US2609468A

US2609468A - Switch actuator for portable hand tools

Info

Publication number: US2609468A
Application number: US163876A
Authority: US
Inventors: Gubbins Charles Henry
Original assignee: Wolf Electric Tools Ltd
Current assignee: Wolf Electric Tools Ltd
Priority date: 1950-03-31
Filing date: 1950-05-24
Publication date: 1952-09-02
Anticipated expiration: 1969-09-02
Also published as: GB667508A; DE857179C

Description

s p 2, 1952 c. H. GUBBINS 2,609,468

SWITCH ACTUATOR FOR PORTABLE HAND TOOLS Filed May 24, 1950 2 sass'rs-srms'r 2 H63, H64.

55 28 34 40 88 I\\ I\'\ f\\] Q2 l6 J l6 25a M 56 A b E: 33 1, 5/ 24 21 25 4 l5 J 2 M '8 nun; S 1 l4": /4 m 2/ 1e 4 /5 Patented Sept. 2, 1952 1 swrron ACTUATOR/FOR PORTABLE '1 r rmnn'roors 1 Charles Henry Gubbins, Iiondon,;'England,asi signor to Wolf Electric Tools England, a British company Limited, London,

Application'May 24, 1950, Serial No. 163,876 In Great Britain March 31, 1950 [2 Claims. (01. 200-157) The invention relates to portable hand tools of the kind in'which a shaft carrying, or adapted tofcarry, an implement such as a drill, reamer, box-spanner or grinding wheel, is driven from an electric motor which forms part of the tool and to which the flow of current is controlled by a switch actuated by a trigger which, in turn, is operated by a finger of the user of the tool.

In tools of this type as hitherto constructed, the trigger is normally held in off position by means of a spring, and to avoid constant pressureon the trigger when the tool is in use it is customary to provide a detent or plunger which is mounted on a convenient part of the casing of the tool and engages by spring pressure, or can be engaged, in a hole or recess in the trigger when the latter is in its on" position. This arrangement has the disadvantage that, when it is desired to restore the trigger to its inoperative position for cutting oil the supply of current to the motor, it is first necessary to release the detent or plunger. Thus with one hand holding the tool, the operator has to use his other hand to release the trigger and this is an inconvenience,

especially where the'user needs the other hand.

for steadying the work or tool.

The object of the present invention is to provide a trigger arrangement of such a nature-that the trigger, when moved to on" position will automatically be retained in that position, but can be released for movement to oii position merely by the expedient of manipulating the trigger itself. Hence, by means of the invention, the need for providing a detent or plunger or such-like accessory for holding the trigger in on position is dispensed with and the user need use only one hand for holding the tool and operating the trigger under all conditions.

According to the invention, in a portable hand tool of the kind referred to, the trigger is mounted in a guideway for bodily movement from oif" to on position against the pressure of a spring, the guideway being provided with a recess in which a projection on the trigger engages as the result of pressure on the trigger from the said spring when the trigger is moved to its on" position, the arrangement being such that, when the trigger is moved in a direction which is angular to its normal direction of movement, the said projection will be disengaged from the said recess, whereupon the spring will act to restore the trigger to its off position.

The invention will now be described inigreater detail with reference to the accompanyingdrawings, in which: w n

Figure l1 isdalongitudinal sectional view of a typical construction of. portable hand tool with the improved trigger arrangement applied there- Figure 2 isa front .end view of the tool; Figure3 is a rear end view, partly in section, of the tool; z Figure {is a side elevational view, partly in section, of therearward part of the tool, showing the trigger in' its off position;

Figure 5 is a view similar to that of Figure 4, showing the trigger in its on" position, and

Figure 6 is a perspective view illustrating part of the switch mechanism.

The tool illustrated comprises a casing made up of a main body part I, a front cover plate 2 and a rear cover plate3, the three parts being secured together by screws 4. The casing accommodates an electric motor having a field winding 5 and a rotor 6 (Figure 1). The shaft 1 of the rotor drives, through toothed wheels 8 and 9, a spindle II] which projects through the end cap 2 and is fitted with a chuck II for holding a drill or other implement (not shown).

' The lower portion of the main body part I of thejcasingis designed to form a trigger-guard I2 and part of a hollow hand-grip l3 the remaining part of which is formed by the lower part of the cover cap 3. The hollow hand-grip accommodates switch mechanism comprising a block I4 of electrical insulating material which is secured in position by one of the screws 4 and is formed with an upwardly extending rear wall lda-yjoined by side walls Mb. The block I4 is fitted'with two spaced contact blades I5 towhich electric leads it from a flexible cable I! and to the motor 5, 6, are connected by means of terminal screws It, the cable passing out through a hole in the base of the hand-grip I3 and being adapted for connection to a source of electric current. The cable I! includes a safety earth lead I9 which is connected to the base of the handgrip by a terminal screw 20 so as to protect the user of the toolagainst electric shock in the event of a short circuit.

A tumbler 2| is arranged between the side walls Mb ofthe' block it and consists of a block of electrical insulating material fitted with bifurcated contact blades 22, the tumbler being mounted for a rocking movement by the provision thereon of laterally projecting pins 23 engaging in slots 24 inthe side walls Mb of the block [4. When the tumbleris rocked in a clockwise direction the contact-blades thereon will engage with the contact blades 15 on th'e' block I 4, thereby'olosing 3 the circuit to the electric motor 5, 6. When the tumbler is rocked in. an anti-clockwise direction the blades 22 will be moved out of engagement with the blades I5 to open the circuit.

The tumbler 21 is actuated by a trigger 25 in the construction and arrangement of, which the present invention is characterised, as will now be described.

The main body part I of the casing of the tool.

is formed with a web 26 which extends rearward.. ly and lies at a distance above the trigger-guard thus tending also to cant the trigger in an anti- .When th trigger 25 is pulled backwardly from [2, the trigger 25 being arranged in the space between the web 26 and trigger-guard I2 and having a concave forward edge 25a for erigage ment by a finger of the user, leaving the trigger with an overhanging and forwardly projecting upper part 25b,

The internal edge of the trigger-guard l2 is recessed downwardly to provide a shoulder 21- followed by a rearwardly extending plain face 28, while the under surface of the web 2 5 is recessed upwardly; to provide-a shoulder 29 followed by a rearwardly extending plain face 38 lying in parallelism with the face 28. The lower edge of the trigger is formed with a projection 3|, the depth of the trigger when measured be.- tween its upper edge and the lower edge of the said projection being such thatthe trigger, when in its forward (inoperative) position, has a snug sliding fit between the plain .faces 28 and 3B which thereby constitute a guideway for the trigger.

At the rearward end or the plain-face 28-, the material of the main body part I of the casing is downwardly stepped to provide a recess having a shoulder 32- fo-llow'ed by a rearwardly extending plain face 33. With this arrangement, the distance between the plain face 33 and the plain face of the web 26 will be noticeably greater than the depth of the trigger when measured as previously directed. I I

The rearward part of the trigger 25 is formed with a recess 34 in which is arranged a sliding sleeve 35 carrying a ball 36 which projects partway out of the sleeve and bears against the upper edge of the tumbler: 2 l, the ballbeing maintained in resilient engagement with the said edge by means of a compressionspring 3'! acting between the ball and the inner end of the recess 3t. The ball. 36' is. so located relatively to the length of the tumbler 2i, that, when the trigger 25 is in its forward (inoperative) position, the ball will lie to the left of a} vertical line passing through the axis of the tumbler pins 23, thereby maintaining the, tumbler in oii position as depicted in Figures 1 and 4. When the trigger is moved rearwardly the ball will roll along the upper edge of the tumbler and, in so doing, will cause the tumbler to rock, in a clockwise direction, thereby .bringin'gthec'ontact blades 22 into circuit-closing engagement with the contact blades l5, as depicted inFigure 5. When, as depicted in the sam figure, the trigger has reached the limit of its rearward movement, 'the ball 36 will lie to the right of the vertical line passing through the axis of the tumbler pins 23', thereby maintaining the tumbler'in onf position so long. as the trigger remainsin its rearward position.

When the trigger isin inoperative position, the limit; of its forward movement is. deter-mined by engagement Of the free end of the overhanging part 25b thereof with the shoulder. 29 on: the

web- 23. and by engagement. of theiforward edge or theprojection 3i with the:slIoulder- 2-1 onythe; 75

clockwise direction.

its initial inoperative position against the pressureof. the spring 38, for the purpose of rocking thetumbler2=l into on position, the trigger will first move. with a simple rectilinear movement owing-to the guiding effect aiiorded by the plain :faceslZlSfand 39. When the trigger has been pulled so'far back as to bring the ball 36 to the l rear of th vertical centre-line through the axis leaving theother hand of the user free.

of the tumbler pins (thereby bringing the tumbler into onfi position), the projection 3| on the trigger." will leave the plain face 28 andbe brought opposite. therecess definedby theshoulder. 32- and plaingfaceit on the main body part I. As the spring, 3.8 applies its pressure to the upper part of the, trigger, the latter will, as a result, be canted in an anti-clockwise direction, thereby causing the forward. edge of the projection 3! to engage. with theshoulder 21, as depicted in Figure. 5j..j The trigger will thus be locked in on positionand will remain in that position for so longas-is desired. without the-need for maintainin'gi finger-pressure on the trigger.

When it is. desired to release the trigger for the l purpOse of bringing the tumbler to off."position,

it, suflices. merely toapply an upwardly directed pressure, by .means of the trigger-finger, to the overhanging part 251) of the trigger. The trig- .ger will thusbe canted in a clockwise direction SOJas to bring the forward end ofv the projection 3|: out of engagement with the shoulder 21, and

the spring 38 will then act to drive the trig er 'torelease the trigger, when desired, in the manner already described. Release of the trigger can be effected instantaneously bypressurefrom a finger of "the hand. used. for gripping the tool, while This .istof importance where theotherhand is required a. spindle projectingirom said casing and adapted "switoh- "comprising .a pair of parallel guiding for steadying the work. or tool and the user desires a rapid switch-off. at a particular moment.

;.I..claim:'

1.. lnia'portableihald tool comprising a casing.

to. carry. a working implement and an electric motor mounted within said casing and adaptedto drive said spindle,.the provision of a switch to control the fiow of. current to said motor. said frames formed on said. casing, a trigger mounted. between. said guiding faces to control said switch; afspring acting on said trigger, primarily to :maintain said trigger inthe position corresponding to thef ofi position of the switch. one of said guiding faces formed with a recess and the trigger formedwith a projection the arrangement beingsuch thatwhen the trigger is moved to the position corresponding to the onff'position of the switch the recess and the projection will be brought into register and the spring will tend to cant the trigger to engage said projection and recess for the purpose of retaining the switch in the on position until the trigger is canted in the opposite direction when the projection will be disengaged from the recess whereupon the spring will tend to return the trigger to the position corresponding to the o position of the switch.

2. A switch according to claim 1, wherein said switch is contained within a hollow hand-grip formed in the casing and the trigger is arranged in the locality of said hand-grip, the trigger being formed with an overhanging part which, when 15 2,488,637

said trigger is retained in the position corresponding to the on position of the switch, is adapted to be moved in a direction at right angles to the normal movements of the trigger to cause disengagement of the projection from the recess so that the spring may then urge the trigger towards its 01f position.

CHARLES HENRY GUBBINS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,283,778 Wilhide May 19, 1942 2,373,842 Mitchell Apr. 17, 1945 2,487,011 Wilhide Nov. 1, 1949 Moss Nov. 22, 1949 FOREIGN PATENTS Number Country Date 474,135 Germany Mar. 14, 1929