US3022769A

US3022769A - Universal tool element retainer for rotary-hammer devices

Info

Publication number: US3022769A
Application number: US30006A
Authority: US
Inventors: Oliver O Amundsen; Harold R Botefuhr
Original assignee: Skil Corp
Current assignee: Skil Corp
Priority date: 1960-05-18
Filing date: 1960-05-18
Publication date: 1962-02-27
Anticipated expiration: 1979-02-27
Also published as: DE1427754A1; GB969008A; CH408754A

Description

Feb. 27, 1962 O. O. AMUNDSEN ETAL UNIVERSAL TOOL ELEMENT RETAINER FOR ROTARY-HAMMER DEVICES 2 Sheets-Sheet 1 Filed May 18, 1960 Feb. 27, 1962 Q Q AMUNDSEN ETAL 3,022,769

UNIVERSAL TOOL ELEMENT RETAINER FOR ROTARY-HAMMER DEVICES Filed May 18, 1960 2 Sheets-Sheet 2 9 can UNIVERSAL TGJL ELEMENT RETAENER FQR RGTABY-HAMMER DEVECES Sliver 0. Amundsen and Harold R Botefuhr, Chicago,

BL, assignors to Sidl Corporation, Qhicago, ill, a corporaiion of Delaware Filed Islay 1S, 1966, Ser. No. dildllid 8 Claims. (Cl. lilo-32) The present invention relates to a tool element retainer for rotary-hammer devices and, more particularly, to a retainer for retaining in such rotary-hammer devices onepiece tool elements having integral shank portions provided with necked or reduced-in-cliameter portions defining annular grooves.

An important object of the invention is to provide a new and improved retainer for retaining tool elements in a rotary-hammer device during rotary and hammer-like actuation thereof and during withdrawal of such tool eie ments from the work.

Another important object of the invention is to provide a new and improved tool element retainer for a rotaryhammer device wherein the retainer is resiliently mounted on the nose end of the rotary-hammer device and is embracingly engageable in an annular groove formed in the tool element mounted in the device for actuation thereby.

A further important object of he invention is to provide a new and improved tool element retainer of the character described which is readily adjustable between a series of positions for retaining engagement in tool element grooves of various diameters.

A further object of the invention is to provide a new and improved tool element retainer of the character described which is resiliently latched in any one of its tool element retaining positions.

Further objects of the invention are to provide a new and improved tool element retainer of the character described which is readily movable to an outof-the-way position for inserting tool elements in the rotary-hammer device or removing them therefrom, which is: easily and economically fabricated; readily assemblable on the nose i. he

Fatented Felt. 2?, W62

' line ld1tl of PEG. 9; and

end of a rotary-hammer device; rugged; and, requires no lubrication or maintenance.

Certain other objects of the invention will, in part, be obvious, and will in part appear hereinafter.

For a more complete understanding of the nature and scope of the invention reference may now be had to the accompanying drawings wherein:

FIG. 1 is a side elevational view of a rotary-hammer device with the nose portion thereof being shown in vertical section including a tool element retainer embodying the invention, mounted on the nose portion of the device;

FIG. 2 is a top plan view of the nose portion of the rotary-harnmer device of FIG. 1 and showing a tool element having a small diameter annular groove mounted in the device;

FIG. 3 is a vertical section taken generally on the line 33 of FIG. 2;

FIG. 4 is a vertical section taken generally on the line 4-4 of FIG. 3;

FIG. 5 is a top plan View similar to PEG. 2 and showing a tool element having a large diameter annular groove mounted in the device;

FIG. 6 is a vertical section taken generally on the line 6-6 of FIG. 5;

FIG. 7 is a vertical section taken generally on the line 77 of FIG. 6;

FIG. 8 is a top plan View similar to Fig. 2 with the etainer shown in its out-of-the-way position for inserting tool elements in the device and removing them therefrom;

FIG. 9 is a front end view of the device as shown in FIG. 8;

FIG. 11 is a side elevational view of one of the guideposts of the tool element retainer.

The tool element retainer of the invention is adapted for use with a hand-operable power tool such as the rotary-hammer device 15 shown in FIG. 1. The rotaryhammer device 15 includes a multi-part housing including a tubular portion 1%, a first handgrip l9, and a second gripping handle 2% which projects laterally from one side of the device 15. The rotary-hammer device 15 further includes an electric motor (not shown) which is adapted to be connected to a power source through a power cord 22. The electric drive motor circuit includes a conventional on-and-ofi' switch which is controlled by a triggerlike member 23 associated with the handgrip 19.

The rotary-hammer device 15 includes a cylinder 25 which is rotatably mounted within the tubular housing portion 18 and is operably connected through a suitable gear train to the electric motor whereby during energization of the motor, the cylinder 25 may be rotated within the housing portion 18. As shown in FIG. 1, the forward end of the cylinder 25 is rotatably mounted in the the forward end of the housing portion 13 by a suitable bearing 26. An axially bored, exterially threaded drive member 27 is threadedly secured in the forward end of the cylinder 25: for rotation therewith, and an axially bored nonrotatable'nose member 28 is secured on the forward end of the tubular housing portion 18. The bore of the drive member 27 is provided with an internal hexagonal formation 2% and the bore of the nose member 28 is provided with an internal hexagonal formation 3%.

Tool elements adapted to be actuated by the rotaryhammer device 35 are provided, with shank portions adapted to be inserted through the bores 3i? and 29 of the nose member 23 and the drive member 27, respectively. Tool elements adapted to be rotated have shank portions provided with external hexagonal formations adapted for rotary driving engagement with the hexagonal formation 29 of the drive member 27 whereby such tool ele ments are operably connected for rotation with the cylinder 25. Non-rotatable tool elements are provided with rounded shank portions extending through the drive member 27 whereby to prevent rotary driving engagement thereof with the cylinder 25. Such tool elements may be provided with external hexagonal formations for sliding interengagement with the internal hexagonal formation 30 of the nose member 28 whereby to insure non-rotation thereof.

Rotatable or non-rotatable tool elements adapted for reciprocal hammer-like actuation are provided with long shank portions which project through the drive member 27 and into the cylinder 25 for impact engagement by a striker member 32 (FIG. 1) which is pneumatically reciprocated Within the rotary cylinder 25. The striker member 32 is pneumatically reciprocated in the cylinder 25 as a result of reciprocation in the rear end of the cylinder 25 of a power piston (not shown) which is operably connected in known manner to the electric motor. Suitable porting is provided in the cylinder 25 for the pneumatic actuation of the striker member 32. Rotaryhammer devices of this type are fully disclosed in copending applications Serial No. 18,550, filed March 30, 1%0, and Serial No. 19,874, filed April 4, 1960. Thus, the striker member 32 may be reciprocally actuated simultaneously with rotation of the cylinder 25 whereby to provide a tool element mounted in the device with a combined rotary-hammering action. Tool elements adapted for non-reciprocal actuation are provided with short shank portions which terminate within the drive 3 member 27 and do not project-into the cylinder 25 for impact engagement by the striker member 32. When the short shank tool elements are mounted in the rotaryhammer device 15, certain of the ports in the cylinder 25 become eil'ective to render the striker member 32 inoperable whereby to prevent undue wear of the parts.

It is necessary to provide suitable means for retaining all of the above discussed tool elernents in the rotaryhammer device 15 during actuation thereof, particularly those tool elements adapted to have a hammer-like action imparted thereto by the striker member 32, and also for retaining such tool elements in the device 15 when they are being withdrawn from the work. Suitable one-piece tool elements having specially designed integral shank portions have been developed for use in the rotaryhammer device 15.

The shank portions of these one-piece tool elements are provided with necked or reduced-in-diameter portions defining annular grooves which are adapted for co-action with the tool element retainer of the invention whereby the tool elements are retained in the rotary-hammer device 15 both during reciprocal actuation thereof and when they are being withdrawn from the material being worked. These specially designed tool elements fall into two general groups. One group of tool elements has a relatively small diameter annular groove formed thereon for interengagement with the tool element retainer and the other group of tool elements has a relatively larger diameter annular groove formed thereon for interengagement with the tool element retainer.

The present invention is primarily concerned with the development of a new and improved universal tool element retainer for use with the rotary-hammer'device 15 and which is adapted for retaining engagement with tool elements having either the small diameter annular grooves or the large diameter annular grooves A universal tool element retainer embodying the inventionmay best be described with reference to FIGS. 2, 3 and 4. 'A pair of guide-posts 3:; are slidably mounted in a pair of longitudinally extending through bores extending through both an outer flange portion of the nose member 28 and an enlarged nose end portion of the tubular housing portion 18. The bores are disposed on opposite sides of the rotary axis of the rotary-hammer device 15 and in a horizontal plane extending therethrough. As best shown in FIG. 11, each guide-post 35 is provided with an external thread 38 on its rear end and an integral head 39 on its forward end with the head 39 being provided with a reduced-in-diameter portion 40 disposed rearwardly thereof. The shank of each guide-post 35 is characterized by an enlarged diameter portion or integral abutment member 41 which is spaced rearwardly from the reduced-indiameter head portion 49.

An elongated bracket or saddle member 44 is mounted on the forward ends of the guide-posts 35 and is provided with a forwardly offset central portion 46 (FIG. 2). The forwardly oifset portion 45 of the bracket 44 is provided with a downwardly opening generally V-shaped slot 47 which is in vertical alignment with the rotary axis of the rotary-hammer device 15. As best illustrated in FIG. 3, each end of the bracket 44 is mounted on one of the guide-posts 35 by means of a vertically elongated slot 49 having a width slightly greater than the diameter of the shank portion of the guide-post 35. Each of the slots 49 is provided with a pair of enlarged

portions

56 and 51 having diameters slightly greater than the diameter of the reduced-in-diameter head portions 4% of the guideposts 35. One enlarged portion is located at the upper endof each slot 49 with the other enlarged portion 51 being spaced downwardly therefrom approximately midway between the opposite ends of the slot 49. Due to the slotted mounting of the bracket 4 t on the guide-posts 4, t 35, the bracket 44 is movable not only longitudinally of the guide-posts 35 but also in a direction normal thereto.

The central portion of the bracket 44 containing the generally V-shaped slot 47 is adapted for embracing engagement in an annular groove formed in the shank of a tool element mounted in the rotary-hammer device 15 whereby to retain the tool element in the device 15 during rotary and/or hammering actuation thereof. In the embodiment of the tool element retainer illustrated in the drawings, the bracket or saddle member 44 is movable in a plane normal to the guide-posts 35 between an out-of-the-way position, permitting the insertion of tool elements in the rotary-hammer device 15 and the removal of the tool elements therefrom, and two tool element retaining positions.

In H65. 2, 3 and 4, the bracket 44 is shown in its first tool element retaining position in retaining engagement in a small diameter annular groove 52 of a tool element 53 which is mounted in the rotary-hammer device 15. The tool element 53, which is adapted for nonrotary hammer-like action, is provided with a rounded shank portion 54 which extends through the drive member 27 and into the cylinder 25 for impact engagement by the striker member 32. To insure non-rotation of the tool element 53 the portion extending through the nose member 28 is provided with an external hexagonal formation 55 for slidable interengagement with the internal hexagonal formation 30 of the non-rotatable nose member 28. The bracket 44 is in its lowermost position with the reduced-in-diameter head portions 40 of the guideposts 35 fitted in the enlarged portions 51 of the elongated slots 49 formed in the ends of the bracket 44 whereby to retain the bracket 44 in its adjusted position. The radius of curvature of the closed end of the V-shaped slot 47 is approximately equal to the diameter of the necked portion of the tool element 53 defining the annular groove 52 whereby the end of the slot 47 is in embracing engagement with the necked portion 52 of the tool element 53.

In FIGS. 5, 6 and 7, the bracket 44 is shown in its second tool element retaining position in retaining engagement with a tool element 56 mounted in the rotary-harnmer device 15 and having a necked shank portion defining a large diameter annular groove 57. The tool element 56,- which is adapted for combined rotary andhammering action, includes a shank portion 58 which projects through the drive member 27 and into the cylinder 25 for impact engagement by the striker member 32. portion 58 is provided with an external hexagonal formation 59 for slidable interengagement with the internal hexagonal formation 29 "of the drive member 27 whereby the'tool element 56 is in rotary driving engagement with the cylinder 25. In this second tool element retaining position of the bracket 44, the reduced-in-diameter head portions 46 of the guide-posts 35 are fitted in the enlarged portions 51 of the elongated slots 49 whereby to retain the bracket 44 in its second tool element retaining position. This second tool element retaining position of the bracket 44 corresponds to the large diameter annular groove 57 of the tool element 56 whereby only the wider outer edge portions of the generally V-shaped slot 47 are arranged in embracing engagement with the annular groove 57. Because of the variation in width of the sides of the generally V-shaped slot 47, the bracket 44 is adapted for retaining engagement with tool elements having an: nular grooves of various diameters.

In FIGS. 8, 9 and 10, the bracket 44- is shown. in its uppermost or out-of-the-way position whereby to permit the insertion of tool element into the rotary-hammer device and their removal therefrom. in this position of the bracket 44, the shank portions of the guide-posts 35 intermediate the reduced-in-diameter head portions 4i) and the abutment members 41 are disposed in thejlower non enlarged ends of the elongated slots 49 (FIG. 9) with The shank s eaves the reduced-in-diameter head portions being disposed forv 'ardly of the front surface of the bracket 44, as shown in FIG. 8.

Particularly because of the reciprocal, hammer-like action imparted to certain of the tool elements mounted in the rotary-hammer device 15 by the striker member 32, the guide-posts 35 the bracket M. carried thereon in retaining engagement with the tool elements are resiliently mounted on the nose end of the rotary-hammer device 15. A nut 62 is ad'astably mounted on the threaded rear end 33 or" each of the guide-posts A coil spring 63 is disposed about the rear portion of each oi the guide-posts 35 with each spring seated between a pair of flanged bushings 64 which are slidably disposed on each guidepost 35 between the nut 62 and the rear surface of the enlarged nose portion of the tubular housing portion The springs 63 tend to urge the guide-posts 35 in a r"arware. direction relative to the nose end or" the rotny hammer device 35. To complete the resilient mounting of the guide-pests 35 a coil spring es is disposed about the shank portion of each gui e-post forwardly of the nose member in with each spring as being seated beas tween the front surface of outwardly flanged portion of the nose membc 28 and an abutment washer d! disposed in abutting engagement against the rear end or" abu ment member 4-1. The springs es tend to urge the guide-posts 35 in a forward direction, the springs 63 and the springs as are preset tion thereof. Be ause or the greater impact shock absorbed by the rear coil springs 63 during h .nner-like reciprocation of the tool elements, the springs 63 erably of greater strength than the forward coil With the guide-posts resiliently mounted in the manner described, the braclce is enabled to ei'lectivelv retain the tool elements in rotaryhammer device despite the vigorous and pow rful rotary-hammer tction thereof and despite the som es consic able force required to idraw the tool elements fr work. Oil-setting the central portion of the bracket forwardly of end portions thereof serves to increase the rigidity of the bracke 1.

in order to adjust the bra ket as in a direction normal to the guide-posts 35 between its various tool element reng positions, it is necessary to bodily move the bracket 44 inwardly toward the nose cud of the rotary-hammer device 35 sufficiently to disengage the reduccd-in-diameter head portions of the guide-posts 35 from the enlarged portions Si) or 51 or the elongfltcd slots 42 after wnicl the bracket be freely moved in a direction normal to the guide-posts 35. To provide means for re siliently latching the bracket f in its various tool element retaining positions, a coil spring "ill of relatively less strength than either the coil springs es or the coil springs tid is disposed about the for rd end portion of each of the guide-posts and seated between the abutment washer s7 and a flanged bushing '71 which is slidably fitted over both the reduced-in .iameter head portion 4 and the enlarged d' ter abutment member 5 each guide-post The springs 749 thus serve to urge the bracket forwardly on guide posts 35 whereby to resiliently retain the bracket 24 in any one of its tool element retaining positions or in its out-of-the-way position.

in operation, to move the bracket from one of its tool element retaining positions to either its otne tool element retaining position or its out-of-tl1e-way position, the bracket is manually depressed inwardly toward the nose of the rotary mmer device 15 sufiiciently to disengage the reducedin-o ameter head portions td of the guide-posts 35from the enlarged portions St? or 5'1 of the elongated slots 49 whereby the bracket 44 be readily shifted in a direction normal to the guide-posts 35 into either its out-ot-the-way position or into its other tool element retaining position. In order to facilitate manual adjustment or repositioning of the bracket 44, each end are pret of the bracket 44 is provided with a readily grippable projection '75.

' It will be understood that certain changes may be made in the construction or arrangement of the universal tool element retainer for a rotary-hammer device disclosed herein without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. A retainer for retaining tool elements in a rotaryhammer device comprising, a pair of guide-posts mounted on the nose end of the rotary-hammer device with said posts being located on opposite sides of the rotary axis of the device, a bracket member mounted on the forward ends of said guide-posts and being movable relative to both of said guide-posts in a direction normal thereto and in a straight path between operable and inoperable positions, and an open ended slot formed in one edge of said bracket whereby said bracket in its operable position is adapted for embracing engagement in a necked portion of a tool element mounted in the device whereby to retain the tool element in the device during actuation thereof and during withdrawal of the tool element from the material being worked, said bracket when in its inoperable position permitting tool elements to be inserted into the nose end of the device and removed therefrom.

2. A retainer for retaining tool elements in a rotaryhammer device comprising, a pair of guide posts mounted on the noseend of the rotary-hammer device on opposite sides of the rotary axis thereof, a bracket mounted on the forward ends of said guide-posts, and a generally ll-shaped slot formed in one edge of said bracket in alignment with the rotary axis of the device whereby said bracket is adapted to be embracingly received in an annular groove defined by a necked'portion of the shank of a tool element mounted in the device for retaining the tool element in the device during actuation thereof, said bracket being movable relative to said posts in a direction normal thereto and toward the rotary axis of the device from an out-of-the-way position permitting insertion of a tool element into the nose end of the device into a series of tool element retaining positions corresponding to the diameter of the annular groove of the particular tool element mounted in the device, the varying width of said V-shaped slot accommodating tool elements having annular grooves of various diameters.

3. A retainer for retaining tool elements in a rotaryhammer device comprising, a pair of guide-posts mounted in the nose portion of the rotary-hammer device one on each side of the rotary axis thereof, each of said posts having an integral head on its forward end with said head having a rearwardly disposed reduced-in-diameter portion, abutment means on each guide-post spaced rearwardly of said reduccd-in-diameter head portion, a bracket mounted on the forward ends of said guide-posts by means of elongated slots formed one in each end thereof whereby said bracket is movable in a direction normal to said guide-posts, a generally ll-shaped slot formed in one edge or" said bracket intermediate the ends thereof and in alignment with the rotary axis of the rotaryhammer device whereby said bracket is adapted to be embracingly received in an annular groove defined by a necked portion of the shank of a tool element mounted in the device to retain the tool element in the device during actuation thereof, said bracket being movable in said normal direction from an out-of-the-way position permitting insertion of a tool element into the nose portion or" the device into any one of a series of tool-elementretaining positions corresponding to the diameter of the annular groove of the particular tool element mounted in the device, the varying width of said V-shaped slot accommodating tool elements having annular grooves of various diameters, each of said elongated mounting slots in the endsof said bracket having a series of spaced apart enlarged portions of a size to receive said reduced-indiameter head portions of said guide-posts with the positionsof said enlarged portions corresponding to said toolelement-retaining positions of said bracket, and a coil spring disposed about the forward portion of each guidepost and'seated between said bracket and said abutment means whereby to resiliently retain said bracket in any one of its tool-element-retaining positions with the reduced-in-diameter head portions of said guide-posts re ceived in the appropriate enlarged portions of said mounting slots, said bracket being movable between its out-ofthe-way position and its series of tool-element-retaining positions by manually depressing the bracket against the action of said springs until said reduced-in-diameter head portions of said guide-posts are disengaged from said enlarged portions of said elongated mounting slots.

4. A retainer for retaining tool elements in a rotaryhammer device comprising, a pair of guide-posts slidably mounted in the nose end of the rotary-hammer device with said posts being located on opposite sides of the rotary axis of the device, a bracket member mounted on the forward ends of-said guide-posts for movement relative to both of said guide-posts in a direction normal thereto and in a straight path between operable and inoperable positions, an open-ended slotformed in one edge of said bracket whereby said bracket in its oper able position is adapted for embracing engagement in an annular groove formed in a tool element'mounted in the device whereby to retain the tool elementin the device during actuation thereof, said bracket when in its inoperable position'permitting tool elements to be inserted into the nose end of the device and removed therefrom, first resilient means urging said guide-posts in a rearward direction, and second resilient means: urging said guide-posts in a forward direction, said first and second resilient means permitting said retaining bracket to accommodate reciprocal, hammer-like action imparted to the tool element by the rotary-hammer device.

5. A retainer for retaining tool elements in a rotaryhammer device comprising, a pair of guide posts slidably mounted in the nose end of the r ota-ry-harnmer-device on opposite sides of the rotary axis thereof, a bracket mounted on the forward ends of said guide posts, a generally V- shaped slot formed in one edge of said bracket in alignment with the rotary axis of the device whereby said bracket is adapted to be embracingly received in an annular groove defined by a necked portion of the shank of a tool element mounted in the device for retaining-the toolelement in the device during actuation thereof, said bracket being movable relative to said posts in a direction normal thereto and toward the rotary axis of the device from an out-of-the-way position permiting insertion of a tool element into the nose end of the device into a series of tool element retaining positions corresponding to the diameter of the annular groove of the particular tool element mounted in the device, the varying width of said V-shaped slot accommodating too-l elements having annular grooves of various diameters, first resilient means urging said guide-posts in a forward direction, and second resilient means urging said guide-posts in a rearward direction.

6. A tool element retainer as recited in claim having resilient means for releasably retaining said bracket in each ofsaid tool elementretaining positions.

7. A retainer for retaining tool elements in a rotaryhammer device comprising, a pair of guide-posts slidably extending through a pair of bores formed in the nose portion of the rotary-hammer device one on each side of the rotary axis thereof, each of said posts having a nut adiustably threaded on its rear end and an integral head on its forward end with said head having a rearward ly disposed reduced-in diarneter portion, abutment means on each guide-post spaced rearwardly of said reduced-indiameter head, portion and forwardly of the nose portion of therotary-hammer device, a first coil spring disposed about the rear portion of each guide-post and sea-ted be tween said adjustable nut and-the nose portion of the device whereby to urge said guide-posts in a rearward direction, a second relatively weaker coil spring disposed about the forward portion of each guide-post and'seated between said abutment means and the nose portion of the device whereby to urge said guide-posts in a forward direction, a bracket member slidably mounted on the forward ends of said guide-posts for longitudinal slidable movement between said heads and said abutment means, said bracket being mounted on said guide-posts by means of elongated slots formed one in each end thereof whereby said bracket is also movable in a direction normal to said guide-posts, a generally V-shaped slot formed in one edge of said bracket intermediate the ends thereof and in alignment with the rotary axis of the rotary-hammer de ice whereby said bracket is adapted to be embracingly received in an annular groove defined by a reduced-indiarneter shank portion of a tool element mounted in the dcviceto retain the tool element in the device during actuation thereof, said bracket being movable in said normal direction from an out-of-the-way position permitting insertion of a tool element into the nose portion of the device into any one of a series of tool-element-retaining positions corresponding to the diameter of the annular groove ofv the particular tool element mounted in the device, the varying width of said V-shaped slot accommodating tool elements having annular grooves of various diameters, each of said elongated mounting slots in the ends of said bracket having a series of spaced apart enlarged portions of a size to receive said reduced-indiameter head portions of said guide-posts with the positions of said enlarged portions corresponding to said toolelement-retaining positions of said bracket, and a third coil spring disposed about the forward portion of each guide-post'and seated between said bracket and said abutment means whereby to resiliently retain said bracket in any one of its tool-element-ret-aining positions with the reduced-in-diameter head portions of said guide-posts received in the appropriate enlarged portions of said mounting slots, said bracket being movable between its out-ofthe-way position and its series of tool-element-retaining positions by manually depressing the bracket against the action of said third coil springs until said reduced-indiarneter headportions of said guide posts are disengaged from said enlarged portions of said elongated mounting s ots.

8. A tool element retainer as recited in claim 7 wherein the portion of said bracket containing said generally V-shaped slot is offset forwardly of the ends of the bracket to increase the rigidity of said bracket and wherein the ends of said bracket are provided with manually grippable projections facilitating movement of said bracket between its various positions.

ReferencesCited in the file of this patent UNITED STATES PATENTS 1,164,560 Weiner Dec. 14, 1915 1,295,439 Convenley Feb. 25, 1919 1,472,496 Scheib Oct. 30, 1923 1,675,432 Smith July 3, 1928 1,684,177 Gartin Sept. 11, 1928 1,831,818 McKenny Nov. 17, 1931 1,969,798 Hultquist Aug. 14, 1934 2,844,378 Whistler et a1. May 22, 1958 FOREIGN PATENTS 107,129 Austria Aug, 25, 1927 316,933 Great Britain May 8, 1930