Patent Publication Number: US-2017370447-A1

Title: Hydraulic tensioner with cantilever shipping spring

Description:
FIELD OF THE INVENTION 
     The invention relates to a hydraulic chain tensioner having a piston longitudinally movable in a cylindrical aperture of the tensioner, and more particularly to a securing feature for holding the piston assembled internally within the cylindrical aperture of the hydraulic tensioner during shipping, installation and service. 
     BACKGROUND 
     There is a desire to provide a cost-effective piston securing feature in order to avoid disassembly of parts during shipping and installation of a hydraulic tensioner, and to further allow resetting the piston during a service situation. 
     SUMMARY 
     A hydraulic tensioner for an endless loop power transmission member can include a housing having a cylindrical aperture and a piston slidably received within the cylindrical aperture for movement between an extended position and a retracted position. A tensioner spring can bias the piston outwardly from the cylindrical aperture toward the extended position. The piston and the cylindrical aperture can define an expandable fluid chamber. The hydraulic tensioner can include a cantilever spring having a first end attachable to the housing and a second end releasably engageable with the piston for retaining the piston in the retracted position within the cylindrical aperture of the hydraulic tensioner against urging of the tensioner spring during shipment and installation. The second end of the cantilever spring can be disengageable from the piston allowing movement of the piston outwardly toward the extended position with respect to the cylindrical aperture of the housing after installation to enable operation of the hydraulic tensioner. 
     A hydraulic tensioner can include a housing having a longitudinal cylindrical aperture and defining a fluid passage in fluid communication with an interior of the cylindrical aperture. The hydraulic tensioner can include a piston received in the cylindrical aperture for longitudinal movement between an extended position and a retracted position. A tensioner spring can be positioned within the cylindrical aperture to bias the piston toward the extended position with respect to the cylindrical aperture. A cantilever spring can be attachable to the housing at one end with a free end for retaining the piston within the cylindrical aperture of the housing. The piston and the cylindrical aperture of the housing can define a fluid chamber between the housing and the piston. The piston can have a spring-retention groove formed on a nose end of the piston. The cantilever spring can have a first end attachable to the housing and a second end releasably engageable with the spring retention groove of the piston for retaining the piston within the cylindrical aperture of the hydraulic tensioner during shipment and installation. The second end of the cantilever spring can be disengageable with the spring retention groove allowing longitudinal movement of the piston outwardly with respect to the housing to enable operation of the hydraulic tensioner. 
     A hydraulic tensioner can be assembled for an endless loop power transmission member. The hydraulic tensioner can have a housing having a cylindrical aperture. The method can include inserting a tensioner spring into the cylindrical aperture, inserting a slideable tensioning piston into the cylindrical aperture for movement between an extended position and a retracted position, and attaching a cantilever spring to the housing. A fluid chamber can be defined between the cylindrical aperture of the housing and the piston. The tensioner spring can bias the piston outwardly with respect to the cylindrical aperture of the housing. The cantilever spring can have a first end attachable to the housing and a second end releasably engageable with the piston for retaining the piston within the hydraulic tensioner against urgings of the tensioner spring during storage, shipment and installation. The second end of the cantilever spring can be disengageable with the piston allowing movement of the piston outwardly with respect to the housing to enable operation of the hydraulic tensioner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  is a cross sectional view of a hydraulic tensioner having a housing defining a cylindrical aperture with a piston slidably received with the cylindrical aperture of a housing for movement between an extended position and a retracted position, a spring biasing the piston toward the extended position with respect to the cylindrical aperture, and a cantilever spring having a first end attachable to the housing and a second end releasably engageable with the piston for retaining the piston in the retracted position within the cylindrical aperture against urgings of the spring during storage, shipment and installation; 
         FIG. 2  is a top view of the hydraulic tensioner of  FIG. 1  showing a spring-retention groove formed on a nose end of the piston and the second end of the cantilever spring engageable with the spring-retention groove securing the cantilever spring to the nose end of the piston and retaining the piston within the cylindrical aperture of the housing against the urging of the tensioner spring; 
         FIG. 3  is a perspective view of the hydraulic tensioner of  FIG. 1  showing a hooked end formed at the second of the cantilever spring engageable with the spring-retention groove and a spring-receiving slot formed in the housing fixedly receiving the first end of the cantilever spring; and 
         FIG. 4  is an exploded view of the hydraulic tensioner of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIGS. 1-4 , a tensioning system for imparting tension to an endless loop power transmission member can include a hydraulic tensioner  10 . By way of example and not limitation, the endless loop power transmission member can include a chain or a belt encircling a driving sprocket and at least one driven sprocket. The hydraulic tensioner  10  can include a housing  12  supporting a hollow longitudinal sleeve  14  defining an interior aperture. The interior aperture can be a cylindrical aperture and a slideable piston  16  can be slidably received within the cylindrical aperture within sleeve  14  for longitudinal movement between an extended position and a retracted position, and a tensioner spring  36  biasing the piston  16  toward the extended position with respect to the cylindrical aperture  14 . The piston  16  and the cylindrical aperture  15  can define an expandable fluid chamber  18 . In operation, fluid enters the fluid chamber  18  through a fluid passage  39  formed in the housing  12  from a source of pressurized fluid, such as an oil pump or reservoir. The hydraulic tensioner  10  can include a cantilever spring  20  having a first end  22  attachable to the housing  12  and a second end  24  releasably engageable with the piston  16  for retaining the piston  16  in the retracted position within the cylindrical aperture  15  of the hydraulic tensioner  10  against urgings of the biasing spring  36  during storage, shipment and installation. The second end  24  can be disengageable from the piston  16  to allow longitudinal movement of the piston  16  outwardly toward the extended position with respect to the cylindrical aperture  15  of the housing  12 . The second end  24  of the cantilever spring  20  can be re-engaged with an outer end of the piston  16  for retaining the piston  16  within the cylindrical aperture of the housing during service situations, by way of example and not limitation, such as service situations requiring repair, replacement, or adjustment of the endless loop power transmission member. 
     As best shown in  FIGS. 1 and 3 , by way of example and not limitation, the hydraulic tensioner  10  can include a spring-receiving slot  30  formed in the housing  12  of the hydraulic tensioner  10  for receiving the first end  22  of the cantilever spring  20 . The cantilever spring  20  can be retained by the housing during both shipment and operation of the hydraulic tensioner  10 , if desired. Alternatively, the cantilever spring  20  can be releasably engaged and disengaged with respect to retaining notches at both ends for separation from the housing  12 , if desired. The spring-receiving slot  30  can include a hook-shaped slot formed in the housing  12 . The first end  22  of the cantilever spring  20  can include a shaped end complementary to the shape of the spring-receiving slot  30  such that the first end  22  can be fixedly secured within the spring-receiving slot  30 . By way of example and not limitation, the spring-receiving slot  30  can be located on the housing  12  along a surface adjacent to an outwardly extending nose end  26  of the piston  16 . The second end  24  of the cantilever spring  20  can move relative to the fixed first end  22 . As best shown in  FIGS. 1-3 , a spring-retention groove  32  can be formed on the nose end  26  of the piston  16  for retention of the second end  24  of the cantilever spring  20 . As best shown in  FIGS. 1 and 3 , the cantilever spring  20  can include a hooked end  34  at the second end  24  of the cantilever spring  20 . The cantilever spring  20  can include a flat bar, wire, or cross-sectional spring material. The hooked end  34  can be engageable with the spring-retention groove  32  for securing the cantilever spring  20  to the nose end  26  of the piston  16 . By way of example and not limitation, the cantilever spring  20  can engage the piston  16  via a pin-in-hole connection or other retention method. When the piston  16  is spring-loaded during shipment of the hydraulic tensioner  10 , the piston  16  can be secured within the cylindrical aperture of the sleeve  14  by engagement of the cantilever spring  20  with the piston  16 . It should be recognized by those skilled in the art that the first and/or second ends  22 ,  24  interfacing between the cantilever spring  20  and the piston  16 , and/or the cantilever spring  20  and the housing  12 , could be modified to allow the cantilever spring  20  to be symmetrical with respect to the first end  22  and second end  24 . 
     Referring now to  FIGS. 3-4 , a longitudinal cylindrical sleeve  14  can be supported by the housing  12  of the hydraulic tensioner  10 . The cylindrical sleeve  14  can be secured to the housing  12 . The cylindrical sleeve  14  can include a first end  38  located inwardly with respect to the housing  12  and a second end  40  located outwardly with respect to the housing  12 . The second end  40  can receive the piston  16  and allow for longitudinal movement of the piston  16  inwardly and outwardly within the cylindrical aperture defined by the sleeve  14  with respect to the housing  12 . It should be recognized by those skilled in the art that the shape of the housing  12  supporting the cylindrical sleeve  14  can be modified. The housing  12  can include bolt apertures  60 ,  62  for attaching the hydraulic tensioner  10  to an engine. The housing  12  can include a seat portion  25  enclosing a fluid passage  39 . The housing  12  can include a support band  27  for retaining the cylindrical sleeve  14  when the cylindrical sleeve  14  is seated with respect to the seat portion  25 . The cylindrical sleeve  14  can define a notch or window  42  located at the second end  40  with spaced side walls  42   a ,  42   b . As best seen in  FIGS. 1, 3 and 4 , the hydraulic tensioner  10  can include a snap ring  44  fixed to an outer circumference of the piston  16  and selectively engageable within one of the plurality of grooves  16   a  formed on an external surface of the piston  16 . As best seen in  FIG. 3 , the snap ring  44  can have at least one projection  50 ,  52  extending radially outwardly with respect to the piston  16  and engageable within the window  42 . The side walls  42   a ,  42   b  of the window  42  allow the outer ends  50 ,  52  of the snap ring  44  to expand slightly as increased hydraulic fluid pressure within the expandable fluid chamber ratchets the piston  16  outwardly in response to gradual elongation and wear of the endless loop power transmission member, corresponding to reduced back pressure from the endless loop power transmission member on the piston  16 , thereby moving the snap ring  44  from one groove  16   a  to another groove  16   a  of the piston  16  as the piston  16  extends outwardly from the cylindrical aperture of the housing to maintain a desired pressure on the endless loop power transmission member. As best seen in  FIG. 1 , the cylindrical sleeve  14  includes an inner annular groove having sidewalls  14   a ,  14   b  for receiving the snap ring  44  and for limiting longitudinal movement of the piston  16  within the cylindrical aperture of the housing  12  when back pressure from the endless loop power transmission member is substantially balanced with fluid pressure within the expandable fluid chamber of the hydraulic tensioner. Elongation of the endless loop power transmission member reduces back pressure from the endless loop power transmission member on the piston  16 , and allows the hydraulic fluid pressure within the expandable fluid chamber of the housing  12  to ratchet the piston  16  outwardly driving the snap ring  44  into another groove  16   a  of the piston  16  extending the piston  16  to an incrementally expanded outwardly extended position. 
     As best shown in  FIGS. 1 and 4 , the hydraulic tensioner  10  can include at least one check valve  46 ,  48  received within the cylindrical aperture of the sleeve  14 . The tensioner spring  36  can be interposed between a first check valve  46  and a second check valve  48  within the cylindrical sleeve  14 . The tensioner spring  36  biases the piston  16  in an outward direction from the cylindrical aperture of the sleeve  14 . The first check valve  46  prevents back flow of the hydraulic fluid out of the expandable chamber of the housing  12 , thereby preventing inward movement of the piston  16  beyond the degree allowed by the interaction of snap ring  44  with the side wall  14   b  of the sleeve  14 . The second check valve  48  allows intermittent lubrication of the endless loop power transmission member as the piston  16  is “pumped” between the extended and retracted positions during longitudinal movement of the snap ring  44  between the end limits of travel defined by the side walls  14   a ,  14   b  of the inner annular groove of the sleeve  14 . 
     In operation, the piston  16  can be assembled within the hydraulic tensioner  10  for storage and shipping of the hydraulic tensioner  10  prior to installation of the hydraulic tensioner  10  into a working environment. When the piston  16  is positioned for shipping, the hooked end  34  formed at the second end  24  of the cantilever spring  20  can engage the spring-retention groove  32  in response to applied force against the cantilever spring  20  towards the piston  16 . The second end  24  of the cantilever spring  20  can move relative to the first end  22  of the cantilever spring  20  fixed to the housing  12 . The spring-retention groove  32  can retain the hooked end  34  formed at the second end  24  for securing the cantilever spring  20  to the nose end  26  of the piston  16  and retaining the piston  16  when the piston  16  is spring-loaded by the tensioner spring  36  during assembly to prepare the assembled hydraulic tensioner  10  for shipment. After installation of the hydraulic tensioner  10  into a working environment, by way of example and not limitation, such as an internal combustion engine, an electric engine drive train, or a hybrid drive train, force can be applied against the piston  16  such that the piston  16  can move inwardly with respect to the housing  12 . The hooked end  34  can disengage the spring-retention groove  32  in response to the applied force against the piston  16 . The piston  16  can then be released for longitudinal movement outwardly toward an extended position with respect to the cylindrical sleeve  14  of the housing  12  for normal operation of the hydraulic tensioner  10  within the working environment. The second end  24  of the cantilever spring  20  can move away from the piston  16  towards a non-tensioned state. The cantilever spring  20  can be in a non-tensioned state and disengaged from the piston  16  during operation within the working environment. By way of example and not limitation, the first end  22  of the cantilever spring  20  can remain fixed to the housing  12  during operation within the working environment such that the hydraulic tensioner  10  can be reset during a service application by re-engaging the cantilever spring  20  with the spring-retention groove  32  in the nose  26  of the piston  16 . 
     A hydraulic tensioner  10  for an endless loop power transmission member can be assembled for storage and shipment. The hydraulic tensioner  10  can include a housing  12  having a cylindrical aperture. The method for assembling the hydraulic tensioner  10  can include mounting a sleeve  14  having a cylindrical aperture to the housing  12 , inserting a tensioner spring  36  into the cylindrical sleeve  14 , inserting a slideable tensioning piston  16  into the cylindrical sleeve  14  for movement between an extended position and a retracted position, and attaching a cantilever spring  20  to the housing  12 . A fluid chamber can be defined between the cylindrical sleeve  14  of the housing  12  and the piston  16  and the piston can be spring-loadable by the tensioner spring  36 . The cantilever spring  20  can have a first end  22  attachable to the housing  12  and a second end  24  releasably engageable with the piston  16  for retaining the piston  16  within the hydraulic tensioner  10  against urgings of the tensioner spring  36  during storage and shipment. The second end  24  of the cantilever spring  20  can be disengageable with the piston  16  allowing movement of the piston  16  outwardly with respect to the housing  12 . The method can further include forming a spring receiving slot  30  in the housing  12  for receiving the first end  22  of the cantilever spring. The method can further include forming a spring-retention groove  32  on a nose end  26  of the piston and engaging a hooked end  34  located at the second end  24  of the cantilever spring  20  with the spring-retention groove  32 . The hooked end  34  can engage the spring-retention groove for securing the cantilever spring  20  to the nose end  26  of the piston  16  and retaining the piston  16  against the urging of the tensioner spring  36 . The hooked end  34  can engage the spring-retention groove  32  in response to force applied against the cantilever spring  20  by the tensioner spring  36  through the piston  16 . The method can further include applying force against the piston  16  to move the piston  16  inwardly with respect to the housing  12  and disengaging the hooked end  34  with respect to the spring-retention groove  32  in response to the force applied. The piston  16  can be operable for movement outwardly with respect to the housing  12  and the cantilever spring  20  in a non-tensioned state during operation within a working environment. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.