates with recesses of the housing and the dampening piston to limits its stroke while allowing a return movement in the dampening direction opposite to the chain tightening direction. A mounting ring maintains the piston in a shipping position.

U.S. Patent No. 5,704,860, entitled "Transport Locking System for a Chain Tensioner" and issued January 6, 1998 to Stief, discloses a chain tensioner with a damping piston in a guide bore. A stop ring between the damping piston and the housing cooperates with grooves and stops on the housing and damping piston to prevent the damping piston from sliding too far into the housing. The stop ring also serves the function of the mounting ring in the two previously-described patents and is clamped in a locking position between two inclined contact surfaces on the housing and damping piston to allow the damping piston to be locked in position in the bore.

Japanese Patent Application Publication No. 2005-42860, entitled "Chain

Tensioner" by Seiji et al. and published February 17, 2005, discloses a chain tensioner capable of facilitating assembly, compact in size, and low in cost that prevents the moving amount of a plunger from being influenced by functions of the tensioner after release during the initial set-up of the tensioner. A register ring locked between two sets of grooves maintains the piston in a shipping position.

In the above-mentioned references, the reset and activation features and positions are separate from the ratchet feature of the tensioner. The above-mentioned references are hereby incorporated by reference herein.

SUMMARY OF THE INVENTION

A push-to-release mechanism may be reset to a shipping condition from any piston position by opening a ratchet clip through the application of an external force on the ratchet clip legs. A tensioner with a push-to-release mechanism includes a piston housing, a piston, a piston spring, and a ratchet clip. The piston housing includes a reset opening circumferentially extending around a first circumferential portion of the outer end of a piston bore and a ratchet groove extending outward from the piston bore and

circumferentially around a second circumferential portion of the piston bore and axially aligned with the first circumferential portion. The piston includes piston teeth separated by tooth grooves. The piston spring biases the piston in a protruding direction from the piston bore. The ratchet clip includes a curved portion having a free state diameter less than the tooth groove diameter. The curved portion is axially aligned with the ratchet groove and extends around the outer surface of the piston, and the first and second legs of the ratchet clip extend into the reset opening of the piston housing.

When the piston is released with the ratchet clip contacting a reset portion of the ratchet groove of the piston housing and axially aligned with one of the tooth grooves of the piston, the ratchet clip is captured between one of the piston teeth of the piston and the reset portion of the piston housing in a shipping condition. Methods of placing the tensioner in the shipping condition and releasing the tensioner from the shipping condition are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a partial cross sectional view of a clip ratchet-style tensioner in an

embodiment of the present invention.

Fig. 2 shows a perspective view of the clip ratchet-style tensioner of Fig. 1.

Fig. 3 a shows a side view of the piston of the tensioner of Fig. 1.

Fig. 3b shows a side view of the ratchet clip of the tensioner of Fig. 1.

Fig. 3c shows a side view of the bore insert of the tensioner of Fig. 1.

Fig. 4 shows a side perspective view of a piston with a ratchet clip in one of the piston tooth grooves in an embodiment of the present invention.

Fig. 5 shows a front perspective view of the tensioner with the ratchet clip in an open position.

Fig. 6 shows a partial cross sectional view of the outer end of the piston and bore insert with the tensioner ready to be placed in a shipping position.

Fig. 7a shows a close-up view of the piston tooth and bore insert groove profiles with the tensioner in a shipping position. Fig. 7b shows the tensioner of Fig. 7a with the piston partially pressed in during the release process.

Fig. 7c shows the tensioner of Fig. 7a with the piston pressed in far enough for the ratchet clip to seat fully in the piston tooth.

Fig. 8a shows a side view of the outer piston end of a tensioner with the piston and ratchet clip in an extended free position.

Fig. 8b shows the tensioner of Fig. 8a with the piston and ratchet clip pushed inward

toward the piston bore to contact the chamfered bottom surface with the ratchet clip.

Fig. 8c shows the tensioner of Fig. 8b with the piston released slightly to align the ratchet clip with the reset ratchet groove.

Fig. 8d shows the tensioner of Fig. 8c with the ratchet clip opened in the reset ratchet groove.

Fig. 8e shows the tensioner of Fig. 8d with the piston retracted and the ratchet clip aligned with one of the piston tooth grooves.

Fig. 8f shows the tensioner of Fig. 8e with the ratchet clip closed on one of the piston tooth grooves.

Fig. 8g shows the tensioner of Fig. 8f with the ratchet clip closed and aligned with the shipping feature.

Fig. 8h shows the tensioner of Fig. 8g with the ratchet clip opened in the shipping feature and the piston released to place the tensioner is a shipping position.

Fig. 9a shows the tensioner of Fig. 8d with the ratchet clip aligned with the reset ratchet groove.

Fig. 9b shows the tensioner of Fig. 9a with the ratchet clip closed. Fig. 9c shows the tensioner of Fig. 9b with the piston released. Fig. 10 shows the tensioner of Fig. 8h with the piston pushed in to activate the tensioner from the shipping position.

Fig. 11 shows a side perspective view of a piston with a ratchet clip in one of the piston tooth grooves in an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A mechanism that allows the tensioner to be activated at engine assembly without requiring the removal of an external shipping component provides several benefits. The push-to-release mechanism is superior to the above-mentioned prior art mechanisms, because the shipping feature is combined with the backlash groove to allow a more compact axial package with the push-to-release mechanism. In most shipping mechanisms of the prior art, the piston needs to be fully extended and then pushed all the way back from that position to be reset. The push-to-release mechanism, however, may be reset from any piston position by opening the ratchet clip by applying an external force on the ratchet clip legs.

Embodiments of the present invention may be used with either a chain tensioner or a belt tensioner that uses a clip-style ratchet. A shipping feature is located inside the tensioner body or bore insert, against which the ratchet clip wire is pressed by the piston tooth profile as the piston is outwardly biased by the piston spring force.

The push-to-release mechanism includes a piston with a tooth profile shape portion, a tensioner piston spring applying a compression load, a ratchet clip compressed between the piston and a shipping feature, a tensioner housing having an internal feature in a reset ratchet groove, and an activation force to move the piston inwardly in the tensioner. The ratchet clip has a radial biasing force toward the piston.

Referring to Fig. 1, the tensioner 10 includes a piston housing 11 including a tensioner body 12 and a bore insert 20. The tensioner body 12 includes a tensioner bore 14 and two mounting holes 16, 18 for mounting the tensioner 10 onto a surface. The bore insert 20 defines a piston bore 22, and the bore insert 20 is received by the tensioner bore 14. The piston 24 is received by in the piston bore 22 and is biased outward from the piston bore 22 by a piston spring 26 mounted in a pressure chamber 28 in the piston 24. A check valve assembly 30 permits hydraulic fluid into the pressure chamber 28 while preventing hydraulic fluid from leaving the pressure chamber 28 and returning to the hydraulic fluid supply line (not shown). An optional flow control device 32 controls flow of hydraulic fluid out the vent 34 of the piston 24. A chain tensioning front surface of a tensioner arm (not shown) having an arcuate shape contacts a chain or belt to maintain tension in the chain or belt. The tensioner arm is preferably rotatably mounted to a fixed pivot (not shown). The piston 24 contacts a back surface of the tensioner arm to support the tensioner arm and extends as the chain or belt ages to maintain tension in the chain or belt. A ratchet clip 36 sits in a ratchet groove 38 of the bore insert 20 of the piston housing 11. The piston 24 is free to move outward (upward) in the state of Fig. 1. If a sudden downward force is applied to the piston 24 by a tensioned chain or belt through the tensioner arm, the ratchet clip 36 contacts the chamfered bottom surface 40 of the ratchet groove 38 to prevent further retraction of the piston 24, thereby providing an anti-return function to prevent tooth jump failure during engine operation. The ratchet clip preferably serves as the only device to engage the piston teeth and provide the ratcheting and the anti- return function, with no separate pawl being used.

The piston housing 11 includes a reset opening 42 at the outer ends of the tensioner bore 14 and the piston bore 22, respectively, out of which the ends of the ratchet clip 36 extend. The reset opening 42 circumferentially extends around a circumferential portion of the outer end of the piston bore. More specifically, the tensioner body 12 includes a body opening 44 along a portion of the side of the tensioner bore 14 at the outer end of the tensioner bore 14, and the bore insert 20 includes an insert opening 46 along a portion of the side of the piston bore 22 at the outer end of the piston bore 22. The ends of the ratchet clip 36 extend into the reset opening 42, as shown in Fig. 2.

Fig. 3a shows the piston 24 with a plurality of piston teeth 50 around the middle of the outer circumference of the piston 24 and tooth grooves 52 between the piston teeth 50. The tensioner may be placed in a shipping condition with the ratchet clip 36 seated in any of the tooth grooves 52. The piston 24 does not include an outer reset groove. Fig. 3b shows that the ratchet clip 36 has a curved portion 54 inwardly biased to have a free-state diameter less than or equal to the root diameter of the tooth grooves 52 of the piston 24. A pair of clip legs 56, 58, when moved toward each other against the bias of the curved portion 54, allows the radius of curvature of the curved portion 54 to be increased. The ratchet clip 36 is preferably a formed wire with a round cross section, and more preferably a substantially circular cross section, of the curved portion 54.

Fig. 3c shows that the ratchet groove 38 in the bore insert 20 includes a pair of an upper ratchet groove 60 and a lower ratchet groove 62 separated by a shipping feature 64 with a smaller radius of curvature than the lower and upper ratchet grooves 60, 62. The lower ratchet groove 62 serves as a reset ratchet groove 62 that guides the ratchet clip 36 and prevents the ratchet clip 36 from tilting when the ratchet clip 36 is opened during a reset process.

Fig. 4 shows an alternative design for a piston 124 that includes an outer reset groove 126. In embodiments including this piston 124, the outer reset groove 126 provides an additional location for the ratchet clip 36 to seat, and hence an additional position for the piston 124, in a shipping condition.

Fig. 5 shows a tensioner 110 with the ratchet clip 36 in an open position. A clip leg 58 of the ratchet clip 36 has been clipped in place onto a reset feature 15 extending from the body opening 44 of the tensioner body 12 of the piston housing 11. Clipping the clip leg 58 of the ratchet clip 36 onto the reset feature 15 prevents the ratchet clip 36 from moving during the process of resetting the tensioner 110 to a shipping condition. Although the reset feature 15 is shown as a protrusion or wall extending from the edge of the tensioner body 12 at the body opening 44, the reset feature 15 may have any shape that engages the clip leg 58 of the ratchet clip 36 to maintain it in a fixed position during the resetting process. Also, the reset feature 15 may alternatively extend from other locations at the edge of the reset opening 42 of the piston housing 11 , including the edge of the insert opening 46 of the bore insert 20, within the spirit of the present invention.

Fig. 6 shows a tensioner 110 ready to be placed in a shipping condition. Although the ratchet clip 36 is seated in one of the piston tooth grooves 52, and thus is not preventing outward movement of the piston 124, the ratchet clip 36 is also aligned with the shipping feature 64. By applying a force to the clip legs to seat the ratchet clip 36 in the shipping feature 64 and releasing the piston 124, the piston 124 extends until the ratchet clip 36 becomes pinned between a piston tooth 50 and the shipping feature 64, thereby placing the tensioner into a shipping condition. This process is shown more clearly in Fig. 7a, Fig. 7b, and Fig. 7c. Preferred ratchet tooth and ratchet groove profiles for the piston 124 and piston housing 11, respectively, are shown in Fig. 7a, Fig. 7b, and Fig. 7c. The shipping feature 64 is an extension in the middle of the ratchet groove 38 and forms and separates the reset ratchet groove 62 from the upper ratchet groove 60. Other complementary ratchet tooth and ratchet groove profiles, however, may be used within the spirit of the present invention. In Fig. 7a, the tensioner is in a shipping condition with the ratchet clip 36 pinned between a piston tooth 50 and the piston housing 11, preventing the piston 124 from extending outward from the piston housing 11. In Fig. 7b, the piston 124 has been pushed into the piston housing 11 slightly. The ratchet clip 36 has begun to move toward the tooth groove 52 and is almost clear of the shipping feature 64. In Fig. 7c, the ratchet clip 36, biased to retract, has now seated in the root diameter of the tooth groove 52. The piston 124 is now free to extend outward from the piston housing 11, with the ratchet clip 36 seated in the root diameter of the tooth groove 52, until the ratchet clip 36 contacts the top edge 69 of the ratchet groove 38. The piston 124 may continue to extend outward from the piston housing 11 , but the ratchet clip 36 must slide along the passing piston teeth 50 and tooth grooves 52.

To activate the tensioner from a shipping condition, an external force greater than the outward piston spring biasing force is applied inwardly to the piston so that the ratchet clip is released and seats on the root diameter of the piston tooth, allowing the piston to extend out to an operating position. Usually, the external force is applied by the tensioner arm through tension in the timing chain created by torque on the valve train coming from rotation of the crankshaft or camshafts of the engine. The activation torque on the crankshaft or camshafts is generally applied manually during engine assembly but may alternatively come from cranking or firing of the engine. In a shipping condition, the tensioner spring applies an outward load to the piston.

The tooth profile of the piston expands the clip radially against the shipping feature on the piston housing. The ratchet clip is pressed between the piston and the piston housing shipping feature and holds the piston. A shipping feature, for example a piston housing shipping groove feature, preferably holds the ratchet clip in place.

The tensioner is activated from the shipping condition by application of a load to the piston that is greater than the spring load. When the piston is pushed inward toward the piston housing, the piston clip, which applies a radial biasing force toward the piston, slides down to the root diameter of the piston tooth and away from the shipping feature of the piston housing so that the piston becomes free to move with respect to the piston housing.

The tensioner preferably also includes a reset feature. To reset the tensioner, the ratchet clip is opened by applying an external load to the clip legs. Optionally, a reset wall step of the piston housing contacts one side of the clip leg during opening. A reset ratchet groove of the piston housing optionally guides the clip opening and prevents tilting during reset regardless of load direction applied.

The root diameter of the piston profile is preferably larger than the inside diameter of the ratchet clip in its free state such that the ratchet clip applies a radial

clamping/biasing force on the piston during operation. The tensioner spring force must be strong enough to hold the ratchet clip between the piston and the piston housing against the bias of the ratchet clip.

The system uses a tooth profile of the piston sliding coaxially to a piston bore. Between the piston and the cylinder are preferably a check valve, a piston spring, and an optional flow control device to provide the hydraulic tensioning function.

In a method of placing a tensioner into a shipping condition, a ratchet clip is pressed between a chamfered angled area of a piston tooth profile and a shipping feature of the piston housing. A piston spring load holds the ratchet clip in position, because the spring load is higher than the clamping load of the ratchet clip.

A method of resetting the tensioner 110 to the shipping condition is shown in Fig. 8a through Fig. 8h. The tensioner 110 is reset from a state, such as the state shown in Fig. 8a, where the piston 124 is protruded from the piston housing 11 to take up chain slack, and the ratchet clip 36 is at a random position inside the ratchet groove 38 of the piston housing. The piston 124 is first pushed back into the piston housing 11, as shown in Fig. 8b, until the ratchet clip 36 contacts the chamfered bottom surface 40 of the ratchet groove 38. The piston 124 is then moved out slightly, as shown in Fig. 8c, preferably about 0.1 mm or generally to align the ratchet clip 36 with the reset ratchet groove 62, to allow the ratchet clip 36 to be free from friction to be opened. A load is then applied to one clip leg 56 until the opposite leg 58 contacts the reset wall step 15 and the ratchet clip 36 is opened with the curved portion of the ratchet clip 36 extending into the lower outer ratchet groove 62, as shown in Fig. 8d. In some embodiments, a hole is added on the engine front cover to allow easier access to the ratchet clip for resetting after engine assembly is complete.

Alternatively, the ratchet clip 36 may be opened by applying opposing forces on each leg 56, 58 of the ratchet clip 36, for example by using fingers or pliers.

With the ratchet clip 36 opened such that the piston 124 is free to move with respect to the piston housing 11, the piston 124 is moved to a position with one of the piston tooth grooves 52 aligned with the ratchet clip 36, as shown in Fig. 8e. The ratchet clip 36 may be aligned with any piston tooth groove 52 or with the outer reset groove 126 at the top of the piston 124 with the piston 124 completely pushed in. The clip 36 is then released to engage the tooth groove that it is aligned with, as shown in Fig. 8f. The piston 124 and piston clip 36 are then moved together to the correct shipping position with respect to the piston housing 11, i.e., the piston clip 36 aligned with the shipping feature 64 of the ratchet groove 38, as shown in Fig. 8g. Finally, when the piston clip 36 is to engage one of the piston teeth 50, a force is applied to the clip leg 56 to expand the diameter of the curved portion of the ratchet clip 36 such that the curved portion of the ratchet clip 36 sits in the central groove 64. The piston 124 is then released to capture the ratchet clip 36 between the piston 124 and the piston housing 11 in a shipping condition, as shown in Fig. 8h. The tensioner 110 is then ready to be activated by pushing on the piston 124.

Fig. 9a through Fig. 9c show the final steps of resetting the tensioner 110 to a shipping condition with the ratchet clip 36 seated in the outer reset groove 126 instead of one of the tooth grooves 52. From the state shown in Fig. 8d with the ratchet clip 36 opened such that the piston 124 is free to move with respect to the piston housing 11, the piston 124 is moved to a position with the outer reset groove 126 aligned with the clip 36, as shown in Fig. 9a. The reset clip 36 is then released to engage the outer reset groove 126, as shown in Fig. 9b. Finally, the piston 124 is released to place the tensioner 110 into the shipping condition shown in Fig. 9c. In this shipping condition, the ratchet clip 36 is aligned with the upper outer ratchet groove 60. The tensioner 110 is then ready to be activated by applying a load to open the ratchet clip 36.

In a method of activating a tensioner from a shipping condition of the ratchet clip seated in one of the piston tooth grooves, the piston is pushed down to release the ratchet clip, as shown in Fig. 10. The piston 124 is preferably pushed inward toward the piston housing 11 by a load applied by the engine valve train torque to the tensioner through the chain and the tensioner arm that is sufficient to overcome the load of the piston spring. When the piston is pushed inward toward the piston housing 11 , the ratchet clip is released from the shipping feature 64 and slides down to engage the root diameter of the piston tooth based on the ratchet clip's clamping load. With the ratchet clip seated completely on the root diameter of the piston tooth, there is enough radial clearance of the piston from the shipping feature 64 of the piston housing to allow the piston to move outward freely to its operation position.

Fig. 11 shows an alternative design for a tensioner 210. Instead of a bore insert and a tensioner body, the piston housing 211 is a single integral unit. The tensioner 210 includes the piston housing 211 with a piston bore 222 and two mounting holes 216, 218 for mounting the tensioner 210 onto a surface. The piston 24 is received by the piston bore 222 and is biased outward from the piston bore 222 by a piston spring 26 mounted in a pressure chamber 28 in the piston 24. A check valve assembly 230 permits hydraulic fluid into the pressure chamber 28 while preventing hydraulic fluid from leaving the pressure chamber 28 and returning to the hydraulic fluid supply line (not shown). An optional flow control device 32 controls flow of hydraulic fluid out the vent 34 of the piston 24. A ratchet clip 36 sits in a ratchet groove 238 of the piston housing 211. As in the previous embodiments, the piston housing 211 includes a reset opening along a portion of the side of the piston bore at the outer end of the piston bore, out of which the ends of the ratchet clip 36 extend. In preferred embodiments, the ratchet clip 36 provides an anti-return function to prevent tooth jump failure during engine operation in addition to the role of retaining the piston 24 in its shipping position through the mechanism discussed herein, with no separate pawl being used. Although a preferred piston tooth profile is shown in the figures, the piston tooth profile shape may be any chamfer shape. The piston tooth and the ratchet clip may have one of several alternative geometries. In some embodiments, a straight portion

substantially parallel to the piston bore wall is added on to the angled chamfer of at least one tooth profile so that the piston has to be pushed a greater distance before the clip is able to slide down to the base of the tooth groove and allow the piston to be released.

The shipping feature may have one of several alternative configurations. An alternative shipping feature geometry may include an additional straight portion substantially parallel to the piston bore wall in the middle of the central ratchet groove to provide more allowance during assembly or reset. Although the push-to-release mechanism is described for use with a tensioner system, the mechanism may be used with any device where a retention feature is desirable.

The piston geometry, clip load direction, and shipping groove feature may be reversed such that the piston has the shipping groove feature, the clip has the outward directional load and the piston housing has the chamfer shape. In such alternative embodiments, the locations of the ratchet teeth and the ratchet groove are reversed, with the ratchet teeth being located along the piston bore of the piston housing and the ratchet shipping groove being formed in the piston. In such alternative embodiments, the ratchet clip preferably serves as the only device to engage the piston teeth and provide the ratcheting and the anti-return function, with no separate pawl being used. Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention.

Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.