Patent GB-145044-A (GB)
Title: Improvements in weighing machines
IPC: G01G1/38
Filed: 1920-06-14
Abstract: 145,044. Boston Scale & Machine Co., (Assignees of Foote, T. M.). Feb. 21, 1914, [Convention date]. Sliding - weight apparatus.- In a weighing machine, the load is balanced automatically bv a poise which is moved rapidly and continuously along a beam by an electric motor to a position beyond the balancing point and is then given a slower stepby-step movement back to the position of equilibrium. The platform is connected in the usual manner to the beam A carrying a poise B traversed by a screw 3. A continuouslydriven electric motor 27 drives the screw 3 through a system of gear-wheels including two loose wheels 15, 17 which rotate in opposite directions on a shaft 9 connected to the screw 3 by bevel-wheels 7. A centrifugal governor 57 maintains the motor at a constant speed by making and breaking the motor circuit. Attached to the gearwheels 15, 17 respectively are electro-magnetic clutch coils 63, 65 energized from mains P, N, and between the clutch coils is arranged a clutch disk 67 fast on the shaft 9. The poise is thus driven in one direction or the other according to which clutch coil is energized, this being determined by electrical contacts 85, 101 above and below the beam. In the case of each clutch coil the current is supplied through a continuous contact ring and is taken off at both a continuous and a sectional ring comprising insulation and conductive portions. While contacts 79, 95 are opened the last-named continuous ring for each coil is cut out and the operative sectional ring produces intermittent energization of its clutch coil, and consequently gives a step-by-step movement to the poise. Assuming a load to be placed on the machine, a handle 203 is moved to the left and, as described below, unlocks the beam and causes the poise to move a short distance inward. The poise then moves rapidly outward to a position beyond the balancing point. The beam sinks on ,to the contact 101, the clutch coil 65 is de-energized, the clutch coil 63 is energized, and the direction of movement of the shaft 9 and poise B is reversed. A slipping friction clutch 111 on the shaft 9 liberates the spring contact 79 and rotates towards the contact 95. The sectional contact ring of the energized clutch coil being now in operation, the poise is driven step-by-step until the balancing point is reached when the beam is clear of both contacts 85, 101. The extent of the step-by-step movement is regulated by an adjustment on the slipping friction clutch 111, and is arranged so that the balance is attained before the friction clutch closes the contact 95 and thus produces a continuous rapid movement of the poise. A few seconds after the beam has assumed its position of equilibrium, it is automatically locked by means of spring-pressed arms 133. The arms are normally held in the unlocked position by means of a lever 141 held by an armature catch 147. An electro-magnet 69 de-energized with the clutch coils, that is, when the beam is in equilibrium, liberates its armature 195, and a spring 194 causes the armature to push a disk 161 into driving engagement with a friction disk rotating continuously at a low speed. A pin 167 on the disk 161 closes a spring contact 155 and energizes an electro-magnet 153 so as to release the locking-arms 133. A spring 171 returns the disk 161 when the electro-magnet 69 is next energized by the initiation of the next weighing operation. By turning the handle 203 to the left, the beam is unlocked by means of a rod 201 and levers 199, 137. The handle cannot, however, be turned to unlock the beam until released by an electromagnetic catch 211 operated by the closure of contacts 223, 225 when the printing handle 255 is actuated to obtain a printed record of the weight. At each actuation of the handle 203, a contact 226 moving therewith temporarily closes a circuit through the clutch coil 63 and causes the poise to move inwards so as to throw the beam out of balance and cause a cycle of operations to be performed if a second load equal to the first is weighed. Printed records, apparatus for giving.- Fig. 9 shows the printing-mechanism, which is carried by the beam, and embodies a set of type-wheels 229 mounted on an extension of the screw shaft A. A series of hammers 231 are secured to a shaft 234 and are raised by an arm 259 when the printing handle 255 is raised. A roller 263 engaging an incline 259<a> pushes the arm 259 out of engagement with the hammers which then fall and make a record on a paper ribbon fed from a roll 237 to a roll 243, an ink ribbon 245 being also provided. The paper ribbon and the ink ribbon are advanced at each operation of the printing-handle by means of a link 265 and pawl mechanisms 269, 277. The printing- handle is locked by a catch 293 until the poise has reached the balancing point and the beam has been locked by the tripping of the catch 147, Fig. 1. The catch 147 then completes a circuit through contacts 301, 303 and through an electromagnet 299, Fig. 9, and releases the printing- handle. A set of weight-indicating wheels 307 is actuated from the printing-wheels.