Preliminary thrusting mechanism for a screw device

• US 5,582,072 A
• Filed: 02/08/1994
• Issued: 12/10/1996
• Est. Priority Date: 02/08/1993
• Status: Expired due to Term

• Current Assignee: NSK Limited
• Original Assignee: NSK Limited
• Inventors: Yamaguchi, Toshiaki, Miyaguchi, Kazuo
• Primary Examiner(s): Marmor, Charles A.
• Assistant Examiner(s): GRABOW, TROY E
• Application Number:
  US08/194,370
• Time in Patent Office: 1,036 Days
• Field of Search: 74/441, 74/459
• US Class Current: 74/441
• CPC Class Codes: F16H 25/2209 with arrangements for taking up backlash
• CPC Class Codes: Y10T 74/18728 Backlash
• CPC Class Codes: Y10T 74/19707 Plural longitudinally variably spaced nuts
• CPC Class Codes: Y10T 74/19902 Screw and nut

Abstract

A preliminary thrusting mechanism for a screw device serves to achieve not only constant position type preliminary thrusting but also constant pressure type preliminary thrusting. The preliminary thrusting mechanism includes as essential components a screw shaft having a spirally extending screw groove formed axially along the outer surface thereof, a first nut threadably engaged with the screw shaft, a second nut operatively connected to the first nut in series and threadably engaged with the screw shaft, a rotation stopping unit for preventing the second nut from being rotated relative to the first nut, a thrusting unit including a thrusting member adapted to impart to the first nut and the second nut a certain intensity of thrusting power effective in the opposite direction for allowing them to be displaced away from each other in the axial direction, and a stopping unit for preventing the thrusting member from being displaced further when the thrusting member is displaced by a predetermined distance. In practice, the thrusting unit includes a liquid pressure source, a liquid pressure supplying path and a pressure chamber, and the stopping unit includes flanges each serving to prevent further displacement of the thrusting member.

Claims

1. A preliminary thrusting mechanism for a screw device comprising:

a screw shaft (1) having a spirally extending screw groove formed axially along the outer surface thereof;

a first nut (2) threadably engaged with said screw shaft (1);

a second nut (3) Operatively connected to said first nut (2) in series and threadably engaged with said screw shaft (1);

rotation stopping means (20, 20a, 20b) for preventing said second nut (3) from being rotated relative to said first nut (2);

thrusting means (5, 8, 8a) including a thrusting member (5) operative to impart to said first nut (2) and said second nut (3) a certain intensity of thrusting power effective in the opposite direction for allowing them to be relatively displaced away from each other in the axial direction; and

stopper means for preventing said thrusting member (5) from being displaced further when said thrusting member (5) is displaced by a predetermined distance, in which said stopper means comprises;

an engaging member (6,

     7) having a stopping portion (7a); and

an engaged member (5a) provided with said thrusting member (5) and being brought in contact with said stopping portion (7a), so as to prevent said thrusting member (5) from being displaced further when said thrusting member (5) is displaced by a predetermined distance, in which said engaging member (6,

     7) comprises an inside sleeve (6) including outward orienting flange (6a) coming in contact with the end surface of said first nut (2) and located outside of said screw shaft (1), and an outside sleeve (7) including an inward orienting flange (7a) and located in the vicinity of the outer peripheral surface of said first and second nuts (2 and

     3), wherein said inside sleeve (6) and said outside sleeve (7) are fixed to the end surface of said first nut (2).

2. A preliminary thrusting mechanism for a screw device according to claim 1, in which said engaged member (5a) comprises:

an outward orienting flange (5a) integrally provided with a cylindrical thrusting member (5) and disposed between said inside sleeve (6) and said outside sleeve (7).