Dual-action sander

Abstract: A dual-action sander (10) comprises a housing (12), a motor (18) mounted in the housing, a motor shaft balancer (20) driven by the motor (18) for rotation relative to the housing about a first axis (24), a balancer shaft (30) carried by the balancer (20) for rotation relative thereto about a second axis (32) radially offset relative to the first axis and having a mount for mounting a sanding device (34), and a latch pin (50) slidably supported by the balancer (20) for movement axially thereof between unlatched and latched positions. The latch pin (50) has a first end (50a) engageable with the balancer shaft (30) when the latch pin is in the latched position, thereby to prevent rotation of the shaft relative to the balancer about the second axis (32). A manually operable control member (60) carried by the housing is engageable with a second end (50b) of the latch pin (50) and is movable to displace the pin into the latched position against a spring force biasing the pin towards the unlatched position.

Description: A dual-action sander manually adjustable to selectively drive a sanding device, such as a pad mounting a sand paper disc, for either random orbital movement or orbital movement is disclosed by US Patent Specification 2 794 303. Dual-action sanders formed in accordance with US 2 794 303 have enjoyed wide commercial success, particularly in the automobile aftermarket, wherein the sander is adapted, when operated in the orbital mode, for heavy stock removal, while providing a finish superior to that produced by a typical rotary disc sander. In the random orbital mode, a very fine finish may be obtained. A disadvantage of this prior dual-action sander is in the construction of the locking device employed to retain the sander in its orbital mode. This device features a detent formed as part of a relatively thin sheet metal ring, which is supported on a motor shaft balancer for pivotal or swinging movement for purposes of removably inserting the detent into a radially opening recess formed in a side wall of a sanding device supporting balancer shaft or spindle. The detent is subject to deformation rendering it difficult to properly seat the detent in the recess after extended usage. Further, the mode of supporting the detent requires that the sander motor be turned off before the ring can be manually manipulated for detent insertion/removal purposes. A random orbital sander disclosed in US Patent Specification 4 854 085 comprises a compact drive construction with a motor mounted in a recess of a housing, a rotationally driven balancer keyed to the motor and having a downwardly open recess receiving a bearing, and a balancer shaft which is mounted in the bearing to be freely rotatable about an axis offset relative to the balancer axis and which is provided with attaching means for a sanding element locatable within a shroud fixed to the housing. Such a sander does not, however, include a locking device for the purpose described in US 2 794 303. The present invention is directed to an improved dual-action sander not having the disadvantages of prior commercial sanders formed in accordance with US 2 794 303, and more particularly to an improved locking mechanism for such sanders. This object can be achieved by a dual-action sander as defined in claim 1. In accordance with the present invention, a latch pin is supported for reciprocation between latched and unlatched positions under the control of a housing-mounted control member, which can be operated for purposes of changing between the operating modes of the sander without need for turning off the sander drive motor. Further, that portion of the latch pin arranged for latching engagement with the balancer shaft or spindle for purposes of locking the sander in its orbital mode may be formed of relatively heavy stock material, such as will maximise resistance to deformation. A preferred embodiment of the sander of the present invention will now be more fully described in the following detailed description taken with the accompanying drawings, wherein: Fig. 1 is a fragmentary, partially exposed view of a dualaction sander embodying the present invention; Fig. 2 is a partial, vertical sectional view showing the sander in its orbital mode; Fig. 3 is an enlarged sectional view taken generally along the line 3-3 in Fig. 2; Fig. 4 is a fragmentary sectional view similar to Fig. 2, but showing the sander in its random orbital mode; Fig. 5 is a sectional view taken generally along the line 5-5 in Fig. 2; and Fig. 6 is a sectional view taken generally along the line 6-6 in Fig. 4. Reference is first made to Figs. 1 and 2, wherein a pneumatically driven sander which embodies the present invention is designated as 10 and shown as generally including a housing 12 formed with a manually manipulated handle 14 and a downwardly opening recess 16, a drive motor 18 mounted within the recess, a motor shaft balancer 20 coupled to the motor by a key 22 and adapted to be driven by the motor for rotation about a drive or first axis 24, a bearing 26 fitted within a downwardly opening recess 28 defined by the motor shaft balancer, a balancer shaft 30 carried by the motor shaft balancer via the bearing for free rotational movement relative to the motor shaft balancer about a second axis 32 radially offset relative to the drive axis, a sanding pad 34 removably fixed to the balancer shaft, a shroud 36 depending from the housing, and a seal assembly including a bearing seal 38, a bearing shield 40 and a snap fitted retainer 42. As thus far described, sander 10 is structurally similar to the random orbital sander disclosed in US Patent 4 854 085 whose disclosure is incorporated by reference. Present sander 10 differs from that described in US 4 854 085 in that its manually operable, air flow control device, not shown, is arranged to wholly overlie handle 14, so that the upper surface 12a of housing 12 is unobstructed, and in that a locking means 46 is provided for releasably locking balancer shaft 30 against rotation about second axis 32 relative to motor shaft balancer 20, thereby to provide sander 10 with a dual-action sanding capability similar to that described in US 2 794 303. In accordance with the embodiment, the locking means 46 preferably includes latch means in the form of a latch pin 50 slidably supported for movement lengthwise of a mounting opening 52 formed in motor shaft balancer 20 and extending in alignment with drive axis 24. Mounting opening 52 extends through a motor shaft portion 20a and a balancer portion 20b of motor shaft balancer 20 and opens into recess 28, as best shown in Fig. 2. Latch pin 50 has a first or lower end 50a arranged to removably engage within a slot 56 formed in balancer shaft 30 to extend transversely of second axis 32 and to open relatively towards recess 28, when the latch pin is moved into a lowermost or latched position shown in Figs. 2 and 3 in the manner to be described. Engagement of latch pin 50 within slot 56 locks balancer shaft 30 against rotation about second axis 32 relative to motor shaft balancer 20. Latch pin 50 has a second or upper end 50b arranged to normally project outwardly from the upper end of mounting opening 52 for engagement with a thumb-operated control member 60, which is supported for sliding movement lengthwise of a guide slot 62 formed in housing 12 to extend transversely of drive axis 24. Support for control member 60 may be provided by forming housing 12 with outwardly facing, parallel slide surfaces 62a and 62a arranged to underengage parallel lower edge surfaces 60a and 60a of member 60. Member 60 may be retained in sliding engagement with the housing by forming the member with resiliently deformable, dependent latch members 60b and 60b arranged to snap under the edges of slot 62, as shown in Figs. 5 and 6. Control member 60 is formed with a downwardly facing cam surface or ramp 66, which is arranged to slidably contact latch pin upper end 50b, such that latch pin 50 may be driven downwardly from its unlatched position shown in Figs. 4 and 6 into its latched position shown in Figs. 2 and 5 incident to manually induced sliding displacement of the control member to the right as viewed in Fig. 4. Latch pin 50 may be freed for return to its unlatched position under the bias of a coil return or compression spring 68 by manually sliding member 60 to the left, as viewed in Fig. 2. The opposite ends of cam surface 66 are provided with downwardly facing latching recesses 66a and 66b adapted to removably engage with latch pin 50 for purposes of releasably latching the latch pin alternatively in its unlatched and latched positions, respectively. Spring 68 is shown as being arranged between the upper end of motor shaft portion 20a and a retaining ring 70 snap fitted to latch pin upper end 50b for purposes of providing a resilient bias tending to move latch pin 50 upwardly away from its latched position for return to its unlatched position upon manually induced movement of control member 60 into its release or inoperative position viewed in Fig. 4. In view of the foregoing, it will be understood that manual movement of control member 60 to the right, as viewed in Fig. 4, serves to drive latch pin 50 into its lower latched position, wherein it latches balancer shaft 30 against rotation relative to motor shaft balancer 20 about a second axis 32, whereas manual movement of the control member to the left, as viewed in Fig. 2, permits spring 68 to bias the latch pin for return into its unlatched position, wherein the latch pin is removed from slot 56 and the balance shaft is free to rotate about the second axis. An advantage of the present construction is that an operator may manipulate control member 60 for purposes of changing between the operating modes of sander 10, while motor 18 is in an idling condition. While the present invention has been described for use with a pneumatic motor-operated sander, it is contemplated that the invention has utility for use with electric motor-operated sanders.

Claims: A dual-action sander (10) comprising a housing (12), a motor (18) supported by the housing (12), a motor shaft balancer (20) driven by the motor (18) for rotation relative to the housing about a first axis (24), a balancer shaft (30) carried by the balancer (20) for rotation relative thereto about a second axis (32) radially offset relative to the first axis (24) and having mounting means for mounting a sanding device (34), and locking means (46) for releasably locking the balancer shaft (30) against rotation relative to the balancer (20), characterised in that the locking means (46) comprises latch means (50) supported for movement along the first axis (24) between unlatched and latched positions and a manually operable control member (60) for moving the latch means (50) from the unlatched into the latched position, the latch means (50) when in the unlatched position freeing the balancer shaft (30) for rotation relative to the balancer (20) and when in the latched position engaging with the balancer shaft (30) to lock the same against rotation relative to the balancer (20). A sander according to claim 1, characterised in that the control member (60) is supported by the housing (12) for movement transversely of the first axis (24). A sander according to claim 1 or claim 2, characterised in that the latch means (50) is mounted for sliding movement longitudinally of the balancer (20) in alignment with the first axis (24). A sander according to any one of the preceding claims, characterised in that the balancer (20) has a mounting opening (52) extending therethrough in alignment with the first axis (24), the latch means (50) comprises an elongate latch pin (50) slidably supported in the mounting opening (52) and having a first end (50a) arranged to removably engage the balancer shaft (30) when in the latched position and a second end (50b), and the control member (60) is mounted by the housing (12) for engagement with said second end (50b) and is movable relative to the housing (12) to effect sliding movement of the latch pin (50) to place said first end (50a) in engagement with the balancer shaft (30). A sander according to claim 4, characterised in that the latch pin (50) is resiliently biased towards the unlatched position. A sander according to claim 4, characterised in that the balancer (20) has a motor shaft portion (20a) extending axially through the motor (18) in alignment with the first axis (24) and a balancer portion (20b) having a recess (28) receiving a bearing (26) in which the balancer shaft (30) is mounted for rotation about the second axis (32), wherein the mounting opening (52) opens into the recess (28) and the latch means (50) comprises a slot (56) defined by the balancer shaft (30) to extend transversely of the second axis (32) and to open towards the recess (28), the first end (50a) of the latch pin (50) being removably engageable in the slot (56) for locking the balancer shaft (30) against rotation relative to the balancer (20) when in the latched position, and the control member (60) being operable to effect movement of the latch pin (50) from the unlatched to the latched position. A sander according to claim 6, characterised in that the control member (60) is slidably supported by the housing (12) for movement transversely of the first axis (24) and is formed with a cam surface (66) engaging the second end (50b) of the latch pin (50) and the latch pin (50) is resiliently biased for movement towards the unlatched position, in which position the first end (50a) of the latch pin (50) is removed from the slot (56).

Inventors: HEIDELBERGER RICHARD A, HEIDELBERGER, RICHARD A.
Applicants: DYNABRADE, DYNABRADE, INC.
Application year: 1998
Main classification: B24B23
IPC codes: B24B23