Lock-off means for airless sprayer
This invention relates to airless spray equipment. In particular, the invention relates to safety mechanisms for such airless spray equipment. 
     BACKGROUND OF THE INVENTION 
     Airless spray equipment such as airless paint sprayers is customarily employed in many painting applications. According to conventional airless spraying techniques, the paint or other fluid is maintained in the airless spray equipment under very high hydraulic pressure; this equipment on actuation typically produces spray at from about one to four thousand psi. Airless spray equipment, particularly the manually operated equipment such as airless spray guns, is thus inherently hazardous, as the paint spray in close proximity to the skin of the operator may cause injury to the skin, and further, the highly pressurized spray is capable of penetrating exposed portions of the body, thereby injecting paint into the body. 
     In order to minimize these hazards, numerous safety mechanisms for use in conjunction with such equipment have been proposed. Typically, these safety mechanisms have the disadvantage of requiring manual operation to inactivate the spray equipment, and the efficacy of such safety mechanisms is therefore determined by the conscientiousness of the equipment operator and limited to non-emergency situations. While automatic safety mechanisms, such as that described in U.S. Pat. No. 3,913,844 to Petrovic, are also known in the prior art, mechanisms such as those described by Petrovic are limited in their application to specific circumstances, for example, automatic disablement of the spray equipment when the equipment is dismantled for cleaning. 
     Accordingly, it is an object of the present invention to provide an automatic safety mechanism for airless spray equipment which substantially minimizes the hazards associated with the use of such equipment. 
     It is another object of this invention to provide a safety mechanism for manually-operated airless spray equipment such as airless spray guns which is automatically activated on full release of the spray equipment actuating mechanism. 
     It is an additional object of this invention to provide a safety mechanism for airless spray equipment such as airless spray guns which automatically functions to prevent accidental operation of the spray equipment actuating mechanism, but which can be readily counteracted by the equipment operator. 
     SUMMARY OF THE INVENTION 
     The invention comprises an automatic safety mechanism for airless spray equipment such as airless spray guns of the type having trigger means for actuating the gun spraying mechanism, comprising lock means for automatically locking the trigger means of the spray gun in an &#34;off&#34; or non-spraying position upon full release thereof by the operator. The lock means is adapted for manipulation by the spray gun operator to prevent the automatic locking of the trigger in the &#34;off&#34; position or to disengage the lock means to permit operation of the trigger. 
     The lock means of the invention includes a locking member spring-biased for operative interposition between the trigger and the hand-grip elements of the spray gun to thereby obstruct operation of the trigger into an &#34;on&#34; or spraying position. The locking member is spring-biased and disposed so that upon full release of the trigger, the locking member is automatically interposed between the trigger and hand-grip elements to prevent actuating movement of the trigger, unless the action of the spring is offset by the operator. 
     The lock means is manually disengageable by manual retraction of the locking member from its operative position interposed between the hand-grip and trigger elements of the gun; preferably, the lock means further includes retraction means such as a lever for facilitating manual retraction of the locking member to an inoperative position. In the preferred embodiment of the invention the lock means further includes stop means for positively engaging the locking member in its operative position and for resisting premature inadvertent engagement of the locking member in the operative position during manipulation of the trigger by the operator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective elevation of the spray nozzle head of an airless spray gun incorporating one embodiment of the safety mechanism of this invention; 
     FIG. 5 is a perspective elevation of the spray nozzle head of an airless spray gun incorporating an alternate embodiment of the safety mechanism of this invention; 
     FIG. 2 is a partial sectional view along the lines I--I of FIG. 1; 
     FIG. 3 is an enlarged perspective elevation of the safety mechanism of FIG. 1, in detail, showing the safety mechanism operating to lock the spray nozzle trigger in &#34;off&#34; position; 
     FIG. 4 is an enlarged perspective elevation of the safety mechanism of FIG. 1 in detail, showing the safety mechanism operating to permit actuation of the spray nozzle trigger; 
     FIG. 6 is a partial sectional view along the lines II--II of FIG. 5; 
     FIG. 7 is an enlarged perspective elevation of the safety mechanism of FIG. 5 in detail, showing the safety mechanism operating to lock the spray nozzle trigger in &#34;off&#34; position; and 
     FIG. 8 is an enlarged perspective elevation of the safety mechanism of FIG. 5 in detail, showing the safety mechanism operating to permit actuation of the spray nozzle trigger. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     With particular reference to FIGS. 1-4, an airless spray gun nozzle head is generally shown at 1, with associated hand-grip element 2 and a trigger element 3 which pivots about a trigger pivot pin 4 disposed between projections 6 on the rear portion of hand-grip element 2. The nozzle head 1 further includes the safety mechanism of this invention, comprising lock means generally indicated at 7. As best seen in FIGS. 2-4, the lock means 7 includes a locking member 8 comprising a rigid arm locking member 9 pivotally engaged with a lock pivot pin 10 disposed between projecting ears 11 on the inner surface of hand-grip element 2. The locking member 8 is spring-biased as by tension spring 15a towards the rear portion of the nozzle 1 so that the arm member 9 is urged toward the position shown in FIG. 2, where it is interposed between trigger 3 and hand-grip 2 and acts to obstruct pivotal movement of the trigger 3 toward the hand-grip element 2. 
     The lock means 7 further includes stop means, generally indicated at 13, for positively engaging the locking member 8 and for resisting premature inadvertent engagement of the locking member 8 in the operative position shown in FIG. 2, comprising a first cross-bar member 14 transversely disposed in track means for receiving and guiding the distal end of arm locking member 9 such as a longitudinal slot 16 in the distal portion of trigger element 3. As best seen in FIGS. 3 and 4, the first cross-bar member 14 is disposed forwardly of a second cross-bar member 17 at the proximal end of slot 16 to intersect the path of the arm locking member 9 within the slot 16; the first cross-bar member 14 projects sufficiently to obstruct the travel of the arm locking member 9 within the slot 16 when the trigger element 3 is depressed in an &#34;on&#34; or spraying position, as shown in FIG. 4, but also permits the arm locking member 9 to clear the first cross-bar member 14 and travel to the end of the slot 16 to abut the second cross-bar member 17 upon full release of the trigger element 3 to the &#34;off&#34; or non-spraying position, as shown in FIG. 3. Preferably, the first cross-bar member 14 is tapered as shown, and the arm locking member 9 includes bearing means such as wheel 18 on the distal end thereof for facilitating travel of the arm locking member 9 within the slot 16. The second cross-bar member 17 projects sufficiently to prevent disengagement of the wheel 18 with the slot 16 when the trigger element 3 is fully released. 
     With particular reference to FIGS. 5-8, spray gun nozzle head 1a is shown with associated hand-grip element 2a and trigger element 3a which pivots about trigger pivot pin 4a disposed between projections 6a on the trigger element 3a of nozzle head 1a. The nozzle head 1a further includes an alternate embodiment of the safety mechanism of this invention, comprising lock means generally indicated at 7a. As best seen in FIGS. 6-8, the lock means 7a includes a rigid T-shaped locking member 8a comprising horizontal element 9a and vertical element 10a; horizontal element 9a is disposed between side portions 11a on trigger 3a for pivotal engagement therewith. Locking member 8a is spring-biased by a spring 15 toward the barrel portion 12 of spray gun nozzle head 1a so that vertical element 10a is urged toward the position shown in FIG. 6, where it is interposed between trigger 3a and hand-grip 2a and acts to obstruct pivotal movement of trigger 3a toward hand-grip 2a. 
     Lock means 7a further includes stop means 13a, which functions as previously described. Stop means 13a in this embodiment comprises a projecting wedge 18 vertically disposed on hand-grip 2a in the path of vertical element 10a of locking member 8a. As best seen in FIGS. 7 and 8, the wedge 18 projects sufficiently to obstruct the travel of the vertical element 10a along hand-grip 2a when the trigger 3a is depressed in an &#34;on&#34; or spraying position, as shown in FIG. 8, but also permits the vertical member 10a to clear the head portion of the wedge 18 when the trigger 3a is fully released for operative positive engagement of the vertical member 10a between the head of wedge 18 and the underside of the barrel 12, as shown in FIG. 7. 
     The lock means 7a also includes retraction means generally indicated at 19 comprising a lever 21 affixed to horizontal element 9a of locking member 10a for facilitating retraction of the vertical element 10a of locking member 8a from the operative position illustrated in FIG. 7 to the inoperative position illustrated in FIG. 8, thereby disengaging lock means 7a. The lever 21 is preferably disposed for convenient manipulation by the thumb of the operator. 
     The safety mechanism of the invention operates as follows: 
     With particular reference to the embodiment of the invention, of FIGS. 1-4, trigger 3 of nozzle 1 is operated by the operator by pivotal movement of the trigger 3 about trigger pin 4 toward hand-grip 2 to actuate the spraying mechanism and place the trigger in an &#34;on&#34; or spraying position. Simultaneously with the reciprocal movement of trigger 3 to various &#34;on&#34; positions, wheel 18 of locking member 8 travels reciprocally within slot 16 between first cross-bar member 14 and the distal end of slot 16. As the trigger 3 is fully released, the action of the spring biasing arm locking member 9 forces the wheel 18 over the first cross-bar member 14 and up against the second cross-bar member 17, as shown in FIG. 2. In this position, lock means 7 is positively engaged, and further operation of the trigger 3 is prevented by arm locking member 9, now rigidly interposed between trigger 3 and hand-grip 2. To continue spraying the operator disengages lock means 7 by manually retracting arm locking member 9 from the position shown in FIG. 2, and operating of the trigger 3; after slight operation of the trigger 3, the arm locking member 9 may be released by the operator as it will then be automatically retained in the inoperative position shown in FIG. 4 until the trigger 3 is again fully released. The engagement of lock means 7 upon full release of the trigger 3 may be prevented by manual restraint of the arm locking member 9 against the force of the biasing spring (not shown). 
     The embodiment of the invention illustrated in FIGS. 5-8 operates in a similar fashion. As the trigger 3a is fully released, the action of the spring 15 urges vertical element 10a towards the barrel portion 12 of nozzle 1a, forcing the distal end of the vertical element 10a over projecting wedge 18 and up against the underside of the barrel 12, as shown in FIG. 7. In this position, lock means 7a is positively engaged, and further operation of the trigger 3a is prevented by vertical element 10a, now rigidly interposed between hand-grip 2a and trigger 3a. To continue spraying, the operator disengages lock means 7a by thumbing the lever 21 to retract the vertical element 10a from the position shown in FIG. 6, and operates the trigger 3; after slight operation of the trigger 3, the lever 21 may be released by the operator as the vertical element 10a will then be automatically retained in the inoperative position shown in FIG. 8 until the trigger 3 is again fully released. The engagement of lock means 7a upon full release of the trigger 3 may be prevented by holding lever 21 to restrain the action of vertical element 10a against the force of spring 15.