Please select the most similar patent number from A, B, C and D. Which number is?
Disclosed is a furnace door sealing apparatus for a low-pressure diffusion furnace, the apparatus comprising: a furnace door (1), a fixing shaft (2) and a fixing seat (3) successively arranged from front to back and arranged coaxially. The middle of a rear end face of the furnace door (1) is fixed with a bearing seat (6); a centripetal joint bearing (4) is provided within the bearing seat (6); an outer ring of the centripetal joint bearing (4) is fixed within the bearing seat (6); the inner ring of the centripetal joint bearing (4) is fixedly sheathed on a front end of the fixing shaft (2); a rear end of the fixing shaft (2) is fixed within the fixing seat (3); a front end face of the fixing seat (3) is also fixed with a supporting plate (8); and a plurality of spring adjusting components are provided at intervals on the supporting plate (8).
A: Disclosed is a ball bearing high-speed electric main shaft for milling, comprising an upper bearing seat assembly (5), an upper bearing assembly (6) being fixed via an upper bearing lock nut (17) in a through-hole within the upper bearing seat assembly (5), wherein the front end of a step of the upper bearing seat assembly (5) is fixed to the rear end of a machine body assembly (9), and the front end of a lower bearing assembly (10) is fixed to a lower bearing pressure ring (16) by a lower bearing lock nut (15), and the rear end of a spindle main body of a spindle assembly (7) is fixed to an encoder (18) detecting the rotational speed. The rotational speed of the electric main shaft is adjustable and when operating at a high rotational speed, the main shaft has high accuracy, adequate axial and radial rigidity, and a long service life.
B: Disclosed is a universal pressing roller for a carton sealing machine, falling within the technical field of packaging machinery equipment. The universal pressing roller comprises a shaft fixing frame (1), a shaft (2), a bearing ball (3) and a collar (4), with one end of the shaft (2) being fixed to the shaft fixing frame (1), two sides of the bearing ball (3) being respectively fixed to the middle part of the shaft (2) via the collar (4), a bearing ball outer sleeve (5) being sleeved on the bearing ball (3), the bearing ball (3) and the bearing ball outer sleeve (5) being slidable relative to each other, a bearing seat (6) being fixed to the bearing ball outer sleeve (5), and a rubber wheel (7) being provided on the outer side of the bearing seat (6). Since the middle part of the shaft of the universal pressing roller is provided with the bearing ball, the rubber wheel on the shaft can self-adjust an angle according to the angle of a contact surface of a to-be-sealed carton in contact with the rubber wheel, so that the sticking of same with tape is smooth and nice-looking, without changing the original shape of the carton. Furthermore, the universal pressing roller is simple in structure, and is safe, stable, convenient and reliable during use. With the universal pressing roller, the cartons have a consistent and nice look after being sealed. The universal pressing roller is suitable for assembly line work, and can be used to make improvements on almost all the existing carton sealing machines to solve the general problem of the carton surface not being parallel to the roller, and is suitable for being popularized.
C: An electromagnetic dog clutch, which is used for solving the technical problem that friction easily occurs between a bearing seat and an end cover of a movable gear sleeve in an existing electromagnetic dog clutch. The electromagnetic dog clutch comprises a movable gear sleeve (5) and a fixed gear sleeve (12) which are in meshing transmission with each other, a first end cover (6) is provided at an outer side of the movable gear sleeve (5), a bearing (1) is provided on the outer circumference of the movable gear sleeve (5), the bearing (1) is embedded within a bearing seat (7), a positioning surface is provided at a rear end of the bearing seat (7), a front end of the first end cover (6) is a vertical flat surface fitted with the positioning surface of the bearing seat (7), a positioning pin (15) is provided at the front end of the first end cover (6), a positioning hole is provided at the rear end of the bearing seat (7) in cooperation, and the positioning pin (15) is inserted into the positioning hole to allow the relative axial movement and limit the relative rotational movement between the bearing seat (7) and the first end cover (6), avoiding friction between the two.
D: Disclosed is an environment-friendly thermal treatment furnace, comprising a furnace body (1) and a furnace door (2), wherein a furnace opening (1-1) is provided on a side surface of the furnace body (1) and the furnace door (2) is provided on the furnace opening (1-1), which is characterized in that: a connection rod (3) is arranged on the side surface of the furnace body (1) which is provided with the furnace opening (1-1), two cross bars (4) are fixed to the connection rod (3), and two ends of the connection rod (3) are hinged with the furnace body (1); upper and lower sides of the furnace door (2) are respectively connected to the two cross bars (4) via a strut (5), a waist-shaped hole (6) is provided on each of the upper and lower sides of the furnace door (2) respectively, and the length of the waist-shaped hole (6) extends from the point close to the furnace body (1) to the direction away from the furnace body (1), and one end of the strut (5) is fixed with the cross bar (4), and the other end of the strut (5) extends into the waist-shaped hole (6) to be hinged with the furnace door (2); A retaining ring (7) and a sealing ring (8) are provided on an inner side of the furnace door (2), and the sealing ring (8) is fitted inside the retaining ring (7), a groove (9) matched with the retaining ring (7) and the sealing ring (8) is provided on the outer periphery of the furnace opening (1-1) of the furnace body (1), the sealing ring (8) and the retaining ring (7) are provided with through-holes (10) on side surfaces, and filter screens (11) are provided on the through-holes (10) of the retaining ring (7).
Answer: D