US3356814A - Trigger lock arrangement for power tools - Google Patents

Description

Dec. 5, 1967 A. H. FRANCE. JR 3,356,814

TRIGGER LOCK ARRANGEMENT FOR POWER TOOLS Filed Oct. 24. 1965 V0 INVENTOR.

ALF/e50 H. Hen/v05, Jie.

BY M ATTORNEYS United States Patent Ofiice 3,356,814 Patented Dec. 5, 1967 3,356,814 TRIGGER LOCK ARRANGEMENT FOR POWER TOOLS Alfred H. France, Jr., Baltimore County, Md., assignor to The Black and Decker Manufacturing Company,

Towson, Md., a corporation of Maryland Filed Oct. 24, 1965, Ser. No. 504,697 7 Claims. (Cl. 200-157) ABSTRACT OF THE DISCLOSURE A switch for a portable power tool or appliance which includes an actuator manipulable to switch OFF and to switch ON positions. The switch has a locking member normally biased outwardly to a non-locking position in which an end portion of the locking member projects from the housing. The locking member can be moved inwardly to a locking position after the switch is turned ON to lock the switch in its ON position. The improvement to the switch includes a recess formed in the switch actuator which permits free movement of the locking member to a position in which its end portion is flush with the housing when the switch actuator is in the OFF position. Thus, damage to the locking member and the switch is avoided in the event the tool or appliance, while OFF, is dropped or inadvertently struck against an object.

This invention relates to a lock arrangement to maintain a spring biased trigger switch of a portable power operated device in an on condition, and particularly to an improved trigger switch lock arrangement which prevents damage to the trigger, its associated switch, and to the power operated device, which could occur as the result of shock or impact at an exposed portion of the lock device.

More particularly, the invention relates to a lock arrangement for the trigger and switch of a portable electric tool which prevents damage thereto in the event of shock or impact to the locking device such as can be caused by accidentally dropping or bumping the tool. Portable power driven tools, especially electric drills, are customarily provided with a trigger mounted on a handle of the tool to provide for convenient holding and operation of the tool by the user. The normal arrangement is a trigger connected to a switch so that the motor of the tool is turned on when the trigger is pulled and is immediately turned 01f when the trigger is released, the trigger and switch being returned to the original released position by a return spring. It is also customary to provide a manually operable lock to permit the user of the tool to lock the trigger in the switch on position so the tool remains on after the trigger is released. In the usual arrangement slight pressure on the trigger, in its locked condition, disengages the lock, and the trigger then returns to its switch oif position when released.

As a result of keen competition in the portable power tool field, and because of the large number of portable tools manufactured, small savings in manufacturing costs are quite significant to the overall profit of a particular manufacturer. Hence, trigger operated switches are manufactured from molded plastic materials because of their relatively low cost and excellent electrical insulating properties, and are provided as a preassembled unit which is mounted in the tool handle.

A common lock arrangement for triggers of such portable power tools is a lock pin that has a knob which projects outwardly from the tool housing and is normally spring biased to a non-locking position in which the knob is exposed. A recess is provided in a movable part of the trigger switch to receive the pin after the trigger is pulled to the switch on position. The recess includes a shoulder which faces in a direction opposite to the direction that the movable part of the trigger switch travels when the trigger is pulled and the lock pin can be depressed into the recess to engage behind the shoulder to thus prevent the trigger from moving back to its switch oii position when released. The shortcoming of the presently used trigger and lock pin arrangements when the trigger is in the switch off position, however, is that the knob is exposed and a portion of the trigger switch is then in the path of the lock pin. Hence, damage to the plastic material trigger or switch associate-d with the trigger frequently occurs when the power tool is accidentally dropped or bumped, thereby depressing the lock pin with sufiicient force to break the plastic parts of the trigger switch.

The present invention eliminates the problem of breakage or accidental damage to the trigger or switch housing by impact or force on the lock pin. This is accomplished in an extremely economical manner at practically no additional manufacturing cost. The basic concept is to provide a space or recess to receive the locking pin should it accidentally be depressed when the trigger switch of the power tool is in its off position. This recess permits the pin to move axially against the bias of its return spring without causing any damage to the trigger, its associated switch, or any other portions of the power tool should the tool be dropped so that it lands on the exposed knob portion of the lock pin. It has been found that providing the space or'recess prevents damage to the trigger and switch, not only when the knob of the pin is subjected to an axial force but also when the knob is struck a glancing blow which normally would tend to break off the sleeve portion of the switch housing in which the pin is retained for sliding movement.

Hence, by virtue of the simple expedient of this invention, a trigger and switch arrangement for portable power tools is provided which has essentially the same low cost and convenience of operation of the conventional trigger switch and lock arrangements and which absolutely prevents damage to the trigger or switch as a result of shock or impact on the trigger locking element such as can be caused by dropping the tool so it lands on the locking element.

The advantageous features discussed above will become apparent with reference to the drawings which form a part of this specification and in which FIG. 1 is a front view of a power tool incorporating the damage preventing lock pin arrangement of this invention, with portions of the tool housing cut away to show the trigger switch;

FIG. 2 is a view in section taken along lines 2-2 of FIG. 1;

FIG. 3 is a partial sectional view taken along lines 33 of FIG. 2;

FIG. 4 is a sectional view taken along lines 44 of FIG. 3;

FIG. 5 is an enlarged partial view in section taken along lines 5-5 of FIG. 4; and

FIG. 6 is a pictorial view of the trigger assembly removed from the switch housing.

Referring now to the drawings and particularly to FIGS. 1 and 2, there is shown a power tool in the form of an electric d-rill 1 having a housing 2 with a handle portion 3 depending downwardly from the main or body portion of the housing to provide a conventional pistol grip at handle portion 3 of the power tool. Mounted within handle portion 3 and ofiset slightly toward the upper end of the handle portion is a trigger switch assembly 4 having a trigger assembly 5 and a switch casing 6. Both trigger assembly 5 and switch casing 6 are preferably formed from molded plastic material having good electrically insulating properties. Casing 6, as shown at FIGS. 3 and 4 has a topwall 7, an integral endwall 8 projecting downwardly a short distance and integral with the topwall, and a pair ofsidewalls 9 and 10 which are integral with and project downwardly from the opposite side edges of the topw'all for a distance about twice the length of endwall 8; Insertable into thespace between sidewalls 9 and 10 and belowthe plane of edge 11 of endwall8 is a preassembled stationary contact assembly 12. Stationary contact assembly 12 includes a contact support member 13 of molded plastic material with good electrical insulating properties. Contact support member 13 is of generally rectangular outline configuration and is recessed at one side as at 14 to receive a first pair of stationarycontacts 15 and 16 which form part of a first switch and is similarly recessed at the other side (not shown) to receive a second pair of stationary contacts which form part of a second switch (not shown). Each contact is generally L-shaped and has upwardly projecting portions 17 for engagement by a movable contact.

Wires 18 and 18' of the power cord 20 are connected to stationary contact 15 of both pairs of contacts. Wires 19 and 19 are connected to the opposite terminals of the motor of drill 1.

Stationary contact assembly 12 is secured to casing 6 by a rivet 22 which passes through aligned openings in the contact support member 13 and each of sidewalls 9 and 10 of the casing.

Mounted in casing 6, immediately beneath topwall 7, for sliding movement along. a path parallel with the topwall, is the trigger assembly 5. Trigger assembly includes a finger engaging portion 23 formed integral with an elongated, generally rectangular body portion 24 which is mounted for sliding movement along a straight line path in the generally rectangular space bounded by topwall 7, endwall 8 and portions of sidewalls 9 and above stationary contact assembly 12. Body 24 is provided with two downwardly facing recesses 25 offset slightly on each side of its longitudinal center in which movable contacts 26 are disposed for sliding movement with the body portion in insulated relation with each other. Extending downwardly from the upper wall of each of recesses 25 isa compression spring. 27which normally urge the movable contacts 26 in a direction toward both pairs of stationary contacts and 16.

Above recesses 25, at the end of body 24 opposite from finger engaging portion 23 is a recess 29 which opens toward endwall 8 and is closed at one side to provide a seat 30 for one end of a .helically wound compression spring 31. The other end of compression spring 31 bears against the inner face of endwall 8.

Seat 30 is at one side of a transverse wall 32 of, the body portion of the trigger assembly. At the other side of transverse wall 32 is a notch which provides a transverse stop shoulder 33 engageable with a stop rib 34 projecting from the inner surface of topwall 7 to prevent separation of trigger assembly 5 from switch casing 6. The action ofcompression spring 31 normally urges the trigger to the position of FIG. 4.

Between face 35 of transverse wall 32 and the inner wall 36 of the finger engaging portion 23 of the trigger are a pair of identical recesses 37 and. 38 separated by a wall 39 which provides an abutment surface in the form of a transverse shoulder 40.

Projecting transversely outwardly from sidewall 10 and molded integral therewith, adjacent its upper corner at the edge closest to the trigger is a cylindrical sleeve 41 which provides a guide for a trigger switch lock assembly 42. Lock assembly 42 includes a lock pin 43 the knob and pin can be moved from this first, or released position, to .a second or depressed position (as shown in dotted lines in FIG. 5) against the action of spring 46.

To turn the drill on, trigger portion 23 is grasped and pulled to move the trigger assembly to the position of FIG. 4. Whenmoved to this position, eachof the mow able contacts 26 moves beyond a central rib 47 of con= tact support member 13 to allow the downwardly pro= jecting rounded tips of the movable contact to enga e the contact portions of both pairs of stationary contacts 15 and 16. The movablecontacts thus bridge thefixed contacts to complete the series circuit from Wires 18 and 18 of the supply line to the motor of drill 1. With the trigger depressed to its first or switch on position (FIG; 3), knob 45 may be pressed inwardly (FIG. 3) so that head 44 of the lock. pin enters recess 37 and engages be hind shoulder 40. The trigger may then be released Whereupon the head 44 of the lock pin presents movement of the trigger assembly to its second position of FIG. 4 or 5, in which the switch is off. The lock assembly is fric vtionally retained in its depressed position against the action of spring 46. To release the lock pin, it is merely necessary to depress the trigger slightly whereupon the head 44 disengages from shoulder 40 and compression spring 46 snaps lock assembly 42 back to its disengaged position, as shown in solid lines in FIG. 5. V

In this second position of the trigger assembly, with the switch off, recess 38 is aligned with the head of lock pin 43. Hence, when the pin is depressed, head 44 enters recess 38. Observe that guide 41 and knob 45 are so dimensioned and located within handle Portion 3 of the electric drill that the outer surface 51 of sidewall 48 of the handle portion of the drill is substantially flush with the tip 49 of the knob when'the knob is depressed.- Thus, the knob may be depressed when the trigger is in either its first position in which the switch is off without danger of engaging any part of the molded plastic material of the body portion 24 of trigger assembly 5. By virtue of this arrangement, careless use of the 'drill such as dropping same when the trigger switch is in its second or switch off position so that tip 49 hits a surface merely causes knob 45 to be forced inwardly to the dotted line position of FIG. 5 against the action of spring 46, but without damage to the trigger switch assembly 4.

In the prior art structures, recess 38 was not provided with the result that the full shock of the pin was taken by the body portion of trigger assembly 5. Because trig ger assembly 5 and all portions of switch casing 6 are made of a molded plastic material, for example, a Bakelite which is somewhat brittle, such forces on the locking pin of prior art trigger-switches frequently resulted in cracking or shattering of the trigger assembly or portions of the switch casing. In addition, where the blow or force occurred at an angle to the axis of knob 45 such as indicated by arrow 50 of, FIG. 5, guide 41 of prior art trigger switch would be broken oif, thus requiring replacement of the entire switch assembly. However, with knob 45 free to move when the trigger switch is off as in this invention,- such a glancing blow as shown by the direction of arrow 50, merely causes the knob to deflect and force the head of the pin inwardly into recess 38, without damage to the trigger switch. 7

'Observe withregard to FIGS. 1 and 2 that switch assembly 4 is mounted within the handle portion of the power tool and-is'held in place by appropriate ribs of thehollow'handle portion 3 to retain the trigger and switch in a proper position relative to sidewall 48 of the housing. Hence, the trigger switch can be easily massproduced because of the molded plastic construction and is also easily mounted in the handle of the tool with the outer end of knob 45 in its proper relative position to be substantially flush with the outer surface of the sidewall when the knob is depressed.

In view of the foregoing, it is apparent that applicant has provided a unique trigger and switch of the locking type with a safety feature which prevents breakage of the switch housing or trigger even though of somewhat fragile construction, due to dropping or mishandling of the power tool to cause excessive forces to be applied to the projecting knob of the lock pin. This safety feature is economically provided merely by adding a recess in the body portion of the trigger. The recess positively prevents damage to the fragile parts of the trigger switch in the event of shock or other forces acting on the exposed part of the lock pin by permitting the lock pin to absorb such forces by movement into the recess.

Although a preferred embodiment of the invention is shown and described, it is not intended that the inventive features herein set forth be limited to the preferred embodiment described but that these inventive features have utility in other switches of the locking type.

What is claimed is:

1. In an electric tool having a tool housing;

a switch carried by said housing;

a trigger to operate said switch, said trigger being movable to a first position in which said switch is on, and a second position in which said switch is off; means normally biasing said trigger to said second position;

a lock pin having a knob portion and movable to a depressed position in which said knob is flush with said tool housing, and

a released position in which said knob is exposed for manual movement to said depressed position;

said trigger having a first recess aligned with said lock pin to receive said lock pin with said trigger in said first position;

shoulder means facing toward said first recess and arranged to engage said lock pin with said lock pin in said depressed position and said trigger in said first position;

the improvement comprising a second recess aligned with said lock pin with said trigger in said second position;

said second recess having a depth, measured along the path of travel of said lock pin, at least as great as the length of the exposed portion of said lock pin to enable said lock pin to enter said recess when depressed so that the end of the lock pin is flush with the adjacent portion of said housing; whereby damage to said trigger switch is prevented in the event of shock or impact on said pin caused by dropping or bumping said power tool with said trigger in said second position.

2. An improvement in accordance with claim 1 in which said switch includes a switch housing; and

said trigger, and said locking device are each retained by said switch housing for movement relative to said switch housing.

3. In a trigger operated switch assembly adapted to be mounted in a tool and having a switch housing of molded plastic material; switch means carried by said switch housing; a trigger assembly; first guide means on said housing slidably mounting said trigger assembly for movement along a predetermined path to a first position in which said switch means is in an on condition, and a second position in which said switch means is in an oil condition; means to retain said trigger assembly against separation from said switch housing;

means to normally urge said trigger assembly to said second position;

an abutment shoulder on said trigger assembly and movable therewith along said predetermined path;

a manually operable locking device having an engaging element engageable with said abutment shoulder and a manipulable knob portion fixed thereto;

a second guide means on said housing for mounting said locking device for movement along a predetermined path of travel from a first position in which said shoulder engaging element is disposed in the path of travel of said abutment shoulder, and

a second position in which said shoulder engaging element is spaced from the path of travel of said shoulder;

said abutment shoulder being located on one side of the path of travel of said locking device when said trigger is in said first position, and

on the other side of the path of travel of said locking device when said trigger is in said second position;

said switch housing including means for mounting same in a tool housing in such a manner that said knob portion of said locking element is exposed relative to said tool housing whenever said locking device is in said first position, and

is completely received in and at least flush with said tool housing whenever said locking device is in its second position;

the improvement of means to prevent said locking member as well as the switch itself from being broken in the event the tool, while the trigger is in said second position, is dropped or inadvertently struck against an object;

said means comprising a recess in said trigger assembly to freely accommodate said shoulder engaging member and thus permit movement of said locking member to its second position whenever said trigger assembly is in its second position.

4. A trigger operated switch assembly in accordance with claim 3 in which said trigger assembly is of molded plastic material.

5. In an electric tool or appliance having a housing,

an electric switch in the housing, the switch including a manually manipulated switch actuator having on and otf positions, and

a resiliently biased locking member retractable into the housing whenever the switch actuator is in its on position to selectively lock the switch in the on position, said locking member being resiliently biased toward an extended or non-locking position and havmg an end portion which normally projects beyond an adjacent surface of the housing when the locking member is in the extended position;

the improvement of means to prevent said locking member as well as the switch itself from being broken or damaged in the event the tool, while in its off position, is dropped or struck inadvertently against an object,

said means comprising a recess formed in said switch;

said recess communicating with said locking member in the OE position of the switch and allowing said locking member to be temporarily retracted therein;

said end portion of said locking member when said locking member is so retracted, being at least flush with the adjacent surface of the housing;

whereby said locking member and said switch are protected against accidental breakage.

6. The improvement according to claim 5 wherein 7 8 said switch actuator is movable rectilinearly between its References Cited on and off positions; and FOREIGN PATENTS said locking member is movable rectilinearly along a path transverse to the rectilinear direction of move- 913'389 12/1962 Great Bntam' ment of said switch actuator.

7. The improvement according to claim 5 wherein said recess is formed in said switch actuator. H. BURKS, Assistant Examiner.

5 ROBERT K. SCHAEFER, Primary Examiner.

Claims (1)

1. IN AN ELECTRIC TOOL HAVING A TOOL HOUSING; A SWITCH CARRIED BY SAID HOUSING; A TRIGGER TO OPERATE SAID SWITCH, SAID TRIGGER BEING MOVABLE TO A FIRST POSITION IN WHICH SAID SWITCH IS ON, AND A SECOND POSITION IN WHICH SAID SWITCH IS OFF; MEANS NORMALLY BIASING SAID TRIGGER TO SAID SECOND POSITION; A LOCK PIN HAVING A KNOB PORTION AND MOVABLE TO A DEPRESSED POSITION IN WHICH SAID KNOB IS FLUSH WITH SAID TOOL HOUSING, AND A RELEASED POSITION IN WHICH SAID KNOB IS EXPOSED FOR MANUAL MOVEMENT TO SAID DEPRESSED POSITION; SAID TRIGGER HAVING A FIRST ALIGNED WITH SAID LOCK PIN TO RECEIVE SAID LOCK PIN WITH SAID TRIGGER IN SAID FIRST POSITION; SHOULDER MEANS FACING TOWARD SAID FIRST RECESS AND ARRANGED TO ENGAGE SAID LOCK PIN WITH SAID LOCK PIN IN SAID DEPRESSED POSITION AND SAID TRIGGER IN SAID FIRST POSITION; THE IMPROVEMENT COMPRISING A SECOND RECESS ALIGNED WITH SAID LOCK PIN WITH SAID TRIGGER IN SAID SECOND POSITION; SAID SECOND RECESS HAVING A DEPTH, MEASURED ALONG THE PATH OF TRAVEL OF SAID LOCK PIN, AT LEAST AS GREAT AS THE LENGTH OF THE EXPOSED PORTION OF SAID LOCK PIN TO ENABLE SAID LOCK PIN TO ENTER SAID RECESS WHEN DEPRESSED SO THAT THE END OF THE LOCK PIN IS FLUSH WITH THE ADJACENT PORTION OF SAID HOUSING; WHEREBY DAMAGE OF SAID TRIGGER SWITCH IS PREVENTED IN THE EVENT OF SHOCK OR IMPACT ON SAID PIN CAUSED BY DROPPING OR BUMPING SAID POWER TOOL WITH SAID TRIGGER IN SAID SECOND POSITION.

Images