US3500696A - Two-speed power tool - Google Patents

Description

March 17, 1970 w. A. BERUBE 3,500,696

TWO-SPEED POWER TOOL Filed July 25, 1968 4 Sheets-Sheet 1 Q N (O r in I E J? I IO (0 IO INVENTOR dMma/M flwd ATTORN EYS WARREN A. BERUE 4 Sheets-Sheet 2 Filed July 25, 1968 INVENTOR WARREN A. BERUBE ATTORNEYS March 17, 1970 w. BERUBE 3,500,696

TWO-SPEED POWER TOOL I Filed July 25, 1968 4 Sheets-Sheet 5 INVENTOR WARREN A. BERUBE dmwm M44,

ATTOR NEYS March 17, 1970 w, BERUBE 3,500,596

TWO-SPEED POWER TOOL Filed July 25, 1968 4 Sheets-Sheet 4 INVENTOR WARREN A. BERUBE AT TO RN EYS United States Patent 3,500,696 TWO-SPEED POWER TOOL Warren A. Berube, Camillus, N.Y., assignor to Rockwell Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed July 25, 1968, Ser. No. 747,716 Int. Cl. F16h 3/08, 3/22 U.S. Cl. 74-363 11 Claims ABSTRACT OF THE DISCLOSURE A power tool having a gear selector shiftable by manipulation of an exteriorly accessible operator into engagement with one of two gears to connect a rotatable tool receiving component to the tool motor through one of two drive trains providing different speed ratios between the motor and the tool receiving component. An overcenter spring arrangement keeps the gear selector in firm engagement with the gear selected for engagement by manipulation of the operator.

The present invention relates to power tools and, more particularly, to power tools of the two-speed type. An important and primary object of the present invention is the provision of novel, improved tools of the type just described.

A number of power tools of the two-speed type have heretofore been proposed. Among these are tools disclosed in U.S. Patent Nos. 1,228,828 to Sasgen, 1,475,153 to Athenas, 2,845,806 and 2,911,841 to Miller, 2,899,850 to Selby, 2,942,490, 3,133,450 and 3,213,305 to Riley, 3,178,855 to Enders, and 3,178,956 to Stanley.

The tools of this type heretofore proposed have several drawbacks. First, with only a few exceptions, the speed change is effected by shifting gears into and out of mesh with one another. This method of changing speed has obvious disadvantages.

A second drawback of most heretofore proposed tools of the type in question in the lack of a positive type arrangement for maintaining the movable or shiftable gears in engagement with the gears with which they are meshed by manipulation of the speed selecting mechanism. Accordingly, the vibration generated during normal operation of such a tool or a change in attitude of the tool can cause the gears to become disengaged, which is obviously undersirable.

To remedy this drawback devices for maintaining the gears in mesh in positive fashion have been produced. However, these have for the most part employed a detent type of arrangement which has generally proved to be unsatisfactory.

It is accordingly a further important and primary object of the invention to provide novel, improved two-speed power tools which do not utilize the shifting of gears in changing speed and which are provided with a mechanism capable of positively maintaining the movable speed changing elements of the transmission in the positions to which they are shifted by manipulation of the speed selecting mechanism.

Instead of a movable gear cluster the novel two-speed tools of the present invention utilize a gear selector which can be shifted from one to the other of two limit positions by manipulation of a speed selecting control to drive connect one of two free-running gears to a driven shaft on which they are journalled and thereby change the speed ratio of the transmission. A novel overcenter spring 3,500,696 Patented Mar. 17, 1970 arrangement keeps the gear selector in firm engagement with the gear selector by manipulation of the speed selecting control. Accordingly, the present invention eliminates the problems associated with the use of movable gears as well as those associated with the lack of a suitable arrangement for maintaining the speed changing elements in firm engagement with the elements with which they are engaged. I

A two-speed tool utilizing a gear selector as opposed to a shiftable gear selector has heretofore been proposed in U.S. Pataent No. 2,842,490 to Riley; but this Riley tool lacks a suitable arrangement for retaining the gear selector in the position to which it is shifted by manipulation of the operator accessible speed selector. German Patent No. 533,429 discloses generally a two-speed transmission which utilizes a gear selector and has an overcenter spring for maintaining the selector in the desired position. However, the mechanism for shifting the gear selector described in the German patent employs a crank arrangement which is far too unwieldy'to be used in power tools of the type contemplated by the present invention.

From the foregoing it will be apparent that other primary and important objects of the present invention reside in the provision of novel, improved speed selecting mechanisms for two-speed power tools and in the provision of tools equipped with such mechanisms.

Other important objects, further novel features, and additional advantages of the present invention will be come apparent from the appended claims and as the ensuing detailed description and discussion proceeds in conjunction with the accompanying drawing, in which:

FIGURE 1 is a top view of a two-speed power tool constructed in accord with and embodying the principles of the present invention;

FIGURE 2 is a partial top view of the tool depicted in FIGURE 1 with a portion of the tool casing broken away to show the arrangement of the internal components;

FIGURE 3 is a section through the tool, taken substantially along line 33 of FIGURE 2;

FIGURE 4 is a similar view, taken substantially along line 44 of FIGURE 2;

FIGURE. 5 is a view similar to FIGURE 2 with a number of transmission components removed to show a novel speed selecting mechanism incorporated in the tool;

FIGURE 6 is a perspective view of a speed selecting control and a shift slide employed in the speed selecting mechanism;

FIGURE 7 is a perspective view of a gear selector employed in the tool of FIGURE 1;

FIGURE 8 is a perspective view of a gear employed in the tool; and

FIGURE 9 is a diagrammatic layout of a gear-type transmission employed in the tool of FIGURE 1.

Referring now to the drawing, FIGURES 1 and 2 depict a two-speed power tool 20 constructed in accord with and embodying the principles of the present invention. The major components of tool 20 includes a casing 22 housing a motor 24 which is drive-connected through a two-speed transmission 26 to a rotatably supported tool receiving component 28 provided with an internal socket (not shown) for a drill bit or other tool and rotatably supported in casing 22 by bearings 29 and 30. Tool 20 is also provided with the customary on-off switch (not shown) and with a speed selecting mechanism 31 (see FIGURE 4) including a control knob 32 exteriorly of casing 22. By manipulation of control knob 32 the speed ratio of transmission 26 may be altered so that tool receiving member 28 will rotate at a high speed or a low speed.

The details of casing 22 and motor 24 are of no particular consequence as far as the present invention is concerned. Accordingly, these components will not be described further herein except in conjunction with the novel aspects of tool which constitute the present invention.

Referring now primarily to FIGURE 2, motor 24 is mounted in the rear section 34 of casing 22 with its output shaft 36 extending into forward casing section 38 where it is rotatably supported by bearing 40. Formed on die forward end of output shaft 36 is a pinion 42 which meshes with a gear 44 (see also FIGURE 9) fixed to a longitudinally extending shaft 46 for rotation therewith. Ehaft 46 is rotatably supported in forward casing section 38 in suitable bearings (not shown).

In addition to gear 44, shaft 46 carries gears 48 and 50 {see FIGURES 4 and 9). In the illustrated embodiment )f the invention gear 50 is formed on the shaft, and gear 18 is pinned or otherwise fixed to the shaft for rotation herewith.

Gears 48 and 50 mesh with gears 52 and 54 which are :'ree1y rotatable on a shaft 56 rotatably supported in forvard casing section 38 in bearings 58 and 60. Also carried y shaft 56 is an integrally formed gear 62 which meshes vith a gear 64 fixed to tool receiving member 28 by a ialf-moon key 66, a washer 68, and a threaded reainer 70.

Referring now specifically to FIGURE 9, it will be tpparent from the foregoing that motor 24 drives gears l8 and 50 through a train including gear 42 on the output .haft 36 of the motor, gear 44, and shaft 46, that gears l8 and 50in turn drive gears 52 and 54, and that the shaft $6 on which the latter gears are journalled is drive-coniected to tool receiving member 28 through gears 62 and 54. The drive train between motor 24 and tool receiving nember 28 is completed by coupling one of the two free unning gears 52 and 54 to the shaft 56 on which they ire rotatably journalled. This is accomplished through a gear selector 74 (see FIGURES 2, 7, and 9) which is lidably journalled on shaft 56 and is fixed to the shaft 'or rotation therewith by co-operating external splines 76 )II the shaft and internal splines 78 on the gear selector.

Also formed on gear selector 74 are teeth or lugs 80, vhich are adapted to engage co-operating lugs or projecions 82 on gear 54 and lugs 84 which are similarly .dapted to engage co-operating lugs 86 on free running ;ear 52 (see FIGURES 2 and 8).

With gear selector 74 in the left-hand limit position hown in FIGURE 2, the lugs 80 on the gear selector ngage the lugs 82 on gear 54. Motor 24 accordingly .rives tool receiving member 28 through a drive train ncluding motor output shaft 36, gears 42 and 44, shaft 6, gears 50' and 54, gear selector 74, shaft 56, and gears 2 and 64. Selector 74 may also be moved to the right as hown in FIGURE 2 to a second limit position in which he lugs 84 on the gear selector engage the lugs 86 on free unning gear 52. With the gear selector in this position, rotor 24 drives tool receiving member 28 through a drive rain including the motor output shaft, gears 42 and 44, haft 46, gears 48 and 52, gear selector 74, shaft 56, and ears 62 and 64.

As shown in FIGURE 9, gears 48 and 52 have comarable pitch diameters While gear 50* has a much smaller itch diameter than gear 54. Accordingly, when the latter ears are engaged in the manner just described, the tool :ceiving member 28 is rotated at a relatively low speed 1 comparison to the speed at which it rotates when gear 2 is connected to shaft 56 by gear selector 74 and the rive is accordingly through gears 48 and 52.

One of the novel and most important features of the resent invention is the speed selecting mechanism 31 proided to move gear selector 74 between its two limit posi- 4 tions to provide low and high speed operation and to retain the gear selector in firm engagement with the gear 52 or 54 selected by manipulation of speed selecting control knob 32. Referring now primarily to FIGURES 2, 4, 5, and 6, the major components of mechanism 31 are a shift slide 88, an overcenter spring 90, and the control knob 32 referred to previously. Shift slide 88 includes a main body portion 92 mounted for rectilinear movement along a path parallel to the longitudinal axes of shafts 46 and '56 between the two limit positions shown in full and dotted lines in FIGURE 5 on a track or groove 94 formed in forward casing section 38.

Extending at right angles from the main body portion 92 of the shift slide 88 is a bifurcated portion 95 having two arms 96 and 98 which fit into a peripheral recess 100 in gear selector 74. Accordingly, as shift slide 88 is rectilinearly moved from the left-hand limit position shown in full lines in FIGURE 5 to the right-hand limit position shown in dotted lines in the same figure, the gear selector is moved from the limit position shown in FIGURE 2 in which it drive connects gear 54 to shaft 56 to a limit position in which it drive connects gear 52 to the same shaft. Similarly, shift slide 88 may be moved in the opposite direction to disengage the gear selector from gear 52 and re-engage it with gear 54.

The rectilinear movement of shift slide 88 just described is effected by manipulation of control knob 32 which includes a shaft 104 extending through an aperture 106 in the side wall of the casing. This rotatably supports control knob 32 from the casing from which it is separated by O-ring 108. Control knob 32 is retained in place by a snap-in type retainer 110 fitted in a groove 112 in shaft 104 (see FIGURE 6) with a washer 114 interposed between retainer 110 and the side wall of casing section 38.

Carried on the inner end of shaft 104 and extending parallel to but spaced from the axis of rotation of control knob 32 is an eccentric pin 116 which extends through an elongated, vertical slot 118 in the body 92 of shift slide 88. As knob 32 is rotated, the shift slide moves back and forth along supporting track 94 because of the eccentric disposition of pin 116 with respect to the center of rotation of the control knob. As the shift slide moves back and forth along this track, it changes the speed of transmission 26 by engaging gear selector 74 with a dilferent one of the two free running gears 52 and 54 on shaft 56 as discussed above.

As mentioned above, another important feature of the present invention is a novel overcenter spring arrangement which firmly maintains shift slide 88 in the limit position to which it is displaced by rotaton of control knob 32 and therefore maintains gear selector 74 in firm engagement with one of the two free running gears 52 and 54 despite vibration, alterations in the attitude of the tool, etc. This arrangement includes overcenter spring 90 (best shown in FIGURES 4 and 5 which is of the conventional spring wire type. One of the two legs of spring 90 terminates in a loop 122 fitted in a recess 124 adjacent the free end of eccentric pin 116. A similar loop 126 at the end of the other leg of spring 90 is fitted over a projection 128 extending from the body 92 of shift slide 88. This provides a positive spring bias downwardly, retaining the eccentric pin 116 in the selected position.

Referring now specifically to FIGURE 5, the operation of the shift slide 88 is as follows: in order to move the shift slide 88 laterally from either one to the other of its two limit positions, control knob 32 is manually rotated, moving eccentric pin 116 through approximately of arc. The initial and final portions of movement of eccentric pin 116 are mainly longitudinal in slot 118, against (or with) the bias of spring 90, while the midportion of the travel of eccentric pin 116 is primarily lateral with respect to shift slide 88. Upon completion of the shift by rotation of control knob 32, it can be seen that the eccentric pin 116 has moved into a latching position with respect to slot 118 and is retained there under 5. the bias of spring 90. In order to shift from one speed to another, the eccentric pin must be moved primarily vertically against the bias of spring 90 before any appreciable shifting movement of shift slide 88 takes place. As the rotation of knob 32 is continued with a corresponding displacement of the shift slide, spring 90 exerts a force on it additive to that exerted by rotation of the knob. This snaps the slide to the limit position and, since the spring exerts considerable force on the shift slide in the limit positions, the shift slide remains in these positions despite vibration, changes in attitude of the tool, etc.

From the foregoing description of an exemplary embodiment of the present invention, it will be apparent to those of ordinary skill in the relevant arts that. many modifications may be made without departing from the principles of the present invention. For example, a crank arm can be attached to the shaft 104 of control knob 32 and eccentric pin 116 fastened to the end of the crank arm, if desired. These and other changes of a similar.

nature are accordingly fully intended to be covered in the appended claims to the extent that they are not expressly excluded therefrom.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A power tool comprising a casing, a motor in said casing, a tool receiving member in and rotatably supported from said casing, a first shaft drive-connected to said motor, first and second gears having dissimilar pitch diameters fixed to said shaft for rotation therewith, a second shaft, third and fourth gears on said second shaft meshing with said first and second gears, said third and fourth gears being freely rotatable relative to said second shaft, means drive-connecting said second shaft to said tool receiving member, a gear selector slidable on said second shaft and rotatable therewith, co-operating means on said gear selector and said third gear and on said gear selector and said fourth gear for drive-connecting said selector to said third gear and to said fourth gear, respectively, and speed changing means including a rotatably mounted two-position operator exteriorly of said casing for selectively drive-connecting said gear selector to one of said third and fourth gears when said operator is rotated to one of its two positions and to the other of said third and fourth gears when said operator is rotated to the other of its two positions.

2. The tool of claim 1, wherein said speed changing means further comprises a shift slide having means connecting said gear selector thereto, means mounting said slide in said casing for rectilinear movement along a path parallel to that followed by the gear selector as it is shifted out of engagement with one of said third and fourth gears and into engagement with the other of said third and fourth gears, whereby movement of said shift slide causes said gear selector to slide along said second shaft, said operator being so connected to said shift slide that said shift slide is displaced along said path as said operator is rotated from one to the other of its two positions.

3. The tool of claim 2, wherein said shift slide has an elongated slot therein and including a member carried by said operator and extending through the slot in said shift slide, said operator carried member being parallel to and spaced from the axis of rotation of said operator, whereby rotation of the operator shifts said slide along said path.

4. The tool of claim 3, wherein the slot in the shift slide extends at right angles to the path followed by the shift slide to thereby provide a center position in the movement of said slide, and including an overcenter spring for maintaining said gear selector in engagement with the gear with which it is engaged, one end of said spring being fixed to said shift slide and the other end of said spring being fixed to the member carried by the operator.

5. The tool of claim 2, wherein said gear selector has a peripheral recess and said shift slide has bifurcated arms disposed in said recess, said arms extending normally from the main body portion of the shift slide.

6. The tool of claim 1, together with overcenter spring means for retaining said operator in the position to which it is shifted and thereby keeping said gear selector in engagement with the one of said third and fourth gears with which it is engaged by rotation of said operator.

7. A power tool comprising a casing, a motor in said casing, a tool receiving member in and rotatably supported from said casing, means including a gear selector shiftable between first and second limit positions for selectively drive-connecting said tool receiving member to said motor through either of two alternate gear trains with dissimilar drive ratios whereby said tool receiving member may rotate at either of two different speeds, and means for shifting said gear selector between said limit positions comprising a shift slide having means connecting said gear selector thereto, means mounting said slide in said casing for movement confined to a rectilinear path, a two-position operator accessible from the exterior of the casing, and means so connecting said operator to said shift slide that, as said operator is shifted from one to the other of its two posi tions, said slide is displaced along said rectilinear path and said gear selector thereby shifted from one to the other of its limit positions to change the speed at which the tool receiving member is rotated.

8. The tool of claim 7, wherein said shift slide has an elongated slot therein and said operator is rotatably journalled in said casing and including a member carried by said operator and extending through the slot in said shift slide, said operator carried member being parallel to and spaced from the axis of rotation of said operator, where-by rotation of the operator shifts said slide along said path.

9. The tool of claim 8, including an overcenter spring for maintaining said gear selector in engagement with the gear with which it is engaged, one end of said spring being fixed to said shift slide and the other end of said spring being fixed to the member carried by the operator.

10. A power tool comprising a casing, a motor in said casing, a tool receiving member in and rotatably supported from said casing, means including a gear selector shiftable between first and second limit positions for selectively drive-connecting said tool receiving member to said motor through either of two alternate gear trains with dissimilar drive ratios whereby said tool receiving member may rotate at either of two different speeds, and means for shifting said gear selector between said limit positions comprising a two-position operator exteriorly of the casing, means in said casing operatively connected to said operator and said gear selector for moving the gear selector from one to the other of said limit positions as said operator is shifted from one to the other of its two positions, and an overcenter spring operatively coupled to said operator and to the means for moving the gear selector for maintaining said gear selector in the limit position to which it is moved by the manipulation of said operator.

11. The tool of claim 10, wherein the means for moving said gear selector between said limit positions comprises a shift slide having means connecting said gear selector thereto, means mounting said slide in said casing for movement confined to a rectilinear path, and means so connecting said operator to said shift slide that, as said operator is shifted from one to the other of its two positions, said slide is displaced along said rectilinear path and said gear selector thereby shifted from one to the other of its limit positions, said last-mentioned means including a member carried by said operator and extending through a slot in the shift slide, and wherein one end of said overcenter 7 8 spring is fixed to said shift slide and the other end of said FOREIGN PATENTS spring is fixed to the member carried by the operator. 1 019 O5 4 H1953 France References Cited ARTHUR T. McKEON, Primary Examiner UNITED STATES PATENTS 5 U.S. C1. X.R. 2,068,869 1/1937 Rauen 74-343 X 74 342 2,778,237 1/1957 Romi 74342 X UNITED STATES PATENT OFFICE H CERTIFICATE OF CORRECTION Patent No 0 3 ,500 ,696 March 17 1970 Warren A. Berube It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

after "are" insert the line 40,

should read is line 47, "underline 49, "produced" Column 1, line 29, 111", second occurrence, sirable" should read undesirable should read proposed Signed and sealed this 6th day of October 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR

Edward M.'Fletcher, Jr. it"

Cornmissioner of Patents Attesting Officer

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