Abrading – Frame or mount – Portable abrader
Reexamination Certificate
2002-07-12
2004-08-24
Wilson, Lee D. (Department: 3723)
Abrading
Frame or mount
Portable abrader
C451S359000
Reexamination Certificate
active
06780094
ABSTRACT:
The present invention relates to a powered oscillating hand tool, and especially to a powered oscillating hand tool with interchangeable sanding platen attachments.
Powered oscillating hand tools with sander attachments are well known. Known sanders are usually described as either orbital sanders or random orbit sanders, or may combine both facilities in a single hand tool.
Orbital sanders typically comprise a shaped sanding shoe, the drive system of which exhibits an eccentric motion which is restrained so that the sanding shoe can not spin independently of the motor. Therefore in such orbital sanders there is no free rotation of the sanding shoe about its axis. Such orbital sander shoes are generally used for removal of relatively small quantities of material, for example for detailed work or for finishing. Also the shoe may be shaped for access to awkward corners or the like, and may be used for any removal of material in these places.
In contrast, random orbit sander typically comprise a circular platen driven by a drive system which comprises an eccentric bearing so that the platen can spin independently of the motor, and the platen describes a random orbit. Therefore in random orbit sanders, the sanding platen is permitted free rotation about its axis. Such sanders are in general used for the removal of relatively large quantities of material.
EP-A-0694365 describes a single hand tool that is adapted to receive interchangeable sander platens, and perform a dual function: as an orbital sander with a sanding platen secured against free rotation, and as a random orbit sander, with a freely rotating sanding platen. This reference describes a bearing mounted eccentrically on a first drive shaft, and a second drive shaft mounted on the eccentric bearing on which an orbital sander platen and a random orbit sander platen can be interchangeably mounted. A plurality of flexible columns are fitted to the orbital sander platen and these co-operate with rigid components on the housing so that the orbital platen is prevented from free rotation. Alternatively the position of the flexible columns and rigid components can be interchanged. The interchangeable random orbit sanding platen does not have any similar means to couple with the housing and hence is permitted free rotation.
Where freely rotating or random orbit sanding platens are used it is known to mount a brake in the housing so that the brake is in constant contact with the sanding platen. The brake operates in two ways. When the sander is in use, the brake acts as a platen speed limiter, operating in particular to prevent scratches when the unit is placed on and taken off the work surface. Secondly, when the unit is switched off, the stop time is very much reduced.
EP-A-0713751 describes a brake that is particularly suitable for use in the dual function powered oscillating hand tool of the typed described in EP-A-0694365. It describes brake means comprising an abrasion resistant contact layer mounted on a resilient support member in the form of a ring or one or more posts, and formed from resilient material. The brake is located either on the housing part (facing a reaction surface on the random orbit sanding platen) or on the random orbit sanding platen (facing a reaction surface on the housing), and is arranged so that when the random orbit sanding platen is mounted the resilient material is under compression and provides a resultant load on the reaction surface.
We have designed a hand tool with interchangeable first and second sanding platens (the first sanding platen being capable of free rotation, but the second sanding platen being secured against free rotation) in which an intermediate mounting platen is provided secured to the housing, and located between the housing and the sanding platens. The intermediate mounting platen comprises both a brake for the first sanding platen and a coupling means for securing the second platen against free rotation. The hand tool is a modification of the hand tool described in EP-A-0694365, the entire disclosure of which is incorporated herein by reference.
Accordingly the present invention provides a powered oscillating hand tool comprising a housing; a drive unit contained in the housing and having a first drive shaft (
7
); a bearing (
15
) mounted on the said first drive shaft (
7
) which is located radially eccentrically relative to the first drive shaft (
7
), and which drives a second drive shaft (
14
); a mounting platen (
90
) secured to the housing by means of one or more flexible legs (
80
), and first and second sanding platens interchangeably mountable on the second drive shaft, the first sanding platen being arranged for mounting on the second drive shaft and for free rotation about the second drive shaft, and the second sanding platen being mountable on the second drive shaft but securable against free rotation about the second drive shaft; the mounting platen being provided with (i) brake means for providing braking between the first sanding platen and the secured mounting platen, and (ii) coupling means to couple to the second sanding platen so as to provide the said securement against free rotation of the second sanding platen about the second drive shaft.
The mounting platen of the hand tool of the present invention therefore provides a dual function. It acts as a mounting surface for a braking means for when the first sanding platen (the freely rotating platen) is in place; and it acts as a coupling means to prevent free rotation of the sanding platen when the second sanding platen (the platen secured against free rotation) is in place.
While the first sanding platen is arranged to be mountable on the second drive shaft in such a way that the brake means acts on it, it is also preferably arranged so that neither the mounting platen nor the coupling means on the mounting platen engage it so that it is therefore allowed to rotate freely.
As in the known brakes for hand sander tools, the brake means of the present invention acts in two ways; as a speed limiter, and secondly, when the unit is switched off, to reduce the stop time. The brake acts only to restrain rotation to safe limits, and does not prevent free rotation.
Preferably the brake means is provided on a surface of the mounting platen. For example, it may be a brake pad mounted on the surface of the mounting platen facing the first sanding platen. An especially preferred brake pad comprises an abrasion resistant contact layer mounted on a resilient support member, and the part of the first sanding platen facing the brake pad provides a reaction surface, whereby the resilient material under compression provides a resultant load on the reaction surface. The resilient support member may be in the form of either a ring or one or more posts and be formed from a resilient material. A particularly suitable material for the abrasion resistant contact layer is polytetrafluoroethylene (PTFE) brake material. For increased abrasion resistance, fillers such as carbon powder or glass can be added to the PTFE. Particularly suitable materials for the resilient support member include natural or synthetic rubbers or synthetic foam materials such as polyethylene, polyurethane or PVC-nitrile. Particular embodiments of brake pad that could be used in the present invention are described in EP-A-0713751, the entire disclosure of which is incorporated herein by reference.
The braking means preferably limits the rotational speed of the first platen to an acceptable operating speed, preferably less than 20%, more preferably less than 15%, most preferably about 10% of the rotational speed of the motor. For example, the first driving shaft is typically driven by the motor at a rotational speed of 12000 rpm, which is too fast a speed for safe rotation of the sanding platen, and the brake means limits the operational rotational speed of the first platen to around 1200 rpm, i.e. to 10% of the driving speed.
The mounting platen of the hand tool of the present invention acts not only as a mount for a brake means for the first platen when m
Black & Decker Inc.
Harness & Dickey & Pierce P.L.C.
Wilson Lee D.
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