Abstract:
The present invention provides a power activated wrench with a safety switch for preventing premature activation. The power activated wrench has a wrench body with a tool head assembly and an activation arm for applying torque to the tool head assembly. An activation switch is in operative connection to the activation arm. A safety switch housing is connected to the wrench body and a contact surface connected to the safety switch housing. The proximate connection of the contact surface with a reaction point enables the activation switch.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The following invention relates in general to hydraulic torque wrenches and more particularly to a safety activation device to prevent the wrench from activating before the wrench is in a safe position. 
     2. Description of the Prior Art 
     The petro-chemical industry, as well as industry in general, relies on extensive use of pipes and large valves with bolted or studded flanges. Very large make-up torque of the magnitude of 2,500-5,000 ft-lbs rising to as high as 75,000 ft-lbs are needed to tighten down the nuts on these flanges. Additionally, the break-out torque required may be four or five times the corresponding make-up torque needed for a given flange. Consequently, heavy-duty wrenches, primarily hydraulic torque wrenches, are needed. On such hydraulic torque wrench or power wrench is disclosed in U.S. Pat. No. 4,669,338 to Collins, which is incorporated by reference herein. FIG. 1 illustrates a power wrench such as disclosed in the &#39;338 Patent wherein the ratcheting box wrench referred to generally as  1  is positioned on a flange-nut  2  in a manner so that the wrench body  3  will contact an adjacent flange-nut  4 . Flange-nut  4  provides the reaction point or base from which the ratcheting box wrench  1  will gain leverage. Wrench  1  will have some type of actuation arm which rotates tool head assembly  8 . In the embodiment shown, the activation arm comprises a piston and cylinder assembly. However, other activation arms such as power screws and the like may be utilized. The hydraulic cylinder  5  is activated and its piston rod (not shown) will extend causing the front cylinder clevis  6  to make contact with the lever arm  7  of the tool head assembly  8 . The front cylinder clevis  6  is connected to the lever arm  7  with a connection pin  9 . As the lever arm  7  is turned by the hydraulic cylinder  5 , the tool read assembly  8  rotates. This rotation is further guided by a tracking arm  10  which is an integral part of the tool head assembly  8  located between the retainer arm  11  and the lever arm  7 . The tracking arm  10  moves within an arcuate channel  12  (shown by hidden lines on FIG. 1) within the wrench body  3 . If this tracking arm is properly dimensioned, it will increase the wrench&#39;s ability to operate within a confined space since there will be no need to remove and reattach the wrench to the nut during the exercise of a normal ratchet cycle. 
     It will be understood that when hydraulic fluid flows to cylinder  5  and clevis  6  extends in the direction of force arrow  13 , body  3  will be urged in the direction of force arrow  14  against the reaction point, which is flange-nut  4  in FIG.  1 . Torque is thereby applied to flange nut  2  in the direction indicated by force arrow  15 . Typically, the wrench is activated by an activation switch  16 , which is shown schematically in FIG. 1 as handheld remote  17  with activation button  45 . While not shown in detail, it is known in the art to have a hydraulic fluid source  18  which will transmit hydraulic fluid to lines  9   a  or  9   b  on cylinder  5  in order to extend clevis  6  or retract it. It is similarly well know in the art how to activate transmission of fluid with a handheld remote  17 . In other words, handheld remote is in operative connection with cylinder  5 . 
     This configuration of wrench  1  operates safely as long as body  3  is placed against or very close to flange-nut  4  prior to activating wrench  1  (i.e., applying hydraulic pressure to cylinder  5 ). As may happen through inattentiveness, a worker may position wrench  1  on a flange-nut  2  as seen in FIG.  2 . If the wrench is a ratchet type as disclosed in the above referenced U.S. Pat. No. 4,669,388, the ratcheting mechanism will allow the user to move body  3  against flange-nut  4 . This is the proper manner of positioning wrench  1  before activating hydraulic cylinder  5 . However, if body  3  is not placed safely against flange-nut  4  and if wrench  1  is activated while in this position, there is no reaction point to restrain the movement of body  3  and body  3  will move toward flange-nut  4  quickly and with great force. If a worker has placed his hand or fingers between flange-nut  4  and body  3 , his hand or fingers may be seriously injured or even amputated. What is needed in the art is a wrench which insures body  3  is safely against a reaction point before fluid will flow to hydraulic cylinder  5 . 
     OBJECTS AND SUMMARY OF INVENTION 
     It is an object of this invention to provide a power wrench which is safer to operate than those of the prior art. 
     It is another object of this invention to provide a power wrench which will not activate before the wrench is properly positioned. 
     Therefore, the present invention provides a power activated wrench with a safety switch for preventing premature activation. The power activated wrench has a wrench body with a tool head assembly and an activation arm for applying torque to the tool head assembly. An activation switch is in operative connection to the activation arm. A safety switch housing is connected to the wrench body and a contact surface connected to the safety switch housing. The proximate connection of the contact surface with a reaction point enables the activation switch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a prior art power wrench properly positioned on a flange-nut and against a reaction point. 
     FIG. 2 illustrates the improper positioning of the power wrench away from the reaction point. 
     FIG. 3 illustrates the safety switch housing and contact surface positioned on a power wrench in accordance with the present invention. 
     FIG. 4 illustrates a different embodiment of the safety switch in which the housing is built into the body of the wrench. 
     FIG. 5 a  illustrates a valve which is utilized in one embodiment of the safety switch while the switch is in the enabled position. 
     FIG. 5 b  illustrates the switch of FIG. 5 a  in the non-enabled position. 
     FIG. 6 is a schematic of the pressurized air circuit used in one embodiment of the present invention and the control lines operating the circuit. 
     FIG. 7 is a schematic of an electrical circuit used in an alternate embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 3 illustrates the safety switch  19  of the present invention connected to body  3  of power wrench  1 . Safety switch  19  generally comprises a housing  20  and a contact surface  22 . In the embodiment shown in FIG. 3, contact surface  22  is a contact plate  23 . In this embodiment, the edges of contact plate  23  slightly overlap the outside edge of housing  20  as best seen in FIGS. 5 a  and  5   b.  Contact plate  23  is movably secured to housing  20  by way slots  27  formed therein and a retainer  26  (such as a bolt or pin) extending through slots  27  into housing  20 . While not seen in the figures, it will be understood two more slots  27  are located opposite the side seen in FIGS. 5 a  and  5   b.  Contact plate  23  is thus allowed to move toward and away from housing  20  a distance which is equal to the length of slot  27 , but is biased away from housing  20  by a biasing device such as spring  38  when no external force is applied. While only one spring  38  is shown, it will be understood that a second spring  38  is hidden from view by the portion of contact plate  23  which has not been cut away in FIG.  5 . By moving toward and away from housing  20 , contact plate  23  activates a valve or closes an electrical circuit which will enable handheld remote  17  to activate the source of hydraulic fluid to cylinder  5 . FIGS. 5 a  and  5   b  illustrate one manner in which movement of contact plate  23  activates a valve which enables handheld remote  17 . FIG. 5 a  shows housing  20  with an aperture  31  formed therein. Positioned within aperture  31  is cartridge valve  30 . Cartridge valve  30  includes a series of seals  36  and two apertures  35 . While not shown in the figures, it will be understood that a passage within cartridge valve  30  communicates between the two apertures  35 . A valve spring  39  biases cartridge valve  30  toward the opening of aperture  31 . One suitable cartridge valve is available from Humphrey Products Company, located on Sprinkle Road, Kalamazoo, Mich. 49003 and is designated as model Y125IN. Housing  20  also has three apertures or passages formed therein and communicating with bore  31 . As will be explained more fully below, these passages are air source passage  32 , air activation passage  33  and bleeder passage  34 . It can be seen in FIG. 5 a  that when pressure plate  23  is biased away from housing  20  by springs  38 , the apertures  35  will be aligned with air activation passage  33  and bleeder passage  34 . Thus, pressurized air may escape from air activation passage  33  through bleeder passage  34  and into the atmosphere. Similarly, when pressure plate  23  is depressed against housing  20  as seen in FIG. 5 b,  an adjustment screw  40  moves cartridge valve  30  such that air source passage  32  and air activation passage  33  are in fluid communication. Because it is necessary to position cartridge valve  30  correctly in bore  31  to insure proper alignment of the passages, adjustment screw  40  is threaded through contact plate  23  and engages cartridge valve  30 . It will be readily apparent from FIGS. 5 a  and  5   b  how the advancing or backing out of adjustment screw  40  will align seals  36  and apertures  35  for proper operation of cartridge valve  30 . 
     While FIG. 3 illustrates a housing  20  formed separately from body  3 , an alternate embodiment seen if FIG. 4 incorporates housing  20  into body  3 . In FIG. 4, body  3  has been considerably cut down and is fixed to cylinder  5  by a connector  43 . Connector  43  is shown as simply a plate with screw apertures to engage cylinder  4  and body  3 . Of course, connector  43  could be any means for securely fixing cylinder  5  relative to body  3 . It will be clear to those skilled in the art that a housing  20  can be formed in body  3  by drilling out a bore  31  and passages  32 ,  33 , and  34  similar to that seen in FIGS. 5 a  and  5   b.  Contact plate  23  shown in FIG. 4 will slide over the outer edge of body  3 /housing  20  exactly as seen in FIGS. 5 a  and  5   b.  While not shown in FIG. 4, a small slot will be formed in body  3  adjacent to head assembly  8  in order to accommodate the inward travel of that edge of contact plate  23 . The embodiment of FIG. 4 may be slightly more economical to construct than the embodiment of FIG.  3 . However, FIG. 3 allows more freedom as to where to locate housing  20  along the length of body  3 . This may be important in some applications because different flanges have different spacing between flange nuts. If a flange has a wide spacing between flange nuts, it may be appropriate to locate housing  20  further down body  3  than shown in FIG.  3 . However, the decisions as to how to form housing  20  and where to locate it along body  3  are well within the capabilities of those skilled in the art. The important point is that both embodiments of safety switch  19  seen in FIGS. 3 and 4 operated in the manner described in relation to FIGS. 5 a  and  5   b.    
     The air flow schematic of FIG. 6 more clearly illustrates how the flow of air through safety switch housing  20  enables handheld remote  17  to supply hydraulic fluid to cylinder  5 . While not explicitly shown in the schematic, it will be understood that FIG. 6 describes the invention with pressure plate  23  depressed and thus air source passage  32  in communication with air activation passage  33  as seen in FIG. 5 b.  Pressurized air from a conventional air source  50  (e.g. a compressor, air tank, etc.) will travel though line  54  and enter air source passage  32  and exit through air activation passage  33 . Air source  50  in this embodiment is a 150 psi source, but many variations in pressure may be appropriate depending on the tools operated by the air source. Line  55  will carry this pressurized air to handheld remote  17 . When handheld remote  17  is activated, pressurized air will flow therethrough and open air pilot valve  53 . Air pilot valve  53  may be any commercially available pilot valve capable of carrying out the functions described herein. The opening of air pilot valve  53  will allow pressurized air from source  150  to enter conventional air motor driven hydraulic pump  51 . Air motor/hydraulic pump  51  will supply the hydraulic fluid to cylinder  5  which activates wrench  1 . Thus, it can be seen how air activation passage  33  acts as an enabling passage which enables handheld remote  17  to activate cylinder  5 . 
     As shown in FIG. 5 a,  when pressure plate  23  is not depressed, air activation passage  33  is connected to bleeder passage  34 . This allows pressurized air in line  55  of FIG. 6 to exhaust to the atmosphere. Thus, even if handheld remote  17  is activated, as long as pressure plate  23  is not depressed, no pressurized air will flow to air pilot valve  53  and no air activates air motor hydraulic pump  51 . Therefore, when a power wrench equipped with safety switch  19  (FIG. 3) is positioned incorrectly on a flange-nut  2  as seen in FIG. 2, the activation of handheld remote  17  will not activate the power wrench. The power wrench may only be activated when the pressure plate is positioned against a reaction point such as seen in FIG.  3 . 
     Nor is the present invention limited to systems using pressurized air. FIG. 7 illustrates an electrically controlled circuit for safety switch  19 . The circuit of FIG. 7 generally comprises a higher voltage source  60  (110 volts in the embodiment of FIG.  7 ), a transformer  61  stepping down the higher voltage to a lower voltage (stepped down to 24 volts in the embodiment of FIG.  7 ), solenoid switch  62  and electric motor/hydraulic pump  65 . In this embodiment, housing  20  will include two electrical contacts  64 . One electrical contact is connected to the  24  volt transformer output and the other electrical contact connects with handheld remote  17 . The depressing of pressure plate  23  will bring contacts  64  together and allows the  24  volts to be applied to the switch in handheld remote  17 . On activation of remote  17 , solenoid switch  62  will bring electrical contacts  63  together. As suggested by FIG. 7, the closing of contacts  63  will cause the 110 volts to be applied to electric motor/hydraulic pump  65 , which will supply fluid to cylinder  3  and activate wrench  1 . As with the circuit of FIG. 6, handheld remote  17  in FIG. 7 is not enabled to activate solenoid  62  and cause voltage to reach electric motor/hydraulic pump  65  unless pressure plate  23  is depressed. It will be understood that transformer  61  and solenoid  62  are not strictly needed and that 110 volts could be directly applied to contacts  64 , handheld remote  17 , and motor/pump  65 . However, there are safety benefits to applying only 24 volts to the equipment handled by workers such as wrench  1  and handheld remote  17 . 
     It will be understood that the two circuits seen in FIG.  6  and FIG. 7 are merely illustrative and the same function could be accomplished with an infinite number of variations in such circuits. Nor is the invention considered limited to circuits which are activated by pressure plates or any other device which physically moves toward and away from housing  20 . Rather pressure plate  23  is just one example of a contact surface  22  (FIG. 3) which may be used to enable an activation switch  16  such as handheld remote  17 . Such contact surfaces  22  could include any sensor which senses a reaction point near contact surface  22 ; e.g. magnetic sensors, light sensors or other devices. All that is necessary is that contact surface  22  only enable activation switch  16  when contact surface  22  is sufficiently close to a reaction point that a worker&#39;s fingers or hands cannot easily be placed between the contact surface  22  and the reaction point. Thus, a proximate connection (i.e. actual contact or very close to contact) of contact surface  22  and a reaction point could enable activation switch  19 . Additionally, the fact that the embodiments shown in the figures only illustrate the invention applied to a wrench should not be construed as a limitation. It will be understood that the invention could be applied to other power tools which should be positioned against a reaction point in order to be safely operated. Thus, while the preferred embodiments have been described, it will be appreciated by those skilled in the art that modifications, changes, and improvements may be made without departing from the spirit of the invention defined by the claims.