Patent Publication Number: US-2022234170-A1

Title: Tool with surfaces with a compressive surface stress layer

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to tools, and more particularly to ratchet tools having surfaces provided with a compressive surface stress layer by a cold working process. 
     BACKGROUND OF THE INVENTION 
     Currently many types of ratchet tools are known and used, such as wrenches and/or screwdrivers, or the like. These tools typically include a ratchet mechanism disposed in a cavity of a head portion of the tool. The ratchet mechanism typically includes a pawl and a ratchet gear having a drive portion engageable with a work piece, for example, a bolt head. A first drive direction may be selected, typically using a manually actuable portion, commonly referred to as a reversing lever, so that use of the tool provides torque when engaged with the work piece and rotated in a first direction while slipping or ratcheting when rotated in a second direction. A second drive direction may be selected using the reversing lever that is opposite the first drive direction, and that provides torque and ratcheting in the opposite directions. 
     In operating a dual pawl mechanism the drive direction for the drive portion is dependent on which of two pawls is engaged. This mechanism typically effects the engagement of one pawl and the disengagement of a second pawl via a pawl carrier coupled to a reversing lever. However, certain areas of the ratchet tool experience significant cyclic loading during use. Thus, wear and fatigue can occur in these areas experiencing high loading and/or stress concentration. Typically, ratchet tools are strengthened using advanced metallurgy or by adjusting the design by increasing the radius of corners or using other known transitions to reduce stress concentrations. However, increasing the radius and using other transitions results in an increase in the size of the tool and/or decreases the amount of space in the cavity of the head portion of the tool. Additionally, advanced metallurgy processes increase manufacturing costs and complexity. 
     SUMMARY OF THE INVENTION 
     The present invention relates broadly to a tool, such as a ratchet tool, including a head portion with a cavity that is adapted to at least partially enclose a ratchet mechanism that includes a pawl and a ratchet gear having a drive portion engageable with a work piece. The ratchet tool has one or more surfaces provided with a compressive residual stress layer via a cold working process, such as, for example, shot peening. The present invention results in a ratchet tool with improved wear and fatigue life without having an increased size and/or expensive manufacturing costs compared to current solutions. 
     In an embodiment, the present invention broadly comprises a ratchet tool. The ratchet tool includes a head portion having a cavity adapted to at least partially enclose components for providing torque to a working piece. Surfaces of the cavity are provided with a compressive residual stress layer. 
     In another embodiment, the present invention broadly comprises a ratchet gear for a ratchet tool. The ratchet gear is adapted to be rotatably disposed in a cavity of the ratchet tool and includes a body portion, a toothed portion adapted to selectively engage with a pawl, and a drive portion that projects from the body portion and is adapted to project outwardly from the cavity to engage a work piece. Surfaces of the ratchet gear are provided with a compressive residual stress layer. 
     In another embodiment, the present invention broadly comprises a method of manufacturing a ratchet tool having a head portion with a cavity adapted to at least partially enclose a ratchet gear. The method includes cold working surfaces of the cavity to create a compressive residual stress layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated. 
         FIG. 1  is an exploded, perspective view of an exemplar tool, according to an embodiment of the present invention. 
         FIG. 2  is an assembled, perspective view of the tool of  FIG. 1 . 
         FIG. 3  is a side view of an exemplar ratchet gear of the tool of  FIG. 1 . 
         FIG. 4  is a detailed, top view of a head portion of the tool of  FIG. 1 . 
         FIG. 5  is a plot diagram of residual stress as a function of depth from a surface as a result of an exemplary cold working process, such as shot peening. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is susceptible of embodiments in many different forms, there is shown in the drawings, and will herein be described in detail, embodiments of the invention, including a preferred embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the present invention and is not intended to limit the broad aspect of the invention to any one or more embodiments illustrated herein. As used herein, the term “present invention” is not intended to limit the scope of the claimed invention, but is instead used to discuss exemplary embodiments of the invention for explanatory purposes only. 
     The present invention broadly includes a tool, such as a ratchet tool, having a head portion with a cavity that is adapted to at least partially contain a ratchet gear. The ratchet tool has surfaces provided with a compressive residual stress layer via a cold working process, such as, for example, shot peening. The present invention results in a ratchet tool with improved wear and fatigue life without having an increased size and/or expensive manufacturing costs compared to current solutions. 
     Referring to the Figures, an exemplary tool  100 , such as, for example, a dual-pawl ratchet wrench, having a head portion  102  and a handle portion  104  is depicted. The head portion  102  includes a cavity  106  for at least partially enclosing components of the tool  100  for providing torque to a working piece (not shown) such as a socket and/or a fastener. 
     The head portion  102  includes first and second pawls  108 ,  110  disposed in the cavity  106 . The first and second pawls  108 ,  110  are selectively engageable with a ratchet gear  112  that is operatively engageable with the work piece in a well-known manner. When one of the first and second pawls  108 ,  110  engages the ratchet gear  112 , torque drive is permitted with rotation of the head portion  102  in a first rotational direction while ratcheting occurs with rotation of the head portion  102  in a second rotational drive direction opposite the first rotational drive direction. Conversely, when the other of the first and second pawls  108 ,  110  is engaged with the ratchet gear  112 , torque drive is permitted with rotation of the head portion  102  in the second rotational drive direction while ratcheting occurs with rotation of the head portion  102  in the first rotational drive direction. 
     The cavity  106  includes several portions for receiving and at least partially enclosing components of the tool  100  therein. The ratchet gear  112  is received in a first large generally circular portion of the cavity  106 , referred to herein as the drive cavity portion  114 . The ratchet gear  112  has a generally circular body portion  116  with a toothed portion  118 , and a drive portion  120 , such as, for example, a drive lug, projecting from the body portion  116 . The toothed portion  118  engages with pawl teeth  122  formed on each of the pawls  108 ,  110  for selective engagement with the pawls  108 ,  110  to provide torque drive through the drive portion  120  in either of the first and second rotational drive directions. In an embodiment, as illustrated in  FIG. 3 , the drive portion  120  includes an aperture  124  adapted to allow an outwardly biased ball (not shown) to pass therethrough in a well-known manner. 
     A cover plate  126  is secured to the head portion  102  to enclose the components of the tool  100  in the cavity  106  in a well-known manner. In an embodiment, the cover plate  126  is retained to the head portion  102  using fasteners  128 , such as, for example, screws, rivets, etc. The cover plate  126  includes an opening  130 , such as, for example, a circular bore, through which the drive portion  120  projects for operative engagement with the work piece. The opening  130  also defines a bearing surface for the body portion  116  to position the ratchet gear  112 . 
     The first and second pawls  108 ,  110  are located in a second portion of the cavity  106 , referred to herein as the pawl cavity portion  132 . The drive cavity portion  114  and pawl cavity portion  130  overlap or communicate to allow the first and second pawls  108 ,  110  to selectively move into and out of engagement with the toothed portion  118  of the ratchet gear  112 . 
     As will be discussed below, an actuator  134  for selectively engaging and disengaging the first and second pawls  108 ,  110  with the ratchet gear  112  is provided in a well-known manner. In an embodiment, the actuator  134  is received in a third portion of the cavity  106 , referred to herein as the actuator cavity portion  136 . A throughbore  138  ( FIG. 4 ) is provided on the head portion  102  to allow the actuator  134  to extend through the head portion  102  so that a lever portion  140  of the actuator  132  is positioned on the outside of the head portion  102  and is adapted to be manually operated to select a torque drive direction by a user. A seal  142  is positioned around the actuator  132  to impede or prevent contaminants from entering the cavity  106  through the throughbore  138 . In an embodiment, the actuator  134  is assembled with the head portion  102  by inserting the lever portion  140  into the pawl cavity portion  132  from a first side of the head portion  102 , and by extending the lever portion  140  through the throughbore  138  to a second side of the head portion  102 , which promotes the ability to utilize the seal  142  for preventing ingress of contaminants. The actuator  134  includes a disc portion  144  sized to prevent complete passage through the opening, so that the actuator  134  can be mounted in only one direction. The seal  142  is compressed and/or held in position between the disc portion  144  and the lever portion  140  of the actuator  134 , which is itself held in position by a spacer  146 , discussed below, which is held in place by the cover plate  126 . The actuator  134  is selectively positioned to select one of the pawls  108 ,  110  for selecting the torque drive direction. Each of the pawls  108 ,  110  has a selector post for being manipulated by a recess  148  of the disc portion  144  in a well-known manner. 
     A bias member  150 , such as, for example, a coil spring is positioned between the pawls  108 ,  110 , the ends of the bias member  150  being received and retained by a bore  152  formed in a side of each pawl  108 ,  110 , the respective bores  152  of the two pawls  108 ,  110  being in an opposed orientation so that the bias member  150  biases the pawls  108 ,  110  away from each other. In this manner, when the disc portion  144  catches a selector post of one of the pawls  108 ,  110  to move the respective pawl, the bias member  150  causes the other pawl to shift position. Additionally, the bias member  150  allows the pawl engaged with the toothed portion  118  to cam or deflect away from the toothed portion  118  when the head portion  102  is rotated opposite the selected torque drive direction to allow slippage in that direction, the bias member  150  then forcing the pawl to return to engagement with the toothed portion  118  when rotation of the head portion  102  ceases. 
     As noted above, the spacer  146  is provided to position the reversing lever actuator  134 . The spacer is adapted to receive a post portion  154  of the actuator  134  is received by a spacer bore  156 . The post portion  154  forms a pivot, with a generally circular geometry, and the spacer bore  156  is generally circular so as to form a pivot or bearing surface with the reversing lever post  144 . 
     The tool  100  is preferably designed to provide a tactile feel for the user to identify when the actuator  134  is in a proper position for selection of one of the torque drive directions. Towards this end, a ball and detent structure are provided, as is common in devices of this type. More specifically, the spacer  146  has a throughbore  158  into which a ball  160  and biasing member  162 , such as, for example, a spring, are inserted. The biasing member  162  contacts and is retained in the throughbore  158  by the cover plate  126 . Therefore, as the actuator  134  is rotated, the ball  160  contacts and moves along a surface of the disc portion  144 . More specifically, the surface of the disc portion  144  includes a pair of detents or troughs  164  positioned thereon to correspond to proper positions for the ball  160  when the actuator  134  is in the proper position for selection of the first and second drive directions. 
     A seal  166 , such as, for example an o-ring, is disposed between the cover plate  126  and the ratchet gear  112 . In an embodiment, the seal  166  is a The body portion  116  positions the seal  166  to keep containments from entering the cavity  106  via the opening  130 . 
     Although the tool  100  is described herein as a dual pawl ratchet wrench, the invention is not limited as such and any ratchet type tool could be used, such as, for example, wrenches, screwdrivers, or the like that typically include a ratchet mechanism disposed in a cavity of a head portion of the tool. 
     Referring to  FIG. 4 , one or more surfaces of the tool  100  include a compressive residual stress layer created by a cold working process, such as, for example, shot peening. The compressive residual stress layer can be up to a depth of 0.02 inches and at least through the first 0.002 inches. In an embodiment, a sidewall forming the periphery of the cavity  160  includes a compressive residual stress layer created by a cold working process, such as, for example, shot peening. In another embodiment, the drive cavity edge  168  and/or a pawl cavity edge  170  includes a compressive residual stress layer created by a cold working process, such as, for example, shot peening. The drive cavity edge  168  is where the sidewall of the cavity  160  meets a surface  180  of the head portion  102  that encloses one side of the cavity  160  in the drive cavity portion  114 . The pawl cavity edge  170  is where the sidewall of the cavity  160  meets the surface  180  of the head portion  102  that encloses one side of the cavity  160  in the pawl cavity portion  132 . In another embodiment, the surface  180  of the head portion  102  that encloses one side of the cavity  160  includes a compressive residual stress layer created by a cold working process, such as, for example, shot peening. 
     In another embodiment, one or more surfaces of the ratchet gear  112  include a compressive residual stress layer created by a cold working process, such as, for example, shot peening. The compressive residual stress layer can be up to a depth of 0.02 inches and at least through the first 0.002 inches. As described above and referring to  FIG. 3 , the ratchet gear  112  includes the body portion  116 , toothed portion  118 , drive portion  120 , and aperture  124 . A first radius  172  transitions from the drive portion  120  to the body portion  116 , and a second radius  174  transitions from the body portion  116  to the toothed portion  118 . In an embodiment, the surface of the ratchet gear  112  include a compressive residual stress layer created by a cold working process, such as, for example, shot peening. In another embodiment, the toothed portion  118  may include a compressive residual stress layer created by a cold working process, such as, for example, shot peening. In another embodiment, the respective surfaces of the first radius  172  and/or the second radius  174  may each include a compressive residual stress layer created by a cold working process, such as, for example, shot peening. In another embodiment, the surface of the drive portion  120  may include a compressive residual stress layer created by a cold working process, such as, for example, shot peening. 
     An example of compressive residual stress plotted as a function of depth from the surface is illustrated in  FIG. 5 . The plot shows the compressive residual stress at various depths from a surface as a result of shot peening the surface. 
     An exemplary method of manufacturing an exemplary tool, such as the tool  100  is described hereinbelow. For example, the tool  100  including a head portion  102  having a cavity  160  adapted to at least partially enclose components of the tool  100  including a ratchet gear  112  is provided. 
     One or more surfaces of the cavity  160  are cold worked, such as, for example, by shot peening, thereby creating a compressive residual stress layer. The surfaces can be cold worked to have a compressive residual stress layer up to a depth of 0.02 inches and at least through the first 0.002 inches. In an embodiment, the sidewall forming the periphery of the cavity  160  includes a compressive residual stress layer created by a cold working process, such as, for example, shot peening. In another embodiment, the drive cavity edge  168  and/or the pawl cavity edge  170  include a compressive residual stress layer created by a cold working process, such as, for example, shot peening. In another embodiment, the surface  180  includes a compressive residual stress layer created by a cold working process, such as, for example, shot peening. 
     One or more surfaces of the ratchet gear  112  are cold worked, such as, for example, by shot peening, thereby creating a compressive residual stress layer. The surfaces can be cold worked to have a compressive residual stress layer up to a depth of 0.02 inches and at least through the first 0.002 inches. In an embodiment, the entire ratchet gear  112  is cold worked, such as, for example, by shot peening, thereby creating a compressive residual stress layer. In another embodiment, the toothed portion  118  is cold worked, such as, for example, by shot peening, thereby creating a compressive residual stress layer. In another embodiment, the first radius  172  and/or the second radius  174  are cold worked, such as, for example, by shot peening, thereby creating a compressive residual stress layer. In another embodiment, the drive portion  120  is cold worked, such as, for example, by shot peening, thereby creating a compressive residual stress layer. 
     As used herein, the term “coupled” can mean any physical, electrical, magnetic, or other connection, either direct or indirect, between two parties. The term “coupled” is not limited to a fixed direct coupling between two entities. 
     The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of the inventors&#39; contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.