|Publication number||USRE33145 E|
|Application number||US 07/260,178|
|Publication date||Jan 9, 1990|
|Filing date||Oct 19, 1988|
|Priority date||Apr 8, 1985|
|Publication number||07260178, 260178, US RE33145 E, US RE33145E, US-E-RE33145, USRE33145 E, USRE33145E|
|Original Assignee||Milwaukee Electric Tool Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (12), Classifications (12), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
There are portable drill stands having an electromagnetic base enabling the stand to be secured to a ferromagnetic plate or the like. The plate must have substantial thickness to have enough iron in the magnetic field to develop adequate holding power. Such tools involve elaborate safety interlocks to prevent use and dropping of the tool when power fails, etc. The tools cannot be used on relatively thin materials such as the sheet metal used in shelves, cabinets, ducts, etc. Such drill presses can be difficult or impossible to use in drilling a hole in an overhead member.
This invention is directed to provide a permanent magnet base for portable power tools.
This invention provides a portable tool having a permanent magnet base for holding the tool on ferromagnetic material. The area of the permanent magnet field is substantial with the result that the holding power is great and can hold a rather heavy tool on relatively thin sheet metal and the like.
The invention provides means for rendering the permanent magnet field substantially ineffective to permit the machine to be moved easily. This is accomplished by providing a number of magnetic shunts actuated by handle means used in lifting the machine. The shunt is not complete so there is some magnetic flux at all times. This results in a small but helpful magnetic force facilitating handling the tool. A further object is to prevent release of the magnet force until the electric power has been cut off.
A further feature is the provision of an interlock preventing closure of the motor switch unless the magnetic fields in the base are additive and the base is resting on a support surface to push the probe into the base.
This invention is described in connection with a hole cutting power tool claimed in Application Ser. No. 720,860. The quick change cutting tool disclosed herein is claimed in Ser. No. 720,859. The coolant dispensing mechanism is claimed is Ser. No. 720,861. The tool feed handle construction is claimed in Ser. No. 720,858.
FIG. 1 is a side elevation with part of the housing and coolant reservoir broken away.
FIG. 2 is an enlarged detailed section showing the magnetic base structure with the magnetic fields reinforcing.
FIG. 3 is similar to FIG. 2 but the magnetic fields cancel in this view.
FIG. 4 is a vertical section through FIG. 2 along the switch rod.
FIG. 5 is a detailed section showing how the lever/handle actuates the upper magnet assembly.
The portable hole cutting tool 10 includes a motor housing 12 mounted on a magnetic base 14 with a coolant reservoir 16 secured to the base behind the housing 12. The magnetic base has two permanent magnet assemblies 26, 28 with one (28) mounted on top of and movable relative to the bottom assembly 26. As seen in cross section, the thin parts 18 are the permanent magnets while the thick plates 20 are the ferromagnetic material, i.e., steel. The magnets are magnetized so that confronting faces of the magnets have similar polarities as indicated in the drawings. The alternating magnets and steel pieces in the lower assembly 26 are tied together by tie rods 22 running the length of the assembly and through the ends 24 of the base 14. The upper assembly is tied by rods 23. The tie rods 22, 23 straddle the sensor structure 46 to be described. When the upper magnetic assembly 28 is positioned as shown in FIG. 2, the upper magnets are aligned with the lower magnets of similar polarity. Thus, the steel pieces between the upper and lower magnets are alternately North and South and this will set up a magnetic field attracting the base of the tool to a ferromagnetic material contacting the base. The upper magnetic assembly is slightly shorter than the lower magnet assembly so there is always some flux effective even when the upper magnetic assembly is shifted to the right by a distance adequate to align the upper magnets with lower magnets of opposite polarization as shown in FIG. 3 and the fields of the upper and lower assemblies substantially shunt each other leaving only a small net force holding the tool on the work surface. This is desireable because it improves the handling characteristics of the tool.
Shifting the upper magnetic assembly 28 relative to the lower assembly 26 is controlled by handle 30 which has a hand grip 32 at the distal end of the crank arms 34 straddling the reservoir 16 and pivoted on shaft 36 fixed in the rear of the housing. The short leg 38 of each crank 34 is received in a slot 40 of an aluminum (non-magnetic) actuating block 42. The actuating block has an elongated central opening 44 through which the sensing probe 46 and switch rod 48 extend. The elongated opening 44 permits the upper magnetic assembly 28 to shift relative to the lower magnetic assembly 26 and relative to the sensor 46 and rod 48.
The non-magnetic block 42 is provided with a transverse groove 50 on the underside permitting cross pin 52 mounted transversely in the switch rod 48 to come up into the groove 50 when the magnetic assembly is active (as shown in FIG. 2). If the upper magnetic assembly 28 has been shifted to the right (FIG. 3), the groove is shifted and cannot receive cross pin 52 and switch rod 48 cannot be raised to its upper position to close switch 54 which is a toggle switch having its actuating handle 56 received in hole 58 in the switch rod. Thus, it will be appreciated the upper magnetic assembly 28 must be in the active position (FIG. 2) to permit the switch 54 to be closed to turn on the motor in housing 12.
It will be noted the sensor 46 is reciprocally mounted on the lower end of the switch rod 48 with the cross pin or stop 52 extending through the hole 60 in the sensor. Thus, the sensor can move relative to the cross pin 52 within the limited range of movement permitted by the cross pin 52 engaging opening 60. The sensor is biased downwardly by spring 62 compressed between the upper end of the sensor 46 and the pin 36 extending through slot 64 in the switch rod 48. It will be appreciated that in the position shown in FIG. 2 the sensor has been pushed upwardly by reason of engagement with a flat surface. This enables the switch rod 48 to be raised, as illustrated, to close the switch 54. If the tool is knocked over or the like so the sensor is no longer pushed into the base by reason of contact with a work surface, the spring 62 will force the sensor downwardly out of the base and that will cause the aperture 60 to pull pin 52 down and pull the switch rod 48 down to actuate the bat switch handle 56 to turn off switch 54 and deenergize the motor.
When the magnetic assembly is positioned as shown in FIG. 2 and the sensor is retracted, the motor can be energized by lifting the knob 49 on the switch rod 48. The knob 49 is depressed to turn the motor off. The upper magnetic assembly is actuated by actuating lever 30. The lever is locked in either the magnet energized (FIG. 2) or the magnet deenergized position (FIG. 3) by a latch arrangement which includes the U-shaped latch member 66. The cross leg of the U extends through the slots in the crank arms 34 and the open ends are turned in at 68 to engage either the "on" slot 70 or the "off" slot 72 in the side plate 74 (FIG. 1). The in-turned ends 68 are biased into engagement with either of the slots by a tension spring 76. When it is desired to go from the "on" to "off" or from "off" to "on" mode, the cross piece 66 of the latch is pulled rearwardly to disengage the ends 68 from the slot and permit the lever to be actuated. When the cross piece 66 is released, spring 76 will pull the latch ends 68 back into the appropriate slot.
The motor in housing 12 drives spindle 78 (FIG. 8) on which a hole cutting tool 108 is mounted. Details of the drive, chuck etc. can be seen in Application Ser. No. 720,860. The cutting tool is fed into the material to be cut by actuating handle 130. A center indicator 146 acts as a slug ejector as the cutter is retracted from the work.
As noted above the upper assembly shunts the field of the lower assembly when the assemblies are positioned as in FIG. 3. Since there are more magnets in the lower assembly there is still a magnetic field effective to hold the power tool on a ferromagnetic material, albeit with greatly reduced force. This helps in positioning the tool and holding the position while the handle 30 is actuated to make the fields additive.
|Cited Patent||Filing date||Publication date||Applicant||Title|
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|US3237789 *||Dec 26, 1962||Mar 1, 1966||Guilbert Inc||Unloading apparatus for dumb waiters and the like|
|US4012162 *||Feb 10, 1975||Mar 15, 1977||Warren Wesley S||All purpose magnetic base drill|
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US5275514 *||Dec 9, 1992||Jan 4, 1994||Eclipse Magnetics Ltd.||Drill support|
|US5598104 *||Oct 13, 1994||Jan 28, 1997||International Business Machines Corporation||Breakaway test probe actuator used in a probing apparatus|
|US7494306 *||Jul 13, 2005||Feb 24, 2009||Nitto Kohki Co., Ltd.||Rotary cutting machine|
|US7862267||Jan 16, 2009||Jan 4, 2011||Nitto Kohki Co., Ltd.||Rotary cutting machine|
|US8376667||Jul 24, 2008||Feb 19, 2013||Milwaukee Electric Tool Corporation||AC/DC magnetic drill press|
|US8545139 *||May 4, 2010||Oct 1, 2013||C & E Fein Gmbh||Magnetic drilling stand with holding force monitoring|
|US9561568||Apr 25, 2014||Feb 7, 2017||Black & Decker Inc.||Magnetic drill press with alternate power source|
|US20080286063 *||Jul 13, 2005||Nov 20, 2008||Keisuke Shimada||Rotary Cutting Machine|
|US20090028653 *||Jul 24, 2008||Jan 29, 2009||Wilbert Edward D||Ac/dc magnetic drill press|
|US20090129880 *||Jan 16, 2009||May 21, 2009||Nitto Kohki Co., Ltd.||Rotary cutting machine|
|US20100290847 *||May 4, 2010||Nov 18, 2010||Martin Beichter||Magnetic Drilling Stand With Holding Force Monitoring|
|EP0554017A1 *||Jan 22, 1993||Aug 4, 1993||Eclipse Magnetics Limited||A support for a machine tool|
|U.S. Classification||408/76, 408/712, 408/710, 279/128|
|International Classification||B23Q3/154, B25H1/00|
|Cooperative Classification||B25H1/0071, B23Q3/1546, Y10T279/23, Y10T408/554|
|European Classification||B25H1/00C4B1, B23Q3/154C|
|Jul 19, 1990||FPAY||Fee payment|
Year of fee payment: 4
|Mar 13, 1992||AS||Assignment|
Owner name: MILWAUKEE ELECTRIC TOOL CORPORATION A CORP. OF
Free format text: CORRECTIVE ASSIGNMENT TO CORRECT NAME OF ASSIGNEE PREVIOUSLY RECORDED ON REEL 4409 FRAME 207/;ASSIGNOR:PALM, BERNHARD;REEL/FRAME:006050/0922
Effective date: 19920219
|Apr 11, 1994||FPAY||Fee payment|
Year of fee payment: 8
|Apr 9, 1998||FPAY||Fee payment|
Year of fee payment: 12