Tool with linear drive mechanism

A hand tool with a mechanical linear drive mechanism coupled to a linear activated working implement. The drive mechanism includes a geared planetary roller screw that includes a torque tube connected to a roller screw's nut body. The planetary roller screw includes a fixed outer race, a rotating set of grooved rollers axially aligned inside the outer race, a cylindrical nut body located inside the set of grooved roller, a plurality of inner rollers axially aligned and inside the nut body, a threaded shaft axially aligned and inside the inner rollers, and a torque tube axially aligned inside the inner rollers. The torque tube is connected at one end to a gear box which is coupled to an electric motor. When the electric motor is activated, the torque tube is rotated which causes a threaded shaft in the tool to move axially. A working implement is coupled to the distal end of the threaded shaft.

TECHNICAL FIELD

This invention relates to linear drive mechanisms, and more particularly to linear drive mechanism that are portable and compact.

BACKGROUND ART

Portable hand tools are commonly used by emergency personnel to bend, spread or cut metal pieces to free drivers and passengers from their vehicles after accidents. The working implements on these hand tools are actuated by a linear mechanism coupled to a hydraulic cylinder. The hydraulic cylinder is coupled to a gas or electricity powered hydraulic pump.

One drawback with power hand tools that use hydraulic pumps is the hydraulic pump's periodic inspection and maintenance requirements. Another drawback is the tool's housing is elongated to accommodate the hydraulic pump, the linear mechanism and the working implement.

What is needed is a portable hand tool with an electric, non-hydraulic linear drive mechanism coupled to a working implement.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a portable hand tool with a lightweight, compact linear drive mechanism that uses a roller screw coupled to the tool's working implement.

The linear drive mechanism includes a roller screw threaded shaft with an external nut and rollers mounted over an axially aligned threaded shaft longitudinally aligned inside the tool's elongated body. In one embodiment, the proximal end of the threaded shaft is coupled to a gearbox that is coupled to an electric motor that can be operated in both forward and reverse directions. The gearbox includes a plurality of gears configured to reduce the RPM output from the electric motor. In the first embodiment, the gearbox is also coupled to a frictional clutch configured to engage the inside surface of the roller screw shaft when rotated a specific amount. In a second embodiment, the frictional clutch is eliminated and replaced by a multiple stage gear box.

When the electric motor is activated, the frictional clutch or multiple stage gear box causes the threaded shaft to rotate. In the first embodiment, as the threaded shaft is rotated, the roller screw's nut body moves longitudinally inside the tool's elongated body. In the second embodiment, the nut body is fixed axially inside the tool's outer housing so as the nut body is rotated, the threaded shaft moves axially inside the tool's outer housing.

Mounted distally inside the elongated body and adjacent to the distal end of the roller nut is a tool implement coupler that attaches to a tool implement that extends from tool's distal end. The tool implement may include two pivoting cutting jaws, two pivoting spreader jaws, or a ram bar. A rechargeable battery s attached to the proximal end of the elongated housing to energize the electric motor.

In the second embodiment, the mechanical linear drive is a geared planetary roller screw that includes a torque tube connected to a roller screw's nut body. The planetary roller screw includes a fixed outer race, a rotating set of grooved rollers axially aligned inside the outer race, a cylindrical nut body located inside the set of grooved rollers, a plurality of threaded inner rollers axially aligned and inside the nut body, a threaded shaft axially aligned and inside the inner rollers, and a torque tube fixed to the nut body. The nut body operates as an inner race for the grooved inner rollers. The torque tube is connected at one end to the gear box coupled to an electric motor. When electric motor is activated, the torque tube is rotated which causes a threaded shaft in the tool to move axially inside the tool. A working implement is coupled to the distal end of the threaded shaft.

BEST MODE FOR CARRYING OUT THE INVENTION

A tool10with a lightweight linear drive mechanism12in the tool's elongated body15and designed to provide 70,000 to 120,000 lbs of force to the tool's working implement70.FIG. 1discloses a first embodiment of the tool10that includes a roller screw assembly shown and described in U.S. Pat. No. 7,044,017 and incorporated herein. The roller screw assembly includes a roller screw shaft22and a nut body50mounted over the outer surface of the roller screw shaft22. Disposed inside the nut body50is a plurality of longitudinally aligned rollers54designed to remain in constant contact with formed helical threads23on the outer surface of the roller screw shaft22and with grooves51formed on the interior surface of the nut body50during operation. The rollers54, however, can shift axially and re-positioned with respect to both the nut body50and the roller screw shaft22as the roller screw shaft22is rotated while remaining in rolling contact with the nut body50.

The grooves51on the nut body50are helical over most of the inside surface of the nut body50. Over a small region of the inside surface of the center bore, hereinafter referred to as the cross-over region, the grooves51extend radically outward and axially. Located inside the nut body50is a plurality of longitudinally aligned rollers54. Formed over the outer surface of the rollers54are non-helical grooves55that mesh with a plurality of closed, partially helical grooves51on the nut body50and with the helical threads23on the roller screw shaft22that extends through the nut body50. When the rollers54travel through the cross-over region, two compression rings on the opposite ends of the rollers54force the rollers54radially outward so they maintain engagement with the grooves51on the nut body50.

Because the grooves51in the cross-over region extend axially, the rollers54are shifted axially regarding the nut body50and roller screw shaft22when centrally disposed in the cross-over region. As the rollers54leave the cross-over region, they are extended axially and returned to the original starting point of the grooves51on the nut body50.

The grooves55on the rollers54are non-helical and designed to engage both the closed grooves51on the nut body50and on the helical threads23on the roller screw shaft22. The diameters of the roller screw shaft22, the nut body50, and rollers54are sufficient in size so that when the grooves55on the rollers54engage the grooves51on the nut body50in the cross-over region, they progressively disengage from the helical threads23on the shaft22enabling the rollers54to move axially with respect to the nut body50. As the rollers54leave the cross-over region, they travel axially and re-engage the helical threads23on the roller screw shaft22. With each rotation of the roller screw shaft22inside the nut body50, the rollers54are in constant rolling contact with the grooves51on the nut body50.

The above described roller screw assembly12is longitudinally aligned inside the hollow cavity18formed in the hand tool's elongated body15. The roller screw shaft22is coaxially aligned inside the cavity18and includes a longitudinally aligned cavity24. Mounted inside the cavity24and adjacent to the proximal end of the roller screw shaft22is an electric motor30. Mounted adjacent to the electric motor30and inside the cavity24is a gearbox36. The gearbox36is coupled to the drive shaft on the electric motor30and configured to reduce the RPM output from the electric motor30.

The opposite end of the gearbox36is coupled to a frictional clutch40also located inside the distal end of the cavity24. When the electric motor30is activated, the gear box36causes the frictional clutch40to rotate that eventually engages the exposed section of the inside surface of the roller screw shaft22and causing the roller screw shaft22to rotate inside the nut body50.

Longitudinally aligned and located distally inside the elongated body15is an elongated push cap60. The push cap60includes a wide proximal section and a narrow front neck section. The distal end of the roller screw shaft22extends into the center bore formed in the push cap60. When assembled, the end surface of the proximal section abuts the distal end surface of the nut body50. When roller screw shaft22is rotated, the nut body50travels longitudinally inside the elongated body15in a fore or aft direction depending on the direction of rotation of the electric motor30.

Mounted on the distal end of the push cap60is a pivot pin65coupled to toggle linkage68. The toggle linkage68is connected to one or more cutter or spreader blades70used on the working implement.

The roller screw shaft22is held coaxially inside the elongated body15and the push cap60by bearings85. The roller screw shaft22includes a perpendicular aligned base that fits inside the proximal wide end section of the elongated body15. The electric motor30is held inside the proximal end of the roller screw shaft22by a transverse member that extends across the proximal end opening. The electric motor30includes a secondary shaft coupled to an electrical brake mounted on the proximal end of the elongated body15.

A rechargeable battery90may be attached to the proximal end of the elongated body15to energize the electric motor30.

FIGS. 2-10show a second embodiment of the tool200with a lightweight linear drive mechanism that uses an electric motor assembly205coupled to a multiple stage gear box220used in place of the frictional clutch40. Coupled to the gear box220is a geared planetary roller screw250that is used in place of the roller screw assembly described above. The geared planetary roller screw250is similar to the roller screw shown in U.S. Pat. No. 2,683,379 (Strandgren) which is now incorporated herein.

As shown inFIG. 4, the geared planetary roller screw250includes a fixed cylindrical, fixed outer race260axially aligned inside the tool's outer housing210. The outer race260includes a plurality of internal, non-helical grooves264. A dowel pin268is inserted in between the outer housing210and the outer race260to hold the outer race260inside the tool200. A set screw270is used to retain the dowel pin268in the outer housing210.

Located adjacent inside the outer race260is a plurality of outer grooved rollers275. Formed on each end of the outer grooved rollers275are axially aligned axles278that engage bores formed on two spacer rings280coaxially aligned inside the outer housing210. Each grooved roller275includes a plurality of non-helical grooves282configured to mesh with the non-helical grooves264formed on the outer race260. During operation, the set of grooved rollers275and the two spacer rings280rotate inside the outer housing210.

Located adjacent and inside the grooved rollers275is a cylindrical nut body288configured to rotate inside the outer housing210. The nut body288includes a plurality of external non-helical threads290that mesh with the non-helical grooves282on the grooved rollers275. The nut body288acts as an inner race for the outer groove rollers275. The nut body288also includes a plurality of internal helical threads292. The non-helical threads290on the external surface of the nut body288allow the nut body288to rotated but prevent the nut body288from moving axially inside the outer housing210.

Located adjacent and inside the nut body288is a plurality of axially aligned inner rollers300. Each inner roller300includes external helical threads304that mesh with the internal helical threads292on the inside surface of the nut body288. Each inner roller300includes at its opposite ends a set gear teeth306that engage two ring gears305aligned transversely inside the outer housing210. Formed on the two ring gears305are a plurality of external teeth306that mesh with the gear teeth302on opposite ends of the inner rollers300. During operation the inner rollers300individually rotate on their longitudinally axis and rotate around a threaded shaft310that extends coaxially and inside the outer housing210.

The threaded shaft310includes a plurality of helical external threads314that extend substantially the entire length and mesh with the helical threads304on the inner rollers300. In the embodiment shown herein, the threaded shaft310is approximately twice as long as the inner rollers300. The threaded shaft310is hollow with a proximal end and a distal end. Attached to the distal end is a combination end cap/clevis320.

Disposed inside the outer housing210is a torque tube330that includes a narrow cylindrical hollow neck334and a wide cylindrical body338. The neck334is configured to surround the rear portion of the threaded shaft310that extends rearward from the inner rollers300. The wide cylindrical body338is configured to extend outward and partially extend around the exterior surface of the nut body288. Formed the inside surface of the wide cylindrical body338and the adjacent surface of the nut body288is keyway. A complementary key340is inserted into the two keyways to affix the torque tube330to the nut body288. Formed on the proximal end of the torque tube330are one or more receiving bores that receive pegs222that extend longitudinally inward from the gear box220.

During operation, the electric motor205is activated which causes the pegs222on the gear box220to rotate. The rotation of the pegs222on the gear box220causes the torque tube330to rotate which causes the nut body288to rotate. Because the grooved rollers275prevent the nut body288from moving longitudinally inside the outer housing210, the inner rollers300engage the threads304on the threaded shaft310causing the threaded shaft310to move longitudinally inside the outer housing210.

FIGS. 2 and 3show the tool200attached to a tool implement350with two cutting jaws360,380extending from the distal end of the outer housing210. The two cutting jaws360,380include cutting blade edges366,386and middle sections365,385, respectively, rotatingly coupled together by a rigid front pin390. The rear section361,381of each jaws360,380, respectively, is pivotally connected to a linkage arm353,355, respectively. The rear end of each linkage arm353,355is connected to a combination end cap/clevis320(shown inFIG. 4) which is connected to the end cap320. The front end of each linkage arm353,355is connected to a cutting jaws360,380via pins362,382, respectively. During use, the threaded shaft310moves axially inside the outer housing210causing the rear sections361,381of the two jaws360,380, respectively, to move towards or away from the front pin390and thereby opening and closing the jaws360,380.

FIGS. 11 and 12are side elevational views of a tool implement400with two spreader jaws410,420that extend from the distal end of the outer tool housing212. The spreader jaws410,420are connected to linkage arms353,355and operate in a manner that enable the spreader arms410,420to open and close.

FIG. 13is a side elevational view of a tool implement500with a ram bar510extending longitudinally from the distal end of the tool housing. The ram bar510is connected directly to the distal end of the end cap or to the threaded shaft.

INDUSTRIAL APPLICABILITY

This invention has application in the portable hand tool and emergency equipment industries, and more particularly in such industries that need tools and equipment to covert rotation movement from an electric motor to a linear activated tool implement.