Abstract:
An electrical tool includes a trigger lock assembly having a trigger lock member, a detent assembly, and a return spring. The trigger lock member is movable relative to a trigger between a neutral position, in which the trigger is movable between an off position and an on position, a lock-off position, in which the trigger is prevented from moving from the off position, and a lock-on position, in which the trigger is maintained in the on position. The detent assembly is operable to releaseably retain the trigger lock member in each position and includes a recess associated with each position. The detent assembly also includes a projection selectively engageable in one of the recesses to releasably retain the trigger lock member in the associated position, and a biasing member biasing the projection into engagement. The return spring is operable to bias the trigger lock member toward the neutral position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 13/571,816, filed Aug. 10, 2012, which claims priority to U.S. Provisional Patent Application No. 61/521,903, filed Aug. 10, 2011, to U.S. Provisional Patent Application No. 61/521,987, filed Aug. 10, 2011, to U.S. Provisional Patent Application No. 61/612,835, filed Mar. 19, 2012, to U.S. Provisional Patent Application No. 61/612,846, filed Mar. 19, 2012, and to U.S. Provisional Patent Application No. 61/613,888, filed Mar. 21, 2012, the entire contents of all of which are hereby incorporated by reference. 
     This application is related to U.S. patent application Ser. No. 13/572,085, filed Aug. 10, 2012, now U.S. Pat. No. 8,528,782, the entire contents of which are also hereby incorporated by reference. 
    
    
     FIELD 
     The present invention relates to grease guns and, more particularly, to a grease gun with a trigger lock assembly. 
     SUMMARY 
     Grease guns are commonly used in work shops, industry and garages to apply lubricant (e.g., grease) to specific points on a piece of machinery. Grease guns typically include a coupler positioned on the end of a hose that can be fitted to grease fittings or zerks which in turn provide fluid access to specific joints, gears, and other important parts of the machine which the grease gun then pumps lubricant into by way of a manual or powered pump. 
     In one independent embodiment, a grease gun may generally include a housing defining an air purge opening, and an air purge pin defining an aperture and being positionable within the air purge opening, where the aperture of the pin is not aligned with the air purge opening in a closed position, and where the aperture in the pin is aligned with the air purge opening in an open position to allow flow through the air purge opening. 
     In some constructions, the housing may define a pin opening communicating with the air purge opening, the pin being movably supported in the pin opening between the closed and positions. The air purge opening extends in a direction, and the pin opening extending transverse to the air purge opening. 
     The housing includes a first wall defining the air purge opening and a second wall. In some constructions, the pin may include an actuator portion engageable by a user, the actuator portion being located on the second wall and spaced from the air purge opening. 
     In some constructions, the grease gun may include a biasing member (e.g., a spring) biasing the pin to the closed position. The biasing member may be positioned between a portion of the pin and a portion of the adjacent housing. The pin may include a retainer engageable with the housing to prevent the pin from being removed (e.g., forced by the biasing member) from the housing. The retainer may be positionable (e.g., removable) to allow the pin to be removed from the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a grease gun. 
         FIG. 2  is an assembly view of the grease gun shown in  FIG. 1 . 
         FIG. 3  is a perspective view of a portion of a grease gun and shows a pump housing and an air purge pin with the pin in a closed position. 
         FIG. 4  is a perspective view of the pump housing and the pin with the pin in an open position. 
         FIG. 5  is a perspective view of the pin, the stop, the retaining ring, and the spring shown in  FIG. 4 . 
         FIG. 6  is a perspective view of the pin shown in  FIG. 5 . 
         FIG. 7  is an end view of the stop shown in  FIG. 5 . 
         FIG. 8  is a perspective view of a portion of another embodiment of a grease gun and shows a pump housing and a purge assembly with the purge assembly in a closed condition. 
         FIG. 9  is another perspective view of the portion of the grease gun shown in  FIG. 8  with the purge assembly in an open condition. 
         FIG. 10  is a section view taken generally along line  10 - 10  in  FIG. 8 . 
         FIG. 11  is a section view taken generally along line  11 - 11  in  FIG. 8 . 
         FIG. 12  is a section view taken generally along line  12 - 12  in  FIG. 9 . 
         FIG. 13  is a perspective view of the valve assembly shown in  FIGS. 10-12 . 
         FIG. 14  is a perspective view of another embodiment of a grease gun. 
         FIG. 15  is a rear perspective view of the grease gun shown in  FIG. 14 . 
         FIG. 16  is a perspective view of the grease gun shown in  FIG. 14  with a portion of the housing removed for clarity and illustrating the locking element in a locked position. 
         FIG. 17  is a perspective view of the portion of the grease gun shown in  FIG. 16  and illustrating the locking element in an unlocked position. 
         FIG. 18  is a rear perspective view of the grease gun shown in  FIG. 14  with a portion of the housing removed for clarity and illustrating the trigger in an off position. 
         FIG. 19  is a rear perspective view of the portion of the grease gun shown in  FIG. 18  and illustrating the trigger in an on position. 
         FIG. 20  is a detailed view of a trigger lock of a trigger assembly. 
     
    
    
     Before any independent embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of embodiment and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other independent embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
       FIGS. 1-2  illustrate an electrically powered grease gun  10 . In the illustrated construction, the grease gun  10  includes a housing  14 , a motor  18  supported by (e.g., positioned within) the housing  14 , a pump assembly  22  driven by the motor  18 , a barrel assembly  26  configured to receive a lubricant cartridge (not shown), and an output hose  30  fitted with a coupler  34 . Although the illustrated construction is shown with a flexible output hose  30 , in alternate constructions (not shown), a rigid output hose may be used. 
     In the illustrated construction, the motor  18  is powered by an 18 volt battery. However, in other constructions, the motor  18  may be powered by a different electrical power source, such as different battery types, line power (plugged into a wall outlet, a generator) etc. In still other constructions, the motor  18  may be designed for and powered by a different power source, such as a pneumatic power source. 
       FIGS. 3-4  illustrate a pump body  38  configured to replace the pump body  40  illustrated in  FIGS. 1-2 . When assembled, the pump body  38  is coupled to the housing  14  of the grease gun  10  and acts as a mounting point for the barrel assembly  26 . More specifically, the pump body  38  includes a threaded ridge  42  to which the barrel assembly  26  may be releaseably attached defining a storage volume  46  therebetween. For operation, a new or replaceable lubricant cartridge (not shown) is placed within the storage volume  46  to be dispensed from the output hose  30 . 
     The pump body  38  also includes a cylinder  50  extending substantially along the end wall  54  and configured to receive a piston  58 . During operation, rotation of the motor  18  causes the piston  58  to reciprocate within the cylinder  54 , draw lubricant from the lubricant cartridge and pump it, under pressure, through the output hose  30 . 
     A purge assembly  62  provides selective fluid communication between the storage volume  46  and the surrounding atmosphere. More specifically, the purge assembly  62  includes a first opening  66  extending through the end wall  54  of the pump body  38  and a second opening  70  intersecting the first opening  66 . In the illustrated construction, the second opening  70  extending substantially perpendicular to the first opening  66  through an adjacent side wall  74  of the pump body  38 . In the illustrated construction, the second opening  70  is open on both ends. 
     Illustrated in  FIGS. 3-7 , the purge assembly  62  also includes a pin  78  configured to be at least partially received and move within the second opening  70  between a closed position (see  FIG. 3 ), in which the first opening  66  is blocked by a portion of the pin  78  and the storage volume  46  is not in fluid communication with the surrounding atmosphere, and an open or purge position (see  FIG. 4 ), in which the first opening  66  is not blocked and the storage volume  46  is in fluid communication with the surrounding atmosphere. In the illustrated construction, the pin  78  is biased towards the closed position by a biasing member (e.g., a spring  82 ) positioned between the pin  78  (e.g., engaging a recess  76  in the end of the pin  78 ) and a flat  86  formed by the pump body  38 . 
     The pin  78  includes a substantially cylindrical body  90  sized to prevent flow through the second opening  70  in all positions of the pin  78 . A seal arrangement (not shown) may also be provided to seal one or both ends of the second opening  70 . 
     Illustrated in  FIG. 6 , the pin  78  also includes a flat surface  118  positioned proximate the inner end of the body  90  to produce a side wall  122 . When assembled, the flat surface  118  interacts with a stop  98  (described below). The pin  78  also includes a groove  126  sized to at least partially receive a retaining ring  102  (described below) therein. 
     An aperture  94  extends transversely through the cylindrical body  90 . The aperture  94  is positioned and sized such that, when the pin  78  is in the open position, the aperture  94  at least partially aligns with the first opening  66  to place the storage volume  46  in fluid communication with the atmosphere, and, when the pin  78  is in the closed position, the aperture  94  does not align with the first opening  66 . In the closed position, the solid portion of the pin  78  is positioned to block the first opening  66 . The degree of alignment of the aperture  94  with the first opening  66  may affect the rate of purging (e.g., complete alignment results in maximum flow, and partial alignment may result in reduced flow). 
     A stop  98  is fixedly coupled to the pin  78  by a retaining ring  102  positioned in the groove  126  of the pin  78 . The stop  98  has a substantially square profile and is configured such that one of the flat surfaces of the stop  98  slides along a flat surface  106  formed by the pump body  38 , restricting rotation of the pin  78  within the second opening  70 . More specifically, the stop  98  maintains the rotational position of the pin  78  within the second opening  70  so that the axis of the aperture  94  always aligns with the axis of the first opening  70 . In the illustrated construction, the stop  98  also acts as a motion limiter, restricting the pin  78  from being forced out of the second opening  70  by the spring  82 . 
     Illustrated in  FIG. 7 , the stop  98  includes an interior aperture  130  that is substantially “D” shaped. When assembled, the stop  98  is introduced axially over the interior end of the pin  78  with the flat portion of the aperture  130  engaging the flat surface  118  of the pin  78 , such that the stop  98  and the pin  78  cannot rotate with respect to one another. The stop  98  is axially biased towards the outer end of the pin  78  until it contacts the side wall  122 , exposing the groove  126  and allowing the retaining ring  102  to be installed therein, locking the stop  98  in place. 
     Once installed, the stop  98  is adjustable (e.g., removable) to allow the pin  78  to be removed from the pump body  38  (e.g., for maintenance, disassembly, etc.). To do so, the user first removes the retaining ring  102  and then slides the stop  98  axially off the pin  78 , freeing the pin  78  to be removed from the second opening  70 . To return the pin  78  to its assembled configuration, the user inserts the pin  78  back into the second opening  70  as described above, and the stop  98  can be re-installed and secured with the retaining ring  102 . 
     During operation, the user utilizes the purge assembly  62  to bleed or purge any air trapped within the storage volume  46 , for example, when a new or replacement cartridge of lubricant has been placed within the barrel assembly  26 . After the new cartridge has been installed, the user can purge the system by moving the pin  78  (e.g., by pressing on the actuator end of the pin  78 ) in a purge direction A (see  FIGS. 3-4 ), causing the pin  78  to move from the closed position to the open position, which in turn places the storage volume  46  in fluid communication with the surrounding atmosphere through the aperture  94 . The user then advances a plunger  110  in a direction B (see  FIG. 1 ), forcing the air out of the storage volume  46  until grease begins to emerge from the first opening  66 . The user then releases the pin  78 , and the spring  82  biases the pin  78  to return to the closed position, sealing the storage volume  46  from the surrounding atmosphere. The user may then operate the grease gun  10 . 
     In prior air purge assemblies (see, for example,  FIG. 2 ), the pin  114  is positioned in and moved axially in the air purge opening (not shown). With this prior arrangement, the pin  114 , even in the open position, interferes with the flow of air/grease attempting to escape. 
     In contrast, in the present arrangement, the aperture  94  and the first opening  66  are opened without interference (there is no structure positioned in the pathway created by the aperture  94  and the first opening). The present design may also allow a user to control of the rate of purging by selectively partially aligning the aperture  94  and the first opening  66 . 
     Also, in the prior arrangement (with the pin  114  positioned in the air purge opening), the user&#39;s finger may also at least partially block the air purge opening impeding air/grease escaping the system and/or resulting in grease getting on the user&#39;s fingers. In contrast, in the present design, the user&#39;s fingers when engaging the pin  78  are not positioned near the air purge opening (the aperture  94  and the first opening  66 ). 
     In another embodiment (not shown), the pin  78  may be configured to rotate about it&#39;s axis between the open position, in which the axis of the aperture  94  is aligned with the axis of the first opening  66 , and the closed position, in which the axis of the aperture  94  is at an angle with respect to the axis of the first opening  66 . The user would rotate the pin  78  generally 90 degrees from the open position to the closed position so the axis of the aperture  94  is perpendicular the axis of the first opening  66 . In such an embodiment, the pin  78  would not move axially within the second opening  70 , as described above. 
       FIGS. 8-13  illustrate an alternate embodiment of a portion of a grease gun including a pump body  38 ′ and a purge assembly. The illustrated alternate embodiment includes much of the same structure and has many of the same properties as that illustrated in  FIGS. 3-7 . Common elements have been given the same reference numbers “′”. The following description focuses primarily upon structure and features of the alternate embodiment that differ from those discussed above. 
     Illustrated in  FIGS. 8-9 , the pump body  38 ′ includes a substantially horizontal groove  200  formed in the side of the body. The groove  200 ′ acts as a guide for a portion of a button  204 ′ of the valve assembly  212 ′ (described below), when assembled. 
     Illustrated in  FIGS. 8-13 , the purge assembly  62 ′ includes a channel  208 ′ formed by the pump body  38 ′ and a valve assembly  212 ′ positioned within the channel  208 ′. The valve assembly  212 ′ provides selective fluid communication between the storage volume  46  and the surrounding atmosphere. 
     The channel  208 ′ includes a first portion  216 ′, extending substantially perpendicular the end wall  54 ′, and a second portion  220 ′ extending perpendicularly from the first portion  216 ′ to the outside of the pump body  38 ′, generally terminating proximate the side of the pump body  38 ′. The first portion  216 ′ of the channel  208 ′ includes an annular wall  224 ′ extending inwardly from the end wall  54 ′ to produce a distal end  228 ′ and a seat  232 ′. The seat  232 ′ is shaped to form a seal with the valve assembly  212 ′, when assembled, isolating the storage volume  46  from the surrounding atmosphere. 
     The channel  208 ′ also includes a recess  236 ′ substantially opposite the distal end  228 ′ of the annular wall  224 ′. The recess  236 ′ positions the valve assembly  212 ′, when assembled, within the channel  208 ′ while allowing the plunger  240 ′ to move axially therethrough. In the illustrated construction, the recess  236 ′ is sized to create a seal with the plunger  240 ′ and to force escaping grease and air through the second portion  220 ′ of the channel  208 ′. 
     The channel  208 ′ is sized such that no external force (e.g., force from the user) is necessary to purge the air and grease from the storage volume  46  when the valve assembly  212 ′ is in the open position. Rather, the illustrated two leg design purges air and grease from the storage volume  46  by pressure from return spring  28  only. 
     Illustrated in  FIGS. 8-13 , the valve assembly  212 ′ includes a plunger  240 ′, a button  204 ′ coupled to the plunger  240 ′, and a spring  244 ′. When assembled, the valve assembly  212 ′ is at least partially positioned within the channel  208 ′ and is adjustable between a closed condition (see  FIG. 11 ), in which the storage volume  46  is isolated from the surrounding atmosphere, and an open condition (see  FIG. 12 ), in which the storage volume  46  is in fluid communication with the surrounding atmosphere. In the illustrated construction, the spring  244 ′ extends between the button  204 ′ and the end wall  54 ′ to bias the valve assembly  212 ′ towards the closed condition. 
     The plunger  240 ′ includes an elongated stem  248 ′ with an enlarged head  252 ′ at one end. An o-ring  256 ′ extends along the periphery of the head  252 ′ to produce a seal with the seat  232 ′ of the annular wall  224 ′. When assembled, the plunger  240 ′ moves axially within the first portion  216 ′ of the channel  208 ′ between a closed position, in which the o-ring  256 ′ is seated against the seat  232 ′ (see  FIG. 10 ), and an open position, in which the head  252 ′ is spaced a distance from the annular wall  224 ′ to allow fluid (e.g., air and/or grease) to pass therebetween (see  FIG. 12 ). 
     Illustrated in  FIGS. 8-13 , the button  204 ′ is coupled to the stem  248 ′ of the plunger  240 ′ opposite the head  252 ′ and is positioned outside the pump body  38 ′. During operation, the user manually presses the button  204 ′ in a direction C (see  FIGS. 10-12 ) to adjust the valve assembly  212 ′ from the closed condition toward the open condition. 
     The button  204 ′ is substantially “L” shaped and includes a first leg  260 ′, coupled to the stem  248 ′ of the plunger  240 ′, and a second leg  264 ,&#39; at least partially received within and slidable along the groove  200 ′ of the pump body  38 ′. The button  204 ′ also includes a cylindrical protrusion  268 ′ extending from the first leg  260 ′ to be received within a boss  272 ′ formed on the pump body  38 ′. When assembled, the protrusion  268 ′ at least partially positions the button  204 ′ in axial alignment with the first portion  216 ′ of the channel  208 ′ while allowing the button  204 ′ to translate axially. 
     In alternate embodiments (see  FIGS. 14-15 ), the button  204 ″ may include a cap  205 ″ coupled to the stem of the plunger. In such embodiments, the button  204 ″ does not include a second leg (such as the second leg  264 ′). 
     The button  204 ′ defines an aperture  276 ′ in the second leg  260 ′ sized to correspond with the second portion  220 ′ of the channel  208 ′. When assembled, the aperture  276 ′ is positioned such that it aligns with the channel  208 ′ when the valve assembly  212 ′ is in the open position (see  FIG. 9 ) and not aligned with the channel  208 ′ when the valve assembly  212 ′ is in the closed position (see  FIG. 8 ). As such, the second leg  264 ′ of the button  204 ′ shields the channel  208 ′ from the outside elements when the button  204 ′ is in the closed position. When the button  204 ′ moves from the open position to the closed position, the edge of the aperture  276 ′ acts as a shear, separating the purged grease from the device  10  so it can be more easily discarded without requiring the user to physically touch the grease. 
     During operation, the user utilizes the purge assembly  62 ′ to bleed or purge any air trapped within the storage volume  46 , for example, when a new or replacement cartridge of lubricant has been placed within the barrel assembly  26 ′. After the new cartridge has been installed, the user can purge the system by pressing the button  204 ′ in the direction C, causing the valve assembly  212 ′ to be adjusted from the closed condition to the open condition, which in turn places the storage volume  46  in fluid communication with the surrounding atmosphere through the channel  208 ′. More specifically, when the user depresses the button  204 ′, the head  252 ′ of the plunger  240 ′ is moved away from the seat  232 ′ (described above), and the aperture  276 ′ of the button  204 ′ is placed in alignment with the channel  208 ′. 
     The user then advances the plunger  110  in a direction B (see  FIG. 1 ), forcing the air out of the storage volume  46  until grease begins to emerge from the channel  208 ′. The user then releases the button  204 ′, and the spring  244 ′ biases the valve assembly  212 ′ to return to the closed condition, sealing the storage volume  46  from the surrounding atmosphere and shearing off the purged grease. The user may then operate the grease gun  10 . 
       FIGS. 15-20  illustrate an alternate embodiment of a grease gun  10 ″. The illustrated alternate embodiment includes much of the same structure and has many of the same properties as the embodiments illustrated in  FIGS. 1-13 . Common elements have been given the same reference numbers “″”. The following description focuses primarily upon the structure and features of the alternate embodiment that differ from those discussed above 
     Illustrated in  FIG. 15 , the grease gun  10 ″ includes an illumination device or LED  300 ″. The LED  300 ″ is positioned within the handle portion  304 ″ of the housing  14 ″ such that the LED&#39;s light beam is directed toward a work area (e.g., slightly upwardly). During operation, the LED is controlled from a switch (not shown) that is operated independently from the trigger  308 ″. In alternate embodiments, the LED may be turned on and off by the trigger  308 ″. 
     Illustrated in  FIGS. 16-20  the grease gun  10 ″ also includes a trigger assembly  312 ″ coupled to the housing  14 ″ and configured to activate and deactivate the motor of the grease gun  10 ″. The trigger assembly  312 ″ includes a trigger  308 ″, pivotably coupled to the housing  14 ″ and movable between a rest or off position ( FIG. 18 ) and an activated or on position ( FIG. 19 ). During operation, the user pivots the trigger  308 ″ (generally against a return spring) from the off position toward the on position to activate the motor and dispense grease. More specifically, pivoting the trigger  308 ″ toward the on position causes a protrusion  320 ″ to contact an electrical switch  324 ″ to supply electrical power from the battery (not shown) to the motor. 
     The trigger assembly  312 ″ also includes a trigger lock  328 ″. The trigger lock  328 ″ includes an elongated element that is linearly movable with respect to the housing  14 ″ between a neutral position, in which the trigger  308 ″ is able to rotate between the on and off positions, a lock-off position ( FIG. 17 ), in which the trigger  308 ″ is locked in the off position, and a lock-on position ( FIG. 19 ), in which the trigger  308 ″ is maintained in the on position. More specifically, the trigger lock  328 ″ can be moved from the neutral position to the lock-off position by sliding the trigger lock  328 ″ in a first direction A when the trigger  308 ″ is in the off position. Furthermore, the trigger lock  328 ″ can be moved from the neutral position to the lock-on position by sliding the trigger lock  328 ″ in a second direction B opposite the first direction A when the trigger  308 ″ is in the on position. In the illustrated construction, the trigger lock  328 ″ is biased in the first direction A (e.g., toward the lock-off position) by a biasing member or spring  309 ″. 
     The trigger lock  328 ″ also includes (see  FIG. 20 ) a set of ridges  350 ″ which define detent recesses  352 ″ therebetween. The recesses  352 ″ are engaged by a spring member  354 ″ providing a detent projection to selectively maintain the trigger lock  328 ″ in each of its three positions (described above). In the illustrated construction, the first detent ridge  350   a ″ extends higher than the second detent ridge  350   b ″. As such, the return spring  309 ″ is able to bias the trigger lock  328 ″ from the lock-on position to the neutral position (over the second detent ridge  350   b ″) but is not able to bias the trigger lock  328 ″ from the neutral position to the lock-off position (over the first detent ridge  350   a ″). Therefore, the user must manually overcome the first detent  350   a ″ to place the trigger lock  328 ″ in the lock-off position. 
     In the illustrated embodiment, the trigger lock  328 ″ also includes a hook  332 ″ extending therefrom. When the trigger lock  328 ″ is in the lock-off position, the hook  332 ″ contacts the top edge  358 ″ of the trigger  308 ″ and restricts pivoting movement of the trigger  308 ″ from the off position toward the on position. When the trigger lock  328 ″ is in the neutral position, the hook  332 ″ does not contact the trigger  308 ″ so that the trigger  308 ″ is free to move between the on and off positions. 
     When the trigger lock  328 ″ is moved to the lock-on position, the hook  332 ″ is at least partially received within an aperture  346 ″ formed by the trigger  308 ″. As such, the trigger  308 ″ cannot return to the off position from the on position. During use, if the user wishes to lock the trigger  308 ″ in the on position, the user must first manually activate the trigger  308 ″, moving it from the off position to the on position. Once the trigger  308 ″ is in the on position, the user manually moves the trigger lock  328 ″ from the neutral position to the lock-on position, against the force of the return spring  309 ″. The user then removes pressure from the trigger  308 ″. 
     To return the trigger  308 ″ to the off position, the user re-applies pressure to the trigger  308 ″, at which point the return spring  309 ″ will automatically move the trigger lock  328 ″ to the neutral position. The trigger  308 ″ then returns to the off position automatically when pressure is released. 
     In an alternate construction, the trigger lock  328 ″ may be movable between a lock position and an unlock position. When the trigger lock  328 ″ is in the lock position, the trigger  308 ″ cannot be pivoted with respect to the housing  18 ″, and, when the trigger lock  328 ″ is in the unlock position, the trigger  308 ″ is free to pivot between the off and on positions. 
     More specifically, when the trigger  308 ″ is in the off position, the hook  332 ″ contacts the top  342 ″ of the lock element  336 ″. In contrast, when the trigger lock  332 ″ is in the unlocked position, the hook  332 ″ is at least partially received within an aperture  346 ″ formed by the lock element  336 ″ when the trigger  308 ″ is in the on position. As such, the trigger lock  328 ″ operates when the trigger  308 ″ is in both the on and off positions. The trigger lock  328 ″ can be used both to stop the trigger  308 ″ from being pivoted from the off position toward the on position (e.g., to prevent accidental activation of the grease gun  10 ″) as well as to lock the trigger  308 ″ in the on position (e.g., for prolonged use). In some embodiments, the trigger lock  328 ″ may be spring loaded or biased towards the unlocked position. In such embodiments, when the trigger  308 ″ is locked in the on position, the user can further depress the trigger  308 ″ causing the trigger lock  332 ″ to automatically return to the unlocked position, freeing the trigger  308 ″ to be pivoted with respect to the housing  14 ″. 
     Although the invention has been described in detail with reference to certain independent embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention as described.